CA2162719A1

CA2162719A1 - Optical laminator

Info

Publication number: CA2162719A1
Application number: CA002162719A
Authority: CA
Inventors: Rengan Kannabiran; Leroy C. Vargas
Original assignee: Individual
Current assignee: Polaroid Corp
Priority date: 1994-03-11
Filing date: 1995-03-02
Publication date: 1995-09-14
Also published as: US5512126A; JPH08510702A; EP0697962A1; WO1995024311A1

Abstract

An apparatus and method for substantially interfacially adhering a suitable protective overcoat onto a receiving surface utilizes therein an optical lamination roller. The optical lamination roller is configured to be capable of substantially transmitting and concentrating optical radiation toward a protective overcoat. Irradiation of the protective overcoat in cooperation with compressive forces generated at the nip effectuate bonding between the protective overcoat and the receiving surface. The optical lamination system provides fast and energy efficient throughout with enhanced reliability of operation.

Description

~WO 95/24311 2 ~ 6 2 7 1 ~ PCT/US95/02747 OPTICAL LAMINATOR

Pield of the Invention In general, the present invention relates to l~min~tors, and more particularly, to optical l~min~tion systems useful for substantially interfacially 7~tlh~ring a protective overcoat onto a receiving surface wherein the protectiveovercoat is capable of being made bondable to the receiving surface upon exposure to optical radiation, the optical radiation being tr~n~mitted through and concentrated by an optically transparent l~min~tion roller.

Back~eround of the Invention Oftentim~s it will be advantageous that a certain surface, due to its fragility and/or en~/i,vnlllellt~l sensitivity, be secured with an a~lvpliate protective coating or layer. In this regard, the application of a protective overcoat onto such a surface by means of l~min~tion has become a favored practice. One surface that benefits from such l~min~tion is an image surface of a thermal im~ging mP-lium, such as described in Tnt~rn~tional Patent Application No.
PCT/US87/03249 (Publication No. WO 88/04237) (Etzel), the image surface being formed after imagewise development of the m~ m's image-forming layer.
More particularly, Tntern~tional Patent Application No.
PCT/US87/03249 describes a thermal im~ging m~ m and a process for forming an image in which a layer of a porous or particulate im~ging m~t~-ri~l (preferably, a layer of carbon black) is deposited on a heat-activatable image-forming surface of a first sheet-like element, the layer having a cohesive strength greater than its adhesive strength to the first sheet-like element. Portions of this ~27~9 thermal im~ging m~ m are then exposed to brief and intense radiation (for example, laser sc~nning), to firmly attach exposed portions of the im~ging m:~teri~l to the first sheet-like e.lem~nt Finally, those portions of the im~ging m~teri~l not exposed to the radiation (and thus not firmly ~tt~rh~ to the first S sheet-like element) are removed, thereby forming a binary image surface comprising a plurality of first areas where the im:~ging material is adhered to the first sheet-like element and a plurality of second areas where the first sheet-like element is free from the im~ging m~teri~l In an embodiment of the thermal im~ging me~ m described by Tntern~tional Patent Application No. PCT/US87/03249, the im~ging material is covered with a second l~min~tt-d sheet-like element so that the im~ging m~teri~lis confined between the first element and this second element. After im~ing and separation of the second element (with the unexposed portions of the im~ging m~t~ri~l) from the first element, a pair of image sl-rf~ces is obtained. The first image surface comprises exposed portions of image-forming substance more firrnly ~tt;~r~hecl to the first element by heat activation of the heat-activatable image-forming surface. The second image surface comprises non-exposed portions of the image-forming substance carried or transferred to the second sheet elem.ont Either of the pair of image surfaces may, for reasons of informational content, ~esth~tic or otherwise, be desirably considered the principal image surface, and all of the following discussion is applicable to both types of image surface.
While the image-forming process described in Tntern~tional Patent Application No. PCT/US87/03249 is capable of producing high quality, high resolution images, the durability of the image surfaces produced by this process may be in~ pliate for certain desired applications. ~ the fini~h~d image surface, the porous or particulate im~gin~ m~t~ri~l, typically carbon black admixed with a binder, lies exposed (unprotected). The image may, thus, be vulnerable to being smeared, damaged or removed by, for example, fingers or skin surfaces (especially if moist), solvents or friction during manual or otherh~n(1ling of the image.

~WO 95/24311 2 1 ~ 2 7 i 9 PCT/U595/02747 In consideration of its unprotected condition it may be desirable to protect the image surface of the developed thermal im~ging mP~ m by the application of a protective overcoat, such as a thin, transparent, but durable layer, such as described in Tntem:~tional Patent Application No. PCT/US91/08345 (Publication No. WO 92/09930) (Fehervari et al.); and pending U.S. Application Serial No. 08/065345 (Bloom et al.).
T ~min~tion of protective overcoats, such as those described in the cited patent applications, has been accomplished using a continuous roll or carrier web to conduct the durable layer to the imaged sheets, the durable layertypicaily being associated with an adhesive layer. Fed through a nip existing between paired compression rollers, activation energy to fuse the durable layer to the imaged sheet is provided by thermal heating elements integrated into or withthe paired colllplession rollers. Generally, the top roller is actively heated and the bottom roller allowed to reach a steady state telllpeldLurc; well above room l~m})eld~ulc~ by conduction. T ~min~tion is effected by the coop~ldlive influences of both compression and thermal hto~ting While such method has provided good results, aspects intrincic to such l;~nnin~tion techniques may become inconci~tent for certain applications or when certain functionalities are desired.
Some of such aspects may be noted.
First, it will be appreciated that heated colll~r~ssion rollers generally have considerable thermal mass. When energized (heated) from a cold start, a delay may be ~nticirate(l before such rollers reach a surface telllpeldLu adequate to conduct s~ti~f~rtory l~min~tion.
Further, since heat is transferred by conduction from a heated roller to the receiving surface of a web m~tPri~l, matter between the heated roller and the receiving surface is heated to at least the lelll~eldlur~ attained at the receiving surface. This imposes substantial tenlp~ldlule restrictions when using a low Tg web m~t~ri~l, such as polyester. Such material's thermoplastic nature compels colll~alatively precise control of post-nip material geometry to preventundesirable web distortion.

