Polarizing plate and liquid crystal display device

Abstract

The present application provides a polarizing plate and a liquid crystal display device. The polarizing plate uses a common PET film as a polarizing plate protective film, and in a liquid crystal display device equipped with the polarizing plate, even if a surface film having a low haze anti-glare layer, a transparent hard coating layer is used on the viewing side for the purpose of preventing whitening of black display, there are no problems such as inclined rainbow stripes, the legibility is good, and it can be manufactured at a low cost. The polarizing plate is characterized in that it contains a polarizing element in which iodine is adsorbed to a polyvinyl alcohol-based resin layer and oriented, a light scattering film layer is laminated on one face of the polarizing element via an adhesive layer, the light scattering film layer has a light scattering layer on the polarizing element side with a polyester resin-based stretched film as a base material, and in the light scattering layer, 1) the internal haze is 50-95%, and 2) the arithmetic average roughness Ra of the surface unevenness shape based on JIS B0601 is 0-0.30 µm.

Description

[0001] This application is a divisional application of the original Chinese patent application filed on February 3, 2019, with application number 201910108682.0 and entitled "Polarizing plate and liquid crystal display device". Technical Field

[0002] The present invention relates to a polarizing plate having a light scattering film layer stacked on top of it, and a liquid crystal display device equipped with the polarizing plate. Background Technology

[0003] In recent years, liquid crystal displays (LCDs) have been widely used due to their thinness, light weight, and low power consumption. An LCD device has a liquid crystal panel component, which is formed by bonding polarizing plates to both sides of liquid crystal cells using an adhesive. Display is achieved by controlling the light emitted from a backlight component using the liquid crystal panel component. Here, the polarizing plate consists of polarizing elements and protective films bonded to both sides. Typically, polarizing elements are obtained by dyeing a stretched polyvinyl alcohol (PVA) film using iodine or dichroic dyes. As the protective film, acylated cellulose film is mainly used.

[0004] For such LCDs, there has always been a demand for further thinning, weight reduction, and cost reduction. As a proposal to address these requirements, an attempt was made to replace the acylated cellulose film on the outside of the polarizer protective film when it is attached to the LCD with an inexpensive and mechanically strong stretched polyethylene terephthalate film (hereinafter also referred to as PET film).

[0005] However, it is well known that if the acylated cellulose membrane is replaced with the commonly used PET membrane, the rainbow-like patterns (hereinafter referred to as "tilted rainbow patterns") will be more noticeable when viewed from an oblique direction, resulting in poor recognizability (e.g., Patent Document 1).

[0006] To address this problem, for example, Patent Document 2 discloses a method that uses a stretched PET film in the back-side protective film of the polarizer attached to the back side of the liquid crystal cell, and makes the viewing-side protective film of the viewing-side polarizer an anti-glare film with a high-haze anti-glare layer, thereby reducing tilting rainbow patterns. However, this method does not sufficiently improve the tilting rainbow pattern, and because there is a high-haze anti-glare layer on the viewing side, indoor lighting light is scattered and reflected on the surface of the anti-glare layer, resulting in a whitening of the displayed image, especially black, leading to a significant deterioration in image quality. To prevent the whitening of black, a protective film with a low-haze anti-glare layer and a transparent hard coating (hereinafter referred to as "low-haze film") must be used on the viewing side.

[0007] Patent document 3 describes that in a liquid crystal display device that uses a white light-emitting diode as the backlight source, by using a polyester film with an in-plane retardation of 3000 to 30000 nm for the incident-side polarizer protective film of the polarizer disposed on the incident light side (also called the "back-side polarizer") or the emitting-side polarizer protective film disposed on the emitting light side (also called the "viewing-side polarizer"), the aforementioned tilting rainbow pattern can be suppressed.

[0008] However, although such polyester films with high in-plane retardation are available on the market, they are more expensive than commonly used PET films, making them unsuitable for applications where cost reduction is the goal. Furthermore, since in-plane retardation is proportional to thickness, it is difficult to reduce the film thickness to achieve the high in-plane retardation described above, making them unsuitable for thin and lightweight applications.

[0009] Furthermore, in the aforementioned Patent Document 3, the backlight source needs to use a white light-emitting diode with a wide emission spectrum. However, in recent years, in order to expand the color reproduction area, light sources with sharp emission spectra have been tried (e.g., Patent Document 4). The content of Patent Document 3 is not suitable for such a purpose.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2010-107892

[0013] Patent Document 2: Japanese Patent Application Publication No. 2009-109993

[0014] Patent Document 3: International Publication No. WO2011 / 162198

[0015] Patent Document 4: Japanese Patent Application Publication No. 2012-169271 Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] In view of the above situation, the subject of the present invention, that is, the problem to be solved by the present invention, is to provide a polarizing plate that uses a commonly used PET film as the protective film for the polarizing plate. In a liquid crystal display device equipped with this polarizing plate, even if a surface film with a low-haze anti-glare layer and a transparent hard coating is used on the viewing side, especially for the purpose of preventing black from turning white, there are no problems such as tilting rainbow patterns, good visibility, and it can be manufactured inexpensively. Furthermore, a liquid crystal display device with good visibility equipped with such a polarizing plate is provided. In addition, a thin polarizing plate that is also suitable for thinning liquid crystal display devices is provided.

[0018] Methods for solving problems

[0019] The inventors have conducted repeated and careful studies on the back-side polarizing plate of the two polarizing plates attached to both sides of the liquid crystal cell. As a result, they discovered that by using conventional polarizing plate manufacturing methods, using a light-scattering film with a specific light-scattering layer as the back-side protective film based on stretched polyester film, and attaching the light-scattering layer of the light-scattering film to the polarizing element, a polarizing plate with good visibility can be produced inexpensively even using commonly used stretched PET. This polarizing plate will not produce tilted rainbow patterns even if a low-haze film is used for the viewing-side protective film of the viewing-side polarizing plate, thus completing the present invention.

[0020] The problem to be solved by the present invention can be solved by a polarizing plate with the following structure. That is, a polarizing plate, characterized in that it comprises a polarizing element (P) formed by adsorbing iodine onto a polyvinyl alcohol-based resin layer and orienting it, and a light scattering film layer (DF) is laminated on one surface of the polarizing element (P) with an adhesive layer (AL1) in between. The light scattering film layer (DF) is based on a polyester resin-based stretched film and has a light scattering layer (DL) on the polarizing element (P) side. In the light scattering layer (DL), 1) the internal haze is 50-95%, and 2) the surface roughness Ra based on JIS B0601 is 0-0.30 μm.

