Set of polarization plates and image display unit including the same

Abstract

To provide a set of polarization plates, where open hole portions thereof are only slightly displaced from each other, and which has small difference between a displacement amount of a visible side polarization plate and a displacement amount of a back side polarization plate.SOLUTION: The set of polarization plates includes a rectangle first polarization plate disposed on a visible side of an image display cell and a rectangle second polarization plate disposed on a back side. The first polarization plate comprises a first polarizer and a protective layer disposed on one side of the first polarizer, and a first adhesive layer disposed on an image display cell side while the second polarization plate comprises: a second polarizer and a protective layer disposed on one side thereof; a reflection type polarizer disposed on a side of the second polarizer opposite the image display cell; and a second adhesive layer disposed on a side of the image display cell. 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 while the second polarizer has an absorption axis in a long side direction. Each of the first polarization plate and the second polarization plate has an open hole at each end or in the vicinity thereof and in a position corresponding to each other.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In image display devices such as mobile phones and notebook personal computers, polarizing plates are widely used to realize image display and / or enhance the performance of the image display. In recent years, due to 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 through holes at positions corresponding to the camera unit have also come to be widely used. In such polarizing plates having through holes, there are various considerations in the through holes or their vicinity.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0005] The polarizer set of the present invention comprises a rectangular first polarizer disposed on the viewing side of the image display cell, and a rectangular second polarizer disposed on the back side of the image display cell. The first polarizer has a first polarizer and a protective layer disposed on at least one side of the first polarizer, and a first adhesive layer disposed on the image display cell side; the second polarizer 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 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 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 polarizer and the second polarizer each have through holes at their respective ends or in the vicinity thereof and at corresponding positions with respect to each other. In one embodiment, the distance A from the outermost part on the image display cell side of the first adhesive layer to the center part in the thickness direction of the first polarizer 1 (μm), the thickness T pol1 (μm) of the first polarizer, the creep value C psa1 (μm / hr) of the first adhesive layer, the thickness T psa1 (μm) of the first adhesive layer, and the thickness T pro1 (μm) of the protective layer in the first polarizer satisfy 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 part on the image display cell side of the second adhesive layer to the center part in the thickness direction of the second polarizer 2 (μm), the thickness T pol2 (μm) of the second polarizer, the creep value C psa2 (μm / hr) of the second adhesive layer, the thickness T psa2 (μm) of the second adhesive layer, and the thickness T pro2 (μm) of the protective layer in the second polarizer satisfy the following relationship: (A2 ×T pol2 )×(C psa2 ×T psa2 ) / T pro2 =K 2 ≦300×10 2 (μm 3 / hr). In one embodiment, the above 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 above first adhesive layer is 100 (μm / hr) or less. In one embodiment, the thickness T pol2 of the above second polarizer is 10 μm or less. In one embodiment, the above K 1 and K 2 are each 150×10 2 (μm 3 / hr) or less. In one embodiment, the thickness T pol1 of the above first polarizer is 10 μm or less. In one embodiment, the thickness T psa1 of the above first adhesive layer and the thickness T psa2 of the above second adhesive layer are each 10 μm to 22 μm. In one embodiment, the above through-hole is formed at each corner of the above first polarizing plate and the above second polarizing plate. In one embodiment, the distance from the longitudinal center to the longitudinal end when the above first polarizer and the above second polarizer are viewed in plan is L 1 , the longitudinal distance from the longitudinal center of the above first polarizer and the above second polarizer to the center of the above through-hole is L 2 , the distance from the short-side center to the short-side end of the above first polarizer and the above second polarizer is W 1 , and the short-side distance from the short-side center of the above first polarizer and the above second polarizer to the center of the above through-hole is W 2When this is the case, the through hole is formed at a position where 0.85 ≦ L 2 / L 1 ≦ 0.99 and 0.50 ≦ W 2 / W 1 ≦ 0.99 are satisfied in each of the first polarizer and the second polarizer. 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, an image display device is provided. This image display device includes an image display cell and a set of the above-described polarizing plates, 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.

Advantages of the Invention

[0006] According to an embodiment of the present invention, it is possible to provide a set of polarizing plates in which the deviation in the through hole portion of each polarizing plate is small and the difference between the deviation amount of the viewing-side polarizing plate and the deviation amount of the back-side polarizing plate is very small. The small deviation in the through hole portion of each polarizing plate means that the effects can be synergistically exerted when the polarizing plates are set. The very small difference in the deviation amount means that there are extremely great design advantages 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 having only the camera portion as a non-display area and / or a bezel-less image display device.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0008] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. For clarity, the drawings are schematically shown, and further, the ratios of lengths, widths, thicknesses, etc., and angles, etc. in the drawings are different from the actual ones.

