JP4528645B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element in which the orientation of ferroelectric liquid crystal is controlled.

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

  Ferroelectric liquid crystals are difficult to align due to their higher molecular ordering than nematic liquid crystals, and defects such as zigzag defects and hairpin defects are likely to occur. Such defects cause a decrease in contrast due to light leakage. Become. In particular, in a ferroelectric liquid crystal that does not pass through the SmA phase, two regions having different layer normal directions (hereinafter referred to as “double domain”) are generated (FIG. 4). Such a double domain causes a black / white reversal display during driving, which is a serious problem (FIG. 5). As a method for improving the double domain, there is known an electric field applied slow cooling method in which a liquid crystal cell is heated to a temperature equal to or higher than a cholesteric phase and gradually cooled while a DC voltage is applied (Non-Patent Document 2). When the temperature rises again above the phase transition point, alignment disturbance occurs, and there is a problem that alignment disturbance occurs in a portion where the electric field between the pixel electrodes does not act.

  As a liquid crystal alignment treatment technique, there is a technique using an alignment film, and there are a rubbing method and a photo alignment method. In the rubbing method, a substrate coated with a polyimide film is rubbed to align a polyimide polymer chain in the rubbing direction, thereby aligning liquid crystal molecules on the film. The rubbing method is excellent in controlling the alignment of nematic liquid crystal, and is a technique generally used industrially. In addition, the photo-alignment method irradiates a polymer or a single molecule with light whose polarization is controlled, causes a photoexcitation reaction (decomposition, isomerization, dimerization) and imparts anisotropy to the polymer film. The liquid crystal molecules on the film are aligned. However, it is difficult to suppress the occurrence of double domains by using either method, and it is difficult to obtain monodomain orientation.

  Moreover, although it does not have monostability, as a method of improving the alignment defect of the ferroelectric liquid crystal, Patent Document 1 discloses that a photo-alignment process is performed on the upper and lower alignment films and then the respective alignment films are formed. A method of aligning ferroelectric liquid crystal by forming a nematic liquid crystal layer by applying nematic liquid crystal and aligning and fixing the liquid crystal, and causing the nematic liquid crystal layer to act as an alignment film is disclosed. However, this method does not suppress the occurrence of alignment defects in a ferroelectric liquid crystal having monostability, and no method for improving the double domain is described.

  On the other hand, in recent years, full-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. In the color filter system, a white light source is used as a backlight, and color display is realized by 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. Therefore, the color display can be made high definition, 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. This problem can be solved by using a ferroelectric liquid crystal, but the ferroelectric liquid crystal has a problem that alignment defects are likely to occur as described above, and has not been put into practical use.

JP 2002-532755 A NONAKA, T., LI, J., OGAWA, A., HORNUNG, B., SCHMIDT, W., WINGEN, R., and DUBAL, H., 1999, Liq. Cryst., 26, 1599. PATEL, J., and GOODBY, J. W., 1986, J. Appl. Phys., 59, 2355.

  In the liquid crystal display device using the ferroelectric liquid crystal, the present invention can obtain the monodomain alignment of the ferroelectric liquid crystal without forming alignment defects such as double domains, and raises the temperature to the phase transition temperature or higher. However, it is a main object to provide a liquid crystal display element excellent in alignment stability that hardly causes alignment disorder.

  In order to achieve the above object, the present invention provides a first substrate, an electrode layer formed on the first substrate, a first alignment film formed on the electrode layer, and the first alignment film. A reactive liquid crystal side substrate having a reactive liquid crystal layer formed by immobilizing reactive liquid crystals, a second substrate, an electrode layer formed on the second substrate, and an electrode layer on the electrode layer The counter substrate having the formed second alignment film is disposed so that the reactive liquid crystal layer of the reactive liquid crystal side substrate and the second alignment film of the counter substrate face each other, and the reactive liquid crystal side substrate and the above Provided is a liquid crystal display element characterized by sandwiching a ferroelectric liquid crystal between opposing substrates.

  According to the present invention, since the reactive liquid crystal layer is formed by fixing the reactive liquid crystal aligned by the first alignment film, it can function as an alignment film for aligning the ferroelectric liquid crystal. In addition, reactive liquid crystals are relatively similar in structure to ferroelectric liquid crystals, so the interaction with ferroelectric liquid crystals is stronger and the ferroelectricity is more effective than when only an alignment film is used. The alignment of the liquid crystal can be controlled. Therefore, by forming the reactive liquid crystal layer on the first alignment film, it is possible to suppress the occurrence of alignment defects such as double domains and obtain the monodomain alignment of the ferroelectric liquid crystal. In addition, the alignment treatment is performed using the alignment film and the reactive liquid crystal layer regardless of the voltage application slow cooling method, so that the alignment is maintained even if the temperature is raised above the phase transition temperature, and the double domain, etc. This has the advantage that the occurrence of orientation defects can be suppressed.

  In the present invention, a second reactive liquid crystal layer formed by immobilizing reactive liquid crystal may be formed on the second alignment film. In this case, the reactive liquid crystal constituting the reactive liquid crystal layer is formed. The reactive liquid crystals constituting the second reactive liquid crystal layer preferably have different compositions. This is because the reactive liquid crystal can control the alignment of the ferroelectric liquid crystal more effectively than the case where only the alignment film is used as described above. In addition, since the reactive liquid crystal constituting the reactive liquid crystal layer and the reactive liquid crystal constituting the second reactive liquid crystal layer have different compositions, the occurrence of alignment defects such as double domains is suppressed, and the ferroelectricity This is because the monodomain alignment of the liquid crystal can be obtained.

  In the said invention, it is preferable that the said reactive liquid crystal layer expresses a nematic phase. This is because the nematic phase is relatively easy to control the alignment among the liquid crystal phases.

  Moreover, in the said invention, it is preferable that the said reactive liquid crystal has a polymerizable liquid crystal monomer. The polymerizable liquid crystal monomer can be aligned at a lower temperature than other polymerizable liquid crystal materials, that is, a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, and has high sensitivity in alignment, and can be easily aligned. Because you can.

