JP2000066173A - Manufacture of liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a liquid crystal device that is capable of narrowing the distribution of network mesh size of a transparent solid material which has three-dimensional network structure and is contained in a dimmer layer of the device, while keeping the network mesh size large, and accordingly, excellent in contrast and responsiveness by irradiating a dimmer layer forming material contg. a liquid crystal material and a compound having an energy ray (ultraviolet or visible ray, or the like)curable functional group (s), with energy rays through a substrate while lowering the temp. of the dimmer layer forming material from a temp. at which the dimmer layer forming material shows an isotropic liquid phase, and polymerizing the compound having an energy ray-curable functional group (s). SOLUTION: This manufacture comprises: interposing a dimmer layer forming material contg. a liquid crystal material and a compound having an energy ray (ultraviolet or visible ray, or the like)-curable functional group (s), between two substrates at least any one of which is transparent; and irradiating the dimmer layer forming material with energy rays through the transparent substrate, while lowering the temp. of the dimmer layer forming material from a temp. at which the dimmer layer forming material shows an isotropic liquid phase, to polymerize the compound having an energy ray-curable functional group (s) and to manufacture the objective liquid crystal device having a dimmer layer consisting of a continuous layer of the liquid crystal material and a transparent solid material existing in the continuous layer in a three-dimensional network state. As the liquid crystal material, that having positive dielectric-constant anisotropy is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal device having a large display area, and more particularly to a method for electrically or thermally controlling light blocking, transmission, and scattering. By displaying figures and switching the display with high-speed response, high-information display bodies such as display boards such as advertising boards, guide boards and decorative display boards, displays such as OA equipment, and projections such as projectors The present invention relates to a method for manufacturing a liquid crystal device used as a display device.

[0002]

2. Description of the Related Art JP-A-1-198725 and JP-A-2-85822 disclose that a liquid crystal material forms a continuous layer, and a three-dimensional network-like polymer substance is formed in the continuous layer. A light scattering type liquid crystal device having a dimming layer is disclosed.

In such a light-scattering type liquid crystal device, in the case of electric driving, a dimming layer containing a liquid crystal material and an energy ray-curable compound is formed between at least one transparent substrate having an electrode layer. While interposing a material, while maintaining the light modulating layer forming material in an isotropic liquid state, energy rays,
For example, it is manufactured by polymerizing a polymerizable compound in the light modulating layer forming material by irradiation with actinic rays to form a light modulating layer composed of a liquid crystal material and a transparent polymer substance.

[0004]

In order to realize the high contrast, low voltage drivability, high-speed response, low hysteresis, and high steepness (high γ) required for a liquid crystal device, the polymer network size should be 0.3 to 0.3. It is required to keep the thickness at 3 μm, more preferably about 0.6 to 1.5 μm, and narrow the distribution.

However, according to the known manufacturing method,
Molding conditions, for example, by adjusting the composition ratio of the liquid crystal material and the photopolymerizable compound, the curing temperature, the curing speed, etc.
Although it was possible to narrow the distribution of the polymer network size, as the distribution became narrower, the network size tended to be smaller than the intended range. By selecting liquid crystal materials and photopolymerizable compounds, and their combinations,
Although it was possible to circumvent this restriction, a method for keeping the polymer network size large in any system and narrowing its distribution is required in any system because it significantly narrows the range of system selection. Was.

An object of the present invention is to provide a method for manufacturing a liquid crystal device having a continuous layer of a liquid crystal material and a dimming layer made of a transparent solid substance existing in a three-dimensional network in the continuous layer. In view of the above, an object of the present invention is to provide a method of manufacturing a liquid crystal device capable of narrowing the distribution of a transparent solid substance while maintaining a large mesh size in order to obtain a liquid crystal device having excellent contrast and responsiveness.

[0007]

Means for Solving the Problems The present inventors diligently studied a method for narrowing the distribution while maintaining the polymer network size at 0.3 to 3 μm, and completed the present invention.

That is, in order to solve the above-mentioned problems, the present invention comprises (I) (1) a liquid crystal material and a compound having an energy ray-curable functional group between two substrates, at least one of which has transparency. And (2) irradiating energy rays through the substrate while lowering the temperature from a temperature at which the dimming layer forming material exhibits an isotropic liquid phase, thereby causing energy ray curability. A dimming layer supported between two substrates, comprising a second step of polymerizing a compound having a functional group, wherein the dimming layer includes a continuous layer of a liquid crystal material and a three-dimensional structure in the continuous layer of the liquid crystal material. Provided is a method for manufacturing a liquid crystal device having a dimming layer made of a transparent solid substance existing in a network.

According to another aspect of the present invention, there is provided (II) (1) a liquid crystal material and an energy ray-curable functional group provided on at least one of two substrates having transparency. A first step of coating a light modulating layer forming material containing a compound having the following formula: (2) applying energy rays to the light modulating layer forming material while lowering the temperature from a temperature at which the light modulating layer forming material exhibits an isotropic liquid phase. Irradiating, thereby polymerizing a compound having an energy ray-curable functional group, and (3) a third step of overlaying the other substrate on the polymerized light modulating layer forming material. A light modulating layer supported between two substrates, the light modulating layer comprising a continuous layer of a liquid crystal material and a transparent solid substance existing in a three-dimensional network in the continuous layer of the liquid crystal material. To provide a method for manufacturing a liquid crystal device having

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The liquid crystal material used in the present invention may be any material which is generally recognized as a liquid crystal material in this technical field, and need not be a single liquid crystal compound. It may be a mixture containing two or more liquid crystal compounds or substances other than the liquid crystal compounds. The liquid crystal material also preferably has a positive dielectric anisotropy.

