Polarizer

Abstract

To provide a method of manufacturing a polarizing plate, which minimizes crack generation and prevents iodine elution in areas including edges during a heat shock test that involves repetitively switching between a low temperature (-40°C) condition and a high temperature (85°C) condition.SOLUTION: A polarizing plate manufacturing method is provided, comprising a first lamination step for pasting an optical film on at least one surface of a polarizer with a thickness of 15 μm or less to form a first laminate, and a humidification processing step for holding the first laminate in a gas phase with a relative humidity of 75%RH or higher at a temperature of 35°C or higher.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a polarizing plate, and further to a polarizer, a polarizing plate, and an image display device including the same.

Background Art

[0002] Patent Document 1 proposes a method for manufacturing a polarizer in which a portion with a low boric acid concentration is formed at an end by bringing the polarizer into contact with a treatment liquid at 50°C or higher.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the manufacturing method described in Patent Document 1, in a plan view of a portion where the polarizer is brought into contact with a treatment liquid at 50°C or higher, a portion with a low boric acid concentration is formed over the entire region from the end and up to 50 μm or more from the end, and iodine leakage occurs at a width exceeding 300 μm from the end and the end.

[0005] An object of the present invention is to provide a method for manufacturing a polarizing plate in which the occurrence of cracks is suppressed in a heat shock test that repeats low temperature (-40°C) conditions and high temperature (85°C) conditions, and iodine leakage does not occur in a region including the end. Another object of the present invention is to provide a polarizer in which cracks are suppressed and iodine leakage does not occur in a region including the end, and a polarizing plate including the polarizer.

Means for Solving the Problems

[0006] The present invention provides the following method for manufacturing a polarizing plate, a polarizer, a polarizing plate, and an image display device. [1] A method for manufacturing a polarizing plate, comprising: a first lamination step of producing a first laminate by laminating an optical film on at least one side of a polarizer having a thickness of 15 μm or less; a humidification treatment step of holding the first laminate in a gas phase at a temperature of 35°C or higher and a relative humidity of 75% RH or higher; and a method for manufacturing a polarizing plate including the above steps. [2] The method for manufacturing a polarizing plate according to [1], further comprising a forming step of forming the first laminate before the humidification treatment step. [3] The method for manufacturing a polarizing plate according to [2], wherein in the forming step, a deformed portion is formed on the first laminate. [4] The method for manufacturing a polarizing plate according to [2] or [3], further comprising a cutting step of cutting the first laminate before the humidification treatment step. [5] The method for manufacturing a polarizing plate according to [4], wherein in the cutting step, the first laminate is cut so that in a plan view of the first laminate, the position of the end of the optical film and the position of the end of the polarizer are the same. [6] A polarizer containing a resin film containing boric acid and iodine, having a thickness of 15 μm or less, wherein in a region including the end of the polarizer, there is a region containing boric acid at a concentration lower than the concentration of boric acid in a region other than the said region, and no iodine loss occurs in the region including the end of the polarizer. [7] A polarizing plate having the polarizer according to [6] and an optical film laminated on at least one side of the polarizer. [8] The polarizing plate according to [7], wherein in an end portion in a plan view of the polarizing plate, the position of the end of the polarizer and the position of the end of the optical film are the same. [9] An image display device including the polarizing plate according to [8].

[10] The image display device according to [9], having a camera hole.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a method for manufacturing a polarizing plate in which the occurrence of cracks is suppressed in a heat shock test that repeats low-temperature (-40°C) conditions and high-temperature (85°C) conditions, and iodine loss does not occur in the region including the end portions. Further, according to the present invention, it is possible to provide a polarizer in which cracks are suppressed in a heat shock test (hereinafter, also referred to as a heat shock test for simplicity) that repeats low-temperature (-40°C) conditions and high-temperature (85°C) conditions, and iodine loss does not occur in the region including the end portions, and a polarizing plate including the polarizer.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the following drawings, the scale is appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component. In the drawings, equivalent components are denoted by equivalent reference numerals. X, Y, and Z shown in each figure mean three mutually orthogonal coordinate axes. The directions indicated by the XYZ coordinate axes in each figure are common to each figure.

[0010] <Method for Manufacturing a Polarizing Plate> The method for manufacturing a polarizing plate according to an embodiment of the present invention includes a first lamination step of laminating an optical film on at least one side of a polarizer having a thickness of 15 μm or less to produce a first laminate, and a humidification treatment step of holding the first laminate in a gas phase at a temperature of 35°C or higher and a relative humidity of 75% RH or higher.

[0011] The polarizing plate obtained by the method for manufacturing a polarizing plate may have optical films on both sides of the polarizer. As shown in FIG. 1, in the polarizing plate 1, the polarizer 2 is disposed between the first optical film 3 and the second optical film 4. Hereinafter, the first optical film and the second optical film may be collectively referred to as an optical film or a pair of optical films.

[0012] (First Lamination Step) In the first lamination step, a first laminate is produced by overlapping and laminating a polarizer and an optical film with each other. The polarizer and the optical film may be in the form of long strips. When the polarizer is overlapped so as to be disposed between a pair of optical films, as shown in FIG. 2, in the first laminate 10, the polarizer 7 is located between the pair of first optical films 5 and 9. The optical film can be laminated on the polarizer via an adhesive layer made of an adhesive.

[0013] Polarizer The polarizer may be, for example, a polarizer in which iodine is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film, and the polyvinyl alcohol molecular chains are crosslinked with boric acid. The polarizer can be an absorption-type polarizer having 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 orthogonal to the absorption axis (parallel to the transmission axis).

[0014] The polarizer can be produced, for example, by subjecting a polyvinyl alcohol-based resin film (hereinafter also referred to as a PVA film) to a stretching treatment, a dyeing treatment, and a crosslinking treatment. The stretching treatment, the dyeing treatment, and the crosslinking treatment can be carried out by known methods. The polyvinyl alcohol-based resin film may be in the form of a long strip or in the form of a single sheet.