  Furthermore, in the said invention, it is preferable that the said polymeric liquid crystal monomer is a monoacrylate monomer or a diacrylate monomer. This is because the monoacrylate monomer or diacrylate monomer can be easily polymerized while maintaining the orientation state in a good state.

  Furthermore, in the said invention, it is preferable that the said diacrylate monomer is a compound represented by following formula (1).

  Here, X in the formula is hydrogen, alkyl having 1 to 20 carbons, alkenyl having 1 to 20 carbons, alkyloxy having 1 to 20 carbons, alkyloxycarbonyl having 1 to 20 carbons, formyl, carbon number 1-20 alkylcarbonyl, C1-C20 alkylcarbonyloxy, halogen, cyano or nitro is represented, m represents an integer within the range of 2-20.

  Moreover, in the said invention, it is preferable that the said diacrylate monomer is a compound represented by following formula (2).

Here, Z ²¹ and Z ²² in the formula are each independently directly bonded —COO—, —OCO—, —O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡. C—, —OCH ₂ —, —CH ₂ O—, —CH ₂ CH ₂ COO—, —OCOCH ₂ CH ₂ —, m represents 0 or 1, and n represents an integer in the range of 2-8. To express.

  In the present invention, it is preferable that the first alignment film and the second alignment film are photo-alignment films. This is because the photo-alignment process at the time of forming the photo-alignment film is a non-contact alignment process, so that it is useful in that there is no generation of static electricity and dust and quantitative alignment control is possible.

  Further, in the present invention, the ferroelectric liquid crystal preferably exhibits monostability. This is because by using a ferroelectric liquid crystal exhibiting monostability, it can be effectively used for various applications.

  In the present invention, the ferroelectric liquid crystal preferably does not have a smectic A phase in the phase series. As described above, the ferroelectric liquid crystal having no smectic A phase in the phase series is likely to cause an alignment defect such as a double domain, but the ferroelectric liquid crystal is sandwiched between the reactive liquid crystal layer and the second alignment film. This is because the occurrence of alignment defects such as double domains can be suppressed, and a remarkable effect can be obtained by using the present invention.

  Further, in the present invention, 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. This is because the manufacturing process becomes easy and the drive voltage can be lowered.

  In addition, the liquid crystal display element of the present invention 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 in which a matrix of TFT elements is arranged between an electrode and a substrate can be formed and used as a color liquid crystal display element.

  Furthermore, the liquid crystal display element of the present invention is preferably driven by a field sequential color system. The liquid crystal display device has a high response speed and can align the ferroelectric liquid crystal without causing alignment defects. By driving the field sequential color method, the viewing angle is wide and the high-definition full-color video is available. This is because display can be realized.

  The liquid crystal display device of the present invention can align the ferroelectric liquid crystal without forming alignment defects such as zigzag defects, hairpin defects and double domains, and the alignment is disturbed even when the temperature is raised above the phase transition temperature. It is possible to obtain a liquid crystal display element excellent in alignment stability that is less likely to cause the occurrence of misalignment.

Hereinafter, the liquid crystal display element of the present invention will be described in detail.
The liquid crystal display element of the present invention is formed on a first substrate, an electrode layer formed on the first substrate, a first alignment film formed on the electrode layer, and the first alignment film, A reactive liquid crystal side substrate having a reactive liquid crystal layer formed by immobilizing reactive liquid crystal, a second substrate, an electrode layer formed on the second substrate, and a first layer formed on the electrode layer A counter substrate having two alignment films is disposed so that the reactive liquid crystal layer of the reactive liquid crystal side substrate faces the second alignment film of the counter substrate, and the reactive liquid crystal side substrate and the counter substrate are disposed between. It is characterized by sandwiching a ferroelectric liquid crystal.

  Such a liquid crystal display element of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the liquid crystal display element of the present invention. As shown in FIG. 1, the liquid crystal display element of the present invention includes a first substrate 1a, an electrode layer 2a formed on the first substrate 1a, and a first alignment film 3a formed on the electrode layer 2a. A reactive liquid crystal side substrate 11 having a reactive liquid crystal layer 4 formed on the first alignment film 3a, a second substrate 1b, and an electrode layer 2b formed on the second substrate 1b. The counter substrate 12 has a second alignment film 3b formed on the electrode layer 2b. Further, a ferroelectric liquid crystal is sandwiched between the reactive liquid crystal layer 4 of the reactive liquid crystal side substrate 11 and the second alignment film 3 b of the counter substrate 12 to form the liquid crystal layer 5.

  Since the reactive liquid crystal layer 4 is formed on the first alignment film 3a, the reactive liquid crystal constituting the reactive liquid crystal layer 4 is aligned by the first alignment film 3a. For example, the reactive liquid crystal layer 4 is formed by polymerizing with ultraviolet rays to fix the alignment state of the reactive liquid crystal. Thus, the reactive liquid crystal layer 4 has a function as an alignment film for aligning the ferroelectric liquid crystal constituting the liquid crystal layer 5 since the alignment state of the reactive liquid crystal is fixed. . In addition, the reactive liquid crystal that forms the reactive liquid crystal layer is relatively similar in structure to the ferroelectric liquid crystal, so that the interaction with the ferroelectric liquid crystal becomes stronger. The orientation can be controlled more effectively.

  In the liquid crystal display element of the present invention, the ferroelectric liquid crystal can be aligned without forming alignment defects such as double domains by forming the reactive liquid crystal layer on one of the upper and lower alignment films. There is an effect. In addition, the alignment treatment is performed using the alignment film and the reactive liquid crystal layer regardless of the voltage application slow cooling method, so that the alignment is maintained even if the temperature is raised above the phase transition temperature, and the double domain, etc. This has the advantage that the occurrence of orientation defects can be suppressed.

