JP5878746B2 - Composite polarizing plate set, liquid crystal panel and liquid crystal display device - Google Patents

Description

  The present invention relates to a composite polarizing plate set including two composite polarizing plates respectively disposed on both surfaces of a liquid crystal cell, a liquid crystal panel including the same, and a liquid crystal display device. More specifically, each composite polarizing plate of the composite polarizing plate set is formed by laminating a linear polarizing film and a retardation film.

  A polarizing plate is widely used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. Generally, a polarizing plate is a liquid crystal in a form in which a transparent polymer film having optical properties is bonded to a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film, depending on the application and required performance. Often applied to a display device. For example, when a polarizing plate of an elliptical polarization mode or a circular polarization mode is used, a liquid crystal cell having a retardation film such as a 1 / 2λ plate or a 1 / 4λ plate is bonded. Used on the surface.

  A polarizing plate obtained by laminating such a polarizing film and a retardation film is subjected to stress on the retardation film due to the shrinkage of the polarizing film in a high temperature environment such as when a backlight is used. "Heat unevenness") is likely to occur. Although this thermal unevenness is likely to occur at the edge from the center of the polarizing plate, if this reaches the image display area, light leakage occurs during black display of the liquid crystal display device, resulting in an increase in black luminance and display quality. There was a problem of lowering.

  As a method for reducing the thermal unevenness as described above, methods for improving the characteristics of the polarizing plate itself are known (Patent Documents 1 to 4). For example, in Japanese Patent Application Laid-Open No. 2003-167120 (Patent Document 1), in a composite polarizing plate in which a linearly polarizing film and a retardation film are laminated, the arrangement angle of the optical axis of the retardation film with respect to the long side of the polarizing film is set. A specific range is disclosed. Japanese Patent Laying-Open No. 2008-40487 (Patent Document 2) discloses that the thickness of the entire polarizing plate is reduced by reducing the thickness of the retardation film to prevent thermal unevenness. International Publication No. 10/32551 (Patent Document 3) discloses that heat unevenness is prevented by using an acrylic retardation film having low hygroscopicity and high heat resistance and improved brittleness. . JP-A-2001-117088 (Patent Document 4) discloses an in-plane stress generated by thermal expansion and contraction by using a stress-relaxing paste when a constituent material of a retardation plate integrated polarizing plate is bonded. Is absorbed by a stress-relaxing adhesive layer to relieve changes in the retardation film and reduce heat unevenness.

JP 2003-167120 A JP 2008-40487 A International Publication No. 10/32551 JP 2001-117088 A

  Since the methods described in Patent Documents 1 to 4 described above are intended to prevent the occurrence of thermal unevenness by improving the properties of the polarizing plate alone, polarizing plates are arranged on both sides of the liquid crystal cell as a polarizing plate set. When used, there is a possibility that thermal unevenness that cannot be overlooked may occur due to the interaction of the characteristics of the two polarizing plates.

  The present invention is a composite polarizing plate set formed by combining two composite polarizing plates in which a polarizing film and a retardation film are bonded, and one composite polarizing plate is disposed on one surface of a liquid crystal cell. An object of the present invention is to provide a novel composite polarizing plate set in which the occurrence of heat unevenness is suppressed when the other composite polarizing plate is disposed and used on the other surface of the liquid crystal cell. It is another object of the present invention to provide a liquid crystal panel and a liquid crystal display device using a composite polarizing plate in which occurrence of such heat unevenness is suppressed.

  As a result of diligent research, the present inventors have found that the occurrence of heat unevenness is improved by the fact that the shrinkage rate of the two composite polarizing plates by heat treatment satisfies a certain relationship, leading to the present invention.

  The present invention is a composite polarizing plate set comprising a first composite polarizing plate disposed on one surface side of a liquid crystal cell and a second composite polarizing plate disposed on the other surface side. The plate has a rectangular shape, and is formed by laminating a first pressure-sensitive adhesive layer bonded to the liquid crystal cell, a first retardation film, and a first linearly polarizing film in this order, and a second composite polarizing plate. Is a rectangular shape, in which a second pressure-sensitive adhesive layer bonded to a liquid crystal cell, a second retardation film, and a second linearly polarizing film are laminated in this order, and the temperature is 85 ° C. for 100 hours. When the heat treatment is performed, S represented by the following formula (1) is a composite polarizing plate set satisfying S <2.0.

Here, the contraction rate of the short side of the first composite polarizing plate by the heat treatment is L _1s , the contraction rate of the long side is L ₁₁ , the contraction rate of the short side of the second composite polarizing plate by the heat treatment is L _2s , and the contraction of the long side _{Let the} rate be _L2l .

  In the composite polarizing plate set, at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer preferably has a loss tangent (tan δ) at a temperature of 85 ° C. of 0.4 or more.

  In the first composite polarizing plate, when the angle α formed by the absorption axis of the first linear polarizing film and the long side of the first composite polarizing plate is 0 ° or more and 45 ° or less, when viewed from the first linear polarizing film side. The angle formed by the slow axis of the first retardation film with respect to the absorption axis of the first linearly polarizing film is preferably in the range of 135 ° ± 20 ° counterclockwise. Furthermore, in the second composite polarizing plate, the angle β formed by the absorption axis of the second linear polarizing film and the long side of the second composite polarizing plate is 45 ° or more and 90 ° or less, and is viewed from the second linear polarizing film side. The angle formed by the slow axis of the second retardation film with respect to the absorption axis of the second linearly polarizing film is preferably in the range of 45 ° ± 20 ° counterclockwise. In addition, α + β is preferably 90 °.

  Further, the present invention comprises a liquid crystal cell and a pair of composite polarizing plates arranged on both sides thereof, and the pair of composite polarizing plates is the composite polarizing plate set described above, the first linearly polarizing film, the first retardation A film, a liquid crystal cell, a second retardation film, and a second linear polarizing film are laminated in this order, and the first composite polarizing plate and the second composite polarizing plate are arranged so that their long sides are parallel to each other. Provide a liquid crystal panel.

