CN114502997A

CN114502997A - Polarizer set and image display device comprising same

Info

Publication number: CN114502997A
Application number: CN202080068862.1A
Authority: CN
Inventors: 森本刚司; 品川玲子; 木村智之
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-09-30
Filing date: 2020-05-26
Publication date: 2022-05-13
Also published as: TW202115436A; WO2021065075A1; JPWO2021065075A1; KR20220067537A

Abstract

The invention provides a polarizing plate group which has small deviation of each polarizing plate in a through hole part and has very small difference between the deviation amount of a visual side polarizing plate and the deviation amount of a back side polarizing plate. The polarizer group includes a rectangular 1 st polarizer disposed on the visible side of the image display unit and a rectangular 2 nd polarizer disposed on the rear side. The 1 st polarizing plate has a 1 st polarizer, a protective layer disposed on at least one side thereof, and a 1 st adhesive layer disposed on the image display unit side, and the 2 nd polarizing plate has a 2 nd polarizer, a protective layer disposed on at least one side thereof, a reflective polarizer disposed on the opposite side of the 2 nd polarizer from the image display unit, and a 2 nd adhesive layer disposed on the image display unit side. The thicknesses of the 1 st polarizer and the 2 nd polarizer are 20 μm or less, respectively, the 1 st polarizer has an absorption axis in the short side direction, and the 2 nd polarizer has an absorption axis in the long side direction. The 1 st polarizing plate and the 2 nd polarizing plate have through holes at their respective ends or at positions near the ends that correspond to each other.

Description

Polarizer set and image display device comprising same

Technical Field

The present invention relates to a polarizer set and an image display device including the same.

Background

Polarizing plates 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 rapid spread of smart phones and touch panel type information processing apparatuses, image display apparatuses equipped with cameras have been widely used. In response to this, polarizing plates having through holes at positions corresponding to the camera sections are also being widely used. In the polarizing plate having such through-holes, various matters to be investigated are included in the through-holes or the vicinity thereof.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2017/047510

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a polarizing plate group in which the deviation of each polarizing plate in a through-hole portion is small and the difference between the deviation amount of a visible-side polarizing plate and the deviation amount of a rear-side polarizing plate is very small.

Means for solving the problems

The polarizer group of the present invention includes a rectangular 1 st polarizer disposed on the visible side of an image display unit, and a rectangular 2 nd polarizer disposed on the back side of the image display unit. The 1 st polarizer comprises a 1 st polarizer, a protective layer disposed on at least one side of the 1 st polarizer, and a 1 st adhesive layer disposed on the image display unit side; the 2 nd polarizing plate has a 2 nd polarizer, a protective layer disposed on at least one side of the 2 nd polarizer, a reflective polarizer disposed on the opposite side of the 2 nd polarizer from the image display unit, and a 2 nd adhesive layer disposed on the image display unit side. The thickness of the 1 st polarizer and the 2 nd polarizer is 20 μm or less, respectively, the 1 st polarizer has an absorption axis in a short side direction, and the 2 nd polarizer has an absorption axis in a long side direction. The 1 st polarizing plate and the 2 nd polarizing plate have through holes at respective ends or at positions near the ends that correspond to each other.

In one embodiment, a distance a from an outermost portion of the 1 st adhesive layer on the image display unit side to a thickness direction center portion of the 1 st polarizer₁(mum) and thickness T of the 1 st polarizer_pol1(mum) creep value C of the 1 st adhesive layer_psa1(μm/hr) and the thickness T of the 1 st adhesive layer_psa1(mum) and the thickness T of the protective layer in the 1 st polarizing plate_pro1(μm) satisfies the following relationship,

(A₁×T_pol1)×(C_psa1×T_psa1)/T_pro1＝K₁≤300×10²(μm³/hr)

a distance A from an outermost portion of the 2 nd adhesive layer on the image display unit side to a thickness direction center portion of the 2 nd polarizer₂(mum) and the thickness T of the 2 nd polarizer_pol2(mum), creep value C of the 2 nd adhesive layer_psa2(μm/hr), thickness T of the 2 nd adhesive layer_psa2(mum) and the thickness T of the protective layer in the 2 nd polarizing plate_pro2(μm) satisfies the following relationship,

(A₂×T_pol2)×(C_psa2×T_psa2)/T_pro2＝K₂≤300×10²(μm³/hr)。

in one embodiment, K is₁And K₂Are respectively 200X 10²(μm³Hr) below.

In one embodiment, the creep value C of the 1 st adhesive layer_psa1Is 100(μm/hr) or less.

In one embodiment, the thickness T of the 2 nd polarizer_pol2Is 10And is less than μm.

In one embodiment, K is₁And K₂Are respectively 150X 10²(μm³Hr) below.

In one embodiment, the thickness T of the 1 st polarizer_pol1Is 10 μm or less.

In one embodiment, the thickness T of the 1 st adhesive layer_psa1And the thickness T of the 2 nd adhesive layer_psa2Respectively 10 to 22 mu m.

In one embodiment, the through-hole is formed in a corner portion of each of the 1 st polarizing plate and the 2 nd polarizing plate.

In one embodiment, a distance from a center in a longitudinal direction to an end in the longitudinal direction in a plan view of the 1 st polarizer and the 2 nd polarizer is L₁And L is a distance from the center of the 1 st polarizer and the 2 nd polarizer in the longitudinal direction to the center of the through hole in the longitudinal direction₂W represents a distance from the center of the 1 st polarizer and the 2 nd polarizer in the short side direction to the end of the short side direction₁And W represents a distance in the short side direction from the center in the short side direction of the 1 st polarizer and the 2 nd polarizer to the center of the through hole₂Then, the through hole is formed in the 1 st polarizer and the 2 nd polarizer respectively at L of 0.85 ≤₂/L₁Less than or equal to 0.99 and less than or equal to 0.50W₂/W₁Less than or equal to 0.99.

In one embodiment, the diameter of the through-hole is 10mm or less.

In one embodiment, the aspect ratio of each of the 1 st polarizing plate and the 2 nd polarizing plate is 1.3 to 2.5.

