JP2007072213A - Viewing angle compensation plate for homeotropically oriented liquid crystal display device and homeotropically oriented liquid crystal display device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viewing angle compensation plate capable of controlling a retardation of the thickness direction in a wide range, and to provide a homeotropically oriented liquid crystal display device excellent in viewing angle characteristics. <P>SOLUTION: The viewing angle compensation plate for homeotropically oriented liquid crystal display device is made of a homeotropically oriented liquid crystal film prepared by homeotropically orienting liquid crystal material exhibiting positive uniaxiality in a liquid crystal state and, thereafter, fixing the orientation. Further, the homeotropically oriented liquid crystal display device is constituted by disposing the viewing angle compensation plate between a linearly polarizing plate and an optically anisotropic element exhibiting 1/4 wavelength retardation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vertical alignment type liquid crystal display device in which liquid crystal molecules are aligned perpendicularly to a substrate when no voltage is applied, and particularly to a vertical alignment type liquid crystal display device having a wide viewing angle and a viewing angle compensation plate for vertical alignment type liquid crystal.

As one of display modes in the liquid crystal display device, there is a vertical alignment mode in which liquid crystal molecules in the liquid crystal cell are aligned perpendicular to the substrate surface in the initial state. When no voltage is applied, the liquid crystal molecules are aligned perpendicular to the substrate surface, and a black display can be obtained by arranging linearly polarizing plates orthogonally on both sides of the liquid crystal cell.
The optical characteristics in the liquid crystal cell are isotropic in the in-plane direction, and ideal viewing angle compensation is easily possible. In order to compensate for positive uniaxial optical anisotropy in the thickness direction of the liquid crystal cell, an optical element having negative uniaxial optical anisotropy in the thickness direction is interposed between one or both surfaces of the liquid crystal cell and the linear polarizing plate. If it is inserted into, a very good black display viewing angle characteristic can be obtained.
When a voltage is applied, the orientation of liquid crystal molecules changes from a direction perpendicular to the substrate surface to a direction parallel to the substrate surface. At this time, it is difficult to make the liquid crystal alignment uniform. When the rubbing process for the substrate surface, which is a normal alignment process, is used, the display quality is significantly lowered.
In order to make the liquid crystal alignment uniform when a voltage is applied, there are proposals such as devising the electrode shape on the substrate, generating an oblique electric field in the liquid crystal layer, and obtaining uniform alignment. According to this method, a uniform liquid crystal alignment can be obtained, but a microscopic non-uniform alignment region is generated, and this region becomes a dark region when a voltage is applied. Therefore, the transmittance of the liquid crystal display device is reduced.

According to Patent Document 1, a configuration is proposed in which linearly polarizing plates disposed on both sides of a liquid crystal element having a liquid crystal layer including a randomly aligned state are replaced with circularly polarizing plates. By replacing the linearly polarizing plate with a circularly polarizing plate that combines a linearly polarizing plate and a quarter-wave plate, a dark region at the time of voltage application can be eliminated and a high transmittance liquid crystal display device can be realized. However, a vertical alignment type liquid crystal display device using a circularly polarizing plate has a problem that viewing angle characteristics are narrower than that of a vertical alignment type liquid crystal display device using a linear polarizing plate. According to Patent Document 2, an optical anisotropic element having a negative uniaxial optical anisotropy or a biaxial optical anisotropic material is proposed as a viewing angle compensation of a vertical alignment type liquid crystal display device using a circularly polarizing plate. Has been. However, an optical anisotropic element having negative uniaxial optical anisotropy can compensate for positive uniaxial optical anisotropy in the thickness direction of the liquid crystal cell, but cannot compensate the viewing angle characteristics of the quarter-wave plate. A sufficient viewing angle characteristic cannot be obtained. Also, when producing a biaxial optically anisotropic material, when the in-plane main refractive index of the resulting retardation plate is nx, ny, the refractive index in the thickness direction is nz, and nx> ny Nz defined by Nz = (nx−nz) / (nx−ny) is −1.0 <Nz <0.1, and there is a limit to stretching in the thickness direction. Can not be controlled. Moreover, in the said manufacturing method, since the elongate film is heat-shrinked with the heat shrink film and it is extended | stretched in the thickness direction, thickness of the obtained phase difference plate increases rather than a elongate film. The thickness of the retardation plate obtained by the manufacturing method is about 50 to 100 μm, which is not sufficient for thinning required for a liquid crystal display device or the like.
Japanese Patent Laid-Open No. 2002-40428 JP 2003-207782 A

  An object of the present invention is to provide a vertical alignment type liquid crystal display device having excellent viewing angle characteristics. It is another object of the present invention to provide a viewing angle compensation plate capable of controlling a thickness direction retardation over a wide range as a viewing angle compensation plate for a vertical alignment type liquid crystal display device.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following viewing angle compensator and a vertical alignment type liquid crystal display device using the same, thereby completing the present invention. It came to.

  That is, the first aspect of the present invention is a viewing angle compensator for a vertical alignment type liquid crystal display device comprising a homeotropic alignment liquid crystal film obtained by homeotropic alignment of a liquid crystal material exhibiting positive uniaxiality in a liquid crystal state and then fixing the alignment. It is.

A second aspect of the present invention is the viewing angle compensation plate for a vertical alignment type liquid crystal display device according to the first aspect of the present invention, which satisfies the following [1] and [2].
[1] 0 nm ≦ Re1 ≦ 20 nm
[2] −500 nm ≦ Rth1 ≦ −30 nm
(Here, Re1 means an in-plane retardation value of the homeotropic alignment liquid crystal film, and Rth1 means a retardation value in the thickness direction of the homeotropic alignment liquid crystal film. Re1 and Rth1 are respectively Re1 = (Nx1-Ny1) × d1 [nm], Rth1 = (Nx1-Nz1) × d1 [nm], where d1 is the thickness of the homeotropic alignment liquid crystal film, and Nx1 and Ny1 are the homeotropic alignments. The main refractive index in the plane of the liquid crystal film, Nz1, is the main refractive index in the thickness direction, and Nz1> Nx1 ≧ Ny1.

  According to a third aspect of the present invention, there is provided a vertical alignment type liquid crystal cell including liquid crystal molecules vertically aligned with respect to the substrate surface when no voltage is applied between a pair of substrates provided with electrodes, and above and below the vertical alignment type liquid crystal cell. Vertically disposed two linearly polarizing plates, and a first optical anisotropic element exhibiting a ¼ wavelength phase difference in the plane between both surfaces of the vertical alignment type liquid crystal cell and the linearly polarizing plate. In the alignment type liquid crystal display device, the viewing angle compensation for the vertical alignment type liquid crystal display device according to the first or second aspect of the present invention is provided between the linearly polarizing plate and the first optical anisotropic element. A vertical alignment type liquid crystal display device including a plate.

  According to a fourth aspect of the present invention, there is provided a second optical device further exhibiting a ½ wavelength phase difference between the first optical anisotropic element and the viewing angle compensator for the vertical alignment type liquid crystal display device. The vertical alignment type liquid crystal display device according to the third aspect of the present invention, which has an anisotropic element.

  According to a fifth aspect of the present invention, there is provided a first uniaxial optical anisotropy having at least one sheet in the thickness direction between the first optical anisotropic element and one or both surfaces of the vertical alignment type liquid crystal cell. 3. The vertical alignment type liquid crystal display device according to the third or fourth aspect of the present invention, comprising three optical anisotropic elements.

