JP2006091701A - Polarizing plate and liquid crystal display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate capable of contributing to widening the visibility angle of a liquid crystal display apparatus and the improvement of gradation inversion especially in the lower direction of a panel without losing front contrast. <P>SOLUTION: In the polarizing plate comprising at least an optical anisotropic layer (104), an optical diffusion layer (105) and a polarizing layer (101) formed between the optical anisotropic layer (104) and the optical diffusion layer (105), a ratio occupied by an area whose inclination angle is ≥10° is ≤2% on the face of the optical diffusion layer (105) which is the opposite side to the side on which the polarizing layer (101) is arranged and the surface roughness of the surface of the optical diffusion layer (105) which is the opposite side to the side on which the polarizing layer (101) is arranged is 30 to 300 nm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing plate having a light diffusing film and an optical compensation film, and a liquid crystal display device using the polarizing plate.

  The liquid crystal display device includes a polarizing plate and a liquid crystal cell. Disadvantages in the display quality of the liquid crystal display device are that the viewing angle is limited and external light is reflected. With respect to the viewing angle in the TN mode TFT liquid crystal display device, a wide viewing angle liquid crystal display device is realized by inserting an optical compensation film between the polarizing plate and the liquid crystal cell (see Patent Documents 1 to 3). However, the liquid crystal display device still has a problem that gradation inversion in the lower direction of the panel occurs. To solve this problem, display quality is improved by providing light diffusion means (see Patent Document 4), optical axis conversion plate (see Patent Document 5), and optical means (see Patent Document 6) for diffusing outgoing light on the viewing side surface. It is proposed to improve. However, the specific means described in these are light diffusion means having a highly controlled lens structure or diffractive structure, and are expensive and very difficult to mass-produce.

  A light diffusion film that is inexpensive and excellent in productivity has already been disclosed (Patent Documents 7 to 12). These light diffusing films are used as the outermost layer of the display, and play a role as an antiglare film for preventing a decrease in contrast and reflection of an image due to reflection of external light. The more the light emitted from the backlight is diffused by the light diffusion film installed on the polarizing plate on the viewing side, the more the viewing angle characteristics are improved and the anti-glare property is enhanced. However, if it is diffused too much, the backscattering increases, the front luminance decreases, and the black display may appear whitish when observed from an oblique direction. Or, there is a problem that image blurring occurs in high-definition display.

JP-A-8-50206 Japanese Patent Laid-Open No. 7-191217 European Patent 0911656A2 Japanese Patent No. 2822983 JP 2001-33783 A JP 2001-56461 A JP-A-11-160505 JP-A-11-305010 JP 11-326608 A JP 2000-121809 JP 2000-180611 A JP 2000-338310 A

  It is an object of the present invention to provide a polarizing plate that contributes to widening the viewing angle of a liquid crystal display device, in particular, improving gradation reversal in the lower direction of the panel without impairing the front contrast. It is another object of the present invention to provide a liquid crystal display device that can prevent external light from being reflected and can display an image without being disturbed even by a high-definition liquid crystal display device.

Means for solving the problems are as follows.
[1] A polarizing plate having at least an optically anisotropic layer, a light diffusing layer, and a polarizing layer between the optically anisotropic layer and the light diffusing layer,
The surface of the light diffusing layer opposite to the side on which the polarizing layer is disposed, the ratio of the tilt angle of 10 ° or more is 2% or less, and the surface of the light diffusing layer on which the polarizing layer is disposed A polarizing plate having a surface roughness on the opposite side of 30 to 300 nm.
[2] The polarizing plate according to [1], wherein a low refractive index layer having a refractive index of 1.35 to 1.45 is disposed on the outermost layer on the side opposite to the side where the polarizing layer of the light diffusion layer is disposed.
[3] A liquid crystal display device having a liquid crystal cell and a pair of polarizing plates arranged opposite to each other with the liquid crystal cell interposed therebetween, wherein the polarizing plate arranged on at least the viewing side of the pair of polarizing plates is [1] ] Or [2], and a surface of the polarizing plate on which the optically anisotropic layer is disposed is opposed to the liquid crystal cell side.
[4] It further has a collimating means for collimating the light incident from the backlight, and the means sets the angle at which the half value of the front luminance is 40 degrees or less in the vertical profile of the emitted light luminance. [3] The liquid crystal display device.

In this specification, the Re retardation value and the Rth retardation value are calculated based on the following.
Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at the wavelength λ. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is incident on light having a wavelength of λ nm from the direction inclined by + 40 ° with respect to the film normal direction with the Re (λ) and slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis). The retardation value measured in this way, and the retardation value measured by making light of wavelength λ nm incident from a direction tilted by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis. KOBRA 21ADH is calculated based on the retardation value measured in (1). At this time, it is necessary to input an assumed value of average refractive index and a film thickness. KOBRA 21ADH calculates nx, ny, and nz in addition to Rth (λ).
The average refractive index of 1.48 is used for cellulose acetate, but polymer film values for typical optical applications other than cellulose acetate include cycloolefin polymer (1.52), polycarbonate (1.59), poly Values such as methyl methacrylate (1.49) and polystyrene (1.59) can be used. As the average refractive index value of other existing polymer materials, the polymer handbook (John Wiley & Sons, Inc.) and the catalog values of polymer films can be used. In the case of a material whose average refractive index is unknown, it can be measured using an Abbe refractometer.

  According to the present invention, it is possible to improve the wide viewing angle of the liquid crystal display device, particularly the gradation inversion in the lower direction of the panel, without impairing the front contrast. In addition, the reflection of external light can be prevented, and an image without any dullness can be realized even with a high-definition liquid crystal display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
[Polarizer]
The present invention relates to a polarizing plate having at least an optically anisotropic layer, a light diffusing layer, and a polarizing layer disposed between these layers. The polarizing plate of the present invention may have a layer other than the above three types of layers, or may have a plurality of the same type of layers.
FIG. 1 shows a schematic sectional view of an embodiment of the polarizing plate of the present invention. The polarizing plate shown in FIG. 1A includes an optical anisotropic layer 104 and a light diffusion layer 105 with a polarizing layer 101 interposed therebetween. Between the polarizing layer 101 and the optically anisotropic layer 104, a layer 102 made of a polymer film that functions as a support for the optically anisotropic layer 104 and also serves as a protective layer for the polarizing layer 101, and the polarizing layer Between the layer 101 and the light diffusion layer 105, a layer 103 made of a polymer film that functions as a support for the light diffusion layer 105 and also as a protective layer for the polarizing layer 101 is disposed. The polarizing plate shown in FIG. 1B further has a low refractive index layer 106 on the light diffusion layer 105 of the polarizing plate of FIG.

  The polarizing plate shown in FIG. 1A includes, for example, an optical compensation film having an optically anisotropic layer formed from a composition containing a liquid crystal compound on the surface of a polymer film, and a surface of the polymer film, for example. In addition, a light diffusing film having a light diffusing layer formed from a dispersion of inorganic or organic material particles can be produced by adhering it to the surface of the polarizing film. The polarizing plate shown in FIG. 1B can be similarly produced. For example, the polarizing plate shown in FIG. 1A may be produced, and then the low refractive index layer may be formed on the surface of the light diffusion layer. In addition, a light diffusion film having a low refractive index layer on the surface may be bonded to the surface of the polarizing film.

  In the polarizing plate of the present invention, the optically anisotropic layer optically compensates for the liquid crystal cell and contributes to the expansion of the viewing angle, and the light diffusion layer improves the downward viewing angle and provides an antiglare effect. Contributes to prevention of tone reversal and image reflection. In order to improve the downward viewing angle by the light diffusion layer, it is necessary to diffuse the incident light to some extent. The greater the diffusion effect, the better the viewing angle characteristics and antiglare properties. In order to maintain the brightness of the front in terms of display quality, it is necessary to increase the transmittance as much as possible. However, if it is diffused too much, backscattering increases and the brightness decreases. It also causes blurring of the image. In the present invention, the inclination angle distribution of the light diffusion layer and the surface roughness are within a predetermined range, thereby reducing the reflection of the image and increasing the viewing angle of the liquid crystal display device, particularly the gradation in the lower direction of the panel. A polarizing plate that contributes to improving reversal is provided.

Hereinafter, various materials used for the polarizing plate of the present invention will be described.
[Light diffusion layer]
In the present invention, the light diffusing layer has a plane in which the proportion of the region having an inclination angle of 10 ° or more is 2% or less and the surface roughness is 30 to 300 nm. The surface having such characteristics is a surface opposite to the side on which the polarizing layer is disposed. The inclination angle distribution of the surface is determined by the following method. First, a sample having a light diffusion layer formed on the surface of a support is prepared. Assuming a vertex of a triangle having an area of 0.5 to 2 square microns at the interface of the support with the light diffusion layer, three perpendicular lines extending vertically upward from that point intersect the surface of the light diffusion layer. A triangle is formed by three points. The angle formed by the normal of the triangular surface and the perpendicular extending vertically upward from the transparent film is defined as the surface inclination angle. The ratio of the tilt angle distribution, that is, the ratio of the region tilted at a specific tilt angle to the entire surface was measured by dividing the interface into 0.25 square millimeters with respect to the light diffusion layer of the support and dividing it into triangles. It can be determined for the number of all measurement points at the time.