[0015] For example, first, the PVA film is stretched in a uniaxial direction or a biaxial direction. The dichroic ratio of the polarizer stretched in the uniaxial direction tends to be high. Subsequently to the stretching, the PVA film is dyed with iodine, a dichroic dye (polyiodine), or an organic dye using a dyeing solution. The dyeing solution may contain boric acid, zinc sulfate, or zinc chloride. The PVA film may be washed with water before dyeing. By the water washing, dirt and the anti-blocking agent are removed from the surface of the PVA film. Also, as a result of the PVA film swelling by the water washing, uneven dyeing (dyeing spots) is likely to be suppressed. The PVA film after dyeing is treated with a crosslinking agent solution containing boric acid (for example, an aqueous solution of boric acid) for crosslinking. After the treatment with the crosslinking agent, the PVA film is washed with water and then dried. Through the above procedure, a polarizer including a resin film containing boric acid and iodine is obtained. The polyvinyl alcohol (PVA)-based resin is obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be, for example, polyvinyl acetate which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer (for example, ethylene-vinyl acetate copolymer). Other monomers copolymerizable with vinyl acetate may be, in addition to ethylene, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, or acrylamides having an ammonium group. The polyvinyl alcohol-based resin may be modified with aldehydes. The modified polyvinyl alcohol-based resin may be, for example, partially formalized polyvinyl alcohol, polyvinyl acetal, or polyvinyl butyral. The polyvinyl alcohol-based resin may be a polyene-based alignment film such as a dehydration product of polyvinyl alcohol or a dehydrochlorination product of polyvinyl chloride. Dyeing may be performed before stretching, or stretching may be performed in the dyeing solution. The length of the stretched resin film may be, for example, 3 to 7 times the length before stretching.

[0016] The thickness of the polarizer may be, for example, 15 μm or less, preferably 10 μm or less, and more preferably 8 μm or less. The thickness of the polarizer is usually 1 μm or more, and may be, for example, 3 μm or more. The thinner the polarizer, the easier it is to suppress the shrinkage or expansion of the polarizer itself due to temperature changes, and the easier it is to suppress the change in the dimensions of the polarizer itself. As a result, it becomes difficult for stress to act on the polarizer, and cracks in the polarizer tend to be suppressed.

[0017] (Optical film) The optical film may be a thermoplastic resin having translucency. The optical film may be an optically transparent thermoplastic resin. The resin constituting the optical film may be, for example, a chain polyolefin resin, a cyclic olefin polymer resin (COP resin), a cellulose ester resin, a polyester resin, a polycarbonate resin, a (meth)acrylic resin, a polystyrene resin, or a mixture or copolymer thereof.

[0018] When the polarizing plate has a first optical film and a second optical film, the composition of the first optical film may be exactly the same as the composition of the second optical film. For example, both the first optical film and the second optical film may contain a cyclic olefin polymer resin (COP resin). When the first optical film and the second optical film contain a cyclic olefin polymer resin (COP resin), the effects of the present invention are easily obtained. When the polarizing plate has a first optical film and a second optical film, the composition of the first optical film may be different from the composition of the second optical film.

[0019] The glass transition temperature of the first optical film and the second optical film is preferably 100°C or higher and 200°C or lower, or 120°C or higher and 150°C or lower. When the glass transition temperature of each of the first optical film and the second optical film is within the above range, the first optical film and the second optical film are likely to fuse with each other due to the heat generated by polishing the ends of each optical film.

[0020] The chain polyolefin resin may be a homopolymer of a chain olefin such as, for example, a polyethylene resin or a polypropylene resin. The chain polyolefin resin may also be a copolymer composed of two or more chain olefins.

[0021] The cyclic olefin polymer resin (cyclic polyolefin resin) may be, for example, a ring-opening (co)polymer of a cyclic olefin or an addition polymer of a cyclic olefin. The cyclic olefin polymer resin may be, for example, a copolymer (e.g., a random copolymer) of a cyclic olefin and a chain olefin. The chain olefin constituting the copolymer may be, for example, ethylene or propylene. The cyclic olefin polymer resin may also be a graft polymer obtained by modifying the above polymers with an unsaturated carboxylic acid or its derivative, or a hydride thereof. The cyclic olefin polymer resin may be, for example, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer.

[0022] The cellulose ester resin may be, for example, cellulose triacetate (triacetyl cellulose (TAC)), cellulose diacetate, cellulose tripropionate, or cellulose dipropionate. These copolymers may also be used. A cellulose ester resin in which a part of the hydroxyl groups is modified with other substituents may also be used.

[0023] A polyester resin other than the cellulose ester resin may also be used. The polyester resin may be, for example, a polycondensate of a polyvalent carboxylic acid or its derivative and a polyhydric alcohol. The polyvalent carboxylic acid or its derivative may be a dicarboxylic acid or its derivative. The polyvalent carboxylic acid or its derivative may be, for example, terephthalic acid, isophthalic acid, dimethyl terephthalate, or dimethyl naphthalenedicarboxylate. The polyhydric alcohol may be, for example, a diol. The polyhydric alcohol may be, for example, ethylene glycol, propanediol, butanediol, neopentyl glycol, or cyclohexanedimethanol.

[0024] The polyester resin may be, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethylene terephthalate, or polycyclohexanedimethylene naphthalate.

[0025] The polycarbonate resin is a polymer in which polymerization units (monomers) are bonded via carbonate groups. The polycarbonate resin may be a modified polycarbonate having a modified polymer skeleton, or may be a copolymerized polycarbonate.

[0026] (Meth)acrylic resins may be, for example, poly(meth)acrylate esters (e.g., polymethyl methacrylate (PMMA)); methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-(meth)acrylate ester copolymers; methyl methacrylate-acrylate ester-(meth)acrylic acid copolymers; (meth)acrylic acid methyl-styrene copolymers (e.g., MS resins); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid norbornyl copolymer, etc.).

[0027] Each of the first optical film and the second optical film may contain at least one additive selected from the group consisting of a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.

[0028] The thickness of the first optical film may be, for example, 5 μm or more and 90 μm or less, or 10 μm or more and 60 μm or less. The thickness of the second optical film may also be, for example, 5 μm or more and 90 μm or less, or 10 μm or more and 60 μm or less.

[0029] At least one of the first optical film and the second optical film may be a film having an optical function. The film having an optical function may be, for example, a retardation film or a brightness enhancement film. For example, by stretching the film made of the above thermoplastic resin or forming a liquid crystal layer or the like on the film, a retardation film with an arbitrary retardation value can be obtained.

[0030] The first optical film may be laminated on the polarizer via an adhesive layer. The second optical film may also be laminated on the opposite side of the first optical film of the polarizer via an adhesive layer. The adhesive layer may contain an aqueous adhesive such as polyvinyl alcohol. The adhesive layer may also contain an active energy ray curable resin described later.

[0031] The active energy ray curable resin is a resin that cures when irradiated with active energy rays. The active energy rays may be, for example, ultraviolet rays, visible light, electron beams, or X-rays. For example, the active energy ray curable resin may be an ultraviolet curable resin.

[0032] The active energy ray curable resin may be a single type of resin or may contain a plurality of types of resins. For example, the active energy ray curable resin may contain a cationically polymerizable curable compound or a radically polymerizable curable compound. The active energy ray curable resin may contain a cationic polymerization initiator or a radical polymerization initiator for initiating the curing reaction of the above curable compound.

