Polarizing plate, polarizing plate set, and image display device

Abstract

The present invention provides a polarizing plate, wherein a through hole is formed near an end portion, and cracks around the through hole are significantly suppressed. The polarizing plate of the present invention has a polarizer, an adhesive layer, and a protective layer disposed on at least one side of the polarizer. The polarizing plate has a rectangular shape and is formed with a through hole. The thickness of the polarizer is less than 10 μm. The diameter of the through hole is 5 mm or less, and the through hole is formed at a position within 11 mm from the long side and within 11 mm from the short side.

Description

Technical Field

[0001] The present invention relates to a polarizing plate, a polarizing plate set and an image display device. Background Art

[0002] Polarizing plates are widely used in image display devices such as mobile phones and laptop computers to achieve image display and / or improve the performance of the image display. In recent years, due to the rapid popularization of smart phones and touch panel information processing devices, image display devices equipped with cameras are widely used. Correspondingly, polarizing plates having through holes at positions corresponding to the camera parts are also widely used. In polarizing plates having such through holes, there are various research items in the through holes or in the vicinity thereof.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 047510 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The present invention has been made to solve the above-mentioned conventional problems, and a main object of the present invention is to provide a polarizing plate having through holes formed near the end portions and significantly suppressing cracks around the through holes.

[0008] Means used to solve problems

[0009] The polarizing plate of the embodiment of the present invention has a polarizer, an adhesive layer and a protective layer disposed on at least one side of the polarizer. The polarizing plate has a rectangular shape and is formed with a through hole. The thickness of the polarizer is less than 10 μm. The diameter of the through hole is less than 5 mm, and the through hole is formed at a position within 11 mm from the long side and within 11 mm from the short side.

[0010] In one embodiment, the thickness of the polarizer is 8 μm or less. In one embodiment, the thickness of the polarizer is 6 μm or less.

[0011] In one embodiment, after the polarizing plate is bonded to a glass plate via the adhesive layer and subjected to a heat shock test in which the polarizing plate is offset at the through hole portion and is less than 120 μm, the heat shock test being a test in which the operation of keeping the temperature at -40°C for 30 minutes and then keeping the temperature at 85°C for 30 minutes is repeated 100 times.

[0012] In one embodiment, two through holes are formed in the polarizing plate, and both through holes are formed within 11 mm from the long side and within 11 mm from the short side.

[0013] In one embodiment, the absorption axis of the polarizer extends along the short side direction. In another embodiment, the absorption axis of the polarizer extends along the long side direction.

[0014] According to another aspect of the present invention, a polarizing plate set is provided, comprising a polarizing plate having an absorption axis extending in the short side direction and a polarizing plate having an absorption axis extending in the long side direction, wherein through holes of each polarizing plate are formed at corresponding positions.

[0015] According to another aspect of the present invention, an image display device is provided, which includes an image display unit and the polarizing plate.

[0016] Another embodiment of the image display device of the present invention includes an image display unit and the above polarizing plate set, wherein one polarizing plate in the polarizing plate set is arranged on the visible side of the image display unit, and the other polarizing plate in the polarizing plate set is arranged on the back side of the image display unit.

[0017] Effects of the Invention

[0018] According to the embodiment of the present invention, in a polarizing plate having through holes formed near the end, by optimizing the diameter of the through holes, the formation position of the through holes and the thickness of the polarizer, a polarizing plate in which cracks around the through holes are significantly suppressed can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A This is a schematic plan view of a polarizing plate for explaining one embodiment of the present invention.

[0020] Figure 1B It is a schematic diagram for explaining the formation position of the through hole in the polarizing plate according to the embodiment of the present invention.

[0021] Figure 1C This is a schematic plan view for explaining how a plurality of through holes are formed in a polarizing plate according to an embodiment of the present invention.

[0022] Figure 2 1 is a schematic cross-sectional view of the polarizing plate taken along line II-II in FIG. 1 .

[0023] Figure 3 This is an enlarged cross-sectional view of a main part for explaining the displacement of a through-hole portion of a polarizing plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. It should be noted that the accompanying drawings are schematically shown for ease of observation, and the ratios and angles of length, width, thickness, etc. in the accompanying drawings are different from the actual ones.

[0025] A. Polarizing plate

[0026] A-1. Overall structure of polarizing plate

[0027] Figure 1A A schematic plan view of a polarizing plate for explaining one embodiment of the present invention; Figure 2 for Figure 1A Schematic cross-sectional view of a polarizing plate along line II-II. The polarizing plate 100 of the illustrated example includes a polarizer 11, a protective layer (hereinafter sometimes referred to as an outer protective layer) 12 disposed on one side of the polarizer 11, a protective layer (hereinafter sometimes referred to as an inner protective layer) 13 disposed on the other side of the polarizer 11, and an adhesive layer 20. Depending on the purpose and the desired configuration, etc., either the outer protective layer 12 or the inner protective layer 13 may be omitted.

