TWI904245B - Polarizing plate, polarizing plate with cover glass and image display device - Google Patents

Abstract

This invention provides a polarizing plate that exhibits minimal displacement in the through-hole portion even under high-temperature environments, and significantly suppresses air bubbles in the through-hole portion when used to fill adhesive covering a glass laminate in an image display device. The polarizing plate of this invention comprises: a polarizing element; a protective layer disposed on at least one side of the polarizing element; and an adhesive layer; and has a through-hole formed therein. The thickness of the polarizing element is 15 μm or less, and | _b1 - _b2 | is 45 mm or less. Here, _b1 is the distance along the absorption axis of the polarizing element from the center of the through-hole to one end of the polarizing plate, and _b2 is the distance along the absorption axis of the polarizing element from the center of the through-hole to the other end of the polarizing plate.

Description

Polarizing plate, polarizing plate with cover glass and image display device

The present invention relates to a polarizing plate, a polarizing plate covered with a cover glass, and an image display device. More specifically, the present invention relates to a polarizing plate having an adhesive layer and forming through holes, a polarizing plate covered with a cover glass, and an image display device comprising such a polarizing plate.

Polarizing plates are widely used in image display devices such as mobile phones and laptops to achieve image display and/or improve the performance of such image display. In recent years, it has been hoped that polarizing plates will also be used in image display devices equipped with cameras, smartwatches, and automotive dashboards, and there are cases where polarizing plates have through holes. However, in polarizing plates with through holes, there is a problem that the polarizing plate may shift (actually, the adhesive layer may shift) at the through hole area under high-temperature environments.

However, to impart surface hardness and impact resistance to the image display device, a laminated cover glass is often used on the outermost surface of the image display device. In the case of a laminated cover glass in an image display device that includes a polarizing plate with through-holes, the through-holes are typically used to fill the adhesive layer of the cover glass. However, in image display devices where the through-holes are filled with adhesive, air bubbles may form in the filled portion (through-hole portion) due to heat treatment during manufacturing processes. Previous Art Documents Patent Documents

Patent Document 1: International Publication No. 2017/047510 Patent Document 2: Japanese Patent Application Publication No. 2016-094569

[The problem that the invention aims to solve]

This invention addresses the aforementioned problems. Its main objective is to provide a polarizing plate that exhibits minimal displacement in the through-hole portion, even under high-temperature conditions. Furthermore, in image display devices where the through-hole is used to fill the adhesive covering the glass laminate, air bubbles in the through-hole portion are significantly suppressed. [Technical Means for Solving the Problem]

The polarizing plate of the present invention comprises: a polarizing element; a protective layer disposed on at least one side of the polarizing element; and an adhesive layer; and has a through hole formed therein. The thickness of the polarizing element is 15 μm or less, and | _b1 - _b2 | is 45 mm or less. Here, _b1 is the distance from the center of the through hole to one end of the polarizing plate along the absorption axis of the polarizing element, and _b2 is the distance from the center of the through hole to the other end of the polarizing plate along the absorption axis of the polarizing element. In one embodiment, the polarizing plate has a rectangular shape, and when viewed from the side, the absorption axis of the polarizing element is at a 135° clockwise direction from the long side, and the through hole is formed at the upper right corner. In another embodiment, the polarizing plate has a rectangular shape, and when viewed from the side, the absorption axis of the polarizing element is oriented at a 45° clockwise direction from the long side, with the through hole formed at the upper left corner. Furthermore, in yet another embodiment, the polarizing plate has a rectangular shape, the absorption axis of the polarizing element is oriented along the short side, and when viewed from above, the through hole is formed at the end of the long side and the center of the short side. In one embodiment, the thickness of the polarizing element is 8 μm or less. In one embodiment, the creep value of the adhesive layer is 140 μm/hr or less. According to another aspect of the present invention, an image display device is provided. The image display device includes an image display unit and the aforementioned polarizing plate, the polarizing plate being adhered to the image display unit via the aforementioned adhesive layer. According to another aspect of the invention, a polarizing plate with a cover glass is provided. The polarizing plate with the cover glass has: a polarizing element; a protective layer disposed on at least one side of the polarizing element; an adhesive layer; another adhesive layer disposed on the side of the polarizing element opposite to the adhesive layer; and a cover glass, adhered to the other adhesive layer; and has a through hole filled with an adhesive forming the other adhesive layer, wherein the thickness of the polarizing element is 15 μm or less, and | _b1 - _b2 | is 45 mm or less. [Effects of the invention]

According to an embodiment of the present invention, a polarizing plate with through holes can be realized, and even in high-temperature environments, the displacement in the through hole portion is small. Furthermore, in an image display device, when the through holes are used to fill the adhesive covering the glass laminate, the bubbles in the through hole portion can be significantly suppressed.

The following description, with reference to the drawings, illustrates specific embodiments of the invention, but the invention is not limited to these embodiments. Furthermore, the drawings are provided in a schematic manner for ease of observation, and therefore, the ratios of length, width, thickness, etc., as well as angles, in the drawings differ from the actual dimensions.

A. Overall Structure of the Polarizing Plate Figure 1A is a schematic top view illustrating the formation position of the through hole in a polarizing plate according to one embodiment of the present invention; Figure 1B is a schematic top view illustrating the formation position of the through hole in a polarizing plate according to another embodiment of the present invention; Figure 1C is a schematic top view illustrating the formation position of the through hole in a polarizing plate according to yet another embodiment of the present invention; Figure 2 is a schematic cross-sectional view of the through hole portion of the polarizing plate. The polarizing plate of this invention (polarizing plates 100, 101, and 102 in the examples) includes: a polarizing element 11; a protective layer (hereinafter, sometimes referred to as an outer protective layer) 12 disposed on one side of the polarizing element 11; a protective layer (hereinafter, sometimes referred to as an inner protective layer) 13 disposed on the other side of the polarizing element 11; and an adhesive layer 20. The adhesive layer 20 is used to attach the polarizing plate 100 to the image display unit. Depending on the purpose and required configuration, either the outer protective layer 12 or the inner protective layer 13 may be omitted.

A through-hole 30 is formed in the polarizing plate. By forming the through-hole, for example, in the case of a camera built into an image display device, adverse effects on the camera's performance can be prevented. The through-hole can be formed by various methods, such as laser processing, cutting with an end mill, or punching with a Thomson cutter or Pinnacle cutter. The polarizing plate is typically rectangular in shape. In this specification, the term "rectangular shape" also includes shapes with irregularly shaped parts, such as the R-shape with chamfered vertices as shown in Figures 1A-1C. Although not shown, multiple through-holes may be provided. Furthermore, the top view shape of the through-hole can be any suitable shape depending on the purpose. As specific examples of top-view shapes, circles, ellipses, squares, rectangles, and combinations thereof (e.g., rectangles with rounded ends) can be provided simultaneously with the through-hole. Furthermore, irregularly shaped processing portions (e.g., U-shaped notches, V-shaped notches) can be provided at the same time as the through-hole. The inventors have discovered a new problem: when the through-hole is formed on a polarizing plate, in a high-temperature environment, the polarizing plate shifts at the through-hole portion (essentially the adhesive layer shifts: hereinafter sometimes referred to as paste shift), resulting in a risk of light leakage at the through-hole portion; this problem is solved by adopting the specific configuration of the embodiment of the present invention (described later). That is, the present invention solves a new problem that was previously unknown, and the resulting effect is unexpectedly superior. Furthermore, the inventors have discovered that by adopting a specific configuration of the embodiment of the present invention (described below), bubbles, known as delayed bubbles, can also be significantly suppressed. Details of delayed bubbles are as follows. In order to impart surface hardness and impact resistance to the image display device, there is a case where a glass laminate covers the outermost surface of the image display device. In the case of a glass laminate covering the image display device that includes a polarizing plate with through holes, the through holes are typically used to fill the adhesive of the glass laminate. A typical method of this type of filling involves bonding a laminate of cover glass and adhesive sheet to the polarizing plate using vacuum lamination. In most cases, no identifiable bubbles are present immediately after vacuum lamination, but bubbles may appear during subsequent heat durability tests of the image display device. These bubbles are typically caused by the contractile stress of the polarizing plate applied to the filling area. These bubbles are called delayed bubbles. Delayed bubbles are larger than fine bubbles, occupying a certain proportion of the top-view area of the through-hole. Delayed bubbles are unacceptable both from an aesthetic point of view and from the perspective of camera performance in the camera section corresponding to the through-hole. Therefore, by suppressing delayed bubbles, the product value of image display devices can be significantly increased.

In the embodiments of the present invention, the thickness of the polarizing element is 15 μm or less, preferably 10 μm or less, more preferably 8 μm or less, further preferably 7 μm or less, particularly preferably 6 μm or less, and even more preferably 5 μm or less. The thickness of the polarizing element is, for example, 1 μm or more, or, for example, 2 μm or more. By setting the thickness of the polarizing element within this range, thermal shrinkage of the polarizing element itself can be suppressed. As a result, deformation of the adhesive layer (resulting in paste shift) that may be caused by thermal shrinkage of the polarizing element can be suppressed.

