JP2010277018A - Polarizing plate excellent in durability, method of manufacturing the same, and image display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-durability polarizing plate 10, which includes a polarizer 1 that will not break, even by sudden temperature change and having a transparent protective layer 2 formed on its one side and an adhesive layer 6 formed on its the other side, and is stuck and used to an image display element 20 via the adhesive layer 6. <P>SOLUTION: The transparent protective layer is formed on one side of the polarizer formed of a polyvinyl alcohol resin film; while on the other side of the polarizer, the adhesive layer is formed or an adhesive layer, a transparent polymer film and the adhesive layer are formed, in this order. After being cut into a desired shape, the polarizing plate is used by being stuck to the image display element via the outermost side adhesive layer; and the polarizing plate is cut into the desired shape by laser beams with a wavelength of 9.4 μm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polarizing plate used in an image display device such as a liquid crystal display device, and an image display device using the same. More specifically, the present invention relates to a thin polarizing plate excellent in durability against a rapid temperature change, and an image display device using the same.

  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. An image display device is obtained by bonding to the element.

  FIG. 4 is a schematic cross-sectional view showing a general example in the case where such a conventional polarizing plate and a retardation film are laminated thereon. That is, the transparent protective layers 2 and 2 a are provided on both surfaces of the polarizer 1 to constitute the polarizing plate 16. In the case of distribution in this state, usually, an adhesive layer 8 for bonding to an image display element or the like is provided on at least one side (in the figure, transparent protective layer 2a side), and further to the image display element or the like on the outside thereof. A separator (not shown) is provided for temporarily protecting the surface until the substrates are bonded. In addition, the retardation film 3 is bonded to the transparent protective layer 2a side of the polarizing plate 16 via the pressure-sensitive adhesive layer 8, and a pressure-sensitive adhesive layer 8a for bonding to an image display element or the like is further formed on the outside thereof. Provided and may be distributed as a polarizing plate 17 with a retardation film. In general, a separator 9 is provided outside the pressure-sensitive adhesive layer 8a to temporarily protect the surface of the pressure-sensitive adhesive layer 8a until it is bonded to an image display element or the like.

  By the way, in recent years, 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 reduction in thickness and weight of the polarizing plate used there. In addition, because of the wide variety of places of use due to the mobile use, there is a demand for durability that is higher than the conventional one while being thin and light.

  In order to meet the demands for thinning and weight reduction as described above, if the polarizer or the 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 an adhesive is used. In the method of laminating a transparent protective layer, there is a limit to obtaining a thin and light polarizing plate from the viewpoint of handling at work. Moreover, it replaces with the structure which provides the transparent protective layers 2 and 2a on both surfaces of the polarizer 1 as shown in FIG. 4, and is transparent on the side bonded to other optical films, such as an image display element or retardation film 3. The protective layer 2a is omitted, and a pressure-sensitive adhesive layer is provided directly on the polarizer 1, or another optical film such as a retardation film 3 is laminated via an adhesive or a pressure-sensitive adhesive to reduce the thickness of the polarizing plate. There are also attempts to do this. However, in this case, particularly when placed in a high temperature environment, there has been a problem that the dimensional change accompanying the expansion and contraction of the polarizer 1 becomes large and the durability is not always sufficient.

  On the other hand, the proposal which replaces the triacetyl cellulose film as a transparent protective layer with other resin is also made conventionally. For example, in JP 2000-199819 A (Patent Document 1), a transparent thin film layer is provided 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 is also disclosed that a protective layer made of a transparent film is disposed on the transparent thin film layer. Japanese Patent Application Laid-Open No. 2000-321430 (Patent Document 2) discloses that a cyclic olefin is formed on at least one surface of a polyvinyl alcohol polarizer via an adhesive composed of a mixture of a polyvinyl alcohol adhesive and a two-component adhesive. A polarizing plate in which a protective film made of a resin is laminated is disclosed. JP-A-2001-305345 (Patent Document 3) discloses a protective film made of norbornene resin on at least one surface of a polarizer made of polyvinyl alcohol sheet with an aqueous polymer-isocyanate adhesive interposed therebetween. A laminated polarizing plate is disclosed.

  If the transparent film thru | or the cyclic olefin-type resin film (norbornene-type resin film also substantially synonymous) disclosed by these patent documents 1-3 is comprised with what has a function of retardation film, it will affix on an image display element. By reducing the number of members, a thin polarizing plate can be obtained. However, when an adhesive is used for laminating the polarizer and the transparent polymer film, the adhesive is applied to the polarizer and dried or cured, and then the polymer film is laminated. Since it is difficult to stack the optical axis at a certain angle with respect to the polarizer axis, it is easy to form an elliptical or circular polarization mode polarizing plate that is particularly useful for mobile image display devices. There is a problem to do.