  In the liquid crystal display element of the present invention, for example, as shown in FIG. 1, polarizing plates 6a and 6b may be provided outside the first substrate 1a and the second substrate 1b. Only light that is polarized and polarized in the alignment direction of the liquid crystal molecules can be transmitted. The polarizing plates 6a and 6b 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 6a is placed so as to be aligned with the orientation of the liquid crystal molecules, so that the light transmitted through the polarizing plate 6a cannot rotate the polarization direction by 90 °, and the polarizing plate 6b It is cut off and darkened. On the other hand, in the voltage application state, the orientation of the liquid crystal molecules is set so as to have an angle θ (preferably θ = 45 °) with respect to the polarizing plates 6a and 6b. It twists and passes through the polarizing plate 6b and becomes bright. As described above, the liquid crystal display element of the present invention uses the ferroelectric liquid crystal as a black and white shutter, and thus has an advantage that the response speed can be increased.

  In the liquid crystal display element of the present invention, for example, as shown in FIG. 2, the counter substrate 12 is a TFT substrate in which thin film transistors (TFTs) 7 are arranged in a matrix, and the reactive liquid crystal side substrate 11 has a common electrode 8a over the entire area. The common electrode substrate formed in the above is preferably a combination of the two substrates. An active matrix liquid crystal display element using such a TFT will be described below.

  In FIG. 2, the reactive liquid crystal side substrate 11 is a common electrode substrate whose electrode layer is a common electrode 8a, while the counter substrate 12 is composed of an x electrode 8b, a y electrode 8c, and a pixel electrode 8d. The TFT substrate is configured. In such a liquid crystal display element, the x electrode 8b and the y electrode 8c are arranged vertically and horizontally, and the TFT element 7 is operated by applying a signal to these electrodes to drive the ferroelectric liquid crystal. be able to. A portion where the x electrode 8b and the y electrode 8c intersect is insulated by an insulating layer (not shown), and the signal of the x electrode 8b and the signal of the y electrode 8c can operate independently. A portion surrounded by the x electrode 8b and the y electrode 8c 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 8d 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 8b and the y electrode 8c. In FIG. 2, the liquid crystal layer and the second alignment film are omitted.

  Further, the liquid crystal display element of the present invention can be used as a color display by forming a micro color filter in which TFT elements are arranged in a matrix between the common electrode 8a and the first substrate 1a.

In FIG. 2, the side on which the common electrode 8a is formed is the reactive liquid crystal side substrate 11, and the side on which the TFT element 7, the pixel electrode 8d and the like are formed is the counter substrate 12, but the liquid crystal display element of the present invention is The configuration is not limited to this, and the side on which the common electrode is formed may be a counter substrate, and the side on which a TFT element, a pixel electrode, or the like is formed may be a reactive liquid crystal side substrate.
Each component of the liquid crystal display element of the present invention will be described in detail below.

1. Components of Liquid Crystal Display Element (1) Reactive Liquid Crystal Side Substrate First, the reactive liquid crystal side substrate will be described. The reactive liquid crystal side substrate in the present invention is formed on a first substrate, an electrode layer formed on the first substrate, a first alignment film formed on the electrode layer, and the first alignment film. And a reactive liquid crystal layer. Hereinafter, each structure of such a reactive liquid crystal side substrate will be described.

(I) Reactive liquid crystal layer The reactive liquid crystal layer used in the present invention is formed on the first alignment film, and is formed by fixing the reactive liquid crystal. The reactive liquid crystal is aligned by the first alignment film. For example, the reactive liquid crystal layer is formed by irradiating ultraviolet rays to polymerize the reactive liquid crystal and fixing the alignment state. Thus, in the present invention, since the reactive liquid crystal layer is formed by fixing the alignment state of the reactive liquid crystal, it can function as an alignment film for aligning the ferroelectric liquid crystal. Further, since the reactive liquid crystal is fixed, it has an advantage that it is not affected by temperature or the like. Furthermore, reactive liquid crystals are relatively similar in structure to ferroelectric liquid crystals, and the interaction with the ferroelectric liquid crystals is stronger, so the ferroelectric liquid crystals are more effective than using only an alignment film. Can be controlled.

  Such a reactive liquid crystal preferably exhibits a nematic phase. This is because the nematic phase is relatively easy to control the alignment among the liquid crystal phases.

  The reactive liquid crystal preferably has a polymerizable liquid crystal material. This is because the alignment state of the reactive liquid crystal can be fixed. As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used. In the present invention, a polymerizable liquid crystal monomer is preferably used. The polymerizable liquid crystal monomer can be aligned at a lower temperature than other polymerizable liquid crystal materials, that is, a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, and has high sensitivity in alignment, and can be easily aligned. Because you can.

  The polymerizable liquid crystal monomer is not particularly limited as long as it is a liquid crystal monomer having a polymerizable functional group, and examples thereof include a monoacrylate monomer and a diacrylate monomer. These polymerizable liquid crystal monomers may be used alone or in combination of two or more.

  As a monoacrylate monomer, the compound represented, for example by a following formula can be illustrated.

In the above formula, A, B, D, E and F represent benzene, cyclohexane or pyrimidine, and these may have a substituent such as halogen. A and B, or D and E may be bonded via a bonding group such as an acetylene group, a methylene group, or an ester group. M ¹ and M ² may be any of a hydrogen atom, an alkyl group having 3 to 9 carbon atoms, an alkoxycarbonyl group having 3 to 9 carbon atoms, or a cyano group. Furthermore, the acryloyloxy group at the end of the molecular chain and A or D may be bonded via a spacer such as an alkylene group having 3 to 6 carbon atoms.

  Moreover, as a diacrylate monomer, the compound as shown to a following formula can be mentioned, for example.

  In the above formula, X and Y are hydrogen, alkyl having 1 to 20 carbons, alkenyl having 1 to 20 carbons, alkyloxy having 1 to 20 carbons, alkyloxycarbonyl having 1 to 20 carbons, formyl, carbon number 1-20 alkylcarbonyl, C1-C20 alkylcarbonyloxy, halogen, cyano or nitro is represented. M represents an integer in the range of 2-20.

