JPH07104251A - Liquid crystal device and its production - Google Patents

Abstract

PURPOSE:To provide the subject device excellent in low voltage driving property, high contrast, time-division driving property, and bright screen, and having large resistance and high voltage holding rate without dissolving a thermal polymn. inhibitor into a liquid crystal material after photopolymn. by imparting the thermal polymn. inhibitor with photopolymerizing property. CONSTITUTION:A light-controlling layer forming material is interposed between two substrates one of which is transparent and has an electrode layer. This light-controlling layer forming material consists of a liquid crystal material, photopolymerizable compsn. containing photopolymerizable thermal polymn. inhibitor, photopolymn. initiator, and as necessary, chain moving agent, photosensitizer, dye, crosslinking agent, and the others. The polymerizable compsn. is polymerized by irradiating it with active rays to produce the device. The thermal polymn. inhibitor is a compd. having photopolymerizing property and photopolymerizable vinyl groups or acryloyl groups. Therefore, the residual thermal polymn. inhibitor hardly dissolves in the liquid crystal material, but is contained in the transparent polymer material in the light-controlling layer. Thus, decrease in the resistance of the liquid crystal device can be suppressed and the voltage holding rate can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device having a large area and a method for manufacturing the same, more specifically,
It is possible to electrically control the blocking and opening of the visual field, and the limiting, blocking and transmitting of light or illumination light.
It is used as a screen for blocking the field of view in building windows, show windows, etc., and as a curtain for daylighting control. It also displays characters and figures, and electrically switches the display with high-speed response to display OA equipment, etc. The present invention relates to a liquid crystal device used as a display device such as a high information display body, an advertising board, a guide board, and a decorative display board.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal device having a light control layer made of a liquid crystal material and a transparent polymer material between two substrates having at least one transparent electrode layer (hereinafter referred to as "liquid crystal device"). ) Is composed of a liquid crystal material, a photopolymerizable composition containing a polymerization inhibitor which is a low molecular weight organic compound, and a photopolymerization initiator between at least one transparent substrate having an electrode layer. A photochromic composition was polymerized by exposing a light control layer forming material and irradiating with an ultraviolet ray to form a light control layer composed of a liquid crystal material and a transparent polymer material.

[0003]

However, since the thermal polymerization inhibitors that have been used conventionally are low molecular weight organic compounds, most of them were dissolved in the liquid crystal material even after the completion of photopolymerization. Such a liquid crystal device has problems that the resistance is low, the power consumption is increased, the life is shortened, and the display screen flickers due to a decrease in the voltage holding ratio.

The problem to be solved by the present invention is that after the photopolymerization by light irradiation is completed, the thermal polymerization inhibitor does not dissolve in the liquid crystal material, and the low voltage driveability, high contrast,
An object of the present invention is to provide a liquid crystal device excellent in time-division drivability, a bright screen, and the like, and having a large resistance and a high voltage holding ratio, and a manufacturing method thereof.

[0005]

The present inventor has achieved the present invention as a result of extensive studies to solve the above-mentioned problems.

That is, in order to solve the above problems, the present invention has two substrates, at least one of which has an electrode layer and which is transparent, and a dimming layer supported between these substrates. Is composed of a transparent polymer material obtained by polymerizing a photopolymerizable composition comprising (1) a liquid crystal material and (2) a photopolymerizable composition containing a thermal polymerization inhibitor and a photopolymerization initiator in the liquid crystal. In a liquid crystal device, the thermal polymerization inhibitor has photopolymerizability, and a liquid crystal material and a (meth) acryloyloxy group between at least one transparent substrate having an electrode layer. A photopolymerizable composition containing a photopolymerizable thermal polymerization inhibitor containing, and sandwiching a light control layer forming material containing a photopolymerization initiator, then irradiated with actinic rays, the photopolymerizable composition By polymerizing
Provided is a method for manufacturing a liquid crystal device which forms a light control layer made of the liquid crystal material and a transparent polymer material.

The liquid crystal device of the present invention is characterized in that the transparent polymer substance formed by light irradiation contains a photopolymerizable composition and a photopolymerization inhibitor having a (meth) acryloyloxy group. It is a transparent polymer substance obtained by copolymerizing a molecular substance forming material.

