JP2004294983A - Retardation plate integrated type polarizing film and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation plate integrated type polarizing film thinned while maintaining optical characteristic by integrating a retardation plate using an organic clay complex with a polarizer, and to make a liquid crystal display device thin and inexpensive by applying the polarizing film to the liquid crystal display device. <P>SOLUTION: The retardation plate integrated type polarizing film is constituted by providing a retardation plate having a layer composed of composition containing at least one kind of organic clay complex and at least one kind of (meth)acrylic resin which can be dispersed in an organic solvent at least by one at least on one side of a polarizer. The retardation plate of the retardation plate integrated type polarizing film is set so that its retardation value on a plane is <20nm and is smaller than a retardation value in a thickness direction. The retardation plate integrated type polarizing film is arranged at least on one side of a liquid crystal cell so as to constitute a liquid crystal display device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a retardation plate-integrated polarizing film used by being bonded to a liquid crystal cell, and a liquid crystal display device using the same.
[0002]
[Prior art]
2. Description of the Related Art Liquid crystal display devices (hereinafter, sometimes referred to as LCDs) have been widely used as flat display devices from small to large display devices. However, LCDs have viewing angle characteristics in which the contrast decreases when viewed from an oblique direction, or the display characteristics deteriorate due to the occurrence of grayscale inversion where the brightness is inverted in grayscale display. There is a strong demand for improvements.
[0003]
In recent years, a vertical alignment nematic liquid crystal display device (VA-LCD) has been developed as an LCD system for improving the viewing angle characteristics, for example, as disclosed in Japanese Patent No. 2548979 (Patent Document 1). . As described in SID 97 DIGEST, pp. 845-848 (Non-Patent Document 1), VA-LCD uses two negative uniaxial retardation films each having an optical axis in a direction perpendicular to the film surface as a liquid crystal. By arranging it above and below the cell, a wider viewing angle characteristic can be obtained. This LCD is further provided with a uniaxial orientation retardation having a positive refractive index anisotropy having an in-plane retardation value of about 50 nm. It is known that a wider viewing angle characteristic can be realized by applying a film.
[0004]
As such a negative uniaxial retardation film having an optical axis in a direction perpendicular to the film surface, for example, Japanese Patent Application Laid-Open No. 10-104428 (Patent Document 2) discloses at least one kind of film that can be dispersed in an organic solvent. A retardation film having a layer containing an organoclay composite is disclosed. The technology disclosed herein uses, as an organoclay composite, for example, a composite of a clay mineral having a layered structure and an organic compound, which is used alone or in combination with a hydrophobic resin, to form a single film or a transparent resin. By using a film formed on a substrate, the film has excellent optical properties, does not cause problems such as peeling even in a high temperature and high humidity environment, has excellent durability, and has a retardation value within the film plane. This is to obtain a retardation film smaller than the retardation value in the thickness direction.
[0005]
The retardation film disclosed in Patent Literature 2 optimizes the optical characteristics of the retardation film, so that the field of view of the LCD in various modes such as twisted nematic (TN), vertical alignment (VA), and optical compensation bend (OCB) is obtained. Although it can be used for angle compensation, when it is used by mounting on these LCDs, it is usually necessary to attach a polarizing film with a protective layer in which a transparent resin film is laminated on both surfaces of a polarizer to this retardation film. Therefore, there has been a problem that the thickness of the LCD itself is increased and the cost is increased.
[0006]
[Patent Document 1] Japanese Patent No. 2548979
[Patent Document 2] JP-A-10-104428
[Non-Patent Document 1] SID 97 DIGEST, p. 845-848
[0007]
[Problems to be solved by the invention]
In view of this situation, the present inventor has conducted intensive studies and has found that at least one side of the polarizer contains at least one kind of organoclay composite dispersible in an organic solvent and at least one kind of (meth) acrylic resin. The present invention has been completed by developing a retardation plate-integrated polarizing film provided with a retardation plate having at least one layer made of a composition to be formed.
[0008]
Therefore, one of the objects of the present invention is to provide a retardation plate integrated polarizing film in which a retardation plate using an organoclay composite is integrated with a polarizer to reduce the thickness while maintaining optical characteristics. Is to do. Another object of the present invention is to provide a retardation plate-integrated polarizing film excellent in durability. Still another object of the present invention is to apply the retardation plate-integrated polarizing film to a liquid crystal display device so as to reduce the thickness and cost of the liquid crystal display device.
