WO2000060409A1

WO2000060409A1 - Liquid crystal dimmer

Info

Publication number: WO2000060409A1
Application number: PCT/JP2000/001874
Authority: WO
Inventors: Yuichi Yano
Original assignee: Nippon Sheet Glass Co., Ltd.
Priority date: 1999-04-02
Filing date: 2000-03-27
Publication date: 2000-10-12
Also published as: WO2000060409A8

Abstract

A liquid crystal dimmer in which transparent conductive films are provided on the mutually opposed faces of a pair of transparent substrates and a medium holding therein a liquid crystal material and a dichroic dye aligned according to the alignment of the liquid crystal material. The index of double refraction (Δn) of the liquid crystal material is less than 0.15. The relationship between the absorptance (A//) along the major axis of the molocule of the dichroic dye and the absorptance (A ) along the minor axis thereof is expressed by 1.0≥[(A//-A )/(A//+2A )]≥0.75. Another liquid crystal dimmer is disclosed in which the ratio (liquid crystal content) of the liquid crystal material to the medium is 50 wt.% or more, the ratio of concentration of the dichroic dye to that of the liquid crystal is 1 wt.% or more, and the distance between the transparent conductive films is in the range from 10 to 40 νm.

Description

Description Liquid crystal dimmer Technical field

The present invention relates to a liquid crystal light adjuster, and more particularly, to a liquid crystal light adjuster that can be used as a screen for blocking a visual field in a window or a partition of an automobile or a building, or as a curtain for controlling lighting.

7 'landscape technology

In recent years, the need to adjust the transmittance of glass has been increasing in many fields using glass. In particular, in applications such as construction or automobiles, it is desired to arbitrarily adjust the transmittance of window glass from the viewpoint of privacy protection and lighting control. ) Is drawing attention.

In order to meet this demand, a liquid crystal dimmer having excellent durability and a dimming function that is easy to increase the area is disclosed in, for example, Japanese Patent Publication No. 58-501613. (NCA P: Nematic Curvil inear Aligned Phase) liquid crystal dimmer and liquid obtained by the phase separation method described in Japanese Patent Publication No. 60-502218. Product dimmers are known. These liquid crystal light adjusters operate based on the following principle. In other words, the liquid crystal dimmer disclosed in the above-mentioned publication in which small droplets of a liquid crystal substance are dispersed in an inexpensive polymer has a curved surface of a polymer wall when no voltage is applied (hereinafter referred to as “when no voltage is applied”). When the liquid crystal is aligned along the optical path, the optical path is twisted, and the light is reflected and scattered at the interface between the polymer and the liquid crystal droplets, so that it appears milky.

On the other hand, when a voltage is applied (hereinafter referred to as “when a voltage is applied”), the liquid crystal in the liquid crystal droplet is arranged in the direction of the electric field by an external electric field, and the ordinary refractive index (no) of the liquid crystal and the refractive index of the polymer (np ), The light incident perpendicular to the liquid crystal dimmer surface passes through the liquid crystal dimmer without reflection at the interface between the polymer and the polymer, so that the liquid crystal dimmer becomes transparent. As described above, the degree of scattering of the incident light in the liquid crystal light adjuster is adjusted by the applied voltage. Therefore, when the liquid crystal light adjuster is used, for example, as a window of a building or a window of an automobile, its design may be significantly impaired.

Therefore, a technique for coloring a liquid crystal light adjuster has attracted attention. As a means for solving this problem, for example, Japanese Unexamined Patent Publication No. 3-66162 discloses a method in which a dichroic dye is added to a liquid crystal material used for a liquid crystal light adjuster, and the light is applied when no voltage is applied. A method for increasing light absorption is disclosed.

As described above, Japanese Patent Application Laid-Open No. Sho 58-5016-131, Japanese Patent Application Laid-Open No. Sho 60-520218 and Japanese Patent Laid-Open No. Hei 3-66162 are disclosed. In the disclosed liquid crystal light adjuster, when no voltage is applied, light is scattered and absorbed, so that the visual field is blocked and darkened. On the other hand, when a voltage is applied, the liquid crystal light adjuster is transparent, so that a transmitted image is clearly recognized and displayed, as in a normal transparent window, and a visual field can be secured.

