JPH052156A - Production of liquid crystal device - Google Patents

Abstract

PURPOSE:To prevent photodeterioration and to improve a specific resistance value and voltage holding rate by irradiating a light control layer forming material with visible rays and forming a light control layer constituted by dispersing a transparent solid material into the continuous layer of a liquid crystal material. CONSTITUTION:This process for production of the liquid crystal device having the light control layer consisting of the liquid crystal material and the transparent solid material consists in interposing the light control layer forming material contg. the liquid crystal material, a photopolymerizable compsn. and a photopolymn. initiator between two sheets of substrates which have electrode layers and at least one of which are transparent, then irradiating the material with the light to polymerize the photopolymerizable compsn. The photopolymerizable compsn. is polymerized by the irradiation with the light in the above-mentioned process. The liquid crystal material to be used in such a case is preferably a compounded compsn. and is used with proper selection and compounding by taking the characteristics of the liquid crystal material, i.e., the phase transition temps. of an isotropic liquid and liquid crystal, m. p., viscosity, refractive index anisotropy (DELTAn), dielectric constant anisotropy (DELTAepsilon), and the solubility with the photopolymerizable compsn., etc., into consideration.

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 that does not need them and has a bright contrast, a method of dispersing liquid crystal droplets in a polymer by encapsulating liquid crystal and forming the polymer into a film is known. (JP-A-58-501631 gazette, USP 4,435,047)
Specification, Japanese Patent Publication No. 61-501345, Japanese Patent Laid-Open No. 62-48789
Issue).

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.

As described above, there are known some techniques other than those described above in which the polymer containing the encapsulated liquid crystal dispersed therein is used as a thin film.
In No. 08, liquid crystal dispersed in epoxy resin, Japanese Patent Application Sho
No. 61-305528, JP-A-62-2231 discloses that a liquid crystal and a photocurable resin are phase-separated by irradiating a liquid mixture of the photocurable resin and the liquid crystal with ultraviolet rays, and the liquid crystal is dispersed in the resin. A method of forming the light control layer has been reported.

A driving voltage of a liquid crystal device having such a light control layer needs to be about 20 V or higher, and in many cases, a high voltage of 40 V or higher is required. Furthermore, in order to obtain the light-scattering performance and light-transmitting performance required for a liquid crystal device, it is necessary to optimize the matching and mismatching of the refractive indices of the liquid crystal material and the resin component, and select a combination of the liquid crystal material and the resin material. There was a limit above.

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 formed by forming a continuous layer of a liquid crystal material and forming a three-dimensional network polymer substance 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, it is possible to produce a liquid crystal device having a light control layer composed of a liquid crystal material and a transparent polymer substance as described above. From the viewpoint of efficiency and the like, a method of mainly irradiating ultraviolet rays as the energy for polymerization has been used.

[0009]

However, the liquid crystal device obtained by irradiating the light control layer forming material with ultraviolet rays in this way has a low specific resistance of the liquid crystal material due to photodegradation due to ultraviolet ray irradiation. Accordingly, there are problems that the power consumption of the liquid crystal device increases, the life of the liquid crystal device decreases, and the display screen flickers due to a decrease in the voltage holding ratio.

Further, the ultraviolet irradiation device generates high energy, which is harmful to the human body such as generation of ozone and skin damage. Especially, when manufacturing a large-area liquid crystal device, a large amount of it is required. Since the above-mentioned ultraviolet rays are irradiated, and an expensive apparatus is required, it has been a practical problem to irradiate the ultraviolet rays for polymerization.

The problem to be solved by the present invention is to provide a method of manufacturing a liquid crystal device in which the liquid crystal material has a high specific resistance and a high voltage holding ratio and consumes less power, and further a method of manufacturing a liquid crystal device which does not affect the human body. To provide.

[0012]

In the manufacture of liquid crystal devices, the present inventors have found that photo-deterioration of liquid crystal materials due to ultraviolet irradiation is larger than expected, which leads to a decrease in the specific resistance and voltage holding ratio of the liquid crystal devices. As a result of discovering that there is a problem, and conducting intensive research to solve this problem, the present invention has been achieved.

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 visible light to polymerize the polymerizable composition.

In the liquid crystal device manufacturing method of the present invention, the light control layer forming material is irradiated with visible light, so that the liquid crystal material is hardly photo-degraded, and the performance of the liquid crystal device can be fully utilized.

