JP6324366B2 - Polarizer - Google Patents

Description

  The present invention relates to a polarizing plate that can be used for various optical applications.

With the demand for thinning a polarizing plate, it has been studied to arrange a protective film made of a transparent resin that is usually bonded to both sides of a polarizer only on one side of the polarizer.
For example, Patent Document 1 discloses a liquid crystal panel in which a substrate of a liquid crystal cell, an adhesive layer, and a polarizer are laminated.

  In order to satisfy the demand for thinning the polarizing plate, for example, 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. A polarizing plate has been developed (Patent Document 2).

JP 2006-292939 A JP 2010-39458 A

  The polarizing plate having the above structure is likely to change in the positive curl direction (direction in which the end portion is lifted) due to its configuration. For example, when the polarizing plate is exposed to a high temperature condition, in particular, a condition in which high temperature and low temperature are repeated (hereinafter, sometimes referred to as “cooling circulation environment”), the polarizer and the reflective polarizing plate may contract. Further, the protective film may be warped due to the shrinkage. In addition, since the adhesive to the panel bonded to the glass panel is subjected to the condition that the force of warping toward the reflective polarizing plate and the adhesive force between the adhesive and the glass panel act in the opposite direction, eventually. Cohesive failure can occur in the panel paste. When cohesive failure occurs in the glue to the panel, part of the glue to the panel remains in the protective film and the rest remains in the glass panel, which not only adversely affects the appearance but is also incorporated into the liquid crystal display device. Sometimes, light leakage occurs at the end of the liquid crystal display device, and the display quality is degraded.

  For this reason, it is required to suppress the warpage of the protective film and the like due to the shrinkage of the polarizer and the reflective polarizing plate, and further to suppress the cohesive failure of the paste against the panel. The configuration using a film is not sufficient because the above problem may occur.

  Then, an object of this invention is to provide the polarizing plate by which the curvature resulting from the shrinkage | contraction of a polarizer and a reflective polarizing plate was suppressed. Furthermore, this invention aims at providing the polarizing plate by which the cohesive failure of the adhesive layer bonded by the glass panel of a liquid crystal cell was suppressed, for example.

The present invention includes the following.
[1] A polarizing plate in which a reflective polarizing plate, a first pressure-sensitive adhesive layer, a polarizer, a protective film, and a second pressure-sensitive adhesive layer are laminated in this order, and the reflective polarizing plate The interlayer thickness from the first pressure-sensitive adhesive layer side surface to the surface on the opposite side of the protective film in the second pressure-sensitive adhesive layer is 60 μm or less, and the tensile elastic modulus at 85 ° C. of the protective film is The polarizing plate which is 2500 MPa or less.
[2] The polarizing plate according to [1], wherein the protective film is a cyclic polyolefin resin film.
[3] The polarizing plate according to [1], wherein the protective film is an acrylic resin film.
[4] The polarizing plate according to any one of [1] to [3], wherein the thickness of the first pressure-sensitive adhesive layer is 20 μm or less.
[5] The polarizing plate according to any one of [1] to [4], wherein the second pressure-sensitive adhesive layer has a storage elastic modulus at 80 ° C. of 0.025 MPa or more and a thickness of 10 to 30 μm. .
[6] The polarizing plate according to any one of [1] to [5], wherein the polarizer has a thickness of 10 μm or less.
[7] The polarized light according to any one of [1] to [6], wherein the reflective polarizing plate has at least two thin films, and the at least two thin films have different refractive index anisotropy. Board.

  According to the present invention, a thin polarizing plate can be obtained. Further, even when the polarizing plate is exposed to a high temperature condition, particularly in a cold circulation environment, the warping of the polarizing plate is suppressed, and further, the cohesive failure of the second pressure-sensitive adhesive layer can be suppressed.

FIG. 1 illustrates a schematic cross-sectional view of a preferred layer structure in the polarizing plate of the present invention. FIG. 2A is a schematic cross-sectional view when warping occurs in the positive curl direction in the polarizing plate. FIG. 2B is a photomicrograph of the polarizing plate observed from the reflective polarizing plate 12 side when the polarizing plate is warped in the positive curl direction.

  Hereinafter, although the polarizing plate concerning this invention is demonstrated using a figure suitably, this invention is not limited to these embodiment.

The polarizing plate of the present invention is a polarizing plate in which a reflective polarizing plate, a first pressure-sensitive adhesive layer, a polarizer, a protective film, and a second pressure-sensitive adhesive layer are laminated in this order,
The interlayer thickness from the first pressure-sensitive adhesive layer side surface in the reflective polarizing plate to the surface on the opposite side of the protective film in the second pressure-sensitive adhesive layer is 60 μm or less,
The protective film has a tensile elastic modulus at 85 ° C. of 2500 MPa or less.

  For example, as shown in FIG. 1, the polarizing plate of the present invention includes a reflective polarizing plate 12, a first pressure-sensitive adhesive layer 13, a polarizer 11, a protective film 22, and a second pressure-sensitive adhesive layer 23. Is a polarizing plate 100 laminated in this order.

  The polarizing plate in the present invention is an interlayer thickness from the surface on the first pressure-sensitive adhesive layer side in the reflective polarizing plate to the surface opposite to the protective film in the second pressure-sensitive adhesive layer (hereinafter simply referred to as “interlayer thickness”). However, it is 60 μm or less, preferably 55 μm or less, more preferably 47 μm or less. The lower limit of the interlayer thickness from the first pressure-sensitive adhesive layer side surface in the reflective polarizing plate to the surface on the opposite side of the protective film in the second pressure-sensitive adhesive layer is preferably 20 μm, more preferably 30 μm, particularly Preferably it is 40 micrometers.

  The interlayer thickness is preferably 20 to 60 μm, more preferably 20 to 55 μm, and more preferably 20 to 47 μm.

  Here, the interlayer thickness corresponds to, for example, the interlayer thickness (D) in FIG. In this case, the interlayer thickness (D) corresponds to the total thickness of the first pressure-sensitive adhesive layer 13, the polarizer 11, the protective film 22, and the second pressure-sensitive adhesive layer 23.