Dimming bodies used as windows of automobiles or windows of buildings, partitions, etc., are required to have transparency and visibility when they are transparent, as in the case of conventional glass plates. In addition, when it is opaque, there is a strong demand that the field of vision is sufficiently blocked to ensure privacy, and that it is necessary to block lighting.

However, if the transmittance when no voltage is applied is reduced in order to improve the visual field control performance, the transmittance when a negative voltage is applied also decreases. In addition, the haze ratio at the time of applying a voltage is increased, and the transparency is reduced. On the other hand, if the transmittance at the time of applying a voltage is increased, the transmittance at the time of applying no voltage is also increased, and sufficient visual field control ability cannot be obtained. For this reason, in the liquid crystal light adjuster according to the prior art, the change width of the visible light transmittance (hereinafter referred to as “ΔΤν is”) is 30% or more, and the haze ratio is 10%. The following were not obtained: Here, the haze ratio indicates a ratio of scattered light to total transmitted light.

When the liquid crystal light adjuster is used as a window or a partition of a building, the opening often has a large area of lm ² or more. Since the liquid crystal dimmer is basically an electric drive type, the current consumption is small. However, when the area is 1 m ² or more, the current consumption as one element increases considerably.

In addition, liquid crystal light adjusters in which a dichroic dye is added to the liquid crystal The current consumption is larger than that of a liquid crystal dimmer without the liquid crystal. The reason is that the liquid crystal light adjuster to which the dichroic dye is added has a large change in the visible light transmittance when no voltage is applied and no voltage applied, and thus the visual field control performance is improved. This is because the resistance value is considered to be a state in which the impurities are increased and the resistance value is reduced.

If the current consumption increases, self-heating occurs during continuous energization, which may cause deterioration due to changes in the material of the liquid crystal material or polymer, or may cause a large amount of current at the moment the voltage is applied, causing damage to the electrodes. Therefore, the reliability as a liquid crystal light adjuster was insufficient. Ming disclosure

The present invention has been made in view of the above-mentioned problems of the prior art, and a first object of the present invention is to provide a liquid crystal light control device which is easy to increase in area, and has excellent visual field control performance and transparency when voltage is applied. Is to provide.

A second object is to provide a highly reliable liquid crystal light modulator that can be easily increased in area and consumes less current.

The liquid crystal light adjuster according to the first invention of the present invention is characterized in that a transparent conductive film is provided on each of opposing surfaces of a pair of transparent substrates, and a liquid crystal material and a dichroic color that is oriented according to the orientation of the liquid crystal material. A liquid crystal light adjuster in which a medium holding ^ is interposed between the transparent conductive films, wherein the liquid crystal material has a birefringence (hereinafter referred to as “Δη”) of 0.15 or less. And the absorbance of the dichroic dye in the major axis direction (hereinafter referred to as “Α〃”) and the minor axis direction (hereinafter referred to as “Α 丄”) satisfy the following formula (1). It is characterized by.

1.0 ≥ [(Α〃1Α 丄) / (A // + 2 A 丄)] ≥0.7.5 (1)

Adjustment of liquid crystal dimmer performance can be done by selecting several factors that make up the liquid crystal dimmer: In other words, the following five points are the most effective ways to increase ΔΤνis.

1) Increase the order parameter of dichroic dye (hereinafter referred to as “s”)

2) Increase Δη of liquid crystal material

3) Reduce the liquid crystal material droplet (capsule diameter) (hereinafter referred to as “D”)

4) Increase the ratio (liquid crystal ratio) of the liquid crystal material to the medium (polymer) 5) Increase the distance (thickness) (t) between the transparent conductive films

Here, S is represented by the following formula (2), and indicates the parallelism of the dye molecule absorption axis with respect to the alignment direction of the liquid crystal molecules. Practically, it is an amount that controls the display contrast of the liquid crystal element. As S approaches 1, a brighter and clearer display becomes possible.

S = [(A〃A 丄) / (A〃 + 2A 丄)] (2)

The methods 3) and 5) above require the application of a larger voltage, so that the same applied voltage reduces the transmittance when the voltage is applied and increases the haze rate.