  Furthermore, examples of the diacrylate monomer include compounds represented by the following formula.

In the above formula, Z ²¹ and Z ²² are each independently directly bonded —COO—, —OCO—, —O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C—. _{, -OCH 2 -, - CH 2} O -, - CH 2 CH 2 COO -, - OCOCH 2 CH 2 - represents a. M represents 0 or 1, and n represents an integer in the range of 2-8.

In the present invention, among them, compounds represented by the above formula (1) and the above formula (2) are preferably used. In the case of the compound represented by the above formula (1), X is preferably an alkyloxycarbonyl having 1 to 20 carbon atoms, methyl or chlorine, and particularly an alkyloxycarbonyl having 1 to 20 carbon atoms, particularly CH _3. Preferably it is (CH ₂ ) ₄ OCO.

  Among the above, the polymerizable liquid crystal monomer used in the present invention is preferably a diacrylate monomer. This is because the diacrylate monomer can be easily polymerized while maintaining the orientation state in a good state.

  The polymerizable liquid crystal monomer described above does not have to exhibit a nematic phase. In the present invention, these polymerizable liquid crystal monomers may be used as a mixture of two or more as described above, and the composition in which these are mixed, that is, the reactive liquid crystal exhibits a nematic phase. It is because it is good.

  Furthermore, in this invention, you may add a photoinitiator and a polymerization inhibitor to the said reactive liquid crystal as needed. For example, when polymerizing a polymerizable liquid crystal material by electron beam irradiation, a photopolymerization initiator may not be necessary, but in the case of polymerization by, for example, ultraviolet irradiation, usually photopolymerization is started. This is because the agent is used for promoting the polymerization.

  Examples of the photopolymerization initiator that can be used in the present invention include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, benzoylmethyl benzoate, and 4-benzoyl-4'-methyldiphenyl sulfide. Benzylmethyl ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoyl formate, 2 -Methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, -(4- Dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl)- 2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythioxanthone, etc. Can be mentioned. In addition to the photopolymerization initiator, it is also possible to add a sensitizer as long as the object of the present invention is not impaired.

  The amount of the photopolymerization initiator added is generally 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. It can be added to the liquid crystal.

  The thickness of the reactive liquid crystal layer used in the present invention is preferably in the range of 1 nm to 1000 nm, more preferably in the range of 3 nm to 100 nm. This is because if the reactive liquid crystal layer is thicker than the above range, anisotropy more than necessary occurs, and if it is thinner than the above range, the predetermined anisotropy may not be obtained. Therefore, the thickness of the reactive liquid crystal layer may be determined according to the required anisotropy.

  Next, a method for forming the reactive liquid crystal layer will be described. The reactive liquid crystal layer is formed by applying a reactive liquid crystal layer coating liquid containing the reactive liquid crystal on the first alignment film, performing an alignment treatment, and fixing the alignment state of the reactive liquid crystal. be able to.

  Further, instead of applying the coating liquid for the reactive liquid crystal layer, a method of forming a dry film or the like in advance and laminating it on the first alignment film can also be used. It is preferable to use a method in which a liquid crystal is dissolved in a solvent to prepare a coating liquid for a reactive liquid crystal layer, which is applied onto the first alignment film, and the solvent is removed. This is because this method is relatively simple in terms of steps.

  The solvent used in the coating liquid for the reactive liquid crystal layer is not particularly limited as long as it can dissolve the reactive liquid crystal and the like and does not inhibit the alignment ability of the first alignment film. For example, hydrocarbons such as benzene, toluene, xylene, n-butylbenzene, diethylbenzene and tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene and diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 2 Ketones such as 1,4-pentanedione; esters such as ethyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone; 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl Amide solvents such as acetamide; t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethyleneglycol Alcohols such as hexylene glycol, phenols, phenols such as phenol and parachlorophenol, and one or more cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and ethylene glycol monomethyl ether acetate can be used. .

  Further, if only a single type of solvent is used, the solubility of the reactive liquid crystal or the like may be insufficient, or the first alignment film may be eroded as described above. However, this inconvenience can be avoided by using a mixture of two or more solvents. Among the above-mentioned solvents, hydrocarbons and glycol monoether acetate solvents are preferable as the sole solvent, and mixed solvents of ethers or ketones and glycol solvents are preferable as the mixed solvent. It is. The concentration of the coating liquid for the reactive liquid crystal layer depends on the solubility of the reactive liquid crystal and the thickness of the reactive liquid crystal layer to be formed. It is preferably adjusted in the range of 1 to 20% by weight. If the concentration of the coating liquid for the reactive liquid crystal layer is lower than the above range, the reactive liquid crystal may be difficult to align. Conversely, if the concentration of the coating liquid for the reactive liquid crystal layer is higher than the above range, This is because, since the viscosity of the liquid crystal layer coating liquid is increased, it may be difficult to form a uniform coating film.

  Furthermore, the following compounds can be added to the reactive liquid crystal layer coating liquid within the range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amine epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meth) Acry Photopolymerizable compound in epoxy (meth) acrylate obtained by reacting an acid; photopolymerizable liquid crystal compound having an acryl group or methacryl group and the like. The amount of these compounds added to the reactive liquid crystal is selected within a range that does not impair the object of the present invention. Addition of these compounds improves the curability of the reactive liquid crystal, increases the mechanical strength of the resulting reactive liquid crystal layer, and improves its stability.

  Examples of the method for applying such a coating liquid for a reactive liquid crystal layer include spin coating, roll coating, printing, dip coating, curtain coating (die coating), casting, bar coating, and blade coating. Method, spray coating method, gravure coating method, reverse coating method, extrusion coating method and the like.

  Further, after the reactive liquid crystal layer coating liquid is applied, the solvent is removed. The removal of the solvent is performed, for example, by removing under reduced pressure or removing by heating, or by a combination of these.

  In the present invention, the reactive liquid crystal applied as described above is aligned by the first alignment film so as to have liquid crystal regularity. That is, a nematic phase is developed in the reactive liquid crystal. This is usually performed by a method such as a method of performing a heat treatment below the NI transition point. Here, the NI transition point indicates the temperature at which the liquid crystal phase transitions to the isotropic phase.

