JP2008197310A - Thin polarizing plate, composite polarizing plate, image display device, and method for manufacturing composite polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin polarizing plate using a viscous adhesive agent which has removability immediately after formation, excels in work efficiency in stacking on an adherend such as a retardation film, and excels in transparency, exhibits good adhesion to the adherend and excels also in durability after hardening treatment, and a thin composite polarizing plate in which a retardation film is stacked thereon, and to apply the same to an image display device. <P>SOLUTION: The polarizing plate is a polarizing plate 10 in which a viscous adhesive layer 2 is disposed on at least one surface of a polarizer 1, and the composite polarizing plate is a composite polarizing plate in which a retardation film 6 is stacked on the viscous adhesive layer 2, wherein the viscous adhesive layer 2 is formed on the polarizer 1 in a thickness of 1-30 μm from a mixture consisting primarily of an adhesive base polymer-containing adhesive composition, a polymerizable compound and a polymerization initiator, and the viscous adhesive layer 2 exhibits removability immediately after formation but adheres tightly by hardening treatment after stacking the retardation film 6. An image display device is obtained by combining such composite polarizing plates 15, 16 with an image display element 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate used in an image display device such as a liquid crystal display device, a composite polarizing plate obtained by laminating a retardation film thereon, and an image display device in which any of them is arranged. The polarizing plate of the present invention achieves good durability at the same time with a thin configuration, and is excellent in workability when laminated so that the optical axis of the adherend is at a predetermined angle with respect to the polarization axis of the polarizer. In particular, it is suitable for various image display devices for mobile use for the purpose of reducing the thickness of the module itself. The present invention also relates to a method for manufacturing the above-described composite polarizing plate.

  Conventionally, liquid crystal display devices have been used in desktop calculators, electronic timepieces, and the like, but their use has been rapidly expanding in recent years. That is, liquid crystal display devices have been used from mobile devices such as mobile phones to large televisions regardless of screen size. In addition to liquid crystal display devices, organic electroluminescence (organic EL) display devices also tend to increase mainly in mobile applications. The polarizing plates used in these image display apparatuses are not only in increasing demand but also required to have performance suitable for each application.

  The polarizing plate generally used in the image display apparatus as described above is a triacetyl cellulose film via a liquid adhesive on both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film. It is manufactured with the structure which laminated | stacked the transparent protective layer represented by. In this state, or if necessary, an image display such as a liquid crystal cell or an organic EL display element in a form in which various optical layers such as a retardation film and an optical compensation film having optical characteristics are bonded via an adhesive or an adhesive. Used by being attached to the element.

  FIG. 4 is a cross-sectional schematic view showing a general example of such a conventional polarizing plate and a composite polarizing plate having a retardation film laminated thereon. That is, the transparent protective layers 4 and 5 are provided on both surfaces of the polarizer 1 to constitute the polarizing plate 11. Further, a retardation film 6 is bonded to one transparent protective layer 5 side through a pressure-sensitive adhesive layer 3, and further, a pressure-sensitive adhesive layer 7 for bonding to an image display element or the like on the outer side. Are provided to constitute the composite polarizing plate 17. Typically, a separator 9a is provided outside the pressure-sensitive adhesive layer 7 to protect the surface temporarily until it is bonded to an image display element or the like.

  By the way, recently, in an image display device for mobile use such as a mobile phone, the whole module is being thinned and slimmed from the viewpoint of design and portability. As a matter of course, there is a demand for further thinning the polarizing plate used there. In addition, since mobile devices are used in various places due to the use of mobile devices, there is a demand for durability that is higher than the conventional one while having a thin configuration.

  In order to meet the demands for thinning as described above, if the polarizer or transparent protective layer of the polarizing plate is simply thinned, the polarizer has a characteristic that it is easy to tear in the stretching direction, and it is transparent via a liquid adhesive. In the method of laminating a protective layer, there is a limit in obtaining a thin and light polarizing plate from the viewpoint of handling at work.

  Therefore, instead of the configuration in which the transparent protective layers 4 and 5 are provided on both surfaces of the polarizer 1 as shown in FIG. 4, the transparent protective layer 5 on the side to be bonded to another optical film such as the retardation film 6 is provided. It has been known for some time that the polarizing plate is thinned by laminating another optical film such as the retardation film 6 directly on the polarizer 1 via a pressure-sensitive adhesive or an adhesive. The pressure-sensitive adhesive or adhesive used in such a configuration is strongly required to have excellent transparency as well as good adhesion to an adherend. Furthermore, when forming an elliptically polarized light or a circularly polarized light mode polarizing plate that is effective as a composite polarizing plate for mobile use, it is desired to have excellent workability in the lamination process.

  As an example of a pressure-sensitive adhesive (pressure-sensitive adhesive), JP-A-3-12471 (Patent Document 1) can be mentioned, which is composed of an acrylic polymer containing an acrylic acid alkyl ester as a component, and its crosslinking. A pressure sensitive adhesive is disclosed in which the degree is 50 to 95% by weight based on the gel fraction and the weight average molecular weight of the uncrosslinked polymer is 100,000 or more. The pressure-sensitive adhesive has removability, so it can be said that the workability in the lamination process is excellent, but it has poor durability such as heat resistance and moist heat resistance, and also has sufficient adhesion to the adherend. There is a problem that is not.

  On the other hand, as examples of liquid adhesives, JP-A 2000-199819 (Patent Document 2), JP-A 2000-321430 (Patent Document 3) and JP-A 2001-305345 (Patent Document 4) are listed. be able to. That is, Patent Document 2 discloses that a polarizing plate with a transparent thin film layer is formed by applying a resin solution with a solvent that does not dissolve the film on one or both sides of a polarizer made of a hydrophilic polymer. It also describes that a protective layer made of a transparent film is disposed on the transparent thin film layer. In Patent Document 3, a protective film made of a cyclic olefin resin is laminated on at least one surface of a polyvinyl alcohol polarizer through an adhesive made of a mixture of a polyvinyl alcohol adhesive and a two-component adhesive. A polarizing plate is disclosed. Patent Document 4 discloses a polarizing plate in which a protective film made of a norbornene resin is laminated on at least one surface of a polarizer made of a polyvinyl alcohol sheet via an aqueous polymer-isocyanate adhesive.