In the method 4), when the liquid crystal ratio is high, the capsules are bonded to each other, and when D is too large, a point-like defect is caused, and the quality is deteriorated.

Further, in the method 2), the haze ratio at the time of applying a voltage increases as Δη increases.

On the other hand, the method 1) can increase ΔΤν is without a decrease in transmittance due to a decrease in transmittance at the time of applying a voltage and a decrease in haze ratio.

However, if the value of 1 ^ exceeds 0.15, the difference between the extraordinary light refractive index (ne) of the liquid crystal and the refractive index of the polymer increases, and the haze ratio increases when a voltage is applied. If Δη exceeds 0.15, a haze ratio of 10% or less cannot be secured.

Further, when S is less than 0.75, Α〃 also decreases with a decrease in S, which decreases the light absorption performance of the dye, thereby increasing the visible light transmittance when no voltage is applied. As a result, ΔΤν i s does not exceed 29%.

On the other hand, by using a dichroic dye having S of 0.75 or more as in the present invention and using a liquid crystal material having a Δn force of 0.15 or less, ΔΤν is 30% or more. In addition, it is possible to secure a haze ratio of 10% or less.

It is known that △ n is represented by the following equation (3), where n o is the ordinary refractive index of the liquid crystal material and ne is the extraordinary refractive index of the liquid crystal material.

An = ne— no (3

According to a second aspect of the present invention, a transparent conductive film is provided on each of opposing surfaces of a pair of transparent substrates, and a liquid crystal material and a dichroic dye that is oriented according to the orientation of the liquid crystal material are held therein. Liquid crystal light adjuster having a medium formed between the transparent conductive films, A mixing ratio of the liquid crystal material (hereinafter referred to as a “liquid crystal ratio”) is 50 wt% or more, a concentration ratio of the dichroic dye to the liquid crystal material is 1% or more, and Is in the range of 10 to 40 ^ m.

To ensure sufficient visual field control performance,

1) Increase the liquid crystal ratio to 50 wt% or more

2) Make the concentration ratio of dichroic dye to liquid crystal material 1wt% or more

And in addition to this,

3) Set the distance (thickness) (t) between the transparent conductive films in the range of 10 to 40 z ^ m.

As a result, current consumption (I) ≤ 0.2 A / m ² can be ensured, and the control width of transmitted light can be increased.

On the other hand, when the liquid crystal ratio outside the range of the present invention is less than 50 wt%, the amount of the liquid crystal unit and the amount of the interface between the liquid crystal and the polymer decrease, so that the scattered light decreases. Accordingly, the distance of light passing through the dye is shortened, and the amount of absorbed light is also reduced, so that the visible light transmittance when no voltage is applied increases. On the other hand, the visible light transmittance when voltage is applied hardly changes. As a result, the change width of the visible light transmittance is small, and sufficient visual field control performance cannot be obtained. Further, when the concentration ratio of the dichroic dye is less than lwt%, the light absorption performance of color ^ is reduced, so that the visible light transmittance is also reduced, and sufficient visual field control performance cannot be obtained.

In addition, it is difficult to increase the liquid crystal ratio to more than 80 wt% in order to secure adhesion to the transparent conductive film, optical uniformity, physical durability, and the like. It is preferable to be ¥%.

Also, if the concentration ratio of the dichroic dye to the liquid crystal material is excessively large, the visible light transmittance when voltage is applied becomes too low, and it becomes difficult to secure a sufficient visual field. It is preferably set to wt%.

Best mode for implementing Ming

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these examples. Not something.

The liquid crystal material used in the present invention is not particularly limited, but is preferably a nematic liquid crystal, a cholesteric liquid crystal, or a smectic liquid crystal. Among them, a nematic liquid crystal is preferable, and a nematic liquid crystal having a positive dielectric anisotropy is particularly preferable.

Examples of dichroic dyes include anthraquinone dyes and diazo dyes.