  Furthermore, the present invention provides a liquid crystal display device comprising a backlight and the liquid crystal panel.

  According to the present invention, the occurrence of thermal unevenness in a composite polarizing plate set is reduced, and the display quality of a liquid crystal panel and a liquid crystal display device using the same can be improved.

It is the schematic for demonstrating the preferable arrangement | positioning relationship of each element in the composite polarizing plate set which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the liquid crystal panel which consists of a composite polarizing plate set and a liquid crystal cell concerning this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the liquid crystal display device which concerns on this invention. 6 is a diagram illustrating an in-plane luminance distribution of Example 1. FIG. 6 is a diagram illustrating an in-plane luminance distribution of Example 2. FIG. FIG. 6 is a diagram showing an in-plane luminance distribution of Example 3. 6 is a diagram showing an in-plane luminance distribution of Comparative Example 1. FIG. 10 is a diagram illustrating an in-plane luminance distribution of Comparative Example 2. FIG. 10 is a diagram illustrating an in-plane luminance distribution of Comparative Example 3. FIG.

<Composite polarizing plate set>
The present invention is a composite polarizing plate set including a first composite polarizing plate disposed on one surface side of a liquid crystal cell and a second composite polarizing plate disposed on the other surface side. The first composite polarizing plate has a rectangular shape, and is formed by laminating a first pressure-sensitive adhesive layer bonded to a liquid crystal cell, a first retardation film, and a first linearly polarizing film in this order. The 2 composite polarizing plate has a rectangular shape, and is formed by laminating a second pressure-sensitive adhesive layer bonded to the liquid crystal cell, a second retardation film, and a second linearly polarizing film in this order.

  When the composite polarizing plate set of the present invention is subjected to heat treatment at a temperature of 85 ° C. for 100 hours, S represented by the following formula (1) satisfies S <2.0, and preferably S <1. 5 is satisfied.

here,
L _1s : Shrinkage ratio of the short side of the first composite polarizing plate by the heat treatment,
L ₁₁ : contraction rate of the long side of the first composite polarizing plate by the heat treatment,
L _2s : Shrinkage ratio of the short side of the second composite polarizing plate by the heat treatment,
L _2l : represents the shrinkage ratio of the long side of the second composite polarizing plate by the heat treatment.

Here, the shrinkage due to the heat treatment, and the length prior to the heat treatment of 100 hours at a temperature 85 ° C. L _b, the length of the after performing a heat treatment for 100 hours at a temperature 85 ° C. and L _a, the following It is a value shown by Formula (2). In addition, the length of the short side of the composite polarizing plate referred to in the present specification is the distance between the intermediate points of the two long sides, and the length of the long side of the composite polarizing plate is the intermediate point of the two short sides. Is the distance between.

  When the composite polarizing plate set has the heat shrinkage characteristics as described above, it is possible to suppress the occurrence of heat unevenness in the image display area when mounted on the liquid crystal panel. The heat shrinkage characteristics as described above can be obtained by appropriately selecting the first pressure-sensitive adhesive layer used in the first composite polarizing plate and the second pressure-sensitive adhesive layer used in the second composite polarizing plate. This can be realized by selecting the arrangement relationship of elements within a preferable range. At least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer preferably has a loss tangent (tan δ) at a temperature of 85 ° C. of 0.4 or more. More preferably, both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer have a loss tangent (tan δ) at a temperature of 85 ° C. of 0.4 or more.

  FIG. 1 is a schematic diagram for explaining a preferable arrangement relationship of each element in the composite polarizing plate set according to the present invention. In FIG. 1A, the first composite polarizing plate 10 is disposed on one surface of the liquid crystal cell 30, and the second composite polarizing plate 20 is disposed on the other surface. The first composite polarizing plate 10 includes a first linear polarizing film 11 and a first retardation film 12 disposed on the inside thereof, and the second composite polarizing plate 20 is disposed on the second linear polarizing film 21 and on the inside thereof. The second retardation film 22 is provided. The 1st composite polarizing plate 10 and the 2nd composite polarizing plate 20 are arrange | positioned and used so that the long side may become parallel, as shown to Fig.1 (a). A straight line C shown in FIG. 1A is a straight line parallel to the long sides of the first composite polarizing plate 10 and the second composite polarizing plate 20.

  1B shows the straight line C shown in FIG. 1A, the absorption axis 11A of the first linear polarizing film 11, the slow axis 12B of the first retardation film 12, and the slow axis 22B of the second retardation film. FIG. 5 is a schematic diagram showing the angular relationship of the absorption axis 21A of the second linearly polarizing film 22.

  In the first composite polarizing plate 10, the angle formed by the absorption axis 11A of the first linear polarizing film 11 and the long side of the first composite polarizing plate 10, that is, the angle α formed by the straight line C is preferably 0 ° or more and 45. ° or less. The angle θ1 formed by the slow axis 12B of the first retardation film 12 with respect to the absorption axis 11A of the first linearly polarizing film 11 when viewed from the first linearly polarizing film 11 side is preferably 135 ° counterclockwise. The range is ± 20 °.

  In the second composite polarizing plate 20, the angle formed by the absorption axis 21A of the second linear polarizing film 21 and the long side of the second composite polarizing plate 20, that is, the angle β formed by the straight line C is preferably 45 ° or more and 90 °. It is as follows. The angle formed by the slow axis 22B of the second retardation film 22 with respect to the absorption axis 21A of the second linearly polarizing film 21 when viewed from the second linearly polarizing film 21 side is preferably 45 ° ± counterclockwise. The range is 20 °. FIG. 1B shows the relationship seen from above in FIG. That is, the relationship between the absorption axis 21A and the slow axis 22B is shown when viewed from the second retardation film 22 side. The angle θ2 formed by the slow axis absorption axis 21 of the second retardation film 22 with respect to the absorption axis 21A of the second linear polarizing film 21 when viewed from the second retardation film 22 side is preferably 45 ° ± clockwise. The range is 20 °. Α + β is 90 °. That is, the first linearly polarizing film 11 and the second linearly polarizing film 21 have a relationship such that their absorption axes 11A and 21A are orthogonal to each other.