[0009]
[Means for Solving the Problems]
That is, according to the present invention, at least one side of the polarizer is provided with at least one layer made of a composition containing at least one kind of organoclay composite dispersible in an organic solvent and at least one kind of (meth) acrylic resin. There is provided a retardation plate-integrated polarizing film provided with a retardation plate having a layer. The retardation plate provided in the retardation plate-integrated polarizing film can have an in-plane retardation value of less than 20 nm and an in-plane retardation value smaller than the thickness direction retardation value. . If the retardation plate has such optical characteristics, the viewing angle of the LCD in various modes such as TN, VA, and OCB can be compensated.
[0010]
The layer comprising the composition containing the organoclay composite and the (meth) acrylic resin constituting the above retardation plate is advantageously formed on the surface of the transparent resin substrate. Therefore, in this case, the retardation plate has a layer made of a composition containing an organoclay composite and a (meth) acrylic resin formed on at least one surface of the transparent resin substrate. It is advantageous that the retardation value is less than 20 nm and the in-plane retardation value is smaller than the retardation value in the thickness direction.
[0011]
These retardation plate integrated polarizing films are combined with a liquid crystal cell to form a liquid crystal display device. Therefore, according to the present invention, there is also provided a liquid crystal display device including at least one of the above-described polarizing films integrated with a retardation plate and a liquid crystal cell.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. In the present invention, a retardation plate having a specific composition is provided on at least one side of the polarizer to obtain a polarizing film integrated with a retardation plate. The polarizer may be any as long as it has a selective transmission ability for linearly polarized light in a specific vibration direction, and specifically, a polymer composition containing a dichroic dye, a liquid crystal polymer containing a dichroic dye, and the like. Is obtained by orienting the polymer by a method such as uniaxial stretching. Typically, a polyvinyl alcohol resin is used as a polymer constituting the polarizer, and iodine or a dichroic dye is typically used as a dichroic dye. Examples of the polarizer include uniaxially stretched polyvinyl alcohol with iodine molecules adsorbed and oriented, and uniaxially stretched polyvinyl alcohol with an azo dichroic dye adsorbed and oriented. These dichroic dyes adsorb and orient polyvinyl alcohol polarizers absorb linearly polarized light that has a vibrating surface in the dichroic dye orientation direction and transmit linearly polarized light that has a vibrating surface in a direction perpendicular to it. Having.
[0013]
The retardation plate provided on at least one side of the polarizer is configured to have a layer made of a composition containing an organic clay composite dispersible in an organic solvent and a (meth) acrylic resin. Examples of the organoclay composite used for this purpose include, for example, a composite of a clay mineral having a layered structure and an organic compound. Clay minerals having a layered structure usually have an oxygen atom or a hydroxyl group in the surface of the structure of Si-O, Si-OH or Al-OH, and furthermore, exchangeable cations and their hydrated ions occupy between crystal layers. Have been. An organic clay complex can be obtained by a method of forming a complex by reacting an oxygen atom or a hydroxyl group with an organic compound or a method of forming a complex by exchanging an exchangeable cation with an organic cation.
[0014]
The smectite family and swelling mica, which are a kind of clay mineral, are composed of Al and Fe (III) in the tetrahedral layer of the crystal structure, Si and Fe (III) in the octahedral layer, and octahedral. The Mg in the layer is isomorphically substituted with Li, and the resulting negative layer charge is transferred to the Na between the crystal layers.⁺, K⁺, Ca²⁺, Mg²⁺, Al²⁺Such as exchangeable cations. Since these clay minerals have relatively weak bonds between the unit crystal layers, the layers easily spread, and when dispersed in water, the unit crystal layers swell until they become colloidal, forming a sol in water. And exhibit a cation exchange capacity. This cation exchange is effective for complexing with organic compounds.The smectite family has a relatively small layer charge with respect to other clay minerals, can easily form a sol, and has a high cation exchange capacity. It is preferably used for body production. Further, the smectite group is excellent in transparency, and thus is preferably used as a retardation plate.
[0015]
Examples of those belonging to the smectite group include hectorite, montmorillonite, bentonite, and the like, substituted substances, derivatives and mixtures thereof. Among them, those chemically synthesized are preferably used for a retardation plate because they have few impurities and are excellent in transparency. In particular, synthetic hectorite whose particle size is controlled to be small is preferably used because scattering of visible light is suppressed.