  Although not shown in FIG. 1, for example, a layer other than the above layers may be provided between the reflective polarizing plate 12 and the second pressure-sensitive adhesive layer 23 shown in FIG. 1. In such a case, the thickness of the newly provided layer is also included in the interlayer thickness. Moreover, the polarizer 11 and the protective film 22 are normally bonded together through the adhesive bond layer. The thickness of the adhesive layer can also be included in the interlayer thickness.

  The interlayer thickness of the polarizing plate in the present invention can be measured using a measurement method known in the technical field.

  In the polarizing plate of the present invention, the tensile elastic modulus at 85 ° C. of the protective film is 2500 MPa or less, preferably the tensile elastic modulus is 2200 MPa or less, more preferably 1800 MPa or less.

  The tensile elastic modulus at 85 ° C. of the protective film is usually 600 MPa or more, preferably 1400 MPa or more, and more preferably 1500 MPa or more.

  Moreover, Preferably, the tensile elasticity modulus in 85 degreeC of a protective film is 600-2500 Mpa, More preferably, it is 1400-2200 Mpa, More preferably, it is 1500-1800 Mpa.

In the polarizing plate of the present invention, the interlayer thickness from the first pressure-sensitive adhesive layer side surface in the reflective polarizing plate to the surface on the opposite side of the protective film in the second pressure-sensitive adhesive layer is included in the predetermined range of the present application. In addition, since the tensile elastic modulus at 85 ° C. of the protective film is included in the predetermined range of the present application, for example, even if the polarizing plate is exposed to a high temperature condition, particularly in a cold circulation environment, the reflective polarizing plate , Warpage of the first pressure-sensitive adhesive layer, the polarizer, the protective film, and further the second pressure-sensitive adhesive layer can be suppressed. As a result, warpage of the entire polarizing plate can be suppressed.
Here, that a polarizing plate is exposed to high temperature conditions means that a polarizing plate is exposed to the temperature of 70 to 95 degreeC for 30 to 60 minutes, for example.

  When the polarizing plate is exposed to a high temperature condition, at least one of the reflective polarizing plate, the first pressure-sensitive adhesive layer, the polarizer, the protective film, and the second pressure-sensitive adhesive layer has a positive curl direction (edge In more detail, it can be lifted and warped in such a way that its end faces the reflective polarizing plate.

  In addition, when the polarizing plate in this invention is exposed to high temperature conditions and a slight curvature may arise in a polarizing plate, a reflection type polarizing plate, a 1st adhesive layer, a polarizer, a protective film, and a 2nd adhesion The agent layer can warp together. Therefore, in the polarizing plate of the present invention, usually, delamination cannot occur between at least one of the reflective polarizing plate, the first pressure-sensitive adhesive layer, the polarizer, the protective film, and the second pressure-sensitive adhesive layer.

  Due to the warpage of the polarizing plate, the second pressure-sensitive adhesive layer may also be warped (lifted), and the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer may be coherently broken. Thus, when cohesive failure occurs in the second pressure-sensitive adhesive layer, a part of the second pressure-sensitive adhesive remains in the protective film, and the rest of the second pressure-sensitive adhesive is bonded to the second pressure-sensitive adhesive. Remaining on the substrate, eg glass panel. Such a state is also referred to as a state where glue streaks are generated in this specification. Further, in the present invention, the glue stripe means, for example, a continuous stripe-like or radial stripe of the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer remaining on a glass panel or the like.

Such warpage can be evaluated by measuring the amount of warpage in the present invention. For example, the amount of warpage is determined by laminating the second pressure-sensitive adhesive layer of the polarizing plate on a glass panel and leaving it for 50 hours, with 30 minutes under an environment of −40 ° C. and then 30 minutes under an environment of 85 ° C. About the polarizing plate after, the relative height of the bulge of an edge part with respect to the horizontal surface of the in-plane center part in the surface on the opposite side to the 1st adhesive layer of a reflective polarizing plate is measured.
FIG. 2A is a schematic cross-sectional view when warping occurs in the positive curl direction in the polarizing plate. For example, the amount of warpage of the polarizing plate after standing for 50 hours in the above-mentioned cold heat circulation environment is as shown in the figure, the rising height of the entire end portion of the entire polarizing plate 100, and the reflective polarizing plate of the polarizing plate 100 It can be calculated from the distance from the height of the horizontal plane at the in-plane central portion of the surface on the opposite side to the first adhesive layer 13. However, the deformation | transformation aspect of each layer is an example, and is not limited to this form. FIG. 2A is an example in the case where the amount of contraction of the polarizer is larger than the amount of contraction of the reflective polarizing plate after standing for 50 hours in the cold heat circulation environment. Further, for example, depending on the type and thickness of the reflective polarizing plate, a different deformation mode from that shown in FIG.
Preferably, the amount of warpage of the polarizing plate of the present invention is 0.1 to 10 μm, more preferably 0.1 to 8 μm. When the amount of warpage exceeds the above range, significant cohesive failure occurs in the second pressure-sensitive adhesive layer. If the cohesive failure of the second pressure-sensitive adhesive layer is significant, not only the appearance of the polarizing plate is adversely affected, but also light leakage occurs at the edge of the liquid crystal display device when incorporated in the liquid crystal display device, and the display quality is increased. Decreases. For example, in the case of a polarizing plate having a length of 12 to 16 cm and a width of 6 to 10 cm, the amount of warpage is 0.1 to 10 μm, more preferably 0.1 to 8 μm.

On the other hand, for example, as shown in FIG. 2A, from the surface of the glass panel on the second adhesive layer side, the end of the polarizing plate that floats up, that is, the glass panel side of the second adhesive layer remaining on the protective film It is also possible to measure the distance from the surface edge (hereinafter also referred to as “lift amount”). In this case, a preferable lifting amount is 0.1 to 10 μm, more preferably 0.1 to 8 μm. When the lifting amount exceeds the above range, significant cohesive failure occurs in the second pressure-sensitive adhesive layer. If the cohesive failure of the second pressure-sensitive adhesive layer is significant, not only the appearance of the polarizing plate is adversely affected, but also light leakage occurs at the edge of the liquid crystal display device when incorporated in the liquid crystal display device, and the display quality is increased. Decreases.
Moreover, in the case of a polarizing plate having a length of 12 to 16 cm and a width of 6 to 10 cm, the lifting amount is preferably 0.1 to 10 μm, more preferably 0.1 to 8 μm.
The relationship between the value of the “warp amount” and the value of the “lift amount” is not particularly limited as long as each value is within the above range. For example, when the value of “warp amount” is the maximum value, the value of “lift amount” may be the minimum value. The value of “warp amount” and the value of “lift amount” may be approximate.

