JP2005258430A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element using a ferroelectric liquid crystal, which takes on a monostable mode of operation by using a material exhibiting a chiral smectic C phase via a smectic A phase in a temperature lowering process as the ferroelectric liquid crystal. <P>SOLUTION: There is provided the liquid crystal display element which is characterized by comprising the ferroelectric liquid crystal interposed between two substrates, electrodes and optical alignment films respectively and sequentially formed on mutually opposite faces of the substrates, wherein components of the optical alignment films interposing the ferroelectric liquid crystal are different from each other in composition and the ferroelectric liquid crystal exhibits the chiral smectic C phase via the smectic A phase in the temperature lowering process and further exhibits monostability in the chiral smectic C phase. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display element using ferroelectric liquid crystal, and more particularly to a liquid crystal display element in which the alignment of ferroelectric liquid crystal is controlled using a photo-alignment film.

  Liquid crystal display elements have been widely used from large displays to portable information terminals because of their thinness and low power consumption, and their development is actively underway. So far, liquid crystal display elements have been developed and put to practical use, such as TN mode, STN multiplex drive, and active matrix drive using thin layer transistors (TFTs) for TN, but these use nematic liquid crystals. In addition, the response speed of the liquid crystal material is as slow as several ms to several tens of ms, and it cannot be said that it is sufficiently compatible with moving image display.

  Ferroelectric liquid crystal (FLC) is a liquid crystal suitable for high-speed devices because its response speed is as short as μs order. Ferroelectric liquid crystal is widely known as a bistable one proposed by Clark and Lagerwol, which has two stable states when no voltage is applied (FIG. 4), but is limited to switching in two states, light and dark. However, although it has a memory property, it has a problem that gradation display cannot be performed.

  In recent years, the state of a liquid crystal layer when a voltage is not applied has been stabilized in one state (hereinafter referred to as “monostable”). ) Is continuously changed and the transmitted light intensity is analog-modulated so that gradation display is possible (Non-Patent Document 1, FIG. 4).

As the liquid crystal exhibiting monostability, a ferroelectric liquid crystal that changes phase with the cholesteric phase (Ch) -chiral smectic C (SmC ^* ) phase in the temperature lowering process and does not pass through the smectic A (SmA) phase is usually used.

On the other hand, as a ferroelectric liquid crystal, there is a material that changes phase with Ch-SmA-SmC ^* in the temperature lowering process and exhibits an SmC ^* phase via an SmA phase. Among the ferroelectric liquid crystal materials currently reported, Then, compared with the former material that does not pass through the SmA phase, most of them have such a phase sequence. However, a ferroelectric liquid crystal having such a phase sequence is generally used with respect to a single-layer normal. It is known to have two stable states and exhibit bistability (FIG. 5).

  As a method for monostabilizing such a ferroelectric liquid crystal, there is a polymer stabilization method. In the polymer stabilization method, a ferroelectric liquid crystal mixed with an ultraviolet curable monomer is injected into an alignment-treated liquid crystal cell, and the polymer is polymerized by irradiating with ultraviolet rays while a DC or AC voltage is applied. However, there are problems in that the manufacturing process becomes complicated and the drive voltage increases.

  In general, as a liquid crystal alignment treatment technique, there is a technique using an alignment film, which includes a rubbing method and a photo alignment method. The rubbing method is to orient the liquid crystal molecules on the film by orienting the polyimide polymer chain in the rubbing direction by rubbing the substrate coated with the polyimide film, and is excellent in the alignment control of the nematic liquid crystal, In general, this technique is also used industrially. However, this method has problems such as generation of static electricity and dust, non-uniform orientation control force and tilt angle due to differences in rubbing conditions, and unevenness during large-area processing, and molecular ordering is higher than nematic liquid crystals. However, it is difficult to control the alignment and is not suitable for the alignment treatment method of the ferroelectric liquid crystal in which alignment defects are easily generated.

  As a non-contact alignment method replacing the rubbing method, there is a photo alignment method. The photo-alignment method irradiates a polymer or monomolecule with light with controlled polarization and causes photoexcitation reaction (decomposition, isomerization, dimerization) to impart anisotropy to the polymer or monomolecular film. This aligns the liquid crystal molecules on the film. This method is useful in that there is no generation of static electricity or dust, which is a problem of the rubbing method, and it is possible to quantitatively control the alignment treatment. However, no report has been found so far in which a monostable operation mode is realized using a ferroelectric liquid crystal having essentially bistability even when this method is used.

  On the other hand, when the ferroelectric liquid crystal exhibits monostability as described above, it does not have a memory property. Therefore, active matrix driving in which an active element such as a transistor or a diode is added to each pixel is suitable. In particular, the use of an active matrix system using a TFT element as an active element is useful in that a target pixel can be reliably turned on and off and a high-quality display can be achieved.

  In recent years, color liquid crystal display elements have been actively developed. As a method for realizing color display, there are generally a color filter method and a field sequential color method. The color filter system realizes color display by using a white light source as a backlight and attaching R, G, B micro color filters to each pixel. On the other hand, the field sequential color system switches the backlight to R, G, B, R, G, B ... in time, and opens and closes the black and white shutter of the ferroelectric liquid crystal to synchronize with it, and the afterimage effect of the retina Thus, the colors are mixed temporally to realize color display. In this field sequential color system, color display is possible with one pixel, and it is not necessary to use a color filter with low transmittance, so that bright and high-definition color display is possible, and low power consumption and low cost can be realized. Useful in terms.

However, since the field sequential color system divides one pixel in time, in order to obtain good moving image display characteristics, it is necessary that the liquid crystal as a black and white shutter has high-speed response. Although this problem can be solved by using a ferroelectric liquid crystal, the ferroelectric liquid crystal has a problem that alignment defects are likely to occur as described above. Further, as described above, it is desirable that the ferroelectric liquid crystal display a monostable operation mode in order to enable gradation display by analog modulation as described above and realize high-definition color display. However, the ferroelectric liquid crystal materials exhibiting monostability are limited, the range of material selection of the ferroelectric liquid crystal is narrow, it is difficult to meet various required characteristics, and it has not been put into practical use.
NONAKA, T., LI, J., OGAWA, A., HORNUNG, B., SCHMIDT, W., WINGEN, R., and DUBAL, H., 1999, Liq. Cryst., 26, 1599.

  The present invention relates to a liquid crystal display element using a ferroelectric liquid crystal, and uses a material that develops a chiral smectic C phase as a ferroelectric liquid crystal via a smectic A phase in the temperature lowering process. It is a main object to provide the liquid crystal display element shown.

  As a result of intensive studies in view of the above circumstances, the present inventors formed photo-alignment films on the opposing surfaces of the two substrates, respectively, and by using materials having different compositions as the materials of the photo-alignment films, The present inventors have found that a ferroelectric liquid crystal having a phase sequence as described above exhibits a monostable operation mode.

That is, in the present invention, a first photo-alignment processing substrate having a first substrate, an electrode layer provided on the first substrate, and a first photo-alignment film formed on the electrode layer, and A second photo-alignment processing substrate having a second substrate, an electrode layer provided on the second substrate, and a second photo-alignment film formed on the electrode layer, the first photo-alignment film and the above-mentioned A liquid crystal display element that is disposed so as to face the second photo-alignment film and sandwiches a ferroelectric liquid crystal between the first photo-alignment film and the second photo-alignment film,
The constituent materials of the first photo-alignment film and the second photo-alignment film have different compositions from each other,
A liquid crystal display element characterized in that the ferroelectric liquid crystal exhibits a chiral smectic C phase via a smectic A phase in the temperature lowering process and exhibits monostability in the chiral smectic C phase. It is to provide.

In the liquid crystal display device of the present invention, the first photo-alignment film and the second photo-alignment film have different compositions across the ferroelectric liquid crystal, so that the SmC ^* phase is changed via the SmA phase in the temperature lowering process. The monostable operation mode can be realized by using the ferroelectric liquid crystal shown.

