JP3308353B2 - Liquid crystal optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / scattering type liquid crystal optical element suitable for multiplex driving.

[0002]

2. Description of the Related Art Three modes of a liquid crystal optical element based on the principle of light scattering are known: dynamic scattering (DS), phase transition (PC), and polymer dispersion type.

[0003] DS mode, between the transparent electrode-bearing substrate, which dielectric anisotropy adding a conductive material enclosing a negative liquid crystal and a transparent state where no voltage is applied, it is higher than the threshold voltage the voltage and a state with reduced transparently rate to cause dynamic scattering by application of, and controls the two-state.

[0004] PC mode, a cholesteric liquid crystal sealed between the transparent electrode-bearing substrate oriented treatment if necessary, by the presence or absence of the voltage application, the nematic phase of the homeotropic alignment (the transmission), the focal-conic or planar orientation cholesteric phase of the (scattered), and controls the two-state.

The polymer-dispersed liquid crystal uses a composite of liquid crystal and polymer for an optical element, and has various modes. In particular, RAMHikmet, J. Appl. Phys., 68 (9) 4406 (1
990), and the method disclosed in JP-A-4-227684 discloses the addition of 1-10 wt% of acrylate to nematic liquid crystal, forming a so-called anisotropic gel, sandwiched it between the transparent electrode-bearing substrate In addition, two states, transmission when no voltage is applied and scattering when a voltage is applied, are controlled.

In the case of a liquid crystal electric element of a type in which liquid crystal molecules are dispersed and held in a matrix of a relatively large amount of polymer, a scattering state is created by a difference in refractive index between the liquid crystal and the polymer. Rather, the scattering-transmission state is created by the difference in the alignment state of the liquid crystal, and it can be said that the polymer plays the role of fixing the alignment and increasing the degree of scattering in the scattering state.

[0007] In this way, by forming the anisotropic gel in the liquid crystal in the form of e Meotoropikku, the state of non-voltage application becomes a scattering state, the voltage application state becomes a transparent state.

[0008]

A common problem with each of the above modes is that they are not suitable for multiplex driving. In order to perform multiplex driving, the voltage-transmittance curve is steep,
Or it is necessary to have a bistability with a memory characteristic. However, in any of the modes, the steepness when realigning the liquid crystal by applying a voltage is not sufficient, and it cannot be said that the mode substantially has a memory property.

It has been reported that the PC mode may have a slight memory property. In other words, the nematic phase of the homeotropic arrangement in the PC mode has an imperfect but nematic memory depending on the pitch, and when the applied voltage is suddenly reduced to a voltage lower than the rising voltage of the liquid crystal, the nematic phase takes about several milliseconds to several seconds. The phases are maintained and a bistable state is formed. However, since the pitch or the like has a memory property only under specific conditions, there is a problem that the degree of freedom in element design for adjusting hue in a scattering state, adjustment of a driving voltage, and the like is small. For example, in the PC mode, it is assumed that the transmission scattering control is performed by using Proceedings of the SID,
Publications such as Vol. 26, No. 4, p. 243, 1985. are known. In this mode, scattering when no voltage is applied is not sufficient,
In other words, there is a drawback that a high transmittance in the off, In order to improve this, a shorter pitch length of Nejirenema tee click alignment of the liquid crystal, or a method such as increasing the Thickness of the liquid crystal layer Although it is conceivable, in this case, it is difficult to keep the memory property stable.

As described above, in the PC mode, it is difficult to display a large-capacity display with good contrast unless active driving using a TFT or the like is performed.

Further, the polymer dispersed liquid crystal has a higher degree of scattering at the time of scattering than the PC mode, but has a disadvantage that the driving voltage is increased. This is because the voltage drop between the substrates is consumed in the polymer portion. Therefore, in the multiplex driving of particular pulse application needs, but ing to apply a very high voltage, the driving IC capable of withstanding such voltages are at present very few. As described above, the height of the driving voltage is a unique and essential problem for the liquid crystal element containing a polymer.

[0012]

According to the present invention, there is provided a liquid crystal optical element having a nematic liquid crystal, a chiral nematic liquid crystal or a cholesteric liquid crystal interposed therebetween, the liquid crystal being generated when a voltage higher than a rising threshold voltage of the liquid crystal is applied. A polymer that is used to stabilize the homeotropic alignment state of the liquid crystal is dispersed in the liquid crystal to improve the steepness of the rising of the liquid crystal, and the homeotropic state of the liquid crystal generated when a voltage higher than the threshold voltage is applied. Provided is a liquid crystal optical element that has a memory property in a homeotropic alignment state by stabilizing a tropic alignment state and increases a difference (hysteresis) between a rising threshold voltage and a falling threshold voltage of a liquid crystal. The purpose is to:
According to the present invention, sufficient memory bistable type transmission having - after scattering-type device can be obtained, the driving voltage becomes possible to suppress the scattering - transmission type display device, in particular, of paper white It is possible to make practical use of a reflective large-capacity display element having a background color.