In the present invention, the “glue stripe length” is calculated by observing the polarizing plate from the reflective polarizing plate side and measuring the length of the observed glue stripe. Specifically, the distance between the straight line formed by connecting the lower ends of both sides of the convex part in the observed glue stripe and the vertex of the convex part is measured, this measurement is performed several times, and the maximum of the obtained measurement results The value is “glue line length”.
For example, when the polarizing plate is observed from the reflective polarizing plate side, glue streaks are observed as shown in FIG. 2 (B), and the length of the glue streak from the lower end on both sides of the convex portion and the apex of the convex portion is observed. Calculated.
The glue streak length can be measured by a method known in the art. The paste streak length is preferably less than 100 μm, more preferably less than 50 μm. By including the paste streak length within such a range, the visibility of the polarizing plate cannot be adversely affected. On the other hand, when the glue stripe length is 100 μm or more, the visibility of the polarizing plate is adversely affected, and the appearance of the polarizing plate is also deteriorated.

In a preferred embodiment, when the amount of warpage is 0.1 to 10 μm, the paste stripe length is 5 to 90 μm, and more preferably 5.0 to 50 μm.
In another preferred embodiment, when the lifting amount is 5.0 μm, the glue stripe length is 5 to 90 μm, more preferably 5.0 to 50 μm.

  In the present invention, the “glue displacement distance” indicates the moving distance of the polarizing plate end due to the contraction of the polarizing plate. For example, the paste displacement distance is the distance between the end of the polarizing plate from the end of the polarizing plate immediately after being bonded to a substrate such as a glass panel to the end of the polarizing plate after standing for 240 hours in an environment of 85 ° C. It may be a moving distance. As shown in FIG. 2 (B), when the polarizing plate is observed from above, the glue shift distance is from the end of the polarizing plate immediately after being bonded to a substrate such as a glass panel to the end of the polarizing plate after shrinkage. Can be shown. Note that the end portion of the polarizing plate shown in FIG. 2B means the end portion of the reflective polarizing plate 12. Also, the paste displacement distance may vary depending on the combination of the second pressure-sensitive adhesive and the polarizer used.

[Reflective polarizing plate]
The reflective polarizing plate is also called a brightness enhancement film, and a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmitted polarized light and reflected polarized light or scattered polarized light is used. As described above, by arranging the reflective polarizing plate above the polarizer, it is possible to improve the emission efficiency of linearly polarized light emitted from the polarizer by using retroreflected light that is reflected polarized light or scattered polarized light. it can. The reflective polarizing plate is laminated in contact with the first pressure-sensitive adhesive layer.

  The reflective polarizing plate can be, for example, an anisotropic reflective polarizer. An example of an anisotropic reflective polarizer is an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is DBEF made of 3M ( JP-A-4-268505). Such a reflective polarizing plate is a reflective polarizing plate formed by stretching a multilayer laminate composed of at least two thin films having different refractive index anisotropies. Therefore, such a reflective polarizing plate has at least two thin films, and the stretched at least two thin films have different refractive index anisotropy.

  Another example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ / 4 plate, and a specific example thereof is a PCF manufactured by Nitto Denko (JP-A-11-231130, etc.). Yet another example of an anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer (US) that emits reflected polarized light even in the visible light region by finely processing the metal. Patent No. 6288840, etc.), a film (JP-A-8-184701) obtained by adding metal fine particles into a polymer matrix and stretching.

  An optical layer such as a hard coat layer, an antiglare layer, a light diffusing layer, and a retardation layer having a retardation value of ¼ wavelength is provided on the surface opposite to the first pressure-sensitive adhesive layer in the reflective polarizing plate. It may be provided. By forming the optical layer, the adhesion to the backlight tape and the uniformity of the display image can be improved. The thickness of the reflective polarizing plate can be about 5 to 100 μm, but is preferably 10 to 40 μm, more preferably 10 to 30 μm from the viewpoint of thinning the polarizing plate.

  In the polarizing plate of the present invention, the surface of the reflective polarizing plate on the first pressure-sensitive adhesive layer side can be subjected to a surface activation treatment. This surface activation treatment is performed prior to bonding of the reflective polarizing plate and the first pressure-sensitive adhesive layer. Thereby, the polarizing plate excellent in wet heat durability in which peeling between a 1st adhesive layer and a reflective polarizing plate does not arise easily in a wet heat environment is obtained.

  The surface activation treatment may be a surface hydrophilization treatment, and may be a dry treatment or a wet treatment. Examples of the dry treatment include discharge treatment such as corona treatment, plasma treatment and glow discharge treatment; flame treatment; ozone treatment; UV ozone treatment; ionizing active ray treatment such as ultraviolet treatment and electron beam treatment. Examples of the wet treatment include ultrasonic treatment using a solvent such as water or acetone, alkali treatment, anchor coat treatment, and the like. These processes may be performed alone or in combination of two or more.

  Among these, the surface activation treatment is preferably a corona treatment and / or a plasma treatment from the viewpoint of the effect of suppressing peeling of the reflective polarizing plate in a wet heat environment and the productivity of the polarizing plate. According to these surface activation treatments, even when the thickness of the reflective polarizing plate is thin, for example, 30 μm or less, peeling occurs between the first pressure-sensitive adhesive layer and the reflective polarizing plate in a humid heat environment. Can be effectively suppressed. A surface activation treatment may also be performed on the surface of the first pressure-sensitive adhesive layer on the luminance reflective polarizing plate side.

