JP2010060787A - Polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate in which a polarizer is hardly cleaved in the case where the plate is exposed to a high temperature environment, a low temperature environment or such an environmental change that a high temperature environment and a low temperature environment are repeated, and which is excellent in reliability of display quality. <P>SOLUTION: A polarizing plate obtained by laminating a protective film on at least one surface of a polarizer is cut into a prescribed shape so that the average number of cracks each having a length of ≥50 μm is ≤10 pieces per 100 mm of the length in the direction parallel to the surface of the polarizer, in a polarizer part of the end face not parallel to the stretching direction of the polarizer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarizing plate in which a protective film is laminated on at least one surface of a polarizer, and an image display device using the polarizing plate.

  Liquid crystal display devices are used in televisions, personal computers, mobile phones, and the like, and in recent years, the demand has increased rapidly. A polarizing plate, which is an essential member of a liquid crystal display device, is usually a transparent resin film, such as a tri-crystalline resin, with an adhesive layer interposed between at least one surface of a polarizer made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. It has a structure in which a cellulose acetate-based protective film typified by acetylcellulose is laminated, and this is cut according to the screen size of the liquid crystal panel. In order to finish the end surface (cut surface), cutting is also considered. For example, Japanese Patent Application Laid-Open No. 2001-54845 (Patent Document 1) discloses that between a polarizer and a protective film by pressing during cutting. In order to scrape off the protruding adhesive, it is disclosed that a plurality of polarizing plates are overlapped and the end face is finished with a rotary blade in a state where the end face of the rotary blade faces the end face. Japanese Patent Application Laid-Open No. 2003-220512 (Patent Document 2) discloses that the end face is continuously rough-cut and finish-cut by a fly-cut method in order to scrape off the protruding adhesive.

  The polarizing plate thus obtained is bonded to a liquid crystal panel with an adhesive and mounted on a liquid crystal display device, but when exposed to an environmental change such as a high temperature environment or a low temperature environment, or repeated high temperature environment and low temperature environment, Stress may be generated due to a difference in contraction and expansion between the polarizer and the protective film, and the polarizer may be torn from the end face toward the inside, thereby deteriorating the display quality. In order to solve such a problem, it has been proposed that the polarizer is not exposed at the end face. For example, Japanese Patent Laid-Open No. 10-206633 (Patent Document 3) discloses a cutting tool in which a polarizing plate is heated. It is disclosed that the end portion of the protective film is caused to undergo thermal deformation by covering the end portion of the polarizer thereunder. Japanese Unexamined Patent Application Publication No. 2004-21088 (Patent Document 4) and Japanese Unexamined Patent Application Publication No. 2006-195209 (Patent Document 5) disclose that an end face of a polarizing plate is covered with a resin. Furthermore, in JP-A-2006-106016 (Patent Document 6), an adhesive layer is formed on a protective film of a polarizing plate, and after cutting the polarizing plate in this state, the end face is cut. It is disclosed that the end face is covered with an adhesive.

JP 2001-54845 A JP 2003-220512 A Japanese Patent Laid-Open No. 10-206633 JP 2004-21088 A JP 2006-195209 A JP 2006-106016 A JP 2008-51964 A

  However, the polarizing plate in which the polarizer is not exposed at the end face as described above, the end face is likely to be fused or deformed by heating (Patent Document 3), and it takes time and effort to manufacture (Patent Document 4, 5) The end face is easily sticky (Patent Document 6). Therefore, the object of the present invention is that the polarizer is difficult to tear when exposed to an environmental change such as a high temperature environment and a low temperature environment, or a high temperature environment and a low temperature environment, even if the polarizer is exposed at the end face. An object of the present invention is to provide a polarizing plate having excellent display quality reliability.

  As a result of intensive studies, the inventors have cut a polarizing plate in which a protective film is laminated on at least one surface of a polarizer into a predetermined shape, and in the polarizer portion of the predetermined end surface, a long crack is formed. The present inventors have found that the above-mentioned object can be achieved by reducing the amount, and have completed the present invention. That is, the present invention is a polarizing plate in which a protective film is laminated on at least one surface of a polarizer and is cut into a predetermined shape, and in the polarizer portion of the end surface that is not parallel to the stretching direction of the polarizer, Provided is a polarizing plate characterized in that the number of cracks having a length of 50 μm or more is 10 or less in terms of an average value per 100 mm length in a direction parallel to the polarizer surface. Moreover, according to this invention, an image display apparatus provided with this polarizing plate and an image display element is also provided.