  When using such an adhesive and laminating a retardation film as a protective layer for a polarizer, the adhesive is in liquid form, and after coating and drying or curing, the retardation film is laminated. In the process, it becomes difficult to accurately align the optical axis of the retardation film with a predetermined angle with respect to the polarization axis of the polarizer, and in particular, an elliptically or circularly polarizing plate is formed. There is a problem that workability is not good.

  Therefore, in the field of polarizing plates for mobile applications that aim to reduce the thickness by reducing the number of constituent members, while maintaining thin and good durability, also in the laminating step with a polymer film or other optical layer having optical properties, Development of a thin polarizing plate using a pressure-sensitive adhesive or an adhesive that does not impair the workability, that is, a pressure-sensitive adhesive having the characteristics of the pressure-sensitive adhesive and the adhesive, is required.

  In addition, a photo-curing adhesive having both pressure-sensitive adhesive and adhesive properties is also known. For example, Japanese Patent Application Laid-Open No. 2004-118078 (Patent Document 5) discloses that a heat is applied to at least one surface of a polarizer. A photocurable adhesive comprising an adhesive composition containing a thermoplastic polymer, a photocationic polymerizable compound and a photocationic polymerization initiator on a polarizing plate laminated with a protective film made of a plastic saturated norbornene resin. It is disclosed that an agent layer is provided and irradiated with an active energy ray and then attached to an adherend.

Japanese Patent Laid-Open No. 3-12471 JP 2000-199819 A JP 2000-32430 A JP 2001-305345 A Japanese Patent Laid-Open No. 2004-118078

  An object of the present invention is to bond a retardation film that also serves as a protective layer to an polarizer via an adhesive layer, to solve the problems described above when obtaining a thin composite polarizing plate, and immediately after being formed Has removability and is excellent in workability in the step of laminating the optical axis of the adherend at a predetermined angle with respect to the polarization axis of the polarizer, and after being bonded by the curing process, Provided are a thin polarizing plate using an adhesive having excellent transparency and good adhesion to an adherend and excellent durability, and a thin composite polarizing plate having a retardation film laminated thereon. There is. Another object of the present invention is to apply these polarizing plate or composite polarizing plate to an image display device.

  In order to achieve the above object, the present invention has the characteristics of a pressure-sensitive adhesive having removability immediately after being formed, and is cured after being laminated with the adherend, so that the adherend is good. An adhesive that exhibits adhesiveness and also has the properties of an adhesive having excellent durability is used.

  Specifically, the polarizing plate of the present invention has a pressure-sensitive adhesive layer formed on at least one surface of a polarizer, and the pressure-sensitive adhesive layer includes a pressure-sensitive adhesive composition containing a sticky base polymer, polymerization. After forming the polymer film, the film is formed on the polarizer so as to have a thickness of 1 to 30 μm from the mixture containing the active compound and the polymerization initiator as the main components. It is comprised by what adhere | attaches firmly by the hardening process.

It is effective to provide the adhesive layer on one side of the polarizer and a protective layer made of a transparent resin film on the other side. In this polarizing plate, the polarizer can be composed of a polyvinyl alcohol-based resin film in which a dichroic dye such as iodine or a dichroic organic dye is adsorbed and oriented. The adhesive layer is cured by irradiation with active energy rays and / or heating, the shear modulus at 23 ° C. after curing is 5 × 10 ⁴ Pa or more, and the yellowness is 5 or less. Is preferred. Furthermore, it is preferable that a separator that has been treated with a release agent such as silicone is present on the exposed surface of the adhesive layer.

  Moreover, according to this invention, the composite polarizing plate by which the retardation film which serves as the function of a protective layer is arrange | positioned at the adhesive layer side of the polarizing plate which has the said adhesive layer is also provided. Thereby, it can be set as the thin composite polarizing plate of an elliptical or circular polarization mode. A normal pressure-sensitive adhesive layer may be provided on the surface of the retardation film opposite to the surface in contact with the adhesive layer.

  An optical layer exhibiting another optical function can be further laminated on the polarizing plate or the composite polarizing plate. For example, a polarizing plate in which the adhesive layer is provided on one side of the polarizer and a transparent protective layer is provided on the other side, or a composite polarizing plate in which a retardation film or the like is disposed on the adhesive layer side The plate may have a surface treatment layer such as a hard coat layer, an antireflection layer, or an antiglare layer (also referred to as an antiglare layer) on the opposite surface of the transparent protective layer in close contact with the polarizer.

  In addition, a polarizing plate in which the adhesive layer is provided on one side of the polarizer and a transparent protective layer is provided on the other side if necessary, or a composite in which a retardation film or the like is disposed on the adhesive layer side. In the polarizing plate, a reflective plate or a transflective plate is bonded to the side opposite to the surface of the polarizer in contact with the adhesive layer (on the outside when a transparent protective layer is provided) Alternatively, a transflective thin composite polarizing plate may be formed.

  Furthermore, a polarizing plate in which the adhesive layer is provided on one side of the polarizer and a transparent protective layer is provided on the other side if necessary, or a composite in which a retardation film or the like is disposed on the side of the adhesive layer In the polarizing plate, a brightness enhancement system can be used by attaching a brightness enhancement film to the opposite side of the polarizer in contact with the adhesive layer (or outside if a transparent protective layer is provided) A thin composite polarizing plate can also be formed.

  The image display device of the present invention includes an image display element such as a liquid crystal cell or an organic EL display element, and the polarizing plate or the composite polarizing plate. In this image display device, the polarizing plate or the composite polarizing plate is disposed on at least one surface of the image display element.

  According to the present invention, there is further provided a method for producing the above-described composite polarizing plate, which includes an adhesive composition containing an adhesive base polymer on at least one surface of a polarizer, a polymerizable compound, and a polymerization initiator. An adhesive layer having a thickness of 1 to 30 μm formed from a mixture containing as a main component is provided, a retardation film serving also as a protective layer is laminated on the adhesive layer, and then active energy rays The adhesive layer is cured by irradiation and / or heating.

