Polarizing plate set and image display device including the same

Abstract

The present invention provides a polarizing plate group in which the displacement of each polarizing plate in the through-hole portion is small and the difference between the displacement of the polarizing plate on the visible side and the displacement of the polarizing plate on the back side is very small. The polarizing plate group includes a rectangular first polarizing plate arranged on the visible side of an image display unit and a rectangular second polarizing plate arranged on the back side. The first polarizing plate has a first polarizer, a protective layer arranged on at least one side thereof, and a first adhesive layer arranged on the image display unit side, and the second polarizing plate has a second polarizer, a protective layer arranged on at least one side thereof, a reflective polarizer arranged on the side opposite to the image display unit of the second polarizer, and a second adhesive layer arranged on the image display unit side. The thickness of the first polarizer and the second polarizer is respectively less than 20 μm, 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 respective ends or positions corresponding to each other near the ends.

Description

Technical Field

[0001] The invention relates to a polarizing plate group and an image display device comprising the polarizing plate group. Background Art

[0002] Polaroids have been widely used in image display devices such as mobile phones and notebook personal computers for the purpose of realizing image display and / or improving the performance of the image display. In recent years, with the rapid popularization of smart phones and touch panel information processing devices, image display devices equipped with cameras have been increasingly widely used. Correspondingly, polaroids having through holes at positions corresponding to camera parts have also been increasingly widely used. In polaroids having such through holes, various research items are included for the through holes or their vicinity.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 047510 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The present invention is made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate set in which the displacement of each polarizing plate in the through-hole portion is small and the difference between the displacement of the polarizing plate on the viewing side and the displacement of the polarizing plate on the back side is very small.

[0008] Solutions to the problem

[0009] The polarizing plate set of the present invention comprises a rectangular first polarizing plate arranged on the visible side of an image display unit, and a rectangular second polarizing plate arranged on the back side of the image display unit. The first polarizing plate comprises 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 unit side; the second polarizing plate comprises 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 unit, and a second adhesive layer arranged on the image display unit side. The thickness of the first polarizer and the second polarizer is respectively less than 20 μm, 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 respective ends or positions corresponding to each other near the ends.

[0010] In one embodiment, the distance A from the outermost portion of the first adhesive layer on the image display unit side to the center portion in the thickness direction of the first polarizer is 1(μm), the thickness T of the first polarizer pol1 (μm), the creep value C of the first adhesive layer psa1 (μm / hr), the thickness T of the first adhesive layer psa1 (μm), and the thickness T of the protective layer in the first polarizer pro1 (μm) satisfies the following relationship,

[0011] (A 1 ×T pol1 )×(C psa1 ×T psa1 ) / T pro1 =K 1 ≤300×10 2 (μm 3 / hr)

[0012] A distance A from the outermost portion of the second adhesive layer on the image display unit side to the center portion in the thickness direction of the second polarizer 2 (μm), the thickness T of the second polarizer pol2 (μm), the creep value C of the second adhesive layer psa2 (μm / hr), the thickness T of the second adhesive layer psa2 (μm), and the thickness T of the protective layer in the second polarizer pro2 (μm) satisfies the following relationship,

[0013] (A 2 ×T pol2 )×(C psa2 ×T psa2 ) / T pro2 =K 2 ≤300×10 2 (μm 3 / hr).

[0014] In one embodiment, the above K 1 and K 2 200×10 2 (μm 3 / hr) or less.

[0015] In one embodiment, the creep value C of the first adhesive layer is psa1 It is 100 (μm / hr) or less.

[0016] In one embodiment, the thickness T of the second polarizer is pol2 Less than 10 μm.

[0017] In one embodiment, the above K 1 and K 2150×10 2 (μm 3 / hr) or less.

[0018] In one embodiment, the thickness T of the first polarizer is pol1 Less than 10 μm.

[0019] In one embodiment, the thickness T of the first adhesive layer is psa1 and the thickness T of the second adhesive layer psa2 They are 10μm to 22μm respectively.

[0020] In one embodiment, the through hole is formed at a corner portion of each of the first polarizer and the second polarizer.

[0021] In one embodiment, the distance from the center in the longitudinal direction to the end in the longitudinal direction when the first polarizer and the second polarizer are viewed from above is denoted by L. 1 The length direction distance from the length direction center of the first polarizer and the second polarizer to the center of the through hole is L. 2 The distance from the center of the short side direction of the first polarizer and the second polarizer to the end of the short side direction is set as W. 1 The distance in the short-side direction from the center of the short-side direction of the first polarizer and the second polarizer to the center of the through hole is set as W. 2 When the through hole is formed in the first polarizer and the second polarizer respectively at a position satisfying 0.85≤L 2 / L 1 ≤0.99 and 0.50≤W 2 / W 1 ≤0.99 position.

[0022] In one embodiment, the diameter of the through hole is 10 mm or less.

[0023] In one embodiment, the aspect ratios of the first polarizer and the second polarizer are respectively 1.3 to 2.5.

[0024] According to another aspect of the present invention, an image display device is provided, which includes an image display unit and the above-mentioned polarizing plate group, wherein the first polarizing plate is arranged on the visible side of the image display unit, and the second polarizing plate is arranged on the back side of the image display unit.

[0025] Effects of the Invention

[0026] According to an embodiment of the present invention, a polarizing plate group can be provided in which the offset of each polarizing plate in the through-hole portion is small, and the difference between the offset of the visible side polarizing plate and the offset of the back side polarizing plate is very small. When the offset of each polarizing plate in the through-hole portion is small, the effect can be synergistically exerted when the polarizing plate group is manufactured. When the difference in the offset is very small, the design advantage is extremely obvious when the polarizing plate group is applied to an image display device. For example, the polarizing plate group can be applied to an image display device with only a camera portion as a non-display area and / or a frameless image display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic plan view for explaining a first polarizing plate and a second polarizing plate in a polarizing plate set according to one embodiment of the present invention.

[0028] Figure 2 yes Figure 1 The schematic cross-sectional views of each of the first polarizer and the second polarizer in the polarizer set taken along the II-II line are schematic cross-sectional views for explaining the configuration positions of each of the first polarizer and the second polarizer.

[0029] Figure 3 is included Figure 1 A cross-sectional schematic diagram of an image display device with a polarizing plate group.

[0030] Figure 4 This is an enlarged cross-sectional view of a main part for explaining the displacement of the polarizing plate used in the polarizing plate set according to the embodiment of the present invention at the through-hole portion.