  The constituent material of the first photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction, and the constituent material of the second photo-alignment film is photoisomerized. A photoisomerization type material containing a photoisomerization reactive compound that imparts anisotropy to the photoalignment film by causing a reaction is preferable. Alternatively, the constituent material of the first photo-alignment film and the second photo-alignment film is preferably a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction. This is because the use of such a combination of materials can further enhance the alignment control ability of the ferroelectric liquid crystal.

  In the photoreactive material, the photoreaction is preferably a photodimerization reaction or a photolysis reaction. This is because by using these photoreactions, it becomes easier to impart anisotropy to the photo-alignment film.

  Further, when the constituent material of the first photo-alignment film and the second photo-alignment film is the photoreactive material, the constituent material of the first photo-alignment film causes the photodimerization reaction to It is a photoreactive material that imparts anisotropy to the photoalignment film, and the constituent material of the second photoalignment film is a photoreactive type that imparts anisotropy to the photoalignment film by causing a photodecomposition reaction. It is preferable that it is material.

  The photoreactive material that imparts anisotropy to the photoalignment film by causing the photodimerization reaction has a dichroism having a radical polymerizable functional group and different absorption depending on the polarization direction. It is preferable to contain the photodimerization reactive compound which has. This is because anisotropy can be easily imparted to the photo-alignment film by radical polymerization of the reaction sites aligned in the polarization direction.

  The photodimerization reactive compound is preferably a dimerization reactive polymer containing any one of cinnamate ester, coumarin, and quinoline as a side chain. This is because anisotropy can be easily imparted to the photo-alignment film by radical polymerization of α and β unsaturated ketone double bonds aligned parallel to the polarization direction as reaction sites.

  The photodimerization reactive compound is preferably at least one of dimerization reactive polymers represented by the following formula.

This is because the dimerization reactive polymer requires less energy for the reaction, and it is possible to select a functional group suitable for the R ¹¹ and R ¹² moieties.

  The photoisomerization-reactive compound preferably has a dichroism that varies in absorption depending on the polarization direction, and generates a photoisomerization reaction upon irradiation with light. This is because anisotropy can be easily imparted to the photo-alignment film by causing isomerization of the reaction site oriented in the polarization direction of the photoisomerization-reactive compound having such characteristics.

  In the photoisomerization-reactive compound, the photoisomerization reaction is preferably a cis-trans isomerization reaction. This is because either the cis isomer or the trans isomer is increased by light irradiation, whereby anisotropy can be imparted to the photo-alignment film.

  The photoisomerization reactive compound is preferably a compound having an azobenzene skeleton in the molecule. Since the azobenzene skeleton causes a cis-trans isomerization reaction by light irradiation, anisotropy is easily imparted to the photo-alignment film by including a compound having an azobenzene skeleton in the molecule as a constituent material of the photo-alignment film. Because it can. Further, the anisotropy imparted to the photo-alignment film by having the azobenzene skeleton is particularly suitable for the alignment control of the ferroelectric liquid crystal.

  The photoisomerization reactive compound is preferably at least one monomolecular compound having an azobenzene skeleton represented by the following formula as a side chain.

In the above formula, each R ²¹ independently represents a hydroxyl group. R ²² represents a linking group represented by-(α-β-α) _g- (γ) _h- , and R ²³ is represented by-(γ) _h- (α-β-α) _g-. Represents a linking group. Here, α represents a divalent hydrocarbon group, and β represents —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O—, or —OCONH—. And g represents an integer of 0 to 3. γ represents a divalent hydrocarbon group when g is 0, and when g is an integer of 1 to 3, —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O— or —OCONH— is represented, and h represents 0 or 1. R ²⁴ each independently represents a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group, or a methoxycarbonyl group. However, the carboxyl group may form a salt with an alkali metal. R ²⁵ each independently represents a carboxyl group, a sulfo group, a nitro group, an amino group, or a hydroxyl group. However, the carboxyl group or the sulfo group may form a salt with the alkali metal.

  The photoisomerization reactive compound is preferably a polymerizable monomer having an azobenzene skeleton as a side chain. By including a polymerizable monomer having an azobenzene skeleton as a side chain as a constituent material of the photo-alignment film, anisotropy can be easily imparted to the photo-alignment film, and the anisotropy can be stabilized. It is.

  The photoisomerizable compound is preferably at least one polymerizable monomer having an azobenzene skeleton represented by the following formula as a side chain.

In the above formula, each R ³¹ is independently (meth) acryloyloxy group, (meth) acrylamide group, vinyloxy group, vinyloxycarbonyl group, vinyliminocarbonyl group, vinyliminocarbonyloxy group, vinyl group, isopropenyloxy. Represents a group, isopropenyloxycarbonyl group, isopropenyliminocarbonyl group, isopropenyliminocarbonyloxy group, isopropenyl group, or epoxy group. R ³² represents a linking group represented by-(α-β-α) _g- (γ) _h- , and R ³³ is represented by-(γ) _h- (α-β-α) _g-. Represents a linking group. Here, α represents a divalent hydrocarbon group, and β represents —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O—, or —OCONH—. And g represents an integer of 0 to 3. γ represents a divalent hydrocarbon group when g is 0, and when g is an integer of 1 to 3, —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O— or —OCONH— is represented, and h represents 0 or 1. R ³⁴ each independently represents a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group, or a methoxycarbonyl group. However, the carboxyl group may form a salt with an alkali metal. R ²⁵ each independently represents a carboxyl group, a sulfo group, a nitro group, an amino group, or a hydroxyl group. However, the carboxyl group or the sulfo group may form a salt with the alkali metal.

  The ferroelectric liquid crystal preferably constitutes a single phase. The liquid crystal display element of the present invention can obtain a good alignment even when a single-phase ferroelectric liquid crystal is used, and it is not necessary to use a technique such as a polymer stabilization method in order to control the alignment. The manufacturing process is facilitated and the driving voltage can be lowered.

  The liquid crystal display element is preferably driven by an active matrix method using a thin film transistor (TFT). This is because by adopting an active matrix system using a TFT element, a target pixel can be reliably turned on and off, so that a high-quality display is possible. Furthermore, a TFT substrate in which TFT elements are arranged in a matrix on one substrate and a common electrode substrate in which a common electrode is formed over the entire display portion on the other substrate are combined, and the common electrode substrate is shared. A micro color filter arranged in a matrix of TFT elements may be formed between the electrode and the substrate, and used as a color liquid crystal display element.

  The liquid crystal display element is preferably driven by a field sequential color system. The liquid crystal display element has a high response speed, can align the ferroelectric liquid crystal without causing alignment defects, and further exhibits a monostable operation mode, thereby enabling gradation display. For this reason, driving by the field sequential color system can realize bright and high-definition color moving image display with low power consumption and low cost, a wide viewing angle, and the like.

The liquid crystal display element of the present invention has an effect that a monostable operation mode can be realized by using a ferroelectric liquid crystal that expresses an SmC ^* phase via an SmA phase in a temperature lowering process. Since the liquid crystal display element of the present invention has such effects, it is useful in that gradation display is possible, a viewing angle is wide, and a high-definition color moving image display can be obtained. Further, according to the present invention, there is an advantage that the range of selection of the material of the ferroelectric liquid crystal that can be used for such a liquid crystal display element is widened to meet various required characteristics.

