CN116235101A - Polarizing plate, polarizing plate with cover glass, and image display device - Google Patents

Abstract

The present invention provides a polarizing plate, which has small deflection in a through hole part even under a high-temperature environment, and in an image display device, when the through hole is filled with an adhesive for covering glass lamination, bubbles in the through hole part can be remarkably restrained. The polarizing plate of the present invention comprises: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; and has a through hole formed therein, the thickness of the polarizing plate is 15 μm or less, |b ₁ －b ₂ The I is below 45 mm. Here, b ₁ B is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing plate ₂ Is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing plate.

Description

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

Technical Field

The present invention relates to a polarizing plate, a polarizing plate with cover glass, and an image display device. More specifically, the present invention relates to a polarizing plate having an adhesive layer and having through holes formed therein, a polarizing plate with cover glass, and an image display device including the polarizing plate.

Background Art

In image display devices such as mobile phones and notebook personal computers, polarizing plates are widely used to realize image display and/or improve the performance of the image display. In recent years, it is expected that polarizing plates are also used in image display devices equipped with cameras, smart watches, instrument panels of automobiles, etc., and there are cases where through holes are formed in polarizing plates. However, in polarizing plates with through holes, there is a problem that the polarizing plates are offset (essentially the offset of the adhesive layer) in the through hole portion under high temperature environment.

However, in order to give the image display device surface hardness and impact resistance, there is a case where a cover glass is laminated on the outermost surface of the image display device. When a cover glass is laminated on an image display device including a polarizing plate having a through hole, the through hole is typically filled with an adhesive for laminating the cover glass. However, in the image display device in which the through hole is filled with an adhesive, there is a case where bubbles are generated in the filled portion (through hole portion) due to a heat treatment in a manufacturing step or the like.

Prior Art Literature

Patent Literature

Patent Document 1: International Publication No. 2017/047510

Patent Document 2: Japanese Patent Application Publication No. 2016-094569

Summary of the invention

The present invention is made to solve the above-mentioned previous problems, and its main purpose is to provide a polarizing plate in which the displacement in the through hole portion is small even in a high temperature environment, and in an image display device, when the through hole is used to fill the adhesive covering the glass laminate, the bubbles in the through hole portion can be significantly suppressed.

The polarizing plate of the present invention comprises: a polarizer; a protective layer disposed on at least one side of the polarizer; and an adhesive layer; and a through hole is formed, the thickness of the polarizer is 15 μm or less, and |b ₁ -b ₂ | is 45 mm or less. Here, b ₁ is the distance from the center of the through hole to one end of the polarizer in the absorption axis direction of the polarizer, and b ₂ is the distance from the center of the through hole to the other end of the polarizer in the absorption axis direction of the polarizer.

In one embodiment, the polarizing plate has a rectangular shape, and when viewed from the self-recognition side, the absorption axis direction of the polarizer is 135° in the clockwise direction from the long side direction, and the through hole is formed in the upper right corner. In another embodiment, the polarizing plate has a rectangular shape, and when viewed from the self-recognition side, the absorption axis direction of the polarizer is 45° in the clockwise direction from the long side direction, and the through hole is formed in the upper left corner. Furthermore, in another embodiment, the polarizing plate has a rectangular shape, the absorption axis direction of the polarizer is the short side direction, and when viewed from above, the through hole is formed at the end of the long side direction and the center of the short side direction.

In one embodiment, the polarizer has a thickness of 8 μm or less.

In one embodiment, the adhesive layer has a creep value of 140 μm/hr or less.

According to another aspect of the present invention, an image display device is provided, which includes an image display unit and the polarizing plate, wherein the polarizing plate is attached to the image display unit via the adhesive layer.

According to another embodiment of the present invention, a polarizing plate with cover glass is provided. The polarizing plate with cover glass comprises: a polarizer; a protective layer disposed on at least one side of the polarizer; an adhesive layer; another adhesive layer disposed on the side of the polarizer opposite to the adhesive layer; and a cover glass bonded via the another adhesive layer; and a through hole is formed, the through hole is filled with an adhesive constituting the another adhesive layer, and the thickness of the polarizer is 15 μm or less, and |b ₁ -b ₂ | is 45 mm or less.

According to an embodiment of the present invention, a polarizing plate can be realized which has a through hole and in which the offset in the through hole portion is small even in a high temperature environment, and in an image display device, when the through hole is used to fill the adhesive covering the glass laminate, the bubbles in the through hole portion can be significantly suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic plan view illustrating formation positions of through holes in a polarizing plate according to one embodiment of the present invention.

1B is a schematic plan view illustrating the formation positions of through holes in a polarizing plate according to another embodiment of the present invention.

FIG. 1C is a schematic plan view illustrating the formation positions of through holes in a polarizing plate according to still another embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a through-hole portion of a polarizing plate according to an embodiment of the present invention.

3 is an enlarged cross-sectional view of a main part for explaining displacement of a through-hole portion in a polarizing plate according to an embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments. Furthermore, the drawings are schematically shown for easy observation, and further, the ratios of length, width, thickness, etc., and angles, etc. in the drawings are different from the actual ones.

A. Overall composition of polarizing plate

FIG. 1A is a schematic top view illustrating the formation position of the through hole in the polarizing plate of one embodiment of the present invention; FIG. 1B is a schematic top view illustrating the formation position of the through hole in the polarizing plate of another embodiment of the present invention; FIG. 1C is a schematic top view illustrating the formation position of the through hole in the polarizing plate of another embodiment of the present invention; and FIG. 2 is a schematic cross-sectional view of the through hole portion of the polarizing plate. The polarizing plate of the embodiment of the present invention (polarizing plates 100, 101, 102 in the example) has: a polarizer 11; a protective layer (hereinafter, sometimes referred to as an outer protective layer) 12, which is arranged on one side of the polarizer 11; a protective layer (hereinafter, sometimes referred to as an inner protective layer) 13, which is arranged on the other side of the polarizer 11; and an adhesive layer 20. The adhesive layer 20 is used to bond the polarizing plate 100 to the image display unit. Depending on the purpose and the required structure, 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, when a camera is built into the image display device, it is possible to prevent the performance of the camera from being adversely affected. The through hole can be formed by various methods, such as laser processing, cutting processing using an end mill, punching processing using a Thomson knife or a Pinnacle (registered trademark) knife, etc. The polarizing plate typically has a rectangular shape. In this specification, when "rectangular shape" is mentioned, it also includes a shape including a special-shaped processed portion, such as an R shape with chamfered vertices as shown in Figures 1A to 1C. Although not shown in the figure, a plurality of through holes can be provided. The top view shape of the through hole can adopt any appropriate shape according to the purpose. As specific examples of the top view shape, a circle, an ellipse, a square, a rectangle, and a combination thereof (for example, a rectangle with an arc-shaped end) as shown in the example in the figure can be cited. Furthermore, a special-shaped processed portion (for example, a U-shaped notch, a V-shaped notch) can be provided while providing the through hole. The inventors and others have discovered the following new problem: when a through hole is formed in a polarizing plate, in a high temperature environment, the polarizing plate shifts in the through hole portion (substantially, the adhesive layer shifts: hereinafter sometimes referred to as paste shift), resulting in a concern that light leakage may occur in the through hole portion; this problem has been solved by adopting a specific structure (described later) of an embodiment of the present invention. That is, the present invention solves a new problem that has been unknown so far, and the effect obtained thereby is unexpectedly excellent. Furthermore, the inventors and others have found that by adopting a specific structure (described later) of an embodiment of the present invention, bubbles called delayed bubbles can also be significantly suppressed. The details of delayed bubbles are as follows. In order to impart surface hardness and impact resistance to an image display device, there is a case where a cover glass is layered on the outermost surface of the image display device. In the case of laminating a cover glass in an image display device including a polarizing plate having a through hole, the through hole is typically filled with an adhesive used to laminate the cover glass. Such filling is typically performed by laminating a laminate of a cover glass and an adhesive sheet to a polarizing plate using vacuum lamination. In most cases, there are no identifiable bubbles in the filling part immediately after vacuum lamination, but bubbles may be generated in the subsequent heating durability test of the image display device. Such bubbles are typically generated due to the shrinkage stress of the polarizing plate applied to the filling part. Such bubbles are called delayed bubbles. Delayed bubbles are larger ones that occupy a certain percentage of the top view area of the through hole rather than fine ones. Delayed bubbles are not allowed to exist from the perspective of appearance or from the perspective of the camera performance of the camera part arranged at a position corresponding to the through hole. Therefore, by suppressing delayed bubbles, the commercial value of the image display device can be significantly improved.