The liquid crystal material used in the present invention 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, a chiral compound, a dichroic dye, or the like may be appropriately contained.

The liquid crystal material used in the present invention is preferably a compounded composition comprising at least one compound selected from the following compound group. The properties of the liquid crystal material, that is, the phase of the isotropic liquid and the liquid crystal are preferable. For the purpose of improving the transition temperature, melting point, viscosity, Δn, Δε, solubility with the polymerizable composition and the like, they can be appropriately selected, blended and used.

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-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 and the like can be mentioned.

The compound having an energy ray-curable functional group used in the present invention, that is, a compound which is cured by a polymerization reaction or a cross-linking reaction by an energy ray, is a compound which can obtain a transparent cured product by irradiation with the energy ray. Any material can be used as long as the mixture with the liquid crystal material dissolves in a liquid state at a high temperature and separates in a liquid state at a low temperature. The expression that a cured product is obtained by irradiation with an energy ray as used herein includes one that is photocured only in the presence of a photopolymerization initiator.

Examples of the compound having an energy ray-curable functional group include radical addition polymerizable monomers and / or oligomers, cation addition polymerizable monomers and / or oligomers, ring-opening polymerization type monomers and / or oligomers, and the like. Can be Specifically, vinyl monomers and / or oligomers, particularly acryloyl and / or methacryloyl groups in the molecule (hereinafter acryloyl groups and / or
Alternatively, those containing a methacryloyl group referred to as (meth) acryloyl group, N-substituted maleimide, epoxy compound and the like can be preferably used. Among these, monomers and / or oligomers having a (meth) acryloyl group in the molecule are particularly preferred because they have a high polymerization rate and are easy to balance mechanical properties, electrical properties, and optical properties. Also,
Monomers and / or oligomers containing two or more polymerizable functional groups in the molecule (ie, polyfunctional monomers and / or oligomers) are preferred.

The compound having an energy ray-curable functional group which can be used in the present invention includes, for example, 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-hydroxy Ethyl, 2-hydroxypropyl, 3-chloro-2
Acrylates, methacrylates or fumarates having groups such as hydroxypropyl, dimethylaminoethyl, diethylaminoethyl; ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl Poly (meth) acrylate or poly (meth) acrylate such as glycol, trimethylolpropane, glycerin and pentaerythritol; vinyl acetate, vinyl acetate or vinyl benzoate, acrylonitrile, cetyl vinyl ether, limonene, cyclohexene, diallyl phthalate, 2-3 -Or 4-vinylpyridine, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-hydrido Carboxymethyl acrylamide or N-
Hydroxyethyl methacrylamide and their alkyl ether compounds; 3 to 1 mole of trimethylolpropane
Di or tri (meth) of triol obtained by adding at least mole of ethylene oxide or propylene oxide
Acrylate; di (meth) acrylate of diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol;
Reaction product of 1 mole of 2-hydroxyethyl (meth) acrylate with 1 mole of phenyl isocyanate or n-butyl isocyanate; poly (meth) acrylate of dipentaerythritol; poly (meth) of tris- (hydroxyethyl) -isocyanuric acid Acrylate; poly (meth) acrylate of tris- (hydroxyethyl) -phosphoric acid; mono (meth) acrylate or di (meth) acrylate of di- (hydroxyethyl) -dicyclopentadiene; neopentyl glycol diacrylate pivalate; Caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate; linear aliphatic diacrylate; polyolefin-modified neopentyl glycol diacrylate; polyethylene glycol di (meth) a Relate, epoxy resin (meth) acrylic acid esters, of the polyester resin (meth)
Acrylic esters, (meth) acrylic esters of polyether resins, (meth) acrylic esters of polybutadiene resins, and polyurethane resins having a (meth) acryloyl group at the molecular terminal can be cited.

It may be a compound mixture having an energy-ray-curable functional group, wherein monomers, oligomers,
Alternatively, it may be a mixture of a monomer and an oligomer.
Further, a mixture of a polyfunctional monomer and / or oligomer and a monofunctional monomer and / or oligomer is also preferably used. By using these mixtures, the degree of freedom in adjusting the compatibility with liquid crystal materials, mechanical properties, optical properties such as refractive index, and electrical properties is increased.

A material in which a mixture with a liquid crystal material is compatible in a liquid state at a high temperature and undergoes phase separation in a liquid state at a low temperature is defined as having a compatible region within a temperature range in which the light modulating layer forming material as the mixture exists as a liquid. And a phase separation region. At this time, the liquid state may be a liquid state of the compound phase having the energy ray-curable functional group, and the liquid crystal material phase may be in a liquid crystal state or a crystalline state. Since these conditions are different depending on the combination with the liquid crystal material to be mixed and used, general classification is difficult. However, the conditions can be determined by a simple experiment in which the compatibility is changed by changing the mixing ratio and the temperature.