That is, the present invention provides at least one substrate with a plurality of electrodes on which vertical alignment processing has been performed, a liquid crystal layer sandwiched between the substrates and having a positive dielectric anisotropy and having a spontaneous twisting property, Alignment means for aligning the liquid crystal molecules in a direction substantially perpendicular to the substrate over the entire thickness direction of the liquid crystal layer,
By adjusting the alignment regulating force of the alignment means with respect to the spontaneous twisting force of the liquid crystal layer to a predetermined strength, when a saturation voltage is applied between the electrodes, the liquid crystal layer substantially takes on homeotropic alignment, When no voltage is applied between the electrodes, a substantially twisted orientation is taken. When a predetermined intermediate voltage smaller than the saturation voltage is applied between the electrodes, the memory property between the homeotropic orientation and the twisted orientation is obtained. And the orientation means comprises a group
After adding the polymer material to the liquid crystal layer sandwiched between the plates,
With the liquid crystal layer in homeotropic alignment, the polymer
It is intended to provide a liquid crystal optical element obtained by curing a material .

The liquid crystal material used in the present invention does not need to be a single liquid crystal compound, but may be a mixture containing two or more liquid crystal compounds or a substance containing a substance other than the liquid crystal compound. Any material that is recognized as a liquid crystal material in the technical field may be used. Among them Ru der those having a positive dielectric anisotropy. As the liquid crystal used, those having a twisted structure, smectic liquid crystal, nematic liquid crystal, chiral nematic liquid crystal, cholesteric liquid crystal is desirable, in particular, chiral nematic liquid crystal is desirable. To improve the performance, a cholesteric liquid crystal, and a chiral smectic liquid crystal or the like, dichroic dye, conventional dyes, pigments and the like may be contained as appropriate.

The liquid crystal material used in the present invention is desirably a compounded composition comprising at least one compound selected from the group of compounds shown below, and the properties of the liquid crystal, such as the phase transition temperature between an isotropic liquid and a liquid crystal, Melting point, viscosity, refractive index anisotropy (Δn),
It is desirable to appropriately select and use it for the purpose of improving the dielectric anisotropy (Δε), the solubility with the polymer material to be dispersed, and the like. Then, the response characteristic of the liquid crystal optical element in which, in consideration of characteristics such as rise threshold voltage, likewise the chiral substance also shown below were added and mixed a cholesteric liquid crystal, it is desirable to use as the chiral nematic liquid crystal.

[0016] In this case, that the twist pitch of the liquid crystal molecules after the addition and mixing is less than or equal to 10 times the Thickness of the liquid crystal layer,
It is desirable from the characteristics of the liquid crystal optical element, such as the response characteristics and the steepness of the rise, and more desirably 0.5 times or less from the viewpoint of the scattering ability (white turbidity) when a voltage equal to or lower than the liquid crystal rise threshold voltage is applied.

When the pitch exceeds 0.8 μm, and preferably exceeds 1.0 μm, almost white light is scattered. Therefore, depending on the applied voltage, two states, a white scattered state and a transparent state, may be taken. become able to. On the other hand, when the pitch is 0.2 μm to 0.8 μm, selective reflection occurs due to the pitch, and two states of a colored scattering state and a transparent state can be obtained by applying an applied voltage.

[0018] As the liquid crystal material, for example, 4-substituted benzoic acid 4-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted-4-biphenylene Li glycol 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, 1- ( 4-substituted phenyl ) -4 -substituted cyclohexane, 4-substituted 4 "-substituted terphenyl, 1- (4' -substituted
4-biphenyl Li Le) -4 - substituted cyclohexane, 2-
(4-substituted phenyl) 5-substituted pyrimidine and the like.

As the chiral substance, a chiral nematic liquid crystal is generally used, and 4 ′-(optically active (hereinafter abbreviated to) 2-methylbutyl) -4-cyanobiphenyl,
4 '-(3-methylpentyl) -4-cyanobiphenyl, 4'-(2-methylbutoxy) -4-cyanobiphenyl , 4- (2-methylbutyl) benzoic acid 4 -cyanophenyl ester, 4- (2- Methylbutoxy) benzoic acid
4-cyanophenyl ester, 4- (2-methylbutoxy) benzoic acid 4'-cyano-4-biphenylene Li glycol ester, 4- (2-methylbutoxy) benzoic acid 4'-cyano
-4-biphenylene Li glycol ester, 4- (p-2-methylstyrene-butylphenyl) - 4'-cyano biphenyl, 4- (2-
Methylbutyl) cyclohexanecarboxylic acid 4' -cyano
-4-biphenylene Li glycol ester, 4-alkoxy-4'
(2-methylbutyl) azoxybenzene, 4- alkyl Le
Off Eniru benzoic acid 2 Mechirubuchi Rue ester, 4-al <br/> Koki Schiff Eniru benzoic acid 2 Mechirubuchi Rue ester and the like.

