JP2010039458A - Polarizing plate, manufacturing method therefor, and composite polarizing plate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate thinned and light-weighted by reducing members, while maintaining a high function, by bonding a transparent protection film onto one face of a polarizer, and by bonding a highly functional plastic substrate on the other face via a pressure sensitive adhesive layer. <P>SOLUTION: This polarizing plate 10 is laminated with the first pressure sensitive adhesive layer 1, the transparent protection film 2, the polarizer 3, the second pressure sensitive adhesive layer 4, and the transparent plastic substrate 5 in this order, and the second pressure sensitive adhesive layer 4 is constituted of one exhibiting 0.15-1 MPa of storage elasticity within a temperature range of 23-80°C. The transparent protection film 2 and the first pressure sensitive adhesive layer 1 are laminated in this order on one face of the polarizer 3, the second pressure sensitive adhesive layer 4 exhibiting the high storage elasticity is formed on the other face of the polarizer 3, a polarizing plate precursor 9 is prepared thereby, and the transparent plastic substrate 5 is laminated on the second pressure sensitive adhesive layer 4. This manufacturing manner can also cope quickly with small lot multi-product production. <P>COPYRIGHT: (C)2010,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 a manufacturing method thereof. The polarizing plate of the present invention has a thin and light structure even when it has high functions such as high hardness and brightness improvement. This polarizing plate is particularly useful for various image display devices for mobile applications in which the module itself is thin, light and hard. The present invention also relates to a composite polarizing plate using this polarizing plate.

  Conventionally, liquid crystal display devices have been used in desktop calculators and electronic watches, but more recently, they have come to be used regardless of screen size, from mobile devices such as mobile phones to large-sized TVs. The use is expanding rapidly. In addition, as an image display device other than a liquid crystal display device, an organic electroluminescence (organic EL) display device tends to increase in demand mainly for mobile applications. In a liquid crystal display device, a pair of polarizing plates are usually disposed on the front and back of a liquid crystal cell. In organic EL display devices, a polarizing plate, particularly an elliptical or circularly polarizing plate, is often provided on the viewing side of the organic EL element to provide an antireflection function. As for the polarizing plates used in these image display devices, not only the demand is increasing with the development thereof, but also the performance suitable for each application is required.

  A traditional polarizing plate that is widely used in the image display device as described above has a liquid adhesive on both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film. A transparent protective film, particularly a triacetyl cellulose film is used for the production. This is used as it is or, if necessary, in a form in which various optical layers such as a phase difference plate having optical properties and an optical compensation film are bonded together, and using a pressure sensitive adhesive (adhesive), a liquid crystal cell, an organic EL element, etc. The image display device is used to form an image display device.

  By the way, in recent years, in an image display apparatus for mobile use such as a mobile phone, it is rapidly progressing to make the entire module thin and slim 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, with the thinning of mobile phones, products from which front plates made of acrylic resin films, etc. used in conventional mobile phones have been removed are also being adopted. In addition, a polarizing plate excellent in surface hardness is demanded.

  FIG. 4 is a schematic cross-sectional view showing a layer configuration of a polarizing plate conventionally used in the past and an example in which a plastic substrate is arranged on one side thereof. Traditionally, as shown in FIG. 3, the transparent protective films 2 and 2 are bonded to both sides of the polarizer 3, and pressure-sensitive bonding for bonding to another member such as an optical film or an image display element on one side thereof. The polarizing plate 30 is configured by disposing the agent layer 1. A separator 7 is provided on the surface of the pressure-sensitive adhesive layer 1 to temporarily protect the surface until it is bonded to another member such as an image display element. In order to provide such a polarizing plate 30 with a high hardness function or a brightness enhancement function, when the transparent plastic substrate 5 is laminated, the second pressure-sensitive adhesive layer 34 is usually used. In this case, however, the overall thickness increases, which is contrary to the market demand for thinning for mobile use.

  In order to meet the demands for reduction in thickness and weight as described above, simply by thinning the polarizer or the transparent protective film of the polarizing plate, the polarizer has a characteristic that it is easily broken in the stretching direction, and an adhesive. From the viewpoint of handling at the time of work in the method of laminating a transparent protective film via a film, there was a limit in obtaining a thin and light polarizing plate. It is also known to reduce the thickness by omitting one of the protective films bonded to both sides of the polarizer. However, a polarizer made of a polyvinyl alcohol resin generally shrinks easily in a high temperature environment, and in a form in which the polarizer is sandwiched between two protective films, the shrinkage is suppressed by a protective film on both sides. When the film is omitted, there is a problem that the shrinkage suppressing effect is weakened and the dimensional change becomes large when exposed to a high temperature environment.

  In order to meet the demand for increasing the hardness of the polarizing plate surface, for example, in JP-A-2006-106427 (Patent Document 1) and JP-A-9-113728 (Patent Document 2), A proposal has been made to increase the hardness by subjecting a surface treatment to mainly triacetylcellulose. However, in order to increase the hardness, it is necessary to increase the thickness of the hard coat layer formed by the surface treatment, which not only contradicts the above market demand for thinning, but also increases the thickness of the hard coat layer. Since problems such as an increase in curl due to the occurrence of the problem occur, there is also a problem that productivity is remarkably lowered. Further, as the thickness increases, the winding length per roll produced by roll-to-roll also decreases, so that the production efficiency may be lowered.

  On the other hand, especially on the viewing side of the liquid crystal cell and the polarizing plate disposed on the organic EL element, various surface treatment layers such as a hard coat layer, an antiglare layer and an antireflection layer are provided according to the manufacturer and type of the display device. Therefore, the required performance is diverse. On the other hand, normal polarizing plate production is performed in a roll of several hundred meters, so it is difficult to respond quickly to high-mix low-volume production for small-area products, especially for mobile applications, and production yield deteriorates. There are concerns. Therefore, for polarizing plates for mobile use, it is required to develop a polarizing plate that is thin and has high hardness, and that can be adapted to high-mix low-volume production.

  JP, 2004-262071, A (patent documents 3) is an example of a method of pasting another sheet on a polarizing plate produced in roll form.