[0031] Figure 5 This is a schematic plan view for explaining the formation positions of the through holes in the polarizing plate used in the polarizing plate set according to the embodiment of the present invention.

[0032] Figure 6 This is a perspective schematic diagram of an example of a reflection-type polarizer that can be used in the second polarizing plate in the polarizing plate set according to the embodiment of the present invention.

[0033] Explanation of symbols

[0034] 10 1st polarizer

[0035] 11. 1st polarizer

[0036] 12 Outer protective layer

[0037] 13 Inner protective layer

[0038] 14 1st adhesive layer

[0039] 15 Through hole

[0040] 20 2nd polarizer

[0041] 21 Second polarizing filter

[0042] 22 Outer protective layer

[0043] 23 Inner protective layer

[0044] 24 Second adhesive layer

[0045] 25 Through hole

[0046] 100 Polarizer Set

[0047] 120 Image display unit

[0048] 200 Image display device DETAILED DESCRIPTION

[0049] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. It should be noted that the accompanying drawings are schematically shown for easy observation, and the ratios of length, width, thickness, etc., and angles, etc. in the accompanying drawings are different from the actual ones.

[0050] A. Overview of Polarizer Set

[0051] Figure 1 1 is a schematic plan view illustrating a first polarizer and a second polarizer in a polarizer set according to an embodiment of the present invention; Figure 2 yes Figure 1 A schematic cross-sectional view of the first polarizer and the second polarizer in the polarizer set along the II-II line; Figure 3 is included Figure 1 Schematic cross-sectional view of an image display device including a polarizing plate group. The polarizing plate group 100 shown in the figure includes 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 corresponding to the top view shape of the image display unit, and the rectangular shape has a long side and a short side. It should be noted that when the "rectangular shape" is mentioned in this specification, it also includes the following: Figure 1 As shown in the figure, each vertex is chamfered, including the shape of the R-shaped special-shaped processing part. Figure 3As shown, the first polarizing plate 10 is arranged on the visible side of the image display unit 120, and the second polarizing plate 20 is arranged on the back side of the image display unit 120. In the example shown in the figure, the first polarizing plate 10 has a first polarizer 11, a protective layer (outer protective layer) 12 arranged on the visible side of the first polarizer 11, a protective layer (inner protective layer) 13 arranged on the image display unit side of the first polarizer 11, and a first adhesive layer 14 arranged as the outermost layer on the image display unit 120 side. The first adhesive layer 14 is used to bond the first polarizing plate 10 to the image display unit 120. One of the protective layers 12 and 13 may be omitted depending on the purpose, etc. The second polarizing plate 20 includes a second polarizer 21, a reflective polarizer 26 disposed on the back side (opposite to the image display unit) of the second polarizer 21, a protective layer (inner protective layer) 23 disposed on the image display unit side of the second polarizer 21, and a second adhesive layer 24 disposed as the outermost layer on the image display unit 120 side. The second adhesive layer 24 is used to bond the second polarizer 20 to the image display unit 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. In the example shown in the figure, the outer protective layer of the second polarizer is omitted, but the reflective polarizer 26 can also be disposed on the back side (opposite to the image display unit) of the outer protective layer. The reflective polarizer 26 is bonded to the second polarizer 21 or the outer protective layer (if present) via any appropriate adhesive layer (for example, a thickness of 2 μm to 20 μm).

[0052] In an embodiment of the present invention, the first polarizer 10 has a through hole 15, and the second polarizer 20 has a through hole 25. The through holes 15 and 25 are formed at respective ends or near the ends of the first polarizer and the second polarizer, and at positions corresponding to each other. By forming the through holes, for example, in the case where a camera is built into an image display device, it is possible to prevent adverse effects on the performance of the camera. Furthermore, by forming the through holes at the ends or near the ends of the polarizer, when the polarizer is applied to the 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, for example, laser processing, cutting processing using an end mill, punching processing using a Thomson knife or a pinnacle knife (registered trademark), etc. It should be noted that the "arranged at positions corresponding to each other" in this specification means that when two polarizers are overlapped, the through holes overlap.

[0053] like Figure 1 As shown, the first polarizer 11 has an absorption axis Ab in the short side direction. 1 The second polarizer 21 has an absorption axis Ab in the long side direction. 2. The rectangular film tends to shrink easily in the long side direction but not easily in the short side direction. Furthermore, the polarizer (ultimately the polarizer) tends to shrink easily in the absorption axis direction. Therefore, by setting the absorption axis direction of the second polarizer that is not easily shrunk due to the inclusion of a reflective polarizer as the long side direction of the film (the direction that is easy to shrink) and the absorption axis direction of the first polarizer that is easy to shrink compared to the second polarizer as the short side direction of the film (the direction that is not easy to shrink), the offset of each polarizer in the through hole portion can be reduced, and the difference between the offset of the first polarizer and the offset of the second polarizer can be reduced.

[0054] If necessary, a phase difference layer may also be provided in the first polarizer 10 and / or the second polarizer 20. The type, quantity, combination, configuration position, and characteristics of the phase difference layer may be appropriately set according to the purpose. For example, the phase difference layer may be a λ / 2 wave plate, a λ / 4 wave plate, or a stack thereof. The λ / 2 wave plate and the λ / 4 wave plate typically have a refractive index characteristic of nx>ny≥nz. The in-plane phase difference Re(550) of the λ / 2 wave plate is preferably 180nm to 320nm, and the in-plane phase difference Re(550) of the λ / 4 wave plate is preferably 100nm to 200nm. In addition, for example, the phase difference layer may also be a stack of a negative B plate (nx>ny>nz), a positive C plate (nz>nx=ny) or a positive B plate (nz>nx>ny). It should be noted that in this specification, "Re(λ)" is the in-plane phase difference measured at 23°C with light of a wavelength of λnm. For example, "Re(550)" is the in-plane phase difference measured at 23°C with light of a wavelength of 550nm. When the thickness of the layer (film) is set to d(nm), Re(λ) can be calculated according to the formula: Re(λ)=(nx-ny)×d. "Rth(λ)" is the phase difference in the thickness direction measured at 23°C with light of a wavelength of λnm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C with light of a wavelength of 550nm. When the thickness of the layer (film) is set to d(nm), Rth(λ) can be calculated according to the formula: Rth(λ)=(nx-nz)×d. "nx" is the refractive index in the direction where the in-plane refractive index reaches the maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction) in the plane, and "nz" is the refractive index in the thickness direction.