The medium (polymer) that holds the liquid crystal material is a material that is selected so that the refractive index (n) of the medium matches the ordinary light refractive index (no) of the liquid crystal material, and partitions the liquid crystal into multiple volumes. What is necessary is just to hold | maintain, and it can use regardless of the kind of inorganic and organic. Among them, it is preferable to use a resin that can easily adjust the refractive index and manufacture a large-area liquid crystal light adjuster. In particular, the latex described in Japanese Patent Application Laid-Open No. 60-252687 is a suitable material, and has good adhesiveness to a substrate (transparent conductive film), optical uniformity, and physical durability. It is possible to provide an excellent liquid crystal light adjuster.

Further, as a substrate with a transparent conductive film used in the present invention, a glass plate or a plastic film having an indium tin oxide (ITO) film or a tin oxide (Sn〇 ₂ ) film formed on the surface is applied. be able to.

The liquid crystal light adjuster of the present invention is, in particular, a liquid crystal material having a birefringence (Δη) of 0.15 or less, an absorbance in the long axis direction of the molecule (Α〃) and an absorbance in the short axis direction of the molecule (Α 丄). ≥0.7 ((に対するに用い) / (A // + 2A 丄)) ≥0.75 When the ratio is at least 50 wt%, the concentration ratio of the dichroic dye to the liquid crystal material is at least 1 wt%, and the distance between the transparent conductive films is within the range of 10 to 40 m. It is preferable that it is constituted.

The liquid crystal light adjuster of the present invention is produced, for example, by the following method.

First, a liquid crystal substance and an aqueous phase are mixed to form an emulsion, and the emulsion is added to a latex, or a liquid crystal substance and a latex are directly mixed to form an emulsion. When preparing the emulsion, it is preferable to add a surfactant in order to form stable liquid crystal particles. Mixing is performed with various mixers such as a blender and a colloid mill. Next, a crosslinking agent is added to crosslink the latex to form a medium, Then, the medium is applied to a transparent substrate on which a transparent conductive film is formed by a knife blade or other suitable means, and dried. Then, it is bonded to another transparent substrate with a transparent conductive film to obtain a liquid crystal light adjuster.

Hereinafter, specific examples of the present invention will be described.

[Example and Comparative Example of First Invention]

(Example 1)

Liquid crystal ZL I—4 1 7 1 (Merck, Δη = 0.097) and 1 wt% of dichroic dye G—24 1 (JASCO, S = 0.80) as surfactant 0.5 wt% of IGE PAL CO-610 (manufactured by GAF) was added, and they were added with 40 wt% of latex particles so that the liquid crystal ratio became 60 wl;%. (Manufactured by Zeneca), and the mixture was stirred for 10 minutes at 7000 rpm using a homogenizer to obtain an emulsion. The average capsule diameter of the emulsion was 4 m. Next, the crosslinking agent CX-100 (manufactured by Zeneki Co., Ltd.) was added at a ratio of 3 wt% to R-967 with gentle mixing. This mixture was indium tin oxide using a Doc Yuichi blade.

The film was coated on a polyethylene terephthalate (PET) film on which a (ITO) film had been previously coated and dried. After drying, another PET film with an ITO film and a laminated liquid light conditioner were obtained. The thickness (distance between the transparent conductive films) was 25 zm.

A voltage of sine wave / 100 V / 50 Hz was applied to the liquid crystal dimmer thus obtained, and the performance was measured.As a result, ΔΤν is 30% and the haze ratio was 8%. there were. Therefore, a liquid product dimmer having sufficient visual field control performance and sufficient transparency when voltage is applied was obtained.

(Comparative Example 1)

Liquid crystal ZL I— 4 1 7 1 (Merck, Δη = 0.097) and 1 wt% of dichroic dye G 2 89 (Nippon Kogaku Dye Laboratories, S = 0.73) as surfactant 0.5 Wt% of IGE PALC〇—610 (manufactured by GAF) was added, and Neorez R-976 containing 40 wt% of latex particles was added so that the liquid crystal ratio became 60 wL%. (Zeneca) and stirred at 7000 rpm for 10 minutes using a homogenizer to obtain an emulsion. The average capsule diameter of the emulsion was 4 m. Next While mixing, a crosslinking agent CX-100 (manufactured by Zeneki) was added at a ratio of 3 wt% to R-967. Using a doctor blade, this mixture is indium tin oxide

The film was applied on a polyethylene terephthalate (PET) film on which a (ITO) film had been previously coated and dried. After drying, another PET film with an ITO film and a laminated liquid crystal light modulator were obtained. The thickness (the distance between the transparent conductive films) was 25 m.