Cholesteric liquid crystals include cholester chloride
Terol, fatty acid cholesterol ester, nonanoic acid
Lesterol, cholesterol acetate, alkyl carbonate
Sterol ester, methyl cholesterol carbonate, carbonic acid
Ethyl cholesterol, cholesterol benzoate, benzoate
Δ5,6-cholesten-3β-ol perfume, p (Or
o, m) -Substituted benzoic acid cholesterol ester, p-
Cholesterol methoxybenzoate, p-aminobenzoic acid
Cholesterol, phenyl fatty acid and its derivatives
Sterol ester, cholesterol p-aminocinnamate
, Sitosterol ester, butyric acid citrate, repose
Perfumed acid (OrIts derivatives) cholestanol esters,
Cholestanol benzoate, cholestadienes of benzoic acid
Tell, etc.

As the alignment means of the present invention, any material can be used as long as it is substantially transparent and does not extremely hinder the operation of liquid crystal molecules. From this viewpoint, it is preferable that a certain amount of a polymer material is dispersed in the liquid crystal layer. The alignment means of the present invention needs to have an alignment force for aligning the liquid crystal molecules in a direction substantially perpendicular to the substrate. Such alignment force, a polymer material, was added to the liquid crystal layer, also to cure the polymeric material in a state in which the liquid crystal layer took homeotropic orientation by a gel, a polymer material kill is granted.

[0022] That is, the voltage on the saturation electric pressure of the rising of the liquid crystal is applied to the mixture was held on the substrate, after the liquid crystal in homeotropic alignment, also EXPOSURE This <br/> and equal for heating Thereby, a polymer acting on the liquid crystal is dispersed in the liquid crystal so as to stabilize the homeotropic alignment of the liquid crystal. Note that the Kokodei intends EXPOSURE generally ultraviolet radiation, or an electron beam irradiation. When the heating is performed, it is preferable to perform the heating at a temperature lower than the phase transition temperature of the liquid crystal.

The polymer thus obtained has a regulating force on the liquid crystal so that the liquid crystal is stabilized in a homeotropic state.

[0024] when a voltage is not applied by spontaneous twisting power of the liquid crystal, disordered focal conic alignment or show a strong scattering state resulting cholesteric equality of planar orientation (cloudy). When a voltage is applied, a homeotropic arrangement is obtained in any case, and the transmittance increases.

At this time, since the homeotropic alignment state is stabilized by the action of the alignment means as compared with the case where no polymer is contained, the rising threshold voltage is lowered and the rising steepness is improved. by this,
There is an improvement in the contrast when time-division driving is performed.

[0026] As the polymer compound of the photocurable or you can use a thermosetting compound. When a photocurable compound is used, a photocuring initiator may be added to increase the curing speed. In particular, as long as it can photocuring by radical species, kill appearance quality, the excellent device reliability by creating.

When a photocurable compound is used, for example, a photocurable vinyl compound is preferably used. The photocurable vinyl compound, when large another, and it can decompose cured by light irradiation, are classified into those which polymerized and cured.

Polymerization and curing can be further classified into photodimerization and polymerization polymerization. The former is light
Among the curable vinyl compounds, many have a cinnamoyl group or a cinnamylidene group.
Etc. Le are exemplified. The latter is a monomer or oligomer is activated by light, mutually or are intended to polymerization curing with other polymers or oligomers, monomers, photo-curable bi
Among the benzyl compounds, acryloyl, allyl, spirane, and vinylbenzene monomers, oligomers, and polymers are exemplified.

Specific examples of the polymerized polymer include monoacrylate, diacrylate, N-substituted acrylamide, N-vinylpyrrolidone, styrene and derivatives thereof, polyol acrylate, polyester acrylate, urethane acrylate, epoxy acrylate, and the like. Examples include compounds having monofunctional and polyfunctional vinyl groups represented by silicone acrylate, fluoroalkyl acrylate, polyacrylate having a polybutadiene skeleton, polyacrylate having an isocyanuric acid skeleton, acrylate having a hydantoin skeleton, and unsaturated cycloacetal. You.

[0030] In the present invention, these various light curable vinyl compound may be used, the use of accession Li Royle compound, excellent effects and homogeneity of the cured product of the liquid crystal after exposure light are possible, also cured curing rate by exposure light fast preferable because it is stable. The acryloyl group of the acryloyl-based compound referred to here is α-position,
β-position hydrogen atom is phenyl group, alkyl group, halogen atom
And may be substituted with a substituent, a cyano group or the like.

Further, the curable compound may be administered alone or may be used in multiple mixing modifiers necessary elements create, may contain a modifier such as the device produced. Specifically, a crosslinking agent, a surfactant, a diluent, a thickener, a defoaming agent, an adhesion-imparting agent, a stabilizer, an absorbent, a coloring matter, a polymerization accelerator, a chain transfer agent,
It may contain a polymerization inhibitor and the like.