The thermal polymerization inhibitor refers to a compound which inhibits a polymerization reaction, and is a compound having an action of inhibiting a catalytic function or a compound which reacts with generated free radicals and interferes with its growth. Examples of the thermal polymerization inhibitor used in the present invention include hydroquinone, benzoquinone, and pyrogallo-
And various phenol derivatives such as phenothiazine and phenothiazine.

The thermal polymerization inhibitor used in the present invention is preferably used in the range of 10 to 1000 PPM with respect to the polymerizable composition.

In the liquid crystal device of the present invention, the thermal polymerization inhibitor is a photopolymerizable thermal polymerization inhibitor having a polymerizable functional group such as a (meth) acryloyloxy group. When the polymerization inhibitor itself forms a copolymer with the photopolymerizable composition, the thermal polymerization inhibitor and its residue are fixed to the transparent polymer substance by chemical bonding.

As such a thermal polymerization inhibitor, for example,
SUMILIZER GM (manufactured by Sumitomo Chemical Co., Ltd.) and the like can be mentioned.

The thermal polymerization inhibitor used in the present invention may be a mixture of ordinary polymerization inhibitors having a low molecular weight within a range that does not affect the liquid crystal device.

The substrate used in the present invention may be a rigid material such as glass or metal, or a flexible material such as a plastic film. The two substrates are opposed to each other and are separated by an appropriate distance, at least one of which has transparency, and a liquid crystal layer and a transparent polymer substance layer sandwiched between the two substrates. The light control layer consisting of must be visible from the outside world. However, complete transparency is not essential.

If the liquid crystal device is used to act on light passing from one side of the device to the other, the two substrates are both provided with appropriate transparency. . Appropriate transparent or opaque electrodes may be provided on the entire surface or a part of the substrate depending on the purpose. However, in the case of a flexible material such as plastic, it can be used for the liquid crystal device of the present invention after being fixed to a rigid material such as glass or metal.

In addition, a spacer for holding a space can be usually provided between the two substrates, as in the well-known liquid crystal device.

As the spacer, for example, Mylar,
Alumina, rod-type glass fiber, glass beads, polymer beads, and other various liquid crystal cells can be used.

The liquid crystal material used in the present invention does not have to be a single liquid crystal compound, and may be a mixture containing two or more kinds of liquid crystal compounds or substances other than the liquid crystal compounds. Any material generally recognized as a liquid crystal material in this technical field may be used, and one having a positive dielectric anisotropy is preferable.

The liquid crystal used is preferably a nematic liquid crystal, a smectic liquid crystal or a cholesteric liquid crystal, and particularly preferably a nematic liquid crystal. In order to improve the performance, a cholesteric liquid crystal, a chiral nematic liquid crystal, a chiral smectic liquid crystal or the like, or a chiral compound may be appropriately contained.

The liquid crystal material used in the present invention is preferably a blended composition comprising one or more compounds selected from the compound group shown below, and the characteristics of the liquid crystal material, that is, the phase transition between the isotropic liquid and the liquid crystal. It may be appropriately selected and blended for the purpose of improving temperature, melting point, viscosity, refractive index anisotropy (Δn), dielectric anisotropy (Δε), solubility with a polymerizable composition and the like. it can.

Examples of the liquid crystal material include 4-substituted benzoic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted biphenyl ester, 4- (4-substituted cyclohexanecarbonyloxy)
Benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted cyclohexyl ester, 4-substituted 4'-substituted Biphenyl, 4-substituted phenyl 4'-substituted cyclohexane, 4
-Substituted 4 "-substituted terphenyl, 4-substituted biphenyl 4'-substituted cyclohexane, 2- (4-substituted phenyl)
A 5-substituted pyrimidine etc. can be mentioned.

The content of the liquid crystal material in the light control layer forming material is
70 to 95% by weight is preferable, 75 to 90% by weight
Is particularly preferred.

