JPH0566387A - Liquid crystal device manufacturing method - Google Patents

Abstract

(57) [Abstract] [Purpose] In a liquid crystal device having a light control layer in which a transparent solid substance is dispersed in a continuous layer of a liquid crystal material, by irradiating with an ultraviolet irradiation device having uniform irradiation intensity,
The white turbidity unevenness of the obtained liquid crystal device is improved and the driving characteristics are made uniform. [Structure] A light control layer forming material containing a liquid crystal material, a photopolymerizable composition, and a photopolymerization initiator is used with an irradiation device in which the intensity of ultraviolet rays to be irradiated is 70% or more on a substrate surface.
Irradiation with ultraviolet rays forms a light control layer in which a transparent solid substance is dispersed in a continuous layer of a liquid crystal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal device capable of forming a large area, and more particularly, to blocking or opening a field of view and limiting or blocking transmission of light or illumination light.
The transmission can be electrically operated, and it is used as a screen for blocking the field of view in building windows and show windows, and as a curtain for daylighting control. The present invention relates to a method for manufacturing a liquid crystal device which is used as a high information display body such as a display of an OA equipment or a projection device, an advertising board, a guide board, a decorative display board, etc. by electrically switching the display.

[0002]

2. Description of the Related Art Conventionally, liquid crystal devices are TN (twisted nematic) type and S type using nematic liquid crystals.
A TN (super twisted nematic) type has been put into practical use. Also, a liquid crystal device using a ferroelectric liquid crystal has been proposed.

However, these liquid crystal devices require a polarizing plate and also require an alignment treatment.

On the other hand, as a method of manufacturing a large-sized and inexpensive liquid crystal device which does not need them and has a bright contrast, liquid crystal droplets are dispersed in a polymer by encapsulating liquid crystal, and the polymer is formed into a film. A method is known (Japanese Patent Publication No. 58-501631), USP
No. 4,435,047, Special Table Sho 61-50134
5 and JP-A-62-48789).

In the technology disclosed in the above specification, liquid crystal molecules encapsulated by polyvinyl alcohol are present in the presence of an electric field if they have a positive dielectric anisotropy in the thin layer. Below, the liquid crystal molecules are aligned in the direction of the electric field, and the ordinary refractive index n _{o of the} liquid crystal and the refractive index n _{p of the} polymer are
When are equal, transparency is expressed. When an electric field is removed, the liquid crystal molecules are returned to the random sequence, the refractive index of the liquid crystal droplets is deviated from the n _o, the liquid crystal droplets scatter light at the boundary surface, since blocking the transmission of light, Ususotai is It becomes cloudy.

[0006] In addition to the above-mentioned techniques, there are some known techniques in which a polymer containing dispersed encapsulated liquid crystals is used as a thin film.
No. 021208 discloses a liquid crystal dispersed in an epoxy resin, Japanese Patent Application No. 61-305528 and Japanese Patent Laid-Open No. 6-305528.
JP-A-2-2231 discloses that a liquid crystal and a photocurable resin are phase-separated by irradiating a liquid mixture of a photocurable resin and a liquid crystal with ultraviolet rays to form a light control layer in which the liquid crystal is dispersed in the resin. How to do is reported.

A driving voltage in a liquid crystal device having such a light control layer requires about 20 V or more, and in many cases requires a high voltage of 40 V or more.

Further, the light scattering performance required for liquid crystal devices,
In order to obtain the light transmission performance, it is necessary to optimize the matching or non-matching of the refractive indexes of the liquid crystal material and the resin component, and there is a limitation in selecting the combination of the liquid crystal material and the resin material.

From these problems, in order to enable low voltage driving characteristics, high contrast, and time division driving, which are important characteristics required for practical use of the liquid crystal device as described above, JP-A-1-198725 has been proposed. The publication discloses a liquid crystal device having a dimming layer in which a liquid crystal material forms a continuous layer, and a transparent polymer substance having a three-dimensional mesh structure is formed in the continuous layer.

In such a liquid crystal device, a light control layer forming material containing a liquid crystal material, a photopolymerizable composition and a photopolymerization initiator is interposed between two transparent substrates having electrode layers,
By irradiating light to polymerize the photopolymerizable composition, a liquid crystal device having a light control layer composed of the liquid crystal material and the transparent polymer substance as described above can be manufactured.

