JP4862281B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element in which a ferroelectric liquid crystal exhibits a monostable operation mode.

  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). Ferroelectric liquid crystals that can exhibit monostability include materials that change phase with the cholesteric phase (Ch) -chiral smectic C (SmC ^* ) phase in the temperature lowering process and do not pass through the smectic A (SmA) phase, In the process, there is a material that changes phase with Ch-SmA-SmC ^* and exhibits the SmC ^* phase via the SmA phase (FIG. 4).

  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. Further, the ferroelectric liquid crystal having no SmA phase in the phase series generates two regions having different layer normal directions (hereinafter referred to as “double domain”) (FIG. 4). Such a double domain causes a black / white reversal display during driving, which is a serious problem (FIG. 5). On the other hand, a ferroelectric liquid crystal having an SmA phase in a phase series usually has two stable states with respect to a single-layer normal, and is known to exhibit bistability. It is difficult to obtain.

  In general, as an alignment treatment technique for liquid crystals, there is a technique using an alignment film, which includes 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 obtain mono-stabilized ferroelectric liquid crystal alignment using either method.

  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 the ferroelectric liquid crystal having monostability.

  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, ... temporally, and synchronizes with it to open and close the black-and-white shutter of the ferroelectric liquid crystal, 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.

  The main object of the present invention is to provide a liquid crystal display element using a ferroelectric liquid crystal, in which the ferroelectric liquid crystal exhibits a monostable operation mode.

  As a result of intensive studies in view of the above circumstances, the present inventors fixed a reactive liquid crystal containing a specific compound on at least one opposing surface of two alignment films that control the alignment of the ferroelectric liquid crystal. By providing the reactive liquid crystal layer, it was found that the ferroelectric liquid crystal exhibits a monostable operation mode, and the present invention was completed.

That is, 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. A reactive liquid crystal side substrate formed on a film and having a reactive liquid crystal layer formed by fixing a reactive liquid crystal, a second substrate, an electrode layer formed on the second substrate, and the electrode layer A counter substrate having a second alignment film formed thereon 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 a liquid crystal display element having a liquid crystal layer made of a ferroelectric liquid crystal sandwiched between the opposing substrates,
A liquid crystal display element, wherein the reactive liquid crystal includes a compound (1) represented by the following formula.

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 —, wherein l and m represent 0 or 1, and n is within the range of 2-8. Represents an integer. Moreover, R in the formula represents alkyl having 1 to 5 carbon atoms when l = 1, and represents hydrogen or alkyl having 1 to 5 carbon atoms when l = 0.

  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, since the compound represented by the above formula is relatively similar in structure to the ferroelectric liquid crystal, when the compound represented by the above formula is included in the reactive liquid crystal, And the alignment of the ferroelectric liquid crystal can be controlled more effectively than when only the alignment film is used. Furthermore, in the present invention, since the reactive liquid crystal layer is formed on the first alignment film, the liquid crystal layer is sandwiched between alignment films having different compositions. Therefore, zigzag defects, hairpin defects, double domains, etc. The occurrence of alignment defects can be suppressed, and a monostable operation mode can be realized using a ferroelectric liquid crystal.

  In the present invention, a second reactive liquid crystal layer formed by fixing the reactive liquid crystal may be formed on the second alignment film, and 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, 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, thereby causing alignment defects such as zigzag defects, hairpin defects, and double domains. This is because a monostable operation mode can be realized using a ferroelectric liquid crystal.

  In the present invention, the first alignment film or the second alignment film is preferably a photo-alignment film. 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 constituent material of the photo-alignment film is a photo-reactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction or the photo-alignment by causing a photoisomerization reaction. A photoisomerization type material containing a photoisomerization reactive compound that imparts anisotropy to the film is preferable. It is because anisotropy can be easily imparted to the photo-alignment film by using such a material.