[First adhesive layer]
The first pressure-sensitive adhesive layer is a layer interposed between the polarizer and the reflective polarizing plate. The first pressure-sensitive adhesive layer is typically directly laminated on the polarizer so that the polarizer and the first pressure-sensitive adhesive layer are in contact with each other.
The first pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition whose main component is a resin such as acrylic, rubber-based, urethane-based, ester-based, silicone-based, or polyvinyl ether-based. Among these, a pressure-sensitive adhesive composition having an acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer is preferable. The pressure-sensitive adhesive composition may be an active energy ray curable type or a thermosetting type.

  Examples of the acrylic base polymer include (meth) acrylic acid ester bases such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Polymers and copolymer base polymers using two or more of these (meth) acrylic acid esters are preferably used. The base polymer is preferably copolymerized with a polar monomer. 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 carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as (meth) acrylate.

  The pressure-sensitive adhesive composition usually further contains a crosslinking agent. As a crosslinking agent, a metal ion having a valence of 2 or more, which forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound, which forms an amide bond with a carboxyl group; Examples thereof include epoxy compounds and polyols that form ester bonds with carboxyl groups; polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

  The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and has an adhesive property even before irradiation with active energy rays. It is a pressure-sensitive adhesive composition having such a property that it can be adhered to an adherend such as the like and can be cured by irradiation with active energy rays to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably ultraviolet curable. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Further, if necessary, a photopolymerization initiator, a photosensitizer and the like may be contained.

  The pressure-sensitive adhesive composition contains fine particles for imparting light scattering properties; beads; resins other than the base polymer; tackifiers; fillers; antioxidants; ultraviolet absorbers; pigments; be able to.

  A 1st adhesive layer can be formed by apply | coating the organic solvent dilution liquid of the said adhesive composition on a base material, and making it dry. The substrate can be a polarizer, a reflective polarizing plate, a separator or the like. When the active energy ray-curable pressure-sensitive adhesive composition is used, a desired cured product can be obtained by irradiating the formed pressure-sensitive adhesive layer with active energy rays.

  The first pressure-sensitive adhesive layer preferably exhibits a storage elastic modulus of 0.15 to 1.2 MPa in a temperature range of 23 to 80 ° C. Thereby, the dimensional change which is easy to generate | occur | produce with shrinkage | contraction of a polarizer in heat-resistant and cold-heat circulation environment can be suppressed, and durability of a polarizing plate can be improved. In addition, when a liquid crystal display device equipped with a polarizing plate (for example, a liquid crystal display device for a small-to-medium-sized mobile terminal) is placed in a heat-resistant and cold-circulating environment, the movement of the polarizing plate is suppressed. Can improve the reliability.

  “Shows a storage elastic modulus of 0.15 to 1.2 MPa in a temperature range of 23 to 80 ° C.” means that the storage elastic modulus is a value within 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 within the above range is exhibited at the temperature in this range. Can be seen. The storage elastic modulus of the first pressure-sensitive adhesive layer is 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 described later. Can do.

  As a method for adjusting the storage elastic modulus to the above range, an active energy ray-curable type is further prepared by further adding an oligomer, specifically, a urethane acrylate-based oligomer, to a pressure-sensitive adhesive composition containing a base polymer and a crosslinking agent. The pressure-sensitive adhesive composition (preferably an ultraviolet curable pressure-sensitive adhesive composition) is mentioned. More preferably, the adhesive layer is appropriately cured by irradiating active energy rays.

  The thickness of the first pressure-sensitive adhesive layer can be 30 μm or less. The thickness is preferably 25 μm or less, particularly preferably 20 μm or less, and particularly preferably 15 μm or less. When the thickness of the 1st adhesive layer exists in such a range, the dimensional change of a polarizing plate can be suppressed, maintaining favorable workability. In addition, the thickness of the first pressure-sensitive adhesive layer can be adjusted as appropriate so that the interlayer thickness falls within a predetermined range.

[Polarizer]
A polarizer is an absorptive polarizer that has the property of absorbing linearly polarized light having a vibration plane parallel to the absorption axis and transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to the transmission axis). In addition, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be suitably used. The polarizer is, for example, a step of uniaxially stretching a polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye; a polyvinyl on which the dichroic dye is adsorbed It can be produced by a method comprising a step of treating an 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 polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having ammonium groups, and the like.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can be determined according to JIS K 6726.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizer (polarizing film). The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based raw film is not particularly limited, but in order to make the thickness of the polarizer 10 μm or less, it is preferable to use a film having a thickness of about 5 to 35 μm. More preferably, it is 20 μm or less.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

  In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a polyvinyl alcohol-based resin film is swollen using a solvent. The draw ratio is usually about 3 to 8 times.

  As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

As a dyeing treatment with iodine, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine content in the aqueous solution can be about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide can be about 0.5 to 20 parts by weight per 100 parts by weight of water. Moreover, the temperature of this aqueous solution can be about 20-40 degreeC. On the other hand, as a dyeing treatment with a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye is usually employed. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The content of the dichroic organic dye in this aqueous solution can be about 1 × 10 ⁻⁴ to 10 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution can be about 20 to 80 ° C.

  As boric acid treatment after dyeing with a dichroic dye, a method of immersing a dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution is usually employed. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of boric acid in the boric acid-containing aqueous solution can be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in this aqueous solution can be about 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution can be 50 ° C. or higher, for example, 50 to 85 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C.

  A polarizer is obtained by performing a drying process after washing with water. The drying process can be performed using a hot air dryer or a far infrared heater. The thickness of the polarizer is preferably 15 μm or less, and more preferably 10 μm or less. Setting the thickness of the polarizer to 15 μm or less is advantageous for reducing the thickness of the polarizing plate and thus the liquid crystal display device. The thickness of the polarizer is usually 4 μm or more. The thickness of the polarizer can be adjusted as appropriate so that the interlayer thickness falls within a predetermined range.

