JP7686565B2 - Polarizing plate set and image display device including said set - Google Patents

Description

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

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 panel type information processing devices, image display devices equipped with cameras have become widely used. Correspondingly, polarizing plates having a through hole at a position corresponding to the camera unit have also become widely used. In such polarizing plates having a through hole, various considerations must be made at or near the through hole.

International Publication No. 2017/047510

The present invention has been made to solve the above-mentioned problems of the conventional art, and its main objective is to provide a set of polarizing plates in which the misalignment at the through-hole portions 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 rear-side polarizing plate is very small.

The polarizing plate set of the present invention comprises 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. The first polarizing plate has a first polarizer, 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, a protective layer arranged on at least one side of the second polarizer, a reflective polarizer arranged on the opposite side of the second polarizer to 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. 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 ₁ (μm) from an outermost portion of the first pressure-sensitive adhesive layer on the image display cell side to a center portion in a thickness direction of the first polarizer, a thickness T _pol1 (μm) of the first polarizer, a creep value C _psa1 (μm/hr) of the first pressure-sensitive adhesive layer, a thickness T _psa1 (μm) of the first pressure-sensitive adhesive layer, and a thickness T _pro1 (μm) of a protective layer in the first polarizing plate satisfy the following relationship:
(A ₁ ×T _pol1 ) × (C _psa1 × T _psa1 )/T _pro1 = K ₁ ≦300 × 10 ² (μm ³ /hr)
A distance _A2 (μm) from the outermost part of the second pressure-sensitive adhesive layer on the image display cell side to the center in the thickness direction of the second polarizer, a thickness _Tpol2 (μm) of the second polarizer, a creep value _Cpsa2 (μm/hr) of the second pressure-sensitive adhesive layer, a thickness _Tpsa2 (μm) of the second pressure-sensitive adhesive layer, and a thickness _Tpro2 (μm) of the protective layer in the second polarizing plate satisfy the following relationship:
(A ₂ ×T _pol2 ) × (C _psa2 × T _psa2 )/T _pro2 = K ₂ ≦300 × 10 ² (μm ³ /hr).
In one embodiment, K ₁ and K ₂ are each 200×10 ² (μm ³ /hr) or less.
In one embodiment, the creep value C _psa1 of the first pressure-sensitive adhesive layer is 100 (μm/hr) or less.
In one embodiment, the second polarizer has a thickness T _pol2 of 10 μm or less.
In one embodiment, K ₁ and K ₂ are each 150×10 ² (μm ³ /hr) or less.
In one embodiment, the first polarizer has a thickness T _pol1 of 10 μm or less.
In one embodiment, the thickness T _psa1 of the first pressure-sensitive adhesive layer and the thickness T _psa2 of the second pressure-sensitive adhesive layer are each 10 μm to 22 μm.
In one embodiment, the through holes are formed in corners of the first polarizing plate and the second polarizing plate.
In one embodiment, when the first polarizer and the second polarizer are viewed in a plane, the distance from the longitudinal center to the longitudinal ends _{is L1} , the longitudinal distance from the longitudinal center of the first polarizer and the second polarizer to the center of the through hole is _L2 , the distance from the lateral center to the lateral ends of the first polarizer and the second polarizer _{is W1} , and the lateral distance from the lateral center of the first polarizer and the second polarizer to the center of the through hole is _W2 , the through hole is formed at a position in the first polarizer and the second polarizer that satisfies 0.85≦ _L2 / _{L1 ≦} 0.99 and 0.50≦ _W2 /W1≦0.99, respectively.
In one embodiment, the through hole has a diameter of 10 mm or less.
In one embodiment, the first polarizing plate and the second polarizing plate each have an aspect ratio of 1.3 to 2.5.
According to another aspect of the present invention, there is provided an image display device comprising an image display cell and the above-described set of polarizing plates, the first polarizing plate being disposed on the viewing side of the image display cell, and the second polarizing plate being disposed on the back side of the image display cell.

According to an embodiment of the present invention, it is possible 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 misalignment amount of the viewing side polarizing plate and the back side polarizing plate is very small. The small misalignment at the through-hole portion of each polarizing plate can have a synergistic effect when the polarizing plates are used as a set. The very small difference in the amount of misalignment has an extremely large design advantage when the set of polarizing plates is applied to an image display device. For example, the set of polarizing plates can be applied to an image display device in which only the camera portion is a non-display area and/or a bezel-less image display device.

