JP3512967B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a reflective liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, notebook computers, sub-notebook computers, mobile phones, PHS (Personal Handyphone Syste)
m), PDA (Personal Digital Assistants), and other portable information devices have received a great deal of attention. In these devices, low power consumption is indispensable because a battery is used from the viewpoint of portability, and low power consumption is also required for display elements mounted in mobile information devices. However, a conventional transmissive liquid crystal display device that requires a backlight has high power consumption, and there is a strong demand for a low power consumption reflective liquid crystal display device that does not require a backlight.

As such a reflection type liquid crystal display device, there is a display device which uses a cholesteric liquid crystal material to perform display in a mode called a selective reflection mode. JE Adams, WEH
ass, JJ Wyscocki et al. (Xerox Co.) (for example, Phys. Rev. Lett., 24, 577 (197
0)). Selective reflection means that the wavelength defined by the product of the pitch length of the helical periodic structure and the average refractive index of the liquid crystal substance in the planar structure is the reflection maximum, and the circularly polarized light component in the same rotation direction as the helix is selected selectively. It is a phenomenon that reflects on.
In the selective reflection mode, the helical pitch is adjusted so as to reflect visible light, and display is performed by using the selective reflection state in the planar structure and the scattering state in the focal conic structure. However, in the liquid crystal display device using the selective reflection mode, there is a problem that only one circularly polarized light component in the selective reflection region is reflected and the other circularly polarized light component cannot be used, and it is difficult to whiten the reflection wavelength region. There's a problem.

On the other hand, some proposals have been made aiming to improve the brightness by a laminated structure (for example, Japanese Patent Laid-Open No. 7-83200).
-287214). The method proposed in Japanese Patent Laid-Open No. 7-287214 uses a polymer dispersed cholesteric liquid crystal (PDCLC) in which a cholesteric liquid crystal or a chiral nematic liquid crystal is dispersed in a polymer, and a first circularly polarized light component is reflected. The PDCLC layer and the second PDCLC layer that reflects the other circularly polarized light component are laminated without a separation layer. In this system, it is the cholesteric liquid crystal or chiral nematic liquid crystal dispersed in the polymer that determines the circularly polarized light component to be reflected.

However, the reflection type liquid crystal display device proposed in Japanese Patent Application Laid-Open No. 7-287214 is a device in which two kinds of optically active liquid crystal substances having mutually different induced helical orientations are held in an optically inactive polymer. Since two kinds of cholesteric liquid crystals (or chiral nematic liquid crystals) mutually diffuse between the first layer and the second layer, there is a big problem that the reduction of the reflection intensity cannot be avoided.

To avoid this problem, Japanese Patent Laid-Open No. 7-28
As mentioned in 7214, it is necessary to provide a separation layer between the first PDCLC layer and the second PDCLC layer to suppress interdiffusion. However, the provision of the separation layer causes problems such as a voltage drop and a cost increase due to an increase in manufacturing steps.

[0007]

As described above, in the conventional reflection type liquid crystal display device, it is difficult to secure sufficient brightness because only one circularly polarized light component is used, and the reflection wavelength There is a problem that it is difficult to secure whiteness because the area is narrow and monochromatic. Also,
In the case of a laminated structure aiming at improvement of brightness as in Japanese Patent Laid-Open No. 7-287214, it is necessary to provide a separation layer between the respective layers because the reflection strength is lowered due to mutual diffusion of the liquid crystal substance between the respective layers. However, there is a problem that the cost increases due to the increase in the manufacturing process.

The object of the present invention is to improve the brightness and to alleviate the monochromaticity in the reflection wavelength region by the laminated structure, and to maintain good display quality even if the liquid crystal substance diffuses between the layers. An object is to provide a liquid crystal display device.

[0009]

A liquid crystal display device according to the present invention includes a pair of counter substrates, at least one of which is transparent and faces each other, an optically active polymer and a space between the pair of counter substrates together with the polymer. Composed of a plurality of thin films containing a liquid crystal substance having a helical pitch that exhibits a cholesteric phase in a state of being sandwiched between and a liquid crystal substance that reflects light in the visible region, and in at least two thin films, a helical induction direction of the polymer with respect to the liquid crystal substance and And / or a display layer configured to have different helical forming power.