[0028] In an embodiment of the present invention, the thickness of the polarizer 11 is less than 10 μm, preferably less than 8 μm, more preferably less than 6 μm, and further preferably less than 5 μm. The thickness of the polarizer is, for example, greater than 1 μm, and for example, greater than 2 μm. If the thickness of the polarizer is within such a range, the cracks around the through hole can be significantly suppressed by the synergistic effect of the effect produced by the optimization of the diameter of the through hole and the optimization of the formation position of the through hole. The absorption axis of the polarizer 11 can extend in the long side direction or in the short side direction.

[0029] The polarizing plate 100 typically has the following Figure 1A The rectangular shape shown in FIG. In this specification, the term "rectangular shape" also includes the following: Figure 1A The R shape obtained by chamfering each vertex shown includes a shape of a special-shaped processed portion.

[0030] In an embodiment of the present invention, a through hole 30 is formed in the polarizing plate 100. By forming the through hole, for example, in the case where an image display device has a built-in camera, it is possible to prevent the performance of the camera from being adversely affected. The through hole 30 is typically formed at the end of the polarizing plate or in the vicinity thereof, preferably at a corner as shown in the illustrated example. By forming the through hole at the end of the polarizing plate or in the vicinity thereof, when the polarizing plate is applied to an image display device, the effect on the image display can be reduced to a minimum. The top view shape of the through hole 30 can adopt any appropriate shape depending on the purpose and the desired structure of the image display device. As a representative example, an approximately circular shape as shown in the illustrated example can be cited. The through hole can be formed by various methods such as laser processing, cutting processing using an end mill, punching processing using a Thomson knife or a Pinnacle (registered trademark) knife, etc.

[0031] In the embodiment of the present invention, the diameter of the through hole is typically less than 5 mm, preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. If the diameter of the through hole is within such a range, the cracks around the through hole can be significantly suppressed by the synergistic effect of the effect produced by the optimization of the thickness of the polarizer and the optimization of the formation position of the through hole.

[0032] In an embodiment of the present invention, the through hole 30 is formed at a position within 11 mm from the long side and within 11 mm from the short side. The through hole is preferably formed at a position within 11 mm from the long side and within 3 mm from the short side, or within 3 mm from the long side and within 11 mm from the short side, or within 9 mm from the long side and within 7 mm from the short side, or within 7 mm from the long side and within 9 mm from the short side; more preferably, it is formed at a position within 5 mm from the long side and within 3 mm from the short side, or within 3 mm from the long side and within 5 mm from the short side; further preferably, it is formed at a position within 3 mm from the long side and within 3 mm from the short side. According to an embodiment of the present invention, even in the case where a through hole is formed near the end, cracks around the through hole can be significantly suppressed. As a result, even in the case where the camera part is set close to the end in an image display device due to design requirements, it can be applied, and a polarizing plate with excellent durability can be achieved. Therefore, the polarizing plate of the embodiment of the present invention has very high industrial and commercial value. Figure 1B As shown, in this specification, the distance from the long side to the through hole refers to the distance from the long side (i.e., the periphery of the polarizing plate) to the end of the through hole on the side of the polarizing plate periphery on the straight line connecting the long side and the center of the through hole in a direction orthogonal to the long side (i.e., the direction in which the short side extends). Figure 1BAs shown, the distance from the short side to the through hole refers to the distance from the short side (i.e., the periphery of the polarizing plate) to the end of the polarizing plate peripheral side of the through hole on a straight line connecting the short side and the center of the through hole in a direction orthogonal to the short side (i.e., the direction in which the long side extends).

[0033] You can also Figure 1C In the example shown in the figure, two through holes are formed, but the number of through holes can be three, or more than four. Figure 1C In the case where two through holes are formed as shown, both through holes are formed within 11 mm from the long side and within 11 mm from the short side. The through hole is preferably formed within 11 mm from the long side and within 3 mm from the short side, or within 3 mm from the long side and within 11 mm from the short side, or within 9 mm from the long side and within 7 mm from the short side, or within 7 mm from the long side and within 9 mm from the short side; more preferably, it is formed within 5 mm from the long side and within 3 mm from the short side, or within 3 mm from the long side and within 5 mm from the short side; further preferably, it is formed within 3 mm from the long side and within 3 mm from the short side. It should be noted that, for example, Figure 1C In the case where two through holes are formed as shown in FIG, the two through holes may also be replaced by one elongated elliptical through hole.