Examples of the photo-curing initiator include benzoin ether, benzophenone, acetophenone, and thioxanthone.

[0033] As the polymer in the present invention, when using a heat-curable compound, guanamine resin, bismaleimide triazine resin, phenolic resin, unsaturated polyester resin, furan resin, polyimide, polyurethane, polydiallyl phthalate, polyvinyl esters, melamine resins, urea resins, isobutylene - maleic anhydride copolymer, epoxy resins, DFK resin, xylene resin, coumarone resin, ketone resin, polyethylene Oki shea de, polyvinylidene chloride latex, polyterpenes, polyvinyl alcohol, polyvinyl ether, Poribinirubuchi Rat,
Examples include polyvinyl formal, polyvinyl polypropionate, maleic resin, and silicone.

[0034] In the case of using a thermoplastic type compounds, A <br/> ionomers, A acrylonitrile - ethylene - propylene - diene - styrene resin, acrylonitrile - styrene resins, acrylonitrile - butadiene - styrene resin (ABS), ABS - polyvinyl chloride resin, acrylonitrile - chlorinated instead styrene - styrene resins, methyl methacrylate - butadiene - styrene resin, liquid crystal polymer,
Ethylene - vinyl chloride copolymers, ethylene - vinyl acetate copolymer, ethylene - vinyl alcohol copolymers, chlorinated polyvinyl chloride, chlorinated polypropylene, Fang aromatic polyester, phenoxy resin, polytetrafluoroethylene, Te tiger fluoro ethylene - f hexafluoropropylene copolymer, Te tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, Te tetrafluoroethylene - ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, polyacrylate, Polyamide, polyacetal, polyamideimide, polyarylate, polyetherimide, polyetheretherketone, polyethylene, polyethylene terephthalate, polyvinylidene chloride, polyvinyl chloride ,
Po polycarbonate, polyvinyl acetate, polysulfone, polystyrene, polyparabanic acid, poly-para-methyl styrene, polyphenylene ether, polybutadiene, polyphenylene scan Ruff I de, polybutylene terephthalate, polypropylene, polymethyl methacrylate, methyl pentene polymers, cellulose derivatives (ethyl cellulose ,
Other) polyvinyl acetate, Ru etc. there.

In the present invention, the alignment regulating force of the alignment means with respect to the spontaneous twisting force of the liquid crystal layer is adjusted to a predetermined strength.

Various empirical formulas are known for the spontaneous twisting force of the liquid crystal layer. However, it is actually difficult to greatly change the spontaneous twisting force of the liquid crystal. Rather, by adjusting the addition amount of the liquid crystal layer of the alignment means serving polymeric material, wear respective forces in adjustment.

The amount to be added is a polymer material in the liquid crystal layer, by weight with respect to the liquid crystal polymer composite layer 0. 1-10% ,
0 especially. It is preferable to select from 5 to 5%. If the amount is too small, a necessary alignment regulating force cannot be obtained. If the amount is too large, the driving voltage becomes too large. Further, since force to the liquid crystal to a homeotropic state is too strong, the scattering state becomes unstable, increasing the light transmittance at the time of no voltage is applied, or, occurs decrease in the reflectance in the reflection mode There is a risk. It has been found that, when the driving voltage is about 2 to 3% of the polymer material, the driving voltage is more surprisingly decreased when the polymer material is added in a larger amount. It is presumed that, at this amount, the decrease in the drive voltage due to the orientation force of the polymer material and the increase in the drive voltage due to the voltage drop are in a state of being balanced.

When the vertical alignment treatment is performed on the cell substrate, the inventor adjusts the alignment regulating force of the alignment means against the spontaneous twisting force of the liquid crystal layer to a predetermined strength, so that a bistable having a so-called memory property is obtained. I found that I could take a state. That is, when a specific intermediate voltage lower than the saturation voltage is applied between the electrodes, a bistable state having memory properties of homeotropic alignment and twisted alignment can be obtained.

In this case, by applying an intermediate voltage (hereinafter, also referred to as a bias voltage), a homeotropic arrangement caused by application of a saturation voltage is stably present, and the liquid crystal optical element maintains a transparent state. At this time, even if a voltage equal to the bias voltage is applied in the scattering state (white turbidity) when no voltage is applied, no alignment change occurs in the liquid crystal element and the liquid crystal element remains opaque. A stable state (bistable state) exists. Therefore, multiplex driving using this bistable state becomes possible,
A large-capacity display with high contrast can be performed without using active driving using a TFT or the like.

[0040] In the present invention, another advantage of performing the vertical alignment treatment substrate is greatly reduced cormorants Rukoto the driving voltage. In particular, when multiplex driving is performed, a higher pulse amplitude is required. Therefore, from the viewpoint of using a driving IC, it is extremely necessary to lower the driving voltage.