[Protective film]
A protective film is a film laminated | stacked on the surface on the opposite side to the 1st adhesive layer in a polarizer. The protective film is a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a polyolefin such as a chain polyolefin resin (polypropylene resin, etc.) or a cyclic polyolefin resin (norbornene resin, etc.). Cellulose resins such as triacetyl cellulose and diacetyl cellulose; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resins; Acrylic resins such as (meth) acrylic resins; Polystyrene resins; Polyvinyl chloride resin; Acrylonitrile butadiene styrene resin; Acrylonitrile styrene resin; Polyvinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether It may be a film made of polyimide resin or the like; system resin; polysulfone resins; poly (ether sulfone) resins; polyarylate resin; polyamide-imide resin. Among them, it is preferable to use a polyolefin resin or an acrylic resin, and it is particularly preferable to use a cyclic polyolefin resin.

  Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  Cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used. In a preferred embodiment, the protective film according to the present invention contains a cyclic polyolefin resin.

  Cellulosic resins are those in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp) are substituted with acetyl groups, propionyl groups and / or butyryl groups. Further, it refers to a cellulose organic acid ester or a cellulose mixed organic acid ester. Examples include cellulose acetates, propionic acid esters, butyric acid esters, and mixed esters thereof.

  Preferable specific examples of the acrylic resin film include a film containing a methyl methacrylate resin. The methyl methacrylate resin is a polymer containing 50% by weight or more of methyl methacrylate units. The content of methyl methacrylate units is preferably 70% by weight or more, and may be 100% by weight. The polymer having a methyl methacrylate unit of 100% by weight is a methyl methacrylate homopolymer obtained by polymerizing methyl methacrylate alone.

  This methyl methacrylate-based resin is usually a monofunctional monomer mainly composed of methyl methacrylate and a polyfunctional monomer used as necessary, as a radical polymerization initiator and as required. It can be obtained by polymerization in the presence of a chain transfer agent.

  Monofunctional monomers that can be copolymerized with methyl methacrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxy methacrylate. Methacrylic acid esters other than methyl methacrylate such as ethyl; methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate Acrylic acid esters such as: 2- (hydroxymethyl) methyl acrylate, 3- (hydroxyethyl) methyl acrylate, 2- (hydroxymethyl) ethyl acrylate, and 2- (hydroxymethyl) Hydroxyacrylic esters such as butyl crylate; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; Substituted styrenes such as vinyltoluene and α-methylstyrene; Acrylonitrile and methacrylate Examples thereof include unsaturated nitriles such as nitrile; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. Such monomers may be used alone or in combination of two or more.

  Examples of the polyfunctional monomer that can be copolymerized with methyl methacrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate. , Nonaethylene glycol di (meth) acrylate, and ethylene glycol such as tetradecaethylene glycol (meth) acrylate or the oligomers of both end hydroxyl groups esterified with acrylic acid or methacrylic acid; both ends of propylene glycol or its oligomer A hydroxyl group esterified with acrylic acid or methacrylic acid; neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, and butanediol di Those obtained by esterifying a hydroxyl group of a dihydric alcohol such as (meth) acrylate with acrylic acid or methacrylic acid; bisphenol A, an alkylene oxide adduct of bisphenol A, or both terminal hydroxyl groups of these halogen-substituted products with acrylic acid or methacrylic acid Esterified; esterified polyhydric alcohols such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylic acid, and those obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl groups; Epoxy of glycidyl acrylate or glycidyl methacrylate to acids, adipic acid, terephthalic acid, phthalic acid, dibasic acids such as halogen substitution products thereof, and alkylene oxide adducts thereof Those with shea groups by ring-opening addition; aryl (meth) acrylate; and diaryl compounds of divinylbenzene, and the like. Among these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and neopentyl glycol dimethacrylate are preferably used.

  The methyl methacrylate resin may be a modified methyl methacrylate resin modified by performing a reaction between functional groups of the resin. As the reaction, for example, demethanol condensation reaction in a polymer chain between a methyl ester group of methyl acrylate and a hydroxyl group of 2- (hydroxymethyl) methyl acrylate, and a carboxyl group of acrylic acid and 2- (hydroxymethyl) ) Intrapolymer dehydration condensation reaction with hydroxyl group of methyl acrylate.

  It is also useful to control the retardation value of the protective film to a value suitable for a liquid crystal display device. For example, it is preferable to use a film having a substantially zero retardation value for an in-plane switching (IPS) mode liquid crystal display device. A retardation value of substantially zero means that the in-plane retardation value at a wavelength of 590 nm is 10 nm or less, the absolute value of the thickness direction retardation value at a wavelength of 590 nm is 10 nm or less, and the thickness direction position at a wavelength of 480 to 750 nm. The absolute value of the phase difference value is 15 nm or less.

  Depending on the mode of the liquid crystal display device, the protective film may be stretched and / or shrunk to give a suitable retardation value.

  Although the thickness of a protective film can be about 1-30 micrometers, 5-25 micrometers is preferable from viewpoints, such as intensity | strength and a handleability, and 5-20 micrometers is more preferable. When the thickness is within this range, the polarizer is mechanically protected, and the polarizer does not shrink even when exposed to a humid heat environment, and stable optical characteristics can be maintained. In addition, the thickness of a protective film can be adjusted suitably so that the said interlayer thickness may become a predetermined range.

  A protective film can be bonded to a polarizer via an adhesive layer. As the adhesive forming the adhesive layer, a water-based adhesive or an active energy ray-curable adhesive can be used.

  Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, and the like. Among these, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used. Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying a polymer, a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof, or the like can be used. The water-based adhesive can contain a crosslinking agent such as an aldehyde compound, an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, or a polyvalent metal salt.

  When using a water-based adhesive, it is preferable to carry out a drying step in order to remove water contained in the water-based adhesive after bonding the polarizer and the protective film. After the drying process, for example, a curing process for curing at a temperature of about 20 to 45 ° C. may be provided.

  The active energy ray-curable adhesive refers to an adhesive that cures when irradiated with active energy rays such as ultraviolet rays, for example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, Examples thereof include a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from the photopolymerizable monomer. Examples of the photopolymerization initiator include those containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photocurable epoxy monomer and a cationic photopolymerization initiator can be preferably used.