According to other aspects of the present invention, an image display device is provided. The image display device includes an image display unit and the polarizer group, wherein the 1 st polarizer is disposed on a visible side of the image display unit, and the 2 nd polarizer is disposed on a rear surface side of the image display unit.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiments of the present invention, it is possible to provide a polarizer group in which the deviation of each polarizer in the through hole portion is small and the difference between the deviation amount of the visible-side polarizer and the deviation amount of the back-side polarizer is very small. When the deviation of each polarizing plate in the through-hole portion is small, the effect can be synergistically exerted when the polarizing plate group is formed. When the difference in the amounts of shift is very small, the advantage in design is very significant when the polarizer group is applied to an image display device. For example, the polarizer group may be applied to an image display device having only a camera section as a non-display region and/or a frameless image display device.

Drawings

Fig. 1 is a schematic plan view illustrating a 1 st polarizing plate and a 2 nd polarizing plate in a polarizing plate group according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of the 1 st polarizing plate and the 2 nd polarizing plate in the polarizing plate group of fig. 1 taken along the line II-II, and is a schematic cross-sectional view illustrating the arrangement positions of the 1 st polarizing plate and the 2 nd polarizing plate.

Fig. 3 is a schematic cross-sectional view of an image display device including the polarizer set of fig. 1.

Fig. 4 is an enlarged cross-sectional view of a principal part illustrating the offset of the polarizing plate used in the polarizing plate set according to the embodiment of the present invention in the through-hole portion.

Fig. 5 is a schematic plan view illustrating a formation position of a through-hole in a polarizing plate used in a polarizing plate group according to an embodiment of the present invention.

Fig. 6 is a schematic perspective view of an example of a reflective polarizer that can be used in the 2 nd polarizing plate in the polarizing plate group according to the embodiment of the present invention.

Description of the symbols

10 st polarizing plate

11 st polarizer

12 outer protective layer

13 inner protective layer

14 st adhesive layer

15 through hole

20 nd 2 polarizing plate

21 nd 2 polarizer

22 outer protective layer

23 inner protective layer

24 nd 2 adhesive layer

25 through hole

100 polarizer group

120 image display unit

200 image display device

Detailed Description

Specific embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The drawings are schematically illustrated for easy viewing, and the ratios and angles of the length, width, thickness, and the like in the drawings are different from those in reality.

A. Outline of the polarizer group

Fig. 1 is a schematic plan view illustrating a 1 st polarizing plate and a 2 nd polarizing plate in a polarizing plate group according to an embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of the 1 st polarizer and the 2 nd polarizer of the polarizer set of FIG. 1 taken along line II-II; fig. 3 is a schematic cross-sectional view of an image display device including the polarizer set of fig. 1. The polarizer set 100 illustrated in the figure includes a 1 st polarizer 10 and a 2 nd polarizer 20. The 1 st polarizing plate and the 2 nd polarizing plate each have a rectangular shape having a long side and a short side corresponding to the plan view shape of the image display unit. In the present specification, the term "rectangular shape" also includes a shape including a deformed portion including an R-shape in which each vertex is chamfered as shown in fig. 1. As shown in fig. 3, the 1 st polarizing plate 10 is disposed on the viewing side of the image display unit 120, and the 2 nd polarizing plate 20 is disposed on the rear side of the image display unit 120. In the illustrated example, the 1 st polarizing plate 10 includes a 1 st polarizer 11, a protective layer (outer protective layer) 12 disposed on the visible side of the 1 st polarizer 11, a protective layer (inner protective layer) 13 disposed on the image display unit side of the 1 st polarizer 11, and a 1 st pressure-sensitive adhesive layer 14 disposed as the outermost layer on the image display unit 120 side. The 1 st adhesive layer 14 is used to attach the 1 st polarizer 10 to the image display unit 120. One of the

protective layers

12 and 13 may be omitted depending on the purpose. The 2 nd polarizing plate 20 includes a 2 nd polarizer 21, a reflective polarizer 26 disposed on the back side (the side opposite to the image display unit) of the 2 nd polarizer 21, a protective layer (inner protective layer) 23 disposed on the image display unit side of the 2 nd polarizer 21, and a 2 nd adhesive layer 24 disposed as the outermost layer on the image display unit 120 side. The 2 nd adhesive layer 24 is used to attach the 2 nd polarizer 20 to the image display unit 120. In the 2 nd polarizing plate 20, a reflective polarizer 26 is disposed instead of the outer protective layer. That is, in the 2 nd polarizing plate 20, the reflective polarizer 26 also serves as an outer protective layer. In the illustrated example, the outer protective layer of the 2 nd polarizing plate is omitted, but the reflective polarizer 26 may be disposed on the back side (the side opposite to the image display unit) of the outer protective layer. The reflective polarizer 26 is bonded to the 2 nd polarizer 21 or the outer protective layer (if present) via an arbitrary appropriate adhesive layer (for example, 2 μm to 20 μm thick).

In the embodiment of the present invention, the 1 st polarizing plate 10 has the through-hole 15, and the 2 nd polarizing plate 20 has the through-hole 25. The through-

holes

15 and 25 are formed at or near the ends of the 1 st polarizing plate and the 2 nd polarizing plate, respectively, at positions corresponding to each other. By forming the through-hole, for example, when a camera is incorporated in the image display device, adverse effects on the performance of the camera can be prevented. Further, by forming the through-holes at or near the end portions of the polarizing plate, when the polarizing plate is applied to an image display device, the influence of the through-holes on image display (for example, light leakage at the through-hole portions) can be minimized. The through-hole can be formed by various methods such as laser processing, cutting processing by an end mill, and punching processing by a thomson knife or a sharp knife (registered trademark). In the present specification, the phrase "disposed at positions corresponding to each other" means that the through-holes overlap each other when the two polarizing plates are stacked.

As shown in FIG. 1, the 1 st polarizer 11 has an absorption axis Ab in the short side direction₁The 2 nd polarizer 21 has an absorption axis Ab in the longitudinal direction₂. Rectangular films tend to shrink easily in the longitudinal direction and not easily in the short-side direction. Further, the polarizer (eventually, the polarizing plate) tends to be easily contracted in the absorption axis direction. Therefore, by setting the absorption axis direction of the 2 nd polarizing plate which is less likely to shrink due to the inclusion of the reflective polarizer as the longitudinal direction of the film (direction in which shrinkage is likely to occur), and setting the absorption axis direction of the 1 st polarizing plate which is more likely to shrink than the 2 nd polarizing plate as the short-side direction of the film (direction in which shrinkage is less likely to occur), it is possible to reduce the deviation of each polarizing plate in the through-hole portion and reduce the difference between the deviation of the 1 st polarizing plate and the deviation of the 2 nd polarizing plate.

