JPH05107528A - Liquid crystal device and its production - Google Patents

Abstract

PURPOSE:To provide a liquid crystal device with which initial orientation or orientation for rewriting can be done only by heating and cooling without impressing an electric field. CONSTITUTION:This device consists of a pair of conductive substrates and a light-controlling layer between these conductive substrates. This light- controlling layer consists of a three-dimensional structure of liquid crystal material having positive dielectric anisotropy and polymer material. At least one of the conductive substrates is made as a transparent electrode, and the liquid crystal side of at least one substrate has a function to perpendicularly orient the liquid crystal. Thus, the liquid crystal part can be perpendicularly oriented without an electric field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to two kinds of liquid crystal states,
That is, the present invention relates to a liquid crystal device that controls light by utilizing an alignment state and a random state. Liquid crystal devices display information such as images by electrically or thermally controlling the optical properties of part or all of the area inside the device, that is, the transmission, absorption, confusion, reflection, etc. of light. And
It is used as an electronic display, a still image display medium, and a memory medium.

[0002]

2. Description of the Related Art As a conventional thermal writing phase transition type liquid crystal light modulating device, one in which a smectic liquid crystal material is sandwiched between two substrates subjected to alignment treatment is known. This liquid crystal device has an alignment order in a smectic phase and is transparent as a light source by subjecting a liquid crystal side substrate to a vertical alignment treatment with an aligning agent. When the liquid crystal layer is heated to the phase transition temperature or higher to be in the I phase state and then rapidly cooled to be in the smectic phase state, the light scattering state in which the distribution is disordered does not return to the transparent state. The temperature rising and quenching cycles are caused by absorption of laser light at the time of writing an image or heating by a heating element or the like patterned on the device, so that the contrast of the liquid crystal device largely depends on the scattering ability of the light scattering state. Therefore, in the liquid crystal device having the above structure, the scattering ability needs to depend only on the disorder of the alignment of the liquid crystal, and there is a problem that the maximum contrast is about several tens to one.

Therefore, in order to make up for the drawback of the light modulation device that the contrast is low, there has been proposed a liquid crystal device in which encapsulated liquid crystal is dispersed in a polymer to form a film as a light control layer (liquid crystal layer) (Japanese Patent Laid-Open No. 58-58). -50163
1, USP 4435047). In this liquid crystal device, the liquid crystal enclosed in the capsule has a positive dielectric anisotropy, and the alignment vector is aligned in the direction of the electric field in the electric field of the nematic phase, and the refractive index no of the liquid crystal and the polymer When the refractive indices np are equal, the film becomes transparent.
When the electric field is removed, the liquid crystal becomes a random arrangement, and the liquid crystal droplets scatter light at the boundary surface and block the transmitted light, so that the film becomes cloudy. When the electric field is removed, the transparent state rapidly transitions to the clouded state. However, when cooled to the smectic A state while maintaining the electric field, the alignment vector alignment is almost maintained, and even if the electric field is removed, the transparent state is transparent. The condition persists. On the other hand, in the case where the nematic phase is in a cloudy state, the film remains cloudy even in the smectic state A by cooling.

Also in this liquid crystal device, an image is written by absorption of laser light or heating by a heating element or the like patterned on the device, similarly to the above-mentioned thermal writing phase transition type liquid crystal light modulation device. Here, since the scattering ability in the light-scattering state is amplified by the effect of the interface between the liquid crystal and the resin, the maximum contrast can be about 100: 1. Further, by adding a dichroic dye to the liquid crystal material, it can be used as a reflection type light modulation device or a transmission type light modulation device having a higher contrast or a higher color selectivity.