23l~7~ ~
Further, heat recovery rate characteri~tics of the roller used for heat transfer to the l~min~te may limit the rate at which l~min~tion can be contlllcted if the web length passing through the nip is longer than the cil~;ull~'Gnce of the heated roller. If full equilibration is not achieved, thenconditions will change abruptly as the energy depleted portion of the roll surface begins the next cycle.
Further, for systems with large surface areas, heat loss by convection and radiation can become substantial. Heat loss requires provision ofcostly "make up" energy. Lost heat can also affect materials or electric colllponents within the vicinity of the l~min~tor over time.
Further, large physical structures once brought to thermal equilibrium present a problem if service to elements in their vicinity is required.
Safety may be culll~,ulllised when working on or near these heated components.
The time required to cool to a safe level once power is cut can be substantial.
In light of the above, need exists for a l~min~ting system useful for l~min~ting a protective overcoat onto a receiving surface yet minimi7ing or obviating difficulties that manifest in certain l~min~tion processes that utilize heated cc,lll~l~ssion rollers.

Sullllllaly of the Invention In consideration of the above mentioned need, the present invention provides an optical l~min~tion system useful for subst~nti~lly intr.rf~r.i~lly ~-lhrring a suitable protective overcoat onto a receiving surface. The optical l~min~tion system utilizes therein an optical l~min:~tion roller configured to be capable of substantially tr~n~mitting and concenL~Lillg optical radiation toward the protective overcoat preferably and sl-bst~nti~lly at a nip, the nip being formed between the optical l~min~tion roller and a paired pressure roller or like-functioning resisting member or object. ~radiation of the protective overcoat incooperation with co~ ulessive forces generated at the nip effectuate bonding n between the p~ute~ e overcoat and the receiving surface.

~wo 95/24311 216 ~ 7 i 9 PCT/US95/0~747 In light of the above, it is one object of the present invention to provide an optical l~min~tion system utili7ing an optical l~min~tion roller whereby response time of the optical l~min~tion system corresponds with the time constant of its primary energy source.
It is a further object of the present invention to provide an optical larnination system wherein protective overcoat material is transported cont~tingco~ tivcly cool surfaces during l~min~tion thereby rP~ cing deformation in a reslllting l~min~tP,, It is a further object of the present invention to provide an optical l:~min~tion system whereby l~min~tion may be con~luc.te.-l at rates generally dictated by processes in the nip region.
It is a further object of the present invention to provide an optical l~min~tion system lltili7.ing an optical l~min~tion roller, the optical l~min~tion roller having substantially equal energy transfer capacity over its entire circumference.
It is a further object of the present invention to provide an optical l~min~tion system utili7in~ an optical l~min~tion roller, the optical l~min~tionroller having no appreciable memory effect.
It is another object of the present invention to provide an optical l~min~tion system useful for subst~nti~lly interfacially ~rlhP.ring a protectiveovercoat onto a receiving surface when the protective overcoat and receiving surface are continuously conveyed belwGell an optical l~min~tion roller and a source of re-cict~n~e and wherein the protective overcoat is capable of being made bondable to the lcceivillg surface upon irradiation with optical radiation, the optical l~min~tor compri.cing an optical l~min~tion roller positioned to establish a nip zone when brought into association with the recict~n~e source, the optical l~min~tion roller being axially rotatable and configured to transmit and conce~ dte optical radiation in the production of an activation zone; conveying means for effec.tll~ting the positioning of the protective overcoat into the nip zone in optical contiguity with the optical l~min~tion roller; colllplGssillg means for generating a colll~lessive force at the nip zone, the Colll~-Gs~ivG force being of a 2 ~ 2~19 -6-magnitl-cle sufficient to promote the a-lh~-ring of the protective overcoat after exposure onto the receiving surface; and an optical radiation source capable of ~-mitting optical radiation at an intensity sufficient to activate the protective overcoat when the optical radiation is tran~mittç-l and concentrated by the optical lamin~tion roller; the optical radiation source capable of ~.mittin~ optical radiation through the optical lamination roller.
It is another object of the present invention to provide an optical l~mination process for substanti~lly int~ lly a-lh~ring a protective overcoat onto a receiving surface, the optical lamination process comrri~ing the steps ofproviding a protective overcoat capable of being made bondable to the receiving surface upon irradiation with optical radiation; insertingly conveying a first region of the protective overcoat into substantial interfacial association with a first region of the receiving surface into a nip, the nip being established by an optical lamin~tion roller brought into association with a resistance source, the optical l~min~tion roller being axially rotatable and configured to transmit andconcçntratç optical radiation in the production of an activation zone; bonding the first region of the protective overcoat to the first region of the receiving surface by tran~mitting optical radiation through the optical lamination roller to irradiate the inserted first region of the protective overcoat, the tran~mi~ion of the optical radiation establishing an activation zone on the protective overcoat wherein theprotective overcoat becomes bondable to the receiving surface, and generating compressive force in the nip to ~les~ulc;wise urge the protective overcoat onto the receiving surface; and repeating the conveying, cc,l~ ssing, and bonding steps until the protective overcoat is substanti~lly int~rfacially adhered onto the receiving surface.

Brief Description of the Drawin~s Each of FIGURES 1 to 8 provide schematic views of an embodiment of the optical larnination system according to the present invention.