  According to a sixth aspect of the present invention, the first optical anisotropic element has a quarter-wave phase difference in a plane and has negative biaxial optical anisotropy in the thickness direction. It is a vertical alignment type liquid crystal display device according to any one of the third to fifth aspects of the invention.

  A seventh aspect of the present invention is any one of the third to sixth aspects of the present invention, wherein one substrate of the vertical alignment type liquid crystal cell is a substrate having a region having a reflection function and a region having a transmission function. 2. A vertical alignment type liquid crystal display device described in 1).

Hereinafter, the present invention will be described in detail.
First, the viewing angle compensation plate for a vertical alignment type liquid crystal display device of the present invention will be described.
The viewing angle compensator for a vertical alignment type liquid crystal display device of the present invention comprises a homeotropic alignment liquid crystal film in which a liquid crystal material exhibiting positive uniaxial property is homeotropically aligned in a liquid crystal state and then fixed in alignment. In the present invention, selection of a liquid crystal material and an alignment substrate is extremely important for obtaining a liquid crystal film in which the homeotropic alignment of the liquid crystal material is fixed.

  The liquid crystal material used in the present invention contains at least a side chain type liquid crystalline polymer such as poly (meth) acrylate or polysiloxane as a main constituent component. Further, the side chain type liquid crystal polymer used in the present invention has a polymerizable oxetanyl group at the terminal. More specifically, the side chain obtained by homopolymerizing the (meth) acrylic moiety of the (meth) acrylic compound having an oxetanyl group represented by the formula (1) or copolymerizing with another (meth) acrylic compound. A preferred example is a liquid crystalline polymer material.

In the above formula (1), R ₁ represents hydrogen or a methyl group, R ₂ represents hydrogen, a methyl group or an ethyl group, and L ₁ and L ₂ each independently represent a single bond, —O—, —O—CO. -Represents either-or -CO-O-, M represents Formula (2), Formula (3) or Formula (4), and n and m each independently represent an integer of 0 to 10.
-P ₁ -L ₃ -P ₂ -L ₄ -P _3- (2)
-P ₁ -L ₃ -P _3- (3)
-P _3- (4)

In formulas (2) to (4), P ₁ and P ₂ each independently represent a group selected from formula (5), P ₃ represents a group selected from formula (6), and L ₃ and L ₄ are Each represents a single bond, —CH═CH—, —C≡C—, —O—, —O—CO— or —CO—O—.

  The method for synthesizing these (meth) acrylic compounds having an oxetanyl group is not particularly limited, and can be synthesized by applying a method used in an ordinary organic chemical synthesis method. For example, by combining a site having an oxetanyl group and a site having a (meth) acrylic group by means such as Williamson's ether synthesis or ester synthesis using a condensing agent, oxetanyl group and (meth) acrylic group 2 A (meth) acrylic compound having an oxetanyl group having two reactive functional groups can be synthesized.

  It is represented by the following formula (7) by homopolymerizing the (meth) acrylic group of the (meth) acrylic compound having an oxetanyl group represented by the formula (1) or copolymerizing with another (meth) acrylic compound. A side-chain liquid crystalline polymer substance containing units can be obtained. The polymerization conditions are not particularly limited, and normal radical polymerization or anionic polymerization conditions can be employed.

As an example of radical polymerization, a (meth) acrylic compound is dissolved in a solvent such as dimethylformamide (DMF), and 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), or the like is used as an initiator. The method of making it react at 60-120 degreeC for several hours is mentioned. Moreover, in order to make the liquid crystal phase appear stably, copper bromide (I) / 2,2′-bipyridyl series, 2,2,6,6-tetramethylpiperidinooxy free radical (TEMPO) series, etc. are used. A method of controlling the molecular weight distribution by conducting living radical polymerization as an initiator is also effective. These radical polymerizations are preferably performed under deoxygenation conditions.
Examples of anionic polymerization include a method in which a (meth) acrylic compound is dissolved in a solvent such as tetrahydrofuran (THF) and reacted with a strong base such as an organic lithium compound, an organic sodium compound, or a Grignard reagent as an initiator. In addition, the molecular weight distribution can be controlled by optimizing the initiator and the reaction temperature for living anionic polymerization. These anionic polymerizations must be performed strictly under dehydration and deoxygenation conditions.

  In addition, the (meth) acryl compound to be copolymerized at this time is not particularly limited and may be anything as long as the synthesized polymer substance exhibits liquid crystallinity, but in order to increase the liquid crystallinity of the synthesized polymer substance, A (meth) acrylic compound having a mesogenic group is preferred. For example, a (meth) acrylic compound represented by the following formula can be exemplified as a preferred compound.

Here, R represents hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a cyano group.
The side chain type liquid crystalline polymer substance preferably contains 5 to 100 mol% of the unit represented by the formula (7), and particularly preferably contains 10 to 100 mol%. The side chain type liquid crystalline polymer substance preferably has a weight average molecular weight of 2,000 to 100,000, particularly preferably 5,000 to 50,000.

  The liquid crystal material used in the present invention may contain various compounds that can be mixed without impairing liquid crystallinity, in addition to the side-chain liquid crystalline polymer substance. Examples of compounds that can be contained include compounds having a cationic polymerizable functional group such as an oxetanyl group, an epoxy group, and a vinyl ether group, various polymer substances having film-forming ability, and various low-molecular liquid crystal compounds exhibiting liquid crystallinity. And polymer liquid crystalline compounds. When the side chain liquid crystalline polymer substance is used as a composition, the proportion of the side chain liquid crystalline polymer substance in the entire composition is 10% by mass or more, preferably 30% by mass or more, and more preferably. Is 50 mass% or more. If the content of the side chain type liquid crystalline polymer substance is less than 10% by mass, the concentration of the polymerizable group in the composition becomes low, and the mechanical strength after polymerization becomes insufficient.

  In addition, the liquid crystal material is subjected to alignment treatment, and then the oxetanyl group is cationically polymerized to crosslink to fix the liquid crystal state. For this reason, it is preferable that the liquid crystal material contains a photocation generator and / or a thermal cation generator that generates cations by an external stimulus such as light or heat. If necessary, various sensitizers may be used in combination.

The photo cation generator means a compound capable of generating a cation by irradiating with light having an appropriate wavelength, and examples thereof include organic sulfonium salt systems, iodonium salt systems, and phosphonium salt systems. Antimonates, phosphates, borates and the like are preferably used as counter ions of these compounds. Specific examples of the compound include Ar ₃ S ⁺ SbF ₆ ⁻ , Ar ₃ P ⁺ BF ₄ ⁻ and Ar ₂ I ⁺ PF ₆ ⁻ (wherein Ar represents a phenyl group or a substituted phenyl group). In addition, sulfonate esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoinsulfonate, and the like can also be used.

  The thermal cation generator is a compound capable of generating a cation when heated to an appropriate temperature, for example, benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters, Examples thereof include sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complexes, diaryliodonium salts-dibenzyloxycopper, and boron halide-tertiary amine adducts.