[0009] A. Schematic of a set of polarizing plates FIG. 1 is a schematic plan view for explaining a first polarizing plate and a second polarizing plate in a set of polarizing plates according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view taken along line II-II of each of the first polarizing plate and the second polarizing plate in the set of polarizing plates of FIG. 1; FIG. 3 is a schematic cross-sectional view of an image display device including the set of polarizing plates of FIG. 1. The set 100 of polarizing plates in the illustrated example consists of a first polarizing plate 10 and a second polarizing plate 20. Each of the first polarizing plate and the second polarizing plate has a rectangular shape having a long side and a short side corresponding to the planar shape of the image display cell. In the present specification, when referring to a "rectangular shape", a shape including a deformed portion such as an R shape with chamfered vertices as shown in FIG. 1 is also included. 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 includes a first polarizer 11, a protective layer (outer protective layer) 12 disposed on the viewing side of the first polarizer 11, a protective layer (inner protective layer) 13 disposed on the image display cell side of the first polarizer 11, and a first adhesive layer 14 disposed 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 and the like, 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 disposed on the back side (opposite side to the image display cell) of the second polarizer 21, a protective layer (inner protective layer) 23 disposed on the image display cell side of the second polarizer 21, and a second adhesive layer 24 disposed 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 the 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 disposed on the back side (opposite side to the image display cell) of the outer protective layer. The reflective polarizer 26 is bonded to the second polarizer 21 or the outer protective layer (if present) via an arbitrary appropriate adhesive layer (for example, having 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 respective ends of the first polarizing plate and the second polarizing plate and at corresponding positions with respect to each other. By forming the through-holes, for example, when an image display device incorporates a camera, an adverse effect on the camera performance can be prevented. Further, by forming the through-holes at or near the ends of the polarizing plate, when the polarizing plate is applied to an image display device, the influence of the through-holes on the image display (for example, light leakage in the through-hole portion) can be minimized. The through-holes can be formed by various methods such as laser processing, cutting with an end mill, punching with a Thomson blade or a Pinnacle (registered trademark) blade, and the like. In the present specification, "provided at corresponding positions with respect 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 and the second polarizer 21 has an absorption axis Ab in the long side direction 2 The rectangular film has a tendency to contract easily in the long side direction and hardly contract in the short side direction. Further, the polarizer (and as a result, the polarizing plate) has a tendency to contract easily in the absorption axis direction. Therefore, by including the reflective polarizer, the absorption axis direction of the second polarizing plate that is difficult to contract is set to the long side direction of the film (the direction in which it is easy to contract), and the absorption axis direction of the first polarizing plate that is easier to contract than the second polarizing plate is set to the short side direction of the film (the direction in which it is difficult to contract), so that the displacement in the through-hole portion of each polarizing plate can be reduced, and the difference between the displacement of the first polarizing plate and the displacement of the second polarizing plate can be reduced.

[0012] If necessary, a retardation layer may be provided on the first polarizing plate 10 and / or the second polarizing plate 20. The type, number, combination, arrangement position, and characteristics of the retardation layer can 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 thereof. The λ / 2 plate and the λ / 4 plate typically have refractive index characteristics of nx > ny ≥ nz. For the λ / 2 plate, the in-plane retardation Re(550) is preferably 180 nm to 320 nm, and for the λ / 4 plate, the in-plane retardation Re(550) is preferably 100 nm to 200 nm. Also, 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 the in-plane retardation measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. Rth(λ) is obtained 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 where the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal 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 polarizer set will be specifically described below. Note that the first polarizer and the second polarizer are collectively referred to as the polarizer, the first polarizer element and the second polarizer element are collectively referred to as the polarizer element, the respective protective layers in the first polarizer and the second polarizer are collectively referred to as the protective layer, and the first adhesive layer and the second adhesive layer are collectively referred to as the adhesive layer for explanation. Therefore, for example, when it is said that "the polarizer is", it may mean that "the first polarizer and the second polarizer are respectively". On the other hand, when it is necessary to separately describe the first polarizer and the second polarizer, "the first" or "the second" is specified.