  A method for measuring the tilt angle will be described in more detail. First, a sample in which a light diffusion layer is formed on the surface of a transparent film is prepared. A perpendicular line is extended vertically upward from any three points A, B, C on the interface with the light diffusion layer of the transparent film, and the points where the three points intersect the surface of the light diffusion layer are A ′, B ′, C 'And. An inclination angle is defined as an angle θ formed by a normal line D ′ of the triangle A′B′C ′ plane and a perpendicular line O ′ extending vertically upward from the transparent film. The measurement area is preferably 0.25 square millimeters or more, and the area to be measured is divided into triangles, the respective inclination angles are measured, and the obtained inclination angles are averaged to obtain the average inclination angle of the surface. There are several devices to measure, but an example will be described. A case will be described in which an SXM520-AS150 model manufactured by Micromap (USA) is used as the apparatus. For example, when the objective lens is 10 times, the measurement unit of the tilt angle is 0.85 square micron and the measurement range is 0.48 square millimeter. If the magnification of the objective lens is increased, the measurement unit and the measurement range are reduced accordingly. The measurement data can be analyzed using software such as MAT-LAB, and the tilt angle distribution can be calculated. As a result, it is possible to easily obtain the ratio of the inclination angle of 10 ° or more.

  In the present invention, the ratio of the inclination angle of the surface of the light diffusion layer of 10 ° or more is preferably 2% or less, and more preferably 1% or less. If the ratio of the tilt angle is 10 ° or more exceeds 2%, the black display will appear whitish due to the scattered light, which is not preferable. Further, the average inclination angle of the surface of the light diffusion layer is desirably 1 ° or more and less than 5 °. Further, the inclination angle may have a maximum at a certain angle, and the maximum may be two or more. For example, an aspect in which the inclination angle is 1 °, the inclination angle of 10 ° or more is 2% or less, and the average inclination angle is 4 °; the inclination angle is 1.5 ° and 5 °, and the maximum is 10 And an aspect in which the inclination angle is not less than 2% and the average inclination angle is 6 °.

  The surface roughness Ra of the light diffusion layer can be measured using an atomic force microscope or the like. Ra is preferably 30 nm or more and 300 nm or less, more preferably 50 nm or more and 250 nm or less, and most preferably 100 nm or more and 200 nm or less. When Ra becomes small, the antiglare property becomes insufficient, and the downward gradation inversion deteriorates. On the other hand, when it becomes larger, it causes blurring and glare of the image in the high-definition liquid crystal display device. Any attempt to improve glare by having internal scattering or internal haze will always reduce contrast. By controlling the average tilt angle distribution and the surface roughness within the above ranges, blur and glare in a high-definition liquid crystal display device can be prevented while providing viewing angle characteristics, contrast, and antiglare properties.

  The inclination angle distribution and Ra of the surface of the light diffusion layer are set to one or more values such as the size of the light diffusing particles, the number of particles, the ratio of the binder and particles in the light diffusion layer, and the dry film thickness. Thus, the preferred range can be controlled. The surface shape can also be controlled by changing the coating liquid physical properties, coating conditions, and drying conditions. Embossing is also suitable for precise surface design. The embossing process is described in detail in Japanese Patent Laid-Open No. 2000-329905. A light diffusion layer having a desired surface shape can be produced by setting the embossing roll to a desired surface inclination angle distribution and Ra. However, the method for obtaining the surface shape is not limited to these.

  As a method for obtaining the uneven shape, Japanese Patent Application Laid-Open No. 2000-329905 discloses a method for providing an uneven shape after forming an antireflection film. Specifically, after applying an antireflection layer, the antireflection film is pressed with an embossing roll. The pressure at this time is preferably 1 kgf / cm or more and 1000 kgf / cm or less, and the temperature is preferably 25 ° C. or more and 300 ° C. or less. Moreover, the material of a roll is various and metals and plastics, such as iron and aluminum, are used.

  The light diffusion layer is preferably not a layer having a uniform refractive index, but a refractive index nonuniform layer in which particles are dispersed in the material. The refractive index of the material forming the light diffusion layer is preferably 1.50 or more and 1.65 or less. The high refractive index material is a fine particle having a particle size of 100 nm or less comprising a monomer having two or more ethylenically unsaturated groups and at least one oxide selected from titanium, aluminum, indium, zinc, tin, antimony, and zirconium. In such a case, it is described in JP-A-8-110401 and the like that the particle size of the fine particles is sufficiently smaller than the wavelength of light so that no scattering occurs and the optically behaves as a uniform substance.

  The light diffusion layer preferably has a hard coat property. For the formation of the light diffusion layer, a polymer having a saturated hydrocarbon or polyether as the main chain is preferably used, and a polymer having a saturated hydrocarbon as the main chain is more preferable. The binder polymer is preferably crosslinked. The polymer having a saturated hydrocarbon as the main chain is preferably obtained by a polymerization reaction of an ethylenically unsaturated monomer. In order to obtain a crosslinked binder polymer, it is preferable to use a monomer having two or more ethylenically unsaturated groups. In order to obtain a high refractive index, the monomer structure preferably contains at least one selected from an aromatic ring, a halogen atom other than fluorine, sulfur, phosphorus, and nitrogen atoms.

  Examples of monomers having two or more ethylenically unsaturated groups include esters of polyhydric alcohols and (meth) acrylic acid (eg, ethylene glycol di (meth) acrylate, 1,4-dichlorohexane diacrylate, pentaerythritol). Tetra (meth) acrylate), pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate , Pentaerythritol hexa (meth) acrylate, 1,2,3-cyclohexanetetramethacrylate, polyurethane polyacrylate, polyester polyacrylate), vinylbenzene and its derivatives (examples) 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (eg, divinyl sulfone), acrylamide (eg, methylenebisacrylamide) and methacrylamide are included .

  Examples of the high refractive index monomer include bis (4-methacryloylthiophenyl) sulfide, vinyl naphthalene, vinyl phenyl sulfide, 4-methacryloxyphenyl-4'-methoxyphenyl thioether and the like. The polymer having a polyether as the main chain is preferably synthesized by a ring-opening polymerization reaction of a polyfunctional epoxy compound. These monomers having an ethylenically unsaturated group need to be cured by a polymerization reaction by ionizing radiation or heat after coating.

  Polymerization of the monomer having an ethylenically unsaturated group can be performed by irradiation with ionizing radiation or heating in the presence of a photo radical initiator or a thermal radical initiator. Accordingly, a coating liquid containing a monomer having an ethylenically unsaturated group, a photo radical initiator or a thermal radical initiator, preferably mat particles and an inorganic filler is prepared, and the coating liquid is applied on a transparent support and then ionizing radiation. Alternatively, it can be cured by a polymerization reaction by heat to form an antireflection film. Examples of the photo radical polymerization initiator include acetophenones, benzophenones, Michler's benzoylbenzoate, amyloxime ester, tetramethylthiuram monosulfide, and thioxanthones.

  In particular, photocleavable photoradical polymerization initiators are preferred. The photocleavable photoradical polymerization initiator is described in the latest UV curing technology (P.159, issuer; Kazuhiro Takasawa, publisher; Technical Information Association, published in 1991). Examples of commercially available photocleavable photoradical polymerization initiators include Irgacure (651, 184, 907) manufactured by Ciba Geigy Japan. It is preferable to use a photoinitiator in the range of 0.1-15 mass parts with respect to 100 mass parts of polyfunctional monomers, More preferably, it is the range of 1-10 mass parts. In addition to the photopolymerization initiator, a photosensitizer may be used. Specific examples of the photosensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, Michler's ketone and thioxanthone.

  Instead of or in addition to the monomer having two or more ethylenically unsaturated groups, a crosslinked structure may be introduced into the binder polymer by the reaction of a crosslinkable group. Examples of the crosslinkable functional group include isocyanate group, epoxy group, aziridine group, oxazoline group, aldehyde group, carbonyl group, hydrazine group, carboxyl group, methylol group and active methylene group. Vinylsulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer for introducing a crosslinked structure. A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used. In the present invention, the cross-linking group is not limited to the above compound, and may be one showing reactivity as a result of decomposition of the functional group. These compounds having a crosslinking group need to be crosslinked by heat after application.

The light diffusion layer has a particle diameter of 100 nm made of at least one oxide selected from titanium, aluminum, indium, zinc, tin, antimony and zirconium in order to increase the refractive index of the material forming the light diffusion layer. Hereinafter, it is preferable to contain fine particles of 50 nm or less. Examples of the fine particles include TiO ₂ , Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , Sb ₂ O ₃ , ITO, ZrO _{2 and the} like. The addition amount of the inorganic fine particles is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, and particularly preferably 30 to 60% by mass with respect to the total mass of the light diffusion layer.