As described above, since at least two thin films are made to have different helix-inducing directions and / or helix-forming forces of the polymer with respect to the liquid crystal substance, it is possible to improve the brightness and alleviate the monochromaticity in the reflection wavelength region. Is possible.

Further, since an optically active polymer can be used and the liquid crystal substance can be made common to each layer, even when the liquid crystal substance is diffused between a plurality of thin films by directly adhering the thin films adjacent to each other, , It is possible to maintain good display quality. Therefore, it is not necessary to provide a separation layer between the respective layers, and it is possible to suppress an increase in cost due to an increase in manufacturing steps.

The liquid crystal substance is not particularly limited as long as it exhibits a cholesteric phase when sandwiched between opposed substrates together with an optically active polymer and has an effective helical pitch for reflecting light in the visible region. It is not something that will be done. Here, the light in the visible region refers to light having a wavelength of 400 to 760 nm. Alternatively, a mixture containing two or more kinds of liquid crystal substances or substances other than liquid crystal substances may be used. For example, nematic liquid crystal, cholesteric liquid crystal, mixture of nematic liquid crystal and cholesteric liquid crystal, mixture of nematic liquid crystal and optically active substance,
A mixture of a nematic liquid crystal and a nematic liquid crystal having an optically active site can be used.

When the liquid crystal substance has a homeotropic structure, in order to realize a high contrast display by minimizing the light scattering, the refractive index of the liquid crystal substance with respect to ordinary light should be closer to the refractive index of the polymer. Is desirable. When an optically active substance is mixed, the helical forming power (Helical Twisting Power) defined by the reciprocal 1 / pc of the product of the helical pitch length p and the weight concentration c of the optically active substance, the desired selective reflection wavelength, and the optical The content may be set in consideration of the spiral forming power of the active polymer. From the viewpoint of keeping the driving voltage low, it is preferable that the ratio of the twist elastic constant to the dielectric anisotropy of the liquid crystal material is small. From the viewpoint of improving reflectance, refractive index anisotropy (birefringence)
Is preferably large. Further, a dichroic dye or the like may be mixed for the purpose of adjusting the color tone of selective reflection. In this case, ideally, a material exhibiting absorption characteristics outside the selective reflection wavelength region is suitable.

The electrode used for applying a voltage to the liquid crystal substance is not limited as long as at least the electrode on the observer side is transparent. As the transparent electrode, for example, a thin film of ITO (indium tin oxide) can be used. The other electrode that does not require transparency is aluminum, nickel, copper, silver,
Various electrode materials such as gold and platinum can be used. Further, for forming electrodes on the substrate, vapor deposition, sputtering,
A usual method such as photolithography can be used.

The substrate on which the electrodes are arranged is not particularly limited as long as it has sufficient strength and insulating properties and at least the substrate on the observer side is transparent. For example, glass, plastic, ceramic or the like can be used.

It is preferable to form an insulating thin film on the surface of the electrode. The material of the insulating thin film is not limited as long as it is not reactive or soluble in the liquid crystal material and electrically insulating. For example, as a known material, polyimide, polyamide, polyvinyl alcohol,
Examples thereof include organic substances such as polyacrylamide, cyclized rubber, novolac resin, polyester, polyurethane, acrylic resin, bisphenol resin and gelatin, and inorganic substances such as silicon oxide and silicon nitride.

As the method for forming the alignment film, a coating method by spin coating, a Langmuir-Blodgett method for forming a thin film by transferring a monomolecular film formed on the water surface onto a substrate and laminating the film, a vapor deposition method, etc. Known methods can be cited, and a forming method suitable for each material may be selected. Further, the thickness of the insulating thin film is not particularly limited as long as voltage can be sufficiently applied to the liquid crystal layer, but from the viewpoint of low voltage driving, it is desirable that it is thin within a range that does not impair the insulating property. Alignment treatment on the insulating thin film is not always necessary, but alignment treatment such as rubbing may be appropriately performed.

Spacers are used to more accurately control the distance between the opposing substrates. The spacers may be formed by a method in which spherical ones are scattered on the substrate surface, or the columnar bodies are arranged at regular intervals on the substrate so that the spacers are uniformly dispersed in the surface with little risk of the spacers coming close to each other when the substrates are combined. You may form by the method of arrange | positioning. In particular, in the case of manufacturing a laminated structure, it is possible to control the distance between the opposing substrates more precisely by using the columnar spacer.