The light modulating layer forming material in the present invention contains the above-mentioned liquid crystal material and a compound having an energy ray-curable functional group as essential components, and the composition is such that the content of the liquid crystal material is 50 to 90% by weight. And more preferably 70 to 90% by weight. When the content of the liquid crystal material is lower than this value, the liquid crystal material is difficult to form a continuous layer, and the polymer network size tends to be a small value of less than 0.3 μm. However, according to the production method of the present invention, the diameter of the liquid crystal material phase can be increased as compared with the conventional method, even if the composition has a low liquid crystal material content.

The light modulating layer forming material may contain other optional components. For example, a polymerization initiator, a chain transfer agent, a dye, a crosslinking agent, a spacer, and the like can be used. In the present invention, when light is used as the energy ray, the light-modulating layer forming material is photopolymerized for the purpose of expanding the range of usable compounds having an energy ray-curable functional group and increasing the polymerization rate. It is also preferable to include an initiator.

As the photopolymerization initiator, for example, 2-hydroxy-2-methyl-1-phenylpropan-1-one ("Darocur 1" manufactured by Ciba Specialty Chemical Co., Ltd.)
173 "), 1-hydroxycyclohexylphenyl ketone (" Irgacure 184 "manufactured by Ciba Specialty Chemicals), 1- (4-isopropylphenyl)-
2-hydroxy-2-methylpropan-1-one ("Darocur 111" manufactured by Ciba Specialty Chemicals, Inc.)
6 "), benzyldimethyl ketal (" Irgacure 651 "manufactured by Ciba Specialty Chemicals), 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (Ciba Specialty Chemicals) “IRGACURE 907”, 2,4-diethylthioxanthone (Nippon Kayaku Co., Ltd. “Kayacure DE”)
TX ") and ethyl p-dimethylaminobenzoate (" Kayacure EPA "manufactured by Nippon Kayaku Co., Ltd.), isopropylthioxanthone (" Cantacure ITX "manufactured by Ward Prekinsopp) and p-dimethylaminobenzoic acid And a mixture with ethyl. The use ratio of the photopolymerization initiator is preferably in the range of 0.1 to 10% by weight of the polymerizable composition.

The substrate used in the present invention may be a rigid material, for example, a plastic plate, glass, metal, or the like, or may be a flexible material, for example, a plastic film or sheet. . And the board is
Two sheets are obtained facing each other at an appropriate interval. In addition, at least one of them must be transparent so that the dimming layer sandwiched between the two can be seen from the outside. However, complete transparency is not essential. If the liquid crystal device is used to act on light passing from one side to the other, both substrates are provided with the appropriate transparency. Appropriate transparent and opaque electrodes may be disposed on the entire or partial surface of the substrate depending on the purpose. The electrode is preferably arranged on the side in contact with the light modulating layer forming material. In the case of a flexible material such as a plastic film, the material can be fixed to a rigid material, for example, glass, metal, or the like, and then used in the manufacturing method of the present invention.

In order to control the thickness of the transparent solid substance to be uniformly adhered to the substrates, it is preferable to interpose a spacer for maintaining a space between the two substrates, similarly to a well-known liquid crystal device. This is particularly suitable in the case of a manufacturing method in which photocuring is performed in a state where a light modulating layer forming material is interposed between two substrates. The spacer may be mixed with a solution containing a liquid crystal material and a polymerizable compound, or a solution containing an organic solvent and a polymerizable compound, or may be applied or sprayed on one substrate.

As the spacer, for example, Mylar,
Various types of liquid crystal cells such as alumina, rod-type glass fibers, glass beads, and polymer beads can be used without particular limitation.

The first of the manufacturing methods according to the present invention is a method in which the temperature is lowered and photo-curing is performed in a state in which the dimming layer forming material is interposed between two substrates. The method of shaping the light modulating layer forming material between the two substrates is optional, and the material can be poured between the two substrates.
Lamination of another substrate on one substrate can be adopted. The method of coating the substrate is arbitrary, and for example, brush coating, casting, discharge from a nozzle, coating with a coating bar or the like, roller coating, or the like can be employed.

A second method of the production method of the present invention is a method in which a light modulating layer forming material is applied to a substrate, the temperature is reduced and photo-curing is performed, and then another substrate is superimposed thereon in close contact. . In this case, the coating method is the same as described above.

The first manufacturing method has an advantage that the adhesion between the dimming layer and the electrode is easily maintained high, and is suitable when a rigid substrate is used. On the other hand, the second method has an advantage that a spacer is not required, and is suitable for a liquid crystal device having a small size or a case where a flexible substrate is used.

When the liquid crystal device manufactured by the manufacturing method of the present invention is used for electrically driven applications, it is necessary to provide electrode layers on both sides of the light control layer. Is preferably used. At this time, in order to enable low-voltage driving, it is preferable to dispose an electrode on the side in contact with the light control layer.

The thickness of the light control layer can be appropriately set according to the purpose of use. However, in order to obtain a sufficient contrast between the opacity due to light scattering and the transparency achieved electrically or thermally, the thickness of the light control layer is preferably 1: 1. The range is preferably from 30 to 30 μm, and more preferably from 5 to 20 μm.