In an embodiment of the present invention, the thickness of the polarizer is less than 15 μm, preferably less than 10 μm, more preferably less than 8 μm, and further preferably less than 7 μm, particularly preferably less than 6 μm, and particularly preferably less than 5 μm. The thickness of the polarizer is, for example, more than 1 μm, and, for example, more than 2 μm. By setting the thickness of the polarizer to such a range, the thermal shrinkage of the polarizer itself can be suppressed. As a result, the deformation of the adhesive layer that may be caused by the thermal shrinkage of the polarizer can be suppressed (resulting in paste offset).

Furthermore, in the embodiment of the present invention, |b ₁ -b ₂ | is 45 mm or less, preferably 30 mm or less, more preferably 20 mm or less, further preferably 10 mm or less, and particularly preferably 5 mm or less. The smaller |b ₁ -b ₂ | is, the better, and the best is 0 (zero). If |b ₁ -b ₂ | is within this range, the paste deviation in the through-hole portion under a high temperature environment can be reduced, and delayed bubbles can be suppressed. On the other hand, |a ₁ -a ₂ | does not substantially contribute to suppressing the paste deviation in the through-hole portion or suppressing delayed bubbles. That is, even if |a ₁ -a ₂ | is changed, the paste deviation and delayed bubbles are not suppressed. Here, _b1 is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizer, _b2 is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizer, _a1 is the distance from the center of the through hole to one end of the polarizing plate in the direction perpendicular to the absorption axis direction of the polarizer, and _a2 is the distance from the center of the through hole to the other end of the polarizing plate in the direction perpendicular to the absorption axis direction of the polarizer. That is, by optimizing the orientation of the absorption axis of the polarizer relative to the position of the through hole, both paste shift and retardation bubbles can be suppressed.

The relationship between _a1 , _a2 , _b1 and _b2 and the formation position of the through hole is specifically described with reference to FIGS. 1A to 1C. In FIG. 1A, the following form is shown: the polarizing plate is rectangular, and when observed from the visual side of the image display device (the opposite side of the adhesive layer), the absorption axis direction A of the polarizer is 135° in the clockwise direction relative to the long side direction. In this form, 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 in a direction orthogonal to the absorption axis direction A when looking down at the polarizing plate from the visual side (in FIG. 1A, on a straight line representing the distances _a1 and _a2 ), the paste offset and delayed bubbles can be suppressed. On the other hand, if | _a1 - _a2 | is adjusted to minimize the impact on image display, the through hole 30 can be preferably formed in the upper right corner. FIG. 1B shows a form in which 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 plate is 45° in the clockwise direction relative to the long side direction. In this form, both paste offset and delayed bubbles can be suppressed by optimizing |b ₁ -b ₂ |, and |a ₁ -a ₂ | can be adjusted to minimize the impact on image display. As a result, in this form, the through hole 30 can be preferably formed in the upper left corner. FIG. 1C shows a form in which the polarizing plate is rectangular, and the absorption axis direction A of the polarizing plate is the short side direction (orthogonal to the long side direction). In this form, both paste offset and delayed bubbles can be suppressed by optimizing |b ₁ -b ₂ |, and |a ₁ -a ₂ | can be adjusted to minimize the impact on image display. As a result, in this form, the through hole 30 can be preferably formed at the end of the long side direction and the center of the short side direction. As described above, according to the embodiment of the present invention, regardless of the planar shape of the polarizing plate (for example, even when the planar shape is special), the relationship between the position of the through hole and the absorption axis direction that can suppress paste displacement and delay bubbles can be determined by optimizing |b ₁ -b ₂ |. Furthermore, the influence of the through hole on image display can be minimized by adjusting |a ₁ -a ₂ |.

In one embodiment, as shown in FIG. 3 , in a state where the polarizing plate 100 is bonded to a glass plate (which may correspond to a substrate of an image display unit) 120 via an adhesive layer 20, 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 even more 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, and, for example, 20 μm. Furthermore, the paste offset D refers to the largest portion of the polarizing plate away from the through hole portion when observed in cross section. The reference of the through hole portion can be representatively the lower end of the adhesive layer. That is, when the polarizing plate is shifted mainly due to the contraction of the polarizer 11 (to the right in the example shown in the figure), the adhesive layer 20 stays on the glass plate 120 to which it is bonded, so the shift is observed in the through-hole portion. Furthermore, as shown in FIG. 3 , the polarizing plate is typically shifted in the through-hole portion away from the through-hole side (the right side in FIG. 3 ), and the portion opposite thereto is shifted in a manner protruding into the through-hole (the left side in FIG. 3 ). As described above, according to an embodiment of the present invention, the newly discovered problem of paste shift in the through-hole portion under a high temperature environment can be solved. Specifically, the paste shift amount D after a specific heating test can be set to the range described above.

In one embodiment, the polarizing plate may form an adhesive void portion in the through hole 30 portion so that the end face of the adhesive layer 20 is closer to the inner side in the surface direction than the end face of the polarizing plate (substantially the polarizer 11 or the inner protective layer 13 (if present)). The size of the adhesive void portion is preferably less than 300 μm, more preferably less than 200 μm, further preferably less than 150 μm, particularly preferably less than 100 μm, and even more preferably less than 80 μm. The lower limit of the size of the adhesive void portion may be, for example, 10 μm. In this specification, the "size of the adhesive void portion" refers to the maximum length from the end face of the polarizing plate (substantially the polarizer 11 or the inner protective layer 13 (if present)) to the end face of the adhesive layer 20.

In an embodiment of the present invention, the dimensional shrinkage rate of the polarizing plate after the heating test is preferably less than 1.0%, more preferably less than 0.6%, and further preferably less than 0.3%. 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 is the dimensional shrinkage rate of the entire polarizing plate attached to the glass plate. When the polarizing plate described below further has an optical functional layer (such as a phase difference layer, a reflective polarizer), it refers to the dimensional shrinkage rate of the entire polarizing plate including the optical functional layer. Furthermore, the "size" in the following formula is the size of the polarizing plate (substantially a polarizer) in the absorption axis direction.

Dimensional shrinkage (%) = {(dimensions before heating test - dimensions after heating test) / dimensions before heating test} × 100

The diameter R of the through hole 30 is preferably less than 10 mm, more preferably less than 8 mm, and further preferably less than 5 mm. The lower limit of the diameter of the through hole is, for example, 1.5 mm, and further, for example, it can be 2 mm. The ratio D/R of the paste offset D to the diameter R of the through hole is preferably less than 15%, more preferably less than 10%, further preferably less than 6%, and particularly preferably less than 5%. On the other hand, the smaller the lower limit of D/R, the better. According to an embodiment of the present invention, since the paste offset D is very small as described above, D/R can be set to such a range even if the diameter of the through hole is reduced. Therefore, even if the diameter of the through hole is reduced, it is substantially possible to prevent adverse effects on camera performance. As a result, the polarizing plate of an embodiment of the present invention can be applied to an image display device in which only the camera portion is used as a non-display area and/or a frameless image display device.

The polarizing plate of the embodiment of the present invention can be used as a viewing side polarizing plate, and can also be used as a back side polarizing plate. Furthermore, the polarizing plate of the embodiment of the present invention can also have any appropriate optical functional layer according to the purpose. As the optical functional layer, for example, a phase difference layer, a conductive layer for a touch panel, and a reflective polarizer can be cited.