The said light diffusing layer, light diffusing, antiglare property imparted, the reflectivity deterioration prevention by interference, for the purpose of color unevenness prevention, inorganic compound or organic polymer matting particles are used, for example, silica particles, TiO ₂ Particles, Al ₂ O ₃ particles, crosslinked acrylic particles, styrene particles, crosslinked styrene particles, melamine resin particles, benzoguanamine resin particles, crosslinked siloxane particles and the like are preferably used. Organic polymer particles are more preferable from the viewpoints of good dispersion stability (because of good affinity with the binder) and good sedimentation stability (because of low specific gravity) of the particles in the coating liquid during production. The average particle size of the mat particles is from 0.3 μm to 10.0 μm, more preferably from 0.5 μm to 7.0 μm, and even more preferably from 1 μm to 6 μm. The shape of the mat particles can be either spherical or indefinite, but the spherical shape is preferable in order to obtain a stable antiglare property. Two or more different kinds of particles may be used in combination. Further, it is preferable to use mat particles having a particle size larger than one third of the thickness of the light diffusion layer. The particle size distribution can be measured by a Coulter counter method, a centrifugal sedimentation method, or the like, but the distribution is considered in terms of the particle number distribution.

  The light diffusion layer is prepared by preparing a coating liquid containing at least one of the above monomers capable of forming a film by curing, a polymerization initiator, inorganic fine particles, and the like, and applying the coating liquid to a surface of a support such as a polymer film. It can be formed by applying to the substrate, drying it as desired, and then curing it by irradiating with ultraviolet rays or the like. Application may be performed by any method such as dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, and extrusion coating (US Pat. No. 2,681,294). Good. Two or more layers may be applied simultaneously. The method of simultaneous application is described in US Pat. Nos. 2,761,791, 2,941,898, 3,508,947, and 3,526,528 and Yuji Harasaki, Coating Engineering, page 253, Asakura Shoten (1973).

The dry film thickness of the light diffusion layer is preferably 2 μm or more and 10 μm, more preferably 3 or more and 6 μm or less.
Further, the haze of the light diffusing film is preferably 0% to 18%, more preferably 0% to 15% in a system in which the layer containing particles does not have internal scattering. The system having internal scattering in the layer containing particles is preferably 15% to 80%, more preferably 20% to 65%.

[Low refractive index layer]
In order to provide an antireflection function, it is preferable to dispose a low refractive index layer on the light diffusion layer. The refractive index of the low refractive index layer is preferably 1.35 or more and 1.45 or less, more preferably 1.35 or more and 1.42 or less, and most preferably 1.35 or more and 1.40 or less. In the antireflection film, the low refractive index layer preferably satisfies the following formula (I).
mλ / 4 × 0.7 <n1d1 <mλ / 4 × 1.3 (I)
In the formula, m is a positive odd number (generally 1), n1 is the refractive index of the low refractive index layer, and d1 is the film thickness (nm) of the low refractive index layer.

  For the low refractive index layer, it is preferable to use a fluorine-containing compound and inorganic fine particles that are crosslinked by heat or ionizing radiation and have a dynamic friction coefficient of 0.03 to 0.15 and a contact angle with water of 90 ° to 120 °. . As a crosslinkable fluoropolymer compound that can be used for the low refractive index layer, in addition to a perfluoroalkyl group-containing silane compound (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane), Examples thereof include fluorine-containing copolymers having a fluorine-containing monomer and a monomer for imparting a crosslinkable group as structural units. Specific examples of the fluorine-containing monomer unit include, for example, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc. ), (Meth) acrylic acid partial or fully fluorinated alkyl ester derivatives (for example, Biscoat 6FM (manufactured by Osaka Organic Chemicals) and M-2020 (manufactured by Daikin)), fully or partially fluorinated vinyl ethers, and the like. As a monomer for imparting a crosslinkable group, in addition to a (meth) acrylate monomer having a crosslinkable functional group in the molecule like glycidyl methacrylate, it has a carboxyl group, a hydroxyl group, an amino group, a sulfonic acid group, etc. ) Acrylate monomers (for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate, etc.). It is described in each direction of JP-A-10-25388 and JP-A-10-147739 that the latter can introduce a crosslinked structure after copolymerization.

  Further, not only a polymer having the above-mentioned fluorine-containing monomer as a structural unit but also a copolymer with a monomer not containing a fluorine atom may be used. There are no particular limitations on the monomer units that can be used in combination. For example, olefins (ethylene, propylene, isoprene, vinyl chloride, vinylidene chloride, etc.), acrylic esters (methyl acrylate, methyl acrylate, ethyl acrylate, acrylic acid 2) -Ethylhexyl), methacrylates (methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, etc.), styrene derivatives (styrene, divinylbenzene, vinyltoluene, α-methylstyrene, etc.), vinyl ethers (methyl) Vinyl ether), vinyl esters (vinyl acetate, vinyl propionate, vinyl cinnamate, etc.), acrylamides (N-tertbutylacrylamide, N-cyclohexylacrylamide, etc.), methacrylamides, Krilo nitrile derivatives and the like can be mentioned.

  As the inorganic fine particles used in the low refractive index layer, amorphous particles are preferably used, preferably made of a metal oxide, nitride, sulfide or halide, and particularly preferably a metal oxide. As metal atoms, Na, K, Mg, Ca, Ba, Al, Zn, Fe, Cu, Ti, Sn, In, W, Y, Sb, Mn, Ga, V, Nb, Ta, Ag, Si, B Bi, Mo, Ce, Cd, Be, Pb and Ni are preferred, and Mg, Ca, B and Si are more preferred. An inorganic compound containing two kinds of metals may be used. A particularly preferred inorganic compound is silicon dioxide, ie silica. Further, from the viewpoint of a low refractive index, hollow silica is most preferable. The average particle size of the inorganic fine particles is preferably 0.001 or more and 0.2 μm or less, and more preferably 0.005 or more and 0.05 μm or less. The particle diameter of the fine particles is preferably as uniform (monodispersed) as possible. The addition amount of the inorganic fine particles is preferably 5% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 70% by mass or less, and more preferably 20% by mass or more and 50% by mass or less of the total mass of the low refractive index layer. A mass% or less is more preferable. The inorganic fine particles are preferably used after being subjected to a surface treatment. The surface treatment method includes physical surface treatment such as plasma discharge treatment and corona discharge treatment and chemical surface treatment using a coupling agent, but the use of a coupling agent is preferred. As the coupling agent, an organoalkoxy metal compound (eg, titanium coupling agent, silane coupling agent) is preferably used. Silane coupling treatment is particularly effective when the inorganic fine particles are silica.

[Optically anisotropic layer]
In the present invention, the optically anisotropic layer preferably contains a liquid crystal compound fixed in an aligned state. The optically anisotropic layer can be formed from a composition containing a liquid crystal compound. The optically anisotropic layer is formed on a transparent support or an alignment film. Examples of a method for aligning an optical anisotropic layer without using an alignment film include a method of applying an electric field or a magnetic field while heating the optical anisotropic layer on the support to a temperature at which a discotic liquid crystal layer can be formed. Can do.

  The optically anisotropic layer is preferably a layer made of a compound having a discotic structural unit. That is, the optically anisotropic layer is preferably a layer of a low molecular weight liquid crystal discotic compound such as a monomer or a polymer layer obtained by polymerization (curing) of a polymerizable liquid crystal discotic compound. Examples of the discotic (discotic) compound include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physicslett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, page 2655 (1994), and azacrown-based and phenylacetylene-based macrocycles. The above discotic (discotic) compounds generally have a structure in which these are used as a mother nucleus at the center of a molecule, and a linear alkyl group, an alkoxy group, a substituted benzoyloxy group, etc. are radially substituted as the linear chain. , Which shows liquid crystallinity and is generally called a discotic liquid crystal. However, when such an aggregate of molecules is uniformly oriented, it exhibits negative uniaxiality, but is not limited to this description. Further, in the present invention, it is not necessary that the final product is formed from a discotic compound, for example, the low molecular discotic liquid crystal has a group that reacts with heat, light, or the like. As a result, it may be polymerized or cross-linked by reaction with heat, light or the like, resulting in high molecular weight and loss of liquid crystallinity.

  Preferred examples of the discotic compound are shown below.

  The optically anisotropic layer is preferably formed using an alignment film and a gas-liquid interface. Specifically, it is preferable to prepare by providing an alignment film on a transparent support and then forming an optically anisotropic layer on the alignment film, but it is not limited thereto.

  The optically anisotropic layer is a layer made of a compound having a discotic structural unit, and the surface of the discotic structural unit is inclined with respect to the transparent support surface, and the surface of the discotic structural unit and the transparent support surface Is preferably changed in the depth direction of the optical anisotropic layer while locally fluctuating.