  As described above, the reactive liquid crystal has a polymerizable liquid crystal material, and in order to fix the alignment state of such a polymerizable liquid crystal material, a method of irradiating active radiation that activates polymerization is used. . The active radiation as used herein refers to radiation capable of causing polymerization of the polymerizable liquid crystal material. If necessary, a photopolymerization initiator may be included in the polymerizable liquid crystal material.

  The actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material, but usually ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus. Irradiation light having a wavelength of 150 to 500 nm, preferably 250 to 450 nm, and more preferably 300 to 400 nm is used.

  In the present invention, a method of irradiating ultraviolet rays with active radiation to a polymerizable liquid crystal material in which the photopolymerization initiator generates radicals with ultraviolet rays and the polymerizable liquid crystal material undergoes radical polymerization is a preferable method. . This is because the method using ultraviolet rays as actinic radiation is an already established technique, and therefore it can be easily applied to the present invention including the photopolymerization initiator to be used.

  As the light source of this irradiation light, low pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), high pressure discharge lamp (high pressure mercury lamp, metal halide lamp), short arc discharge lamp (super high pressure mercury lamp, xenon lamp, mercury xenon) Lamp). In particular, the use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity is appropriately adjusted according to the composition of the reactive liquid crystal and the amount of photopolymerization initiator.

  Such irradiation with active radiation may be performed under a temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, or may be performed at a temperature lower than the temperature at which the liquid crystal phase is formed. This is because the alignment state of the polymerizable liquid crystal material once in the liquid crystal phase is not disturbed suddenly even if the temperature is lowered thereafter.

  As a method for fixing the alignment state of the polymerizable liquid crystal material, in addition to the method of irradiating the active radiation, a method of polymerizing the polymerizable liquid crystal material by heating can also be used. As the reactive liquid crystal used in this case, it is preferable that the polymerizable liquid crystal monomer contained in the reactive liquid crystal is thermally polymerized below the NI transition point of the reactive liquid crystal.

(Ii) First Alignment Film Next, the first alignment film used in the present invention will be described. The first alignment film used in the present invention is not particularly limited as long as it can align the reactive liquid crystal and does not adversely affect the alignment state of the reactive liquid crystal. For example, a material subjected to a rubbing treatment, a photo-alignment treatment or the like can be used, but in the present invention, a photo-alignment film subjected to a photo-alignment treatment is preferably used. This is because the photo-alignment process is a non-contact alignment process, which is useful in that it does not generate static electricity or dust and can quantitatively control the alignment process.

  The constituent material of the photo-alignment film, the photo-alignment processing method, and the like are described in the column of the second alignment film of the counter substrate described later, and thus the description thereof is omitted here.

(Iii) 1st board | substrate Next, the 1st board | substrate used for this invention is demonstrated. The 1st board | substrate used for this invention will not be specifically limited if generally used as a board | substrate of a liquid crystal display element, For example, a glass plate, a plastic plate, etc. are mentioned preferably. The surface roughness (RSM value) of the first substrate is preferably 10 nm or less, more preferably 3 nm or less, and still more preferably 1 nm or less. In the present invention, the surface roughness can be measured by an atomic force microscope (AFM: ATOMIC FORCE MICROSCOPE).

(Iv) Electrode layer Next, the electrode layer used in the present invention will be described. The electrode layer used in the present invention is not particularly limited as long as it is generally used as an electrode of a liquid crystal display element, but at least one of the electrode layer of the reactive liquid crystal side substrate and the counter substrate is a transparent conductive layer. It is preferably formed of a body. 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 TFTs, one of the electrode layers of the reactive liquid crystal side substrate and the counter substrate is formed of the transparent conductor. On the other side, an x electrode and a y electrode are arranged in a matrix, and a TFT element and a 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 first substrate by a vapor deposition method such as a CVD method, a sputtering method, or an ion plating method, and the x electrode and the y electrode are formed by patterning this in a matrix shape. Can be formed.

(2) Counter substrate Next, the counter substrate used in the present invention will be described. The counter substrate in the present invention includes a second substrate, an electrode layer formed on the second substrate, and a second alignment film formed on the electrode layer. Hereinafter, each configuration of the counter substrate will be described. The second substrate is the same as that described in the column of the first substrate of the reactive liquid crystal side substrate, and the electrode layer is the same as that described in the column of the electrode layer of the reactive liquid crystal side substrate. Therefore, the description here is omitted.

(I) Second alignment film The second alignment film used in the present invention is not particularly limited as long as the ferroelectric liquid crystal can be aligned. For example, a rubbing process, a photo-alignment process, etc. are performed. In the present invention, it is preferable to use a photo-alignment film that has been subjected to a photo-alignment treatment. This is because the photo-alignment process is a non-contact alignment process, which is useful in that it does not generate static electricity or dust and can quantitatively control the alignment process. Hereinafter, such a photo-alignment film will be described.

(Photo-alignment film)
A photo-alignment film is anisotropic to a film obtained by irradiating a substrate on which a constituent material of the photo-alignment film described later is applied with light with controlled polarization to cause a photoexcitation reaction (decomposition, isomerization, dimerization). Is used to align liquid crystal molecules on 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.

  Here, the photoisomerization reaction refers to a phenomenon in which a single compound changes to another isomer by light irradiation. By using such a photoisomerizable 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.

  In addition, the photoreaction is not 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. Is easier, 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.

  In the present invention, as the constituent material of the photo-alignment film, among the above, it is preferable to use a photoreactive material that imparts anisotropy to the photo-alignment film by causing a photodimerization reaction or a photodecomposition reaction.

  The wavelength region of the light that causes the photoexcitation reaction of the constituent material of the photo-alignment film is preferably in the ultraviolet light range, that is, in the range of 10 nm to 400 nm, and more preferably in the range of 250 nm to 380 nm. .