[0033] The cationically polymerizable curable compound may be, for example, an epoxy-based compound (a compound having at least one epoxy group in the molecule) or an oxetane-based compound (a compound having at least one oxetane ring in the molecule). The radically polymerizable curable compound may be, for example, a (meth)acrylic-based compound (a compound having at least one (meth)acryloyloxy group in the molecule). The radically polymerizable curable compound may also be a vinyl-based compound having a radically polymerizable double bond.

[0034] The active energy ray-curable resin may contain, as necessary, a cationic polymerization accelerator, an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, an antistatic agent, a leveling agent, a solvent, or the like.

[0035] (Humidification treatment step) The humidification treatment is performed by holding the first laminate in a gas phase at a temperature of 35°C or higher and a relative humidity of 75% RH or higher. According to the humidification treatment, in the region including the end portion of the first laminate, a region containing boric acid at a concentration lower than the concentration of boric acid in the region other than this region (hereinafter also referred to as a low boric acid-containing region) is formed, but iodine leakage does not occur, and linear polarization light energy can be exhibited even in the low boric acid-containing region. The polarizing plate manufactured by the manufacturing method of the present invention does not crack even in the heat shock test and can exhibit linear polarization light energy in the region including the end portion.

[0036] As described in Patent Document 1, in order to suppress the occurrence of cracks in the heat shock test, it is known that it is effective to lower the concentration of boric acid contained in the end portion of the polarizer. However, in the manufacturing method described in Patent Document 1, boric acid is removed over the entire region from the end portion of the polarizer to 50 μm or more from the end portion. As a result, iodine leakage occurs over the entire region with a width exceeding 300 μm from the end portion and the end portion of the polarizer, and it has been found that linear polarization light energy cannot be exhibited at the end portion. However, according to the manufacturing method of the present invention, only the excess boric acid contained in the end portion of the polarizer is removed by performing the humidification treatment of holding in a gas phase at a temperature of 35°C or higher and a relative humidity of 75% RH or higher, and iodine leakage is less likely to occur. Therefore, the obtained polarizing plate can suppress the occurrence of cracks in the heat shock test and can exhibit linear polarization light energy at the end portion.

[0037] The concentration of boric acid refers to the concentration of boric acid per unit area including the thickness direction of the polarizing plate, and is measured, for example, by time-of-flight secondary ion mass spectrometry (TOF-SIMS) described in the column of Examples to be described later. In this specification, boric acid includes, for example, boric acid molecules (H3BO3) and borate ions (BO3 3- ). The region where iodine loss occurs (hereinafter also simply referred to as the iodine loss region) is a region visually observed as a region where light is transmitted in the cross Nicol state using a polarizing microscope. Iodine includes, for example, iodine molecules (I2), polyiodine complexes (I3 - , I5 - ), and iodide ions (I - ). In this specification, plan view means looking from the thickness direction of the polarizing plate.

[0038] The temperature of the gas phase is 35°C or higher. When the temperature of the gas phase is 35°C or higher, the excess boric acid contained in the end portion of the polarizing plate tends to be easily removed. From the viewpoint of facilitating the removal of boric acid, the temperature of the gas phase is preferably 40°C or higher. The temperature of the gas phase may be, for example, 90°C or lower, and is preferably 85°C or lower. When the temperature of the gas phase is 90°C or lower, iodine loss tends to be less likely to occur. The temperature of the gas phase can be adjusted within the above range so that the excess boric acid is removed at the end portion of the polarizer and iodine loss does not occur.

[0039] The relative humidity of the gas phase is 75%RH or higher. When the relative humidity is 75%RH or higher, the excess boric acid contained in the end portion of the polarizing plate tends to be easily removed. From the viewpoint of facilitating the removal of boric acid, the relative humidity of the gas phase is preferably 80%RH or higher. The relative humidity of the gas phase may be, for example, 90%RH or lower, and is preferably 85%RH or lower. When the relative humidity of the gas phase is 90%RH or lower, iodine loss tends to be less likely to occur. The relative humidity of the gas phase can be adjusted within the above range so that the excess boric acid is removed at the end portion of the polarizer and iodine loss does not occur.

[0040] The time for performing the humidification treatment may be, for example, 0.5 hours or more and 4 hours or less, preferably 1 hour or more and 3 hours or less, more preferably 1.5 hours or more and 2.5 hours or less, from the viewpoints of ease of removing boric acid and preventing iodine leakage. Further, the humidification treatment is usually continuously performed for the above-mentioned time.

[0041] The humidification treatment can be performed using, for example, a thermo-hygrostat oven.

[0042] When the first laminate has a deformed portion described later, from the viewpoints of suppressing cracks and making iodine leakage less noticeable, preferably, the humidification treatment is performed so that the end region included in the deformed portion is humidified.

[0043] The humidification treatment can be preferably performed so that the concentration of boric acid in the boric acid low-content region becomes higher as it moves away from the end in the inner direction from the end of the polarizing plate, from the viewpoints of suppressing cracks and making iodine leakage less noticeable in the appearance of the polarizing plate. Such a concentration tends to be easily obtained when the temperature of the gas phase is lowered, the relative humidity is lowered, or the time for performing the humidification treatment is shortened under the conditions of the humidification treatment.

[0044] The boric acid low-content region may be formed, for example, in a region exceeding 15 μm in the inner direction from the end in the plan view of the polarizing plate, preferably in a region exceeding 15 μm and less than 200 μm, more preferably in a region of 20 μm or more and 150 μm or less, still more preferably in a region of 20 μm or more and less than 100 μm, and particularly preferably in a region of 20 μm or more and less than 50 μm, from the viewpoint of crack suppression.

[0045] The boric acid low-content region may also be formed in a region of 15 μm or less from the end in the plan view of the polarizing plate. The boric acid low content region may be continuously formed in the entire region within 15 μm from the end portion in the plan view of the polarizing plate and in the entire region more than 15 μm and less than 200 μm in the inner direction from the end portion in the plan view of the polarizing plate. In other words, the boric acid low content region may be formed over the entire region between the end portion in the plan view of the polarizing plate and less than 200 μm from the end portion. When the boric acid low content region is formed over the entire region between the end portion in the plan view of the polarizing plate and less than 200 μm from the end portion, the boundary between the boric acid low content region and the other region can exist in the region between the end portion and less than 200 μm from the end portion. The boric acid low content region is preferably formed over the entire region between the end portion in the plan view of the polarizing plate and 100 μm or less from the end portion, more preferably formed over the entire region between the end portion in the plan view of the polarizing plate and 50 μm or less from the end portion, and still more preferably formed over the entire region between the end portion in the plan view of the polarizing plate and 20 μm or less from the end portion.