JP 2006-106427 A Japanese Laid-Open Patent Publication No. 9-11728 Japanese Patent Laid-Open No. 2004-262071

  The object of the present invention is to adhere a transparent protective film to one side of a polarizer and to bond a high-functional plastic substrate to the other side via a pressure-sensitive adhesive layer, thereby maintaining a high function and a member. An object of the present invention is to provide a polarizing plate that is reduced in thickness and weight by reducing the amount of light. Another object of the present invention is to provide a polarizing plate having a configuration that can cope with a variety of small-quantity production required for mobile applications.

  Furthermore, another object of the present invention is to provide a method for producing a polarizing plate that can be used for high-mix low-volume production required for mobile applications.

  Yet another object of the present invention is to provide a composite polarizing plate that can be thinned and lightened and can be provided with various functions by using such a polarizing plate.

  In order to achieve the above object, according to the present invention, the first pressure-sensitive adhesive layer, the transparent protective film, the polarizer, the second pressure-sensitive adhesive layer, and the transparent plastic substrate are laminated in this order. The second pressure-sensitive adhesive layer is provided with a polarizing plate comprising a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C.

  In this polarizing plate, the polarizer can be a polyvinyl alcohol resin film in which a dichroic dye such as iodine or a dichroic organic dye is adsorbed and oriented. In addition, the second pressure-sensitive adhesive layer exhibiting a relatively high storage elastic modulus as described above can have a thickness of about 1 to 40 μm, and particularly preferably in the range of 3 to 25 μm.

  In this polarizing plate, the transparent plastic substrate disposed on the outermost surface via the second pressure-sensitive adhesive layer preferably has a tensile elastic modulus in the range of 2,500 to 4,000 MPa. By using a transparent plastic substrate having an optical or physical function, a thin and light polarizing plate can be formed by reducing the number of members while providing a high function. For example, a transparent plastic substrate is configured with a surface treatment layer such as a hard coat layer, an antiglare layer, and an antireflection layer on the side opposite to the surface in contact with the second pressure-sensitive adhesive layer. It can be set as the polarizing plate arrange | positioned at a visual recognition side or an organic EL element. Moreover, this transparent plastic substrate can be comprised with a brightness enhancement film, and it can also be set as the polarizing plate arrange | positioned at the back side of a liquid crystal cell. Further, the transparent plastic substrate can be composed of a retardation (retardation film). In this case, the slow axis of the retardation film is at an angle of about 45 ° with the absorption axis of the polarizer. It is advantageous to arrange them so as to cross each other.

  In the polarizing plate of the present invention, the first pressure-sensitive adhesive layer has removability, and it is preferable to dispose a separator that has been treated with a silicone-based release agent on the exposed surface.

  As another form of the polarizing plate of the present invention, a thin polarizing plate in an elliptical or circularly polarizing mode can be formed by using a transparent protective film adhered to a polarizer as a retardation plate or a wave plate. .

  According to the present invention, there is also provided a method for producing the above polarizing plate, which comprises laminating a transparent protective film and a first pressure-sensitive adhesive layer in this order on one side of the polarizer, and the other side of the polarizer. And forming a polarizing plate precursor by forming a second pressure sensitive adhesive layer having a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. A laminating step of laminating a transparent plastic substrate on the second pressure-sensitive adhesive layer of the polarizing plate precursor.

  Furthermore, according to this invention, the composite polarizing plate which consists of a laminated body of the above polarizing plates and the optical layer which shows another optical characteristic is also provided.

  The polarizing plate of the present invention is thin while expressing the high functions required for a polarizing plate for small and medium applications by appropriately selecting a transparent plastic substrate laminated on the second pressure-sensitive adhesive layer. In particular, the second pressure-sensitive adhesive layer formed directly on the polarizer surface and used for bonding to the transparent plastic substrate can be reduced in the temperature range of 23 to 80 ° C. By constituting with a relatively hard material exhibiting a storage elastic modulus of .15 to 1 MPa, it is possible to suppress the dimensional change of the polarizing plate even in a high temperature environment.

  Also, if the transparent plastic substrate is composed of a hard coat film imparted with high hardness, the hard coat film can be bonded to the polarizer via the second pressure-sensitive adhesive layer. -Supports single-wafer type production methods other than mass production by two-roll, and has high production efficiency for product groups such as small and high-mix low-volume products.

  In the method for producing a polarizing plate according to the present invention, a transparent protective film and a first pressure-sensitive adhesive layer are formed in this order on one side of a polarizer, and the other surface exhibits a relatively high storage elastic modulus as described above. A polarizing plate precursor with a pressure-sensitive adhesive layer is prepared, and a transparent plastic substrate is laminated on the second pressure-sensitive adhesive layer, just changing the type of the transparent plastic substrate Thus, various types of polarizing plates according to various required characteristics can be manufactured with high production efficiency.

  Furthermore, the composite polarizing plate according to the present invention is obtained by laminating another optical layer on the thin and light polarizing plate as described above. Like the above polarizing plate, the composite polarizing plate can exhibit the thin and light features and has a high temperature. The dimensional change of the polarizing plate under the environment is suppressed.

  An example of the layer structure of the polarizing plate according to the present invention is shown in a schematic sectional view in FIG. In the present invention, as shown in FIG. 1, a first pressure-sensitive adhesive layer 1, a transparent protective film 2, a polarizer 3, a second pressure-sensitive adhesive layer 4 and a transparent plastic substrate 5 are laminated in this order. Thus, the polarizing plate 10 is configured. And the 2nd pressure sensitive adhesive layer 4 formed in the single side | surface of the polarizer 3 is comprised by what shows the storage elastic modulus of 0.15-1Mpa in the temperature range of 23-80 degreeC. In addition, a separator 7 is arranged on the side opposite to the side facing the transparent protective film 2 of the first pressure-sensitive adhesive layer 1 to temporarily protect the surface until it is bonded to another member. Is customary.

  Here, the second pressure-sensitive adhesive layer 4 “shows a storage elastic modulus of 0.11 to 1 MPa in the temperature range of 23 to 80 ° C.” means that the storage elastic modulus is any temperature in this range. It means taking a value in the above 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.