[0005]

However, according to the liquid crystal device having the above structure, the liquid crystal droplets are only dispersed in the polymer, and the material or treatment for giving the initial alignment is not performed. When applying or rewriting an image, there is a problem that a complicated process of heating while applying an electric field to the entire device must be performed. Further, even if the substrate is subjected to the alignment treatment, the liquid crystal is encapsulated in the capsule, so that the effect is limited to only near the surface of the substrate, and it is necessary to apply an electric field when rewriting an image. Furthermore, in order to hold the alignment of the liquid crystal in the smectic phase, an applied voltage (holding electric field) that exceeds the change in the alignment is required. Therefore, it is necessary to increase the breakdown voltage against the electric field as compared with the conventional liquid crystal device, and when impurities are mixed in the liquid crystal, there is a problem that a short circuit due to application of a high voltage is likely to occur.

The present invention has been made in view of the above circumstances, and the initial orientation and the orientation at the time of rewriting can be performed only by heating and cooling without applying an electric field, so that the operation of the orientation state and the random state can be performed. It is intended to provide an easy liquid crystal device.

[0007]

In order to solve the above-mentioned problems of the conventional example, a liquid crystal device of the present invention comprises a pair of conductive substrates, a liquid crystal material having a positive dielectric anisotropy and a polymer material. And a light control layer held between the conductive substrates in a three-dimensional manner, and at least one of the conductive substrates is a transparent electrode, and the liquid crystal on the liquid crystal side surface of at least one of the conductive substrates. It is characterized by having the vertical alignment ability of. The polymer material in the present invention is composed of a polymeric material or a polymerizable compound or a polymerizable mixture capable of becoming a polymeric material.

Specific polymeric materials include, for example, polyacetal, polyacrylamide, polyacrylate, polyacrylonitrile, polyimide, polyarabinogalactan, polybenzimidazole, poly (benzyl methacrylate), poly (4-bromostyrene). , Poly (butadiene), poly (butadiene) diol, poly (1-butene), poly (butyl acrylate), poly (1,4-butylene terephthalic acid), poly (butyl methacrylate), poly (4-ter- Butylstyrene), poly (caprolactane), poly (caprolactane) diol, poly (caprolactane) triol, polycarbonate, polychloroprene, poly (4-chlorostyrene), poly (cyclohexyl methacrylate), poly (diallyl isophthalate), poly ( Diary phthalate ), Poly (dimethylsiloxane), poly (epichlorohydrin), poly (ethyl acrylate), polyethylene, poly (ethylene oxide), poly (ethylene terephthalate), poly (ethylene imine), poly (acrylic acid 2-
Ethylhexyl), poly (2-ethylhexyl methacrylate), polygalactan, poly (hexadecyl acrylate), poly (hexamethylene dodecanediimide), poly (hexamethylene nonanediimide), poly (hexyl methacrylate), poly (hydroxy methacrylate) Ethyl), poly (isobornyl methacrylate), poly (isobutylene) poly (isobutyl methacrylate), poly (lauryl lactam), poly (lauryl methacrylate), poly (methyl acrylate), polymethylsiloxane, poly (methyl methacrylate) ), Poly (4-methyl-1-pentane), poly (α-methylstyrene), poly (4-methylstyrene), poly (octadecyl methacrylate), polyoxyethylene acetyl ether, polyoxyethylene lauryl ether Tell, Polio Ethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxymethylene, poly (propylene), poly (styrene), poly (tetrafluoro Ethylene), poly (undecane amine), poly (vinyl acetate), poly (vinyl alcohol), poly (4
-Vinyl biphenyl), poly (vinyl butyral), poly (9-vinyl butyral), poly (9-vinyl carbazole), poly (vinyl chloride), poly (vinyl cinnamate),
Poly (vinyl ethyl ether), poly (vinyl former)
), Poly (vinyl isobutyl ether), poly (vinyl methyl ether), poly (vinyl methyl ketone), poly (2-vinylnaphthalene), poly (vinyl pyrrolidone), poly (vinyl vinyl propionate), poly (vinyl) Pyridine borane), poly (vinyl stearate), poly (vinyltoluene) and the like. As the polymer material, the above materials may be used alone, as a mixture, or as a copolymer.