[0021] Furthermore, a preferred polarizing plate is one in which a back layer (BL) with a specific surface irregularity is further laminated on the side of the polyester resin-based stretched film substrate of the light scattering film layer (DF) where the light scattering layer (DL) is not laminated. According to this polarizing plate, when disposed on the back side (backlight side) of the liquid crystal cell, the diffuser sheet disposed between the backlight and the back side polarizing plate can be omitted, which can further contribute to the thinning and cost reduction of the image display device.

[0022] Invention Effects

[0023] According to the present invention, a polarizing plate that does not exhibit tilted rainbow patterns in a liquid crystal display device, despite using a commonly used PET film, can be provided inexpensively. Furthermore, the polarizing plate of the present invention, while using commonly used PET, can provide a polarizing plate and a liquid crystal display device with excellent visibility. Detailed Implementation

[0024] [Polarizing element]

[0025] The polarizing element of the present invention, formed by adsorbing iodine onto a polyvinyl alcohol (hereinafter also referred to as PVA) resin layer and orienting it, can use known polarizing elements. Such polarizing elements are generally formed by using a PVA resin film, dyeing the PVA resin film with iodine, and then subjecting it to uniaxial stretching.

[0026] As mentioned above, PVA-based resins generally use substances obtained by saponifying polyvinyl acetate-based resins. The degree of saponification is about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% to 100 mol%. Besides polyvinyl acetate as a homopolymer of vinyl acetate, copolymers of vinyl acetate with other monomers capable of copolymerization, such as ethylene-vinyl acetate copolymers, can also be used as polyvinyl acetate-based resins. Other monomers capable of copolymerization include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the PVA-based resin is 1000 to 10000, preferably 1500 to 5000. The PVA-based resin can also be modified, for example, by using aldehyde-modified polyvinyl alcohol formaldehyde, polyvinyl alcohol acetal, or polyvinyl alcohol butyral.

[0027] There is no particular limitation on the manufacturing method of polarizing elements. Typical methods include: feeding a pre-wound polyvinyl alcohol (PVA) resin film, stretching, dyeing, cross-linking, etc.; and methods including the process of making a laminate of PVA resin and a stretching resin substrate and stretching the laminate. Any of these methods can be used in this invention.

[0028] Methods for manufacturing these polarizing elements are described in paragraphs

[0109] to

[0128] of Japanese Patent Application Publication No. 2014-48497, and these methods can be used in this invention.

[0029] The thickness of the polarizing element of the present invention is preferably 3 to 35 μm, more preferably 4 to 30 μm, and even more preferably 5 to 25 μm.

[0030] [Light scattering film]

[0031] Next, the light scattering film layer of the present invention will be described. The substrate film of the light scattering film layer of the present invention is a polyester resin-based stretched film.

[0032] (Polyester resin-based stretch film)

[0033] The polyester resin used in this invention is not particularly limited in structure. Preferably, a resin having a structure obtained by condensing an aromatic dicarboxylic acid with an aliphatic diol is used as the main component; more preferably, polyethylene terephthalate or polyethylene naphthalate is used; and particularly preferably, polyethylene terephthalate is preferred. Other copolymer components may also be included without impairing the effects of this invention. Other polymers may also be mixed in.

[0034] The polyester of the present invention may also contain additives such as antioxidants and ultraviolet absorbers as needed.

[0035] The polyester resin-based stretch film of the present invention can be manufactured according to the general method for manufacturing polyester films. For example, the following method can be used: melting and extruding polyester resin into a sheet, stretching the resulting non-oriented polyester film longitudinally at a temperature above the glass transition temperature using the speed difference of rollers, stretching it transversely by a tenter frame, and applying heat treatment.

[0036] The polyester resin-based stretched film of the present invention can be a uniaxial stretched film or a biaxial stretched film, but generally speaking, biaxial stretched films have stronger mechanical strength, which is preferred. Methods for manufacturing uniaxial stretched films include: stretching longitudinally relative to the above-described stretching methods or stretching laterally using a tenter frame, followed by heat treatment.

[0037] The in-plane retardation Re of the polyester resin-based stretched film obtained in this way is typically 500–3000 nm.

[0038] The thickness of the polyester resin-based stretch film of the present invention is preferably 5 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 80 μm.

[0039] In this invention, in order to improve the adhesion to the light scattering layer, it is preferable that at least one side of the polyester resin-based stretch film of this invention has an easy-to-adhere layer with polyester resin, polyurethane resin or polyacrylic resin as the main components.

[0040] Examples of commercially available stretch PET films with an easy-to-adhere layer include "Cosmoshine" (registered trademark) manufactured by Toyobo Co., Ltd., and "Lumirror" (registered trademark) manufactured by Toray Industries, Ltd. Such films are also preferred for use in this invention.

[0041] (Light scattering layer)

[0042] A light-scattering layer is laminated onto the aforementioned polyester resin-based stretched film. The light-scattering layer contains a light-scattering agent and an adhesive. By dispersing light through the polyester film using the light-scattering agent, the light-scattering layer prevents tilted rainbow patterns.

[0043] Light scattering agents are particles that have the property of scattering light, and are broadly classified into inorganic fillers and organic fillers. Examples of inorganic fillers include silicon dioxide, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or mixtures thereof. Among these, silicon dioxide particles are preferred from the perspective of refractive index.

[0044] Specific materials that can be used as organic fillers include, for example, acrylic resins, acrylonitrile resins, polyurethanes, polyvinyl chloride, polystyrene, polyamides, polyacrylonitrile, and silicone resins. Among these, acrylic resins with high transparency are preferred, and polymethyl methacrylate (PMMA) or copolymers of PMMA and styrene are particularly preferred.

[0045] There are no particular limitations on the shape of the light scattering agent, and examples include spherical, cubic, needle-shaped, rod-shaped, spindle-shaped, plate-shaped, scale-shaped, and fibrous. Among these, spherical microbeads with excellent light scattering properties are preferred.

[0046] When using organic fillers as light scattering agents, the average particle size of the light scattering agent is preferably 0.5–6 μm, more preferably 1–6 μm, and even more preferably 1–5 μm. When the light scattering agent is smaller than 0.5 μm, sufficient light scattering effect cannot be obtained. Conversely, when it is larger than 6 μm, the surface unevenness increases, which risks reducing the adhesion to the polarizing element.