  According to the present invention, the retardation film bonded to the polarizer through the adhesive layer also serves as a protective layer, has a thin structure and excellent durability, and can display an image even in a high-temperature and high-humidity environment. It is possible to obtain a thin composite polarizing plate that is less likely to cause appearance defects such as peeling and sliding that deteriorate the appearance quality of the apparatus. This is because a pressure-sensitive adhesive layer formed from a mixture mainly composed of a pressure-sensitive adhesive composition containing a pressure-sensitive base polymer, a polymerizable compound, and a polymerization initiator is provided on at least one surface of the polarizer. . Since the adhesive layer exhibits the characteristics of a pressure-sensitive adhesive having removability immediately after formation, circularly polarized light or elliptically polarized light in which the polarization axis of the polarizer and the optical axis of the retardation film form a predetermined angle. It is excellent in workability in the lamination process for producing a composite polarizing plate such as a mode, and also exhibits sufficient adhesion to the adherend and a high elastic modulus after curing. The deformation | transformation of the produced polarizer is suppressed, generation | occurrence | production of the malfunction between a polarizer and a polymer film is prevented, and favorable durability is obtained.

  The adhesive used in the present invention maintains its transparency even after curing, thereby reducing the possibility of impairing the display quality of the image display device, and reducing the pressure sensitive adhesive layer. The decrease in hardness that is likely to occur in the formed thin polarizing plate can be effectively prevented by the adhesive layer having a high elastic modulus.

  That is, the thin polarizing plate of the present invention can be easily laminated with an adhesive layer formed thereon to form an adherend having optical characteristics so as to form a predetermined axial angle, and also has durability. Has excellent characteristics. Therefore, it is particularly suitable for an image display device for mobile use. Further, by combining this with an image display element such as a liquid crystal cell or an organic EL display element, it is possible to contribute to thinning of the image display apparatus.

  Furthermore, the method for producing a composite polarizing plate according to the present invention includes the step of laminating a retardation film on an uncured adhesive layer by forming the adhesive layer as described above on a polarizer. In addition, the retardation film and the polarizer are firmly bonded to each other by facilitating the axial alignment and curing the adhesive layer after laminating the retardation film.

  Hereinafter, the present invention will be described in detail with appropriate reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate according to the present invention. Referring to FIG. 1, a polarizing plate 10 of the present invention is obtained by providing an adhesive layer 2 on at least one surface of a polarizer 1. The adhesive layer 2 is formed on the polarizer so as to have a thickness of 1 to 30 μm from a mixture containing an adhesive composition containing an adhesive base polymer, a polymerizable compound, and a polymerization initiator as main components. The film is formed in such a manner that it exhibits removability immediately after it is formed, but is composed of a material that is firmly bonded by a curing process after the polymer films are laminated.

  Although such an adhesive layer can be provided on both sides of the polarizer 1, in general, the adhesive layer 2 as described above is provided on one side of the polarizer 1, and the other side of the polarizer 1 is provided. It is advantageous to provide a protective layer 4 made of a transparent resin film. It is customary to place a separator 9 on the exposed surface of the adhesive layer 2 and temporarily protect the surface until it is bonded to another member.

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

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

  The polarizer 1 has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, and a dichroic dye being adsorbed. It is manufactured through a step of treating the polyvinyl alcohol resin film with an aqueous boric acid solution and a step of washing with water after the treatment with the aqueous boric acid solution. As the dichroic dye, iodine or a dichroic organic dye is used.

  The adhesive layer 2 provided on at least one surface of the polarizer 1 has a thickness of 1 to 30 μm from a mixture mainly composed of a pressure-sensitive adhesive composition containing a pressure-sensitive base polymer, a polymerizable compound and a polymerization initiator. Formed with. The adhesive layer 2 exhibits removability immediately after being formed, but after the separator 9 is peeled off and another adherend is laminated thereon, the adhesive layer 2 is cured by an appropriate curing treatment and is cured. Is firmly bonded.

  The pressure-sensitive adhesive composition used for forming the adhesive layer 2 has adhesiveness and compatibility with the polymerizable compound, and does not cause phase separation when mixed with the polymerizable compound. What is necessary is just to select suitably from the various adhesive composition conventionally used for the image display apparatus or the optical film for it. Examples thereof include those containing base polymers such as acrylic, urethane, polyester, rubber, silicone, cellulose, and epoxy. These pressure-sensitive adhesive compositions may be used alone or in combination of two or more. Among these, acrylic, urethane, and polyester that have been widely used for image display devices from the viewpoint of showing good adhesion to an adherend and excellent transparency before curing. Preferably selected from the system and used.

  The polymerizable compound is a photocurable or thermosetting compound comprising a monomer or oligomer containing a functional group that causes a polymerization reaction by a polymerization initiator activated by irradiation with active energy rays and / or heat treatment. Can be used without any particular restrictions. Also, the curing reaction is not particularly limited, but cationic polymerization is preferably used from the viewpoint of reactivity. Specific examples of the polymerizable compound include various compounds having a functional group such as an epoxy group, a vinyl ether group, a hydroxyl group, and an ethyleneimine group. In the present invention, an epoxy compound is particularly preferably used as the cationic polymerizable compound. Specifically, a bisphenol type epoxy resin which is a glycidyl ether of bisphenols such as bisphenol A, bisphenol F, and bisphenol S, Novolak type epoxy resin such as phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolak epoxy resin; glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, polyfunctional type such as epoxidized polyvinylphenol The epoxy resin can be mentioned.

  Next, the polymerization initiator will be described. In the present invention, the cationic polymerizable epoxy polymerizable compound is preferably used as described above. In order to cause the polymerization reaction to occur, it is preferable to add a cationic polymerization initiator. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays and / or heating, and initiates a ring-opening polymerization reaction of an epoxy group. Examples of the photocationic polymerization initiator activated by irradiation with active energy rays include aromatic iodonium salts, onium salts such as aromatic diazonium and salt aromatic sulfonium salts, and iron-allene complexes. it can. Examples of the thermal cationic polymerization initiator activated by heat treatment include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. It can be mentioned, but is not limited to these. These cationic polymerization initiators may be used alone or in admixture of two or more.

  Moreover, in addition to said polymerization initiator, a photosensitizer can also be used together as needed. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesion strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. These may be used alone or in combination.

  As described above, the pressure-sensitive adhesive composition comprising the pressure-sensitive adhesive composition containing the pressure-sensitive base polymer, the polymerizable compound, and the mixture containing the polymerization initiator as the main component is within the range not impairing the effects of the present invention. , Other additives such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, dyes, pigments, etc. Can be blended appropriately. Examples of the ion trapping agent include inorganic compounds such as powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof. Moreover, it can also be set as the adhesive agent which contains microparticles | fine-particles and shows light-scattering property.