2 is a schematic plan view illustrating a first polarizing plate and a second polarizing plate in a set of polarizing plates according to one embodiment of the present invention. FIG. FIG. 2 is a schematic cross-sectional view of the first polarizing plate and the second polarizing plate in the set of polarizing plates in FIG. 1 taken along line II-II, and is a schematic cross-sectional view explaining the respective arrangement positions of the first polarizing plate and the second polarizing plate. 2 is a schematic cross-sectional view of an image display device including the set of polarizing plates of FIG. 1. 5 is an enlarged cross-sectional view of a main portion illustrating a misalignment at a through-hole portion in a polarizing plate used in a polarizing plate set according to an embodiment of the present invention. FIG. 5 is a schematic plan view illustrating the positions at which through holes are formed in polarizing plates used in the polarizing plate set according to the embodiment of the present invention. FIG. FIG. 2 is a schematic perspective view of an example of a reflective polarizer that can be used as a second polarizing plate in a set of polarizing plates according to an embodiment of the present invention.

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 ease of viewing, and the ratios of length, width, thickness, etc., as well as angles, etc., in the drawings differ from the actual ones.

A. Overview of the polarizing plate set 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 along line II-II; 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 is composed of 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 sides and short sides corresponding to the planar shape of the image display cell. In this specification, the term "rectangular shape" also includes a shape including a modified processed portion such as an R 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 back side of the image display cell 120. In the illustrated example, the first polarizing plate 10 has 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 adhesive layer 14 arranged as the outermost layer on the image display cell 120 side. The first adhesive layer 14 is used to bond 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 has a second polarizer 21, a reflective polarizer 26 arranged on the back side (opposite the image display cell) of the second polarizer 21, a protective layer (inner protective layer) 23 arranged on the image display cell side of the second polarizer 21, and a second adhesive layer 24 arranged as the outermost layer on the image display cell 120 side. The second adhesive layer 24 is used to bond the second polarizing plate 20 to the image display cell 120. In the second polarizing plate 20, a reflective polarizer 26 is disposed 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. In the illustrated example, the outer protective layer of the second polarizing plate is omitted, but the reflective polarizer 26 may be disposed on the back side of the outer protective layer (opposite to the image display cell). The reflective polarizer 26 is bonded to the second polarizer 21 or the outer protective layer (if present) via any suitable adhesive layer (for example, a thickness of 2 μm to 20 μm).

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, and at positions corresponding to each other. By forming the through holes, for example, when an image display device has a built-in camera, it is possible to prevent adverse effects on the camera performance. Furthermore, by forming the through holes at or near the ends of the polarizing plate, it is possible to minimize the effect of the through holes on image display (for example, light leakage at the through hole portion) when the polarizing plate is applied to an image display device. The through holes can be formed by various methods, such as laser processing, cutting processing with an end mill, and punching processing with a Thomson blade or a Pinnacle (registered trademark) blade. In this specification, "provided at positions corresponding to each other" means that the through holes overlap when the two polarizing plates are stacked.

As shown in FIG. 1, the first polarizer 11 has an absorption axis Ab ₁ in the short side direction, and the second polarizer 21 has an absorption axis Ab ₂ in the long side direction. A rectangular film tends to shrink easily in the long side direction and not easily in the short side direction. Furthermore, a polarizer (as a result, a polarizing plate) tends to shrink easily in the absorption axis direction. Therefore, by making the absorption axis direction of the second polarizing plate, which is not easily shrinkable due to the inclusion of a reflective polarizer, the long side direction of the film (the direction in which it is easy to shrink), and making the absorption axis direction of the first polarizing plate, which is more easily shrinkable than the second polarizing plate, the short side direction of the film (the direction in which it is difficult to shrink), the misalignment at the through-hole portion of each polarizing plate can be reduced, and the difference between the misalignment of the first polarizing plate and the misalignment of the second polarizing plate can be reduced.

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 may be appropriately set according to the purpose. For example, the retardation layer may be a λ/2 plate, a λ/4 plate, or a laminate of these. The λ/2 plate and the λ/4 plate typically have a refractive index characteristic 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. 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)" is an in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is 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)" is a retardation in the thickness direction measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is 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 maximum (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.