If necessary, a retardation layer may be provided in the 1 st polarizing plate 10 and/or the 2 nd polarizing plate 20. The kind, 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 wave plate, a λ/4 wave plate, or a stacked body thereof. The λ/2 plate and the λ/4 plate typically have refractive index characteristics of nx > ny ≧ nz. The in-plane retardation Re (550) of the λ/2 plate is preferably 180nm to 320nm, and the in-plane retardation Re (550) of the λ/4 plate is preferably 100nm to 200 nm. For example, the retardation layer may be a laminate of a negative B plate (nx > ny > nz), a positive C plate (nz > nx ═ ny) or a positive B plate (nz > nx > ny). In the present specification, "Re (λ)" is an in-plane phase difference measured at 23 ℃ with light having a wavelength of λ nm. For example, "Re (550)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), the following equation can be used: re (λ) was obtained as (nx-ny) × d. "Rth (λ)" is a phase difference in the thickness direction measured at 23 ℃ with light of a wavelength λ nm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), the following equation can be used: rth (λ) is obtained as (nx-nz) × d. "nx" is a refractive index in a direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is a refractive index in the thickness direction.

Hereinafter, the constituent elements of the polarizer group will be specifically described. The following description will discuss a case where the 1 st polarizing plate and the 2 nd polarizing plate are collectively used as polarizing plates, the 1 st polarizer and the 2 nd polarizer are collectively used as polarizers, protective layers of the 1 st polarizing plate and the 2 nd polarizing plate are collectively used as protective layers, and the 1 st adhesive layer and the 2 nd adhesive layer are collectively used as adhesive layers. Therefore, for example, when the term "polarizing plate" is used, the terms "1 st polarizing plate" and "2 nd polarizing plate" may be used. On the other hand, for example, when it is necessary to separately explain the 1 st polarizing plate and the 2 nd polarizing plate, "1 st" or "2 nd" is explicitly described.

B. Polarizing plate

B-1 integral constitution of polarizing plate

In one embodiment, the 1 st polarizing plate 10 preferably satisfies the following relationship:

(A₁×T_pol1)×(C_psa1×T_psa1)/T_pro1＝K₁≤300×10²(μm³/hr)

wherein A is₁Is a distance (μm) from the outermost portion of the 1 st adhesive layer 14 on the image display unit 120 side to the thickness direction center portion of the 1 st polarizer 11; t is_pol1Is the thickness (μm) of the 1 st polarizer 11; c_psa1Is the creep value (μm/hr) of the 1 st adhesive layer 14; t is_psa1Is the thickness (μm) of the 1 st adhesive layer 14; t is_pro1Is the thickness (μm) of the protective layer in the 1 st polarizer 10. Likewise, the 2 nd polarizing plate 20 preferably satisfies the following relationship:

(A₂×T_pol2)×(C_psa2×T_psa2)/T_pro2＝K₂≤300×10²(μm³/hr)。

wherein A is₂Is a distance (μm) from the outermost portion of the 2 nd adhesive layer 24 on the image display unit 120 side to the thickness direction center portion of the 2 nd polarizer 21; t is_pol2Is the thickness (μm) of the 2 nd polarizer 21; c_psa2Is the creep value (μm/hr) of the 2 nd adhesive layer 24; t is_psa2Is the thickness (μm) of the 2 nd adhesive layer 24; t is_pro2Is the thickness (μm) of the protective layer in the 2 nd polarizing plate 20. In this specificationThe "creep value" refers to a creep value at 85 ℃. The creep value can be determined, for example, by the following sequence: attaching an adhesive constituting the adhesive layer to a support plate; applying a 500g load vertically downward in a state where the support plate to which the adhesive is attached is fixed; the amount of offset of the adhesive from the support plate 1 hour after the application of the load was measured and the offset was regarded as a creep value (μm/hr). In addition, the thickness T of the protective layer in the above relation_pro1Can be according to the formula: "total thickness of the 1 st polarizer-thickness of the 1 st adhesive layer-thickness of the 1 st polarizer" was determined. I.e. T_pro1The total thickness of the

protective layers

12 and 13, the thickness of an adhesive layer for attaching the protective layers (including the adhesive layer in the case where the polarizer or the protective layer and the reflective polarizer are bonded via the adhesive layer), and the thickness of a surface treatment layer formed on the protective layer 12 as needed. With respect to T associated with the 2 nd polarizer_pro2The same applies. K₁Value and K₂The values are more preferably 250X 10, respectively²(μm³Hr) or less, more preferably 200X 10²(μm³Hr) or less, particularly preferably 150X 10²(μm³Hr) below. Hereinafter, K is₁Value and K₂The values are collectively referred to as K values. The same applies to the distance a, the creep value, the thickness of the adhesive layer, and the thickness of the protective layer. The lower limit of the K value may be, for example, 15X 10²(μm³In/hr). If the K value is in such a range, the offset of the through hole portion (substantially, the offset of the adhesive layer) can be significantly suppressed. The technical meaning of having a K value below a given value is as follows: the offset of the pressure-sensitive adhesive layer becomes large when the torque force applied to the pressure-sensitive adhesive layer and the ease of movement of the pressure-sensitive adhesive layer itself are large, and becomes small when the suppression force for the movement of the pressure-sensitive adhesive layer is large. The torque force applied to the adhesive layer may be related to a distance from the image display unit to which the polarizing plate is attached to the polarizer and a thickness of the polarizer; ease of movement of the adhesive layer itself may be related to the softness and thickness of the adhesive layer; the restraining force against movement of the adhesive layer may be related to the thickness of the protective layer. By reducing the distance from the image display unit to the polarizer and the thickness of the polarizer, it is possible to reduce the number of the optical elementsReducing the torque force; by setting the creep value of the adhesive layer to a given value or less (constituting the adhesive layer at a relatively hard level) and by reducing the thickness of the adhesive layer, the adhesive layer itself can be made less likely to move; by making the thickness T of the protective layer_proFor the given range, the suppression force against the movement of the adhesive layer can be brought to an appropriate range. Therefore, by adjusting the above-described requirements and controlling the K value to a predetermined value or less, the offset of the pressure-sensitive adhesive layer can be significantly suppressed. Specifically, the distance A is preferably 80 μm or less, more preferably 50 μm or less. The lower limit of the distance a may be, for example, 10 μm. Creep value C_psaPreferably 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 may be, for example, 50 μm/hr. Thickness T of protective layer_proPreferably 15 to 65 μm, more preferably 15 to 55 μm. Thickness T of adhesive layer_psaPreferably 22 μm or less, more preferably 10 to 22 μm. At creep value C_psaIn the case of too small a thickness T, and/or in the case of an adhesive layer_psaIf the amount is too small, stress relaxation may become difficult, and the risk of cracking or peeling may increase. If the thickness T of the protective layer_proIf the amount is too small, the curl adjustment may become difficult.