As a result of measuring the performance of the liquid crystal light control device thus obtained, ΔΤVis was 25%, and the haze ratio was 8%. Since S <0.75, sufficient transparency was obtained when voltage was applied, but visual field control performance was insufficient.

(Comparative Example 2)

Liquid crystal ZL 1 — 3 2 19 (Merck, Δη = 0.205) with 1 wt% of dichroic dye G—24 1 (Japan Photosensitive Dye Laboratories, S = 0.80) Activator I GEPAL CO-610 (manufactured by GAF) was added in an amount of 0.5 wt%, and they were mixed with 40 wt% of latex particles to obtain a liquid crystal ratio of 60 wt%. (Manufactured by Zeneca) and stirred at 7,000 rpm for 10 minutes using a homogenizer to obtain an emulsion. The average capsule diameter of the emulsion was 4 zm. Next, the crosslinking agent CX-100 (manufactured by Zeneki Co., Ltd.) was added at a ratio of 3 wt% to R-967 with gentle mixing. Using a doctor blade, this mixture is indium tin oxide

It was applied on a polyethylene terephthalate (PET) film on which a (ITO) film had been previously coated and dried. After drying, another PET film with an ITO film and a laminated liquid light conditioner were obtained. The thickness (the distance between the transparent conductive films) was 20 m.

As a result of measuring the performance of the liquid crystal light control device thus obtained, ΔΤν is 30% and the haze ratio was 16%. Δn> 0.15, so that sufficient visual field control performance was obtained, but sufficient transparency was not obtained when voltage was applied.

[Example and Comparative Example of Second Invention]

(Example 2)

Liquid crystal ZLI—4 1 7 1 (manufactured by Merck, birefringence (hereinafter referred to as “Δη”) = 0.097) and dichroic dye G-241 (manufactured by Japan Photographic Dye Laboratories, S = 0.8 0) and 0.5wt% of surfactant I GEPAL CO-610 (GAF) These were added to Neorez R-966 (manufactured by Zeneki Co., Ltd.) containing 40 wt% of latex particles so that the liquid crystal ratio became 60 wt%. The mixture was stirred for 0 minutes to obtain an emulsion. The average capsule diameter of the emulsion was 4 / _ΜΉ. Next, a cross-linking agent CX-100 (manufactured by Generic Corporation) was added at a ratio of 3 wt% to R-967 while slowly mixing. The mixture was applied to a polyethylene terephthalate (PET) film previously coated with an indium tin oxide (IT〇) film using a doctor blade and dried. After drying, another PET film with an IT〇 film was laminated and a liquid crystal light modulator was obtained. Thickness (distance between transparent conductive films) is 15

It was 1T1.

A voltage of sine wave of 100 VZ and 50 Hz was applied to the liquid crystal dimmer thus obtained, and the performance was measured. Value. The current consumption was 0.15 A / m ² , no deterioration due to continuous energization or electrode breakdown due to voltage application was observed, and a liquid crystal light modulator with sufficient reliability was obtained.

(Comparative Example 3)

Liquid crystal ZL 1 — 3 2 1 9 (Merck, An = 0.205) with 1 wt% of dichroic dye G-24 1 (Nippon Kogaku Dye Laboratories, S = 0.80) And 0.5% by weight of surfactant IGE PAL CO-610 (manufactured by GAF) were added, and they were added with 40% by weight of latex particles so that the liquid crystal ratio became 60% by weight. -967 (manufactured by Zeneca) and stirred for 10 minutes at 700 rpm using a homogenizer to obtain an emulsion. The average capsule diameter of the emulsion was 4 m. Next, the crosslinking agent CX-100 (manufactured by Zeneki Co., Ltd.) was added to the R-966 at a ratio of 3 wt% with gentle mixing. Using a doctor blade, this mixture is indium tin oxide

It was applied on a polyethylene terephthalate (PET) film on which a (ITO) film had been previously coated and dried. After drying, another PET film with an ITO film and a laminated liquid crystal light modulator were obtained. The thickness (the distance between the transparent conductive films) was 8 m.