In one embodiment, a phase difference layer may be provided between the inner protective layer 13 and the adhesive layer 20. The phase difference layer may be composed of a single layer or may have a laminated structure. When the phase difference layer is composed of a single layer, the phase difference layer typically acts as a λ/4 plate. In this case, the in-plane phase difference Re (550) of the phase difference layer is preferably 100nm to 200nm, more preferably 120nm to 170nm, and further preferably 130nm to 150nm. The angle formed by the absorption axis of the polarizer and the slow phase axis of the phase difference layer is preferably 40° to 50°, more preferably 42° to 48°, and further preferably 44° to 46°. The phase difference layer preferably exhibits an inverse wavelength dispersion characteristic in which the phase difference value increases according to the wavelength of the measured light. In this case, the Re(450)/Re(550) of the phase difference layer is preferably greater than 0.8 and less than 1, and more preferably greater than 0.8 and less than 0.95. The phase difference layer may be a stretched film of a resin film, or may be an alignment cured layer of a liquid crystal compound. In the case where the phase difference layer is composed of a resin film, the phase difference layer may also serve as an inner protective layer. Regarding the phase difference layer composed of a stretched film of a resin film, for example, it is recorded in Japanese Patent Publication No. 2017-54093 and Japanese Patent Publication No. 2018-60014. Specific examples of liquid crystal compounds and details of the method for forming the alignment cured layer are recorded in Japanese Patent Publication No. 2006-163343. The records in the publication, etc. are cited in this specification as a reference. Furthermore, in this specification, "Re(λ)" is the in-plane phase difference measured at 23°C using light with a wavelength of λnm. For example, "Re(550)" is the in-plane phase difference measured at 23°C with light of a wavelength of 550 nm. As for Re(λ), when the thickness of the layer (film) is set to d (nm), it is calculated by the formula: Re(λ) = (nx-ny) × d. nx is the refractive index in the direction where the in-plane refractive index reaches the maximum (i.e., the direction of the slow axis), and ny is the refractive index in the direction orthogonal to the slow axis (i.e., the direction of the fast axis) in the plane.

When the phase difference layer has a stacked structure, the phase difference layer typically has an H layer and a Q layer in order from the polarizing plate side. The H layer typically acts as a λ/2 plate, and the Q layer usually acts as a λ/4 plate. The Re(550) of the H layer is preferably 200nm to 300nm, more preferably 230nm to 290nm, and further preferably 260nm to 280nm. The angle formed by the absorption axis of the polarizer and the slow phase axis of the H layer is preferably 10° to 20°, more preferably 12° to 18°, and further preferably 14° to 16°. The Re(550) of the Q layer is preferably 100nm to 200nm, more preferably 120nm to 170nm, and further preferably 130nm to 150nm. The angle formed by the absorption axis of the polarizer and the slow phase axis of the Q layer is preferably 70° to 80°, more preferably 72° to 78°, and further preferably 74° to 76°. The arrangement order of the H layer and the Q layer can be opposite, and the angle formed by the slow phase axis of the H layer and the absorption axis of the polarizer and the angle formed by the slow phase axis of the Q layer and the absorption axis of the polarizer can also be opposite. The H layer and the Q layer can be a stretched film of a resin film or an alignment solidified layer of a liquid crystal compound.

In one embodiment, a conductive layer for a touch panel may be provided on the side of the inner protective layer 13 (a phase difference layer when present) opposite to the polarizer. With such a configuration, the polarizing plate may be applied to a so-called internal touch panel type input display device in which a touch sensor is assembled between an image display unit and the polarizing plate. The polarizing plate of this embodiment is typically a viewing side polarizing plate.

In one embodiment, a reflective polarizer may be provided on the side of the outer protective layer 12 opposite to the polarizer. The reflective polarizer may also serve as the outer protective layer. The polarizer of this embodiment is typically a back side polarizer. Details of the reflective polarizer are described, for example, in Japanese Patent Publication No. 9-507308 and Japanese Patent Publication No. 2013-235259. The descriptions of these publications are cited in this specification as reference.

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

Hereinafter, the polarizer, the protective layer, and the adhesive layer constituting the polarizing plate will be described in detail.

B. Polarizing plate

B-1. Polarizer

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

As a specific example of a polarizer composed of a single-layer resin film, a PVA-type resin film can be exemplified by subjecting the PVA-type resin film to a dyeing treatment and a stretching treatment (representatively, uniaxial stretching) using iodine. The dyeing using iodine is performed, for example, by immersing the PVA-type resin film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching can be performed after the dyeing treatment, or it can be performed while dyeing. In addition, it can also be dyed after stretching. If necessary, the PVA-type resin film can be subjected to a swelling treatment, a cross-linking treatment, a cleaning treatment, a drying treatment, etc. For example, by immersing the PVA-type resin film in water for washing before dyeing, not only can the stains or anti-caking agents on the surface of the PVA-type resin film be cleaned, but the PVA-type resin film can also be swollen to prevent uneven dyeing.

As a specific example of a polarizer obtained by using a laminate, there can be cited a laminate of a resin substrate and a PVA-type resin layer (PVA-type resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-type resin layer formed by coating the resin substrate. The polarizer obtained by using a laminate of a resin substrate and a PVA-type resin layer formed by coating the resin substrate can be made, for example, by the following steps: a PVA-type resin solution is coated on a resin substrate and dried to form a PVA-type resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-type resin layer; the PVA-type resin layer is made into a polarizer by stretching and dyeing the laminate. In this embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution for stretching. Furthermore, stretching may further include, as needed, stretching the laminate in the air at a high temperature (e.g., above 95°C) before stretching in a boric acid aqueous solution. The obtained laminate of resin substrate/polarizer can be used directly (that is, the resin substrate can be used as a protective layer of polarizer), or the resin substrate can be peeled off from the laminate of resin substrate/polarizer, and any appropriate protective layer can be laminated on the peeling surface according to the purpose. The details of the manufacturing method of such polarizer are recorded in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The records of these patent documents are cited in this specification as a reference.

The thickness of the polarizer is as described in item A.

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

B-2. Protective layer

烯类、聚烯烃类、(甲基)丙烯酸类、乙酸酯类等透明树脂等。又，亦可例举：(甲基)丙烯酸类、胺基甲酸酯类、(甲基)丙烯酸胺基甲酸酯类、环氧类、硅酮类等热固性树脂或紫外线硬化型树脂等。此外，例如亦可例举硅氧烷类聚合物等玻璃态聚合物。又，亦可使用日本专利特开2001-343529号公报(WO01/37007)中所记载的聚合物膜。作为该膜的材料，例如可使用含有于侧链具有经取代或未经取代的亚胺基的热塑性树脂、及于侧链具有经取代或未经取代的苯基以及腈基的热塑性树脂的树脂组合物，例如可例举具有包含异丁烯及N-甲基顺丁烯二酰亚胺的交替共聚物及丙烯腈-苯乙烯共聚物的树脂组合物。该聚合物膜例如可为所述树脂组合物的挤压成形物。The protective layer is formed of any appropriate film that can be used as a protective layer for a polarizing plate. Specific examples of the material that is the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyether sulfones, polysulfones, polystyrenes, polydecenes, and the like.

Transparent resins such as olefins, polyolefins, (meth) acrylic acid, acetates, etc. can also be cited as examples: (meth) acrylic acid, urethane, (meth) acrylic urethane, epoxy, silicone, etc., or ultraviolet curing resins. In addition, glassy polymers such as siloxane polymers can also be cited as examples. In addition, the polymer film described in Japanese Patent Unexamined Publication No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imine group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl and nitrile group in the side chain can be used, for example, a resin composition having an alternating copolymer containing isobutylene and N-methylmaleimide and acrylonitrile-styrene copolymer can be cited. The polymer film can be, for example, an extruded product of the resin composition.

If necessary, the outer protective layer 12 (especially when the polarizing plate is a polarizing plate on the viewing side) may be subjected to surface treatments such as hard coating, anti-reflection, anti-stickiness, and anti-glare. Furthermore/or, the outer protective layer 12 may be subjected to the following treatments as needed, that is, treatments to improve visibility when viewed through polarized sunglasses (representatively, imparting (elliptical) circular polarization functions and imparting ultra-high phase difference). By implementing such treatments, excellent visibility can be achieved even when viewing the display screen through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate can also be suitably applied to image display devices that can be used outdoors.

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

The thickness of the protective layer may be any appropriate thickness. The thickness of the protective layer is, for example, 10 μm to 50 μm, preferably 20 μm to 40 μm. When surface treatment is performed, the thickness of the protective layer includes the thickness of the surface treatment layer.