  The ferroelectric liquid crystal preferably exhibits monostability. This is because the use of the ferroelectric liquid crystal exhibiting monostability makes the effect of the configuration of the present invention remarkable.

  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 element of the present invention has an effect that a monostable operation mode can be realized using a ferroelectric liquid crystal.

  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. A liquid crystal layer made of a ferroelectric liquid crystal is sandwiched.

  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 liquid crystal layer 5 made of 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 3b of the counter substrate 12.

  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. As described above, the reactive liquid crystal layer 4 has a fixed alignment state of the reactive liquid crystal, and thus has a function as an alignment film for aligning the ferroelectric liquid crystal contained in the liquid crystal layer 5. .

Further, the reactive liquid crystal constituting the reactive liquid crystal layer contains the compound (1) represented by the above formula, but the compound (1) is relatively similar in structure to the ferroelectric liquid crystal. Since the interaction with the ferroelectric liquid crystal becomes strong, the alignment can be controlled more effectively than when only the alignment film is used.

  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 installed 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 a voltage application state, linearly polarized light becomes circularly polarized light by setting the orientation of liquid crystal molecules to have an angle θ (preferably θ = 45 °) with respect to the polarizing plates 6a and 6b. The light passes through the polarizing plate 6b and enters a bright state. 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.

  Hereinafter, each constituent member of the liquid crystal display element of the present invention will be described in detail.

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.

(1) 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 containing the compound (1). 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. Further, the compound (1) is relatively similar in structure to the ferroelectric liquid crystal and has a strong interaction with the ferroelectric liquid crystal, so that it is more effective than the case where only the alignment film is used. The orientation of the crystalline liquid crystal can be controlled.

  The reactive liquid crystal used in the reactive liquid crystal layer is not particularly limited as long as it contains the compound (1) represented by the above formula, and may contain other compounds.

  Specific examples of the compound (1) represented by the above formula include Adeka Kiracol PLC-7209 (manufactured by Asahi Denka Kogyo Co., Ltd.).

  Furthermore, in this invention, you may add a photoinitiator and a polymerization inhibitor to the said reactive liquid crystal as needed. For example, when the reactive liquid crystal is polymerized by electron beam irradiation, a photopolymerization initiator may not be necessary, but in the case of polymerization by commonly used, for example, UV 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, dimethylaminomethyl benzoate, 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 mass, preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass. It can be added to the liquid crystal.

  Furthermore, when using the said photoinitiator, a photoinitiator adjuvant can be used together. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

  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 previously forming a dry film or the like made of the reactive liquid crystal and laminating it on the first alignment film can be used. In the invention, it is preferable to use a method in which the reactive 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 phenol and hexylene glycol; phenols such as phenol and parachlorophenol; one or more of 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. , Preferably, it adjusts in the range of 1-20 mass%. 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. Such an alignment treatment 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.

  In order to fix the alignment state of the reactive liquid crystal, a method of irradiating actinic 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.

  Such actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing the reactive liquid crystal, but usually ultraviolet light or visible light is used from the viewpoint of easiness 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.

  As a light source for the irradiation light, a low-pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high-pressure discharge lamp (high-pressure mercury lamp, metal halide lamp), a short arc discharge lamp (ultra-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 irradiation rays may be performed under temperature conditions where the reactive liquid crystal becomes a liquid crystal phase, or may be performed at a temperature lower than the temperature at which the liquid crystal phase becomes. This is because the reactive liquid crystal once in the liquid crystal phase does not suddenly disturb the alignment state even if the temperature is lowered thereafter.

  In addition, as a method of fixing the alignment state of the reactive liquid crystal, a method of polymerizing the reactive liquid crystal by heating can be used in addition to the method of irradiating the active radiation.

(2) 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. Hereinafter, such a photo-alignment film will be described.