  Furthermore, it is also known that the norbornene resin film as described above is bonded to a polarizer using an adhesive. For example, JP-A-6-51117 (Patent Document 4) discloses a polarizing plate in which a thermoplastic saturated norbornene resin film is laminated as a protective layer on at least one surface of a polarizer. Japanese Patent Application Laid-Open No. 8-43812 (Patent Document 5) includes a polarizing plate in which protective films are laminated on both sides of a polarizer, and at least one of the protective films has a function of a retardation film at the same time. As an example of a protective film having a retardation film function, a thermoplastic norbornene-based resin is cited. In these Patent Documents 4 and 5, as an adhesive used for laminating a polarizer and a norbornene resin film, natural rubber, synthetic rubber / elastomer, vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate, Examples thereof include modified polyolefin resin adhesives. However, both publications are limited to the description of the method for forming the pressure-sensitive adhesive layer or the method for laminating with the protective layer, and it can be said that the purpose of forming the thin polarizing plate is realized, but in terms of improving the durability, Specific adhesive properties or effects are not specified.

  In particular, as described above, a pressure-sensitive adhesive layer is directly provided on one side of a polarizer, and the pressure-sensitive adhesive layer is bonded to an image display element, or on one side of a polarizer, a retardation film or the like is interposed via a pressure-sensitive adhesive layer. When another optical film is laminated, an adhesive layer is provided on the outer side, and the outermost adhesive layer is bonded to the image display element, the polarizer shrinks when exposed to a high temperature environment. Along with this, the end of the polarizing plate swelled, and the screen display may be distorted. For this reason, in the field of mobile use polarizing plates that are reduced in thickness and weight by reducing the number of components, it is desired to maintain thin and good durability.

JP 2000-199819 A JP 2000-32430 A JP 2001-305345 A JP-A-6-511117 JP-A-8-43812

For this reason, the present inventors have formed a transparent protective layer on one side of a polarizer comprising a polyvinyl alcohol-based resin film, and an adhesive layer is formed on the other side of the polarizer, or an adhesive layer, transparent The polymer film and the pressure-sensitive adhesive layer are formed in this order, and are bonded to the image display element through the outermost pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer to be bonded to the image display element is 23 to 80. When using a material having a storage elastic modulus of 0.15 to 10 MPa in the temperature range of ° C. and providing this pressure-sensitive adhesive layer on the surface to be bonded to the device, it should be given good durability in a high temperature environment. It was found that even when exposed to a high-temperature environment in a state of being bonded to the glass constituting the image display element, it is possible to suppress the rise of the polarizing plate end due to the contraction of the polarizer. It was filed.
The polarizing plate is an excellent one having the above characteristics, but a transparent protective layer is formed on one side of a polarizing plate having the above configuration, that is, a polarizer made of a polyvinyl alcohol-based resin film. The pressure-sensitive adhesive layer is formed or formed in the order of the pressure-sensitive adhesive layer, the transparent polymer film and the pressure-sensitive adhesive layer, and a polarizing plate having a structure to be bonded to the image display element via the outermost pressure-sensitive adhesive layer, In a so-called polarizing plate having a transparent protective layer only on one side of the polarizer, the polarizing plate is cut into a desired shape when the polarizing plate is bonded to the image display element. In the method, when a sudden temperature change (heat shock) is applied when used as a liquid crystal display device, the polarizer constituting the polarizing plate may be cracked. In there was a problem.

An object of the present invention is to provide a polarizing plate in which a transparent protective layer is formed on one side of a polarizer and an adhesive layer is formed on the other side of the polarizer, and is bonded to an image display element via the adhesive layer. Alternatively, a transparent protective layer is formed on one side of the polarizer, and on the other side of the polarizer, an adhesive layer, a transparent polymer film, and an adhesive layer are formed in this order, with the outermost adhesive layer interposed therebetween. The purpose of the present invention is to provide a polarizing plate that is bonded to an image display element and has excellent durability against a rapid temperature change, in which the polarizer is substantially free of cracks even after being subjected to a rapid temperature change. And Another object of the present invention is to apply this polarizing plate to an image display device.

  In order to achieve the above object, the present invention provides a transparent protective layer formed on one side of a polarizer comprising a polyvinyl alcohol-based resin film, and an adhesive layer is formed on the other side of the polarizer, or an adhesive. A polarizing plate is formed in the order of a layer, a transparent polymer film, and an adhesive layer, and after being cut into a desired shape, is bonded to an image display element through the outermost adhesive layer. In the state where the outermost pressure-sensitive adhesive layer was applied to the glass, when it was subjected to a durability test of 100 cycles with a continuous operation of cooling at a temperature of -45 ° C for 30 minutes and then heating at a temperature of 85 ° C for 30 minutes, An object of the present invention is to provide a polarizing plate substantially free from cracks generated from the end of the polarizer forming the polarizing plate.