[0034] In one embodiment, if Figure 3 As shown, for the polarizing plate 100, after the polarizing plate 100 is bonded to a glass plate (which may correspond to a substrate of an image display unit) 120 via an adhesive layer 20 and subjected to the following heat shock test, the offset D of the polarizing plate at the through-hole portion is preferably 120 μm or less, more preferably 100 μm or less, further preferably 80 μm or less, and particularly preferably 60 μm or less, and the heat shock test is a test in which the operation of keeping at -40°C for 30 minutes and then keeping at 85°C for 30 minutes is repeated 100 times. The smaller the offset D, the better. The lower limit of the offset D may be, for example, 10 μm. The offset D refers to the largest portion of the polarizing plate that is away from the through-hole portion when observed in cross section. The reference of the through-hole portion may be representatively the lower end portion of the adhesive layer. That is, when the polarizing plate is offset (to the right in the illustrated example) mainly due to the contraction of the polarizer 11, the adhesive layer 20 stays on the bonded glass plate 120, and thus an offset is observed in the through-hole portion. It should be noted that, as Figure 3 As shown, the polarizing plate is typically offset at the through hole portion toward a side away from the through hole ( Figure 3 right side), and its opposite portion is offset in such a manner as to protrude toward the through hole ( Figure 3Left side). As such, the offset of the polarizing plate at the through hole portion is substantially the offset of the adhesive layer. If the offset D is within such a range, not only can cracks around the through hole be significantly suppressed, but also light leakage caused by the offset in the image display device can be reduced.

[0035] The ratio D / R of the offset amount D to the diameter R of the through hole is preferably 5% to 30%, and more preferably 10% to 30%. If D / R is within such a range, cracks and light leakage around the through hole can be significantly suppressed.

[0036] In an embodiment of the present invention, the ratio (%) of the residual stress of the through-hole portion to the residual stress at the center of the polarizing plate is preferably 77% or less. The ratio may vary depending on the diameter of the through-hole. When the diameter of the through-hole is 3 mm to 5 mm (for example, 4 mm), the ratio is more preferably 70% or less, further preferably 68% or less, and particularly preferably 65% ​​or less. When the diameter of the through-hole is less than 3 mm (for example, 2 mm), the ratio is more preferably 76% or less, further preferably 74% or less, and particularly preferably 72% or less. Regardless of the diameter of the through-hole, the lower limit of the ratio may be 50%, for example. If the residual stress ratio is within such a range, cracks around the through-hole can be significantly suppressed. Such a residual stress ratio can be achieved by combining the adjustment of the formation position of the through-hole and the above-mentioned offset D. It should be noted that in this specification, "residual stress of the through-hole portion" refers to the residual stress of the portion where the residual stress reaches the maximum at the periphery of the through-hole.

[0037] The polarizing plate of the embodiment of the present invention may further have any appropriate optical functional layer according to the purpose. As the optical functional layer, for example, a phase difference layer, a conductive layer for a touch panel, and a reflective polarizer can be listed. The type, quantity, combination, and configuration position of the optical functional layer assembled in the polarizing plate can be appropriately set according to the purpose.

[0038] The aspect ratio of the polarizing plate of the embodiment of the present invention is preferably 1.3 to 2.5. In this case, the size of the polarizing plate is, for example, 145 mm to 155 mm in the longitudinal direction and 65 mm to 75 mm in the lateral direction, or 230 mm to 240 mm in the longitudinal direction and 140 mm to 150 mm in the lateral direction. That is, the polarizing plate of the embodiment of the present invention can be appropriately used in a smartphone or a tablet computer. As the size of a smartphone, for example, the longitudinal direction can be 120 mm to 200 mm, and the width can be 30 mm to 120 mm.

[0039] Hereinafter, the polarizer, the protective layer, and the pressure-sensitive adhesive layer constituting the polarizing plate will be described in detail.

[0040] A-2. Polarizer

[0041] The polarizer is typically composed of a resin film containing a dichroic substance. As the resin film, any appropriate resin film that can be used as a polarizer can be used. The resin film is typically a polyvinyl alcohol resin (hereinafter referred to as "PVA resin") film. The resin film can be a single-layer resin film or a laminate of more than two layers.

[0042] As a specific example of a polarizer consisting of a single-layer resin film, a polarizer obtained by dyeing and stretching (representatively uniaxial stretching) performed using iodine on a PVA-type resin film can be cited. The dyeing performed using iodine is performed, for example, by immersing the PVA-type resin film in an iodine aqueous solution. The stretching multiple of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or while dyeing. In addition, dyeing can also be performed after stretching. Swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, etc. are performed on the PVA-type resin film as needed. For example, by immersing the PVA-type resin film in water and washing it with water before dyeing, not only can the dirt and anti-adhesion agent on the surface of the PVA-type resin film be washed off, but the PVA-type resin film can also be swollen to prevent uneven dyeing.

[0043] As specific examples of polarizers obtained using laminates, there can be cited: polarizers obtained using a laminate of a resin substrate and a PVA-type resin layer (PVA-type resin film) laminated on the resin substrate, or polarizers obtained using a laminate of a resin substrate and a PVA-type resin layer formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-type resin layer formed by coating on the resin substrate can be made, for example, in the following manner: a PVA-type resin solution is coated on a resin substrate, dried to form a PVA-type resin layer on the resin substrate, thereby obtaining a laminate of a resin substrate and a PVA-type resin layer; the laminate is stretched and dyed, thereby making the PVA-type resin layer into a polarizer. In the present embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution and stretching it. In addition, stretching may also include stretching the laminate in air at a high temperature (for example, above 95°C) before stretching in a boric acid aqueous solution, as needed. The obtained laminate of resin substrate / polarizer can be used directly (that is, the resin substrate can be used as a protective layer of polarizer), or the resin substrate can be peeled off from the laminate of resin substrate / polarizer, and any appropriate protective layer can be laminated on the peeled surface according to the purpose. The details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The records of these patent documents are cited in this specification by reference.