[0014] B. Polarizer B-1. Overall Configuration of Polarizer In one embodiment, the first polarizer 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, A 1 is the distance (μm) from the outermost part on the image display cell 120 side of the first adhesive layer 14 to the center in the thickness direction of the first polarizer element 11; T pol1 is the thickness (μm) of the first polarizer element 11; C psa1 is the creep value (μm / hr) of the first adhesive layer 14; T psa1 is the thickness (μm) of the first adhesive layer 14; 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, A 2is the distance (μm) from the outermost part on the image display cell 120 side of the second adhesive layer 24 to the center in the thickness direction of the second polarizer 21; T pol2 is the thickness (μm) of the second polarizer 21; C psa2 is the creep value (μm / hr) of the second 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, the "creep value" means the creep value at 85°C. The creep value can be measured, for example, by the following procedure: Stick the adhesive constituting the adhesive layer to a support plate. With the support plate with the adhesive attached fixed, apply a 500 g load vertically downward. Measure the amount of displacement of the adhesive from the support plate 1 hour after applying the load, and take the amount of displacement as the creep value (μm / hr). Also, the thickness T pro1 of the protective layer in the above relational expression is obtained 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 protective layer 12 and the protective layer 13 and the thickness of the adhesive layer for attaching the protective layer (including the adhesive layer when the polarizer or the protective film and the reflective polarizer are adhered via the adhesive layer) and the thickness of the surface treatment layer formed on the protective layer 12 as required. The same applies to T pro2 for the second polarizing plate. K 1 value and K 2 value are each more preferably 250×10 2 (μm 3 / hr) or less, still more 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 simply referred to 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 3It can be (in units of / hr). If the K value is within such a range, the deviation of the through-hole portion (substantially, the deviation of the adhesive layer) can be significantly suppressed. The technical meaning of setting the K value to a predetermined value or less is as follows: The deviation of the adhesive layer increases as the moment force applied to the adhesive layer and the ease of movement of the adhesive layer itself increase, and decreases as the restraining force against the movement of the adhesive layer increases. The moment force applied to the adhesive layer may be related to the distance from the image display cell to the polarizer to which the polarizing plate is attached 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; 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 (configuring the adhesive layer to be hard) and reducing the thickness of the adhesive layer, the adhesive layer itself can be made less likely to move; by setting the thickness T pro of the protective layer within a predetermined range, the restraining force against the movement of the adhesive layer can be set within an appropriate range. Therefore, by adjusting each of the above requirements to control the K value to a predetermined value or less, the deviation 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, still 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. When the creep value C psa is too small and / or when the thickness T psa of the adhesive layer is too small, stress relaxation may become difficult and the risk of cracks or peeling may increase. If the thickness T pro of the protective layer is too small, curl adjustment may become difficult.

[0015] As shown in FIG. 4, the polarizing plate (the first polarizing plate 10 in the illustrated example) was subjected to a heating test at 85° C. for 120 hours in a state of being bonded to a glass plate 130 (which can correspond to the substrate of the image display cell). The amount of deviation D in the through-hole portion is, for example, 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, still more preferably 150 μm or less, particularly preferably 120 μm or less, especially preferably 100 μm or less, and most preferably 80 μm or less. The smaller the amount of deviation D, the more preferable it is. The lower limit of the amount of deviation D is 10 μm in one embodiment and 20 μm in another embodiment. Note that the amount of deviation D refers to the maximum portion of the polarizing plate that moves away from the through-hole portion when viewed in cross-section. The reference of the through-hole portion can typically be the lower end portion of the adhesive layer. That is, when the polarizing plate is displaced mainly due to the shrinkage of the polarizer (to the right in the illustrated example), the adhesive layer 14 adheres to the glass plate 130, and thus displacement is recognized in the through-hole portion. As shown in FIG. 4, the polarizing plate typically deviates to the side away from the through-hole in the through-hole portion (right side in FIG. 4), and the opposing portion deviates so as to protrude from the through-hole (left side in FIG. 4). According to the embodiment of the present invention, both the first polarizing plate and the second polarizing plate can reduce the deviation (substantially the deviation of the adhesive layer) in the through-hole portion as described above, so that the effect can be synergistically exhibited when the polarizing plates are set.