The spacer material is not particularly limited in terms of its material as long as it is insulative and does not react or dissolve with the liquid crystal molecules used and is stably dispersed on the substrate. is not. For example, a polymer such as divinylbenzene or polystyrene, an inorganic oxide such as alumina or silica, or the like can be used. It is desirable that the spacer have a narrow particle size distribution.

As a method of forming the columnar bodies on the substrate at regular intervals, a photolithography method can be used. As the material of the columnar body, a positive type or negative type photosensitive resin that has no reactivity or solubility with respect to the liquid crystal material and is electrically insulating can be used. For example, polyimide, polyamide, polyvinyl alcohol, polyacrylamide, cyclized rubber, novolac resin, polyester,
Examples of the photosensitive resin include polyurethane, acrylic resin, bisphenol resin, and gelatin, and negative photosensitive polyimide is generally preferable.

The distance between the opposing substrates is not particularly limited, but it is preferable that the distance is as short as possible within the range where the reflectance is not lowered. This is to realize low voltage driving and faster response.

The optically active polymer is not particularly limited in terms of material as long as it is optically active. It is also possible to use a mixture of an optically active polymer and an optically inactive polymer. It is preferable to use as the optically active polymer, a substance having a liquid crystalline moiety such as a biphenyl structure that interacts with a liquid crystal material in the molecule and forming a transparent solid having a three-dimensional network structure. Acrylic resin can be mentioned as a typical material.

Further, a polymerizable monomer which is a precursor of the polymer material, or an oligomer derived from monomers or a mixture of oligomers and monomers is used from the viewpoint of selection of reactivity and viscosity. A polymer may be obtained by polymerizing and curing with heat or light. From the viewpoint that the pitch length, that is, the reflection wavelength can be selected by controlling the temperature during the polymerization, the photocurability is more preferable. As the polymerizable monomer or oligomer, a monoacrylic monomer or oligomer, which is polymerized and cured by ultraviolet irradiation, or a diacrylic monomer or oligomer, can be mentioned as a preferable material. The α-position and / or β of the vinyl group
The hydrogen at position may be substituted with a phenyl group, an alkyl group, a halogen group, a cyano group or the like. For example, 4′-acryloyl-4- (2-methylbutyl) biphenyl, 4
′ -Acryloyl-4- (2-methylbutoxy) biphenyl, 4′-acryloyl-4- (2-methylheptyloxy) biphenyl, 4 ′-(6-acryloylhexyloxy) -4- (2-methylbutyl) biphenyl, Four
′ -Acryloyl-4- (2-methylbutoxy) cyclohexylphenyl acrylate, 2-methyl-4- (4
-Biphenyl) butyl acrylate, 1,4-di- (4
-(6-Acryloyloxy-3-methylhexyloxy) benzoyloxy) benzene, 1,4-di- (4-
Each S-form and R-form of (6-acryloyloxy-4-methylhexyloxy) benzoyloxy) benzene can be mentioned. As the optically active polymerizable oligomer, oligomers of the above-mentioned monomers, or CC4039L, CC4039R, CC4070L in commercially available materials
(All are Wacker).

When an optically inactive polymer is mixed, 4,4'-bisacryloyl biphenyl, 4-
Acryloyl biphenyl, 4-acryloyl-4'-cyanobiphenyl, 4-cyclohexyl phenyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, or as commercially available and easily available, Kayarad HDDA, Kayarad MAN
DA, Kayarad HX-220, Kayarad HX-62
0, Kayarad R-551, Kayarad R-712, Kayarad R-604, Kayarad R-167 (above, Nippon Kayaku Co., Ltd.), Acryester BZ, Acryester H
X, Acryester HP (above, Mitsubishi Rayon Co., Ltd.) can be used.

Further, a polymerization initiator may be used to accelerate the polymerization. The photopolymerization initiator may be any one suitable for the monomers and oligomers to be selected, and examples thereof include Darocur 1173 (MERCK) and Darocur 1116 (ME.
RCK), Irgacure 184 (Ciba-Geigy),
Irgacure 651 (Ciba-Geigy), Irgacure 907 (Ciba-Geigy), Kayacure DETX (Nippon Kayaku), Kayacure EPA (Nippon Kayaku), etc. can be mentioned. From the viewpoint of maintaining a high liquid crystal retention rate, the amount of the photopolymerization initiator added is preferably in the range of 5% by weight or less based on the monomers and oligomers. Also,
The polymerizable monomer or oligomer may contain a modifier such as a crosslinking agent, a surfactant, a polymerization accelerator, a chain transfer agent, or a photosensitizer, if necessary.