  In the case of having the above arrangement relationship, the second pressure-sensitive adhesive layer preferably has a loss tangent (tan δ) at a temperature of 85 ° C. of 0.4 or more, more preferably the first pressure-sensitive adhesive layer also has a temperature of 85 ° C. The loss tangent (tan δ) is 0.4 or more. By using such a pressure-sensitive adhesive layer, it becomes easier to construct a composite polarizing plate set having heat shrinkage characteristics satisfying the formula (1).

  When the composite polarizing plate set according to the present invention is arranged with a liquid crystal panel to constitute a liquid crystal panel, one of the first composite polarizing plate and the second composite polarizing plate is used as a front side polarizing plate, and the other is used as a back side polarizing plate. The polarizing plate used as the front side polarizing plate and the back side polarizing plate is not limited to one of the first composite polarizing plate and the second composite polarizing plate. Here, the “front side polarizing plate” means a polarizing plate located on the viewing side when the liquid crystal panel is mounted on the liquid crystal display device. Further, the “back-side polarizing plate” means a polarizing plate located on the backlight side when the liquid crystal panel is mounted on the liquid crystal display device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic cross-sectional view showing an example of a layer configuration of a liquid crystal panel including a composite polarizing plate set and a liquid crystal cell according to the present invention. The liquid crystal panel 1 shown in FIG. 2 is an embodiment when the first composite polarizing plate of the composite polarizing plate set according to the present invention is used as a front side polarizing plate and the second composite polarizing plate is used as a back side polarizing plate. . In the present embodiment, the first composite polarizing plate is formed by laminating other arbitrary layers in addition to the laminated structure including the first linearly polarizing film, the pressure-sensitive adhesive layer, the first retardation film, and the first pressure-sensitive adhesive layer. The second composite polarizing plate has a laminated structure composed of the second linearly polarizing film, the second retardation film, and the second pressure-sensitive adhesive layer, and other arbitrary layers are laminated. It has a configuration.

  The liquid crystal panel shown in FIG. 2 includes a liquid crystal cell 30, a first composite polarizing plate 10 disposed on one surface side of the liquid crystal cell 30, and a second composite polarizing plate 20 disposed on the other surface side. . The first composite polarizing plate 10 and the second composite polarizing plate 20 constitute a composite polarizing plate set according to the present invention. Hereinafter, each composite polarizing plate will be described in detail.

[First composite polarizing plate]
The first composite polarizing plate 10 includes a first linear polarizing film 11 and a first retardation film 12 bonded to the first linear polarizing film 11 via a bonding layer 13. And the 1st adhesive layer 15 is laminated | stacked on the surface on the opposite side to the surface at the side of the 1st linear polarizing film 11 of the 1st phase difference film 12, and the 1st phase difference film 12 side of the 1st linear polarizing film 11 is laminated | stacked. The transparent protective layer 14 and the surface treatment layer 16 are laminated in this order on the surface opposite to the surface. The first composite polarizing plate 10 is bonded to the liquid crystal cell 30 via the first pressure-sensitive adhesive layer 15.

(First linear polarizing film)
The first linearly polarizing film 11 is a film having a function of extracting linearly polarized light from incident natural light, and a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be used. The polyvinyl alcohol-based resin constituting the first linearly polarizing film 11 can be obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group. The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. Moreover, the polymerization degree of polyvinyl alcohol-type resin is about 1,000-10,000 normally, Preferably it is about 1,500-5,000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of the first linearly polarizing film 11. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 1 micrometer-150 micrometers. Considering easiness of stretching, the film thickness is preferably 10 μm or more.

  The first linearly polarizing film 11 is a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, a dichroic dye It is manufactured through a step of treating the polyvinyl alcohol-based resin film adsorbed with boric acid aqueous solution and a step of washing with water after the treatment with boric acid aqueous solution. As the dichroic dye, iodine or a dichroic organic dye is used.

(First retardation film)
As the first retardation film 12, a characteristic required as a retardation film, that is, a film whose birefringence is optically uniform is suitably selected, and compensation of retardation by a liquid crystal panel (meaning viewing angle compensation) And the protective function of the first linearly polarizing film 11 is also used. For example, those used in image display devices can be used without limitation, and birefringent films made of stretched films of various transparent polymers, discotic liquid crystals and nematic liquid crystals are aligned and fixed. And films having the above-mentioned liquid crystal layer formed on a film substrate. When the liquid crystal layer is fixed on the film substrate, a cellulose resin film such as triacetyl cellulose is preferably used as the film substrate for supporting the oriented liquid crystal layer.

  Examples of the polymer forming the birefringent film include polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polyolefins such as polypropylene, polyarylate, polyamide, and cyclic olefins such as norbornene. Examples include cyclic polyolefins as monomers. The stretched film may be processed by an appropriate method such as uniaxial or biaxial. Moreover, the birefringent film which controlled the refractive index of the thickness direction of a film by applying shrinkage force and / or extending | stretching force under adhesion | attachment with a heat-shrinkable film can also be used.

