US20070213143A1

US20070213143A1 - Exterior coatings for golf balls

Info

Publication number: US20070213143A1
Application number: US11/370,126
Authority: US
Inventors: Jeffrey Chinn; Peter Yang
Original assignee: Applied Microstructures Inc
Current assignee: Applied Microstructures Inc
Priority date: 2006-03-07
Filing date: 2006-03-07
Publication date: 2007-09-13

Abstract

Improved golf ball exterior coatings which are used to create an extremely uniform hydrophobic or hydrophilic exterior surface on the golf ball. When the surface of the golf ball is hydrophobic, it tends to repel water, and this reduces drag on the golf ball surface as the golf ball travels through the air. When the surface of the golf ball is hydrophilic, the surface of the golf ball wets uniformly and the ball rolls straighter on a wet green, as the forces acting on the ball are more uniform. The hydrophobic or hydrophilic exterior coating is applied to the golf ball using vapor-phase deposition in instances where strict control over coating thickness uniformity, and/or reduced surface roughness is desired.

Description

This application is related to a series of patent applications pertaining to the application of thin film coatings on various substrates, particularly including U.S. patent application Ser. No. 10/862,047, filed Jun. 4, 2004, and entitled “Controlled Deposition of Silicon-Containing Coatings Adhered by an Oxide Layer”; and, U.S. patent application Ser. No. 10/996,520, filed Nov. 19, 2004, and entitled “Controlled Vapor Deposition of Multilayered Coatings Adhered by an Oxide Layer”. Both of these applications are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention pertains to golf balls coated with exterior thin film coatings which affect the performance of the golf ball during play.
2. Brief Description of the Background Art
This section describes background subject matter related to the invention, with the purpose of aiding one skilled in the art to better understand the disclosure of the invention. There is no intention, either express or implied, that the background art discussed in this section legally constitutes prior art.
A multitude of studies have been conducted with respect to aspects of the composition and shape of the golf ball which affect it's performance. One of the more interesting is an article entitled “A St. Mary's Project: The Aerodynamics of Golf Ball Flight”, by Kevin E. Warring, Department of Physics, St. Mary's College of Maryland, St. Mary's City, Md., published in the Spring of 2003. This article provides an introduction to Fluid Dynamics which affect golf ball flight; the dimpled golf ball and drag; the Magnus force (a major force acting on the golf ball due to its spin); and, the modeling of golf ball flight in general. The author explains how to predict the trajectory of a golf ball give its initial launch angle, velocity and spin rate. The article discusses applications of the principles discussed to golf ball design.
A web site at www.indoindians.com/golfbcore.htm, in January 2006 contained an article titled “Dimples Drive Drag Out of Golf Balls”, this article explains that at airspeed, sticky air slows a ball down substantially. The ball is said to get wet as it travels through air, so that the surface of the ball is referred to as a “wetted surface”. The use of dimples on the ball surface is said to make air molecules in the boundary layer adjacent the golf ball surface tumble, so that the boundary layer becomes turbulent. The article teaches that when the boundary layer is turbulent and thin, the ball loses less energy to the free stream air and the drag on the ball is lower. In addition to the discussion of the golf ball in flight, there is a presentation about what happens to a golf ball after it sits at the bottom of a pond. A study was conducted with respect to balls which were permitted to sit in water at temperatures ranging from 36 to 70° F. for a period of six months. The balls were tested using a robotic hitting machine. The average carry, and roll for the new balls was about 251 yards. The average carry and roll for balls that had been in the water for eight days was about 236 yards. After three months, the average carry and roll had decreased to about 226 yards, and after six months, the average carry and roll was about 225 yards. This may be viewed as a six yard loss of distance after eight days, a 12 yard loss after three months, and a 15 yard loss after six months.
U.S. Pat. No. 6,509,410 to Ohira et al., issued Jan. 21, 2003, describes an aqueous coating composition for a golf ball. The aqueous coating composition is said to form a high crosslink density owing to the high hydroxyl value, to contain. The coating produced is said to have high impact resistance, abrasion resistance, contamination resistance, etc. which are equivalent to films produced from organic solvent type coatings. The coating formed is said to be free from cracking or film peeling when hit by a golf club; is said to be low in scratch, abrasion and contamination with grass sap, and is said to provide a coated golf ball which retains gloss and fine appearance.
U.S. Pat. No. 6,806,347 to Hogge et al., issued Oct. 19, 2004, describes golf balls with a thin moisture vapor barrier layer. The golf ball comprises a core, a cover, and at least one water vapor barrier layer, where the water vapor barrier layer comprises at least one layer formed from poly-para-xylene and its derivatives. The patent discusses WVB (water vapor barrier) layers and WVT (water vapor transmission) rates. The thin moisture vapor barrier layer described, which is formed from poly-para-xylene, and its derivatives. Parylenes are selected as materials of choice to form the thin WVB layers, particularly when the parylene is halogenated to include a group VIIA element. The group VIIA element may be fluorine, chlorine, bromine, iodine, or astatine. The preferred element is chlorine. The WVB layer comprising parylenes is typically formed using vapor deposition polymerization at a steady rate. The thickness of the parylene-based WVB layer is said to be controllable at any desired nominal thickness because the WVB layer is formed via vapor deposition polymerization at a steady rate. Thickness of the layer commonly ranges from about 0.025 μm to about 75 μm. The thickness is preferably from about 1 μm to about 25 μm, and most preferably from about 3 μm to about 10 μm. One or more of the thin WVB layers may be disposed between the golf ball core and the cover. Substrates such as golf ball cores and golf ball sub-assemblies are prepared for parylene coating by cleaning off oils and other surface contaminants. The substrate may then be pre-treated by application of a “multi-molecular” layer of organosilane to promote adhesion of the parylene coating. The parylene precursor, a granular white powder, is vaporized at about 150° and 1.0 Torr vacuum in a vaporizer chamber. The resulting gaseous form of stable dimeric di-para-xylene is further heated in a pyrolysis chamber to about 680° C. at about 0.5 Torr vacuum, to directly break the two methylene-methylene bonds and yield stable monomeric diradicals, para-xylene, also in gaseous form. The monomer is then sent to the deposition chamber at ambient temperature and about 0.1 torr vacuum. The resulting parylene coating is said to be very stable and extremely resistant to moisture vapor permeation, chemical attacks and hydrolytic breakdown.
U.S. Patent Application Publication No. US 2005/0009638, of Wu et al., published Jan. 13, 2005, describes golf ball layers formed of polyurethane-based and polyurea-based compositions incorporating block copolymers. The golf balls typically comprise three layers. The core layer is typically formed from a thermoset material or a thermoplastic material. When the cores are formed from a thermoset material, compression molding is typically used to form the core. When the core is thermoplastic, the cores may be injection molded. The intermediate layer may be formed from any suitable method known to those of ordinary skill in the art, and may be formed by blow molding. The outer layer is generally a dimpled cover layer formed by injection molding, compression molding, casting, vacuum forming, powder coating, and the like.
The published application discusses a large amount of material, however, based on the claims, the focus appears to be a golf ball comprising a core and a cover, where the cover is formed from a composition comprising a prepolymer and a curing agent, where the prepolymer includes a first prepolymer and a block copolymer having functional groups at each terminal end, where the composition comprises a hydrophobic A_x-B_y-A_zblock capped between iso-cyanate groups, wherein x, y, and z are independently 1 or greater. The block is typically a styrene-butadiene block. The functional groups at the terminal ends of the block are selected from groups such as hydroxy groups, amino groups, thiol groups, epoxy groups, anhydride groups and combinations of these. The terminal groups are designed to provide a cover which is water resistant. The cover material was molded onto wound cores, and a “conventional coating” was applied over the cover. The golf balls were incubated in a 50% relative humidity and 72° F. environmental chamber and then were removed, weighed and measured. Subsequently the balls were subjected to 100 percent relative humidity at 72° F. and then weighed and measured. Balls with the water resistant cover were shown to have picked up much less weight and to have incurred less size gain due to the exposure to the high relative humidity than a control ball.
When the layer or coating of material applied to the golf ball is an exterior coating, which will experience wear due to mechanical contact or will experience fluid flow over the coated surface, it is helpful to have the coating chemically bonded directly to the substrate surface via chemical reaction of active species which are present in the coating reactants/materials with active species on the underlying substrate surface.
For purposes of illustrating methods of coating formation where vaporous and liquid precursors are used to deposit a coating on a substrate, applicants would like to mention the following publications and patents which relate to methods of coating formation, for purposes of illustration. Most of the background information provided is with respect to various chlorosilane-based precursors; however it is not intended that the present invention be limited to this class of precursor materials.
In an article by Barry Arkles entitled “Tailoring surfaces with silanes”, published in CHEMTECH, in December of 1977, pages 766-777, the author describes the use of organo silanes to form coatings which impart desired functional characteristics to an underlying oxide-containing surface. In particular, the organo silane is represented as R_nSiX_(4-n)where X is a hydrolyzable group, typically halogen, alkoxy, acyloxy, or amine. Following hydrolysis, a reactive silanol group is said to be formed which can condense with other silanol groups, for example, those on the surface of siliceous fillers, to form siloxane linkages. Stable condensation products are said to be formed with other oxides in addition to silicon oxide, such as oxides of aluminum, zirconium, tin, titanium, and nickel. The R group is said to be a nonhydrolyzable organic radical that may possess functionality that imparts desired characteristics. The article also discusses reactive tetra-substituted silanes which can be fully substituted by hydrolyzable groups and how the silicic acid which is formed from such substituted silanes readily forms polymers such as silica gel, quartz, or silicates by condensation of the silanol groups or reaction of silicate ions. Tetrachlorosilane is mentioned as being of commercial importance since it can be hydrolyzed in the vapor phase to form amorphous fumed silica.
The article by Dr. Arkles shows how a substrate with hydroxyl groups on its surface can be reacted with a condensation product of an organosilane to provide chemical bonding to the substrate surface. The reactions are generally discussed and, with the exception of the formation of amorphous fumed silica, the reactions are between a liquid precursor and a substrate having hydroxyl groups on its surface. A number of different applications and potential applications are discussed.
In an article entitled “Organized Monolayers by Adsorption. 1. Formation and Structure of Oleophobic Mixed Monolayers on Solid Surfaces”, published in the Journal of the American Chemical Society, Jan. 2, 1980, pp. 92-98, Jacob Sagiv discussed the possibility of producing oleophobic monolayers containing more than one component (mixed monolayers). The article is said to show that homogeneous mixed monolayers containing components which are very different in their properties and molecular shape may be easily formed on various solid polar substrates by adsorption from organic solutions. Irreversible adsorption is said to be achieved through covalent bonding of active silane molecules to the surface of the substrate.
In June of 1991, D. J. Ehrlich and J. Melngailis published an article entitled “Fast room-temperature growth of SiO₂films by molecular-layer dosing” in Applied Physics Letters 58 (23), pp. 2675-2677. The authors describe a molecular-layer dosing technique for room-temperature growth of α-SiO₂thin films, which growth is based on the reaction of H₂O and SiCl₄adsorbates. The reaction is catalyzed by the hydrated SiO₂growth surface, and requires a specific surface phase of hydrogen-bonded water. Thicknesses of the films is said to be controlled to molecular-layer precision; alternatively, fast conformal growth to rates exceeding 100 nm/min is said to be achieved by slight depression of the substrate temperature below room temperature. Potential applications such as trench filling for integrated circuits and hermetic ultrathin layers for multilayer photoresists are mentioned. Excimer-laser-induced surface modification is said to permit projection-patterned selective-area growth on silicon.
An article entitled “Atomic Layer Growth of SiO₂on Si(100) Using The Sequential Deposition of SiCl₄and H₂O” by Sneh et al. in Mat. Res. Soc. Symp. Proc. Vol 334, 1994, pp. 25-30, describes a study in which SiO₂thin films were said to be deposited on Si(100) with atomic layer control at 600° K. (≅327° C.) and at pressures in the range of 1 to 50 Torr using chemical vapor deposition (CVD).
In U.S. Pat. No. 5,372,851, issued to Ogawa et al. on Dec. 13, 1995, a method of manufacturing a chemically adsorbed film is described. In particular a chemically adsorbed film is said to be formed on any type of substrate in a short time by chemically adsorbing a chlorosilane based surface active-agent in a gas phase on the surface of a substrate having active hydrogen groups. The basic reaction by which a chlorosilane is attached to a surface with hydroxyl groups present on the surface is basically the same as described in other articles discussed above. In a preferred embodiment, a chlorosilane based adsorbent or an alkoxyl-silane based adsorbent is used as the silane-based surface adsorbent, where the silane-based adsorbent has a reactive silyl group at one end and a condensation reaction is initiated in the gas phase atmosphere. A dehydrochlorination reaction or a de-alcohol reaction is carried out as the condensation reaction. After the dehydrochlorination reaction, the unreacted chlorosilane-based adsorbent on the surface of the substrate is washed with a non-aqueous solution and then the adsorbed material is reacted with aqueous solution to form a monomolecular adsorbed film.
In an article entitled “SiO₂Chemical Vapor Deposition at Room Temperature Using SiCl₄and H₂O with an NH₃Catalyst”, by J. W. Klaus and S. M. George in the Journal of the Electrochemical Society, 147 (7) 2658-2664, 2000, the authors describe the deposition of silicon dioxide films at room temperature using a catalyzed chemical vapor deposition reaction. The NH₃(ammonia) catalyst is said to lower the required temperature for SiO₂CVD from greater than 900° K. to about 313-333° K.
U.S. Patent Publication No. US 2002/0065663 A1, published on May 30, 2002, and titled “Highly Durable Hydrophobic Coatings And Methods”, describes substrates which have a hydrophobic surface coating comprised of the reaction products of a chlorosilyl group containing compound and an alkylsilane. The substrate over which the coating is applied is preferably glass. In one embodiment, a silicon oxide anchor layer or hybrid organo-silicon oxide anchor layer is formed from a humidified reaction product of silicon tetrachloride or trichloromethylsilane vapors at atmospheric pressure. Application of the oxide anchor layer is, followed by the vapor-deposition of a chloroalkylsilane. The silicon oxide anchor layer is said to advantageously have a root mean square surface (RMS) roughness of less than about 6.0 nm, preferably less than about 5.0 nm and a low haze value of less than about 3.0%. The RMS surface roughness of the silicon oxide layer is preferably said to be greater than about 4 nm, to improve adhesion. However, too great an RMS surface area is said to result in large surface peaks, widely spaced apart, which begins to diminish the desirable surface area for subsequent reaction with the chloroalkylsilane by vapor deposition. Too small an RMS surface is said to result in the surface being too smooth, that is to say an insufficient increase in the surface area/or insufficient depth of the surface peaks and valleys on the surface.
Simultaneous vapor deposition of silicon tetrachloride and dimethyldichlorosilane onto a glass substrate is said to result in a hydrophobic coating comprised of cross-linked polydimethylsiloxane which may then be capped with a fluoroalkylsilane (to provide hydrophobicity). The substrate is said to be glass or a silicon oxide anchor layer deposited on a surface prior to deposition of the cross-linked polydimethylsiloxane. The substrates are cleaned thoroughly and rinsed prior to being placed in the reaction chamber.
U.S. Pat. No. 5,576,247 to Yano et al., issued Nov. 19, 1996, entitled: “Thin layer forming method where hydrophobic molecular layers preventing a BPSG layer from absorbing moisture”.
Some of the various methods useful in applying layers and coatings to a substrate have been described above. There are numerous other patents and publications which relate to the deposition of functional coatings on substrates, but which appear to be more distantly related to the present invention. To provide a monolayer or a few layers of a functional coating on a substrate surface so that the surface will exhibit particular functional properties it is necessary to tailor the coating precisely. Without precise control of the deposition process, the coating may lack thickness uniformity and surface coverage. The coating may vary in chemical composition across the surface of the substrate, affecting uniformity of behavior of the surface. The presence of non-uniformities may result in functional discontinuities and defects on the coated substrate surface which are unacceptable for the intended application of the coated substrate.
U.S. patent application Ser. No. 10/759,857 of the present applicants describes processing apparatus which can provide specifically controlled, accurate delivery of precise quantities of reactants to the process chamber, as a means of improving control over a coating deposition process. The subject matter of the '857 application is hereby incorporated by reference in its entirety.
The present application is related to an exterior coating for application to a golf ball. In a first instance the exterior coating provides a hydrophobic surface on the golf ball. In a second instance the exterior coating provides a hydrophilic surface on the golf ball. Use of the disclosed method of coating deposition described below enables the precise control of process conditions during deposition of the coatings, the coatings exhibit a uniform functionality over the entire golf ball surface, a nanometer scale functionality which is superior to previous golf ball coatings. Due to the accurate delivery of quantities of reactive materials and the conditions under which the materials can be processed, the cost of coating application is greatly reduced as well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional schematic of one embodiment of the kind of an apparatus which can be used to carry out a vapor deposition of a coating in accordance with the method of the present invention.
FIG. 2 is a schematic which shows the reaction mechanism where tetrachlorosilane and water are reacted with a substrate which exhibits active hydroxyl groups on the substrate surface, to form a silicon oxide layer on the surface of the substrate.
FIG. 3 shows a series of water contact angles measured for various coated surfaces. The higher the contact angle, the higher the hydrophobicity of the coating surface.
FIG. 4A shows a three dimensional schematic of film thickness of a silicon oxide bonding layer coating deposited on a silicon surface as a function of the partial pressure of silicon tetrachloride and the partial pressure of water vapor present in the process chamber during deposition of the silicon oxide coating, where the time period the silicon substrate was exposed to the coating precursors was four minutes after completion of addition of all precursor materials.
FIG. 4B shows a three dimensional schematic of film thickness of the silicon oxide bonding layer illustrated in FIG. 4A as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
FIG. 4C shows a three dimensional schematic of film thickness of the silicon oxide bonding layer illustrated in FIG. 4A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
FIG. 5A shows a three dimensional schematic of film roughness in RMS nm of a silicon oxide bonding layer coating deposited on a silicon surface as a function of the partial pressure of silicon tetrachloride and the partial pressure of water vapor present in the process chamber during deposition of the silicon oxide coating, where the time period the silicon substrate was exposed to the coating precursors was four minutes after completion of addition of all precursor materials.
FIG. 5B shows a three dimensional schematic of film roughness in RMS nm of the silicon oxide bonding layer illustrated in FIG. 5A as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
FIG. 5C shows a three dimensional schematic of film roughness in RMS nm of the silicon oxide bonding layer illustrated in FIG. 5A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials.
FIG. 6 illustrates the minimal thickness of oxide-based bonding layer which is required to provide adhesion of an organic-based layer, as a function of the initial substrate material, when the organic-based layer is one where the end or the organic-based layer which bonds to the oxide-based bonding layer is a silane and where the end of the organic-based layer which does not bond to the oxide-based bonding layer provides a hydrophobic surface. When the oxide thickness is adequate to provide uniform attachment of the organic-based layer, the contact angle on the substrate surface increases to about 110 degrees or greater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