  Moreover, in the above, this invention provides the polarizing plate characterized by using the laser for the cutting process to the desired polarizing plate shape.

  Moreover, in the above, this invention provides the polarizing plate characterized by the laser wavelength used for a cutting process being 9.4 micrometers.

  Further, in the present invention, a transparent protective layer is formed on one side of a polarizer comprising a polyvinyl alcohol-based resin film, and an adhesive layer is formed on the other side of the polarizer, or an adhesive layer, a transparent polymer film. The polarizing plate is formed in the order of the pressure-sensitive adhesive layer and is cut into a desired shape and then bonded to the image display element through the outermost pressure-sensitive adhesive layer, and is cut into the desired shape. In a state where the outermost pressure-sensitive adhesive layer is stuck on glass, cooling is performed at a temperature of −45 ° C. for 30 minutes, followed by heating at a temperature of 85 ° C. for 30 minutes as one cycle. The present invention provides a method for producing a polarizing plate in which cracks generated from the end of the polarizer forming the polarizing plate do not substantially exist when a cycle durability test is performed.

  The present invention also provides a method for producing a polarizing plate, characterized in that, in the above method for producing a polarizing plate, a laser wavelength used for cutting is 9.4 μm.

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 any one of the above polarizing plates. In this image display device, the pressure-sensitive adhesive layer on the outermost side of the polarizing plate is bonded to the image display element.

  In the polarizing plate of the present invention, a transparent protective layer is formed on one side of a polarizer made of a polyvinyl alcohol-based resin film, and an adhesive layer is formed on the other side of the polarizer, or an adhesive layer, a transparent The polarizing plate is formed in the order of the molecular film and the pressure-sensitive adhesive layer, and is used after being cut into a desired shape and bonded to the image display element through the outermost pressure-sensitive adhesive layer. A polarizing plate is formed when a 100 cycles endurance test is performed with a continuous operation of cooling at a temperature of −45 ° C. for 30 minutes and then heating at a temperature of 85 ° C. for 30 minutes with the pressure-sensitive adhesive layer applied to glass. It is possible to provide a polarizing plate excellent in durability against a rapid temperature change in which cracks generated from the end to the inside of the polarizer do not substantially exist, and the present invention further comprises a polyvinyl alcohol resin film. A transparent protective layer is formed on one side of the polarizer, and a pressure-sensitive adhesive layer is formed on the other side of the polarizer, or a pressure-sensitive adhesive layer, a transparent polymer film, and a pressure-sensitive adhesive layer are formed in this order. An outermost polarizing plate that is used after being cut into a shape and then bonded to the image display element via the outermost adhesive layer, and is characterized by performing a desired shape with a laser. When the endurance test of 100 cycles was carried out with one continuous cycle of cooling at a temperature of −45 ° C. for 30 minutes and then heating at a temperature of 85 ° C. for 30 minutes with the adhesive layer of It is possible to provide a polarizing plate excellent in durability against a rapid temperature change in which cracks generated from the end of the polarizer to be formed do not substantially exist.

It is a cross-sectional schematic diagram which shows the example of the laminated constitution of the polarizing plate which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram which shows the example of the laminated constitution of the polarizing plate which concerns on another embodiment of this invention. It is a cross-sectional schematic diagram which shows the example which mounted | wore the liquid crystal panel with the polarizing plate of this invention. It is a cross-sectional schematic diagram which shows the example of a layer structure about the conventional polarizing plate. The cross-sectional photograph after the cutting | disconnection of the test piece A is shown. The cross-sectional photograph after cutting | disconnection of the test piece B is shown.

  Hereinafter, the present invention will be described in detail with appropriate reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view illustrating an example of a layer configuration of a polarizing plate according to an embodiment of the present invention. With reference to FIG. 1, a polarizing plate 10 according to this embodiment has a transparent protective layer 2 formed on one side of a polarizer 1 and an adhesive layer 6 provided on the other side of the polarizer 1. And the adhesive layer 6 is comprised by what shows the storage elastic modulus of 0.15-10 MPa in the temperature range of 23-80 degreeC. It is customary to place a separator 9 on the exposed surface of the pressure-sensitive adhesive layer 6 and temporarily protect the surface until it is bonded to another member.

  FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate according to another embodiment of the present invention. With reference to FIG. 2, a polarizing plate 11 according to this embodiment forms a transparent protective layer 2 on one side of a polarizer 1, and an adhesive layer 7 and a transparent polymer film 3 on the other side of the polarizer 1. , And the pressure-sensitive adhesive layer 6 are provided in this order. And the adhesive layer 6 is comprised by what shows the storage elastic modulus of 0.15-10 MPa in the temperature range of 23-80 degreeC. In this case as well, it is usual to place a separator 9 on the exposed surface of the pressure-sensitive adhesive layer 6 and temporarily protect the surface until it is bonded to another member.

  Here, “showing a storage elastic modulus of 0.15 to 10 MPa in a temperature range of 23 to 80 ° C.” means that the storage elastic modulus takes a value in the above range at any temperature within this range. Since the storage elastic modulus usually decreases gradually as the temperature rises, if both the storage elastic modulus at 23 ° C. and 80 ° C. are within the above range, the storage elastic modulus in the above range is exhibited at the temperature in this range. You can see.

[Polarizer]
The polarizer 1 is a film having a function of extracting linearly polarized light from incident natural light, and a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be used. The polyvinyl alcohol 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 resin is used as a raw 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. Considering 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-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution. As the dichroic dye, iodine or a dichroic organic dye is used.

[Transparent protective layer]
The transparent protective layer 2 provided on one side of the polarizer 1 can be composed of an appropriate transparent film. Among them, a film made of a resin excellent in transparency, optical property uniformity, mechanical strength, thermal stability, etc. is preferably used. For example, cellulose resin films such as triacetyl cellulose and diacetyl cellulose, polyester resin films such as polyethylene terephthalate and polyethylene isophthalate, polybutylene terephthalate, acrylic resin films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate, Examples thereof include a polycarbonate resin film, a polyethersulfone resin film, a polysulfone resin film, a polyimide resin film, a polyolefin resin film, and a cyclic olefin resin film having a cyclic olefin as a monomer such as norbornene. An adhesive or a pressure-sensitive adhesive can be used for bonding the transparent protective layer 2 and the polarizer 1.

[Polymer film or retardation film]
The polymer film 3 used in the form shown in FIG. 2 can be composed of various resins exemplified as the resin constituting the transparent protective layer 2. In particular, it is advantageous that the polymer film 3 has an in-plane retardation and has a function as a retardation film. The polymer film 3 having an in-plane retardation is preferably selected to have characteristics required as a retardation film, that is, its birefringence is optically uniform, and depends on the protective function of the polarizer 1 and the liquid crystal panel. It is used for the purpose of compensation of phase difference (including the meaning of viewing angle compensation). For example, those that have been used in image display devices can be used without limitation, birefringent films made of stretched films of various transparent polymers, films in which discotic liquid crystals and nematic liquid crystals are oriented and fixed. And those having the above-mentioned liquid crystal layer formed on a film substrate. When the liquid crystal layer is fixed on the film substrate, a cellulose resin film such as triacetyl cellulose is preferably used as the film substrate for supporting the oriented liquid crystal layer.

  Examples of the polymer forming the birefringent film include, 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.

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

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

[Adhesive layer]
1 and 2, the pressure-sensitive adhesive layer 6 is arranged on the outermost side of the polarizing plate and is bonded to the image display element. In FIG. 2, the pressure-sensitive adhesive layer that bonds the polarizer 1 and the polymer film 3 together. 7 can be formed on the basis of various adhesives conventionally used for image display devices. For example, those having a base polymer such as acrylic, rubber, urethane, silicone, and polyvinyl ether are used. Moreover, an energy beam curing type, a thermosetting type, etc. may be sufficient. Among these, a pressure-sensitive adhesive having an acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer is preferable.

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

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

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

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

[Storage modulus of adhesive layer]
And in this invention, the adhesive layer 6 arrange | positioned on the outermost side of a polarizing plate and bonded together to an image display element shows the storage elastic modulus of 0.15-10MPa in a temperature range of 23-80 degreeC, ie, it is hard. It is preferable to constitute it. The storage elastic modulus of the pressure-sensitive adhesive can be measured by using a commercially available viscoelasticity measuring device, for example, a viscoelasticity measuring device “DYNAMIC ANALYZER RDA II” manufactured by REOMETRIC as shown in the examples described later. The pressure-sensitive adhesive used in a normal image display device or an optical film therefor has a storage elastic modulus of about 0.1 MPa at most, and in comparison, the storage elastic modulus of the pressure-sensitive adhesive layer 6 is 0.15 to 10 MPa. High value. By using such a hard adhesive that exhibits a high storage elastic modulus, it becomes possible to suppress dimensional changes accompanying the contraction of the polarizer that occurs when placed in a high-temperature environment, and good durability is obtained. .

  In particular, when exposed to a high-temperature environment in a state of being bonded to the glass plate constituting the image display element via the outermost adhesive layer 6 of the polarizing plate, the end of the polarizing plate accompanies the contraction of the polarizer. Phenomenon that part rises can be suppressed.