  The amount of these cation generators added to the liquid crystal material varies depending on the structure of the mesogenic part and spacer part, the oxetanyl group equivalent, the alignment condition of the liquid crystal, etc. constituting the side chain type liquid crystalline polymer material to be used. Although it cannot be said, it is usually 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.2 mass% to 7 mass%, most preferably based on the side chain type liquid crystalline polymer substance. Is in the range of 0.5% to 5% by weight. If the amount is less than 100 mass ppm, the amount of cations generated may not be sufficient and polymerization may not proceed. If the amount is more than 20 mass%, the remaining cation generator remains in the liquid crystal film. It is not preferable because there is a risk that the light resistance and the like may deteriorate due to an increase in the number of objects.

Next, the alignment substrate will be described.
As the alignment substrate, a substrate having a smooth plane is preferable, and examples thereof include a film or sheet made of an organic polymer material, a glass plate, and a metal plate. From the viewpoint of cost and continuous productivity, it is preferable to use a material made of an organic polymer. Examples of organic polymer materials include polyvinyl alcohol, polyimide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, Examples include films made of transparent polymers such as polycarbonate polymers and acrylic polymers such as polymethyl methacrylate. Also, styrene polymers such as polystyrene and acrylonitrile / styrene copolymers, olefin polymers such as polyethylene, polypropylene, and ethylene / propylene copolymers, cyclopolyolefins having a cyclic or norbornene structure, vinyl chloride polymers, nylon and aromatic polyamides. Examples thereof include a film made of a transparent polymer such as an amide polymer. Furthermore, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers Examples thereof include a film made of a transparent polymer such as a polymer, an epoxy-based polymer, and a blend of the above polymers. Among these, plastic films such as triacetyl cellulose, polycarbonate, norbornene polyolefin and the like used as optical films are awarded. Examples of organic polymer film include norbornene such as ZEONOR (trade name, manufactured by ZEON CORPORATION), ZEONEX (trade name, manufactured by ZEON CORPORATION), Arton (trade name, manufactured by JSR Corporation), etc. A plastic film made of a polymer material having a structure is preferable because it has excellent optical properties. Moreover, as a metal film, the said film formed from aluminum etc. is mentioned, for example.

  In order to obtain homeotropic alignment stably using the liquid crystal material described above, the material constituting these substrates has a long chain (usually 4 or more carbon atoms, preferably 8 or more) alkyl group, More preferably, the substrate surface has a compound layer having a long-chain alkyl group. Among them, it is preferable to form a layer made of polyvinyl alcohol having a long-chain alkyl group because the formation method is easy. These organic polymer materials may be used alone as a substrate, or may be formed as a thin film on another substrate. In the field of liquid crystal, rubbing treatment with a cloth or the like is generally performed on a substrate, but the homeotropic alignment liquid crystal film of the present invention is an alignment in which in-plane anisotropy basically does not occur. Because of the structure, rubbing is not necessarily required. However, it is more preferable to apply a weak rubbing treatment from the viewpoint of suppressing repelling when a liquid crystal material is applied. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents the ratio between the movement speed of the cloth and the movement speed of the substrate when the rubbing cloth is wound around a roll and rubbed while the substrate is rubbed. In the present invention, the weak rubbing treatment usually has a peripheral speed ratio of 50 or less, more preferably 25 or less, and particularly preferably 10 or less. When the peripheral speed ratio is greater than 50, the effect of rubbing is too strong, and the liquid crystal material cannot be completely aligned vertically, and there is a possibility that the alignment is tilted in the in-plane direction from the vertical direction.

Next, the manufacturing method of the homeotropic alignment liquid crystal film of this invention is demonstrated. Although the method for producing the liquid crystal film is not limited to these, the above-mentioned liquid crystal material is spread on the above-mentioned alignment substrate, and after aligning the liquid crystal material, light irradiation and / or heat treatment is performed. It can manufacture by fixing the said orientation state.
The liquid crystal material is spread on the alignment substrate to form the liquid crystal material layer. The liquid crystal material is applied directly on the alignment substrate in a molten state, or the liquid crystal material solution is applied on the alignment substrate, and then the coating film is applied. And drying the solvent to distill off the solvent.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystal material of the present invention and can be distilled off under suitable conditions. Generally, ketones such as acetone, methyl ethyl ketone, isophorone, and cyclohexanone, butoxyethyl Ethers such as alcohol, hexyloxyethyl alcohol, methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate and ethyl lactate, phenols such as phenol and chlorophenol, N Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, halogens such as chloroform, tetrachloroethane, dichlorobenzene, etc. Mixing system is preferably used. Further, in order to form a uniform coating film on the alignment substrate, a surfactant, an antifoaming agent, a leveling agent, or the like may be added to the solution.

Regardless of the method of directly applying the liquid crystal material or the method of applying the solution, the application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method may be adopted. it can. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating.
In the method of applying a liquid crystal material solution, it is preferable to include a drying step for removing the solvent after the application. As long as the uniformity of a coating film is maintained, this drying process can employ | adopt a well-known method, without being specifically limited. For example, a method such as a heater (furnace) or hot air blowing may be used.

  The film thickness of the liquid crystal film cannot be generally described because it depends on the type of the liquid crystal display device and various optical parameters, but is usually 0.2 μm to 10 μm, preferably 0.3 μm to 5 μm, more preferably 0.5 μm. ~ 2 μm. When the film thickness is thinner than 0.2 μm, there is a possibility that a sufficient viewing angle improvement or brightness enhancement effect cannot be obtained. If it exceeds 10 μm, the liquid crystal display device may be unnecessarily colored.

  Subsequently, the liquid crystal material layer formed on the alignment substrate is liquid crystal aligned by a method such as heat treatment, and is cured and fixed by light irradiation and / or heat treatment. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the liquid crystal material by heating to the liquid crystal phase expression temperature range of the used liquid crystal material. As conditions for the heat treatment, the optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the liquid crystal material to be used, but it cannot be generally stated, but usually in the range of 10 to 250 ° C., preferably 30 to 160 ° C. In addition, it is preferable to perform heat treatment at a temperature equal to or higher than the glass transition point (Tg) of the liquid crystal material, more preferably at a temperature higher by 10 ° C. than Tg. If the temperature is too low, the liquid crystal alignment may not proceed sufficiently, and if the temperature is high, the cationic polymerizable reactive group in the liquid crystal material and the alignment substrate may be adversely affected. Moreover, about heat processing time, it is 3 seconds-30 minutes normally, Preferably it is the range of 10 seconds-10 minutes. If the heat treatment time is shorter than 3 seconds, the liquid crystal alignment may not be completed sufficiently, and if the heat treatment time exceeds 30 minutes, the productivity is deteriorated.

After the liquid crystal material layer is formed into a liquid crystal alignment by a method such as heat treatment, the liquid crystal material is cured by a polymerization reaction of oxetanyl groups in the composition while maintaining the liquid crystal alignment state. The curing step is aimed at fixing the liquid crystal alignment state of the completed liquid crystal alignment by a curing (crosslinking) reaction and modifying it into a stronger film.
Since the liquid crystal material of the present invention has a polymerizable oxetanyl group, as described above, it is preferable to use a cationic polymerization initiator (cation generator) for the polymerization (crosslinking) of the reactive group. As the polymerization initiator, it is preferable to use a photo cation generator rather than a thermal cation generator.

