Polarizing plate, polarizing plate set and image display device

Abstract

To provide a polarizing plate which has a through hole near an end part and which significantly suppresses cracks around the through hole.SOLUTION: A polarizing plate includes a polarizer, a protective layer provided on at least one side of the polarizer, and an adhesive layer. The polarizing plate is formed into a rectangle shape and has a through hole. The polarizer has a thickness of 10 to 20 μm. After the polarizing plate is subjected to such a heat shock test that the maintenance at 85°C for 30 minutes after at -40°C for 30 minutes is repeated in 100 cycles in a state of a bond to a glass plate through the adhesive layer, its deviation amount at a part of the through hole is more than 160 μm. The through hole has a diameter of 3 to 5 mm and is formed at a position of 11 mm or less from a long side and 3 mm or less from a short side, 3 mm or less from the long side and 11 mm or less from the short side, or 7 mm or less from the long side and 5 mm or less from the short side.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

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

[0002] Polarizing plates are widely used in image display devices such as mobile phones and laptop computers to realize image display and / or improve the performance of the image display. In recent years, with the rapid spread of smartphones and touch-screen information processing devices, image display devices equipped with cameras have become widely used. Accordingly, polarizing plates having through-holes in positions corresponding to the camera units have also become widely used. For such polarizing plates having through-holes, various considerations must be made regarding the through-holes or their vicinity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 047510 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate having a through hole formed near the end, in which cracks around the through hole are significantly suppressed. [Means for solving the problem]

[0005] A polarizing plate according to an embodiment of the present invention includes a polarizer, a protective layer disposed on at least one side of the polarizer, and a pressure-sensitive adhesive layer. The polarizing plate has a rectangular shape and has through-holes formed therein. The polarizer has a thickness of 10 μm to 20 μm. The polarizing plate is attached to a glass plate via the pressure-sensitive adhesive layer, and subjected to a heat shock test in which the polarizing plate is maintained at -40°C for 30 minutes and then at 85°C for 30 minutes, repeated 100 times. After this, the amount of displacement of the polarizing plate at the through-holes is greater than 160 μm. The through-holes have a diameter of 3 mm to 5 mm, and are located within 11 mm from the long sides and 3 mm from the short sides, within 3 mm from the long sides and 11 mm from the short sides, or within 7 mm from the long sides and 5 mm from the short sides. In one embodiment, two through holes are formed, and each of the through holes is formed within 11 mm from the long side and within 3 mm from the short side, within 3 mm from the long side and within 11 mm from the short side, or within 7 mm from the long side and within 5 mm from the short side. In one embodiment, the absorption axis of the polarizer extends in the short side direction, while in another embodiment, the absorption axis of the polarizer extends in the long side direction. In another polarizing plate of the present invention, the through holes have a diameter of less than 3 mm and are formed at positions 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, and the absorption axis of the polarizer in the polarizing plate extends in the direction of the short side. In yet another polarizing plate of the present invention, the through holes have a diameter of less than 3 mm and are formed at positions 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, and the absorption axis of the polarizer in the polarizing plate extends in the long side direction. According to another aspect of the present invention, there is provided a set of polarizing plates, the set of polarizing plates including a polarizer having an absorption axis extending in the short-side direction of the polarizer and a polarizer having an absorption axis extending in the long-side direction of the polarizer, the through-holes of the polarizing plates being formed at positions corresponding to each other. Another polarizing plate set of the present invention consists of the another polarizing plate and the further another polarizing plate, and the through holes of each polarizing plate are formed at positions 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, and at corresponding positions to each other. According to another aspect of the present invention, there is provided an image display device, which includes an image display cell and the above polarizing plate. Another image display device of the present invention includes an image display cell and the above-described set of polarizing plates, wherein one polarizing plate of the set is disposed on the viewing side of the image display cell and the other polarizing plate is disposed on the back side of the image display cell. [Effects of the Invention]