A known method can be used for the method of manufacturing the liquid crystal display device of the present invention. For example, as a method of forming a thin film composed of an optically active polymer and a liquid crystal substance on a counter substrate, PDLC (Polymer Dispersed Liquor) is used.
The same method as the method for producing id Crystal) can be used. That is, a method of polymerizing a mixture of an optically active polymerizable monomer and a liquid crystal substance by heat or light, or dissolving a mixture of an optically active polymer and a liquid crystal substance in an appropriate solvent and then evaporating the solvent. Can be used. Hereinafter, a more specific manufacturing method will be described.

When the optically active polymerizable monomer is used, the following production method can be applied. First, a mixture of an optically active first polymerizable monomer and a liquid crystal substance is sealed between a first substrate and a peeling substrate, polymerized by heat or light, and then the peeling substrate is removed. Thin film first
Is formed on the substrate. As the peeling substrate, not only a substrate having a good peeling property, but also a glass substrate coated with a thin film having a good peeling property can be used. Examples of the material of the substrate or the thin film having such a good peeling property include a fluoropolymer material such as Teflon. Next, a second thin film is formed in the same manner as the first thin film by using an optically active second polymerizable monomer having a helical induction direction and / or a helical forming force with respect to the liquid crystal substance different from that of the first polymerizable monomer. It is formed on the second substrate. Finally, the first and second substrates are sealed so that the first and second thin films are attached to each other.

When an optically active polymerizable monomer is used, the following production method can be applied. First,
A first thin film using a mixture of a liquid crystal substance and an optically active first polymerizable monomer is formed on a first substrate.
The substrate and the second substrate are sealed by a method similar to the usual method for manufacturing a liquid crystal display element. Then, a mixture of a liquid crystal substance and an optically active second polymerizable monomer having a helical induction direction and / or a helical forming force for the liquid crystal substance different from that of the first polymerizable monomer is injected between the sealed substrates. The second thin film is formed by polymerization with heat or light.

In any of the above manufacturing methods, it is desirable to use a spacer in order to control the thickness of the thin film more strictly. In particular, it is desirable to form the above-mentioned columnar body on the substrate.

When an optically active polymer is used, the following manufacturing method can be applied. First, a mixture of an optically active first polymer and a liquid crystal substance is dissolved in an appropriate volatile solvent, and the mixture is applied onto the first substrate by spin coating or the like, and then the solvent is evaporated. Is formed on the first substrate. Similarly, a second thin film is formed on the second substrate by using an optically active second polymer having a helical induction direction and / or a helical forming force with respect to the liquid crystal substance different from that of the first polymer. After that, the first and second
The first and second substrates on which the thin films are formed are sealed.

When an optically active polymer is used, the following production method can be applied. First, in the same manner as in the above manufacturing method, a first thin film including an optically active first polymer and a liquid crystal substance is formed over a first substrate. Then, in the same manner as in the formation of the first thin film, an optically active second polymer having a helical induction direction and / or a helical forming force with respect to the liquid crystal substance different from that of the first polymer is used to form the second thin film into the first thin film. Formed on the thin film of. Finally, the first substrate and the second substrate are sealed.

Further, considering white display or color display, it is possible to further form a multilayer structure. The multilayer structure can be produced by the method described below. When an optically active polymerizable monomer is used, a third,
A thin film such as a fourth film is formed, stacking and peeling are repeated in order, and finally the substrate is sealed. Of course, in this case, the thin films may be laminated on each of the two opposing substrates and then sealed. Also, in the case of forming a thin film by injecting another thin film component described above and then polymerizing the same, a multi-layer structure can be produced by using the release substrate a plurality of times in the same manner.

On the other hand, when an optically active polymer is used, the thin films such as the third, fourth, ... Are laminated in the same manner as the method of forming the second thin film described above. It is possible to make a multilayer structure. Also in this case, not only the first substrate but also the second substrate may be formed with a multilayer structure and then sealed.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a reflective liquid crystal display device according to the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, each thin film has a film thickness in which the selective reflection light is saturated.