As shown in fig. 4, after a heat test at 85 ℃ for 120 hours in a state where a polarizing plate (the 1 st polarizing plate 10 in the example of the figure) 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, 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, particularly preferably 100 μm or less, and most preferably 80 μm or less. The lower limit of the amount of offset D is preferably 10 μm in one embodiment and 20 μm in another embodiment as the amount of offset D is smaller. The offset amount D is the maximum portion of the polarizing plate that is apart from the through hole portion when viewed in cross section. Typically, the reference of the through hole portion may be a lower end portion of the adhesive layer. That is, when the polarizing plate is displaced (to the right side in the illustrated example) mainly by shrinkage of the polarizer, the adhesive layer 14 stays on the glass plate 130 to be bonded, and thus the displacement is recognized in the through hole portion. As shown in fig. 4, typically, the polarizing plate is offset in the through hole portion to a side away from the through hole (right side in fig. 4), and the opposite portion is offset so as to protrude from the through hole (left side in fig. 4). According to the embodiment of the present invention, since the 1 st polarizing plate and the 2 nd polarizing plate can both reduce the deviation of the through hole portion (substantially, the deviation of the adhesive layer) as described above, the effects can be synergistically exhibited when the polarizing plate group is formed.

The difference (absolute value) between the amount of shift of the 1 st polarizing plate and the amount of shift of the 2 nd 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 amounts of offset, the more preferable. The lower limit of the difference in the amounts of offset may be, for example, 3 μm. According to the embodiment of the present invention, the difference between the amount of shift of the 1 st polarizing plate and the amount of shift of the 2 nd polarizing plate can be made very small. As a result, the polarizer group can be applied to an image display device having only the camera section as a non-display region and/or a frameless image display device.

The dimensional shrinkage of the polarizing plate after the heat test is preferably 1.0% or less, more preferably 0.6% or less, and still more preferably 0.3% or less. The lower limit of the dimensional shrinkage is preferably 0.01% as the dimensional shrinkage becomes smaller. The dimensional shrinkage can be determined by the following equation. The dimensional shrinkage ratio is a dimensional shrinkage ratio of the entire polarizing plate attached to the glass plate, and when the polarizing plate further includes an optical functional layer (for example, a retardation layer or a reflective polarizer), the dimensional shrinkage ratio is a dimensional shrinkage ratio of the entire polarizing plate including the optical functional layer. The "dimension" in the following formula is a dimension in the absorption axis direction of the polarizing plate (substantially polarizer).

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

In the polarizing plate, the through-hole may be formed at any appropriate position at or near the end portion according to the purpose. In one embodiment, the through-

holes

15 and 25 are formed in the corner portions of the polarizing plates as shown in fig. 1. The formation position of the through-hole is not limited to the corner portion. The through-hole may be formed at a substantially central portion of the longitudinal end portion of the polarizing plate, at a predetermined position of the longitudinal end portion, at a substantially central portion of the short-side end portion, or at a predetermined position of the short-side end portion. In addition, a plurality of through-holes may be formed, and the through-holes and the notches may be formed in combination.

In one embodiment, as shown in fig. 5, the distance from the center of the polarizer in the longitudinal direction to the end of the polarizer in the longitudinal direction is L₁L represents a distance in the longitudinal direction from the center in the longitudinal direction of the polarizer to the center of the through-hole₂W represents a distance from the center of the polarizer in the short side direction to the end of the polarizer in the short side direction₁And W represents a distance in the short side direction from the center in the short side direction of the polarizer to the center of the through hole₂In the case where the through-hole is formed so as to satisfy 0.85. ltoreq. L₂/L₁W is not less than 0.99 and not less than 0.50₂/W₁Less than or equal to 0.99. L is₂/L₁More preferably 0.90 to 0.97, and still more preferably 0.92 to 0.96. W₂/W₁More preferably 0.75 to 0.95.

The diameter R of the through-hole is preferably 10mm or less, more preferably 8mm or less, and further preferably 5mm or less. The lower limit of the diameter of the through-hole may be, for example, 2mm, and may be, for example, 1.5 mm. The ratio D/R of the offset amount D to the diameter R of the through-hole is preferably 15% or less, more preferably 10% or less, further preferably 6% or less, and particularly preferably 5% or less. On the other hand, the lower the D/R limit, the more preferable. According to the embodiment of the present invention, since the offset amount D is extremely small as described above, D/R can be made to fall within such a range even if the diameter of the through-hole is reduced. Therefore, even if the diameter of the through-hole is reduced, adverse effects on the performance of the camera 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 section as a non-display region and/or a frameless image display device.

The length-width ratio of the polaroid is preferably 1.3-2.5. In this case, the size of the polarizing plate is, for example, 145mm to 155mm in the vertical direction and 65mm to 75mm in the horizontal direction, or 230mm to 240mm in the vertical direction and 140mm to 150mm in the horizontal direction. That is, the polarizing plate according to the embodiment of the present invention can be suitably used for a smartphone or a tablet PC. The smartphone may have a size of 120mm to 200mm in the longitudinal direction and 30mm to 120mm in the width direction, for example.

B-2. polarizer

Typically, the polarizer is formed of a resin film containing a dichroic material. As the resin film, any appropriate resin film that can be used as a polarizer can be used. Typically, the resin film is a polyvinyl alcohol 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.