The polymerizable composition in the present invention comprises a monomer and an oligomer having a polymerizable functional group and, if necessary, a reaction initiator, a sensitizer, a continuous transfer agent and the like.

Examples of the polymerizable compound that can be used in the present invention include vinyl acetate, acrylonitrile, styrene, vinyltoluene, maleic acid, itaconic acid, acrylamide, N-methylolacrylamide, diacetoneacrylamide, 1 , 3-Butadiene, methyl, ethyl, i-propyl, t-butyl as a substituent,
Amyl, 2-ethylhexyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-hexadecyl, n-octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, allyl, methallyl , Lauryl, grindil, 2-
Acrylic acid, methacrylic acid, fumaric acid, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butylene glycol, tetramethylene glycol having a group such as hydroxyethyl. , Mono (meth) acrylic acid esters such as hexamethylene glycol, trimethylol ropane, glycerin and pentaerythritol, or poly (meth) acrylic acid esters vinyl acetate, vinyl butyrate or vinyl benzoate.

Acrylonitrile, acetyl vinyl ether, limonene, cyclohexene, diallyl phthalic acid, diallyl isophthalic acid, 2,3- or 4-vinyl viridine,
Acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-hydroxymethyl acrylamide or N-
Hydroxyethyl acrylamide and their alkyl ether compounds, neopentyl glycol or 1,6-
Di (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of hexanediol, trimethylolpropane 1
Di- or tri (meth) acrylate of triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of bisphenol A, and 2 moles or more of ethylene oxide or propylene oxide per mole of bisphenol A. Di (meth) acrylate of diol obtained by addition, 2
-The reaction product of 1 mol of hydroxyethyl (meth) acrylate and 1 mol of phenyl isocyanate or n-butyl isocyanate, poly (meth) acrylate of dipentaerythritol, long chain Fatty acid diacrylate, aliphatic triacrylate, caprolactone-modified hydroxybivalic acid ester neobentyl glycol diacrylate, tricyclodecanedimethyl diacrylate,
Tris (acryloxyethyl) isocyanurate, polyolefin modified neopentyl glycol diacrylate
You can raise Particularly, a polymerizable compound having two or more (meth) acrylic double bonds is preferable.

Examples of the polymerization initiator that can be used in the present invention include 2-hydroxy-2-methyl-1-
Phenylproban-1-on (Merck's "Darocur 1
173 ",) 1-hydroxycyclohexyl phenyl ketone (" Irgacure 18 "manufactured by Ciba-Geigy)
4 "), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one (" Darocure 1116 "manufactured by Merck & Co., Inc.), benzyl dimethyl ketal (" Irgacure 651 manufactured by Ciba-Geigy "). )) 2-Methyl-1-
[4 (Methylthio) phenyl] -2-morpholinopropanone-1 (“Irgacure 90” manufactured by Ciba-Geigy)
7 "), 2,4-diethylthioxanthone (" Kayacure DETX "manufactured by Nippon Kayaku Co., Ltd.), p-dimethylaminobenzoic acid, (" Kayacure EPA "manufactured by Nippon Kayaku Co., Ltd.), isopropyl thioxanthone (Ward Prekinsop"" Cantacure ITX ") and the like. In particular, liquid 2-hydroxy-2-methyl-1-phenylpropane-1-
ON is preferable in terms of compatibility with the liquid crystal material. Suitable chain transfer agents optionally used in the present invention include butanediol-dithiopropineate, pentaerythritol-tetrakias (β-thiopropineate), triethylene glycol-dimercaptan and the like.

The liquid crystal material used in the present invention exhibits a nematic phase having a positive dielectric constant anisotropy at a high temperature exceeding the use temperature and a smectic A phase at the use environment temperature, and has a liquid crystal concentration of 60% by weight. It is preferable to make it compatible with the polymerizable composition so as to be at least%. Such a liquid crystal material is a commercially available liquid crystal material, for example, BDH as shown in Table 1.
Manufactured by S1, S2, S2C, S3, S4, S5, S6, S
7 or the like is appropriately selected and used. K-S, SN in the table,
NI indicates a phase transition temperature when changing from a solid state to a smectic phase, from a smectic phase to a nematic phase, and from a nematic phase to an I phase.