Furthermore, in the embodiments of the present invention, | _b1 - _b2 | is 45 mm or less, preferably 30 mm or less, more preferably 20 mm or less, further preferably 10 mm or less, and especially preferably 5 mm or less. The smaller | _b1 - _b2 | is, the better, ideally zero. If | _b1 - _b2 | is within this range, the paste shift in the through-hole portion under high-temperature conditions can be reduced, and delayed bubbles can be suppressed. On the other hand, | _a1 - _a2 | does not actually contribute to suppressing paste shift in the through-hole portion or suppressing delayed bubbles. That is, even if | _a1 - _a2 | is changed, paste shift and delayed bubbles will not be suppressed. Here, _b1 is the distance along the absorption axis of the polarizing element from the center of the through-hole to one end of the polarizing plate, _b2 is the distance along the absorption axis of the polarizing element from the center of the through-hole to the other end of the polarizing plate, _a1 is the distance along the direction orthogonal to the absorption axis of the polarizing element from the center of the through-hole to one end of the polarizing plate, and _a2 is the distance along the direction orthogonal to the absorption axis of the polarizing element from the center of the through-hole to the other end of the polarizing plate. That is, by optimizing the orientation of the absorption axis of the polarizing element relative to the through-hole, paste shift and delayed bubbles can be suppressed.

Referring to Figures 1A to 1C, the relationship between the positions of _a1 , _a2 , _b1 , and _b2 and the through-holes is explained in detail. In Figure 1A, the following configuration is shown: the polarizing plate is rectangular, and when viewed from the viewing side of the image display device (opposite to the adhesive layer), the absorption axis direction A of the polarizing element is 135° clockwise relative to the long side direction. In this configuration, when | _b1 - _b2 | is optimized, if the through-hole 30 is formed at any position on a straight line extending from the upper right corner along a direction orthogonal to the absorption axis direction A when viewing the polarizing plate from the viewing side (in Figure 1A, this indicates the straight line from _a1 and _a2 ), then paste shift and delayed bubbles can be suppressed. On the other hand, if the impact on image display is minimized by adjusting | _a1 - _a2 |, the through-hole 30 can be preferably formed in the upper right corner. Figure 1B shows a configuration where the polarizing plate is rectangular, and when viewed from the viewing side of the image display device, the absorption axis direction A of the polarizing element is at a 45° clockwise angle relative to the long side direction. In this configuration, both paste shift and bubble delay can be suppressed by optimizing | _b1 - _b2 |, and the impact on image display can be minimized by adjusting | _a1 - _a2 |. Consequently, in this configuration, the through-hole 30 can be preferably formed in the upper left corner. Figure 1C shows a configuration where the polarizing plate is rectangular, and the absorption axis A of the polarizing element is along the short side (orthogonal to the long side). In this configuration, both paste shift and bubble delay can be suppressed by optimizing | _b1 - _b2 |, and the impact on image display can be minimized by adjusting | _a1 - _a2 |. As a result, in this configuration, the through-hole 30 can be preferably formed at the end of the long side and the center of the short side. As can be seen from the above, according to the embodiment of the present invention, regardless of the planar shape of the polarizing plate (for example, even in cases with a special planar shape), the relationship between the position of the through-hole that suppresses paste shift and bubble delay and the absorption axis direction can be determined by optimizing | _b1 - _b2 |. Furthermore, the impact of the through hole on the image display can be minimized by adjusting | _a1 - _a2 |.

In one embodiment, as shown in Figure 3, with the polarizing plate 100 bonded to the glass plate (a substrate corresponding to an image display unit) 120 via the adhesive layer 20, after the polarizing plate 100 is subjected to a heating test at 85°C for 120 hours, the offset (paste offset) D in the through-hole 30 portion is preferably 150 μm or less, more preferably 120 μm or less, further preferably 100 μm or less, particularly preferably 80 μm or less, and especially preferably 50 μm or less. The smaller the offset D, the better. The lower limit of the paste offset D is, for example, 10 μm, or, for example, 20 μm. Furthermore, the paste offset D refers to the largest portion of the polarizing plate that is farthest from the through-hole portion when observed in cross-section. The reference point for the through-hole portion is typically the lower end of the adhesive layer. That is, when the polarizing plate shifts primarily due to the contraction of the polarizing element 11 (to the right in the example shown), the shift is observed in the through-hole portion because the adhesive layer 20 remains on the adhered glass plate 120. Furthermore, as shown in Figure 3, the polarizing plate is typically shifted away from the through-hole side in the through-hole portion (right side in Figure 3), and the portion opposite it shifts in a manner that protrudes into the through-hole (left side in Figure 3). As described above, according to the embodiments of the present invention, the problem of paste shift in the through-hole portion under high temperature environment can be solved. Specifically, the amount of paste shift D after a specific heating test can be set to the range described above.

In one embodiment, the adhesive layer 20 is formed on the end face of the through hole 30 of the polarizing plate in such a way that it is closer to the inner side in the surface direction than the end face of the polarizing plate (which is essentially the polarizing element 11 or the inner protective layer 13 (if present)). The size of the adhesive gap is preferably 300 μm or less, more preferably 200 μm or less, further preferably 150 μm or less, particularly preferably 100 μm or less, and especially preferably 80 μm or less. The lower limit of the size of the adhesive gap can be, for example, 10 μm. In this specification, "size of adhesive gap" refers to the maximum length from the end face of the polarizing plate (actually the polarizing element 11 or the inner protective layer 13 (if present)) to the end face of the adhesive layer 20.

In the embodiments of the present invention, the dimensional shrinkage rate of the polarizing plate after the aforementioned heating test is preferably 1.0% or less, more preferably 0.6% or less, and even more preferably 0.3% or less. The smaller the dimensional shrinkage rate, the better; the lower limit of the dimensional shrinkage rate can be, for example, 0.01%. Furthermore, the dimensional shrinkage rate is calculated by the following formula. The dimensional shrinkage rate refers to the overall dimensional shrinkage rate of the polarizing plate attached to the glass plate. In the case where the polarizing plate further has an optical functional layer (e.g., a retardation layer, a reflective polarizing element), as described below, it refers to the overall dimensional shrinkage rate of the polarizing plate including the optical functional layer. Furthermore, the "dimensionality" in the following formula refers to the dimension along the absorption axis of the polarizing plate (essentially a polarizing element). Dimensional shrinkage rate (%) = {(Dimensions before heating test - Dimensions after heating test) / Dimensions before heating test} × 100

The diameter R of the through hole 30 is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 5 mm or less. The lower limit of the through hole diameter is, for example, 1.5 mm, or, for example, 2 mm. The ratio D/R of the paste offset D to the through hole diameter R is preferably 15% or less, more preferably 10% or less, even more preferably 6% or less, and particularly preferably 5% or less. Furthermore, the lower limit of D/R is as small as possible. According to the embodiment of the present invention, since the paste offset D is very small as described above, D/R can be set within this range even when the through hole diameter is reduced. Therefore, even when the through hole diameter is reduced, adverse effects on camera performance can be substantially prevented. As a result, the polarizing plate of the present invention can be applied to image display devices that use only the camera section as a non-display area and/or frameless image display devices.

The polarizing plate of this invention can be used as a viewing-side polarizing plate or a rear-side polarizing plate. Furthermore, the polarizing plate of this invention can also have any suitable optical functional layer depending on the purpose. Examples of optical functional layers include, for instance, a phase difference layer, a conductive layer for a touch panel, and a reflective polarizing element.

In one embodiment, a retardation layer may be disposed between the inner protective layer 13 and the adhesive layer 20. The retardation layer may be a single layer or have a multilayer structure. When the retardation layer is a single layer, it typically functions as a λ/4 plate. In this case, the in-plane phase difference Re(550) of the retardation layer is preferably 100 nm to 200 nm, more preferably 120 nm to 170 nm, and even more preferably 130 nm to 150 nm. The angle formed by the absorption axis of the polarizing element and the late-phase axis of the retardation layer is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably 44° to 46°. The retardation layer preferably exhibits inverse wavelength dispersion characteristics, where the phase difference value increases with the wavelength of the measured light. In this case, the Re(450)/Re(550) of the retardation layer is preferably 0.8 or higher and less than 1, more preferably 0.8 or higher and less than 0.95. The retardation layer can be an extension film of a resin film or an alignment and curing layer of a liquid crystal compound. When the retardation layer is composed of a resin film, it can also serve as an inner protective layer. For example, Japanese Patent Application Publication Nos. 2017-54093 and 2018-60014 describe retardation layers composed of extension films of resin films. Specific examples of liquid crystal compounds and details of methods for forming alignment and curing layers are described, for example, in Japanese Patent Application Publication No. 2006-163343. The descriptions in those publications are incorporated herein by reference. Furthermore, in this specification, "Re(λ)" is the in-plane phase difference measured at 23°C using light with a wavelength of λ nm. For example, "Re(550)" is the in-plane phase difference measured at 23°C using light with a wavelength of 550 nm. As for Re(λ), when the thickness of the layer (film) is set to d (nm), it is calculated using the formula: Re(λ) = (nx - ny) × d. nx is the refractive index in the direction where the refractive index reaches its maximum in the plane (i.e., the direction of the late phase axis), and ny is the refractive index in the direction orthogonal to the late phase axis in the plane (i.e., the direction of the early phase axis).