[0047] When using an organic filler as a light scattering agent, the amount of the light scattering agent (calculated relative to 100 parts by weight of the solid component of the polymer composition as a binder forming material) is preferably 5 to 100 parts by weight, more preferably 10 to 70 parts by weight, and even more preferably 20 to 50 parts by weight. If the amount of the light scattering agent is less than the lower limit mentioned above, there is a risk that the light scattering properties will become insufficient. Conversely, if the amount of the light scattering agent exceeds the upper limit mentioned above, the surface roughness will increase, and there is a risk that adhesion to the polarizing element will not be smooth. Furthermore, the amount of the light scattering agent used as an inorganic filler is essentially the same as that used with organic fillers.

[0048] Adhesives can include thermosetting resins and active energy radiation-cured resins. It should be noted that the composition used to form the adhesive may also appropriately incorporate other agents such as micro-inorganic fillers with an average particle size of less than 0.5 μm, curing agents, plasticizers, dispersants, various leveling agents, antistatic agents, ultraviolet absorbers, antioxidants, viscosity modifiers, lubricants, light stabilizers, solvents, etc.

[0049] There are no particular limitations on the base polymer used as the thermosetting resin described above. Examples include acrylic resins, urethane resins, polyester resins, fluorinated resins, silicone resins, polyamide resins, polyimide resins, epoxy resins, UV-curable resins, thermosetting resins, and photocurable resins. One or a mixture of two or more of these polymers can be used. In particular, polyols with high processability and the ability to easily form a light-scattering layer by coating or other methods are preferred as the base polymer. Furthermore, from the viewpoint of improving light transmittance, the base polymer used in the adhesive is preferably transparent, and particularly preferably colorless and transparent.

[0050] Examples of the aforementioned polyols include polyols obtained by polymerizing monomer components containing hydroxyl-containing unsaturated monomers, and polyester polyols obtained under conditions of excess hydroxyl groups. These can be used individually or in combination of two or more. In this invention, it is preferable to use a polyol obtained by polymerizing monomer components containing hydroxyl-containing unsaturated monomers as the main component. The unsaturated monomer is preferably a (meth)acrylic acid monomer, and particularly preferably a (meth)acrylic acid polyol obtained from such a monomer. Specific examples of polyols and preferred embodiments are described in Japanese Patent Application Publication No. 2013-117695, paragraphs

[0050] to

[0057] , which are also suitable for use in this invention.

[0051] When using polyols in adhesives, it is preferable to include at least one selected from polyfunctional isocyanate compounds, melamine compounds, and amino plastic resins among compounds having two or more functional groups that react with the hydroxyl groups of the polyol. This allows the polyols in the adhesive's matrix resin to be linked through a cross-linking structure, resulting in improved stability, stain resistance, flexibility, and weather resistance.

[0052] In this invention, polyfunctional isocyanates are particularly preferred among the above-mentioned compounds. Furthermore, combinations of (meth)acrylic acid polyols and polyfunctional isocyanates are particularly preferred as combinations with the substrate polymer.

[0053] Specific examples and preferred embodiments of compounds having two or more functional groups that react with the hydroxyl groups of polyols are described in Japanese Patent Application Publication No. 2013-117695, paragraphs

[0071] to

[0078] , and can also be used in the present invention.

[0054] Examples of the aforementioned active energy ray-curable resins include: UV-curable resins that are cross-linked and cured by irradiation with ultraviolet light; and electron-ray-curable resins that are cross-linked and cured by irradiation with electron beams. These resins can be appropriately selected from polymerizable monomers and polymerizable oligomers. Among these, (meth)acrylate-based, urethane-based, or (meth)acrylate urethane-based UV-curable resins are preferred.

[0055] As the aforementioned polymerizable monomer, (meth)acrylate monomers having a free radical polymerizable unsaturated group in the molecule are suitable, and polyfunctional (meth)acrylates are preferred. Specific examples and preferred embodiments of polyfunctional (meth)acrylates are described in Japanese Patent Application Publication No. 2013-228720, paragraphs

[0026] to

[0032] , and are also suitable for use in the present invention.

[0056] When using a UV-curable resin as the above-mentioned active energy ray-curable resin, it is desirable to add a photopolymerization initiator in the range of 0.1 to 5 parts by mass relative to 100 parts by mass of the resin. There are no particular limitations on the photopolymerization initiator; examples of polymerizable monomers and polymerizable oligomers having free radical polymerizable unsaturated groups in their molecules include benzophenone, benzylmielone, 2-chlorothiazolone, 2,4-diethylthiazolone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzoin dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, and 2-hydroxy-2-methyl-1-phenylpropane-1-one. Examples of ketones include 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinoacetone-1, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(pyrrolo-1-yl)phenyl]titanium, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2,4,6-trimethylbenzoyl diphenylphosphine oxide. Furthermore, for polymerizable oligomers with cationic polymerizable functional groups in their molecules, aromatic sulfonates and aromatic diazo salts can be listed. Salt, aromatic iodine Salts, metallocene compounds, benzoin sulfonates, etc. It should be noted that these compounds can be used individually or in combination.

[0057] For specific examples, preferred methods, and commercially available products of photopolymerization initiators, please refer to paragraphs

[0064] to

[0067] of Japanese Patent Application Publication No. 2014-170130.

[0058] <Optical properties of the light scattering layer>

[0059] The haze value (internal haze value) inside the light scattering layer in this invention is 50-95%, preferably 55-92%, and particularly preferably 60-90%. If it is within this range, tilted rainbow patterns can be prevented.

[0060] <Surface shape of the light scattering layer>

[0061] For the surface shape of the light scattering layer in this invention, the roughness parameter (arithmetic mean roughness Ra) based on JIS-B0601 is 0 to 0.30 μm, preferably 0 to 0.25 μm, and particularly preferably 0.05 to 0.22 μm. By controlling it within this range, good adhesion to the polarizing element can be obtained.

[0062] <Thickness of the light scattering layer>

[0063] The thickness of the light scattering layer in this invention is preferably 3–30 μm, more preferably 5–20 μm, and particularly preferably 6–15 μm. By controlling it within this range, the optical properties and surface shape of the light scattering layer described below can be appropriately controlled.