  The angle (tilt angle) of the surface of the discotic structural unit has fluctuations at a certain local depth, but generally viewed in the depth direction of the optical anisotropic layer when viewed as the entire optical anisotropic layer, and It increases or decreases with increasing distance from the bottom surface of the optically anisotropic layer. It is preferable that the inclination angle increases with increasing distance while having this fluctuation. Further, the change in the inclination angle includes continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, and intermittent change including increase and decrease. it can. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the inclination angle includes a region that does not change, it is preferable that the inclination angle increases or decreases as a whole. Furthermore, the tilt angle generally increases as a whole of the optically anisotropic layer, and it is particularly preferable to change continuously.

  In general, the optically anisotropic layer is formed by applying a solution obtained by dissolving a discotic compound and other compounds in a solvent onto an alignment film, drying it, and then heating it to a discotic nematic phase formation temperature, and then aligning it (discotic). It is obtained by maintaining the nematic phase and cooling. Alternatively, the optically anisotropic layer may be formed by applying a solution obtained by dissolving a discotic compound and another compound (for example, a polymerizable monomer or a photopolymerization initiator) in a solvent onto the alignment film, drying, and then discotic nematic. It is obtained by heating to the phase formation temperature, followed by polymerization (by irradiation with UV light, etc.) and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound layer used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C. Furthermore, the liquid crystal transition temperature can be appropriately adjusted by other compounds (monomer or the like) mixed in the optically anisotropic layer.

  For example, the tilt angle of the discotic unit on the support side can be generally adjusted by selecting a discotic compound or a material for the alignment film, or by selecting a rubbing treatment method. The inclination angle of the discotic unit on the surface side (air side) is generally selected from the discotic compound or other compounds (eg, plasticizer, surfactant, polymerizable monomer and polymer) used together with the discotic compound. Can be adjusted. Furthermore, the degree of change in the tilt angle can be adjusted by the above selection.

  As the plasticizer, surfactant and polymerizable monomer, any compound is used as long as it has compatibility with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound or does not inhibit the alignment. Can also be used. Among these, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) are preferable. The above compound is generally used in an amount of 1 to 50% by mass (preferably 5 to 30% by mass) based on the discotic compound.

  Any polymer can be used as the polymer as long as it is compatible with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound. Examples of polymers include cellulose esters. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. The polymer is generally 0.1 to 10% by mass (preferably 0.1 to 8% by mass, particularly 0.1 to 5% by mass) based on the discotic compound so as not to inhibit the alignment of the liquid crystalline discotic compound. ). The degree of butyrylation of cellulose acetate butyrate (cellulose acetate butyrate) is preferably 30% or more, particularly preferably in the range of 30 to 80%. The degree of acetylation is preferably 30% or more, particularly preferably in the range of 30 to 80%. The viscosity (value obtained by measurement according to ASTM D-817-72) of cellulose acetate butyrate is preferably in the range of 0.01 to 20 seconds.

  The (color) liquid crystal display device provided with the polarizing plate of the present invention having an optically anisotropic layer having a changing tilt angle has improved viewing angle, and inversion of a black-and-white image or occurrence of gradation or coloring of a display image. There is almost nothing. The reason why the viewing angle of the liquid crystal surface device is improved by using the optically anisotropic layer is estimated as follows. For example, in a liquid crystal display device, in a normally white mode (a mode widely used in TN-LCDs) in which the transmission axes of a polarizer and an analyzer are substantially orthogonal, a portion in a black display state has a voltage applied to the liquid crystal. Is applied, and as the viewing angle is increased, the transmittance of light from the black display portion is remarkably increased, resulting in a sharp decrease in contrast. In this black display state (when voltage is applied), the TN liquid crystal molecules present in the vicinity of the lower substrate surface are substantially parallel to the surface of the substrate, and the TN liquid crystal molecules gradually increase as they move away from the substrate surface. Inclined to become perpendicular to the surface. As the distance from the surface of the lower substrate further increases, the TN liquid crystal molecules gradually tilt in the opposite direction and finally become substantially parallel to the upper substrate surface. Therefore, the liquid crystal cell of the TN-LCD in black display is an optically anisotropic body having a complicated structure in which the tilt angle of the symmetry axis of the liquid crystal molecules changes. For this reason, the discotic structure unit surface of the optically anisotropic layer By three-dimensionally optimizing the change in the tilt angle and the optical anisotropy, it is possible to compensate for the phase difference caused by the tilt of the liquid crystal molecules inside the TN liquid crystal cell when a voltage is applied. Therefore, a color liquid crystal display device including an optical anisotropic layer (optical compensation sheet) having a changing tilt angle can be used to invert a black-and-white image or to display a display image even when the display device is viewed obliquely with a large viewing angle. There is almost no gradation or coloring.

  The haze of the optically anisotropic layer is generally 5.0% or less. Therefore, the optical compensation sheet having the optically anisotropic layer generally has 5.0% or less because the haze of the transparent support is low. The haze is measured according to ASTN-D1003-52. When the haze of the optically anisotropic layer is high, light leakage that appears to be caused by scattering occurs in the black display portion, resulting in a decrease in contrast. This tendency is remarkable when the incident light is tilted in the normal direction and in the upward direction of the image. Therefore, in order to prevent this, the haze is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. In general, haze is caused by the rough surface (fine irregularities, scratches) or internal non-uniformity (existence of minute parts with different refractive indexes). It is necessary to smooth the surface of the anisotropic layer and reduce the non-uniformity of the internal refractive index. The optically anisotropic layer has a smooth surface and a uniform interior, and thus has a low haze. In order to further reduce the haze, for example, it is preferable to form a protective layer or an adhesive layer on the optical anisotropic layer, or to appropriately select the conditions for forming the optical anisotropic layer. The smooth surface of the optical anisotropic layer can be easily obtained as described above.

  A protective layer may be provided on the surface of the optically anisotropic layer. Although there is no restriction | limiting in particular about the material used for formation of this protective layer, A polymer is preferable from a viewpoint of film forming ability, and it is preferable that it is soluble in the solvent which does not melt | dissolve a discotic compound. Specific examples of the polymer include water-soluble polymers such as gelatin, methyl cellulose, alginic acid, pectin gum arabic, pullulan, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, sodium polyvinylbenzene sulfonate, carrageenan, and polyethylene glycol. An adhesive layer can be provided on the optically anisotropic layer instead of the protective layer. The adhesive layer is generally formed when incorporated in a liquid crystal display device. There is no restriction | limiting in particular as a material of an adhesion layer, A transparent adhesive agent thru | or acrylics, a SBR type | system | group, a silicone rubber type | system | group, or an adhesive can be used. From the viewpoint of preventing deterioration of the optical properties of the constituent members, those that do not require a high-temperature process during curing and drying are preferred, and those that do not require a long curing process or drying time are preferred. A smooth surface can be obtained by applying a coating solution for forming an adhesive layer or a protective layer so as to have a smooth surface, whereby haze can be reduced. In the present invention, it is preferable to apply an adhesive layer rather than a protective layer from the viewpoint of productivity. The conditions for forming the optically anisotropic layer are appropriately selected depending on the composition containing the discotic compound (the combination of discotic compounds and the type and amount of other compounds used in combination). The conditions include heating temperature or heating time for forming a desired liquid crystal alignment phase, cooling rate after heating, layer thickness, coating method, and the like. In addition, the discotic compound may form a plurality of different domains depending on the properties of the compound, the formation conditions, etc., and this results in haze due to nonuniformity inside the layer. In order to reduce such haze, even if the discotic compound is made into a mono domain or a plurality of domains are formed, each domain size is set to 0.1 μm or less, preferably 0.08 μm or less. Thus, it is possible to prevent the visible light from being affected.

  The coating liquid for forming the optically anisotropic layer can be prepared by dissolving the discotic compound and the other compounds described above in a solvent. Examples of the solvent include polar solvents such as N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and pyridine; nonpolar solvents such as benzene and hexane; alkyl halides such as chloroform and dichloromethane; acetic acid Mention may be made of esters such as methyl and butyl acetate; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran and 1,2-dimethoxyethane. Alkyl halides and ketones are preferred. Solvents may be used alone or in combination.

  Examples of the application method of the solution include curtain coating, extrusion coating, roll coating, dip coating, spin coating, printing coating, spray coating, and slide coating. In the present invention, a vapor deposition method can also be used in the case of a mixture containing only a discotic compound. In the present invention, continuous coating is preferred. Curtain coating, extrusion coating, roll coating and slide coating are therefore preferred. As described above, the optically anisotropic layer is obtained by applying the coating solution onto the alignment film, drying it, and then heating it to the glass transition temperature or higher (after that, curing it if desired) and then cooling it.