[0006] According to an embodiment of the present invention, in a polarizing plate having a through hole formed near the edge, by combining and optimizing the diameter of the through hole, the position where the through hole is formed, and the amount of displacement of the polarizing plate at the through hole portion after a heat shock test (effectively, the amount of displacement of the adhesive layer), it is possible to realize a polarizing plate in which cracks around the through hole are significantly suppressed. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1 is a schematic plan view illustrating a polarizing plate according to one embodiment of the present invention. [Figure 1B] 5A and 5B are schematic diagrams illustrating positions where through-holes are formed in a polarizing plate according to an embodiment of the present invention. [Figure 1C] FIG. 2 is a schematic plan view illustrating an embodiment in which a plurality of through holes are formed in a polarizing plate according to an embodiment of the present invention. [Figure 2] 2 is a schematic cross-sectional view of the polarizing plate of FIG. 1 taken along line II-II. [Figure 3] 10 is an enlarged cross-sectional view illustrating a main part of a polarizing plate according to an embodiment of the present invention, illustrating a misalignment at a through-hole portion. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Specific embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Note that the drawings are schematic for clarity, and the ratios of length, width, thickness, etc., as well as angles, etc., in the drawings are different from the actual ones.

[0009] A. Polarizing plate A-1. Overall structure of polarizing plate FIG. 1A is a schematic plan view illustrating a polarizing plate according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of the polarizing plate of FIG. 1A taken along line II-II. The polarizing plate 100 shown in the figure 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 a pressure-sensitive adhesive layer 20. Depending on the purpose and desired configuration, either the outer protective layer 12 or the inner protective layer 13 may be omitted. In this embodiment of the present invention, the thickness of the polarizer 11 is 10 μm to 20 μm, and preferably 10 μm to 15 μm.

[0010] Polarizing plate 100 typically has a rectangular shape as shown in Fig. 1A. In this specification, the term "rectangular shape" also encompasses shapes that include irregularly shaped portions, such as an R-shape in which each vertex is chamfered, as shown in Fig. 1A.

[0011] In an embodiment of the present invention, a through hole 30 is formed in the polarizing plate 100. By forming a through hole, for example, when an image display device has a built-in camera, adverse effects on the camera's performance can be prevented. The through hole 30 is typically formed at or near the edge of the polarizing plate, and preferably at a corner as shown in the illustrated example. By forming the through hole at or near the edge of the polarizing plate, effects on image display can be minimized when the polarizing plate is used in an image display device. The planar shape of the through hole 30 can be any appropriate shape depending on the purpose and the desired configuration of the image display device. A typical example is a substantially circular shape as shown in the illustrated example. The through hole can be formed by various methods, such as laser processing, cutting using an end mill, or punching using a Thomson blade or Pinnacle (registered trademark) blade.

[0012] In one embodiment, the diameter of the through hole is typically 3 mm to 5 mm. In this case, the absorption axis of the polarizer 11 may extend in the long-side direction or the short-side direction. That is, as long as the diameter of the through hole is within this range, cracks around the through hole can be significantly suppressed regardless of the absorption axis direction of the polarizer. In this embodiment, the through hole 30 is formed at a position within 11 mm from the long side and within 3 mm from the short side, within 3 mm from the long side and within 11 mm from the short side, or within 7 mm from the long side and within 5 mm from the short side. The through hole is preferably formed at a position within 7 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; more preferably, within 5 mm from the long side and within 3 mm from the short side; and even more preferably, within 3 mm from the long side and within 3 mm from the short side. According to the embodiment of the present invention, cracks around the through hole can be significantly suppressed even when the through hole is formed near the end. As a result, a polarizing plate with excellent durability can be realized that is applicable even in cases where, for example, a camera unit is located close to the edge of an image display device due to design requirements. Therefore, polarizing plates according to embodiments of the present invention are of great industrial and commercial value. In this specification, the distance from the long side to the through-hole refers to the distance from the long side (i.e., the outer periphery of the polarizing plate) to the edge of the through-hole on the outer periphery side of the polarizing plate on a line connecting the long side and the center of the through-hole in a direction perpendicular to the long side (i.e., the direction in which the short side extends), as shown in FIG. 1B. Similarly, the distance from the short side to the through-hole refers to the distance from the short side (i.e., the outer periphery of the polarizing plate) to the edge of the through-hole on the outer periphery side of the polarizing plate on a line connecting the short side and the center of the through-hole in a direction perpendicular to the short side (i.e., the direction in which the long side extends), as shown in FIG. 1B.