~Wo 95/24311 ~ 1 ~ 2 71 9 PCT/US95/02747 FIGURE 1 is a lateral elevation illustrating a l~min~tor having therein an optical l~min~tion system configured according to an embodiment of the present invention.
F~GURE 2 is a bottom plan view of the optical l~min~tor S illustrated in FIGURE 1 with partial cut-away views revealing cross-sectional detail of the l~min~tor's continuous belt assembly frontal roller and cO~ ,ssioninducing drive m~ch~ni.cm FIGURE 3 provides a larger lateral view of the optical l~min~tion system incorporated into the l~min~tor illustrated in FIGURE 1.
F~GURE 4 is a rear lateral, partially cross-sectional view of the optical l~min~tion system as incorporated into the l~min~tor illustrated in F~GURE 1 viewed along section C-C.
FIGURE S is a rear lateral, cross-sectional view of a continuous belt assembly rear roller as incol~olat~d into the l~min~tQr illustrated in FIGURE
1 viewed along section A-A.
F~GURE 6 is a rear lateral, partially cross-sectional view of a resisting colllplession roller as incorporated in the optical l~min~tion system illustrated in F~GURE 1 viewed along section B-B.
FIGURE 7 is a partial top plan detail of a drive and roller shaft arrangement used in a take-up assembly as incolp~,ldled into the l~min~tQr illustrated in F~GURE 1 viewed along section D-D.
FIGURE 8 is a partial top plan view of a drive and roller shaft arrangement used in a rewind assembly as incorporated into the l~min~tor illustrated in FIGURE 1 viewed along section E-E.
FIGURE 9 is a schtq.m~tic cross-sectional view of a l~min~ting sheet and an imaged media having thereon an image surface prior to optical l~min~tion.
FIGURE 10 is a s~ht~m~ti~. cross-sectional view of the l~min~ting sheet and the imaged media of FIGURE 9 during optical l~min~tion.
FIGURE 11 is schematic cross-sectional view of a protected imaged media after optical !~min~tion.

WO 95/24311 PCT/US95/027~7 ~

Detailed Description of the Invention The present invention provides an optical l~min~tion system useful for substantially planewise ~-lhPring a protective overcoat onto a receiving surface, wherein the protective overcoat and receiving surface are continuously conveyed between the optical l~min~ting system and a source of reci~t~nce and the protective overcoat is capable of being made bondable ("activated") to the receiving surface upon its irradiation with optical radiation. The optical l~min~tion system has incu" oldled therein an optically Ll~lsparellt l~min~tion roller (hereinafter, "optical l~min~tion roller" or "optical roller"). The optical l~min~tion roller is configured to be capable of ~ub~ lly tr~ncmitting and concentrating optical radiation toward the protective overcoat for the production of an activation zone thereon. Trr~ tion of the protective overcoat in cooperation with compressive forces generated at the nip effectuate bonding between the protective overcoat and the receiving surface.
The term "optical radiation" as used herein should be construed with reference to electrom~gn~tic radiation capable of being optically manipulated, i.e. manipulated by optical instruments such as lenses. Under one construct, the term "optical radiation" may be considered as analogous to the broader definition of "light" which includes visible, ultraviolet and infrared radiation. In any event, the scope of the term should be dçtçrminPcl with reference to the functionality of the invention's various elements as described herein, particularly in view of the invention's background and objectives.
The term "activation zone" as used herein corresponds to the area of the proteetive overeoat that is irr~ tt~cl by optieal radiation and is thereby "activated". It will be appreciated that in ap~,up,iate protective overcoats, the zone of tr~n.cmitt~d optical irradiation will effect~l~te ch~mi~l and/or physical changes to thereby make the protective overcoat bondable ("activated") to the receiving surface. Since the optieal radiation trancmitt~l through the optieal l~min~tion roller becomes coneçntr~tçcl by the roller, the activation zone produeed by the present invention is eo,llpalatively narrow and intense.

~WO 95/24311 2 ~ ~ ~ 7 1 ~ PCTIUS95/02747 g It is envisioned that the optical l~min~tion system may be incorporated into a wide variety of devices. In a principal application, the optical l~min~tion system is incorporated in a l~min~tor, one representative example being illustrated in FIGURE 1. Although this embodiment will be used to 5 describe the present invention, it will be appreciated that the invention is not limited to such embodiment, and that various ch~ngçs and modifications can be effected therein by one skilled in the pertinent art in view of the present disclosure without departing from the scope or spirit of the invention, as defined in the claims.
As shown in FIGURE 1, optical ~min~tion system 10 is incorporated into l~min~tor 1 together with ~u~po~ g sl1b~cct~mhlies.
Accordingly, aside from optical l~min~tion system 10, l~min~tQr 1 of FIGURE 1 is provided with a spool assembly 100, a take-up assembly 200, a resistant roller assembly 400, and a continuous belt assembly 300, the arrangement being 15 housed in cabinet 8. For further clarity, a larger view of optical l~min~tionsystem 10 in isolation from the other subassemblies of l~min~tor 1 is provided in FIGURE 3.
As shown in FIGURE 3, optical l~min~tion system 10 has provided therein an optical l~min~tion roller 32 perpendicularly displaced from 20 the lateral sides of housing 50 and rotatable around its axis. While optical l~min~tion roller 32 may be fixed along its axis in certain applications, in operation, the optical l~min~tion system 10 of FIGURE 1 obtains benefit by providing optical l~min~tion roller 32 with some degree of movement, generally in the plane in which compression is effect-l~t~-cl (i.e., the vertical plane in25 FIGURES 1 and 3). Such movement provides optical l~min~tion roller 32 with a corresponding degree of resiliency and stress absorptive qll~liti~c which can promote more uniform linear compression during l~min~tion. To provide for such movement, as shown in FIGURE 1, the optical l~min~tion roller 32 is provided with a track eng~ging m~ch~nicm 34 capable of eng~ging and riding on 30 track guides 56 provided in housing 50. The degree of movement provided to optical l~min~tion roller 32 by these or other means may be selected by one WO 95/24311 PCT/US9~/02747 2~G27 1~