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 production 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. It goes without saying that the liquid crystal material used in the present invention does not need to be a single liquid crystal compound,
It may be a mixture containing two or more kinds of liquid crystal compounds or substances other than the liquid crystal compounds, and may be a mixture generally recognized as a liquid crystal material in this technical field, and has a positive dielectric anisotropy. Those are 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 three-dimensional network portion of the transparent solid substance is filled with a liquid crystal material 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 that forms 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, triglyceride Mono (meth) acrylates such as methylolpropane, glycerin and pentaerythritol, or poly (meth) actuates Lilate; 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.

The photopolymerization initiator is 390 to 800 n
Any compound having absorption in the visible light region of m, for example, dicarbonyl compounds such as camphorquinone, 2,4,
Acylphosphine oxide compounds such as 6-trimethylbenzoyldiphenylphosphine oxide and thioxanthone compounds such as 2-chlorothioxanthone can be used. Furthermore, by combining with a sensitizer such as amines Can be improved. In particular, it is desirable to use camphorquinone and an amine sensitizer together.

390 to 800n as a visible light irradiation light source
Any emission source in the wavelength range of m can be used, and for example, sunlight, fluorescent lamps, etc. can be used, but from the viewpoint of polymerization efficiency, a xenon lamp or a halogen lamp is preferable, and the initial purpose of not irradiating ultraviolet rays is achieved. Therefore, it is necessary to cut the wavelength range of 390 nm or less with an optical filter.

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, particularly preferably in the range of 8 to 25 μm.

[0033]

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; applied voltage (Vrms) at which light transmittance becomes 10% when T ₀ is 0% and T ₁₀₀ is 100% (4) V ₉₀ : saturation voltage; Same as above _Applied voltage (V _rms ) at which the light transmittance is 90% (5) CR: Contrast = T ₁₀₀ / T ₀ (6) R: Specific resistance value (Ω · cm) (7) HV: Voltage holding ratio (%) ); Frame frequency 30H
z, voltage 11 V, rectangular wave of 64 μs time in ON state is applied, charge accumulated in ON state is Q ₀ , current in OFF state is measured by high impedance voltmeter, and residual charge is Q , HV = Q / Q ₀ .

(Example 1)

[0036]

[Chemical 1]

A liquid crystal composition (A) consisting of was prepared. The properties of this liquid crystal composition (A) were as follows. Phase transition temperature 68.5 ℃ (N-I) < -25.0 ℃ (C-N) refractive index n _e = 1.787 n _o = 1.583 refractive index anisotropy [Delta] n = 0.254 Threshold Voltage Vth = 1.15V Viscosity at 20 ° C. 59 cp Dielectric anisotropy Δε = 26.9 Liquid crystal composition (A) 80.0%, caprolactone-modified hydroxypivalate neopentylglycol diacrylate as a polymerizable composition (KAYA manufactured by Nippon Kayaku Co., Ltd.
RAD-HX620) 19.2%, camphor quinone 0.4% as a polymerization initiator, and dimethylaminoethyl methacrylate 0.4% as a sensitizer, a light control layer forming material,
It was sandwiched between two ITO electrode glass substrates coated with 12.0 micron glass fiber spacers in the dark, and the entire substrate was kept at 40 ° C so that the light control layer forming material was in an isotropic liquid state. “(ICI visible light irradiation device) is used to irradiate visible light for 60 seconds,
A liquid crystal device having a light control layer with a thickness of 12.3 microns was 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. The characteristics of this device were measured and were as follows.

T ₀ = 5.4%, T ₁₀₀ = 85.7%, CR
= 15.8, V ₁₀ = 5.4V _rms , V ₉₀ = 11.9
V _rms , R = 3.5 × 10 ⁹ Ω · cm, HV = 62.5% From these results, by using the manufacturing method of the present invention, as compared with the liquid crystal device of the comparative example to be described later by the prior art,
It has been clarified that a liquid crystal device having a greatly improved specific resistance value and voltage holding ratio can be obtained.

Comparative Example 1 80.0% of the composition (A) described below as a liquid crystal material, and caprolactone-modified hydroxypivalate neopentyl glycol diacrylate as a polymerizable composition (KAYARAD-HX620 manufactured by Nippon Kayaku Co., Ltd.).
19.6% and benzyl dimethyl ketal (Irgacure 651 manufactured by Ciba-Geigy) as a polymerization initiator.
2% ITO coated with 12.0 micron glass fiber spacer with 4% dimming layer forming material
It is sandwiched between electrode glass substrates under light shielding, and the whole substrate is kept at 40 ° C. so that the light control layer forming material is in an isotropic liquid state,
Ultraviolet rays of 35 mw / cm @ 2 were irradiated for 60 seconds to obtain a liquid crystal device having a light control layer with a thickness of 12.3 microns. 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. The characteristics of this device were measured and were as follows.