[0016] The difference (absolute value) between the amount of deviation of the first polarizing plate and the amount of deviation of the second polarizing plate is, for example, 85 μm or less, preferably 80 μm or less, more preferably 60 μm or less, still more preferably 40 μm or less, and particularly preferably 30 μm or less. The smaller the difference in the amount of deviation, the more preferable it is. The lower limit of the difference in the amount of deviation can be, for example, 3 μm. According to the embodiment of the present invention, the difference between the amount of deviation of the first polarizing plate and the amount of deviation 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 having only the camera portion as a non-display area and / or a bezel-less image display device.

[0017] The dimensional shrinkage rate of the polarizing plate after the above heating test is preferably 1.0% or less, more preferably 0.6% or less, and still more preferably 0.3% or less. The smaller the dimensional shrinkage rate, the more preferable it is. The lower limit of the dimensional shrinkage rate can be, for example, 0.01%. The dimensional shrinkage rate is obtained by the following formula. The dimensional shrinkage rate is the dimensional shrinkage rate of the entire polarizing plate attached to the glass plate. When the polarizing plate further has an optical functional layer (for example, a retardation layer, a reflective polarizer), it means the dimensional shrinkage rate of the entire polarizing plate including the optical functional layer. In the following formula, "dimension" is the dimension in the absorption axis direction of the polarizing plate (substantially, the polarizer). Dimensional shrinkage rate (%) = {(Dimension before heating test - Dimension after heating test) / Dimension before heating test} × 100

[0018] In the polarizing plate, the through holes are formed at any appropriate position at the end or in the vicinity thereof according to 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 formation position of the through holes is not limited to the corners. The through holes may be formed at substantially the center of the longitudinal end of the polarizing plate, at a predetermined position of the longitudinal end, at substantially the center of the short-side end of the polarizing plate, or at a predetermined position of the short-side end. Also, a plurality of through holes may be formed, or a through hole and a notch may be formed in combination.

[0019] In one embodiment, as shown in FIG. 5, the distance from the longitudinal center to the longitudinal end of the polarizer is L 1 , the longitudinal distance from the longitudinal center of the polarizer to the center of the through hole is L 2 , the distance from the short-side center to the short-side end of the polarizer is W 1 , and the short-side distance from the short-side center of the polarizer to the center of the through hole is W 2 When defined as such, the through holes are preferably formed at positions satisfying 0.85 ≦ L 2 / L 1 ≦ 0.99 and 0.50 ≦ W 2 / W 1 ≦ 0.99. L2 / L 1 is more preferably from 0.90 to 0.97, and even more preferably from 0.92 to 0.96. W 2 / W 1 is more preferably from 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 can be, for example, 2 mm, or can 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 the embodiment of the present invention, since the deviation amount D is very small as described above, even if the diameter of the through-hole is reduced, D / R can be made within such a range. Therefore, even if the diameter of the through-hole is reduced, an adverse effect 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 having only the camera part as a non-display area and / or a bezel-less image display device.

[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 length and 65 mm to 75 mm in width, or 230 mm to 240 mm in length and 140 mm to 150 mm in width. That is, the polarizing plate according to the embodiment of the present invention can be suitably used for a smartphone or a tablet PC. As the smartphone size, for example, the length may be 120 mm to 200 mm, and the width may be 30 mm to 120 mm.

[0022] B-2. Polarizer A polarizer is typically composed of a resin film containing a dichroic substance. As the resin film, any suitable 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.

[0023] Specific examples of a polarizer composed of a single-layer resin film include those obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, during the dyeing, or after the stretching and then the dyeing. If necessary, the PVA-based resin film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can the dirt on the surface of the PVA-based film and the blocking inhibitor be washed, but also the PVA-based resin film can be swollen to prevent uneven dyeing and the like.

[0024] Specific examples of the polarizer obtained using the 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 formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it 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; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer; and the like. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include, if necessary, air stretching the laminate at a high temperature (for example, 95° C. or higher) before stretching in the aqueous boric acid solution. The obtained laminate of the resin substrate / polarizer may be used as it is (that is, 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 the resin substrate / polarizer, and an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface and used. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. 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 still 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 such a range, curling during heating can be suppressed well, and good appearance durability during heating can be obtained.

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

[0027] 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 the polarizer. Specific examples of the material that is the main component of the film include cellulose resins such as triacetyl cellulose (TAC), and transparent resins such as polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based resins. Also included are thermosetting resins or ultraviolet curable resins such as (meth)acrylic-based, urethane-based, (meth)acrylic urethane-based, epoxy-based, and silicone-based resins. In addition, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of 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. Examples include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extruded 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 surface treatments such as hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment, as necessary. Further / alternatively, the outer protective layer may be subjected to a treatment (typically, imparting an (elliptical) polarization function or imparting an ultra-high retardation) for improving visibility when viewed through polarized sunglasses, as necessary. By performing such treatments, excellent visibility can be achieved even when the display screen is viewed through a polarizing lens such as polarized sunglasses. Therefore, the set of polarizing plates can also be suitably applied to an image display device that can be used outdoors.