  The photoisomerization type material is not particularly limited as long as it is a material that can impart anisotropy to the photoalignment film by a photoisomerization reaction, but dichroism that makes absorption different depending on the polarization direction. It is preferable to include a photoisomerization reactive compound that has an isomerization reaction upon irradiation with light. 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 isomerization 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 used in the present invention include a monomolecular compound or 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.

  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.

  Among the photomolecular isomerization reactive compounds of the monomolecular compound or polymerizable monomer as described above, the photoisomerization reactive compound used in the present invention 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.

  In addition, 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 material. It is preferable to include a photodimerization reactive compound having a dichroism having a functional group and 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.

  Furthermore, examples of the photoreactive material utilizing photolysis reaction include polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd.

  Moreover, the constituent material of the photo-alignment film used in the present invention may contain an additive as long as the optical alignment property of the photo-alignment film is not hindered. Examples of the additive include a polymerization initiator and a polymerization inhibitor.

  Next, the photo-alignment processing method will be described. First, a coating solution obtained by diluting the constituent material of the above-described photo-alignment film with an organic solvent is applied onto the surface of the second substrate provided with the electrode layer facing the liquid crystal layer, and dried. In this case, the content of the photodimerization reactive compound or photoisomerization reactive compound in the coating liquid is preferably in the range of 0.05% by weight to 10% by weight, More preferably, it is in the range of 2% by weight. If the content is smaller than the above range, it becomes difficult to impart an appropriate anisotropy to the alignment film. Conversely, if the content is larger than the above range, the viscosity of the coating liquid increases, so that a uniform coating film is formed. It is because it becomes difficult to form.

  As a 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 film obtained by applying the above constituent materials is preferably in the range of 1 nm to 1000 nm, more preferably in the range of 3 nm to 100 nm. This is because if the thickness of the film is thinner than the above range, sufficient optical alignment may not be obtained, and conversely, if the thickness is thicker than the above range, it may be disadvantageous in cost.

  The obtained film can impart anisotropy by causing a photoexcitation reaction by irradiating light with polarization controlled. 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 improved, the first alignment film and the second alignment film are not limited. Both the alignment films are preferably in the range of 0 ° to 45 ° oblique to the substrate surface, and more preferably in the range of 20 ° to 45 °.

  Furthermore, when a polymerizable monomer is used as a constituent material of the photo-alignment film, among the above photoisomerization-reactive compounds, after photo-alignment treatment, it is polymerized by heating to form a photo-alignment film. The provided anisotropy can be stabilized.

(Ii) Second Reactive Liquid Crystal Layer In the present invention, a second reactive liquid crystal layer formed by fixing a reactive liquid crystal may be formed on the second alignment film. In this case, it is preferable that the reactive liquid crystal constituting the reactive liquid crystal layer of the reactive liquid crystal side substrate and the reactive liquid crystal constituting the second reactive liquid crystal layer of the counter substrate have different compositions. This is because the reactive liquid crystal can control the alignment of the ferroelectric liquid crystal more effectively than the case where only the alignment film is used, as described above. In addition, since the reactive liquid crystal constituting the reactive liquid crystal layer and the reactive liquid crystal constituting the second reactive liquid crystal layer have different compositions, the occurrence of alignment defects such as double domains is suppressed, and the ferroelectricity This is because the monodomain alignment of the liquid crystal can be obtained.

  In addition, about the reactive liquid crystal used for a 2nd reactive liquid crystal layer, the formation method of a 2nd reactive liquid crystal layer, etc., the column of "(1) reactive liquid crystal side substrate (i) reactive liquid crystal layer" mentioned above. It is the same as that described in.

  In the present invention, the reactive liquid crystal constituting the reactive liquid crystal layer and the reactive liquid crystal constituting the second reactive liquid crystal layer are selected by variously selecting the polymerizable functional group and substituent of the polymerizable monomer described above. The composition of can be different. In this case, the polymerizable functional groups of the polymerizable monomers used for the two reactive liquid crystals may be the same or different. In the present invention, two or more kinds of polymerizable monomers can be used in combination, and the composition can be changed by changing the combination. Furthermore, even when the same combination is used, the composition can be made different by changing the content of each polymerizable monomer.

(3) Liquid Crystal Layer Next, the liquid crystal layer used in the present invention will be described. The liquid crystal layer in the present invention is configured by sandwiching a ferroelectric liquid crystal between the reactive liquid crystal layer and the second alignment film. The ferroelectric liquid crystal used in the liquid crystal layer is not particularly limited as long as it exhibits a chiral smectic C phase (SmC ^* ), but the phase sequence of the ferroelectric liquid crystal is a nematic phase (N)- It is preferable that the material is a material that changes phase with the cholesteric phase (Ch) -chiral smectic C phase (SmC ^* ) or nematic phase (N) -chiral smectic C phase (SmC ^* ) and does not pass through the smectic A phase (SmA). .

  When the liquid crystal display element of the present invention is driven by a field sequential color system, it is preferable to use a liquid crystal material having monostability that does not pass through the smectic A phase. Here, monostable refers to the property of having only one stable state when no voltage is applied as described above, and in particular, half V-shaped driving in which liquid crystal molecules operate only when either positive or negative voltage is applied. This is preferable in that the opening time of the black-and-white shutter can be increased and a bright full-color display can be realized.

  Further, in the present invention, by using such a monostable liquid crystal material that does not pass through the smectic A phase, driving by an active matrix method using a thin film transistor (TFT) is possible, and voltage modulation is performed. Thus, gradation control is possible, and high-definition and high-quality display 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 a polymer stabilization method or a polymer stabilization method. Thus, by using a single-phase ferroelectric liquid crystal, there are advantages that the manufacturing process becomes easy and the drive voltage can be lowered.

  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 thin, the contrast may be lowered. Conversely, if the thickness of the liquid crystal layer is too thick, the ferroelectric liquid crystal may be difficult to align.