The components of the polarizing plate set are specifically described below. The first polarizing plate and the second polarizing plate are collectively referred to as polarizing plates, the first polarizer and the second polarizer are collectively referred to as polarizers, the protective layers in the first polarizing plate and the second polarizing plate are collectively referred to as protective layers, and the first adhesive layer and the second adhesive layer are collectively referred to as adhesive layers. Therefore, for example, when "a polarizing plate" is mentioned, it can mean "the first polarizing plate and the second polarizing plate, respectively." 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" is specified.

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)
Here, _A1 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; and T _pro1 is the thickness (μm) of the protective layer in the first polarizer 10. Similarly, the second polarizer 20 preferably satisfies the following relationship:
(A ₂ ×T _pol2 ) × (C _psa2 × T _psa2 )/T _pro2 = K ₂ ≦300 × 10 ² (μm ³ /hr).
Here, _A2 is the distance (μm) from the outermost part of the second adhesive layer 24 on the image display cell 120 side to the center of the second polarizer 21 in the thickness direction; _Tpol2 is the thickness (μm) of the second polarizer 21; _Cpsa2 is the creep value (μm/hr) of the second adhesive layer 24; _Tpsa2 is the thickness (μm) of the second adhesive layer 24; and _Tpro2 is the thickness (μm) of the protective layer in the second polarizer 20. In this specification, the "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 fixed, a load of 500 g is applied vertically downward. The amount of deviation of the adhesive from the support plate one hour after applying the load is measured, and the amount of deviation is taken as the creep value (μm/hr). The thickness T _pro1 of the protective layer in the above relational expression is calculated from the formula: "total thickness of the first polarizing plate-thickness of the first adhesive layer-thickness of the first polarizer". That is, T _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 protective film and the reflective polarizer are bonded via the adhesive layer), and the thickness of the surface treatment layer formed on the protective layer 12 as necessary. The same applies to T _pro2 related to the second polarizing plate. The _{K 1} value and the K ₂ value are each more preferably 250×10 ² (μm ³ /hr) or less, further preferably 200×10 ² (μm ³ /hr) or less, and particularly preferably 150×10 ² (μm ³ /hr) or less. Hereinafter, the K ₁ value and the K ₂ value 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 may be, for example, 15×10 ² (μm ³ /hr). If the K value is in such a range, the displacement of the through-hole portion (substantially, the displacement of the adhesive layer) can be significantly suppressed. The technical meaning of making the K value equal to or less than a predetermined value is as follows: the displacement of the adhesive layer increases when the moment force applied to the adhesive layer and the ease of movement of the adhesive layer itself are large, and decreases when the restraining force against the movement of the adhesive layer is large. The moment force applied to the 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 adhesive layer itself may be related to the softness and thickness of the adhesive layer; and the restraining force against the movement of the adhesive layer may be related to the thickness of the protective layer. By reducing the distance from the image display cell to the polarizer and the thickness of the polarizer, the moment force can be reduced; by setting the creep value of the adhesive layer to a predetermined value or less (the adhesive layer is hardened) and reducing the thickness of the adhesive layer, the adhesive layer itself can be made difficult to move; by setting the thickness T _pro of the protective layer within a predetermined range, the deterrent force against the movement of the adhesive layer can be set to an appropriate range. Therefore, by adjusting each of the above requirements to control the K value to a predetermined value or less, the slippage of the adhesive layer can be significantly suppressed. Specifically, the above 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 can be, for example, 50 μm/hr. The thickness T _pro of the protective layer is preferably 15 μm to 65 μm, more preferably 15 μm to 55 μm. The thickness T _psa of the adhesive layer is preferably 22 μm or less, more preferably 10 μm to 22 μm. If the creep value C _psa is too small and/or if the thickness T _psa of the adhesive layer is too small, stress relaxation may become difficult, increasing the risk of cracking or peeling. If the thickness T _pro of the protective layer is too small, curl control may become difficult.

As shown in FIG. 4, the polarizing plate (the illustrated example is a first polarizing plate 10) is attached to a glass plate (which may correspond to a 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, and the lower limit of the displacement D is 10 μm in one embodiment and 20 μm in another embodiment. The displacement D refers to the maximum portion of the polarizing plate that is farther from the through-hole portion when viewed in cross section. The reference for the through-hole portion may typically be the lower end of the adhesive layer. That is, when the polarizing plate is shifted (to the right in the illustrated example) mainly due to the 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, since 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, the effect can be synergistically exhibited when the polarizing plates are used as a set.