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

[0030] The thickness of the protective layer can be any appropriate thickness. The thickness of the protective layer is, for example, from 10 μm to 50 μm, preferably from 20 μm to 40 μm. When surface treatment is performed, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer. Here, the "thickness of the protective layer" refers to the respective thicknesses of the outer protective layers 12 and 22 and the inner protective layer 13, which is different from T pro1 and T pro2 in the above formula.

[0031] B-4. Adhesive Layer As described above, the adhesive layer is used to bond the polarizing plate to the image display cell. The adhesive layer can 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 can be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more in the solid content of the adhesive composition. The (meth)acrylic polymer contains alkyl (meth)acrylate as a main component in monomer units. Note that (meth)acrylate refers to acrylate and / or methacrylate. The alkyl (meth)acrylate can be contained at a ratio of preferably 80% by weight or more, more preferably 90% by weight or more in the monomer components forming the (meth)acrylic polymer. Examples of the alkyl group of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms of the alkyl group is preferably 3 to 9, more preferably 3 to 6. A preferred alkyl (meth)acrylate is butyl acrylate. Examples of the monomers (copolymerization monomers) constituting the (meth)acrylic polymer include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, heterocyclic ring-containing vinyl monomers, etc. Representative examples of the copolymerization monomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, N-vinyl-2-pyrrolidone. The acrylic adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include epoxy group-containing silane coupling agents. Examples of the crosslinking agent include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Further, the acrylic adhesive composition may contain an antioxidant and / or a conductive agent. As described above, the thickness of the adhesive layer is preferably 22 μm or less, more preferably 10 μm to 22 μm.Details of the adhesive layer or the acrylic adhesive composition are described, for example, in JP-A-2006-183022, JP-A-2015-199942, JP-A-2018-053114, JP-A-2016-190996, and WO2018 / 008712, and the descriptions in these publications are incorporated herein by reference.

[0032] The storage elastic modulus G of the adhesive layer at -40°C 2 ’ is preferably 1.0×10 5 (Pa) or more, more preferably 1.0×10 6 (Pa) or more, still more preferably 1.0×10 7 (Pa) or more, particularly preferably 1.0×10 8 (Pa) or more. The storage elastic modulus G 2 ’ can be, for example, 1.0×10 9 (Pa) or less.

[0033] B-5. Reflective polarizer As described above, the reflective polarizer 26 can be provided on the side opposite to the image display cell 120 (the back side) of the second polarizing plate 20. By providing the reflective polarizer, the second polarizing plate is less likely to shrink than the first polarizing plate. As a result, by setting the absorption axis direction of the second polarizing plate in the long side direction of the film (the direction in which shrinkage is likely to occur) and the absorption axis direction of the first polarizing plate in the short side direction of the film (the direction in which shrinkage is less likely to occur), the deviation in the through-hole portion of each polarizing plate can be reduced, and the difference between the deviation of the first polarizing plate and the deviation of the second polarizing plate can be reduced.

[0034] The reflective polarizer has a 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, as an example, a linear polarization separation type reflective polarizer will be described. Examples of the circular polarization separation type reflective polarizer include, for example, a laminate of a film in which a cholesteric liquid crystal is immobilized and a λ / 4 plate.

[0035] FIG. 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 laminated. For example, the total number of layers of such a multilayer laminate can be 50 to 1000. 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 and the refractive index ny in the y-axis direction of layer B are substantially the same. 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 becomes the reflection axis and the y-axis direction becomes 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. Note that the x-axis direction corresponds to the stretching direction of the reflective polarizer in the manufacturing method of the reflective polarizer.

[0036] The above layer A is preferably composed of a material that exhibits birefringence by stretching. Representative 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 above layer B is preferably composed of a material that does not substantially exhibit birefringence even when stretched. Representative examples of such materials include copolyesters of naphthalenedicarboxylic acid and terephthalic acid.