  When the polarizing plate of the present invention is exposed to a high temperature environment, a low temperature environment, or an environmental change that repeats a high temperature environment and a low temperature environment, the polarizer is difficult to tear and has excellent display quality reliability.

(Polarizer)
As the polarizer, a hydrophilic resin film, typically a film made of a polyvinyl alcohol-based resin such as polyvinyl alcohol or partially formalized polyvinyl alcohol is used as a raw film, and this is subjected to stretching treatment and iodine or dichroic dye. A dichroic substance is dyed and adsorbed and oriented to the dichroic substance. When natural light is incident, an appropriate substance that transmits linearly polarized light can be used. In particular, those excellent in light transmittance and degree of polarization are preferable. The stretching process is usually uniaxial stretching, and may be performed before the dyeing process, may be performed simultaneously with the dyeing process, or may be performed after the dyeing process. Moreover, you may perform appropriate processes, such as a crosslinking process, in an appropriate order and system.

  In this specification, the stretching direction in the stretching process is referred to as the stretching direction of the polarizer. And the extending | stretching direction of this polarizer corresponds with the absorption-axis direction of a polarizer normally, and is orthogonally crossed with the transmission-axis direction of a polarizer.

(Protective film)
The material used for the protective film is preferably an optically transparent resin. Examples thereof include a cellulose acetate resin such as triacetyl cellulose, a polyester resin such as polyethylene terephthalate, and polymethyl methacrylate. Examples thereof include thermoplastic resins such as non-crystalline cyclic polyolefins having monomers such as acrylic resins, polycarbonate resins, and norbornene compounds.

  The protective film may be a single layer film or a multilayer film. For example, the protective film laminated on one surface of the polarizer may be an antiglare film in which a hard coat layer having a fine uneven surface shape is formed on one surface of the resin base film, In this case, it is preferable to arrange a polarizer on the resin base film side. The resin base film may be a single layer film or a multilayer film. For example, at least one transparent resin layer made of a transparent resin, a transparent binder resin, and the transparent binder resin It may be a multilayer film having at least one light diffusion layer containing fine particles having different refractive indexes.

(Resin base film having a light diffusion layer)
The resin base film having the light diffusion layer may have a three-layer structure in which the light diffusion layer is sandwiched between two transparent resin layers, or a transparent resin layer and a light diffusion layer laminated thereon. Although it may be a two-layer structure, a three-layer structure is preferable. In the case of a two-layer structure, the surface of the light diffusion layer is exposed on either side of the resin base film, the surface smoothness is deteriorated, and the micro uneven shape of the hard coat layer is unexpectedly affected. This is because there is a possibility that inconveniences such as bonding bubbles may occur when the film is used while being bonded to an image display device. In addition, it is possible to obtain a resin base film composed of a laminate of three or more layers by alternately arranging transparent resin layers and light diffusion layers so that the surface of the light diffusion layer is not exposed. In view of the above, a three-layer structure is preferable.

  The transparent resin used for the transparent resin layer and the transparent binder resin used for the light diffusing layer are preferably optically transparent resins, and examples thereof include the materials used for the protective film previously. Such as cellulose acetate resin such as triacetyl cellulose, polyester resin such as polyethylene terephthalate, acrylic resin such as polymethacrylate, polycarbonate resin, amorphous cyclic polyolefin using norbornene compound as monomer, etc. A plastic resin is mentioned. The transparent resin used for the transparent resin layer and the transparent binder resin used for the light diffusion layer may be the same or different from each other. Among these resins, it is preferable to use an acrylic resin having excellent transparency and weather resistance and high surface hardness. As the acrylic resin, a methacrylic resin is essential, and a material obtained by mixing an additive or the like as required and melt-kneading is used.

  The methacrylic resin is a polymer mainly composed of methacrylic acid ester, and may be a homopolymer of one kind of methacrylic acid ester, or a co-polymer of methacrylic acid ester with other methacrylic acid ester or acrylic acid ester. It may be a polymer. As the methacrylic acid ester, alkyl methacrylate is preferable, and examples thereof include methyl methacrylate, ethyl methacrylate, and butyl methacrylate, and the alkyl group usually has about 1 to 4 carbon atoms. Moreover, as an acrylic ester which can be copolymerized with a methacrylic ester, an alkyl acrylate is preferable, and examples thereof include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. The number of carbons is usually about 1-8. In addition to these, the copolymer contains an aromatic vinyl compound such as styrene which is a compound having at least one polymerizable carbon-carbon double bond in the molecule, a vinyl cyanide compound such as acrylonitrile, and the like. Also good.