First, a basic embodiment of the present invention will be described. First, a first basic embodiment will be described with reference to FIG. Reference numerals 1a and 1b are counter substrates, 2a and 2b are electrodes formed on the opposing surfaces of the counter substrates 1a and 1b, and 3 is a spacer. Reference numerals 4a and 4b are thin films made of an optically active polymer and a liquid crystal material, and the thin films 4a and 4b form a display layer. In addition, normally, the counter substrate 1 on which the electrodes 2a and 2b are formed
An alignment film is formed on the facing surfaces of a and 1b.

The thin film 4a is a nematic liquid crystal substance 11a.
And an optically active polymer 12a that induces a right helix with respect to the nematic liquid crystal substance 11a. In addition, the thin film 4b is formed of the nematic liquid crystal material 11b.
And an optically active polymer 12b that induces a left helix with respect to the nematic liquid crystal substance 11b. The nematic liquid crystal substances 11a and 11b are the same substance, but the helical orientations are different depending on the surrounding polymers 12a and 12b. In addition, the helix forming forces of the polymers 12a and 12b with respect to the liquid crystal substance are equal to each other.

When no voltage is applied, the right circularly polarized light component is reflected by the planar structure formed on the thin film 4a, while the left circularly polarized light component is reflected by the planar structure formed on the thin film 4b. Further, when a voltage is applied, both thin films 4a and 4b have a homeotropic structure.

FIG. 5 shows the reflection spectrum A observed in the liquid crystal display device of the present embodiment. In the conventional liquid crystal display device (see FIG. 4, constituent elements corresponding to those in FIG. 1 are denoted by the same reference numerals. FIG. 3 is a diagram showing a comparison with a reflection spectrum B observed in FIG.

As is apparent from FIG. 5, the reflection intensity of this embodiment is twice as high as that of the conventional type, and a bright display can be obtained. This is because the conventional type reflects only one circularly polarized light component and transmits the other circularly polarized light component, whereas the liquid crystal display device of the present embodiment reflects the circularly polarized light components in both left and right directions. This is because. Further, when a voltage is applied, both thin films 4a and 4b have a homeotropic structure in which they are in an optically transmissive state, so that almost no reflected light is observed and the contrast doubles as compared with the conventional type.

Further, in this embodiment, since the low molecular weight nematic liquid crystal material is common to the thin films 4a and 4b, the liquid crystal material is moved between these two layers by directly joining the adjacent thin films. However, the optical characteristics of the display element do not deteriorate. On the other hand, the method disclosed in Japanese Unexamined Patent Publication No. 7-287214 described in the section of the prior art, that is, 2 in which optically inactive polymers have mutually different induced helical orientations
In the case of a method of holding a kind of optically active liquid crystal substance, the reflection intensity is lowered because these two kinds of optically active materials mutually diffuse. Therefore, in this respect, the liquid crystal display device according to the present invention and the liquid crystal display device disclosed in JP-A-7-287214 are essentially different from each other.

Next, regarding the second basic embodiment,
This will be described with reference to FIG. The components corresponding to those of the first basic embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, the thin film 4c is composed of a liquid crystal substance which exhibits a cholesteric phase by itself (takes a right helix by itself) and an optically active polymer which induces a left helix with respect to this liquid crystal substance. It is configured. The thin film 4d is composed of a liquid crystal substance that exhibits a cholesteric phase by itself (takes a right helix by itself) and an optically active polymer that induces a right helix with respect to this liquid crystal substance. As in the first embodiment, the nematic liquid crystal substances in the thin films 4c and 4d are the same substance, and the helical forming forces of the polymers in the thin films 4c and 4d on the liquid crystal substance are equal to each other.

When no voltage is applied, the thin film 4c forms a planar structure having a helix longer than the pitch length induced by the optically active polymer, and the thin film 4d forms a helix shorter than the pitch length induced by the optically active polymer. To form a planar structure. Further, when a voltage is applied, both thin films 4c and 4d have a homeotropic structure.

FIG. 6 is a diagram showing the reflection spectrum A observed in the liquid crystal display device of the present embodiment in comparison with the reflection spectrum B observed in the conventional liquid crystal display device (see FIG. 4). .