The temperature at which the light modulating layer forming material is shaped is preferably a temperature at which the liquid crystal material in the light modulating layer forming material and the compound having an energy ray-curable functional group are compatible. It is possible to form a liquid film at the temperature at which phase separation occurs and then to a compatibilizing temperature to obtain a homogeneous phase, and then proceed to the next step, as long as some phase separation occurs. However, even after the phase separation has progressed, it is difficult to return to a uniform phase even at the solution temperature, which is not preferable.

While observing the light control layer forming material with a microscope,
When the temperature is lowered from the temperature at which the liquid crystal material and the compound having the energy-ray-curable functional group are compatible, the light-modulating layer forming material undergoes phase separation, and the droplets mainly composed of the liquid-crystal material become energy-ray-cured. It occurs in a continuous layer mainly composed of a compound having an acidic functional group, and is observed to undergo phase separation. At this time, the temperature at which phase separation starts depends on the cooling rate, and the higher the cooling rate, the lower the temperature. In the present invention, the temperature at which phase separation starts when measured at a temperature lowering rate of 2 ° C. per minute is referred to as “phase separation point”. Since it is difficult to accurately measure the temperature of the light-modulating layer forming material formed thinly, the temperature of the light-modulating layer forming material in the present invention is the temperature of the substrate surface.

An object of the present invention is to irradiate an energy ray while lowering the temperature of a shaped light modulating layer forming material from a temperature at which a single isotropic liquid phase is exhibited to cure a compound having an energy ray-curable functional group. It is where to let.

At this time, when the temperature at which the irradiation of the energy beam is started is (i) above the phase separation point, and (ii) below the phase separation point, the light control layer forming material is still at the implemented temperature drop rate. The temperature may be a temperature that is an isotropic liquid phase, or (iii) a temperature equal to or lower than a temperature at which the liquid crystal material and the compound having an energy-ray-curable functional group start phase separation at the implemented cooling rate. In addition, although the temperature of the light control layer forming material may increase due to the energy of the light beam itself or the heat of polymerization due to the irradiation of the energy beam, the temperature at the start of the irradiation of the energy beam is a problem in the present invention. The temperature may increase after the start of irradiation.

The present invention provides (i) a manufacturing method in which the material for forming a light modulating layer starts irradiation with energy rays at a temperature higher than the phase separation temperature while the temperature is lowered. This is a preferable method when the cooling rate is high, for example, when the cooling rate is 0.5 ° C. or more per second. At this time, the temperature at which the irradiation of energy rays is started is preferably equal to or lower than (phase separation point + 10 ° C.). If the energy beam irradiation temperature is higher than this, the polymer network size becomes too small, which is not preferable. If the temperature decreasing rate is smaller than this, the approach of the conventional method of performing energy pre-irradiation at an isothermal temperature is asymptotic, and the effect of the present invention is reduced. The upper limit of the effect temperature is not particularly limited, but is preferably 1000 ° C. or less per second, and more preferably 100 ° C. or less per second. If the cooling rate is greater than this value, it is difficult to control the cooling rate, and non-uniformity is likely to occur particularly when a large-area liquid crystal device is manufactured.
Such a large cooling rate can be achieved by a method in which a substrate on which a liquid crystal material is sandwiched or coated is brought into contact with a low-temperature metal or liquid. However, if the cooling rate is very fast,
It is difficult to specify an accurate cooling rate in terms of measurement accuracy.

Further, the present invention provides a method for producing a light-modulating layer at a temperature below the phase separation point but at a temperature at which the light modulating layer forming material is still an isotropic liquid phase at the temperature lowering rate. Present. As mentioned above, the phase separation point is
The temperature at which phase separation starts when measured at a temperature lowering rate of 2 ° C. per minute. Therefore, in the practice of the present invention, if a higher cooling rate is adopted, phase separation occurs at a temperature lower than the phase separation point due to the occurrence of a supersaturated state, a time delay of phase separation, and a delay in heat transfer. Starts. Thus, the state "below the phase separation point but still an isotropic liquid phase at the implemented cooling rate" can occur when the cooling rate is greater than 2 ° C per minute. In the production method (ii) of the present invention, the temperature decreasing rate is preferably 0.05 ° C./second or more, more preferably 0.05 ° C./second or more. This method is more preferable than the method (i) because the effect of the present invention can be sufficiently exhibited. If the cooling rate is smaller than this value, it becomes difficult to carry out the present method (ii) stably. Regarding the upper limit of the cooling rate, the above (i)
Is the same as

Further, the present invention provides (iii) a method of irradiating an energy ray simultaneously with or after the phase separation between a liquid crystal material and a compound having an energy ray-curable functional group starts. This production method is also a preferable method because the effects of the present invention can be sufficiently exhibited. The lower limit of the temperature at which the energy beam is irradiated is a range in which the compound phase having the energy ray-curable functional group is in a liquid state.
At this time, the temperature may be lower than the temperature at which the liquid crystal material phase crystallizes, but is preferably a temperature at which the liquid crystal material phase is in a liquid crystal state. In this temperature range, a polymer network structure having a large average network size and uniform dimensions is fixed. When energy rays are irradiated at a temperature at which the liquid crystal material phase is in a crystalline state, the liquid crystal material phase tends to become independent particles.