As a vertical alignment treatment method, there is a solution coating method utilizing a physical adsorption phenomenon, and as an alignment agent, lecithin, stearic acid, hexadecyltrimethylammonium bromide is used.
Mi de (CTAB), using octadecylamine hydrochloride or the like. In addition, there is a solution coating method using the chemical adsorption phenomenon,
Monobasic carboxylic acid chromium complex as the alignment agent (e.g., Shirisuchin acid chromium complex, perfluorononanoic acid chromium complex and the like), organic silane (e.g., n- octadecyl triethoxysilane down) used and the like.

There is a method utilizing plasma polymerization, and hexamethyldisiloxane, perfluorodimethylcyclohexane, tetrafluoroethylene, or the like is used as an aligning agent. Also, there is a method using sputtering, as an alignment agent polytetrafluoroethylene,
Are used. In addition, there is a method in which an alignment agent is dissolved in a liquid crystal, and the liquid crystal is injected into a liquid crystal cell. As a result, a substrate treatment is performed. Acids and the like are used.

When the device of the present invention is manufactured, the mixture of the curable compound and the liquid crystal substance to be adjusted is uniform regardless of whether it is a solution, a viscous material, or a dispersion. What is necessary is just to select the most suitable one according to the element manufacturing method.

Specifically, In ₂ O ₃ —SnO ₂ , Sn
The glass substrate provided with a transparent electrode such as O ₂ is sealed around by arranging so as to face each other cell is generally convenient to inject a liquid, plastic with transparent electrodes, applied to a substrate such as a glass When the opposing substrates are to be overlaid, the viscous state is generally more convenient. At this time, when the liquid crystal optical element of the present invention is used as a reflective display element, the electrode on one side substrate (back side) does not need to be transparent, and an opaque material such as a metal material such as copper or aluminum is used. May be used.

The gap between the substrates can be operated at 1 to 100 μm, but it is appropriate to set the gap at 3 to 40 μm in consideration of the applied voltage and the contrast at the time of ON / OFF.

[0046] In the present invention, a dichroic dye and a mere dye in the liquid crystal, or adding a pigment, or use those colored as the curable compound, or using a colored substrate to the substrate,
A specific color can also be given by laminating color filters.

The liquid crystal optical element of the present invention is in a mode in which the liquid crystal optical element is controlled by a voltage for applying a bistable state of transmission and scattering (white turbidity), and the distance between the substrates is set like a twisted nematic display element by ordinary time division driving. It is not necessary to control strictly, and a liquid crystal light modulator having a large area can be manufactured with extremely high productivity. However, in order to reduce unevenness in the light transmission state, it is preferable that the substrate interval is constant to some extent.
For this purpose, a spacer may be mixed with the liquid crystal material and the raw material of the cured product, or the spacer may be applied on one of the substrates. The spacer, for example, Alumina, rod type of glass fibers, glass beads, polymer beads and the like, those for various liquid crystal cell can be used.

When the liquid crystal optical element of the present invention is driven by applying a voltage, an AC voltage that changes the arrangement of the liquid crystal may be applied, and the size and frequency are not particularly limited. Specifically, an AC voltage of about 5 to 100 V and about 10 to 1000 Hz may be applied.

[0049] Also by the present invention for setting a saturation voltage below the bias voltage of the liquid crystal, it can bistability of scattering state (white turbidity) and homeotropic alignment (transmitting) at take advantage, T
Scattering by it Rukoto without multiplex driving in the active driving of FT, etc. (cloudy) - can provide a liquid crystal optical element of the transmission mode.

Therefore, the present invention can be applied to a display element for which multiplex driving has conventionally been difficult. In particular, it is suitable for a display element that is reflective, bright, and capable of large-capacity display. Further, many uses such as a light control element and an optical shutter are conceivable. In addition, we install in front of light sources such as electric bulbs,
For example, it can also be used for purposes such as electrically switching between a fog lamp and a normal lamp.

Further, in the present invention, one of the electrodes may be used as a mirror as a specular reflection electrode. In this case, the substrate on the back side may be made of opaque glass, plastic, ceramic, or metal.

Further, a color filter may be used in combination, or a dichroic dye may be mixed in the liquid crystal to make a color.
Other displays such as a twisted nematic liquid crystal display element, an electrochromic display element, an electroluminescence display element, and the like may be laminated and used, and various applications are possible.

[0053]

The present invention will be described below in detail with reference to examples. Examples 1 to 6 are examples of the present invention.