[0013] A plurality of through holes may be formed as shown in FIG. 1C. While two through holes are formed in the illustrated example, the number of through holes may be three, four, or more. When two through holes are formed, for example, as shown in FIG. 1C, each of the two through holes is preferably formed within 11 mm from the long side and within 3 mm from the short side, within 3 mm from the long side and within 11 mm from the short side, or within 7 mm from the long side and within 5 mm from the short side; more preferably, within 7 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; even more preferably, within 5 mm from the long side and within 3 mm from the short side; and particularly preferably, within 3 mm from the long side and within 3 mm from the short side. When two through holes are formed, for example, as shown in FIG. 1C, they may be replaced with a single elongated elliptical through hole.

[0014] In another embodiment, the diameter of the through hole is typically less than 3 mm. The diameter of the through hole is preferably 0.5 mm to 2.5 mm. In this case, for example, the absorption axis of the polarizer 11 extends in the direction of the short side. In this example, the through hole is 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; preferably, it is formed at a position within 7 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; more preferably, it is formed at a position within 5 mm from the long side and within 3 mm from the short side; and even more preferably, it is formed at a position within 3 mm from the long side and within 3 mm from the short side. In another example, the absorption axis of the polarizer 11 extends in the direction of the long side. In this example, the through-hole 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; preferably, it is formed at a position within 3 mm from the long side and within 3 mm from the short side. When multiple through-holes (for example, two) are formed, in either example, all of the through-holes are formed at the above positions.

[0015] In an embodiment of the present invention, as shown in FIG. 3 , a polarizing plate 100 is bonded to a glass plate (which may correspond to a substrate of an image display cell) 120 via an adhesive layer 20. The polarizing plate is subjected to a heat shock test in which the polarizing plate is maintained at −40°C for 30 minutes and then maintained at 85°C for 30 minutes, repeating this cycle for 100 cycles. After this, the deviation D of the polarizing plate at the through-hole portion is greater than 160 μm. The deviation D is preferably 180 μm or more, more preferably 200 μm or more, and even more preferably 220 μm or more. The upper limit of the deviation D may be, for example, 300 μm. The deviation D refers to the maximum portion of the polarizing plate that is farthest from the through-hole portion when viewed cross-sectionally. The reference point for the through-hole portion may typically be the lower end of the adhesive layer. That is, when the polarizing plate shifts (to the right in the illustrated example) mainly due to the shrinkage of the polarizer 11, the adhesive layer 20 remains on the adhered glass plate 120, resulting in a discernible deviation at the through-hole portion. As shown in FIG. 3, the polarizing plate typically shifts away from the through-hole portion (right side of FIG. 3), while the opposing portion shifts so as to protrude into the through-hole (left side of FIG. 3). Thus, the shift of the polarizing plate at the through-hole portion is essentially the shift of the adhesive layer. It is understood that a smaller shift amount D is essentially preferable, since this can reduce light leakage caused by the shift in the image display device. Meanwhile, the present inventors have discovered that by setting the shift amount D to a predetermined amount or more, it is possible to release residual stress around the through-hole after a heat shock test, thereby significantly suppressing cracks around the through-hole. That is, according to an embodiment of the present invention, by setting the shift amount D to a predetermined value or more (preferably within a predetermined range), it is possible to significantly suppress cracks around the through-hole while maintaining light leakage within an acceptable range.

[0016] The ratio D / R of the deviation D to the diameter R of the through hole is preferably 40% to 100%, and more preferably 60% to 100%. If D / R is in this range, it is possible to significantly suppress cracks around the through hole while maintaining light leakage within an acceptable range.