  The acrylic resin preferably contains acrylic rubber particles from the viewpoint of impact resistance and film forming property of the film. The amount of acrylic rubber particles that can be contained in the acrylic resin is preferably 5% by weight or more, more preferably 10% by weight or more. The upper limit of the amount of the acrylic rubber particles is not critical, but if the amount of the acrylic rubber particles is too large, the surface hardness of the film is lowered, and when the film is subjected to surface treatment, it is resistant to the organic solvent in the surface treatment agent. Solvent property decreases. Therefore, the amount of acrylic rubber particles that can be contained in the acrylic resin is preferably 80% by weight or less, and more preferably 60% by weight or less.

  The acrylic rubber particles are particles having an elastic polymer mainly composed of an acrylate ester as an essential component, and may be of a single layer structure consisting essentially of this elastic polymer, or this elastic polymer. May be a multi-layer structure having a single layer. Specifically, as this elastic polymer, 50 to 99.9% by weight of an alkyl acrylate and at least one kind of other vinyl monomer copolymerizable therewith, 0 to 49.9% by weight, A cross-linked elastic copolymer obtained by polymerization of a monomer comprising 0.1 to 10% by weight of a polymerizable cross-linkable monomer is preferably used.

  Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and the alkyl group usually has about 1 to 8 carbon atoms. Examples of other vinyl monomers copolymerizable with alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule. More specifically, methacrylic acid Examples thereof include methacrylic acid esters such as methyl, aromatic vinyl compounds such as styrene, and vinylcyan compounds such as acrylonitrile. Examples of the copolymerizable crosslinkable monomer include a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule. (Meth) acrylates of polyhydric alcohols such as (meth) acrylate and butanediol di (meth) acrylate, alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate and methallyl (meth) acrylate, divinyl Benzene is mentioned. In this specification, (meth) acrylate refers to methacrylate or acrylate, and (meth) acrylic acid refers to methacrylic acid or acrylic acid.

  In addition to the acrylic rubber particles, the acrylic resin may contain usual additives such as ultraviolet absorbers, organic dyes, pigments, inorganic dyes, antioxidants, antistatic agents, and surfactants. . Among these, an ultraviolet absorber is preferably used for improving weather resistance. Examples of the ultraviolet absorber include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (5 -Methyl-2-hydroxyphenyl) -2H-benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di -Tert-butyl-2-hydroxyphenyl) -2H-benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5 -Di-tert-butyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-tert-amyl-2-hydroxypheny ) Benzotriazole ultraviolet absorbers such as -2H-benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) -2H-benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2- Hydroxy-4-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4, Examples include 2-hydroxybenzophenone ultraviolet absorbers such as 4′-dimethoxybenzophenone; salicylic acid phenyl ester ultraviolet absorbers such as p-tert-butylphenyl salicylic acid ester and p-octylphenyl salicylic acid ester. It may be used two or more of these. When the acrylic resin contains an ultraviolet absorber, the amount is usually 0.1% by weight or more, preferably 0.3% by weight or more, and preferably 2% by weight or less.

  The internal haze of the resin base film having the light diffusion layer is usually 5% or more, preferably 10% or more. By setting the internal haze to 5% or more, glare can be eliminated, and by setting it to 10% or more, glare can be more effectively eliminated. Further, the internal haze of the resin base film is usually 30% or less. When the internal haze of the resin base film exceeds 30%, when applied to an image display device, the screen becomes dark as a result, and the visibility tends to be impaired. In order to ensure sufficient brightness, the internal haze is preferably 20% or less. The resin base film should have a smooth surface and substantially no external haze.

  The fine particles dispersed in the light diffusion layer are inorganic particles such as calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, and zinc oxide, and fatty acids in these inorganic particles. Inorganic particles such as those that have been surface-treated may be used, but inorganic particles generally have a large particle size distribution and are not easily dispersed in a transparent binder resin. It is preferable to use resin particles because the difference in refractive index between the two tends to decrease the light transmittance. The refractive index of the fine particles needs to have a value different from the refractive index of the transparent binder resin in order to provide a light diffusion function, and the refractive index difference between the two is 0.01 or more. Is preferred. In order to ensure an appropriate internal haze value, it is preferable not to make this difference in refractive index very large. For example, the difference in refractive index between the two is preferably less than 0.02. The refractive index of the fine particles is appropriately selected in consideration of the type of the transparent binder resin used and the like, but when using the transparent binder resin as described above, the refractive index of the fine particles is 1.43 or more and 1.55 or less. It is preferable to select from a range. When an acrylic resin is used for the transparent binder resin, since the refractive index of the acrylic resin is generally about 1.49, the refractive index of the fine particles is from about 1.47 to 1.51. It is preferable to select so as to satisfy the above conditions.