  In particular, in the case of an elliptically or circularly polarizing plate used in an image display device for mobile use, a 1 / 2λ plate or a 1 / 4λ plate is effectively used. The polarizing plate in the elliptical polarization mode or the circular polarization mode has a function of changing the incident polarized light to elliptically polarized light or circularly polarized light when the polarized light is linearly polarized light, and changing it to linearly polarized light when the incident polarized light is elliptically polarized light or circularly polarized light. doing. In particular, as a retardation film capable of changing elliptically polarized light or circularly polarized light into linearly polarized light and linearly polarized light into elliptically polarized light or circularly polarized light, a phase difference of 1/4 wavelength with respect to the wavelength of incident light, called a 1 / 4λ plate, is used. What is shown is used. The 1 / 2λ plate has a function of changing the direction of linearly polarized light. Furthermore, a 1 / 2λ plate and a 1 / 4λ plate are laminated so that the optical axes intersect at a predetermined angle to form a broadband 1 / 4λ plate that exhibits a 1/4 wavelength phase difference over a wide wavelength range. You can also.

  The elliptically polarizing mode polarizing plate is effective for preventing a coloring phenomenon caused by liquid crystal birefringence in a liquid crystal display device. The circularly polarizing mode polarizing plate is a reflective or transflective liquid crystal display device. Is effectively used for the purpose of improving the luminance. The circularly polarizing mode polarizing plate also has an antireflection function.

(First adhesive layer)
The first pressure-sensitive adhesive layer 15 can be formed on the basis of various pressure-sensitive adhesives conventionally used for image display devices. For example, those having a base polymer such as acrylic, rubber, urethane, silicone, and polyvinyl ether are used. Moreover, an energy beam curing type, a thermosetting type, etc. may be sufficient. Note that the pressure-sensitive adhesive layer having a loss tangent (tan δ) at a temperature of 85 ° C. of 0.4 or more can be adjusted by reducing the molecular weight of the base polymer, lowering the gel fraction, adding a plasticizer, or the like. It is preferable that the thickness of the 1st adhesive layer 15 is 3-25 micrometers.

  Although it does not specifically limit as a urethane type adhesive, For example, like the adhesive described in Unexamined-Japanese-Patent No. 2011-26418, the urethane polymer formed by making a polyisocyanate and a polyol react, and a hydroxyl group It is possible to use a resin obtained by further reacting a cyclic acid anhydride with a polyurethane urea obtained by reacting a polyamino compound containing

  The acrylic pressure-sensitive adhesive is not particularly limited, but (meth) acrylate such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, (2-ethylhexyl (meth) acrylate) ) An acrylic ester base polymer and a copolymer base polymer using two or more of these (meth) acrylic esters are preferably used. Furthermore, polar monomers are copolymerized in these base polymers. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, and 2-N, N-dimethylaminoethyl (meth). Mention may be made of monomers having a carboxy group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as acrylate and glycidyl (meth) acrylate.

  These acrylic pressure-sensitive adhesives can of course be used alone, but usually a crosslinking agent is used in combination. As the crosslinking agent, a divalent or polyvalent metal ion that forms a carboxylic acid metal salt with a carboxyl group, a polyamine compound that forms an amide bond with a carboxyl group, Examples thereof include polyepoxy compounds and polyol compounds that form an ester bond with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The energy ray curable adhesive has the property of being cured by irradiation with energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before irradiation with energy rays to adhere to an adherend such as a film. It is a pressure-sensitive adhesive that has the property of being adhered and cured by irradiation with energy rays to adjust the adhesion. As the energy ray curable adhesive, it is particularly preferable to use an ultraviolet curable adhesive. The energy beam curable pressure-sensitive adhesive generally comprises an acrylic pressure-sensitive adhesive and an energy beam polymerizable compound as main components. Usually, a crosslinking agent is further blended, and a photopolymerization initiator and a photosensitizer can be blended as necessary.

  In addition to the above base polymer and crosslinking agent, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer includes, as necessary, the pressure-sensitive adhesive strength, cohesive force, viscosity, elastic modulus, glass transition temperature, etc. In order to adjust, for example, natural or synthetic resins, tackifying resins, antioxidants, dyes, pigments, antifoaming agents, corrosive agents, photopolymerization initiators, and other appropriate additives are added. You can also. Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property. The pressure-sensitive adhesive layer may contain an antioxidant or an ultraviolet absorber. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

  The first pressure-sensitive adhesive layer 15 is formed by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to obtain a solution having a concentration of 10 to 40% by weight, and forming the pressure-sensitive adhesive layer. After directly applying and drying on the surface of the film to be formed, a method of laminating a separator made of a resin film, or after forming an adhesive layer on the separator and transferring it to the surface of the film to be formed, etc. be able to. When forming the pressure-sensitive adhesive layer on the film, a treatment for improving the adhesion, for example, corona treatment, is performed on the surface (one or both) on which the film and the pressure-sensitive adhesive layer are bonded as necessary. You may give it.

(Lamination layer)
The bonding layer 13 for bonding the first linearly polarizing film 11 and the first retardation film 12 is an adhesive layer or an adhesive layer. When the bonding layer 13 is a pressure-sensitive adhesive layer, the pressure-sensitive adhesive used is not particularly limited, and the same pressure-sensitive adhesive as that described for the pressure-sensitive adhesive forming the first pressure-sensitive adhesive layer 15 can be used.

  When the bonding layer 13 is an adhesive layer, the adhesive used is not particularly limited. For example, a water solvent adhesive, an organic solvent adhesive, a hot melt adhesive, and a solventless adhesive are used. Etc. can be used. Examples of the aqueous solvent-based adhesive include a polyvinyl alcohol-based resin aqueous solution and an aqueous two-component urethane emulsion adhesive, and the organic solvent-based adhesive includes, for example, a two-component urethane adhesive. Examples of the adhesive include a one-pack type urethane adhesive and an epoxy adhesive.

  When an aqueous polyvinyl alcohol resin solution is used, the polyvinyl alcohol resin used as an adhesive includes a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as vinyl acetate and this. And vinyl alcohol copolymers obtained by saponifying a copolymer with another copolymerizable monomer, and modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added to the adhesive as an additive. When such an aqueous adhesive is used, the adhesive layer obtained therefrom is usually 1 μm or less, and even when the cross section is observed with a normal optical microscope, the adhesive layer is practically not observed.