Hereinafter, the liquid crystal display element of the present invention will be described in detail. A liquid crystal display element of the present invention includes a first photo-alignment processing substrate having a first substrate, an electrode layer provided on the first substrate, and a first photo-alignment film formed on the electrode layer, and A second photo-alignment-treated substrate having a second substrate, an electrode layer provided on the second substrate, and a second photo-alignment film formed on the electrode layer, and the first photo-alignment film A liquid crystal display element that is disposed so as to face the second photo-alignment film and sandwiches a ferroelectric liquid crystal between the first photo-alignment film and the second photo-alignment film,
The constituent materials of the first photo-alignment film and the second photo-alignment film have different compositions from each other,
The ferroelectric liquid crystal is characterized in that it exhibits a chiral smectic C phase via a smectic A phase in the temperature lowering process and exhibits monostability in the chiral smectic C phase. Here, “monostable” refers to a state in which the state of the liquid crystal layer when no voltage is applied is stabilized in one state as described above. More specifically, as shown in FIG. 3, the ferroelectric liquid crystal molecules 8 have two stable states tilted by a tilt angle ± θ with respect to the layer normal, and the two stable states are placed on a cone. Although it can operate, it means a state in which the ferroelectric liquid crystal molecules 8 are stabilized in any one state on the cone when no voltage is applied.

  Such a liquid crystal display element of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing an example of the liquid crystal display element of the present invention, and FIG. 2 is a schematic sectional view. As shown in the figure, a common electrode 3a is provided on the substrate 4a, and an x electrode 3b, a y electrode 3c, and a pixel electrode 3d are provided on the counter substrate 4b, and these electrodes are formed inside the electrode layer. Are formed with photo-alignment films 2a and 2b. A ferroelectric liquid crystal is sandwiched between the photo-alignment films 2a and 2b to form a liquid crystal layer 1. In FIG. 1, the photo-alignment films 2a and 2b are omitted.

  Polarizing plates 5a and 5b may be provided outside the substrates 4a and 4b, so that incident light becomes linearly polarized light and only light polarized in the alignment direction of liquid crystal molecules can be transmitted. The polarizing plates 5a and 5b are arranged with the polarization direction twisted by 90 °. This controls the direction of the optical axis of the liquid crystal molecules and the magnitude of the birefringence in the voltage non-applied state and the applied state, and creates a bright state and a dark state by using the ferroelectric liquid crystal molecules as a black and white shutter. Can do. For example, when no voltage is applied, the polarizing plate 5a is placed so as to be aligned with the orientation of the liquid crystal molecules, so that the light transmitted through the polarizing plate 5a cannot rotate the polarization direction by 90 °, and the polarizing plate 5b It is cut off and darkened. On the other hand, in the voltage application state, the direction of the liquid crystal molecules changes depending on the voltage, and by rotating by an angle θ from the initial state, the polarization direction of the light is twisted by 90 ° and transmitted through the polarizing plate 5b to become a bright state. . Then, gradation display is possible by controlling the amount of transmitted light by the applied voltage.

The liquid crystal display element of the present invention thus has a photo-alignment film on each of the opposing surfaces of the upper and lower substrates, and the photo-alignment film is composed of materials having different compositions with a ferroelectric liquid crystal in between. Thus, a monostable operation mode can be realized by using a ferroelectric liquid crystal that changes in phase to the SmC ^* phase via the SmA phase in the temperature lowering process. The ferroelectric liquid crystal having such a phase series has a chevron structure in which the smectic layer is shortened in order to compensate for the volume change in the process of the phase change, and the bending direction of the smectic layer is compensated. Due to the formation of domains with different major axis directions of liquid crystal molecules, alignment defects such as zigzag defects and hairpin defects are likely to occur at the boundary surface. According to the present invention, such alignment defects are generated. Therefore, the ferroelectric liquid crystal can be aligned without any problem, so that it is possible to prevent a decrease in contrast due to light leakage.

  In the liquid crystal display element of the present invention, for example, as shown in FIG. 1, one substrate is a TFT substrate in which thin film transistors (TFT elements) are arranged in a matrix, and the other substrate is formed with a common electrode over the entire area. The common electrode substrate is preferably a combination of these two substrates. An active matrix liquid crystal display element using such a TFT element will be described below.

  In FIG. 1, one of the substrates is a common electrode substrate whose electrode is a common electrode 3a, while the counter substrate is composed of an x electrode 3b, a y electrode 3c and a pixel electrode 3d, It has become. In such a liquid crystal display element, the x electrode 3b and the y electrode 3c are arranged vertically and horizontally, and a signal is applied to these electrodes to operate the TFT element 7 to drive the ferroelectric liquid crystal. be able to. A portion where the x electrode 3b and the y electrode 3c intersect with each other is insulated by an insulating layer (not shown), and the signal of the x electrode 3b and the signal of the y electrode 3c can operate independently. A portion surrounded by the x electrode 3b and the y electrode 3c is a pixel which is a minimum unit for driving the liquid crystal display element of the present invention, and at least one TFT element 7 and a pixel electrode 3d are formed in each pixel. ing. In the liquid crystal display element of the present invention, the TFT element 7 of each pixel can be operated by sequentially applying a signal voltage to the x electrode 3b and the y electrode 3c.

  Furthermore, the liquid crystal display element of the present invention can be used as a color liquid crystal display element by forming a micro color filter in which TFT elements 7 are arranged in a matrix between the common electrode 3a and the substrate 4a. Each component of the liquid crystal display element of the present invention will be described in detail below.

1. Constituent members of liquid crystal display element (1) Photo-alignment film The photo-alignment film irradiates the substrate coated with the constituent material of the photo-alignment film described later with light controlled in polarization, and photoexcitation reaction (decomposition, isomerization, dimerization) The liquid crystal molecules on the film are aligned by imparting anisotropy to the film obtained by generating the film.

  The constituent material of the photo-alignment film used in the present invention is particularly limited as long as it has the effect of aligning the ferroelectric liquid crystal (photo-alignment) by irradiating light and causing a photoexcitation reaction. However, such materials can be broadly divided into photoisomerization types in which only the molecular shape changes and reversible orientation changes are possible, and photoreaction types in which the molecules themselves change. In the present invention, there is no particular limitation as long as the composition of the constituent materials of the first photo-alignment film and the second photo-alignment film is different from each other. The photoreactive type and the photoisomerization type may be combined. Alternatively, the composition of the upper and lower photo-alignment films can be changed by using either a photoreactive type or a photoisomerization type material.

  Among these, as a first aspect, the constituent material of the first photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction. The constituent material of the photo-alignment film is preferably a photoisomerization-type material containing a photoisomerization-reactive compound that imparts anisotropy to the photo-alignment film by causing a photoisomerization reaction. As a second aspect, the constituent material of the first photo-alignment film and the second photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction. Preferably there is. By using a combination of these materials, the alignment control ability of the ferroelectric liquid crystal can be further enhanced. In addition, the wavelength region of light in which the constituent material of the photo-alignment film causes a photoexcitation reaction is preferably in the ultraviolet region, that is, in the range of 10 nm to 400 nm, and preferably in the range of 250 nm to 380 nm. More preferred. Hereinafter, the first photoalignment film and the second photoalignment film of the first mode and the second mode will be described, respectively.

a. 1st aspect (1st photo-alignment film)
As described above, the first photo-alignment film used in this embodiment is preferably a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction.

  The photoreaction is not particularly limited as long as the molecule itself is changed by light irradiation and anisotropy can be imparted to the photoalignment property of the photoalignment film. Since it is easier to impart directionality, it is preferably a photodimerization reaction or a photolysis reaction. Here, the photodimerization reaction refers to a reaction in which two reaction molecules oriented in the polarization direction by light irradiation undergo radical polymerization and two molecules are polymerized. By this reaction, the alignment in the polarization direction can be stabilized and anisotropy can be imparted to the photo-alignment film. On the other hand, the photolysis reaction refers to a reaction that decomposes molecular chains such as polyimide oriented in the polarization direction by light irradiation. This reaction leaves molecular chains aligned in the direction perpendicular to the polarization direction, and can provide anisotropy to the photo-alignment film. Examples of the photoreactive material utilizing photolysis reaction include polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd. Among these photoreactive materials, in this embodiment, it is more preferable to use a material that imparts anisotropy to the photoalignment film by a photodimerization reaction because of high exposure sensitivity and wide selection of materials.