C. Adhesive layer

The adhesive layer 20 is used to bond the polarizing plate to the image display unit as described above. The adhesive layer can be typically composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. In the solid content of the adhesive composition, the (meth)acrylic polymer can be contained in the adhesive composition at a ratio 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 an alkyl (meth)acrylate as a monomer unit as a main component. Furthermore, (meth)acrylates refer to acrylates and/or methacrylates. The alkyl (meth)acrylate is preferably contained in the monomer component that forms the (meth)acrylic polymer at a ratio of 80% by weight or more, and more preferably 90% by weight or more. As the alkyl group of the alkyl (meth)acrylate, for example, a straight-chain or branched alkyl group having 1 to 18 carbon atoms can be mentioned. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. A preferred (meth)acrylic acid alkyl ester is butyl acrylate. As monomers (comonomers) constituting (meth)acrylic polymers, in addition to (meth)acrylic acid alkyl esters, there can be mentioned: carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth)acrylic acid esters, heterocyclic vinyl monomers, etc. Representative examples of comonomers include: acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The acrylic adhesive composition preferably contains a silane coupling agent and/or a crosslinking agent. As a silane coupling agent, for example, a silane coupling agent containing an epoxy group can be mentioned. As a crosslinking agent, for example, an isocyanate crosslinking agent and a peroxide crosslinking agent can be mentioned. Furthermore, the acrylic adhesive composition may also contain an antioxidant and/or a conductive agent. The thickness of the adhesive layer is, for example, 50 μm or less, and as described above, preferably 22 μm or less, and more preferably 10 μm to 22 μm. The details of the adhesive layer or the acrylic adhesive composition are, for example, recorded in Japanese Patent Laid-Open No. 2006-183022, Japanese Patent Laid-Open No. 2015-199942, Japanese Patent Laid-Open No. 2018-053114, Japanese Patent Laid-Open No. 2016-190996, and International Publication No. 2018/008712, and the records of these publications are cited in this specification as a reference.

The creep value of the adhesive layer is preferably less than 140 μm/hr, more preferably less than 100 μm/hr, further preferably less than 75 μm/hr, and particularly preferably less than 50 μm/hr. The lower limit of the creep value may be, for example, 20 μm/hr. In this specification, the so-called "creep value" refers to the creep value at 85°C. The creep value can be measured, for example, by the following sequence: the adhesive constituting the adhesive layer is attached to a support plate; the support plate to which the adhesive is attached is fixed, and in this state, a load of 500 g is applied downward in the vertical direction. The amount of displacement of the adhesive from the support plate after the load is applied for 1 hour is measured, and the displacement is taken as the creep value (μm/hr).

The storage modulus G ₂ ' of the adhesive layer at -40°C is preferably 1.0×10 ⁵ (Pa) or more, more preferably 1.0×10 ⁶ (Pa) or more, further preferably 1.0×10 ⁷ (Pa) or more, and particularly preferably 1.0×10 ⁸ (Pa) or more. The storage modulus G ₂ ' may be, for example, 1.0×10 ⁹ (Pa) or less. The storage modulus G ₃ ' of the adhesive layer at 85°C is preferably 1.0×10 ⁵ (Pa) or more, more preferably 3.0×10 ⁵ (Pa) or more, and further preferably 5.0×10 ⁵ (Pa) or more. The storage modulus G ₃ ' may be, for example, 1.0×10 ⁶ (Pa) or less.

D. Image display device

The polarizing plate of the embodiment of the present invention can be applied to an image display device. Therefore, the image display device is also included in the embodiment of the present invention. The image display device includes an image display unit and a polarizing plate. The polarizing plate is the polarizing plate of the embodiment of the present invention described in the above items A to C. The polarizing plate is attached to the image display unit via an adhesive layer. As an image display device, for example, a liquid crystal display device, an organic electroluminescent (EL) display device, and a quantum dot display device can be cited.

E. Polarizing plate with cover glass

When the polarizing plate of the embodiment of the present invention is applied to the viewing side of the image display device, the cover glass can be bonded to the polarizing plate via another adhesive layer (hereinafter, sometimes referred to as the second adhesive layer). Therefore, the embodiment of the present invention includes a polarizing plate with a cover glass layer. In addition, the polarizing plate of the embodiment of the present invention can also be provided in a form in which an isolation member is temporarily adhered instead of the cover glass. In this case, when the image display device is manufactured, the isolation member is peeled off and removed, and the cover glass is bonded via the exposed second adhesive layer. In any case, the through hole can be typically filled with an adhesive constituting the second adhesive layer. The adhesive constituting the second adhesive layer is described below.

Regarding the adhesive constituting the second adhesive layer, when the second adhesive layer is laminated on the polarizing plate, the storage modulus at 60°C is representatively 1.0×10 ⁴ Pa to 1.0×10 ⁵ Pa. Any appropriate adhesive can be used as the adhesive constituting the second adhesive layer, as long as it has such a storage modulus during lamination. Specifically, the adhesive can be a photocurable adhesive or a non-curable adhesive. Furthermore, in this specification, the so-called "photocurable adhesive" refers to an adhesive whose cross-linking reaction is carried out by light irradiation. Therefore, the photocurable adhesive is relatively soft and has excellent deformability during lamination, and after lamination, the desired properties (such as storage modulus) can be given to the adhesive layer by light irradiation. Thereby, the filling property of the special-shaped processing part of the photocurable adhesive is extremely excellent, and the thickness of the second adhesive layer (resulting in the image display device) can be made thinner. Furthermore, even when a thicker frame print layer is formed on the cover glass, good adhesion can be ensured. The so-called "non-hardening adhesive" refers to an adhesive in which the cross-linking reaction is substantially completed and the cross-linking reaction does not substantially proceed after lamination. In other words, the non-hardening adhesive may be a so-called ordinary adhesive. Since the non-hardening adhesive does not require light irradiation (photohardening), it has excellent productivity, and can prevent the occurrence of dents, adhesive overflow from the end of the punched product, and poor operation.

The storage modulus at 60°C before curing of the photocurable adhesive may substantially correspond to the storage modulus during the lamination. As described above, the storage modulus before curing is 1.0×10 ⁵ Pa or less, preferably 1.0×10 ³ Pa to 1.0×10 ⁵ Pa. The storage modulus at 60°C after curing of the photocurable adhesive is preferably 5.0×10 ³ Pa to 5.0×10 ⁵ Pa. The gel fraction of the photocurable adhesive before curing is 0% to 60%, and the gel fraction after curing is 50% to 95%. In the case where the second adhesive layer is composed of the photocurable adhesive, the thickness of the second adhesive layer is preferably 50μm to 500μm, more preferably 75μm to 475μm, and further preferably 100μm to 450μm.

The storage modulus at 60°C when the non-curing adhesive is laminated is preferably 1.0×10 ³ Pa to 8.0×10 ⁴ Pa, more preferably 5.0×10 ³ Pa to 6.0×10 ⁴ Pa. When the second adhesive layer is composed of the 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 further preferably 100 μm to 800 μm.

Hereinafter, the characteristics of the second adhesive layer and the photocurable adhesive constituting the second adhesive layer will be described, and then the non-curable adhesive will be briefly described.

E-1. Characteristics of the second adhesive layer

The glass transition temperature of the second adhesive layer is preferably -3°C or lower, more preferably -5°C or lower, and further preferably -6°C or lower. On the other hand, the glass transition temperature is preferably -20°C or higher, more preferably -15°C or higher, and further preferably -13°C or higher. If the glass transition temperature is within such a range, a second adhesive layer having 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 more, more preferably 1.6 or more, further preferably 1.7 or more, and particularly preferably 1.75 or more. On the other hand, the upper limit of the peak value of tanδ is preferably 3.0 or less, more preferably 2.5 or less, and further preferably 2.3 or less. If the peak value of tanδ is within this range, the second adhesive layer exhibits appropriate deformation behavior (viscoelastic behavior), so it is not easy to form gaps in the special-shaped processing part, and delayed bubbles can be suppressed.

The total light transmittance of the second adhesive layer is preferably 85% or more, more preferably 90% or more. The haze value of the second adhesive layer is preferably 1.5% or less, more preferably 1.0% or less.