  The photo-alignment film is anisotropic to the film obtained by irradiating the substrate coated with the constituent material of the photo-alignment film, which will be described later, with light whose polarization is controlled to cause a photoexcitation reaction (decomposition, isomerization, dimerization). Is used to align the 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 ferroelectric liquid crystals (photo-alignment) by irradiating light and causing a photoexcitation reaction. However, such materials are large, photoreactive materials that impart anisotropy to the photoalignment film by causing a photoreaction, and anisotropic to the photoalignment film by causing a photoisomerization reaction. It can be divided into photoisomerization reaction type materials that impart properties. 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. Each will be described below.

(Photoreactive type)
First, a photoreactive component material will be described. As described above, the photoreactive component material is a material that imparts anisotropy to the photoalignment film by causing a photoreaction. The photoreactive type constituent material used in the present invention is not particularly limited as long as it has such characteristics, but among these, the above light can be produced by causing a photodimerization reaction or a photolysis reaction. A material that imparts anisotropy to the alignment film is preferred.

  Here, the photodimerization reaction refers to a reaction in which a reaction site oriented in the polarization direction by light irradiation undergoes radical polymerization and two molecules are polymerized. This reaction stabilizes the orientation in the polarization direction and makes the photo-alignment film different. It is possible to impart directionality. On the other hand, the photodecomposition reaction is a reaction that decomposes molecular chains such as polyimide oriented in the polarization direction by light irradiation. This reaction leaves a molecular chain oriented in the direction perpendicular to the polarization direction, and is different from the photo-alignment film. It is possible to impart directionality. In the present invention, among these photoreactive materials, 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 a wide range of material selection. .

  The photoreactive material utilizing such a 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 is radically polymerizable. It is preferable that the photodimerization reactive compound which has the dichroism which has the functional group of this and has dichroism which makes absorption different with polarization directions is included. 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 cinnamate, coumarin or 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, and is preferably in the range of 10,000 to 20,000. Is more preferable. 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 a following formula can be illustrated.

In the above formula, M ¹¹ and M ¹² 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 ¹² 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 spacer units.

R ¹ is a group represented by -A ^1- (Z ¹ -B ¹ ) _z -Z ^2- , and R ² is represented by -A ^1- (Z ¹ -B ¹ ) _z -Z ^3-. It is a group. Here, A ¹ and B ¹ are each independently a covalent single bond, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2, It represents 5-diyl or 1,4-phenylene which may have a substituent. 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 ¹ 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 the present invention, 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 mass to 20% by mass, and in the range of 0.1% by mass to 5% by mass 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, a photo-alignment processing method using the photoreactive material will be described. In the present invention, the photo-alignment treatment method is not particularly limited as long as anisotropy can be imparted to the photo-alignment film. For example, the photo-alignment processing method faces the liquid crystal layer of the substrate provided with the electrode layer. The surface can be coated with a coating solution obtained by diluting the constituent material of the photo-alignment film with an organic solvent 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 mass to 10% by mass, and in the range of 0.2% by mass to 2% by mass. 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.

  Note that the photoreactive material using the photodecomposition reaction is not particularly limited as long as it is a material that causes a reaction of decomposing molecular chains such as polyimide oriented in the polarization direction by light irradiation. Examples of such a photoreactive material include polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd.

(Photoisomerization type)
Next, the photoisomerization type material will be described. The photoisomerization type material here is a material that imparts anisotropy to the photo-alignment film by causing a photoisomerization reaction as described above, and is particularly limited as long as it has such characteristics. However, it is preferable to include a photoisomerization reactive compound that imparts anisotropy to the photoalignment film by causing a photoisomerization reaction. By including such a photoisomerization-reactive compound, a stable isomer among a plurality of isomers is increased by light irradiation, so that anisotropy can be easily imparted to the photo-alignment film. It is.

  Such a photoisomerization-reactive compound is not particularly limited as long as it is a material having the above-mentioned characteristics, but has a dichroism that makes absorption different depending on the polarization direction, and light It is preferable that a photoisomerization reaction is caused by irradiation. 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.