[0016]
Examples of the organic compound to be complexed with the clay mineral include a compound capable of reacting with an oxygen atom or a hydroxyl group of the clay mineral, an ionic compound exchangeable with an exchangeable cation, and the like. There is no particular limitation as long as it is capable of swelling or dispersing, but specific examples include a nitrogen-containing compound. Examples of the nitrogen-containing compound include primary, secondary, and tertiary amines, quaternary ammonium compounds, urea, and hydrazine.
[0017]
A quaternary ammonium compound is preferably used because cation exchange is easy. The quaternary ammonium compound is usually introduced as a cation. Examples of the cation include an alkyl group such as dimethyl dioctadecyl ammonium ion, dimethyl benzyl octadecyl ammonium ion, and trioctyl methyl ammonium ion. Those having a benzyl group, those having a long-chain substituent such as methyl diethyl polyoxypropylene ammonium ion (polyoxypropylene has a degree of polymerization of about 25), and those having a cyclic ammonium ion such as dodecylpyridinium ion And the like.
[0018]
These organic compounds are desirably ion-exchanged by using substantially equivalent amounts to the cation exchange capacity of the clay mineral. However, in the production of the organoclay composite, 0.5 to 1. It may be added in a range of about 5 times.
[0019]
These organic clay composites can be prepared by appropriately selecting an organic compound to be used, so that low-polarity organic solvents including aromatic hydrocarbons such as benzene, toluene, and xylene, acetone, methyl ethyl ketone, and methyl isobutyl can be obtained. Various polar organic solvents such as ketones such as ketones, lower alcohols such as methanol, ethanol, and propanol, and halogenated hydrocarbons such as carbon tetrachloride, chloroform, dichloromethane, and dichloroethane. It can be easily dispersed in an organic solvent.
[0020]
Such an organic clay composite that can be dispersed in an organic solvent exhibits an excellent effect of moist heat resistance when used as a retardation plate, but depending on the organic compound to be composited. In some cases, discoloration occurs in a high-temperature environment. If discoloration occurs, it is desirable to suppress the degree of discoloration within an allowable range.
[0021]
When the retardation plate-integrated polarizing film of the present invention is applied to a liquid crystal display device, one or two retardation plate-integrated polarizing films are usually used. Therefore, it is desirable to satisfy the permissible range of discoloration with one polarizing film integrated with a retardation plate, but it is more preferable to satisfy the permissible range of discoloration even when two sheets are used. Here, the permissible range of discoloration is defined as L defined in JIS Z 8729.^*a^*b^*The color difference ΔE between the color before the test in the color system and the color after leaving for 1000 hours in a temperature environment of 80 ° C.^*  Is 5 or less.
[0022]
Suitable commercially available organic clay composites include composites of synthetic hectorite and quaternary ammonium compounds sold under the trade names "Lucentite STN" and "Lucentite SPN" by Corp Chemical Co., Ltd. and so on.
[0023]
The organoclay complex dispersible in an organic solvent as defined in the present invention is usually hydrophobic and, when dispersed in an organic solvent, can swell the unit crystal layer until it becomes colloidal. Therefore, the unit crystal layer can be oriented by applying to a suitable substrate in a state of being swollen and dispersed in this way, drying, and forming a film.
[0024]
The method of using the organic clay composite in combination with a hydrophobic resin is preferably adopted from the viewpoints of easy formation on a substrate, development of optical characteristics and mechanical characteristics. As the hydrophobic resin used for this purpose, a resin soluble in a low-polarity organic solvent such as benzene, toluene and xylene is preferable. Further, when the polarizing film integrated with a retardation plate is applied to a liquid crystal display device with a large size of 15 inches (381 mm) or more on a diagonal, the polarizing film is used in a state where a layer containing an organoclay composite is formed on a transparent resin substrate. However, in order to obtain good wet heat resistance and handleability in the form, it is desirable that the form has strong hydrophobicity and strong adhesion to the transparent resin substrate.
[0025]
Examples of such a hydrophobic resin include a (meth) acrylic resin, a urethane resin, and a polyester resin. Above all, a (meth) acrylic resin is preferable in terms of enhancing the resistance to moist heat and enhancing the adhesion to the transparent resin substrate. Therefore, in the present invention, a composition containing an organoclay composite and a (meth) acrylic resin is used. Here, the (meth) acrylic resin is a polymer containing an acrylate or a methacrylate as a main monomer. Particularly preferred (meth) acrylic resins include butyl acrylate resins and dicyclopentanyl methacrylate resins. These resins may be those which have been polymerized in advance, or may be polymerized by a method such as heat curing or ultraviolet curing during the film forming step using monomers or oligomers. Further, a plurality of these resins may be used in combination. It is also effective to use a mixture of a butyl acrylate resin and a dicyclopentanyl methacrylate resin.