(Transparent protective layer)
The transparent protective layer 14 provided on one side of the first linear polarizing film 11 can be composed of an appropriate transparent film. Among them, a film made of a resin excellent in transparency, optical property uniformity, mechanical strength, thermal stability, etc. is preferably used. For example, cellulose resin films such as triacetyl cellulose and diacetyl cellulose, polyester resin films such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate, acrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate Examples thereof include a film, a polycarbonate resin film, a polyethersulfone resin film, a polysulfone resin film, a polyimide resin film, a polyolefin resin film, and a cyclic olefin resin film having a cyclic olefin as a monomer such as norbornene. An adhesive or a pressure-sensitive adhesive can be used for bonding the transparent protective layer 14 and the first linearly polarizing film 11.

(Other optical layers)
Although the 1st composite polarizing plate 10 is comprised as mentioned above, surface treatment layers 16, such as a hard-coat layer, an antireflection layer, and an anti-glare layer, on the transparent protective layer 14 as needed. May be provided. The hard coat layer is formed to prevent the surface of the polarizing plate from being scratched. The hard coat layer is mainly composed of an ultraviolet curable resin, for example, an acrylic resin or a silicone resin, and the adhesiveness to the transparent protective layer 14. Those having excellent hardness are appropriately selected and can be formed on the surface of the transparent protective layer 14. The antireflection layer is formed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be formed by a known method. The antiglare layer is formed in order to prevent the obstruction of visibility caused by external light reflected on the surface of the polarizing plate, for example, a roughening method by a sandblasting method or an embossing method, In general, the surface of the transparent protective layer 14 is formed to have a concavo-convex structure by a method of applying and curing a coating liquid in which transparent fine particles are mixed with an ultraviolet curable resin.

  Moreover, when the formed 1st adhesive layer 15 is exposed on the surface, it is good to arrange | position a separator in order to prevent contamination. The separator is also preferably used for temporarily protecting the surface of the first pressure-sensitive adhesive layer 15 until the first composite polarizing plate 10 is bonded to an image display element or the like. For example, the separator is transparent such as polyethylene terephthalate. A film made of a resin and treated with a release agent such as silicone is used.

[Second composite polarizing plate]
The second composite polarizing plate 20 includes a second linear polarizing film 21 and a second retardation film 22 bonded to the second linear polarizing film 21 via a bonding layer 23. In the second composite polarizing plate 20, the second pressure-sensitive adhesive layer 25 is further laminated on the surface of the second retardation film 22 opposite to the surface on the second linearly polarizing film 21 side. A transparent protective layer 24 and another optical layer 26 are laminated in this order on the surface opposite to the surface on the second retardation film 22 side. The second composite polarizing plate 20 is bonded to the liquid crystal cell 30 via the second pressure-sensitive adhesive layer 25.

(Second linear polarizing film)
The second linearly polarizing film 21 is a film having a function of extracting linearly polarized light from incident natural light, and a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be used. What was demonstrated about the film 11 can be used similarly. The first linearly polarizing film 11 and the second linearly polarizing film 21 may be the same or different with respect to the outer shape (thickness, etc.), material, and manufacturing method.

(Second retardation film)
As the second retardation film 22, a characteristic required as a retardation film, that is, a film whose birefringence is optically uniform is preferably selected, and the compensation of the retardation and the protection of the second linearly polarizing film 21 are performed. Also used for functions. As the second retardation film 22, those described for the first retardation film 12 can be similarly used. The first retardation film 12 and the second retardation film 22 may be the same or different with respect to the outer shape (thickness and the like), the material, the manufacturing method, and the like.

(Second adhesive layer)
The second pressure-sensitive adhesive layer 25 can be formed on the basis of various pressure-sensitive adhesives conventionally used for image display devices. For example, those having a base polymer such as acrylic, rubber, urethane, silicone, and polyvinyl ether are used. Moreover, an energy beam curing type, a thermosetting type, etc. may be sufficient. In order to obtain a pressure-sensitive adhesive layer having a loss tangent (tan δ) at a temperature of 85 ° C. of 0.4 or more, a pressure-sensitive adhesive having a urethane system as a base polymer is suitable. As the second pressure-sensitive adhesive layer 25, the same material as described for the first pressure-sensitive adhesive layer 15 can be used.

(Lamination layer)
The bonding layer 23 for bonding the second linearly polarizing film 21 and the second retardation film 22 is a pressure-sensitive adhesive layer or an adhesive layer. What was demonstrated about the bonding layer 13 can be used for the bonding layer 23 similarly. The bonding layer 13 and the bonding layer 23 may be the same or different with respect to the outer shape (thickness and the like), the material, the manufacturing method, and the like.

(Transparent protective layer)
The transparent protective layer 24 provided on one side of the second linearly polarizing film can be composed of an appropriate transparent film. As the transparent protective layer 24, those described for the transparent protective layer 14 of the first composite polarizing plate 10 can be similarly used.

(Other optical layers)
On the transparent protective layer 24, an optical layer 26 such as a reflective layer, a semi-transmissive reflective layer, a light diffusing layer, a light collector, or a brightness enhancement film can be further laminated.

  The reflective layer is used in a liquid crystal display device of a type that reflects and displays external light incident from the viewing side. Since the light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. The transflective polarizing plate is used in a liquid crystal display device that displays as a reflective type in a bright place and as a transmissive type using a light source such as a backlight in a dark place. The reflective layer for making a reflective polarizing plate can be formed by a foil or a vapor deposition film made of a metal such as aluminum, for example. The semi-transmissive reflective layer for making a semi-transmissive reflective type polarizing plate is a method of using the above reflective layer as a half mirror, or a light-transmitting reflective plate containing a pearl pigment or the like is bonded to the polarizing plate. It can be formed by a method or the like.

  The diffusion type polarizing plate has a function of diffusing incident light. The light diffusing layer used for this purpose is formed by various methods such as a method of performing a mat treatment on the transparent protective layer 24, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles.