  The method for forming the adhesive layer 2 on the surface of the polarizer 1 is not particularly limited. For example, the adhesive composition as described above is applied to one or both sides of the polarizer 1 to provide an adhesive. After the layer 2 is formed, a method of laminating a separator made of a resin film treated with a silicone-based release agent, or after forming the adhesive layer 2 on the separator as described above, It can be provided by a transfer method or the like. Moreover, when forming the adhesive agent layer 2 on the polarizer 1, as needed, it adheres to the surface (one side or both) to which the polarizer 1 or the adhesive agent layer 2 is bonded together. For example, a corona treatment or the like may be performed.

  The adhesive layer 2 is formed so as to have a thickness of 1 to 30 μm. From the viewpoint of thinning, which is the object of the present invention, and from the viewpoint of suppressing the insufficient curing reaction of the polymerizable compound and the decrease in transparency that are likely to occur when the thickness is increased, the range that does not impair the workability and durability. Therefore, it is preferable to form it thinly.

  It is preferable to provide the adhesive layer 2 as described above on one side of the polarizer 1 and the protective layer 4 made of a transparent resin film on the other side of the polarizer 1. As the protective layer 4, an appropriate transparent film can be used. Among these, a film made of a resin excellent in transparency, uniform optical properties, mechanical strength, thermal stability, etc. is preferably used. For example, cellulose resin films such as triacetyl cellulose and diacetyl cellulose, polyester resin films such as polyethylene terephthalate and polyethylene isophthalate, polybutylene terephthalate, acrylic resin films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate, Examples include, but are not limited to, polycarbonate-based resin films, polyethersulfone-based resin films, polysulfone-based resin films, polyimide-based resin films, polyolefin-based resin films, and cyclic olefin-based resin films containing cyclic olefins such as norbornene. Is not to be done. An adhesive or a pressure sensitive adhesive can be used for bonding the protective layer 4 and the polarizer 1.

  A surface treatment layer such as a hard coat layer, an antireflection layer, or an antiglare layer may be provided on the surface of the protective layer 4 as necessary. The hard coat layer is formed to prevent scratches on the surface of the polarizing plate, and is mainly composed of an ultraviolet curable resin, for example, an acrylic or silicone resin, and the adhesion to the transparent protective layer 4. Those having excellent hardness are appropriately selected and can be formed on the surface of the transparent protective layer 4.

  The antireflection layer is formed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be formed by a known method. The anti-glare layer is formed to prevent disturbance of visibility caused by external light reflected on the surface of the polarizing plate, for example, a roughening method such as a sand blast method or an embossing method, In general, the surface of the transparent protective layer 4 is formed to have a concavo-convex structure by a method of applying and curing a coating liquid in which transparent fine particles are mixed with an ultraviolet curable resin.

  The polarizing plate 10 of the present invention configured as described above can be formed into a composite polarizing plate by arranging a retardation film on the adhesive layer 2 side. FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of the composite polarizing plate according to the present invention. A composite polarizing plate 15 shown in FIG. 2 has a retardation film 6 disposed on the adhesive layer 2 side in a state where the separator 9 is peeled off from the polarizing plate 10 shown in FIG. A pressure-sensitive adhesive layer 7 is provided on the surface of the retardation film 6, and the surface is temporarily protected by a separator 9 a.

  The phase difference film 6 can be comprised with various resin which was illustrated previously as resin which comprises the protective layer 2. As shown in FIG. The retardation film 6 is preferably selected to have the required characteristics, that is, its birefringence is optically uniform. The protective function of the polarizer 1 and compensation of the retardation by the liquid crystal panel (meaning viewing angle compensation) Is also used for the purpose. For example, those conventionally used in image display devices can be used without limitation, birefringent films made of stretched films of various transparent polymers, discotic liquid crystals and nematic liquid crystals are aligned and fixed. Examples include a film and a film substrate on which the liquid crystal layer is formed. When the liquid crystal layer is fixed on the film substrate, a cellulose resin film such as triacetyl cellulose is preferably used as the film substrate for supporting the oriented liquid crystal layer.

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

  The phase difference film 6 can be freely selected from the types of films made of the above-described materials according to practical needs. If necessary, the protective layer 4 provided on the side opposite to the adhesive layer 2 of the polarizer 1 can be composed of a polymer film having a phase difference.

  In particular, in the case of an elliptically polarized light or circularly polarized light mode composite polarizing plate used for an image display device for mobile use, a λ / 2 plate or a λ / 4 plate is effectively used. The elliptically or circularly polarized light composite polarizing plate is an elliptical or circularly polarized light when the incident polarized light is linearly polarized light, and a linearly polarized light when the incident polarized light is elliptically or circularly polarized light. It has a function to change. In particular, as a phase difference plate capable of changing elliptically polarized light or circularly polarized light into linearly polarized light and linearly polarized light into elliptically polarized light or circularly polarized light, it is called a λ / 4 plate, and has a phase difference of ¼ wavelength with respect to the wavelength of incident light. What is shown is used. The λ / 2 plate has a function of changing the direction of linearly polarized light. Furthermore, a λ / 2 plate and a λ / 4 plate are laminated so that the optical axes intersect at a predetermined angle to form a broadband λ / 4 plate that exhibits a phase difference of ¼ wavelength over a wide wavelength range. You can also.

  The elliptically polarizing mode composite polarizing plate is effective for preventing a coloring phenomenon caused by liquid crystal birefringence in a liquid crystal display device, and the circular polarizing mode composite polarizing plate is a reflective or transflective image. In a display device, it is effectively used for the purpose of improving luminance. The circular polarization mode composite polarizing plate also has an antireflection function.

  Next, a curing process for curing the adhesive layer 2 will be described. In the case of curing by irradiation with active energy rays, light is usually used, and examples thereof include visible light, ultraviolet rays, X-rays, electron beams, etc. Among them, relatively high energy can be obtained. It is preferable to use ultraviolet rays having an emission distribution at a wavelength of 400 nm or less. The ultraviolet light source is not particularly limited, and for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, or the like can be used.