  The photoisomerization reaction that produces such a photoisomerization-reactive compound 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 such photoisomerization-reactive compounds include monomolecular compounds and polymerizable monomers that are polymerized by light or heat. These may be selected as appropriate according to the type of ferroelectric liquid crystal used, but the anisotropy is imparted to the photo-alignment film by light irradiation, and then the anisotropy is stabilized by polymerizing. Therefore, it is preferable to use a polymerizable monomer. Among such polymerizable monomers, an acrylate monomer and a methacrylate monomer are preferable because anisotropy is imparted to the photo-alignment film and the polymer can be easily polymerized while maintaining the anisotropy in a good state. .

  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 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.

  Hereinafter, the reason why an anisotropy can be imparted to the photo-alignment film by causing the azobenzene skeleton to undergo a photoisomerization reaction will be described. First, when the azobenzene skeleton is irradiated with linearly polarized ultraviolet light, the trans azobenzene skeleton having the molecular long axis oriented in the polarization direction is changed to a cis isomer as shown in the following formula.

  Since the cis isomer of the azobenzene skeleton is chemically unstable compared to the trans isomer, it thermally or absorbs visible light and returns to the trans isomer. Whether to become the right transformer body occurs with the same probability. 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, by utilizing this phenomenon, the alignment direction of the azobenzene skeleton is aligned, anisotropy is imparted to the photo-alignment film, and the alignment of liquid crystal molecules on the film can be controlled.

  Among such compounds having an azobenzene skeleton in the molecule, examples of the monomolecular compound 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 present invention, various cis-trans isomerization reactive skeletons and substituents can be selected from such photoisomerization reactive compounds according to required characteristics. In addition, these photoisomerization reactive compounds can also be used individually by 1 type or in combination of 2 or more types.

  The photoisomerization type material used in the present invention may contain additives in addition to the above-mentioned photoisomerization reactive compound as long as the photoalignment property of the photoalignment film is not hindered. 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 polymerization inhibitor is preferably in the range of 0.001% by mass to 20% by mass, and in the range of 0.1% by mass to 5% by mass 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.

  The photo-alignment treatment when such a photoisomerization type material is used can be performed by the same method as that when the photoreaction type material is used, but in this case, the light in the coating liquid is used. The content of the isomerization reactive compound is preferably in the range of 0.05% by mass to 10% by mass, and more preferably in the range of 0.2% by mass to 5% by mass. In the case of the photoisomerization type, photo-alignment treatment can also be performed by irradiating non-polarized ultraviolet oblique.

(3) 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).

(4) Electrode layer Next, the electrode layer used for this invention is demonstrated. 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. 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, the electrode layer, and the second alignment film are the same as those described in the above section “1. Reactive liquid crystal side substrate”, and thus the description thereof is omitted here.

  In the present invention, a second reactive liquid crystal layer formed by immobilizing reactive liquid crystals may be formed on the second alignment film. 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. The reactive liquid crystal used for the second reactive liquid crystal layer is not particularly limited as long as it has a composition different from that of the reactive liquid crystal constituting the reactive liquid crystal layer of the first substrate. 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, thereby suppressing the occurrence of alignment defects such as zigzag defects, hairpin defects and double domains. This is because a monostable operation mode can be realized using a ferroelectric liquid crystal.

  As the reactive liquid crystal in the second reactive liquid crystal layer, for example, the compound (1) or the compounds (2) and (3) represented by the following formula can be used.

  Here, in the above formulas (2) and (3), X and Y are hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 1 to 20 carbon atoms, alkyloxy having 1 to 20 carbon atoms, and 1 to 1 carbon atoms. It represents 20 alkyloxycarbonyl, formyl, alkylcarbonyl having 1 to 20 carbons, alkylcarbonyloxy having 1 to 20 carbons, halogen, cyano or nitro. M represents an integer in the range of 2-20.