Since the optically anisotropic layer compensates birefringence due to the liquid crystal cell in the liquid crystal display device, it is preferable that the wavelength dispersion of the optically anisotropic layer is equal to that of the liquid crystal cell. That is, if 450μm and 550μm, respectively R ₄₅₀ and R ₅₅₀ retardation with light of the optically anisotropic layer, the R ₄₅₀ / R ₅₅₀ value representing the wavelength dispersion is preferably 1.0 or more.

[Alignment film]
As described above, an alignment film may be used for forming the optically anisotropic layer. The alignment film is generally provided on a transparent support or an undercoat layer coated on the transparent support. The alignment film functions to define the alignment direction of the liquid crystalline discotic compound provided thereon. The alignment film may be any layer as long as it can impart orientation to the optically anisotropic layer. Preferred examples of the alignment film include a layer subjected to a rubbing treatment of an organic compound (preferably a polymer), an oblique deposition layer of an inorganic compound, and a layer having a microgroove, and ω-tricosanoic acid, dioctadecylmethylammonium chloride and stearyl. Examples thereof include a cumulative film formed by Langmuir-Blodgett method (LB film) such as methyl acid, or a layer in which a dielectric is oriented by applying an electric field or a magnetic field.

  Examples of organic compounds for alignment films include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyl toluene copolymer. , Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and Examples of the compound include a silane coupling agent. Examples of preferred polymers include polyimide, polystyrene, polymers of styrene derivatives, gelatin, polyvinyl alcohol, and alkyl-modified polyvinyl alcohol having an alkyl group (preferably having 6 or more carbon atoms).

Of these, alkyl-modified polyvinyl alcohol is particularly preferable, and has an excellent ability to uniformly align a liquid crystalline discotic compound. This is presumably because of the strong interaction between the alkyl chain on the alignment film surface and the alkyl side chain of the discotic liquid crystal. The alkyl group, having 6 to 14 carbon atoms are _{preferred,, -S -, - (CH 3} ) C (CN) - or _{- (C 2 H 5) N} -CS-S- a through Polyvinyl alcohol It is preferable that it is couple | bonded with. The alkyl-modified polyvinyl alcohol has an alkyl group at the end, and preferably has a saponification degree of 80% or more and a polymerization degree of 200 or more. As the polyvinyl alcohol having an alkyl group in the side chain, commercially available products such as MP103, MP203, R1130 manufactured by Kuraray Co., Ltd. can be used.

  A polyimide film (preferably fluorine atom-containing polyimide) widely used as an alignment film for LCD is also preferable as the organic alignment film. For this, polyamic acid (for example, LQ / LX series manufactured by Hitachi Chemical Co., Ltd., SE series manufactured by Nissan Chemical Co., Ltd., etc.) was applied to the support surface and baked at 100 to 300 ° C. for 0.5 to 1 hour. Thereafter, it is obtained by rubbing. Furthermore, the alignment film of the present invention can be obtained by introducing a reactive group into the polymer or by using the polymer together with a crosslinking agent such as an isocyanate compound and an epoxy compound to cure these polymers. A membrane is preferred.

  Moreover, the rubbing process can utilize a processing method widely adopted as a liquid crystal alignment process of LCD. That is, a method of obtaining alignment by rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average.

Further, as a vapor deposition material for the inorganic oblique vapor deposition film, SiO is representative, metal oxides such as TiO ₂ and ZnO ₂ , fluorides such as MgF ₂ , and metals such as Au and Al. The metal oxide can be used as an oblique deposition material as long as it has a high dielectric constant, and is not limited to the above. The inorganic oblique deposition film can be formed using a deposition apparatus. An inorganic oblique deposition film can be formed by performing deposition while fixing a film (support) or by continuously evaporating by moving a long film.

[Support]
As described above, the light diffusing layer and the optically anisotropic layer may be formed on the support, respectively, and the former may be bonded to the polarizing film as the light diffusing film and the latter as the optical compensation film. Both surfaces to be bonded to the polarizing film are preferably the back surface of the support (the surface on which the light diffusion layer or the optically anisotropic layer is not formed). The support for each of the light diffusing layer and the optically anisotropic layer is preferably transparent, and specifically, a support made of a material having a light transmittance of 80% or more is preferable. Such materials can be obtained from commercial products, such as ZEONEX (manufactured by ZEON Corporation), ARTON (manufactured by Nippon Synthetic Rubber Co., Ltd.) and Fujitac (manufactured by Fuji Photo Film Co., Ltd.). Can be used. In addition, for materials having a large intrinsic birefringence, such as polycarbonate, polyarylate, polysulfone, and polyethersulfone, the conditions for solution casting, melt extrusion, etc., as well as the examination of the stretched state in the longitudinal and transverse directions should be set as appropriate. Can be used. When used as a protective film for a polarizing film, it is most preferable to use cellulose acetate film because of its moisture permeability and the like, and it is widely used.

Hereinafter, the transparent support which can be used for this invention is demonstrated using the cellulose acetate film used widely as an example.
The cellulose acetate film used as the support for the optical compensation film preferably has a Re retardation value of −150 to 20 nm and an Rth retardation value of −300 to 400 nm. Furthermore, although it is optimally adjusted according to the mode of the liquid crystal display device to be incorporated, when two optically anisotropic cellulose acetate films are used for the liquid crystal display device (for example, both supports of the optically anisotropic layer are In the TN mode, the Re retardation value is −100 to 10 nm and the Rth retardation value is preferably 70 to 150 nm; similarly, in the VA mode, the Re retardation value is −100 to Preferably −20 nm and Rth retardation value of 120 to 200 nm; in OCB mode, Re retardation value is −150 to −20 nm and Rth retardation value is preferably −150 to 10 nm; Furthermore, in the IPS mode, the Re retardation value is -1. Is a 0~10nm, Rth retardation value is preferably -300~-100nm.
When one optically anisotropic cellulose acetate film is used for the liquid crystal display device (for example, when the support of the optically anisotropic layer is a cellulose acetate film), the Rth retardation value of the film is −300 to 400 nm. It is preferable that

In the present invention, it is preferable to use cellulose acetate having an acetylation degree of 59.0 to 61.5%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more. The cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.
Cellulose polymers other than cellulose acetate include cellulose alkylcarbonyl ester, alkenylcarbonyl ester or aromatic carbonyl ester, aromatic alkylcarbonyl ester, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate stearate, cellulose acetate benzoate. Can be used alone or in combination with cellulose acetate. Details of the production method of cellulose acetate and the like are described in (Kobayashi Cover Patent) and can be used in the present invention.

[Polarizing layer]
In the present invention, the polarizing layer is made of a general linear polarizing film. The linear polarizing film is manufactured by Optiva Inc. And a polarizing film comprising a binder and iodine or a dichroic dye is preferable. The iodine and the dichroic dye in the linearly polarizing film exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal. Currently, commercially available polarizers are made by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.

  The commercially available polarizing film has iodine or dichroic dye distributed about 4 μm (about 8 μm on both sides) from the polymer surface, and a thickness of at least 10 μm is necessary to obtain sufficient polarization performance. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time. As described above, the lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed on a 17-inch liquid crystal display device.

  The binder of the polarizing film may be cross-linked. As the crosslinked binder, a polymer that can be crosslinked per se can be used. A polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally carried out by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is only necessary to ensure durability at the stage of the final product, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

  As the binder of the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Examples of the polymer include the same polymers as those described for the alignment film. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  The addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the wet heat resistance of the polarizing film are improved.

The polarizing film contains a certain amount of a crosslinking agent that has not reacted even after the crosslinking reaction is completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. In this way, even if the polarizing film is incorporated in a liquid crystal display device and used for a long time or left in a high temperature and high humidity atmosphere for a long time, the degree of polarization does not decrease.
The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.

  As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). Examples of the dichroic dye include compounds described in, for example, the Japan Society for Invention and Innovation, Japanese Patent No. 2001-1745, page 58 (issued on March 15, 2001).

[Production of Polarizing Plate of the Present Invention]
The method for producing the polarizing plate of the present invention is not particularly limited, but is formed on the optical compensation sheet having the support and the optically anisotropic layer formed thereon, the linearly polarizing film, and the support. A light diffusion film having a light diffusion layer (with a low refractive index layer thereon if desired) is formed into a long shape, and is made into a roll form, and a polarizing plate is produced by roll-to-roll. May be. The polarizing plate produced in a long shape is stored and transported in a roll form, and is cut into a desired size at the time of use. Moreover, you may use an adhesive agent if needed at the time of bonding.