E-2. Light-curing adhesive

E-2-1. Characteristics of light-curing adhesives

As described above, the storage modulus of the photocurable adhesive at 60°C before curing is 1.0×10 ⁵ Pa or less, preferably 1.0×10 ³ Pa to 1.0×10 ⁵ Pa, more preferably 5.0×10 ³ Pa to 8.0×10 ⁴ Pa, and further preferably 7.5×10 ³ Pa to 6.0×10 ⁴ Pa. If the storage modulus of the photocurable adhesive before curing is within this range, the photocurable adhesive exhibits appropriate deformation behavior (viscoelastic behavior) and can flow well into every corner of the irregularly shaped processed part. As a result, gaps are less likely to be formed in the irregularly shaped processed part, and delayed bubbles can be suppressed. The storage modulus of the photocurable adhesive at 60° C. after curing is preferably 5.0×10 ³ Pa to 5.0×10 ⁵ Pa, more preferably 7.5×10 ³ Pa to 4.0×10 ⁵ Pa, and further preferably 8.0×10 ³ Pa to 3.0×10 ⁵ Pa. When 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 decreases. As a result, delayed bubbles can be suppressed.

The gel fraction of the photocurable adhesive before curing is preferably 0% to 60%, more preferably 0% to 55%, and further preferably 0% to 50%. If the gel fraction of the photocurable adhesive before curing is within this range, it is easy to achieve the required storage modulus. Therefore, the photocurable adhesive exhibits appropriate deformation behavior (viscoelastic behavior) and can flow well into every corner of the special-shaped processing part. As a result, gaps are not easily formed in the special-shaped processing part, and delayed bubbles can be suppressed. The gel fraction of the photocurable adhesive after curing is preferably 50% to 95%, more preferably 55% to 93%, and further preferably 60% to 90%. If the gel fraction of the photocurable adhesive after curing is within this range, the cover 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 calculated according to the insoluble fraction in solvents such as ethyl acetate. Specifically, the gel fraction is determined as the weight fraction (unit: weight %) of the insoluble component of the adhesive constituting 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 blending amount of the monomer components of the base polymer constituting the adhesive, and the type and blending amount of the crosslinking agent.

E-2-2. Constituent materials of light-curing adhesive

As the photocurable adhesive, any appropriate photocurable adhesive (sometimes simply referred to as an adhesive composition in this item) can be used, as long as it has the characteristics as described above. As the base polymer of the adhesive composition, for example, (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride polymers, modified polyolefins, epoxy polymers, fluorine polymers, natural rubber, synthetic rubber and other rubber polymers can be cited. Preferably, it is a (meth)acrylic adhesive composition comprising a (meth)acrylic polymer as a base polymer. The reason is that it has excellent optical transparency and exhibits moderate adhesive properties such as wettability, cohesion and adhesion, and is also excellent in weather resistance and heat resistance. Furthermore, in this specification, the so-called "(meth)acrylic acid" refers to acrylic acid and/or methacrylic acid.

The (meth)acrylic base polymer (hereinafter, sometimes simply referred to as a base polymer) preferably has a crosslinked structure.

E-2-2-1. (Meth)acrylic base polymer

The (meth)acrylic base polymer contains an alkyl (meth)acrylate as a main monomer component. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group with a carbon number of 1 to 20 is preferably used. The alkyl group of the alkyl (meth)acrylate may have a branch or a cyclic alkyl group. The amount of the alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and further preferably 60% by weight or more, relative to the total amount of the monomer components constituting the (meth)acrylic base polymer. From the viewpoint of setting the glass transition temperature (Tg) of the polymer chain to an appropriate range, the amount of the alkyl (meth)acrylate having a chain alkyl group with a carbon number of 4 to 10 is preferably 30% by weight or more, more preferably 40% by weight or more, and further preferably 45% by weight or more, relative to the total amount of the monomer components constituting the (meth)acrylic base polymer.

(Meth) acrylic base polymer preferably comprises monomer components with crosslinkable functional groups. If this is constituted, the gel fraction of the adhesive can be adjusted to the desired range. As monomer components with crosslinkable functional groups, for example, monomers containing hydroxyl groups and monomers containing carboxyl groups can be exemplified. When the crosslinked structure is introduced by an isocyanate crosslinking agent, the hydroxyl group becomes a reaction point that reacts with the isocyanate group, and when the crosslinked structure is introduced by an epoxy crosslinking agent, the carboxyl group becomes a reaction point that reacts with the epoxy group. It is preferred to use a monomer containing hydroxyl groups as a monomer component with crosslinkable functional groups, so that the crosslinked structure can be introduced by an isocyanate crosslinking agent. If this is constituted, the crosslinking property of the base polymer can be improved, and the second adhesive layer with higher transparency can be obtained. Furthermore, if this is constituted, the so-called acid-free adhesive can be realized.

The amount of the monomer containing hydroxyl groups is preferably 5% to 30% by weight, more preferably 8% to 25% by weight, and further preferably 10% to 20% by weight relative to the total amount of monomer components constituting the (meth) acrylic base polymer. If the amount of the monomer containing hydroxyl groups is within this range, a smaller amount of crosslinking can be used to increase the degree of crosslinking (gel fraction), and as a result, the filling property and operability of the special-shaped processing part of the photocurable adhesive before curing can be improved. Furthermore, since the unreacted hydroxyl groups after crosslinking can form intermolecular hydrogen bonds, the required storage modulus can be achieved even with a smaller gel fraction.

When the second adhesive layer may contact the touch panel sensor, for example, the acid content of the second adhesive layer is preferably small in order to prevent the acid component from corroding the electrode. In this case, the amount of the carboxyl-containing monomer is preferably 0.5 wt % or less, more preferably 0.1 wt % or less, and further preferably 0.05 wt % or less, and ideally 0 (zero) relative to the total amount of monomer components constituting the (meth) acrylic base polymer. If such a structure is used, the acid content in the photocurable adhesive can be preferably set to 100 ppm or less, more preferably 70 ppm or less, and further preferably 50 ppm or less.

The (meth) acrylic base polymer may also include a nitrogen-containing monomer as a monomer component. By appropriately including a high-polarity monomer such as a hydroxyl-containing monomer, a carboxyl-containing monomer, and a nitrogen-containing monomer as a monomer component, a second adhesive layer having excellent balance of storage modulus, adhesion retention, and impact resistance can be formed in the (meth) acrylic base polymer. Relative to the total amount of monomer components constituting the (meth) acrylic base polymer, the amount of high-polarity monomers (the total of hydroxyl-containing monomers, carboxyl-containing monomers, and nitrogen-containing monomers) is preferably 10% by weight to 45% by weight, more preferably 15% by weight to 40% by weight, and further preferably 18% by weight to 35% by weight. It is particularly preferred that the total amount of hydroxyl-containing monomers and nitrogen-containing monomers is within the range. Relative to the total amount of monomer components constituting the (meth) acrylic base polymer, the amount of nitrogen-containing monomers is preferably 3% by weight to 25% by weight, more preferably 5% by weight to 20% by weight, and further preferably 7% by weight to 15% by weight.

The (meth)acrylic polymer may further contain any appropriate monomer component according to the purpose. Specific examples of such monomer components include: monomers containing anhydride groups, caprolactone adducts of (meth)acrylic acid, monomers containing sulfonic acid groups, monomers containing phosphoric acid groups, vinyl monomers such as vinyl acetate, vinyl propionate, styrene, and α-methylstyrene; acrylic monomers containing cyano groups such as acrylonitrile and methacrylonitrile; monomers containing epoxy groups such as glycidyl (meth)acrylate; glycol 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 base polymer preferably contains the most alkyl (meth)acrylate as a monomer component, and more preferably contains the most alkyl (meth)acrylate having a chain alkyl group with a carbon number of 6 or less. If such a composition is used, the peak value of tan δ becomes larger, and the impact resistance can be improved. The amount of alkyl (meth)acrylate having a chain alkyl group with a carbon number of 6 or less is preferably 30% by weight to 80% by weight, more preferably 35% by weight to 75% by weight, and further preferably 40% by weight to 70% by weight relative to the total amount of monomer components constituting the (meth)acrylic base polymer. It is particularly preferred that the content of butyl acrylate as a monomer component is within the above range.

The glass transition temperature (Tg) of the (meth)acrylic base polymer is preferably -50°C or higher. On the other hand, the Tg of the (meth)acrylic base polymer is preferably -5°C or lower, more preferably -10°C or lower, and further preferably -15°C or lower.