  The storage elastic modulus of the pressure-sensitive adhesive layer can be measured 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 below. it can. The pressure-sensitive adhesive layer used in a normal image display device or an optical film therefor has a storage elastic modulus of about 0.1 MPa at the maximum, and compared with that, the second pressure-sensitive adhesive layer defined in the present invention. The storage elastic modulus of the agent layer 4 is 0.15 to 1 MPa. By disposing a pressure-sensitive adhesive layer exhibiting such a high storage elastic modulus, in other words, a hard pressure-sensitive adhesive layer, it is possible to suppress dimensional changes that are likely to occur as the polarizer contracts in a high-temperature environment. It can be set as the polarizing plate which shows high durability.

  By disposing the first pressure-sensitive adhesive layer 1 on the surface opposite to the polarizer 3 of the transparent protective film 2 bonded to one surface of the polarizer 3, other than a phase difference plate, an optical compensation film, etc. Can be bonded to an optical display layer or an image display element such as a liquid crystal cell or an organic EL element.

  In the following, the description will proceed in order for each layer shown in FIG.

[Polarizer]
The polarizer 3 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 3 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 an original film of a polarizer. 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 1-150 micrometers. In consideration of easiness of stretching, the film thickness is preferably 10 μm or more.

  The polarizer 3 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 film]
The transparent protective film 2 is bonded to one side of the polarizer 3. For bonding the polarizer 3 and the transparent protective film 2, an appropriate adhesive such as an aqueous solution, an organic solvent solution, or a solventless type can be used. As the transparent protective film 2, various resin films conventionally known as a protective film for a polarizing plate can be used. In general, a cellulose acetate resin film, particularly a triacetyl cellulose film is preferably used.

  Further, as the transparent protective film 2, a film having a function of a retardation plate or a wave plate can be used. By using the transparent protective film 2 as a retardation plate or a wave plate, an elliptical or circular polarization mode polarizing plate can be formed. In order to impart the function of a retardation plate or a wave plate to the resin film, for example, the retardation may be expressed by stretching a thermoplastic resin film. The kind of the thermoplastic resin constituting the retardation plate or the wave plate is not particularly limited, and examples thereof include the above-described cellulose acetate resins, and cyclic olefin resins such as polycarbonate and norbornene resins.

[Pressure sensitive adhesive layer]
The transparent protective film 2 as described above is laminated on one surface of the polarizer 3, and the first pressure-sensitive adhesive layer 1 is disposed outside the transparent protective film 2. A second pressure-sensitive adhesive layer 4 is disposed on the opposite side of the polarizer 3 from the transparent protective film 2.

  For these pressure-sensitive adhesive layers 1 and 4, those which have been used for image display devices or optical films therefor and which have a tacky and highly transparent resin as a main component can be used. . For example, a pressure-sensitive adhesive mainly containing a resin such as acrylic, rubber, urethane, ester, silicone, or polyvinyl ether is used. Among these, a pressure-sensitive adhesive using an acrylic resin having excellent transparency, weather resistance, heat resistance, and the like as a base polymer is preferable. In particular, it is preferable to select and use a material that retains appropriate wettability and cohesive force, is excellent in adhesion to a substrate, and does not cause peeling problems such as lifting and peeling under heating and humidification conditions. Further, a pressure-sensitive adhesive called an energy ray curable type or a thermosetting type may be used.

  The acrylic resin used for forming the pressure-sensitive adhesive layer is not particularly limited. For example, butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, (meth) acrylic acid A (meth) acrylic acid ester base polymer such as 2-ethylhexyl and a copolymer base polymer using two or more of these (meth) acrylic acid esters are preferably used. Furthermore, polar monomers are copolymerized with these base polymers. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl ( 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 (meth) acrylate.

  These acrylic resins can be used alone or as a pressure-sensitive adhesive, but are usually mixed with a crosslinking agent. 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 include polyepoxy compounds and polyols that form ester bonds with carboxyl groups, and polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The energy ray curable pressure sensitive adhesive has the property of being cured by irradiation of energy rays such as ultraviolet rays and electron beams, and has adhesiveness before the irradiation of energy rays and adheres to films and the like. It is a pressure-sensitive adhesive that has the property of adhering to the body and being cured by irradiation with energy rays to adjust the adhesion. As the energy ray curable pressure sensitive adhesive, it is particularly preferable to use an ultraviolet curable pressure sensitive adhesive. The energy beam curable pressure sensitive adhesive generally comprises an acrylic resin as described above and an energy beam polymerizable compound as main components. Usually, a crosslinking agent is further blended, and a photopolymerization initiator and a photosensitizer may be blended as necessary.

  The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer includes, in addition to the above base polymer and crosslinking agent, pressure-sensitive adhesive pressure-sensitive adhesive, cohesive force, viscosity, elastic modulus, glass Appropriate additives such as natural or synthetic resins, tackifying resins, antioxidants, dyes, pigments, antifoaming agents, corrosives, photoinitiators, etc., for adjusting the transition temperature, etc. Can also be used. Furthermore, it can also be set as the pressure sensitive adhesive layer which contains microparticles | fine-particles and shows light-scattering property.

  The pressure-sensitive adhesive layer is prepared by dissolving or dispersing each component as described above in an organic solvent such as toluene or ethyl acetate to form a pressure-sensitive adhesive composition having a solid content concentration of about 10 to 40% by weight on the substrate. It can be formed by applying to and drying to remove the organic solvent. In the case of an energy ray curable pressure-sensitive adhesive, a desired cured product can be obtained by irradiating the thus formed coating film with energy rays such as ultraviolet rays and electron beams.

  The method for providing the first pressure-sensitive adhesive layer 1 on the surface of the transparent protective film 2 and the method for providing the second pressure-sensitive adhesive layer 4 on the surface of the polarizer 3 are not particularly limited. After the adhesive composition described above is applied to the surface of the transparent protective film 2 or the surface of the polarizer 1 on which the agent layer is to be formed, dried, and further cured by irradiation with energy rays as necessary In addition, a separator that has been subjected to a mold release treatment may be laminated, or a pressure-sensitive adhesive composition may be applied onto the separator, dried, and further cured by irradiation with energy rays as necessary. Then, it may be transferred to the surface of the transparent protective film 2 or the surface of the polarizer 3 and laminated. When the pressure-sensitive adhesive layer formed on the separator is transferred onto the protective film 2 or the polarizer 3, if necessary, the adhesion surface of the film to be transferred and the adhesion surface of the pressure-sensitive adhesive layer are transferred. One or both of them may be subjected to treatment for improving adhesion, for example, corona treatment.