  When a photo cation generator is used, the liquid crystal material can be obtained by adding the photo cation generator to the heat treatment for aligning the liquid crystal under dark conditions (light blocking conditions that do not cause the photo cation generator to dissociate). The liquid crystal can be aligned with sufficient fluidity without curing until the alignment stage. Thereafter, the liquid crystal material layer is cured by generating cations by irradiating light from a light source that emits light of an appropriate wavelength.

As a light irradiation method, a photocation is generated by irradiating light from a light source such as a metal halide lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, an arc lamp, or a laser having a spectrum in the absorption wavelength region of the photocation generator used. Cleave the generator. The dose per square centimeter is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the cumulative dose. However, this is not the case when the absorption region of the photocation generator and the spectrum of the light source are remarkably different, or when the liquid crystal material itself has the ability to absorb the light source wavelength. In these cases, it is possible to adopt a method such as using a suitable photosensitizer or a mixture of two or more photocation generators having different absorption wavelengths.
The temperature at the time of light irradiation needs to be within a temperature range in which the liquid crystal material takes liquid crystal alignment. In order to sufficiently enhance the curing effect, it is preferable to perform light irradiation at a temperature equal to or higher than Tg of the liquid crystal material.

  The liquid crystal material layer produced by the above process is a sufficiently strong film. Specifically, the mesogens are three-dimensionally bonded by the curing reaction, and not only the heat resistance (the upper limit temperature for maintaining the liquid crystal alignment) is improved as compared to before curing, but also scratch resistance, abrasion resistance, crack resistance. The mechanical strength such as property is also greatly improved.

As the alignment substrate, it is not optically isotropic, or the liquid crystal film to be obtained is finally opaque in the intended use wavelength region, or the alignment substrate is too thick, resulting in problems in actual use. When there is a problem such as, a form transferred from a form formed on an alignment substrate to a stretched film having a retardation function may be used. As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a liquid crystal film layer is laminated on a substrate different from the alignment substrate via an adhesive or an adhesive, and then if necessary. Examples thereof include a method of transferring only a liquid crystal film by performing a surface curing treatment using an adhesive or an adhesive and peeling the alignment substrate from the laminate.
The pressure-sensitive adhesive or adhesive used for transfer is not particularly limited as long as it is of optical grade, and generally used ones such as acrylic, epoxy, and urethane can be used.

  The homeotropic alignment liquid crystal layer obtained as described above can be quantified by measuring the optical phase difference of the liquid crystal layer at an angle inclined from the normal incidence. In the case of homeotropic alignment liquid crystal layers, this retardation value is symmetric with respect to normal incidence. Several methods can be used for measuring the optical phase difference. For example, an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments) and a polarizing microscope can be used. This homeotropic alignment liquid crystal layer appears black between the crossed Nicol polarizers. Thus, homeotropic orientation was evaluated.

  The homeotropic alignment liquid crystal film thus obtained has a thickness d1 (μm) = 1 to 1 when the in-plane main refractive index is Nx1, Ny1, the refractive index in the thickness direction is Nz1, and Nx1 ≧ Ny1. When it is about 10, for example, according to the materials described in the examples, (Nx1-Ny1) = 0 to about 0.0005 and (Nx1-Nz1) = − 0.1800 to −0.2000. . In general, Nx1 = 1.53 to 1.55, Ny1 = 1.53 to 1.55, and Nz1 = 1.72 to 1.74.

In the homeotropic alignment liquid crystal film of the present invention, the thickness of the liquid crystal film is d1, the main refractive index in the liquid crystal film surface is Nx1 and Ny1, the main refractive index in the thickness direction is Nz1, and Nz1> Nx1 ≧ Ny1. In this case, the in-plane retardation value (Re1 = (Nx1-Ny1) × d1 [nm]) and the retardation value in the thickness direction (Rth1 = (Nx1-Nz1) × d1 [nm]) are as follows: 1] and [2] are satisfied.
[1] 0 nm ≦ Re1 ≦ 20 nm
[2] −500 nm ≦ Rth1 ≦ −30 nm

  The Re1 and Rth1 values, which are the optical parameters of the homeotropic alignment liquid crystal film, cannot be generally described because they depend on the type of the liquid crystal display device and various optical parameters, but the homeotropic alignment for monochromatic light of 550 nm The retardation value (Re1) in the plane of the liquid crystal film is usually in the range of 0 nm to 20 nm, preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm, and the retardation value (Rth1) in the thickness direction is usually It is controlled to −500 to −30 nm, preferably −400 to −50 nm, and more preferably −400 to −100 nm.

  By setting the Re1 value and the Rth1 value in the above ranges, the viewing angle improving film of the liquid crystal display device can widen the viewing angle while correcting the color tone of the liquid crystal display. When the Re value is larger than 20 nm, the front characteristics of the liquid crystal display element may be deteriorated due to the large front retardation value. Further, when the Rth value is larger than −30 nm or smaller than −500 nm, a sufficient viewing angle improvement effect cannot be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

Next, a vertical alignment type liquid crystal display device using the compensation plate for the vertical alignment type liquid crystal display device of the present invention will be described.
The vertical alignment type liquid crystal display device according to the present invention includes a vertical alignment type liquid crystal cell including a liquid crystal molecule which is vertically aligned with respect to a substrate surface when no voltage is applied between a pair of substrates provided with electrodes, and the vertical alignment type liquid crystal. Two linearly polarizing plates disposed above and below the cell, and a first optical anisotropic element exhibiting a ¼ wavelength phase difference in-plane between both surfaces of the vertical alignment type liquid crystal cell and the linearly polarizing plate In the arranged vertical alignment type liquid crystal display device, at least one viewing angle compensation plate of the present invention is included between the linearly polarizing plate and the first optical anisotropic element.
Further, it is preferable that a second optical anisotropic element exhibiting a half-wave phase difference in the plane is further disposed between the first optical anisotropic element and the viewing angle compensation plate. At least one third optical anisotropic element having negative uniaxial optical anisotropy in the thickness direction is provided between the first optical anisotropic element and one surface or both surfaces of the vertical alignment type liquid crystal cell. It is preferable to arrange. By combining the third optical anisotropic element, a wider viewing angle can be achieved.

  Although there is no restriction | limiting in particular as a liquid crystal display device, Various liquid crystal display devices of a transmissive type, a reflective type, and a semi-transmissive type can be mentioned. The driving method of the liquid crystal cell is not particularly limited, and is a passive matrix method used in STN-LCDs, an active matrix method using active electrodes such as TFT (Thin Film Transistor) electrodes, TFD (Thin Film Diode) electrodes, and a plasma addressing method. Any driving method may be used.

  The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate having the property of aligning the liquid crystal itself, a substrate itself lacking alignment ability, but a transparent substrate provided with an alignment film having the property of aligning liquid crystal, etc. Can also be used. Moreover, well-known things, such as ITO, can be used for the electrode of a liquid crystal cell. The electrode can usually be provided on the surface of the transparent substrate with which the liquid crystal layer is in contact. When a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.