[0017] In an embodiment of the present invention, the ratio (%) of the residual stress in the through-hole portion to the residual stress at the center of the polarizing plate is preferably 77% or less. This ratio can vary depending on the diameter of the through-hole. When the diameter of the through-hole is 3 mm to 5 mm (e.g., 4 mm), this ratio is more preferably 70% or less, even more preferably 68% or less, and particularly preferably 65% ​​or less. When the diameter of the through-hole is less than 3 mm (e.g., 2 mm), this ratio is more preferably 76% or less, even more preferably 74% or less, and particularly preferably 72% or less. The lower limit of this ratio can be, for example, 50%, regardless of the diameter of the through-hole. When the residual stress ratio is within this range, cracks around the through-hole can be significantly suppressed. This residual stress ratio can be achieved by adjusting the position of the through-hole and the above-mentioned deviation amount D in combination. Note that, in this specification, "residual stress in the through-hole portion" refers to the residual stress at the portion of the outer periphery of the through-hole where the residual stress is greatest.

[0018] The polarizing plate according to the embodiment of the present invention may further include any appropriate optical functional layer depending on the purpose. Examples of the optical functional layer include a retardation layer, a conductive layer for a touch panel, and a reflective polarizer. The type, number, combination, and arrangement position of the optical functional layer incorporated in the polarizing plate can be appropriately set depending on the purpose.

[0019] The polarizing plate according to the embodiment of the present invention preferably has an aspect ratio of 1.3 to 2.5. In this case, the size of the polarizing plate is, for example, 145 mm to 155 mm in height and 65 mm to 75 mm in width, or 230 mm to 240 mm in height and 140 mm to 150 mm in width. That is, the polarizing plate according to the embodiment of the present invention can be suitably used in smartphones or tablet PCs. The size of a smartphone may be, for example, 120 mm to 200 mm in height and 30 mm to 120 mm in width.

[0020] The polarizer, protective layer, and adhesive layer that constitute the polarizing plate will be specifically described below.

[0021] A-2. Polarizer A polarizer is typically made of a resin film containing a dichroic material. Any appropriate resin film that can be used as a polarizer can be adopted as the resin film. A typical resin film is a polyvinyl alcohol resin (hereinafter referred to as a "PVA resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

[0022] Specific examples of polarizers composed of a single-layer resin film include PVA-based resin films that have been subjected to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The dyeing with iodine is carried out, for example, by immersing the PVA-based resin film in an aqueous iodine solution. The stretching ratio in the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the film may be dyed after stretching. If necessary, the PVA-based resin film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based resin film in water and washing it before dyeing, it is possible to clean off stains and antiblocking agents on the surface of the PVA-based resin film and also to swell the PVA-based resin film, thereby preventing uneven dyeing.

[0023] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching can optionally further include in-air stretching the laminate at an elevated temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. The obtained resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate and any appropriate protective layer depending on the purpose may be laminated on the peeled surface. Details of such polarizer manufacturing methods are described in, for example, JP 2012-73580 A and Japanese Patent No. 6470455 A. The descriptions of these patent documents are incorporated herein by reference.

[0024] The thickness of the polarizer is as described in the above section A-1.

[0025] The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 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 degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0026] A-3.Protective layer The protective layer is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that can be the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxy resins, and silicones. Other examples include glassy polymers such as siloxane polymers. Polymer films described in JP 2001-343529 A (WO 01 / 37007) can also be used. Examples of materials that can be used for this film include a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in its side chains and a thermoplastic resin having substituted or unsubstituted phenyl and nitrile groups in its side chains, such as a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer.The polymer film can be, for example, an extrusion molded product of the above resin composition.

[0027] The outer protective layer 12 (particularly when the polarizing plate is the viewer-side polarizing plate) may be subjected to a surface treatment such as a hard coat treatment, an anti-reflection treatment, an anti-sticking treatment, or an anti-glare treatment, as needed. Additionally / alternatively, the outer protective layer 12 may be subjected to a treatment to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptical) polarization function or an ultra-high phase difference), as needed. By applying such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate can be suitably applied to image display devices that can be used outdoors.