  Further, the reflection / diffusion polarizing plate is obtained by providing a diffusion reflection layer, for example, by providing a reflection layer reflecting the uneven structure on the fine uneven structure surface of the diffusion type polarizing plate. The reflective layer having a fine concavo-convex structure has advantages such that incident light is diffused by irregular reflection, directivity and glare can be prevented, and unevenness in brightness and darkness can be suppressed. In addition, the resin layer or film containing fine particles has an advantage that incident light and its reflected light are diffused when passing through the layer, and brightness unevenness can be further suppressed. The reflective layer reflecting the surface fine concavo-convex structure can be formed, for example, by directly attaching a metal to the surface of the fine concavo-convex structure by a method such as vapor deposition such as vacuum deposition, ion plating, sputtering, or plating. Examples of the fine particles to be blended for forming the surface fine concavo-convex structure include silica, aluminum oxide, titanium oxide, zirconium oxide, tin oxide, indium oxide, cadmium oxide, and oxide having an average particle diameter of 0.1 to 30 μm. Inorganic fine particles made of antimony or the like, organic fine particles made of a crosslinked or uncrosslinked polymer, etc. can be used.

  The light collector is attached for the purpose of optical path control and can be formed as a prism array sheet, a lens array sheet, a dot attached sheet, or the like.

  The brightness enhancement film has a function of transmitting a part of incident natural light as linearly polarized light or circularly polarized light and reflecting the remaining light for reuse, and is used for the purpose of improving brightness in a liquid crystal display device or the like. . Examples include a reflective linearly polarized light separation sheet, a cholesteric liquid crystal polymer alignment film designed to produce anisotropy in reflectance by laminating a plurality of thin film films having different refractive index anisotropies, and the like. Examples include a reflective circularly polarized light separating sheet in which an oriented liquid crystal layer is supported on a film substrate.

<LCD panel>
The composite polarizing plate set of the present invention can be arranged on both surfaces of the liquid crystal cell 30 to form the liquid crystal panel 1. Typically, the liquid crystal panel 1 can be formed using a liquid crystal cell 30 in a VA (Vertical Alignment) mode, an ECB (Electrically Controlled Birefringence) mode, and an OCB (Optically Compensated Birefringence) mode. In the liquid crystal panel 1, since the composite polarizing plate set according to the present invention is used, the thermal unevenness is reduced and the display quality is improved.

<Liquid crystal display device>
FIG. 3 is a schematic cross-sectional view showing an example of the layer structure of the liquid crystal display device according to the present invention. The liquid crystal display device 2 illustrated in FIG. 3 includes the liquid crystal panel 1 illustrated in FIG. 2, a light diffusion plate 40, and a backlight 50. In the liquid crystal display device 2, the second composite polarizing plate 20 that is the back side polarizing plate in the liquid crystal panel 1 is disposed on the backlight 50 side. Here, a liquid crystal display device provided with a direct-type backlight that is arranged over the entire surface of the liquid crystal panel 1 and irradiates through a light diffusion plate is illustrated. However, the liquid crystal display device of the present invention is an edge of the liquid crystal panel. It is also possible to have a configuration including an edge light type backlight that is arranged on the light source and irradiates via a light guide plate.

(Light diffusion plate)
The light diffusing plate 40 is an optical member having a function of diffusing light from the backlight 50. For example, the light diffusing plate 40 is provided with light diffusibility by forming irregularities on the surface of the thermoplastic resin plate. A coating layer of a resin composition in which particles are dispersed may be provided on the surface to impart light diffusibility. The thickness can be about 0.1-5 mm. Further, between the light diffusion plate 40 and the liquid crystal panel 1, a prism sheet (also called a light condensing sheet, for example, “BEF” manufactured by 3M, etc.) and a brightness enhancement sheet (for example, “DBEF manufactured by 3M, Inc.) are provided. Etc.), a sheet exhibiting other optical functionality, such as a light diffusion sheet, can also be disposed. One or more sheets of other optical functionalities can be arranged as required. Further, as the light diffusion plate 40, for example, a light diffusion plate such as a laminated integrated product of a prism sheet having a cylindrical shape on the surface and a light diffusion plate (for example, one described in JP-A-2006-284597) It is also possible to use an optical sheet in which other functions are combined with each other.

  Such a liquid crystal display device according to the present invention uses the liquid crystal panel according to the present invention, and as with the liquid crystal panel, the thermal unevenness is reduced and the display quality is improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these. Using the composite polarizing plate sets of Examples 1 to 3 and Comparative Examples 1 to 3 described later, “calculation of S value” and “evaluation of heat unevenness” were performed by the following methods. In addition, “measurement of loss tangent (tan δ)” was performed on the pressure-sensitive adhesive layer used for constituting each composite polarizing plate set by the following method.

[Examples 1-3, Comparative Examples 1-3]
<Preparation of first composite polarizing plate>
A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm is uniaxially stretched about 5 times in a dry method, and is further added to pure water at 60 ° C. while maintaining tension. After dipping for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100 at 28 ° C. for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 10.5 / 7.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 10 ° C. for 5 seconds and then dried at 95 ° C. for 152 seconds to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol. This polarizing film was used as the first linear polarizing film.

  A 40 μm-thick film (KC4UY, manufactured by Konica Minolta Opto) made of saponified triacetylcellulose is applied to one side of the first linearly polarizing film obtained above via the following adhesive A. The first retardation film (ZD12-141158-A1330, manufactured by Optes Co., Ltd.) made of a cycloolefin-based resin having a thickness of 32 μm and laminated in advance on the other surface of the first linearly polarizing film. ) Was laminated via the following adhesive B, and the laminate was bonded between two nip rolls. The absorption axis of the first linear polarizing film of the first composite polarizing plate is 26 ° with respect to the short side, and the slow axis of the first retardation film is 135 ° counterclockwise with respect to the absorption axis. Bonded to.