[0046] The end portion of the polarizing plate may not contain boric acid. The boundary between the region where the boric acid low content region is formed and the other region can be determined from the boric acid concentration profile with respect to the distance from the end portion obtained, for example, in the time-of-flight secondary ion mass spectrometry (TOF-SIMS) described in the column of the examples below. For example, when a region where the boric acid ion intensity is constant can be read in the boric acid concentration profile, the average value of the boric acid ion intensity in that region is obtained, and from the end portion to the position where the boric acid ion intensity becomes the above average value can be set as the boric acid low concentration site. When the region where the boric acid ion intensity is constant is difficult to read in the boric acid concentration profile, in the boric acid concentration profile, the average value of the boric acid ion intensity in the range of 30 μm inward from the point where the boric acid ion intensity is maximum is obtained, and from the end portion to the position where the boric acid ion intensity becomes the above average value can be set as the boric acid low concentration site.

[0047] The boric acid low content region may be a single continuous region in the plan view of the polarizing plate or may be divided into a plurality of regions.

[0048] The boric acid low-content region is preferably formed along the outer edge of the polarizing plate from the viewpoint of crack suppression. The boric acid low-content region may be formed along the entire outer edge of the polarizing plate or may be formed along a part of the outer edge of the polarizing plate.

[0049] By performing such a humidification treatment, a polarizer having a region containing boric acid at a lower concentration than the concentration of boric acid in a region other than this region is obtained at the end portion in the plan view of the polarizer. Specifically, this polarizer is a polarizer in which a boric acid low-concentration site having a boric acid concentration lower than the boric acid concentration in the inner region 500 μm or more inside from the end portion is formed. In the inner region, the concentration of boric acid can be substantially uniform. The polarizer 2 shown in FIG. 3 has a boric acid low-concentration site 30 in a region including the end portion in the plan view and can have an inner region 32 500 μm or more inside from the end portion. The inner region 32 can include a region for displaying an image when incorporated into a liquid crystal display device. The boric acid concentration in the intermediate region 31 between the boric acid low-concentration site 30 and the inner region 32 is usually substantially the same as the boric acid concentration in the inner region 32. Further, by performing this humidification treatment, a polarizer in which iodine loss does not occur at the end portion in the plan view of the polarizer is obtained. Specifically, this polarizer is a polarizer in which an iodine low-concentration site having an iodine concentration lower than the iodine concentration in the above inner region is not formed.

[0050] (Forming step) The method for manufacturing a polarizing plate may further include a forming step of forming the first laminate before the humidification treatment step. In the forming step, the first laminate can be formed into a predetermined shape by cutting and / or punching. The cutting and / or punching can be performed by using a blade or irradiating laser light. The laser light may be a CO2 laser.

[0051] The first laminate may have its dimensions adjusted to dimensions that are easy to process through a forming process. Further, a deformed portion may be formed at the outer edge portion of the first laminate by punching or cutting. The deformed portion may be, for example, a concave portion formed at the outer edge portion, a substantially V-shaped portion convex in the inner direction, and a through hole formed in the plane, in a plan view of the first laminate. The first laminate may have two or more deformed portions at the outer edge portion and / or in the plane. The through hole formed in the plane may be the above-described camera hole or the like.

[0052] In a polarizing plate having a deformed portion, stress tends to concentrate on the deformed portion and cracks tend to occur in a heat shock test. Despite having a deformed portion, in the polarizing plate of the present invention, a boric acid low content region is formed in the end region of the deformed portion, so that the occurrence of cracks is likely to be suppressed in a heat shock test.

[0053] The polarizing plate manufactured by the manufacturing method of the present invention is suitable for, for example, an image display device having a camera hole. In an image display device 20 having a camera hole 22, a cover glass 24, an adhesive layer 25, a polarizing plate 21, a liquid crystal panel 23, a polarizing plate 26, a camera 27, and a light shielding tape 28 as shown in FIG. 4, the portion forming the camera hole surrounded by a circle in the figure is likely to be directly visible. If iodine loss occurs in such a portion, the iodine loss is likely to be conspicuous, and as a result, the design property may be deteriorated. However, since iodine loss does not occur in the region including the end portion in the polarizing plate of the present invention, even when it is disposed on the viewing side in the image display device, iodine loss is less conspicuous and deterioration of the design property is less likely to occur.

[0054] When the deformed portion is a concave portion, from the viewpoint of crack suppression, preferably, the depth direction of the concave portion and the absorption axis (elongation axis direction) are formed to be orthogonal. Further, the concave portion may be formed such that its depth direction intersects the absorption axis (elongation axis direction) at an angle of usually 30° or more and 60° or less.

[0055] (Cutting process) The method for manufacturing a polarizing plate may further include a cutting step of bringing an end mill into contact with the outer periphery of the first laminate or the second laminate described below before the humidifying treatment step, and moving the end mill along the outer periphery of the laminate. As shown in FIG. 2, in the entire outer periphery of the first laminate 10 before the cutting step, the positions of the ends of the polarizer 7, the first optical film 5, and the second optical film 9 may be aligned.

[0056] As shown in FIGS. 5 and 6, the end mill 50 used in the cutting step has a blade (edge) 50e protruding on a side surface substantially parallel to its rotation axis 50a. In the cutting step, the side surface of the end mill 50 is brought into contact with the outer periphery (end face) of the first laminate 10, and the rotating end mill 50 is moved along the outer periphery of the first laminate 10. For example, the rotating end mill 50 may be moved along the path indicated by the arrow in FIG. 6. As a result, the outer periphery (end face) of the first laminate 10 is cut or polished by the blade 50e, the outer periphery (end face) of the first laminate 10 becomes smooth, the concave portion 13 is formed, and the inner corners of the concave portion 13 are chamfered. As shown in FIG. 5, after a plurality of first laminates 10 are stacked to form the second laminate 100, the side surface of the end mill 50 may be brought into contact with the outer periphery (end face) of the second laminate 100, and the rotating end mill 50 may be moved along the outer periphery of the second laminate 100. That is, in the cutting step, the outer peripheries of the plurality of first laminates 10 constituting the second laminate 100 may be collectively cut or polished with the end mill 50. In the cutting step, the corner portions located at both ends of the concave portion 13 and the corner portions located at the four corners of the first laminate 10 may each be chamfered.

[0057] The cutting amount of the end mill in the cutting step may be, for example, 10 μm or more and 500 μm or less, preferably 50 rpm or more and 150 μm or less.

[0058] The cutting step may be repeated three or more times. For example, in the third cutting step, the first laminate 10 may be hardly cut, and the chips generated in the second cutting step may be removed from the end face of the first laminate 10. In each cutting step, a plurality of end mills may be used.