[0064] There are no particular limitations on the method for stacking the light-scattering layer, and various known methods can be used. Specific stacking methods include coating methods such as gravure coating, roller coating, bar coating, doctor blade coating, and spray coating. Among these, gravure coating, which can thinly and uniformly coat the polymer composition containing microspheres, is most preferred. In this gravure coating method, considering the formation properties of the light-scattering layer, the gravure line count is preferably 70 to 100, and the rotation speed is preferably 80 to 120.

[0065] (Back side of the light scattering film)

[0066] It is also preferred that the back side of the light scattering film (the side of the substrate where the light scattering layer is not stacked) has an anti-adhesion layer or a light diffusion layer with an uneven surface and a haze of more than 10% (also referred to as "back layer" in this application).

[0067] Below the back-side polarizer, a prism sheet is typically provided for light focusing purposes. This prism sheet can sometimes interfere with pixels, causing moiré patterns. By further laminating a back layer with an uneven surface shape on the back side of the light-scattering film layer as described above, a moiré pattern prevention effect can be achieved, which is therefore preferable. Furthermore, to prevent moiré patterns caused by the prism sheet, a diffuser sheet is sometimes provided opposite the back-side polarizer; however, by further laminating a back layer with an uneven surface shape on the back side of the light-scattering film layer, the diffuser sheet can be omitted, which is preferable from the viewpoint of thinning and reducing the cost of the image display device.

[0068] (Back layer with an uneven surface)

[0069] Next, the “back layer with a surface irregular shape” that can be preferably used in the present invention will be described (hereinafter, the “back layer with a surface irregular shape” will also be simply referred to as the “back layer”).

[0070] The back layer is stacked on the back side of the light scattering film (the side of the substrate from which the light scattering layer is not stacked).

[0071] The backing layer has an adhesive. The backing layer can be formed of adhesive alone, but to obtain a suitable surface texture, it preferably contains fillers. The fillers can be materials exemplified as light-scattering agents used in the aforementioned light-scattering layers.

[0072] From the perspective of easy control of surface shape, spherical particles are preferred, and from the viewpoint of preventing damage to prism sheets, spherical organic fillers are more preferred.

[0073] Among the organic fillers, acrylic resins with high transparency are preferred, and polymethyl methacrylate (PMMA) or copolymers of methyl methacrylate and styrene are particularly preferred.

[0074] When organic fillers are used in the backing layer, the average particle size is preferably 1–20 μm, more preferably 2–15 μm, and even more preferably 3–12 μm. When the particle size is less than 1 μm, it is difficult to obtain sufficient surface unevenness; conversely, when the particle size is greater than 20 μm, the backing layer becomes thicker.

[0075] The adhesive for the backing layer can preferably be the material described in the light scattering layer above. Furthermore, the amount of organic filler (the amount calculated relative to 100 parts by weight of the solid component of the polymer component in the polymer composition that forms the adhesive) is preferably 5 to 100 parts by weight, more preferably 10 to 70 parts by weight, and even more preferably 20 to 50 parts by weight.

[0076] When the amount of organic filler is less than the lower limit mentioned above, there is a risk that the surface unevenness will become insufficient. Conversely, when the amount of organic filler exceeds the upper limit mentioned above, there is a risk that the organic filler will not be properly fixed and will fall off.

[0077] <Optical properties of the back layer>

[0078] The haze value of the back layer in this invention is 3 to 90%, preferably 10 to 80%, and particularly preferably 15 to 70%. If it is within this range, moiré patterns caused by prisms can be prevented.

[0079] It should be noted that the haze of the back layer mentioned here refers to the haze value when the back layer is only laminated onto the PET film substrate without the aforementioned light scattering layer.

[0080] The internal haze value of the backing layer can be controlled by the refractive index difference between the adhesive and the filler in the backing layer. Ideally, the internal haze of the backing layer should be substantially zero; specifically, it is preferably -1% to 1%. This suppresses chromatic aberration in light passing through the backing layer.

[0081] It should be noted that the internal haze of the back layer mentioned here refers to the haze value of the back layer after it is smoothed by methods such as coating the surface of the back layer with an adhesive liquid and curing it, without the aforementioned light scattering layer.

[0082] The specific method for measuring internal haze values ​​is described in the examples described later.

[0083] <Surface shape of the back layer>

[0084] For the surface shape of the back layer in this invention, the roughness parameter (arithmetic mean roughness Ra) based on JIS-B0601 is preferably 0.05–1.50 μm, more preferably 0.08–1.20 μm, even more preferably 0.10–0.90 μm, and particularly preferably 0.10–0.60 μm. By controlling it within this range, both moiré pattern prevention and front brightness can be achieved.

[0085] <Back layer thickness>

[0086] The thickness of the back layer in this invention is preferably 3–20 μm, more preferably 5–17 μm, and particularly preferably 6–15 μm. By controlling it within this range, the optical properties and surface shape of the back layer can be appropriately controlled.

[0087] There are no particular restrictions on the stacking method for the back layer; similar to the light scattering layer, various known methods can be used. Furthermore, the light scattering layer and the back layer can be stacked sequentially in two separate layers, or both layers can be stacked simultaneously. When stacking in two separate layers, the stacking order is not restricted.

[0088] [The layer composition of the polarizing plate]

[0089] The polarizing plate of the present invention can be a polarizing plate with a protective film on only one side of the polarizing element, or a polarizing plate with a protective film on both sides of the polarizing element. In this invention, the preferred layer structure of the polarizing plate is shown below.

[0090] Polyester film / light scattering layer / adhesive layer / polarizing element

[0091] Backing layer / polyester film / light scattering layer / adhesive layer / polarizing element with uneven surface

[0092] Polyester film / light scattering layer / adhesive layer / polarizing element / adhesive layer / protective film

[0093] A backing layer / polyester film / light scattering layer / adhesive layer / polarizing element / adhesive layer / protective film with an uneven surface

[0094] [Another protective film]

[0095] When the polarizing plate of the present invention has a structure in which protective films are provided on both sides, the other protective film may be an acylated cellulose film, a film formed of a polycarbonate resin, a film formed of a cyclic olefin resin such as norbornene, or a (meth)acrylic polymer film. However, when bonding with a water-based adhesive such as PVA adhesive, from the viewpoint of moisture permeability, either an acylated cellulose film or a (meth)acrylic polymer film is preferred, with an acylated cellulose film being the most preferred.

[0096] From an optical point of view, the thickness of the protective film at this point is preferably thin, but if it is too thin, the strength will decrease and the processability will deteriorate. An appropriate film thickness is 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 70 μm.