  The photoreactive material utilizing the photodimerization reaction is not particularly limited as long as it is a material that can impart anisotropy to the photoalignment film by the photodimerization reaction, but it is a radical polymerizable functional group. It is preferable to include a photodimerization reactive compound having dichroism that has different absorption depending on the polarization direction. This is because by radical polymerization of the reaction site oriented in the polarization direction, the orientation of the photodimerization reactive compound is stabilized and anisotropy can be easily imparted to the photo-alignment film.

  Examples of the photodimerization reactive compound having such characteristics include a dimerization reactive polymer having at least one reactive site selected from cinnamate ester, coumarin, quinoline, chalcone group and cinnamoyl group as a side chain. Can do.

  Among these, the photodimerization reactive compound is preferably a dimerization reactive polymer containing any one of cinnamate ester, coumarin and quinoline as a side chain. This is because anisotropy can be easily imparted to the photo-alignment film by radical polymerization of α and β unsaturated ketone double bonds aligned in the polarization direction as reaction sites.

  The main chain of the dimerization reactive polymer is not particularly limited as long as it is generally known as a polymer main chain, but the reaction sites of the side chains such as aromatic hydrocarbon groups are not limited. It is preferable that it does not have a substituent containing a lot of π electrons that hinders the interaction.

  The weight average molecular weight of the dimerization reactive polymer is not particularly limited, but is preferably in the range of 5,000 to 40,000, more preferably in the range of 10,000 to 20,000. It is. The weight average molecular weight can be measured by a gel permeation chromatography (GPC) method. If the weight-average molecular weight of the dimerization reactive polymer is too small, it may not be possible to impart appropriate anisotropy to the photo-alignment film. On the other hand, if it is too large, the viscosity of the coating liquid at the time of forming the photo-alignment film becomes high and it may be difficult to form a uniform coating film.

  As a dimerization reactive polymer, the compound represented by following formula (1) can be illustrated.

In the above formula (1), M ¹ and M ² each independently represent a monomer unit of a monopolymer or a copolymer. Examples thereof include ethylene, acrylate, methacrylate, 2-chloroacrylate, acrylamide, methacrylamide, 2-chloroacrylamide, styrene derivatives, maleic acid derivatives, and siloxane. M ² may be acrylonitrile, methacrylonitrile, methacrylate, methyl methacrylate, hydroxyalkyl acrylate or hydroxyalkyl methacrylate. x and y represent the molar ratio of each monomer unit in the case of a copolymer, and are numbers satisfying 0 <x ≦ 1, 0 ≦ y <1 and satisfying x + y = 1, respectively. It is. n represents an integer of 4 to 30,000. D ¹ and D ² represent a spacer unit.

R ¹ is a group represented by -A- (Z ¹ -B) _z -Z ^2- , and R ² is a group represented by -A- (Z ¹ -B) _z -Z ^3- . Here, A and B are each independently a covalent single bond, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5- Diyl or 1,4-phenylene which may have a substituent is represented. Z ¹ and Z ² are each independently a covalent single bond, —CH ₂ —CH ₂ —, —CH ₂ O—, —OCH ₂ —, —CONR—, —RNCO—, —COO— or — Represents OOC-. R is a hydrogen atom or a lower alkyl group, and Z ³ is a hydrogen atom or an alkyl or alkoxy having 1 to 12 carbon atoms, which may have a substituent, cyano, nitro, or halogen. z is an integer of 0-4. E represents a photodimerization reaction site, and examples thereof include cinnamic acid ester, coumarin, quinoline, chalcone group, cinnamoyl group and the like. j and k are each independently 0 or 1.

  As such a dimerization reactive polymer, More preferably, the compound represented by a following formula can be mentioned.

  Among the dimerization reactive polymers, at least one of compounds 1 to 4 represented by the following formula is particularly preferable.

  In this embodiment, as the photodimerization reactive compound, various photodimerization reaction sites and substituents can be selected from the above-mentioned compounds according to required characteristics. Moreover, the photodimerization reactive compound can also be used individually by 1 type or in combination of 2 or more types.

  In addition to the photodimerization reactive compound, the photoreactive material using photodimerization reaction may contain an additive within a range that does not interfere with the photoalignment property of the photoalignment film. Examples of the additive include a polymerization initiator and a polymerization inhibitor.

  The polymerization initiator or polymerization inhibitor may be appropriately selected from generally known compounds according to the type of the photodimerization reactive compound. The addition amount of the polymerization initiator or the polymerization inhibitor is preferably in the range of 0.001% by weight to 20% by weight, and in the range of 0.1% by weight to 5% by weight with respect to the photodimerization reactive compound. It is more preferable that This is because if the addition amount of the polymerization initiator or polymerization inhibitor is too small, the polymerization may not be started (prohibited), whereas if too large, the reaction may be inhibited.

  Next, the photo-alignment processing method will be described. First, a coating liquid obtained by diluting the constituent material of the above-described photo-alignment film with an organic solvent is coated on the surface of the substrate provided with the electrodes that faces the liquid crystal layer, and dried. In this case, the content of the photodimerization reactive compound in the coating liquid is preferably in the range of 0.05% by weight to 10% by weight, and in the range of 0.2% by weight to 2% by weight. More preferably. If the content of the photodimerization reactive compound is too small, it will be difficult to impart adequate anisotropy to the alignment film. Conversely, if the content is too large, the viscosity of the coating solution will increase, and a uniform coating will be formed. Because it becomes difficult to do.

  As the coating method, a spin coating method, a roll coating method, a rod bar coating method, a spray coating method, an air knife coating method, a slot die coating method, a wire bar coating method, or the like can be used.

  The thickness of the polymer film obtained by coating the constituent materials is preferably in the range of 1 nm to 200 nm, and more preferably in the range of 3 nm to 100 nm. If the thickness of the polymer film is too small, sufficient optical alignment may not be obtained. Conversely, if the thickness is too large, liquid crystal molecules may be disturbed in alignment, and this is not preferable in terms of cost. It is.

  The obtained polymer film can impart anisotropy by causing a photoexcitation reaction by irradiating light with controlled polarization. The wavelength range of the light to be irradiated may be appropriately selected according to the constituent material of the photo-alignment film to be used, but is preferably in the ultraviolet light range, that is, in the range of 100 nm to 400 nm, more preferably 250 nm. Within the range of ˜380 nm.

  The polarization direction is not particularly limited as long as it can cause the above-described photoexcitation reaction. However, since the alignment state of the ferroelectric liquid crystal can be made favorable, the polarization direction is oblique to the substrate surface. It is preferable to be in the range of ° to 45 °, more preferably in the range of 20 ° to 45 °.

(Second photo-alignment film)
Next, the second photo-alignment film used in the first aspect will be described. As described above, the second photo-alignment film used in this embodiment is a photoisomerization-type material containing a photoisomerization-reactive compound that imparts anisotropy to the photo-alignment film by causing a photoisomerization reaction. It is preferable that Here, the photoisomerization reaction refers to a phenomenon in which a single compound changes to another isomer by light irradiation. By using such a photoisomerization type material, a stable isomer among a plurality of isomers is increased by light irradiation, whereby anisotropy can be easily imparted to the photo-alignment film.

  The photoisomerization-reactive compound is not particularly limited as long as it is a material that can impart anisotropy to the photo-alignment film by a photoisomerization reaction. It is preferable that the photoisomerization reaction is caused by light irradiation. Anisotropy can be easily imparted to the photo-alignment film by causing isomerization of the reaction site oriented in the polarization direction of the photoisomerization-reactive compound having such characteristics.

  In the photoisomerization reactive compound, the photoisomerization reaction is preferably a cis-trans isomerization reaction. This is because either the cis isomer or the trans isomer is increased by light irradiation, whereby anisotropy can be imparted to the photo-alignment film.