[0059] The feed rate of the end mill in the cutting process may be 100 mm / min or more and less than 3000 mm / min. The rotational speed of the end mill in the cutting process may be, for example, 500 rpm or more and 60000 rpm or less, preferably 10000 rpm or more and 60000 rpm or less. The cutting angle in the cutting process may be, for example, 30° or more and 70° or less, preferably 45° or more and 65° or less. When the twist angle of the end mill 50 is α, the cutting angle β is defined as 90° - α. As shown in FIG. 6, the twist angle α of the end mill 50 is the angle formed by the direction d1 in which the cutting edge 50e extends on the side surface of the end mill 50 and the rotation axis 50a of the end mill 50. The cutting angle β may be rephrased as the angle formed by the direction d1 in which the cutting edge 50e extends and the direction d2 perpendicular to the rotation axis 50a. The diameter φ (thickness) of the end mill 50 used in the cutting process may be, for example, 3.0 mm or more and 6.0 mm or less.

[0060] By cutting in the state of the first laminate or the second laminate, the first laminate or the second laminate can be cut so that the position of the end of the optical film and the position of the end of the polarizer are the same in the plan view of the first laminate or the second laminate. Therefore, the obtained polarizing plate can have linearly polarized light energy up to the end of the polarizing plate at the end formed by cutting.

[0061] <Polarizer> The polarizer according to another embodiment of the present invention is a polarizer including a resin film containing boric acid and iodine and having a thickness of 15 μm or less. The polarizer may be, for example, a polarizer in which iodine is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film and the polyvinyl alcohol molecular chains are crosslinked with boric acid. The polarizer can be an absorption type polarizer having 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).

[0062] The polarizer has a region containing boric acid at a concentration lower than the concentration of boric acid in the region other than the region including the end portion of the polarizer (hereinafter, also referred to as the boric acid low-content region of the polarizer), and is a polarizer in which iodine loss does not occur in the region including the end portion of the polarizer. Therefore, the polarizer of the present invention can suppress the generation of cracks in the heat shock test and can exhibit linearly polarized light ability also at the end portion.

[0063] From the viewpoint of suppressing cracks and making iodine loss less conspicuous in the appearance of the polarizer, preferably, the concentration of boric acid in the boric acid low-content region of the polarizer increases as it moves away from the end portion in the inner direction from the end portion of the polarizing plate.

[0064] The boric acid low-content region of the polarizer may be formed, for example, in a region exceeding 15 μm in the inner direction from the end portion in the plan view of the polarizer, preferably may be formed in a region exceeding 15 μm and less than 200 μm from the viewpoint of crack suppression, more preferably may be formed in a region of 20 μm or more and 150 μm or less, still more preferably may be formed in a region of 20 μm or more and less than 100 μm, and particularly preferably may be formed in a region of 20 μm or more and less than 50 μm.

[0065] The boric acid low-content region of the polarizer may also be formed in a region of 15 μm or less from the end portion in the plan view of the polarizer. The boric acid low-content region of the polarizer may be continuously formed in the entire region of 15 μm or less from the end portion in the plan view of the polarizer and in the entire region exceeding 15 μm and less than 200 μm in the inner direction from the end portion in the plan view of the polarizer. In other words, the boric acid low-content region of the polarizer may be formed over the entire region between the end portion and less than 200 μm from the end portion in the plan view of the polarizer. When the boric acid low-content region of the polarizer is formed over the entire region between the end portion and less than 200 μm from the end portion in the plan view of the polarizer, the boundary between the boric acid low-content region of the polarizer and the other region can exist in the region between the end portion and less than 200 μm from the end portion. The boric acid low content region of the polarizer is preferably formed over the entire region between the end portion in the plan view of the polarizer and within 100 μm from the end portion, more preferably formed over the entire region between the end portion in the plan view of the polarizer and within 50 μm from the end portion, and even more preferably formed over the entire region between the end portion in the plan view of the polarizer and within 20 μm from the end portion.

[0066] The end portion of the polarizer may not contain boric acid. The boundary between the region where the boric acid low content site is formed and the other regions can be determined by the method described in the above method for manufacturing the polarizing plate.

[0067] The boric acid low content region of the polarizer may be one continuous region in the plan view of the polarizer or may be a region divided into a plurality of regions.

[0068] The boric acid low content region of the polarizer is preferably formed along the outer edge portion of the polarizer from the viewpoint of crack suppression. The boric acid low content region may be formed along the entire outer edge portion of the polarizer or may be formed along a part of the outer edge portion of the polarizer.

[0069] Specifically, the boric acid low content region of the polarizer can be a concentration of boric acid lower than the concentration of boric acid in the inner region 500 μm or more inside from the end portion. In the inner region, the concentration of boric acid can be substantially uniform. As shown in FIG. 3, the polarizer can have a boric acid low concentration site 30 in the region including the end portion in the plan view and an inner region 32 500 μm or more inside from the end portion. The inner region 32 can include a region for displaying an image when incorporated into a liquid crystal display device. The boric acid concentration in the intermediate region 31 between the boric acid low concentration site 30 and the inner region 32 is usually substantially the same as the boric acid concentration in the inner region 32. In addition, a polarizer in which iodine loss has not occurred is specifically a polarizer in which an iodine low concentration site having a concentration of iodine lower than the concentration of iodine in the above inner region is not formed. The presence or absence of the iodine low concentration site can be confirmed by the measurement method described in the column of the examples below.

[0070] Examples and preferred ranges of the thickness of the polarizer are applicable to the examples and preferred ranges in the description of the above-described method for manufacturing a polarizing plate.

[0071] The polarizer may have a deformed portion formed at its outer edge. The deformed portion may be, for example, a concave portion formed at the outer edge, a substantially V-shaped portion convex in the inner direction, or a through hole formed in the plane, in a plan view of the polarizer. The polarizer may have two or more deformed portions at the outer edge and / or in the plane. The through hole formed in the plane may be the above-described camera hole or the like. Since iodine loss does not occur in the region including the end portion, even when used for a polarizing plate disposed on the viewing side in an image display device, iodine loss is less noticeable and a decrease in design property is less likely to occur.

[0072] The polarizer can be manufactured, for example, by subjecting a uniaxially stretched polyvinyl alcohol-based resin film containing boric acid and iodine to a humidifying treatment. Examples and preferred ranges of the conditions of the humidifying treatment are applicable to the examples and preferred ranges of the conditions of the humidifying treatment described in the above-described method for manufacturing a polarizing plate.

[0073] <Polarizing plate> The polarizing plate according to still another embodiment of the present invention has the above-described polarizer and an optical film bonded to at least one side of the polarizer. Examples and preferred ranges of the optical film are applicable to the examples and preferred ranges described in the above-described method for manufacturing a polarizing plate.

[0074] As shown in FIG. 1, the polarizing plate 1 according to the present embodiment includes at least a pair of optical films (3, 4) and a film-like polarizer 2 positioned between the pair of optical films (3, 4). Hereinafter, for convenience of explanation, the polarizing plate 1 composed of the polarizer 2 and the pair of optical films (3, 4) will be mainly described. However, as described later, the number of optical films included in the polarizing plate is not limited to two.