[0011]

A substrate for sandwiching a material for forming a light control layer is irradiated with ultraviolet rays to form a three-dimensional network polymer substance in a continuous layer of a liquid crystal material, thereby forming a light control layer. In the manufacturing process of the liquid crystal device, the characteristics of the liquid crystal device obtained are influenced by the irradiation intensity of the ultraviolet ray used.

The polymerization rate of the photopolymerizable composition, which is the material for forming the light control layer, is influenced by the intensity of the ultraviolet rays to be irradiated, and the white turbidity of the device or the driving voltage varies.

That is, when a liquid crystal device obtained by using an ultraviolet irradiator having a variation in irradiation intensity is used for an active display element, a time division display element, etc., the characteristics as a direct view type display cannot be exhibited. Especially this tendency is
It becomes more prominent as the device area increases.

An object of the present invention is to provide a method for manufacturing a uniform and even device by making the irradiation intensity of ultraviolet rays uniform on the substrate surface.

[0015]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems, and as a result, achieved the present invention.

That is, in order to solve the above problems, the present invention provides a preparation containing a liquid crystal material, a photopolymerizable composition and a photopolymerization initiator between two substrates having at least one transparent electrode layer. A method for producing a liquid crystal device having a light control layer composed of a liquid crystal material and a transparent polymer material by interposing a light layer forming material under light shielding and then irradiating light to polymerize the photopolymerizable composition. In the above, there is provided a method for producing a liquid crystal device, which comprises irradiating ultraviolet rays so that the intensity of the ultraviolet rays to be irradiated is 70% or more on the surface of the substrate.

In the manufacturing method of the present invention, since the light control layer forming material is uniformly irradiated with ultraviolet rays, the light control layer forming material is
The polymerization reaction proceeds uniformly on any part of the substrate, and the resulting liquid crystal device is uniform in appearance such as white turbidity and in characteristics such as driving voltage, resulting in a liquid crystal device with no unevenness, especially as the substrate area increases. This manufacturing method is effective.

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 the liquid crystal layer and the layer having the transparent solid substance sandwiched between the two substrates. The dimming layer is to be visible to 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, both substrates are provided with appropriate transparency. This substrate is transparent depending on the purpose,
Appropriate opaque electrodes may be arranged on the whole surface or a part thereof.

However, in the case of a flexible material such as a plastic film, it can be used in the manufacturing method of the present invention after being fixed to a rigid material such as glass or metal.

A dimming layer made of a liquid crystal material and a transparent solid substance is interposed between the two substrates, and the two substrates are usually spaced apart from each other, as in a known liquid crystal device. It is also possible to interpose a holding spacer.

As the spacer, for example, Mylar,
A variety of liquid crystal cells such as alumina and polymer beads can be used.

The liquid crystal material used in the present invention does not need 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 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 a nematic liquid crystal is particularly preferable. In order to improve the performance, cholesteric liquid crystals, chiral nematic liquid crystals, chiral smectic liquid crystals, chiral compounds, dichroic dyes and the like 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. Temperature, melting point, viscosity, refractive index anisotropy (Δ
n), the dielectric anisotropy (Δε), the solubility with the polymerizable composition, and the like can be taken into consideration and appropriately selected and blended.

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)
-5-substituted pyrimidine etc. can be mentioned.

The content of the liquid crystal material and the polymerizable composition in the light control layer forming material is preferably in the range of 60:40 to 95: 5 by weight, particularly preferably in the range of 75:25 to 85:15. If the amount of the liquid crystal material is too large or too small, the liquid crystal material and the transparent solid substance will not be uniformly dispersed, and the dimming function due to light scattering will not be exhibited, which is not preferable.

The transparent solid substance formed in the light control layer may be one in which the liquid crystal material is spherically dispersed in the polymer, but one having a three-dimensional network structure is more preferable.

It is preferable that the liquid crystal material is filled in the three-dimensional network portion of the transparent solid substance and that the liquid crystal material forms a continuous layer. By forming a disordered state of the liquid crystal material, It is indispensable for forming the optical boundary surface and expressing the scattering of light.