  When using an active energy ray-curable adhesive, after bonding a polarizer and a protective film, a drying step is performed as necessary, and then the active energy ray-curable adhesive is irradiated by irradiating active energy rays. A curing step for curing is performed. The light source of the active energy ray is not particularly limited, but ultraviolet light having a light emission distribution at a wavelength of 400 nm or less is preferable. A wave excitation mercury lamp, a metal halide lamp, etc. can be used.

  In pasting the polarizer and the protective film, saponification treatment, corona treatment, plasma treatment, or the like can be performed on at least one of the pasting surfaces.

[Second adhesive layer]
The pressure-sensitive adhesive forming the second pressure-sensitive adhesive layer may be appropriately selected from conventionally known pressure-sensitive adhesives and peeled off in a high temperature environment where the polarizing plate is exposed, a moist heat environment, or an environment where high and low temperatures are repeated. What is necessary is just to have the adhesiveness of the grade which does not arise. Specific examples include acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, and acrylic pressure-sensitive adhesives are particularly preferable in terms of transparency, weather resistance, heat resistance, and processability.
The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may use the same type of pressure-sensitive adhesive, or may use different types of pressure-sensitive adhesives.
In a preferred embodiment, the second pressure-sensitive adhesive layer is formed from an acrylic pressure-sensitive adhesive.

  For the adhesive, if necessary, a tackifier, plasticizer, glass fiber, glass beads, metal powder, other inorganic powders, fillers, pigments, colorants, fillers, antioxidants, UV absorbers Various additives such as an antistatic agent and a silane coupling agent may be appropriately blended.

  The pressure-sensitive adhesive layer is usually formed by applying a pressure-sensitive adhesive solution on a release sheet and drying the pressure-sensitive adhesive solution. For application onto the release sheet, for example, roll coating methods such as reverse coating and gravure coating, spin coating methods, screen coating methods, fountain coating methods, dipping methods, spraying methods and the like can be employed. The release sheet provided with the pressure-sensitive adhesive layer is used by a method of transferring the release sheet. The thickness of an adhesive layer is about 3-30 micrometers normally, Preferably it is 10-30 micrometers, More preferably, it is 10-25 micrometers. In a preferred embodiment, when the second pressure-sensitive adhesive layer has such a thickness, the polarizing plate can be prevented from being broken, and when incorporated in the liquid crystal display device, light leakage occurs at the end of the liquid crystal display device. It can be suppressed. In addition, the thickness of the second pressure-sensitive adhesive layer can be adjusted as appropriate so that the interlayer thickness falls within a predetermined range.

  The storage elastic modulus at 80 ° C. of the second pressure-sensitive adhesive layer is preferably 0.025 MPa or more, more preferably 0.07 MPa or more. If the storage elastic modulus of the pressure-sensitive adhesive layer is less than 0.025 MPa, the second pressure-sensitive adhesive layer may cause cohesive failure. If the cohesive failure is significant, not only the appearance of the polarizing plate is adversely affected but also the liquid crystal display When incorporated in the device, light leakage occurs at the edge of the liquid crystal display device, which adversely affects the display. Preferably, the storage elastic modulus at 80 ° C. of the second pressure-sensitive adhesive layer is 1.1 MPa or less, preferably 0.9 MPa or less. When the storage elastic modulus of the pressure-sensitive adhesive layer at 80 ° C. exceeds 1.1 MPa, the heat durability against the second pressure-sensitive adhesive layer and glass or panel is deteriorated, and bubbles are easily generated between the layers.

  A separator may be provided to protect the surface of the second adhesive layer until it is bonded to another member. For example, a film made of a transparent resin such as polyethylene terephthalate, which has been treated with a release agent such as silicone, is used.

[Production method of polarizing plate]
The polarizing plate of the present invention includes, for example, the following steps:
Applying a surface activation treatment to the surface of the reflective polarizing plate on the first pressure-sensitive adhesive layer side, and laminating the first pressure-sensitive adhesive layer on the surface subjected to the surface activation treatment;
It is produced through.

  Moreover, the polarizing plate of this invention is a 2nd adhesive layer on the surface on the opposite side to the polarizer in bonding a protective film through the adhesive bond layer on the single side | surface of a polarizer, for example. , Laminating the first pressure-sensitive adhesive layer on the surface of the polarizer opposite to the protective film, and applying a reflective polarizing plate to the surface of the first pressure-sensitive adhesive layer opposite to the polarizer Including laminating. Through these steps, the polarizing plate of the present invention is obtained. In addition, a separator may be temporarily attached to the outer surface of the second pressure-sensitive adhesive layer, and a surface activation treatment may be performed on the bonding surface of the first pressure-sensitive adhesive layer with the reflective polarizing plate.

  The method of bonding the reflective polarizing plate to the first pressure-sensitive adhesive layer may be a single wafer bonding method, or a sheet / roll composite bonding method as described in JP-A-2004-262071. May be. 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.

  Thus, the manufacturing method of the polarizing plate of this invention can be created by a well-known method in the said technical field.

[Liquid Crystal Display]
The polarizing plate according to the present invention can be preferably applied to a liquid crystal display device. The liquid crystal display device includes a liquid crystal cell and a polarizing plate according to the present invention bonded to the surface thereof. The polarizing plate can be bonded to the liquid crystal cell through the second pressure-sensitive adhesive layer. The polarizing plate according to the present invention is usually used as a polarizing plate disposed on the backlight side of the liquid crystal cell. The driving method of the liquid crystal cell may be any conventionally known method, but is preferably the IPS mode. The liquid crystal display device using the polarizing plate according to the present invention is excellent in wet heat durability.

  This invention can obtain an organic electroluminescent display apparatus by bonding a polarizing plate to an organic electroluminescent display through a 2nd adhesive layer.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

The film thickness, tensile modulus, and storage modulus of the pressure-sensitive adhesive layer were measured as follows.

(1) Thickness The thickness was measured using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(2) Tensile modulus A test piece of 2.5 cm width × 10 cm length was cut out from the film. Next, with the upper and lower grips of a tensile tester [manufactured by Shimadzu Corporation AUTOGRAPH AG-1S tester], both ends of the test piece in the long side direction are sandwiched so that the distance between the grips is 5 cm, and the environment at 85 ° C. The tensile modulus at 85 ° C. was calculated from the slope of the initial straight line in the obtained stress-strain curve. This measurement was performed with respect to the “film transport direction (MD direction), and the calculated value was taken as the tensile modulus of the film.