The preferred cooling rate is at least 0.05 ° C. per second, more preferably at least 0.2 ° C. per second. The faster the cooling rate is, the more the uniform polymer network structure is fixed. The upper limit of the cooling rate is the same as in the case of (i), but the inconvenience of increasing the cooling rate is small, so that a higher cooling rate can be adopted as compared with (i) and (ii). .

In the production method (iii) of the present invention, irradiation with energy rays can be started simultaneously with the start of the phase separation.
The energy beam irradiation can be started at the time of growing to a size of about μm. The former is a preferable method when the energy ray intensity is high or when the cooling rate is low.

The time from the start of the phase separation to the irradiation of the energy beam is preferably within 30 seconds, more preferably within 10 seconds. If irradiation is carried out after an excessive time after the phase separation has occurred, a part of the liquid crystal material phase droplets generated by the phase separation will associate and grow into large diameter particles, and the size of the polymer network size after curing will be reduced. This is not preferable because the distribution tends to be large.

The method of lowering the temperature is arbitrary, and a method of bringing the formed light control layer forming material into contact with a low-temperature medium can be adopted. The medium can be a gas, liquid, solid, supercritical fluid, and the gas can be a gaseous atmosphere or a gas stream. The liquid may also be a liquid atmosphere or a liquid stream. Further, the medium to be contacted may be plural regardless of the kind, and may be contacted simultaneously or sequentially. For example, it may be a shower or a mist. The temperature of the medium does not necessarily have to be the target temperature for cooling the dimming layer forming material.For example, the medium is brought into contact with a medium having a temperature lower than the target temperature, and the energy beam is cooled before the dimming layer forming material is cooled to the medium temperature. Can be irradiated, or the temperature can be made higher by a method in which the medium is first brought into contact with a medium at a temperature lower than the target temperature and then brought into contact with the medium at the target temperature. Among them, a gaseous or solid medium is industrially preferable.

Examples of the gaseous medium include air, nitrogen, carbon dioxide, and argon. When the curing reaction is inhibited by oxygen, nitrogen, carbon dioxide, and argon are preferred. The liquid may be a liquefied gas at normal pressure. As a solid medium, chill roll can be preferably used.

The energy ray used may be any ray capable of curing a compound having an energy ray-curable functional group, and ultraviolet rays and visible rays can be preferably used. As the irradiation light source, for example, a device such as a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp or the like can be used. The intensity of the energy beam to be irradiated is preferably from 0.1~5000mW / cm ^2, the range of 10 to 1,000 / cm ² is particularly preferred. The irradiation time is also arbitrary, but is generally 0.1 to
A range of 100 seconds is preferred, and a range of 5 to 60 seconds is particularly preferred. The irradiation wavelength may be appropriately determined in consideration of curability, decomposability of constituent components, and the like. If the light modulating layer forming material contains a photopolymerization initiator, use energy rays that do not cure without the photopolymerization initiator but have a wavelength or intensity that cures in the presence of the photopolymerization initiator. Can also.

When the light modulating layer forming material is shaped so as to be sandwiched between two substrates, the irradiation of energy rays is performed through a transparent substrate. When the light modulating layer forming material is a liquid film coated on a substrate, the light modulating layer may be directly irradiated with energy rays, or may be irradiated through a transparent substrate.

In addition to light, energy rays such as electron rays, X-rays, gamma rays, and beta rays can also be used in the production method of the present invention. When these are used, since there is no need to add a photopolymerization initiator, there is no need to worry about adverse effects on electrical characteristics due to the photopolymerization initiator as an impurity, and the film forming speed is improved. Further, by adding an ultraviolet absorbing substance such as a dye to the light modulating layer forming material, the light modulating layer can be efficiently cured. However, industrially, ultraviolet light or visible light is the easiest to handle and useful.

When the polymerization is hindered by oxygen, the irradiation of energy rays is carried out in a non-oxygen atmosphere to increase the polymerization rate and the residual amount of the compound having an unreacted energy ray-curable functional group. It is possible to lower. As the non-oxygen gas, nitrogen, carbon dioxide, and argon are preferable.

In the manufacturing method of the present invention, the formed light modulating layer forming material is separated from a uniform isotropic liquid by a temperature drop, thereby separating a liquid crystal material phase and a compound phase having an energy ray-curable functional group. Can be confirmed by lowering the temperature under the same conditions under an optical microscope. At this time, it is observed that particles of the liquid crystal material phase are generated by lowering the temperature. However, since the liquid crystal material hardened by irradiation with energy rays is almost completely extracted by the solvent (for example, ethanol), the liquid crystal material is not completely extracted. In the cured state, although the liquid crystal material phase is observed in the form of particles, it can be seen that the liquid crystal material phase in the final molded product forms a continuous layer, in other words, the polymer phase has a network structure. . This can also be confirmed by observing the fracture surface of the final molded product with an electron microscope.

The average size of the mesh of the three-dimensional network formed of the transparent solid material is preferably in the range of 0.3 to 3 μm, more preferably in the range of 0.6 to 1.5 μm.

When the substrate is made of a flexible material such as a plastic film, the obtained liquid crystal device can be used after being fixed to a rigid material such as glass or metal.

[0049]

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples. However, the invention is not limited to these examples. In the following examples, "%" represents "% by weight", and each of the evaluation characteristics means the following symbols and contents.

As an ultraviolet light source, an exposure light source unit 200 manufactured by Ushio Inc. was used.