[Liquid Crystal Display]
The present invention also relates to a liquid crystal display device using the polarizing plate of the present invention. Embodiments in which the present invention is applied to a TN mode liquid crystal display device will be described with reference to the drawings.
The liquid crystal display device of FIG. 2 has a liquid crystal cell composed of an upper substrate 6 and a lower substrate 9 and a liquid crystal layer sandwiched between them and formed from liquid crystal molecules 8. An alignment film (not shown) is formed on the surfaces (opposing surfaces) of the substrates 6 and 9 that are in contact with the liquid crystal molecules 8 if desired. The opposing surface has alignment axes (rubbing axes) 7 and 10 by rubbing treatment or the like, and the alignment of the liquid crystal molecules 7 in a state in which no voltage is applied or in a low application state is controlled. A transparent electrode (not shown) capable of applying a voltage to the liquid crystal layer composed of the liquid crystal molecules 8 is formed on the opposing surfaces of the substrates 6 and 9.

In the TN mode liquid crystal display device of FIG. 2, in a non-driving state in which a driving voltage is not applied to the electrodes, the liquid crystal molecules 8 in the liquid crystal cell are aligned substantially parallel to the substrate surface, and the alignment direction is the upper and lower substrates. It is twisted approximately 90 ° between. As the applied voltage is increased, the liquid crystal molecules 8 gradually stand in a direction perpendicular to the substrate surface while eliminating the twist.
In the TN mode, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is preferably 0.2 to 1.2 μm, and more preferably 0.2 to 0.5 μm. Further, the twist angle (twist angle) of the liquid crystal layer is preferably 80 to 100 °, and more preferably 85 to 95 °. In these ranges, a liquid crystal display device with high white display brightness and a wide viewing angle can be obtained. In order to set the twist angle of the liquid crystal molecules 8 to 80 to 100 °, the angles formed by the rubbing axes 7 and 10 of the substrates 6 and 9 are set to 80 to 100 °. For example, when the horizontal direction in the horizontal plane of the substrate is 0 °, a substrate having a rubbing axis inclined in a direction of about −45 ° is disposed on the backlight side, and the + 45 ° direction is disposed on the viewer side. It is preferable to arrange a substrate having a rubbing axis inclined in a certain direction.

  The liquid crystal material in the liquid crystal cell is not particularly limited as long as it is a nematic liquid crystal. As the dielectric anisotropy Δε is larger, the driving voltage can be reduced. As the refractive index anisotropy Δn is smaller, the thickness (gap) of the liquid crystal layer can be increased, the liquid crystal sealing time can be shortened, and the gap variation can be reduced. In addition, a larger Δn can reduce the cell gap and enable high-speed response.

  The liquid crystal display device of FIG. 2 includes a pair of polarizing plates 2A and 13A disposed on both sides of the liquid crystal cell. The polarizing plates 2A and 13A have linearly polarizing layers 2 and 13 arranged so that the respective absorption axes 3 and 14 are substantially orthogonal. Further, optically anisotropic layers 4 and 11 containing a compound fixed in an arbitrary alignment state are provided between the liquid crystal cell and the polarizing layer, respectively. The optically anisotropic layers 4 and 11 are arranged symmetrically with respect to the liquid crystal cell, respectively, and optically compensate the liquid crystal cell. Each of the optically anisotropic layers 4 and 11 contains a compound whose orientation is controlled by rubbing axes 5 and 12 and fixed in that state.

Below, the preferable angle relationship of the orientation axes 5, 7, 10 and 12 and the absorption axes 3 and 14 in this embodiment is demonstrated. In the following, in FIG. 2, the upper side is the viewing side and the lower side is the backlight side.
First, in order to optically compensate the liquid crystal display device of FIG. 2 more accurately in the vertical direction and to expand the contrast viewing angle in the vertical direction, the absorption axis 3 is set counterclockwise with respect to the rubbing axis 7. The absorber shaft 14 is arranged to be shifted by 0.1 ° to 10 ° (preferably 0.3 to 7 °, more preferably 0.5 to 5 °), and the absorption shaft 14 is 0.1 clockwise relative to the rubbing shaft 10. The rubbing shaft 5 is shifted by 0 ° to 10 ° (preferably 0.3 to 7 °, more preferably 0.5 to 5 °) and / or the rubbing shaft 5 is rotated counterclockwise by 0. 1 ° to 10 ° (preferably 0.3 to 7 °, more preferably 0.5 to 5 °) and the rubbing shaft 12 is arranged in a clockwise direction with respect to the rubbing shaft 10 to 0.1 ° to They are shifted by 10 ° (preferably 0.3-7 °, more preferably 0.5-5 °).

  On the other hand, in order to optically compensate more accurately in the left-right direction of the liquid crystal display device and to enlarge the left-right direction contrast viewing angle, the absorption axis 3 is 0.1 ° to 10 ° clockwise with respect to the rubbing axis 7. And the absorption shaft 14 is positioned 0.1 ° to 10 ° counterclockwise with respect to the rubbing shaft 10 (preferably 0.3 to 7 °, more preferably 0.5 to 5 °). Preferably, the rubbing shaft 5 is shifted by 0.3 to 7 °, more preferably 0.5 to 5 °, and / or the rubbing shaft 5 is 0.1 ° to 10 ° in the clockwise direction with respect to the rubbing shaft 7 (preferably Is shifted by 0.3-7 °, more preferably 0.5-5 °, and the rubbing shaft 12 is 0.1 ° -10 ° (preferably 0) counterclockwise with respect to the rubbing shaft 10. .3-7 °, more preferably 0.5-5 °).

  In the liquid crystal display device of FIG. 2, it is preferable that the absorption axis 3 and the rubbing axis 5 and the absorption axis 14 and the rubbing axis 12 are substantially parallel.

The polarizing plates 2A and 13A on the viewing side are polarizing plates of the present invention, and a light diffusion layer having a surface inclination angle distribution in the predetermined range and a surface roughness in the predetermined range on the viewing side and the backlight side, respectively. 1 and the light diffusion layer 15. Although omitted in FIG. 2, between the polarizing layer 2 and the light diffusing layer 1 and the optically anisotropic layer 4, and between the polarizing layer 13, the light diffusing layer 15, and the optically anisotropic layer 11, respectively. A transparent support made of cellulose acylate film or the like, which is a support for each layer and is a protective layer for the polarizing layer, may be disposed. The light diffusion layer 15 on the backlight side does not have to have a concavo-convex structure, but it is preferable that it has a concavo-convex structure in terms of preventing optical adhesion with the backlight unit. Even if the surface roughness is smaller than that of the light diffusion layer 1 of the viewing side polarizing plate, it is sufficiently effective. A protective film (not shown) near the liquid crystal cell of the polarizing plates 2A and 13A may also serve as a support for the optically anisotropic layers 4 and 11, and the polarizing plates 2A and 13A are optically anisotropic layers. It is incorporated in a liquid crystal display device as a structure integrally laminated with 4 and 11. In the liquid crystal display device of the present invention, the transparent support of the optical compensation sheet and the transparent support of the light diffusion layer also serve as the protective film of the polarizing film, that is, the light diffusion layer, the transparent protective film (also used as the transparent support). ), A polarizing film, a transparent protective film (also used as a transparent support), and an integrated elliptical polarizing plate laminated in the order of the optically anisotropic layer can be used. Since this integrated elliptical polarizing plate includes a light diffusing layer having a light diffusing function and an optically anisotropic layer having optical compensation capability, a liquid crystal display device with a simple configuration can be obtained by using the integrated elliptical polarizing plate. Can be accurately optically compensated, and black-and-white gradation reversal and image reflection can be prevented. In the liquid crystal display device, from the outside of the device (the side far from the liquid crystal cell) (if desired, a low refractive index layer), a light diffusion layer, a transparent protective film (also serving as a transparent support), a polarizing film, a transparent protective film (transparent It is preferable to laminate in the order of a support) and an optically anisotropic layer.
In addition, although the aspect which utilized the polarizing plate of this invention as a polarizing plate of both a visual recognition side and a backlight side was shown in FIG. 2, the liquid crystal display device of this invention is a polarizing plate of this invention. The polarizing plate on the viewing side is preferably the polarizing plate of the present invention.

  From the viewpoint of viewing angle characteristics, it is preferable that light incident from the backlight is collected as much as possible and scattered on the surface. In order to improve the viewing angle characteristics in the downward direction, it is preferable to focus at least in the vertical direction. It is preferable to collect the backlight from the viewpoint of front contrast. If the light is not collected, a decrease in contrast due to light entering from the oblique direction that goes around the front increases. Therefore, it is preferable to use a member for collimating the light incident from the backlight in the liquid crystal display device of the present invention. The collimation is preferably a means that makes it possible to set the angle at which the half value of the front brightness is half or less in the vertical profile of the emitted light brightness. The vertical angle profile of the luminance of light emitted from the backlight can be measured using, for example, EZ-Contrast 160D (manufactured by ELDIM). In addition, as a parallel light means for the backlight, a light shielding louver film (for example, a light control film manufactured by 3M) or a prism condensing sheet (for example, a BEF (Brightness Enhancement Film) manufactured by 3M) can be used.

  FIG. 2 shows a mode of a TN mode liquid crystal display device, but the liquid crystal display device of the present invention is not only a TN mode but also a mode of VA mode, IPS mode, OCB mode, and ECB mode. Also good.