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 more preferable it is. The lower limit of the difference in the amount of misalignment can 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 set of polarizing plates can be applied to an image display device in which only the camera unit is the non-display area and/or a bezel-less image display device.

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 more preferable it is, and the lower limit of the dimensional shrinkage may be, for example, 0.01%. The dimensional shrinkage is calculated by the following formula. The dimensional shrinkage is the dimensional shrinkage of the entire polarizing plate attached to the glass plate, and when the polarizing plate further has an optical functional layer (e.g., a retardation layer, a reflective polarizer), it means the dimensional shrinkage of the entire polarizing plate including the optical functional layer. The "dimension" in the following formula is the dimension in the absorption axis direction of the polarizing plate (substantially, a polarizer).
Dimensional shrinkage rate (%)={(dimension before heating test−dimension after heating test)/dimension before heating test}×100

In the polarizing plate, the through holes are formed at any appropriate position at or near the end depending on the purpose. In one embodiment, the through holes 15 and 25 are formed at each corner of the polarizing plate as shown in FIG. 1. The positions of the through holes are not limited to the corners. The through holes may be formed approximately at the center of the longitudinal end of the polarizing plate, at a specified position of the longitudinal end, at approximately the center of the lateral end, or at a specified position of the lateral end. In addition, multiple through holes may be formed, or a combination of a through hole and a notch may be formed.

In one embodiment, as shown in Fig. 5, when the distance from the longitudinal center of the polarizer to the longitudinal end _{is L1} , the longitudinal distance from the longitudinal center of the polarizer to the center of the through hole _{is L2} , the distance from the lateral center of the polarizer to the lateral end is _W1 , and the lateral distance from the lateral center of the polarizer to the center of the through hole is _W2 , the through hole is preferably formed at a position that satisfies 0.85≦ _L2 / _L1 ≦0.99 and 0.50≦ _W2 / _W1 ≦0.99. _L2 / _L1 is more preferably 0.90 to 0.97, and even more preferably 0.92 to 0.96. _W2 / _W1 is more preferably 0.75 to 0.95.

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 amount of deviation 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 especially preferably 5% or less. On the other hand, the lower limit of D/R is preferably as small as possible. According to the embodiment of the present invention, since the amount of deviation D is very small as described above, even if the diameter of the through hole is made small, D/R can be in such a range. Therefore, even if the diameter of the through hole is made small, adverse effects on the camera performance can be substantially prevented. As a result, the polarizing plate used in the embodiment of the present invention can be applied to an image display device in which only the camera part is a non-display area and/or a bezel-less image display device.

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. In other words, 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.

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

Specific examples of polarizers made of a single-layer resin film include a PVA-based resin film that has been dyed with iodine and stretched (typically, uniaxially stretched). The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing process or while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based resin film may be subjected to a swelling process, a crosslinking process, a cleaning process, a drying process, or the like. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can dirt and antiblocking agents on the surface of the PVA-based film be washed off, but the PVA-based resin film can also be swelled to prevent uneven dyeing.

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

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 thickness of the polarizer is 1 μm in one embodiment, and 3 μm in another embodiment. If the thickness of the polarizer is within this range, curling during heating can be effectively suppressed, and good appearance durability during heating can be obtained.

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

B-3. Protective layer The protective layers 12, 13, and 23 are formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that is 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. In addition, thermosetting resins or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxy resins, and silicones are also included. In addition, glassy polymers such as siloxane polymers are also included. In addition, the polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. As the material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, a resin composition containing an alternating copolymer 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.

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, if necessary. Additionally/alternatively, the outer protective layer may be subjected to a treatment to improve visibility when viewed through polarized sunglasses (typically, imparting an (elliptical) polarization function or imparting an ultra-high phase difference), if necessary. 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 can be suitably applied to an image display device that can be used outdoors.

It is preferable that the inner protective layer 13, 23 is 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 with light having a wavelength of λ nm at 23°C. For example, "Re(550)" is the 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) x d, where d (nm) is the thickness of the layer (film). "Rth(λ)" is the thickness direction retardation measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the thickness direction retardation 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), 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.