[0055] The components of the polarizer group are described in detail below. It should be noted that the first polarizer and the second polarizer are collectively referred to as polarizers, the first polarizer and the second polarizer are collectively referred to as polarizers, the protective layers of the first polarizer and the second polarizer 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 "polarizer" is recorded, it may mean "the first polarizer and the second polarizer, respectively". On the other hand, for example, when the first polarizer and the second polarizer need to be described individually, "the first" or "the second" is clearly recorded.

[0056] B. Polarizer

[0057] B-1. Overall structure of polarizing plate

[0058] In one embodiment, the first polarizer 10 preferably satisfies the following relationship:

[0059] (A 1 ×T pol1 )×(C psa1 ×T psa1 ) / T pro1 =K 1 ≤300×10 2 (μm 3 / hr)

[0060] Among them, A 1 T is the distance (μm) from the outermost portion of the first adhesive layer 14 on the image display unit 120 side to the center portion in the thickness direction of the first polarizer 11; pol1 is the thickness of the first polarizer 11 (μm); C psa1 is the creep value of the first adhesive layer 14 (μm / hr); T psa1 is the thickness of the first adhesive layer 14 (μm); 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:

[0061] (A 2 ×T pol2 )×(C psa2 ×T psa2 ) / T pro2 =K 2 ≤300×10 2 (μm 3 / hr).

[0062] Among them, A 2 T is the distance (μm) from the outermost portion of the second adhesive layer 24 on the image display unit 120 side to the center portion in the thickness direction of the second polarizer 21; pol2is the thickness of the second polarizer 21 (μm); C psa2 is the creep value of the second adhesive layer 24 (μm / hr); T psa2 is the thickness of the second adhesive layer 24 (μm); T pro2 is the thickness (μm) of the protective layer in the second polarizer 20. The "creep value" in this specification refers to the creep value at 85°C. The creep value can be measured, for example, by the following sequence: attaching the adhesive constituting the adhesive layer to the support plate; applying a load of 500g vertically downward while the support plate with the adhesive attached is fixed; measuring the displacement of the adhesive from the support plate 1 hour after the load is applied, and taking the displacement as the creep value (μm / hr). In addition, the thickness T of the protective layer in the above relationship is pro1 It can be calculated according to the formula: "Total thickness of the first polarizing plate - thickness of the first adhesive layer - thickness of the first polarizer". That is, T pro1 The thickness of the protective layer 12 and the protective layer 13 is the total thickness, the thickness of the adhesive layer used to adhere the protective layer (including the adhesive layer when the polarizer or 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 needed. pro2 Same thing. K 1 Value and K 2 The values ​​are more preferably 250×10 2 (μm 3 / hr) or less, more preferably 200×10 2 (μm 3 / hr) or less, particularly preferably 150 × 10 2 (μm 3 / hr) or less. 1 Value and K 2 The values ​​are collectively referred to as K values. The same applies to the distance A, creep value, thickness of the adhesive layer, and thickness of the protective layer. The lower limit of the K value can be, for example, 15×10 2 (μm 3 / hr). If the K value is within such a range, the offset of the through-hole portion (essentially the offset of the adhesive layer) can be significantly suppressed. The technical meaning of making the K value below a given value is as follows: the offset of the adhesive layer becomes larger when the torque force applied to the adhesive layer and the ease of movement of the adhesive layer itself are large, and becomes smaller when the inhibitory force on the movement of the adhesive layer is large. The torque force applied to the adhesive layer may be related to the distance from the image display unit 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; the inhibitory force on the movement of the adhesive layer may be related to the thickness of the protective layer. The torque force can be reduced by reducing the distance from the image display unit to the polarizer and the thickness of the polarizer; the adhesive layer itself can be made less likely to move by making the creep value of the adhesive layer below a given value (forming the adhesive layer at a harder level) and by reducing the thickness of the adhesive layer; and the thickness of the protective layer T pro The given range can make the restraining force on the movement of the adhesive layer reach an appropriate range. Therefore, by adjusting the above-mentioned elements and controlling the K value to be below the given value, the deviation of the adhesive layer can be significantly suppressed. Specifically, the above-mentioned distance A is preferably below 80 μm, more preferably below 50 μm. The lower limit of the distance A can be, for example, 10 μm. The creep value C psa It is preferably 140 μm / hr or less, more preferably 130 μm / hr or less, further preferably 120 μm / hr or less, and particularly preferably 100 μm / hr or less. The lower limit of the creep value may be, for example, 50 μm / hr. The thickness T of the protective layer pro The thickness T of the adhesive layer is preferably 15 μm to 65 μm, and more preferably 15 μm to 55 μm. psa It is preferably 22 μm or less, and more preferably 10 μm to 22 μm. psa When the thickness T of the adhesive layer is too small, and / or psa If the thickness of the protective layer is too small, stress relaxation may become difficult, and the risk of cracking or peeling may increase. pro If it is too small, it may sometimes make curl adjustment difficult.

[0063] like Figure 4As shown, after the polarizer (the first polarizer 10 in the example) is subjected to a heating test at 85°C and for 120 hours in a state where it is bonded to a glass plate (which may correspond to a substrate of an image display unit) 130, the offset D of the through-hole portion is, for example, less than 300 μm, preferably less than 250 μm, more preferably less than 200 μm, further preferably less than 150 μm, particularly preferably less than 120 μm, particularly preferably less than 100 μm, and most preferably less than 80 μm. The smaller the offset D, the better. The lower limit of the offset D is 10 μm in one embodiment and 20 μm in another embodiment. It should be noted that the offset D refers to the largest portion of the polarizer that is away from the through-hole portion when viewed in cross section. Representatively, the reference of the through-hole portion may be the lower end of the adhesive layer. That is, when the polarizer is offset (to the right in the example) mainly due to the contraction of the polarizer, the adhesive layer 14 stays on the bonded glass plate 130, and thus, the through-hole portion is recognized as offset. It should be noted that if Figure 4 As shown, typically, the polarizing plate is offset toward the side away from the through hole at the through hole portion ( Figure 4 ), and its opposite portion is offset in a manner exceeding the through hole ( Figure 4 According to the embodiment of the present invention, the first polarizer and the second polarizer can both reduce the offset of the through hole portion (substantially the offset of the adhesive layer) as described above, and therefore, can synergistically exert their effects when forming a polarizer set.