[0037] The reflective polarizer transmits light having a first polarization direction (e.g., p-wave) at the interface between layer A and layer B and reflects light having a second polarization direction orthogonal to the first polarization direction (e.g., s-wave). The reflected light is partially transmitted as light having the first polarization direction and partially reflected as light having the second polarization direction at the interface between layer A and layer B. Inside the reflective polarizer, such reflection and transmission are repeated many times, whereby the utilization efficiency of light can be increased.

[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, the light that has returned to the outermost part of the reflective polarizer without being finally utilized can be further utilized, so that the light utilization efficiency can be further improved. The reflective layer R typically exhibits a reflective function due to a multilayer structure of a polyester resin layer.

[0039] The total thickness of the reflective polarizer can be appropriately set according to 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] As the reflective polarizer, for example, those described in Japanese Patent Application Laid-Open No. Hei 9-507308 and Japanese Patent Application Laid-Open No. 2013-235259 can be used. The reflective polarizer may be used as a commercially available product as it is, or a commercially available product may be used after secondary processing (for example, stretching). Examples of commercially available products include the product name DBEF manufactured by 3M and the product name APF manufactured by 3M.

[0041] 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 includes an image display cell 120, a first polarizing plate 10 disposed on the viewing side of the image display cell 120, and a second polarizing plate 20 disposed on the back side of the image display cell 120.

[0042] Examples of the image display device include a liquid crystal display device, an organic electroluminescence (EL) display device, and a quantum dot display device. Preferably, it is a liquid crystal display device. This is because the effect of the set of polarizing plates is remarkable.

Examples

[0043] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. Also, unless otherwise specified, "parts" and "%" in the examples are based on weight.

[0044] (1) Deviation amount In the set of polarizing plates obtained in the examples and comparative examples, the first polarizing plate and the second polarizing plate were each attached to a glass plate (manufactured by Matsunami Glass, 350 mm in length × 250 mm in width × 1.1 mm in thickness) via an adhesive layer to prepare test samples. Each test sample was subjected to a heating test at 85°C for 120 hours. After the test, the deviation amount of the first polarizing plate or the second polarizing plate in the through-hole portion (substantially, the first adhesive layer or the second adhesive layer) was measured with an optical microscope (MX61L) manufactured by OLYMPUS. The measurement was performed for each of three test samples, and the maximum value among the three measured values was taken as the deviation amount.

[0045] <Production Example 1> A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate with respect to 100 parts of the monomer mixture (solid content), and nitrogen gas was introduced while gently stirring for nitrogen substitution. After that, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55°C to prepare a solution of an acrylic polymer (a) having a weight average molecular weight (Mw) of 1.56 million. With respect to 100 parts of the solid content of the obtained solution of acrylic polymer (a), 0.1 part of an isocyanate crosslinking agent (trade name: Takenate D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 part of benzoyl peroxide (trade name: Nipper BMT 40SV, manufactured by NOF Corporation), 0.3 part 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), and 0.2 part of an antioxidant (trade name: Irganox 1010, hindered phenol type, manufactured by BASF Japan Ltd.) were blended to obtain an adhesive composition A.

[0046] <Production Example 2> A solution of an acrylic polymer (b) having a weight average molecular weight (Mw) of 1.57 million 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 part of acrylic acid, and 0.4 part of 4-hydroxybutyl acrylate was used. An adhesive composition B was obtained in the same manner as in Production Example 1, except that the acrylic polymer (b) was used, 0.2 part 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 part of lithium bis(trifluoromethanesulfonyl)imide (manufactured by Mitsubishi Materials Corporation) was further added.

[0047] <Production Example 3> A solution of an acrylic polymer (c) with a weight average molecular weight (Mw) of 1.5 million 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. Adhesive composition C was obtained in the same manner as in Production Example 1, except that the acrylic polymer (c) was used, the blending amount of the silane coupling agent was 0.1 part, 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.

[0048] <Production Example 4> A solution of an acrylic polymer (d) with a weight average molecular weight (Mw) of 1.65 million was prepared in the same manner as in Production Example 1. To 100 parts of the solid content of the obtained solution of the acrylic polymer (d), 0.1 part of an isocyanate crosslinking agent (trade name: Takenate D110N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.), 0.3 part of benzoyl peroxide (trade name: Niper BMT 40SV, manufactured by NOF Corporation), and 0.2 part of an acetoacetyl group-containing silane coupling agent (trade name: A-100, manufactured by Soken Chemical & Engineering Co., Ltd.) were blended to obtain adhesive composition D.