When the phasing layer has a multilayer structure, the phasing layer is typically composed of an H layer and a Q layer sequentially from the polarizer side. The H layer is typically used as a λ/2 plate, while the Q layer is usually used as a λ/4 plate. The Re(550) of the H layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and even more preferably 260 nm to 280 nm. The angle formed by the absorption axis of the polarizer and the late-phase axis of the H layer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 14° to 16°. The Re(550) of the Q layer is preferably 100 nm to 200 nm, more preferably 120 nm to 170 nm, and even more preferably 130 nm to 150 nm. The angle formed by the absorption axis of the polarizing element and the late phase axis of the Q layer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 74° to 76°. The arrangement order of the H layer and the Q layer can be reversed, and the angle formed by the late phase axis of the H layer and the absorption axis of the polarizing element, as well as the angle formed by the late phase axis of the Q layer and the absorption axis of the polarizing element, can also be reversed. The H layer and the Q layer can be extension films of the resin film or alignment and curing layers of the liquid crystal compound, respectively.

In one embodiment, a conductive layer for a touch panel can be provided on the side of the inner protective layer 13 (which, if present, is a phase difference layer) opposite to the polarizing element. With this configuration, the polarizing plate can be used in a so-called internal touch panel type input display device in which a touch sensor is assembled between the image display unit and the polarizing plate. A representative example of the polarizing plate in this embodiment is a viewing-side polarizing plate.

In one embodiment, a reflective polarizing element may be disposed on the side of the outer protective layer 12 opposite to the polarizing element. The reflective polarizing element may also serve as the outer protective layer. A representative example of the polarizing plate in this embodiment is a back-side polarizing plate. Details regarding the reflective polarizing element are, for example, described in Japanese Patent No. 9-507308 and Japanese Patent No. 2013-235259. The descriptions in these publications are incorporated herein by reference.

When the polarizing plate of the present invention is rectangular, the aspect ratio is preferably 1.3 to 2.5. In this case, the dimensions of the polarizing plate are, for example, 145 mm to 155 mm in length and 65 mm to 75 mm in width, or 230 mm to 240 mm in length and 140 mm to 150 mm in width. That is, the polarizing plate of the present invention is suitable for use in smartphones or tablet PCs (Personal Computers). As for the size of a smartphone, for example, the length can be 120 mm to 200 mm and the width can be 30 mm to 120 mm.

The following is a detailed explanation of the polarizing element, protective layer, and adhesive layer that constitute the polarizing plate.

B. Polarizing Plate B-1. Polarizing Element A typical polarizing element is composed of a resin film containing a dichroic substance. Any suitable resin film suitable for use as a polarizing element can be used. A representative resin film is a polyvinyl alcohol (PVA) film. The resin film can be a single layer or a laminate of two or more layers.

As a specific example of a polarizing element composed of a single-layer resin film, an example can be a PVA-based resin film subjected to iodine staining and stretching treatments (typically uniaxial stretching). The aforementioned iodine staining is performed, for example, by immersing the PVA-based resin film in an iodine aqueous solution. The stretching ratio of the aforementioned uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after staining, or simultaneously with staining. Alternatively, staining can be performed after stretching. Depending on the requirements, the PVA-based resin film may undergo swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based resin film in water for washing before dyeing, not only can the stains or anti-caking agents on the surface of the PVA-based resin film be washed away, but the PVA-based resin film can also be swollen to prevent uneven dyeing.

As a specific example of a polarizing element obtained by using a laminate, an example of a polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate. A polarizing element obtained by using a resin substrate and a laminate of a PVA-based resin layer formed on the resin substrate can be manufactured, for example, by the following steps: applying a PVA-based resin solution to a resin substrate and allowing it to dry, forming a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and fabricating a polarizing element from the PVA-based resin layer by stretching and dyeing the laminate. In this embodiment, stretching is typically performed by immersing the laminate in an aqueous boric acid solution. Furthermore, the extension may, if necessary, include: air-stretching the laminate at a high temperature (e.g., above 95°C) before stretching in a boric acid aqueous solution. The resulting resin substrate/polarizing element laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizing element), or the resin substrate can be peeled off from the resin substrate/polarizing element laminate, and any suitable protective layer can be laminated on the peeled surface for use, depending on the purpose. Details of such a method for manufacturing a polarizing element are described, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The descriptions in these patent documents are incorporated herein by reference.

The thickness of the polarizing element is as described in item A above.

The polarizing element preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The element's transmittance is, for example, 41.5% to 46.0%, more preferably 43.0% to 46.0%, and even more preferably 44.5% to 46.0%. The polarization degree of the polarizing element is preferably 97.0% or higher, even more preferably 99.0% or higher, and further preferably 99.9% or higher.

B-2. Protective Layer The protective layer is formed from any suitable film that can be used as a protective layer for polarizing elements. Specific examples of materials that are the main components of this film include: cellulose resins such as triacetin (TAC), polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether resins, polyether resins, polystyrene resins, polynorphine resins, polyolefin resins, (meth)acrylic acid resins, acetate resins, and other transparent resins. Also examples include: thermosetting resins or UV-curing resins such as (meth)acrylic acid resins, urethane resins, (meth)acrylate urethane resins, epoxy resins, silicone resins, etc. Furthermore, glassy polymers such as silicone polymers can also be cited. Alternatively, the polymer film described in Japanese Patent Application Publication No. 2001-343529 (WO01/37007) may also be used. As the material for this film, for example, resin compositions containing thermoplastic resins with substituted or unsubstituted imine groups on the side chains, and thermoplastic resins with substituted or unsubstituted phenyl and nitrile groups on the side chains can be used. Examples include resin compositions containing alternating copolymers of isobutylene and N-methylcis-diimidene and acrylonitrile-styrene copolymers. The polymer film may, for example, be an extruded product of the above-mentioned resin compositions.

As needed, the outer protective layer 12 (especially when the polarizing plate is a viewing-side polarizing plate) can be treated with surface treatments such as hard coating, anti-reflective treatment, anti-sticking treatment, and anti-glare treatment. Furthermore/or, the outer protective layer 12 can be treated as needed to improve visibility when viewed through polarized sunglasses (typically by imparting (elliptical) polarization or ultra-high phase difference). By implementing this treatment, excellent visibility can be achieved even when viewing the display image through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate is also suitable for use in outdoor image display devices.

The inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" refers to an in-plane phase difference Re(550) of 0 nm to 10 nm and a thickness-direction phase difference Rth(550) of -10 nm to +10 nm. Here, "Rth(λ)" is the thickness-direction phase difference measured at 23°C using light with a wavelength of λ nm. For example, "Rth(550)" is the thickness-direction phase difference measured at 23°C using light with a wavelength of 550 nm. As for Rth(λ), when the thickness of the layer (film) is set to d (nm), it is obtained by the formula: Rth(λ) = (nx - nz) × d. nz is the refractive index in the thickness direction.

The thickness of the protective layer can be any suitable thickness. For example, the thickness of the protective layer is 10 μm to 50 μm, preferably 20 μm to 40 μm. Furthermore, when a surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

C. Adhesive Layer The adhesive layer 20, as described above, is used to attach the polarizing plate to the image display unit. The adhesive layer is typically composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. In the solid composition of the adhesive composition, the (meth)acrylic polymer may be contained in the adhesive composition at a rate of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. The (meth)acrylic polymer contains alkyl (meth)acrylate as a monomer unit as a main component. Furthermore, (meth)acrylate refers to acrylates and/or methacrylates. Alkyl methacrylates are preferably included in the monomer components forming the (meth)acrylate polymer at a ratio of 80% by weight or more, more preferably 90% by weight or more. Examples of alkyl groups in alkyl (meth)acrylates 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 (comonomers) constituting the (meth)acrylate polymer, besides alkyl (meth)acrylates, include: monomers containing carboxyl groups, monomers containing hydroxyl groups, monomers containing amide groups, (meth)acrylates containing aromatic rings, and vinyl monomers containing heterocyclic rings. Representative examples of comonomers include: acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. Acrylic adhesive compositions preferably contain silane coupling agents and/or crosslinking agents. Examples of silane coupling agents include, for example, silane coupling agents containing epoxy groups. Examples of crosslinking agents include, for example, isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Furthermore, acrylic adhesive compositions may also contain antioxidants and/or conductive agents. The thickness of the adhesive layer is, for example, 50 μm or less, and more preferably 22 μm or less, and more preferably 10 μm to 22 μm, as described above. Details of the adhesive layer or acrylic adhesive composition are set forth in, for example, Japanese Patent Application Publication Nos. 2006-183022, 2015-199942, 2018-053114, 2016-190996, and International Publication No. 2018/008712, the contents of which are incorporated herein by reference.

The creep value of the adhesive layer is preferably below 140 μm/hr, more preferably below 100 μm/hr, further preferably below 75 μm/hr, and particularly preferably below 50 μm/hr. The lower limit of the creep value can be, for example, 20 μm/hr. In this specification, the term "creep value" refers to the creep value at 85°C. The creep value can be determined, for example, by the following procedure: attaching the adhesive layer to a support plate; fixing the support plate with the adhesive attached; and applying a 500 g load downwards in a vertical direction under this condition. Measuring the amount of displacement of the adhesive from the support plate after 1 hour of applying the load, and taking this displacement as the creep value (μm/hr).

