Polarizer set and image display device including the set

Abstract

Provided is a set of polarizing plates in which the deviation of the through-hole portion in each polarizing plate is low, and the difference between the deviation amount of a viewing-side polarizing plate and the deviation amount of a rear surface-side polarizing plate is extremely small. This set of polarizing plates comprises a rectangular first polarizing plate disposed on the viewing side of an image display cell, and a rectangular second polarizing plate disposed on the rear surface side. The first polarizing plate has a first polarizer, a protective layer disposed on at least one side thereof, and a first adhesive layer disposed on the image display cell side. The second polarizing plate has a second polarizer, a protective layer disposed on at least one side thereof, a reflective polarizer disposed on the side of the second polarizer opposite to the image display cell, and a second adhesive layer disposed on the image display cell side. The thicknesses of the first polarizer and the second polarizer are each 20 μm or less. The absorption axis of the first polarizer is in the short-side direction, and the absorption axis of the second polarizer is in the long-side direction. The first polarizing plate and the second polarizing plate each have a through-hole in the end thereof or in the vicinity of the end, in positions corresponding to each other.

Description

Polarizing plate set and image display device including said set

[0001] The present invention relates to a set of polarizing plates and an image display device including the set.

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

[0003] International Publication No. 2017 / 047510

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a set of polarizing plates in which the misalignment at the through-hole portion of each polarizing plate is small, and the difference between the amount of misalignment of the viewer-side polarizing plate and the amount of misalignment of the back-side polarizing plate is very small.

[0005] The polarizing plate set of the present invention comprises a rectangular first polarizing plate disposed on the viewing side of an image display cell and a rectangular second polarizing plate disposed on the back side of the image display cell. The first polarizing plate has a first polarizer and a protective layer disposed on at least one side of the first polarizer, and a first pressure-sensitive adhesive layer disposed on the image display cell side. The second polarizing plate has a second polarizer and a protective layer disposed on at least one side of the second polarizer, a reflective polarizer disposed on the side of the second polarizer opposite the image display cell, and a second pressure-sensitive adhesive layer disposed on the image display cell side. The thicknesses of the first polarizer and the second polarizer are each 20 μm or less, and the first polarizer has an absorption axis in the short-side direction, and the second polarizer has an absorption axis in the long-side direction. The first polarizing plate and the second polarizing plate have through-holes at or near their respective ends and at positions corresponding to each other. In one embodiment, a distance A from the outermost portion of the first pressure-sensitive adhesive layer on the image display cell side to the center of the first polarizer in the thickness direction １ (μm), the thickness T of the first polarizer ｐｏｌ１ (μm), creep value C of the first pressure-sensitive adhesive layer ｐｓａ１ (μm / hr), the thickness T of the first pressure-sensitive adhesive layer ｐｓａ１ (μm), and the thickness T of the protective layer in the first polarizing plate ｐｒｏ１ (μm) satisfies the following relationship: (A １ ×T ｐｏｌ１ ) × (C ｐｓａ１ ×T ｐｓａ１ ) / T ｐｒｏ１ =K １ ≦300×10 ２ (μm ３ / hr) Distance A from the outermost portion of the second pressure-sensitive adhesive layer on the image display cell side to the center of the second polarizer in the thickness direction ２ (μm), the thickness T of the second polarizer ｐｏｌ２ (μm), creep value C of the second pressure-sensitive adhesive layer ｐｓａ２ (μm / hr), the thickness T of the second pressure-sensitive adhesive layer ｐｓａ２ (μm), and the thickness T of the protective layer in the second polarizing plate ｐｒｏ２ (μm) satisfies the following relationship: (A ２ ×T ｐｏｌ２ ) × (Cｐｓａ２ ×T ｐｓａ２ ) / T ｐｒｏ２ =K ２ ≦300×10 ２ (μm ３ / hr). In one embodiment, the K １ and K. ２ are 200 x 10 ２ (μm ３ / hr) or less. ｐｓａ１ In one embodiment, the thickness T of the second polarizer is 100 (μm / hr) or less. ｐｏｌ２ In one embodiment, the K １ and K. ２ are 150 x 10 ２ (μm ３ / hr) or less. ｐｏｌ１ In one embodiment, the thickness T of the first pressure-sensitive adhesive layer is 10 μm or less. ｐｓａ１ and the thickness T of the second pressure-sensitive adhesive layer ｐｓａ２ and are each 10 μm to 22 μm. In one embodiment, the through holes are formed in the corners of the first polarizing plate and the second polarizing plate. In one embodiment, the distance from the center in the longitudinal direction to the end in the longitudinal direction when the first polarizer and the second polarizer are viewed in plan is defined as L １ The distance in the longitudinal direction from the center of the first polarizer and the second polarizer in the longitudinal direction to the center of the through hole is L ２ , the distance from the center to the end of the first polarizer and the second polarizer in the lateral direction is W １ The distance in the lateral direction from the center of the first polarizer and the second polarizer in the lateral direction to the center of the through hole is W ２ When the through holes are formed in the first polarizer and the second polarizer, the through holes are formed in a range of 0.85≦L ２ / L １ ≦0.99 and 0.50≦W ２ / W １≦0.99. In one embodiment, the diameter of the through hole is 10 mm or less. In one embodiment, the aspect ratios of the first polarizing plate and the second polarizing plate are each 1.3 to 2.5. According to another aspect of the present invention, there is provided an image display device. The image display device includes an image display cell and the above-described set of polarizing plates, wherein the first polarizing plate is disposed on the viewing side of the image display cell and the second polarizing plate is disposed on the back side of the image display cell.

[0006] According to an embodiment of the present invention, a polarizing plate set can be provided in which the misalignment at the through-hole portions of each polarizing plate is small and the difference between the misalignment amount of the viewer-side polarizing plate and the back-side polarizing plate is very small. The small misalignment at the through-hole portions of each polarizing plate can synergistically exert its effects when used as a polarizing plate set. The very small difference in misalignment amount has a significant design advantage when the polarizing plate set is applied to an image display device. For example, the polarizing plate set can be applied to an image display device in which only the camera unit is a non-display area and / or a bezel-less image display device.

[0007] FIG. 1 is a schematic plan view illustrating a first polarizing plate and a second polarizing plate in a polarizing plate set according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of each of the first polarizing plate and the second polarizing plate in the polarizing plate set of FIG. 1 taken along line II-II, illustrating the respective arrangement positions of the first polarizing plate and the second polarizing plate. FIG. 3 is a schematic cross-sectional view of an image display device including the polarizing plate set of FIG. 1. FIG. 4 is an enlarged cross-sectional view of a main part illustrating misalignment in a through-hole portion in a polarizing plate used in the polarizing plate set according to an embodiment of the present invention. FIG. 5 is a schematic plan view illustrating the position at which a through-hole is formed in a polarizing plate used in the polarizing plate set according to an embodiment of the present invention. FIG. 6 is a schematic perspective view of an example of a reflective polarizer that can be used for the second polarizing plate in the polarizing plate set according to an embodiment of the present invention.