[0044] The thickness of the polarizer is as described in the above-mentioned item A-1.

[0045] The polarizer preferably exhibits absorption dichroism at any wavelength within the wavelength range of 380 nm to 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

[0046] A-3. Protective layer

[0047] The protective layer is formed by any appropriate film that can be used as a protective layer of a polarizer. As a specific example of the material that becomes the main component of the film, it can be listed: cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyether sulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth) acrylic acid and acetate transparent resins, etc. In addition, it can also be listed: (meth) acrylic acid, carbamate, (meth) acrylic acid carbamate, epoxy, polysiloxane and other thermosetting resins or ultraviolet curing resins, etc. In addition, for example, it can also be listed: glassy polymers such as siloxane polymers. In addition, it is also possible to use the polymer film recorded in Japanese Patent Publication No. 2001-343529 (WO01 / 37007). As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, a resin composition containing an alternating copolymer formed by isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film can be, for example, an extrusion molding of the above resin composition.

[0048] The outer protective layer 12 (especially when the polarizing plate is a visible side polarizing plate) can be subjected to surface treatments such as hard coating, anti-reflection, anti-sticking, and anti-glare as needed. And / or, the outer protective layer 12 can be subjected to treatments to improve visual recognition when viewed through polarized sunglasses as needed (representatively, imparting (elliptical) circular polarization function and imparting ultra-high phase difference). By implementing such treatments, excellent visual recognition can be achieved even when viewing the display screen through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate can also be appropriately applied to image display devices that can be used outdoors.

[0049] The inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0nm to 10nm and the phase difference Rth(550) in the thickness direction is -10nm to +10nm. Here, "Re(λ)" is the in-plane phase difference measured at 23°C using light with a wavelength of λnm. For example, "Re(550)" is the in-plane phase difference measured at 23°C using light with a wavelength of 550nm. When the thickness of the layer (film) is set to d(nm), Re(λ) is calculated by the formula: Re(λ) = (nx-ny)×d. In addition, "Rth(λ)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of λnm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of 550nm. When the thickness of the layer (film) is set to d (nm), Rth (λ) is calculated by the formula: Rth (λ) = (nx-nz) × d. It should be noted that nx is the refractive index in the direction where the refractive index in the plane reaches the maximum (i.e., the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and nz is the refractive index in the thickness direction.

[0050] The thickness of the protective layer may be any appropriate thickness. The thickness of the protective layer is, for example, 10 μm to 50 μm, preferably 20 μm to 40 μm. It should be noted that, when surface treatment is performed, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0051] A-4. Adhesive layer

[0052] The adhesive layer 20 is typically used to bond the polarizing plate to the image display unit. The adhesive layer can be typically composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer can be contained in the adhesive composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more in the solid content of the adhesive composition. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a monomer unit as a main component. It should be noted that (meth)acrylate refers to acrylate and / or methacrylate. In the monomer component forming the (meth)acrylic polymer, an alkyl (meth)acrylate can be contained in a proportion of preferably 80% by weight or more, more preferably 90% by weight or more. As the alkyl group of the alkyl (meth)acrylate, for example, a straight-chain alkyl group or a branched alkyl group having 1 to 18 carbon atoms can be cited. The average number of carbon atoms of the alkyl group is preferably 3 to 9, and more preferably 3 to 6. The preferred alkyl (meth)acrylate is butyl acrylate. As monomers (comonomers) constituting (meth) acrylic polymers, in addition to (meth) acrylic acid alkyl esters, carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth) acrylic esters, heterocyclic vinyl monomers, etc. can also be cited. Representative examples of comonomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The acrylic adhesive composition preferably contains a silane coupling agent and / or a crosslinking agent. As silane coupling agents, for example, epoxy-containing silane coupling agents can be cited. As crosslinking agents, for example, isocyanate crosslinking agents and peroxide crosslinking agents can be cited. In addition, the acrylic adhesive composition can contain an antioxidant and / or a conductive agent. By adjusting the type, quantity, combination, and copolymerization ratio of the monomer unit; the type, quantity, combination, and mixing ratio of the silane coupling agent; and the type, quantity, combination, and mixing ratio of the crosslinking agent, etc., an acrylic adhesive composition (resulting in an adhesive layer) having the desired properties according to the purpose can be obtained. As a result, in the embodiment of the present invention, the above-mentioned desired offset amount D can be achieved. The details of the adhesive layer or the acrylic adhesive composition are described in, for example, Japanese Patent Application Publication No. 2006-183022, Japanese Patent Application Publication No. 2015-199942, Japanese Patent Application Publication No. 2018-053114, Japanese Patent Application Publication No. 2016-190996, and International Publication No. 2018 / 008712, and the descriptions of these publications are incorporated herein by reference.