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. When 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 different from T _pro1 and T _pro2 in the above formula.

B-4. Adhesive layer The adhesive layer is used to bond the polarizing plate to the image display cell as described above. The adhesive layer may typically be composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer may 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 in the solid content of the adhesive composition. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a monomer unit as a main component. Here, (meth)acrylate refers to acrylate and/or methacrylate. The alkyl (meth)acrylate may be contained in the monomer components forming the (meth)acrylic polymer at a ratio of preferably 80% by weight or more, more preferably 90% by weight or more. The alkyl group of the alkyl (meth)acrylate may be, for example, a linear or branched alkyl group having 1 to 18 carbon atoms. The average number of carbon atoms 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 the silane coupling agent include an epoxy group-containing silane coupling agent. Examples of the crosslinking agent include an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent. 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, 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.

The pressure-sensitive adhesive layer has a storage modulus G ₂ ' at -40°C of preferably 1.0 x 10 ⁵ (Pa) or more, more preferably 1.0 x 10 ⁶ (Pa) or more, even more preferably 1.0 x 10 ⁷ (Pa) or more, and particularly preferably 1.0 x 10 ⁸ (Pa) or more. The storage modulus G ₂ ' can be, for example, 1.0 x 10 ⁹ (Pa) or less.

B-5. Reflective polarizer As described above, the reflective polarizer 26 can be provided on the opposite side (back side) of the image display cell 120 of the second polarizer 20. By providing the reflective polarizer, the second polarizer is less likely to shrink than the first polarizer. As a result, by making the absorption axis direction of the second polarizer the long side direction of the film (the direction in which it is easy to shrink) and the absorption axis direction of the first polarizer the short side direction of the film (the direction in which it is difficult to shrink), it is possible to reduce the misalignment at the through-hole portion of each polarizer and to reduce the difference between the misalignment of the first polarizer and the misalignment of the second polarizer.

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 of either a linear polarization separation type or a circular polarization separation type. Below, a linear polarization separation type reflective polarizer is described as an example. An example of a circular polarization separation type reflective polarizer is a laminate of a film with fixed cholesteric liquid crystal and a λ/4 plate.

Figure 6 is a schematic perspective view of an example of a reflective polarizer. The reflective polarizer is a multilayer laminate in which a layer A having birefringence and a layer B having substantially no birefringence are alternately stacked. For example, the total number of layers in such a multilayer laminate can be 50 to 1000. In the illustrated example, the refractive index nx in the x-axis direction of the A layer is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction of the B layer and the refractive index ny in the y-axis direction are substantially the same. Therefore, the refractive index difference between the A layer and the B layer 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 the A layer and the B layer 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.

The A layer is preferably made of a material that exhibits birefringence when stretched. Typical examples of such materials include naphthalene dicarboxylic 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 even when stretched. Typical examples of such materials include copolyesters of naphthalene dicarboxylic acid and terephthalic acid.

A reflective polarizer transmits light having a first polarization direction (e.g., p-waves) at the interface between layers A and B, and reflects light having a second polarization direction (e.g., s-waves) that is perpendicular to the first polarization direction. At the interface between layers A and B, 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 is repeated many times inside the reflective polarizer, thereby increasing the light utilization efficiency.

In one embodiment, the reflective polarizer may include a reflective layer R as the outermost layer on the side opposite the image display cell, as shown in FIG. 6. By providing the reflective layer R, it is possible to further utilize light that is ultimately unused and returns to the outermost part of the reflective polarizer, thereby further increasing the light utilization efficiency. The reflective layer R typically exhibits a reflective function by a multilayer structure of polyester resin layers.

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

As the reflective polarizer, for example, those described in JP-A-9-507308 and JP-A-2013-235259 can be used. As the reflective polarizer, a commercially available product may be used as is, or a commercially available product may be used after secondary processing (e.g., stretching). Examples of commercially available products include DBEF and APF, both manufactured by 3M.

C. Image display device As described above, the set of polarizing plates according to the embodiment of the present invention can be suitably 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 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 the above items A to B. 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.

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 setting polarizing plates is significant.

The present invention will be described in detail below with reference to 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, "parts" and "%" in the examples are based on weight.