  Examples of the photoisomerization-reactive compound include a monomolecular compound and a polymerizable monomer that is polymerized by light or heat. These may be appropriately selected according to the type of the ferroelectric liquid crystal to be used. However, the anisotropy is imparted to the photo-alignment film by light irradiation and then polymerized to stabilize the anisotropy. Therefore, it is preferable to use a polymerizable monomer. Among such polymerizable monomers, after anisotropy is imparted to the photo-alignment film, it can be easily polymerized while maintaining the anisotropy in a good state, so that it is an acrylate monomer or a methacrylate monomer. preferable.

  The polymerizable monomer may be a monofunctional monomer or a polyfunctional monomer. However, since the anisotropy of the photo-alignment film due to polymerization becomes more stable, the bifunctional monomer It is preferable that

  Specific examples of such a photoisomerization-reactive compound include compounds having a cis-trans isomerization-reactive skeleton such as an azobenzene skeleton or a stilbene skeleton.

  In this case, the number of cis-trans isomerization reactive skeletons contained in the molecule may be one or two or more, but the alignment control of the ferroelectric liquid crystal becomes easy. Two are preferable.

  The cis-trans isomerization reactive skeleton may have a substituent in order to further enhance the interaction with the liquid crystal molecules. The substituent is not particularly limited as long as it can enhance the interaction with the liquid crystal molecules and does not interfere with the orientation of the cis-trans isomerization reactive skeleton, and examples thereof include a carboxyl group and a sulfonic acid. A sodium group, a hydroxyl group, etc. are mentioned. These structures can be appropriately selected depending on the type of ferroelectric liquid crystal used.

In addition to the cis-trans isomerization reactive skeleton, the photoisomerization reactive compound contains many π electrons such as aromatic hydrocarbon groups so that the interaction with the liquid crystal molecules can be further enhanced. It may have an included group, and the cis-trans isomerization reactive skeleton and the aromatic hydrocarbon group may be bonded via a bonding group. The bonding group is not particularly limited as long as it can enhance the interaction with the liquid crystal molecule. For example, —COO—, —OCO—, —O—, —C≡C—, —CH ₂ —CH _2- , —CH ₂ O—, —OCH ₂ — and the like can be mentioned.

  In addition, when using a polymerizable monomer as a photoisomerization reactive compound, it is preferable to have the said cis-trans isomerization reactive skeleton as a side chain. By having the cis-trans isomerization reactive skeleton as a side chain, the effect of anisotropy imparted to the photo-alignment film becomes larger, and is particularly suitable for controlling the alignment of ferroelectric liquid crystals Because it becomes. In this case, the aromatic hydrocarbon group or bonding group contained in the molecule is contained in the side chain together with the cis-trans isomerization reactive skeleton so that the interaction with the liquid crystal molecule is enhanced. It is preferable.

  Further, the side chain of the polymerizable monomer may have an aliphatic hydrocarbon group such as an alkylene group as a spacer so that the cis-trans isomerization reactive skeleton can be easily oriented.

  Among the photoisomerization reactive compounds of the monomolecular compound or polymerizable monomer as described above, the photoisomerization reactive compound is preferably a compound having an azobenzene skeleton in the molecule. This is because the azobenzene skeleton contains a lot of π electrons, and thus has a high interaction with liquid crystal molecules and is particularly suitable for controlling the alignment of ferroelectric liquid crystals.

  When the azobenzene skeleton is irradiated with linearly polarized ultraviolet light, as shown in the following formula (2), the trans azobenzene skeleton in which the molecular major axis is oriented in the polarization direction changes to a cis isomer.

  Since the cis isomer of the azobenzene skeleton is chemically unstable compared to the trans isomer, the cis isomer of the azobenzene skeleton is thermally or absorbs visible light and returns to the trans isomer, but at this time, the left trans isomer of the above formula (2) It becomes with the same probability whether it becomes or the right transformer. Therefore, if the ultraviolet light is continuously absorbed, the ratio of the right-side trans isomer increases, and the average orientation direction of the azobenzene skeleton becomes perpendicular to the polarization direction of the ultraviolet light. In the present invention, this phenomenon is utilized to align the orientation direction of the azobenzene skeleton, impart anisotropy to the photo-alignment film, and control the orientation of liquid crystal molecules on the film.

  Among the compounds having an azobenzene skeleton in the molecule, examples of the monomolecular compound include compounds represented by the following formula.

In the above formula, each R ²¹ independently represents a hydroxyl group. R ²² represents a linking group represented by-(α-β-α) _g- (γ) _h- , and R ²³ is represented by-(γ) _h- (α-β-α) _g-. Represents a linking group. Here, α represents a divalent hydrocarbon group, and β represents —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O—, or —OCONH—. And g represents an integer of 0 to 3. γ represents a divalent hydrocarbon group when g is 0, and when g is an integer of 1 to 3, —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O— or —OCONH— is represented, and h represents 0 or 1. R ²⁴ each independently represents a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group, or a methoxycarbonyl group. However, the carboxyl group may form a salt with an alkali metal. R ²⁵ each independently represents a carboxyl group, a sulfo group, a nitro group, an amino group, or a hydroxyl group. However, the carboxyl group or the sulfo group may form a salt with the alkali metal.

  Specific examples of the compound represented by the above formula include compounds represented by the following formula.

  Moreover, as a polymerizable monomer which has the said azobenzene skeleton as a side chain, the compound represented by a following formula can be mentioned, for example.

In the above formula, each R ³¹ is independently (meth) acryloyloxy group, (meth) acrylamide group, vinyloxy group, vinyloxycarbonyl group, vinyliminocarbonyl group, vinyliminocarbonyloxy group, vinyl group, isopropenyloxy. Represents a group, isopropenyloxycarbonyl group, isopropenyliminocarbonyl group, isopropenyliminocarbonyloxy group, isopropenyl group, or epoxy group. R ³² represents a linking group represented by-(α-β-α) _g- (γ) _h- , and R ³³ is represented by-(γ) _h- (α-β-α) _g-. Represents a linking group. Here, α represents a divalent hydrocarbon group, and β represents —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O—, or —OCONH—. And g represents an integer of 0 to 3. γ represents a divalent hydrocarbon group when g is 0, and when g is an integer of 1 to 3, —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O— or —OCONH— is represented, and h represents 0 or 1. R ³⁴ each independently represents a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group, or a methoxycarbonyl group. However, the carboxyl group may form a salt with an alkali metal. R ²⁵ each independently represents a carboxyl group, a sulfo group, a nitro group, an amino group, or a hydroxyl group. However, the carboxyl group or the sulfo group may form a salt with the alkali metal.

  Specific examples of the compound represented by the above formula include compounds represented by the following formula.

  In this embodiment, various cis-trans isomerization reactive skeletons and substituents can be selected from the photoisomerization reactive compounds according to required characteristics. Moreover, the said photoisomerization reaction compound can also be used individually by 1 type or in combination of 2 or more types.

  As a constituent material of the second photo-alignment film used in this embodiment, in addition to the above-mentioned photoisomerization-reactive compound, an additive may be included within a range that does not interfere with the photo-alignment property of the photo-alignment film. When a polymerizable monomer is used as the photoisomerization reactive compound, examples of the additive include a polymerization initiator and a polymerization inhibitor.

  The polymerization initiator or polymerization inhibitor may be appropriately selected from generally known compounds according to the type of photoisomerization reactive compound. The addition amount of the polymerization initiator or the polymerization inhibitor is preferably in the range of 0.001% by weight to 20% by weight, and in the range of 0.1% by weight to 5% by weight with respect to the photoisomerization reactive compound. More preferably, it is within. This is because if the addition amount of the polymerization initiator or polymerization inhibitor is too small, the polymerization may not be started (prohibited), whereas if too large, the reaction may be inhibited.