[0097] Furthermore, as described later, the polarizing plate of the present invention can be used in liquid crystal cells of various display modes, but when the liquid crystal cell is in IPS mode, it is preferable from the viewpoint of optical compensation to have no excess birefringence. Examples of acylated cellulose films that satisfy such conditions include Fuji-TAC ZRD (manufactured by Fuji Film Co., Ltd.), which are preferably used in the present invention.

[0098] [How to make a polarizing plate]

[0099] Next, the method for manufacturing the polarizing plate of the present invention will be described.

[0100] (Lamination of polarizing element (P) to light scattering film (DF))

[0101] The polarizing plate of the present invention can be manufactured by bonding one side of the polarizing element (P) to the light scattering layer (DL) of the light scattering film layer (DF) through an adhesive layer (AL1). Any suitable adhesive can be used in the present invention. Specifically, water-based adhesives, solvent-based adhesives, and active energy radiation-cured adhesives can be used as adhesives.

[0102] Furthermore, the same adhesive used for bonding the light scattering film (DF) can be used to bond the other side of the polarizing element (P) to the protective film layer (PF2).

[0103] As for the aforementioned active energy ray-cured adhesives, any suitable adhesive that can be cured by irradiation with active energy rays can be used. Examples of active energy ray-cured adhesives include, for example, ultraviolet-cured adhesives and electron beam-cured adhesives. Specific examples of curing types of active energy ray-cured adhesives include free radical curing types, cationic curing types, anionic curing types, and combinations thereof (e.g., a mixture of free radical curing types and cationic curing types).

[0104] Examples of adhesives that can be cured by active energy rays include those containing compounds (e.g., monomers and / or oligomers) with free radical polymerizable groups such as (meth)acrylate groups and (meth)acrylamide groups as curing components.

[0105] Specific examples of the above-mentioned active energy ray curing adhesive and its curing method are described, for example, in Japanese Patent Application Publication No. 2012-144690.

[0106] Furthermore, any suitable aqueous adhesive can be used as the aforementioned aqueous adhesive. Among these, an aqueous adhesive containing PVA-based resin (PVA-based adhesive) is preferred. From the perspective of adhesion, the average degree of polymerization of the PVA-based resin contained in the aqueous adhesive is preferably in the range of 100 to 5500, more preferably 1000 to 4500. From the perspective of adhesion, the average degree of saponification is preferably in the range of 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%.

[0107] The PVA-based resin contained in the above-mentioned water-based adhesive preferably contains acetyl groups. This is because it enables excellent adhesion and durability between the PVA-based resin layer and the protective film. The PVA-based resin containing acetyl groups can be obtained, for example, by reacting a PVA-based resin with diketene using any method. Regarding the degree of acetyl group modification in the PVA-based resin containing acetyl groups, a representative value is 0.1 mol% or more, preferably between 0.1 mol% and 20 mol%.

[0108] The resin concentration of the above-mentioned water-based adhesive is preferably 0.1% to 15% by weight, and more preferably 0.5% to 10% by weight.

[0109] The thickness of the adhesive layer can be set to any suitable value. For example, it can be set in such a way that an adhesive layer with the desired thickness can be obtained after curing or heating (drying). The thickness of the adhesive layer is preferably 0.01 μm to 7 μm, more preferably 0.01 μm to 5 μm, even more preferably 0.01 μm to 2 μm, and most preferably 0.01 μm to 1 μm.

[0110] It should be noted that, in this invention, the layer formed by the PVA-based adhesive is referred to as the PVA-based adhesive layer, and the layer formed by the active energy ray curing adhesive is referred to as the active energy ray curing adhesive layer.

[0111] In order to improve the adhesion between the polarizing element and the adhesive, and between the light scattering layer and the adhesive, one or both of the polarizing element and the light scattering layer can be pre-treated with surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation, and primer coating when bonding the polarizing element and the light scattering layer.

[0112] When the polarizing plate of the present invention has protective films on both sides of the polarizing element, the protective films can be laminated one by one or both sides can be laminated at the same time, preferably both sides are laminated at the same time.

[0113] Furthermore, it is preferable that the slow axis direction (the direction of maximum in-plane refractive index) of the polyester resin-based stretched film is substantially parallel or substantially perpendicular to the absorption axis direction of the polarizing element. If this configuration deviates from the above, rainbow patterns may sometimes be observed from the front when mounted on a liquid crystal display device.

[0114] Liquid crystal display device

[0115] The liquid crystal display device of the present invention is characterized by comprising a liquid crystal cell, a polarizing plate (back-side polarizing plate) of the present invention disposed on the backlight side of the liquid crystal cell, and a polarizing plate (viewing-side polarizing plate) disposed on the viewing side. The liquid crystal display device of the present invention does not have particular limitations on the viewing-side polarizing plate, but the haze of the viewing-side protective film of the viewing-side polarizing plate is preferably 0 to 10%, more preferably 0 to 8%, and particularly preferably 0 to 5%. By controlling the haze of the viewing-side protective film within this range, both tilt rainbow effect prevention and black density can be achieved.

[0116] (The structure of a typical liquid crystal display device)

[0117] A liquid crystal display device comprises: a liquid crystal cell formed by carrying liquid crystal between two electrode substrates, two polarizing plates disposed on both sides thereof, and at least one optical compensation film disposed between the liquid crystal cell and the polarizing plates as needed. The polarizing plate of the present invention can be used as the back-side polarizing plate in a pair of polarizing plates.

[0118] The liquid crystal layer of a liquid crystal cell is typically formed by sealing liquid crystal within a space created by sandwiching a spacer between two substrates. A transparent electrode layer is formed on the substrate, serving as a transparent film containing a conductive material. A barrier layer, a hard coating layer, or an undercoat layer (for bonding the transparent electrode layer) may also be further provided in the liquid crystal cell. These layers are typically disposed on the substrate. The substrate of a liquid crystal cell generally has a thickness of 50 μm to 2 mm.

[0119] (Types of LCD display devices)

[0120] The film of this invention can be used in liquid crystal cells of various display modes. Various display modes such as TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Super Twisted Nematic), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and HAN (Hybrid Aligned Nematic) have been proposed. Furthermore, display modes obtained by aligning and segmenting the above display modes have also been proposed. The polarizing plate of this invention is effective in liquid crystal display devices of any display mode. Moreover, it can also be used in any type of liquid crystal display device, including transmissive, reflective, and translucent types.