[0053] The thickness of the adhesive layer is preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm. When the thickness of the adhesive layer is within such a range, the above-described desired offset amount D can be achieved.

[0054] The storage elastic modulus G' of the adhesive layer at -40°C is preferably 1.0×10 5 (Pa) or more, more preferably 1.0×10 6 (Pa) or more, more preferably 1.0×10 7 (Pa) or more, particularly preferably 1.0×10 8 (Pa) or more. The storage elastic modulus G' may be, for example, 1.0×10 9 If the storage elastic modulus of the adhesive layer at -40°C is within such a range, the above-mentioned desired deviation amount D can be achieved.

[0055] B. Polarizing plate set

[0056] The polarizing plate described in the above-mentioned item A can be used as a polarizing plate on the visible side or as a polarizing plate on the back side. By combining two specific embodiments of the polarizing plates described in the above-mentioned item A, a polarizing plate group can be provided. Therefore, the embodiments of the present invention also include such a polarizing plate group. In the polarizing plate group, the through holes of the two polarizing plates constituting the group are respectively formed at positions corresponding to each other. In this specification, "formed at positions corresponding to each other" means that the through holes overlap when the two polarizing plates are overlapped.

[0057] In one embodiment, the polarizing plate group includes a polarizing plate whose absorption axis of the polarizer extends in the short side direction and a polarizing plate whose absorption axis of the polarizer extends in the long side direction. In this case, the through holes of the two polarizing plates are typically formed at positions within 11 mm from the long side and within 11 mm from the short side and corresponding to each other; preferably formed at positions within 11 mm from the long side and within 3 mm from the short side and corresponding to each other, or formed at positions within 3 mm from the long side and within 11 mm from the short side and corresponding to each other, or formed at positions within 9 mm from the long side and within 7 mm from the short side and corresponding to each other, or formed at positions within 7 mm from the long side and within 9 mm from the short side and corresponding to each other; more preferably formed at positions within 5 mm from the long side and within 3 mm from the short side and corresponding to each other, or formed at positions within 3 mm from the long side and within 5 mm from the short side and corresponding to each other; further preferably formed at positions within 3 mm from the long side and within 3 mm from the short side and corresponding to each other.

[0058] C. Image display device

[0059] The polarizing plate and polarizing plate group of the embodiment of the present invention can be applied to an image display device. Therefore, the image display device is also included in the embodiment of the present invention. In one embodiment, the image display device includes an image display unit and a polarizing plate. The polarizing plate is the polarizing plate of the embodiment of the present invention described in the above item A. The polarizing plate is bonded to the image display unit through an adhesive layer. In another embodiment, the image display device includes an image display unit and a polarizing plate group. The polarizing plate group is the polarizing plate group of the embodiment of the present invention described in the above item B. In this case, one polarizing plate in the polarizing plate group is arranged on the visible side of the image display unit, and the other polarizing plate in the polarizing plate group is arranged on the back side of the image display unit. As the image display device, for example, a liquid crystal display device, an organic electroluminescent (EL) display device, and a quantum dot display device can be listed.

[0060] Example

[0061] The present invention is specifically described below by way of examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. In addition, "parts" and "%" in the examples are by weight unless otherwise specified.

[0062] (1) Offset

[0063] The polarizing plates obtained in the examples and comparative examples were adhered to a glass plate (manufactured by Matsunami Glass Co., Ltd., 350 mm in length × 250 mm in width × 1.1 mm in thickness) via an adhesive layer to prepare test samples. The test samples were subjected to the following thermal shock test, which was a test in which the operation of keeping at -40°C for 30 minutes and then keeping at 85°C for 30 minutes was repeated 100 times. The heating rate and cooling rate in the thermal shock test were 10°C / minute. After the test, the offset of the polarizing plate (essentially the adhesive layer) at the through-hole portion was measured using an optical microscope (MX61L) manufactured by Olympus Corporation. It should be noted that three test samples were measured, and the maximum value of the three measured values ​​was taken as the offset.

[0064] (2) Crack

[0065] The polarizing plates obtained in the examples and comparative examples were subjected to a thermal shock test in the same manner as in the "offset" of (1) above. The cracking state of the through-hole portion after the test was observed using an optical microscope (MX61L) manufactured by Olympus Corporation and evaluated according to the following criteria.

[0066] AA: No cracks observed

[0067] A: Only small cracks less than 300 μm in length were observed

[0068] B: Cracks with a length of 300 μm to 1 mm were observed, but no light leakage occurred.