We have developed improved golf ball exterior coatings which are used to create an extremely uniform (to within about ±2 nm) hydrophobic or hydrophilic exterior coating on a golf ball surface. When the surface of the golf ball is hydrophobic, it tends to repel water, and this reduces the condensation of moisture present in the air onto the golf ball as the golf ball travels through the air. As a result, the amount of drag on the golf ball is reduced, increasing the distance of travel which can be achieved in a given stroke. When a golf ball is rolling across grass which exhibits a wet surface, for example dew (condensation on the surface of the grass) is present, or there are wet spots on the grass, there is an advantage when the golf ball has an exterior surface which is hydrophilic. The hydrophilic surface of the golf ball wets uniformly and the ball rolls straighter, as the forces acting on the ball are more uniform. Putting will be better using the golf ball with the hydrophilic surface. When the golf ball is in a sand trap or is on a dry grass surface where some debris is present, there is an advantage in using a golf ball with a hydrophobic surface which will not stick to the sand or to debris present on the grass surface. The ball tends to stay cleaner as it rolls over the green, improving the directionality of travel of the ball during putting, for example.
The hydrophobic or hydrophilic exterior coating is applied to the golf ball using vapor-phase deposition in instances where strict control over coating thickness uniformity, and/or reduced surface roughness is desired. The coating formation method typically employs a batch-like addition and mixing of all of the reactants to be consumed in a given process step, whether that step is one in a series of steps or is the sole step in a coating formation process. In some instances, the coating formation process may include a number of individual steps where repetitive reactive processes are carried out in each individual step. The apparatus used to carry out the method provides for the addition of a precise amount of each of the reactants to be consumed in a single reaction step of the coating formation process. The apparatus may provide for precise addition of quantities of different combinations of reactants during each individual step when there are a series of different individual steps in the coating formation process.
In addition to the control over the amount of reactants added to the process chamber, the present invention requires precise control over the cleanliness of the substrate, the order of reactant(s) introduction, the total pressure (which is typically less than atmospheric pressure) in the process chamber, the partial vapor pressure of each vaporous component present in the process chamber, and the temperature of the substrate and chamber walls. The control over this combination of variables determines the deposition rate and properties of the deposited layers. By varying these process parameters, we control the amount of the reactants available, the density of reaction sites, and the film growth rate, which is the result of the balance of the competitive adsorption and desorption processes on the substrate surface, as well as any gas phase reactions.
The coating deposition process is carried out in a vacuum chamber where the total pressure is lower than atmospheric pressure and the partial pressure of each vaporous component making up the reactive mixture is specifically controlled so that formation and attachment of molecules on a substrate surface are well controlled processes that can take place in a predictable manner, without starving the reaction from any of the precursors.
In some instances, where it is desired to have a particularly uniform growth of the composition across the coating surface, or a variable composition across the thickness of a multi-layered coating, more than one batch of reactants may be charged to the process chamber during formation of the coating.
The coatings formed by the method of the invention are sufficiently controlled that the surface roughness of the coating in terms of RMS is typically less than about 15 nm, and is typically in the range of about 3 nm to 10 nm. However, although the coating itself does not create significant roughness on a surface, the roughness of a substrate surface tends to be replicated in the coated substrate surface. Thus, the roughness on the surface of a golf ball is likely to be in the range of the roughness of the outer layer (typically the cover layer) of the golf ball over which the coating is applied.
The golf ball exterior coating may be a single layer. For example, an oxide layer is generally hydrophilic in nature, and various functionalized organic materials exhibit a hydrophobic chemical group at one end of the molecule which can provide a hydrophobic surface on the golf ball. Frequently, however, the exterior coating includes at least two layers, where the first layer applied over the golf ball surface is an adhesion promoting layer to ensure bonding of a second layer which presents the hydrophilic or hydrophobic properties on the surface of the golf ball. The adhesion promoting layer is required on polymeric surfaces of the kind which are known in the industry for use as an outer cover of a golf ball. Subsequently, this adhesion promoting layer is referred to as a “bonding” layer, for general purposes of description.
An oxide layer has been demonstrated to work well as a bonding layer on the golf ball surface. By controlling the precise thickness, chemical, and structural composition of an oxide layer on a polymeric substrate, for example, we are able to tailor the oxide layer surface characteristics and thickness to meet the requirements for air flow over a golf ball surface. When the golf ball exterior coating is a hydrophobic coating, a bonding layer of oxide is applied first, followed by a layer of organic material which comprises organic molecules which bond to the oxide layer at one end and presents a hydrophobic composition at the other end of the molecule. The hydrophobic surface layer applied over the bonding layer is typically a self-aligned monolayer coating (SAM), which is self limiting in thickness. When the golf ball exterior coating is a hydrophilic coating, a thick oxide layer alone may be used to provide the hydrophilic surface, as mentioned above. In the alternative, a layer of hydrophilic organic material which comprises organic molecules which bond to the oxide layer at one end and present a hydrophilic composition at the other end of the molecule may be used over the oxide surface. An example, not by way of limitation, such an organic material is polyethylene glycol, which is commonly referred to as PEG or as polyethylene oxide (PEO). The precursor for formation of the hydrophilic organic material is typically a functionalized silane containing PEO/PEG groups, where the silane reacts with the oxide bonding layer. The silane functionalized PEG may be used to create a monolayer, a self-aligned monolayer, or a polymerized cross-linked layer. Several coating layers of PEG may be applied to increase the thickness of the PEG layer, so long as the golf balls are not exposed to ambient contaminants between coating steps. The coverage and functionality of the exterior coated surface on the golf ball, whether hydrophobic or hydrophilic, can be controlled on a nanometer scale.
With reference to chlorosilane-based coating systems of the kind described in the Background Art section of this application, for example, and not by way of limitation, the degree of hydrophobicity of the substrate after deposition of an oxide bonding layer and after deposition of an overlying silane-based polymeric material which presents a hydrophobic surface can be uniformly controlled over the substrate surface. By controlling a deposited bonding layer (for example) surface coverage and roughness in a uniform manner (as a function of oxide deposition parameters, for example and not by way of limitation), we are able to control the concentration of OH reactive species on the substrate surface. This, in turn, controls the density of reaction sites needed for subsequent deposition of a silane-based polymeric coating which provides an exterior hydrophobic surface. Control of the substrate surface active site density enables uniform growth and application of high density SAMS.
Another important aspect of the present invention is the surface preparation of the substrate prior to initiation of any exterior coating deposition reaction on the substrate surface. For experimental purposes, we applied exterior coatings to golf balls having a cover layer of an ionomer, for example and not by way of limitation. The ionomer was a sodium or zinc salt of copolymers derived from ethylene and methacrylic acid. A golf ball surface, typically a cover layer, may be formed from materials in addition to ionomers. Such additional materials may comprise polystyrene, polybutadiene, isoprene, polyurea, polyurethane, poly-para-xylene, poly-chloro-para-xylene, poly-dichloro-para-xylene, polyvinylidene chloride, polyvinylchloride, polyvinylchloride, polyacrylonitrile, fluorohalocarbons, fluorinated ethylene propylene copolymer, polytetrafluoroethylene, polyvanilidine fluoride, polyvinyl fluoride, perfluoroalkoxy resins, polyethylene, polyethylene terephthalate, polypropylene high density polyethylene, polyimide, polyamide, acrylic, and combinations thereof.
The surface of the golf balls exhibiting an ionomer cover layer was initially cleaned using isopropyl alcohol to remove any oils or grease that might have been present on the ball surface. Other commonly available solvents used for surface cleaning of plastic materials similar to ionomers may be used to remove oils or grease present on golf ball cover surfaces prior to application of an exterior surface coating over the cover.
Subsequent to the solvent wipe with isopropyl alcohol, the golf ball surfaces were treated with gentle, non-bombarding oxygen-containing plasmas, to further remove organic contaminants. The oxide layer created over a plasma-treated polymeric substrate may comprise aluminum oxide, titanium oxide, or silicon oxide, by way of example and not by way of limitation. When the oxide layer is aluminum or titanium oxide, an auxiliary process chamber (to the process chamber described herein) may be used to create this oxide layer. When the oxide layer is a silicon oxide layer, the silicon oxide layer may be applied in the same processing chamber in which the subsequent deposition of a silane-functionalized external layer is carried out. It is advantageous to carry out the oxygen plasma surface treatment, the oxide layer deposition and the exterior layer deposition the same processing chamber with no intermediate exposure of the golf ball to an uncontrolled ambient. It is also possible to use a combination of processing chambers and to shuttle the golf balls from chamber to chamber under controlled environmental conditions.
In one preferred embodiment, when a hydrophobic exterior surface coating was applied to the golf balls, an oxygen plasma treatment, oxide layer creation and SAM layer application were typically carried out in a single vacuum processing chamber. The pressure in the vacuum processing chamber is typically in the range of about 0.5 torr during the oxygen plasma treatment, in the range of about 6 Torr to 7 Torr during formation of the oxide layer, and in the range of about 2 Torr to 6 Torr during deposition of a SAM layer. The process chamber baseline pressure, prior to initiation of a treatment or deposition of a coating, is in the range of about 20 mTorr. During deposition of the exterior coating layer, which forms the exterior surface of the golf ball, controlling the total pressure in the vacuum processing chamber, the number and kind of vaporous components charged to the process chamber, the partial pressure of each vaporous component, the substrate temperature, the temperature of the process chamber walls, and the time over which particular conditions are maintained, enables control of the chemical reactivity and properties of the exterior surface of the golf ball. By controlling the process parameters, both density of film coverage over the substrate surface and structural composition over the substrate surface are more accurately controlled. Very smooth films, which typically range from about 0.1 nm to less than about 5 nm, and even more typically from about 1 nm to about 3 nm in surface RMS roughness may be applied. These smooth oxide bonding films can be tailored in thickness, roughness, hydrophobicity/hydrophilicity, and density, which makes them able to bond to whatever silane-based functional organic coatings will provide the desired behavior on the golf ball surface. For oxide films used to provide a bonding layer, the thickness of the oxide film typically ranges from about 50 Å to about 500 Å.
Oxide films deposited according to the present method can be used as bonding layers for subsequently deposited chlorosilane-based coating systems where one end of the organic molecule presents chlorosilane, and the other end of the organic molecule presents a fluorine moiety. After attachment of the chlorosilane end of the organic molecule to the substrate, the fluorine moiety at the other end of the organic molecule provides a hydrophobic coating surface. Further, the degree of hydrophobicity and the uniformity of the hydrophobic surface at a given location across the coated surface may be controlled using the oxide-based layer which is applied over the substrate surface prior to application of the chlorosilane-comprising organic molecule. By controlling the oxide-based layer application, the organic-based layer is controlled indirectly. For example, using the process variables previously described, we are able to control the concentration of OH reactive species on the substrate surface. This, in turn, controls the density of reaction sites needed for subsequent deposition of a silane-based polymeric coating. Control of the substrate surface active site density enables uniform growth and application of high density self-aligned monolayer coatings (SAMS), for example.