  The first pressure-sensitive adhesive layer 1 and the second pressure-sensitive adhesive layer 4 can each have a thickness of about 1 to 40 μm, but in order to obtain a thin polarizing plate which is one of the objects of the present invention. For this reason, it is desirable to form a thin film within a range that does not impair properties such as workability and durability. For example, 3 to 25 μm is preferable from the viewpoint of suppressing dimensional change of the polarizing plate while maintaining good workability. Is preferable. Conventionally, a pressure-sensitive adhesive layer for adhering adjacent layers in a polarizing plate or for adhering to an image display element has been standardized to have a thickness of 25 μm. The second pressure-sensitive adhesive layer 4 composed of a material exhibiting a sufficient effect is exhibited even when the thickness is less than 25 μm, for example, 15 μm or 20 μm.

  Moreover, the pressure-sensitive adhesive layers 1 and 4 may contain fine particles for exhibiting light scattering properties, if necessary, glass fibers, glass beads, resin beads, metal powders and other inorganic powders. You may mix | blend the filler which consists of these, a pigment, a coloring agent, antioxidant, a ultraviolet absorber, etc. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

[Second pressure-sensitive adhesive layer]
In the present invention, the second pressure-sensitive adhesive layer 4 formed on the surface of the polarizer 3 is configured to exhibit a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. The means for setting the storage elastic modulus of the second pressure-sensitive adhesive layer 4 to such a high value is not particularly limited. For example, an ordinary pressure-sensitive adhesive composition as described above may be an oligomer, specifically, urethane. It is effective to blend an 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 oligomer, or a sheet-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.

[First pressure-sensitive adhesive layer]
On the other hand, the first pressure-sensitive adhesive layer 1 disposed outside the transparent protective film 2 has no particular limitation on the storage elastic modulus, and as with the second pressure-sensitive adhesive layer 4, high storage. You may comprise with the adhesive composition which shows an elasticity modulus, and you may comprise with a general adhesive composition with a storage elastic modulus lower than it.

[Separator]
The separator 7 temporarily protects the surface of the first pressure-sensitive adhesive layer 1 until the polarizing plate 10 is bonded to another optical layer or an image display element. For example, the separator 7 is a transparent resin such as polyethylene terephthalate. A film obtained by treating the film with a release agent such as silicone is used. In order to temporarily protect the surface of the second pressure-sensitive adhesive layer 4 until the transparent plastic substrate 5 is bonded, the same separator as above can be bonded.

[Transparent plastic substrate]
The transparent plastic substrate 5 to be bonded onto the second pressure sensitive adhesive layer 4 can be used without particular limitation as long as it does not impair transparency. For example, acrylic resins, polyester resins such as polyethylene terephthalate, cyclic olefin resins such as polycarbonate and norbornene resins, various resins such as triacetyl cellulose, polyethylene, polypropylene, polystyrene, polyarylate, and polyvinyl chloride. Can be mentioned. Among these, an acrylic resin film is preferably used from the viewpoints of hardness, transparency, and productivity.

  The resin that is the mother phase of the acrylic resin film is a polymer based on methyl methacrylate (methacrylic resin). In addition to methyl methacrylate homopolymers, methyl methacrylate and other copolymerizable comonomers And a copolymer thereof can be used. Examples of the copolymerizable comonomer include acrylic acid esters such as methyl acrylate and butyl acrylate, aromatic vinyl compounds such as styrene, vinylcyan compounds such as acrylonitrile, and the like. The amount of the comonomer to be copolymerized is not particularly limited, but in the case of an acrylate ester, it is usually about 0.1 to 10% by weight, whereas in the case of an aromatic vinyl compound such as styrene, moisture absorption is suppressed. For this purpose, it is possible to carry out the copolymerization in a relatively large amount, for example, at a ratio of about 10 to 50% by weight.

  These methacrylic resins can be produced by usual methods such as suspension polymerization, emulsion polymerization, and bulk polymerization. Moreover, in order to obtain the viscosity which shows the moldability to a suitable film, it is preferable to use a chain transfer agent at the time of superposition | polymerization. As the chain transfer agent, various known ones such as mercaptans such as dodecyl mercaptan and octyl mercaptan can be used. The amount of the chain transfer agent used may be appropriately determined according to the type and composition of the monomer and the type of chain transfer agent to be used. It is in the range of 5% by weight.

  The transparent plastic substrate 5 preferably has a tensile modulus of elasticity that suppresses deformation of the polarizer 3 in a high-temperature environment. Specifically, the tensile modulus of elasticity is in the range of 2500 to 4,000 MPa. Is preferred. In particular, an acrylic resin film is preferably used because it generally exhibits a tensile elastic modulus of about 3,000 MPa.

  The thickness of the transparent plastic substrate 5 is appropriately selected depending on the applied material, but is generally about 25 to 500 μm, and preferably 40 to 100 μm.

[First form of transparent plastic substrate: substrate with surface treatment layer]
The transparent plastic substrate 5 is provided with various surface treatment layers such as a hard coat layer, an antiglare layer, and an antireflection layer for the purpose of imparting high hardness, antifouling property, and high visibility when applied to an image display device. Can be provided. When the plastic substrate 5 having such a surface treatment layer is used, the surface treatment layer is laminated on the side opposite to the second pressure-sensitive adhesive layer 4, that is, the outermost surface of the polarizing plate 10. . The polarizing plate on which the plastic substrate 5 having the surface treatment layer is laminated is disposed on the viewing side of the liquid crystal cell and the viewing side of the organic EL element.

  The hard coat layer can have a smooth surface or a surface with irregularities. For example, a resin material such as silicone, acrylic or urethane acrylate can be used alone, or a filler can be mixed with the resin. The layer formed by application | coating of what was made to illustrate can be illustrated. The hard coat layer can be provided by applying and curing the above hard coat resin by a known method such as a spin coat method or a micro gravure coat method. The thickness of the hard coat layer is about 1 to 30 μm, preferably 3 μm or more, and preferably 20 μm or less. The refractive index is usually 1.65 or less, preferably 1.45 to 1.65.