The storage modulus _G2 ' of the adhesive layer at -40°C is preferably 1.0 × ^10⁵ (Pa) or more, more preferably 1.0 × ^10⁶ (Pa) or more, further preferably 1.0 × ^10⁷ (Pa) or more, and particularly preferably 1.0 × ^10⁸ (Pa) or more. The storage modulus _G2 ' may, for example, be 1.0 × ^10⁹ (Pa) or less. The storage modulus _G3 ' of the adhesive layer at 85°C is preferably 1.0 × ^10⁵ (Pa) or more, more preferably 3.0 × ^10⁵ (Pa) or more, and further preferably 5.0 × ^10⁵ (Pa) or more. The storage modulus _G3 ' may, for example, be 1.0 × ^10⁶ (Pa) or less.

D. Image Display Device The polarizing plate of this invention can be applied to an image display device. Therefore, an image display device is also included in the embodiments of this invention. The image display device includes an image display unit and a polarizing plate. The polarizing plate is the polarizing plate of the embodiments of this invention described in items A to C above. The polarizing plate is attached to the image display unit by an adhesive layer. Examples of image display devices include liquid crystal displays, organic electroluminescent (EL) displays, and quantum dot displays.

E. Polarizing Plate with Cover Glass When the polarizing plate of the present invention is used on the viewing side of an image display device, the cover glass can be attached to the polarizing plate via another adhesive layer (hereinafter, sometimes referred to as a second adhesive layer). Therefore, the present invention includes a polarizing plate with a cover glass layer. Furthermore, the polarizing plate of the present invention can also be provided with a spacer temporarily attached instead of a cover glass. In this case, during the manufacture of the image display device, the spacer is peeled off, and the cover glass is attached via the exposed second adhesive layer. In either case, the through-hole is typically filled with the adhesive constituting the second adhesive layer. The adhesive constituting the second adhesive layer will now be explained.

Regarding the adhesive constituting the second adhesive layer, a representative storage modulus at 60°C is 1.0 × ^10⁴ Pa to 1.0 × ^10⁵ Pa when the second adhesive layer is deposited on the polarizing plate. Any suitable adhesive can be used to constitute the second adhesive layer, as long as it possesses this storage modulus during deposition. Specifically, the adhesive can be a photocurable adhesive or a non-curable adhesive. Furthermore, in this specification, "photocurable adhesive" refers to an adhesive whose crosslinking reaction is carried out by light irradiation. Therefore, photocurable adhesives are more flexible and deformable during lamination, and after lamination, light irradiation can impart the required properties (such as storage modulus) to the adhesive layer. This results in excellent filling properties of the irregularly shaped portions of photocurable adhesives, allowing for a thinner second adhesive layer (resulting in an image display device). Furthermore, even when forming a thick border printing layer over glass, good adhesion can be ensured. "Non-curable adhesives" refer to adhesives where the crosslinking reaction has essentially ended, and no further crosslinking reaction occurs after lamination. In other words, non-curing adhesives can be considered ordinary adhesives. Because non-curing adhesives do not require light exposure (light curing), they have excellent productivity and can prevent dents, adhesive overflow from the ends of punched products, and operational errors.

The storage modulus of the photocurable adhesive at 60°C before curing can substantially correspond to the storage modulus during the aforementioned lamination. The storage modulus before curing, as described above, is 1.0 × ^10⁵ Pa or less, preferably 1.0 × ^10³ Pa to 1.0 × ^10⁵ Pa. The storage modulus of the photocurable adhesive at 60°C after curing is preferably 5.0 × ^10³ Pa to 5.0 × ^10⁵ Pa. The gel content of the photocurable adhesive before curing is 0% to 60%, and the gel content after curing is 50% to 95%. When the second adhesive layer is composed of a light-curing adhesive, the thickness of the second adhesive layer is preferably 50 μm to 500 μm, more preferably 75 μm to 475 μm, and even more preferably 100 μm to 450 μm.

The storage modulus at 60°C when the non-curing adhesive is laminated is preferably 1.0 × ^10³ Pa to 8.0 × ^10⁴ Pa, more preferably 5.0 × ^10³ Pa to 6.0 × ^10⁴ Pa. When the second adhesive layer is composed of a non-curing adhesive, the thickness of the second adhesive layer is preferably 50 μm to 1000 μm, more preferably 75 μm to 900 μm, and even more preferably 100 μm to 800 μm.

The characteristics of the second adhesive layer and the light-curing adhesive that constitutes the second adhesive layer will be explained below. Then, the non-curing adhesive will be briefly explained.

E-1. Characteristics of the Second Adhesive Layer The glass transition temperature of the second adhesive layer is preferably below -3°C, more preferably below -5°C, and further preferably below -6°C. On the other hand, the glass transition temperature is preferably above -20°C, more preferably above -15°C, and further preferably above -13°C. If the glass transition temperature is within this range, a second adhesive layer with excellent impact resistance can be achieved.

The peak value of the loss tangent tanδ of the second adhesive layer (i.e., tanδ at the glass transition temperature) is preferably 1.5 or higher, more preferably 1.6 or higher, and even more preferably 1.7 or higher, and particularly preferably 1.75 or higher. On the other hand, the upper limit of the peak value of tanδ is preferably 3.0 or lower, more preferably 2.5 or lower, and even more preferably 2.3 or lower. If the peak value of tanδ is within this range, the second adhesive layer exhibits appropriate deformation behavior (viscoelastic behavior), thus preventing the formation of gaps in irregularly shaped processing areas and suppressing delayed bubbles.

The total light transmittance of the second adhesive layer is preferably 85% or higher, and more preferably 90% or higher. The fog value of the second adhesive layer is preferably 1.5% or lower, and more preferably 1.0% or lower.

E-2. Light-curing adhesives E-2-1. Characteristics of light-curing adhesives The storage modulus of the light-curing adhesive at 60°C before curing, as described above, is 1.0 × ^10⁵ Pa or less, preferably 1.0 × ^10³ Pa to 1.0 × ^10⁵ Pa, more preferably 5.0 × ^10³ Pa to 8.0 × ^10⁴ Pa, and even more preferably 7.5 × ^10³ Pa to 6.0 × ^10⁴ Pa. If the storage modulus of the light-curing adhesive before curing is within this range, the light-curing adhesive exhibits appropriate deformation behavior (viscoelastic behavior) and can flow well into all corners of the irregularly shaped processing area. As a result, gaps are less likely to form in the irregularly shaped processing area, and delayed bubbles can be suppressed. The preferred storage modulus of the photocurable adhesive at 60°C after curing is 5.0 × ^10³ Pa to 5.0 × ^10⁵ Pa, more preferably 7.5 × ^10³ Pa to 4.0 × ^10⁵ Pa, and even more preferably 8.0 × ^10³ Pa to 3.0 × ^10⁵ Pa. If the storage modulus of the photocurable adhesive after curing is within this range, the gel elasticity of the second adhesive decreases, and the residual stress becomes smaller. As a result, delayed bubbles can be suppressed.

The gel content of the photocurable adhesive before curing is preferably 0% to 60%, more preferably 0% to 55%, and even more preferably 0% to 50%. If the gel content of the photocurable adhesive before curing is within this range, the required storage modulus can be easily achieved. Therefore, the photocurable adhesive exhibits appropriate deformation behavior (viscoelastic behavior) and can flow well into all corners of the irregularly shaped processing area. As a result, gaps are less likely to form in the irregularly shaped processing area, and delayed bubbles can be suppressed. The gel content of the photocurable adhesive after curing is preferably 50% to 95%, more preferably 55% to 93%, and even more preferably 60% to 90%. If the gel fraction of the photocurable adhesive after curing is within this range, the covering glass, the first polarizing plate, and the image display unit can be firmly fixed. As a result, delayed bubbles can be suppressed. The gel fraction can be determined by the insoluble portion relative to solvents such as ethyl acetate. Specifically, the gel fraction is determined by the weight fraction (in weight %) of the insoluble component of the adhesive layer after immersion in ethyl acetate at 23°C for 7 days relative to the sample before immersion. The gel fraction can be adjusted by appropriately setting the type, combination, and amount of monomer components of the base polymer constituting the adhesive, as well as the type and amount of crosslinking agent.

E-2-2. Constituent Materials of Photocurable Adhesives As a photocurable adhesive, any suitable photocurable adhesive (sometimes referred to simply as an adhesive composition in this section) can be used, as long as it possesses the properties described above. Examples of the base polymers for the adhesive compositions include (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethylene ethers, vinyl acetate/vinyl chloride polymers, modified polyolefins, epoxy polymers, fluoropolymers, natural rubber, synthetic rubber, and other rubber-based polymers. Preferably, it is a (meth)acrylic adhesive composition containing a (meth)acrylic polymer as the base polymer. This is because it possesses excellent optical transparency and exhibits moderate wetting, cohesiveness, and adhesive properties, as well as excellent weather resistance and heat resistance. Furthermore, in this specification, "(meth)acrylic acid" refers to acrylic acid and/or methacrylic acid.

(Meth)acrylic acid-based polymers (hereinafter, sometimes simply referred to as base polymers) preferably have crosslinked structures.

E-2-2-1. (Meth)acrylate-based polymers (Meth)acrylate-based polymers contain alkyl (meth)acrylates as the main monomer component. Alkyl (meth)acrylates with 1 to 20 carbon atoms in the alkyl group are preferably used. The alkyl group of the alkyl (meth)acrylate may be branched or cyclic. The amount of alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, relative to the total amount of monomer components constituting the (meth)acrylate-based polymer. From the viewpoint of setting the glass transition temperature (Tg) of the polymer chain within an appropriate range, the amount of alkyl (meth)acrylate with a chain alkyl group having 4 to 10 carbon atoms is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 45% by weight or more, relative to the total amount of monomer components constituting the (meth)acrylate-based polymer.