  In irradiating the active energy ray, the above light or light source may be used alone for irradiation, or two or more types may be used in combination. When irradiating using two or more types of light sources, any combination of simultaneous irradiation or sequential irradiation may be used. Further, in order to accelerate the curing reaction, heat treatment may be used in combination, and the heat treatment in that case may be performed simultaneously with the irradiation of active energy rays, or may be performed before or after irradiation of active energy rays. Good. Although the temperature of heat processing is not specifically limited, For example, about 30-100 degreeC is preferable.

  In the case of curing by heating, it can be heated by a generally known method, and the conditions are not particularly limited, but usually a thermal cationic polymerization initiator blended in the adhesive composition is used. What is necessary is just to heat to the temperature more than the temperature which generate | occur | produces a cationic seed | species and a Lewis acid. However, if the heating temperature exceeds 100 ° C., defects due to thermal expansion or contraction of the polarizer or protective layer constituting the polarizing plate are likely to occur. The temperature range of 30 to 100 ° C. is preferably used.

  Further, the adhesive layer 2 in the present invention exhibits the characteristics of a pressure-sensitive adhesive having removability immediately after being formed, and is laminated with an adherend, for example, a retardation film 6 also serving as a protective layer. After that, it is bonded by a curing treatment and exhibits good adhesion to the adherend. Therefore, the curing treatment is preferably performed after the protective layer, for example, the retardation film 6 is laminated on the adhesive layer 2 to form the composite polarizing plate 15, and particularly the irradiation of active energy rays is performed on the adhesive layer. 2 is preferably performed from the side of the retardation film 6 laminated on the substrate 2. If the active energy ray to be used is transmissive, the pressure sensitive adhesive layer 7 or other optical layer in which the separator 9a is in close contact with the retardation film 6 is laminated, and then from these layers side You may irradiate an active energy ray.

  Furthermore, the adhesive force before curing of the adhesive in the present invention may be an adhesive force that can be fixed without peeling off the retardation film 6 laminated on the adhesive layer 2. In other words, it is only necessary to have close contact with the contact pressure of a normal pressure-sensitive adhesive, and there is no particular limitation on the numerical value. However, after curing, it is preferable to exhibit high adhesion from the viewpoint of high durability, and after curing, the adhesive layer 2 is firmly bonded to the adhesive layer 2 in a range that does not cause defects such as cracks and cracks in handling operations and the like. Like that.

The above adhesive layer 2 preferably exhibits a shear modulus of 5 × 10 ⁴ Pa or more after the curing treatment. The shear modulus can be determined from the result of a shear tensile test, as shown in the examples described later. A pressure-sensitive adhesive used for a normal polarizing plate has a shear modulus of about 2.5 × 10 ⁴ Pa at most, but in the present invention, shearing of the adhesive layer 2 after curing is performed. By setting the elastic modulus to a value higher than that of a normal pressure-sensitive adhesive, it is possible to suppress the expansion and contraction of the polarizer that occurs in a high-temperature and high-humidity environment. That is, appearance defects such as sliding and peeling that are likely to occur at the end portion of the composite polarizing plate after the durability test is less likely to occur. The upper limit of the shear modulus is not particularly limited, and may be about 10 ⁶ Pa, for example.

  The adhesive layer 2 preferably has a yellowness (YI) of 5 or less, more preferably 3 or less practically after the above curing treatment. Usually, a curable pressure-sensitive adhesive or adhesive may turn yellow depending on the resin or initiator used, the degree of curing treatment, and the like. In the image display device application, if this yellowness is increased, the display quality may be adversely affected. Therefore, it is preferable to reduce the yellowness as much as possible. Yellowness can be measured by the method specified in JIS K 7105-1981. In this case, the smaller the yellowness is, the more preferable, especially 0.

  The composite polarizing plate 15 in which the retardation film 6 is laminated via the adhesive layer 2 according to the present invention is disposed on the surface opposite to the side of the retardation film 6 that is bonded to the adhesive layer 2. The pressure-sensitive adhesive layer 7 can be provided for lamination on an image display element or for lamination on another optical layer. Further, the exposed surface of the pressure-sensitive adhesive layer 7 preferably has a separator 9a treated with a silicone-based release agent.

  The pressure-sensitive adhesive layer 7 provided on the outside of the retardation film 6 may be a common one conventionally used for an image display device or an optical film therefor. For example, those based on acrylic polymers, silicone polymers, polyesters, polyurethanes, and the like can be used. Above all, like acrylic pressure-sensitive adhesives, it has excellent optical transparency, moderate wettability and cohesion, excellent adhesion to substrates, and weather resistance and heat resistance. It is preferable to select and use one that does not cause peeling problems such as floating and peeling under the conditions of heating and humidification.

  The pressure-sensitive adhesive layer 7 may contain fine particles for imparting light scattering properties as necessary, and is filled with glass fiber, glass beads, resin beads, metal powder, other inorganic powders, or the like. An agent, a pigment, a colorant, an antioxidant, an ultraviolet absorber and the like may be blended. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

  The pressure-sensitive adhesive layer 7 is formed by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40% by weight solution, which is the surface of the retardation film 6. A pressure-sensitive adhesive layer is formed on a separator made of a polymer film that has been treated directly with a release agent such as a silicone, and then transferred onto the retardation film 6. It can be done by a method to do. The thickness of the pressure-sensitive adhesive layer 7 is determined according to the adhesive force and the like, but is usually in the range of 1 to 50 μm.

  The method of laminating the polarizing plate 10 on which the adhesive layer 2 is formed and the retardation film 6 is not particularly limited, and may be laminated by a conventionally known technique. For example, a method of laminating the optical axis of the retardation film 6 so as to be orthogonal or parallel to the polarization axis of the polarizer 1 using a bonding roll or the like, or the polarization axis of the polarizer 1. The method of laminating | stacking so that the optical axis of the phase difference film 6 may become a predetermined angle is mentioned. In particular, the composite polarizing plate 15 of the present invention is effectively used in forming a circularly polarized light or an elliptically polarized light mode in which the polarization axis of the polarizer 1 and the optical axis of the retardation film 6 are laminated at a predetermined angle.

  Moreover, the polarizing plate or composite polarizing plate according to the present invention can be laminated with one or more optical layers exhibiting other optical functions when used. The optical layer is not particularly limited, and examples thereof include a reflective layer, a transflective layer, a light diffusion layer, a retardation plate, a light collector, and a brightness enhancement film.