[0075] The optical film means a film-like member (excluding the polarizer 2 itself) that constitutes the polarizing plate 1. For example, the optical film implies a protective film and a release film. Each individual optical film may not have a specific optical function alone. The "film" (optical film) may be paraphrased as "layer" (optical layer). Each of the pair of optical films (3, 4) contains a resin. However, the composition of each of the optical films (3, 4) is not limited. Each of the pair of optical films (3, 4) contains a resin. However, the composition of each of the optical films (3, 4) is not limited.

[0076] The polarizer 2 overlaps directly or indirectly with each of the optical films (3, 4). For example, there may be another optical film between the polarizer 2 and the optical films (3, 4). The polarizer 2 may overlap with each of the optical films (3, 4) via an adhesive layer.

[0077] FIG. 7 shows the surface (light-receiving surface) of the polarizing plate 1 according to the present embodiment. The cross-section of the polarizing plate 1 shown in FIG. 7 is perpendicular to the surface (light-receiving surface) of the polarizing plate 1 and orthogonal to the outer periphery 1p of the polarizing plate 1 located inside the recess 13.

[0078] As shown in FIG. 7, the recess 13 is formed in the outer periphery 1p of the polarizing plate 1. That is, there is a recess 13 in the outer periphery 1p of the polarizing plate 1. The recess 13 may be paraphrased as a depression, a cutout, or a notch. The recess 13 may penetrate the polarizing plate 1 in a direction (Z-axis direction) perpendicular to the surface (light-receiving surface) of the polarizing plate 1. The outer periphery 1p of the polarizing plate 1 may be paraphrased as the outer edge or contour of the polarizing plate 1 (light-receiving surface) viewed from a direction perpendicular to the light-receiving surface of the polarizing plate 1.

[0079] The inner corner 13c of the recess 13 may be a curved surface. That is, the end face of the polarizing plate 1 located at the inner corner 13c of the recess 13 may be a curved surface. That is, the inner corner 13c of the recess may be chamfered. By the inner corner 13c of the recess 13 being a curved surface, cracks at the inner corner 13c of the recess 13 are likely to be suppressed. As shown in FIG. 7, the corners located at both ends of the recess 13 and each of the four corners of the polarizing plate 1 may also be chamfered.

[0080] The width of the recess 13 (the width of the recess 13 in the X-axis direction) is not particularly limited, but may be, for example, 3 mm or more and 160 mm or less. The depth of the recess 13 (the width of the recess 13 in the Y-axis direction) is not particularly limited, but may be, for example, 0.5 mm or more and 160 mm or less. The length of the side (short side) of the polarizing plate 1 in which the recess 13 is formed is not particularly limited, but may be, for example, 30 mm or more and 90 mm or less. The length of the side (long side) of the polarizing plate 1 in which the recess 13 is not formed is not particularly limited, but may be, for example, 30 mm or more and 170 mm or less. The thickness of the entire polarizing plate 1 is not particularly limited, but may be, for example, 30 μm or more and 300 μm or less.

[0081] The recess 13 shown in FIG. 7 is quadrilateral (rectangular). However, the shape of the recess 13 is not limited. For example, the recess 13 may be square. The recess 13 may be a polygon other than a quadrilateral and a triangle. For example, as shown in (a) of FIG. 8, the shape of the recess 13 may be a semi-circle. As shown in (b) of FIG. 8, the shape of the recess 13 may be a triangle. The entire recess 13 may be curved. The recess 13 may be composed of a straight line and a curve. The shapes of the polarizing plates 1 shown in FIGS. 7, 8(a) and 8(b) all have symmetry, but the shape of the polarizing plate 1 may be asymmetric. A plurality of recesses 13 may be formed on the outer periphery 1p of the polarizing plate 1. A plurality of recesses 13 may be formed on one side constituting the outer periphery 1p of the polarizing plate 1. The recess 13 may be formed by cutting out at least one of the four corners of the quadrilateral polarizing plate 1.

[0082] The overall shape of the polarizing plate 1 excluding the recess 13 is substantially rectangular (rectangle). However, the shape of the polarizing plate 1 is not limited. For example, the shape of the polarizing plate 1 may be square. The shape of the polarizing plate 1 may be a polygon other than a quadrilateral, a circle, or an ellipse. The overall shape of each of the polarizer 2 and the optical films (3, 4) may be substantially the same as the shape of the polarizing plate 1. In the case of the rectangular polarizing plate 1 shown in FIG. 6, the recess 13 is formed on the short side of the polarizing plate 1, but the recess 13 may be formed on the long side of the polarizing plate 1.

[0083] As shown in FIG. 9, the polarizer 1 may have a through hole in the plane in a plan view. The diameter of the through hole may be, for example, 0.5 mm or more and 30 mm or less, preferably 1 mm or more and 10 mm or less.

[0084] (Other embodiments of the polarizing plate) For example, in addition to a pair of optical films including a first optical film and a second optical film, the polarizing plate may further include another optical film containing a resin. That is, the polarizing plate may include three or more optical films. For example, as shown in FIG. 10, the polarizing plate may include a first optical film 3 and a second optical film 4, a polarizer 2 positioned between the first optical film 3 and the second optical film 4, and a third optical film 15 overlapping the first optical film 3. The third optical film 15 may be overlapped with the first optical film 3 via the above-described adhesive layer. The resin contained in the third optical film 15 may be at least any one of the above-described resins listed as the resins contained in each of the first optical film 3 and the second optical film 4. The composition of the third optical film 15 may be the same as the composition of the first optical film 3. The composition of the third optical film 15 may be different from the composition of the first optical film 3. The composition of the third optical film 15 may be the same as the composition of the second optical film 4. The composition of the third optical film 15 may be different from the composition of the second optical film 4. The thickness of the third optical film 15 may be, for example, 5 μm or more and 200 μm or less. The third optical film 15 may be peeled off and removed from the polarizing plate during the manufacturing process of the image display device. That is, the third optical film 15 may be a temporary optical film.

[0085] The polarizing plate may further include an adhesive layer that overlaps one of the pair of optical films and a release film that overlaps the adhesive layer. For example, the polarizing plate shown in FIG. 10 may further include an adhesive layer that overlaps the second optical film 4 and a release film that overlaps the adhesive layer. The adhesive layer may include, for example, a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, or a urethane pressure-sensitive adhesive. The thickness of the adhesive layer may be, for example, 2 μm or more and 100 μm or less. The resin contained in the release film may be at least any one of the above resins listed as the resins contained in each of the first optical film 3 and the second optical film 4. The composition of the release film may be the same as the composition of the first optical film 3. The composition of the release film may be different from the composition of the first optical film 3. The composition of the release film may be the same as the composition of the second optical film 4. The composition of the release film may be different from the composition of the second optical film 4. The thickness of the release film may be, for example, 10 μm or more and 100 μm or less. The release film may be peeled off and removed from the polarizing plate during the manufacturing process of the image display device. The release film may be disposed on both surfaces of the polarizing plate via the adhesive layer.