[0026]
Commercially available suitable hydrophobic (meth) acrylic resins include butyl acrylate-based acrylic resins sold by Toagosei Co., Ltd. under the trade name "Aron S1601", and Shin-Nakamura Chemical Co., Ltd. ), A methacrylic resin mainly composed of dicyclopentanyl methacrylate sold under the trade name of “Vanaresin MKV-115”.
[0027]
The composition ratio of the organic clay composite dispersible in the organic solvent and the (meth) acrylic resin is preferably in the range of 1: 2 to 10: 1 by weight ratio of the former: the latter, and the ratio of the organoclay composite to the (meth) acrylic resin is This is preferable for improving mechanical properties such as preventing cracking of a layer made of an acrylic resin. The solid content concentration of the dispersion is not particularly limited as long as the dispersion after preparation does not gel or become cloudy for several days, but is usually the total of the organoclay composite and the (meth) acrylic resin. The solid content is used in the range of about 3 to 15% by weight. The optimum solid content concentration is set for each composition because it differs depending on the type of the organic clay composite and the (meth) acrylic resin and the composition ratio of both. In addition, various additives such as a viscosity modifier for improving the coating property when forming a film on the substrate and a crosslinking agent for further improving the hydrophobicity and durability may be added.
[0028]
The layer made of the composition containing the organoclay composite and the (meth) acrylic resin may be separated from the substrate used for film formation to form a single film, or a film may be formed thereon using a transparent resin substrate. The phase difference plate can be used as it is. Alternatively, as long as the film can be formed without impairing the characteristics of the polarizer, the film can be formed directly on the polarizer. When the substrate to be formed is a flat plate, the layer structure of the unit crystal layer of the organoclay composite is parallel to the flat plate surface, and the in-plane direction is randomly oriented. Therefore, a refractive index structure in which the refractive index in the film plane is larger than the refractive index in the film thickness direction is exhibited. Due to this refractive index anisotropy, the in-plane retardation value is less than 20 nm, and the in-plane retardation value is smaller than the retardation value in the thickness direction. The obtained polarizing film can be obtained.
[0029]
When a layer made of a composition containing an organoclay composite and a (meth) acrylic resin is provided on at least one surface of a transparent resin substrate and used as it is as a retardation plate, an optically isotropic transparent substrate is used as the substrate. A resin substrate can be used. When an isotropic transparent resin substrate is used, the in-plane retardation value is reduced in the thickness direction in a state in which a layer made of a composition containing an organoclay composite and a (meth) acrylic resin is laminated. It becomes a smaller phase difference plate. Also in this case, the in-plane retardation value of the laminated retarder can be less than 20 nm. By integrating such a retarder with a polarizer, a polarizing film integrated with a retarder can be obtained.
[0030]
The optically isotropic transparent resin substrate is not particularly limited as long as it is a film having a small orientation and excellent uniformity and having a thickness of about 50 to 200 μm, but the in-plane retardation value is 20 nm. Films controlled to less than are preferred. Examples of such an optically isotropic resin film serving as a substrate include a cellulose resin film, a polycarbonate resin film, a polystyrene resin film, a polysulfone resin film, and a (meth) resin film formed by a solvent casting method. An acrylic resin film, a cyclic polyolefin resin film, and a (meth) acrylic resin film, a cyclic polyolefin resin film, and a polycarbonate resin film each formed by a precision melt extrusion method with low residual stress can be exemplified. . Among them, preferred are cellulose-based resin films formed by solvent casting, cyclic polyolefin-based resin films formed by solvent casting or melt extrusion, polycarbonate-based films formed by solvent casting or melt extrusion. A resin film is exemplified. In particular, a cellulose ester film, particularly a triacetyl cellulose film, formed by a solvent casting method is preferable.