  Means for increasing the storage elastic modulus of the pressure-sensitive adhesive layer 6 bonded to the image display element as described above is not particularly limited. For example, an ordinary pressure-sensitive adhesive composition as described above may include an oligomer, specifically It is effective to blend urethane acrylate oligomer. Preferably, such a urethane acrylate oligomer blended and then cured by irradiation with energy rays exhibits a high storage elastic modulus. A pressure-sensitive adhesive composition containing a urethane acrylate-based oligomer, or a film-like pressure-sensitive adhesive obtained by coating it on a support film and curing it with ultraviolet rays is known and can be obtained from a pressure-sensitive adhesive manufacturer.

  When the form shown in FIG. 2 is adopted, the pressure-sensitive adhesive layer 7 for bonding the polarizer 1 and the transparent polymer film 3 is the same as the pressure-sensitive adhesive layer 6 disposed on the outermost side and has a high storage elastic modulus. It may be composed of a material having a lower storage elastic modulus than that of the pressure-sensitive adhesive layer 6, but it may be composed of a material having a high storage elastic modulus to cause a dimensional change accompanying the contraction of the polarizer. It is preferable to suppress.

[Other explanation about adhesive layer]
The pressure-sensitive adhesive layers 6 and 7 are formed by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to obtain a solution having a concentration of 10 to 40% by weight. After directly applying to the surface of the film to be formed and drying, a method of laminating the separator 9 made of a resin film, or after forming a pressure-sensitive adhesive layer on the separator 9, on the surface of the film to be formed It can be carried out by a transfer method or the like. When forming the pressure-sensitive adhesive layer on the film, a treatment for improving the adhesion, for example, corona treatment, is performed on the surface (one or both) on which the film and the pressure-sensitive adhesive layer are bonded as necessary. You may give it.

  The separator 9 temporarily protects the surface of the pressure-sensitive adhesive layer 6 until the polarizing plates 10 and 11 are bonded to an image display element. For example, the separator 9 is a silicone-based film made of a transparent resin such as polyethylene terephthalate. Those subjected to treatment with a release agent such as are used.

  The thickness of the pressure-sensitive adhesive layers 6 and 7 can usually be about 1 to 40 μm. In order to obtain a thin polarizing plate which is the object of the present invention, it is desirable to form the adhesive layers 6 and 7 thinly within a range not impairing properties such as workability and durability, for example, 3 to 25 μm. This is suitable for obtaining good durability while maintaining good processability.

[Other optical layers]
The polarizing plate of the present invention is configured as described above, and an optical layer having other optical functions can be laminated on the transparent protective layer 2 as necessary.

  For example, when this polarizing plate is disposed on the display surface (viewing side) of the image display element, a surface treatment layer such as a hard coat layer, an antireflection layer, or an antiglare layer is provided on the transparent protective layer. May be. The hard coat layer is formed to prevent scratches on the surface of the polarizing plate. The hard coat layer is mainly composed of an ultraviolet curable resin, for example, an acrylic resin or a silicone resin, and the adhesiveness to the transparent protective layer 2. Those having excellent hardness are appropriately selected and can be formed on the surface of the transparent protective layer 2.

  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 2 is formed to have a concavo-convex structure by, for example, a method of applying and curing a coating liquid in which transparent fine particles are mixed with an ultraviolet curable resin.

  On the other hand, when this polarizing plate is disposed on the opposite side (rear side) of the display surface of the liquid crystal cell, on the transparent protective layer 2, a reflective layer, a transflective layer, a light diffusing layer, a light collector, and a luminance improvement A film or the like can be laminated.

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

  The diffusion type polarizing plate has a function of diffusing incident light. For the light diffusion layer used for that purpose, various methods such as a method of performing a mat treatment on the transparent protective layer 4 on the polarizer 1, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles are used. Formed.

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

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

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

  The various optical layers as described above can be integrated with the transparent protective layer 2 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 may be appropriately selected. You can select and use one. It is preferable to use a pressure-sensitive adhesive from the viewpoint of simplicity of bonding work and prevention of optical distortion. As an example of an adhesive, the thing similar to having demonstrated the adhesive layers 6 and 7 previously with reference to FIG.1 and 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. As a separator, the thing similar to what was demonstrated previously can be used.