[0086] The polarizing plate may further include at least one selected from the group consisting of a reflective polarizing film, an antiglare function film, an antireflection function film, a reflective film, a transflective film, a viewing angle compensation film, a window film, an antistatic layer, a hard coat layer, an optical compensation layer, a touch sensor layer, and an antifouling layer as an optical film or layer.

[0087] <Image display device> The polarizing plate can be used in an image display device. Examples of the image display device include a liquid crystal display device, an organic EL display device, and the like. The polarizing plate may be used for the polarizing plate disposed on the viewing side of the image display device, may be used for the polarizing plate disposed on the backlight side of the image display device, or may be used for the polarizing plates on both the viewing side and the backlight side. Since the color bleeding portion is less conspicuous, the design is less likely to be impaired even when the polarizing plate is used on the viewing side of the image display device. Therefore, the image display device is suitable as an image display device having a camera hole, such as a mobile device such as a smartphone or a mobile phone, and an image display device used for a personal computer or the like.

Example

[0088] Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “%” and “parts” are mass % and parts by mass, respectively, unless otherwise specified.

[0089] [Heat shock test] The polarizing plates obtained in the examples and comparative examples were bonded to Corning glass using an adhesive layer. This glass-bonded sample was placed in a thermal shock tester, and the operation of “holding in a tank at -40 ° C for 30 minutes and then immediately transferring to a tank at 85 ° C and holding for 30 minutes” was defined as one cycle, and a heat shock test was repeated 100 cycles. The presence or absence of cracks was confirmed using an optical microscope.

[0090] [Measurement of boric acid concentration] Boric acid ions (BO3 were measured by time-of-flight secondary ion mass spectrometry (TOF-SIMS). 3-) The concentration distribution was determined. As shown in Fig. 11, the protective film laminated on the optical film 5 (thickness 52 μm) side of the polarizing plate 110 was peeled off, the separate film laminated on the adhesive layer on the optical film 9 (thickness 21 μm) side was peeled off, and one end region including the corner of the concave portion was cut out 1 mm (1000 μm) in length toward the inside of the polarizing plate with a width of 100 μm to obtain a measurement sample 200. The measurement sample 200 had an optical film 201 (thickness 52 μm), an adhesive layer 202 (thickness 1 μm), a polarizer 203 (thickness 8 μm), an adhesive layer 204 (thickness 1 μm), an optical film 205 (thickness 21 μm), and an adhesive layer 206 (thickness 20 μm) in this order. The ion beam was irradiated while scanning the measurement region 207 on the side surface in the length direction (1000 μm) of the measurement sample 200 to obtain a two-dimensional distribution of the signal intensity of borate ions on this side surface. A portion corresponding to the side surface of the polarizer was cut out from the obtained two-dimensional distribution, and the integrated value of the signal intensity was plotted with respect to the length direction of the measurement sample 200 to obtain a profile of the borate concentration with respect to the length direction. The conditions of time-of-flight secondary ion mass spectrometry (TOF-SIMS) are shown below. Note that the measurement of the borate concentration was performed in the state of the polarizing plate, and the obtained borate concentration can be regarded as the borate concentration of the polarizer. Device name: Product name: PHI TRIFT V nano TOF (ULVAC-PHI, Inc.) Irradiated primary ion: Au3 + Primary ion acceleration voltage: 30 kV Spatial resolution of ion beam: 1 μm × 1 μm Area of measurement region: 200 μm × 200 μm From the obtained borate concentration profile, the average value of the borate ion intensity in the range where the distance from the end is 30 μm or more and 60 μm or less was determined. The portion from the end to the position where the borate ion intensity becomes the above average value was defined as the low borate concentration portion, and the length of the region where the low borate concentration portion is formed from the end of the polarizing plate (the length of the low borate concentration portion) was measured.

[0091] [Iodine loss] The portion of the polarizing plate that had been subjected to base treatment was observed by transmitted light using an optical microscope. The optical microscope image was captured into a personal computer, and the length of the region where the low-iodine concentration portion was formed (the length of the low-iodine concentration portion) from the end of the polarizing plate was measured as follows. In the optical microscope image captured on the personal computer, the low-iodine concentration portion appears bright and the inner region appears dark to the naked eye. Image processing was performed on the optical microscope image to convert it into a 256-level black-and-white image (brightness 255 is white and 0 is black) such that the brightness of the low-iodine concentration portion becomes 180 - 220 and the brightness of the inner region becomes 100 - 140, and it was confirmed whether there was a low-iodine concentration portion by designating the region where the brightness was 180 or more (white) as the low-iodine concentration portion.

[0092] [Polarizer with a thickness of 8 μm] A polyvinyl alcohol film with a thickness of 20 μm (average degree of polymerization of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 4.9 times by dry stretching, and while maintaining the tension, it was immersed in pure water at 60°C for 1 minute, and then immersed in an aqueous solution with a weight ratio of iodine / potassium iodide / water of 0.05 / 5 / 100 at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution with a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72°C for 300 seconds. Subsequently, after washing with pure water at 26°C for 20 seconds, it was dried at 65°C to obtain a polarizer with a thickness of 8 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

[0093] [Polarizer with a thickness of 12 μm] Using a polyvinyl alcohol film with a thickness of 30 μm, a polarizer with a thickness of 12 μm was obtained in the same manner as the polarizer with a thickness of 8 μm, except that it was uniaxially stretched about 5.0 times by dry stretching to obtain a polarizer with a thickness of 12 μm.

[0094] [Polarizer with a thickness of 28 μm] Using a polyvinyl alcohol film with a thickness of 75 μm, a polarizer with a thickness of 28 μm was obtained in the same manner as the polarizer with a thickness of 8 μm, except that it was uniaxially stretched about 4 times by dry stretching to obtain a polarizer with a thickness of 28 μm.

[0095] [Optical Film] COP: A cycloolefin resin film with a thickness of 23 μm (manufactured by Nippon Zeon Co., Ltd.). TAC: A triacetyl cellulose film with a thickness of 20 μm (manufactured by Konica Minolta, Inc.).

[0096] [Water-based Adhesive] To 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol (KL-318 manufactured by Kuraray Co., Ltd.) were dissolved, and to the aqueous solution, 1.5 parts of a polyamide epoxy-based additive (Sumirez Resin (registered trademark) 650(30), an aqueous solution with a solid content concentration of 30% manufactured by Sumitomo Chemical Tex Co., Ltd.), which is a water-soluble epoxy compound, were added to obtain a water-based adhesive.