[0031]
Further, when a uniaxially oriented film having a negative refractive index anisotropy is used as the transparent resin substrate, the retardation value (R) in the film plane and the inclination of the retardation axis by 40 degrees with the slow axis as the inclination axis. Retardation value (R₄₀) Ratio (R₄₀/ R) is 0.9 to 1.1, and a polarizing film integrating such a retardation plate improves the viewing angle characteristics of a super twisted nematic (STN) -LCD. Film can be advantageously used. As a uniaxially oriented film having a negative refractive index anisotropy, a resin having a negative refractive index anisotropy such as a polystyrene resin or a (meth) acrylic resin is formed into a film by a solvent casting method, and then uniaxially stretched. Although it is preferable to use a polystyrene resin from the viewpoint of easy development of retardation. Examples of the polystyrene-based resin include polystyrene, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene copolymer.
[0032]
On the other hand, when a uniaxially oriented film having a positive refractive index anisotropy is used as the transparent resin substrate, R₄₀/ R 2 can be a retardation plate larger than 1.1, and a polarizing film integrating such a retardation plate is used as a film for improving viewing angle characteristics in VA-LCD, OCB-LCD and the like. Can be used advantageously. As the uniaxially oriented film having a positive refractive index anisotropy, a resin having a positive refractive index anisotropy such as a polycarbonate-based resin, a polyester-based resin, a polysulfone-based resin, a cyclic polyolefin-based resin, and a cellulose-based resin is used as a solvent. A film obtained by forming a film by a casting method and then uniaxially stretching can be exemplified.
[0033]
In order to further enhance the adhesion between the transparent resin substrate and the layer containing the organic clay composite and the (meth) acrylic resin dispersible in an organic solvent, an anchor coat layer may be provided on the transparent resin substrate, Means for performing a surface treatment such as a corona treatment on the surface of the resin substrate is preferably used. The anchor coat layer is not particularly limited as long as it can uniformly apply a liquid obtained by dispersing the organoclay composite in an organic solvent on the substrate and can improve the adhesive force. A (meth) acrylic resin or the like can be used.
[0034]
The method of forming an anchor coat layer on a transparent resin substrate and the method of forming a layer composed of an organoclay composite and a (meth) acrylic resin on an anchor coat layer or a transparent resin substrate are particularly limited. Instead, various coating methods such as a direct gravure method, a reverse gravure method, a die coating method, a comma coating method, and a bar coating method can be used. Among them, a comma coating method, a die coating method using no backup roll, and the like are preferably used because of excellent thickness accuracy.
[0035]
The retardation plate-integrated polarizing film of the present invention is a VA-LCD, a TN-LCD,
It can be used for improving the viewing angle characteristics of STN-LCD and OCB-LCD. However, depending on the applied LCD, an organic clay dispersible in an organic solvent can be obtained so that an optimal retardation value (R ') in the thickness direction can be obtained. The thickness of the layer containing the composite and the (meth) acrylic resin after film formation is controlled. This thickness is usually set in the range of 1 to 50 μm, though it depends on the optical characteristics of the organoclay composite and the composition ratio of the organoclay composite and the (meth) acrylic resin.
[0036]
The retardation plate manufactured in this way has excellent transparency, and usually has a light transmittance of 80% or more necessary for application to LCDs. The polarizing film can be used without particularly adversely affecting the display.
[0037]
In the present invention, the polarizer described above, for example, a polarizer made of a polyvinyl alcohol-based resin, is provided on at least one side with a layer made of the composition containing the organic clay composite and the (meth) acrylic resin described above. A retardation plate is provided to form a retardation plate integrated polarizing film. As a method of integrating the retardation plate with the polarizer, as described above, after providing a layer made of a composition containing an organoclay composite and a (meth) acrylic resin on various substrates as described above, an adhesive layer such as an adhesive A method of bonding and integrating a polarizer with an adhesive or an adhesive, etc., and bonding the various substrates as described above to an adhesive layer, for example, a polarizer with an adhesive or an adhesive to form a polarizing plate, and then forming an organic layer thereon. A method of providing a layer composed of a composition containing a clay composite and a (meth) acrylic resin, and forming a layer composed of a composition containing an organic clay composite and a (meth) acrylic resin directly on a polarizer A method or the like can be adopted.
[0038]
Polarizers are generally inferior in durability as a polyvinyl alcohol-based resin as described above, and are distributed in the form of a polarizing film with a protective layer coated on both sides with a transparent resin film, but in the present invention, The protective layer on the side where the retardation plate is laminated is omitted, and the above retardation plate is laminated directly on the polarizer or, if necessary, via an adhesive layer. As a result, the overall thickness can be reduced. When a layer made of a composition containing an organic clay composite and a (meth) acrylic resin is directly formed on a polarizer, a polarizing film integrated with a retardation plate is obtained as it is. Here, when the above-mentioned layer is formed on one surface of the polarizer, it is preferable to appropriately provide a protective layer made of a transparent resin film on the other surface of the polarizer via an adhesive layer. As the protective layer, a cellulose resin film, particularly a triacetyl cellulose film is preferably used.