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

[0009] A. Overview of Polarizing Plate Sets FIG. 1 is a schematic plan view illustrating a first polarizing plate and a second polarizing plate in a polarizing plate set according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of the first polarizing plate and the second polarizing plate in the polarizing plate set of FIG. 1 taken along line II-II; and FIG. 3 is a schematic cross-sectional view of an image display device including the polarizing plate set of FIG. 1. The polarizing plate set 100 in the illustrated example comprises a first polarizing plate 10 and a second polarizing plate 20. The first polarizing plate and the second polarizing plate each have a rectangular shape having long and short sides corresponding to the shape of the image display cell in a planar view. Note that the term "rectangular shape" used herein also encompasses shapes including irregularly shaped portions, such as the rounded shape in which each vertex is chamfered, as shown in FIG. 1. As shown in FIG. 3, the first polarizing plate 10 is disposed on the viewing side of the image display cell 120, and the second polarizing plate 20 is disposed on the rear side of the image display cell 120. In the illustrated example, the first polarizing plate 10 includes a first polarizer 11, a protective layer (outer protective layer) 12 arranged on the viewing side of the first polarizer 11, a protective layer (inner protective layer) 13 arranged on the image display cell side of the first polarizer 11, and a first pressure-sensitive adhesive layer 14 arranged as the outermost layer on the image display cell 120 side. The first pressure-sensitive adhesive layer 14 is used to attach the first polarizing plate 10 to the image display cell 120. Depending on the purpose, one of the protective layers 12 and 13 may be omitted. The second polarizing plate 20 includes a second polarizer 21, a reflective polarizer 26 arranged on the back side of the second polarizer 21 (the side opposite the image display cell), a protective layer (inner protective layer) 23 arranged on the image display cell side of the second polarizer 21, and a second pressure-sensitive adhesive layer 24 arranged as the outermost layer on the image display cell 120 side. The second pressure-sensitive adhesive layer 24 is used to attach the second polarizing plate 20 to the image display cell 120. In the second polarizing plate 20, a reflective polarizer 26 is arranged instead of an outer protective layer. That is, in the second polarizing plate 20, the reflective polarizer 26 also serves as the outer protective layer. Although the outer protective layer of the second polarizing plate is omitted in the illustrated example, the reflective polarizer 26 may be arranged on the back side of the outer protective layer (the side opposite to the image display cell).The reflective polarizer 26 is attached to the second polarizer 21 or the outer protective layer (if present) via any suitable adhesive layer (for example, with a thickness of 2 μm to 20 μm).

[0010] In an embodiment of the present invention, the first polarizing plate 10 has a through-hole 15, and the second polarizing plate 20 has a through-hole 25. The through-holes 15 and 25 are formed at or near the ends of the first polarizing plate and the second polarizing plate, respectively, and at positions corresponding to each other. Forming the through-holes can prevent adverse effects on the performance of a camera, for example, when the image display device has a built-in camera. Furthermore, forming the through-holes at or near the ends of the polarizing plates can minimize the effect of the through-holes on image display (e.g., light leakage through the through-holes) when the polarizing plates are used in an image display device. The through-holes can be formed by various methods, such as laser processing, cutting with an end mill, or punching with a Thomson blade or Pinnacle (registered trademark) blade. In this specification, "formed at positions corresponding to each other" means that the through-holes overlap when the two polarizing plates are stacked.

[0011] As shown in FIG. 1, the first polarizer 11 has an absorption axis Ab in the short side direction. １ The second polarizer 21 has an absorption axis Ab in the long side direction. ２ The rectangular film tends to shrink easily in the long-side direction and not easily in the short-side direction. Furthermore, the polarizer (and consequently the polarizing plate) tends to shrink easily in the absorption axis direction. Therefore, by aligning the absorption axis direction of the second polarizing plate, which is less likely to shrink due to the inclusion of a reflective polarizer, with the long-side direction of the film (the direction in which it is more likely to shrink), and by aligning the absorption axis direction of the first polarizing plate, which is more likely to shrink than the second polarizing plate, with the short-side direction of the film (the direction in which it is less likely to shrink), it is possible to reduce the misalignment at the through-hole portions of each polarizing plate and to reduce the difference in misalignment between the first polarizing plate and the second polarizing plate.

[0012] If necessary, the first polarizing plate 10 and / or the second polarizing plate 20 may be provided with a retardation layer. The type, number, combination, arrangement position, and characteristics of the retardation layer can be appropriately set depending on the purpose. For example, the retardation layer may be a λ / 2 plate, a λ / 4 plate, or a laminate thereof. λ / 2 plates and λ / 4 plates typically have refractive index characteristics of nx>ny≧nz. The λ / 2 plate preferably has an in-plane retardation Re(550) of 180 nm to 320 nm, and the λ / 4 plate preferably has an in-plane retardation Re(550) of 100 nm to 200 nm. Furthermore, for example, the retardation layer may be a laminate of a negative B plate (nx>ny>nz) and a positive C plate (nz>nx=ny) or a positive B plate (nz>nx>ny). In this specification, "Re(λ)" refers to an in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, "Re(550)" refers to an in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). "Rth(λ)" refers to a retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" refers to a retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). "nx" is the refractive index in the direction in which the in-plane refractive index is greatest (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.

[0013] The components of the polarizing plate set will be specifically described below. The first polarizing plate and the second polarizing plate will be collectively referred to as polarizing plates, the first polarizer and the second polarizer as polarizers, the protective layers of the first polarizing plate and the second polarizing plate as protective layers, and the first adhesive layer and the second adhesive layer as adhesive layers. Therefore, for example, when referring to a "polarizing plate," it can mean "each of the first polarizing plate and the second polarizing plate." On the other hand, when it is necessary to separately describe the first polarizing plate and the second polarizing plate, for example, "first" or "second" will be specified.