The transparent polymer material formed in the light control layer may be dispersed in the form of particles in a continuous layer of a liquid crystal material, but one having a three-dimensional network structure is more preferable. Further, the liquid crystal material may be dispersed in a droplet shape in the transparent polymer material.

It is preferable that the three-dimensional network portion of the transparent polymer material is filled with a liquid crystal material and the liquid crystal material forms a continuous layer. By forming a disordered state of the liquid crystal material, An optical boundary surface is formed between liquid crystal materials to cause light scattering.

The transparent polymer material present in the continuous layer of the liquid crystal material is not limited to a solid material, but may be one having flexibility, flexibility and elasticity as long as it is suitable for the purpose.

A photocurable resin obtained by polymerizing a polymer-forming monomer or oligomer is preferable as a material for providing these transparent polymer materials.

Examples of the monomer forming the transparent polymer substance include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol and trimethylol. Mono (meth) acrylates or poly (meth) acrylates such as propane, glycerin and pentaerythritol; neopentyl glycol 1
Di (meth) acrylate of diol obtained by adding 2 moles or more of ethylene oxide or propylene oxide to moles; or diol of triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane. Tri (meth) acrylate; Di (meth) acrylate of diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A; 1 mol of 2-hydroxyethyl (meth) acrylate and phenyl isocyanate or n-butyl. Reaction product with 1 mol of isocyanate; poly (meth) acrylate of dipentaerythritol; pivalate ester neopentyl glycol diacrylate; caprolactone-modified hydroxypivalate ester Neopentyl glycol diacrylate; linear aliphatic diacrylate; and polyolefin modified neopentyl glycol diacrylate.

Examples of the high molecular weight oligomer include epoxy (meth) acrylate, polyester (meth) acrylate, polyurethane (meth) acrylate, polyether (meth) acrylate, polyolefin (meth) acrylate, silicon (meth) acrylate. -T and the like.

The liquid crystal device of the present invention can be manufactured as follows.

At least one of which has an electrode layer and is transparent 2
Between the two substrates, (1) a liquid crystal material, (2) a photopolymerizable composition containing a photopolymerizable thermal polymerization inhibitor and (3) a photopolymerization initiator, and optionally a chain transfer agent and a photosensitizer. Sensitizer,
It can be produced by interposing a light control layer forming material composed of a dye, a cross-linking agent, and the like and irradiating with actinic rays to polymerize the polymerizable composition.

In order to allow the light control layer forming material to exist between the two substrates, the light control layer forming material may be injected between the substrates, but a suitable solution coater or spin coater may be provided on one of the substrates. You may apply | coat uniformly using the etc., and then the other board | substrate may be piled up and pressure-bonded.

Further, the dimming layer forming material is applied to one of the substrates in a uniform thickness, and the polymerizable composition is polymerized and cured by irradiation with actinic rays to form the dimming layer, and then the other. The method of manufacturing a liquid crystal device in which the substrates of (1) and (2) are attached is also effective.

In the method for producing a liquid crystal device of the present invention, active rays are irradiated as polymerization energy. However, irradiation with active rays while maintaining the isotropic liquid state of the light control layer forming material is It is preferable for forming a uniform light control layer.

In order to polymerize the photopolymerizable composition in the liquid crystal material, light irradiation intensity and irradiation amount above a certain level are required, but the reactivity of the photopolymerizable composition and the photopolymerization initiator are required. The formation of a three-dimensional network structure of transparent polymer substances depends on the type and concentration of
Further, the size of the mesh can be made uniform, and as a result, the obtained liquid crystal device has a clear threshold voltage and sharpness, and time-division driving becomes possible.

[0034]

EXAMPLES The present invention will be described in more detail below by showing Examples of the present invention. However, the invention is not limited to these examples.

In the following examples, "%" represents "% by weight", and the symbols of the evaluation characteristics are shown in Table 1 below.
Represents the meaning and contents shown in.