E-2-2-2. Cross-linked structure

The polymer having a cross-linked structure introduced into a (meth)acrylic base polymer can be obtained, for example, by the following methods: (1) a method of polymerizing a (meth)acrylic polymer having a functional group that can react with a cross-linking agent, adding a cross-linking agent, and reacting the (meth)acrylic polymer with the cross-linking agent; and (2) a method of introducing a branched structure (cross-linked structure) into a polymer chain by including a polyfunctional compound in the polymer components. These methods may also be used in combination.

唑啉类交联剂、氮丙啶类交联剂、碳二酰亚胺类交联剂、金属螯合物类交联剂等。其中，就与基础聚合物的羟基或羧基的反应性较高，容易导入交联结构的方面考虑，较佳为异氰酸酯类交联剂及环氧类交联剂。该等交联剂与导入至基础聚合物中的羟基或羧基等官能基反应而形成交联结构。如上所述，于采用基础聚合物不包含羧基的无酸粘接剂的情形时，较佳为藉由基础聚合物中的羟基与异氰酸酯类交联剂导入交联结构。Specific examples of the crosslinking agent in the method of (1) allowing the base polymer to react with the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents,

Azoline crosslinking agent, aziridine crosslinking agent, carbodiimide crosslinking agent, metal chelate crosslinking agent, etc. Among them, isocyanate crosslinking agent and epoxy crosslinking agent are preferred in terms of high reactivity with the hydroxyl or carboxyl group of the base polymer and easy introduction of the crosslinked structure. These crosslinking agents react with functional groups such as hydroxyl or carboxyl groups introduced into the base polymer to form a crosslinked structure. As described above, in the case of an acid-free adhesive in which the base polymer does not contain a carboxyl group, it is preferred to introduce the crosslinked structure by the hydroxyl group in the base polymer and the isocyanate crosslinking agent.

The crosslinking agent can be used in an amount of preferably 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 particularly preferably 0.07 to 0.2 parts by weight relative to 100 parts by weight of the base polymer. By setting the amount of the crosslinking agent used in this range, the gel fraction can be within the desired range.

E-2-2-3. Polyfunctional compounds

In the method of including a polyfunctional compound in the polymerization component of the base polymer of (2), the monomer components constituting the (meth)acrylic base polymer and the total amount of the polyfunctional compound for introducing the cross-linking structure may be reacted at once, or the polymerization may be carried out in multiple stages. As a method of carrying out polymerization in multiple stages, the following method is preferred: a monofunctional monomer constituting the (meth)acrylic base polymer is polymerized (prepolymerized) to prepare a partial polymer (prepolymer composition), and a polyfunctional compound such as a polyfunctional (meth)acrylate is added to the prepolymer composition to polymerize the prepolymer composition and the polyfunctional monomer (formal polymerization). The prepolymer composition is a partial polymer containing a polymer with a low degree of polymerization and unreacted monomers.

By prepolymerizing the constituents of the (meth)acrylic base polymer, the branching points (crosslinking points) of the multifunctional compound can be uniformly introduced into the (meth)acrylic base polymer. In addition, a mixture of a low molecular weight polymer or a partial polymer and an unpolymerized monomer component (adhesive composition) can be applied to a substrate, and then formally polymerized on the substrate to form an adhesive layer. Since low polymer compositions such as prepolymer compositions have low viscosity and excellent coating properties, the productivity of the adhesive layer can be improved and the thickness of the adhesive layer can be made uniform by applying a mixture of a prepolymer composition and a multifunctional compound, i.e., an adhesive composition, on a substrate.

As a multifunctional compound for introducing a cross-linked structure, a compound containing two or more polymerizable functional groups (ethylenically unsaturated groups) having unsaturated double bonds in one molecule can be cited. A representative multifunctional compound is a photopolymerizable multifunctional compound. As a multifunctional compound, a multifunctional (meth)acrylate is preferably used in view of the ease of copolymerization with the monomer component of the (meth)acrylic polymer. In the case of introducing a branched (cross-linked) structure by active energy line polymerization (photopolymerization), a multifunctional (meth)acrylate is preferably used.

The molecular weight of the polyfunctional compound is preferably 1500 or less, more preferably 1000 or less. The lower limit of the molecular weight may be, for example, 500. The functional group equivalent (g/eq) of the polyfunctional compound is preferably 50 to 500, more preferably 70 to 300, and further preferably 80 to 200. With such a configuration, the viscoelasticity of the photocurable adhesive can be appropriately adjusted.

The polyfunctional compound can be used in a ratio of preferably 1 to 6 parts by weight, more preferably 2 to 5 parts by weight, and further 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 photocurable adhesive (resulting in the second adhesive layer) is insufficient. If the amount used is too large, the second adhesive layer formed is too hard and the impact resistance is insufficient. Furthermore, the processability and/or processing dimensional stability of the photocurable adhesive are insufficient.

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

E-2-2-4. Adhesive composition

The adhesive composition (photocurable adhesive) may contain a photopolymerization initiator, an oligomer, a silane coupling agent, in addition to the base polymer, the crosslinking agent, and the polyfunctional compound, and may contain any appropriate additives according to the purpose.

类光聚合起始剂、酰基氧化膦类光聚合起始剂。光聚合起始剂可单独使用亦可将2种以上并用。粘接剂组合物中的光聚合起始剂的含量相对于基础聚合物100重量份，较佳为0.01重量份～5重量份，更佳为0.05重量份～3重量份。Examples of the photopolymerization initiator include benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, benzyl photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, 9-oxysulfuryl chloride photopolymerization initiators,

The photopolymerization initiator may be a photopolymerization initiator of the type or an acylphosphine oxide type. The photopolymerization initiator may be used alone or in combination of two or more. The content of the photopolymerization initiator in the adhesive composition is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, relative to 100 parts by weight of the base polymer.

As the oligomer, any appropriate oligomer can be used. By using an oligomer, the viscoelasticity (thus, the filling property and workability of the special-shaped processing part) and the adhesion of the photocurable adhesive can be adjusted. The oligomer is preferably a (meth)acrylic oligomer. (Meth)acrylic oligomers have excellent compatibility with the base polymer.

The weight average molecular weight of the oligomer is preferably about 1000 to 30000, more preferably 1500 to 10000, and still more preferably 2000 to 8000. When the weight average molecular weight of the oligomer is within such a range, excellent adhesion and adhesion retention can be achieved.

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

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

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

As for the additives, any appropriate additives can be used according to 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 release films temporarily attached to both surfaces.

More detailed matters of the adhesive composition (photocurable adhesive) are described in Japanese Patent Application No. 2018-218422 applied by the present applicant. The description of this application is cited in this specification as a reference.

E-3. Non-hardening adhesive

As a non-hardening adhesive, any appropriate non-hardening adhesive can be used as long as it has the characteristics as described above. By appropriately adjusting the type, combination and blending amount of the monomer components, as well as the type, quantity, combination, blending amount, etc. of the cross-linking agent, silane coupling agent and additives, a non-hardening adhesive having the required storage modulus can be obtained (the result is the second adhesive layer). As a non-hardening adhesive, for example, the adhesive recorded in the item C regarding the first and second adhesive layers, the adhesive recorded in Japanese Patent Application No. 2019-196942 applied for by the present applicant, and the adhesive recorded in Japanese Patent Application No. 2016-94569. The records of the application and the gazette are cited in this specification as a reference.

E-4. Assembly of optical components

As described above, the adhesive (adhesive composition) constituting the second adhesive layer can be provided as an adhesive sheet. In the production of the image display device, the adhesive sheet can be provided as a component of an optical component together with the polarizing plate of an embodiment of the present invention. Therefore, the component of such an 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 (back side polarizing plates). That is, in the production of the image display device, the adhesive sheet, the polarizing plate of an embodiment of the present invention (viewing side polarizing plate) and the second polarizing plate (back side polarizing plate) can be provided as a component of an optical component.

[Example]

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

(1) Size of adhesive gap

The cross-section of the adhesive layer in the through-hole of the polarizing plate used in Examples and Comparative Examples was observed with an optical microscope, and the length of the adhesive layer from the outer edge to the inner side in the plane direction where the defect was the largest was measured, which was defined as the size L (μm) of the adhesive void.

(2) Paste offset

The polarizing plate used in the embodiments and comparative examples was bonded to the glass, and after being treated in an autoclave (50°C/0.5MPa/15min), a heating test (85°C, 120h) was performed. The through holes of the sample after the test were observed with 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 deformed portion was measured using an optical microscope (MX61L) manufactured by OLYMPUS. Furthermore, three test samples were measured, and the maximum value of the three measured values was taken as the offset.