  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 obtained by heating the ferroelectric liquid crystal into a liquid crystal cell in which a reactive liquid crystal side substrate and a counter substrate are previously prepared, and is injected using the capillary effect and sealed with an adhesive. Thus, a liquid crystal layer can be formed. The thickness of the liquid crystal layer can be adjusted by a spacer such as beads.

(4) Polarizing plate Next, the polarizing plate used for this invention is demonstrated. The polarizing plate in the present invention is not particularly limited as long as it transmits only a specific direction among the wave of light, and a polarizing plate generally used as a polarizing plate of a liquid crystal display element can be used.

2. Next, a method for manufacturing a liquid crystal display element of the present invention will be described. The liquid crystal display element of this invention can be manufactured by the method generally used as a manufacturing method of 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 the first substrate by the vapor deposition method described above to form a common electrode on the entire surface. Furthermore, a photo-alignment film material is applied on the common electrode, and a photo-alignment process is performed to form a first alignment film. A reactive liquid crystal layer coating is applied on the first alignment film, and the reactive liquid crystal is aligned and fixed to form a reactive liquid crystal layer, which is used as a reactive liquid crystal side substrate. On the second substrate, an x electrode and a y electrode are formed by patterning a transparent conductive film on a matrix, and a switching element and a pixel electrode are provided. Further, a photo-alignment film material is applied on the x electrode, the y electrode, the switching element, and the pixel electrode, and a photo-alignment process is performed to form a second alignment film, thereby forming a counter substrate. Beads are dispersed as spacers on the second alignment film of the counter substrate thus formed, and a sealant is applied to the periphery so that the reactive liquid crystal layer of the reactive liquid crystal side substrate and the photo alignment film of the counter substrate face each other. Bond together and heat-press. 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. Next, the use of the liquid crystal display element of the present invention will be described. The liquid crystal display element of the present invention is preferably driven by an active matrix system using a thin film transistor (TFT), and can be a color liquid crystal display element by adopting a color filter system or a field sequential color system. In the present invention, the color display is possible by arranging the micro color filter on the TFT substrate side or the common electrode substrate side. However, the micro color filter is used by utilizing the high-speed response of the ferroelectric liquid crystal. Therefore, color display by a field sequential color system is possible in combination with an LED light source. In addition, 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, and thus has a wide viewing angle, high speed response, and high definition. Color display can be realized.

  Among these, the liquid crystal display element of the present invention is preferably driven by a field sequential color system. This is because, as described above, the field sequential color method divides one pixel in time and particularly requires high-speed response in order to obtain good moving image display characteristics.

  In this case, as the ferroelectric liquid crystal, it is preferable to use a material having monostable characteristics that expresses a chiral smectic C phase from a cholesteric phase without passing through a smectic A phase. Such a material exhibits electro-optic characteristics in which the inclination of the major axis of liquid crystal molecules is the same when a positive voltage is applied and when a negative voltage is applied, and the light transmittance with respect to the applied voltage is asymmetric. This characteristic is referred to herein as half-V shaped switching (HV-shaped switching). By using a material exhibiting such HV-shaped switching characteristics, the opening time as a black and white shutter can be made sufficiently long. Accordingly, each color that can be switched over time can be displayed brighter, and a bright full-color liquid crystal display element can be realized.

  When the ferroelectric liquid crystal exhibits monostability, the liquid crystal display element of the present invention is basically driven by an active matrix system using TFTs, but can also be driven by a segment system.

  In addition, this invention is not limited to the said 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.

  Hereinafter, the present invention will be specifically described with reference to examples.

[Example 1]
As a material for the alignment film, a compound A represented by the following formula I was used, and as a liquid crystal material for the reactive liquid crystal layer, a compound B represented by the following formula II was used.

A solution of 2% by weight of Compound A dissolved in cyclopentanone was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. After drying at 180 ° C. for 10 minutes in an oven, polarized ultraviolet rays were exposed to 100 mJ / cm ² from an angle of 30 ° with respect to the substrate surface at 25 ° C. Further, a solution of 2% by weight of Compound B dissolved in cyclopentanone was spin-coated at a rotation speed of 4000 rpm for 30 seconds on one substrate and dried at 55 ° C. for 3 minutes. And 1000 mJ / cm ² exposure. Thereafter, a 1.5 μm spacer was sprayed on one substrate, and a sealing material was applied to the other substrate with a seal dispenser. The substrate was assembled in an antiparallel state parallel to the polarized UV irradiation direction, and thermocompression bonded. The liquid crystal is “R2301” (manufactured by Clariant). The liquid crystal is attached to the upper part of the injection port, and is injected at a temperature 10 ° C. to 20 ° C. higher than the nematic phase-isotropic phase transition temperature using an oven. When returned to 1, monodomain alignment without alignment defects was obtained.

[Example 2]
As the liquid crystal material of the reactive liquid crystal layer, the compound B represented by the above formula II was used.

A polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd. was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. After drying in an oven at 180 ° C. for 10 minutes, polarized ultraviolet rays were exposed to 100 J / cm ² at 25 ° C. Further, a solution of 2% by weight of Compound B dissolved in cyclopentanone was spin-coated at a rotation speed of 4000 rpm for 30 seconds on one substrate and dried at 55 ° C. for 3 minutes. And 1000 mJ / cm ² exposure. Thereafter, the cells were assembled by the method described above, and liquid crystal was injected. As a result, monodomain alignment without alignment defects was obtained.

[Example 3]
The compound A represented by the above formula I was used as the material for the alignment film, and the compound C represented by the following formula III was used as the liquid crystal material for the reactive liquid crystal layer.

A solution of 2% by weight of Compound A dissolved in cyclopentanone was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. After drying at 180 ° C. for 10 minutes in an oven, polarized ultraviolet rays were exposed to 100 mJ / cm ² from an angle of 30 ° with respect to the substrate surface at 25 ° C. Further, a 2 wt% compound C solution dissolved in cyclopentanone was spin-coated on one substrate at a rotational speed of 4000 rpm for 30 seconds and dried at 55 ° C. for 3 minutes. And 1000 mJ / cm ² exposure. Thereafter, the cells were assembled by the method described above, and liquid crystal was injected. As a result, monodomain alignment without alignment defects was obtained.