[0014] B. Polarizing Plate B-1. Overall Configuration of Polarizing Plate In one embodiment, the first polarizing plate 10 preferably satisfies the following relationship: (A １ ×T ｐｏｌ１ ) × (C ｐｓａ１ ×T ｐｓａ１ ) / T ｐｒｏ１ =K １ ≦300×10 ２ (μm ３ / hr) where A １ is the distance (μm) from the outermost portion of the first pressure-sensitive adhesive layer 14 on the image display cell 120 side to the center of the first polarizer 11 in the thickness direction; T ｐｏｌ１ is the thickness (μm) of the first polarizer 11; C ｐｓａ１ is the creep value (μm / hr) of the first pressure-sensitive adhesive layer 14; T ｐｓａ１ is the thickness (μm) of the first pressure-sensitive adhesive layer 14; T ｐｒｏ１ is the thickness (μm) of the protective layer in the first polarizing plate 10. Similarly, the second polarizing plate 20 preferably satisfies the following relationship: (A ２ ×T ｐｏｌ２ ) × (C ｐｓａ２ ×T ｐｓａ２ ) / T ｐｒｏ２ =K ２ ≦300×10 ２ (μm ３ / hr), where A ２ is the distance (μm) from the outermost portion of the second pressure-sensitive adhesive layer 24 on the image display cell 120 side to the center of the second polarizer 21 in the thickness direction; T ｐｏｌ２ is the thickness of the second polarizer 21 (μm); Cｐｓａ２ is the creep value (μm / hr) of the second pressure-sensitive adhesive layer 24; T ｐｓａ２ is the thickness (μm) of the second adhesive layer 24; T ｐｒｏ２ is the thickness (μm) of the protective layer in the second polarizing plate 20. In this specification, "creep value" means the creep value at 85°C. The creep value can be measured, for example, by the following procedure: the adhesive constituting the adhesive layer is attached to a support plate. With the support plate to which the adhesive is attached being fixed, a load of 500 g is applied vertically downward. One hour after applying the load, the amount of displacement of the adhesive from the support plate is measured, and this amount of displacement is taken as the creep value (μm / hr). Furthermore, the thickness T of the protective layer in the above relational expression is ｐｒｏ１ is calculated from the formula: "total thickness of the first polarizing plate - thickness of the first adhesive layer - thickness of the first polarizer". ｐｒｏ１ is the total thickness of the total thickness of the protective layer 12 and the protective layer 13, the thickness of the adhesive layer for attaching the protective layer (including the adhesive layer when the polarizer or the protective film is attached to the reflective polarizer via the adhesive layer), and the thickness of the surface treatment layer formed on the protective layer 12 as needed. ｐｒｏ２ The same applies to K. １ value and K ２ The values ​​are preferably 250×10 ２ (μm ３ / hr) or less, and more preferably 200 × 10 ２ (μm ３ / hr) or less, and particularly preferably 150 × 10 ２ (μm ３ / hr) or less. １ value and K ２ The values ​​are collectively referred to simply as the K value. The same applies to the distance A, the creep value, the thickness of the adhesive layer, and the thickness of the protective layer. The lower limit of the K value is, for example, 15×10 ２ (μm ３ / hr). If the K value is within this range, the displacement of the through-hole portion (substantially, the displacement of the pressure-sensitive adhesive layer) can be significantly suppressed. The technical significance of setting the K value to a predetermined value or less is as follows: the displacement of the pressure-sensitive adhesive layer increases when the moment force applied to the pressure-sensitive adhesive layer and the ease of movement of the pressure-sensitive adhesive layer itself are large, and decreases when the restraining force against the movement of the pressure-sensitive adhesive layer is large. The moment force applied to the pressure-sensitive adhesive layer may be related to the distance from the image display cell to which the polarizing plate is attached to the polarizer and the thickness of the polarizer; the ease of movement of the pressure-sensitive adhesive layer itself may be related to the softness and thickness of the pressure-sensitive adhesive layer; and the restraining force against the movement of the pressure-sensitive adhesive layer may be related to the thickness of the protective layer. The moment force can be reduced by reducing the distance from the image display cell to the polarizer and the thickness of the polarizer; the creep value of the pressure-sensitive adhesive layer can be set to a predetermined value or less (the pressure-sensitive adhesive layer can be made hard) and the thickness of the pressure-sensitive adhesive layer can be made thin, making the pressure-sensitive adhesive layer itself less likely to move; the thickness T of the protective layer ｐｒｏ By setting the value of K in a predetermined range, it is possible to set the restraining force against the movement of the pressure-sensitive adhesive layer in an appropriate range. Therefore, by adjusting each of the above requirements to control the K value to a predetermined value or less, it is possible to significantly suppress the slippage of the pressure-sensitive adhesive layer. Specifically, the distance A is preferably 80 μm or less, more preferably 50 μm or less. The lower limit of the distance A can be, for example, 10 μm. The creep value C ｐｓａ is preferably 140 μm / hr or less, more preferably 130 μm / hr or less, even more preferably 120 μm / hr or less, and particularly preferably 100 μm / hr or less. The lower limit of the creep value may be, for example, 50 μm / hr. The thickness T of the protective layer ｐｒｏ The thickness T of the adhesive layer is preferably 15 μm to 65 μm, and more preferably 15 μm to 55 μm. ｐｓａ is preferably 22 μm or less, and more preferably 10 μm to 22 μm. ｐｓａ is too small, and / or the thickness T ｐｓａ If the thickness T of the protective layer is too small, stress relaxation becomes difficult and the risk of cracking or peeling increases. ｐｒｏ If it is too small, it may be difficult to adjust the curl.

[0015] As shown in FIG. 4 , a polarizing plate (the illustrated example is a first polarizing plate 10) is attached to a glass plate (which may correspond to the substrate of an image display cell) 130 and subjected to a heating test at 85°C for 120 hours. The displacement D at the through-hole portion is, for example, 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, particularly preferably 120 μm or less, particularly preferably 100 μm or less, and most preferably 80 μm or less. The smaller the displacement D, the more preferable it is. In one embodiment, the lower limit of the displacement D is 10 μm, and in another embodiment, 20 μm. The displacement D refers to the maximum portion of the polarizing plate that is farthest from the through-hole portion when viewed in cross section. The reference point for the through-hole portion may typically be the lower end of the adhesive layer. That is, when the polarizing plate shifts (to the right in the illustrated example) mainly due to shrinkage of the polarizer, the adhesive layer 14 remains on the adhered glass plate 130, and the shift is recognized in the through-hole portion. As shown in Fig. 4 , the polarizing plate typically shifts away from the through-hole portion (right side of Fig. 4 ), and the opposing portion shifts so as to protrude into the through-hole (left side of Fig. 4 ). According to the embodiment of the present invention, both the first polarizing plate and the second polarizing plate can reduce the shift in the through-hole portion (effectively, the shift of the adhesive layer) as described above, and therefore, when the polarizing plates are used as a set, the effects can be synergistically exhibited.