Organic-based functional hydrophobic layer precursors other than the silanes may be used as well. The stability of the coating on the exterior surface of the golf ball frequently depends on the thickness of the oxide-based bonding layer. In some instances, better structural stability is provided by a multilayered structure of repeated layers of oxide-based bonding layers interleaved with organic-based layers.
In instances where it is desired to create multilayered coatings, for example and not by way of limitation, it is advisable to use oxygen plasma treatment prior to and between coating deposition steps. This oxygen plasma treatment activates dangling bonds on the substrate surface, which dangling bonds may be exposed to a controlled partial pressure of water vapor to create a new concentration of OH reactive sites on the substrate surface. The coating deposition process may then be repeated, using a silane to create an oxide bonding layer or a silane-functionalized organic molecule to create a hydrophobic layer on the golf ball surface, by way of example, and not by way of limitation.
The hydrophobicity of a given substrate surface may be measured using a water droplet shape analysis method, for example. The range in hydrophobicity of the exterior surface of the golf ball is typically controlled to provide a water wetted contact angle ranging from about 100° to about 125°. FIG. 3 shows a series of water contact angles measured for various coated surfaces. The higher the contact angle, the higher the hydrophobicity of the coating surface. A golf ball surface having a hydrophilic surface is typically controlled to provide a water wetted contact angle ranging from about 5° to about 60°.
A computer driven process control system may be used to provide for a series of additions of reactants to the process chamber in which the layer or coating is being formed. This process control system typically also controls other process variables, such as (for example and not by way of limitation), total process chamber pressure (typically less than atmospheric pressure), substrate temperature, temperature of process chamber walls, temperature of the vapor delivery manifolds, processing time for given process steps, and other process parameters if needed.
As a preface to the more detailed description provided below, it should be noted that, as used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents, unless the context clearly dictates otherwise.
As a basis for understanding the invention, it is important to discuss a processing apparatus which permits precise control over the addition of coating precursors and other vaporous components present within the reaction/processing chamber in which the coating is applied. The apparatus described below is not the only apparatus in which the present invention may be practiced, it is merely an example of one apparatus which may be used. One skilled in the art will recognize equivalent elements in other forms which may be substituted and still provide an acceptable processing system.
I. An Apparatus for Vapor Deposition of Thin Coatings
FIG. 1 shows a cross-sectional schematic of an apparatus 100 for vapor deposition of thin coatings. The apparatus 100 includes a process chamber 102 in which thin (typically 20 Å to 500 Å thick) coatings are vapor deposited. A substrate 106 to be coated rests upon a temperature controlled substrate holder 104, typically within a recess 107 in the substrate holder 104.
Depending on the chamber design, the substrate 106 may rest on the chamber bottom (not shown in this position in FIG. 1). Attached to process chamber 102 is a remote plasma source 110, connected via a valve 108. Remote plasma source 110 may be used to provide a plasma which is used to clean and/or convert a substrate surface to a particular chemical state prior to application of a coating (which enables reaction of coating species and/or catalyst with the surface, thus improving adhesion and/or formation of the coating); or may be used to provide species helpful during formation of the coating (not shown) or modifications of the coating after deposition. The plasma may be generated using a microwave, DC, or inductive RF power source, or combinations thereof. The process chamber 102 makes use of an exhaust port 112 for the removal of reaction byproducts and is opened for pumping/purging the chamber 102. A shut-off valve or a control valve 114 is used to isolate the chamber or to control the amount of vacuum applied to the exhaust port. The vacuum source is not shown in FIG. 1.
The apparatus 100 shown in FIG. 1 is illustrative of a vapor deposited coating which employs two precursor materials and a catalyst. One skilled in the art will understand that one or more precursors and from zero to multiple catalysts may be used during vapor deposition of a coating. A catalyst storage container 116 contains catalyst 154, which may be heated using heater 118 to provide a vapor, as necessary. It is understood that precursor and catalyst storage container walls, and transfer lines into process chamber 102 will be heated as necessary to maintain a precursor or catalyst in a vaporous state, minimizing or avoiding condensation. The same is true with respect to heating of the interior surfaces of process chamber 102 and the surface of substrate 106 to which the coating (not shown) is applied. A control valve 120 is present on transfer line 119 between catalyst storage container 116 and catalyst vapor reservoir 122, where the catalyst vapor is permitted to accumulate until a nominal, specified pressure is measured at pressure indicator 124. Control valve 120 is in a normally-closed position and returns to that position once the specified pressure is reached in catalyst vapor reservoir 122. At the time the catalyst vapor in vapor reservoir 122 is to be released, valve 126 on transfer line 119 is opened to permit entrance of the catalyst present in vapor reservoir 122 into process chamber 102 which is at a lower pressure. Control valves 120 and 126 are controlled by a programmable process control system of the kind known in the art (which is not shown in FIG. 1).
A Precursor 1 storage container 128 contains coating reactant Precursor 1, which may be heated using heater 130 to provide a vapor, as necessary. As previously mentioned, Precursor 1 transfer line 129 and vapor reservoir 134 internal surfaces are heated as necessary to maintain a Precursor 1 in a vaporous state, minimizing and preferably avoiding condensation. A control valve 132 is present on transfer line 129 between Precursor 1 storage container 128 and Precursor 1 vapor reservoir 134, where the Precursor 1 vapor is permitted to accumulate until a nominal, specified pressure is measured at pressure indicator 136. Control valve 132 is in a normally closed position and returns to that position once the specified pressure is reached in Precursor 1 vapor reservoir 134. At the time the Precursor 1 vapor in vapor reservoir 134 is to be released, valve 138 on transfer line 129 is opened to permit entrance of the Precursor 1 vapor present in vapor reservoir 134 into process chamber 102, which is at a lower pressure. Control valves 132 and 138 are controlled by a programmable process control system of the kind known in the art (which is not shown in FIG. 1).
A Precursor 2 storage container 140 contains coating reactant Precursor 2, which may be heated using heater 142 to provide a vapor, as necessary. As previously mentioned, Precursor 2 transfer line 141 and vapor reservoir 146 internal surfaces are heated as necessary to maintain Precursor 2 in a vaporous state, minimizing, and preferably avoiding condensation. A control valve 144 is present on transfer line 141 between Precursor 2 storage container 146 and Precursor 2 vapor reservoir 146, where the Precursor 2 vapor is permitted to accumulate until a nominal, specified pressure is measured at pressure indicator 148. Control valve 141 is in a normally-closed position and returns to that position once the specified pressure is reached in Precursor 2 vapor reservoir 146. At the time the Precursor 2 vapor in vapor reservoir 146 is to be released, valve 150 on transfer line 141 is opened to permit entrance of the Precursor 2 vapor present in vapor reservoir 146 into process chamber 102, which is at a lower pressure. Control valves 144 and 150 are controlled by a programmable process control system of the kind known in the art (which is not shown in FIG. 1).
During formation of a coating (not shown), golf ball surfaces 105 are supported by a substrate holder 106, which typically is a supporting structure which contains a number of golf balls, with pins holding the golfballs in a manner that essentially all of the surface of the golfballs is exposed during processing. At least one incremental addition of vapor equal to the vapor reservoir 122 of the catalyst 154, and the vapor reservoir 134 of the Precursor 1, or the vapor reservoir 146 of Precursor 2 may be added to process chamber 102. The total amount of vapor added is controlled by both the adjustable volume size of each of the expansion chambers (typically 50 cc up to 1,000 cc) and the number of vapor injections (doses) into the reaction chamber. Further, the set pressure 124 for catalyst vapor reservoir 122, or the set pressure 136 for Precursor 1 vapor reservoir 134, or the set pressure 148 for Precursor 2 vapor reservoir 146, may be adjusted to control the amount (partial vapor pressure) of the catalyst or reactant added to any particular step during the coating formation process. This ability to control precise amounts of catalyst and vaporous precursors to be dosed (charged) to the process chamber 102 at a specified time provides not only accurate dosing of reactants and catalysts, but repeatability in the vapor charging sequence.
This apparatus provides a relatively inexpensive, yet accurate method of adding vapor phase precursor reactants and catalyst to the coating formation process, despite the fact that many of the precursors and catalysts are typically relatively non-volatile materials. In the past, flow controllers were used to control the addition of various reactants; however, these flow controllers may not be able to handle some of the precursors used for vapor deposition of coatings, due to the low vapor pressure and chemical nature of the precursor materials. The rate at which vapor is generated from some of the precursors is generally too slow to function with a flow controller in a manner which provides availability of material in a timely manner for the vapor deposition process.
The apparatus discussed above allows for accumulation of the specific quantity of vapor in the vapor reservoir which can be charged (dosed) to the reaction. In the event it is desired to make several doses during the coating process, the apparatus can be programmed to do so, as described above. Additionally, adding of the reactant vapors into the reaction chamber in controlled aliquots (as opposed to continuous flow) greatly reduces the amount of the reactants used and the cost of the coating.
One skilled in the art of chemical processing of a number of substrates, such as golf balls, simultaneously will recognize that a processing system which permits heat and mass transfer uniformly over the entire surface of substrate is important. A number of different designs of substrate holders for golfballs are possible which will permit coating of essentially all of the golf ball surface. In addition, it is possible to rotate the golf ball and repeat the treatment or coating deposition step prior to going on to the next step in the coating process to ensure that the entire surface of the golf ball is coated. For example, the ball may be rotated during progress of the plasma cleaning step, during process of the oxide layer formation, and during deposition of the functional organic precursor material which forms a hydrophobic surface on the exterior of the golf ball.
II. Exemplary Embodiments of the Method of the Invention:
A method of the invention provides for vapor-phase deposition of coatings onto a golf ball surface, where a processing chamber of the kind, or similar to the processing chamber described above is employed. Each coating precursor is transferred in vaporous form to a precursor vapor reservoir in which the precursor vapor accumulates. A nominal amount of the precursor vapor, which is the amount required for a coating layer deposition is accumulated in the precursor vapor reservoir. The at least one coating precursor is charged from the precursor vapor reservoir into the processing chamber in which the golfballs are to be coated. In some instances at least one catalyst vapor is added to the process chamber in addition to the at least one precursor vapor, where the relative quantities of catalyst and precursor vapors are based on the physical characteristics to be exhibited by the coating. In some instances a diluent gas is added to the process chamber in addition to the at least one precursor vapor (and optional catalyst vapor). The diluent gas is chemically inert and is used to increase a total desired processing pressure, while the partial pressure amounts of coating precursors and optionally catalyst components are varied.
The example embodiments described below are with reference to formation of a bonding oxide layer with an overlying silane-based polymeric layer which presents a hydrophobic functional group on the outer surface of the golf ball. However, it is readily apparent to one of skill in the art that the concepts involved can be applied to additional coating compositions and combinations which have different functionalities, to provide golf balls having additional functional characteristics.