[0069] C: Cracks are obvious and light leakage occurs

[0070] <Production Example 1>

[0071] A monomer mixture containing 80.3 parts of butyl acrylate, 16 parts of phenoxyethyl acrylate, 3 parts of N-vinyl-2-pyrrolidone, 0.3 parts of acrylic acid and 0.4 parts of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen introduction tube and a condenser. Then, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts by weight of ethyl acetate were added to 100 parts of the monomer mixture (solid content), and nitrogen was introduced while slowly stirring to perform nitrogen replacement. Then, the liquid temperature in the flask was maintained at about 55°C, and a polymerization reaction was performed for 8 hours, thereby preparing a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.5 million. 0.1 part of an isocyanate crosslinking agent (trade name: TAKENATE D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 part of benzoyl peroxide (trade name: NYPER BMT 40SV, manufactured by NOF Corporation), 0.1 part of a mercapto group-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy content: 30%, mercapto equivalent: 450 g / mol), 0.2 part of an antioxidant (trade name: Irganox 1010, hindered phenol, manufactured by BASF Japan Ltd.), and 5 parts of a conductive agent (1-ethyl-3-methylimidazole) were added to 100 parts of the solid content of the obtained acrylic polymer solution. Bis(trifluoromethanesulfonyl)imide salt, ionic liquid manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), thereby obtaining an adhesive composition.

[0072] <Example 1>

[0073] As a thermoplastic resin substrate, a long amorphous polyethylene terephthalate copolymer film (thickness: 100 μm) having a Tg of about 75° C. was used, and one surface of the resin substrate was subjected to a corona treatment.

[0074] To 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (polymerization degree of 4200, saponification degree of 99.2 mol %) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name GOHSEFIMER) in a ratio of 9:1, 13 parts by weight of potassium iodide were added, and the resulting substance was dissolved in water to prepare a PVA aqueous solution (coating solution).

[0075] The PVA aqueous solution was applied onto the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

[0076] The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (length direction) in an oven at 130° C. (auxiliary stretching treatment in air).

[0077] Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution prepared by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilization treatment).

[0078] Next, in a dyeing bath (an iodine aqueous solution obtained by combining iodine and potassium iodide in a weight ratio of 1:7 relative to 100 parts by weight of water) at a liquid temperature of 30°C, the film is immersed for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the final polarizer reaches the desired value (dyeing treatment).

[0079] Next, the film was immersed in a crosslinking bath (boric acid aqueous solution containing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid per 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment).

[0080] Then, the laminate is immersed in an aqueous boric acid solution (boric acid concentration of 4 wt %, potassium iodide concentration of 5 wt %) at a liquid temperature of 70°C, and simultaneously uniaxially stretched in the longitudinal direction (length direction) between rollers with different circumferential speeds so that the total stretching ratio reaches 5.5 times (underwater stretching treatment).

[0081] Then, the laminated body was immersed in a cleaning bath (an aqueous solution prepared by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).

[0082] Then, the film was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75° C. while being dried in an oven maintained at about 90° C. (drying shrinkage treatment).

[0083] In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, thereby obtaining a laminate having a structure of resin substrate / polarizer.

[0084] The HC-TAC film is bonded to the polarizer surface of the above-mentioned laminate. It should be noted that the HC-TAC film is a film having a hard coating (HC) layer (7 μm thick) formed on a triacetyl cellulose (TAC) film (25 μm thick), and is bonded in such a way that the TAC film becomes the polarizer side. Next, the resin substrate is peeled off, and an adhesive layer (20 μm thick) is formed on the peeling surface using the adhesive composition of Manufacturing Example 1, thereby obtaining a polarizing plate having a long shape having a structure of HC layer / outer protective layer / polarizer / adhesive layer. The polarizing plate is punched into a shape with a size of 142.0 mm in the longitudinal direction and 66.8 mm in the transverse direction, and an R portion with an R of 7.0 mm is provided at the four corners. At this time, the punching is performed in such a way that the absorption axis direction of the polarizer is the short side direction. Then, a through hole with a diameter of 4 mm is formed at a position 2 mm away from the long side and 2 mm away from the short side. The through hole is formed by end milling. The feed rate of the end mill is 500 mm / min, the rotation speed is 2500 rpm, and the cutting amount is 0.1 mm. In this way, a polarizing plate with through holes is produced. The obtained polarizing plate is provided for the evaluation of (2) above. The results are shown in Table 1 together with the detailed structure of the polarizing plate. It should be noted that in Table 1, "0°" represents the long side direction and "90°" represents the short side direction.

[0085] <Example 2>

[0086] A polarizing plate was produced in the same manner as in Example 1 except that the through-holes were formed at 6 mm from the long side and 4 mm from the short side. The obtained polarizing plate was evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0087] <Examples 3 to 6>

[0088] Polarizing plates were prepared in the same manner as in Example 1 except that the through-holes were formed at the positions shown in Table 1. The obtained polarizing plates were subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configuration of the polarizing plates.