  The fine particles are preferably spherical or nearly spherical considering the isotropic and uniformity of scattering. In addition, particles having fine irregularities on the surface and amorphous particles are not preferable because unexpected scattering may occur due to structures such as fine irregularities on the surface smaller than the particle size. . The weight average particle diameter of the fine particles is preferably 4 μm or more and 20 μm or less, and more preferably 5 μm or more and 12 μm or less. When the weight average particle diameter of the fine particles is less than 4 μm, the scattered light intensity on the wide angle side increases, and as a result, when applied to an image display device, the contrast tends to decrease. Moreover, when the weight average particle diameter exceeds 20 μm, the required scattering effect may not be obtained, or it may be necessary to increase the thickness of the resin base film in order to obtain the required scattering effect.

  Specific examples of the fine particles preferably used include spherical or nearly spherical resin beads. Examples of suitable resin beads include melamine beads (refractive index 1.57), polymethyl methacrylate beads (refractive index). 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index 1.50 to 1.59), polycarbonate beads (refractive index 1.59), polyethylene beads (refractive index 1.53), polychlorinated Examples thereof include vinyl beads (refractive index 1.46) and silicone resin beads (refractive index 1.46).

  The fine particles in the light diffusion layer are preferably contained in an amount of 5 to 20 parts by weight with respect to 100 parts by weight of the transparent binder resin. If the content of the fine particles is less than 5 parts by weight, uniform and sufficient internal scattering cannot be obtained, and glare tends to occur when an antiglare film is obtained. On the other hand, if the content of fine particles exceeds 20 parts by weight, internal scattering increases, resulting in high haze, the screen becomes dark when applied to an image display device, and visibility is impaired. The scattered light intensity on the side also rises and tends to lower the contrast when applied to an image display device.

  The thickness of the resin base film having a light diffusion layer is preferably 30 μm or more and 250 μm or less, more preferably 40 μm or more and 170 μm or less. When the thickness of the resin base film is less than 30 μm, it may be difficult to obtain sufficient scattering characteristics. Moreover, it is not preferable that the thickness of the resin base film exceeds 250 μm from the viewpoint of the recent demand for thinning of the image display device, cost, and the like. From the viewpoint of reducing the thickness of the entire antiglare film, it is more preferably 150 μm or less, and further preferably 120 μm or less. The thickness of the transparent resin layer is not particularly limited, but can be, for example, 10 μm or more and 50 μm or less, and preferably 15 μm or more and 40 μm or less. The thickness of the light diffusion layer is not particularly limited, but can be, for example, 20 μm or more and 150 μm or less, and preferably 30 μm or more and 90 μm or less.

  The resin composition used for forming the light diffusion layer can be obtained by mixing a transparent binder resin (for example, methacrylic resin, acrylic rubber particles and other additives) and fine particles, and melt-kneading them.

  As a method for obtaining a resin base film from a resin composition containing fine particles constituting a transparent resin and a light diffusion layer constituting a transparent resin layer, a method using a feed block, a method using a multi-manifold die, etc. Various generally known methods can be used. Among them, for example, a method of laminating via a feed block, multilayer melt extrusion from a T die, and forming a film by contacting at least one side of the obtained laminated film material with a roll or a belt is a film having good surface properties. It is preferable at the point obtained. In particular, from the viewpoint of improving the surface smoothness and surface glossiness of the resin base film, a method of forming a film by bringing both surfaces of the laminated film obtained by the multilayer melt extrusion molding into contact with the roll surface or the belt surface Is preferred. In the roll or belt used in this case, the surface of the roll or belt in contact with the transparent resin constituting the transparent resin layer is preferably a mirror surface for imparting smoothness to the film surface.

(Hard coat layer)
The method for producing the hard coat layer with surface irregularities is not particularly limited. For example, a resin solution in which a filler is dispersed is applied onto a resin base film, and the coating film is adjusted to apply the filler. Examples thereof include a method of forming random irregularities by exposing the surface, and an embossing method disclosed in JP-A-2006-53371.