Due to the need to control the functionality of the coating at dimensions as small as nanometers, the surface preparation of the golfball substrate, typically a cover layer of the golf ball of the kind known generally in the art, prior to application of the coating is very important. As an initial, optional step, the golf ball may be wiped, dipped, or sprayed (for example) with a degreasing solvent which will not attack the surface of the golf ball cover. As previously described, we used isopropyl alcohol for degreasing of the ball surface. Subsequently, the golf ball surface was treated to remove contaminants by exposure to a uniform, non-physically-bombarding plasma which is typically created from a plasma source gas containing oxygen. The plasma may be a remotely generated plasma which is fed into a processing chamber in which a substrate to be coated resides. Depending on the coating to be applied directly over the golf ball surface, the plasma treatment of the golf ball surface may be carried out in the chamber in which the coating is to be applied. This has the advantage that the golf ball surface is easily maintained in a controlled environment between the time that the surface is treated in preparation for coating, and the time at which the coating is applied. Alternatively, it is possible to use a large system which includes several processing chambers and a centralized transfer chamber which allows transfer of golf balls from one chamber to another via a robot handling device, where the centralized handling chamber as well as the individual processing chambers are each under a controlled environment. A single chamber golf ball coating device is advantageous in size and cost. Replaceable liners can be used inside the chamber and replaced periodically, as a means of preventing oxide and organic polymeric build-up on the process chamber walls.
Depending on the polymeric composition on the golf ball cover, in some instances it is necessary not only to remove contaminants from the surface of the golf ball, but also to generate —OH functional groups on the surface of the golf ball cover material (in instances where such —OH functional groups are not already present).
When a silicon oxide layer is applied to the golfball surface, to provide a bonding layer, the oxide layer may be created using the well-known catalytic hydrolysis of a chlorosilane, such as a tetrachlorosilane, in the manner previously described. A subsequent attachment of an organo-chlorosilane, which may or may not include a functional moiety, may be made to impart a particular function to the finished coating. By way of example and not by way of limitation, the hydrophobicity or hydrophilicity of the coating surface may be altered by the functional moiety present on a surface of an organo-chlorosilane which becomes the exterior surface of the coating.
The oxide layer, which may be silicon oxide or another oxide, may be formed using the method of the present invention by vapor phase hydrolysis of the chlorosilane, with subsequent attachment of the hydrolyzed silane to the substrate surface. Alternatively, the hydrolysis reaction may take place directly on the surface of the golf ball, where moisture has been made available on the golf ball surface to allow simultaneous hydrolyzation and attachment of the chlorosilane to the golf ball surface. The hydrolysis in the vapor phase using relatively wide range of partial pressure of the silicon tetrachloride precursor in combination with a partial pressure in the range of 10 Torr or greater of water vapor will generally result in rougher surfaces on the order of 5 nm RMS or greater, where the thickness of the film formed will typically be in the range of about 20 nm or greater. Thinner films of the kind enabled by one of the embodiments of applicants' invention typically exhibit a 1-5 nm RMS finish and are grown by carefully balancing the vapor and surface hydrolysis reaction components. For example, and not by way of limitation, for a thin film of an oxide-based layer, prepared on a silicon substrate, where the oxide-based layer exhibits a thickness ranging from about 2 nm to about 15 nm, typically the oxide-based layer exhibits a 1-5 nm RMS finish. We have obtained such films in an apparatus of the kind previously described, where the partial pressure of the silicon tetrachloride is in the range of about 0.5 to 4.0 Torr, the partial pressure of the water vapor is in the range of about 2 to about 8 Torr, where the total process chamber pressure ranges from about 3 Torr to about 10 Torr, where the golfball temperature ranges from about 20° C. to about 60° C., where the process chamber walls are at a temperature ranging from about 30° C. to about 60° C., and where the time period over which the golf ball is exposed to the combination of silicon tetrachloride and water vapor ranges from about 2 minutes to about 12 minutes. This deposition process will be described in more detail subsequently herein, with reference to FIGS. 6A through 6C.
A multilayered coating process may include plasma treatment of the surface of one deposited layer prior to application of an overlying layer. Typically, the plasma used for such treatment is a low density plasma. This plasma may be a remotely generated plasma. The most important feature of the treatment plasma is that it is a “soft” plasma which affects the exposed surface enough to activate the surface of the layer being treated, but not enough to etch through the layer. The apparatus used to carry out the method provides for the addition of a precise amount of each of the reactants to be consumed in a single reaction step of the coating formation process. The apparatus may provide for precise addition of different combinations of reactants during each individual step when there are a series of different individual steps in the coating formation process. Some of the individual steps may be repetitive.
One example of the application of the method described here is deposition of a multilayered coating including at least one oxide-based layer. The thickness of the oxide-based layer depends on the end-use application for the multilayered coating. The oxide-based layer (or a series of oxide-based layers alternated with organic-based layers) may be used to increase the overall thickness of the multilayered coating (which typically derives the majority of its thickness from the oxide-based layer), and depending on the mechanical properties to be obtained, the oxide-based layer content of the multilayered coating may be increased when more coating rigidity and abrasion resistance is required.
The oxide-based layer is frequently used to provide a bonding surface for subsequently deposited various molecular organic-based coating layers. When the surface of the oxide-based layer is one containing —OH functional groups, the organic-based coating layer typically includes, for example and not by way of limitation, a silane-based functionality which permits covalent bonding of the organic-based coating layer to —OH functional groups present on the surface of the oxide-based layer. When the surface of the oxide-based layer is one capped with halogen functional groups, such as chlorine, by way of example and not by way of limitation, the organic-based coating layer includes, for example, an —OH functional group, which permits covalent bonding of the organic-based coating layer to the oxide-based layer functional halogen group.
By controlling the precise thickness, chemical, and structural composition of an oxide-based layer on a golf ball, for example, we are able to direct the coverage and the functionality of a coating applied over the bonding oxide layer. The coverage and functionality of the coating can be controlled over the entire golf ball surface on a nm scale. Specific, different thicknesses of an oxide-based golf ball bonding layer are required on different golf balls covering layers. Some golf ball cover layers require an alternating series of oxide-based/organic-based layers to provide surface stability for a coating structure.
With respect to golf ball surface properties, such as hydrophobicity or hydrophilicity, for example, a silicon surface becomes hydrophilic, to provide a 5 degree water contact angle (or less), after plasma treatment when there is some moisture present. Not much moisture is required, for example, typically the amount of moisture present after pumping a chamber from ambient air down to about 15 mTorr to 20 mTorr is sufficient moisture. Glass and polystyrene materials become hydrophilic, to a 5 degree water contact angle, after the application of about 80 Å or more of an oxide-based layer. An acrylic surface requires about 150 Å or more of an oxide-based layer to provide a 5 degree water contact angle.
There is also a required thickness of oxide-based layer to provide a good bonding surface for reaction with a subsequently applied organic-based layer. By a good bonding surface, it is meant a surface which provides full, uniform surface coverage of the organic-based layer. By way of example, about 80 Å or more of a oxide-based bonding layer over a silicon substrate provides a uniform hydrophobic contact angle, about 112 degrees, upon application of a SAM organic-based layer deposited from an FDTS (perfluorodecyltrichlorosilanes) precursor. About 150 Å or more of oxide-based substrate bonding layer is required over a glass substrate or a polystyrene substrate to obtain a uniform coating having a similar contact angle. About 400 Å or more of oxide-based substrate bonding layer is required over an acrylic substrate to obtain a uniform coating having a similar contact angle.
The organic-based layer precursor, in addition to containing a functional group capable of reacting with the oxide-based layer to provide a covalent bond, may also contain a functional group at a location which will form the exterior surface of the attached organic-based layer. This functional group may subsequently be reacted with other organic-based precursors, or may be the final layer of the coating and be used to provide surface properties of the coating, such as to render the surface hydrophobic or hydrophilic, by way of example and not by way of limitation. The functionality of an attached organic-based layer may be affected by the chemical composition of the previous organic-based layer (or the chemical composition of the initial substrate) if the thickness of the oxide layer separating the attached organic-based layer from the previous organic-based layer (or other substrate) is inadequate. The required oxide-based layer thickness is a function of the chemical composition of the substrate surface underlying the oxide-based layer, as illustrated above. In some instances, to provide structural stability for the surface layer of the coating, it is necessary to apply several alternating layers of an oxide-based layer and an organic-based layer.
With reference to chlorosilane-based coating systems of the kind described in the Background Art section of this application, where one end of the organic molecule presents chlorosilane, and the other end of the organic molecule presents a fluorine moiety, after attachment of the chlorosilane end of the organic molecule to the substrate, the fluorine moiety at the other end of the organic molecule provides a hydrophobic coating surface. Further, the degree of hydrophobicity and the uniformity of the hydrophobic surface at a given location across the coated surface may be controlled using the oxide-based layer which is applied over the substrate surface prior to application of the chlorosilane-comprising organic molecule. By controlling the oxide-based layer application, the organic-based layer is controlled indirectly. For example, using the process variables previously described, we are able to control the concentration of OH reactive species on the substrate surface. This, in turn, controls the density of reaction sites needed for subsequent deposition of a silane-based polymeric coating. Control of the substrate surface active site density enables uniform growth and application of high density self-aligned monolayer coatings (SAMS), for example.
We have discovered that it is possible to convert a hydrophilic-like substrate surface to a hydrophobic surface by application of an oxide-based layer of the minimal thickness described above with respect to a given substrate, followed by application of an organic-based layer over the oxide-based layer, where the organic-based layer provides hydrophobic surface functional groups on the end of the organic molecule which does not react with the oxide-based layer. However, when the initial substrate surface is a hydrophobic surface and it is desired to convert this surface to a hydrophilic surface, it is necessary to use a structure which comprises more than one oxide-based layer to obtain stability of the applied hydrophilic surface in water. It is not always just the thickness of the oxide-based layer or the thickness of the organic-based layer which is controlling. The structural stability provided by a multilayered structure of repeated layers of oxide-based material interleaved with organic-based layers provides excellent results.
After deposition of a first organic-based layer, and prior to the deposition of a subsequent layer in a multilayered coating, it is advisable to use an in-situ oxygen plasma treatment. This treatment activates reaction sites of the first organic-based layer and may be used as part of a process for generating an oxide-based layer or simply to activate dangling bonds on the substrate surface. The activated dangling bonds may be exploited to provide reactive sites on the substrate surface. For example, an oxygen plasma treatment in combination with a controlled partial pressure of water vapor may be used to create a new concentration of OH reactive species on an exposed surface. The activated surface is then used to provide covalent bonding with the next layer of material applied. A deposition process may then be repeated, increasing the total coating thickness, and eventually providing a surface layer having the desired surface properties. In some instances, where the substrate surface includes metal atoms, treatment with the oxygen plasma and moisture provides a metal oxide-based layer containing —OH functional groups. This oxide-based layer is useful for increasing the overall thickness of the multilayered coating and for improving mechanical strength and rigidity of the multilayered coating.