skilled in the art depending on the application and the device into which the optical l~min~tion system 10 is incorporated. It is envisioned that in certain applications, the optical l~min~tion roller 32 may be used as a primary means for achieving co~ ,ressi~e ples~ule and would accordingly benefit from an extended degree of mobility.
In accord with the present invention, bonding of a protective overcoat onto a receiving surface is comm~nre-l by the activation of the protective overcoat, activation being occasioned by irradiation with optical radiation. In the embodiment represented by the optical l~min~tion system 10 of FIGURE 3, optical radiation is emitted by optical radiation source 20. Optical radiation source 20 is positioned externally and above optically transparent roller 32 such that optical radiation may be emitted directly at and through optically transparent roller 32. Further toward this end, optical radiation source 20 is provided with a reflector 22 to reflect light toward the direction of desired tr~ncmiccion as well as prevent the radiant heating of other parts of the l~min~tor.
In view of the present disclosure, it is envisioned that the use of mirrors, prisms, and the like would provide any person skilled in the pertinent art with other ~ltern~tive positions for the optical radiation source 20 without subct~nti~lly departing from the means, functions, and results obtained by the embodiment as illustrated.
As shown in FIGURES 3 and 4, optical radiation source 20 is mounted to housing 50 by means of side support 24a, 24b and top support 26. In the embodiment illustrated, side ~iU~)Ol~ 24a, 24b, and top support 26 are configured, or otherwise ~tt~rh~cl to housing 50, to permit both angular and vertical displ~rennrnt of optical radiation source 20 relative to the location of optical l~min~tion roller 32. By variably positioning the optical radiation source 20 in accordance with the known optical properties of cylin~lric~l lenses, one may vary the intensity, area andlor the location of the activation zone relative to the nip. Details concerning the optical properties of cylintlric~l lenses may be found in several arcescihle references, for example, G.A. Boutry, Instrumental Optics,Interscience Publishers Inc., 1962, pp. 218-237; J.P.C. Southall, Mirrors, Prisms ~O 95/2431 1 21~ 2 7 ~ ~ PCT/US95/02747 and Lenses, 3rd Ed., Dover Publications, Inc. 1964, pp. 300-328; and D.H.
Jacobs, Fundamentals of Optical Engineering, MacGraw-Hill Book Company, 1943. In a preferred l~min~tion technique, the optical radiation source is positioned so that the intensity of the activation zone is at peak at or imm~ t~ly S U~L1G~11 from the nip. It is believed that in such arrangement, adhesive flow (i.e., in protective overcoats reliant on th~rm~lly activated adhesives) occurs in a manner that reduces curl in the res-llting l~min~t~.
Any number of optical radiation sources may be selected by one skilled in the art in view of a desired application, possible c~ntli~l~t~s wouldinclude in~n-lescent light, infrared ell~iLIGl~, and ultraviolet el,uLLel,. For l~min~tion processes involving the production of tack welds or stripes of bondedm~t~ri~l, optical radiation point sources that may be considered would include diode lasers or arc lamps. In the embodiment described in detail herein, an infrared emitter is preferred.
When lltili7in~ an infrared radiation source, optical l~min~tion roller 32 may be constructed from any number of m~tt~.ri~l~, including quartz, fused ~ min~, glass, or composite structures with an outer shell of durable m~t~ri~l filled with a suitable inner core of optical m~t-o.ri~l. When constructed of quartz, it will be appreciated that optical l~min~tion roller 32 will absorb comparatively less infrared radiation, and thus promote higher tr~n~mic~ion of such optical radiation toward the activation zone. Accordingly, in considerationof energy efficiency, optical l~min~tion roller 32 is preferably made of quartz when optical radiation source 20 is an infrared radiation source. If desired, the surface of optical l~min~tion roller 32 may be m~k~(l to produce very sha~rp edged G~O~7U1G areas, for example, for applications which require light bonded tabs.
As will be appreciated from FIGURE 1, the optical l~min~tion roller 32 of optical l~min~tion system 10 is positioned relative to, for example, a resisting compression roller 410 of resisting colllplGssion roller assembly 400 such that a nip is formed therebetween. By pressurewise urging resisting colllplGssion roller 410 toward optical l~min~tion roller 32, colllplGssion roller WO 95/24311 PCT/US95/02747 ~
~1~2~9 assembly 400 is capable of actively providing a means by which compression is effectll~tP~l in the nip zone. Other means that would provide the same functionality may be used in substitute for the mech~ni~m.c described herein without departing from the spirit of the invention. For example, compression may be achieved by utili7ing a flat plate or platen instead of a col.lplcssion roller.
Alternatively, optical l~min~tion roller 32 may be configured so it may be pressurewise urged towards a fixed compression roller. Alternatively, optical l~min~tion system 10 may be pushed in its entirety toward a solid surface, thereby producing both a nip and compressive force. In such ~ltern~tive, the receiving surface itself passively provides the rç~i.ct~nre against the forward movement of optical l:~min~tion system 10, co~pt;l~Lillg to form compressive force.
In the embodiment described herein, the colll~l~;ssi~le functionality of the resisting compression roller 410 is supported by the combination of wedge plate 440 and pivoting support plate 430.
As shown in FIGURES 1, wedge plate 440 has provided thereon wedge plate guide 442. As shown in FIGURE 6, wedge plate 440 is ~tt~he~l perpendicular to bottom cross-bar 448, cross-bar 448 having centrally thereon screw eng~gemPnt block 446 (FIGURE 2), block 446 having rotatably inserted therein screw member 1~1~1 (as :-ct~l~ted by vertical compression roller drive assembly 447). Rotation of screw member 444 results in either the forward or reverse movement of wedge plate 440 relative to pivoting support plate 430 (See directional arrow in FIGURE 2).
Pivoting support plate 430, pivotable along axle 320, has therein provided cam follower 432 ~ng~ged with and movable along wedge plate guide 442. l~e~i~ting compression roller 410 is axially rotatably mounted on cc,lllpl~;ssion roller slide 420, slide 420 being slidably engaged in vertical roller guide 434 provided on pivotal support plate 430. Vertical displacement of resisting co~llplession roller 410 toward or away from optical l~min~tion roller 32 is effect~l~ted by the movement of cam follower 432 along wedge plate guide 442 when wedge plate 440 is moved relative to pivoting support plate 430. In this ~WO 95/24311 Z 1 6 2 ~ ~ 9 PCTrUS95/02747 regard, and with reference to FIGURE 1, forward (or reverse) movement of wedge plate 440 results in the upward (or downward) vertical displacement of cam follower 432, which in turn results in the upward (or downward) ~ct~l~te~l pivot of pivoting support plate 430, which in turn results in the substantially S upward (or dowl~wal-l) vertical displacement of resisting colllpl~ssion roller 410 relative to optical l~min~tion roller 32, and thereby effecting colllplcssion.
As illllstr~tecl in FIGURE 1, resisting compression roller 410 iS
also indirectly associated (through its ~tt~ehment with colllpLession roller slide 420) with die spring 422. The arrangement reciliently urges resisting colll~l~ssion roller 410 toward the nip along the path defined by the vertical roller guide 434. While such me~h~nicm allows some degree of compression, colllplc;ssive force is primarily provided by the combinations associated with the aforementioned wedge plate 440 and pivoting support plate 430.
As illustrated in FIGURE 1, a drive assembly for rotatably driving resisting compression roller 410 may comprise a series of grooved guide wheels 452,454, and 456 having eng~g~l therethrough drive belt 6. Apart from grooved guide wheels 452,454, and 456, drive belt 6 is eng~ged with belt drive wheel 450and belt çng~ging wheel 412 of resisting colll~ression roller 410. Rotation of belt drive wheel 450 is effected by motor 310, a motor shared with continuous belt assembly 300. By the arrangement of wheels 452,454,456,450,412, and drive belt 6, rotation of belt drive wheel 450 will effectuate corresponding rotation of resisting compression roller 410.
In concl~lcting l~min~tion, it will be appreciated that colllprt;s~ion, by whatever means sçlecte-l is desirably accomplished so that force is distributed ullirollllly in the intended area of coln~ression. For ex~mple, if l~min~tion iscarried out under the condition of an uneven distribution of pressure, then the protective overcoat may not be uniformly bonded to the receiving surface; that is, the protective overcoat will not be suff1ciently bonded to the part of the receiving surface where the pressure is lower. Further, the uneven distribution of pressure;
i.e., a difference in pressure, may cause either the protective overcoat, the receiving surface, or both to me~n-1er, and the me~ndering of such may form 2~X~ 14-wrinkles on the film. In addition to potential media related shortcomings, uneven co~ r~ssion can also contribute to possible m~ch~nic~l failures. In l~min~tors wherein compression is accomplished by paired opposing rollers, uneven compression will increase the likelihood that the paired rollers will skew relative to each other, thus either displacing or destroying the linearity of a nip existing th~lGbeLween. Skewing becomes more pronounced with the utilization of higher compressive forces. T~min:~tion cannot be accomplished s~ti~f;lctQrily under such condition.
To assist in obtaining a uniforrn distribution of pressure and to reduce skewing (thereby allowing the use of greater compressive forces), opticall~min~tion roller is provided with bracing means, an example of which is epl~sellLed in the FIGURES as paired rollers 40a and 40b.
As shown in FIGURES 1, 3, and 4, optical l~min~tion roller 32 is braced in the upward vertical direction by paired rollers 40a and 40b. Paired rollers 40a and 40b are arranged to frictionally abut along opposing corresponding sides of the upper half of optical l~min~tion roller 32. Paired rollers 40a and 40b abut optical l~min~tion roller 32 "frictionally", such that axial rotation of one of the rollers results in a responsive corresponding axial rotation of the other rollers. In this regard, paired rollers 40a and 40b are preferably provided with a rubber surface. The arr~ngem~.nt of the paired rollers 40a and 40b afford optical l~min~tion roller 32 with the capacity to axially rotate while being continuously and uniformly braced. Such provides particular advantage to coll~dLively wider rollers which have a greater tendency to bend during COlll~l`e;SSiOn. To m~int~in the frictional abutment of paired rollers 40a and 40b 2~ with optical l~min~tion roller 32 while allowing some degree of vertical movement within guides 56, a leaf spring 58 is provided.
While equivalent bracing means can be selected and employed by one ordinarily skilled in the aIt, with particular regard to the means represented by paired rollers 40a and 40b, it may be noted that solidity of optical l~min~tion roller 32 will provide advantage over hollow transparent rollers or drums. For certain l~min~tion procedures utili7ing compressive forces of colll~a dtively large ~WO 9S/24311 2 ~ 6 2 7 ~ ~ PCT/IJS95/02747 m~gnit~ld~, hollow transparent rollers are to be disfavored for their tendency to shatter in such environment.
To further reduce the possibility of skewing, optical l~min~tion roller 32 may be also provided with springs (not shown) eng~ging the distal endsof optical l~min~tion roller 32 for the purpose of buttressing roller 32 in the horizontal plane. Suitable m~ch~nismc may be added to reduce any interference with the axial rotation of optical l~min~tion roller 32.
In accordance with the present invention, a protective overcoat and a receiving surface are conveyed through the nip where the protective overcoat is subjected to plt;S~LIl`~ and optically generated heat, the combination sufficient to cooperatively effectuate l~min~tion onto the receiving surface. Inthe l~min~tor illustrated in FIGURE 1, the conveyance of the protective overcoatand the conveyance of the receiving surface are effect~l~tecl by distinct mPch~nical elemPntc, i.e., a protective overcoat conveying means and a continuous belt assembly 300, respectively.
As illustrated in F~GURE 1, the protective overcoat conveying means for collv~yillg a pl~,tec~iv-e overcoat borne on a carrier web to the nip comprises a spool assembly 100 and a take-up assembly 200. Spool assembly 100 is configured to releasably house a supply of the "carrier web-borne"
(hereinafter, "web-borne") protective overcoat; take-up assembly 200 is configured to actively provide the driving force for transport of the protectiveovercoat from spool assembly 100 into the nip by actively capturing spent carrier web.
As shown in FIGURE 1 and 8, spool assembly 100 is c(lmpri~e(l of spool shaft 112 and a pair of abutting rubber rollers 120 and 122, the arrangement being supported in spool assembly housing 108. As shown in FIGURE 8, spool shaft 112 is associated with brake 130 while rubber roller 120 is associated with rewind motor 140. In operation, a supply of web-borne protective overcoat is wound around spool shaft 112 and fed downstream toward the nip through abutting rollers 120 and 122. When the protective overcoat is desired for l~min~tion, the supply is released by appropliately tli~eng~ging brake 2~6~