  In addition, the liquid crystal display device of the present invention is not limited to the configuration shown in FIG. 2 and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizing film. In the case of use as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a backlight using a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. The backlight preferably includes means for condensing light, and among them, it is preferable to include a prism sheet. In addition, the liquid crystal display device of the present invention may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and reflected on the back surface of the liquid crystal cell or the inner surface of the lower substrate of the liquid crystal cell. Install the membrane. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Furthermore, the liquid crystal display device of the present invention may be an anti-transmission type in which a reflection portion and a transmission portion are provided in one pixel of the display device in order to achieve both transmission and reflection modes.

  The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using a three-terminal or two-terminal anti-conductor element such as TFT or MIM. Of course, an embodiment applied to a passive matrix liquid crystal display device represented by STN type called time-division driving is also effective.

The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.
A liquid crystal display device having the structure shown in FIG. 2 was produced. That is, from the observation direction (upper), an upper polarizing plate (having a light diffusion layer and an optically anisotropic layer), a color filter (not shown), a liquid crystal cell (upper substrate, liquid crystal layer, lower substrate), lower polarizing plate A plate (having an optically anisotropic layer) was laminated, and a backlight (not shown) using a cold cathode fluorescent lamp was disposed below the lower polarizing plate.

Below, the manufacturing method of each used member is demonstrated.
[Preparation of optical compensation film]
<Preparation of cellulose acetate film>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.
Cellulose acetate solution composition Cellulose acetate having an acetylation degree of 60.7 to 61.1% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first Solvent) 336 parts by mass Methanol (second solvent) 29 parts by mass 1-butanol (third solvent) 11 parts by mass

  In another mixing tank, 16 parts by mass of the following retardation increasing agent, 92 parts by mass of methylene chloride and 8 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution. A dope was prepared by mixing 474 parts by mass of the cellulose acetate solution with 25 parts by mass of the retardation increasing agent solution and stirring sufficiently. The addition amount of the retardation increasing agent was 6.0 parts by mass with respect to 100 parts by mass of cellulose acetate.

  The obtained dope was cast using a band stretching machine. After the film surface temperature on the band reaches 40 ° C., the film is dried for 1 minute with warm air of 70 ° C., and the film is dried for 10 minutes with 140 ° C. drying air, and the residual solvent amount is 0.3 mass%. Of cellulose acetate film (thickness: 80 μm) was prepared. About the produced cellulose acetate film (transparent support body, transparent protective film), the Re retardation value and Rth retardation value in wavelength 546nm were measured using the ellipsometer (M-150, JASCO Corporation make). Re was 8 nm and Rth was 78 nm. The produced cellulose acetate film was immersed in a 2.0 N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid, washed with pure water, and then dried. Thus, a cellulose acetate film for a transparent protective film was produced.

<Preparation of alignment film for optically anisotropic layer>
On this cellulose acetate film, a coating solution having the following composition was applied at 28 mL / m 2 with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds. Next, the formed film was rubbed so as to be oriented in a direction parallel to the in-plane slow axis (direction parallel to the casting direction) of the cellulose acetate film (that is, the rubbing axis is the slow axis of the cellulose acetate film). Parallel to the phase axis).
Alignment film coating solution composition Modified polyvinyl alcohol 20 parts by weight Water 360 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 1.0 part by weight

<Preparation of optically anisotropic layer>
On the alignment film, 91.0 g of the following discotic compound, 9.0 g of ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB551-0.2, Eastman Chemical Co., Ltd.) 2.0 g, Cellulose Acetate Butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.5 g, Photopolymerization Initiator (Irgacure 907, Ciba Geigy Co.) 3.0 g, Sensitizer ( Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd. (1.0 g), a fluoroaliphatic group-containing copolymer (Megafac F780 manufactured by Dainippon Ink Co., Ltd.) 1.3 g dissolved in 207 g of methyl ethyl ketone Then, 6.2 ml / m ^{2 was} applied with a # 3.6 wire bar. This was heated in a constant temperature zone of 130 ° C. for 2 minutes to orient the discotic compound. Next, UV irradiation was performed for 1 minute using a 120 W / cm high pressure mercury lamp in an atmosphere of 60 ° C. to polymerize the discotic compound. Then, it stood to cool to room temperature. Thus, an optically anisotropic layer was formed, and an optical compensation film was produced.

  In the produced optically anisotropic layer, the discotic compound had a hybrid orientation in which the angle (tilt angle) formed by the disc surface and the transparent protective film increased from the transparent protective film toward the air interface. The optically anisotropic layer was a uniform film free from defects such as schlieren. When the polarizing plate was placed in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness could not be detected even when viewed from the front and the direction inclined to 60 ° from the normal.

[Production of light diffusing film]
<Preparation of coating solution for forming light diffusion layer>
250 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (trade name: DPHA, manufactured by Nippon Kayaku Co., Ltd.) was dissolved in 439 g of a mixed solvent of methyl isobutyl ketone / cyclohexanone = 50/50 mass%. 49 g of a photopolymerization initiator (trade name: Irgacure 907, manufactured by Ciba Geigy) and 5.0 g of photosensitizer (trade name: Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) were added to the resulting solution. A solution dissolved in methyl ethyl ketone was added. The solution was filtered through a polypropylene filter having a pore size of 3 μm, and then applied and UV cured to give a refractive index of 1.51.
Forward scattering property-imparting particles (SX-130H, refractive index: 1.1) made of crosslinked polystyrene having an average particle diameter of 1.3 μm in 1000 parts by mass of the coating liquid (solvent-dried and refractive index after UV curing: 1.51). 61, manufactured by Soken Chemical Co., Ltd.) 150 parts by mass, stirred with an air disper for 10 minutes to obtain a mixture, filtered through a polypropylene filter (PPE-03) having a pore size of 3 μm, A light-diffusing layer coating solution was prepared.

<Preparation of coating solution for forming low refractive index layer>
(Synthesis of perfluoroolefin copolymer (1))

Into a stainless steel autoclave with a stirrer of 100 ml, 40 ml of ethyl acetate, 14.7 g of hydroxyethyl vinyl ether and 0.55 g of dilauroyl peroxide were charged, and the inside of the system was deaerated and replaced with nitrogen gas. Further, 25 g of hexafluoropropylene (HFP) was introduced into the autoclave and the temperature was raised to 65 ° C. The pressure when the temperature in the autoclave reached 65 ° C. was 5.4 kg / cm ² . The reaction was continued for 8 hours while maintaining the temperature, and when the pressure reached 3.2 kg / cm ² , the heating was stopped and the mixture was allowed to cool. When the internal temperature dropped to room temperature, unreacted monomers were driven out, the autoclave was opened, and the reaction solution was taken out. The obtained reaction solution was poured into a large excess of hexane, and the polymer was precipitated by removing the solvent by decantation. Further, this polymer was dissolved in a small amount of ethyl acetate and reprecipitated twice from hexane to completely remove the residual monomer. After drying, 28 g of polymer was obtained. Next, 20 g of the polymer was dissolved in 100 ml of N, N-dimethylacetamide, and 11.4 g of acrylic acid chloride was added dropwise under ice cooling, followed by stirring at room temperature for 10 hours. Ethyl acetate was added to the reaction solution, washed with water, the organic layer was extracted and concentrated, and the resulting polymer was reprecipitated with hexane to obtain 19 g of the perfluoroolefin copolymer (1) as a fluoropolymer. The resulting polymer had a refractive index of 1.421.

(Preparation of sol solution a)
A stirrer, a reactor equipped with a reflux condenser, 120 parts of methyl ethyl ketone, 100 parts of acryloyloxypropyltrimethoxysilane (KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.), 3 parts of diisopropoxyaluminum ethyl acetoacetate were added and mixed. Thereafter, 30 parts of ion-exchanged water was added and reacted at 60 ° C. for 4 hours, and then cooled to room temperature to obtain sol solution a. The mass average molecular weight was 1600, and among the components higher than the oligomer component, the component having a molecular weight of 1000 to 20000 was 100%. Further, from the gas chromatography analysis, the raw material acryloyloxypropyltrimethoxysilane did not remain at all.

(Preparation of hollow silica dispersion)
Hollow silica fine particle sol (isopropyl alcohol silica sol, CS60-IPA manufactured by Catalyst Chemical Industry Co., Ltd., average particle diameter 60 nm, shell thickness 10 nm, silica concentration 20%, silica particle refractive index 1.31) in 500 parts by mass, acryloyloxy After adding 30 parts by mass of propyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-5103) and 1.5 parts by mass of diisopropoxyaluminum ethyl acetate, 9 parts by mass of ion-exchanged water were added. After making it react at 60 degreeC for 8 hours, it cooled to room temperature, added 1.8 mass parts of acetylacetone, and obtained the hollow silica dispersion liquid. The resulting hollow silica dispersion had a solid content concentration of 18% by mass and a refractive index after solvent drying of 1.31.