(1) Displacement The first and second polarizing plates in the polarizing plate sets obtained in the examples and comparative examples were attached to a glass plate (manufactured by Matsunami Glass Co., Ltd., length 350 mm x width 250 mm x thickness 1.1 mm) via an adhesive layer to prepare a test sample. Each test sample was subjected to a heating test at 85°C and 120 hours. After the test, the displacement 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 with an optical microscope (MX61L) manufactured by OLYMPUS Corporation. The measurement was performed on three test samples each, and the maximum value of the three measured values was taken as the displacement.

<Production Example 1>
A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate per 100 parts of the monomer mixture (solid content), and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of an 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 type, manufactured by BASF Japan Ltd.) were mixed with 100 parts of the solid content of the obtained solution of acrylic polymer (a) to obtain a pressure-sensitive adhesive composition A.

<Production Example 2>
A solution of an 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 amount: 30%, thiol equivalent: 450 g/mol) was used as a silane coupling agent, no antioxidant was used, and 0.5 parts of bis(trifluoromethanesulfonyl)imide lithium (manufactured by Mitsubishi Materials Corporation) was further added.

<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 the 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 Daiichi Kogyo Seiyaku Co., Ltd.) was added.

<Production Example 4>
A solution of acrylic polymer (d) having a weight average molecular weight (Mw) of 1.65 million 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 mixed with 100 parts of the solid content of the obtained solution of acrylic polymer (d) to obtain a pressure-sensitive adhesive composition D.

<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 (product name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy group amount: 30%, thiol equivalent: 450 g/mol) was used as the silane coupling agent.

Example 1
(Preparation of First Polarizing Plate)
As the polarizer (first polarizer), 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. 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 so that their longitudinal directions were aligned. The HC-TAC film was a film in which a hard coat (HC) layer (thickness 7 μm) was formed on a triacetyl cellulose (TAC) film (thickness 25 μm), 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 the pressure-sensitive adhesive composition B, and a first polarizing plate having a configuration of outer protective layer/first polarizer/inner protective layer/first pressure-sensitive adhesive layer was obtained. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was formed in the corner of the first polarizing plate so that the absorption axis direction of the first polarizer was aligned in the short direction.

(Preparation of Second Polarizing Plate)
A polarizing plate was obtained in the same manner as in 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 normal adhesive layer (thickness 12 μm), and a second adhesive layer (thickness 20 μm) was formed on the surface of the reflective polarizer using the adhesive composition E, to obtain a second polarizing plate having a configuration of reflective polarizer/outer protective layer/second polarizer/inner protective layer/second adhesive layer. The second polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was formed in the corner. At this time, it was punched out so that the absorption axis direction of the second polarizer was the longitudinal direction.

(Polarizing plate set)
The first polarizing plate obtained as described above was used as the viewing 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 above-mentioned evaluation of the amount of misalignment. The results are shown in Table 1 together 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 transverse direction.

<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 the first polarizer so that the absorption axis direction was the longitudinal direction, and a second polarizing plate was prepared by punching out the second polarizer so that the absorption axis direction was the transverse direction. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

Example 2
(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 the first adhesive layer (thickness 20 μm) was formed using the adhesive composition C. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was formed in the corner. At this time, the plate was punched out so that the absorption axis direction of the first polarizer was the short side direction.

(Preparation of Second Polarizing Plate)
As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used, and one side of the resin substrate was subjected to a corona treatment.
A PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4,200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFFIMER") in a ratio of 9:1, and dissolving the resultant in water.
The above PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (machine direction) in an oven at 130° C. (auxiliary in-air stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained 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 (insolubilizing treatment).
Next, the film was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) having a liquid temperature of 30° C. for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would have a desired value (dyeing treatment).
Next, the plate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid 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 with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Thereafter, the film was dried in an oven maintained at about 90° C., while being brought into contact with a SUS heated roll whose surface temperature was maintained at about 75° C. (drying shrinkage treatment).
In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate/second polarizer structure was obtained.
A TAC film (thickness 20 μm) was attached to the polarizer surface (opposite side to the resin substrate) of the obtained laminate as an inner protective layer. Next, the resin substrate was peeled off, and a reflective polarizer (thickness 26 μm) was attached to the peeled surface via a normal adhesive layer (thickness 12 μm). An adhesive layer (thickness 20 μm) was formed on the surface of the inner protective layer using the adhesive composition D, to obtain a second polarizing plate having a configuration of a reflective polarizer/second polarizer/inner protective layer/second adhesive layer. The second polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was formed in the corner. At this time, the plate was punched out so that the absorption axis direction of the second polarizer was the longitudinal direction.