  The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited as long as it has a negative dielectric anisotropy, and various ordinary low-molecular liquid crystal substances and polymer liquid crystals capable of constituting various liquid crystal cells. Materials and mixtures thereof. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired. If a chiral agent is added to a vertically aligned liquid crystal layer using a liquid crystal material exhibiting negative dielectric anisotropy and the liquid crystal molecules are rotated when voltage is applied, the rotation of the liquid crystal molecules when voltage is applied should be stabilized. Can do. Furthermore, when the rubbing directions of the upper and lower substrates are other than the same direction, the trace of the alignment process is not the same direction, so that the streak is less noticeable. In addition, if the liquid crystal layer is twisted by 90 degrees, retardation occurs in the tilt direction of the liquid crystal molecules when tilted by several degrees with respect to the substrate to prevent disclination when a voltage is applied. Since the directions in which the liquid crystal molecules in the vicinity are inclined at an angle of 90 degrees in the vicinity of the upper and lower substrates, the generated retardation can be canceled and a black display with less leakage light can be obtained.

  As the two linearly polarizing plates disposed above and below the vertical alignment type liquid crystal cell, those having a protective film on one side or both sides of the polarizer are usually used. The polarizer is not particularly limited, and various types can be used. For example, for a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene / vinyl acetate copolymer partially saponified film. And polyene-based oriented films such as those obtained by adsorbing dichroic substances such as iodine and dichroic dyes and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  The protective film provided on one side or both sides of the polarizer preferably has excellent transparency, mechanical strength, thermal stability, moisture shielding properties, isotropic properties, and the like. Examples of the material for the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile and styrene copolymer. Examples thereof include styrene polymers such as coalesced (AS resin), polycarbonate polymers, and the like. Polyolefin polymers such as polyethylene, polypropylene, ethylene / propylene copolymers, polyolefins having cyclo or norbornene structures, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Examples of the polymer that forms the protective film include polymer blends. Other examples include films made of thermosetting or ultraviolet curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone. Generally the thickness of a protective film is 500 micrometers or less, and 1-300 micrometers is preferable. In particular, the thickness is preferably 5 to 200 μm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of aqueous adhesives include polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, and the like.

As the protective film, a hard coat layer, an antireflection treatment, an anti-sticking treatment, or a treatment subjected to diffusion or anti-glare treatment can be used.
Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, roughening by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a method or a compounding method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

A circularly polarizing plate is formed by combining a ¼ wavelength plate with a linear polarizing plate. The circularly polarizing plate has a function of changing linearly polarized light into circularly polarized light or changing circularly polarized light into linearly polarized light with a quarter-wave plate.
A linearly polarizing plate is provided on both sides of the vertical alignment type liquid crystal cell, and the first optical anisotropic element having a 1/4 wavelength phase difference in the plane is provided between the linearly polarizing plate and the vertical alignment type liquid crystal cell. Therefore, when no voltage is applied, the phase difference in the observation direction of the liquid crystal layer is zero, so that dark display is possible by making the upper and lower polarizing plates orthogonal to each other, and when the voltage is applied, a phase difference in the observation direction occurs and bright display is possible. . In this case, since the angle formed by the slow axis of the first optical anisotropic element having a phase difference of ¼ wavelength and the absorption axis of the linear polarizing plate is 45 degrees, the liquid crystal layer has a simplest configuration. Polarized light can be obtained.
Further, in the case of a transflective vertical alignment type liquid crystal display device having both a transmission function and a reflection function, in order to obtain a good display characteristic at the time of reflection, a first wavelength having a quarter wavelength phase difference is obtained. It is preferable to use an optical anisotropic element or a second optical anisotropic element having a phase difference of ½ wavelength in the plane between the linearly polarizing plate and the ¼ wavelength plate.

Next, the first optical anisotropic element having a phase difference of ¼ wavelength in the plane or the second optical anisotropic element having a phase difference of ½ wavelength will be described.
As the optical anisotropic element, for example, a film made of an appropriate polymer such as polycarbonate, norbornene resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide is uniaxially or biaxially stretched. A birefringent film, a liquid crystal polymer, etc. manufactured by a method of increasing the phase difference in the thickness direction by thermally shrinking the width direction of the long film by a heat shrinking film as disclosed in JP-A-5-157911 Examples thereof include an alignment film made of a liquid crystal material and a film in which an alignment layer of a liquid crystal material is supported.

When the x direction and the y direction are taken in the in-plane direction and the thickness direction is the z direction, the positive uniaxial optical anisotropic element has a relationship of nx> ny = nz as a refractive index. The positive biaxial optical anisotropic element has a relationship of nx>nz> ny as a refractive index. The negative uniaxial optical anisotropic element has a relationship of nx = ny> nz as a refractive index. The negative biaxial optical anisotropic element has a relationship of nx>ny> nz as a refractive index.
When biaxiality is defined by NZ coefficient = (nx−nz) / (nx−ny), NZ> 1 is a negative two axis, NZ = 1 is a positive one axis, and NZ <1 is a positive two axis. Can be classified.

The first optical anisotropic element showing a phase difference of ¼ wavelength in the plane has a thickness of the first optical anisotropic element d2, a main refractive index in the first optical anisotropic element plane of Nx2, and Ny2, when the main refractive index in the thickness direction is Nz2 and Nx2> Ny2, the in-plane retardation value (Re2 = (Nx2-Ny2) × d2 [nm]) has 80 to 170 nm, When the NZ coefficient of the first optical anisotropic element is NZ2, there is a relationship of -1 <NZ2 <4.
The Re2 and NZ2 values, which are the optical parameters of the first optical anisotropic element, depend on the type of the liquid crystal display device and various optical parameters. The retardation value (Re2) in the optical anisotropic element surface of 1 is usually in the range of 80 nm to 170 nm, preferably 100 nm to 150 nm, more preferably 120 nm to 140 nm, and the NZ2 value is -1 <NZ2 < 4, preferably 0.5 <NZ2 <3, more preferably 1 ≦ NZ2 <3.

The second optical anisotropic element showing a phase difference of ½ wavelength in the plane has a thickness of the second optical anisotropic element d3, a main refractive index in the second optical anisotropic element plane of Nx3, and Ny3, when the main refractive index in the thickness direction is Nz3 and Nx3> Ny3, the in-plane retardation value (Re3 = (Nx3-Ny3) × d3 [nm]) has 200 to 350 nm, When the NZ coefficient of the second optical anisotropic element is NZ3, the relationship is -1 <NZ3 <4.
The Re3 and NZ3 values, which are the optical parameters of the second optical anisotropic element, depend on the type of the liquid crystal display device and various optical parameters. The retardation value (Re3) in the optically anisotropic element surface of 2 is usually in the range of 200 nm to 350 nm, preferably 250 nm to 300 nm, more preferably 260 nm to 280 nm, and the NZ3 value is -2 <NZ3 < 3, preferably -1 <NZ3 <2, more preferably 0 ≦ NZ3 <1.5.

  By setting the Re2, Re3 and NZ2, NZ3 values in the above ranges, the viewing angle improving film of the liquid crystal display device can widen the viewing angle while correcting the color tone of the liquid crystal display. When the Re2 and Re3 values are out of the above ranges, the front characteristics of the liquid crystal display element may be deteriorated due to the influence of the deviation of the front phase difference value. Further, when the NZ2 and NZ3 values are out of the above range, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed obliquely.