(3) Storage elastic modulus The storage elastic modulus G 'of the pressure-sensitive adhesive layer was measured according to the following (I) to (III).
(I) Two samples of 25 ± 1 mg are taken out from the pressure-sensitive adhesive layer, and each is formed into a substantially ball shape.
(II) The obtained approximately ball-shaped sample is attached to the upper and lower surfaces of the I-shaped jig, and the upper and lower surfaces are sandwiched between the L-shaped jig. The configuration of the measurement sample is L-shaped jig / adhesive / I-shaped jig / adhesive / L-shaped jig.
(III) Using the dynamic viscoelasticity measuring device “DVA-220” manufactured by IT Measurement Control Co., Ltd., the storage elastic modulus G ′ of the sample thus prepared was measured at a temperature of 80 ° C., a frequency of 1 Hz, and an initial strain of 1N. Measured under conditions.

[Production of polarizer]
A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 5 times by dry stretching and further kept in a pure water at 60 ° C. while maintaining tension. After being immersed for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizer-1 having a thickness of 7 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

[Example of preparation of first pressure-sensitive adhesive layer]
The organic solvent solution containing the composition shown in Table 1 was applied to the release treatment surface of the separator made of polyethylene terephthalate having a thickness of 38 μm, which had been subjected to the release treatment, so as to have a predetermined thickness after drying with a die coater. Then, a pressure-sensitive adhesive layer with a separator obtained by drying was obtained. Table 1 shows the thickness of the first pressure-sensitive adhesive layer and the storage elastic modulus at 80 ° C. in each Example and Comparative Example.

[Example of preparation of second pressure-sensitive adhesive layer]
An organic solvent solution containing the composition shown in Table 2 was applied to the release treatment surface of a separator made of polyethylene terephthalate having a thickness of 38 μm so as to have a predetermined thickness after drying with a die coater. Then, a pressure-sensitive adhesive layer with a separator obtained by drying was obtained. Table 2 shows the thickness of the first pressure-sensitive adhesive layer and the storage elastic modulus at 80 ° C. in each Example and Comparative Example.

[Reflective polarizing plate]
As the reflective polarizing plate-1, “Advanced Polarized Film, Version 3” (thickness: 26 μm) manufactured by 3M was used.

[Protective film]
The following protective films were used.
COP-1: Cycloolefin-based protective film (manufactured by Zeon Corporation), thickness 13 μm, in-plane retardation value at wavelength 590 nm = 3.46 nm, tensile modulus at 80 ° C. = 1766 MPa.
COP-2: Cycloolefin-based protective film (manufactured by JSR Corporation), thickness 15 μm, in-plane retardation value at wavelength 590 nm = 2.44 nm, tensile modulus at 80 ° C. = 1601 MPa.
Zero TAC: Triacetylcellulose-based protective film (manufactured by Konica Minolta, Inc.), thickness 20 μm, in-plane retardation value at wavelength 590 nm = (1.37) nm, tensile modulus at 80 ° C. = 3956 MPa.
Acrylic-1: (manufactured by Okura Kogyo Co., Ltd.) Heat-resistant acrylic protective film, thickness 21 μm, in-plane retardation value at wavelength 590 nm = −1.6 nm, tensile modulus at 80 ° C. = 2025 MPa.
Acrylic-2: (manufactured by Sumitomo Chemical Co., Ltd.) Rubber particle-added general-purpose acrylic protective film, thickness 21 μm, in-plane retardation value at wavelength 590 nm = −1.6 nm, tensile modulus at 80 ° C. = 820 MPa.

"Preparation of water-based adhesive"
3 parts by weight of carboxyl group-modified polyvinyl alcohol [“KL-318” manufactured by Kuraray Co., Ltd.] was dissolved in 100 parts by weight of water to prepare an aqueous polyvinyl alcohol solution. To the obtained aqueous solution, 1.5 parts by weight of water-soluble polyamide epoxy resin (“Smile Resin 650 (30) manufactured by Taoka Chemical Industry Co., Ltd., solid concentration: 30% by weight)” was added to 100 parts by weight of water. Mixing at a ratio, an aqueous adhesive was obtained.

  100 parts of bis (3,4-epoxycyclohexylmethyl) adipate, 25 parts of diglycidyl ether of hydrogenated bisphenol A, and 4,4′-bis (diphenylsulfonio) diphenyl sulfide bis (hexafluorophosphate as a photocationic polymerization initiator ) (50% propylene carbonate solution) 2.2 parts (active ingredient amount) were mixed and defoamed to prepare an active energy ray-curable adhesive composed of a curable epoxy resin composition.

[Example of production of polarizing plate]
When using water-based adhesive.
First, the protective film 22 was bonded to one side of the polarizer 11 using the aqueous adhesive (thickness 10 to 100 nm). Prior to bonding, a corona treatment of 0.8 kJ / m ² was performed on the bonding surface of the protective film with the polarizer. Then, it was dried at 80 ° C. for 5 minutes and cured at 40 ° C. for 72 hours.

When using an active energy ray-curable adhesive.
A protective film 22 was bonded to one surface of the polarizer 11 using the active energy ray-curable adhesive. Prior to bonding, a corona treatment of 0.8 kJ / m ² was performed on the bonding surface of the protective film with the polarizer. After the polarizer 11 and the protective film 22 were bonded together, ultraviolet irradiation was performed with an ultraviolet irradiation device (lamp: Fusion D lamp, integrated light quantity: 1000 mJ / cm ² ), and left at room temperature for 1 hour.

Subsequently, the 1st adhesive layer was bonded to the surface on the opposite side to the surface where the protective film in a polarizer was laminated | stacked. Prior to bonding, 10.8 kJ / m ² of corona treatment was performed on both the bonding surface of the polarizer and the bonding surface of the first pressure-sensitive adhesive layer.

Next, the 2nd adhesive layer was bonded on the outer surface of the protective film. Prior to bonding, 0.8 kJ / m ² of corona treatment was performed on both the bonding surface of the protective film and the bonding surface of the second pressure-sensitive adhesive layer.