[0054] In the polymer material 2, 2 ', 6, 6'-tetrabromobisphenol A diacrylate, a liquid crystal
B DH Co. "E48" Te, using Merck "CB15", as a chiral compound by an amount listed in Table 1, 2 and benzoin methyl ether as a photocuring initiator, 2 ',
0.02 parts were used for 1 part of 6,6'-tetrabromobisphenol A diacrylate to be uniformly dissolved to prepare a liquid crystal polymer mixture. Further, the surface of the glass substrate with ITO was subjected to an orientation treatment as shown in Table 1. In the case of vertical alignment treatment, processing reagent der Ru n - According to the octadecyl triethoxysilane emissions (manufactured by Tokyo Kasei Kogyo Co., Ltd.). In the case of the parallel orientation treatment, the surface was rubbed to a thickness of 50 nm.
Thick polyimide alignment film (manufactured by Hitachi Chemical Industry Co., Ltd. LX-580
0). Approximately one spacer having a diameter shown in Table 1 per 1 mm ² was sprayed on the substrate to form a cell, and then the above liquid crystal polymer mixture was injected into the cell. At this time, the natural length of twist of the liquid crystal (twisted pitch) had become about 0.2 times the substrate cell spacing (Thickness of the liquid crystal layer).

After sealing the injection hole, while applying an AC voltage of 30 V (50 Hz) shown in Table 1, the ultraviolet irradiation device (SUNCURRIGHT manufactured by Asahi Glass Co., Ltd.) was used for about 20 hours.
And min exposure light, when stopping the application of voltage, elements exposed entire surface became cloudy was obtained. Transmittance before the voltage application, and the saturation voltage (40V, 50 Hz) the transmittance upon application shown in Table 1 (permeameter: Otsuka Electronics Co., Ltd. LCD7000). In addition, the respective voltage-light transmittance curves are shown in the drawing numbers shown in Table 1.

[0056]

[Table 1]

[0057] Example 1, in Example 2, to create the elements in exactly the same conditions except not applying a voltage of at EXPOSURE, respective voltage - shows the light transmittance curve 1, Figure 2. solid line
Indicates the case where the voltage at the time of exposure was applied, and
This is the case where no voltage was applied. It can be seen that the steepness of the rise of the liquid crystal is significantly improved by the voltage application exposure. In this case, the polymer was transparent immediately after the polymerization, but once it was made opaque by applying a voltage, it remained opaque even when no voltage was applied. 1 and 2 show voltage-light transmittance curves at this time.

Example 6 is an example in which the pitch is reduced to take two states of color scattering and transparent. The scattering color became green. Further, in this example, a device was prepared under exactly the same conditions except that the substrate was subjected to a parallel alignment process instead of the vertical alignment process, and a voltage-light transmittance curve was shown by a dotted line in FIG . In the case of the vertically aligned product, a substantially transparent state appears at about 34 V and saturation occurs.
It becomes almost transparent at 0 V, but at least 50 V
The transparent state continues to change up to the vicinity. As described above, it can be seen that the voltage threshold value is significantly reduced in the vertically aligned product.

The effect of the vertical alignment processing of the substrate is also evident by comparing FIGS. 1, 6, and 7. FIG.
In this case, the voltage starts rising from around 7V and is almost completely saturated at 10V. In FIG. 6 without the alignment process and in FIG. 7 with the parallel alignment process, in FIG.
It rises almost at around V, but continues to rise around 30 V thereafter.

FIG. 4 shows the voltage-light transmittance curves for a cell gap of 20 μm for a liquid crystal-polymer composite having a high molecular weight of 2% by weight (solid line) and 3% by weight.
(Dotted line) . It can be seen that the one with 3% by weight starts up at a lower voltage.

The memory performance of each device was evaluated below.

In the device of Example 1, a rectangular wave of 8 V (50 Hz) was applied from a state where no voltage was applied, and a white turbid state (transmittance 1) was applied.
0.5%) and then a rectangular wave of 12.5 V (5
0 Hz) to make the device transparent (transmittance 79.1).
%), And immediately reduce the applied voltage to 8 V again. Then, the element does not return to the previous cloudy state, but maintains a transparent state. This state is maintained for 1 hour or more at 25 ° C. Hereinafter, the application of the voltage of 8V shown here is referred to as the application of the bias voltage of 8V, and the application of the voltage of 12.5V is expressed as the application of the rising voltage.

As a comparative example, the photocured product was not added to the liquid crystal.
Except that neither exposure light in accordance created a device in the same manner as in Example 1. The same measurement was performed, but in a transparent state (transmittance 9
0.2%) was maintained for only about 1 to 3 seconds. As a result, there was no significant change even if the bias voltage was changed in a range where the transmittance at the time of applying the bias voltage was not significantly changed, or if the rising voltage was changed.

In the device of Example 2, a rectangular wave of 17 V (50 Hz) was applied as a bias voltage from a state where no voltage was applied, and a white turbid state (transmittance of 6.4%) was confirmed. A voltage of 50 Hz) was applied, and it was confirmed that the device became transparent (transmittance: 74.0%), and the applied voltage was quickly reduced to a bias voltage of 17 V again. Then, the element does not return to the previous cloudy state, but maintains a transparent state. This state is maintained for 1 hour or more at 25 ° C.