As a specific example of the polarizer made of a single-layer resin film, there is a polarizer obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The dyeing with iodine can be performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. In addition, dyeing may be performed after stretching. The PVA-based resin film may be subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA-based resin film in water and washing it with water before dyeing, not only dirt and an antiblocking agent on the surface of the PVA-based film can be washed off, but also the PVA-based resin film can be swollen to prevent uneven dyeing and the like.

Specific examples of the polarizer obtained using the laminate include: a polarizer obtained by using a laminate of a resin substrate and a PVA type resin layer (PVA type resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA type resin layer formed on the resin substrate by coating. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating can be produced by the following method: for example, a laminate of a resin substrate and a PVA type resin layer is obtained by applying a PVA type resin solution to the resin substrate and drying the solution to form the PVA type resin layer on the resin substrate; the laminate is stretched and dyed to produce a polarizer from the PVA type resin layer. In the present embodiment, the stretching typically includes performing stretching by immersing the laminate in an aqueous boric acid solution. Further, the stretching may further include stretching the laminate in a gas atmosphere at a high temperature (for example, 95 ℃ or higher) before the stretching in the boric acid aqueous solution, as necessary. The obtained resin base material/polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer), or the resin base material may be peeled off from the resin base material/polarizer laminate and an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of such a method for producing a polarizer are described in, for example, japanese patent laid-open publication No. 2012 and 73580 and japanese patent No. 6470455. The descriptions of these patent documents are incorporated herein by reference.

The thickness of the polarizer is preferably 20 μm or less, more preferably 12 μm or less, and 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. When the thickness of the polarizer is in such a range, curling during heating can be favorably suppressed, and favorable durability of appearance during heating can be obtained.

The polarizer preferably exhibits dichroism of absorption at any wavelength of 380nm to 780 nm. The polarizer has a monomer transmittance of, 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.

B-3 protective layer

The protective layers 12, 13, and 23 may be formed of any appropriate film that can be used as a protective layer for a polarizer. Specific examples of the material to be the main component of the film include: cellulose resins such as cellulose Triacetate (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyether sulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth) acrylic acids, and transparent resins such as acetates. In addition, there may be enumerated: thermosetting resins such as (meth) acrylic resins, urethane resins, (meth) acrylic urethane resins, epoxy resins, silicone resins, and ultraviolet-curable resins. In addition, for example, a glassy polymer such as a siloxane polymer can be used. Further, the polymer film described in Japanese patent application laid-open No. 2001-343529 (WO01/37007) may be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain can be used, and examples thereof include: a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion-molded product of the above resin composition.

The outer protective layer (particularly, the outer protective layer 12 of the 1 st polarizing plate) may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-sticking treatment, antiglare treatment, or the like as required. Further, the outer protective layer may be subjected to a process for improving visibility when viewed through polarized sunglasses (typically, a process for imparting an (elliptical) polarization function or a process for imparting an ultrahigh phase difference) as necessary. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through a polarized lens such as a polarized sunglass. Therefore, the polarizing plate group can be suitably used also for an image display device that can be used outdoors.

The inner

protective layers

13, 23 are preferably optically isotropic. In the present specification, "optically isotropic" means that the in-plane retardation Re (550) is 0 to 10nm and the retardation Rth (550) in the thickness direction is-10 to +10 nm. Here, "Re (λ)" is an in-plane phase difference measured at 23 ℃ with light of wavelength λ nm. For example, "Re (550)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), the following equation can be used: re (λ) was obtained as (nx-ny) × d. "Rth (. lamda.)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of. lamda.nm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), the following equation can be used: rth (λ) is obtained as (nx-nz) × d. nx is a refractive index in a direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), ny is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and nz is a refractive index in the thickness direction.

The thickness of the protective layer may take any suitable thickness. The thickness of the protective layer is, for example, 10 to 50 μm, preferably 20 to 40 μm. When the surface treatment is performed, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer. Here, the "thickness of the protective layer" is the thickness of each of the outer protective layers 12 and 22 and the inner protective layer 13, and T in the above formula_pro1And T_pro2Different.

B-4 adhesive layer

As described above, the adhesive layer is used to attach the polarizing plate to the image display unit. The adhesive layer may be representatively formed of an acrylic adhesive (acrylic adhesive composition). The acrylic pressure-sensitive adhesive composition typically contains a (meth) acrylic polymer as a main component. The (meth) acrylic polymer may be contained in the adhesive composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more, of the solid content of the adhesive composition. The (meth) acrylic polymer contains, as a main component, an alkyl (meth) acrylate as a monomer unit. The term (meth) acrylate refers to acrylate and/or methacrylate. The alkyl (meth) acrylate may be contained in the monomer component forming the (meth) acrylic polymer in a proportion of preferably 80% by weight or more, more preferably 90% by weight or more. Examples of the alkyl group of the alkyl (meth) acrylate include: a linear or branched alkyl group having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. The preferred alkyl (meth) acrylate is butyl acrylate. As the monomer (comonomer) constituting the (meth) acrylic polymer, in addition to the alkyl (meth) acrylate, there can be mentioned: carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth) acrylates, heterocyclic vinyl group-containing monomers, and the like. Typical 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. Examples of the silane coupling agent include: an epoxy group-containing silane coupling agent. Examples of the crosslinking agent include: isocyanate crosslinking agents and peroxide crosslinking agents. In addition, the acrylic adhesive composition may further contain an antioxidant and/or a conductive agent. As described above, the thickness of the pressure-sensitive adhesive layer is preferably 22 μm or less, and more preferably 10 to 22 μm. The details of the adhesive layer or the acrylic adhesive composition are described in, for example, Japanese patent laid-open Nos. 2006-183022, 2015-199942, 2018-053114, 2016-190996 and International publication No. 2018/008712, and the descriptions of these publications are incorporated herein by reference.

Storage modulus G of adhesive layer at-40 deg.C₂' preferably 1.0X 10⁵(Pa) or more, more preferably 1.0X 10⁶(Pa) or more, preferably 1.0X 10⁷(Pa) or more, particularly preferably 1.0X 10⁸(Pa) or more. Storage modulus G₂' for example, it may be 1.0X 10⁹(Pa) is as follows.