As can be seen from FIG. 6, the reflection spectrum A of the present embodiment has a wider reflection wavelength range than the reflection spectrum B of the conventional type. Thus, the thin films 4c and 4d
Since the wavelength regions reflected by are shifted from each other, the reflected light becomes a little white and the monochromaticity, which is a difficulty of the selective reflection mode, is alleviated. When a voltage is applied, both thin films 4c and 4d have a homeotropic structure in an optically transparent state.

Also in this embodiment, as in the first embodiment, the low molecular weight nematic liquid crystal material is used as the thin films 4c and 4c.
Since it is common to d, even if the liquid crystal material moves between these two layers, the optical characteristics of the display element do not deteriorate.

Next, regarding the third basic embodiment,
This will be described with reference to FIG. The components corresponding to those of the first basic embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, six layers of thin films 4e to 4j having opposite spiral directions are provided for three types having different spiral pitch lengths. That is, the thin films 4e to 4j are formed by using a total of 6 types of optically active polymers and nematic liquid crystal substances in which the induced helical orientations are opposite to those of the three types having different helical forming powers to the liquid crystal substance. Become.

When no voltage is applied, the right helix planar structure 4e and the left helix planar structure 4f which reflect blue color,
A green spiral reflecting right spiral planar structure 4g and a left spiral planar structure 4h, a red reflecting right spiral planar structure 4i and a left spiral planar structure 4j are formed. Further, when a voltage is applied, all of the thin films 4e to 4j have a homeotropic structure.

FIG. 7 is a diagram showing the reflection spectrum A observed in the liquid crystal display device of the present embodiment in comparison with the reflection spectrum B observed in the conventional liquid crystal display device (see FIG. 4). .

As can be seen from FIG. 7, the reflection spectrum A of this embodiment is different from the reflection spectrum B of the conventional type.
As the reflection wavelength range expands, the reflection intensity also increases. Therefore, whitening is possible, so that the monochromaticity, which is a drawback of the selective reflection mode, is improved and a bright display can be obtained. When a voltage is applied, all six layers have a homeotropic structure and are optically transparent.

In the present embodiment as well, as in the first embodiment and the like, the low molecular weight nematic liquid crystal material is common to the thin films 4e to 4j, so that even if the liquid crystal material moves between the layers, the optical element of the display element is not changed. The characteristics do not deteriorate.

In the present embodiment, the thin films 4e-4e
The stacking order of j is not particularly limited. Next,
A more specific embodiment of the present invention will be described.

First, the first specific embodiment will be described. First, polyimide (AL-1051: Nippon Synthetic Rubber Co., Ltd.) as an alignment film was cast on the electrode surfaces of two glass substrates with ITO electrodes by a spinner to a thickness of 70 nm. Further, CYTOP (Asahi Glass), which is a fluororesin, was cast on another glass substrate by spin coating to obtain a release substrate. Then, an epoxy adhesive for bonding is applied to a predetermined position on the release substrate surface by a conventional method,
Resin spacer balls having a diameter of 5 μm were dispersed on one of the glass substrates with the ITO electrode. Then, the peeling substrate and the glass substrate with the ITO electrode were attached and sealed.

Next, the nematic liquid crystal E48 (MERC
K company) 47 wt%, optically active polymerizable monomer (S)-
1,4-di (4- (6-acryloyloxy-3-methylhexyloxy) benzoyloxy) benzene 53w
t%, polymerization initiator Darocur 1173 (MERCK)
A mixture obtained by adding 0.5% by weight to the polymerizable monomer was injected by a conventional method, and ultraviolet irradiation was performed using a high pressure mercury lamp in a state where the liquid crystal substance had a planar structure.

Next, the peeling substrate was peeled off from the glass substrate with the ITO electrode, and a thin film made of an optically active polymer and a nematic liquid crystal was formed on the glass substrate. In the same manner, the nematic liquid crystal E48 (M
ERCK) 47 wt% and optically active polymerizable monomer (R) -1,4-di (4- (6-acryloyloxy-
A thin film made of a mixture of 3-methylhexyloxy) benzoyloxy) benzene 53 wt% was prepared.