  The reflective composite polarizing plate is used in a liquid crystal display device of a type that reflects incident light from the viewing side and displays it. Since a light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. The transflective composite polarizing plate is used in a liquid crystal display device that displays as a reflective type in a bright place and as a transmissive type using a light source such as a backlight in a dark place. The reflective layer for making a reflective composite polarizing plate can be formed, for example, by attaching a foil or a vapor deposition film made of a metal such as aluminum to the protective layer 4 on the polarizer 1. In addition, the semi-transmissive reflective layer for making a semi-transmissive reflective type composite polarizing plate is a method of using the reflective layer as a half mirror, or a light-transmitting reflective plate containing a pearl pigment or the like. It can be formed by the method to do.

  On the other hand, the diffusion type composite polarizing plate has a function of diffusing incident light. For example, a method of performing a mat treatment on the protective layer 4 on the polarizer 1, and applying a resin containing fine particles A light diffusing layer having a fine concavo-convex structure is formed on the surface by using various methods such as a method of bonding a film containing fine particles.

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

  Examples of the phase difference plate include the same ones as described for the phase difference film 6 with reference to FIG.

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

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

  The various optical layers as described above are integrated with a polarizing plate or a composite polarizing plate using a pressure-sensitive adhesive or an adhesive, but the pressure-sensitive adhesive or the adhesive used for this purpose is not particularly limited, and is appropriately selected. What is necessary is just to select and use. It is preferable to use a pressure-sensitive adhesive from the viewpoint of easy bonding work and prevention of optical distortion. As an example of a pressure sensitive adhesive, the thing similar to having demonstrated the pressure sensitive adhesive layer 7 previously with reference to FIG. 2 can be mentioned. In addition, when the formed pressure-sensitive adhesive layer is exposed on the surface, a separator is preferably disposed for preventing contamination. The same separator as described above is used as the separator.

  The polarizing plate or the composite polarizing plate of the present invention can be arranged in various image display elements to form an image display device. For example, it can be arranged on one or both sides of a liquid crystal cell to form a liquid crystal display device. The liquid crystal cell used is arbitrary. For example, a liquid crystal display using various liquid crystal panels such as an active matrix driving type represented by a thin film transistor type and a simple matrix driving type represented by a super twisted nematic type. A device can be formed. When the composite plate or the composite polarizing plate of the present invention is provided on both sides of the liquid crystal cell, both may be the same or different.

  FIG. 3 is a schematic sectional view showing an example in which the composite polarizing plate according to the present invention is mounted on a liquid crystal panel. In this example, the state in which the separator 9a is peeled off from the composite polarizing plate 15 shown in FIG. 2 is attached to one side (upper side in the figure) of the liquid crystal cell 20 through the pressure-sensitive adhesive layer 7, and On the other surface of the liquid crystal cell 20 (the lower side of the figure), the pressure-sensitive adhesive layer 7 / the retardation film 6 / the adhesive layer 2 / the polarizer 1 / the transparent protective layer 4 are laminated in this order (in this state) Further, a composite polarizing plate 16 in which another optical layer 8 is laminated on the outside of the composite polarizing plate 16 is attached via the pressure-sensitive adhesive layer 7. The liquid crystal display device of this example is provided on the lower side of the figure when the upper side of the figure is the viewing side and the backlight is arranged. In this case, the other optical layer 8 can be a reflective layer, a transflective layer, a light collector, a brightness enhancement film, or the like.

  Furthermore, the composite polarizing plate of the present invention is also effectively used in a circularly polarized or elliptically polarized mode having an antireflection function in an image display device other than a liquid crystal display device, for example, a flat display such as an organic EL display device. Of course, the image display device to which the polarizing plate or the composite polarizing plate of the present invention is applied is not limited to those exemplified here.

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

[Example 1]
A protective film made of a 45 μm thick triacetyl cellulose film having a hard coat layer on the surface of a polarizer made of a 25 μm thick film in which iodine is adsorbed and oriented on polyvinyl alcohol is formed of polyvinyl alcohol and a water-soluble epoxy. A polarizing plate bonded with an adhesive made of an aqueous solution containing a resin was prepared.

  Separately, an adhesive solution comprising a mixture of a pressure-sensitive adhesive composition based on a polyester resin, a bisphenol-type epoxy photopolymerizable compound, and an iodonium-based cationic photopolymerization initiator is used as a silicone-based release agent. The film was coated on a 38 μm thick polyethylene terephthalate film (separator) using a bar coater and dried to obtain a sheet-like adhesive. The thickness of the adhesive layer was 10 μm after drying. The sheet-like adhesive obtained here was bonded to the polyvinyl alcohol film side of the polarizing plate to produce a thin polarizing plate with an adhesive corresponding to FIG.

[Example 2]
After separating the separator from the thin polarizing plate obtained in Example 1, a retardation film made of a norbornene resin having a thickness of 40 μm and an in-plane retardation of 140 nm on the adhesive layer surface [Sekisui Chemical Co., Ltd. ) “Essina Film”: trade name] was laminated using a laminator so that its optical axis was 45 degrees counterclockwise with respect to the polarizing absorption axis of the polarizing plate. Next, an acrylic pressure-sensitive adhesive having a thickness of 25 μm is formed on the retardation film side, and a separator made of a polyethylene terephthalate film that has been subjected to a release treatment is laminated thereon. The thin composite polarizing plate corresponding to FIG. 2 was produced by irradiating and curing ultraviolet rays with an integrated light quantity of 000 mJ / cm ² . The total thickness of the obtained thin composite polarizing plate was 147 μm excluding the outermost separator.

[Comparative Example 1]
Instead of the sheet-like adhesive used in Example 1, an acrylic pressure-sensitive adhesive (referred to as pressure-sensitive adhesive A) is formed to a thickness of 15 μm on a separator made of a polyethylene terephthalate film subjected to a release treatment. This was used, and this was bonded to the polyvinyl alcohol film side of the same polarizing plate used in Example 1 to produce a thin polarizing plate. Also, after peeling the separator from the thin polarizing plate, the same retardation film, acrylic pressure-sensitive adhesive, and separator as used in Example 2 were sequentially applied to the pressure-sensitive adhesive surface of Example 2 and A thin composite polarizing plate was produced by laminating in the same procedure. The total thickness of the obtained thin composite polarizing plate was 153 μm excluding the outermost separator.