  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, or an ultraviolet ray. In general, it is formed to have a concavo-convex structure on the surface of the transparent plastic substrate 5 by a method of applying and curing a coating liquid in which transparent fine particles are mixed with a curable resin. If the above-described hard coat layer is formed in a state in which surface irregularities are provided, it becomes an antiglare layer.

  The antireflection layer is formed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be provided by a known method. For example, it can be formed by providing a layer of an organic substance, a metal, a metal compound, or the like using a coating method such as microgravure coating or a physical vapor deposition method such as vapor deposition or sputtering.

  Examples of the organic substance used for forming the antireflection layer include a polymer into which a fluorine atom is introduced. As the metal, aluminum, silver or the like can be preferably used. Metal compounds are generally inorganic, and inorganic oxides, inorganic sulfides, inorganic fluorides, and the like can be used. Examples of the inorganic oxide include silicon oxide, zinc oxide, titanium oxide, niobium oxide, cerium oxide, indium-tin oxide, tungsten oxide, molybdenum oxide, antimony oxide, aluminum oxide, and zirconium oxide. Examples of inorganic sulfides include zinc sulfide and antimony sulfide. Examples of inorganic fluorides include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, yttrium fluoride, lanthanum fluoride, cerium fluoride, fluoride Examples include samarium, niobium fluoride, and lead fluoride. In the case of providing an antireflection layer, it is sufficient that there is at least one layer composed of these organic substances, metals, metal compounds, etc., but a multilayer may be used as necessary.

  The antireflection layer can be provided directly on the resin substrate, but it is more effective to provide it on the hard coat layer. For the purpose of reducing the moisture permeability, a method of forming a metal compound film on the hard coat layer by sputtering is particularly suitable. As an example of the plastic substrate 5 provided with a suitable surface treatment layer, a transparent acrylic hard coat layer is formed for the purpose of imparting strength and an antireflection function, and an antireflection made of a metal compound is further formed thereon. A layer formed by sputtering can be mentioned.

[Second form of transparent plastic substrate: brightness enhancement film]
In the present invention, a brightness enhancement film can be used as the transparent plastic substrate 5. The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device or the like. For example, a plurality of thin film films having different refractive index anisotropies are laminated to produce anisotropy in reflectance. And a reflection type linearly polarized light separating sheet designed in the above, an oriented film of a cholesteric liquid crystal polymer, and a circularly polarized light separating sheet having the oriented liquid crystal layer supported on a film substrate. As a commercially available reflective linearly polarized light separating sheet, “DBEF” sold by 3M Company in the US [Sumitomo 3M Co., Ltd. in Japan] can be mentioned. The polarizing plate using the brightness enhancement film as the transparent plastic substrate 5 is disposed on the back side of the liquid crystal cell.

[Third form of transparent plastic substrate: substrate having phase difference]
In the present invention, the transparent plastic substrate 5 may also have a phase difference, that is, a phase difference film. In this case, the retardation film is preferably disposed so that the slow axis of the retardation film intersects with the absorption axis of the polarizer at an angle of about 45 °. As retardation films, polyvinyl alcohol, polycarbonate, polyester, polyarylate, polyimide, polyolefin, cyclic polyolefin, polystyrene, polysulfone, polyethersulfone, polyvinylidene fluoride / polymethyl methacrylate, liquid crystal polyester, acetylcellulose, ethylene-acetic acid Examples thereof include an optical film in which refractive index anisotropy is expressed by stretching a polymer film made of a saponified vinyl copolymer, polyvinyl chloride, or the like. In addition, a film that exhibits refractive index anisotropy by applying and aligning a liquid crystalline compound on an optically isotropic substrate having no phase difference, or an anisotropic refractive index by applying an inorganic layered compound A film exhibiting properties can also be used as a retardation film. When the retardation film is used as a transparent plastic substrate, it preferably exhibits a quarter wavelength retardation with respect to the wavelength of incident light, and the in-plane retardation value in that case is generally about 90 to 200 μm, Preferably it is 120-160 micrometers. The quarter wave plate has a function of changing linearly polarized light emitted from the polarizer into elliptically polarized light or circularly polarized light. If a polarizing plate using a retardation film as a transparent plastic substrate 5 is arranged on the front side of the liquid crystal cell, when the screen of the liquid crystal panel is viewed with polarized sunglasses, the polarization axis of the polarized sunglasses and the polarization axis of the polarizing plate are It becomes possible to eliminate the visual defect caused by the orthogonality. Here, the polarized sunglasses are glasses in which a polarizing plate is incorporated, and transmit only linearly polarized light that vibrates in one direction (for example, the horizontal direction or the vertical direction).

[Production method of polarizing plate]
Next, the manufacturing method of the polarizing plate which concerns on this invention is demonstrated based on FIG. In this method, first, in the polarizing plate precursor preparation step, as shown in FIG. 2A, a transparent protective film 2 and a first pressure-sensitive adhesive layer 1 are laminated in this order on one side of a polarizer 3, On the other surface of the child 3, the second pressure-sensitive adhesive layer 4 having a storage elastic modulus of 0.15 to 1 MPa in the temperature range of 23 to 80 ° C. as described above is formed. The precursor 9 is produced. A separator 7 for temporarily protecting the surface of the first pressure-sensitive adhesive layer 1 is usually provided, and the surface is also temporarily attached to the outer side of the second pressure-sensitive adhesive layer 4. It is customary to provide a protective separator 8.

  Next, the separator 8 is peeled off from the second pressure-sensitive adhesive layer 4, and in the laminating step, as shown in FIG. 2B, the separator 8 is transparent to the second pressure-sensitive adhesive layer 4 of the polarizing plate precursor 9. A plastic substrate 5 is laminated.

  Thus, the polarizing plate precursor 9 laminated in the order of the first pressure-sensitive adhesive layer 1 / transparent protective film 2 / polarizer 3 / second pressure-sensitive adhesive layer 4 is prepared in advance, and then the first By taking the form of laminating the transparent plastic substrate 5 on the second pressure-sensitive adhesive layer 4, it becomes possible to produce a polarizing plate having various functions only by changing the transparent plastic substrate 5. Therefore, according to the various types of functions provided to the transparent plastic substrate 5, it is possible to quickly cope with a variety of small-quantity production.