Finally, two glass substrates with ITO electrodes were attached so that the thin films face each other, and a liquid crystal display device was produced. The display state of the manufactured element was voltage off (0
V) green in selective reflection state (maximum reflection wavelength 550 nm)
And the reflectance was 140%. When the voltage was turned on (rectangular wave, Vp = 60 V, 60 Hz), the light was transmitted, and the contrast with the voltage turned off was 70.

The display characteristics were determined by measuring the brightness (Y value) of the reflected light and the reflection spectrum of the reflected light in the normal direction of the substrate by injecting white light from the normal direction of the glass substrate surface of the display element from the direction of 10 to 20 degrees. evaluated. The reflectance of the perfect diffuse reflector was set to 100%. This evaluation method is the same in other specific embodiments.

Next, a second specific embodiment will be described. In this embodiment, the nematic liquid crystal E48 (MERCK) 47 wt% in the first specific embodiment is used.
40 wt% of nematic liquid crystal E48 (MERCK)
A liquid crystal display device was produced in the same manner as in the first specific embodiment except that the mixture was changed to 7 wt% of the optically active agent CB15 (MERCK).

The display state of the manufactured element was voltage off (0
V) was whitish green in the selective reflection state, had two reflection maximum wavelengths (490 nm, 610 nm), and had a reflectance of 100%. Voltage on (square wave, Vp = 60
(V, 60 Hz), a transmissive state was obtained, and the contrast with voltage off was 50.

Next, a third specific embodiment will be described. First, in the same manner as in the first specific embodiment, a thin film made of an optically active polymer, a nematic liquid crystal substance and a polymerization initiator was formed on one of the glass substrates with an ITO electrode. Next, an epoxy adhesive for bonding is applied at a predetermined position on the thin film, and a resin spacer ball having a diameter of 5 μm is sprinkled on the other glass substrate with ITO electrodes.
Both substrates were stuck together and sealed.

Then, in the same manner as in the first specific embodiment, an optically active polymerizable monomer having a different spiral-induced orientation, a nematic liquid crystal and a polymerization initiator were injected between the sealed substrates, and then ultraviolet light was emitted. The monomer was polymerized by irradiation to produce a liquid crystal display device.

It has been confirmed that the display characteristics of the element manufactured according to this embodiment are similar to those of the first specific embodiment. Next, a fourth specific embodiment will be described.

In this embodiment, photosensitive polyimide is used as the material of the alignment film and the columnar spacer in order to control the gap more accurately. First, one glass substrate with an ITO electrode was spin-coated with a photosensitive polyimide, and 1
Prebaking was performed under the usual conditions of 10 ° C. and 15 minutes.
Then, the polyimide film was exposed through a photomask on which a spacer pattern was formed. By heating this substrate at 170 ° C. for 10 minutes on a hot plate, the photosensitive resin on the substrate side is polymerized, and the solubility of the light-irradiated portion and the portion polymerized by heat treatment in the developing solution becomes slow. This photosensitive resin is developed by spraying a developing solution (QZ3301: Ciba Geigy) under pressure with nitrogen gas, spraying a mixed solution of a developing solution and a rinsing solution (QZ3311: Ciba Geigy), and rinsing (QZ3312: Rinse with Ciba Geigy) and spin dry with nitrogen gas. The substrate was cured at 250 ° C. for 1 hour to form a cylindrical spacer having a height of 5 μm and a diameter of 15 μm and an alignment film having a thickness of 120 nm.

Next, a nematic liquid crystal E48 (MERCK) 47 is manufactured by the same method as in the first specific embodiment.
wt% and optically active polymerizable monomer (S) -1, 4-
A thin film consisting of 53 wt% of di (4- (6-acryloyloxy-3-methylhexyloxy) benzoyloxy) benzene was formed on the above alignment film. After forming an alignment film on the other glass substrate with ITO electrode by the same method, 47 wt% of E48 (MERCK) and the optically active polymerizable monomer (R) -1,4-di (4- (6- A thin film of 53 wt% of acryloyloxy-3-methylhexyloxy) benzoyloxy) benzene was formed on the alignment film.

Finally, two glass substrates with ITO electrodes were attached to each other so that the positions of the spacers would be aligned to produce a liquid crystal display element. It was confirmed that the display characteristics of the device manufactured according to this embodiment are similar to those of the first specific embodiment.