[0016] The difference (absolute value) between the amount of misalignment of the first polarizing plate and the amount of misalignment of the second polarizing plate is, for example, 85 μm or less, preferably 80 μm or less, more preferably 60 μm or less, even more preferably 40 μm or less, and particularly preferably 30 μm or less. The smaller the difference in the amount of misalignment, the better. The lower limit of the difference in the amount of misalignment may be, for example, 3 μm. According to an embodiment of the present invention, the difference between the amount of misalignment of the first polarizing plate and the amount of misalignment of the second polarizing plate can be made very small. As a result, the polarizing plate set can be applied to an image display device in which only the camera unit is a non-display area and / or a bezel-less image display device.

[0017] The dimensional shrinkage of the polarizing plate after the 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, the better, and the lower limit of the dimensional shrinkage can be, for example, 0.01%. The dimensional shrinkage is calculated using the following formula. The dimensional shrinkage is the dimensional shrinkage of the entire polarizing plate attached to the glass plate, and in the case where the polarizing plate further has an optically functional layer (for example, a retardation layer, a reflective polarizer), it means the dimensional shrinkage of the entire polarizing plate including the optically functional layer. In the formula below, the "dimension" refers to the dimension in the absorption axis direction of the polarizing plate (substantially, the polarizer). Dimensional shrinkage (%) = {(dimension before heating test - dimension after heating test) / dimension before heating test} x 100

[0018] In the polarizing plate, the through holes are formed at any appropriate position at or near the edge depending on the purpose. In one embodiment, the through holes 15 and 25 are formed at the respective corners of the polarizing plate as shown in FIG. 1 . The positions at which the through holes are formed are not limited to the corners. The through holes may be formed at approximately the center of the longitudinal edge of the polarizing plate, at a predetermined position at the longitudinal edge, at approximately the center of the lateral edge, or at a predetermined position at the lateral edge. Furthermore, a plurality of through holes may be formed, or a combination of a through hole and a notch may be formed.

[0019] In one embodiment, as shown in FIG. 5, the distance from the center of the polarizer in the longitudinal direction to the end of the polarizer in the longitudinal direction is L １ , the distance in the longitudinal direction from the center of the polarizer in the longitudinal direction to the center of the through-hole is L ２ , the distance from the center of the polarizer in the lateral direction to the end in the lateral direction is W １ The distance in the lateral direction from the center of the polarizer in the lateral direction to the center of the through-hole is W ２ When the through hole is set to 0.85≦L ２ / L １ ≦0.99 and 0.50≦W ２ / W １ It is formed at a position that satisfies the condition L≦0.99. ２ / L １is more preferably 0.90 to 0.97, and even more preferably 0.92 to 0.96. ２ / W １ is more preferably 0.75 to 0.95.

[0020] The diameter R of the through hole 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 diameter of the through hole may be, for example, 2 mm, or may be, for example, 1.5 mm. The ratio D / R of the deviation amount D to the diameter R of the through hole is preferably 15% or less, more preferably 10% or less, even more preferably 6% or less, and particularly preferably 5% or less. On the other hand, the lower limit of D / R is preferably as small as possible. According to embodiments of the present invention, since the deviation amount D is very small as described above, D / R can be kept within this range even if the diameter of the through hole is reduced. Therefore, even if the diameter of the through hole is reduced, adverse effects on camera performance can be substantially prevented. As a result, the polarizing plate used in embodiments of the present invention can be applied to image display devices in which only the camera portion is a non-display area and / or bezel-less image display devices.

[0021] The polarizing plate preferably has an aspect ratio of 1.3 to 2.5. In this case, the size of the polarizing plate is, for example, 145 mm to 155 mm in height and 65 mm to 75 mm in width, or 230 mm to 240 mm in height and 140 mm to 150 mm in width. That is, the polarizing plate according to the embodiment of the present invention can be suitably used in smartphones or tablet PCs. The size of a smartphone may be, for example, 120 mm to 200 mm in height and 30 mm to 120 mm in width.

[0022] B-2. Polarizer A polarizer is typically made of a resin film containing a dichroic material. Any appropriate resin film that can be used as a polarizer can be adopted as the resin film. A typical resin film is a polyvinyl alcohol-based resin (hereinafter referred to as a "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

[0023] A specific example of a polarizer composed of a single-layer resin film is a PVA-based resin film that has been subjected to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or while dyeing. Alternatively, the stretching may be performed before dyeing. If necessary, the PVA-based resin film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based resin film in water and washing it before dyeing, it is possible to clean off dirt and antiblocking agents on the surface of the PVA-based resin film and also to swell the PVA-based resin film, thereby preventing uneven dyeing and the like.

[0024] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the solution to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching may, if necessary, further involve in-air stretching of the laminate at an elevated temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. The obtained resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled from the resin substrate / polarizer laminate and any appropriate protective layer depending on the purpose may be laminated on the peeled surface. Details of such methods for producing polarizers are described in, for example, JP-A-2012-73580 and Japanese Patent No. 6,470,455. The descriptions of these patent documents are incorporated herein by reference.

[0025] The thickness of the polarizer is preferably 20 μm or less, more preferably 12 μm or less, and even more preferably 10 μm or less. The lower limit of the polarizer thickness is 1 μm in one embodiment, and 3 μm in another embodiment. When the polarizer thickness is within this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0026] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0027] B-3. ​​Protective Layer The protective layers 12, 13, and 23 are formed of any appropriate film that can be used as a protective layer for a polarizer. Specific examples of materials that can be the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxy resins, and silicone resins. Other examples include glassy polymers such as siloxane polymers. Polymer films described in JP 2001-343529 A (WO 01 / 37007) can also be used. Examples of materials that can be used for this film include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in its side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in its side chain, such as a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extrusion molded product of the above resin composition.

[0028] The outer protective layer (particularly the outer protective layer 12 of the first polarizing plate) may be subjected to a surface treatment such as a hard coat treatment, an anti-reflection treatment, an anti-sticking treatment, or an anti-glare treatment, as needed. Additionally / alternatively, the outer protective layer may be subjected to a treatment to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptically) circular polarization function or an ultra-high phase difference), as needed. By performing such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate set may also be suitably applied to image display devices that can be used outdoors.

[0029] The inner protective layers 13, 23 are preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm and the thickness direction retardation Rth(550) is -10 nm to +10 nm. Here, "Re(λ)" is the in-plane retardation measured at 23°C with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation measured at 23°C with light having a wavelength of 550 nm. Re(λ) is calculated by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). "Rth(λ)" is the thickness direction retardation measured at 23°C with light having a wavelength of λ nm. For example, "Rth(550)" is the thickness direction retardation measured at 23°C with light having a wavelength of 550 nm. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d (nm) is the thickness of the layer (film), where nx is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), ny is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and nz is the refractive index in the thickness direction.