[0064] The difference (absolute value) between the offset of the first polarizer and the offset of the second polarizer is, for example, less than 85 μm, preferably less than 80 μm, more preferably less than 60 μm, further preferably less than 40 μm, and particularly preferably less than 30 μm. The smaller the difference in offset, the better. The lower limit of the difference in offset can be, for example, 3 μm. According to an embodiment of the present invention, the difference between the offset of the first polarizer and the offset of the second polarizer can be made very small. As a result, the polarizer group can be applied to an image display device with only a camera portion as a non-display area and / or a frameless image display device.

[0065] The dimensional shrinkage rate of the polarizer after the above-mentioned heating test is preferably less than 1.0%, more preferably less than 0.6%, and further preferably less than 0.3%. The smaller the dimensional shrinkage rate, the more preferred it is. The lower limit of the dimensional shrinkage rate can be, for example, 0.01%. It should be noted that the dimensional shrinkage rate can be calculated by the following formula. Among them, the dimensional shrinkage rate refers to the dimensional shrinkage rate of the entire polarizer pasted on the glass plate. When the polarizer further has an optical functional layer (for example, a phase difference layer, a reflective polarizer), it refers to the dimensional shrinkage rate of the entire polarizer including the optical functional layer. It should be noted that the "size" in the following formula is the size of the polarizer (essentially a polarizer) in the absorption axis direction.

[0066] Dimensional shrinkage (%) = {(dimensions before heating test - dimensions after heating test) / dimensions before heating test} × 100

[0067] In the polarizing plate, the through holes can be formed at any appropriate position at the end or near the end according to the purpose. Figure 1 As shown in the figure, the through holes are formed at the corners of the polarizers. It should be noted that the formation position of the through holes is not limited to the corners. The through holes can be formed in the approximate center of the longitudinal end of the polarizer, can be formed at a given position of the longitudinal end, can be formed in the approximate center of the short side end, and can also be formed at a given position of the short side end. In addition, a plurality of through holes can be formed, and the through holes and the notches can be formed in combination.

[0068] In one embodiment, if Figure 5 As shown in the figure, the distance from the center of the polarizer in the longitudinal direction to the end in the longitudinal direction is set to L 1 The lengthwise distance from the center of the polarizer to the center of the through hole is L. 2 The distance from the center of the short side of the polarizer to the end of the short side is W. 1 , and the distance in the short-side direction from the center of the short-side direction of the polarizer to the center of the through hole is set as W 2 When the through hole is formed, it is preferred to satisfy 0.85≤L 2 / L 1 ≤0.99 and 0.50≤W 2 / W 1 ≤0.99 position. L 2 / L 1 More preferably, it is 0.90 to 0.97, and even more preferably, it is 0.92 to 0.96. 2 / W 1 More preferably, it is 0.75 to 0.95.

[0069] The diameter R of the through hole is preferably less than 10 mm, more preferably less than 8 mm, and further preferably less than 5 mm. The lower limit of the diameter of the through hole may be, for example, 2 mm, and may be, for example, 1.5 mm. The ratio D / R of the offset D to the diameter R of the through hole is preferably less than 15%, more preferably less than 10%, further preferably less than 6%, and particularly preferably less than 5%. On the other hand, the smaller the lower limit of D / R, the better. According to an embodiment of the present invention, the offset D is very small as described above, so even if the diameter of the through hole is reduced, D / R can be within such a range. Therefore, even if the diameter of the through hole is reduced, adverse effects on camera performance can be substantially prevented. As a result, the polarizer used in an embodiment of the present invention can be applied to an image display device having only a camera portion as a non-display area and / or a frameless image display device.

[0070] The aspect ratio of the polarizer is preferably 1.3 to 2.5. In this case, the size of the polarizer 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 polarizer of the embodiment of the present invention can be suitably used in a smart phone or a tablet PC. As the size of a smart phone, for example, the vertical length can be 120 mm to 200 mm, and the width can be 30 mm to 120 mm.

[0071] B-2. Polarizer

[0072] Typically, the polarizer is formed of a resin film containing a dichroic substance. As the resin film, any appropriate resin film that can be used as a polarizer can be used. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA resin") film. The resin film can be a single-layer resin film or a laminate of two or more layers.

[0073] As a specific example of a polarizer composed of a single-layer resin film, there can be cited a polarizer obtained by subjecting a PVA-type resin film to a dyeing treatment using iodine and a stretching treatment (representatively uniaxial stretching). The above-mentioned dyeing using iodine can be performed, for example, by immersing the PVA-type film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after the dyeing treatment, or it can be performed while dyeing. In addition, dyeing can also be performed after stretching. The PVA-type resin film can be subjected to swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, etc. as needed. For example, by immersing the PVA-type resin film in water for washing before dyeing, not only can the dirt and anti-blocking agent on the surface of the PVA-type film be washed away, but the PVA-type resin film can also be swelled to prevent uneven dyeing.

[0074] As specific examples of polarizers obtained using a laminate, there can be listed: a laminate using a resin substrate and a PVA-type resin layer (PVA-type resin film) laminated on the resin substrate, or a laminate using a resin substrate and a PVA-type resin layer formed by coating the resin substrate. The polarizer obtained using a laminate using a resin substrate and a PVA-type resin layer formed by coating the resin substrate can be made by the following method: for example, a PVA-type resin solution is applied to a resin substrate, and the PVA-type resin layer is formed on the resin substrate by drying, thereby obtaining a laminate of the resin substrate and the PVA-type resin layer; the laminate is stretched and dyed to make the PVA-type resin layer into a polarizer. In the present embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution for stretching. In addition, stretching may further include stretching the laminate in a gas atmosphere at a high temperature (for example, above 95°C) before stretching in a boric acid aqueous solution as required. The obtained laminate of resin substrate / polarizer can be used directly (that is, the resin substrate can be made into a protective layer of polarizer), or the resin substrate can be peeled off from the laminate of resin substrate / polarizer, and any appropriate protective layer consistent with the purpose can be laminated on the peeled surface for use. The details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The records of these patent documents are cited in this specification as a reference.

[0075] The thickness of the polarizer is preferably 20 μm or less, more preferably 12 μm or less, and further 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 well suppressed and good appearance durability during heating can be obtained.

[0076] 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 polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

[0077] B-3. ​​Protective layer

[0078] The protective layers 12, 13, and 23 can be formed of any appropriate film that can be used as a protective layer of a polarizer. Specific examples of the material that is the main component of the film include: cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth) acrylic acid, acetates and other transparent resins. In addition, thermosetting resins or ultraviolet curing resins such as (meth) acrylic acid, carbamates, (meth) acrylic acid carbamates, epoxies, silicones, etc. can also be listed. In addition, glassy polymers such as siloxane polymers can also be listed. In addition, the polymer film described in Japanese Patent Publication No. 2001-343529 (WO01 / 37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl and nitrile group in the side chain can be used, and for example, a resin composition containing an alternating copolymer formed by isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film can be, for example, an extrusion molding of the above resin composition.