[0028] The inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm and the thickness direction retardation Rth(550) is -10 nm to +10 nm. Here, "Re(λ)" refers to the in-plane retardation measured at 23°C with light having a wavelength of λ nm. For example, "Re(550)" refers to the thickness direction retardation measured at 23°C with light having a wavelength of 550 nm. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d (nm) is the thickness of the layer (film). Furthermore, "Rth(λ)" refers to the thickness direction retardation measured at 23°C with light having a wavelength of λ nm. For example, "Rth(550)" refers to the thickness direction retardation measured at 23°C with light having a wavelength of 550 nm. Rth(λ) is calculated by the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film), where nx is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), ny is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and nz is the refractive index in the thickness direction.

[0029] The protective layer may have any appropriate thickness. The thickness of the protective layer is, for example, 10 μm to 50 μm, and preferably 20 μm to 40 μm. If a surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0030] A-4.Adhesive layer The pressure-sensitive adhesive layer 20 is typically used to bond a polarizing plate to an image display cell. The pressure-sensitive adhesive layer may typically be composed of an acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition). The acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer may be contained in the pressure-sensitive adhesive composition in an amount of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more of the solid content of the pressure-sensitive adhesive composition. The (meth)acrylic polymer contains alkyl (meth)acrylate as a main component as a monomer unit. Here, (meth)acrylate refers to acrylate and / or methacrylate. The alkyl (meth)acrylate may be contained in an amount of preferably 80% by weight or more, more preferably 90% by weight or more of the monomer components forming the (meth)acrylic polymer. Examples of the alkyl group of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3 to 9, more preferably 3 to 6. A preferred alkyl (meth)acrylate is butyl acrylate. Examples of monomers (copolymerizable monomers) constituting the (meth)acrylic polymer include, in addition to alkyl (meth)acrylates, carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocycle-containing vinyl monomers. Representative examples of copolymerizable monomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The acrylic pressure-sensitive adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include epoxy group-containing silane coupling agents. Examples of the crosslinking agent include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Furthermore, the acrylic pressure-sensitive adhesive composition may contain an antioxidant and / or a conductive agent.By adjusting the type, number, combination, and copolymerization ratio of the monomer units, the type, number, combination, and blending ratio of the silane coupling agents, and the type, number, combination, and blending ratio of the crosslinking agents, an acrylic pressure-sensitive adhesive composition (and consequently, a pressure-sensitive adhesive layer) having the desired properties according to the purpose can be obtained. As a result, in the embodiment of the present invention, the desired displacement amount D can be achieved. Details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described in, for example, JP 2006-183022 A, JP 2015-199942 A, JP 2018-053114 A, JP 2016-190996 A, and WO 2018 / 008712 A, the disclosures of which are incorporated herein by reference.

[0031] The thickness of the pressure-sensitive adhesive layer is preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm. If the thickness of the pressure-sensitive adhesive layer is within this range, the desired displacement amount D can be achieved.

[0032] The storage modulus G' of the pressure-sensitive adhesive layer at -40°C is preferably 1.0 x 10 5 (Pa) or more, and more preferably 1.0 × 10 6 (Pa) or more, and more preferably 1.0 × 10 7 (Pa) or more, and particularly preferably 1.0 × 10 8 (Pa) or more. The storage modulus G' is, for example, 1.0 × 10 9 (Pa) or less. If the storage modulus at −40° C. of the pressure-sensitive adhesive layer is within this range, the desired displacement amount D can be achieved.

[0033] B. Setting the polarizing plate The polarizing plate described in Section A above may be used as either a viewer-side polarizing plate or a rear-side polarizing plate. A polarizing plate set can be provided by combining two specific embodiments of the polarizing plates described in Section A above. Therefore, the embodiments of the present invention also encompass such polarizing plate sets. In a polarizing plate set, the two polarizing plates constituting the set have through-holes 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 stacked.