  In the polarizing plate precursor production step, the polarizing plate precursor 9 is finally laminated in the order of the first pressure-sensitive adhesive layer 1 / transparent protective film 2 / polarizer 3 / second pressure-sensitive adhesive layer 4. The order of stacking is not particularly limited. For example, the transparent protective film 2 is laminated on one side of the polarizer 3, the first pressure sensitive adhesive layer 1 is provided thereon, and then the other side of the polarizer 3 is 0 in a temperature range of 23 to 80 ° C. The operation may be performed in the order of forming the second pressure-sensitive adhesive layer 4 exhibiting a storage elastic modulus of .15 to 1 MPa, or the transparent protective film 2 is laminated on one side of the polarizer 3, On the other surface, a second pressure-sensitive adhesive layer 4 having a storage elastic modulus of 0.11 to 1 MPa in the temperature range of 23 to 80 ° C. is formed, and the transparent protective film 2 / polarizer 3 / second sensitivity is formed. You may operate in the order of setting it as the layer structure of the pressure adhesive layer 4, and finally providing the 1st pressure sensitive adhesive layer 1 on the transparent protective film 2. FIG.

  The transparent protective film 2 and the first pressure-sensitive adhesive layer 1 are laminated in this order on one side of the polarizer 3, and the second pressure-sensitive adhesive layer 4 is prepared on the other side of the polarizer 3. In pasting the transparent plastic substrate 5 to which a high function is imparted to the second pressure-sensitive adhesive layer 4 of the polarizing plate precursor 9 described above, it is described in the single-wafer laminating technique or the Patent Document 3. Such a sheet-roll composite bonding method can be employed. In addition, when it can be produced in a long length and the required quantity is large, a roll-to-roll bonding method is also useful.

[Composite polarizing plate]
The polarizing plate 10 of the present invention having the layer configuration shown in FIG. 1 or obtained as shown in FIG. 2B is laminated with an optical layer showing other optical characteristics to form a composite polarizing plate. be able to. FIG. 3 is a schematic cross-sectional view showing an example of the layer structure of the composite polarizing plate. In this case, usually, the separator 7 is peeled off from the first pressure-sensitive adhesive layer 1 in FIG. 1 or FIG. 2 (B), and another optical layer 15 is laminated on the first pressure-sensitive adhesive layer 1. Is done. A third pressure-sensitive adhesive layer 16 for bonding to another member such as an image display element can be provided on the surface of the other optical layer 15. When the third pressure-sensitive adhesive layer 16 is provided, it is usual that the separator 19 is further bonded and the surface thereof is temporarily protected until it is bonded to another member. As the third pressure-sensitive adhesive layer 16, the same material as that described above for the first pressure-sensitive adhesive layer 1 can be used, and the separator 19 has also been described above for the separator 7. The same thing as can be used. When the polarizing plate of the present invention is applied to a liquid crystal cell to form a liquid crystal display device, it is particularly useful to make such a composite polarizing plate.

[Optical layer constituting composite polarizing plate]
Examples of the optical layer 15 exhibiting other optical characteristics typically include a retardation plate and an optical compensation film. As described above, the retardation plate can be composed of a stretched thermoplastic resin film, for example, polycarbonate resin, polysulfone resin, polyarylate resin, triacetyl cellulose, diacetyl cellulose, cyclic polyolefin resin. A film obtained by stretching a resin film made of resin or the like to develop an in-plane direction retardation is used. The optical compensation film is for compensating the optical retardation when the polarizing plate is mounted on a liquid crystal display. For example, the optical compensation film is formed by forming a coating layer of an inorganic layered compound to express the retardation in the thickness direction. Examples thereof include a film and an optical compensation film on which a coating layer of a liquid crystal compound is formed. Commercially available optical compensation films with a liquid crystal compound coating layer include “Wide View” (sometimes referred to as “WV film”) sold by FUJIFILM Corporation, Nippon Oil Corporation There are “Nisseki NH Film” sold by Co., Ltd.

  The angle formed between the slow axis of the retardation plate or the optical compensation film and the absorption axis of the polarizer 3 is not particularly limited, and is appropriately set according to the specifications of the applied liquid crystal cell. When an optical compensation film is bonded to form a composite polarizing plate, compared with a laminated polarizing plate and retardation plate, the occurrence of color loss can be more effectively suppressed. preferable.

[Image display device]
The polarizing plate 10 of the present invention as shown in FIG. 1 and the composite polarizing plate 20 of the present invention as shown in FIG. 3 are bonded to an image display element such as a liquid crystal cell or an organic EL element, and an image display device is obtained. It can be. If it is the polarizing plate 10 of FIG. 1, the separator 7 will be peeled and removed from there, and the 1st pressure sensitive adhesive layer 1 will be bonded to an image display element. In the case of the composite polarizing plate of FIG. 3, the separator 19 is peeled and removed therefrom, and the third pressure-sensitive adhesive layer 16 is bonded to the image display element. When applied to a liquid crystal cell, the polarizing plate 10 or the composite polarizing plate 20 of the present invention is bonded to at least one surface thereof. Moreover, when applying to an organic EL element, the polarizing plate 10 or the composite polarizing plate 20 of this invention is bonded by the visual recognition side.

  Hereinafter, the present invention will be described more specifically with reference to comparative examples. However, the present invention is not limited to the following examples. In the following examples, the storage elastic modulus of the pressure-sensitive adhesive is a value measured by the following method.

<Measurement method of elastic modulus>
A cylindrical specimen of 8mmφ × 1mm thickness was made from pressure sensitive adhesive, and storage elastic modulus (G ′) was measured by a torsional shear method with a frequency of 1 Hz using a REOMETRIC viscoelasticity measuring instrument “DYNAMIC ANALYZER RDA II”. Asked.