Next, a third optical anisotropic element having negative uniaxial optical anisotropy in the thickness direction will be described.
The third optically anisotropic element is not particularly limited, but the non-liquid crystal material is excellent in heat resistance, chemical resistance, transparency, and rigidity. For example, cellulose triacylate, ZEONEX, Polymers such as polyolefins such as ZEONOR (both manufactured by Nippon Zeon Co., Ltd.) and AERTON (manufactured by JSR Co., Ltd.), polyamide, polyimide, polyester, polyetherketone, polyaryletherketone, polyamideimide, polyesterimide and the like are preferable. . Any one kind of these polymers may be used alone, or a mixture of two or more kinds having different functional groups, such as a mixture of polyaryletherketone and polyamide. Among such polymers, polyimide is particularly preferable because of its high transparency and high orientation. Examples of the liquid crystal material include a cholesteric alignment film made of a liquid crystal material such as a cholesteric liquid crystal polymer, and a film in which a cholesteric alignment layer of the liquid crystal material is supported by a film.

  The third optical anisotropic element has a thickness d4 of the third optical anisotropic element, Nx4 and Ny4 as main refractive indices in the third optical anisotropic element surface, and Nz4 as a main refractive index in the thickness direction. When Nx4 ≧ Ny4, the in-plane retardation value (Re4 = (Nx4-Ny4) × d4 [nm]) is 0 to 20 nm, and the retardation value in the thickness direction (Rth4 = (Nx4-Nz4)). Xd1 [nm]) is 50 to 500 nm.

The Re4 and Rth4 values, which are the optical parameters of the third optical anisotropic element, depend on the type of the liquid crystal display device and various optical parameters. The retardation value (Re4) in the optical anisotropic element surface 3 is usually in the range of 0 nm to 20 nm, preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm, and the retardation value in the thickness direction (Rth4). ) Is usually controlled to 50 to 500 nm, preferably 80 to 400 nm, more preferably 100 to 300 nm.
By setting the Re4 value and the Rth4 value in the above ranges, the viewing angle improving film of the liquid crystal display device can widen the viewing angle while correcting the color tone of the liquid crystal display. When the Re4 value is larger than 20 nm, the front characteristics of the liquid crystal display element may be deteriorated due to the large front phase difference value. When the Rth4 value is smaller than 50 nm or larger than 500 nm, a sufficient viewing angle improvement effect cannot be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  The first, second and third optically anisotropic elements and homeotropic alignment liquid crystal film can be produced by sticking each other through an adhesive layer. Further, after transferring the homeotropic alignment liquid crystal film produced on the substrate to the first or second optical anisotropic element through the adhesive layer, the third optical anisotropic liquid not used for the transfer is transferred to the first or second optical anisotropic element. It can be produced by further bonding the element through an adhesive layer.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is appropriately used as a base polymer. Can be selected and used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  The pressure-sensitive adhesive layer can be formed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. , A method in which it is directly attached on the liquid crystal layer by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on the separator according to the above and transferred onto the liquid crystal layer Examples include methods. The pressure-sensitive adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, glass fibers, glass beads, metal powder, fillers made of other inorganic powders, pigments, colorants, You may contain the additive added to adhesion layers, such as antioxidant. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  In addition, when transferring the homeotropic alignment liquid crystal film to the first or second optical anisotropic element via the pressure-sensitive adhesive layer, the surface of the homeotropic alignment liquid crystal film is surface-treated to adhere to the pressure-sensitive adhesive layer. Can be improved. The surface treatment means is not particularly limited, and a surface treatment method such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, or plasma treatment that can maintain the transparency of the liquid crystal layer surface can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.

Further, by using one substrate of the vertical alignment type liquid crystal cell as a substrate having a region having a reflection function and a region having a transmission function, a transflective vertical alignment type liquid crystal display device can be obtained.
A region having a reflection function (hereinafter sometimes referred to as a reflective layer) included in the transflective electrode used in the transflective vertical alignment liquid crystal display device is not particularly limited, and may be aluminum, silver, Examples thereof include metals such as gold, chromium and platinum, alloys containing them, oxides such as magnesium oxide, dielectric multilayer films, liquid crystals exhibiting selective reflection, or combinations thereof. These reflective layers may be flat or curved. Furthermore, the reflective layer is processed to have a surface shape such as an uneven shape to give diffuse reflection, to the electrode on the electrode substrate opposite to the viewer side of the liquid crystal cell, or a combination thereof It may be.

  The vertical alignment type liquid crystal display device of the present invention can be provided with other constituent members in addition to the constituent members described above. For example, by attaching a color filter to the liquid crystal display device of the present invention, a color liquid crystal display device capable of performing multicolor or full color display with high color purity can be manufactured.

  The homeotropic alignment liquid crystal film of the present invention is useful as a viewing angle compensator for a vertical alignment liquid crystal display device, and the vertical alignment liquid crystal display device of the present invention is bright and capable of high contrast display in all directions. is there.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, each analysis method used in the Example is as follows.
⁽¹⁾ Measurement compound of 1 H-NMR was dissolved in deuterated chloroform and measured by ¹ H-NMR of 400 MHz (Variant Co. INOVA-400).
(2) Measurement of GPC The compound was dissolved in tetrahydrofuran, and TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 were connected in series with a Tosoh 8020GPC system and measured using tetrahydrofuran as an eluent. Polystyrene standards were used for molecular weight calibration.
(3) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(4) Parameter measurement of liquid crystal film Obi Scientific Instruments Co., Ltd. automatic birefringence meter KOBRA21ADH was used.

[Example 1]
A liquid crystalline polymer represented by the following formula (8) was synthesized. The molecular weight was Mn = 8000 and Mw = 15000 in terms of polystyrene. In addition, although Formula (8) is described with the structure of a block polymer, it represents the component ratio of a monomer.

After dissolving 1.0 g of the polymer of the formula (8) in 9 ml of cyclohexanone and adding 0.1 g of a triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich) in the dark, A solution of liquid crystal material was prepared by filtering insoluble matter with a 0.45 μm polytetrafluoroethylene filter.
The alignment substrate was prepared as follows. A 38 μm thick polyethylene naphthalate film (manufactured by Toray Industries, Inc.) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., MP-203) (the solvent was water and isopropyl alcohol). (A mixed solvent having a weight ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes. Subsequently, it was rubbed with a rayon rubbing cloth. The film thickness of the obtained PVA layer was 1.2 μm. The peripheral speed ratio during rubbing (moving speed of rubbing cloth / moving speed of substrate film) was 4.

The liquid crystal solution described above was applied to the alignment substrate thus obtained by spin coating. Next, it was dried on a hot plate at 60 ° C. for 10 minutes and heat-treated in an oven at 150 ° C. for 2 minutes to align the liquid crystal material. Next, the sample is placed in close contact with an aluminum plate heated to 60 ° C., and then a 600 mJ / cm ² ultraviolet light (however, measured at 365 nm) is irradiated with a high-pressure mercury lamp lamp to cure the liquid crystal material. It was.
Since the polyethylene naphthalate film used as the substrate has a large birefringence and is not preferable as an optical film, the obtained liquid crystalline film on the alignment substrate was transferred to a TAC film via an ultraviolet curable adhesive. That is, on the cured liquid crystal material layer on the polyethylene naphthalate film, an adhesive is applied to a thickness of 5 μm, laminated with a triacetyl cellulose (TAC) film, and irradiated with ultraviolet rays from the TAC film side. After the adhesive was cured, the polyethylene naphthalate film was peeled off.