[0089] <Example 7>

[0090] A polarizing plate of long size was obtained in the same manner as in Example 1. The polarizing plate was punched into a shape with a length of 142.0 mm and a width of 66.8 mm, and an R portion with an R of 7.0 mm was provided at the four corners. At this time, the punching was performed in such a way that the absorption axis direction of the polarizer was the long side direction. The subsequent steps were the same as in Example 1, thereby producing a polarizing plate having a through hole with a diameter of 4 mm at a position 2 mm from the long side and 2 mm from the short side. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0091] <Example 8>

[0092] A polarizing plate was produced in the same manner as in Example 7 except that the through-holes were formed at 6 mm from the long side and 4 mm from the short side. The obtained polarizing plate was evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0093] <Examples 9 to 12>

[0094] Polarizing plates were prepared in the same manner as in Example 7 except that the through-holes were formed at the positions shown in Table 1. The obtained polarizing plates were subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configuration of the polarizing plates.

[0095] <Example 13>

[0096] A polarizing plate was produced in the same manner as in Example 1 except that a through hole with a diameter of 2 mm was formed. 2 Laser Formation The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0097] <Example 14>

[0098] A polarizing plate was produced in the same manner as in Example 13 except that the through-holes were formed at 6 mm from the long side and 4 mm from the short side. The obtained polarizing plate was evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0099] <Examples 15 to 18>

[0100] Polarizing plates were prepared in the same manner as in Example 13 except that the through-holes were formed at the positions shown in Table 1. The obtained polarizing plates were subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configuration of the polarizing plates.

[0101] <Example 19>

[0102] A polarizing plate was produced in the same manner as in Example 7 except that a through hole having a diameter of 2 mm was formed. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0103] <Example 20>

[0104] A polarizing plate was produced in the same manner as in Example 19 except that the through-holes were formed 6 mm from the long side and 4 mm from the short side. The obtained polarizing plate was evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0105] <Examples 21 to 24>

[0106] Polarizing plates were prepared in the same manner as in Example 19 except that the through-holes were formed at the positions shown in Table 1. The obtained polarizing plates were subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configuration of the polarizing plates.

[0107] <Comparative Example 1>

[0108] A film (thickness of 12 μm) obtained by uniaxially stretching a polyvinyl alcohol (PVA) resin film in a long shape and containing iodine in the length direction (MD direction) was used as a polarizer. The long-shaped HC-TAC film as the outer protective layer and the long-shaped acrylic resin film (thickness of 20 μm) as the inner protective layer were bonded to both sides of the polarizer in such a way that the length directions of each other were aligned. It should be noted that the HC-TAC film was bonded in such a way that the TAC film became the polarizer side. An adhesive layer (thickness of 20 μm) was formed on the surface of the inner protective layer using the adhesive composition of Manufacturing Example 1, thereby obtaining a long-shaped polarizing plate. The polarizing plate was punched into a shape with a size of 142.0 mm in the longitudinal direction and 66.8 mm in the transverse direction, and an R portion with an R of 7.0 mm was provided at the four corners. At this time, the polarizer was punched in such a way that the absorption axis direction of the polarizer was the short side direction. Then, a through hole with a diameter of 4 mm was formed at a position 8 mm from the long side and 6 mm from the short side in the same manner as in Example 1. In this manner, a polarizing plate having through holes was produced. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0109] <Comparative Example 2>

[0110] A polarizing plate was produced in the same manner as in Comparative Example 1 except that the through-holes were formed 10 mm from the long side and 8 mm from the short side. The obtained polarizing plate was evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0111] <Comparative Example 3>

[0112] A long-sized polarizing plate was obtained in the same manner as in Comparative Example 1. The polarizing plate was punched into a shape with a length of 142.0 mm and a width of 66.8 mm, and an R portion with an R of 7.0 mm was provided at the four corners. At this time, the punching was performed in such a way that the absorption axis direction of the polarizer was the long side direction. The subsequent steps were the same as in Comparative Example 1, thereby producing a polarizing plate having a through hole with a diameter of 4 mm at a position 8 mm from the long side and 6 mm from the short side. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0113] <Comparative Example 4>

[0114] A polarizing plate was produced in the same manner as in Comparative Example 3 except that the through-holes were formed 10 mm from the long side and 8 mm from the short side. The obtained polarizing plate was evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0115] <Comparative Example 5>

[0116] A polarizing plate was produced in the same manner as in Comparative Example 1 except that the through-holes were formed at a position 6 mm from the long side and 4 mm from the short side and the diameter of the through-holes was set to 2 mm. 2 Laser Formation The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0117] <Comparative Examples 6 to 7>

[0118] Polarizing plates were prepared in the same manner as in Comparative Example 5 except that the through-holes were formed at the positions shown in Table 1. The obtained polarizing plates were evaluated in the same manner as in Example 1. The results are shown in Table 1 together with the detailed configuration of the polarizing plates.