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

  Pressure sensitive adhesive A: Polyethylene terephthalate film (separator) having a thickness of 38 μm obtained by releasing an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate-based crosslinking agent to a copolymer of butyl acrylate and acrylic acid A sheet-like pressure-sensitive adhesive obtained by coating the mold release surface with a die coater so that the thickness after drying becomes 15 μm and drying. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

  Pressure-sensitive adhesive B: A commercially available sheet-like feeling in which a release-treated surface of a 38 μm-thick polyethylene terephthalate film (separator) subjected to a release treatment is provided with an acrylic pressure-sensitive adhesive layer having a thickness of 15 μm Pressure adhesive. No urethane acrylate oligomer is blended. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

  Pressure-sensitive adhesive C: Commercially sheet-like feeling in which a release-treated surface of a 38 μm-thick polyethylene terephthalate film (separator) subjected to a release treatment is provided with an acrylic pressure-sensitive adhesive layer having a thickness of 25 μm Pressure adhesive. No urethane acrylate oligomer is blended. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

[Reference Example 1] Preparation of a hard coat resin film The UV curable hard coat agent “GRANDIC PC1141” sold by DIC Corporation is applied to one side of an acrylic resin film, and the film thickness after drying using a bar coater. After applying to about 10 μm, the solvent was removed by drying. In this state, a “D bulb” lamp manufactured by Fusion was used as a light source, and ultraviolet rays were continuously irradiated twice with an integrated light amount of 561 mJ / cm ² to form a hard coat layer. The thickness of the hard coat layer after curing was 8.3 μm. The elastic modulus of this acrylic resin film with a hard coat layer was 3,000 MPa. The surface of the film on which the hard coat layer is not formed is attached to a glass plate through a pressure-sensitive adhesive layer having a thickness of about 25 μm and then hardened according to JIS K 5400-1990 except that the load is 500 g. The pencil hardness on the surface of the coat layer was measured. As a result, this hard coat layer exhibited a pencil hardness of 3H.

[Example 1]
In this example, a polarizing plate according to the present invention having the layer structure shown in FIG. 2B was produced according to the process shown in FIG. First, a 40 μm thick triacetyl cellulose film as a protective film 2 was bonded to one side of a 25 μm thick polarizer 3 in which iodine was adsorbed and oriented on a polyvinyl alcohol film via an epoxy adhesive. Next, the pressure-sensitive adhesive A (15 μm thickness) shown above was bonded to the polarizer 3 side on the pressure-sensitive adhesive layer side to form a second pressure-sensitive adhesive layer 4. Further, on the protective film 2 side, the pressure-sensitive adhesive C (25 μm thickness) shown above is bonded on the pressure-sensitive adhesive layer side to form the first pressure-sensitive adhesive layer 1, and the polarizing plate Precursor 9 was obtained. A separator 7 is provided on the surface of the first pressure-sensitive adhesive layer 1, and a separator 8 is provided on the surface of the second pressure-sensitive adhesive layer 4.

  The separator 8 on the second pressure-sensitive adhesive layer 4 is peeled off from the obtained polarizing plate precursor 9, and the acrylic resin film with a hard coat layer produced in Reference Example 1 is applied to the pressure-sensitive adhesive layer 4. The transparent plastic substrate 5 was formed by bonding on the side opposite to the hard coat layer, and the polarizing plate 10 corresponding to FIG. The total thickness of the obtained polarizing plate 10 was 193 μm except for the separator 7 covering the first pressure-sensitive adhesive layer 1.

[Comparative Example 1]
A 40 μm thick triacetyl cellulose film as a protective film was bonded to both sides of the same 25 μm thick polyvinyl alcohol film as used in Example 1 via an epoxy adhesive. On one side, the pressure-sensitive adhesive B (15 μm thickness) shown above was pasted on the pressure-sensitive adhesive layer side, and the separator was peeled and removed. The acrylic resin film with a hard coat layer was pasted on the side opposite to the hard coat layer. On the other hand, the pressure sensitive adhesive C (25 μm thickness) shown above is applied to the surface of the protective film of the triacetyl cellulose opposite to the protective film in which the pressure sensitive adhesive B and the acrylic resin film with a hard coat layer are laminated. The polarizing plate was produced by laminating on the pressure adhesive layer side.

  The polarizing plate produced here has a protective film / polarizer / protective film layer structure, a plastic substrate (acrylic resin film with a hard coat layer) on one side, and a pressure-sensitive adhesive layer on the other side. It is a thing of the structure used traditionally as a polarizing plate arrange | positioned at the visual recognition side of a liquid crystal cell. The total thickness of this polarizing plate was 233 μm excluding the separator covering the pressure-sensitive adhesive layer on one side.

[Comparative Example 2]
A polarizing plate was produced in the same manner as in Example 1 except that the pressure sensitive adhesive A (high elastic modulus, 15 μm thickness) was changed to the pressure sensitive adhesive B (low elastic modulus, 15 μm thickness).

[Heat resistance durability test]
The polarizing plates obtained in Example 1 and Comparative Examples 1 and 2 were cut into a diagonal size of 3 inches (about 76 mm), and a pressure-sensitive adhesive layer on one side thereof (in Example 1, the first pressure-sensitive adhesive). Layer 1 and Comparative Example 1 and 2 are 25 μm-thick pressure-sensitive adhesive layer), and the separator is peeled off, and the pressure-sensitive adhesive layer is attached to a 0.7 mm-thick glass plate at a temperature of 50 ° C. Autoclaving was performed for 20 minutes under the condition of a pressure of 0.5 MPa. After natural cooling, each sample was put into an oven at 85 ° C. and subjected to a heat durability test for 500 hours. The dimensions before and after the durability test were measured using a two-dimensional measuring instrument “NEXIV VMR-12072” manufactured by Nikon Corporation, and the dimensional change rate was calculated by the following equation.
Dimensional change rate (%) = [(dimension before test−dimension after test) / dimension before test] × 100

  The above test results are summarized in Table 1 together with the total thickness of each polarizing plate.

  As can be seen from Table 1, the polarizing plate of the present invention produced in Example 1 is a transparent plastic through the second pressure-sensitive adhesive layer 4 as compared with the polarizing plate having the conventional layer structure (Comparative Example 1). Since the board | substrate 5 is laminated | stacked so that it may serve also as the protective layer of the polarizer 3, the number of the unit films which comprise a polarizing plate can be reduced, and it will become thin and lightweight. In addition, since the second pressure-sensitive adhesive layer 4 is a hard material having a storage elastic modulus of 0.19 MPa even at 80 ° C., the dimensional change when placed under a high temperature condition of 85 ° C. for 500 hours. The rate is 1.5%, and dimensional changes at high temperatures can be effectively prevented as compared with Comparative Example 2 using a general soft pressure-sensitive adhesive.