The intensity of the ultraviolet light was measured using a unimeter “UIT-101” manufactured by Ushio Inc. and a light receiving element “UVD-365P”.
D].

The average diameter and the variation coefficient (= standard deviation / average value) of the polymer network are SALD-2 manufactured by Shimadzu Corporation.
000 type light scattering measurement device.

T ₀ : turbidity; light transmittance (%) when applied voltage is 0 T ₁₀₀ : transparency; light transmittance (%) when light transmittance hardly increases as applied voltage is increased

The evaluated electrical characteristics are as follows. V ₁₀ : threshold voltage; applied voltage (V _rms ) at which light transmittance becomes 10% when T ₀ is 0% and T ₁₀₀ is 100% V ₉₀ : saturation voltage; light transmittance becomes 90% as above Applied voltage (V _rms )

Embodiment 1 Embodiment 1 is an example in which energy rays are irradiated while the temperature of the light control layer forming material is uniform and isotropic liquid while the temperature is lowered.

<Light control layer forming material> As a liquid crystal material, (A) a liquid crystal composition having the following composition (A) 70.0% (B) as a compound having an energy ray-curable functional group, isomiristyl acrylate (Kyoei Chemical Co., Ltd.) 45.2% Isocetyl acrylate (“TO-1336” manufactured by Toagosei Co., Ltd.) 44.8% 1,6-hexanediol diacrylate 9.6%, and (C) ultraviolet light As a polymerization initiator, 0.4% of benzyldimethyl ketal (“Irgacure 651” manufactured by Merck) was uniformly mixed at 35 ° C. to prepare a light modulating layer forming material.

<Composition of Liquid Crystal Composition (A)>:

[0058]

Embedded image

The physical properties of the liquid crystal composition (A) are as follows. Transition temperature 103.0 ℃ (N-I) refractive index _{n e = 1.777 n o = 1.513} Δn = 0.264 dielectric anisotropy [Delta] [epsilon] = 10.47 voltage holding ratio 99.7%

<Preparation of Uncured Sample>
At 5 ° C., between a glass substrate having two ITO electrodes coated with a 11.0 μ glass fiber spacer,
An uncured sample was produced by sandwiching the electrode inside.

<Measurement of Phase Separation Temperature> The uncured sample was placed on a metal temperature control stage, and the temperature was lowered at a rate of 2 ° C./min from 40 ° C. while observing with a polarizing microscope through an observation hole. At 1 ° C., phase separation was started, and fine particles showing nematicity appeared from an isotropic uniform liquid state. That is, the phase separation point of the light modulating layer forming material was 32.1 ° C.

<Ultraviolet curing> The temperature of the uncured sample prepared in the same manner as above was lowered on the temperature control stage. The temperature was lowered from 40 ° C. at a rate of 1 ° C./sec and maintained at a constant temperature of 20 ° C. When the temperature reached 35 ° C., the compound having an energy-ray-curable functional group was cured by irradiating ultraviolet rays at an angle of 45 ° on the upper surface of the sample for 60 seconds, to obtain a liquid crystal device. When the ultraviolet irradiation was started, the light modulating layer forming material was an isotropic uniform liquid.

<Measurement of Electrical and Optical Properties> The nematic / isotropic (NI) transition temperature of the liquid crystal material in the light control layer of the light scattering type liquid crystal device obtained as described above was measured. ° C. Table 1 shows the measurement results of the relationship between the applied voltage and the light transmittance of the liquid crystal device.

<Measurement of Phase Separation Structure> The average network size and variation coefficient (= standard deviation / average value) of the obtained liquid crystal device measured by the light scattering method are shown in Table 2.

When the glass substrate on which the electrodes were formed was broken in liquid nitrogen, the light control layer was exposed to the surface and washed with methanol. As a result, the liquid crystal material was almost completely washed out. This indicates that the liquid crystal material phase is a continuous layer. When this sample was observed with a scanning electron microscope (SEM), it was observed that the polymer phase had a three-dimensional network structure.

Example 2 Example 2 is an example of irradiating an energy ray at a temperature lower than the phase separation point but at a temperature at which the light modulating layer forming material is still an isotropic liquid phase while the temperature is lowered.

A liquid crystal device was obtained in the same manner as in Example 1 except that the irradiation of the energy ray was started when the temperature of the light control layer forming material reached 30 ° C. When the energy beam irradiation was started, the light modulating layer forming material was in an isotropic liquid phase.

Tables 1 and 2 show the electrical and optical characteristics and the polymer network size of the liquid crystal device obtained in Example 2 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Example 2 had a three-dimensional network structure as in Example 1.

[Embodiment 3] Embodiment 3 is an example in which an energy beam is irradiated after the phase separation of the light control layer forming material is started by lowering the temperature.

In Example 1, the cooling rate was set to 0.5
° C, and a liquid crystal device was obtained in the same manner as in Example 1 except that the energy ray irradiation was started when the temperature of the light control layer forming material reached 28 ° C. Note that under these temperature-lowering conditions, phase separation started at 30.5 ° C. That is, irradiation with energy rays was started 5 seconds after the start of phase separation. At the time of starting the energy beam irradiation, fine particles were generated in the light control layer forming material.