[0014]

[Table 1]

Further, the liquid crystal materials shown in Table 2 may be appropriately mixed and used, and a chiral component may be added if necessary.

[0016]

[Table 2]

As the two conductive substrates, for example, a plastic film or the like can be used, and when the liquid crystal device is driven by an electric field, electrodes are formed on the inner surface of each substrate. At least one surface of the electrode surface in contact with the light control layer made of a liquid crystal material and a polymer material has a vertical alignment ability. In order to have the vertical alignment ability, (1) the surface of the conductive substrate is coated with resylene, (2) the surface of the conductive substrate is treated with a silane coupling agent or a higher alkylamine, (3) the surface of the electrode or There is a method such as using polypropylene in which carbon black is dispersed as the electrode itself. In particular, the polypropylene having the carbon black (3) dispersed therein is effective because of its strong orientation ability.

The liquid crystal device of the present invention is composed of a liquid crystal material having a positive dielectric anisotropy and a polymer material, between a pair of conductive substrates having at least one conductive surface capable of vertically aligning liquid crystals. By sandwiching the high temperature compatible material, the polymer material is phase-separated from the liquid crystal material by cooling to form a microstructure in which the liquid crystal material and the polymer material are three-dimensionally interconnected,
At the same time, the liquid crystal is vertically aligned to be manufactured.

As another manufacturing method, a liquid crystal material having a positive dielectric anisotropy is polymerized with a liquid crystal material having a positive dielectric anisotropy between a pair of conductive substrates in which at least one conductive surface has a liquid crystal vertical alignment capability. A mixture with a polymerizable composition that becomes a polymer material is sandwiched, and the polymerizable composition is polymerized to be phase-separated from the liquid crystal material as a polymer material while maintaining the temperature below the N (phase) -I (phase) transition temperature of the liquid crystal. This is performed by forming a microstructure in which a material and a polymer material are interconnected three-dimensionally, and at the same time vertically aligning the liquid crystal. Polymerization in which the polymerizable composition is phase-separated from the liquid crystal material as a polymer material is performed while keeping the liquid crystal composition at the NI transition temperature or lower. To interpose the mixture between the two conductive substrates, it may be performed by injecting a mixed solution between the substrates, but it is applied on one substrate using a coater such as a spinner or a bar coater, Then, the other substrate may be arranged so as to be stacked.

[0020]

According to the liquid crystal device of the present invention, since the liquid crystal material and the polymer material are three-dimensionally interconnected to form a microstructure, the electrode surface has a large area in direct contact with the liquid crystal surface. , Because the liquid crystal forms a continuous phase over a wide range, the alignment ability of the electrode surface propagates throughout the liquid crystal,
Vertical alignment of the liquid crystal portion can be easily realized by a very weak electric field as compared with the case without the electric field or the case where the alignment treatment is not performed. For example, in a conventional resin-dispersed liquid crystal display using a smectic liquid crystal, in order to realize vertical alignment in the smectic A phase by cooling from the nematic phase, when the liquid crystal layer thickness is 20 to 30 μm, 2
It was necessary to apply an AC voltage of 0 to 30V. On the other hand, in the liquid crystal device of the present invention, vertical alignment can be realized by applying a voltage of at most about several V with almost no electric field.