[Comparative Example 2]
Instead of the sheet-like adhesive used in Example 1, an acrylic pressure-sensitive adhesive (referred to as pressure-sensitive adhesive B) is formed to a thickness of 15 μm on a separator made of a polyethylene terephthalate film subjected to a release treatment. This was used, and this was bonded to the polyvinyl alcohol film side of the same polarizing plate used in Example 1 to produce a thin polarizing plate. Also, after peeling the separator from the thin polarizing plate, the same retardation film, acrylic pressure-sensitive adhesive, and separator as used in Example 2 were sequentially applied to the pressure-sensitive adhesive surface of Example 2 and A thin composite polarizing plate was produced by laminating in the same procedure. The total thickness of the obtained thin composite polarizing plate was 152 μm excluding the outermost separator.

[Comparative Example 3]
On one side of a polarizer made of the same polyvinyl alcohol film as used in Example 1, a protective film made of a triacetyl cellulose film having a thickness of 45 μm having a hard coat layer on the surface has no hard coat layer. A polarizing plate was prepared in which a protective film made of a 40 μm thick triacetyl cellulose film having no hard coat layer was bonded to each surface via an adhesive made of an aqueous solution containing polyvinyl alcohol and a water-soluble epoxy resin. The same pressure sensitive adhesive A as used in Comparative Example 1 was bonded to the triacetyl cellulose film side having no hard coat layer to produce a polarizing plate with a pressure sensitive adhesive. Further, after peeling the separator, the same retardation film, acrylic pressure-sensitive adhesive, and separator as used in Example 2 were sequentially laminated on the pressure-sensitive adhesive surface in the same procedure, and combined. A polarizing plate was produced. The composition of this composite polarizing plate is a typical example of a conventional composite polarizing plate that is usually commercially available. The total thickness of the obtained composite polarizing plate was 193 μm excluding the outermost separator.

  The properties of the adhesive and pressure-sensitive adhesive used in the above Examples and Comparative Examples, and the performance of the obtained composite polarizing plate were evaluated according to the following methods. Table 1 shows the properties of the adhesive and the pressure-sensitive adhesive, and Table 2 shows the evaluation results of the composite polarizing plate.

[Shear modulus of adhesive or pressure sensitive adhesive]
Cut the polarizing plate with the adhesive or pressure sensitive adhesive formed (before laminating the retardation film) into a size of 50 mm x 10 mm, and only 10 mm of the long side of 50 mm is made into glass Paste (bonding area is 100 mm ² ). In the case of the adhesive of Example 1, in this state, it is cured by irradiating with ultraviolet rays with an integrated light amount of 1,000 mJ / cm ² from the glass surface side, and then at a temperature of 50 ° C. and a pressure of 0.5 MPa. After carrying out an autoclave treatment for 20 minutes, it is used for measurement of shear modulus. On the other hand, in the case of the pressure-sensitive adhesive of the comparative example, after being autoclaved at a temperature of 50 ° C. and a pressure of 0.5 MPa for 20 minutes while being bonded to glass as described above, the shear modulus was measured. To serve. Using a tensile test device (Autograph manufactured by Shimadzu Corporation), one chuck grips the end of the polarizing plate, the other chuck grips the glass, the distance between chucks is 10 cm, and the pulling speed is 0.2 mm / A tensile test is performed under the conditions of a temperature of 23 ° C., a stress-strain curve is obtained, a tangent is drawn at the initial rise of the curve, and a shear modulus is obtained from the inclination.

[Yellowness of adhesive or pressure sensitive adhesive (YI)]
The adhesive of Example 1 is bonded to soda glass in the state of being formed on the separator, irradiated with ultraviolet light with an integrated light amount of 1,000 mJ / cm ² from the separator side, cured, and measured for yellowness. Sample for use. Moreover, the pressure-sensitive adhesive of a comparative example is bonded to soda glass in a state where it is formed on a separator to obtain a yellowness measurement sample. For these samples, the spectral transmittance at a wavelength of 380 to 780 nm was measured using a spectrophotometer (“UV-2450” manufactured by Shimadzu Corporation), and X, Y according to JIS K 7105-1981. , Z tristimulus values are obtained, and yellowness (YI) is obtained by the following equation based on these values.

[Adhesion of adhesive or pressure sensitive adhesive]
The same hard coat of a polarizing plate as that used in Comparative Example 3, in which a triacetyl cellulose film having a hard coat layer on one side of a polarizer and a triacetyl cellulose film having no hard coat layer on the other side were bonded to each other The adhesive or pressure-sensitive adhesive on the separator used in Examples and Comparative Examples is attached to the triacetylcellulose film side having no layer, and cut into a size of 25 mm × 250 mm. Separately, the same retardation film (“Essina film”) as used in Examples and Comparative Examples is bonded to soda glass through an acrylic pressure-sensitive adhesive. After the separator is peeled off from the polarizing plate to which the above adhesive or pressure sensitive adhesive is attached, it is attached onto the retardation film attached to the soda glass. In the case of the adhesive of Example 1, in this state, a sample that was autoclaved for 20 minutes at a temperature of 50 ° C. and a pressure of 0.5 MPa (before curing), and 1,000 mJ / cm ² from the soda glass side. A sample (after curing) is prepared by irradiating and curing with ultraviolet light at an integrated light quantity of, followed by autoclaving at a temperature of 50 ° C. and a pressure of 0.5 MPa for 20 minutes. On the other hand, in the case of the pressure-sensitive adhesive of the comparative example, autoclaving is performed for 20 minutes at a temperature of 50 ° C. and a pressure of 0.5 MPa while being bonded to the retardation film as described above. After autoclaving, let stand for 1 day, and then use a tensile tester (Autograph made by Shimadzu Corporation) and phase difference film (“Essina Film”) according to JIS K 6854-2: 1999 180 degree peel test (gripping movement speed 300mm / min) so that it peels between the adhesive layer and the pressure-sensitive adhesive layer or pressure-sensitive adhesive layer. Adhesive strength of the adhesive or pressure-sensitive adhesive (N / 25mm) )

[Pencil hardness of composite polarizing plate]
After the composite polarizing plates obtained in Example 2 and Comparative Examples 1 to 3 were attached to the glass on the respective pressure-sensitive adhesive sides, the pencil scratch value (in accordance with JIS K 5600-5-4: 1999) Measure pencil hardness).