B-5. reflection type polarizer

As described above, the reflective polarizer 26 may be provided on the opposite side (rear side) of the 2 nd polarizing plate 20 from the image display unit 120. By providing the reflective polarizer, the 2 nd polarizing plate is less likely to shrink than the 1 st polarizing plate. As a result, by setting the absorption axis direction of the 2 nd polarizing plate to the longitudinal direction of the film (direction in which shrinkage is easy), and setting the absorption axis direction of the 1 st polarizing plate to the short side direction of the film (direction in which shrinkage is not easy), it is possible to reduce the misalignment of each polarizing plate in the through-hole portion, and to reduce the difference between the misalignment of the 1 st polarizing plate and the misalignment of the 2 nd polarizing plate.

The reflective polarizer has a function of transmitting polarized light of a specific polarization state (polarization direction) and reflecting light of other polarization states. The reflective polarizer may be a linearly polarized light separating type or a circularly polarized light separating type. Hereinafter, a reflective polarizer of a linearly polarized light splitting type will be described as an example. As the circularly polarized light separating type reflective polarizer, for example: a laminate of a film obtained by immobilizing cholesteric liquid crystal and a lambda/4 wave plate.

Fig. 6 is a schematic perspective view of an example of a reflection type 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 may be 50 to 1000. In the illustrated example, the refractive index nx in the x-axis direction of the a layer is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction of the B layer is substantially the same as the refractive index ny in the y-axis direction. Therefore, the refractive index difference between the a layer and the B layer is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis, and the y-axis direction becomes the transmission axis. The difference between the refractive index of the layer A and the refractive index of the layer B in the x-axis direction is preferably 0.2 to 0.3. The x-axis direction corresponds to the stretching direction of the reflective polarizer in the method for manufacturing the reflective polarizer.

The a layer is preferably formed of a material exhibiting birefringence by stretching. Typical examples of such materials include: naphthalenedicarboxylic acid polyesters (e.g., polyethylene naphthalate), polycarbonates, and acrylic resins (e.g., polymethyl methacrylate). Polyethylene naphthalate is preferred. The B layer is preferably formed of a material that exhibits substantially no birefringence even when stretched. Typical examples of such materials include copolyesters of naphthalenedicarboxylic acid and terephthalic acid.

The reflective polarizer transmits light (for example, p-wave) having a 1 st polarization direction at an interface between the a layer and the B layer, and reflects light (for example, s-wave) having a 2 nd polarization direction orthogonal to the 1 st polarization direction. The reflected light is transmitted as light having the 1 st polarization direction partially at the interface between the a layer and the B layer, and is reflected as light having the 2 nd polarization direction partially. Such reflection and transmission are repeated a plurality of times inside the reflective polarizer, and thus the light utilization efficiency can be improved.

In one embodiment, the reflective polarizer may include a reflective layer R as an outermost layer on the side opposite to the image display unit, as shown in fig. 6. By providing the reflective layer R, light that is not finally used and returns to the outermost portion of the reflective polarizer can be further used, and therefore, the light use efficiency can be further improved. Typically, the reflective layer R exhibits a reflective function by a multilayer structure of a polyester resin layer.

The overall thickness of the reflective polarizer may be appropriately set according to the purpose, the total number of layers included in the reflective polarizer, and the like. The total thickness of the reflective polarizer is preferably 10 μm to 150 μm.

As the reflective polarizer, for example, the reflective polarizers described in JP-A-9-507308 and JP-A-2013-235259 can be used. The reflection polarizer may be used as it is or after being subjected to secondary processing (e.g., stretching). Examples of commercially available products include: trade name DBEF manufactured by 3M company, and trade name APF manufactured by 3M company.

C. Image display device

As described above, the polarizer group according to the embodiment of the present invention can be suitably used for 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 polarizer group. The polarizer group is the polarizer group 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 unit 120, a 1 st polarizing plate 10 disposed on the viewing side of the image display unit 120, and a 2 nd polarizing plate 20 disposed on the back side of the image display unit 120.

Examples of the image display device include: liquid crystal display devices, organic Electroluminescence (EL) display devices, and quantum dot display devices. Preferably a liquid crystal display device. The reason for this is that the effect by the polarizer group is significant.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Evaluation items in examples are as follows. Unless otherwise specified, "part(s)" and "%" in the examples are based on weight.

(1) Offset amount

The 1 st polarizing plate and the 2 nd polarizing plate in the polarizing plate group obtained in the examples and comparative examples were respectively bonded to a glass plate (350 mm in the longitudinal direction, 250mm in the transverse direction, 1.1mm in thickness, manufactured by Sonlang glass Co., Ltd.) via an adhesive layer to prepare a test sample. Each test sample was subjected to a heating test at 85 ℃ for 120 hours. After the test, the amount of shift of the 1 st polarizing plate or the 2 nd polarizing plate (substantially, the 1 st adhesive layer or the 2 nd adhesive layer) penetrating the hole portion was measured by an optical microscope (MX61L) manufactured by OLYMPUS corporation, respectively. The measurement was performed on 3 test samples, and the maximum value among the 3 measurement values was used as the offset amount.

< production example 1 >

A four-necked flask equipped with a stirring blade, a thermometer, a nitrogen-introducing tube and a condenser was charged with a monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate. Further, 0.1 part of 2, 2' -azobisisobutyronitrile as a polymerization initiator was added together with 100 parts by weight of ethyl acetate to 100 parts by weight of the monomer mixture (solid content), nitrogen gas was introduced while slowly stirring to replace nitrogen gas, and then the liquid temperature in the flask was kept near 55 ℃ to conduct polymerization for 8 hours, thereby preparing a solution of the acrylic polymer (a) having a weight average molecular weight (Mw) of 156 ten thousand. An adhesive composition A was obtained by mixing 0.1 part of an isocyanate crosslinking agent (trade name: Takenate D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui chemical Co., Ltd.), 0.3 part of benzoyl peroxide (trade name: Nyper BMT 40SV, manufactured by Nippon oil & fat Co., Ltd.), 0.3 part of a sulfur-containing hydroxysilane coupling agent (trade name: X-41-1810, manufactured by shin-Etsu chemical Co., Ltd., alkoxy group amount: 30%, thiol equivalent weight: 450g/mol) and 0.2 part of an antioxidant (trade name: Irganox 1010, hindered phenol, manufactured by BASF Japan K.K.) with respect to 100 parts of the solid content of the obtained acrylic polymer (a).