[0121] When the polarizing plate of the present invention is attached to the back of the liquid crystal cell of the above-mentioned IPS mode, it can suppress light leakage when viewed from an oblique direction during black display, and is therefore particularly preferred.

[0122] Example

[0123] The present invention will now be described in detail based on embodiments. The materials, reagents, quantities, proportions, and operations shown in the following embodiments can be appropriately modified without departing from the spirit of the invention. Therefore, the present invention is not limited to the following embodiments.

[0124] [Fabrication of light scattering film]

[0125] (Preparation of polyester resin-based stretch film substrate)

[0126] Using the same method as WO2011 / 162198

[0076] (Comparative Example 1), a long roll biaxially stretched PET film with an easy-to-adhere layer on both sides and a film thickness of approximately 38 μm was obtained. The in-plane retardation Re of this film was 1178 nm, the slow axis was in the width direction (perpendicular to the length direction), and the haze was 0.2%.

[0127] (Layering of light scattering layers)

[0128] As a polymer composition for light scattering containing a light scattering agent and a binder, a polymer composition comprising 43 parts of acrylic polyol (base polymer), 21 parts of methyl methacrylate-styrene copolymer particles (refractive index: 1.52) with an average particle size of 3 μm, 6 parts of isocyanate-based curing agent, and a solvent was used. The proportions of each component are mass ratios converted from solid components. A 15 g / m² polymer composition for light scattering was laminated onto the surface of this substrate layer using a gravure coating method. 2 (Conversion of solid components) thus yields light scattering film 1. At this point, the refractive index of the adhesive is 1.50.

[0129] The light scattering layer was evaluated according to the following "Evaluation Method for Light Scattering Layers". The internal haze of the light scattering layer was 80%, and the arithmetic mean roughness Ra was 0.05 μm.

[0130] For light scattering film 1, light scattering films 2–6 were fabricated by changing the amount of light scattering agent particles and the thickness of the light scattering layer, and were evaluated in the same manner as light scattering film 1. The results are shown in Table 1.

[0131] [Evaluation method for light scattering layer]

[0132] (1-1) Haze

[0133] [1] The total haze value (H) of the obtained light scattering film was measured using JIS-K7136 as the standard: a haze meter NDH2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. was used.

[0134] [2] For the surface of the light scattering layer, the substance obtained by removing the light scattering agent from the above-mentioned polymer composition for light scattering is coated with a rod coater at approximately 2 g / m². 2 The amount of (solid composition conversion) is used to smooth the surface, creating a film with surface haze removed. The film is measured using the same method as above, and the internal haze value (Hin) is obtained from the difference between the haze value of the film and that of the substrate film.

[0135] (1-2) Surface shape of the light scattering layer (arithmetic mean roughness Ra)

[0136] Based on JIS-B0601 (1994, 2001), the measurements were performed using the SURFCORDER-MODELSE-3500 manufactured by Kosaka Research Institute Co., Ltd.

[0137] (Fabrication of a light-scattering film with only a back layer)

[0138] As a polymer composition for the backing layer containing organic fillers and binders, a polymer composition consisting of 43 parts of acrylic polyol (base polymer), PMMA particles with an average particle size of 10 μm (refractive index: 1.50), 6 parts of isocyanate-based curing agent, and solvent was used. The parts indicated are mass ratios converted from solid components. It should be noted that the amount of PMMA particles added should be adjusted so that the Ra (arithmetic mean roughness) after lamination is as shown in Table 1.

[0139] For biaxially stretched PET films with an easy-to-bond layer but without the aforementioned light-scattering layer, gravure coating at 7 g / m 2 (Solid component conversion) A polymer composition for a back layer is stacked to obtain a light scattering film 21 having only a back layer.

[0140] By changing the amount of filler and the thickness of the backing layer, light scattering films 22-25 are fabricated in the same manner as light scattering film 21.

[0141] (Fabrication of a light-scattering film with a light-scattering layer and a backing layer)

[0142] In addition to stacking the back layer of light scattering films 21-24, which only have a back layer, on the surface of the unstacked light scattering layer of the light scattering film 2, light scattering films 11-14 are also fabricated in the same way.

[0143] Similarly, except that the back layer of the light scattering film 22, which only has a back layer, is stacked on the surface of the unstacked light scattering layers of the light scattering films 4, 3, and 1, the light scattering films 15 to 17 are also fabricated in the same way.

[0144] [Evaluation method for the back layer]

[0145] (2-1) Haze

[0146] [1] The total haze value (H) of the obtained light scattering film was measured using JIS-K7136 as the standard: a haze meter NDH2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. was used.

[0147] The haze of the light scattering film 21-25 with only a back layer was measured and taken as the haze of the back layer. Regarding the haze of the back layer having both a light scattering layer and a back layer, the value of the light scattering film 21-25 prepared with the same formulation was taken as the haze of the back layer.

[0148] [2] On the back layer of the light scattering films 21-25 having only a back layer, the substance obtained by removing the light scattering agent from the above-mentioned polymer composition for the back layer is coated with a rod coater at approximately 2 g / m². 2The amount of (solid component conversion) is used to smooth the surface, thus creating a film with surface haze removed. The film is measured using the same method as described above, and the internal haze value (Hin) of the back layer is obtained from the difference between the haze value and that of the substrate film. Regarding the internal haze of the back layer, which has a light scattering layer and a back layer, the internal haze value of a light scattering film 21 to 25 made with the same formulation is used as the internal haze of the back layer.

[0149] (2-2) Surface shape of the back layer (arithmetic mean roughness Ra)

[0150] Based on JIS-B0601 (1994, 2001), the measurements were performed using the SURFCORDER-MODELSE-3500 manufactured by Kosaka Research Institute Co., Ltd.

[0151] [Table 1]

[0152]

[0153] It should be noted that the light scattering films 1 to 6 in Table 1 are composed of a light scattering layer on one side of a polyester resin stretch film substrate without a back layer.

[0154] The light scattering films 11 to 17 are composed of a light scattering layer on one side of a polyester resin-based stretched film substrate and a back layer on the other side.

[0155] Furthermore, the light scattering films 21 to 25 are composed of a back layer but no light scattering layer on one side of a polyester resin-based stretch film substrate.

[0156] Furthermore, the internal haze of the back layer of light scattering films 21–25 is 0%.

[0157] [Production of polarizing plates]

[0158] Next, a polarizing plate is made using the light scattering films 1-6, 11-17, 22, and 25 prepared above, as well as a biaxially stretched PET film without a stacked light scattering layer.