(Polarizing plate set)
The first polarizing plate obtained as described above was used as the viewing-side polarizing plate, and the second polarizing plate was used as the back-side polarizing plate to form a polarizing plate set of this example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

<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 the first polarizer so that the absorption axis direction was the longitudinal direction, and a second polarizing plate was prepared by punching out the second polarizer so that the absorption axis direction was the transverse direction. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

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 the first adhesive layer (thickness 20 μm) was formed using adhesive composition C instead of adhesive composition B. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was formed in the corner. At this time, it was punched out so that the absorption axis direction of the first polarizer was the short side direction.

(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 (thickness 20 μm) was attached to the polarizer surface (opposite side to the resin substrate) of the obtained laminate as an inner protective layer. Next, the resin substrate was peeled off, and a reflective polarizer (thickness 26 μm) was attached to the peeled surface via a normal adhesive layer (thickness 12 μm). A second adhesive layer (thickness 20 μm) was formed on the surface of the inner protective layer using adhesive composition D, and a second polarizing plate having a reflective polarizer/second polarizer/inner protective layer/second adhesive layer structure was obtained. 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 at the corner. At this time, the punching was performed so that the absorption axis direction of the second polarizer was the longitudinal direction.

(Polarizing plate set)
The first polarizing plate obtained as described above was used as the viewing-side polarizing plate, and the second polarizing plate was used as the back-side polarizing plate to form a polarizing plate set of this example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

<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 the first polarizer so that the absorption axis direction was the longitudinal direction, and a second polarizing plate was prepared by punching out the second polarizer so that the absorption axis direction was the transverse direction. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

Example 4
(Preparation of First Polarizing Plate)
A laminate having a resin substrate/polarizer structure 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 (the surface opposite to the resin substrate) of the obtained laminate. Next, the resin substrate was peeled off, and a pressure-sensitive adhesive layer (thickness 15 μm) was formed on the peeled surface using the pressure-sensitive adhesive composition A, to obtain a first polarizing plate having a structure 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 further, a through hole having a diameter of 3.9 mm was formed in the corner. At this time, the plate was punched out so that the absorption axis direction of the first polarizer was the short side direction.

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

(Polarizing plate set)
The first polarizing plate obtained as described above was used as the viewing-side polarizing plate, and the second polarizing plate was used as the back-side polarizing plate to form a polarizing plate set of this example. The obtained polarizing plate set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

<Comparative Example 4>
(Preparation of First Polarizing Plate)
As the polarizer (first polarizer), a film (thickness 22 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. A long TAC film (thickness 40 μm) serving as an outer protective layer and a long acrylic resin film (thickness 30 μm) serving as an inner protective layer were attached to both sides of this polarizer so that their longitudinal directions were aligned. A pressure-sensitive adhesive layer (thickness 20 μm) was formed on the surface of the inner protective layer using the pressure-sensitive adhesive composition D, and a first polarizing plate having a configuration of outer protective layer/first polarizer/inner protective layer/first pressure-sensitive adhesive layer was obtained. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was formed in the corner. At this time, the first polarizing plate was punched out so that the absorption axis direction of the first polarizer was the short side direction.

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

(Polarizing plate set)
The first polarizing plate obtained as described above was used as the viewing-side polarizing plate, and the second polarizing plate was used as the rear-side polarizing plate to form a polarizing plate set of 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 together with the detailed configurations of the first polarizing plate and the second polarizing plate.

As is clear from Table 1, the polarizing plate set of the embodiment 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 embodiment of the present invention has an extremely large design advantage when applied to an image display device.

The polarizing plate set of the present invention is suitable for use in image display devices, and in particular, can be suitable for use in image display devices having a camera unit, such as smartphones, tablet PCs, or smart watches.