[Cutting processing of polarizing plate into desired shape]
As shown in FIG. 1 or FIG. 2, a transparent protective layer is provided on one side of a polarizer made of a polyvinyl alcohol-based resin film, a pressure-sensitive adhesive layer is provided on the other side of the polarizer, and a separator is provided on the exposed surface of the pressure-sensitive adhesive layer. A polarizing plate that is laminated or laminated in the order of a pressure-sensitive adhesive layer, a transparent polymer film and a pressure-sensitive adhesive layer, and a separator is usually composed of a long sheet shape with a large area, and is a liquid crystal television. , Cut into a desired shape according to the image display element applied to personal phones, in-vehicle navigation systems, liquid crystal color projectors, laptop computers, etc., and then the image display element through the outermost adhesive layer Used by being pasted together.
As a method of cutting into a desired shape, conventionally, the cutting has been performed by cutting with a sharp blade or punching with a mold, and in a polarizing plate having transparent protective layers on both sides of a polarizer as shown in FIG. When the durability test of 100 cycles was performed with one cycle of continuous operation of cooling at a temperature of −45 ° C. for 30 minutes and then heating at a temperature of 85 ° C. for 30 minutes with the outermost pressure-sensitive adhesive layer applied to the glass. In FIG. 1, there was no problem that cracks occurred in the polarizer, but a thin polarizing plate having a transparent protective layer on only one of the polarizers in FIG. 1 or FIG. When a polarizing plate having a structure is cut into a desired shape with a blade, cracks occur in the polarizer after the durability test.

  In the present invention, a laser is used in cutting a thin polarizing plate having a transparent protective layer only on one side of the polarizer as shown in FIG. 1 or FIG. By adopting the cutting method, it is possible to provide a polarizing plate that does not substantially have cracks generated from the end of the polarizer forming the polarizing plate even after the durability test.

  The cutting process of a polarizing plate by a laser in the present invention is a method of cutting the polarizing plate by irradiating the polarizing plate with a generally known infrared laser beam. As the infrared laser, a known method such as a carbon dioxide laser, a YAG laser, or a UV laser can be used, but a carbon dioxide laser is recommended in terms of workability.

  The cutting speed depends on the thickness of the polarizing plate to be cut, but is 1 m / min or more, preferably 5 to 60 m / min if the thickness of the polarizing plate is in the range of 70 to 500 μm. If the cutting speed is less than 1 m / min, the productivity tends to be inferior. Moreover, although the output of an infrared laser is based on the thickness of a polarizer, a desired cutting speed, etc., it is normally used within the range of 10W-400W. The laser wavelength used in the present invention is a polarizing plate in which a transparent protective layer is formed only on one side of the polarizer targeted by the present invention, in particular, in the cutting processing of a thin polarizing plate, the laser wavelength is 9.4 μm It is recommended to use In the case of cutting using such a laser wavelength, for example, compared to what was cut using a laser wavelength of 10.6 μm, without the melt projecting on the cut end face of the polarizing plate, without melting deformation, The cut end face is beautiful. Therefore, in the pasting to the image display element, the separator film constituting the polarizing plate can be easily peeled off and the pasting end face is also beautiful, which causes problems such as air entrainment and peeling. It is preferable because it does not occur.

[Image display element]
The polarizing plate of the present invention cut into a desired shape as described above 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 provide a liquid crystal display device. The liquid crystal cell to be used is arbitrary, for example, an active matrix drive type represented by VA (Vertical Allignment), IPS (In-plane Switching), ECB (Electrically Controlled Birefringence), OCB (Optically Compensated Birefringence) mode, etc. Liquid crystal display devices using various liquid crystal panels including simple matrix drive type represented by STN (Super Twisted Nematic) mode and static drive type represented by TN (Twisted Nematic) mode Can be formed. When providing the polarizing plate of this invention in the both sides of a liquid crystal cell, both may be the same and may differ.

  In the IPS mode liquid crystal display device, in the viewing side polarizing plate, when there is a member having a retardation in the thickness direction between the polarizer and the liquid crystal cell, the color change from the oblique direction becomes large. Therefore, as shown in FIG. 1, if a configuration in which the pressure-sensitive adhesive layer 6 is provided on one surface of the polarizer 1 is adopted and directly bonded to the liquid crystal cell via the pressure-sensitive adhesive layer 6, a space between the polarizer and the liquid crystal cell is obtained. There is no retardation in the thickness direction. Therefore, the configuration shown in FIG. 1 is particularly effective for an IPS mode liquid crystal cell.

  In addition, in the VA, ECB, OCB, STN, and TN mode liquid crystal display devices, if there is no planar phase difference between the liquid crystal cell and the viewing side and / or the back side polarizer, the viewing angles on the top, bottom, left, and right are extremely high. It will become narrower. Therefore, as shown in FIG. 2, a configuration in which transparent protective layer 2 / polarizer 1 / adhesive layer 7 / polymer film 3 (particularly retardation film) / adhesive layer 6 is provided in this order is adopted. When bonded to the liquid crystal cell via the layer 6, the viewing angle can be increased. Therefore, the configuration shown in FIG. 2 is particularly effective for VA, ECB, OCB, STN, and TN mode liquid crystal cells, particularly VA mode liquid crystal cells.