A voltage of sine wave / 100 VZ 50 Hz was applied to the liquid crystal dimmer thus obtained, and the performance was measured.As a result, the change width of the visible light transmittance was sufficiently 20%. However, the current consumption was 0.3 A / m ² , indicating deterioration due to continuous energization and voltage application. The electrode was broken and the reliability was insufficient. Industrial applicability

As described in detail above, in the liquid crystal light adjuster according to the first invention of the present invention, Δη of the liquid crystal material is 0.15 or less, and the absorbance of the dichroic dye in the molecular long axis direction (Α 〃) and the absorbance (Α 丄) in the minor axis direction of the molecule satisfy 1.0 ((Α〃- の) Z (A // + 2A 丄)) ≥0.75 A liquid crystal light modulator composed of: Δ 、 ν is 30% or more, and has a light control performance of a haze ratio of 10% or less, so that it has excellent visual field control performance and transparency when voltage is applied, and A large-area liquid crystal light modulator can be obtained easily and at low cost.

The liquid crystal light adjuster according to the second invention of the present invention has a liquid crystal ratio of 50 wt% or more, a dichroic dye concentration ratio to a liquid crystal material of 1 wt% or more, and the transparent conductive material. A liquid crystal dimmer configured so that the distance between the films is in the range of 10 to 40 / im, and the above configuration can ensure a current consumption (I) ≤ 0.2 Zm ² , thereby improving reliability. Thus, a large-area liquid crystal light modulator excellent in controllability and visual field controllability can be obtained easily and at low cost.

When the liquid crystal light control device of the present invention is used as, for example, a window of an automobile, a window of a building, a screen for blocking a view in a partition, or a curtain for lighting control, a liquid crystal light control having a laminated glass function is provided. It can be glass.

Claims

Claims (1) A medium in which a transparent conductive film is provided on each of opposing surfaces of a pair of transparent substrates, and a liquid crystal material and a dichroic dye oriented according to the orientation of the liquid crystal material are held therein. A liquid crystal light modulator interposed between the transparent conductive films, wherein the liquid crystal material has a birefringence (Δη) of 0.15 or less, and an absorbance of the dichroic dye in a molecular long axis direction ( (1) A liquid crystal light modulator characterized in that the following formula is established between the absorbance in the minor axis direction of the molecule (Α 丄).

1. 0≥ [(A // — Α 丄) / (A // + 2 A 丄)] ≥0.7.5

(2) The liquid crystal light control device according to claim 1, wherein the change width of the visible light transmittance is 30% or more and the haze ratio is 10% or less.

(3) A transparent conductive film is provided on each of the opposing surfaces of a pair of transparent substrates, and a medium containing a liquid crystal material and a dichroic dye oriented in accordance with the orientation of the liquid crystal material is placed on the transparent conductive film. A liquid crystal light modulator interposed between the films, wherein a ratio of the liquid crystal material to the medium is 50 wt% or more, and a concentration ratio of the dichroic dye to the liquid crystal material is 1% or more; And a distance between the transparent conductive films is in a range of 10 to 40 μιτι.

(4) The liquid crystal material according to claim 3, wherein the birefringence (Δη) of the liquid crystal material is 0.15 or less, and the absorbance (Α〃) of the dichroic dye in the molecular major axis direction and the molecular minor axis direction Absorbance of

(Α 丄) is a liquid crystal light modulator characterized by the following formula:

1. 0≥ C (Α〃1 Α 丄) No (A // + 2A 丄)] ≥0.75

(5) The liquid crystal light control device according to (3) or (4), wherein the compounding ratio of the liquid crystal material to the medium is 60 to 70 wt%.

(6) The liquid crystal light adjuster according to any one of claims 3 to 5, wherein a concentration ratio of the dichroic dye to the liquid crystal material is 1 to 10 wt%.