130. In certain instances, it is desirable to rewind the web-borne protective overcoat (or the spent carrier web) back onto spool shaft 112. To this end, rewind motor 140 is provided with a clutch 142, the combination capable of being operated in association with brake 130 to urge reversed axial rotation of spool shaft 112.
It will be appreciated that without a~pr~ iate controls, tensioning of the protective overcoat will vary as the supply housed in spool assembly 100 is reduced during continued operation of l~min~tor 1. It will be further appreciated that applopliate tensioning of the protective overcoat is important in pl~vellLing the protective overcoat from m~nflering as it is transported through the nip, the effects of which may cause j~mming Appropriate tensioning is also desirable to ensure that the protective overcoat enters the nip in a substantially flat state to prevent wrinkling and to promote contact (optical contact) with optical l~min~tion roller 32 to make more consistent the formation of the activation zone by tr~n~mitt~cl optical radiation. Further, lack of uniform tensioning may result in thickne~ deviations in the l~min~te which manifest as "ribbing" or curl.
To promote a~pl,J~liate tensioning, spool assembly 100 is further provided with tensioning means comprising pivoting dancer bar 124 and extPn~ling bar 126. As shown in FIGURE 1, pivoting dancer bar 124 is provided with a roller at a free end. Pivoting dancer bar 124 is capable of pivoting at an end opposite the free end to allow movement to a second position 124a.
Extension bar 126 is provided with a roller at one end. At an opposite end, extension bar 126 is furnit~h~d with a guide 128, which provides for lateral movement of the extension bar relative to housing 108. Tensioning is controlled through these means by varying the relative locations of pivoting dancer bar 124and extension bar 126, and thereby varying the (li~t~n~e through which the protective overcoat is transported. Analogous corresponding tensioning means are provided in take-up assembly 200. As shown in FIGURES 1 and 7, the corresponding tensioning means comprise pivoting dancer bar 224 (pivotable to position 224a) with guide roller 214 and extension bar 226 with guide roller 218.