As a comparative example, the photocured product was not added to the liquid crystal.
Except that neither exposure light in accordance created a device in the same manner as in Example 2. The same measurement was performed, but in a transparent state (transmittance 9
0.4%) was maintained for only about one second. As a result, even if the bias voltage and the rising voltage were variously changed, there was no significant change.

In the device of Example 3, a rectangular wave of 15 V (50 Hz) was applied as a bias voltage from a state where no voltage was applied, and a white turbid state (transmittance of 5.0%) was confirmed. A voltage of 50 Hz) was applied, and it was confirmed that the device became transparent (transmittance: 74.2%), and the applied voltage was quickly reduced to a bias voltage of 15 V again. Then, the element does not return to the previous cloudy state, but maintains a transparent state. This state is maintained for 1 hour or more at 25 ° C.

As a comparative example, the photocured product was not added to the liquid crystal.
Except that neither exposure light in accordance created a device in the same manner as in Example 4. The same measurement was performed, but in a transparent state (transmittance 9
0.4%) was maintained for about 1 second or less. As a result, even if the bias voltage and the rising voltage were variously changed, there was no significant change.

In the device of Example 4, a rectangular wave of 25 V (50 Hz) was applied as a bias voltage from a state where no voltage was applied, and a white turbid state (transmittance of 3.6%) was confirmed. A voltage of 50 Hz) was applied, and it was confirmed that the device became transparent (transmittance: 71.0%). Then, the applied voltage was quickly reduced to a bias voltage of 25 V again. Then, the element does not return to the previous cloudy state, but maintains a transparent state. This state is maintained for 1 hour or more at 25 ° C.

As a comparative example, the photocured product was not added to the liquid crystal.
Except that neither exposure light in accordance created a device in the same manner as in Example 4. The same measurement was performed, but in a transparent state (transmittance 9
0.8%) was maintained for about 1 second or less. As a result, even if the bias voltage and the rising voltage were variously changed, there was no significant change.

In the device of Example 5, a rectangular wave of 21.5 V (50 Hz) was applied as a bias voltage from a state where no voltage was applied, and a white turbid state (transmittance of 2.3%) was confirmed. A voltage of 35 V (50 Hz) was applied, and it was confirmed that the device became transparent (transmittance: 67.7%).
Reduce to 5V. Then the element does not return to the previous cloudy state,
Keep transparent. This condition is 1 at 25 ° C.
Keep infinite for more than an hour.

As a comparative example, the photocured product was not added to the liquid crystal.
Except that neither exposure light in accordance created a device in the same manner as in Example 5. The same measurement was performed, but in a transparent state (transmittance 9
0.8%) was maintained for about 1 second or less. As a result, even if the bias voltage and the rising voltage were variously changed, there was no significant change.

In the device of Example 7, similarly to the device of Example 1, a square wave of 8 V
(50 Hz) to confirm a cloudy state (transmittance: 8.9%).
A voltage of 2.5 V (50 Hz) is applied, and it is confirmed that the device becomes transparent (transmittance: 76.6%), and the applied voltage is quickly reduced to the bias voltage of 8 V again. At this time, unlike the device of Example 1, the transparent state was not maintained, and the transmittance decreased with time. The time required for the transmittance to decrease to 60% was 50 msec. Further, the same examination was conducted by setting the rising voltage to a rectangular wave of 15 V (50 Hz). However, the transparent state (transmittance: 83.3%) was not maintained, and the time required for the transmittance to decrease to 60% was 70 msec. Was. Even if the bias voltage was variously changed within a range where the transmittance at the time of applying the bias voltage was not significantly increased, the transparent state was not maintained.

In the device of Example 8, similarly to the device of Example 1, a square wave of 8 V
(50 Hz) to confirm a cloudy state (transmittance: 8.6%), and then as a rising voltage, a rectangular wave 1
A voltage of 2.5 V (50 Hz) is applied, and it is confirmed that the device becomes transparent (transmittance: 71.7%). Then, the applied voltage is quickly reduced to the bias voltage of 8 V again. At this time, unlike the device of Example 1, the transparent state was not maintained, and the transmittance decreased with time. The time required for the transmittance to fall to 60% was 90 msec. Further, the same examination was performed by setting the rising voltage to a rectangular wave of 15 V (50 Hz), but the transparent state (transmittance: 76.6%) was not maintained, and the time required for the transmittance to decrease to 60% was 500 msec.
Met. Even if the bias voltage was variously changed within a range where the transmittance at the time of applying the bias voltage was not significantly increased, the transparent state was not maintained.

[0074]

As described above, the present invention provides a novel liquid crystal optical element. In a liquid crystal optical element having a nematic liquid crystal, a chiral nematic liquid crystal or a cholesteric liquid crystal interposed therebetween, the liquid crystal optical element has a voltage higher than the saturation voltage of the liquid crystal. the polymer was subjected to stabilize the homeotropic alignment state of the liquid crystal that occurs when the voltage applied is performed dispersed in the liquid crystal, improves the rising steepness of the liquid crystal, the threshold voltage or higher There cause memory property to <br/> by Riho Meotoropikku arrangement state to stabilize the homeotropic alignment state of the liquid crystal that occurs when applied, the liquid crystal of the rise threshold voltage and fall threshold A liquid crystal display device characterized by increasing the voltage difference (hysteresis) is obtained.