(3) Bubble evaluation

The image display device products obtained in the examples and comparative examples were vacuum laminated, autoclaved (50°C/0.5MPa/15min), and UV (Ultraviolet) cured (illuminance 150mW/ ^cm2 , irradiation dose 3000mJ). Then, the samples were subjected to a heating test (85°C, 24h), and the state of bubbles was observed visually or under an optical microscope when they were taken out. The measurement was carried out under the condition of n=6, and the evaluation was carried out according to the following criteria.

4: No bubbles were found in all samples

3: A few bubbles can be seen in samples that are less than half full, but there is no problem in use

2: A few bubbles were visible in more than half of the samples, but there were no problems in use.

1: All samples have bubbles

<Production 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, a thermometer, a nitrogen inlet tube, and a cooler. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile and 100 parts by weight of ethyl acetate were added as polymerization initiators to 100 parts of the monomer mixture (solid content), and nitrogen was introduced while slowly stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was maintained at about 55°C, and a polymerization reaction was performed for 8 hours to prepare a solution of an acrylic polymer. With respect to 100 parts of the solid content of the obtained acrylic polymer solution, 0.3 parts of benzoyl peroxide (trade name: Nyper BMT 40SV, manufactured by NOF Corporation) as a crosslinking agent, 0.1 parts of an isocyanate crosslinking agent (trade name: Takenate D110N, manufactured by Mitsui Chemicals Co., Ltd.), and 0.2 parts of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain an adhesive composition.

Next, the solution of the acrylic adhesive composition was applied to one side of a polyethylene terephthalate film (release film: manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) treated with a silicone release agent so that the thickness of the adhesive layer after drying was 20 μm, and dried at 155° C. for 1 minute to form an adhesive layer (1) on the surface of the release film. The creep value of the adhesive layer (1) was 120 μm/hr.

<Production 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, a thermometer, a nitrogen inlet tube, and a cooler. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile and 100 parts by weight of ethyl acetate were added as polymerization initiators to 100 parts of the monomer mixture (solid content), and nitrogen was introduced while slowly stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was maintained at about 55°C, and a polymerization reaction was performed for 8 hours to prepare a solution of an acrylic polymer. With respect to 100 parts of the solid content of the obtained acrylic polymer solution, 0.1 parts of benzoyl peroxide (trade name: Nyper BMT 40SV, manufactured by NOF Corporation) as a crosslinking agent, 8 parts of an isocyanate crosslinking agent (trade name: Coronate L, manufactured by Tosoh Corporation) and 0.2 parts of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain an adhesive composition.

Next, the solution of the acrylic adhesive composition was applied to one side of a polyethylene terephthalate film (release film: manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) treated with a silicone release agent so that the thickness of the adhesive layer after drying was 20 μm, and dried at 155° C. for 1 minute to form an adhesive layer (2) on the surface of the release film. The creep value of the adhesive layer (2) was 35 μm/hr.

<Production Example 3: Preparation of a Photocurable Adhesive Constituting a 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 isostearyl acrylate (ISTA) was added. Furthermore, 0.2 parts of 2,2'-azobisisobutyronitrile 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 to 100 parts of the monomer mixture (solid content), and stirred for 1 hour in a nitrogen atmosphere at 23°C, and nitrogen replacement was performed. Then, the mixture was reacted at 56°C for 5 hours, and then reacted at 70°C for 3 hours to prepare a solution of an acrylic base polymer. In the obtained solution of the acrylic base polymer, the following post-addition components were added to 100 parts of the base polymer, and the mixture was uniformly mixed to prepare a photocurable adhesive b. The storage modulus of the photocurable adhesive b at 60°C before curing was 4.7×10 ⁴ Pa, and the storage modulus at 60°C after curing was 1.0×10 ⁵ Pa. The gel fraction before curing was 40%, and the gel fraction after curing was 80%.

(Later added ingredients)

Dipentaerythritol hexaacrylate as a multifunctional compound (light hardener): 2 parts

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 (light hardener): 3 parts

Photopolymerization initiator (trade name: "Irgacure 184", manufactured by BASF): 0.2 parts

(Manufacturing of Adhesive Sheet)

The photocurable adhesive b was applied to a 75 μm thick polyethylene terephthalate (PET) film ("DIAFOIL MRF75" manufactured by Mitsubishi Chemical Corporation) having a silicone release layer on the surface, and heated at 100°C for 3 minutes to remove the solvent, and then the same release PET film as described above was attached to the surface. The laminate obtained in this way was aged at 25°C for 3 days to obtain an adhesive sheet I with release films temporarily attached to both sides.

<Manufacturing Example 4: Preparation of Polarizing Plate>

A polyvinyl alcohol film with a thickness of 30 μm was dyed on one side and stretched to 3 times on the other side in a 0.3% iodine solution at 30°C for 1 minute between rollers with different speed ratios. Then, it was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes and stretched until the combined stretching ratio reached 6 times. Subsequently, it was washed by immersing in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds and then dried at 50°C for 4 minutes to obtain a polarizer with a thickness of 12 μm. A triacetyl cellulose (TAC) film with a hard coating as an outer protective layer (the hard coating thickness is 2 μm and the TAC thickness is 25 μm) and a TAC film (thickness is 25 μm) as an inner protective layer were respectively attached to both sides of the polarizer. The liquid crystal alignment solidification layer H and the liquid crystal alignment solidification layer Q were transferred to the inner protective layer side of the polarizing plate in sequence. In this way, a polarizing plate (1) is manufactured. Furthermore, the liquid crystal alignment cured layer H and the liquid crystal alignment cured layer Q are manufactured in the following manner.

A liquid crystal composition (coating liquid) was prepared by dissolving 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name "Paliocolor LC242", represented by the following formula) and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF: trade name "Irgacure 907") in 40 g of toluene.

[Chemistry 1]

The surface of the polyethylene terephthalate (PET) film (thickness 38 μm) is rubbed with a rubbing cloth to perform an alignment treatment. The direction of the alignment treatment is set to be 15° relative to the direction of the absorption axis of the polarizer when observed from the viewing side when attached to the polarizing plate. The liquid crystal coating liquid is applied to the alignment treated surface by a rod coater and heated and dried at 90°C for 2 minutes to align the liquid crystal compound. A metal halide lamp is used to irradiate the liquid crystal layer formed in this way with 1 mJ/ ^cm2 of light to harden the liquid crystal layer, thereby forming a liquid crystal alignment solidified layer H on the PET film. The thickness of the liquid crystal alignment solidified layer H is 2.5 μm, and the in-plane phase difference Re (550) is 270 nm. Furthermore, the liquid crystal alignment solidified layer H has a refractive index distribution of nx＞ny＝nz. A liquid crystal alignment cured layer Q was formed on the PET film in the same manner as described above, except that the coating thickness was changed and the alignment treatment direction was set to be 75° relative to the absorption axis of the polarizer when viewed from the visual side. The liquid crystal alignment cured layer Q had a thickness of 1.5 μm and an in-plane phase difference Re (550) of 140 nm. Furthermore, the liquid crystal alignment cured layer Q had a refractive index distribution of nx>ny=nz.

<Manufacturing Example 5: Preparation of Polarizing Plate>

A polyvinyl alcohol film with a thickness of 30 μm was dyed on one side and stretched to 3 times on the other side in a 0.3% iodine solution at 30°C for 1 minute between rollers with different speed ratios. Then, it was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes and stretched until the combined stretching ratio reached 6 times. Subsequently, it was washed by immersing in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds and then dried at 50°C for 4 minutes to obtain a polarizer with a thickness of 12 μm. A triacetyl cellulose (TAC) film with a hard coating as an outer protective layer (the hard coating layer thickness is 2 μm, and the TAC thickness is 25 μm) and an acrylic resin film (thickness is 20 μm) as an inner protective layer were respectively bonded to both sides of the polarizer to produce a polarizing plate (2).

<Manufacturing Example 6: Preparation of Polarizing Plate>

1. Preparation of polarizer

As the thermoplastic resin substrate, an amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) having a long strip shape, a water absorption of 0.75%, and a Tg of about 75° C. was used. One surface of the resin substrate was subjected to a corona treatment.