  Such a photo-alignment treatment method for the second photo-alignment film can be carried out in the same manner as described in the first photo-alignment film. In this case, the photoisomerization reactivity in the coating liquid is used. The content of the compound is preferably in the range of 0.05% by weight to 10% by weight, and more preferably in the range of 0.2% by weight to 5% by weight. In the second photo-alignment film, the photo-alignment process can also be performed by irradiating non-polarized ultraviolet rays obliquely. The light irradiation direction is not particularly limited as long as it can cause the above-described photoexcitation reaction. However, since the alignment state of the ferroelectric liquid crystal can be made favorable, The angle is preferably within the range of 10 ° to 45 °, more preferably within the range of 30 ° to 45 °. Furthermore, when the polymerizable monomer as described above is used as the photoisomerization-reactive compound, after performing the photo-alignment treatment in the same manner as described in the first photo-alignment film, the polymer is obtained by heating. And anisotropy imparted to the photo-alignment film can be stabilized.

B. Second Aspect In the second aspect, as the photoreactive material suitably used as the constituent material of the first photo-alignment film and the second photo-alignment film, the “first photo-alignment film” in the first aspect Since it is the same as what was described, description here is abbreviate | omitted. Among these, in this embodiment, the constituent material of the first photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photodimerization reaction, and the configuration of the second photo-alignment film The material is preferably a photoreactive material that imparts anisotropy to the photoalignment film by causing a photodecomposition reaction. The combination of these materials is particularly suitable for controlling the alignment of ferroelectric liquid crystals, and can align ferroelectric liquid crystals without causing alignment defects such as zigzag defects and hairpin defects. It is because it can be set as the liquid crystal display element which shows.

(2) Liquid Crystal Layer The liquid crystal layer used in the present invention is constituted by sandwiching a ferroelectric liquid crystal with the photo-alignment film. In the present invention, the ferroelectric liquid crystal is a material that expresses the SmC ^* phase via the SmA phase in the temperature lowering process and exhibits monostability in the SmC ^* phase.

The phase series of the ferroelectric liquid crystal used in the present invention is not particularly limited as long as it exhibits the SmC ^* phase via the SmA phase in the temperature lowering process, and the high temperature side or the low temperature side of these liquid crystal phases. Other liquid crystal phases may be exhibited. Among these, since the range of material selection is wide, it is preferable to use a material that expresses the SmC ^* phase from the Ch phase via the SmA phase. Such a ferroelectric liquid crystal can be variously selected from commonly known materials according to required characteristics.

In addition, as such a ferroelectric liquid crystal, a single material exhibiting an SmC ^* phase can be used, but there is a case where a non-chiral liquid crystal (hereinafter referred to as a host liquid crystal) having a low viscosity and easily exhibiting an SmC phase. In addition, by adding a small amount of an optically active substance that does not exhibit an SmC phase by itself but induces large spontaneous polarization and an appropriate helical pitch, a material exhibiting the above phase sequence has a low viscosity, and more It is preferable because fast response can be realized.

  The ferroelectric liquid crystal used in the present invention preferably constitutes a single phase. Here, constituting a single phase means that a polymer network is not formed as in the polymer stabilization method. By using a single-phase ferroelectric liquid crystal as described above, there are advantages that the manufacturing process becomes easy and the driving voltage can be lowered.

The host liquid crystal is preferably a material exhibiting an SmC phase in a wide temperature range, and can be used without particular limitation as long as it is generally known as a host liquid crystal of a ferroelectric liquid crystal. For example, the general formula:
_{^{Ra-Q 1 -X- (Q 2}} -Y) m -Q 3 -Rb
(In the formula, Ra and Rb are each a linear or branched alkyl group, alkoxy group, alkoxycarbonyl group, alkanoyloxy group or alkoxycarbonyloxy group, and Q ¹ , Q ² and Q ³ are each 1 , 4-phenylene group, 1,4-cyclohexylene group, pyridine-2,5-diyl group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, 1,3-dioxane-2,5 -Diyl group, and these groups may have a substituent such as a halogen atom, a hydroxyl group, a cyano group, and X and Y are -COO-, -OCO-, -CH ₂ O-,- OCH ₂ —, —CH ₂ CH ₂ —, —C≡C—, or a single bond, and m is 0 or 1.) can be used. As the host liquid crystal, the above compounds can be used alone or in combination of two or more.

The optically active substance added to the host liquid crystal is not particularly limited as long as it is a material having a large spontaneous polarization and the ability to induce an appropriate helical pitch, and is generally added to a liquid crystal composition exhibiting an SmC phase. Any known material can be used. In particular, a material that can induce large spontaneous polarization with a small addition amount is preferable. Examples of such an optically active substance include the following general formula:
^{Rc-Q 1 -Za-Q 2} -Zb-Q 3 -Zc-Rd
(In the formula, Ra, Q ¹ , Q ² and Q ³ represent the same meaning as in the above general formula, and Za and Zb are —COO—, —OCO—, —CH ₂ O—, —OCH ₂ —, —CH _{2, respectively.} CH ₂ —, —C≡C—, —CH═N—, —N═N—, —N (→ O) ═N—, —C (═O) S— or a single bond, and Rc is asymmetric. A linear or branched alkyl group which may have a carbon atom, an alkoxy group, an alkoxycarbonyl group, an alkanoyloxy group or an alkoxycarbonyloxy group, wherein Rd is a linear or branched group having an asymmetric carbon atom; And an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkanoyloxy group or an alkoxycarbonyloxy group, and Rc and Rd may be substituted with a halogen atom, a cyano group or a hydroxyl group. Can be used. As the optically active substance, the above compounds may be used alone or in combination of two or more.

  Specific examples of the ferroelectric liquid crystal used in the present invention include “FELIXM4851-100” manufactured by Clariant.

  The thickness of the liquid crystal layer composed of the ferroelectric liquid crystal is preferably in the range of 1.2 μm to 3.0 μm, more preferably 1.3 μm to 2.5 μm, still more preferably 1.4 μm to 2 μm. Within the range of 0.0 μm. This is because if the thickness of the liquid crystal layer is too small, the contrast may decrease. Conversely, if the thickness is too large, alignment may be difficult.

  As a method for forming the liquid crystal layer, a method generally used as a method for manufacturing a liquid crystal cell can be used. For example, an isotropic liquid is formed by heating the ferroelectric liquid crystal into a liquid crystal cell formed by previously forming an electrode on a substrate and providing the photo-alignment film, and is injected using the capillary effect. A liquid crystal layer can be formed by sealing with an adhesive. The thickness of the liquid crystal layer can be adjusted by a spacer such as beads.

(3) Substrate The substrate used in the present invention is not particularly limited as long as it is generally used as a substrate for a liquid crystal display element, and preferred examples include a glass plate and a plastic plate. The surface roughness (RSM value) of the substrate is preferably 10 nm or less, more preferably 3 nm or less, and further preferably 1 nm or less. In the present invention, the surface roughness can be measured by an atomic force microscope (AFM: ATOMIC FORCE MICROSCOPE).

(4) Electrode layer Although the electrode layer used for this invention will not be specifically limited if it is generally used as an electrode layer of a liquid crystal display element, At least one may be formed with a transparent conductor. preferable. Preferred examples of the transparent conductor material include indium oxide, tin oxide, indium tin oxide (ITO), and the like. When the liquid crystal display element of the present invention is an active matrix type liquid crystal display element using a TFT element, one of the upper and lower electrode layers is an entire surface common electrode formed of the transparent conductor, and the other is x The electrode and the y electrode are arranged in a matrix, and the TFT element and the pixel electrode are arranged in a portion surrounded by the x electrode and the y electrode. In this case, it is preferable that the difference between the uneven portions of the electrode layer formed by the pixel electrode, the TFT element, the x electrode, and the y electrode is 0.2 μm or less. This is because if the difference between the concave and convex portions of the electrode layer exceeds 0.2 μm, alignment disorder is likely to occur.