Among the above, compounds represented by the above formulas (1) and (2) are preferably used. In the case of the compound represented by the above formula (1), R, l, m and n in the above formula are different from the reactive liquid crystal constituting the reactive liquid crystal layer of the reactive liquid crystal side substrate. In the case of the compound represented by the above formula (2), X is preferably an alkyloxycarbonyl having 1 to 20 carbon atoms, methyl or chlorine, and especially an alkyloxycarbonyl having 1 to 20 carbon atoms, particularly CH _3. Preferably it is (CH ₂ ) ₄ OCO.

  In the present invention, the composition of the reactive liquid crystal composing the reactive liquid crystal layer and the reactive liquid crystal composing the second reactive liquid crystal layer can be selected by selecting various functional groups and substituents of the compound (1). Can be different. In the present invention, two or more types of reactive liquid crystals 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 respective contents and additives.

3. Next, the liquid crystal layer used in the present invention will be described. The liquid crystal layer in the present invention is made of a ferroelectric liquid crystal, and is constituted by being sandwiched between the reactive liquid crystal layer and the second alignment film.

(1) Ferroelectric liquid crystal The ferroelectric liquid crystal constituting the liquid crystal layer is not particularly limited as long as it exhibits a chiral smectic C phase (SmC ^* ), but exhibits monostability. Preferably there is. This is because the use of the ferroelectric liquid crystal exhibiting monostability makes the effect of the configuration of the present invention remarkable. Here, “showing monostability” means a state in which the state of the ferroelectric liquid crystal when no voltage is applied is stabilized in one state. More specifically, as illustrated in FIG. 6, the ferroelectric liquid crystal A can operate on the cone between two states inclined by a tilt angle ± θ with respect to the layer normal z, but no voltage is applied. Sometimes the ferroelectric liquid crystal A is stabilized in any one state on the cone.

  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 ferroelectric liquid crystal used in the present invention has a nematic phase (N) -cholesteric phase (Ch) -chiral smectic C phase (SmC ^* ) or a nematic phase (N) -chiral smectic C phase (SmC ^* ). The material is roughly classified into a material (first embodiment) that does not have a smectic A phase (SmA) in the phase sequence and a material (second embodiment) that has SmA in the phase sequence. Hereinafter, the ferroelectric liquid crystal of each aspect will be described.

(Ferroelectric liquid crystal of the first embodiment)
The ferroelectric liquid crystal of this embodiment is a material (first embodiment) whose phase series changes phase with N-Ch-SmC ^* or N-SmC ^* and does not pass through SmA.

  The ferroelectric liquid crystal of this embodiment can be driven by an active matrix method using a thin film transistor (TFT), and has an advantage that gradation control is possible by voltage modulation. Therefore, by using the ferroelectric liquid crystal of this embodiment, a liquid crystal display element capable of realizing high-definition and high-quality display can be obtained. The ferroelectric liquid crystal of this embodiment can be suitably used when the liquid crystal display element of the present invention is driven by a field sequential color method.

  The ferroelectric liquid crystal of this embodiment is preferably a liquid crystal material having monostability. 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 color display can be realized.

  Specific examples of the ferroelectric liquid crystal used in this embodiment include “R2301” sold by AZ Electronic Materials.

(Ferroelectric liquid crystal of the second embodiment)
The ferroelectric liquid crystal of this embodiment is a material that can exhibit the SmC ^* phase via the SmA phase in the temperature lowering process and can exhibit monostability in the SmC ^* phase.
The ferroelectric liquid crystal of this embodiment can be driven by an active matrix method using a thin film transistor (TFT) by using a liquid crystal material having monostability like the ferroelectric liquid crystal of the first embodiment described above. In addition, gradation control is possible by voltage modulation, and high-definition and high-quality display can be realized. Furthermore, the ferroelectric liquid crystal of this embodiment has an advantage in that the range of selection of materials is wide.