[0030] 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, and preferably 20 μm to 40 μm. If a surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer. The "thickness of the protective layer" here refers to the thickness of each of the outer protective layers 12, 22 and the inner protective layer 13, and is calculated by the formula T ｐｒｏ１ and T ｐｒｏ２ is different from.

[0031] B-4. Pressure-Sensitive Adhesive Layer As described above, the pressure-sensitive adhesive layer is used to bond the polarizing plate to the image display cell. The pressure-sensitive adhesive layer can typically be composed of an acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition). The acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a primary component. The (meth)acrylic polymer can be contained in the pressure-sensitive adhesive composition in an amount of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more of the solid content of the pressure-sensitive adhesive composition. The (meth)acrylic polymer contains alkyl(meth)acrylate as a primary monomer unit. Note that (meth)acrylate refers to acrylate and / or methacrylate. The alkyl(meth)acrylate can be contained in an amount of, preferably 80% by weight or more, more preferably 90% by weight or more of the monomer components forming the (meth)acrylic polymer. Examples of the alkyl group of the alkyl(meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. A preferred alkyl (meth)acrylate is butyl acrylate. Examples of monomers (copolymerizable monomers) constituting the (meth)acrylic polymer include, in addition to alkyl (meth)acrylates, carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocycle-containing vinyl monomers. Representative examples of copolymerizable monomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The acrylic pressure-sensitive adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of silane coupling agents include epoxy group-containing silane coupling agents. Examples of crosslinking agents include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Furthermore, the acrylic pressure-sensitive adhesive composition may contain an antioxidant and / or a conductive agent. As described above, the thickness of the pressure-sensitive adhesive layer is preferably 22 μm or less, and more preferably 10 μm to 22 μm.Details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described in, for example, JP 2006-183022 A, JP 2015-199942 A, JP 2018-053114 A, JP 2016-190996 A, and WO 2018 / 008712 A, and the descriptions in these publications are incorporated herein by reference.

[0032] Storage modulus G of adhesive layer at -40°C ２ ' is preferably 1.0 x 10 ５ (Pa) or more, more preferably 1.0 × 10 ６ (Pa) or more, and more preferably 1.0 × 10 ７ (Pa) or more, and particularly preferably 1.0 × 10 ８ (Pa) or more. Storage modulus G ２ ' is, for example, 1.0 x 10 ９ (Pa) or less.

[0033] B-5. Reflective Polarizer As described above, the reflective polarizer 26 can be provided on the side of the second polarizing plate 20 opposite the image display cell 120 (back side). By providing a reflective polarizer, the second polarizing plate is less likely to shrink than the first polarizing plate. As a result, by aligning the absorption axis direction of the second polarizing plate with the long side direction of the film (the direction in which it shrinks easily) and the absorption axis direction of the first polarizing plate with the short side direction of the film (the direction in which it shrinks less), it is possible to reduce the misalignment at the through-hole portions of the respective polarizing plates and to reduce the difference in misalignment between the first polarizing plate and the second polarizing plate.

[0034] A reflective polarizer has the function of transmitting polarized light in a specific polarization state (polarization direction) and reflecting light in other polarization states. The reflective polarizer may be a linear polarization separation type or a circular polarization separation type. Hereinafter, a linear polarization separation type reflective polarizer will be described as an example. Note that an example of a circular polarization separation type reflective polarizer is a laminate of a film on which a cholesteric liquid crystal is fixed and a λ / 4 plate.

[0035] FIG. 6 is a schematic perspective view of an example of a reflective polarizer. A reflective polarizer is a multilayer laminate in which birefringent layers A and substantially non-birefringent layers B are alternately stacked. For example, the total number of layers in such a multilayer laminate can be 50 to 1,000. In the illustrated example, the refractive index nx in the x-axis direction of layer A is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction of layer B and the refractive index ny in the y-axis direction are substantially identical. Therefore, the refractive index difference between layer A and layer B is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction is the reflection axis, and the y-axis direction is the transmission axis. The refractive index difference between layer A and layer B in the x-axis direction is preferably 0.2 to 0.3. The x-axis direction corresponds to the stretching direction of the reflective polarizer in the manufacturing method of the reflective polarizer.

[0036] The A layer is preferably made of a material that exhibits birefringence upon stretching. Typical examples of such materials include naphthalenedicarboxylic acid polyesters (e.g., polyethylene naphthalate), polycarbonates, and acrylic resins (e.g., polymethyl methacrylate). Polyethylene naphthalate is preferred. The B layer is preferably made of a material that does not substantially exhibit birefringence upon stretching. Typical examples of such materials include copolyesters of naphthalenedicarboxylic acid and terephthalic acid.

[0037] A reflective polarizer transmits light having a first polarization direction (e.g., p-wave) and reflects light having a second polarization direction (e.g., s-wave) perpendicular to the first polarization direction at the interface between the A layer and the B layer. At the interface between the A layer and the B layer, part of the reflected light is transmitted as light having the first polarization direction and part is reflected as light having the second polarization direction. This reflection and transmission are repeated many times inside the reflective polarizer, thereby increasing the light utilization efficiency.

[0038] In one embodiment, the reflective polarizer may include a reflective layer R as the outermost layer on the side opposite to the image display cell, as shown in Fig. 6. By providing the reflective layer R, light that is ultimately unused and returns to the outermost part of the reflective polarizer can be further utilized, thereby further improving the light utilization efficiency. The reflective layer R typically exhibits a reflective function by virtue of a multilayer structure of polyester resin layers.

[0039] The total thickness of the reflective polarizer can be appropriately set depending on the purpose, the total number of layers included in the reflective polarizer, etc. The total thickness of the reflective polarizer is preferably 10 μm to 150 μm.

[0040] Examples of reflective polarizers that can be used include those described in JP-A-9-507308 and JP-A-2013-235259. Commercially available reflective polarizers may be used as they are, or may be used after secondary processing (e.g., stretching). Examples of commercially available reflective polarizers include those manufactured by 3M under the trade names DBEF and APF.

[0041] C. Image Display Device As described above, the polarizing plate set according to the embodiment of the present invention can be suitably applied to an image display device. Accordingly, an image display device is also encompassed in the embodiments of the present invention. The image display device includes an image display cell and a set of polarizing plates. The set of polarizing plates is the set of polarizing plates according to the embodiment of the present invention described in sections A and B above. As shown in FIG. 3 , the image display device 200 has an image display cell 120, a first polarizing plate 10 arranged on the viewing side of the image display cell 120, and a second polarizing plate 20 arranged on the back side of the image display cell 120.

[0042] Examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, and quantum dot display devices. Liquid crystal display devices are preferred, as the effect of using polarizing plates is significant.

[0043] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are by weight.