  As the electrode layer, a transparent conductive film can be formed on the substrate by a vapor deposition method such as a CVD method, a sputtering method, or an ion plating method, and an x electrode and a y electrode are obtained by patterning this in a matrix. be able to.

(5) Polarizing plate The polarizing plate used in the present invention is not particularly limited as long as it transmits only a specific direction in the wave of light, and is generally used as a polarizing plate of a liquid crystal display element. Can be used.

2. Method for Manufacturing Liquid Crystal Display Element The liquid crystal display element of the present invention can be manufactured by a method generally used as a method for manufacturing a liquid crystal display element. Hereinafter, as an example of a method for manufacturing a liquid crystal display element of the present invention, a method for manufacturing an active matrix liquid crystal display element using TFT elements will be described. First, a transparent conductive film is formed on one substrate by the above-described vapor deposition method to form a common electrode on the entire surface. On the other substrate, an x electrode and a y electrode are formed by patterning a transparent conductive film in a matrix, and a switching element and a pixel electrode are provided.

  Next, a photo-alignment film material having a different composition is coated on the two substrates on which the electrodes are formed, and a photo-alignment process is performed to form a photo-alignment film. Beads are dispersed as spacers on one of the photo-alignment films formed in this way, spacers are applied to the periphery, and the two substrates are bonded so that the photo-alignment films face each other. Crimp. Then, the ferroelectric liquid crystal is injected in an isotropic liquid state using the capillary effect from the injection port, and the injection port is sealed with an ultraviolet curable resin or the like. Thereafter, the ferroelectric liquid crystal can be aligned by slow cooling. Thus, the liquid crystal display element of this invention can be obtained by sticking a polarizing plate on the upper and lower sides of the obtained liquid crystal cell.

3. Application of Liquid Crystal Display Element The liquid crystal display element of the present invention can be used as a color liquid crystal display element by adopting a color filter system or a field sequential color system. The color liquid crystal display element using the liquid crystal display element of the present invention can align the ferroelectric liquid crystal without causing alignment defects such as zigzag defects and hairpin defects, thereby preventing a decrease in contrast ratio due to light leakage. be able to. In the liquid crystal display element of the present invention, the ferroelectric liquid crystal exhibits monostability, enables gradation display by analog modulation, has a wide viewing angle, has high-speed response, and high-definition color display. Can be realized. Especially, it is preferable to drive the liquid crystal display element of this invention by a field sequential color system. This is because by adopting the field sequential color system, it is possible to obtain a bright color display with low power consumption and low cost.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The following examples illustrate the present invention in more detail. In addition, the compounds 1-4 represented by a following formula were used as a photodimerization reactive polymer, and the compounds i-v represented by a following formula were used as a photoisomerization reactive compound.

(Example 1)
A solution of 2% by weight of Compound 1 dissolved in cyclopentanone and a solution of 1% by weight of Compound v dissolved in N-methyl-2-pyrrolidinone and 2-n-butoxyethanol (50:50 w%) were each made of ITO. Two coated glass substrates were spin-coated at 4000 rpm for 30 seconds. The substrate coated with the compound 1 solution was spin-dried in an oven at 180 ° C. for 10 minutes, and then exposed to polarized ultraviolet rays at 25 ° C. at an angle of 30 ° with respect to the substrate surface at 100 mJ / cm ² to give the compound v solution. The spin-coated substrate was dried in an oven at 100 ° C. for 1 minute, and then exposed to polarized ultraviolet rays at 25 ° C. for 1000 mJ / cm ² and then heated at 150 ° C. for 1 hour in a nitrogen atmosphere. A spacer of 1.5 μm was sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. Thereafter, the substrate was assembled in an antiparallel state parallel to the direction of polarized ultraviolet light irradiation, and thermocompression bonding was performed. Use "FELIXM4851-100" (manufactured by Clariant) as the liquid crystal, apply the liquid crystal to the top of the injection port, and use an oven to inject at a temperature 10 ° C to 20 ° C higher than the nematic phase-isotropic phase transition temperature. When the temperature was returned to room temperature, a monodomain phase free from alignment defects was obtained.

(Example 2)
A solution of 2% by weight of Compound 1 dissolved in cyclopentanone and a polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd. were each spin-coated at a rotational speed of 4000 rpm for 30 seconds on two glass substrates coated with ITO. For a substrate coated with polyimide “RN1199”, except that the substrate was exposed to 100 J / cm ² polarized ultraviolet light, a cell was assembled in the same manner as in Example 1 above, and liquid crystal was injected. A phase was obtained.

(Comparative Example 1)
A solution of 2% by weight of Compound 1 dissolved in cyclopentanone was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. Further, when exposure drying was performed under the same conditions as in Example 1 and cell assembly was performed, a monodomain phase was not obtained, and alignment defects such as zigzag defects and hairpin defects occurred.

(Comparative Example 2)
A solution of 1% by weight of compound v dissolved in N-methyl-2-pyrrolidinone and 2-butoxyethanol (50:50 w%) was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. . Further, when exposure drying was performed under the same conditions as in Example 1 and cell assembly was performed, a monodomain phase was not obtained, and alignment defects such as zigzag defects and hairpin defects occurred.

(Example 3)
A solution of 2% by weight of Compound 1 dissolved in cyclopentanone and a solution of 1% by weight of Compound i dissolved in N-methyl-2-pyrrolidinone and 2-n-butoxyethanol (50:50 w%) were each made of ITO. Two coated glass substrates were spin-coated at 4000 rpm for 30 seconds. The substrate coated with the compound 1 solution was spin-dried in an oven at 180 ° C. for 10 minutes, and then exposed to polarized UV light at 25 ° C. at an angle of 30 ° with respect to the substrate surface at 100 mJ / cm ² to give the compound i solution. The spin-coated substrate was dried in an oven at 100 ° C. for 1 minute, and then exposed to polarized ultraviolet rays at 25 ° C. for 1000 mJ / cm ² . A spacer of 1.5 μm was sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. Thereafter, the substrate was assembled in an antiparallel state parallel to the direction of polarized ultraviolet light irradiation, and thermocompression bonding was performed. The liquid crystal is “R2301” (manufactured by Clariant). The liquid crystal is attached to the upper part of the injection port and injected using an oven at a temperature 10 to 20 ° C. higher than the nematic phase-isotropic phase transition temperature. As a result, a monodomain phase free from alignment defects was obtained.

(Comparative Example 3)
A solution of 2% by weight of compound i dissolved in N-methyl-2-pyrrolidinone and 2-n-butoxyethanol (50:50 w%) is spun on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. Coated. Further, after drying and exposure processing under the above conditions, the cells were assembled and liquid crystal was injected. As a result, a monodomain phase was not obtained, and alignment defects such as double domains, zigzag defects, and hairpin defects occurred.

Example 4
A monodomain phase having no alignment defect was obtained in the same manner as in Example 3 except that Compound 2 was used instead of Compound 1 in Example 3.

(Example 5)
A monodomain phase having no alignment defect was obtained in the same manner as in Example 3 except that Compound 3 was used instead of Compound 1 in Example 3.

(Example 6)
A monodomain phase having no alignment defect was obtained in the same manner as in Example 3 except that Compound 4 was used instead of Compound 1 in Example 3.

(Example 7)
A monodomain phase having no alignment defect was obtained in the same manner as in Example 3 except that Compound ii was used instead of Compound i in Example 3.