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 acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") in a ratio of 9:1, 13 parts by weight of potassium iodide was added and dissolved in water to prepare a PVA aqueous solution (coating solution).

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

The obtained laminate was subjected to free-end uniaxial stretching treatment in the longitudinal direction (length direction) between rolls of different peripheral speeds in an oven at 130° C. until it was stretched to 2.4 times (in-air auxiliary stretching treatment).

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

Next, the film was immersed in a dyeing bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 relative to 100 parts by weight of water) at a liquid temperature of 30° C. for 60 seconds while adjusting the concentration so that the single body transmittance (Ts) of the finally obtained polarizing film became a specific value (dyeing treatment).

Next, the film was immersed in a cross-linking bath (boric acid aqueous solution prepared by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (cross-linking treatment).

Then, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4.0 wt %, potassium iodide: 5.0 wt %) at a liquid temperature of 70°C, and was uniaxially stretched (underwater stretching treatment) in the longitudinal direction (length direction) between rollers having different peripheral speeds so that the total stretching ratio became 5.5 times.

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

Then, the laminate was dried in an oven maintained at 90°C while being brought into contact with a heated roller made of SUS (Steel Use Stainless, Japanese stainless steel standard) maintained at 75°C for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction after the drying shrinkage treatment was 5.2%.

In this way, a polarizing plate having a thickness of 5 μm was formed on the resin substrate.

2. Production of polarizing plate

The HC-TAC film is bonded to the polarizer surface of the obtained resin substrate/polarizer laminate via an ultraviolet curing adhesive. Specifically, the curing adhesive is applied in a manner to a thickness of 1.0 μm, and the bonding is performed using a roller press. Then, UV light is irradiated from the HC-TAC film side to cure the adhesive. Furthermore, the HC-TAC film is a film having a hard coating (HC) layer (thickness 7 μm) formed on a triacetylcellulose (TAC) film (thickness 25 μm), and is bonded in a manner such that the TAC film is located on the polarizer side. Subsequently, the resin substrate is peeled off, and a TAC film (thickness 20 μm) is bonded to the peeled surface in the same manner as described above. In this way, a polarizing plate (3) is produced.

<Example 1>

1. Formation of through holes

The adhesive layer (1) obtained in Manufacturing Example 1 is formed on the surface of the liquid crystal alignment solidified layer Q of the polarizing plate (1) obtained in Manufacturing Example 4 as a polarizing plate with an adhesive layer. The polarizing plate with an adhesive layer is punched out to a size of 145 mm in length and 68 mm in width. At this time, the punching is performed in a manner that the absorption axis direction of the polarizer is 135° in the clockwise direction relative to the long side direction. Furthermore, a through hole with a diameter of 3.9 mm is formed in the upper right corner of the punched polarizing plate with an adhesive layer by an end mill. In this way, a polarizing plate (polarizing plate with an adhesive layer) as shown in Figure 1A is produced. The | _b1 - _b2 | of the obtained polarizing plate is 0 mm. In addition, the size L of the adhesive gap portion is 90 μm. The polarizing plate is provided for the evaluation of (2). The results are shown in Table 1.

2. Production of products corresponding to image display devices

The polarizing plate with an adhesive layer obtained in 1. is bonded to one side of a glass plate (corresponding to the image display unit) via the adhesive layer. Then, one release film of the adhesive sheet I obtained in Manufacturing Example 3 is peeled off and bonded to a cover glass (manufactured by Matsunami Glass Co., Ltd., with a thickness of 0.8 mm) by a roller laminating machine. Then, the other release film of the adhesive sheet I is peeled off, and a vacuum laminating machine is used to make it in close contact with the surface of the polarizing plate with an adhesive layer and fill the through holes with the adhesive sheet. The conditions for vacuum lamination are as follows: heating and pressing at 0.2 MPa and 60°C (standby time 90 seconds), followed by vacuum lamination at 100 Pa for 10 seconds. Furthermore, a metal halide lamp (300 mW/cm ² ) is used to irradiate ultraviolet rays with a cumulative light amount of 3000 mJ/cm ² from the cover glass side to cure the photocurable adhesive. Then, an autoclave treatment (50°C/0.5 MPa/15 min) was performed. In this way, an image display device-compatible product was produced. The obtained image display device-compatible product was subjected to the bubble evaluation in (3) above. The results are shown in Table 1.

<Example 2>

A polarizing plate (polarizing plate with adhesive layer) and an image display device were produced in the same manner as in Example 1, except that the through holes were formed at the ends in the long-side direction and the center in the short-side direction. The |b ₁ -b ₂ | of the obtained polarizing plate was 41 mm. The size L of the adhesive gap was 90 μm. The obtained polarizing plate and image display device were evaluated in the same manner as in Example 1. The results are shown in Table 1. In Table 1, the ends in the long-side direction and the center in the short-side direction are simply referred to as "center".

<Examples 3 to 7 and Comparative Examples 1 to 4>

A polarizing plate (a polarizing plate with an adhesive layer) and a corresponding image display device are manufactured in the same manner as in Example 1, except that the type and size of the polarizing plate, the type of the adhesive layer, and the formation position of the through hole are shown in Table 1. Furthermore, the size L of the adhesive gap portion is adjusted by changing the feed speed or rotation speed of the drill and the cutting amount during the end milling process for forming the through hole. Here, Examples 4 and 6 correspond to the form shown in Figure 1A, Example 7 corresponds to the form shown in Figure 1B, and Examples 3 and 5 correspond to the form shown in Figure 1C. The obtained polarizing plate and corresponding image display device are respectively subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Table 1]

As can be seen from Table 1, the amount of paste displacement in the through-hole portion of the polarizing plate of the example of the present invention after the heating test is significantly smaller than that of the comparative example, and retardation bubbles are suppressed.

[Industrial Applicability]

The polarizing plate of the present invention is suitable for use in an image display device, and in particular, can be suitably used in an image display device having a camera unit, such as a smart phone, a tablet PC, or a smart watch.

Description of Reference Numerals

11: Polarizer

12: Outer protective layer

13: Inner protective layer

20: Adhesive layer

30:Through hole

100: Polarizing plate

Claims (8)

1. A polarizing plate comprising: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; and an adhesive layer; and formed with through-holes, The polarizer has a thickness of 15 μm or less, |b ₁ -b ₂ | is less than 45mm, Here, _b1 is the distance from the center of the through hole to one end of the polarizer in the direction of the absorption axis of the polarizer, and _b2 is the distance from the center of the through hole to the other end of the polarizer in the direction of the absorption axis of the polarizer. 2. The polarizing plate according to claim 1, which has a rectangular shape, and when viewed from the viewing side, the direction of the absorption axis of the polarizing plate is a direction that is 135° clockwise from the long side direction, and the through hole formed in the upper right corner. 3. The polarizing plate according to claim 1, which has a rectangular shape, and when viewed from the viewing side, the direction of the absorption axis of the polarizing plate is a direction that is 45° clockwise from the long side direction, and the through hole formed in the upper left corner. 4. The polarizing plate according to claim 1, which has a rectangular shape, the absorption axis direction of the polarizer is a short side direction, and when viewed from above, the through hole is formed at the end of the long side direction and the short side direction of the central part. 5. The polarizing plate according to any one of claims 1 to 4, wherein the thickness of the polarizing plate is 8 μm or less. 6. The polarizing plate according to any one of claims 1 to 5, wherein the adhesive layer has a creep value of 140 μm/hr or less. 7. An image display device, comprising: an image display unit and the polarizing plate according to any one of claims 1 to 6; and The polarizing plate is bonded to the image display unit via the adhesive layer. 8. A polarizing plate with a cover glass, comprising: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; another adhesive layer disposed on the polarizing plate the opposite side of the adhesive layer; and cover glass, which is bonded via the other adhesive layer; and A through hole is formed, and the through hole is filled with the adhesive constituting the other adhesive layer, The polarizer has a thickness of 15 μm or less, |b ₁ -b ₂ | is less than 45mm, Here, _b1 is the distance from the center of the through hole to one end of the polarizer in the direction of the absorption axis of the polarizer, and _b2 is the distance from the center of the through hole to the other end of the polarizer in the direction of the absorption axis of the polarizer.

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