[0034] In one embodiment, the polarizing plate set includes a polarizing plate having a through hole with a diameter of 3 mm to 5 mm and an absorption axis of the polarizer extending in the short-side direction, and a polarizing plate having a through hole with a diameter of 3 mm to 5 mm and an absorption axis of the polarizer extending in the long-side direction. In this case, the through holes of the two polarizing plates are typically located within 11 mm from the long side and within 3 mm from the short side, within 3 mm from the long side and within 11 mm from the short side, or within 7 mm from the long side and within 5 mm from the short side; preferably within 7 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; more preferably within 5 mm from the long side and within 3 mm from the short side; and even more preferably within 3 mm from the long side and within 3 mm from the short side.

[0035] In another embodiment, the polarizing plate set includes a polarizing plate having a through hole with a diameter of less than 3 mm and an absorption axis of the polarizer extending in the short side direction, and a polarizing plate having a through hole with a diameter of less than 3 mm and an absorption axis of the polarizer extending in the long side direction. In this case, the through holes of the two polarizing plates are typically formed at positions 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, preferably within 3 mm from the long side and within 3 mm from the short side, and at corresponding positions.

[0036] C. Image display device The polarizing plate and the polarizing plate set according to the embodiments of the present invention can be applied to an image display device. Therefore, the image display device is also encompassed in the embodiments of the present invention. In one embodiment, the image display device includes an image display cell and a polarizing plate. The polarizing plate is the polarizing plate according to the embodiment of the present invention described in Section A above. The polarizing plate is attached to the image display cell via an adhesive layer. In another embodiment, the image display device includes an image display cell and a set of polarizing plates. The set of polarizing plates is the polarizing plate set according to the embodiment of the present invention described in Section B above. In this case, one polarizing plate in the set of polarizing plates is disposed on the viewing side of the image display cell, and the other polarizing plate is disposed on the back side of the image display cell. Examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, and quantum dot display devices. [Example]

[0037] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are by weight.

[0038] (1) Amount of deviation The polarizing plates obtained in the examples and comparative examples were attached to a glass plate (manufactured by Matsunami Glass Co., Ltd., 350 mm long x 250 mm wide x 1.1 mm thick) via an adhesive layer to prepare a test sample. This test sample was subjected to a heat shock test in which the sample was held at -40°C for 30 minutes and then at 85°C for 30 minutes, repeating this cycle for 100 cycles. The temperature increase and decrease rates in the heat shock test were 10°C / min. After the test, the amount of displacement of the polarizing plate (effectively the adhesive layer) at the through-hole portion was measured using an optical microscope (MX61L) manufactured by Olympus Corporation. Measurements were performed on three test samples, and the maximum of the three measurements was taken as the amount of displacement. (2) Ratio of residual stress at the through-hole to the residual stress at the center of the polarizer The calculation was performed using stress analysis simulation. The simulation was performed using the following commercial software and methods. Software: MSC Software's nonlinear structural analysis software Marc Method: Finite Element Method (FEM) (3) Cracks The polarizing plates obtained in the examples and comparative examples were subjected to a heat shock test in the same manner as in the "shift amount" in (1) above. After the test, the state of cracks in the through-holes was observed using an optical microscope (MX61L) manufactured by OLYMPUS Corporation, and evaluated according to the following criteria. AA: No cracks were observed A: Only small cracks less than 300 μm in length were observed B: Cracks 300 μm to 1 mm in length were observed, but no light leakage occurred. C: Cracks were noticeable and light leakage occurred.