[0079] The outer protective layer (particularly the outer protective layer 12 of the first polarizer) can be subjected to surface treatments such as hard coating, anti-reflection, anti-adhesion, and anti-glare as required. And / or, the outer protective layer can also be subjected to a treatment to improve the visual recognition when visually recognized through polarized sunglasses (representatively, a treatment to impart (elliptical) circular polarization function, a treatment to impart ultra-high phase difference). By implementing such a treatment, even when the display screen is visually recognized through polarized sunglasses and other polarized lenses, excellent visual recognition can be achieved. Therefore, the polarizer group can also be suitable for an image display device that can be used outdoors.

[0080] The inner protective layers 13 and 23 are preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0nm to 10nm, and the phase difference Rth(550) in the thickness direction is -10nm to +10nm. Here, "Re(λ)" is the in-plane phase difference measured at 23°C with light of wavelength λnm. For example, "Re(550)" is the in-plane phase difference measured at 23°C with light of wavelength 550nm. When the thickness of the layer (film) is set to d(nm), Re(λ) can be calculated according to the formula: Re(λ) = (nx-ny)×d. "Rth(λ)" is the phase difference in the thickness direction measured at 23°C with light of wavelength λnm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C with light of wavelength 550nm. When the thickness of the layer (film) is set to d (nm), Rth (λ) can be calculated according to the formula: Rth (λ) = (nx-nz) × d. nx is the refractive index in the direction where the refractive index in the plane reaches the 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.

[0081] The thickness of the protective layer can be any appropriate thickness. The thickness of the protective layer is, for example, 10 μm to 50 μm, preferably 20 μm to 40 μm. It should be noted that, in the case of surface treatment, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer. It should be noted that the "thickness of the protective layer" here refers to the thickness of the outer protective layer 12, 22 and the inner protective layer 13, respectively, and T in the above formula is pro1 and T pro2 different.

[0082] B-4. Adhesive layer

[0083] As described above, the adhesive layer is used to bond the polarizer to the image display unit. The adhesive layer can be typically formed by an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth) acrylic polymer as a main component. In the solid content of the adhesive composition, the (meth) acrylic polymer can be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. The (meth) acrylic polymer contains an alkyl (meth) acrylate as a monomer unit as a main component. It should be noted that (meth) acrylate refers to acrylate and / or methacrylate. In the monomer component forming the (meth) acrylic polymer, the alkyl (meth) acrylate can be preferably contained at a ratio of 80% by weight or more, more preferably 90% by weight or more. As the alkyl group of the alkyl (meth) acrylate, for example: a linear or branched alkyl group having 1 to 18 carbon atoms can be cited. The average number of carbon atoms of the alkyl group is preferably 3 to 9, more preferably 3 to 6. The preferred alkyl (meth) acrylate is butyl acrylate. As monomers (comonomers) constituting (meth) acrylic polymers, in addition to (meth) alkyl esters, carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth) acrylates, heterocyclic vinyl-containing monomers, etc. can also be listed. Representative examples of comonomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The acrylic adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. As a silane coupling agent, for example, epoxy-containing silane coupling agents can be listed. As a crosslinking agent, for example, isocyanate crosslinking agents and peroxide crosslinking agents can be listed. In addition, the acrylic adhesive composition may also contain an antioxidant and / or a conductive agent. As described above, the thickness of the adhesive layer is preferably less than 22 μm, and more preferably 10 μm to 22 μm. The details of the adhesive layer or the acrylic adhesive composition are described in, for example, Japanese Patent Application Publication No. 2006-183022, Japanese Patent Application Publication No. 2015-199942, Japanese Patent Application Publication No. 2018-053114, Japanese Patent Application Publication No. 2016-190996, and International Publication No. 2018 / 008712, and the descriptions of these publications are incorporated herein by reference.

[0084] Storage modulus G of adhesive layer at -40°C 2 'Preferably 1.0×10 5 (Pa) or more, more preferably 1.0×10 6 (Pa) or more, more preferably 1.0×10 7 (Pa) or more, particularly preferably 1.0×10 8 (Pa) or more. Storage modulus G2 For example, it can be 1.0×10 9 (Pa) or less.

[0085] B-5. Reflective polarizer

[0086] As described above, the reflective polarizer 26 can be provided on the side (back side) opposite to the image display unit 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 that is easy to shrink) and making the absorption axis direction of the first polarizer the short side direction of the film (the direction that is not easy to shrink), the displacement of each polarizer in the through hole portion can be reduced, and the difference between the displacement of the first polarizer and the displacement of the second polarizer can be reduced.

[0087] The reflective polarizer has the function of transmitting polarized light of a specific polarization state (polarization direction) and reflecting light of other polarization states. The reflective polarizer can be a linear polarized light separation type or a circular polarized light separation type. As an example, a linear polarized light separation type reflective polarizer is described below. It should be noted that as a circular polarized light separation type reflective polarizer, for example, a laminate of a film formed by fixing cholesteric liquid crystal and a λ / 4 wave plate can be cited.

[0088] Figure 6 It is a three-dimensional schematic diagram of an example of a reflective polarizer. The reflective polarizer is a multilayer laminate formed by alternating layers A having birefringence and layers B having substantially no birefringence. For example, the total number of layers of such a multilayer laminate can be 50 to 1000. In the example shown in the figure, the refractive index nx of layer A in the x-axis direction is greater than the refractive index ny in the y-axis direction, and the refractive index nx of layer B in the x-axis direction is substantially the same as the refractive index ny in the y-axis direction. 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. It should be noted that the x-axis direction corresponds to the stretching direction of the reflective polarizer in the method for manufacturing a reflective polarizer.

[0089] The above-mentioned A layer is preferably formed of a material that shows birefringence by stretching. Representative examples of such materials include naphthalene dicarboxylic acid polyester (e.g., polyethylene naphthalate), polycarbonate, and acrylic resin (e.g., polymethyl methacrylate). Polyethylene naphthalate is preferred. The above-mentioned B layer is preferably formed of a material that does not substantially show birefringence even when stretched. Representative examples of such materials include copolymerized polyesters of naphthalene dicarboxylic acid and terephthalic acid.