[0021]

EXAMPLES Specific examples of the present invention will be described below. In the first example, 80% by weight of a cyanobiphenyl-based smectic liquid crystal mixture (“S2” manufactured by BDH) as a liquid crystal material and 2-hydroxy-2-methyl-1-phenylpropan-1-one (as a polymerization initiator) 0.4% by weight of "Darocur 1173" manufactured by Merck Japan Co., 19.6% by weight of 1,6-hexanediol diacrylate ("Kayarad HDDA" manufactured by Nippon Kayaku Co., Ltd.) as a polymer compound, and as a spacer for the mixture. A small amount of glass filler having an average particle size of 17 μm was added, and the mixture was treated by an ultrasonic cleaner for 10 minutes and mixed. The liquid after mixing was uniform and transparent, and it could be confirmed that the liquid crystal material and the polymerizable compound were completely dissolved. Silane coupling agent (Dow Corning D
C5700) 2 electrodes 50mm x 50 which treated the electrode surface
The liquid was inserted between ITO (indium tin oxide) glass plates having a size of mm, the entire ITO glass plate was kept at 35 ° C., and the entire ITO glass plate was uniformly irradiated with ultraviolet rays for curing. The electrode spacing of the liquid crystal device is 20 μm. The device, in which the resin component in the solution was cured by the irradiation of ultraviolet rays, became uniformly transparent over the entire surface of the ITO glass. When the liquid crystal device was locally heated by scanning with laser light and then rapidly cooled, it became cloudy and opaque. When the whole was further heated and then cooled, it became transparent again.

In the second embodiment, as a liquid crystal material, a cyanobiphenyl-based smectic liquid crystal mixture (“S” manufactured by BDH) is used.
2 ") 80% by weight, 2-hydroxy-
0.4% by weight of 2-methyl-1-phenylpropan-1-one (“Darocur 1173” manufactured by Merck Japan Ltd.),
As a polymer compound, 1,6-hexanediol diacrylate (“Kayarad HDDA” manufactured by Nippon Kayaku Co., Ltd.) was used.
A small amount of 6 wt% of a glass filler having an average particle size of 17 μm was added as a spacer for the mixture, and the mixture was treated by an ultrasonic cleaner for 10 minutes and mixed. The liquid after mixing was uniform and transparent, and it could be confirmed that the liquid crystal material and the polymerizable compound were completely dissolved. The liquid was inserted between a 50 mm × 50 mm ITO (indium tin oxide) glass plate and a carbon black-dispersed polycarbonate film, and ultraviolet rays were uniformly applied to the entire ITO glass plate to cure it. The electrode spacing of the liquid crystal device is 20 μm. The device, in which the resin component in the solution was cured by the irradiation of ultraviolet rays, became uniformly transparent over the entire surface of the ITO glass. When the liquid crystal device was locally heated by scanning with laser light and then rapidly cooled, it became cloudy and opaque. When the whole was further heated and then cooled, it became transparent again.

In the third embodiment, as a liquid crystal material, a cyanobiphenyl-based smectic liquid crystal mixture (“S” manufactured by BDH) is used.
2 ") 80% by weight, 2-hydroxy-
0.4% by weight of 2-methyl-1-phenylpropan-1-one (“Darocur 1173” manufactured by Merck Japan Ltd.),
As a polymer compound, 1,6-hexanediol diacrylate (“Kayarad HDDA” manufactured by Nippon Kayaku Co., Ltd.) was used.
A small amount of 6 wt% of a glass filler having an average particle size of 17 μm was added as a spacer for the mixture, and the mixture was treated by an ultrasonic cleaner for 10 minutes and mixed. The liquid after mixing was uniform and transparent, and it could be confirmed that the liquid crystal material and the polymerizable compound were completely dissolved. Two 50 mm x 50 mm ITO (indium oxide.
The liquid was inserted between tin) glass plates, the entire ITO glass plate was kept at 35 ° C., and the entire ITO glass plate was uniformly irradiated with ultraviolet rays for curing. The electrode spacing of the liquid crystal device is 20 μm. The device, in which the resin component in the solution was cured by the irradiation of ultraviolet rays, became uniformly transparent over the entire surface of the ITO glass. When the liquid crystal device was locally heated by scanning with laser light and then rapidly cooled, it became cloudy and opaque. When the whole was further heated and then cooled, it became transparent again.