Tables 1 and 2 show the electrical and optical characteristics and polymer network dimensions of the liquid crystal device obtained in Example 3 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Example 3 had a three-dimensional network structure as in Example 1.

Example 4 Example 4 is an example in which the time from the start of the phase separation of the light modulating layer forming material due to the temperature decrease until the irradiation with the energy beam is slightly increased.

[0075] In the same manner as in Example 3 except that the ultraviolet irradiation was performed 10 seconds after the start of the phase separation,
A liquid crystal device was obtained.

Tables 1 and 2 show the electrical and optical characteristics and polymer network dimensions of the liquid crystal device obtained in Example 4 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Example 4 had a three-dimensional network structure as in Example 1.

Example 5 Example 5 is an example in which the time from the start of the phase separation of the light modulating layer forming material due to the temperature decrease until the irradiation with the energy beam is further extended.

Example 3 was repeated in the same manner as in Example 3 except that the ultraviolet irradiation was performed 20 seconds after the start of the phase separation.
A liquid crystal device was obtained.

Tables 1 and 2 show the electrical and optical characteristics and the polymer network size of the liquid crystal device obtained in Example 5, which were measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Example 5 had a three-dimensional network structure as in Example 1.

[Embodiment 6] Embodiment 6 is an example in the case where the cooling rate is high.

Example 3 was the same as Example 3 except that the temperature of the temperature control stage was kept constant at 10 ° C., the uncured sample at 40 ° C. was placed on the stage, and the ultraviolet irradiation was performed simultaneously with the start of the phase separation. Thus, a liquid crystal device was obtained. At this time, the time from placing the uncured sample on the stage until the start of phase separation was about 0.6 seconds. That is, the cooling rate is calculated as 16.7 ° C. per second. Since the temperature of the uncured sample is observed at the temperature of the temperature control stage, the temperature of the uncured sample at the start of the phase separation is unknown.

Tables 1 and 2 show the electrical and optical characteristics and the polymer network size of the liquid crystal device obtained in Example 6, which were measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Example 6 had a three-dimensional network structure as in Example 1.

[Example 7] In Example 7, a material for forming a light control layer was applied to the surface of one substrate, irradiated with energy rays, and then the other substrate was coated on the material for forming a light control layer. It is an example of the manufacturing method of stacking.

In Example 3, the light modulating layer forming material was applied to a thickness of 11.0 μ at 35 ° C. using a roller coater on the electrode side surface of the glass substrate having the ITO electrode. Example 3 was repeated except that a cured sample was prepared and the uncured sample was cured by ultraviolet irradiation, and then a glass substrate having another ITO electrode was brought into close contact with the cured sample with the electrode inside. A liquid crystal device was obtained in the same manner as described above.

Tables 1 and 2 show the electrical and optical characteristics and polymer network dimensions of the liquid crystal device obtained in Example 7 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light modulating layer of the liquid crystal device obtained in Example 7 had a three-dimensional network structure as in Example 1.

[Comparative Example 1] Comparative Example 1 is an example of a conventional technique in which an energy ray is irradiated at a constant temperature at which a light control layer forming material is a uniform isotropic liquid.

The procedure of Example 1 was repeated except that the temperature of the temperature control stage was adjusted to a constant temperature of 35 ° C., the uncured sample was set on the stage, and ultraviolet light was irradiated for 60 seconds from 1 minute later. In the same manner as in 1, a liquid crystal device was obtained. At this time, the dimming layer forming material at the start of ultraviolet irradiation is:
It was an isotropic homogeneous liquid state.

Tables 1 and 2 show the electrical and optical characteristics and polymer network dimensions of the liquid crystal device obtained in Comparative Example 1 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Comparative Example 1 had a three-dimensional network structure as in Example 1.

Comparative Example 2 Comparative Example 2 is an example in which the intensity of ultraviolet rays is increased in a conventional technique in which an energy ray is irradiated at a constant temperature at which a light control layer forming material is a uniform isotropic liquid.

In Comparative Example 1, the intensity of the ultraviolet light was set to 60 mw.
/ Cm ² and the UV irradiation time was 20 seconds
A liquid crystal device was obtained in the same manner as in Comparative Example 1.

Tables 1 and 2 show the electrical and optical characteristics and polymer network size of the liquid crystal device obtained in Comparative Example 2 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Comparative Example 2 had a three-dimensional network structure as in Example 1.

[Comparative Example 3] Comparative Example 3 is an example in which the intensity of ultraviolet rays is reduced in a conventional technique in which an energy ray is irradiated at a constant temperature at which a light control layer forming material is a uniform isotropic liquid.

In Comparative Example 1, the intensity of the ultraviolet light was 7 mw /
cm ² and the UV irradiation time was 180 seconds
A liquid crystal device was obtained in the same manner as in Comparative Example 1.

Tables 1 and 2 show the electrical and optical characteristics and polymer network dimensions of the liquid crystal device obtained in Comparative Example 3 measured in the same manner as in Example 1.

It was confirmed that the polymer of the light control layer of the liquid crystal device obtained in Comparative Example 3 had a three-dimensional network structure as in Example 1.