[0159] (Fabrication of polarizing elements)

[0160] A 40 μm thick PVA film with an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% was immersed in warm water at 25°C for 120 seconds to allow it to swell. Then, it was immersed in a 0.6 wt% aqueous solution of iodine / potassium iodide (weight ratio = 2 / 3) and dyed while being stretched to 2.1 times its original size. Finally, it was stretched in an acidic bath containing boric acid and potassium iodide at 60°C, washed with water, and dried to fabricate a 15 μm thick polarizing element.

[0161] (Preparation of adhesive for polarizing plates)

[0162] A modified PVA resin containing acetyl groups (GOHSENX Z-410, manufactured by Nippon Synthetic Chemicals Co., Ltd.) was dissolved in water to prepare an aqueous solution A with a solid content adjusted to 3%. Maleic acid was then added to aqueous solution A to bring the concentration to 0.5% by weight, followed by the addition of glyoxal as a crosslinking agent. With Z-410 weighing 100 units, the amount of glyoxal added was 5 units by weight. Sodium hydroxide was added to the aqueous solution to adjust the pH to 2.5, yielding an adhesive for polarizing plates.

[0163] (Saponification of acylated cellulose membranes)

[0164] A commercially available acylated cellulose membrane (Fuji-TAC ZRD40, manufactured by Fuji Membrane Co., Ltd.: membrane thickness 40 μm) was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, then washed with water. Next, it was immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, followed by a 30-second water bath under running water to neutralize the membrane. Then, it was repeatedly dehydrated three times using an air knife. After removing the water, it was dried in a 70°C drying zone for 15 seconds to produce the saponified membrane.

[0165] (Making of polarizing plates)

[0166] After corona treatment of the light scattering layer surface of the light scattering film prepared above, the above adhesive is coated, so that the thickness of the adhesive layer after drying is 150 nm. The above adhesive is coated on one side of the acylated cellulose film after saponification treatment, so that the thickness of the adhesive layer after drying is 150 nm.

[0167] Next, a light scattering film coated with the above-mentioned adhesive and an acylated cellulose film are laminated on both sides of the polarizing element using a roller laminator, such that the slow axis of the above-mentioned biaxially stretched PET film of the light scattering film substrate is perpendicular to the absorption axis of the polarizing element. Then, it is dried at 60°C for 10 minutes to obtain the polarizing plate 1 involved in the present invention.

[0168] For polarizing plate 1, as shown in Table 2, the type of light scattering film and the bonding surface with the polarizing element are changed to make polarizing plates 2-6, 11-17, and 21-27.

[0169] It should be noted that polarizing plate 21 uses the side opposite to the stacked surface of the light scattering layer to bond the light scattering film 1 to the polarizing element. Polarizing plates 22 and 23 are light diffusion films that only have a back layer and no light diffusion layer, and the easy-to-adhere layer of the PET substrate opposite to the back layer is bonded to the polarizing element. Polarizing plates 25 to 27 are configured to have only an outer protective film and no inner protective film. In addition, polarizing plates 24 and 27 use biaxially stretched PET without a stacked light scattering layer as the outer protective film to replace the light scattering film layer.

[0170] [Manufacturing of Liquid Crystal Display Devices]

[0171] An LG Display 32MP58HQ monitor (equipped with a white LED Edge Light backlight and IPS LCD cells; structure from bottom to top: light guide plate, diffuser, two prism sheets, and another diffuser) was disassembled. The backlight-side polarizer attached to the LCD cells was peeled off and replaced with polarizers 1-6, 11-17, and 21-27. The side without the light-scattering film was attached to the LCD cells using adhesive. The diffuser, which was positioned opposite the topmost back-side polarizer, was removed. The components were then reassembled to create image display devices 1-6, 11-17, and 21-27. These were evaluated according to the "Evaluation Method for Image Display Devices" described below. The results are shown in Table 2.

[0172] [Evaluation Method for Image Display Devices]

[0173] (3-1) Tilted rainbow pattern

[0174] Display the image in white and observe it from all angles: tilt, 60 degrees, and 45 degrees. Evaluate the rainbow effect in six stages according to the following criteria.

[0175] ◎: The rainbow pattern is completely invisible at polar angles of 60 degrees and 45 degrees.

[0176] 〇: At an polar angle of 60 degrees, rainbow patterns can be barely observed, but are almost invisible. At an polar angle of 45 degrees, rainbow patterns are completely invisible.

[0177] △: Rainbow patterns can be observed at a polar angle of 60 degrees, but they are not obvious. Rainbow patterns are not visible at a polar angle of 45 degrees.

[0178] X: Faint rainbow patterns can be seen at a polar angle of 60 degrees. Rainbow patterns are not visible at a polar angle of 45 degrees.

[0179] XX: The rainbow pattern is clearly visible. The rainbow pattern can be observed at a polar angle of 45 degrees.

[0180] XXX: The rainbow pattern is clearly visible. It is also clearly visible at an extreme angle of 45 degrees.

[0181] (3-2) Moiré pattern

[0182] Set the monitor to white display and observe from all angles from 0 to 60 degrees. Evaluate the moiré pattern in 6 stages according to the following judgment criteria.

[0183] ◎: Moiré patterns are not visible from any angle.

[0184] 〇: Moiré patterns are virtually invisible from all angles.

[0185] △: Moiré patterns can be observed in some areas, but they are not obvious.

[0186] X: Faint moiré patterns can be seen in some places.

[0187] XX: In some places, the moiré pattern can be clearly seen.

[0188] XXX: The moiré pattern is clearly visible overall.

[0189] (3-3) Front brightness

[0190] Before disassembly and after attaching the polarizing plate of the embodiments and comparative examples of the present invention, a white display was made, and the front brightness was measured. The front brightness was evaluated in three stages according to the following judgment criteria.

[0191] 〇: The brightness is above 95% compared to the brightness before decomposition.

[0192] △: Brightness is above 90% but less than 95% relative to the brightness before decomposition. X: Brightness is less than 90% relative to the brightness before decomposition.

[0193] [Table 2]

[0194]

[0195] ※The polarizing plate 21 uses the opposite side to bond the light scattering film and the polarizing element, forming the following structure.

[0196] Light scattering layer / polyester film / adhesive layer / polarizing element / adhesive layer / protective film

[0197] For the image display device shown in Table 1, based on the tilted rainbow pattern described above (3-1), when the image is viewed from the front ("front rainbow pattern observation"), no front rainbow pattern was observed in the entire image display.