In the fourth embodiment, as a liquid crystal material, a cyanobiphenyl-based smectic liquid crystal mixture (“S” manufactured by BDH) is used.
2 ") 80% by weight, 2-hydroxy-
0.4% by weight of 2-methyl-1-phenylpropan-1-one (“Darocur 1173” manufactured by Merck Japan Ltd.),
As a polymer compound, 1,6-hexanediol diacrylate (“Kayarad HDDA” manufactured by Nippon Kayaku Co., Ltd.) was used.
6% by weight, anthraquinone-based dye (“LCD121” manufactured by Nippon Kayaku Co., Ltd.) 0.1% as a dichroic dye, and a small amount of a glass filler having an average particle size of 17 μm as a spacer of the mixture, and treated with an ultrasonic cleaner for 10 minutes. And mixed. The liquid after mixing was a uniform, transparent solution colored in blue, and it was confirmed that the liquid crystal material and the polymerizable compound were completely dissolved. Two 50mm with the electrode surface treated with lecithin
The above liquid is inserted between ITO glass plates of 50 mm x 50 mm, and the entire ITO glass plate is kept at 35 ° C.
Then, the entire ITO glass plate was uniformly irradiated with ultraviolet rays for curing. The electrode spacing of the liquid crystal device is 20 μm. The device, in which the resin component in the solution was cured by the irradiation of ultraviolet rays, became uniformly transparent over the entire surface of the ITO glass. When the liquid crystal device was locally heated by scanning with laser light and then rapidly cooled, a blue state was obtained. When the whole was further heated and then cooled, it became transparent again.

According to the above-described embodiment, the light control layer sandwiched between the conductive substrates is made of a liquid crystal in a transparent state in which a liquid crystal material having a positive dielectric anisotropy and a polymer compound are mixed. Since it is cured between the conductive substrates having the vertical alignment ability, the light control layer can maintain the transparent state.
The light control layer can be controlled to be transparent or opaque only by heating or cooling without applying an electric field.

[0026]

According to the present invention, the initial alignment of liquid crystal and the alignment at the time of rewriting can be performed only by heating and cooling without applying an electric field. Therefore, the liquid crystal has flexibility, high definition, high resolution and a large area. It is possible to obtain a liquid crystal device that is easy to manufacture, has a memory property, and is easy to operate. Further, according to the method of the present invention, the liquid crystal device having the above structure can be easily manufactured.

Claims (3)

[Claims] 1. A pair of conductive substrates, and a light control layer in which a liquid crystal material having a positive dielectric anisotropy and a polymer material are three-dimensionally intertwined with each other and held between the conductive substrates. Then
A liquid crystal device, wherein at least one of the conductive substrates is a transparent electrode, and the surface of at least one of the conductive substrates on the side of the light control layer has a vertical alignment capability of the liquid crystal. 2. A high temperature compatible material composed of a liquid crystal material having a positive dielectric anisotropy and a polymer material is provided between a pair of conductive substrates having at least one conductive surface capable of vertically aligning liquid crystals. A liquid crystal characterized in that the polymer material is phase-separated from the liquid crystal material by sandwiching and cooling to form a microstructure in which the liquid crystal material and the polymer material are interconnected three-dimensionally, and at the same time, the liquid crystal is vertically aligned. Device manufacturing method. 3. A polymerizable composition which becomes a polymer material by a polymerization reaction with a liquid crystal material having a positive dielectric anisotropy between a pair of conductive substrates in which at least one conductive surface has a vertical alignment ability of liquid crystal. The polymerizable composition is phase-separated from the liquid crystal material as a polymer material by polymerizing while keeping the mixture below the NI transition temperature of the liquid crystal, and the liquid crystal material and the polymer material are interconnected three-dimensionally. A method for manufacturing a liquid crystal device, which comprises forming a microstructure having the above structure and at the same time vertically aligning the liquid crystal.