  FIG. 3 is a schematic cross-sectional view showing an example in which the polarizing plate according to the present invention is mounted on a liquid crystal panel. In this example, basically, the polarizing plates 11 having the form shown in FIG. 2 are arranged on both surfaces of the liquid crystal cell 20. That is, the adhesive layer 6 / polymer film (retardation film) 3 / adhesive layer 7 / polarizer 1 / surface treatment layer 4 is provided on one side (upper side in the figure) of the liquid crystal cell 20 from the liquid crystal cell 20 side. Polarizing plate 12 laminated in the order of transparent protective layer 2 (surface treatment layer 4 is outside) (this corresponds to the state in which separator 9 is peeled off from polarizing plate 11 shown in FIG. 2 except that surface treatment layer 4 is provided) Is attached). Further, on the other side of the liquid crystal cell 20 (the lower side of the figure), from the liquid crystal cell 20 side, the pressure-sensitive adhesive layer 6 / polymer film (retardation film) 3 / pressure-sensitive adhesive layer 7 / polarizer 1 / transparent protective layer. 2 / Polarizing plate 13 laminated in the order of the other optical layer 5 (this corresponds to the state where the separator 9 is peeled off from the polarizing plate 11 shown in FIG. 2 except that the other optical layer 5 is provided. ) Is attached. In the liquid crystal display device of this example, the upper side of the figure is the viewing side, and when a backlight is provided, it is arranged on the lower side of the figure. In this case, the surface treatment layer 4 can be a hard coat layer, an antireflection layer, an antiglare layer, or the like. The other optical layer 5 can be a reflective layer, a transflective layer, a light collector, a brightness enhancement film, or the like.

  Furthermore, the 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. Those skilled in the art will easily understand that when the image display element is an organic EL display element, the polarizing plate of the present invention may be bonded to one side thereof, that is, the viewing side display surface. Of course, the image display apparatus to which the polarizing plate of the present invention is applied is not limited to the one 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. In the following examples, the heat cycle test for measuring the storage elastic modulus of the pressure-sensitive adhesive and the durability of the polarizing plate to a sudden temperature change is a value measured by the following method.

[Measurement method of storage modulus]
A cylindrical test piece of 8 mmΦ × 1 mm thickness was prepared from the adhesive, and the storage elastic modulus was obtained by a torsional shear method with a frequency of 1 Hz using a measuring instrument “DYNAMIC ANALYZER RDA II” manufactured by REOMETRIC.

[Heat cycle test]
Using a thermal shock device (trade name: TSA-71L-A manufactured by ESPEC CORP.), Cooling is performed at a temperature of −45 ° C. for 30 minutes and then heated at a temperature of 85 ° C. for 30 minutes. The endurance test was conducted, and the crack occurrence state over the entire length of the polarizing plate as the test piece was examined visually.

  In the following examples, the following were used as pressure-sensitive adhesives.

  Adhesive A: Polyethylene terephthalate film (thickness: 38 μm) obtained by subjecting an organic solvent solution in which a urethane acrylate oligomer is blended to a copolymer of butyl acrylate and acrylic acid to which an isocyanate-based crosslinking agent has been added to a release treatment. A sheet-like pressure-sensitive adhesive coated on the release treatment surface of the separator) so that the thickness after drying with a die coater is 25 μm. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

[Example 1]
Adhesion made of an aqueous solution containing polyvinyl alcohol and a water-soluble epoxy resin with a transparent protective layer made of a triacetyl cellulose film having a thickness of 40 μm on one surface of a polarizer made of 25 μm thick with iodine adsorbed and oriented on polyvinyl alcohol 1 is bonded to the other surface of the polyvinyl alcohol polarizer, and a separator film made of a polyethylene terephthalate film having a thickness of 38 μm is bonded to the surface of the pressure-sensitive adhesive A. A thin polarizing plate (polarizing plate size: 1 m × 1 m) was obtained.

The polarizing plate thus obtained was used with a carbon dioxide laser having laser wavelengths of 10.6 μm and 9.4 μm, and the polarizing plate absorption axis was 2.5 inches diagonal so that the polarizing axis was 83 degrees clockwise with respect to the long side ( 50 mm × 40 mm) to obtain a test piece A (processed with a laser wavelength of 10.6 μm) and a test piece B (processed with a laser wavelength of 9.4 μm). Moreover, the polarizing plate is made of a super cutter (trade name: TMC-R-1200, trade name: TMC-R-1200, blade is made by Hadano, trade name: PN112N). A test piece C was obtained by cutting into a diagonal size of 2.5 inches (50 mm × 40 mm) so that the rotation was 83 degrees.
<Devices used and operating conditions>
Laser wavelength 10.6 μm: Cut using a carbon dioxide laser device manufactured by Shinrad (trade name: firestar f400) at a cutting speed of 1 m / min and a laser output of 7 w.
Laser wavelength: 9.4 μm: Cut using a carbon dioxide laser device manufactured by Coherent (trade name: Film Cutting) at a cutting speed of 10.2 m / min and a laser output of 22 w.