EXAMPLE ONE

Deposition of a Silicon Oxide Layer Having a Controlled Number of OH Reactive Sites Available on the Oxide Layer Surface
FIG. 2 shows a schematic 200 of the mechanism of bonding oxide layer formation. In particular, a substrate 202, plasma-cleaned golf ball layer surface, for example, may have some OH groups 204 present on the surface 203. A chlorosilane 208, such as the tetrachlorosilane shown, and water 206 are reacted with the OH groups 204, either simultaneously or in sequence, to produce the oxide layer 205 shown on surface 203 of substrate 202 and byproduct HCl 210. In addition to chlorosilane precursors, chlorosiloxanes, fluorosilanes, and fluorosiloxanes may be used to provide the oxide bonding layer.
Subsequently, the surface of the oxide layer 205 can be further reacted with water 216 to replace C1 atoms on the upper surface of oxide layer 205 with OH groups 217, to produce the hydroxylated layer 215 shown on surface 203 of substrate 202 and byproduct HCl 220. By controlling the amount of water used in both reactions, the frequency of OH reactive sites available on the oxide surface is controlled. The process may be repeated any number of times to produce an oxide bonding layer of the desired thickness.

EXAMPLE TWO

To evaluate process parameters useful in preparation of a silicon oxide bonding layer, silicon oxide layers were applied over a glass substrate. The glass substrate was treated with an oxygen plasma in the presence of residual moisture which was present in the process chamber (after pump down of the chamber to about 20 mTorr) to provide a clean surface (free from organic contaminants) and to provide the initial OH groups on the glass surface.

Various process conditions for the subsequent reaction of the OH groups on the glass surface with vaporous tetrachlorosilane and water are provided below in Table I, along with data related to the thickness and roughness of the oxide coating obtained and the contact angle (indicating hydrophobicity/hydrophilicity) obtained under the respective process conditions. A lower contact angle indicates increased hydrophilicity and an increase in the number of available OH groups on the silicon oxide surface.

TABLE I


Deposition of a Silicon Oxide Layer of Varying Hydrophilicity

		Partial	Partial
		Pressure	Pressure				SiO₂
	Order	SiCl₄	H₂O	Reaction	Coating	Coating	Contact
Run	of	Vapor	Vapor	Time	Thickness	Roughness	Angle***
No.	Dosing	(Torr)	(Torr)	(min.)	(nm)	(RMS, nm)*	(°)

1	First²	0.8	4.0	10	3	1	<5
	SiCl ₄
2	First¹	4.0	10.0	10	35	5	<5
	H₂O
3	First²	4.0	10.0	10	30	4	<5
	SiCl₄

	Partial	Partial				FOTS
	Pressure	Pressure				Surface
Order	FOTS	H₂O	Reaction	Coating	Coating	Contact
of	Vapor	Vapor	Time	Thickness	Roughness	Angle***
Dosing	(Torr)	(Torr)	(min.)	(nm)**	(RMS, nm)*	(°)

1	First³	0.2	0.8	15	4	1	108
	FOTS
2	First³	0.2	0.8	15	36	5	109
	FOTS
3	First³	0.2	0.8	15	31	4	109
	FOTS

*Coating roughness is the RMS roughness measured by AFM (atomic force microscopy).
**The FOTS coating layer was a monolayer which added ≈1 nm in thickness.
***Contact angles were measured with 18 MΩ D.I. water.
¹The H₂O was added to the process chamber 10 seconds before the SiCl₄was added to the process chamber.
²The SiCl₄was added to the process chamber 10 seconds before the H₂O was added to the process chamber.
³The FOTS was added to the process chamber 5 seconds before the H₂O was added to the process chamber.
⁴The substrate temperature and the chamber wall temperature were each 35° C. for both application of the SiO₂bonding/bonding layer and for application of the FOTS organosilane overlying monolayer (SAM) layer.