[0097] [Example 1] An optical film (COP film) subjected to corona discharge treatment was laminated via a water-based adhesive on both sides of an 8-μm polarizer. An adhesive was applied to the surface of one optical film opposite to the polarizer to form an adhesive layer, and a separate film was laminated thereon. This separate film was peelable from the adhesive layer. A protective film was laminated on the surface of another optical film opposite to the polarizer of the optical film provided with the adhesive layer. This protective film was peelable from the optical film. The polarizing plate thus obtained was cut into chips of 5.5 cm square, and a special-shaped processing was performed to provide a through-hole with a diameter of 6 mm using a punching blade.

[0098] The obtained polarizing plate was subjected to a humidification treatment by continuously holding it in a gas phase at a temperature of 85 °C and a relative humidity of 85% for 2 hours. In this way, the polarizing plate of Example 1 was obtained. The results are shown in Table 1. In addition, no light leakage occurred due to iodine loss in this polarizing plate, and the length from the end of the low iodine concentration part was 0 μm.

[0099] [Example 2] A polarizing plate of Example 2 was produced in the same manner as in Example 1 except that the conditions of the humidification treatment were changed to the conditions shown in Table 1. The results are shown in Table 1. Further, Fig. 12 shows the measurement results of the boric acid concentration with respect to the distance from the end of the polarizing plate. Furthermore, Fig. 13 shows the iodine leakage observation results.

[0100] [Example 3] A polarizing plate of Example 3 was produced in the same manner as in Example 1 except that the conditions of the humidification treatment were changed to the conditions shown in Table 1. The results are shown in Table 1.

[0101] [Comparative Example 1] A polarizing plate of Comparative Example 1 was produced in the same manner as in Example 1 except that the conditions of the humidification treatment were changed to the conditions shown in Table 1. The results are shown in Table 1.

[0102] [Comparative Example 2] A polarizing plate of Comparative Example 2 was produced in the same manner as in Example 1 except that the conditions of the humidification treatment were changed to the conditions shown in Table 1. The results are shown in Table 1.

[0103] [Comparative Example 3] A polarizing plate of Comparative Example 3 was produced in the same manner as in Example 1 except that it was immersed in warm water at 74 °C for 16 minutes instead of performing the humidification treatment. The results are shown in Table 1. The iodine leakage observation results are shown in Fig. 14. In this polarizing plate, an iodine low-concentration portion due to iodine leakage occurred, and its length was about 250 μm.

[0104]

Table 1

[0105] [Example 4] An optical film COP subjected to corona discharge treatment was bonded via an aqueous adhesive to one surface of a 12 μm polarizer, and an optical film TAC subjected to corona discharge treatment was bonded via an aqueous adhesive to the other surface to produce a polarizing plate. The obtained polarizing plate was chip-cut into a 5.5 cm square and subjected to a shaping process of providing a through-hole with a diameter of 6 mm.

[0106] The obtained polarizing plate was subjected to a humidification treatment in which it was held in a gas phase at a temperature of 85°C and a relative humidity of 85% for 2 hours. In this way, the polarizing plate of Example 4 was obtained. The results are shown in Table 2.

[0107] [Example 5] A polarizing plate of Example 5 was produced in the same manner as in Example 4, except that the conditions of the humidification treatment were changed to the conditions shown in Table 2. The results are shown in Table 2.

[0108] [Comparative Example 4] A polarizing plate of Comparative Example 4 was produced in the same manner as in Example 4, except that the conditions of the humidification treatment were changed to the conditions shown in Table 2. The results are shown in Table 2.

[0109] [Comparative Example 5] A polarizing plate of Comparative Example 5 was produced in the same manner as in Example 4, except that the conditions of the humidification treatment were changed to the conditions shown in Table 2. The results are shown in Table 2.

[0110] [Comparative Example 6] A polarizing plate of Comparative Example 6 was produced in the same manner as in Example 4, except that the conditions of the humidification treatment were changed to the conditions shown in Table 2. The results are shown in Table 2.

[0111] [Table 2]

[0112] [Comparative Example 7] An optical film COP subjected to corona discharge treatment was laminated via an aqueous adhesive on one surface of a 28-μm polarizer, and an optical film TAC subjected to corona discharge treatment was laminated via an aqueous adhesive on the other surface to produce a polarizing plate. The obtained polarizing plate was chip-cut into a 5.5-cm square and subjected to a profiling process of providing a through-hole with a diameter of 6 mm.

[0113] The obtained polarizing plate was subjected to a humidification treatment in which it was held in a gas phase at a temperature of 85°C and a relative humidity of 85% for 2 hours. In this way, the polarizing plate of Comparative Example 7 was obtained. The results are shown in Table 3 together with the results of Example 1 and Example 2.

[0114] [Comparative Example 8] A polarizing plate of Comparative Example 8 was produced in the same manner as in Comparative Example 7, except that the conditions of the humidification treatment were changed to the conditions shown in Table 3. The results are shown in Table 3 together with the results of Example 1 and Example 2.

[0115]

Table 3

Explanation of Reference Signs

[0116] 1 Polarizing plate, 2,7 Polarizer, 3,5 First optical film, 4,9 Second optical film, 10 First laminate, 13 Recess, 14 Through hole, 15 Third optical film, 20 Image display device, 21 Polarizing plate, 22 Camera hole, 23 Liquid crystal panel, 24 Cover glass, 25 Adhesive layer, 26 Polarizing plate, 27 Camera, 28 Light-shielding tape, 30 Low-concentration boric acid part, 31 Intermediate region, 32 Inner region, 50 End mill, 50e Edge, 100 Second laminate, 110 Polarizing plate, 200 Measurement sample, 201,205 Optical film, 202,204 Adhesive layer, 203 Polarizer, 206 Adhesive layer, 207 Measurement region, α Twist angle, β Cutting angle

Claims

1. A polarizing plate comprising a resin film containing boric acid and iodine, a polarizer having a thickness of 8 μm or less, a first optical film bonded to one side of the polarizer, and a second optical film bonded to the side of the polarizer opposite to the first optical film side, wherein both the first optical film and the second optical film contain a cyclic olefin polymer resin, in a region including the end portion of the polarizer, there is a boric acid low-content region containing boric acid at a concentration lower than the concentration of boric acid in a region other than the region, and the boric acid low-content region is formed in a region of 47 μm or more and less than 200 μm in the inner direction from the end portion of the polarizer in a plan view, when the polarizing plate is observed using a polarizing microscope, and the region visually observed as the region where light is transmitted in a cross Nicol state is defined as an iodine removal region, the iodine removal region does not occur in the region including the end portion of the polarizer. A polarizing plate.

2. The polarizing plate according to claim 1, wherein at the end portion of the polarizing plate in a plan view, the position of the end portion of the polarizer is the same as the positions of the end portions of the first optical film and the second optical film.

3. An image display device including the polarizing plate according to claim 2.

4. The image display device according to claim 3, having a camera hole.

Images