[0039] <Production Example 1> A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 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. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts by weight of ethyl acetate were charged per 100 parts of the monomer mixture (solids). Nitrogen gas was introduced with gentle stirring to replace the atmosphere. The temperature in the flask was maintained at around 55°C, and the polymerization reaction was carried out for 8 hours to prepare an acrylic polymer solution with a weight-average molecular weight (Mw) of 1.5 million. 0.1 parts of an isocyanate crosslinking agent (trade name: Takenate D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 parts of benzoyl peroxide (trade name: Niper BMT 40SV, manufactured by Nippon Oil & Fats Co., Ltd.), 0.1 parts of a thiol group-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy group content: 30%, thiol equivalent: 450 g / mol), 0.2 parts of an antioxidant (trade name: Irganox 1010, hindered phenol, manufactured by BASF Japan Ltd.), and 5 parts of a conductive agent (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, an ionic liquid manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) were blended with 100 parts of the solid content of the obtained acrylic polymer solution to obtain a pressure-sensitive adhesive composition.

[0040] Example 1 A long polyvinyl alcohol (PVA) resin film was doped with iodine and uniaxially stretched in the machine direction (MD) to obtain a film (12 μm thick) used as the polarizer. A long HC-TAC film (outer protective layer) and a long acrylic resin film (20 μm thick) (inner protective layer) were laminated to both sides of this polarizer, aligning their longitudinal directions. The HC-TAC film was a triacetyl cellulose (TAC) film (25 μm thick) with a hard coat (HC) layer (7 μm thick), and the TAC film was laminated to the polarizer side. A pressure-sensitive adhesive layer (20 μm thick) was formed on the surface of the inner protective layer using the pressure-sensitive adhesive composition of Production Example 1 to obtain a long polarizing plate. This polarizing plate was punched into a shape measuring 142.0 mm long and 66.8 mm wide, with rounded corners of 7.0 mm radius. The punching was performed so that the absorption axis direction of the polarizer was aligned with the short side direction. Furthermore, through holes with a diameter of 4 mm were formed 2 mm from the long side and 2 mm from the short side. The through holes were formed by end milling. The end mill feed rate was 500 mm / min, the rotation speed was 2500 rpm, and the removal depth was 0.1 mm. In this way, a polarizing plate with through holes was produced. The obtained polarizing plate was subjected to the evaluation (3) above. The results are shown in Table 1, along with the detailed structure of the polarizing plate. In Table 1, "0°" means the long side direction, and "90°" means the short side direction.

[0041] <Example 2> A polarizing plate was produced in the same manner as in Example 1, except that the through holes were formed at positions 6 mm from the long side and 4 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, along with the detailed configuration of the polarizing plate.

[0042] <Comparative Examples 1 and 2 and Examples 3 and 4> Polarizing plates were produced in the same manner as in Example 1, except that the positions at which the through holes were formed were as 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.

[0043] <Example 5> A long polarizing plate was obtained in the same manner as in Example 1. This polarizing plate was punched out to a size of 142.0 mm in length and 66.8 mm in width. At this time, the punching was performed so that the absorption axis direction of the polarizer was aligned with the long side direction. The following procedure was performed in the same manner as in Example 1 to prepare a polarizing plate having through holes with a diameter of 4 mm located 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, along with the detailed configuration of the polarizing plate.

[0044] Example 6 A polarizing plate was produced in the same manner as in Example 5, except that the through holes were formed at positions 6 mm from the long side and 4 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, along with the detailed configuration of the polarizing plate.

[0045] <Comparative Examples 3 and 4 and Examples 7 and 8> Polarizing plates were produced in the same manner as in Example 5, except that the positions at which the through holes were formed were as 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, along with the detailed configuration of the polarizing plates.

[0046] Example 9 A polarizing plate was produced in the same manner as in Example 1, except that through-holes with a diameter of 2 mm were formed. The through-holes were formed using a CO2 laser. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configuration of the polarizing plate.

[0047] <Comparative Example 5> A polarizing plate was produced in the same manner as in Example 9, except that the through holes were formed at positions 6 mm from the long side and 4 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, along with the detailed configuration of the polarizing plate.

[0048] <Comparative Examples 6 and 7 and Examples 10 and 11> Polarizing plates were produced in the same manner as in Example 9, except that the positions at which the through holes were formed were as 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, along with the detailed configuration of the polarizing plates.