We learned that very different film thicknesses and film surface roughness characteristics can be obtained as a function of the partial pressures of the precursors, despite the maintenance of the same time period of exposure to the precursors. Table II below illustrates this unexpected result.

TABLE II


Response Surface Design* Silicon Oxide Layer Deposition

		Partial	Partial	Substrate			Coating
		Pressure	Pressure	and			Surface
	Total	SiCl₄	H₂O	Chamber	Reaction	Coating	Roughness
Run	Pressure	Vapor	Vapor	Wall Temp.	Time	Thickness	RMS
No.	(Torr)	(Torr)	(Torr)	(° C.)	(min.)	(nm)	(nm)

1	9.4	2.4	7	35	7	8.8	NA
2	4.8	0.8	4	35	7	2.4	1.29
3	6.4	2.4	4	35	4	3.8	1.39
4	14.0	4.0	10	35	7	21.9	NA
5	7.8	0.8	7	35	4	4.0	2.26
6	11.0	4.0	7	35	10	9.7	NA
7	11.0	4.0	7	35	4	10.5	NA
8	12.4	2.4	10	35	4	14.0	NA
9	6.4	2.4	4	35	10	4.4	1.39
10	9.4	2.4	7	35	7	8.7	NA
11	12.4	2.4	10	35	10	18.7	NA
12	9.4	2.4	7	35	7	9.5	NA
13	8.0	4.8	4	35	7	6.2	2.16
14	10.8	0.8	10	35	7	6.9	NA
15	7.8	0.8	7	35	10	4.4	2.24

*(Box-Behnken) 3 Factors, 3 Center Points
NA = Not Available, Not Measured

In addition to the tetrachlorosilane described above as a precursor for oxide formation, other chlorosilane precursors such a trichlorosilanes, dichlorosilanes work well as a precursor for oxide formation. Examples of specific advantageous precursors include hexachlorodisilane (Si₂Cl₆) and hexachlorodisiloxane (Si₂Cl₆O). As previously mentioned, in addition to chlorosilanes, chlorosiloxanes, fluorosilanes, and fluorosiloxanes may also be used as precursors.
Similarly, the vapor deposited silicon oxide coating from the SiCl₄and H₂O precursors was applied over glass, polycarbonate, acrylic, polyethylene and other plastic materials using the same process conditions as those described above. Prior to application of the silicon oxide coating, the surface to be coated was treated with an oxygen plasma.

EXAMPLE THREE

In the preferred embodiment discussed in detail below, the silicon oxide bonding layer was applied over golf ball having a polymeric cover layer of ionomer, which exhibited a contact angle coming out of the box which ranged between about 80° and about 90°. The golf ball was wiped with isopropyl alcohol to remove any grease or oils present on the golf ball surface. The golf ball surface was then treated with an oxygen plasma in the presence of residual moisture which was present in the process chamber (after pump down of the chamber to about 20 mTorr) to provide a clean surface (free from organic contaminants) and to provide the initial OH groups on the golf ball surface. In a process chamber of the kind described above, the flow rate of oxygen was about 400 sccm, and the RF power applied to create the plasma was about 200 W, with the exposure time of the golf ball being about 5 minutes at 35° C.
A silicon oxide coating of the kind described above was applied over the golf ball surfaces by treatment with a combination of silicon tetrachloride and water vapor in the manner described above. This produced a hydrophilic surface on the golf balls. In one embodiment the amount of silicon tetrachloride (SiCl₄) charged to the reactor was 1 each 300 cc volumetric charge at 18 Torr, which was used in combination with 4 each 300 cc volumetric charges at 18 Torr of water (H₂O). The pressure in the process chamber with all reagents added was about 7 Torr, the temperature in the process chamber was about 35° C., and the deposition time period (reaction time) was about 10 minutes. This produced an oxide coating having a thickness of about 120 Å to about 150 Å. This oxide thickness is acceptable for use as a bonding oxide layer.
When the oxide layer is to be used as a single layer to provide a hydrophilic surface on the golf ball, a thicker coating is preferred. A coating having a thickness ranging from about 200 Å to about 2,000 Å may be used. The thicker coating may be generated using the process described above, where the deposition step is repeated a number of times. The length of the repeated step commonly ranges from about 2 minutes to about 10 minutes, depending on the overall thickness of the oxide layer which is to be obtained.
When the oxide layer is to act as a bonding layer, subsequent to deposition of the oxide layer, a functionalized organic layer is applied over the surface of the oxide layer to create a specialized hydrophilic or a hydrophobic surface.
When the exterior surface on the golf ball is to be a specialized hydrophilic surface, a functionalized organic material such as a silane functionalized PEO or PEG layer may be deposited over the oxide bonding layer. The functionalized silane precursor vapor containing PEO/PEG groups may be reacted with the hydrophilic silicon oxide layer to form a layer selected from the group consisting of a monolayer, a self-aligned mono-layer, and a polymerized cross-linked layer. Although just one layer of PEO/PEG may be applied, when it is desired to increase the thickness of the PEO/PEG layer, the deposition step may be repeated a number of times. For example, to apply an mPEG layer, mPEG (methoxy(polyethyleneoxy) propyltrimethoxysilane, Gelest P/N SIM 6492.7, MW=450−620 was used, or to apply a PEG layer, (polyethyleneoxy) propyltrichlorosilane, Gelest P/N SIM 6492.66, MW=450−620) was charged to the process chamber from a vapor reservoir of 300 cc, where the mPEG or PEG vapor pressure in the vapor reservoir was about 0.5 Torr. (Combinations of mPEG with PEG may also be used.) Four chamber volumes of mPEG or PEG were charged, creating a partial pressure of about 250 mTorr in the coating process chamber. The substrate was exposed to mPEG vapor or to the PEG vapor each time for a time period of 15 minutes. The substrate temperature and the temperature of the process chamber walls was about 350° C. The MPEG coating or PEG coating thickness obtained was about 20 Å.
When the exterior surface on the golf ball is to be a hydrophobic surface, a self aligned monolayer (SAM) coating formed from an organic precursor, for example and not by way of limitation from fluoro-tetrahydrooctyldimethylchlorosilane (FOTS), or from perfluorodecyltrichlorosilane (FDTS) may be applied over an oxide bonding layer. A FDTS hydrophobic exterior surface layer may be applied using 4 each 300 cc volumes at 0.5 Torr of FDTS and 1 each 300 cc volume at 18 Torr of H₂O. The overall pressure in the process chamber after addition of all reactants was about 5 Torr, the temperature in the process chamber was about 35° C., and the deposition time period (reaction time) was about 15 minutes. This produced a FDTS coating thickness of about 15 Å.
Functional properties designed to meet a particular functionality for the golf ball can be tailored by either sequentially adding an organo-silane precursor to the oxide coating precursors or by using an organo-silane precursor(s) for formation of the last, top layer coating. Organo-silane precursor materials may include functional groups such that the silane precursor includes an alkyl group, an alkoxyl group, an alkyl substituted group containing fluorine, an alkoxyl substituted group containing fluorine, a vinyl group, an ethynyl group, or a substituted group containing a silicon atom or an oxygen atom, by way of example and not by way of limitation. In particular, organic-containing precursor materials such as (and not by way of limitation) silanes, chlorosilanes, fluorosilanes, methoxy silanes, alkyl silanes, amino silanes, epoxy silanes, glycoxy silanes, and acrylosilanes are useful in general.
Some of the particular precursors used to produce coatings are, by way of example and not by way of limitation, perfluorodecyltrichlorosilanes (FDTS), undecenyltrichlorosilanes (UTS), vinyl-trichlorosilanes (VTS), decyltrichlorosilanes (DTS), octadecyltrichlorosilanes (OTS), dimethyldichlorosilanes (DDMS), dodecenyltricholrosilanes (DDTS), fluoro-tetrahydrooctyldimethylchlorosilanes (FOTS), perfluorooctyldimethylchlorosilanes, aminopropylmethoxysilanes (APTMS), fluoropropylmethyldichlorosilanes, and perfluorodecyldimethylchlorosilanes. The OTS, DTS, UTS, VTS, DDTS, FOTS, and FDTS are all trichlorosilane precursors. The other end of the precursor chain is a saturated hydrocarbon with respect to OTS, DTS, and UTS; contains a vinyl functional group, with respect to VTS and DDTS; and contains fluorine atoms with respect to FDTS (which also has fluorine atoms along the majority of the chain length). Other useful precursors include 3-aminopropyltrimethoxysilane (APTMS), which provides amino functionality, and 3-glycidoxypropyltrimethoxysilane (GPTMS). One skilled in the art of organic chemistry can see that the vapor deposited coatings from these precursors can be tailored to provide particular functional characteristics for a coated surface. The use of precursors which provide a fluorine-containing surface as the exterior surface of the golf ball provide excellent hydrophobic properties. These precursors are favored in the present golf ball applications.
Most of the silane-based precursors, such as commonly used di- and tri-chlorosilanes, for example and not by way of limitation, tend to create agglomerates on the surface of the substrate during the coating formation. These agglomerates can cause structure malfunctioning or stiction. Such agglomerations are produced by partial hydrolysis and polycondensation of the polychlorosilanes. This agglomeration can be prevented by precise metering of moisture in the process ambient which is a source of the hydrolysis, and by carefully controlled metering of the availability of the chlorosilane precursors to the coating formation process. The carefully metered amounts of material and careful temperature control of the substrate and the process chamber walls can provide the partial vapor pressure and condensation surfaces necessary to control formation of the coating on the surface of the substrate rather than promoting undesired reactions in the vapor phase or on the process chamber walls.

EXAMPLE FOUR

When the oxide-forming silane and the organo-silane which includes the functional moiety are deposited simultaneously (co-deposited), the reaction may be so rapid that the sequence of precursor addition to the process chamber becomes critical. For example, in a co-deposition process of SiCl₄/FOTS/H₂O, if the FOTS is introduced first, it deposits on the glass substrate surface very rapidly in the form of islands, preventing the deposition of a homogeneous composite film. Examples of this are provided in Table III, below.

When the oxide-forming silane is applied to the substrate surface first, to form the oxide layer with a controlled density of potential OH reactive sites available on the surface, the subsequent reaction of the oxide surface with a FOTS precursor provides a uniform film without the presence of agglomerated islands of polymeric material, examples of this are provided in Table III below.