[Durability evaluation of composite polarizing plate]
When the composite polarizing plates obtained in Examples and Comparative Examples are viewed from the triacetyl cellulose film side where no adhesive or pressure sensitive adhesive is formed, the polarizing absorption axis of the polarizing plate is 0 degree with respect to the long side. Cut to a diagonal size of 3.0 inches (approx. 7.6 cm) and affix to a glass plate with a thickness of 0.7 mm, then autoclave for 20 minutes at a temperature of 50 ° C. and a pressure of 0.5 MPa. I do. Each sample is then subjected to a heat test in which it is placed in an oven kept at a temperature of 85 ° C. and kept for 500 hours, and a wet heat test in which it is placed in an oven at a temperature of 60 ° C. and a relative humidity of 90% and kept for 500 hours. After the test, the sample is taken out of the oven, and the presence or absence of appearance defects (peeling, decoloring, film interlayer sliding, etc.) at the film edge is visually observed, and the appearance quality is evaluated according to the following criteria.

(Evaluation criteria)
◯: Level at which no defects are observed at the film edge and there is no practical problem.
Δ: A slight defect is observed at the edge of the film, but at a practically acceptable level.
X: Level at which defects are clearly seen at the edge of the film and is not practically acceptable.

  As is apparent from Table 1, the adhesive used in the polarizing plate of Example 1 and the composite polarizing plate of Example 2 was used in a comparative example for a retardation film as a protective layer immediately after being formed. Since it has the same adhesive strength as the pressure sensitive adhesives A and B, it can be re-peeled. On the other hand, after curing, the adhesive layer causes cohesive failure of the adhesive layer, and the adherend It was confirmed that a high adhesion force was exhibited with respect to (retardation film). Furthermore, this adhesive had a yellow level after curing at the same level as the acrylic pressure-sensitive adhesive used in the comparative example.

  Further, as is clear from the results of durability evaluation shown in Table 2, in the thin composite polarizing plate of Example 2 using an adhesive, the adhesive after curing is an adherend (retardation film). It exhibits good adhesion to and exhibits high elasticity, so it has good durability without causing any defects in appearance quality even when placed in high temperature and high humidity environments. Was confirmed. Furthermore, since the cured adhesive has a higher elastic modulus than the pressure-sensitive adhesive, it has been found that it has a pencil hardness equivalent to that of a conventional polarizing plate, despite having a thinned configuration. .

  On the other hand, in the composite polarizing plates of Comparative Example 1 and Comparative Example 2 using the pressure sensitive adhesive A or B, an interlayer slip (between the polarizer and the retardation film) of about 400 μm from the peripheral part in a heating test at 85 ° C. In the wet heat test at 60 ° C., a decolorization phenomenon of about 500 μm was observed from the periphery. Further, the composite polarizing plate having the conventional structure of Comparative Example 3 is at a level that is practically acceptable in both the 85 ° C. heating test and the 60 ° C. wet heat test, but the above-described range is about 200 μm from the peripheral portion. A defect was observed.

  From the above results, in the polarizing plate and the composite polarizing plate of the present invention, the adhesive layer formed on the polarizer shows good adhesion to the adherend after curing and has a high elastic modulus. Therefore, it has been confirmed that, while adopting a thin configuration, it has higher durability than a conventional polarizing plate or a composite polarizing plate. Further, it was found that, even after being cured, transparency was maintained, and the pencil hardness was comparable to that of a conventional polarizing plate or composite polarizing plate due to the properties of the adhesive.

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the polarizing plate which concerns on this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the composite polarizing plate which concerns on this invention. It is a cross-sectional schematic diagram which shows the example which mounted | wore the liquid crystal panel with the composite polarizing plate of this invention. It is a cross-sectional schematic diagram which shows the general example of the conventional polarizing plate and the composite polarizing plate which laminated | stacked retardation film on it.

Explanation of symbols

1 ... Polarizer,
2 ... Adhesive layer,
3. Pressure sensitive adhesive layer (conventional),
4, 5 ... Transparent protective layer,
6 ... retardation film,
7 …… Pressure sensitive adhesive layer,
8 …… Other optical layers,
9, 9a …… Separator,
10 …… Polarizing plate,
11 …… Polarizing plate (conventional),
15, 16 ... Composite polarizing plate,
17 …… Composite polarizing plate (conventional),
20: Liquid crystal cell.

Claims (8)

  A polarizing plate in which an adhesive layer is formed on at least one surface of a polarizer, wherein the adhesive layer includes an adhesive composition containing an adhesive base polymer, a polymerizable compound, and a polymerization initiator Is formed on the polarizer so as to have a thickness of 1 to 30 μm, and exhibits removability immediately after being formed, but it is stronger by the curing treatment after laminating the polymer films. A polarizing plate characterized by adhering to the film.   The polarizing plate according to claim 1, wherein the adhesive layer is provided on one side of the polarizer, and a protective layer made of a transparent resin film is provided on the other side of the polarizer.   The polarizing plate according to claim 1, wherein the polarizer is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film. The adhesive layer is cured by irradiation with active energy rays and / or heating, and has a shear elastic modulus at 23 ° C. of 5 × 10 ⁴ Pa or more after curing and a yellowness of 5 or less. The polarizing plate in any one of -3.   5. A composite polarizing plate, wherein a retardation film that also functions as a protective layer is laminated on the adhesive layer side of the polarizing plate according to claim 1.   An optical layer exhibiting another optical function is laminated on the polarizing plate or the composite polarizing plate according to any one of claims 1 to 5.   An image display device comprising: an image display element; and the polarizing plate or the composite polarizing plate according to claim 1.   At least one surface of the polarizer is provided with a pressure-sensitive adhesive layer having a thickness of 1 to 30 μm formed from a pressure-sensitive adhesive composition containing a pressure-sensitive base polymer, a polymerizable compound, and a mixture mainly composed of a polymerization initiator. A composite film comprising: a retardation film having a protective layer function laminated on the adhesive layer; and then curing the adhesive layer by irradiation with active energy rays and / or heating. Manufacturing method of polarizing plate.

Images