[Example 2]
In this example, the transparent plastic substrate is made of a cyclic polyolefin resin, and a quarter-wave plate [trade name “SES430140S”, sold by Sumitomo Chemical Co., Ltd.] that exhibits an in-plane retardation of 140 nm at a wavelength of 590 nm ] Was used. Then, in the same manner as in Example 1, except that the slow axis of the quarter-wave plate as the transparent plastic substrate 5 is crossed at an angle of 45 ° with the absorption axis of the polarizer, A plate was made.

[Reference Example 2]
A polarizing plate was produced in the same manner as in Example 2, except that the angle between the slow axis of the quarter-wave plate and the absorption axis of the polarizer was 0 °.

[Comparative Example 3]
Except for changing the transparent plastic substrate to the same quarter-wave plate as used in Example 2 and pasting so that its slow axis intersects with the absorption axis of the polarizer at an angle of 45 °, A polarizing plate was produced in the same manner as in Comparative Example 1.

[Observation with polarized sunglasses]
Prepare a 2.8 inch diagonal (approx. 71 mm) liquid crystal display device (trade name “EXILIM Keitai W53CA” from Casio Computer Co., Ltd.) and peel off the polarizing plate located on the viewing side from the liquid crystal cell. It was. On the other hand, the polarizing plates obtained in Example 2, Reference Example 2 and Comparative Example 3 were cut into a diagonal size of 2.8 inches (about 71 mm), and a pressure-sensitive adhesive layer on one side (Example 2 and Reference). In Example 2, the separator was peeled off from the first pressure-sensitive adhesive layer 1 and in Comparative Example 3 the pressure-sensitive adhesive layer having a thickness of 25 μm, and the pressure-sensitive adhesive layer was peeled off from the viewing side polarizing plate. Then, the liquid crystal display device having a diagonal size of 2.8 inches was prepared on the viewing side of the liquid crystal display device so that the absorption axis direction was the same as that of the original polarizing plate. The obtained liquid crystal display device was turned on, and the image was observed through polarized sunglasses. Observation was performed from 360 ° in all directions with respect to the screen of the liquid crystal display device, and evaluation was performed according to the following criteria.

○: Images can be viewed from all directions.
×: There is an angle at which the image cannot be visually recognized.

  The above test results are summarized in Table 2 together with the total thickness of each polarizing plate.

  As can be seen from Table 2, the polarizing plate of the present invention prepared in Example 2 and Reference Example 2 is formed by laminating a quarter wavelength plate on a polarizing plate (protective film / polarizer / protective film) having a traditional layer structure. Compared to Comparative Example 3 having the above-described configuration, a quarter-wave plate is laminated on one side of the polarizer via the second pressure-sensitive adhesive layer 4, so the number of unit films constituting the polarizing plate is reduced. Can be made thinner and lighter. When such a quarter wave plate is used as the transparent plastic substrate 5, the slow axis of the quarter wave plate intersects with the absorption axis of the polarizer at an angle of 45 ° as in the second embodiment. Therefore, it is possible to ensure good visibility when viewing the screen through polarized sunglasses, as compared with Reference Example 2 in which the angle is 0 °.

It is a cross-sectional schematic diagram which shows the layer structure of the polarizing plate which concerns on this invention. It is a cross-sectional schematic diagram which shows the manufacturing method of the polarizing plate which concerns on this invention for every process, Comprising: (A) represents a polarizing plate precursor preparation process, (B) represents a lamination process. It is a cross-sectional schematic diagram which shows the example of the layer structure of the composite polarizing plate which concerns on this invention. It is a cross-sectional schematic diagram which shows the layer structure of the polarizing plate conventionally used conventionally, and the example which arrange | positions a plastic substrate in the single side | surface.

Explanation of symbols

1 …… First pressure sensitive adhesive layer,
2 ... Transparent protective film,
3 ... Polarizer,
4, 34 ... second pressure sensitive adhesive layer,
5 ... Transparent plastic substrate,
7, 8, 19 ... separator,
9 …… Polarizing plate precursor,
10 …… Polarizing plate,
15. Other optical layers,
16 ... Third pressure sensitive adhesive layer,
20 ... Composite polarizing plate,
30: Conventional traditional polarizing plate.

Claims (9)

  A first pressure-sensitive adhesive layer, a transparent protective film, a polarizer, a second pressure-sensitive adhesive layer, and a transparent plastic substrate are laminated in this order, and the second pressure-sensitive adhesive layer is 23 A polarizing plate having a storage elastic modulus of 0.15 to 1 MPa in a temperature range of -80 ° C.   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 polarizing plate according to claim 1 or 2, wherein the second pressure-sensitive adhesive layer has a thickness in the range of 3 to 25 µm.   The polarizing plate according to any one of claims 1 to 3, wherein the transparent plastic substrate has a tensile elastic modulus in a range of 2,500 to 4,000 MPa.   The polarizing plate according to claim 1, wherein the transparent plastic substrate has a surface treatment layer on the side opposite to the surface in contact with the second pressure sensitive adhesive.   The polarizing plate according to claim 1, wherein the transparent plastic substrate is a brightness enhancement film.   The polarizing plate according to claim 1, wherein the transparent plastic substrate has a phase difference, and a slow axis thereof intersects with an absorption axis of the polarizer at an angle of about 45 °. A transparent protective film and a first pressure-sensitive adhesive layer are laminated in this order on one side of the polarizer, and the other side of the polarizer exhibits a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. A polarizing plate precursor preparation step of forming a second pressure sensitive adhesive layer to prepare a polarizing plate precursor, and a lamination in which a transparent plastic substrate is laminated on the second pressure sensitive adhesive layer of the polarizing plate precursor The manufacturing method of the polarizing plate characterized by including a process.   A composite polarizing plate comprising a laminate of the polarizing plate according to claim 1 and an optical layer exhibiting other optical properties.

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