TABLE III


Deposition of a Coating Upon a Silicon Substrate*
Using Silicon tetrachloride and FOTS Precursors

						Substrate
			Partial	Partial	Partial	and
		Total	Pressure	Pressure	Pressure	Chamber
		Pres-	SiCl₄	FOTS	H₂O	Wall
Run		sure	Vapor	Vapor	Vapor	Temp.
No.		(Torr)	(Torr)	(Torr)	(Torr)	(° C.)

1	FOTS + H₂O	1	—	0.2	0.8	35
2	H₂O + SiCl ₄	141	4	—	100.8	35
	followed by		—	0.20
	FOTS + H₂O
3	FOTS +	14.2	4	0.2	10	35
	SiCl₄+ H₂O
4	SiCl₄+ H₂O	14	4	—	10	35
5	SiCl₄+ H₂O	5.8	0.8	—	5	35
6	SiCl₄+ H₂O	14	4	—	10	35
	repeated twice

		Coating
Reaction	Coating	Roughness	Contact
Time	Thickness	(nm)**	Angle***
(min.)	(nm)	RMS	(°)

1	15	0.7	0.1	110
2	10 + 15	35.5	4.8	110
3	15	1.5	0.8	110
4	10	30	0.9	<5
5	10	4	0.8	<5
6	10 + 10	55	1	<5

*The silicon substrates used to prepare experimental samples described herein exhibited an initial surface RMS roughness in the range of about 0.1 nm, as measured by Atomic Force Microscope (AFM).
**Coating roughness is the RMS roughness measured by AFM.
***Contact angles were measured with 18 MΩ D.I. water.

An example process description for Run No. 2 was as follows.
Step 1. Pump down the reactor and purge out the residual air and moisture to a final baseline pressure of about 30 mTorr or less.
Step 2. Perform O₂plasma clean of the substrate surface to eliminate residual surface contamination and to oxygenate/hydroxylate the substrate. The cleaning plasma is an oxygen-containing plasma. Typically the plasma source is a remote plasma source, which may employ an inductive power source. However, other plasma generation apparatus may be used. In any case, the plasma treatment of the substrate is typically carried out in the coating application process chamber. The plasma density/efficiency should be adequate to provide a substrate surface after plasma treatment which exhibits a contact angle of about 10° or less when measured with 18 MΩ D.I. water. The coating chamber pressure during plasma treatment of the substrate surface in the coating chamber was 0.5 Torr, and the duration of substrate exposure to the plasma was 5 minutes.
Step 3. Inject SiCl₄and within 10 seconds inject water vapor at a specific partial pressure ratio to the SiCl₄, to form a silicon oxide base layer on the substrate. For example, for the glass substrate discussed in Table III, 1 volume (300 cc at 100 Torr) of SiCl₄to a partial pressure of 4 Torr was injected, then, within 10 seconds 10 volumes (300 cc at 17 Torr each) of water vapor were injected to produce a partial pressure of 10 Torr in the process chamber, so that the volumetric pressure ratio of water vapor to silicon tetrachloride is about 2.5. The substrate was exposed to this gas mixture for 1 min to 15 minutes, typically for about 10 minutes. The substrate temperature in the examples described above was in the range of about 35° C. Substrate temperature may be in the range from about 20° C. to about 80° C. The process chamber surfaces were also in the range of about 35° C.
Step 4. Evacuate the reactor to <30 mTorr to remove the reactants.
Step 5. Introduce the chlorosilane precursor and water vapor to form a hydrophobic coating. In the example in Table III, FOTS vapor was injected first to the charging reservoir, and then into the coating process chamber, to provide a FOTS partial pressure of 200 mTorr in the process chamber, then, within 10 seconds, H₂O vapor (300 cc at 12 Torr) was injected to provide a partial pressure of about 800 mTorr, so that the total reaction pressure in the chamber was 1 Torr. The substrate was exposed to this mixture for 5 to 30 minutes, typically 15 minutes, where the substrate temperature was about 35° C. Again, the process chamber surface was also at about 35° C.
An example process description for Run No. 3 was as follows.
Step 1. Pump down the reactor and purge out the residual air and moisture to a final baseline pressure of about 30 mTorr or less.
Step 2. Perform remote O₂plasma clean to eliminate residual surface contamination and to oxygenate/hydroxylate the glass substrate. Process conditions for the plasma treatment were the same as described above with reference to Run No. 2.
Step 3. Inject FOTS into the coating process chamber to produce a 200 mTorr partial pressure in the process chamber. Then, inject 1 volume (300 cc at 100 Torr) of SiCl₄from a vapor reservoir into the coating process chamber, to a partial pressure of 4 Torr in the process chamber. Then, within 10 seconds, inject ten volumes (300 cc at 17 Torr each) of water vapor from a vapor reservoir into the coating process chamber, to a partial pressure of 10 Torr in the coating process chamber. Total pressure in the process chamber is then about 14 Torr. The substrate temperature was in the range of about 35° C. for the specific examples described, but could range from about 15° C. to about 80° C. The substrate was exposed to this three gas mixture for about 1-15 minutes, typically about 10 minutes.
Step 4. Evacuate the process chamber to a pressure of about 30 mTorr to remove excess reactants.

EXAMPLE FIVE

FIG. 5 illustrates contact angles for a series of surfaces exposed to water, where the surfaces exhibited different hydrophobicity, with an increase in contact angle representing increased hydrophobicity. This data is provided as an illustration to make the contact angle data presented in tables herein more meaningful.

EXAMPLE SIX

FIG. 4A shows a three dimensional schematic 400 of film thickness of a silicon oxide bonding layer coating deposited on a silicon surface as a function of the partial pressure of silicon tetrachloride and the partial pressure of water vapor present in the process chamber during deposition of the silicon oxide coating, where the temperature of the substrate and of the coating process chamber walls was about 35° C., and the time period the silicon substrate was exposed to the coating precursors was four minutes after completion of addition of all precursor materials. The precursor SiCl₄vapor was added to the process chamber first, with the precursor H₂O vapor added within 10 seconds thereafter. The partial pressure of the H₂O in the coating process chamber is shown on axis 402, with the partial pressure of the SiCl₄shown on axis 404. The film thickness is shown on axis 406 in Angstroms. The film deposition time after addition of the precursors was 4 minutes. The thinner coatings exhibited a smoother surface, with the RMS roughness of a coating at point 408 on Graph 400 being in the range of 1 nm (10 Å). The thicker coatings exhibited a rougher surface, which was still smooth relative to coatings generally known in the art. At point 410 on Graph 400, the RMS roughness of the coating was in the range of 4 nm (40 Å). FIG. 5A shows a three dimensional schematic 500 of the film roughness in RMS, nm which corresponds with the coated substrate for which the coating thickness is illustrated in FIG. 4A. The partial pressure of the H₂O in the coating process chamber is shown on axis 502, with the partial pressure of the SiCl₄shown on axis 504. The film roughness in RMS, nm is shown on axis 506. The film deposition time after addition of all of the precursors was 7 minutes. As previously mentioned, the thinner coatings exhibited a smoother surface, with the RMS roughness of a coating at point 508 being in the range of 1 nm (10 Å) and the roughness at point 510 being in the range of 4 nm (40 Å).
FIG. 4B shows a three dimensional schematic 420 of film thickness of the silicon oxide bonding layer illustrated in FIG. 4A as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials. The time period of exposure of the substrate is shown on axis 422 in minutes, with the H₂O partial pressure shown on axis 424 in Torr, and the oxide coating thickness shown on axis 426 in Angstroms. The partial pressure of SiCl₄in the silicon oxide coating deposition chamber was 0.8 Torr.
FIG. 4C shows a three dimensional schematic 440 of film thickness of the silicon oxide bonding layer illustrated in FIG. 4A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials. The time period of exposure is shown on axis 442 in minutes, with the SiCl₄partial pressure shown on axis 446 in Torr, and the oxide thickness shown on axis 446 in Angstroms. The H₂O partial pressure in the silicon oxide coating deposition chamber was 4 Torr.
A comparison of FIGS. 4A-4C makes it clear that it is the partial pressure of the H₂O which must be more carefully controlled in order to ensure that the desired coating thickness is obtained.
FIG. 5B shows a three dimensional schematic 520 of film roughness of the silicon oxide bonding layer illustrated in FIG. 4B as a function of the water vapor partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials. The time period of exposure of the substrate is shown on axis 522 in minutes, with the H₂O partial pressure shown on axis 524 in Torr, and the surface roughness of the silicon oxide layer shown on axis 526 in RMS, nm. The partial pressure of the SiCl₄in the silicon oxide coating deposition chamber was 2.4 Torr.
FIG. 5C shows a three dimensional schematic 540 of film roughness thickness of the silicon oxide bonding layer illustrated in FIG. 4A as a function of the silicon tetrachloride partial pressure and the time period the substrate was exposed to the coating precursors after completion of addition of all precursor materials. The time period of exposure is shown on axis 542 in minutes, with the SiCl₄partial pressure shown on axis 544 in Torr, and the surface roughness of the silicon oxide layer shown on axis 546 in RMS, nm. The partial pressure of the H₂O in the silicon oxide coating deposition chamber was 7.0 Torr.
A comparison of FIGS. 5A-5C makes it clear that it is the partial pressure of the H₂O which must be more carefully controlled in order to ensure that the desired roughness of the coating surface is obtained.
FIG. 6 shows a graph 600, which illustrates the relationship between the hydrophobicity obtained on the surface of a SAM layer deposited from perfluorodecyltrichlorosilane (FDTS), as a function of the thickness of an oxide-based layer over which the FDTS layer was deposited. The oxide layer was deposited in the manner described above, using tetrachlorosilane precursor, with sufficient moisture that a silicon oxide surface having sufficient hydroxyl groups present to provide a surface contact angle (with a DI water droplet) of 5 degrees was produced.
The oxide-based layer and the organic-based layer generated from an FDTS precursor were deposited as follows: The process chamber was vented and the substrate was loaded into the chamber. Prior to deposition of the oxide-based layer, the surface of the substrate was plasma cleaned to eliminate residual surface contamination and to oxygenate/hydroxylate the substrate. The chamber was pumped down to a pressure in the range of about 30 mTorr or less. The substrate surface was then plasma treated using a low density, non-physically-bombarding plasma which was created externally from a plasma source gas containing oxygen. The plasma was created in an external chamber which is a high efficiency inductively coupled plasma generator, and was fed into the substrate processing chamber. The plasma treatment was in the manner previously described herein, where the processing chamber pressure during plasma treatment was in the range of about 0.5 Torr, the temperature in the processing chamber was about 35° C., and the duration of substrate exposure to the plasma was about 5 minutes.
After plasma treatment, the processing chamber was pumped down to a pressure in the range of about 30 mTorr or less to evacuate remaining oxygen species. Optionally, processing chamber may be purged with nitrogen up to a pressure of about 10 Torr to about 20 Torr and then pumped down to the pressure in the range of about 30 mTorr. An adhering oxide-based layer was then deposited on the substrate surface. The thickness of the oxide-based layer depended on the substrate material, as previously discussed. SiCl₄vapor was injected into the process chamber at a partial pressure to provide a desired nominal oxide-based layer thickness. To produce an oxide-based layer thickness ranging from about 30 Å to about 400 Å, typically the partial pressure in the process chamber of the SiCl₄vapor ranges from about 0.5 Torr to about 4 Torr, more typically from about 1 Torr to about 3 Torr. Typically, within about 10 seconds of injection of the SiCl₄vapor, water vapor was injected at a specific partial pressure ratio to the SiCl₄to form the adhering silicon-oxide based layer on the substrate. Typically the partial pressure of the water vapor ranges from about 2 Torr to about 8 Torr, and more typically from about 4 Torr to about 6 Torr. (Several volumes of SiCl₄and/or several volumes of water may be injected into the process chamber to achieve the total partial pressures desired, as previously described herein.) The reaction time to produce the oxide layer may range from about 5 minutes to about 15 minutes, depending on the processing temperature, and in the exemplary embodiments described herein the reaction time used was about 10 minutes at about 35° C.
After deposition of the oxide-based layer, the chamber was once again pumped down to a pressure in the range of about 30 mTorr or less. Optionally, the processing chamber may be purged with nitrogen up to a pressure of about 10 Torr to about 20 Torr and then pumped down to the pressure in the range of about 30 mTorr, as previously described. The organic-based layer deposited from an FDTS precursor was then produced by injecting FDTS into the process chamber to provide a partial pressure ranging from about 30 mTorr to about 1500 mTorr, more typically ranging from about 100 mTorr to about 300 mTorr. The exemplary embodiments described herein were typically carried out using an FDTS partial pressure of about 150 mTorr. Within about 10 seconds after injection of the FDTS precursor, water vapor was injected into the process chamber to provide a partial pressure of water vapor ranging from about 300 mTorr to about 1000 mTorr, more typically ranging from about 400 mTorr to about 800 mTorr. The exemplary embodiments described herein were typically carried out using a water vapor partial pressure of about 600 mTorr. The reaction time for formation of the organic-based layer (a SAM) ranged from about 5 minutes to about 30 minutes, depending on the processing temperature, more typically from about 10 minutes to about 20 minutes, and in the exemplary embodiments described herein the reaction time used was about 15 minutes at about 35° C.
The data presented in FIG. 6 indicates that to obtain the maximum hydrophobicity at the surface of the FDTS-layer, it is not only necessary to have an oxide-based layer thickness which is adequate to cover the substrate surface, but it is also necessary to have a thicker layer in some instances, depending on the substrate underlying the oxide-based layer Since the silicon oxide layer is conformal, it would appear that the increased thickness is not necessary to compensate for roughness, but has a basis in the chemical composition of the substrate. However, as a matter of interest, the initial roughness of the silicon wafer surface was about 0.1 RMS nm, and the initial roughness of the glass surface was about 1-2 RMS nm.
The FIG. 6 graph 600 shows the contact angle of a DI water droplet, in degrees, on axis 624, as measured for an oxide-based layer surface over different substrates, as a function of the thickness of the oxide-based layer in Angstroms shown on axis 622. Curve 626 illustrates a silicon-oxide-based layer deposited over a single crystal silicon wafer surface. Curve 628 represents a silicon-oxide-based layer deposited over a glass surface. Curve 630 illustrates a silicon-oxide-based layer deposited over a polystyrene surface. Curve 632 shows a silicon-oxide-based layer deposited over an acrylic surface. The FDTS-generated SAM layer provides an upper surface containing fluorine atoms, which is generally hydrophobic in nature. The maximum contact angle provided by this fluorine-containing upper surface is about 117 degrees. As illustrated in FIG. 6, this maximum contact angle, indicating an FDTS layer covering the entire substrate surface is only obtained when the underlying oxide-based layer also covers the entire substrate surface at a particular minimum thickness. There appears to be another factor which requires a further increase in the oxide-based layer thickness, over and above the thickness required to fully cover the substrate, with respect to some substrates. It appears this additional increase in oxide-layer thickness is necessary to fully isolate the surface organic-based layer, a self-aligned-monolayer (SAM), from the effects of the underlying substrate. It is important to keep in mind that the thickness of the SAM deposited from the FDTS layer is only about 10 Å to about 20 Å.
The stability of the deposited SAM organic-based layers can be increased by baking for about one half hour at 110° C., to crosslink the organic-based layers. Baking of a single pair of layers is not adequate to provide the stability which is observed for the multilayered structure, but baking can even further improve the performance of the multilayered structure.
The integrated method for creating a multilayered structure of the kind described above includes: Treatment of the substrate surface to remove contaminants and to provide either —OH or halogen moieties on the substrate surface, typically the contaminants are removed using a low density oxygen plasma, or ozone, or ultra violet (UV) treatment of the substrate surface. The —OH or halogen moieties are commonly provided by deposition of an oxide-based layer in the manner previously described herein. At least one SAM or other functional organic layer is then vapor deposited over the oxide-based layer surface.
It is also possible to apply a hydrophobic exterior layer to a golf ball surface using an amine-functionalized perfluoro organic precursor. An example precursor is icosakaihena-fluoro-1,1,2,2-tetrahydro-dodecyl-(tris-dimethylamino) silane. A tris-amine provides excellent bonding directly to the golf ball surface, without the need for an oxide bonding layer. Four injections of the precursor from a 300 cc reservoir, where the reservoir pressure was 250 mTorr per injection was used. A reaction time of about 15 minutes at about 35° C. provided an excellent hydrophobic exterior coating.
The above described exemplary embodiments are not intended to limit the scope of the present invention, as one skilled in the art can, in view of the present disclosure expand such embodiments to correspond with the subject matter of the invention claimed below.