  When the obtained optical film (PVA layer / liquid crystal layer / adhesive layer / TAC film) is observed under a polarizing microscope, there is no disclination and the monodomain has a uniform orientation. It was found that the homeotropic orientation has a structure. The in-plane retardation (Re1) of the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation in the thickness direction (Rth1) was −50 nm. In addition, since the TAC film alone was negative uniaxial and the in-plane retardation was 0.5 nm and the retardation in the thickness direction was +40 nm, the retardation of the liquid crystal layer alone was Re 0.5 nm, Rth was estimated to be -90 nm.

[Example 2]
In Example 1, an optical film was produced in the same manner as in Example 1 except that the thickness of the homeotropic alignment liquid crystal film was 1.0 μm. The in-plane retardation (Re1) of the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation in the thickness direction (Rth1) was −125 nm. Since the TAC film alone was negative uniaxial and the in-plane retardation was 0.5 nm and the retardation in the thickness direction was +40 nm, the retardation of the liquid crystal layer alone was Re1 of 0.5 nm, Rth1 was estimated to be -165 nm.

[Example 3]
In Example 1, an optical film was produced in the same manner as in Example 1 except that the thickness of the homeotropic alignment liquid crystal film was 0.9 μm. The retardation (Re1) in the in-plane direction of the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation (Rth1) in the thickness direction was -95 nm. Since the TAC film alone was negative uniaxial and the in-plane retardation was 0.5 nm and the retardation in the thickness direction was +40 nm, the retardation of the liquid crystal layer alone was Re1 of 0.5 nm, Rth1 was estimated to be -135 nm.

[Example 4]
A vertical alignment type liquid crystal display device of Example 4 will be described with reference to FIGS.
A transparent electrode 3 made of a material having a high transmittance made of an ITO layer is formed on the substrate 1, a counter electrode 4 is formed on the substrate 2, and a liquid crystal exhibiting negative dielectric anisotropy between the transparent electrode 3 and the counter electrode 4 A liquid crystal layer 5 made of a material is sandwiched.
Vertical alignment films (not shown) are formed on the surfaces of the transparent electrode 3 and the counter electrode 4 that are in contact with the liquid crystal layer 5. After the alignment film is applied, at least one alignment film such as rubbing is aligned. Processing is in progress.
The liquid crystal molecules of the liquid crystal layer 5 have a tilt angle of 1 ° with respect to the vertical direction of the substrate surface by an alignment treatment such as rubbing on the vertical alignment film.
Since a liquid crystal material exhibiting negative dielectric anisotropy is used for the liquid crystal layer 5, when a voltage is applied between the transparent electrode 3 and the counter electrode 4, the liquid crystal molecules are inclined in a direction parallel to the substrate surface. .
As the liquid crystal material of the liquid crystal layer 5, Ne (refractive index for extraordinary light) = 1.561, No (refractive index for normal light) = 1.478, ΔN (Ne−No) = 0.083 A liquid crystal material having
A linearly polarizing plate 7 (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the display surface side (upper side of the figure) of the vertical alignment type liquid crystal cell 6, and between the upper side linearly polarizing plate 7 and the liquid crystal cell 6. The third optical anisotropic element 8 (ARTON manufactured by JSR Corporation), the first optical anisotropic element 9 (ZEONOR manufactured by Nippon Zeon Co., Ltd.), and the homeotropic alignment liquid crystal film 10 produced in Example 1 are disposed. did. A linearly polarizing plate 11 (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the back side of the vertical alignment type liquid crystal cell 6 (the lower side in the figure). A third optically anisotropic element 12 (ARTON manufactured by JSR Corporation), a first optically anisotropic element 13 (ZEONOR manufactured by Nippon Zeon Co., Ltd.), and the homeotropic alignment liquid crystal film 14 of Example 1 were disposed therebetween. .
The first optical anisotropic elements 9 and 13 are optical elements having an in-plane optical axis and positive uniaxial optical anisotropy. The directions of the absorption axes of the linearly polarizing plates 7 and 11 indicated by arrows in FIG. 2 were set to 45 degrees and 135 degrees, respectively. The slow axis directions of the first optical anisotropic elements 9 and 13 indicated by arrows in FIG. 2 are 90 degrees and 0 degrees, respectively, and a phase difference of 137.5 nm is shown in the in-plane Re2.
The third optical anisotropic elements 8 and 12 exhibit a phase difference of approximately 0 nm in the in-plane Re4 and 130 nm in the thickness Rth4.
The homeotropic alignment liquid crystal films 10 and 14 exhibit an in-plane Re1 phase difference of 0.5 nm and a thickness Rth1 of −50 nm.
FIG. 3 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.

[Example 5]
A vertical alignment type liquid crystal display device of Example 5 will be described with reference to FIGS.
Using the homeotropic alignment liquid crystal film produced in Example 2, the first optical anisotropic elements 9 and 13 of Example 4 are optical elements having negative biaxial optical anisotropy (Zeonor manufactured by Nippon Zeon Co., Ltd.). And a vertical alignment type liquid crystal display device was fabricated in the same manner as in Example 4 except that the third optical anisotropic elements 8 and 12 were omitted.
The orientations of the absorption axes of the linearly polarizing plates 7 and 11 indicated by arrows in FIG. 5 were in-plane 45 degrees and 135 degrees, respectively. The slow axis directions of the first optical anisotropic elements 9 and 13 indicated by arrows in FIG. 5 are 90 degrees and 0 degrees, respectively, the in-plane Re2 has a phase difference of 137.5 nm, and the NZ coefficient is NZ2 = 2. 5 is shown.
The homeotropic alignment liquid crystal films 10 and 14 exhibit a phase difference of 0.5 nm in the in-plane Re1 and −125 nm in the thickness Rth1.
FIG. 6 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.

[Example 6]
A vertical alignment type liquid crystal display device of Example 6 will be described with reference to FIGS.
The substrate 1 is provided with a reflective electrode 15 made of an Al layer and made of a highly reflective material and the transparent electrode 3 made of an ITO layer and made of a highly transparent material. The substrate 2 is provided with a counter electrode 4. 15, and a liquid crystal layer 5 made of a liquid crystal material exhibiting negative dielectric anisotropy is sandwiched between the transparent electrode 3 and the counter electrode 4.
Vertically oriented alignment films (not shown) are formed on the surfaces of the reflective electrode 15, the transparent electrode 3, and the counter electrode 4 that are in contact with the liquid crystal layer 5. After the alignment film is applied, at least one alignment film is formed. Alignment treatment such as rubbing is performed.
The liquid crystal molecules of the liquid crystal layer 5 have a tilt angle of 1 ° with respect to the vertical direction of the substrate surface by an alignment treatment such as rubbing on the vertical alignment film.
Since a liquid crystal material exhibiting negative dielectric anisotropy is used for the liquid crystal layer 5, when a voltage is applied between the reflective electrode 15, the transparent electrode 3 and the counter electrode 4, the liquid crystal molecules are parallel to the substrate surface. Tilt toward.
As the liquid crystal material of the liquid crystal layer 5, the same material as in Example 3 was used.
A linearly polarizing plate 7 (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the display surface side (upper side of the figure) of the transflective vertical alignment type liquid crystal cell 16, and the upper linear polarizing plate 7 and the liquid crystal Between the cells 6, a third optical anisotropic element 8 (ARTON manufactured by JSR Corporation), a first optical anisotropic element 9 (ZEONOR manufactured by Nippon Zeon Co., Ltd.), and a second optical anisotropic element 17 (Japan) The homeotropic alignment liquid crystal film 10 of Example 3 was disposed. A linearly polarizing plate 11 (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the back side of the vertical alignment type liquid crystal cell 16 (the lower side in the figure). Between the third optical anisotropic element 12 (ARTON manufactured by JSR Corporation), the first optical anisotropic element 13 (ZEONOR manufactured by Nippon Zeon Co., Ltd.), and the second optical anisotropic element 18 (Nippon Zeon Corporation) ) ZEONOR), homeotropic alignment liquid crystal film 14 of Example 3 was disposed.
The first optical anisotropic elements 9 and 13 and the second optical anisotropic elements 17 and 18 are formed of optical elements having an in-plane optical axis and positive uniaxial optical anisotropy. The directions of the absorption axes of the linearly polarizing plates 7 and 11 indicated by arrows in FIG. 8 were set to 15 degrees and 105 degrees, respectively. The slow axis directions of the first optical anisotropic elements 9 and 13 indicated by arrows in FIG. 8 are 90 degrees and 0 degrees, respectively, and a phase difference of 137.5 nm is shown in the in-plane Re2. The slow axis orientations of the second optical anisotropic elements 17 and 18 indicated by arrows in FIG. 8 are 30 degrees and 120 degrees, respectively, and a phase difference of 275 nm is indicated in the in-plane Re3.
The third optical anisotropic elements 8 and 12 exhibit a phase difference of approximately 0 nm in the in-plane Re4 and 105 nm in the thickness Rth4.
The homeotropic alignment liquid crystal films 10 and 14 have an in-plane Re1 of 0.5 nm and a thickness Rth1 of −95 nm.
FIG. 9 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.