  When a hard coat layer is formed by applying a resin solution in which a filler is dispersed on a resin base film, the refractive index of the filler and the hard coat layer are adjusted in order to appropriately adjust the internal haze of the hard coat layer. It is necessary to adjust the ratio of the refractive index of the resin (hard coat resin) serving as the base material. Further, surface irregularities may be formed by dispersing porous silica secondary particles made of amorphous silica primary particles smaller than the wavelength of visible light (about 100 nm or less) in the hard coat resin. When the former method is used, since the hard coat resin often exhibits a refractive index of around 1.50, polymethyl methacrylate beads (refractive index 1.49) or methyl methacrylate / styrene copolymer resin beads (Refractive index 1.50 to 1.59), polyethylene beads (refractive index 1.53) and the like may be appropriately selected and used.

  As the resin in which the filler is dispersed, an ultraviolet curable resin, a thermosetting resin, an electron beam curable resin, or the like can be used, and an ultraviolet curable resin is preferably used from the viewpoint of productivity, hardness, and the like. A commercially available product can be used as the ultraviolet curable resin. For example, one or more polyfunctional acrylates such as trimethylolpropane triacrylate and pentaerythritol tetraacrylate, and “Irgacure 907”, “Irgacure 184” (above, manufactured by Ciba Specialty Chemicals), “ A mixture with a photopolymerization initiator such as “Lucirin TPO” (manufactured by BASF) can be used as an ultraviolet curable resin. For example, when an ultraviolet curable resin is used, after the filler is dispersed in the ultraviolet curable resin, the resin composition is applied to a resin base film and irradiated with ultraviolet rays, whereby the filler is contained in the hard coat resin. A dispersed hard coat layer can be formed.

  In the case of forming a hard coat layer having a fine uneven shape by an embossing method, as disclosed in the above Japanese Unexamined Patent Application Publication No. 2006-53371 or the like, a mold having a fine uneven shape is used. The shape may be transferred to a transparent resin film. The transfer to the mold-shaped film is preferably carried out by embossing, and UV embossing using an ultraviolet curable resin is preferred as embossing.

  In the UV embossing method, a UV curable resin layer is formed on the surface of a resin base film, and the UV curable resin layer is cured while being pressed against the rugged surface of the mold. Transferred to the resin layer. Specifically, an ultraviolet curable resin is applied on the resin base film, and the applied UV curable resin is adhered to the uneven surface of the mold, and ultraviolet rays are irradiated from the resin base film side. Then, the ultraviolet curable resin is cured, and then the shape of the mold is transferred to the ultraviolet curable resin by peeling the resin base film on which the cured ultraviolet curable resin layer is formed from the mold. The kind of ultraviolet curable resin is not particularly limited. Further, instead of the ultraviolet curable resin, a visible light curable resin that can be cured with visible light having a wavelength longer than that of ultraviolet light may be used by appropriately selecting a photoinitiator.

  The thickness of the hard coat layer is not particularly limited, but is preferably 2 μm or more and 20 μm or less. If the thickness of the hard coat layer is less than 2 μm, sufficient hardness cannot be obtained and tends to be easily scratched. If the thickness is greater than 20 μm, the film tends to break or the film curls due to curing shrinkage of the hard coat layer. As a result, productivity tends to decrease.

  The surface haze of the hard coat layer is usually 15% or less from the viewpoint of suppressing whitening, and is preferably 5% or less in order to more effectively suppress whitening. However, when it is less than 0.5%, it is not preferable because sufficient antiglare property is not exhibited. In addition, as described above, since the resin base film is provided with the ability to prevent glare due to scattering, the internal haze of the hard coat layer having fine unevenness is essentially unnecessary, and internal scattering In order to control the characteristics and the reflection characteristics independently, it is preferable that the characteristics are substantially zero.

A low reflection film may be provided on the uneven surface side of the hard coat layer. Even in the absence of a low reflection film, a sufficient antiglare function is exhibited, but the antiglare property can be further improved by providing a low reflection film on the outermost surface. The low reflection film can be formed by providing a layer of a low refractive index material having a lower refractive index on the hard coat layer. Specific examples of such a low refractive index material include lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), aluminum fluoride (AlF ₃ ), cryolite (3NaF · AlF ₃ or Na ₃ AlF _6). ) And other inorganic low-reflective materials containing acrylic resin, epoxy resin, etc .; fluorine-based or silicone-based organic compounds, thermoplastic resins, thermosetting resins, UV-curable resins, etc. An organic low reflection material can be mentioned.