[0044] (1) Misalignment Amount The first polarizing plate and the second polarizing plate in the polarizing plate sets obtained in the Examples and Comparative Examples were each attached to a glass plate (manufactured by Matsunami Glass Co., Ltd., 350 mm long x 250 mm wide x 1.1 mm thick) via an adhesive layer to prepare a test sample. Each test sample was subjected to a heating test at 85°C for 120 hours. After the test, the misalignment amount of the first polarizing plate or the second polarizing plate (effectively the first adhesive layer or the second adhesive layer) at the through-hole portion was measured using an optical microscope (MX61L) manufactured by Olympus Corporation. The measurement was performed on three test samples each, and the maximum of the three measured values ​​was taken as the misalignment amount.

[0045] Production Example 1 A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts by weight of ethyl acetate were charged relative to 100 parts of the monomer mixture (solid content). Nitrogen gas was introduced with gentle stirring to replace the atmosphere with nitrogen, and the liquid temperature in the flask was maintained at around 55°C, allowing a polymerization reaction to occur for 8 hours to prepare a solution of acrylic polymer (a) having a weight average molecular weight (Mw) of 1,560,000. 0.1 parts of an isocyanate crosslinking agent (trade name: Takenate D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 parts of benzoyl peroxide (trade name: Niper BMT 40SV, manufactured by Nippon Oil & Fats Co., Ltd.), 0.3 parts of a thiol group-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy group amount: 30%, thiol equivalent: 450 g / mol), and 0.2 parts of an antioxidant (trade name: Irganox 1010, hindered phenol-based, manufactured by BASF Japan Ltd.) were blended relative to 100 parts of the solids content of the obtained solution of acrylic polymer (a), to obtain a pressure-sensitive adhesive composition A.

[0046] Production Example 2 A solution of acrylic polymer (b) having a weight average molecular weight (Mw) of 1,570,000 was prepared in the same manner as in Production Example 1, except that a monomer mixture containing 81.8 parts of butyl acrylate, 16 parts of phenoxyethyl acrylate, 1.5 parts of N-vinyl-2-pyrrolidone, 0.3 parts of acrylic acid, and 0.4 parts of 4-hydroxybutyl acrylate was used. A pressure-sensitive adhesive composition B was obtained in the same manner as in Production Example 1, except that the acrylic polymer (b) was used, 0.2 parts of a thiol group-containing silane coupling agent (trade name: X-41-1056, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy group content: 30%, thiol equivalent: 450 g / mol) was used as the silane coupling agent, no antioxidant was used, and 0.5 parts of lithium bis(trifluoromethanesulfonyl)imide (manufactured by Mitsubishi Materials Corporation) was further added.

[0047] Production Example 3 A solution of an acrylic polymer (c) having a weight average molecular weight (Mw) of 1,500,000 was prepared in the same manner as in Production Example 1, except that a monomer mixture containing 80.3 parts of butyl acrylate, 16 parts of phenoxyethyl acrylate, 3 parts of N-vinyl-2-pyrrolidone, 0.3 parts of acrylic acid, and 0.4 parts of 4-hydroxybutyl acrylate was used. A pressure-sensitive adhesive composition C was obtained in the same manner as in Production Example 1, except that the acrylic polymer (c) was used, the amount of silane coupling agent was 0.1 parts, and 5 parts of a conductive agent (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, an ionic liquid manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added.

[0048] <Production Example 4> A solution of an acrylic polymer (d) having a weight average molecular weight (Mw) of 1,650,000 was prepared in the same manner as in Production Example 1. 0.1 parts of an isocyanate crosslinking agent (trade name: Takenate D110N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 parts of benzoyl peroxide (trade name: Niper BMT 40SV, manufactured by Nippon Oil & Fats Co., Ltd.), and 0.2 parts of an acetoacetyl group-containing silane coupling agent (trade name: A-100, manufactured by Soken Chemical & Engineering Co., Ltd.) were blended with 100 parts of the solids content of the obtained solution of the acrylic polymer (d) to obtain a pressure-sensitive adhesive composition D.

[0049] <Production Example 5> A pressure-sensitive adhesive composition E was obtained in the same manner as in Production Example 1, except that 0.2 parts of a thiol group-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy group content: 30%, thiol equivalent: 450 g / mol) was used as the silane coupling agent.

[0050] Example 1 (Preparation of First Polarizing Plate) A film (thickness 12 μm) obtained by incorporating iodine into a long polyvinyl alcohol (PVA)-based resin film and uniaxially stretching it in the longitudinal direction (MD direction) was used as the polarizer (first polarizer). A long HC-TAC film serving as an outer protective layer and a long acrylic resin film (thickness 20 μm) serving as an inner protective layer were bonded to both sides of this polarizer, with their longitudinal directions aligned. The HC-TAC film was a triacetyl cellulose (TAC) film (thickness 25 μm) with a hard coat (HC) layer (thickness 7 μm) formed on it, and the TAC film was bonded to the polarizer side. A pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer: thickness 20 μm) was formed on the surface of the inner protective layer using pressure-sensitive adhesive composition B, to obtain a first polarizer having a configuration of outer protective layer / first polarizer / inner protective layer / first pressure-sensitive adhesive layer. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and through holes with a diameter of 3.9 mm were formed in the corners of the first polarizing plate so that the absorption axis direction of the first polarizer was aligned with the short side direction.

[0051] (Preparation of Second Polarizing Plate) A polarizing plate was obtained in the same manner as the first polarizing plate, except that a TAC film (thickness: 25 μm) was used instead of the HC-TAC film as the outer protective layer. Furthermore, a reflective polarizer (thickness: 26 μm) was bonded to the surface of the outer protective layer via a conventional pressure-sensitive adhesive layer (thickness: 12 μm), and a second pressure-sensitive adhesive layer (thickness: 20 μm) was formed on the surface of the reflective polarizer using pressure-sensitive adhesive composition E, thereby obtaining a second polarizing plate having a configuration of reflective polarizer / outer protective layer / second polarizer / inner protective layer / second pressure-sensitive adhesive layer. The second polarizing plate was punched out to a size of 148 mm long and 70 mm wide, and 3.9 mm diameter through-holes were formed in the corners. The punching was performed so that the absorption axis direction of the second polarizer was aligned in the longitudinal direction.

[0052] (Polarizing Plate Set) The first polarizing plate obtained as described above was used as the viewer-side polarizing plate, and the second polarizing plate was used as the rear-side polarizing plate, to form a polarizing plate set for this example. The obtained polarizing plate set was subjected to the evaluation of the amount of misalignment described above. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate. In Table 1, "0°" means the longitudinal direction, and "90°" means the lateral direction.