< production example 2 >

A solution of an acrylic polymer (b) having a weight-average molecular weight (Mw) of 157 ten thousand 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 part of a thiol-containing silane coupling agent (trade name: X-41-1056, manufactured by shin-Etsu chemical Co., Ltd., alkoxy amount: 30% and thiol equivalent weight: 450g/mol) was used as the silane coupling agent, no antioxidant was used, and 0.5 part of lithium bis (trifluoromethanesulfonyl) imide (manufactured by Mitsubishi corporation) was further added.

< production example 3 >

A solution of an acrylic polymer (c) having a weight-average molecular weight (Mw) of 150 ten thousand 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 part of acrylic acid and 0.4 part of 4-hydroxybutyl acrylate was used. An acrylic polymer (c) was used, and a silane coupling agent was added in an amount of 0.1 part, and a conductive agent (1-ethyl-3-methylimidazole) was added

Bis (trifluoromethanesulfonyl) imide and 5 parts of an ionic liquid manufactured by first industrial pharmaceutical co., ltd.) were added to the reaction solution to prepare a pressure-sensitive adhesive composition C, and the mixture was subjected to vacuum distillation to obtain a pressure-sensitive adhesive composition C.

< production example 4 >

A solution of the acrylic polymer (d) having a weight average molecular weight (Mw) of 165 ten thousand was prepared in the same manner as in production example 1. An adhesive composition D was obtained by mixing 0.1 part of an isocyanate crosslinking agent (trade name: Takenate D110N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui chemical Co., Ltd.), 0.3 part of benzoyl peroxide (trade name: Nyper BMT 40SV, manufactured by Nippon fat and oil Co., Ltd.) and 0.2 part of an acetoacetylsilane-containing coupling agent (trade name: A-100, manufactured by Sokko chemical Co., Ltd.) with 100 parts of the solid content of the obtained solution of the acrylic polymer (D).

< production example 5 >

A pressure-sensitive adhesive composition E was obtained in the same manner as in production example 1, except that 0.2 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% and thiol group equivalent weight: 450g/mol) was used as the silane coupling agent.

< example 1 >

(preparation of the No. 1 polarizing plate)

As the polarizer (1 st polarizer), a film (thickness 12 μm) obtained by uniaxially stretching a long polyvinyl alcohol (PVA) -based resin film in the longitudinal direction (MD direction) while containing iodine was used. On both sides of the polarizer, a long HC-TAC film as an outer protective layer and a long acrylic resin film (20 μm thick) as an inner protective layer were bonded so that the longitudinal directions thereof were aligned with each other. The HC-TAC film was a film in which a Hard Coat (HC) layer (thickness 7 μm) was formed on a triacetyl cellulose (TAC) film (thickness 25 μm), and was bonded so that the TAC film was on the polarizer side. An adhesive layer (1 st adhesive layer: thickness 20 μm) was formed on the surface of the inner protective layer using adhesive composition B, and a 1 st polarizing plate having a configuration of outer protective layer/1 st polarizer/inner protective layer/1 st adhesive layer was obtained. The 1 st polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 1 st polarizer was punched so that the absorption axis direction was the short side direction.

(preparation of No. 2 polarizing plate)

A polarizing plate was obtained in the same manner as in the case of the 1 st 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 reflection type polarizer (thickness 26 μm) was bonded to the surface of the outer protective layer via a normal adhesive layer (thickness 12 μm), and a 2 nd adhesive layer (thickness 20 μm) was formed on the surface of the reflection type polarizer using the adhesive composition E, to obtain a 2 nd polarizing plate having a configuration of reflection type polarizer/outer protective layer/2 nd polarizer/inner protective layer/2 nd adhesive layer. The No. 2 polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 2 nd polarizer was punched so that the absorption axis direction thereof was the longitudinal direction.

(group of polarizers)

The polarizing plate group of the present example was prepared by using the 1 st polarizing plate obtained as described above as a visible-side polarizing plate and the 2 nd polarizing plate as a back-side polarizing plate. The obtained polarizer group was subjected to the evaluation of the above-described offset amount. The results are shown in table 1 together with the detailed configurations of the 1 st polarizing plate and the 2 nd polarizing plate. In table 1, "0 °" indicates the longitudinal direction, and "90 °" indicates the short side direction.

< comparative example 1 >

A polarizing plate group was obtained in the same manner as in example 1 except that the 1 st polarizing plate was produced by punching so that the absorption axis direction of the 1 st polarizer was the longitudinal direction, and the 2 nd polarizing plate was produced by punching so that the absorption axis direction of the 2 nd polarizer was the short side direction. The obtained polarizer group was subjected to the same evaluation as in example 1. The results are shown in table 1 together with the detailed configurations of the 1 st polarizing plate and the 2 nd polarizing plate.

< example 2 >

(preparation of the No. 1 polarizing plate)

A 1 st polarizing plate having a configuration of outer protective layer/1 st polarizer/inner protective layer/1 st adhesive layer was obtained in the same manner as in example 1 except that the 1 st adhesive layer (thickness: 20 μm) was formed using the adhesive composition C. The 1 st polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 1 st polarizer was punched so that the absorption axis direction was the short side direction.

(preparation of No. 2 polarizing plate)

As the thermoplastic resin substrate, a long amorphous ethylene terephthalate film (thickness: 100 μm) copolymerized with isophthalic acid having a Tg of about 75 ℃ was used, and one surface of the resin substrate was subjected to corona treatment.

To 100 parts by weight of a PVA resin obtained by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (trade name "GOHSEFIMER" manufactured by Nippon synthetic chemical Co., Ltd.) at a ratio of 9:1, 13 parts by weight of potassium iodide was added, and the obtained mixture was dissolved in water to prepare an aqueous PVA solution (coating liquid).

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

The resulting laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) to 2.4 times in an oven at 130 ℃ (stretching treatment was assisted in a gas atmosphere).

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

Next, the resultant polarizer was immersed for 60 seconds (dyeing treatment) in a dyeing bath (aqueous iodine solution prepared by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ while adjusting the concentration so that the monomer transmittance (Ts) of the polarizer finally obtained became a desired value.

Subsequently, the substrate was immersed in a crosslinking bath (aqueous boric acid solution prepared by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (crosslinking treatment).