[0090] 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). After the reflection, part of the light is transmitted as light having a first polarization direction at the interface between layer A and layer B, and part is reflected as light having a second polarization direction. Such reflection and transmission are repeated many times inside the reflective polarizer, thereby improving the efficiency of light utilization.

[0091] In one embodiment, the reflective polarizer can also be Figure 6 As shown, a reflective layer R is included as the outermost layer on the opposite side of the image display unit. By providing the reflective layer R, the light that is ultimately not utilized and returns to the outermost portion of the reflective polarizer can be further utilized, thereby further improving the efficiency of light utilization. Typically, the reflective layer R exhibits a reflective function through a multilayer structure of a polyester resin layer.

[0092] The total thickness of the reflective polarizer can be appropriately set depending on the purpose, the total number of layers included in the reflective polarizer, etc. The total thickness of the reflective polarizer is preferably 10 μm to 150 μm.

[0093] As the reflective polarizer, for example, the reflective polarizers described in Japanese Unexamined Patent Publication No. 9-507308 and Japanese Unexamined Patent Publication No. 2013-235259 can be used. The reflective polarizer can be a commercial product as it is, or a commercial product can be subjected to secondary processing (e.g., stretching) before use. Examples of commercial products include DBEF manufactured by 3M and APF manufactured by 3M.

[0094] C. Image display device

[0095] As described above, the polarizing plate set of the embodiment of the present invention can be suitably used in an image display device. Therefore, the image display device is also included in the embodiment of the present invention. The image display device includes an image display unit and a polarizing plate set. The polarizing plate set is the polarizing plate set of the embodiment of the present invention described in the above items A to B. Figure 3 As shown, the image display device 200 includes an image display unit 120 , a first polarizing plate 10 disposed on the visible side of the image display unit 120 , and a second polarizing plate 20 disposed on the back side of the image display unit 120 .

[0096] Examples of image display devices include liquid crystal display devices, organic electroluminescent (EL) display devices, and quantum dot display devices. Liquid crystal display devices are preferred because the effect brought about by the polarizing plate group is significant.

[0097] Example

[0098] The present invention will be described in detail below with reference to the examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. In addition, unless otherwise specified, the "parts" and "%" in the examples are weight references.

[0099] (1) Offset

[0100] The first polarizer and the second polarizer in the polarizer group obtained in the embodiment and the comparative example were respectively pasted to a glass plate (manufactured by Matsunami Glass Co., Ltd., 350 mm long × 250 mm wide × 1.1 mm thick) via an adhesive layer as test samples. Each test sample was subjected to a heating test at 85°C and 120 hours. After the test, the offset of the first polarizer or the second polarizer (substantially the first adhesive layer or the second adhesive layer) of the through-hole portion was measured using an optical microscope (MX61L) manufactured by OLYMPUS. It should be noted that the measurement was performed on three test samples, and the maximum value of the three measured values ​​was taken as the offset.

[0101] <Production Example 1>

[0102] A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was added together with 100 parts by weight of ethyl acetate relative to 100 parts of the monomer mixture (solid content), and nitrogen was introduced while slowly stirring to replace the nitrogen atmosphere. The liquid temperature in the flask was maintained at about 55°C, and a polymerization reaction was performed for 8 hours to prepare a solution of an acrylic polymer (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 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: Nyper BMT 40SV, manufactured by NOF Corporation), 0.3 parts of a thiol-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy content: 30%, thiol equivalent: 450 g / mol), and 0.2 parts of an antioxidant (trade name: Irganox 1010, hindered phenol, manufactured by BASF Japan Co., Ltd.) were added to obtain an adhesive composition A.

[0103] <Production Example 2>

[0104] 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. 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 parts of a thiol-containing silane coupling agent (trade name: X-41-1056, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy content: 30%, thiol equivalent: 450 g / mol) was used as a silane coupling agent, no antioxidant was used, and 0.5 parts of lithium bis(trifluoromethanesulfonyl)imide (manufactured by Mitsubishi Materials Corporation) was further added.

[0105] <Production Example 3>

[0106] A solution of an acrylic polymer (c) having a weight average molecular weight (Mw) of 1.5 million was prepared in the same manner as in Preparation 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. The acrylic polymer (c) was used, the amount of the silane coupling agent was 0.1 parts, and a conductive agent (1-ethyl-3-methylimidazole) was added. A pressure-sensitive adhesive composition C was obtained in the same manner as in Production Example 1 except that 5 parts of bis(trifluoromethanesulfonyl)imide and 5 parts of an ionic liquid manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. were used.

[0107] <Production Example 4>

[0108] A solution of an acrylic polymer (d) having a weight average molecular weight (Mw) of 1,650,000 was prepared in the same manner as in Production Example 1. To 100 parts of the solid content of the obtained solution of the acrylic polymer (d), 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: Nyper BMT 40SV, manufactured by NOF Corporation), and 0.2 parts of an acetoacetyl group-containing silane coupling agent (trade name: A-100, manufactured by Soken Chemical Co., Ltd.) were added to obtain an adhesive composition D.

[0109] <Production Example 5>

[0110] Adhesive composition E was obtained in the same manner as in Production Example 1 except that 0.2 parts of a thiol-containing silane coupling agent (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., alkoxy content: 30%, thiol equivalent: 450 g / mol) was used as the silane coupling agent.

[0111] <Example 1>

[0112] (Preparation of the first polarizing plate)

[0113] As a polarizer (first polarizer), a film (thickness 12 μm) obtained by making a long strip of polyvinyl alcohol (PVA) resin film contain iodine and uniaxially stretch it in the longitudinal direction (MD direction) was used. On both sides of the polarizer, a long strip of HC-TAC film serving as an outer protective layer and a long strip of acrylic resin film serving as an inner protective layer were respectively bonded in such a manner that their longitudinal directions were consistent with each other. It should be noted that the HC-TAC film is a film having a hard coating (HC) layer (thickness 7 μm) formed on a triacetylcellulose (TAC) film (thickness 25 μm), and the TAC film was bonded in such a manner that it became the polarizer side. An adhesive layer (first adhesive layer: thickness 20 μm) was formed on the surface of the inner protective layer using adhesive composition B, thereby obtaining a first polarizer having the 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 a through hole with a diameter of 3.9 mm was formed at the corner portion. At this time, the plate was punched out so that the absorption axis direction of the first polarizer was the short side direction.