Claims

1. An exterior coating for a golf ball which renders the exterior surface of said golf ball hydrophobic or hydrophilic, wherein said coating thickness is uniform over said golf ball surface within ±2 nm.

2. An exterior coating for a golf ball in accordance with claim 1, wherein said coating provides a hydrophobic surface on said golf ball.

3. An exterior coating for a golf ball in accordance with claim 2, wherein said coating includes at least two layers, where the interior layer in contact with the golf ball cover layer is an oxide bonding layer, and the exterior layer, which forms an exterior surface of the coating is an organic-comprising hydrophobic layer.

4. An exterior coating for a golf ball in accordance with claim 2, wherein said coating is a single organic layer, where the organic layer was generated from a precursor comprising at least one amine-functionalized terminal group and fluorine-containing terminal groups, where the at least one amine-functionalized terminal group was reacted with the golf ball cover layer and wherein the fluorine-containing groups are presented on an exterior surface of the golf ball.

5. An exterior coating for a golf ball in accordance with claim 3, wherein said exterior hydrophobic layer presents fluorine atoms at the surface of the golf ball.

6. An exterior coating for a golf ball in accordance with claim 3, wherein said exterior coating exhibits a surface roughness ranging from about 3 nm RMS to about 16 nm RMS.

7. An exterior coating for a golf ball in accordance with claim 3 or claim 4, wherein said exterior coating overall thickness ranges from about 1.5 nm to about 500 nm.

8. An exterior coating for a golf ball in accordance with claim 3 or claim 4, wherein said exterior layer is formed from a SAM.

9. An exterior coating for a golf ball in accordance with claim 2, wherein said water contact angle ranges from about 100° to about 125°.

10. An exterior coating for a golf ball in accordance with claim 1, or claim 2, or claim 3, or claim 4, applied over a golf cover layer surface comprising a polymer selected from the group consisting of ionomers, polystyrene, polybutadiene, isoprene, polyurea, polyurethane, poly-para-xylene, poly-chloro-para-xylene, poly-dichloro-para-xylene, polyvinylidene chloride, polyvinylchloride, polyvinylchloride, polyacrylonitrile, fluorohalocarbons, fluorinated ethylene propylene copolymer, polytetrafluoroethylene, polyvanilidine fluoride, polyvinyl fluoride, perfluoroalkoxy resins, polyethylene, polyethylene terephthalate, polypropylene high density polyethylene, polyimide, polyamide, acrylic, and combinations thereof.

11. An exterior coating for a golf ball in accordance claim 1, wherein said coating provides a hydrophilic surface on said golf ball.

12. An exterior coating for a golf ball in accordance with claim 11, wherein said coating comprises an oxide layer.

13. An exterior coating for a golf ball in accordance with claim 12, wherein said coating is an oxide layer.

14. An exterior coating for a golf ball in accordance with claim 13, wherein said coating thickness ranges from about 15 nm to about 500 nm.

15. An exterior coating for a golf ball in accordance with claim 14, wherein said exterior coating surface roughness ranges from about 1 nm RMS to about 10 nm RMS.

16. An exterior coating for a golf ball in accordance with claim 12, wherein said coating also includes an organic layer which is bonded to said oxide layer and which presents a hydrophilic exterior surface.

17. An exterior coating for a golf ball in accordance with claim 16, wherein said organic layer comprises PEG.

18. An exterior coating for a golf ball in accordance with claim 17, wherein said exterior coating exhibits a surface roughness ranging from about 3 nm RMS to about 16 nm RMS.

19. An exterior coating for a golf ball in accordance with claim 16, wherein said organic layer thickness ranges from about 1.5 nm to about 25 nm.

20. An exterior coating for a golf ball in accordance with claim 16, wherein said organic layer is formed from a SAM.

21. An exterior coating for a golf ball in accordance with claim 11, wherein said water contact angle ranges from about 5° to about 60°.

22. An exterior coating for a golf ball in accordance with claim 11, or claim 12, or claim 16, applied over a golf cover layer surface comprising a polymer selected from the group consisting of ionomers, polystyrene, polybutadiene, isoprene, polyurea, polyurethane, poly-para-xylene, poly-chloro-para-xylene, poly-dichloro-para-xylene, polyvinylidene chloride, polyvinylchloride, polyvinylchloride, polyacrylonitrile, fluorohalocarbons, fluorinated ethylene propylene copolymer, polytetrafluoroethylene, polyvanilidine fluoride, polyvinyl fluoride, perfluoroalkoxy resins, polyethylene, polyethylene terephthalate, polypropylene high density polyethylene, polyimide, polyamide, acrylic, and combinations thereof.

23. A method of applying an exterior coating over a golf ball surface, wherein said exterior coating is deposited using vapor deposition.

24. A method in accordance with claim 23, wherein said exterior coating is deposited to have a thickness ranging from about 2 nm to about 2,000 nm.

25. A method in accordance with claim 23, wherein said exterior coating includes at least two vapor deposited layers, wherein the interior layer in contact with the golf ball cover layer is a vapor deposited oxide bonding layer, and the exterior layer which makes up the exterior surface of the coating is a vapor deposited organic-comprising layer.

26. A method in accordance with claim 25, wherein said vapor deposited organic-comprising layer presents an exterior surface on the golf ball which is hydrophilic.

27. A method in accordance with claim 26, wherein said vapor deposited organic-comprising layer presents an exterior surface on the golf ball which is hydrophobic.

28. A method in accordance with claim 23, wherein prior to vapor deposition of said exterior coating, a surface of said golf ball to which the exterior coating is to be applied is treated with an oxygen-comprising plasma.