Finally, the separator of the first pressure-sensitive adhesive layer is peeled off and subjected to a corona treatment of 0.8 kJ / m ^{2 on} one side of the reflective polarizing plate. It stuck on the outer surface of the adhesive layer of, and the polarizing plate was obtained.

  The structures of the polarizing plates thus obtained are shown in Table 3 (Examples) and Table 4 (Comparative Examples). Moreover, the physical property evaluation of each obtained polarizing plate was performed according to the following description.

[Measurement of interlayer thickness]
The interlayer thickness from the first pressure-sensitive adhesive layer side surface of the reflective polarizing plate to the surface of the second pressure-sensitive adhesive layer opposite to the protective film was calculated. Table 3 (Examples) and Table 4 (Comparative Examples) show the interlayer thicknesses in Examples and Comparative Examples. The thicknesses of the various layers were measured using a digital micrometer “MH-15M” manufactured by Nikon Corporation. The interlayer thickness was calculated by adding the thickness of each layer.

[Measurement of warpage]
About the polarizing plate produced above, the curvature amount was measured with the following method. First, in the produced polarizing plate, the surface opposite to the protective film in the second pressure-sensitive adhesive layer is bonded to glass (manufactured by Corning, product number: EAGLE XG ^{(registered trademark)} ), and the cooling and heating cycle (to -40 ° C) The mixture was allowed to stand for 50 hours in an environment of 30 minutes and then 1 cycle at 85 ° C. for 30 minutes. About the polarizing plate in which curvature generate | occur | produced, the value which pulled the height of the center part in a polarizing plate surface from the height of the swelling part of an edge part was measured as curvature amount. For the measurement of the amount of warpage, the average value of the amount of warpage obtained by measuring the warp height of the end three times using (product number: PLu neox 3D Optical Profiler manufactured by SENSOFAR) is shown in Table 3 (Example) and Table 4 (Comparative example).

[Measurement of glue stripe length]
In the polarizing plate used in the measurement of the amount of warpage, when warpage occurs, the second pressure-sensitive adhesive layer may cause cohesive failure, and the second pressure-sensitive adhesive layer side in the protective film and the second pressure-sensitive adhesive in the glass panel In some cases, the second pressure-sensitive adhesive was divided on the layer side, and the second pressure-sensitive adhesive remained on each of the protective film and the glass panel.
Here, the second pressure-sensitive adhesive remaining on the glass panel surface was present in a continuous streak-like or radial form. The length of the streaks of the second adhesive remaining on the glass panel, that is, the length of the glue streaks, (for example, manufactured by KEYENCE, product number: VHX-1000) at a magnification of 500x, for example, The lengths of the glue stripes shown in FIGS. 2 (A) and 2 (B) were measured. The length of the three glue streaks was measured, and the maximum value obtained was taken as the glue streak length in each example and comparative example. The results are shown in Table 3 (Examples) and Table 4 (Comparative Examples).

[Appearance evaluation]
Regarding the polarizing plate used in the measurement of the amount of warpage, the appearance of the polarizing plate was observed. Evaluation was performed according to the following criteria. The visibility of the glue stripes was confirmed with a magnifying glass, and then light leakage of the polarizing plate was observed in a state where it was overlapped with the glass laminated with another polarizing plate so as to be crossed Nicol.
A: The visibility of the polarizing plate was very good, and no light leakage from the polarizing plate was observed.
○: Visibility of the polarizing plate was good, and light leakage of the polarizing plate was not observed.
(Triangle | delta): The visibility of a polarizing plate was bad or the light omission of a polarizing plate was observed.
X: The visibility of the polarizing plate was poor, and light leakage of the polarizing plate was observed.

  From these results, the polarizing plate of the present invention can obtain a thin polarizing plate. Further, even when the polarizing plate is exposed to a high temperature condition, particularly in a cold circulation environment, the warping of the polarizing plate is suppressed, and further, the cohesive failure of the second pressure-sensitive adhesive layer can be suppressed. Moreover, even when the polarizing plate of the present invention is exposed to a high temperature condition, particularly in a cold circulation environment, the visibility of the polarizing plate is very good, and light leakage of the polarizing plate does not occur.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate by which the curvature resulting from the shrinkage | contraction of a polarizer and a reflective polarizing plate was suppressed is provided. Furthermore, according to this invention, the polarizing plate by which the cohesive failure of the adhesive layer bonded by the glass panel of the liquid crystal panel was also suppressed is provided.

DESCRIPTION OF SYMBOLS 11 Polarizer 12 Reflective polarizing plate 13 1st adhesive layer 22 Protective film 23 2nd adhesive layer 24 Base material 100 Polarizing plate

Claims (5)

A reflective polarizing plate, a first pressure-sensitive adhesive layer, a polarizer, an adhesive layer, a protective film, and a second pressure-sensitive adhesive layer laminated in this order, wherein the reflective type The interlayer thickness from the first pressure-sensitive adhesive layer side surface of the polarizing plate to the surface opposite to the protective film in the second pressure-sensitive adhesive layer is 20 μm or more and 60 μm or less, and the protective film at 85 ° C. The tensile modulus is 2500 MPa or less,
Said first adhesive layer, shows the storage modulus 0.15~1.2MPa in the temperature range of from 23 to 80 ° C. (Note that the first pressure-sensitive adhesive layer, storage modulus at 25 ° C. 0 The protective film is a polarizing plate , which is a cyclic polyolefin resin film or an acrylic resin film, except for the case of .5 MPa or less . The polarizing plate according to claim 1, wherein a thickness of the first pressure-sensitive adhesive layer is 20 μm or less. It said second adhesive layer has a storage elastic modulus at 80 ° C. is not less than 0.025 MPa, a thickness of 10 to 30 [mu] m, polarizing plate according to claim 1 or 2. The polarizer has a thickness of at 10μm or less, the polarizing plate according to any one of claims 1-3. The reflective polarizing has a thin film of at least two layers, the thin film of at least two layers, the refractive index anisotropy is different polarizing plate according to any one of claims 1-4.