The (meth)acrylic acid-based polymer preferably contains a monomer component having crosslinkable functional groups. With this configuration, the gel fraction of the adhesive can be adjusted to the desired range. Examples of monomer components having crosslinkable functional groups include monomers containing hydroxyl groups and monomers containing carboxyl groups. When the crosslinking structure is introduced using an isocyanate crosslinker, the hydroxyl group becomes the reaction site with the isocyanate group; when the crosslinking structure is introduced using an epoxy crosslinker, the carboxyl group becomes the reaction site with the epoxy group. It is preferable to use a monomer containing hydroxyl groups as the monomer component having crosslinkable functional groups, thereby allowing the crosslinking structure to be introduced using an isocyanate crosslinker. This configuration enhances the crosslinking properties of the base polymer and allows for the acquisition of a second adhesive layer with higher transparency. Furthermore, this configuration enables the creation of a so-called acid-free adhesive.

Relative to the total amount of monomer components constituting the (meth)acrylic acid-based polymer, the amount of hydroxyl-containing monomers is preferably 5% to 30% by weight, more preferably 8% to 25% by weight, and even more preferably 10% to 20% by weight. If the amount of hydroxyl-containing monomers is within this range, a smaller amount of crosslinking agent can be used to increase the degree of crosslinking (gel fraction), thereby improving the filling and handling properties of the photocurable adhesive in irregularly shaped processing sections before curing. Furthermore, since unreacted hydroxyl groups after crosslinking can form intermolecular hydrogen bonds, the required storage modulus can be achieved even with a smaller gel fraction.

In cases where the second adhesive layer may come into contact with a touch panel sensor, to prevent acid components from corroding the electrode, it is preferable that the acid content of the second adhesive layer is relatively small. In this case, relative to the total amount of monomer components constituting the (meth)acrylic acid-based polymer, the amount of carboxyl-containing monomers is preferably 0.5% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less, ideally zero. With this configuration, the acid content in the photocurable adhesive is preferably set to 100 ppm or less, more preferably 70 ppm or less, and even more preferably 50 ppm or less.

(Meth)acrylate-based polymers may also include nitrogen-containing monomers as monomer components. By appropriately including highly polar monomers such as hydroxyl-containing monomers, carboxyl-containing monomers, and nitrogen-containing monomers as monomer components in (meth)acrylate-based polymers, a second adhesive layer with an excellent balance of storage modulus, adhesion retention, and impact resistance can be formed. The amount of highly polar monomers (the sum of hydroxyl-containing monomers, carboxyl-containing monomers, and nitrogen-containing monomers) relative to the total amount of monomer components constituting the (meth)acrylate-based polymer is preferably 10% to 45% by weight, more preferably 15% to 40% by weight, and even more preferably 18% to 35% by weight. It is particularly preferred that the sum of hydroxyl-containing monomers and nitrogen-containing monomers falls within the above range. The amount of nitrogen-containing monomers is preferably 3% to 25% by weight, more preferably 5% to 20% by weight, and even more preferably 7% to 15% by weight, relative to the total amount of monomer components constituting the (meth)acrylic acid-based polymer.

(Meth)acrylate polymers may also contain any suitable monomer components depending on the purpose. Specific examples of such monomer components include: monomers containing anhydride groups, caprolactone adducts of (meth)acrylate, monomers containing sulfonic acid groups, monomers containing phosphoric acid groups, vinyl acetate, vinyl propionate, styrene, α-methylstyrene, and other vinyl monomers; acrylic monomers containing cyano groups, such as acrylonitrile and methacrylonitrile; epoxy monomers containing epoxy groups, such as glycidyl (meth)acrylate; diol acrylate monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylate monomers such as tetrahydrofurfuryl (meth)acrylate, fluoro(meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl (meth)acrylate.

The (meth)acrylic-based polymer preferably contains the most alkyl (meth)acrylate as a monomer component, more preferably the most alkyl (meth)acrylate with a chain alkyl group having 6 or fewer carbon atoms. This configuration results in a larger tanδ peak value, improving impact resistance. The amount of alkyl (meth)acrylate with a chain alkyl group having 6 or fewer carbon atoms is preferably 30% to 80% by weight, more preferably 35% to 75% by weight, and even more preferably 40% to 70% by weight, relative to the total amount of monomer components constituting the (meth)acrylic-based polymer. It is particularly preferred that the content of butyl acrylate as a monomer component falls within the above range.

The glass transition temperature (Tg) of (meth)acrylic acid-based polymers is preferably above -50°C. On the other hand, the Tg of (meth)acrylic acid-based polymers is preferably below -5°C, more preferably below -10°C, and even more preferably below -15°C.

E-2-2-2. Crosslinking Structure A polymer with a crosslinking structure can be introduced into a (meth)acrylic acid-based polymer, for example, by the following methods: (1) polymerizing a (meth)acrylic acid-based polymer having functional groups that can react with a crosslinker, and then adding a crosslinker to react the (meth)acrylic acid-based polymer with the crosslinker; and (2) introducing a branched structure (crosslinking structure) into the polymer chain by including a polyfunctional compound in the polymerizing composition of the polymer, etc. These methods can also be used in combination.

Specific examples of crosslinking agents used in the method of reacting the base polymer with the crosslinking agent described in (1) above include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, isocyanate-based and epoxy-based crosslinking agents are preferred due to their high reactivity with the hydroxyl or carboxyl groups of the base polymer and their ease of incorporating crosslinking structures. These crosslinking agents react with the functional groups such as hydroxyl or carboxyl groups introduced into the base polymer to form crosslinking structures. As mentioned above, when using an acid-free adhesive whose base polymer does not contain carboxyl groups, it is preferable to introduce a crosslinking structure by using hydroxyl groups in the base polymer and isocyanate-based crosslinkers.

The crosslinking agent can be used at a ratio of 0.03 to 0.5 parts by weight, more preferably 0.05 to 0.3 parts by weight, further preferably 0.06 to 0.25 parts by weight, and most preferably 0.07 to 0.2 parts by weight, relative to 100 parts by weight of the base polymer. By setting the amount of crosslinking agent used within this range, the gel fraction can be kept within the aforementioned desired range.

E-2-2-3. Multifunctional Compounds In the method of including multifunctional compounds in the polymerization composition of the basic polymer described in (2) above, the monomer components constituting the (meth)acrylate-based polymer can react with the entire amount of the multifunctional compound used to introduce the crosslinking structure in one step, or the polymerization can be carried out in multiple stages. As a method for multi-stage polymerization, the following method is preferred: a portion of the polymer (prepolymer composition) is prepared by polymerizing the monofunctional monomers constituting the (meth)acrylate-based polymer (prepolymerization); a multifunctional compound such as a polyfunctional (meth)acrylate is added to the prepolymer composition to polymerize the prepolymer composition with the multifunctional monomers (formal polymerization). The prepolymer composition is a portion of the polymer containing a polymer with a low degree of polymerization and unreacted monomers.

By prepolymerizing the components of (meth)acrylic acid-based polymers, the branching points (crosslinking points) of multifunctional compounds can be uniformly introduced into the (meth)acrylic acid-based polymers. Alternatively, a mixture of low molecular weight polymers or a portion of the polymer with unpolymerized monomer components (adhesive composition) can be applied to a substrate, followed by formal polymerization on the substrate to form an adhesive layer. Since low-polymerization compositions such as prepolymer compositions have low viscosity and excellent coatability, the method of applying a mixture of prepolymer compositions and multifunctional compounds (i.e., the adhesive composition) to a substrate followed by formal polymerization can improve the productivity of the adhesive layer and achieve a more uniform thickness.

As a polyfunctional compound used to introduce cross-linking structures, examples include compounds containing two or more polymerizable functional groups (ethylene unsaturated groups) with unsaturated double bonds in one molecule. Photopolymerizable polyfunctional compounds are representative examples. Considering the ease with which polyfunctional compounds can copolymerize with monomer components of (meth)acrylate polymers, polyfunctional (meth)acrylates are preferred. In cases where branched (cross-linking) structures are introduced via active energy line polymerization (photopolymerization), polyfunctional (meth)acrylates are preferred.

The molecular weight of the multifunctional compound is preferably below 1500, more preferably below 1000. For example, the lower limit of the molecular weight can be 500. The functional group equivalent (g/eq) of the multifunctional compound is preferably 50–500, more preferably 70–300, and even more preferably 80–200. With this configuration, the viscoelasticity of the photocurable adhesive can be appropriately adjusted.

The multifunctional compound can be used at a ratio of 1 to 6 parts by weight, more preferably 2 to 5 parts by weight, and even more preferably 2.5 to 4 parts by weight relative to 100 parts by weight of the base polymer. If the amount used is too small, the adhesion retention of the light-curing adhesive (resulting in a second adhesive layer) will be insufficient. If the amount used is too large, the formed second adhesive layer will be too hard and lack impact resistance. Consequently, the processability and/or dimensional stability of the light-curing adhesive will be insufficient.