In order to interpose the light control layer forming material between the two substrates, this light control layer forming material may be injected between the substrates, but a suitable solution coater or spin coater for one substrate may be used. May be applied uniformly, and then the other substrate may be superposed and pressure-bonded.

Further, the light control layer forming material is applied on one substrate to a uniform thickness, the photopolymerizable composition is polymerized to form a cured light control layer, and then the other substrate is bonded. A liquid crystal device manufacturing method is also effective.

A synthetic resin is suitable as the transparent solid substance of the present invention. A photo-curable resin obtained by polymerizing a polymer-forming monomer or oligomer is preferable as a material that gives a three-dimensional network structure.

As a method for forming a three-dimensional network structure by the transparent solid substance formed between the substrates, visible light is emitted while maintaining the light control layer forming material enclosed in the cell in an isotropic liquid state. The method of irradiating and polymerizing a photopolymerizable composition is mentioned.

Examples of the polymer-forming monomer forming the transparent solid substance include styrene, chlorostyrene,
α-methylstyrene, divinylbenzene: As a substituent, methyl, ethyl, propyl, butyl, amyl, 2-
Ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, allyl, methallyl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, Acrylate, methacrylate or fumarate having a group such as dimethylaminoethyl, diethylaminoethyl, etc .; ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, tri Mono (meth) acrylates such as methylolpropane, glycerin and pentaerythritol, or poly (meth) a Relate; vinyl acetate, vinyl butyrate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, limonene, cyclohexene, diallyl phthalate, diallyl isophthalate, 2-, 3- or 4-
Vinyl pyridine, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-hydroxymethyl acrylamide or N-hydroxyethyl methacrylamide and their alkyl ether compounds, trimethylolpropane, 1 mol of ethylene oxide or propylene oxide of 3 mol or more Di- or tri (meth) acrylate of triol obtained by addition, di (meth) acrylate of diol obtained by addition of 2 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol, 2-hydroxyethyl (meth) )
Reaction product of 1 mol of acrylate and 1 mol of phenyl isocyanate or n-butyl isocyanate, poly (meth) acrylate of dipentaerythritol, poly (meth) acrylate of tris- (hydroxyethyl) -isocyanuric acid, tris- (hydroxyethyl) ) -Phosphoric acid poly (meth) acrylate, di- (hydroxyethyl) -dicyclopentadiene mono (meth) acrylate or di (meth) acrylate, pivalic acid neopentyl glycol di (meth) acrylate, caprolactone modified hydroxypivalic acid Examples include neopentyl glycol di (meth) acrylate, linear aliphatic di (meth) acrylate, polyolefin-modified neopentyl glycol di (meth) acrylate, and the like.

As the polymer-forming oligomer, for example, epoxy (meth) acrylate, polyester (meth) acrylate, polyurethane (meth) acrylate, polyether (meth) acrylate and the like can be used.

Examples of the polymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one ("Darocur 1173" manufactured by Merck), 1-hydroxycyclohexyl phenyl ketone ("Ciba Geigy" manufactured by Ciba Geigy). Irgacure 184 "), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-
On (Merck "Darocur 1116"), benzyl dimethyl ketal (Ciba Geigy "Irgacure 651"), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (Ciba) -A mixture of Geigy's "Irgacure 907"), 2,4-diethylthioxanthone (Nippon Kayaku's "Kayacure DETX") and ethyl p-dimethylaminobenzoate (Nippon Kayaku's "Kayacure-EPA"). , Isopropyl thioxanthone ("Cantacure I" manufactured by Ward Prekinsop Co., Ltd.
TX ") and a mixture of ethyl p-dimethylaminobenzoate and the like.

As the ultraviolet irradiation light source, for example, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp or the like can be used.

The irradiation intensity of ultraviolet rays on the substrate surface is 1 mW / cm when measured using an ultraviolet illuminometer ("UIT-101" manufactured by Ushio Inc., light receiving wavelength 365 nm).
² or more, preferably 10 mW / cm ² or more, and the unevenness of the irradiation intensity within the substrate surface is 7
0% or more is required.

The thickness of the light control layer of the liquid crystal device obtained by the present invention is preferably in the range of 5 to 50 μm, and 8 to 25 μm.
Is particularly preferred.