[0114] (Preparation of the Second Polarizing Plate)

[0115] As the outer protective layer, a TAC film (thickness 25 μm) was used instead of the HC-TAC film. Except for this, a polarizer was obtained in the same manner as the first polarizer. Furthermore, a reflective polarizer (thickness 26 μm) was bonded to the surface of the outer protective layer via a common adhesive layer (thickness 12 μm), and a second adhesive layer (thickness 20 μm) was formed on the surface of the reflective polarizer using adhesive composition E, thereby obtaining a second polarizer having a structure of reflective polarizer / outer protective layer / second polarizer / inner protective layer / second adhesive layer. The second polarizer was punched out into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was further formed at the corner. At this time, the punching was performed in such a way that the absorption axis direction of the second polarizer was the length direction.

[0116] (Polarizer Set)

[0117] The first polarizer obtained as described above was used as the visible side polarizer, and the second polarizer was used as the back side polarizer to prepare the polarizer set of this embodiment. The obtained polarizer set was provided for the above-mentioned evaluation of the offset. The results are shown in Table 1 together with the detailed structure of the first polarizer and the second polarizer. It should be noted that in Table 1, "0°" represents the longitudinal direction, and "90°" represents the short side direction.

[0118] <Comparative Example 1>

[0119] A polarizing plate set was obtained in the same manner as in Example 1 except that the first polarizer was punched out so that the absorption axis direction was the longitudinal direction to produce the first polarizer, and the second polarizer was punched out so that the absorption axis direction was the short side direction to produce the second polarizer. 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 structures of the first polarizer and the second polarizer.

[0120] <Example 2>

[0121] (Preparation of the first polarizing plate)

[0122] The first polarizer having the 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 adhesive composition C. The first polarizer was punched into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was further formed at the corner. At this time, the punching was performed in such a way that the absorption axis direction of the first polarizer was the short side direction.

[0123] (Preparation of the Second Polarizing Plate)

[0124] As the thermoplastic resin substrate, a long amorphous polyethylene terephthalate copolymer film (thickness: 100 μm) having a Tg of about 75° C. was used, and one surface of the resin substrate was subjected to a corona treatment.

[0125] To 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a ratio of 9:1, 13 parts by weight of potassium iodide were added, and the resulting mixture was dissolved in water to prepare a PVA aqueous solution (coating liquid).

[0126] The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C., thereby forming a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

[0127] The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (length direction) in an oven at 130° C. (auxiliary stretching treatment in an atmosphere).

[0128] Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilization treatment).

[0129] Next, the film was immersed in a dyeing bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 per 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single body transmittance (Ts) of the final polarizer would reach the desired value (dyeing treatment).

[0130] Next, the sample was immersed in a crosslinking bath (boric acid aqueous solution containing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid per 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment).

[0131] Then, while 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, it was uniaxially stretched (stretching treatment in aqueous solution) between rollers with different circumferential speeds so that the total stretching ratio in the longitudinal direction (length direction) reached 5.5 times.

[0132] Then, the laminated body was immersed in a cleaning bath (an aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).

[0133] Thereafter, the film was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75° C. while being dried in an oven maintained at about 90° C. (drying shrinkage treatment).

[0134] In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, thereby obtaining a laminate having a structure of resin substrate / second polarizer.

[0135] A TAC film (thickness 20 μm) is attached as an inner protective layer to the polarizer surface (the surface on the opposite side of the resin substrate) of the obtained laminate. Next, the resin substrate is peeled off, and a reflective polarizer (thickness 26 μm) is attached to the peeled surface via a common adhesive layer (thickness 12 μm). An adhesive layer (thickness 20 μm) is formed on the surface of the inner protective layer using adhesive composition D, and a second polarizer having a structure of reflective polarizer / second polarizer / inner protective layer / second adhesive layer is obtained. The second polarizer is punched out into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm is further formed at the corner. At this time, the punching is performed in such a way that the absorption axis direction of the second polarizer is the length direction.

[0136] (Polarizer Set)

[0137] The first polarizer obtained as described above was used as the visible side polarizer, and the second polarizer was used as the back side polarizer to prepare the polarizer set of this embodiment. The obtained polarizer set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structures of the first polarizer and the second polarizer.

[0138] <Comparative Example 2>

[0139] A polarizing plate set was obtained in the same manner as in Example 2 except that the first polarizer was punched out so that the absorption axis direction was the longitudinal direction to produce the first polarizer, and the second polarizer was punched out so that the absorption axis direction was the short side direction to produce the second polarizer. 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 structures of the first polarizer and the second polarizer.

[0140] <Example 3>

[0141] (Preparation of the first polarizing plate)

[0142] As the inner protective layer, a cycloolefin resin film (thickness 13 μm) was used instead of the acrylic resin film, and the first adhesive layer (thickness 20 μm) was formed by using the adhesive composition C instead of the adhesive composition B. The first polarizer having the structure of outer protective layer / first polarizer / inner protective layer / first adhesive layer was obtained in the same manner as in Example 1. The first polarizer was punched into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was further formed at the corner. At this time, the punching was performed in such a way that the absorption axis direction of the first polarizer was the short side direction.

[0143] (Preparation of the Second Polarizing Plate)

[0144] A laminate having a structure of resin substrate / second polarizer was obtained in the same manner as in Example 2. A TAC film (thickness 20 μm) was bonded to the polarizer surface (the surface opposite 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 bonded to the peeled surface via a common 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 polarizer having a structure of reflective polarizer / second polarizer / inner protective layer / second adhesive layer was obtained. The second polarizer was punched out into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was further formed at the corner. At this time, the punching was performed in such a manner that the absorption axis direction of the second polarizer was the length direction.

[0145] (Polarizer Set)

[0146] The first polarizer obtained as described above was used as the visible side polarizer, and the second polarizer was used as the back side polarizer to prepare the polarizer set of this embodiment. The obtained polarizer set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structures of the first polarizer and the second polarizer.

[0147] <Comparative Example 3>

[0148] A polarizing plate set was obtained in the same manner as in Example 3 except that the first polarizer was punched out so that the absorption axis direction was the longitudinal direction to produce the first polarizer, and the absorption axis direction of the second polarizer was punched out so that the absorption axis direction was the short side direction to produce the second polarizer. 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 structures of the first polarizer and the second polarizer.