[0049] <Production Example 5> Adhesive composition E was obtained in the same manner as in Production Example 1, except that 0.2 part 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> (Production of the first polarizing plate) As the polarizer (first polarizer), a film (thickness 12 μm) obtained by adding iodine to 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 with each other. The HC-TAC film is a film in which a hard coat (HC) layer (thickness 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness 25 μm), and it was bonded so that the TAC film was on the polarizer side. An adhesive layer (first adhesive layer: thickness 20 μm) was formed on the surface of the inner protective layer using an adhesive composition B, and a first polarizing plate having a configuration of outer protective layer / first polarizer / inner protective layer / first adhesive layer was obtained. The first polarizing plate was punched out into a size of 148 mm in length and 70 mm in width, and further, a through hole with a diameter of 3.9 mm was formed at the corner. At this time, it was punched out so that the absorption axis direction of the first polarizer was the short side direction.

[0051] (Production of the second polarizing plate) A polarizing plate was obtained in the same manner as in the case of 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. Further, 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 an adhesive composition E, and a second polarizing plate having a configuration of reflective polarizer / outer protective layer / second polarizer / inner protective layer / second adhesive layer was obtained. The second polarizing plate was punched out into a size of 148 mm in length and 70 mm in width, and further, a through hole with a diameter of 3.9 mm was formed at the corner. At this time, it was punched out so that the absorption axis direction of the second polarizer was the longitudinal direction.

[0052] (Setting of the polarizing plate) 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 set of polarizing plates of this example. The obtained set of polarizing plates was subjected to the evaluation of the above-mentioned deviation amount. 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 short-side direction.

[0053] <Comparative Example 1> A set of polarizing plates was obtained in the same manner as in Example 1, except that the first polarizing plate was produced by punching out the first polarizer so that the absorption axis direction thereof was in the longitudinal direction, and the second polarizing plate was produced by punching out the second polarizer so that the absorption axis direction thereof was in the short-side direction. The obtained set of polarizing plates 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.

[0054] <Example 2> (Production of the first polarizing plate) A first polarizing plate having a structure of an outer protective layer / a first polarizer / an inner protective layer / a 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 further, through holes having a diameter of 3.9 mm were formed at the corners. At this time, it was punched out so that the absorption axis direction of the first polarizer was in the short-side direction.

[0055] (Production of the second polarizing plate) As the thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) which was long and had a Tg of about 75°C was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin in which 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 "Gosefimer") were mixed at a ratio of 9:1, and the resulting mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (length direction) in an oven at 130°C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer became a desired value (dyeing treatment). Next, the laminate was immersed in a crosslinking bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 70°C (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%), uniaxial stretching was performed in the longitudinal direction (length direction) between rolls with different peripheral speeds so that the total stretching ratio became 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a cleaning bath at a liquid temperature of 20°C (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (cleaning treatment). Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a laminate having a structure of resin substrate / second polarizer was obtained. A TAC film (20 μm thick) was laminated as an inner protective layer on the surface of the obtained laminate on the side opposite to the resin substrate. Next, the resin substrate was peeled off, and a reflective polarizer (26 μm thick) was laminated on the peeled surface via a normal adhesive layer (12 μm thick). An adhesive layer (20 μm thick) was formed on the surface of the inner protective layer using an adhesive composition D, and a second polarizing plate having a structure of reflective polarizer / second polarizer / inner protective layer / second adhesive layer was obtained. The second polarizing plate was punched into a size of 148 mm in length and 70 mm in width, and further, through holes with a diameter of 3.9 mm were formed at the corners. At this time, it was punched so that the absorption axis direction of the second polarizer was in the longitudinal direction.

[0056] (Set of polarizing plates) 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 set of polarizing plates of this example. The obtained set of polarizing plates 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.

[0057] <Comparative Example 2> A set of polarizing plates was obtained in the same manner as in Example 2, except that the first polarizing plate was produced by punching out the first polarizer so that the absorption axis direction was in the longitudinal direction, and the second polarizing plate was produced by punching out the second polarizer so that the absorption axis direction was in the short-side direction. The obtained set of polarizing plates 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.

[0058] <Example 3> (Production of the first polarizing plate) Instead of using an acrylic resin film as the inner protective layer, a cycloolefin resin film (thickness 13 μm) was used, and a first adhesive layer (thickness 20 μm) was formed using an adhesive composition C instead of the adhesive composition B. In the same manner as in Example 1, a first polarizing plate having a configuration of an outer protective layer / a first polarizer / an inner protective layer / a first adhesive layer was obtained. The first polarizing plate was punched into a size of 148 mm in length and 70 mm in width, and further, a through hole with a diameter of 3.9 mm was formed at the corner. At this time, it was punched so that the absorption axis direction of the first polarizer was in the short side direction.