[0053] Comparative Example 1 A polarizing plate set was obtained in the same manner as in Example 1, except that a first polarizing plate was prepared by punching out so that the absorption axis direction of the first polarizer was the longitudinal direction, and a second polarizing plate was prepared by punching out so that the absorption axis direction of the second polarizer was the lateral direction. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0054] Example 2 (Preparation of First Polarizing Plate) A first polarizing plate having a structure of outer protective layer / first polarizer / inner protective layer / first pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that a first pressure-sensitive adhesive layer (thickness: 20 μm) was formed using pressure-sensitive adhesive composition C. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and through-holes with a diameter of 3.9 mm were formed in the corners. At this time, the punching was performed so that the absorption axis direction of the first polarizer was in the short direction.

[0055] (Preparation of Second Polarizing Plate) A long, amorphous, isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of approximately 75°C was used as the thermoplastic resin substrate. One side of the resin substrate was subjected to a corona treatment. A PVA-based resin (100 parts by weight of a 9:1 mixture of 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 "GOHSEFIRM") was dissolved in water to prepare an aqueous PVA 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 13 μm-thick PVA-based resin layer, producing a laminate. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (in-air auxiliary stretching treatment). Next, the laminate was immersed for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40°C (insolubilization treatment), then immersed for 60 seconds in a dyeing bath (an iodine aqueous solution obtained by blending iodine and potassium iodide with 100 parts by weight of water in a weight ratio of 1:7) having a liquid temperature of 30°C while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment), then immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40°C (crosslinking treatment). The laminate was then immersed in a boric acid aqueous solution (boric acid concentration 4 wt %, potassium iodide concentration 5 wt %) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls operating at different peripheral speeds to a total stretch ratio of 5.5 (underwater stretching treatment). The laminate was then immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment). The laminate was then dried in an oven maintained at approximately 90°C, and brought into contact with a SUS heated roll maintained at a surface temperature of approximately 75°C (drying shrinkage treatment). In this way, a polarizer having a thickness of approximately 5 μm was formed on the resin substrate, and a laminate having a resin substrate / second polarizer configuration was obtained.A TAC film (20 μm thick) was bonded to the polarizer surface (the surface opposite to the resin substrate) of the resulting laminate as an inner protective layer. The resin substrate was then peeled off, and a reflective polarizer (26 μm thick) was bonded to the peeled surface via a conventional pressure-sensitive adhesive layer (12 μm thick). A pressure-sensitive adhesive layer (20 μm thick) was formed on the surface of the inner protective layer using pressure-sensitive adhesive composition D, yielding a second polarizing plate having a configuration of reflective polarizer / second polarizer / inner protective layer / second pressure-sensitive adhesive layer. The second polarizing plate was punched out to a size of 148 mm long and 70 mm wide, and a through-hole with a diameter of 3.9 mm was formed in the corner. The punching was performed so that the absorption axis direction of the second polarizer was aligned in the longitudinal direction.

[0056] (Polarizing Plate Set) The first polarizing plate obtained as described above was used as the viewer-side polarizing plate, and the second polarizing plate was used as the rear-side polarizing plate to form a polarizing plate set for this example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0057] Comparative Example 2 A polarizing plate set was obtained in the same manner as in Example 2, except that a first polarizing plate was prepared by punching out so that the absorption axis direction of the first polarizer was the longitudinal direction, and a second polarizing plate was prepared by punching out so that the absorption axis direction of the second polarizer was the lateral direction. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0058] Example 3 (Preparation of First Polarizing Plate) A first polarizing plate having a structure of outer protective layer / first polarizer / inner protective layer / first adhesive layer was obtained in the same manner as in Example 1, except that a cycloolefin resin film (thickness 13 μm) was used as the inner protective layer instead of the acrylic resin film, and that adhesive composition C was used instead of adhesive composition B to form the first adhesive layer (thickness 20 μm). The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and through holes with a diameter of 3.9 mm were formed in the corners. The punching was performed so that the absorption axis direction of the first polarizer was in the short direction.

[0059] (Preparation of Second Polarizing Plate) A laminate having a resin substrate / second polarizer structure was obtained in the same manner as in Example 2. A TAC film (20 μm thick) was attached as an inner protective layer to the polarizer surface (the surface opposite the resin substrate) of the obtained laminate. The resin substrate was then peeled off, and a reflective polarizer (26 μm thick) was attached to the peeled surface via a conventional pressure-sensitive adhesive layer (12 μm thick). A second pressure-sensitive adhesive layer (20 μm thick) was formed on the surface of the inner protective layer using pressure-sensitive adhesive composition D, thereby obtaining a second polarizing plate having a reflective polarizer / second polarizer / inner protective layer / second pressure-sensitive adhesive layer structure. The second polarizing plate was punched out to a size of 148 mm long and 70 mm wide, and 3.9 mm diameter through-holes were formed in the corners. The punching was performed so that the absorption axis direction of the second polarizer was aligned in the longitudinal direction.

[0060] (Polarizing Plate Set) The first polarizing plate obtained as described above was used as the viewer-side polarizing plate, and the second polarizing plate was used as the rear-side polarizing plate to form a polarizing plate set for this example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0061] Comparative Example 3 A polarizing plate set was obtained in the same manner as in Example 3, except that a first polarizing plate was prepared by punching out so that the absorption axis direction of the first polarizer was the longitudinal direction, and a second polarizing plate was prepared by punching out so that the absorption axis direction of the second polarizer was the lateral direction. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0062] Example 4 (Preparation of First Polarizing Plate) A laminate having a resin substrate / polarizer configuration was obtained in the same manner as in the second polarizing plate of Example 2. An HC-TAC film was attached as an outer protective layer to the polarizer surface of the obtained laminate (the surface opposite to the resin substrate). The resin substrate was then peeled off, and a pressure-sensitive adhesive layer (15 μm thick) was formed on the peeled surface using pressure-sensitive adhesive composition A, thereby obtaining a first polarizing plate having a configuration of outer protective layer / first polarizer / inner protective layer / first pressure-sensitive adhesive layer. The first polarizing plate was punched out to a size of 148 mm long and 70 mm wide, and through-holes with a diameter of 3.9 mm were formed in the corners. The punching was performed so that the absorption axis direction of the first polarizer was aligned in the short direction.

[0063] (Second Polarizing Plate) The same second polarizing plate as in Example 3 was used.