  At this time, the hardness of the nip roll was 78 using a durometer type A based on JIS K7215. While maintaining the tension of the laminate at 430 N / m, drying was performed for 228 seconds in a drying oven maintained at 60 ° C. to 90 ° C. Triacetyl cellulose film / adhesive A / first linearly polarizing film / adhesive B / A laminate comprising a cycloolefin-based resin film (first retardation film) was obtained. And the 1st adhesive layer was formed in either of the following adhesive layers AD on the surface on the opposite side to the 1st linearly polarizing film side of a 1st phase difference film, and the 1st composite polarizing plate was obtained. In each Example or each Comparative Example, the pressure-sensitive adhesive layer shown in Table 1 was used as the first pressure-sensitive adhesive layer.

<Production of second composite polarizing plate>
In the second composite polarizing plate, each element is the same as that used in the first composite polarizing plate, triacetyl cellulose film / adhesive A / second linear polarizing film / adhesive B / cycloolefin resin film ( A laminate made of a second retardation film was used. In the production of this laminate, the absorption axis of the second linearly polarizing film of the second composite polarizing plate is 64 ° with respect to the short side, and the slow axis of the second retardation film is counterclockwise with respect to the absorption axis. Lamination was performed so as to be 45 ° around.

  And the 2nd adhesive layer was formed in one of said adhesive layers AD on the surface on the opposite side to the 2nd linearly polarizing film side of a 2nd phase difference film, and the 2nd composite polarizing plate was obtained. In each Example or each Comparative Example, the pressure-sensitive adhesive layer shown in Table 1 was used as the second pressure-sensitive adhesive layer.

<Preparation of adhesive>
(Adhesive A)
In 100 parts by weight of water, 4 parts by weight of acetoacetyl group-modified polyvinyl alcohol (Gosephemer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), sodium glyoxylate (SPM-01, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 4 parts by weight were dissolved to prepare a polyvinyl alcohol-based resin adhesive A.

(Adhesive B)
In 100 parts by weight of water, 2 parts by weight of acetoacetyl group-modified polyvinyl alcohol (Gosephemer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), sodium glyoxylate (SPM-01, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 2 parts by weight were dissolved to prepare a polyvinyl alcohol resin adhesive B.

<Formation of adhesive layer>
(Adhesive layer A: Acrylic adhesive layer)
An organic solvent solution of an acrylic pressure-sensitive adhesive obtained by adding an isocyanate crosslinking agent to a copolymer of butyl acrylate, methyl acrylate, 2-phenoxyethyl acrylate, and 2-hydroxyethyl acrylate is subjected to a release treatment. A sheet-like pressure-sensitive adhesive layer with a release film was formed on a release treatment surface of a 38 μm thick polyethylene terephthalate film (release film) by coating with a die coater so that the thickness after drying was 25 μm. This pressure-sensitive adhesive layer was designated as pressure-sensitive adhesive layer A. When tan δ of the pressure-sensitive adhesive layer A was measured by the following measuring method, tan δ at 85 ° C. was 0.19.

(Adhesive layer B: Acrylic adhesive layer)
An organic solvent solution of an acrylic pressure-sensitive adhesive obtained by adding an isocyanate-based crosslinking agent to a copolymer of butyl acrylate and acrylic acid was released from a 38 μm-thick polyethylene terephthalate film (release film) subjected to a release treatment. A sheet-like pressure-sensitive adhesive layer with a release film was formed on the mold-treated surface by coating with a die coater so that the thickness after drying was 25 μm. This pressure-sensitive adhesive layer was designated as pressure-sensitive adhesive layer B. When tan δ of the pressure-sensitive adhesive layer B was measured by the following measurement method, tan δ at 85 ° C. was 0.20.

(Adhesive layer C: Mixed layer of acrylic adhesive and urethane adhesive)
An organic solvent solution in which a urethane acrylate oligomer is blended with a copolymer of butyl acrylate and acrylic acid and an isocyanate cross-linking agent is added to a release film of a 38 μm-thick polyethylene terephthalate film (release film) subjected to a release treatment. A sheet-like pressure-sensitive adhesive layer coated so that the thickness after drying with a die coater was 25 μm was formed on the mold-treated surface. This pressure-sensitive adhesive layer was designated as pressure-sensitive adhesive layer C. When tan δ of the pressure-sensitive adhesive layer C was measured by the following measurement method, tan δ at 85 ° C. was 0.14.

(Adhesive layer D: Urethane-based adhesive layer)
Release of a 38 μm-thick polyethylene terephthalate film (release film) from which a urethane resin composed mainly of polypropylene glycol and isophorone diisocyanate and an organic solvent solution to which an isocyanate-based crosslinking agent is added are subjected to a release treatment. A sheet-like pressure-sensitive adhesive layer coated so that the thickness after drying with a die coater was 20 μm was formed on the treated surface. This pressure-sensitive adhesive layer was designated as pressure-sensitive adhesive layer D. When tan δ of the pressure-sensitive adhesive layer D was measured by the following measurement method, tan δ at 85 ° C. was 0.43.

[Calculation of S value]
In performing “calculation of the S value”, the shrinkage ratio L _1s of the short side of the first composite polarizing plate by the heat treatment, the shrinkage rate L _1l of the long side of the first composite polarizing plate, the shrinkage rate L _2s of the short side of the second composite polarizing plate by the heat treatment, The long side shrinkage ratio _L2l was calculated based on the following measured values. First, a 91 mm × 52 mm first composite polarizing plate and a second composite polarizing plate are made of glass having a thickness of 0.7 mm through the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer provided on each composite polarizing plate. The plates were attached to both surfaces so that the absorption axes of the polarizing plates were orthogonal to each other, and autoclaved for 20 minutes under conditions of a temperature of 50 ° C. and a pressure of 0.5 MPa. After natural cooling, for each of the first composite polarizing plate and the second composite polarizing plate of each sample (glass plate with a composite polarizing plate set), the length of the short side and the long side is set to 2 manufactured by Nikon Corporation. The measurement was performed using a dimension measuring instrument “NEXIV VMR-12072”.