(Polarizer)
The polarizing plate of the present invention is formed by laminating a protective film on at least one surface of a polarizer. This polarizing plate is generally manufactured in a size larger than a predetermined shape by laminating a protective film on at least one surface of a polarizer via an adhesive, and then cut into a predetermined shape. Is done. As the adhesive, an ultraviolet curable adhesive such as epoxy or acrylate may be used, or a water based adhesive such as polyvinyl alcohol or urethane may be used, but UV curable in terms of productivity and quality. It is preferable to use an adhesive. The cutting method is not particularly specified, but may be a general film cutting method using a super cutter, a Thomson type punching machine, a cross cutter, a guillotine blade cutting machine, or the like. Further, a cutting method using a laser beam as disclosed in JP 2008-051964 A may be used.

  The shape of the polarizing plate obtained by cutting is appropriately selected depending on the shape of the liquid crystal panel screen to be applied, but since the screen shape of the liquid crystal panel is usually a rectangular shape, it is usually a rectangular shape. It is. Further, this rectangular shape may be composed of two sides parallel to the stretching direction of the polarizer and two sides perpendicular to the stretching direction of the polarizer, and is not parallel to the stretching direction of the polarizer. It may consist of four sides.

  And in this invention, about the polarizing plate cut | disconnected by the predetermined shape obtained in this way, in the polarizer part of the end surface which is not parallel to the extending | stretching direction of a polarizer among the end surfaces (cut surface), ie, a polarizer end surface, it is long. The number of cracks having a thickness of 50 μm or more is expressed as an average value per 100 mm length in the direction parallel to the polarizer surface, and is 10 or less. In this way, in the polarizer portion of the predetermined end face, by reducing long cracks, the polarizer is exposed to an environment change such as a high temperature environment, a low temperature environment, or a high temperature environment and a low temperature environment. A polarizing plate which is difficult to tear and has excellent display quality reliability can be obtained. The number of cracks defined above is preferably 5 or less, more preferably 1 or less, and even more preferably substantially zero.

  The number of cracks specified above is the number of cracks having a length of 50 μm or more, and the number of cracks having a length of 50 μm or more is observed for all of the end faces of the polarizing plate that are not parallel to the stretching direction of the polarizer. Divide by the total length (mm) of the observed end face in the direction parallel to the polarizer surface and multiply the quotient by 100. For example, if the polarizing plate is cut into a rectangular shape composed of two sides parallel to the stretching direction of the polarizer and two sides perpendicular to the stretching direction of the polarizer, Count the number of cracks with a length of 50 μm or more in the polarizer portions on the two end faces along the two vertical sides, and divide the number by the sum of the lengths of the two sides perpendicular to the stretching direction of the polarizer. And multiply by 100. Further, if the polarizing plate is cut into a rectangular shape consisting of four sides that are not parallel to the stretching direction of the polarizer, the four end faces along the four sides, that is, the polarizer part of all the end faces, The number of cracks having a length of 50 μm or more is counted, the number is divided by the sum of the lengths of the four sides, that is, the entire circumference, and multiplied by 100.

  Since the crack usually exists in the form of a line or band in a direction substantially parallel to the polarizer surface, the length of the line or band may be set as the length of the crack. The number of cracks having a length of 50 μm or more is 10 or less per arbitrary section having a length of 100 mm in the direction parallel to the polarizer surface in the polarizer portion on the end face not parallel to the stretching direction of the polarizer. Preferably, it is 5 or less, more preferably 1 or less.

  In order to satisfy the number of cracks specified above, at least the end face that is not parallel to the stretching direction of the polarizer among the end faces of the polarizing plate is cut to remove the cracks on the end face that have occurred during cutting or the like. At that time, depending on the material of the polarizing plate and the state of the end face, etc., the cutting amount is increased or the number of times of cutting is increased more carefully than the known polarizing plate end face cutting. Need to do. As a cutting method, for example, a method of cutting end surfaces of a plurality of stacked polarizing plates with a rotary blade as disclosed in Patent Documents 1 and 2 is preferably employed in terms of production efficiency.

  In the cutting process, it is preferable to sandwich the cut polarizing plate with a resin plate of the same size and cut the entire resin plate together because the end of the polarizing plate is fixed and it is difficult to generate cracks. The resin plate is preferably a soft material, for example, a polystyrene sheet. In order to suppress stress during cutting, it is preferable to use a resin plate having a thickness of at least 1 mm. The upper limit of the thickness is not particularly established, but is preferably 20 mm or less in consideration of productivity, polishing scraps, and the like.