(Example 8)
A solution of 2% by weight of Compound 1 dissolved in cyclopentanone and a solution of 1% by weight of Compound iii dissolved in N-methyl-2-pyrrolidinone and 2-n-butoxyethanol (50:50 w%) were each made of ITO. Two coated glass substrates were spin-coated at 4000 rpm for 30 seconds. The substrate coated with the compound 1 solution was spin-dried in an oven at 180 ° C. for 10 minutes, and then exposed to polarized ultraviolet rays at 25 ° C. at an angle of 30 ° with respect to the substrate surface at 100 mJ / cm ² to give the compound iii solution. The spin-coated substrate was dried in an oven at 100 ° C. for 1 minute, and then exposed to polarized ultraviolet rays at 25 ° C. for 1000 mJ / cm ² and then heated at 150 ° C. for 1 hour in a nitrogen atmosphere. A spacer of 1.5 μm was sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. Thereafter, the substrate was assembled in an antiparallel state parallel to the direction of polarized ultraviolet light irradiation, and thermocompression bonding was performed. The liquid crystal is “R2301” (manufactured by Clariant). The liquid crystal is attached to the upper part of the injection port and injected using an oven at a temperature 10 to 20 ° C. higher than the nematic phase-isotropic phase transition temperature. As a result, a monodomain phase free from alignment defects was obtained.

Example 9
A monodomain phase having no alignment defect was obtained in the same manner as in Example 8 except that Compound iv was used instead of Compound iii in Example 8.

It is a schematic perspective view which shows an example of the liquid crystal display element of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. It is a schematic diagram which shows the behavior of a ferroelectric liquid crystal molecule. It is the graph which showed the change of the transmittance | permeability with respect to the applied voltage of a ferroelectric liquid crystal. It is the figure which showed the difference in the orientation defect by the difference in the phase sequence which a ferroelectric liquid crystal has.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal layer 2a, 2b ... Photo-alignment film | membrane 3a ... Common electrode 3b ... X electrode 3c ... Y electrode 3d ... Pixel electrode 4a, 4b ... Substrate 5a, 5b ... Polarizing plate 7 ... TFT element 8 ... Ferroelectric liquid crystal molecule

Claims (17)

A first photo-alignment processing substrate having a first substrate, an electrode layer provided on the first substrate, and a first photo-alignment film formed on the electrode layer; a second substrate; A second photo-alignment processing substrate having an electrode layer provided on two substrates and a second photo-alignment film formed on the electrode layer, wherein the first photo-alignment film and the second photo-alignment film are A liquid crystal display element that is arranged so as to face each other and sandwich a ferroelectric liquid crystal between the first photo-alignment film and the second photo-alignment film,
The constituent materials of the first photo-alignment film and the second photo-alignment film have different compositions from each other,
A liquid crystal display element, wherein the ferroelectric liquid crystal exhibits a chiral smectic C phase via a smectic A phase in a temperature lowering process and exhibits monostability in the chiral smectic C phase. The constituent material of the first photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction, and the constituent material of the second photo-alignment film is photoisomerized 2. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a photoisomerization type material containing a photoisomerization reactive compound that imparts anisotropy to the photoalignment film by causing a reaction. 3. The liquid crystal according to claim 2, wherein the photoisomerization reactive compound has dichroism that makes absorption different depending on a polarization direction, and causes a photoisomerization reaction by light irradiation. 4. Display element. 4. The liquid crystal display element according to claim 2, wherein the photoisomerization reaction is a cis-trans isomerization reaction. 5. The liquid crystal display element according to claim 2, wherein the photoisomerization reactive compound is a compound having an azobenzene skeleton in a molecule. The liquid crystal according to any one of claims 2 to 5, wherein the photoisomerization-reactive compound is a monomolecular compound having an azobenzene skeleton represented by the following formula as a side chain. Display element.

(In the above formula, each R ²¹ independently represents a hydroxyl group. R ²² represents a linking group represented by-(α-β-α) _g- (γ) _h- , and R ²³ represents -(Γ) _h- (α-β-α) _g -represents a linking group, where α represents a divalent hydrocarbon group, and β represents -O-, -CO-O-. , -OCO-, -CONH-, -NHCO-, -NHCO-O-, or -OCONH-, and g represents an integer of 0 to 3. γ is a divalent hydrocarbon when g is 0. And when g is an integer of 1 to 3, it represents -O-, -CO-O-, -OCO-, -CONH-, -NHCO-, -NHCO-O-, or -OCONH-, h independently each .R ²⁴ represents 0 or 1, a halogen atom, a carboxyl group, a halogenated methyl group, halogenated methoxy group, a cyano group A nitro group, a methoxy group or a methoxycarbonyl group. However, the carboxyl group of the alkali metal and good .R ²⁵ also form a salt are each independently a carboxyl group, a sulfo group, a nitro group, an amino group Or a hydroxyl group, provided that a carboxyl group or a sulfo group may form a salt with an alkali metal.) The liquid crystal display element according to any one of claims 2 to 6, wherein the photoisomerization-reactive compound is a polymerizable monomer having an azobenzene skeleton as a side chain. The liquid crystal according to any one of claims 2 to 7, wherein the photoisomerization-reactive compound is a polymerizable monomer having an azobenzene skeleton represented by the following formula as a side chain. Display element.

(In the above formula, each R ³¹ is independently (meth) acryloyloxy group, (meth) acrylamide group, vinyloxy group, vinyloxycarbonyl group, vinyliminocarbonyl group, vinyliminocarbonyloxy group, vinyl group, isopropenyl. An oxy group, an isopropenyloxycarbonyl group, an isopropenyliminocarbonyl group, an isopropenyliminocarbonyloxy group, an isopropenyl group, or an epoxy group, and R ³² represents — (α-β-α) _g- (γ) _h. - represents a linking group represented by, R ³³ represents - a represents a linking group represented here, alpha is a divalent hydrocarbon group _{- (γ) h - (α} -β-α) g. Β represents —O—, —CO—O—, —OCO—, —CONH—, —NHCO—, —NHCO—O—, or —OCONH—, and g represents an integer of 0-3. Γ represents a divalent hydrocarbon group when g is 0, and when g is an integer of 1 to 3, —O—, —CO—O—, —OCO—, —CONH—, — NHCO-, -NHCO-O-, or -OCONH- represents h or 0 or 1. R ³⁴ independently represents a halogen atom, a carboxyl group, a halogenated methyl group, a halogenated methoxy group, or a cyano group. , A nitro group, a methoxy group, or a methoxycarbonyl group, provided that the carboxyl group may form a salt with an alkali metal, and each R ²⁵ independently represents a carboxyl group, a sulfo group, a nitro group, or an amino group. Represents a group or a hydroxyl group, provided that a carboxyl group or a sulfo group may form a salt with an alkali metal.) 2. The constituent material of the first photo-alignment film and the second photo-alignment film is a photo-reactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction. The liquid crystal display element as described in. The constituent material of the first photo-alignment film is a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photodimerization reaction, and the constituent material of the second photo-alignment film is photodecomposition The liquid crystal display element according to claim 9, wherein the liquid crystal display element is a photoreactive material that imparts anisotropy to the photoalignment film by causing a reaction. The liquid crystal display element according to any one of claims 2 to 9, wherein the photoreaction is a photodimerization reaction or a photodecomposition reaction. The photoreactive material that imparts anisotropy to the photo-alignment film by causing the photodimerization reaction has a dichroism having a radical polymerizable functional group and different absorption depending on the polarization direction. The liquid crystal display element according to claim 11, further comprising a photodimerization reactive compound. The liquid crystal display element according to claim 12, wherein the photodimerization reactive compound is a dimerization reactive polymer containing any of cinnamate, coumarin, or quinoline as a side chain. The liquid crystal display element according to claim 12, wherein the photodimerization reactive compound is at least one of dimerization reactive polymers represented by the following formula.

The liquid crystal display element according to any one of claims 1 to 14, wherein the ferroelectric liquid crystal constitutes a single phase. 16. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is driven by an active matrix system using a thin film transistor. The liquid crystal display element according to any one of claims 1 to 16, wherein the liquid crystal display element is driven by a field sequential color system.

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