Next, these samples were put into an oven maintained at 85 ° C. and heat-treated for 100 hours. About each of the 1st composite polarizing plate and the 2nd composite polarizing plate of the sample after this heat processing, the length of a short side and a long side was used for the Nikon Corporation 2-dimensional measuring instrument "NEXIV VMR-12072". Measured. Using the above measured values, the short side shrinkage L _1s and the long side shrinkage L _1l of the first composite polarizing plate by the heat treatment, the short side of the second composite polarizing plate by the heat treatment based on the formula (2) The shrinkage rate L _2s and the long side shrinkage rate L ₂₁ were determined. Then, these values were substituted into the equation (1) to obtain the value of S. The value of S is shown in Table 1.

[Evaluation of thermal unevenness]
A 91 mm × 52 mm first composite polarizing plate and a second composite polarizing plate are formed on a glass plate having a thickness of 0.7 mm through the first adhesive layer or the second adhesive layer provided on each composite polarizing plate. The two polarizing plates were pasted so that the absorption axes of the polarizing plates were orthogonal to each other, and autoclaved for 20 minutes under the conditions of a temperature of 50 ° C. and a pressure of 0.5 MPa. After natural cooling, each sample was put into an oven maintained at 85 ° C. and subjected to heat treatment for 100 hours. The degree of thermal unevenness of the sample after the heat treatment was visually evaluated in five stages of 1 to 5. “No unevenness occurred at all” was evaluated as “1”, and “unevenness was clearly generated at all sides” was evaluated as “5”. That is, the higher the numerical value of the evaluation, the more remarkable the occurrence of unevenness. The results are shown in Table 1. In addition, the in-plane luminance distribution of the sample after the heat treatment was measured with “Eye-scale 4W” manufactured by I-System. The measurement results of the luminance distributions of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIGS.

[Measurement of tan δ]
The pressure-sensitive adhesive layers A to D were laminated on a resin film having a size of 4 cm × 4 cm and a thickness of 100 μm to prepare a test piece. For this test piece, tan δ at 85 ° C. is obtained by a torsional shear method with a frequency of 1 Hz using a parallel plate with a diameter of 25 mm with an instrument “Physica MCR301” manufactured by Anton-Paar in accordance with JIS K7244-10. It was.

  As shown in Table 1 and FIGS. 4 to 6, Examples 1 to 3 having an S value of 2.0 or less give good results in which no or very little thermal unevenness is observed in the “evaluation of thermal unevenness”. It was.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal panel, 2 Liquid crystal display device, 10 1st composite polarizing plate, 11 1st linearly polarizing film, 11A Absorption axis, 12 1st phase difference film, 12B Slow axis, 13, 23 Bonding layer, 15 1st adhesion Agent layer, 14, 24 transparent protective layer, 16 surface treatment layer, 20 second composite polarizing plate, 21 second linearly polarizing film, 21A absorption axis, 22 second retardation film, 22B slow axis, 23 adhesive layer, 25 second adhesive layer, 26 optical layer, 30 liquid crystal cell, 40 light diffusion plate, 50 backlight.

Claims (4)

A composite polarizing plate set comprising a first composite polarizing plate disposed on one surface side of the liquid crystal cell and a second composite polarizing plate disposed on the other surface side,
The first composite polarizing plate has a rectangular shape, and is formed by laminating a first pressure-sensitive adhesive layer bonded to the liquid crystal cell, a first retardation film, and a first linearly polarizing film in this order. ,
The second composite polarizing plate has a rectangular shape, and a second pressure-sensitive adhesive layer bonded to the liquid crystal cell, a second retardation film, and a second linearly polarizing film are laminated in this order. ,
The second pressure-sensitive adhesive layer is made of a urethane-based pressure-sensitive adhesive, and a loss tangent (tan δ) at a temperature of 85 ° C. is 0.4 or more.
A composite polarizing plate set in which S represented by the following formula (1) satisfies S <2.0 when heat treatment is performed at a temperature of 85 ° C. for 100 hours.

(Here, the shrinkage rate of the short side of the first composite polarizing plate by the heat treatment is L _1s , the shrinkage rate of the long side is L ₁₁ , and the shrinkage rate of the short side of the second composite polarizing plate by the heat treatment is L _2s. The contraction rate of the long side is L _2l .) In the first composite polarizing plate, an angle α formed by an absorption axis of the first linear polarizing film and a long side of the first composite polarizing plate is 0 ° or more and 45 ° or less, and from the first linear polarizing film side. The angle formed by the slow axis of the first retardation film with respect to the absorption axis of the first linearly polarizing film when viewed is in a range of 135 ° ± 20 ° counterclockwise,
In the second composite polarizing plate, an angle β formed by an absorption axis of the second linear polarizing film and a long side of the second composite polarizing plate is 45 ° or more and 90 ° or less, and from the second linear polarizing film side. The angle formed by the slow axis of the second retardation film relative to the absorption axis of the second linearly polarizing film when viewed is in a range of 45 ° ± 20 ° counterclockwise,
The composite polarizing plate set according to claim 1 , wherein α + β is 90 °. It consists of a liquid crystal cell and a pair of composite polarizing plates arranged on both sides,
The pair of composite polarizing plates is the composite polarizing plate set according to claim 1 or 2 ,
The first linearly polarizing film, the first retardation film, the liquid crystal cell, the second retardation film, and the second linearly polarizing film are laminated in this order,
A liquid crystal panel in which the first composite polarizing plate and the second composite polarizing plate are arranged so that their long sides are parallel to each other. A liquid crystal display device comprising a backlight and the liquid crystal panel according to claim 3 .