~WO 95/24311 ~ 1 ~ 2 ~1 9 PCT/tlS95132747 As suggested above, the forward drive means for transporting the protective overcoat from spool assembly 100 into the nip is furnichPcl by take-up assembly 200. As illustrated in FIGURES 1 and 7, take-up assembly 200 is comprised of take-up shaft 212, take-up shaft 212 being rotatably supported in take-up assembly housing 208 and cool)e~ g in use with dancer roller 214, stripper roller 216 and extension bar roller 218. As shown in FIGURE 7, take-up shaft 212 is rotationally driven by motor 210, which when activated allows the capture of spent carrier web. Forward driving force is generated by the ongoing winding of the carrier web around take-up shaft 212 during capture.
In substantial synchronicity with the transport of protective overcoat, during l~min~tion, a receiving surface is conveyed into the nip by means of continuous belt assembly 300. As illustrated in FIGURES 1, 2, and 5, continuous belt assembly is comprised of an idler roller 360 and a drive roller 330 encircled by continuous belt 2. Drive roller 330 is rotatably mounted through side plate 9 by means of axle 320. Rotation is enh~n~ed by the use of bearings 322 and 324. Drive roller shaft 320 extends past side plate 9 to contact motor 310, thereby providing means for generating rotational driving force to drive roller 330. Details and operation of continuous belt assembly 300, modifications and ~lt~rn~tives thereto, will be a~ent to one skilled in the art in view of the present disclosure.
Configured in accordance with the embodiment described herein, the optical l~min~tion system of the present invention is prim~rily directed to l~min~tion processes employing protective overcoats capable of being made contiguously bondable to a receiving surface upon irradiation to optical radiation substantially at the point of irradiation. The term "contiguously bondable" is to be construed herein as the capacity to be bonded to an ~ iate receiving surface that is co,ll~l~ssively brought into contiguous, i.e., touching, association with the receiving s~rface In accordance with such par~m~tt~r~ protective overcoats of various configurations may be employed successfully in the practiceof the present invention. It will be appreciated that certain protective overcoat confi~nrations may be employed usefully with certain types of optical radiation WO 9S/24311 PCT/US95/02747 ~
2~ ~2~ 1L5 -18-and not others. It will be further appreciated that a protective overcoat, in addition to providing important protective functionality, may serve also to impart to a receiving surface certain desired aesthetic or decorative effects. For exarnple, in certain applications, it may be desirable to provide an overcoat with an imagewise dispersal or pattern of pi~mPnt~ or colorants. T ~mination of such overcoat onto a receiving surface provides aesthetic functionality, aside from inherent protective functionality, such as in the lamin~tion of a wood-pattçrn~dovercoat onto the surface of, for example, particle board. Several other functions exist and applications in fields other than im~ging will gçn~rally vary depending upon the nature of the receiving surface and desired effects. Accordingly, the term "p.ote~;Live overcoat" should be given liberal construction.
In a specific, representative application of the present invention, a durable layer (cf., protective overcoat) is optically lamin~t~d onto the image surface (cf., receiving surface) of a developed thermal im~ging media.
FIGURE 9 of the acco,.. panying drawings shows in section a l~min~ting sheet (generally decign~t~cl 900) disposed over image media 950, the image media 950 having a binary image surface 950 formed on substrate 954. In addition to the aforementioned Tnt.orn~tional Patent Application No.
PCT/US87/03249 (Etzel), examples and methods of obtaining image media 950 may be extracted from the discussions provided in U.S. Pat. No. 5,155,003, issued to K.C. Chang on October 13, 1992, and U.S. Pat. No. 5,200,297, issued to N.F. Kelly on April 6, 1993. While these examples all relate to thermal im~ging media wherein the receiving snrfa~es are porous or particulate image bearing surfaces developed by laminar separation, use of the present invention is not limited to developed thermal im~ging media, but rather, can also be used advantageously for the protection of images prepared by resort to other known imaging methods, including those prepared by thermal dye transfer, ink jet, and laser ablation transfer methods. Even more generally, the present invention may be utilized for the lamination of any surface on which an optical lamin~tion roller of the present invention may be rolled with an established, subst~ntially uniform, linear nip.