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 (12)

A polarizing plate set including a rectangular first polarizing plate and a rectangular second polarizing plate,
the first polarizing plate has a first polarizer, a protective layer disposed on at least one side of the first polarizer, and a first pressure-sensitive adhesive layer provided for bonding the first polarizing plate to an image display cell;
the second polarizing plate has a second polarizer, a protective layer arranged on at least one side of the second polarizer , a second pressure -sensitive adhesive layer provided for attaching the second polarizing plate to an image display cell, and a reflective polarizer arranged on the side of the second polarizer opposite to the second pressure-sensitive adhesive layer;
The first polarizer and the second polarizer each have a thickness of 20 μm or less;
The first polarizer has an absorption axis in a short side direction, and the second polarizer has an absorption axis in a 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;
a distance A ₁ (μm) from the outermost portion of the first pressure-sensitive adhesive layer to the center portion of the first polarizer in the thickness direction, a thickness T _pol1 (μm) of the first polarizer, a creep value C _psa1 (μm/hr) of the first pressure-sensitive adhesive layer, a thickness T _psa1 (μm) of the first pressure-sensitive adhesive layer, and a thickness T _pro1 (μm) of the protective layer in the first polarizing plate satisfy the following relationship:
(A ₁ ×T _pol1 ) × (C _psa1 × T _psa1 )/T _pro1 = K ₁ ≦300 × 10 ² (μm ³ /hr)
A polarizing plate set in which a distance _A2 (μm) from the outermost portion of the second pressure-sensitive adhesive layer to the center in the thickness direction of the second polarizer, a thickness _Tpol2 (μm) of the second polarizer, a creep value _Cpsa2 (μm/hr) of the second pressure-sensitive adhesive layer, a thickness _Tpsa2 (μm) of the second pressure-sensitive adhesive layer, and a thickness _Tpro2 (μm) of a protective layer in the second polarizing plate satisfy the following relationships:
(A ₂ ×T _pol2 ) × (C _psa2 × T _psa2 )/T _pro2 = K ₂ ≦300 × 10 ² (μm ³ /hr)
Here, the creep value is the amount of displacement of the adhesive when a load of 500 g is applied at 85° C. for 1 hour, the thickness _Tpro1 of the protective layer in the first polarizing plate is calculated from the formula: "total thickness of the first polarizing plate-thickness of the first adhesive layer-thickness of the first polarizer", and the thickness _Tpro2 of the protective layer in the second polarizing plate is calculated from the formula: "total thickness of the second polarizing plate-thickness of the second adhesive layer-thickness of the second polarizer". The set of polarizing plates according to claim 1 , wherein K ₁ and K ₂ are each 200×10 ² (μm ³ /hr) or less. The set of polarizing plates according to claim 1 or 2, wherein the creep value C _psa1 of the first pressure-sensitive adhesive layer is 100 (μm/hr) or less. The set of polarizing plates according to claim 1 , wherein the second polarizer has a thickness T _pol2 of 10 μm or less. The set of polarizing plates according to claim 1 , wherein K ₁ and K ₂ are each 150×10 ² (μm ³ /hr) or less. The set of polarizing plates according to claim 1 , wherein the first polarizer has a thickness T _pol1 of 10 μm or less. The set of polarizing plates according to any one of claims 1 to 6, wherein the thickness T _psa1 of the first pressure-sensitive adhesive layer and the thickness T _psa2 of the second pressure-sensitive adhesive layer are each 10 µm to 22 µm. The set of polarizing plates according to any one of claims 1 to 7, wherein the through holes are formed in the corners of the first polarizing plate and the second polarizing plate. The set of polarizing plates described in claim 8, wherein when the distance from the longitudinal center to the longitudinal ends of the first polarizer and the second polarizer when viewed in a plane _{is L1} , the longitudinal distance from the longitudinal center of the first polarizer and the second polarizer to the center of the through hole is L2, the distance from the lateral center to the lateral ends of the first polarizer and the second polarizer is _W1 , and the lateral distance from the lateral center of the first polarizer and the second polarizer to the center of the through hole is _W2 , the through hole is formed at a position in each of the first polarizer and the second polarizer that satisfies 0.85≦ _L2 / _L1 ≦0.99 and 0.50≦ _W2 / _W1 ≦0.99. The set of polarizing plates according to any one of claims 1 to 9, wherein the through holes have a diameter of 10 mm or less. The set of polarizing plates according to any one of claims 1 to 10, wherein the aspect ratio of the first polarizing plate and the second polarizing plate is 1.3 to 2.5, respectively. An image display device comprising an image display cell and a set of polarizing plates according to any one of claims 1 to 11, 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.

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