Using the test pieces A, B, and C obtained in Example 1, the polarizing plate was subjected to a heat cycle test. As a result, in the test piece using a laser, neither A nor B had any cracks or cracks in the polarizer forming the polarizing plate. On the other hand, in the polarizer of the test piece C using a normal blade, that is, a super cutter, 100 or more cracks were observed on the long side parallel to the PL absorption axis.
In addition, the cross-sectional photograph after cut | disconnecting test piece A and B is shown as FIG. 5 (test piece A) and FIG. 6 (test piece B).

[Comparative Example 1]
A transparent protective layer made of a triacetyl cellulose film having a thickness of 40 μm is attached to both sides of a polarizer made of the same polyvinyl alcohol as used in Example 1 via an adhesive made of an aqueous solution containing polyvinyl alcohol and a water-soluble epoxy resin. Polarization corresponding to FIG. 4 by pasting together, sticking adhesive A on the other side of the polyvinyl alcohol polarizer, and pasting a separator film made of a polyethylene terephthalate film with a thickness of 38 μm on the surface of adhesive A A plate (polarizing plate size: 1 m × 1 m) was obtained.

  The polarizing plate thus obtained was 2.5 inches diagonal (50 mm) so that the polarizing plate absorption axis was 83 degrees clockwise with respect to the long side using the super cutter used in Example 1. A test piece D was obtained by cutting into a size of × 40 mm).

  Using the test piece D, the dew condensation test and the heat cycle test of the polarizing plate were conducted. As a result, no crack was observed on the end face of the polarizer.

  The polarizing plate of the present invention has a thin and lightweight structure and is excellent in durability in a rapid temperature change. In particular, the present invention is useful for various image display devices for mobile use in which the module itself is thin and light and the durability is improved.

DESCRIPTION OF SYMBOLS 1 Polarizer 2,2a Transparent protective layer 3 Polymer film (retardation film)
4 Other optical layers (surface treatment layers)
5 Other optical layers (such as brightness enhancement films)
6 Adhesive layer (high storage modulus)
7 Adhesive layer 8, 8a Adhesive layer (conventional)
9 Separator 10-13 Polarizing plate 16, 17 Polarizing plate (conventional)
20 Image display element (liquid crystal cell)

Claims (6)

  A transparent protective layer is formed on one side of a polarizer made of a polyvinyl alcohol-based resin film, and an adhesive layer is formed on the other side of the polarizer, or an adhesive layer, a transparent polymer film, and an adhesive layer. It is a polarizing plate that is formed in order and cut and processed into a desired shape and then bonded to the image display element via the outermost adhesive layer, and the outermost adhesive layer is attached to glass. In a state where the endurance test of 100 cycles was performed with a continuous operation of cooling at a temperature of −45 ° C. for 30 minutes and then heating at a temperature of 85 ° C. for 30 minutes as one cycle, the inner side from the end of the polarizer forming the polarizing plate A polarizing plate substantially free from cracks.   The polarizing plate according to claim 1, wherein a laser is used for cutting into a desired polarizing plate shape.     The polarizing plate according to claim 1 or 2, wherein the laser wavelength used for the cutting process is 9.4 µm.   A transparent protective layer is formed on one side of a polarizer made of a polyvinyl alcohol-based resin film, and an adhesive layer is formed on the other side of the polarizer, or an adhesive layer, a transparent polymer film, and an adhesive layer. A polarizing plate that is formed in order and cut and processed into a desired shape, and then bonded to the image display element via the outermost adhesive layer, and the desired shape is cut with a laser. In the state where the outermost pressure-sensitive adhesive layer is pasted on glass, 100 cycles of durability test is performed with one cycle as a continuous operation of cooling at a temperature of −45 ° C. for 30 minutes and then heating at a temperature of 85 ° C. for 30 minutes. A method for producing a polarizing plate, which, when carried out, is substantially free from cracks generated from the end of the polarizer forming the polarizing plate.   The method for producing a polarizing plate according to claim 4, wherein a laser wavelength used for the cutting process is 9.4 μm.   An image display device comprising an image display element and the polarizing plate according to claim 1, wherein an adhesive layer on the outermost side of the polarizing plate is bonded to the image display element.

Images