[0038]

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

In the following examples, "parts" and "%" represent "parts by weight" and "% by weight", respectively. Each of the evaluation characteristics means the following symbols and contents. (1) T ₀ : White turbidity; light transmittance (%) when applied voltage is 0 (2) T ₁₀₀ : Transparency; Light transmittance when the applied voltage hardly increases with increasing applied voltage ( %) (3) V ₁₀ : threshold voltage; T ₀ = 0%, T ₁₀₀ = 100
% And the when the applied voltage light transmittance is _{10% (V rms) (4} ) V 90: saturation voltage; applied voltage ibid light transmittance is _{90% (V rms) (5} ) CR: Contrast = T ₁₀₀ / T ₀ (6) γ: steepness; V ₉₀ / V ₁₀ (Example 1)

[0040]

[Chemical 1]

A liquid crystal composition (A) consisting of was prepared.

The various properties of this liquid crystal composition (A) were as follows.

This liquid crystal composition (A) was 80.0%, and as a polymerizable composition, caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate ("KAYARAD-HX620" manufactured by Nippon Kayaku Co., Ltd.) 19.6%.
And 1-phenyl-2-hydroxy-as a polymerization initiator
A dimming layer forming material composed of 0.4% of 2-methylpropan-1-one (“Darocur 1173” manufactured by Merck & Co., Inc.) was used as 1
It is sandwiched between two A4 size ITO electrode glass substrates coated with 2.0 micron glass fiber spacers, and the entire substrate is kept at 38 ° C. so that the light control layer forming material becomes an isotropic liquid state, After adjusting the UV irradiation intensity of the central part of the substrate to 35 mw / cm ² , it was irradiated with UV light for 60 seconds, and a liquid crystal device with a light control layer with a thickness of 11.6 μm, which had no opaque appearance Obtained.
When the light control layer of the obtained liquid crystal device was observed with an electron microscope, a three-dimensional mesh-like transparent solid substance could be confirmed.
As shown in FIG. 1, the ultraviolet irradiation intensity at 9 points on the surface of a substrate of A4 size and the characteristics of the device at the corresponding site were measured, and the results are shown in Table 1.

[0044]

[Table 1]

Comparative Example 1 A sample having the same composition as in Example 1 was irradiated with ultraviolet rays under the same conditions by using an apparatus different from the ultraviolet ray irradiation apparatus used in Example 1, and the obtained device was as follows. It was not preferable as a liquid crystal device because the appearance had white turbidity unevenness.

When the light control layer of the obtained liquid crystal device was observed with an electron microscope, a transparent solid substance having a three-dimensional mesh could be confirmed, but the size of the mesh was uneven depending on the measurement site and was uniform throughout. Was not. The ultraviolet irradiation intensity and the characteristics of the device at the relevant site were measured, and the results are shown in Table 2.

[0047]

[Table 2]

[0048]

According to the manufacturing method of the present invention, since the substrates sandwiching the light control layer forming material are irradiated with uniform ultraviolet rays in a short time,
It is possible to provide a liquid crystal device in which the light control layer is uniformly formed, the appearance has no unevenness of white turbidity, and the characteristics are uniform. This manufacturing method is particularly effective when the substrate area is large.

Therefore, the manufacturing method of the present invention is useful as a manufacturing method of a liquid crystal device such as a display of a computer terminal and an optical shutter for projection.

[Brief description of drawings]

FIG. 1 was a graph showing the ultraviolet irradiation intensity and the device characteristics on the surface of an A4 size substrate in Examples and Comparative Examples.
It is drawing which shows the site | part of a point.

[Explanation of symbols]

1-9 Area where UV irradiation intensity and device characteristics were measured

Claims (1)

[Claims] 1. An ultraviolet light is applied after a light control layer forming material containing a liquid crystal material, a photopolymerizable composition and a photopolymerization initiator is interposed between two substrates having at least one transparent electrode layer. When the photopolymerizable composition is polymerized by irradiation, the intensity of ultraviolet rays irradiated in the method for producing a liquid crystal device having a light control layer composed of a liquid crystal material and a transparent solid substance is 70% on the substrate surface. A method of manufacturing a liquid crystal device, which comprises using the ultraviolet irradiation device as described above.