In one embodiment, the multifunctional compound is preferably a compound containing three or more photopolymerizable functional groups per molecule, and more preferably a (meth)acrylate containing three or more photopolymerizable functional groups per molecule. By using a photopolymerizable compound with three or more functions, the adhesion retention of the photocurable adhesive (resulting in a second adhesive layer) can be further improved. A photopolymerizable compound with two functions can also be used in combination with a photopolymerizable compound with three or more functions. The photopolymerizable compound with three or more functions can be used at a ratio of preferably 0.5 parts by weight to 5 parts by weight, more preferably 1 part by weight to 4.5 parts by weight, and further preferably 2 parts by weight to 4 parts by weight relative to 100 parts by weight of the base polymer.

E-2-2-4. Adhesive Compositions Adhesive compositions (photocurable adhesives) may include, in addition to the base polymer, crosslinking agent, and multifunctional compound described above, photopolymerization initiators, oligomers, silane coupling agents, and any suitable additives as needed.

Examples of photopolymerization initiators include: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketone-based photopolymerization initiators, and 9-oxosulfuron-methyl. This is a photopolymerization initiator, specifically a phosphine oxide photopolymerization initiator. The photopolymerization initiator can be used alone or in combination with two or more. The content of the photopolymerization initiator in the adhesive composition is preferably 0.01 to 5 parts by weight, and more preferably 0.05 to 3 parts by weight, relative to 100 parts by weight of the base polymer.

As an oligomer, any suitable oligomer can be used. By using oligomers, the viscoelasticity (and thus the filling and workability of the profiled parts) and adhesion of the light-curing adhesive can be adjusted. (Meth)acrylic oligomers are preferred. (Meth)acrylic oligomers have excellent compatibility with the base polymer.

The weight-average molecular weight of the oligomer is preferably about 1,000 to 30,000, more preferably 1,500 to 10,000, and even more preferably 2,000 to 8,000. If the weight-average molecular weight of the oligomer is within this range, excellent adhesion and adhesion retention can be achieved.

The Tg of the oligomer is preferably above 20°C, more preferably above 50°C, further preferably above 80°C, and especially preferably above 100°C. On the other hand, the Tg of the oligomer is preferably below 200°C, more preferably below 180°C, and further preferably below 160°C. If the Tg of the oligomer is within this range, a second adhesive layer with excellent adhesion can be formed.

The oligomer content in the adhesive composition is preferably 0.1 to 10 parts by weight, and more preferably 0.2 to 5 parts by weight, relative to 100 parts by weight of the base polymer. If the oligomer content is within this range, the processability and dimensional stability of the photocurable adhesive can be well maintained, and a second adhesive layer with excellent adhesion can be formed.

As a silane coupling agent, any suitable silane coupling agent can be used. By using a silane coupling agent, the adhesion of the light-curing adhesive can be adjusted. The content of the silane coupling agent in the adhesive composition is preferably 0.01 parts by weight to 5 parts by weight, and more preferably 0.03 parts by weight to 2 parts by weight, relative to 100 parts by weight of the base polymer.

Regarding additives, any appropriate additive may be used depending on the purpose.

In one embodiment, the adhesive composition (photocurable adhesive) may be provided as an adhesive sheet having a thickness corresponding to the thickness of the second adhesive layer and having a release film temporarily adhered to both sides.

More detailed information about the adhesive composition (light-curing adhesive) is set out in Japanese Patent Application No. 2018-218422 filed by the applicant. The contents of that application are incorporated herein by reference.

E-3. Non-curing adhesives As non-curing adhesives, any suitable non-curing adhesive can be used, as long as it possesses the characteristics described above. By appropriately adjusting the type, combination, and amount of monomer components, as well as the type, quantity, combination, and amount of crosslinking agents, silane coupling agents, and additives, a non-curing adhesive with the required storage modulus can be obtained (resulting in a second adhesive layer). Examples of non-curing adhesives include, for instance, the adhesives described in item C above for the first and second adhesive layers, the adhesives described in Japanese Patent Application No. 2019-196942 filed by the applicant, and the adhesives described in Japanese Patent Application No. 2016-94569. The descriptions in these applications and publications are incorporated herein by reference.

E-4. Components of an Optical Component As described above, the adhesive (adhesive composition) constituting the second adhesive layer can be provided as an adhesive sheet. In the manufacture of the image display device, this adhesive sheet can be provided together with the polarizing plate of the embodiment of the present invention as a component of the optical component. Therefore, such a component of the optical component is also included in the embodiment of the present invention. In one embodiment, the component of the optical component may further include other polarizing plates (rear-side polarizing plates). That is, in the manufacture of the image display device, the adhesive sheet, the polarizing plate of the embodiment of the present invention (viewing-side polarizing plate), and the second polarizing plate (rear-side polarizing plate) can be provided as components of the optical component. [Embodiment]

The present invention will now be described in detail with reference to embodiments, but the present invention is not limited to these embodiments. The evaluation items in the embodiments are as follows. In addition, unless otherwise specified, "parts" and "%" in the embodiments are based on weight.

(1) Size of adhesive voids: The cross-sectional state of the adhesive layer in the through-hole of the polarizing plate used in the embodiments and comparative examples was observed using an optical microscope. The length of the portion where the adhesive layer defect is largest from the outer edge to the inner side of the surface was measured and set as the size L (μm) of the adhesive voids. (2) Paste offset: The polarizing plate used in the embodiments and comparative examples was bonded to glass and treated in a high-pressure autoclave (50℃/0.5 MPa/15 min), followed by a heating test (85℃, 120 h). The through-hole of the sample after the test was observed using an optical microscope, and the deformed portion of the adhesive at the end of the polarizing plate in the through-hole was measured as the displacement of the through-hole. The deformation was measured using an optical microscope (MX61L) manufactured by OLYMPUS. Furthermore, three test samples were measured, and the maximum value among the three measurements was taken as the offset. (3) Bubble evaluation The corresponding images of the image display devices obtained in the examples and comparative examples were vacuum laminated, then subjected to high-pressure autoclave treatment (50℃/0.5 MPa/15 min), and then UV (Ultraviolet) curing (irradiance 150 mW/cm ² , irradiation dose of 3000 mJ). Then, the samples were subjected to a heating test (85℃, 24 h), and the state of the bubbles was observed visually or with an optical microscope when they were removed. The measurements were performed under the condition of n=6, and the evaluation was carried out according to the following criteria. 4: No bubbles were observed in any of the samples. 3: Less than half of the samples showed a few bubbles, but there were no problems with their use. 2: More than half of the samples showed a few bubbles, but there were no problems with their use. 1: All samples contained bubbles.

<Example 1: Preparation of Adhesive Layer (1)> A monomer mixture containing 99 parts of butyl acrylate (BA) and 1 part of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and cooler. Then, relative to 100 parts of the monomer mixture (solid component), 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) and 100 parts by weight of ethyl acetate were added as polymerization initiators. While slowly stirring, nitrogen was introduced for nitrogen replacement. The liquid temperature in the flask was maintained at approximately 55°C, and the polymerization reaction was carried out for 8 hours to prepare an acrylic polymer solution. For every 100 parts of the solids content of the obtained acrylic polymer solution, 0.3 parts of benzoyl peroxide (trade name: Nyper BMT 40SV, Nippon Yushi Co., Ltd.) as a crosslinking agent, 0.1 parts of an isocyanate-based crosslinking agent (trade name: Takenate D110N, Mitsui Chemicals Co., Ltd.), and 0.2 parts of a silane coupling agent (trade name: KBM-403, Shin-Etsu Chemical Co., Ltd.) were added to obtain an adhesive composition. Next, a solution of the aforementioned acrylic adhesive composition was applied to one side of a polyethylene terephthalate membrane (separator membrane: Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) treated with a silicone-based release agent, with the dried adhesive layer thickness being 20 μm. The membrane was then dried at 155°C for 1 minute, forming an adhesive layer (1) on the surface of the separator membrane. The creep value of the adhesive layer (1) was 120 μm/hr.

<Example 2: Preparation of Adhesive Layer (2)> A monomer mixture containing 94.9 parts of butyl acrylate (BA), 5 parts of acrylic acid, and 0.1 parts of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and cooler. Then, relative to 100 parts of the monomer mixture (solid component), 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) and 100 parts by weight of ethyl acetate were added as polymerization initiators. While slowly stirring, nitrogen was introduced for nitrogen replacement. The liquid temperature in the flask was maintained at approximately 55°C, and the polymerization reaction was carried out for 8 hours to prepare an acrylic polymer solution. For every 100 parts of the solids content of the obtained acrylic polymer solution, 0.1 parts of benzoyl peroxide (trade name: Nyper BMT 40SV, manufactured by Nippon Yushi Co., Ltd.) as a crosslinking agent, 8 parts of an isocyanate-based crosslinking agent (trade name: Coronate L, manufactured by Tosoh Co., Ltd.), and 0.2 parts of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to obtain an adhesive composition. Next, a solution of the aforementioned acrylic adhesive composition was applied to one side of a polyethylene terephthalate membrane (separator membrane: Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) treated with a silicone-based release agent, with the dried adhesive layer thickness being 20 μm. The membrane was then dried at 155°C for 1 minute, forming an adhesive layer (2) on the surface of the separator membrane. The creep value of the adhesive layer (2) was 35 μm/hr.