[0119] <Comparative Example 8>

[0120] A polarizing plate was produced in the same manner as in Comparative Example 3 except that the through-holes were formed at a position 6 mm from the long side and 4 mm from the short side and the diameter of the through-holes was set to 2 mm. 2 Laser Formation The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0121] <Comparative Examples 9 to 10>

[0122] Polarizing plates were prepared in the same manner as in Comparative Example 8 except that the through-holes were formed at the positions shown in Table 1. The obtained polarizing plates were subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configuration of the polarizing plates.

[0123] <Example 25>

[0124] A laminate of a resin substrate / polarizer was obtained in the same manner as in Example 1. An HC-COP film was bonded to the polarizer surface of the laminate. It should be noted that the HC-COP film is a film having an HC layer (2 μm thick) formed on a cycloolefin resin (COP) film (25 μm thick), and is bonded in such a way that the COP film becomes the polarizer side. Next, the resin substrate was peeled off, a COP film was bonded to the peeled surface, and an adhesive layer (20 μm thick) was formed on the surface of the COP film using the adhesive composition of Manufacturing Example 1, thereby obtaining a long-sized polarizing plate having a structure of HC layer / outer protective layer / polarizer / inner protective layer / adhesive layer. The polarizing plate was punched out into a shape with a size of 142.0 mm in the longitudinal direction and 66.8 mm in the lateral direction, and an R portion with an R of 7.0 mm was provided at the four corners. At this time, the punching was performed in such a way that the absorption axis direction of the polarizer was the short side direction. Then, a through hole having a diameter of 3.9 mm was formed at a position 2.6 mm from the long side and 4.3 mm from the short side. In this manner, a polarizing plate having a through hole was produced. The obtained polarizing plate was subjected to the same evaluation as in Example 1.

[0125] <Example 26>

[0126] A polarizing plate of long size was obtained in the same manner as in Example 25. The polarizing plate was punched into a shape with a size of 142.0 mm in the longitudinal direction and 66.8 mm in the transverse direction, and an R portion with an R of 7.0 mm was provided at the four corners. At this time, the punching was performed in such a way that the absorption axis direction of the polarizer was the long side direction. The subsequent steps were the same as in Example 25, thereby producing a polarizing plate having a through hole with a diameter of 3.9 mm at a position 2.6 mm from the long side and 4.3 mm from the short side. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structure of the polarizing plate.

[0127] Table 1

[0128]

[0129] As can be seen from Table 1, in the polarizing plates of Examples of the present invention, by reducing the thickness of the polarizer, the occurrence of cracks in the through-hole portion after the heat shock test was significantly suppressed.

[0130] Industrial Applicability

[0131] The polarizing plate of the present invention can be suitably used in an image display device, and in particular, can be suitably used in an image display device having a camera portion such as a smartphone, a tablet computer, or a smart watch.

[0132] Description of symbols

[0133] 11. Polarizer

[0134] 12 Outer protective layer

[0135] 13 Inner protective layer

[0136] 20 Adhesive layer

[0137] 30 Through Hole

[0138] 100 Polarizing Plate

Claims

1. A polarizing plate, comprising a polarizer, an adhesive layer, and a protective layer disposed on at least one side of the polarizer, and having a rectangular shape and a through hole, wherein: The thickness of the polarizer is less than 10 μm. The diameter of the through hole is less than 5 mm. The through hole is formed at a position within 11 mm from the long side and within 11 mm from the short side, and After the polarizing plate is subjected to the following heat shock test in a state where the polarizing plate is bonded to a glass plate via the adhesive layer, the displacement amount of the polarizing plate at the through-hole portion is 120 μm or less. The thermal shock test is a test in which an operation of maintaining at -40°C for 30 minutes and then maintaining at 85°C for 30 minutes is repeated 100 times.

2. The polarizing plate according to claim 1, wherein The polarizer has a thickness of 8 μm or less.

3. The polarizing plate according to claim 2, wherein: The polarizer has a thickness of 6 μm or less.

4. The polarizing plate according to any one of claims 1 to 3, wherein The polarizing plate has two through holes formed therein, and The through holes are each formed at a position within 11 mm from the long side and within 11 mm from the short side.

5. The polarizing plate according to any one of claims 1 to 3, wherein The absorption axis of the polarizer extends along the short side direction.

6. The polarizing plate according to any one of claims 1 to 3, wherein The absorption axis of the polarizer extends along the long-side direction.

7. A polarizing plate assembly, wherein: The polarizing plate set comprises the polarizing plate according to claim 5 and the polarizing plate according to claim 6, and The through holes of the polarizing plates are formed at positions corresponding to each other.

8. An image display device, wherein: The image display device includes an image display unit and the polarizing plate according to any one of claims 1 to 6.

9. An image display device, wherein: The image display device comprises an image display unit and the polarizing plate set according to claim 7, and One polarizing plate in the polarizing plate set is arranged on the viewing side of the image display unit, and the other polarizing plate in the polarizing plate set is arranged on the back side of the image display unit.

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