(Image display device)
The image display device of the present invention is a combination of the polarizing plate of the present invention and an image display element. Here, the image display element is typically a liquid crystal panel having a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates and displaying an image by changing the alignment state of the liquid crystal by applying a voltage. The polarizing plate of the present invention can be applied to various known displays such as a display panel, a CRT display, and an organic EL display. The protective film laminated on one surface of the polarizer is an antiglare film in which a hard coat layer having a fine uneven surface shape is formed on one surface of the resin base film, and the resin base film side When applying the polarizing plate of the present invention in which a polarizer is disposed in an image display device, the polarizing plate is disposed on the viewing side of the image display element with the hard coat layer side facing outside. In addition, although a polarizing plate is normally bonded to an image display element with an adhesive, formation of the adhesive layer on the polarizing plate may be performed before cutting the polarizing plate. As described above, the image display device including the polarizing plate of the present invention is resistant to tearing the polarizer even when it is exposed to a high temperature environment, a low temperature environment, or an environment change that repeats a high temperature environment and a low temperature environment. Excellent in reliability.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
(A) Production of Resin Base Film An acrylic resin containing 30 parts by weight of acrylic rubber particles in 70 parts by weight of a copolymer of methyl methacrylate / methyl acrylate = 96/4 (weight ratio) (refractive index 1.49). Resin and methyl methacrylate / styrene copolymer beads (refractive index 1.505, weight average particle diameter 8 μm) are mixed with a Henschel mixer so that the beads are 15 parts by weight with respect to 100 parts by weight of the acrylic resin. Then, the mixture was melt-kneaded with a first extruder (screw diameter 65 mm, uniaxial, with a vent (manufactured by Toshiba Machine Co., Ltd.)) and supplied to the feed block. In addition, an acrylic resin in which 30 parts by weight of acrylic rubber particles are contained in 70 parts by weight of a copolymer (refractive index 1.49) of methyl methacrylate / methyl acrylate = 96/4 (weight ratio) is second extruded. The mixture was melt-kneaded with a machine (screw diameter: 45 mm, uniaxial, with vent (manufactured by Hitachi Zosen)) and supplied to the feed block. The resin supplied to the feed block from the first extruder becomes a light diffusion layer (intermediate layer), and the resin supplied to the feed block from the second extruder becomes a transparent resin layer (surface layer: both sides) Co-extrusion molding was performed at 265 ° C., and a three-layer resin base film having a thickness of 80 μm (intermediate layer 50 μm, surface layer 15 μm × 2) was produced through a roll unit set at 85 ° C.

(B) Production of antiglare film On one surface of the resin base film produced in (A) above, a coating solution containing an ultraviolet curable resin, fine particles, a photopolymerization initiator and an organic solvent was applied, and after drying, An antiglare film was produced by irradiating ultraviolet rays to form a hard coat layer having fine irregularities.

(C) Preparation of polarizing plate A polarizer comprising an iodine-stained polyvinyl alcohol stretched film is prepared, and the surface opposite to the hard coat layer of the antiglare film prepared in (B) above is prepared on one side of the polarizer. A norbornene resin film (Optes Co., Ltd. “ZEONOR FILM”) is bonded to the other side of the film via an ultraviolet curable adhesive, and UV light is irradiated from the norbornene resin film surface to obtain a polarizing plate. Got. Further, the norbornene-based resin film surface of this polarizing plate was subjected to corona treatment to form an acrylic pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive-attached polarizing plate.

(D) Cutting the polarizing plate The polarizing plate with the adhesive prepared in the above (C) is 212.2 mm in the super-cutter ("NS1200" manufactured by Hadano Seiki Seisakusho Co., Ltd.) with the short side extending in the direction of the polarizer. The chip was cut into a rectangular shape so that the long side was 370.6 mm in the direction perpendicular to the stretching direction. The blade of the super cutter was inserted from the hard coat layer surface (the surface opposite to the adhesive layer).

(E) Cutting processing of polarizing plate 25 to 30 polarizing plates (hereinafter referred to as chip-cut products) chip-cut in the above (D) are laminated, and two polystyrene plates (4 mm thick) of the same size as the chip-cut products are used. I caught it. In addition, it is sandwiched between two 363.3 mm x 205.2 mm metal pressers, and adjusted so that the four sides of the chip-cut product and polystyrene plate protrude 2 mm or more from the end of the presser. It was mounted on the base of “NCP22-2B” manufactured by Iron Works.

  Adjust the three blades so that the cutting amount of the rotary blade is 0.7mm for the first blade, 0.2mm for the second blade, and 0.1mm for the third blade on one rotary disk of the fly-cut cutting machine. Three sets, i.e., nine were installed. Subsequently, the chip-cut product and polystyrene laminate previously mounted on the pedestal were cut at a rotational speed of 5520 rotations / minute of the rotating disk and a feed rate of 650 mm / minute of the pedestal. At this time, two facing end faces of the laminate were simultaneously cut. The following evaluations were performed on the chip-cut products after cutting (hereinafter referred to as test pieces) obtained in this way, and the results are shown in Table 1.