<Example 3: Preparation of a light-curing adhesive constituting the second adhesive layer> A monomer mixture containing 65 parts of butyl acrylate (BA), 5 parts of cyclohexyl acrylate (CHA), 10 parts of N-vinyl-2-pyrrolidone (NVP), 15 parts of 4-hydroxybutyl acrylate (4HBA), and 5 parts of isostearate acrylate (ISTA) was added. Then, relative to 100 parts of the monomer mixture (solid component), 0.2 parts of 2,2'-azobisisobutyronitrile (2,2'-) as a polymerization initiator, 0.065 parts of α-thioglycerol (TGR) as a chain transfer agent, and 233 parts by weight of ethyl acetate were added. The mixture was stirred for 1 hour at 23°C under a nitrogen atmosphere, followed by nitrogen purging. Then, an acrylic-based polymer solution was prepared by reacting at 56°C for 5 hours, followed by reacting at 70°C for 3 hours. To the acrylic-based polymer solution obtained above, the following additives were added to 100 parts of the base polymer, and the mixture was homogeneously mixed to prepare photocurable adhesive b. The storage modulus of photocurable adhesive b at 60°C before curing was 4.7 × ^10⁴ Pa, and the storage modulus at 60°C after curing was 1.0 × ^10⁵ Pa. Furthermore, the gel content before curing was 40%, and the gel content after curing was 80%. (Added later) 2 parts of dipentaerythritol hexaacrylate as a multifunctional compound (photocuring agent); 3 parts of polypropylene glycol diacrylate (trade name: APG400, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., polypropylene glycol #400 (n=7) diacrylate, functional group equivalent 268 g/eq) as a multifunctional compound (photocuring agent); 0.2 parts of photopolymerization initiator (trade name: "Irgacure184", manufactured by BASF). (Preparation of adhesive sheet) The photocurable adhesive b is applied to a 75 μm thick polyethylene terephthalate (PET) film (DIAFOIL manufactured by Mitsubishi Chemical Co., Ltd.) with a silicone-based release layer. After removing the solvent by heating at 100°C for 3 minutes, the same release PET film as described above is laminated onto the surface. The laminate obtained in this way is aged at 25°C for 3 days to obtain an adhesive sheet I with release film temporarily adhered to both sides.

<Example 4: Fabrication of a Polarizing Plate> A 30 μm thick polyvinyl alcohol film was subjected to dyeing and stretching to 3 times its original length at 30°C for 1 minute in a 0.3% iodine solution between rollers of varying speeds. Then, it was stretched to 6 times its original length by immersing it in an aqueous solution containing 4% boric acid and 10% potassium iodide for 0.5 minutes at 60°C. Finally, the film was washed by immersion in an aqueous solution containing 1.5% potassium iodide for 10 seconds at 30°C and dried at 50°C for 4 minutes, resulting in a 12 μm thick polarizing element. A triacetin (TAC) film with a hard coating layer (2 μm thick, TAC thickness 25 μm) serving as the outer protective layer and a TAC film with a thickness of 25 μm serving as the inner protective layer are respectively bonded to both sides of the polarizing element. A liquid crystal alignment and curing layer H and a liquid crystal alignment and curing layer Q are sequentially transferred to the inner protective layer side of the polarizing plate. Thus, the polarizing plate (1) is manufactured. Furthermore, the liquid crystal alignment and curing layer H and the liquid crystal alignment and curing layer Q are manufactured in the following manner.

A liquid crystal compound (coating solution) was prepared by dissolving 10 g of a polymerizable liquid crystal (manufactured by BASF Corporation, trade name "Paliocolor LC242", denoted by the following formula) exhibiting a nematic liquid crystal phase and 3 g of a photopolymerization initiator (manufactured by BASF Corporation, trade name "Irgacure 907") corresponding to the polymerizable liquid crystal compound in 40 g of toluene. [Chem. 1] Alignment treatment was performed by rubbing the surface of a polyethylene terephthalate (PET) film (38 μm thick) with a rubbing cloth. The alignment direction was set to be 15° relative to the absorption axis of the polarizing element when viewed from the self-viewing side when bonded to a polarizing plate. The liquid crystal coating liquid was applied to the alignment-treated surface using a rod coater and dried at 90°C for 2 minutes to align the liquid crystal compounds. The liquid crystal layer formed in this manner was then irradiated with light of 1 mJ/ ^cm² using a metal halide lamp to harden the liquid crystal layer, thereby forming a liquid crystal alignment cured layer H on the PET film. The thickness of the liquid crystal alignment cured layer H was 2.5 μm, and the in-plane phase difference Re(550) was 270 nm. Furthermore, the liquid crystal alignment and curing layer H has a refractive index distribution of nx > ny = nz. Except for changing the coating thickness and setting the alignment treatment direction to be 75° relative to the absorption axis of the polarizing element when viewed from the self-viewing side, the liquid crystal alignment and curing layer Q is formed on the PET film in the same manner as described above. The thickness of the liquid crystal alignment and curing layer Q is 1.5 μm, and the in-plane phase difference Re(550) is 140 nm. Furthermore, the liquid crystal alignment and curing layer Q has a refractive index distribution of nx > ny = nz.

<Example 5: Fabrication of a Polarizing Plate> A 30 μm thick polyvinyl alcohol film was subjected to simultaneous dyeing and stretching to 3 times its original length in a 0.3% iodine solution at 30°C for 1 minute between rollers with different speed ratios. Then, it was simultaneously stretched to 6 times its original length by immersing it in an aqueous solution containing 4% boric acid and 10% potassium iodide for 0.5 minutes at 60°C. Finally, it was stretched to a total stretch ratio of 6 times. After washing by immersion in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds, it was dried at 50°C for 4 minutes to obtain a 12 μm thick polarizing element. A triacetin (TAC) film with a hard coating (2 μm thick, TAC thickness 25 μm) serving as the outer protective layer and an acrylic resin film (20 μm thick) serving as the inner protective layer are respectively bonded to both sides of the polarizing element to fabricate a polarizing plate (2).

<Example 6: Fabrication of Polarizing Plate> 1. Fabrication of Polarizing Element An amorphous polyethylene terephthalate (PET) film (thickness: 100 μm) with a strip shape, a water absorption rate of 0.75%, and a Tg of approximately 75°C was used as the thermoplastic resin substrate. Corona treatment was applied to one side of the resin substrate. 13 parts by weight of potassium iodide were added to 100 parts by weight of a PVA-based resin, prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoethyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") in a 9:1 ratio. The solution was dissolved in water to prepare a PVA aqueous solution (coating solution). The aforementioned PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60°C to form a 13 μm thick PVA-based resin layer, thus creating a laminate. In an oven at 130°C, the obtained laminate was subjected to free-end uniaxial stretching treatment in the longitudinal direction (length direction) between rollers with varying circumferential speeds until it was stretched to 2.4 times its original length (air-assisted stretching treatment). Then, the laminate was immersed in an insoluble bath at 40°C (a boric acid aqueous solution prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insoluble treatment). Next, the polarizing film was immersed in a staining bath (an iodine aqueous solution prepared by mixing iodine and potassium iodide in a 1:7 weight ratio relative to 100 parts by weight of water) at a temperature of 30°C for 60 seconds while adjusting the concentration, so that the monomer transmittance (Ts) of the final polarizing film reached a specific value (staining treatment). Then, it was immersed in a crosslinking bath (a boric acid aqueous solution prepared by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid relative to 100 parts by weight of water) at a temperature of 40°C for 30 seconds (crosslinking treatment). Then, while immersing the laminate in a boric acid aqueous solution (4.0 wt% boric acid, 5.0 wt% potassium iodide) at 70°C, it undergoes uniaxial stretching (underwater stretching treatment) in the longitudinal direction (length direction) at a total stretch ratio of 5.5 times between rollers with varying circumferential speeds. Then, the laminate is immersed in a washing bath at 20°C (an aqueous solution prepared by adding 4 parts by weight of potassium iodide to 100 parts by weight of water) (washing treatment). Then, while drying in an oven maintained at 90°C, the laminate is simultaneously brought into contact with a heating roller manufactured by SUS (Steel Use Stainless, Japanese standard) with a surface temperature maintained at 75°C for approximately 2 seconds (drying shrinkage treatment). The width shrinkage rate of the laminate after the drying shrinkage treatment is 5.2%. Thus, a polarizing element with a thickness of 5 μm is formed on the resin substrate.

2. Fabrication of the Polarizing Plate An HC-TAC film is bonded to the surface of the polarizing element in the aforementioned resin substrate/polarizing element laminate using a UV-curing adhesive. Specifically, the adhesive is applied with a curing agent thickness of 1.0 μm and bonded using a rolling mill. Then, UV light is irradiated from the HC-TAC film side to cure the adhesive. Furthermore, the HC-TAC film is formed on a triacetyl cellulose (TAC) film (25 μm thick) with a hard coating (HC) layer (7 μm thick), and is bonded with the TAC film positioned on the polarizing element side. Next, the resin substrate is peeled off, and a TAC film (20 μm thick) is bonded to the peeled surface in the same manner as described above. Thus, the polarizing plate (3) is fabricated.

<Example 1> 1. Formation of a through hole: An adhesive layer (1) obtained in Example 1 is formed on the surface of the liquid crystal alignment and curing layer Q of the polarizing plate (1) obtained in Example 4, serving as a polarizing plate with an adhesive layer. The polarizing plate with the adhesive layer is punched to a size of 145 mm in length and 68 mm in width. At this time, the punching is performed at a 135° clockwise direction relative to the long side direction of the absorption axis of the polarizing element. Furthermore, a through hole with a diameter of 3.9 mm is formed at the upper right corner of the punched polarizing plate with the adhesive layer by an end milling cutter. Thus, a polarizing plate (with an adhesive layer) as shown in Figure 1A was produced. The | _b1 - _b2 | of the obtained polarizing plate was 0 mm. Also, the size L of the adhesive voids was 90 μm. The polarizing plate was then used for the evaluation described in (2) above. The results are shown in Table 1.