[0149] <Example 4>

[0150] (Preparation of the first polarizing plate)

[0151] A laminate having a structure of resin substrate / polarizer was obtained in the same manner as the second polarizer of Example 2. An HC-TAC film was bonded to the polarizer surface (the surface opposite to the resin substrate) of the obtained laminate as an outer protective layer. Next, the resin substrate was peeled off, and an adhesive layer (thickness 15 μm) was formed on the peeled surface using adhesive composition A, thereby obtaining a first polarizer having a structure of outer protective layer / first polarizer / inner protective layer / first adhesive layer. The first polarizer was punched out into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was further formed at the corner. At this time, the punching was performed in such a way that the absorption axis direction of the first polarizer was the short side direction.

[0152] (Second polarizing plate)

[0153] The same second polarizing plate as in Example 3 was used.

[0154] (Polarizer Set)

[0155] The first polarizer obtained as described above was used as the visible side polarizer, and the second polarizer was used as the back side polarizer to prepare the polarizer set of this embodiment. The obtained polarizer set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structures of the first polarizer and the second polarizer.

[0156] <Comparative Example 4>

[0157] (Preparation of the first polarizing plate)

[0158] As a polarizer (first polarizer), a film (thickness 22 μm) obtained by making a long strip of polyvinyl alcohol (PVA) resin film contain iodine and uniaxially stretching it in the length direction (MD direction) was used. On both sides of the polarizer, a long strip of TAC film (thickness 40 μm) serving as an outer protective layer and a long strip of acrylic resin film (thickness 30 μm) serving as an inner protective layer were respectively attached in a manner that their length directions were consistent with each other. An adhesive layer (thickness 20 μm) was formed on the surface of the inner protective layer using adhesive composition D, and a first polarizer having a structure of outer protective layer / first polarizer / inner protective layer / first adhesive layer was obtained. The first polarizer was punched into a size of 148 mm in length and 70 mm in width, and a through hole with a diameter of 3.9 mm was further formed at the corner. At this time, the punching was performed in a manner that the absorption axis direction of the first polarizer was the short side direction.

[0159] (Second polarizing plate)

[0160] The same second polarizing plate as in Example 1 was used.

[0161] (Polarizer Set)

[0162] The first polarizer obtained as described above was used as a visible side polarizer, and the second polarizer was used as a back side polarizer to prepare a polarizer set of this comparative example. The obtained polarizer set was subjected to the same evaluation as in Example 1. The results are shown in Table 1 together with the detailed structures of the first polarizer and the second polarizer.

[0163]

[0164] It is clear from Table 1 that the polarizer set of the embodiment of the present invention can significantly reduce the difference (absolute value) between the offset amount of the first polarizer and the offset amount of the second polarizer compared to the comparative example. Therefore, the polarizer set of the embodiment of the present invention has a very obvious design advantage when applied to an image display device.

[0165] Industrial Applicability

[0166] The polarizing plate set of the present invention can be suitably used in an image display device, and in particular, can be suitably used in an image display device having a camera unit such as a smartphone, a tablet PC, or a smart watch.

Claims

1. A polarizing plate set comprising a rectangular first polarizing plate arranged on the visible side of an image display unit, and a rectangular second polarizing plate arranged on the back side of the image display unit, in, The first polarizing plate comprises a first polarizer, a protective layer disposed on at least one side of the first polarizer, and a first adhesive layer disposed on the image display unit side. The second polarizing plate comprises a second polarizer, 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 unit, and a second adhesive layer disposed on the image display unit side. The thickness of the first polarizer and the second polarizer are respectively less than 20 μm. 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 have through holes at respective ends or at positions corresponding to each other near the ends. The distance A1 (μm) from the outermost portion of the first adhesive layer on the image display unit side to the center portion of the first polarizer in the thickness direction, the thickness T of the first polarizer pol1 (μm), creep value C of the first adhesive layer at 85°C psa1 (μm / hr), the thickness T of the first adhesive layer psa1 (μm), and the thickness T of the protective layer in the first polarizer pro1 (μm) satisfies the following relationship, (A1×T pol1 )×(C psa1 ×T psa1 ) / T pro1 =K1≤300×10 2 (μm 3 / hr) The distance A2 (μm) from the outermost portion of the second adhesive layer on the image display unit side to the center portion of the second polarizer in the thickness direction, the thickness T of the second polarizer pol2 (μm), creep value C of the second adhesive layer at 85°C psa2 (μm / hr), the thickness T of the second adhesive layer psa2 (μm), and the thickness T of the protective layer in the second polarizer pro2 (μm) satisfies the following relationship, (A2×T pol2 )×(C psa2 ×T psa2 ) / T pro2 =K2≤300×10 2 (μm 3 / hr)。 2. The polarizer set according to claim 1, wherein: The K1 and K2 are 200×10 2 (μm 3 / hr) or less.

3. The polarizer set according to claim 1, wherein: The creep value C of the first adhesive layer at 85°C psa1 It is 100 (μm / hr) or less.

4. The polarizer set according to claim 1, wherein: The thickness T of the second polarizer is pol2 Less than 10 μm.

5. The polarizer set according to claim 1, wherein: The K1 and K2 are 150×10 2 (μm 3 / hr) or less.

6. The polarizer set according to claim 1, wherein: The thickness T of the first polarizer is pol1 Less than 10 μm.

7. The polarizing plate set according to claim 1, wherein: The thickness T of the first adhesive layer psa1 and the thickness T of the second adhesive layer psa2 They are 10μm to 22μm respectively.

8. The polarizing plate set according to any one of claims 1 to 7, wherein: The through hole is formed at a corner portion of each of the first polarizer and the second polarizer.

9. The polarizer set according to claim 8, wherein: When the distance from the center in the length direction to the end in the length direction when looking down at the first polarizer and the second polarizer is set to L1, the distance in the length direction from the center in the length direction of the first polarizer and the second polarizer to the center of the through hole is set to L2, the distance from the center in the short side direction to the end in the short side direction of the first polarizer and the second polarizer is set to W1, and the distance in the short side direction from the center in the short side direction of the first polarizer and the second polarizer to the center of the through hole is set to W2, the through hole is formed in the first polarizer and the second polarizer at positions satisfying 0.85≤L2 / L1≤0.99 and 0.50≤W2 / W1≤0.99, respectively.

10. The polarizing plate set according to any one of claims 1 to 7, wherein: The diameter of the through hole is less than 10 mm.

11. The polarizing plate set according to any one of claims 1 to 7, wherein: The aspect ratios of the first polarizer and the second polarizer are respectively 1.3 to 2.

5. 12 . An image display device comprising an image display unit and the polarizing plate set according to claim 1 , wherein the first polarizing plate is arranged on a visible side of the image display unit, and the second polarizing plate is arranged on a back side of the image display unit.

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