(Preparation of composition for forming low refractive index layer)
Perfluoroolefin copolymer (1) 41.6 parts by mass, mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, Nippon Kayaku Co., Ltd.) 10.4 parts by mass, hollow silica 30.0 Parts by mass, photoradical generator Irgacure 907 (Ciba Specialty Chemicals Co., Ltd.) 2.2%, terminal methacrylate group-containing silicone resin X-22-164C (Shin-Etsu Chemical Co., Ltd.) 2.3 parts by mass, 13.5 parts by mass of sol liquid a (all the above are mass% of only solid content) is mixed and dissolved in methyl ethyl ketone so that the solid content concentration becomes 7 mass%, and the composition Ln-2 for forming a low refractive index layer is obtained. Prepared. The refractive index of the coating film formed using this coating solution was 1.425 (550 nm).

The above light diffusion layer coating solution is applied onto a triacetylcellulose support (TD-80UF manufactured by Fuji Photo Film Co., Ltd.) using a bar coater, dried at 120 ° C., and an oxygen concentration of 0.1 volume. % Of the sample was irradiated with ultraviolet rays having an illuminance of 400 mW / cm ² and an irradiation amount of 300 mJ / cm ² using a 160 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) while purging with a nitrogen purge. The coating layer was cured. A sample was prepared by changing the coating amount of the light diffusion layer from 0.5 μm to 7 μm.
For Example 4, the low refractive index coating solution was applied onto the light diffusion layer using a bar coater, dried at 90 ° C. for 15 seconds, and then the oxygen concentration was 0.1% by volume or less. Using a 240 W / cm air-cooled metal halide lamp (made by Eye Graphics Co., Ltd.) while purging with an atmosphere of nitrogen, it was cured by irradiating with ultraviolet rays having an irradiance of 600 mW / cm ² and an irradiation amount of 600 mJ / cm ^2. A low refractive index layer having a thickness of 0.096 μm was formed. Various desired samples having different surface inclination angle distributions and surface roughnesses were prepared as shown in the table by combinations of the crosslinked polystyrene particle diameter and film thickness of the light diffusion layer.

<Evaluation of light diffusion layer>
-Ratio of tilt angle of 10 ° or more The apparatus uses Micromap (USA) SXM520-AS150 type, the objective lens is 10 times, the tilt angle measurement unit is 0.85 square micron unit, and the measurement range is 0.48. Square millimeter. As described above, the measurement data was analyzed using MAT-LAB, and the tilt angle distribution was calculated.

・ Surface roughness (Ra)
Evaluation was performed using an atomic force microscope (SPI-3800N AFM; manufactured by Seiko Instruments Inc.). On the surface of the produced light diffusion film, measurement is performed at an area of 1 μm × 1 μm at random from an area of 100 cm ² , and an average value of average surface roughness (Ra) at a total of 10 locations (area of 1 mm ² ) is obtained. It was.

<Preparation of polarizing plate>
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. Next, using the polyvinyl alcohol-type adhesive agent, the produced optical compensation sheet was affixed on one side of the polarizing film on the support surface. Further, a cellulose triacetate film (TD-80U, manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. The absorption axis of the polarizing film and the slow axis (parallel to the casting direction) of the support of the optical compensation sheet were arranged in parallel. This was used as a polarizing plate on the backlight side.
The polarizing plate on the viewing side has the light diffusion film prepared as described above on the surface opposite to the optical compensation film attached in the same manner to the polarizing film, and the light diffusing layer becomes the surface opposite to the polarizing layer. As above, it was pasted using the above-mentioned pressure-sensitive adhesive. This was used as a viewing side polarizing plate.

  The manufactured polarizing plate is applied to the TN cell of a commercially available UXGA 15-inch TFT-TN liquid crystal display through an adhesive so that the optical compensation sheet is on the liquid crystal cell side. I stuck them one by one. At this time, the absorption axis direction of the polarizing plate is parallel to the rubbing direction of the facing liquid crystal cell, and the orientation control direction of the optical anisotropic layer is observed to be antiparallel to the rubbing direction of the facing liquid crystal cell. The liquid crystal display device was manufactured by adjusting the angle so that the angle on the person side was 3 ° counterclockwise and the angle on the backlight side was 3 ° clockwise.

<Evaluation with TN liquid crystal cell>
The viewing angle characteristics of the liquid crystal display device thus manufactured were measured using EZ-Contrast 160D (manufactured by ELDIM), and the downward inversion angles and front contrast of L0 / L1 and L1 / L2 were determined. Further, the degree to which black appears to be black, antiglare property, and glare of the image were evaluated.

<The extent that black appears to be black>
Black looks black: ◎
Black is slightly whitish: ○
Black is white and cannot be used: ×

<Evaluation of antiglare property> A bare fluorescent lamp (800 cd / cm ² ) without a louver was projected, and the degree of blur of the reflected image was evaluated according to the following criteria.
The outline of the fluorescent lamp is almost completely unknown: ◎
The fluorescent lamp is blurred, but the outline can be identified: ○
There is almost no blurring of fluorescent light: ×

<Glitter evaluation> Visual evaluation was performed according to the following criteria.
No glare: ◎
Slight glare, but acceptable level: ○
There is glare and is not acceptable: ×

Examples 1 to 6 provided with a light diffusion layer having a surface with a surface roughness Ra of 30 to 300 nm and a ratio of the inclination angle of 10 ° or more is 2% or less, the downward gradation inversion, anti-glare property, It was good in terms of both glare and blackness. In particular, since the liquid crystal display device of Example 4 is provided with a low refractive index layer as the outermost layer, reflection of external light can be prevented and display quality is excellent.
On the other hand, in Comparative Example 1, the ratio of the inclination angle of 10 ° or more is 0%. However, since the surface roughness Ra is low at less than 10 nm and the surface is clear, the reflection of external light is a concern, and Dazzle and lower gradation inversion are inferior compared to Examples 1-6. Further, in Comparative Example 2 in which the ratio of the tilt angle distribution of 10 ° or more exceeds 2%, the screen becomes whitish when black is displayed, and the image quality is inferior. Furthermore, in Comparative Example 3 in which the surface roughness Ra exceeds 300 nm, the glare is deteriorated and the image quality is also inferior.

  In Table 1, Examples 3, 5 and 6 are liquid crystal display devices in which the polarizing plate having the same configuration is used as the viewing side polarizing plate, but the condensing conditions of the backlight are different. In any case, the light is condensed under the condition that the half value of the front luminance in the vertical profile of the emitted light luminance of the backlight is 40 degrees or less, and thus no glare occurs. On the other hand, for the liquid crystal display device having the same configuration as in Examples 3, 5 and 6, it was collected under the condition that the half value of the front luminance in the vertical profile of the emitted light luminance of the backlight was about 50 degrees or about 80 degrees. As a result of evaluation in the same manner, slight glare was observed under the condition of about 50 degrees, and further glare was observed under the condition of about 80 degrees.

It is a schematic sectional drawing of embodiment of the polarizing plate of this invention. 1 is a schematic diagram illustrating an embodiment of a liquid crystal display device of the present invention.

Explanation of symbols

1, 15, 105 Light diffusing layer 2, 13, 101 Polarizing layer (linearly polarizing film)
3, 14 Absorption axis 4, 11, 104 Optically anisotropic layer 5, 12 Orientation axis 2A, 13A Polarizing plate 6, 9 Substrate for liquid crystal cell 8 Liquid crystal layer (liquid crystal molecule)
7, 10 Orientation axis for liquid crystal layer 106 Low refractive index layer 102, 103 Layer made of polymer film

Claims (4)

A polarizing plate having at least an optically anisotropic layer, a light diffusing layer, and a polarizing layer between the optically anisotropic layer and the light diffusing layer,
The surface of the light diffusing layer opposite to the side on which the polarizing layer is disposed, the ratio of the tilt angle of 10 ° or more is 2% or less, and the surface of the light diffusing layer on which the polarizing layer is disposed A polarizing plate having a surface roughness on the opposite side of 30 to 300 nm. The polarizing plate of Claim 1 which has a low-refractive-index layer with a refractive index of 1.35 to 1.45 in the outermost layer on the opposite side to the side where the said polarizing layer of the said light-diffusion layer is arrange | positioned. 3. A liquid crystal display device comprising a liquid crystal cell and a pair of polarizing plates disposed opposite to each other with the liquid crystal cell interposed therebetween, wherein the polarizing plate disposed on at least the viewing side of the pair of polarizing plates. A liquid crystal display device, wherein the surface of the polarizing plate on which the optically anisotropic layer is disposed is opposed to the liquid crystal cell side. 4. A collimating means for collimating light incident from the backlight is further provided, and the means sets the angle at which the half value of the front luminance is 40 degrees or less in the vertical profile of the emitted light luminance. A liquid crystal display device according to 1.

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