  Conventionally, a ferroelectric liquid crystal having such a phase series has a chevron structure in which the distance between smectic layers is reduced during the phase change process, and the smectic layer is bent to compensate for the volume change. There is a problem that domains having different major axis directions of liquid crystal molecules are formed depending on the direction, and alignment defects called zigzag defects and hairpin defects are likely to occur at the interface. However, according to the present invention, the ferroelectric liquid crystal can be aligned without causing such alignment defects by forming the above-described reactive liquid crystal layer and alignment film, so that the contrast due to light leakage is increased. There is an advantage that it is possible to prevent a decrease in the above.

The ferroelectric liquid crystal of the present embodiment is not particularly limited as long as it exhibits an SmC ^* phase via the SmA phase in the temperature lowering process, and other liquid crystal phases on the high temperature side or the low temperature side of these liquid crystal phases. May be shown. 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 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 1 - (} Q 2 -Y 1) 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, and a cyano group, and X ¹ and Y ¹ are each —COO—, —OCO—, —CH ₂ O— , —OCH ₂ —, —CH ₂ CH ₂ —, —C≡C—, or a single bond, and m ′ is 0 or 1.). 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, Rd, 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 this embodiment include “FELIX M4851-100” manufactured by AZ Electronic Materials.

(2) Others The thickness of the liquid crystal layer is preferably in the range of 1.2 μm to 3.0 μm, more preferably in the range of 1.3 μm to 2.5 μm, and still more preferably in the range of 1.4 μm to 2.0 μm. Is within. 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 a liquid crystal layer in the present invention, a method generally used as a method for producing 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 prepared by previously forming an electrode layer on a substrate and providing the photo-alignment film, and is injected using the capillary effect. The 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.

4). Next, the polarizing plate used in the present invention will be described. 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.

5. Next, a method for manufacturing a liquid crystal display element of the present invention will be described. As a manufacturing method of the liquid crystal display element of the present invention, a known method can be generally used as a manufacturing method of the liquid crystal display element, and it is not particularly limited. Hereinafter, as an example of a method for manufacturing a liquid crystal display element of the present invention, a case where an active matrix liquid crystal display element using a TFT element is used will be described as an example.

  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. On the other hand, on the second 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, the constituent materials of the first alignment film and the second alignment film are coated on the electrode layers formed on the first substrate and the second substrate in this way, respectively, and an alignment treatment is performed as necessary. A first alignment film and a second alignment film are formed. A reactive liquid crystal containing the compound (1) is further coated on the first alignment film, and fixed with ultraviolet rays or the like to form a reactive liquid crystal layer.

  Beads are dispersed as spacers on the surface of either the reactive liquid crystal layer or the second alignment film formed in this way, a sealant is applied around the surface, and the reactive liquid crystal side substrate and the counter substrate are The reactive liquid crystal layer of the reactive liquid crystal side substrate and the second alignment film of the counter substrate are bonded so as to face each other, and thermocompression bonded. After thermocompression bonding, the ferroelectric liquid crystal is injected from the injection port in the state of isotropic liquid using the capillary effect, 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.

6). 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 method using TFTs, but can also be driven by a segment method.

  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.

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

(Example)
A 2% by mass solution of the compound I represented by the following formula dissolved in cyclopentanone was spin-coated at a rotational speed of 4000 rpm for 30 seconds on two glass substrates coated with ITO. After drying in an oven at 180 ° C. for 10 minutes, polarized ultraviolet rays were exposed at 25 ° C. for 100 mJ / cm ² . Furthermore, a solution of 2% by mass of Adeka Kiracol PLC-7209 (Asahi Denka Kogyo Co., Ltd.) dissolved in cyclopentanone on one substrate was spin-coated at a rotational speed of 4000 rpm for 30 seconds and laminated at 55 ° C. for 3 minutes. After drying, non-polarized ultraviolet rays were exposed to 1000 mJ / cm ² at 55 ° C.
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 a state parallel to the polarized UV irradiation direction and thermocompression bonded. Use "R2301" (manufactured by AZ Electronic Materials) as the liquid crystal, attach the liquid crystal to the top of the injection port, and inject using the oven at a temperature 10 to 20 ° C higher than the nematic phase-isotropic phase transition temperature. When it was slowly returned to room temperature, monodomain alignment was obtained.