[0039]
On the other hand, when a layer made of a composition containing an organoclay composite and a (meth) acrylic resin is provided on a transparent resin substrate and used as a retardation plate as it is, when a polarizer is laminated thereon, the retardation plate is used. A polarizer may be laminated on any of the substrate surface and the surface of the layer made of the above composition, and in consideration of the ease of bonding of the two and the viewing angle characteristics when combined with a liquid crystal cell, the optimum. What is necessary is just to employ | adopt a structure. In this case, the retardation plate and the polarizer are bonded via an adhesive layer, for example, an aqueous solution adhesive such as polyvinyl alcohol or an adhesive such as acrylic. Generally, it is advantageous to laminate a polarizer on the substrate surface of the retardation plate. For example, when a cellulose-based resin is used as the substrate film constituting the retardation plate, the substrate side and the polyvinyl alcohol-based polarizer can be bonded via a polyvinyl alcohol-based aqueous solution adhesive. There is an advantage that the thickness of the plate-integrated polarizing film can be reduced. Also in this case, a transparent resin film, for example, a protective layer made of a cellulose resin film such as a triacetyl cellulose film is provided on the side of the polarizer on which the retardation plate is not provided, via an adhesive layer. Good.
[0040]
When a polarizer is bonded to a transparent resin substrate via an adhesive layer to form a polarizing plate, and then a layer containing a composition containing an organoclay composite and a (meth) acrylic resin is provided, If a layer made of the above composition can be formed without impairing the properties, a layer made of the composition containing the above organic clay composite and (meth) acrylic resin is provided directly on the polarizer side. be able to. In this case, since the transparent resin substrate serves as a protective layer of the polarizer, the substrate is preferably an optically isotropic transparent resin. When a polarizer is bonded to a transparent resin substrate via an adhesive layer, and a layer made of a composition containing the organic clay composite and the (meth) acrylic resin is provided on the transparent resin substrate side, It is also preferable to provide a protective layer made of a transparent resin film, for example, a cellulose resin film such as a triacetyl cellulose film via an adhesive layer on the surface opposite to the surface on which the transparent resin substrate is bonded.
[0041]
When the thus obtained retardation plate-integrated polarizing film is applied to a liquid crystal display device, at least one sheet of the retardation plate-integrated polarizing film may be used and combined with a liquid crystal cell. Usually, this retardation plate integrated polarizing film is arranged on one side or both sides of a liquid crystal cell in a liquid crystal display device. Also, usually, the polarizing film integrated with the retarder is attached to the liquid crystal cell such that the retarder side faces the liquid crystal cell, in other words, the polarizer is located farther from the liquid crystal cell. When the retardation plate-integrated polarizing film of the present invention is used on one side of a liquid crystal cell, an ordinary polarizing film is arranged on the other side of the cell, or another retardation film is combined in addition to the ordinary polarizing film. Can be arranged. When the retardation plate-integrated polarizing film of the present invention is used on both sides of the liquid crystal cell, the characteristics of the retardation plate portions of these two retardation plate-integrated polarizing films may be equal or different on both sides of the cell. Those having characteristics can also be used.
[0042]
Further, the retardation plate-integrated polarizing film of the present invention can be used by being laminated with various retardation films, and further, if necessary, a reflection plate, a semi-transmission reflection plate, a diffusion film, and a brightness enhancement film. It is also possible to use various optical films together. When the polarizing film integrated with a retardation plate is bonded to another optical film or when the polarizing film is bonded to a liquid crystal cell, an acrylic adhesive or the like can be used. The thickness of the pressure-sensitive adhesive is usually about 15 to 30 μm.
[0043]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. In Examples,% representing the content or the use amount is based on weight unless otherwise specified. The materials used in the examples are as follows.
[0044]
(A) Resin
Trade name "Aron S1601": Toagosei Co., Ltd., acrylic resin mainly composed of butyl acrylate.
Trade name "Vanaresin MKV-115": a methacrylic resin mainly composed of dicyclopentanyl methacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.