~WO 95/24311 ~ i 6 ~ 71 ~ PCT/US95/02747 T ~min~ting sheet 900 comprises an adhesive layer 908, a durable layer 906, a release layer 904, and a support layer 902. As noted in aforementioned International Patent Application PCT/US91/08345 (Fehervari et al.), advantage is obtained when l~min~ting sheet 900 is larger in both surface S rlimPn~ions (i.e., length and width) than image media 950.
The durable layer 906 of the l~min~ting sheet 900 may be formed from any m~teri~l, such as a cured acrylic polymer, which confers the desired ~rûpellies upon the durable layer formed on the image. For example, International Patent Application No. PCT/US91/08345 describes an embodiment wherein the durable layer is coated as a discontinuous layer from a latex which clears during l~min~tion to produce a clear durable layer. As described, the durable layer comprised 80% by weight acrylic polymer, 10% by weight polyethylene/~al~rlll wax, and 10% by weight aqueous-based nylon binder, and was prepared by mixing the polymer and wax latices, adding the binder, then adding a silicone surfactant. In U.S. Patent Application Serial No. 08/065,345, a durable layer is described as substantially transparent and compri~ing a polymeric organic m~t~ri~l having therein incorporated a siloxane.
In general, it is preferred that the durable layer 906 when l~min~tPcl over the binary imaged surface 952 of image media 950 not have a thi~kn~c~ greater than about 30 ~Lm, since thicker durable layers may, is some cases, cause optical problems in viewing the image due to internal reflections and/or refraction effects within the durable layer. Desirably, the thiçkn~sc of the durable layer 906 does not exceed 10, Lm, and more desirably this thicknto~c is in the range of 2 to 6 ~m. The durable layer 906 should of course be resistant to m~teri~l~ with which it is likely to come into contact, including the m~t~ri~lc which may be used to clean the protected imaged media. Although the exact m~tt~ri~l~ which may contact the image will vary with the int~ntl~d uses of the protected image media, in general it is desirable that the m~teri~l for the durable layer 906 be ~llbsl~nti~lly un~h~n~ecl by contact with water, iso~lu~anol and petroleum tli~ti~ t~s Preferably, the durable layer 906 should be resistant to any other materials with which it may come into contact, for example, accidental spills of coffee, which have a very deleterious effect on some plastics.
It will be appreciated that the protection of the imaged media 950 conferred by the durable layer 906 is increased when the durable layer 906 has high lubricity. Preferably, at least one of a wax, a solid silicone and silicones--rf~ct~nt is included in the durable layer 906 to increase the lubricity of this layer.
Some durable layers can be satisfactorily l~min~t~d onto an image simply as results of thermal and compressive forces incident to optical l~min~tion according to the present invention. Such durable layers are typically provided with a dye, colorant, or like compound incorporated therein having either actinic ~lupe,Lies or capable of converting optical energy into thermal energy. When exposed to optical radiation, such durable layers are "activated" by the opticalradiation so that they become bondable to desired receiving surfaces. When employing infrared radiation, such durable layer should preferably incorporate infrared dyes. It will be appreciated, however, that in general practice, it will be desirable to associate the durable layer 906 with an adhesive layer 904 (see below), and in such in~t~nres, the adhesive layer 908 may incol~oldle therein the dye, colorant, or like col"p~,u.ld (see below).
The support layer 902 of the l~min~tin~ sheet 900 may be formed from any m:~t~ri~l which can with~t~n-l the conditions which are required to l~min~tt~ the l~min~ting sheet 900 to the imaged media 950 and which is sufficiently coherent and adherent to the durable layer 906 to permit displacement of the support layer 902 away from the protected imaged media after l~min~tion, with removal of those portion of the durable layer 906 which extend beyond the periphery of the substrate 954. For use in accordance with thepresent invention, the support layer 902 should be a plastic film substantially transparent to the optical radiation tr~n~mittecl by optical radiation source 20. If desired, the support layer 902 may be treated with a subcoat or other surface treatment, such as those well-known to those skilled in the coating art, to control 21~7~ g ~0 95/24311 PCTrUS95/02747 its surface characteristics, for exarnple to increase or decrease the adhesion of the durable layer 906 or other layers (see below) to the support layer 902.
The l~min~ting sheet 900 may comprise additional layers besides the durable layer 906 and support layer 902. For example, the l~min~ting sheet S 900 may comprise a release layer 904 interposed between the durable layer 906 and the support layer 902, this release layer 904 being such that, in the areas where the durable layer 906 remains ~tt~-~he~l to the image media 950, separation of the durable layer 906 from the support layer 902 occurs by failure within or on the surface of the release layer 904. As with the support layer 902, the releaselayer should be made from a m~teri~l subst~nti~lly transparent to the optical radiation tr~ncmittecl by optical radiation source 20, preferably an optically transparent wax or silicone.
The l~min~ting sheet may also compri~e an adhesive layer 908 disposed on the surface of the durable layer 906 remote from the support layer 902 so that, during the l~min~tion, the durable layer is adhered to the image surface by the adhesive layer 908. As suggested above, some durable layers can be s~ti~f~ctorily l~min~ted onto an image simply as a result of thermal and compressive forces incident to optical l~min~tion according to the present invention. In other cases, however, the use of an adhesive layer 908 iS desirable to achieve strong adhesion between the durable layer 906 and the imaged media 950, and/or to modify the activation energy needed for l~min~tion. Various differing types of adhesive may be used to form the adhesive layer. For example,the adhesive layer 908 rnight be formed from a thermoplastic adhesive having a glass transition temperature in the range of about 120C (in which case, bondability is effected by the conductive heating of the adhesive layer above its glass transition le~ eldlul~ when ~ çnt areas of a suitable durable layer are optically activated). ~ltçrn~tively, the adhesive layer 908 may be formed from athermoplastic adhesive having a glass transition telll~eldLul~ in the range of about 120C and having incorporated therein a dye, colorant, or like coll~oulld capable of absorbing optical radiation (in which case, bondability is effected when the adhesive layer is locally heated above its glass transition te~llpeldlur~ by the WO 9S/24311 PCT/US9S/02747 ~
21~7~