[0059] (Production of the second polarizing plate) In the same manner as in Example 2, a laminate having a configuration of a resin substrate / a second polarizer was obtained. A TAC film (thickness 20 μm) was laminated on the surface of the polarizer of the obtained laminate (the surface opposite to the resin substrate) as the inner protective layer. Next, the resin substrate was peeled off, and a reflective polarizer (thickness 26 μm) was laminated on 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 an adhesive composition D, and a second polarizing plate having a configuration of a reflective polarizer / a second polarizer / an inner protective layer / a second adhesive layer was obtained. The second polarizing plate was punched into a size of 148 mm in length and 70 mm in width, and further, a through hole with a diameter of 3.9 mm was formed at the corner. At this time, it was punched so that the absorption axis direction of the second polarizer was in the long side direction.

[0060] (Setting of the polarizing plate) 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 set of polarizing plates of this example. The obtained set of polarizing plates 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.

[0061] <Comparative Example 3> A first polarizing plate was produced by punching out such that the absorption axis direction of the first polarizer was the longitudinal direction, and a second polarizing plate was produced by punching out such that the absorption axis direction of the second polarizer was the short-side direction. A set of polarizing plates was obtained in the same manner as in Example 3 except for the above. The obtained set of polarizing plates 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.

[0062] <Example 4> (Production of the first polarizing plate) A laminate having a resin base material / polarizer structure was obtained in the same manner as the second polarizing plate of Example 2. An HC-TAC film was laminated on the polarizer surface (the surface opposite to the resin base material) of the obtained laminate as an outer protective layer. Next, the resin base material was peeled off, and an adhesive layer (thickness: 15 μm) was formed on the peeled surface using the adhesive composition A to obtain a first polarizing plate having a structure of outer protective layer / first polarizer / inner protective layer / first adhesive layer. The first polarizing plate was punched out to a size of 148 mm in length and 70 mm in width, and further, through holes having a diameter of 3.9 mm were formed at the corners. At this time, it was punched out such that the absorption axis direction of the first polarizer was the short-side direction.

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

[0064] (Set of polarizing plates) 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 set of polarizing plates of this example. The obtained set of polarizing plates 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.

[0065] <Comparative Example 4> (Production of the 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 bonded to both sides of this polarizer so that their longitudinal directions were aligned with each other. An adhesive layer (thickness: 20 μm) was formed on the surface of the inner protective layer using an adhesive composition D, and a first polarizing plate having a configuration of outer protective layer / first polarizer / inner protective layer / first 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 further, through holes with a diameter of 3.9 mm were formed at the corners. At this time, it was punched out so that the absorption axis direction of the first polarizer was in the short-side direction.

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

[0067] (Set of polarizing plates) 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 set of polarizing plates for this comparative example. The obtained set of polarizing plates 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.

[0068]

Table 1

[0069] As is clear from Table 1, the set of polarizing plates of the examples of the present invention can make the difference (absolute value) between the deviation amount of the first polarizing plate and the deviation amount of the second polarizing plate significantly smaller than that of the comparative example. Therefore, the set of polarizing plates of the examples of the present invention has extremely great design advantages when applied to an image display device.

Industrial applicability

[0070] The polarizer set of the present invention is suitably used in an image display device, and in particular, can be suitably used in an image display device having a camera unit typified by a smartphone, a tablet PC, or a smartwatch.

Explanation of Reference Numerals

[0071] 10 First polarizer 11 First polarizer element 12 Outer protective layer 13 Inner protective layer 14 First adhesive layer 15 Through hole 20 Second polarizer 21 Second polarizer element 22 Outer protective layer 23 Inner protective layer 24 Second adhesive layer 25 Through hole 100 Polarizer set 120 Image display cell 200 Image display device

Claims

[Claim 1] A polarizing plate set including a rectangular first polarizing plate arranged on a viewing side of an image display cell and a rectangular second polarizing plate arranged on a back side of the image display cell, 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 disposed 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 side of the second polarizer opposite to the image display cell, and a second pressure-sensitive adhesive layer arranged on the image display cell side; 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 set of polarizing plates.

Images