2. Fabrication of the Image Display Device Corresponding Product: The polarizing plate with an adhesive layer obtained in step 1 above is adhered to one side of a glass plate (corresponding to the image display unit) via the adhesive layer. Next, one release film of adhesive sheet I obtained in Manufacturing Example 3 is peeled off and bonded to the covering glass (manufactured by Matsunami Glass Co., Ltd., 0.8 mm thick) using a roller laminator. Then, the other release film of adhesive sheet I is peeled off and a vacuum laminator is used to ensure close contact with the surface of the polarizing plate with the adhesive layer, and the through holes are filled with adhesive sheet. The vacuum lamination conditions are as follows: heating and pressing are performed at 0.2 MPa and 60°C (standby time 90 seconds), followed by vacuum lamination at 100 Pa for 10 seconds. Then, the photocurable adhesive is cured by irradiating the glass side with ultraviolet light with a cumulative light intensity of 3000 mJ/ ^cm² using a metal halide lamp (300 mW/ ^cm² ). Then, it is subjected to autoclave treatment (50°C/0.5 MPa/15 min). In this way, an image display device corresponding product is produced. The obtained image display device corresponding product is subjected to the bubble evaluation in (3) above. The results are shown in Table 1.

<Example 2> Except that the through-hole is formed at the end in the long side direction and the center in the short side direction, the polarizing plate (polarizing plate with adhesive layer) and the corresponding image display device are manufactured in the same manner as in Example 1. The | _b1 - _b2 | of the obtained polarizing plate is 41 mm. Also, the size L of the adhesive gap is 90 μm. The obtained polarizing plate and the corresponding image display device are evaluated in the same way as in Example 1. The results are shown in Table 1. Furthermore, in Table 1, the end in the long side direction and the center in the short side direction are simply referred to as "center".

<Examples 3-7 and Comparative Examples 1-4> Except for the types and sizes of the polarizing plate, the types of adhesive layers, and the formation positions of the through holes as shown in Table 1, the polarizing plate (with an adhesive layer) and the corresponding image display device were manufactured in the same manner as in Example 1. Furthermore, the size L of the adhesive gaps was adjusted during the milling process of forming the through holes by changing the feed rate or rotation speed and cutting amount of the drill bit. Here, Examples 4 and 6 correspond to the form shown in FIG. 1A, Example 7 corresponds to the form shown in FIG. 1B, and Examples 3 and 5 correspond to the form shown in FIG. 1C. The obtained polarizing plates and corresponding image display devices were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Table 1] polarizing plate Polarizing element thickness [μm] Adhesive Axis angle [°] Through hole position Through hole diameter [mm] Long side [mm] Short side [mm] |b ₁ －b ₂ | [mm] Size L [μm] of adhesive voids Paste offset [μm] Bubble assessment Implementation Example 1 Polarizing plate(1) 12 Adhesive (1) 135 Top right corner 3.9 145 68 0 90 95 2 Implementation Example 2 Polarizing plate(1) 12 Adhesive (1) 135 central 3.9 145 68 41 90 129 2 Implementation Example 3 Polarizing plate(2) 12 Adhesive (1) 90 central 3.9 148 70 0 90 71 3 Implementation Example 4 Polarizing plate(1) 12 Adhesive (2) 135 Top right corner 3.9 145 68 0 30 38 4 Implementation Example 5 Polarizing plate(3) 5 Adhesive (1) 90 central 3.9 148 70 0 90 30 4 Implementation Example 6 Polarizing plate(1) 12 Adhesive (1) 135 Top right corner 3.9 145 68 0 45 90 3 Implementation Example 7 Polarizing plate(1) 12 Adhesive (1) 45 Top left corner 3.9 145 68 0 45 90 3 Comparative example 1 Polarizing plate(1) 12 Adhesive (1) 45 Top right corner 3.9 145 68 82 90 250 1 Comparative example 2 Polarizing plate(2) 12 Adhesive (1) 0 Top right corner 3.9 148 70 138 90 231 1 Comparative example 3 Polarizing plate(2) 12 Adhesive (1) 90 Top right corner 3.9 148 70 60 90 199 1 Comparative example 4 Polarizing plate(2) 12 Adhesive (1) 0 central 3.9 148 70 138 90 239 1

As shown in Table 1, the paste offset in the through-hole portion of the polarizing plate in the embodiment of the present invention after heating test is significantly smaller than that in the comparative example, and delayed bubbles are suppressed. [Industrial Applicability]

The polarizing plate of this invention is suitable for use in image display devices, especially for image display devices with camera units, such as smartphones, tablet PCs, or smartwatches.

11: Polarizing element 12: Outer protective layer 13: Inner protective layer 20: Adhesive layer 30: Through hole 100: Polarizing plate 101: Polarizing plate 102: Polarizing plate 120: Glass plate a ₁ : Distance from the center of the through hole to one end of the polarizing plate in a direction orthogonal to the absorption axis of the polarizing element a ₂ : Distance from the center of the through hole to the other end of the polarizing plate in a direction orthogonal to the absorption axis of the polarizing element b ₁ : Distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing element b ₂ : Distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing element A: Absorption axis direction D: Offset R: Diameter

Figure 1A is a schematic top view illustrating the formation location of the through-hole in a polarizing plate according to one embodiment of the present invention. Figure 1B is a schematic top view illustrating the formation location of the through-hole in a polarizing plate according to another embodiment of the present invention. Figure 1C is a schematic top view illustrating the formation location of the through-hole in a polarizing plate according to yet another embodiment of the present invention. Figure 2 is a schematic cross-sectional view of the through-hole portion of a polarizing plate according to an embodiment of the present invention. Figure 3 is an enlarged cross-sectional view illustrating the main offset portion of the through-hole portion in a polarizing plate according to an embodiment of the present invention.

30: Through-hole 100: Polarizing plate a ₁ : Distance from the center of the through-hole to one end of the polarizing plate in a direction orthogonal to the absorption axis of the polarizing element a ₂ : Distance from the center of the through-hole to the other end of the polarizing plate in a direction orthogonal to the absorption axis of the polarizing element b ₁ : Distance from the center of the through-hole to one end of the polarizing plate in the absorption axis direction of the polarizing element b ₂ : Distance from the center of the through-hole to the other end of the polarizing plate in the absorption axis direction of the polarizing element A: Absorption axis direction

Claims (8)

A polarizing plate includes: a polarizing element; a protective layer disposed on at least one side of the polarizing element; and an adhesive layer; a through hole is formed therein, and the polarizing element has a rectangular shape. When viewed from the side, the absorption axis of the polarizing element is oriented at a 135° clockwise direction from the long side. The through hole is formed at the upper right corner. The thickness of the polarizing element is 15 μm or less, and | _b1 - _b2 | is 45 mm or less. Here, _b1 is the distance from the center of the through hole to one end of the polarizing plate along the absorption axis of the polarizing element, _{and b2} is the distance from the center of the through hole to the other end of the polarizing plate along the absorption axis of the polarizing element. A polarizing plate includes: a polarizing element; a protective layer disposed on at least one side of the polarizing element; and an adhesive layer; a through hole is formed therein, and the polarizing element has a rectangular shape. When viewed from the side, the absorption axis of the polarizing element is at a 45° angle clockwise from the long side. The through hole is formed at the upper left corner. The thickness of the polarizing element is 15 μm or less, and | _b1 - _b2 | is 45 mm or less. Here, _b1 is the distance from the center of the through hole to one end of the polarizing plate along the absorption axis of the polarizing element, _{and b2} is the distance from the center of the through hole to the other end of the polarizing plate along the absorption axis of the polarizing element. A polarizing plate includes: a polarizing element; a protective layer disposed on at least one side of the polarizing element; and an adhesive layer; a through hole is formed therein, and the polarizing element has a rectangular shape, wherein the absorption axis of the polarizing element is in the direction of its short side, and when viewed from above, the through hole is formed at the end of the long side and the center of the short side, the thickness of the polarizing element is 15 μm or less, and | _b1 - _b2 | is 45 mm or less, where _b1 is the distance from the center of the through hole to one end of the polarizing plate in the direction of the absorption axis of the polarizing element, and _b2 is the distance from the center of the through hole to the other end of the polarizing plate in the direction of the absorption axis of the polarizing element. For example, the polarizing plate of any of the claims 1 to 3, wherein the thickness of the polarizing element is less than 8 μm. For example, the polarizing plate of any of the claims 1 to 3, wherein the creep value of the adhesive layer is less than 140 μm/hr. For example, the polarizing plate in claim 4, wherein the creep value of the adhesive layer is less than 140 μm/hr. The polarizing plate of any of claims 1 to 3 is a polarizing plate with a cover glass, and further comprises: another adhesive layer disposed on the side of the polarizing element opposite to the adhesive layer; and a cover glass bonded by the other adhesive layer; and the through hole is filled with the adhesive constituting the other adhesive layer. An image display device includes: an image display unit and a polarizing plate as claimed in any one of claims 1 to 7; wherein the polarizing plate is attached to the image display unit via the aforementioned adhesive layer.