absorption of optical radiation by the dye, colorant, or like compound).
Alternatively, the adhesive layer 908 might be formed of an infrared or ultraviolet curable adhesive (in which case, bondability is effected by exposing the adhesive to infrared or ultraviolet radiation, thereby curing the adhesive layer).
In the l~min~tion of imaged media 950 in accordance with a method embodiment of the present invention, l~min~ting sheet 900 and imaged media 950 are concurrently transported (in the direction of arrow d) into the nip between optical l~min~tion roller 32 and resisting compression roller 410. Whilesubmitted to colllplessive forces between optical l~min~tion roller 32 and resisting co~ ssion roller 410, l~min~ting sheet 900 is irradiated with optical radiation at the nip, the optical radiation being emitted from optical radiationsource 20 and thereafter tr~n~mitte~l and concentrated by optical l~min~tion roller 32. An activation zone (of colll~dlively high activation energy) is thereby formed in the area of irradiation. The activation energy so produced effects, for example, adhesive flow from adhesive layer 908 in the area around the nip, which in cooperation with the coll,~,c;ssive forces, effects the bonding of l~min~ting sheet 900 to the imaged media 950 at the point of co",~lc;s~.ion.
In typical practice, the l~min~ting sheet 900 and imaged media 950 are uninterruptedly fed through the nip, irradiated and co",pr~ssed such that the l~min~ting sheet 900 is blanketwise bonded to the imaged media. It is envisioned, however, that for certain applications, discontinuous bonding may bemore suitable. Additionally, as intlir~t~cl above, the optical radiation source 20 may be moved in the direction of arrow n, for example, and the activation zone correspondingly shifted to an area upstream of the nip. Variations (and bene~ltsthereof) in the location of optical radiation source 20 will be a~t;nl to one skilled in the art in view of the present disclosure.
Subsequent to the desired bonding of l~min~ting sheet 900 to imaged media 950, as shown in FIGURE 11, the carrier web 902 (and release layer 904) is l~min~rly separated from the durable layer 906 adhered (by adhesive layer 908) to the imaged media 950. In the embodiment herein described, separation occurs downstream of the nip as the carrier web 902 (and release layer ~WO95/24311 2 ~ 7 1 ~ PCT/US95/02747 904) is guided sharply around stripper roller 216, and the spent web captured bytake-up assembly 200. Because the carrier web 902 (and release layer 904) is thinner and accordingly more flexible than the protected imaged media, the sharpbending of the carrier web 902 (and release layer 904) causes it to mP~h~ni~lly S peel away from the protected imaged media, rçslllting in a fini~h.o.cl product.

Claims

1. An optical laminator useful for substantially interfacially adhering a protective overcoat onto a receiving surface when the protective overcoat and receiving surface are continuously conveyed between an optical lamination rollerand a source of resistance and wherein the protective overcoat is capable of being made bondable to the receiving surface upon irradiation with optical radiation, the optical laminator comprising an optical lamination roller positioned to establish a nip zone when brought into association with the resistance source, the optical laminationroller being axially rotatable and configured to transmit and concentrate optical radiation in the production of an activation zone;
conveying means for effectuating the positioning of the protective overcoat into the nip zone in optical contiguity with the optical lamination roller;
compressing means for generating a compressive force at the nip zone, the compressive force being of a magnitude sufficient to promote the adhering of the protective overcoat after exposure onto the receiving surface; and an optical radiation source capable of emitting optical radiation at an intensity sufficient to activate the protective overcoat when the optical radiation is transmitted and concentrated by the optical lamination roller; the optical radiation source capable of emitting optical radiation through the optical lamination roller.

2. The optical laminator of claim 1, wherein the optical radiation source is capable of emitting optical radiation through the optical lamination roller substantially toward the nip zone.

3. The optical laminator of claim 2, wherein the nip zone is substantially within the activation zone.

4. The optical laminator of claim 1, wherein the optical radiation emitted by the optical radiation source is infrared radiation; and the optical lamination roller is a substantially solid quartz roller.

5. The optical laminator of claim 1, further comprising a pressure roller, the pressure roller being the source of resistance, the pressure roller being axially rotatable and movable toward the optical lamination roller.

6. The optical laminator of claim 5, wherein the compressing means comprises urging means for pressurwise urging the pressure roller toward the optical lamination roller, whereby the nip zone is established.

7. The optical laminator of claim 6, further comprising bracing means for bracing the optical lamination roller when compressive force is generated at the nip zone, the bracing means comprising a first abutting roller and a second abutting roller, the first abutting roller frictionally abutting the optical lamination roller along a first width, the second abutting roller frictionally abutting the optical lamination roller along a corresponding second width.

8. An optical lamination process for adhering a protective overcoat onto a receiving surface, the optical lamination process comprising the steps ofproviding a protective overcoat capable of being made bondable to the receiving surface upon irradiation with optical radiation;
insertingly conveying a first region of the protective overcoat in substantial interfacial association with a first region of the receiving surface into a nip, the nip being established by an optical lamination roller brought into association with a resistance source, the optical lamination roller being axially rotatable and configured to transmit and concentrate optical radiation in the production of an activation zone;
bonding the first region of the protective overcoat to the first region of the receiving surface by a) transmitting optical radiation through the optical lamination roller to irradiate the inserted first region of the protective overcoat, the transmission of the optical radiation establishing an activation zone on theprotective overcoat wherein the protective overcoat becomes bondable to the receiving surface, and b) generating compressive force in the nip to pressurewise urge the protective overcoat onto the receiving surface; and repeating the conveying, compressing, and bonding steps until the protective overcoat is adhered onto the receiving surface.

9. The process of claim 8, wherein the protective overcoat provided is a laminar structure comprising at least a substrate, a release layer, an adhesive layer and a durable layer.

10. The process of claim 8, wherein the transmitted optical radiation is infrared radiation and the optical lamination roller is a substantially solidquartz roller.

11. The process of claim 8, wherein the optical radiation is transmitted through the optical lamination roller substantially towards the nip.

12. The process of claim 11, wherein the nip is substantially within the activation zone.