[0036]

[Table 1]

(Example 1) As a liquid crystal material, "PN-0" was used.
08 "(manufactured by Rodic) 80.0%, as a photopolymerizable monomer," MANDA "(manufactured by Nippon Kayaku Co., hydroxypivalate ester neopentyl glycol diacrylate, as a thermal polymerization inhibitor," Sumilyzer ( SU
MILIZER) GM ": 2- (2'-acryloyloxy-
3'-tert-butyl-5'-methylphenyl) 4-methyl-6-tert-butylphenol 0.3%) 1
3.86%, lauryl acrylate (made by Tokyo Kasei)
Two ITO electrodes coated with 11.0 μm glass fiber spacers were prepared using a light control layer forming material consisting of 5.94% and 0.4% of “Irgacure 651” (manufactured by Ciba Geigy) as a photopolymerization initiator. 50mW / c while sandwiching the glass substrate and keeping the whole substrate at 20.4 ℃
Ultraviolet light having an intensity of m ² was irradiated for 60 seconds to obtain a liquid crystal device in which the entire surface of the substrate was uniformly clouded.

When the light control layer of the obtained liquid crystal device was observed with an electron microscope, a three-dimensional network structure composed of a transparent solid substance could be confirmed.

When the relationship between the applied voltage and the light transmittance of the obtained liquid crystal device was measured, T ₀ = 4.0% and T ₁₀₀ = 8.
9.1%, CR = 22.3, V 10 = 4.3V rms, V 90
= 9.1 V _rms , and the resistance value measured by the AC wave method was 1.8 × 10 ¹⁰ Ω · cm.

(Comparative Example 1) Hydroquinone monomethyl ether was used as a thermal polymerization inhibitor in an amount of 0.
A liquid crystal device was produced in the same manner as in Example 1 except that 2% was used.

The relationship between the applied voltage and the light transmittance of this liquid crystal device measured in the same manner as in Example 1 is T ₀ = 3.9.
%, T ₁₀₀ = 87.6%, CR = 22.5, V 10 = 4.
9V _{rm s,} a V ₉₀ = 10.3 V _rms, resistance, 3.
The value was as low as 7 × 10 ⁹ Ω · cm.

The above results are shown in Table 2 below.

[0043]

[Table 2]

As can be seen from Table 2, it is clear that the liquid crystal device of the present invention has a much higher resistance than the liquid crystal device of the comparative example.

[0045]

In the liquid crystal device of the present invention, the residue of the thermal polymerization inhibitor hardly dissolves in the liquid crystal material,
Since it is contained in the transparent polymer substance in the light control layer, it is possible to suppress the decrease in the resistance value of the liquid crystal device, improve the voltage holding ratio, and obtain a high-contrast liquid crystal device that eliminates screen flicker. be able to. Therefore, it is not only a conventional liquid crystal device for dimming of this kind, but also extremely useful as a liquid crystal device for display of OA equipment such as a computer, a projection, a viewfinder, and the like, which is thinner and more advanced. is there.

Claims (5)

[Claims] 1. At least one transparent substrate having an electrode layer, and a dimming layer supported between these substrates, wherein the dimming layer comprises (1) a liquid crystal material and (2). In a liquid crystal device composed of a transparent polymer material obtained by polymerizing a photopolymerizable composition comprising a photopolymerizable composition containing a thermal polymerization inhibitor and a photopolymerization initiator in the liquid crystal, the thermal polymerization inhibitor is A liquid crystal device having a polymerizability. 2. The liquid crystal device according to claim 1, wherein the thermal polymerization inhibitor has a photopolymerizable vinyl group. 3. The liquid crystal device according to claim 1, wherein the thermal polymerization inhibitor is a compound having an acryloyl group. 4. The liquid crystal device according to claim 1, 2 or 3, wherein the light control layer has a transparent polymer substance having a three-dimensional network shape in a continuous layer of the liquid crystal material. 5. A photopolymerizable composition containing a liquid crystal material and a photopolymerizable thermal polymerization inhibitor containing a (meth) acryloyloxy group, between two substrates having at least one transparent electrode layer. After sandwiching a light control layer-forming material containing a photopolymerization initiator, the light control is performed by irradiating with actinic rays to polymerize the photopolymerizable composition, thereby comprising the liquid crystal material and the transparent polymer material. A method of manufacturing a liquid crystal device for forming a layer.