[0045]
(B) Organic clay composite
Trade name "Lucentite STN": manufactured by Corp Chemical Co., Ltd., composed of a complex of synthetic hectorite and a quaternary ammonium compound, and having excellent dispersibility in a highly polar solvent.
Trade name "Lucentite SPN": manufactured by Corp Chemical Co., Ltd., composed of a complex of synthetic hectorite and a quaternary ammonium compound, and excellent in dispersibility in a nonpolar solvent.
[0046]
The measurement and evaluation of the physical properties of the samples were performed by the following methods.
[0047]
(1) In-plane retardation value of retardation plate: R
The measurement is carried out by a rotating analyzer using monochromatic light having a wavelength of 559 nm using "KOBRA-21ADH" manufactured by Oji Scientific Instruments.
[0048]
(2) Retardation value in the thickness direction of retardation plate: R '
In-plane retardation value R, retardation value R measured at an angle of 40 degrees with the in-plane slow axis as the tilt axis₄₀, The thickness d of the retardation plate, and the average refractive index of the retardation plate (assumed to be 1.5)._x, N_y  And n_zIs calculated, and then R ′ is calculated by equation (4).
[0049]
R = (n_x-N_y) × d (1)
R₄₀= (N_x-N_y') × d / cos (φ) (2)
(N_x+ N_y+ N_z) /3=1.5 (3)
R '= [(n_x+ N_y) / 2-n_z) × d (4)
here,
φ = sin^-1[Sin (40 °) /1.5] = 25.374
n_y'= N_y× n_z/ [N_y ²× sin²(Φ) + n_z ²× cos²(Φ)]^1/2
[0050]
Example 1
A 80 μm-thick triacetyl cellulose film [“Konica TAC KC80CA” manufactured by Konica Corporation; trade name] was used as an isotropic transparent resin substrate. On the other hand, 1.7% of the acrylic resin "Aron S1601", 7.7% of the organoclay composite "Lucentite STN", 2.6% of the organoclay composite "Lucentite SPN", and 61.6% of toluene. %, And an organic solvent dispersion containing 26.4% of acetone, which was applied to the above substrate using a bar coater so that the film thickness after drying was about 14 μm, and then heated at 85 ° C. in an oven. Drying in the inside gave a retardation plate. The optical characteristics of the retardation plate obtained in this way are R₀= 3 nm, R '= 279 nm.
[0051]
A polyethylene terephthalate protective film having an acrylic pressure-sensitive adhesive on one side was bonded to the pressure-sensitive adhesive side on the coating film of the retardation plate. Next, this retardation plate with a protective film is immersed in a 2N aqueous solution of potassium hydroxide for 1 minute to saponify the surface of the substrate on which the protective film is not provided, and this is washed with pure water for 5 minutes. And dried. On the other hand, a polarizer was prepared by uniaxially stretching a polyvinyl alcohol film to adsorb and orient iodine. On one surface of this polyvinyl alcohol polarizer, the saponified substrate surface of the retardation plate obtained above is bonded using an adhesive made of a polyvinyl alcohol aqueous solution, and at the same time, the same saponification is performed on the other surface of the polarizer. A treated triacetylcellulose film [“Konica TAC KC80CA” manufactured by Konica Corporation; trade name] was pasted together using the same adhesive as above to obtain a retardation plate-integrated polarizing film.
[0052]
Example 2
The surface of the same triacetylcellulose film used in Example 1 was 70 W / m²/ Min), and this was used as a transparent resin substrate. On the other hand, 1.5% of acrylic resin "Aron S1601", 1.5% of methacrylic resin "Vanaresin MKV-115", 6.75% of organoclay composite "Lucentite STN", and organoclay composite An organic solvent dispersion containing 2.25% of “Lucentite SPN”, 70.4% of toluene, and 17.6% of methylene chloride was prepared, and this was dried on the above-mentioned substrate to a film thickness of about It was applied using a bar coater so as to have a thickness of 15 μm, and then dried in an oven at 85 ° C. to obtain a retardation plate. The optical characteristics of the retardation plate obtained in this way are R₀= 3 nm, R '= 279 nm.