[Example 4]
As the liquid crystal material of the reactive liquid crystal layer, the compound C represented by the above formula III was used.
A polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd. was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. After drying in an oven at 180 ° C. for 10 minutes, polarized ultraviolet rays were exposed to 100 J / cm ² at 25 ° C. Further, a 2 wt% compound C solution dissolved in cyclopentanone was spin-coated on one substrate at a rotational speed of 4000 rpm for 30 seconds and dried at 55 ° C. for 3 minutes. And 1000 mJ / cm ² exposure. Thereafter, the cells were assembled by the method described above, and liquid crystal was injected. As a result, monodomain alignment without alignment defects was obtained.

[Example 5]
As the material for the alignment film, the compound A represented by the above formula I is used, and as the liquid crystal material for the reactive liquid crystal layer, the compound B represented by the above formula II and the compound C represented by the above formula III are used. Using.
A solution of 2% by weight of Compound A dissolved in cyclopentanone was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. After drying at 180 ° C. for 10 minutes in an oven, polarized ultraviolet rays were exposed to 100 mJ / cm ² from an angle of 30 ° with respect to the substrate surface at 25 ° C. Further, a 2 wt% compound B solution dissolved in cyclopentanone on one substrate and a 2 wt% compound C solution dissolved in cyclopentanone on the other substrate were spun at a rotational speed of 4000 rpm for 30 seconds. After coating and laminating and drying at 55 ° C. for 3 minutes, non-polarized ultraviolet light was exposed to 1000 mJ / cm ² at 55 ° C. Thereafter, the cells were assembled by the method described above, and liquid crystal was injected. As a result, monodomain alignment without alignment defects was obtained.

[Comparative Example 1]
As the material of the alignment film, the compound A represented by the above formula I was used.

  A solution of 2% by weight of Compound A dissolved in cyclopentanone was spin-coated on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. Furthermore, when cells were assembled by the method described above and liquid crystal was injected, monodomain alignment was not obtained, and alignment defects such as double domains, zigzag defects, and hairpin defects occurred.

[Comparative Example 2]
As a material for the alignment film, polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd. was used, and spin coating was performed on two glass substrates coated with ITO at a rotational speed of 4000 rpm for 30 seconds. After drying in an oven at 180 ° C. for 10 minutes, polarized ultraviolet rays were exposed to 100 J / cm ² at 25 ° C. Thereafter, when cells were assembled by the method described above and liquid crystal was injected, monodomain alignment was not obtained, and alignment defects such as double domains, zigzag defects, and hairpin defects occurred.

It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. It is a schematic perspective view which shows an example of the liquid crystal display element of this invention. 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. It is the photograph which showed the double domain which is the orientation defect of a ferroelectric liquid crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... 1st board | substrate 1b ... 2nd board | substrate 2a, 2b ... Electrode layer 3a ... 1st orientation film 3b ... 2nd orientation film 4 ... Reactive liquid crystal layer 5 ... Liquid crystal layer 6a, 6b ... Polarizing plate 11 ... Reactive liquid crystal side Substrate 12 ... Counter substrate

Claims (9)

A first substrate; an electrode layer formed on the first substrate; a first alignment film formed on the electrode layer; and a reactive liquid crystal formed on the first alignment film and exhibiting a nematic phase. A reactive liquid crystal side substrate having a reactive liquid crystal layer fixed in a state having liquid crystal regularity, a second substrate, an electrode layer formed on the second substrate, and on the electrode layer The counter substrate having the formed second alignment film is disposed so that the reactive liquid crystal layer of the reactive liquid crystal side substrate faces the second alignment film of the counter substrate, and the reaction of the reactive liquid crystal side substrate is performed. A ferroelectric liquid crystal is sandwiched between the conductive liquid crystal layer and the second alignment film of the counter substrate;
The ferroelectric liquid crystal does not have a smectic A phase in a phase series, exhibits monostability, is driven by a half V-shape , and enables gradation display by voltage change .
Furthermore, the ferroelectric liquid crystal exhibits monodomain alignment in a liquid crystal layer. The liquid crystal display element according to claim 1 , wherein the reactive liquid crystal includes a polymerizable liquid crystal monomer. The liquid crystal display element according to claim 2 , wherein the polymerizable liquid crystal monomer is a monoacrylate monomer or a diacrylate monomer. The liquid crystal display element according to claim 3 , wherein the diacrylate monomer is a compound represented by the following formula (1).

(Here, X is hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 1 to 20 carbon atoms, alkyloxy having 1 to 20 carbon atoms, alkyloxycarbonyl having 1 to 20 carbon atoms, formyl, carbon Represents an alkylcarbonyl having 1 to 20 carbon atoms, an alkylcarbonyloxy having 1 to 20 carbon atoms, halogen, cyano or nitro, and m represents an integer within the range of 2 to 20.) The liquid crystal display element according to claim 3 , wherein the diacrylate monomer is a compound represented by the following formula (2).

(Wherein Z ²¹ and Z ²² in the formula are each independently directly bonded —COO—, —OCO—, —O—, —CH ₂ CH ₂ —, —CH═CH—, —C ≡C—, —OCH ₂ —, —CH ₂ O—, —CH ₂ CH ₂ COO—, —OCOCH ₂ CH ₂ —, m represents 0 or 1, and n represents an integer in the range of 2-8. Represents.) The liquid crystal display element according to any one of claims 1 to 5, wherein the first alignment film and the second alignment film are photo-alignment films. The ferroelectric liquid crystal, the liquid crystal display device according to any one of claims of claims 1 to 6, characterized in that it constitutes a single phase. The liquid crystal display device according to any one of claims of claims 1 to 7, characterized in that driving by an active matrix system using a thin film transistor. The liquid crystal display element according to any one of claims 1 to 8 , wherein the liquid crystal display element is driven by a field sequential color system.

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