[0198] The following information can be obtained from the results shown in Table 2.

[0199] 1. If the polarizing plate protective film uses commonly used stretched PET film, it will produce slanted rainbow patterns.

[0200] 2. By setting an internal light-scattering layer with an internal haze of 50-95% between the stretched PET and the polarizing element, tilted rainbow patterns can be prevented.

[0201] 3. Regardless of whether there is an inner protective film, the same effect of preventing tilted rainbow patterns can be achieved.

[0202] 4. When a light scattering layer is provided on the outside of the polarizing plate, it does not prevent rainbow patterns.

[0203] 5. The moiré pattern improvement effect is high when there is a light scattering layer and a back layer with an uneven shape.

[0204] 6. In particular, the moiré pattern improvement effect is high when the backing layer has an uneven shape with an arithmetic mean roughness Ra of 0.10 to 0.90 μm.

[0205] 7. When there is no light scattering layer but only a back layer with an uneven shape, there is almost no effect in preventing rainbow patterns.

[0206] Next, the relationship between whitening (whitening when displaying black) and prevention of tilted rainbow patterns when using a high-haze anti-glare film as a prior art is shown, as well as the advantages of the present invention.

[0207] (Production of low-haze anti-glare film)

[0208] According to Example 1 described in Japanese Patent Application Publication No. 2013-228720, paragraphs

[0120] to

[0141] and

[0156] , a low-haze anti-glare film was obtained. The haze of the low-haze anti-glare film is 3%.

[0209] (Production of high-haze anti-glare film)

[0210] According to the anti-glare protective film (C) described in Japanese Patent Application Publication No. 2009-109993, paragraphs

[0074] to

[0079] , a high-haze anti-glare film was obtained. The haze of the high-haze anti-glare film is 44%.

[0211] (Watching the making of the side polarizer)

[0212] The low-haze and high-haze anti-glare films were saponified according to the above-described (saponification of acylated cellulose film) procedure. Then, for polarizing plate 1, polarizing plate 31 was fabricated by replacing the light-scattering film layer with the saponified low-haze anti-glare film, and polarizing plate 32 was fabricated by replacing it with the high-haze anti-glare film. For any polarizing plate, the surface of the anti-glare film that adheres to the polarizing element is the surface without the anti-glare layer.

[0213] [Manufacturing of Liquid Crystal Display Devices]

[0214] The LG Display monitor (32MP58HQ: equipped with a white LED Side Light type backlight and IPS mode LCD cell) was disassembled. The backlight-side polarizing plate attached to the LCD cell was peeled off, as shown in Table 3, and replaced with polarizing plate 12 or polarizing plate 13. The inner protective film side was then attached to the LCD cell using adhesive. The viewing-side polarizing plate was peeled off and replaced with polarizing plate 31 or polarizing plate 32. The side without the anti-glare film was then attached. The diffuser sheet corresponding to the topmost back-side polarizing plate was removed. The monitor was then reassembled to create image display devices 31 to 33. In the following evaluation method, the tilting rainbow effect was evaluated for black density using the same method as for image display device 1. The results are shown in Table 3.

[0215] (3-4) Dark and dense feel

[0216] Generally speaking, in a typical home environment where a TV is used (approximately 200Lx), the panel is driven with a black display. The sense of blackness is confirmed by visual inspection and the following criteria.

[0217] A: The blackness is excellent.

[0218] B: The blackness is good.

[0219] C: Although it appears slightly whitish, it is within acceptable limits.

[0220] D: The whitening is obvious.

[0221] [Table 3]

[0222]

[0223] Based on the results shown in Table 3, the following information can be obtained.

[0224] 1. If the protective film is combined with the back-side polarizing plate of the commonly used stretched PET film and the high-haze anti-glare film on the viewing side, it can reduce the tilt rainbow pattern but not sufficiently. In addition, it will also produce a new problem of black display turning white.

[0225] 2. By using the polarizing plate of the present invention, it is possible to achieve both prevention of tilted rainbow patterns and dense black (the degree of black is very good).

Claims

1. A polarizing plate assembly, characterized in that, It features a viewing side polarizer and a rear side polarizer. The viewing-side polarizing plate has a viewing-side protective film. The haze of the protective film on the viewing side is 0-5%. The back-side polarizing plate is a polarizing plate containing a polarizing element P obtained by adsorbing iodine onto a polyvinyl alcohol-based resin layer and orienting it. On one surface of the polarizing element P, a light scattering film layer DF is stacked across an adhesive layer AL1, the thickness of which is 0.01 μm to 1 μm. The light scattering film layer DF uses a polyester resin-based stretched film as the substrate, and has a light scattering layer DL on the polarizing element P side. The light scattering layer DL is directly laminated to the polarizing element P via an adhesive layer AL1. In the light scattering layer DL, 1) the internal haze is 50-95%, and 2) the surface roughness Ra, based on JIS B0601, is 0-0.30 μm. The light scattering layer DL is a layer formed by dispersing particles with an average particle size of 0.5-6 μm within an adhesive. The light scattering film layer DF is further laminated with a back layer BL on one side of the unlaminated light scattering layer DL of the polyester resin-based stretched film substrate. The back layer BL has an uneven surface shape and prevents moiré patterns caused by prism sheets. The back layer BL contains filler. The surface roughness of the back layer BL is 0.10~0.60 μm based on the arithmetic mean roughness Ra of JIS B0601.

2. The polarizing plate assembly as described in claim 1, characterized in that, On the back side polarizing plate, a protective film layer PF2 is further laminated on the other side of the polarizing element P through the adhesive layer AL2.

3. The polarizing plate assembly as described in claim 1 or 2, characterized in that, The in-plane retardation Re of the polyester resin-based stretched film is 500~3000 nm.

4. The polarizing plate assembly as described in claim 1, characterized in that, The adhesive is a curing adhesive containing (meth)acrylic polyol and polyfunctional isocyanate.

5. The polarizing plate assembly as described in claim 1 or 2, characterized in that, The backing layer BL is a layer formed by dispersing particles with an average particle size of 1~20μm within an adhesive.

6. The polarizing plate assembly as described in claim 1 or 2, characterized in that, The haze of the back layer BL is 3-90%.

7. The polarizing plate assembly as described in claim 2, characterized in that, The adhesive layer AL1 or adhesive layer AL2 is a PVA-based adhesive layer or an active energy radiation-cured adhesive layer.

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