[0049] Example 12 A polarizing plate was produced in the same manner as in Example 5, except that through holes with a diameter of 2 mm were formed. The obtained polarizing plate was subjected to the same evaluations as in Example 1. The results are shown in Table 1, along with the detailed configuration of the polarizing plate.

[0050] <Comparative Example 8> A polarizing plate was produced in the same manner as in Example 12, except that the through holes were formed at positions 6 mm from the long side and 4 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, along with the detailed configuration of the polarizing plate.

[0051] <Comparative Examples 9 to 12> Polarizing plates were produced in the same manner as in Example 12, except that the positions at which the through holes were formed were as 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, along with the detailed configuration of the polarizing plates.

[0052] [Table 1]

[0053] As is clear from Table 1, the polarizing plates of the examples of the present invention significantly suppressed the occurrence of cracks in the through-hole portions after the heat shock test. [Industrial Applicability]

[0054] The polarizing plate of the present invention can be suitably used in image display devices, and in particular, can be suitably used in image display devices having a camera unit, such as smartphones, tablet PCs, or smartwatches. [Explanation of symbols]

[0055] 11 Polarizer 12 Outer protective layer 13 Inner protective layer 20 adhesive layer 30 Through Holes 100 polarizing plate

Claims

1. A rectangular polarizing plate having a polarizer, a protective layer disposed on at least one side of the polarizer, and a pressure-sensitive adhesive layer, and having through holes formed therein, the thickness of the polarizer is 10 μm to 20 μm, and the absorption axis of the polarizer extends in the short side direction; the polarizing plate is attached to a glass plate via the pressure-sensitive adhesive layer, and then subjected to a heat shock test in which 100 cycles of holding the polarizing plate at −40° C. for 30 minutes and then at 85° C. for 30 minutes are repeated, after which the amount of displacement of the polarizing plate at the through-hole portion is greater than 160 μm, The through hole has a diameter of less than 3 mm; The through hole is 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. Polarizer: Here, the distance from the long side to the through hole is the distance from the long side to the end of the through hole on the outer periphery of the polarizing plate on a straight line connecting the long side and the center of the through hole in a direction perpendicular to the long side; and the distance from the short side to the through hole is the distance from the short side to the end of the through hole on the outer periphery of the polarizing plate on a straight line connecting the short side and the center of the through hole in a direction perpendicular to the short side.

2. A rectangular polarizing plate having a polarizer, a protective layer disposed on at least one side of the polarizer, and an adhesive layer, and having through holes formed therein, the thickness of the polarizer is 10 μm to 20 μm, and the absorption axis of the polarizer extends in the long side direction; the polarizing plate is attached to a glass plate via the pressure-sensitive adhesive layer, and then subjected to a heat shock test in which 100 cycles of holding the polarizing plate at −40° C. for 30 minutes and then at 85° C. for 30 minutes are repeated, after which the amount of displacement of the polarizing plate at the through-hole portion is greater than 160 μm, The through hole has a diameter of less than 3 mm; The through hole 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. Polarizer: Here, the distance from the long side to the through hole is the distance from the long side to the end of the through hole on the outer periphery of the polarizing plate on a straight line connecting the long side and the center of the through hole in a direction perpendicular to the long side; and the distance from the short side to the through hole is the distance from the short side to the end of the through hole on the outer periphery of the polarizing plate on a straight line connecting the short side and the center of the through hole in a direction perpendicular to the short side.

3. A polarizing plate comprising the polarizing plate according to claim 1 and the polarizing plate according to claim 2, the through holes of each polarizing plate are formed at positions 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, and at positions corresponding to each other; A set of polarizing plates.

4. An image display device comprising an image display cell and a polarizing plate according to claim 1 or 2.

5. An image display cell and a set of polarizing plates according to claim 3, one polarizing plate of the set of polarizing plates is disposed on the viewing side of the image display cell, and the other polarizing plate is disposed on the back side of the image display cell; Image display device.

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