(End face condition)
The state of the end face of the test piece was visually observed. The case where stickiness due to the pressure-sensitive adhesive was seen was rated as x, and the case where it was not seen was marked as ◯.

(Number of cracks on the end face of the polarizer)
One piece is taken out from the test piece, and the polarizer part of the end surface along the two long sides is observed with an optical microscope ("Microscope HMX800" manufactured by Keyence Corporation) at a magnification of 100 to 500 times. The number of cracks having a length of 50 μm or more was counted, the number was divided by the sum of the two long side lengths (mm), and multiplied by 100 to obtain the number of cracks per 100 mm long side (pieces / 100 mm). The same applies to cracks having a length of less than 50 μm.

(An endurance test)
Ten sheets were taken out from the test pieces and bonded to glass (Corning 0.7 mm) through the adhesive layer. Bonding was performed using Haltec (“Haltec HAL650” manufactured by Sankyo Co., Ltd.), and the test pieces were bonded to both the front and back surfaces of the glass in order to prevent the test pieces from shrinking due to heat shrinkage. Subsequently, these were put into a heat shock oven (“TSA301L-W” manufactured by ESPEC), and a heat shock test was performed by repeating a cycle of −35 ° C./1 hour and 70 ° C./1 hour 120 times. The observation was performed using a backlight or a three-wavelength tube fluorescent lamp in a dark room. When one or more polarizers having a length of 2 mm or more were observed, the test piece was considered to have been torn.

<Example 2>
In the production (A) of the resin base film, the same operation as in Example 1 was performed except that the roll unit was changed to a more elastic type. About the obtained test piece, evaluation similar to Example 1 was performed and the result was shown in Table 1.

<Comparative Example 1>
Other than adjusting the blade so that the cutting amount of the rotary blade of the fly-cut cutting machine is 0.2 mm for the first blade, 0.2 mm for the second blade, and 0.1 mm for the third blade in the polarizing plate cutting (E) The same operation as in Example 1 was performed. About the obtained test piece, evaluation similar to Example 1 was performed and the result was shown in Table 1.

<Comparative example 2>
In Example 1, the process was performed until the polarizing plate was cut (D) and the polarizing plate was not cut (E). The test piece was evaluated in the same manner as in Example 1, and the results are shown in Table 1. .

<Comparative Example 3>
In Example 2, the test was performed until the polarizing plate was cut (D) and the polarizing plate was not cut (E). The test piece was evaluated in the same manner as in Example 1, and the results are shown in Table 1. .

<Reference example>
In the cutting process (E) of the polarizing plate, the same operation as in Example 1 was performed except that the feed rate of the pedestal was changed to 428 mm / min. By slowing down the feed rate of the pedestal, the contact time between the end face of the chip-cut product and the blade became longer, the temperature of the chip-cut product became high, and the end face was fused and deformed, so the operation was stopped.

Claims (9)

  A polarizing plate in which a protective film is laminated on at least one surface of a polarizer and is cut into a predetermined shape, and a crack having a length of 50 μm or more is formed in a polarizer portion on an end surface that is not parallel to the stretching direction of the polarizer. The polarizing plate is characterized in that the number is 10 or less in terms of an average value per 100 mm length in a direction parallel to the polarizer surface.   The polarizing plate according to claim 1, wherein an end surface that is not parallel to the stretching direction of the polarizer is cut.   The polarizing plate according to claim 1 or 2, which is cut into a rectangular shape.   The protective film laminated on one surface of the polarizer is an antiglare film in which a hard coat layer having a fine uneven surface shape is formed on one surface of the resin base film, and the resin base film side The polarizing plate in any one of Claims 1-3 by which the polarizer is arrange | positioned.   The polarizing plate according to claim 4, wherein the resin base film is a multilayer film having a transparent resin layer, a transparent binder resin, and a light diffusion layer containing fine particles having a refractive index different from that of the transparent binder resin.   The polarizing plate according to claim 5, wherein the transparent resin constituting the transparent resin layer is an acrylic resin.   The polarizing plate according to claim 5 or 6, wherein the transparent binder resin is an acrylic resin.   An image display apparatus comprising the polarizing plate according to claim 1 and an image display element.   An image display device comprising the polarizing plate according to any one of claims 4 to 7 and an image display element, wherein the polarizing plate is disposed on the viewing side of the image display element with the hard coat layer side facing outside.