In the device of the present invention, when a polymer is dispersed in a liquid crystal, a voltage is applied to the liquid crystal and the liquid crystal is formed in a homeotropic state. Therefore, the generated and dispersed polymer is stabilized in a homeotropic state of the liquid crystal. As such, it has a regulating power for liquid crystals. The scattering state disturbed initial alignment of the liquid crystal for the case of using the nematic liquid crystal is a polymer (cloudiness) occurs in the absence of an applied voltage, mosquitoes Ira Rene Matic liquid crystal, the focal conic sequence alignment disorder of the case of using the cholesteric liquid crystal or show a strong scattering state caused a cholesteric phase of planar orientation (cloudy). When a voltage is applied, a homeotropic arrangement is obtained in any case, and the transmittance is improved. At that time, the homeotropic alignment state is stabilized by the action of the polymer as compared with the case where no polymer is included, and the rising threshold voltage is reduced and the rising steepness is improved. The contrast is improved.

By performing the vertical alignment treatment, the memory property appears stably. When a bias voltage lower than the saturation voltage is applied, the homeotropic alignment caused by the voltage application is stably present, and the liquid crystal optical element is transparent. Maintain state. At this time, even if a voltage equal to the bias voltage is applied in the scattering state (white turbidity) when no voltage is applied, no alignment change occurs in the liquid crystal element and the liquid crystal element remains opaque. A stable state (bistable state) exists.

On the other hand, it has been found that the drive voltage is greatly reduced by subjecting the substrate to the vertical alignment treatment. Accordingly, the IC of been driving circuit, it is possible to open the developing for conducting Maruchipure Tsu <br/> box drive.

Therefore, multiplex driving using this bistable state can be performed, and large-capacity display with high contrast can be performed without depending on active driving using a TFT or the like.

The liquid crystal optical element of the present invention does not require a polarizing plate and is excellent in appearance quality and production.
In particular, it can be used for inexpensive and large-capacity display elements, and can be widely used for inexpensive and high-performance dimming and optical shutters.

[Brief description of the drawings]

FIG. 1 is a graph showing a voltage-light transmittance curve of a liquid crystal optical element of the present invention and a liquid crystal optical element of a comparative example.

FIG. 2 is a graph showing a voltage-light transmittance curve of another embodiment of the liquid crystal optical element of the present invention.

FIG. 3 is a graph showing a voltage-light transmittance curve of another embodiment of the liquid crystal optical element of the present invention.

FIG. 4 is a graph showing a voltage-light transmittance curve of another embodiment of the liquid crystal optical element of the present invention.

FIG. 5 is a graph showing a voltage-light transmittance curve of another embodiment of the liquid crystal optical element of the present invention.

FIG. 6 is a graph showing a voltage-light transmittance curve of another example of the conventional liquid crystal optical element.

FIG. 7 is a graph showing a voltage-light transmittance curve of another example of a conventional liquid crystal optical element.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Kumai 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture In-house AG Technology Co., Ltd. Asahi Glass Co., Ltd. Central Research Laboratory (56) References JP-A-55-111918 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1337

Claims (4)

(57) [Claims] At least one sheet has been subjected to a vertical alignment treatment.
Substrate with multiple electrodes, Positive dielectric anisotropy sandwiched between the substrates and spontaneous twisting
A liquid crystal layer having a liquid crystal layer and liquid crystal molecules substantially vertically
And an alignment means for causing the liquid crystal layer to be aligned in a perpendicular direction.
By adjusting the regulating force to a predetermined strength, the electrode
When a saturation voltage is applied during the
Takes a pick orientation and no voltage is applied between the electrodes
In such a case, the electrodes take a substantially twisted orientation and become saturated between the electrodes.
When a predetermined intermediate voltage smaller than the sum voltage is applied
Is the memory property between homeotropic and twisted orientations
To have a bistable state with, The alignment means consists of a polymer material in the liquid crystal layer sandwiched between the substrates.
Liquid crystal layer took homeotropic alignment after adding
The polymer material is cured in the state Liquid crystal optical element. 2. The liquid crystal optical element according to claim 1, wherein the amount of the polymer material added is 0.1 to 10% by weight based on the liquid crystal layer. 3. The liquid crystal layer has a twist alignment pitch of 0.8 μm.
The liquid crystal optical element according to claim 1 or 2, wherein 4. A pitch of the liquid crystal layer having a twist orientation of 0.2 μm.
The liquid crystal optical element according to claim 1, wherein the thickness is from 0.8 μm to 0.8 μm.