T ₀ = 2.4%, T ₁₀₀ = 85.9%, CR
_{= 35.8, V 10 = 8.3V rms} , V 90 = 13.2
V _rms , ΔV = 1.25, R = 6.2 × 10 ⁸ Ω · c
m, HV = 20.5% (Example 2) 80.0% of a nematic liquid crystal composition (B) (Rodick Co., RO-571) as a liquid crystal material,
Caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate (KAYARAD-HX620 manufactured by Nippon Kayaku Co., Ltd.) 13.2%, trimethylolpropane triacrylate 2.5%, lauryl acrylate-as a polymerizable composition. 1% of a dimming layer-forming material containing 0.4% of camphorquinone as a polymerization initiator and 0.4% of dimethylaminoethyl methacrylate as a sensitizer.
It is sandwiched between two ITO electrode glass substrates coated with 2.0 micron glass fiber spacers in the dark, and the whole substrate is kept at 37 ° C so that the light control layer forming material is in an isotropic liquid state. (Visible light irradiation device manufactured by ICI Co., Ltd.) was used for irradiation for 60 seconds to obtain a liquid crystal device having a light control layer with a thickness of 12.3 microns. 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 was confirmed. The characteristics of this liquid crystal device were measured and were as follows.

T ₀ = 6.2%, T ₁₀₀ = 86.5%, CR
= 13.9, V ₁₀ = 1.4V _rms , V ₉₀ = 5.2V _rms ,
R = 1.8 × 10 ¹⁰ Ω · cm, HV = 73.8% From these results, by using the manufacturing method of the present invention, as compared with the liquid crystal device of the comparative example to be described later according to the prior art,
It has been clarified that a liquid crystal device having a greatly improved specific resistance value and voltage holding ratio can be obtained.

(Comparative Example 2) A nematic liquid crystal composition (B) (RO-571, manufactured by Rodick) as a liquid crystal material 8
0.0%, caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate as a polymerizable composition (KAYARAD-HX620 manufactured by Nippon Kayaku Co., Ltd.) 13.6
%, Trimethylolpropane triacrylate 2.5
%, Lauryl acrylate 3.5%, and benzyl dimethyl ketal (Irgacure 651, manufactured by Ciba-Geigy Co., Ltd.) 0.4% as a polymerization initiator, a light control layer forming material, a 12.0 micron glass fiber spacer. of the applied pinching in the dark on two ITO electrodes glass substrate, the light control layer-forming material keeps the entire substrate so that the isotropic liquid state 37 ° C., 60 with ultraviolet rays at 35 mW / cm ²
Irradiation for 2 seconds gave a liquid crystal device having a light control layer with a thickness of 12.1 μm. 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. The characteristics of this device were measured and were as follows.

T ₀ = 4.4%, T ₁₀₀ = 86.7%, CR
= 19.7, V ₁₀ = 2.5V _rms , V ₉₀ = 6.2V _rms ,
R = 6.2 × 10 ⁹ Ω · cm, HV = 36.5%

[0044]

By using the manufacturing method of the present invention, it is possible to obtain a liquid crystal device which can provide a bright screen without a polarizing plate, can be driven at a low voltage, can have a high contrast, and can be driven in a time division manner. Provided is a liquid crystal device capable of preventing photodegradation of a liquid crystal material due to conventional ultraviolet irradiation, and improving the specific resistance value and voltage holding ratio characteristics and the flicker of a screen, which have been problems particularly in a light scattering liquid crystal device. be able to.

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

Claims (4)

[Claims] 1. A light control layer-forming material containing a liquid crystal material, a photopolymerizable composition and a photopolymerization initiator is interposed between two substrates, at least one of which has an electrode layer and which is transparent, and then light is applied. 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, by polymerizing the photopolymerizable composition by irradiation, visible light is irradiated to perform polymerization. Liquid crystal device manufacturing method. 2. The method for manufacturing a liquid crystal device according to claim 1, wherein the light control layer has a transparent solid substance formed by forming a three-dimensional network structure in a continuous layer of a liquid crystal material. 3. The method for producing a liquid crystal device according to claim 1, wherein the photopolymerization initiator has absorption in a visible light region. 4. The method for producing a liquid crystal device according to claim 1, 2 or 3, wherein the light control layer forming material contains a sensitizer.