[0064] (Polarizing Plate Set) The first polarizing plate obtained as described above was used as the viewer-side polarizing plate, and the second polarizing plate was used as the rear-side polarizing plate to form a polarizing plate set for this example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0065] Comparative Example 4 (Preparation of First Polarizing Plate) A film (22 μm thick) obtained by incorporating iodine into a long polyvinyl alcohol (PVA)-based resin film and uniaxially stretching it in the longitudinal direction (MD direction) was used as the polarizer (first polarizer). A long TAC film (40 μm thick) serving as an outer protective layer and a long acrylic resin film (30 μm thick) serving as an inner protective layer were attached to both sides of this polarizer, with their longitudinal directions aligned. A pressure-sensitive adhesive layer (20 μm thick) was formed on the surface of the inner protective layer using pressure-sensitive adhesive composition D, resulting in a first polarizing plate having a configuration of outer protective layer / first polarizer / inner protective layer / first pressure-sensitive adhesive layer. The first polarizing plate was punched out to a size of 148 mm long and 70 mm wide, and 3.9 mm diameter through-holes were formed in the corners. The punching was performed so that the absorption axis direction of the first polarizer was aligned in the short direction.

[0066] (Second Polarizing Plate) The same second polarizing plate as in Example 1 was used.

[0067] (Polarizing Plate Set) The first polarizing plate obtained as described above was used as the viewer-side polarizing plate, and the second polarizing plate was used as the rear-side polarizing plate to form a polarizing plate set for this comparative example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1, along with the detailed configurations of the first polarizing plate and the second polarizing plate.

[0068]

[0069] As is clear from Table 1, the polarizing plate set of the example of the present invention can significantly reduce the difference (absolute value) between the amount of misalignment of the first polarizing plate and the amount of misalignment of the second polarizing plate compared to the comparative example. Therefore, the polarizing plate set of the example of the present invention has a significant advantage in terms of design when applied to an image display device.

[0070] The polarizing plate set of the present invention can be suitably used in image display devices, and in particular, can be suitably used in image display devices having a camera unit, such as smartphones, tablet PCs, or smartwatches.

[0071] REFERENCE SIGNS LIST 10 First polarizing plate 11 First polarizer 12 Outer protective layer 13 Inner protective layer 14 First adhesive layer 15 Through hole 20 Second polarizing plate 21 Second polarizer 22 Outer protective layer 23 Inner protective layer 24 Second adhesive layer 25 Through hole 100 Set of polarizing plates 120 Image display cell 200 Image display device

Claims

1. A polarizing plate set consisting of a rectangular first polarizing plate arranged on the viewing side of an image display cell and a rectangular second polarizing plate arranged on the back side of the image display cell, wherein the first polarizing plate has a first polarizer and a protective layer arranged on at least one side of the first polarizer, and a first adhesive layer arranged on the image display cell side, the second polarizing plate has a second polarizer and a protective layer arranged on at least one side of the second polarizer, a reflective polarizer arranged on the side of the second polarizer opposite the image display cell, and a second adhesive layer arranged on the image display cell side, the thicknesses of the first polarizer and the second polarizer are each 20 μm or less, the first polarizer has an absorption axis in the short side direction, and the second polarizer has an absorption axis in the long side direction, and the first polarizing plate and the second polarizing plate have through holes at or near their respective ends and at positions corresponding to each other.

2. Distance A from the outermost portion of the first pressure-sensitive adhesive layer on the image display cell side to the center of the first polarizer in the thickness direction １ (μm), the thickness T of the first polarizer ｐｏｌ１ (μm), creep value C of the first pressure-sensitive adhesive layer ｐｓａ１ (μm / hr), the thickness T of the first pressure-sensitive adhesive layer ｐｓａ１ (μm), and the thickness T of the protective layer in the first polarizing plate ｐｒｏ１ (μm) satisfies the following relationship, (A １ ×T ｐｏｌ１ ) × (C ｐｓａ１ ×T ｐｓａ１ ) / T ｐｒｏ１ =K １ ≦300×10 ２ (μm ３ / hr) the distance A from the outermost portion of the second pressure-sensitive adhesive layer on the image display cell side to the center in the thickness direction of the second polarizer ２ (μm), the thickness T of the second polarizer ｐｏｌ２ (μm), creep value C of the second pressure-sensitive adhesive layer ｐｓａ２ (μm / hr), the thickness T of the second pressure-sensitive adhesive layer ｐｓａ２ (μm), and the thickness T of the protective layer in the second polarizing plate ｐｒｏ２ The set of polarizing plates according to claim 1 , wherein (A) satisfies the following relationship: ２ ×T ｐｏｌ２ ) × (C ｐｓａ２ ×T ｐｓａ２ ) / T ｐｒｏ２ =K ２ ≦300×10 ２ (μm ３ / hr) 3. The above K １ and K. ２ But each is 200 x 10 ２ (μm ３ The set of polarizing plates according to claim 2 , wherein the average linearity is 1 / hr or less.

4. Creep value C of the first adhesive layer ｐｓａ１ The set of polarizing plates according to claim 2 or 3, wherein the linearity is 100 (μm / hr) or less.

5. Thickness T of the second polarizer ｐｏｌ２ The set of polarizing plates according to claim 1 , wherein the thickness is 10 μm or less.

6. The above K １ and K. ２ But each is 150 x 10 ２ (μm ３ 6. The set of polarizing plates according to claim 2, wherein the average linearity is 100% or less.

7. Thickness T of the first polarizer ｐｏｌ１ The set of polarizing plates according to claim 1 , wherein the thickness is 10 μm or less.

8. Thickness T of the first adhesive layer ｐｓａ１ and the thickness T of the second adhesive layer ｐｓａ２ The set of polarizing plates according to any one of claims 1 to 7, wherein each of the polarizing plates is 10 µm to 22 µm.

9. The set of polarizing plates according to any one of claims 1 to 8, wherein the through holes are formed in the corners of each of the first polarizing plate and the second polarizing plate.

10. The distance from the center to the end in the longitudinal direction when the first polarizer and the second polarizer are viewed in a plane is defined as L １ The distance in the longitudinal direction from the center of the first polarizer and the second polarizer in the longitudinal direction to the center of the through hole is L ２ The distance from the center to the end of the first polarizer and the second polarizer in the short side direction is W １ The distance in the short-side direction from the center of the first polarizer and the second polarizer in the short-side direction to the center of the through hole is W ２ When the through hole is formed in each of the first polarizer and the second polarizer, the L ２ / L １ ≦0.99 and 0.50≦W ２ / W １ The set of polarizing plates according to claim 9 , which are formed at positions satisfying ≦0.

99.

11. The set of polarizing plates according to any one of claims 1 to 10, wherein the through holes have a diameter of 10 mm or less.

12. The set of polarizing plates according to any one of claims 1 to 11, wherein the aspect ratio of the first polarizing plate and the aspect ratio of the second polarizing plate are each 1.3 to 2.

5.

13. An image display device comprising an image display cell and a set of polarizing plates according to any one of claims 1 to 12, wherein the first polarizing plate is disposed on the viewing side of the image display cell and the second polarizing plate is disposed on the rear side of the image display cell.

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