[0102]

[Table 1]

From the results shown in Table 1, the liquid obtained in each Example
The crystal device was compared with the liquid crystal device obtained in each comparative example.
And V₉₀And (V₉₀-V_Ten) Is obviously small
You. In particular, the liquid crystal device obtained in Example 1 has an equivalent average
Comparison with the liquid crystal device obtained in Comparative Example 1 having a mesh size
Then T₀It is clear that this is also low. Obtained in Example 6
Liquid crystal device is a comparative example with the same average mesh size
T compared to the liquid crystal device obtained in₀It is clear that it is also low
It is easy. The liquid crystal device obtained in Example 7 is
The liquid crystal device obtained in Comparative Example 3 having the same average mesh size
T compared to the chair ₀It is clear that this is also low. one
On the other hand, the liquid crystal devices obtained in each comparative example had the same average mesh size.
T compared to the liquid crystal device of the embodiment having a₀Is high
And V₉₀And (V₉₀-V_Ten) Is also clear
is there.

[0104]

[Table 2]

From the results shown in Table 2, the liquid crystal device obtained in Example 1 has a larger mesh size than the liquid crystal device obtained in Comparative Example 1 which is a conventional production method, despite having a larger average mesh size. It is clear that the coefficient of variation is small. Also,
It is clear that the liquid crystal devices obtained in Examples 2, 3 and 7 have a smaller network variation coefficient than the liquid crystal device obtained in Comparative Example 3 having a relatively close average network size.
Similarly, it is clear that the liquid crystal device obtained in Example 6 has a smaller network variation coefficient than the liquid crystal device obtained in Comparative Example 1 having a relatively close average network size. Furthermore, it is clear that the liquid crystal devices obtained in Examples 4 and 5 have a smaller network variation coefficient than the liquid crystal devices obtained in the respective comparative examples, despite the increased average network size.

On the other hand, it is clear that the liquid crystal device obtained in Comparative Example 1 has a large network variation coefficient despite its small average network size. Further, the liquid crystal device obtained in Comparative Example 2 has a reduced network variation coefficient as compared with Comparative Example 1, but
It is clear that the average mesh size is also reduced.
Further, it is clear that the liquid crystal device obtained in Comparative Example 3 has a large average network size and a large network variation coefficient.

As described above, from the results shown in Tables 1 and 2, it can be seen that, according to the method of manufacturing a light-scattering type liquid crystal liquid crystal device of the present invention, it is possible to manufacture a liquid crystal device having good light scattering properties. Is evident.

[0108]

According to the manufacturing method of the present invention, there is provided a liquid crystal device having a continuous layer of a liquid crystal material and a dimming layer made of a transparent solid substance existing in a three-dimensional network in the continuous layer. In addition, a liquid crystal device having a narrow distribution can be manufactured while keeping the mesh size of the transparent solid substance in the light control layer large, so that a liquid crystal device excellent in contrast and responsiveness can be provided.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masao Aizawa 8-2 Ayase, Hasuda-shi, Saitama F-term (reference) 2H089 HA04 JA04 KA08

Claims (6)

[Claims] (1) a first step of interposing a liquid crystal layer-forming material containing a liquid crystal material and a compound having an energy ray-curable functional group between two substrates, at least one of which has transparency; and (2) A second step of irradiating an energy ray through a substrate while lowering the temperature from a temperature at which the light modulating layer forming material exhibits an isotropic liquid phase, thereby polymerizing a compound having an energy ray-curable functional group. A light modulating layer supported between two substrates, comprising a continuous layer of a liquid crystal material and a transparent solid substance present in a three-dimensional network in the continuous layer of the liquid crystal material. A method for manufacturing a liquid crystal device having an optical layer. 2. A light modulating layer forming material containing a liquid crystal material and a compound having an energy ray-curable functional group is coated on one of two substrates, at least one of which has transparency. A first step to perform, (2) a compound having an energy ray-curable functional group by irradiating an energy ray to the material constituting the dimming layer while lowering the temperature from a temperature at which the dimming layer forming material exhibits an isotropic liquid phase. And (3) a third step of superimposing the other substrate on the polymerized light modulating layer forming material, wherein the light modulating layer is supported between the two substrates. A method for manufacturing a liquid crystal device having a continuous layer of a liquid crystal material and a dimming layer made of a transparent solid substance existing in a three-dimensional network in the continuous layer of the liquid crystal material. 3. The temperature decreasing rate is 0.05 to 100 per second.
0 ° C. range, and (2) the temperature at which the energy beam irradiation is started is measured in a temperature range in which the light modulating layer forming material is in an isotropic liquid phase and at a temperature decreasing rate of 2 ° C. per minute. 3. The method for manufacturing a liquid crystal device according to claim 1, wherein the temperature is equal to or lower than a phase separation starting temperature of the light modulating layer forming material. 4. An energy beam is irradiated after the liquid crystal material and the compound having an energy ray-curable functional group are separated by lowering the temperature from a temperature at which the light modulating layer forming material is an isotropic liquid phase. A method for manufacturing a liquid crystal device according to claim 1. 5. The method for manufacturing a liquid crystal device according to claim 1, wherein the irradiation of energy rays is started within 30 seconds after starting the phase separation. 6. The method according to claim 1, wherein the rate of temperature decrease from the temperature at which the liquid crystal material and the compound having an energy ray-curable functional group are compatible is in the range of 0.1 to 100 ° C./sec. The manufacturing method of the liquid crystal device described in the above.