[0053]
A polyethylene terephthalate protective film having an acrylic pressure-sensitive adhesive on one side was bonded to the pressure-sensitive adhesive side on the coating film of the retardation plate. Next, this retardation plate with a protective film is immersed in a 2N aqueous solution of potassium hydroxide for 1 minute to saponify the surface of the substrate on which the protective film is not provided, and this is washed with pure water for 5 minutes. And dried. On the other hand, a polarizer was prepared by uniaxially stretching a polyvinyl alcohol film to adsorb and orient iodine. On one surface of this polyvinyl alcohol polarizer, the saponified substrate surface of the retardation plate obtained above is bonded using an adhesive made of a polyvinyl alcohol aqueous solution, and at the same time, the same saponification is performed on the other surface of the polarizer. A treated triacetylcellulose film [“Konica TAC KC80CA” manufactured by Konica Corporation; trade name] was pasted together using the same adhesive as above to obtain a retardation plate-integrated polarizing film.
[0054]
By bonding each of the retardation plate-integrated polarizing films obtained in Examples 1 and 2 to the front and / or back surface of the liquid crystal cell via the retardation plate-side adhesive, an LCD having a wide viewing angle can be obtained. Become.
[0055]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the retardation plate-integrated polarizing film which can be made thin and which is excellent in optical characteristics is provided. The polarizing film integrated with a retardation plate has excellent durability even when used in a large size of 15 inches or more on a diagonal. This retardation plate-integrated polarizing film has an optical characteristic in which the in-plane retardation value of the retardation plate portion is smaller than the retardation value in the thickness direction. It can be used effectively to improve angular characteristics. By using the polarizing film integrated with a retardation plate, a liquid crystal display device having not only excellent viewing angle characteristics but also excellent cost can be obtained.

Claims (15)

At least one side of the polarizer is provided with a retardation plate having at least one layer made of a composition containing at least one kind of organoclay composite dispersible in an organic solvent and at least one kind of (meth) acrylic resin. A retardation plate-integrated polarizing film, characterized in that: The polarizing film integrated with a retardation plate according to claim 1, wherein the organic clay composite is a composite of a clay mineral having a layered structure and an organic compound. The polarizing film integrated with a retardation plate according to claim 2, wherein the clay mineral is a smectite group or swellable mica. The polarizing film integrated with a retardation plate according to claim 3, wherein the clay mineral is a smectite group selected from hectorite, montmorillonite, and bentonite, or a substituted or derivative thereof. The polarizing film integrated with a retardation plate according to any one of claims 2 to 4, wherein the organic compound is selected from an amine, a quaternary ammonium compound, urea, and hydrazine. The retardation plate-integrated polarizing film according to any one of claims 1 to 5, wherein the (meth) acrylic resin is selected from a butyl acrylate resin and a dicyclopentanyl methacrylate resin. The retardation plate-integrated polarizing film according to any one of claims 1 to 6, wherein the organoclay composite and the (meth) acrylic resin are present in a weight ratio of 1: 2 to 10: 1. The retardation film according to any one of claims 1 to 7, wherein the retardation film has an in-plane retardation value of less than 20 nm and an in-plane retardation value is smaller than a retardation value in a thickness direction. Body type polarizing film. The retardation plate has a layer made of a composition containing an organoclay composite and a (meth) acrylic resin formed on at least one surface of a transparent resin substrate, and has an in-plane retardation of the retardation plate. The retardation plate-integrated polarizing film according to any one of claims 1 to 7, wherein the retardation value is less than 20 nm, and the in-plane retardation value is smaller than the retardation value in the thickness direction. The polarizing film integrated with a retardation plate according to claim 9, wherein the transparent resin substrate is optically isotropic. The isotropic transparent resin substrate was formed of a cellulose resin formed by a solvent casting method, a cyclic polyolefin resin formed by a solvent casting method or a melt extrusion method, or formed by a solvent casting method or a melt extrusion method. The polarizing film integrated with a retardation plate according to claim 10, which is a polycarbonate resin. The layer according to any one of claims 9 to 11, wherein the layer comprising the composition containing the organoclay composite and the (meth) acrylic resin is formed on at least one surface of the transparent resin substrate via an anchor coat layer. Polarizer with integrated retarder. The phase difference according to any one of claims 9 to 11, wherein the layer comprising the composition containing the organoclay composite and the (meth) acrylic resin is formed on at least one surface of a transparent resin substrate whose surface is corona-treated. Plate-integrated polarizing film. 14. The retardation plate-integrated polarizing film according to claim 1, wherein the layer comprising the composition containing the organoclay composite and the (meth) acrylic resin has a thickness of 1 to 50 [mu] m. A liquid crystal display device comprising at least one polarizing film integrated with a retardation plate according to claim 1 and a liquid crystal cell.