(Comparative example)
A solution of 2% by mass of the above compound I 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 in an oven at 180 ° C. for 10 minutes, polarized ultraviolet rays were exposed at 25 ° C. for 100 mJ / cm ² .
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 a state parallel to the polarized UV irradiation direction and thermocompression bonded. Use "R2301" (manufactured by AZ Electronic Materials) as the liquid crystal, attach the liquid crystal to the top of the injection port, and inject using the oven at a temperature 10 to 20 ° C higher than the nematic phase-isotropic phase transition temperature. When the temperature was slowly returned to room temperature, monodomain alignment was not obtained, and alignment defects such as double domain 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. It is the schematic explaining the monostability 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 A… Ferroelectric liquid crystal molecules

Claims (6)

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 immobilizing reactive liquid crystal A reactive liquid crystal side substrate having a reactive liquid crystal layer, a second substrate, an electrode layer formed on the second substrate, and a counter substrate having a second alignment film formed on the electrode layer Are arranged such 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 a ferroelectric liquid crystal is formed between the reactive liquid crystal layer and the second alignment film. A liquid crystal display element sandwiching a liquid crystal layer,
The ferroelectric liquid crystal exhibits monostability;
A liquid crystal display element, wherein the reactive liquid crystal contains a compound (1) represented by the following formula.

(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 —, wherein l and m represent 0 or 1, and n is in the range of 2-8 In addition, R in the formula represents an alkyl having 1 to 5 carbon atoms when l = 1, and represents hydrogen or an alkyl having 1 to 5 carbon atoms when l = 0. ) 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 immobilizing reactive liquid crystal A reactive liquid crystal side substrate having a reactive liquid crystal layer; a second substrate; an electrode layer formed on the second substrate; a second alignment film formed on the electrode layer; A counter substrate having a second reactive liquid crystal layer formed on the alignment film and immobilizing the reactive liquid crystal is used as a reactive liquid crystal layer of the reactive liquid crystal side substrate and a second reactive liquid crystal of the counter substrate. A liquid crystal display element which is disposed so as to face each other, and a liquid crystal layer made of a ferroelectric liquid crystal is sandwiched between the reactive liquid crystal layer and the second reactive liquid crystal layer,
The ferroelectric liquid crystal exhibits monostability;
Reactive liquid crystal which constitutes the reactive liquid crystal and the second reactive liquid crystal layer forming the reactive liquid crystal layer, Ri different composition der,
Wherein the reactive liquid crystal which constitutes the reactive liquid crystal layer, the liquid crystal display device you characterized in that includes a compound represented by the following formula (1).

(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 - represents, l and m represent 0 or 1, n is in the range of 2 to 8 In addition, R in the formula represents an alkyl having 1 to 5 carbon atoms when l = 1, and represents hydrogen or an alkyl having 1 to 5 carbon atoms when l = 0. )   The liquid crystal display element according to claim 1, wherein the first alignment film or the second alignment film is a photo-alignment film.   The constituent material of the photo-alignment film is a photo-reactive material that imparts anisotropy to the photo-alignment film by causing a photoreaction, or anisotropy to the photo-alignment film by causing a photoisomerization reaction. 4. The liquid crystal display element according to claim 3, which is a photoisomerization type material containing a photoisomerization reactive compound to be imparted. The liquid crystal display device according to any one of claims of claims 1 to 4, characterized in that driving by an active matrix system using a thin film transistor. The liquid crystal display device according to be driven by a field sequential color system from claim 1, wherein in any of claims to claim 5.

Images