[Comparative Example 1]
A vertical alignment type liquid crystal display device shown in FIG. 10 was produced in the same manner as in Example 4 except that the homeotropic alignment liquid crystal films 10 and 14 of Example 4 were omitted.
FIG. 11 shows the angular relationship between the constituent members.
FIG. 12 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.
Comparing the omnidirectional isocontrast curves in FIG. 3 and FIG. 6 with FIG. 12, it can be seen that a wide viewing angle characteristic can be obtained when a homeotropic alignment liquid crystal film is used.

[Comparative Example 2]
A transflective vertical alignment type liquid crystal display device shown in FIG. 13 was produced in the same manner as in Example 6 except that the homeotropic alignment liquid crystal films 10 and 14 of Example 6 were omitted.
FIG. 14 shows the angular relationship between the constituent members.
FIG. 15 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.
Comparing the omnidirectional isocontrast curves in FIGS. 9 and 15, it can be seen that a wide viewing angle characteristic can be obtained by using a homeotropic alignment liquid crystal film.

1 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Example 1. FIG. FIG. 3 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Example 1. It is a figure which shows contrast ratio when the vertical alignment type liquid crystal display device in Example 1 is seen from all directions. 6 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Example 2. FIG. FIG. 6 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Example 2. It is a figure which shows contrast ratio when the vertical alignment type liquid crystal display device in Example 2 is seen from all directions. 6 is a schematic cross-sectional view of a transflective vertical alignment liquid crystal display device used in Example 3. FIG. FIG. 6 is a plan view showing the angular relationship of each component of the transflective vertical alignment type liquid crystal display device used in Example 3. FIG. 10 is a diagram showing a contrast ratio when the transflective vertical alignment type liquid crystal display device in Example 3 is viewed from all directions. 6 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Comparative Example 1. FIG. 6 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Comparative Example 1. FIG. It is a figure which shows the contrast ratio when the vertical alignment type liquid crystal display device in Comparative Example 1 is viewed from all directions. 6 is a schematic cross-sectional view of a transflective vertical alignment liquid crystal display device used in Comparative Example 2. FIG. FIG. 10 is a plan view showing the angular relationship of each component of the transflective vertical alignment type liquid crystal display device used in Comparative Example 2. It is a figure which shows the contrast ratio when the transflective vertical alignment liquid crystal display device in Comparative Example 2 is viewed from all directions.

Explanation of symbols

1, 2 Substrate 3 Transparent electrode 4 Counter electrode 5 Liquid crystal layer (Vertical alignment)
6 Vertical alignment type liquid crystal cell 7, 11 Linearly polarizing plate 8, 12 Third optical anisotropic element 9, 13 First optical anisotropic element 10, 14 Homeotropic alignment liquid crystal film 15 Reflective electrode 16 Transflective vertical Alignment type liquid crystal cell 17, 18 Second optical anisotropic element

Claims (7)

  A viewing angle compensator for a vertical alignment type liquid crystal display device comprising a homeotropic alignment liquid crystal film in which a liquid crystal material exhibiting positive uniaxiality is homeotropically aligned in a liquid crystal state and then fixed in alignment. The viewing angle compensator for a vertical alignment type liquid crystal display device according to claim 1, wherein the following [1] and [2] are satisfied.
[1] 0 nm ≦ Re1 ≦ 20 nm
[2] −500 nm ≦ Rth1 ≦ −30 nm
(Here, Re1 means an in-plane retardation value of the homeotropic alignment liquid crystal film, and Rth1 means a retardation value in the thickness direction of the homeotropic alignment liquid crystal film. Re1 and Rth1 are respectively Re1 = (Nx1-Ny1) × d1 [nm], Rth1 = (Nx1-Nz1) × d1 [nm], where d1 is the thickness of the homeotropic alignment liquid crystal film, and Nx1 and Ny1 are the homeotropic alignments. (The main refractive index Nz1 in the liquid crystal film plane is the main refractive index in the thickness direction, and Nz1> Nx1 ≧ Ny1.)   Between a pair of substrates provided with electrodes, a vertical alignment type liquid crystal cell including liquid crystal molecules vertically aligned with respect to the substrate surface when no voltage is applied, and two straight lines arranged above and below the vertical alignment type liquid crystal cell In a vertical alignment type liquid crystal display device in which a polarizing plate and a first optical anisotropic element showing a phase difference of ¼ wavelength in the plane are arranged between both surfaces of the vertical alignment type liquid crystal cell and the linear polarizing plate, 3. A vertically aligned liquid crystal comprising at least one viewing angle compensator for a vertically aligned liquid crystal display device according to claim 1 between the linearly polarizing plate and the first optical anisotropic element. Display device.   Between the first optical anisotropic element and the viewing angle compensator for the vertical alignment type liquid crystal display device, there is further provided a second optical anisotropic element showing a phase difference of ½ wavelength in the plane. 4. A vertical alignment type liquid crystal display device according to claim 3, wherein:   At least one third optical anisotropic element having negative uniaxial optical anisotropy in the thickness direction is provided between the first optical anisotropic element and one surface or both surfaces of the vertical alignment type liquid crystal cell. 5. The vertical alignment type liquid crystal display device according to claim 3, wherein the vertical alignment type liquid crystal display device is provided.   6. The first optical anisotropic element according to claim 3, wherein the first optical anisotropic element exhibits a quarter-wave phase difference in a plane and has negative biaxial optical anisotropy in a thickness direction. 4. A vertical alignment type liquid crystal display device according to 1. 7. The vertical alignment type liquid crystal display device according to claim 3, wherein one substrate of the vertical alignment type liquid crystal cell is a substrate having a region having a reflection function and a region having a transmission function. .

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