Next, a fifth specific embodiment will be described. First, nematic liquid crystal E48 (MERCK)
47 wt%, optically active polymerizable monomer (S) -1, 4
-Di (4- (6-acryloyloxy-3-methylhexyloxy) benzoyloxy) benzene 53 wt%,
A mixture prepared by adding 0.5 wt% of a polymerization initiator Darocur 1173 (MERCK) to a polymerizable monomer is dissolved in chloroform (Wako Pure Chemical Industries, Ltd.) and spun on a glass substrate with an ITO electrode to a film thickness of 5 μm. Coated
Subsequently, the polymerizable monomer is polymerized by irradiation with ultraviolet light in a nitrogen atmosphere to produce an optically active polymer (S form).
And a thin film of nematic liquid crystal was formed.

Next, the nematic liquid crystal E48 (MERC
K company) 47 wt%, optically active polymerizable monomer (R)-
1,4-di (4- (6-acryloyloxy-3-methylhexyloxy) benzoyloxy) benzene 53w
t%, polymerization initiator Darocur 1173 (MERCK)
A mixture obtained by adding 0.5% by weight to the polymerizable monomer was dissolved in chloroform (Wako Pure Chemical Industries, Ltd.), and spin-coated on the above thin film so that the film thickness was 5 μm. Subsequently, by irradiation with ultraviolet light in a nitrogen atmosphere, a thin film composed of an optically active polymer (R body) and a nematic liquid crystal was formed.

Finally, the other glass substrate with the ITO electrode was sealed so that the electrode surface and the above thin film were bonded to each other, and a liquid crystal display element was produced. It was confirmed that the display characteristics of the device manufactured according to this embodiment are similar to those of the first specific embodiment. In addition to the embodiments described above, the present invention can be variously modified and implemented without departing from the spirit thereof.

[0070]

In the present invention, at least two thin films are made to have different helix-inducing directions and / or helix-forming forces of the polymer with respect to the liquid crystal substance, so that it is possible to improve brightness and alleviate monochromaticity in the reflection wavelength region. It becomes possible to measure. Further, since the liquid crystal substance can be made common to each layer by using an optically active polymer, even when the liquid crystal substance is diffused between a plurality of thin films by directly adjoining the thin films adjacent to each other, it is preferable. The display quality can be maintained. Therefore, it is not necessary to provide a separation layer between the respective layers, and it is possible to suppress an increase in cost due to an increase in manufacturing steps.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a first basic embodiment of the present invention.

FIG. 2 is a diagram showing an example of a second basic embodiment of the present invention.

FIG. 3 is a diagram showing an example of a third basic embodiment of the present invention.

FIG. 4 is a diagram showing an example of a liquid crystal display device according to a conventional technique.

FIG. 5 is a diagram showing the reflection intensity of the liquid crystal display device according to the first basic embodiment of the present invention in comparison with a conventional liquid crystal display device.

FIG. 6 is a diagram showing a reflection intensity of a liquid crystal display device according to a second basic embodiment of the present invention in comparison with a conventional liquid crystal display device.

FIG. 7 is a diagram showing the reflection intensity of a liquid crystal display device according to a third basic embodiment of the present invention in comparison with a conventional liquid crystal display device.

[Explanation of symbols]

1a, 1b ... Counter substrate 4a-4j ... thin film 11a, 11b ... Liquid crystal substance 12a, 12b ... Optically active polymer

Continuation of the front page (56) Reference JP-A-7-287214 (JP, A) JP-A-60-191203 (JP, A) JP-A-4-284418 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G02F 1/1334 G02F 1/1335 G02F 1/1347

Claims (4)

(57) [Claims] 1. A pair of opposing substrates, at least one of which is transparent and faces each other, an optically active polymer, and a cholesteric phase in a state of being sandwiched between the pair of opposing substrates together with the polymer, and visible. A plurality of thin films including a liquid crystal material having a helical pitch that reflects light in a region, and in at least two thin films, a helical induction direction and / or a helical formation of the polymer with respect to the liquid crystal material based on the optical activity of the polymer. A liquid crystal display device, comprising: a display layer configured to have different forces. 2. The liquid crystal display device according to claim 1, wherein the thin films adjacent to each other are directly bonded to each other. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal material is configured to be able to diffuse between the plurality of thin films. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal substance exhibits a cholesteric phase by itself.