Then, while immersing the laminate in an aqueous boric acid solution (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%) having a liquid temperature of 70 ℃, uniaxial stretching was performed between rolls having different peripheral speeds so that the total stretching ratio in the longitudinal direction (longitudinal direction) became 5.5 times (stretching treatment in an aqueous solution).

Then, the laminate was immersed in a cleaning bath (aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a liquid temperature of 20 ℃.

Then, while drying in an oven maintained at about 90 ℃, the sheet was contacted with a heated roll made of SUS maintained at a surface temperature of about 75 ℃ (drying shrinkage treatment).

In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate/2 nd polarizer was obtained.

A TAC film (20 μm in thickness) was attached as an inner protective layer to the polarizer surface (the surface opposite to the resin substrate) of the obtained laminate. Then, the resin substrate was peeled off, and a reflection type polarizer (thickness 26 μm) was bonded to the peeled surface via a normal pressure-sensitive adhesive layer (thickness 12 μm). An adhesive layer (thickness: 20 μm) was formed on the surface of the inner protective layer using adhesive composition D, and a 2 nd polarizing plate having a configuration of reflective polarizer/2 nd polarizer/inner protective layer/2 nd adhesive layer was obtained. The No. 2 polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 2 nd polarizer was punched so that the absorption axis direction thereof was the longitudinal direction.

(group of polarizers)

The polarizing plate group of the present example was prepared by using the 1 st polarizing plate obtained as described above as a visible-side polarizing plate and the 2 nd polarizing plate as a back-side polarizing plate. The obtained polarizer group was subjected to the same evaluation as in example 1. The results are shown in table 1 together with the detailed configurations of the 1 st polarizing plate and the 2 nd polarizing plate.

< comparative example 2 >

A polarizing plate group was obtained in the same manner as in example 2 except that the polarizing plate group was obtained by punching the polarizing plate group so that the absorption axis direction of the 1 st polarizer was the longitudinal direction to produce a 1 st polarizing plate and the polarizing plate group was obtained by punching the polarizing plate group so that the absorption axis direction of the 2 nd polarizer was the short side direction to produce a 2 nd polarizing plate. The obtained polarizer group was subjected to the same evaluation as in example 1. The results are shown in table 1 together with the detailed configurations of the 1 st polarizing plate and the 2 nd polarizing plate.

< example 3 >

(preparation of the No. 1 polarizing plate)

A 1 st polarizing plate having a configuration of outer protective layer/1 st polarizer/inner protective layer/1 st adhesive layer was obtained in the same manner as in example 1 except that a cycloolefin resin film (thickness 13 μm) was used instead of the acrylic resin film as the inner protective layer and an adhesive composition C was used instead of the adhesive composition B to form a 1 st adhesive layer (thickness 20 μm). The 1 st polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 1 st polarizer was punched so that the absorption axis direction was the short side direction.

(preparation of No. 2 polarizing plate)

A laminate having a resin base material/2 nd polarizer structure was obtained in the same manner as in example 2. A TAC film (20 μm thick) was attached as an inner protective layer to the polarizer surface (the surface opposite to the resin substrate) of the laminate thus obtained. Next, the resin substrate was peeled off, and a reflective polarizer (thickness 26 μm) was bonded to the peeled surface via a normal pressure-sensitive adhesive layer (thickness 12 μm). A2 nd adhesive layer (thickness: 20 μm) was formed on the surface of the inner protective layer using adhesive composition D, and a 2 nd polarizing plate having a configuration of reflective polarizer/2 nd polarizer/inner protective layer/2 nd adhesive layer was obtained. The No. 2 polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 2 nd polarizer was punched so that the absorption axis direction thereof was the longitudinal direction.

(group of polarizers)

< comparative example 3 >

A polarizing plate group was obtained in the same manner as in example 3 except that the 1 st polarizing plate was produced by punching so that the absorption axis direction of the 1 st polarizer was the longitudinal direction, and the 2 nd polarizing plate was produced by punching so that the absorption axis direction of the 2 nd polarizer was the short side direction. The obtained polarizer group was subjected to the same evaluation as in example 1. The results are shown in table 1 together with the detailed configurations of the 1 st polarizing plate and the 2 nd polarizing plate.

< example 4 >

(preparation of the No. 1 polarizing plate)

A laminate having a resin substrate/polarizer structure was obtained in the same manner as in the 2 nd polarizing plate of example 2. An HC-TAC film was bonded as an outer protective layer to the polarizer surface (the surface opposite to the resin substrate) of the obtained laminate. Next, the resin substrate was peeled off, and an adhesive layer (thickness: 15 μm) was formed on the peeled surface using the adhesive composition a, thereby obtaining a 1 st polarizing plate having a configuration of outer protective layer/1 st polarizer/inner protective layer/1 st adhesive layer. The 1 st polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 1 st polarizer was punched so that the absorption axis direction was the short side direction.

(No. 2 polarizing plate)

The same 2 nd polarizing plate as in example 3 was used.

(group of polarizers)

< comparative example 4 >

(preparation of the No. 1 polarizing plate)

As the polarizer (1 st polarizer), a film (thickness: 22 μm) obtained by uniaxially stretching a long polyvinyl alcohol (PVA) -based resin film in the longitudinal direction (MD direction) while containing iodine was used. On both sides of the polarizer, a long TAC film (thickness: 40 μm) as an outer protective layer and a long acrylic resin film (thickness: 30 μm) as an inner protective layer were bonded so that the longitudinal directions thereof were aligned 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 1 st polarizing plate having a configuration of outer protective layer/1 st polarizer/inner protective layer/1 st adhesive layer was obtained. The 1 st polarizing plate was punched to have a length of 148mm and a width of 70mm, and a through-hole having a diameter of 3.9mm was formed in a corner portion. At this time, the 1 st polarizer was punched so that the absorption axis direction was the short side direction.

(No. 2 polarizing plate)

The same 2 nd polarizing plate as in example 1 was used.

(group of polarizers)

The polarizing plate group of this comparative example was prepared by using the 1 st polarizing plate obtained as described above as a visible-side polarizing plate and the 2 nd polarizing plate as a back-side polarizing plate. The obtained polarizer group was subjected to the same evaluation as in example 1. The results are shown in table 1 together with the detailed configurations of the 1 st polarizing plate and the 2 nd polarizing plate.

As is clear from table 1, the polarizer group of the embodiment of the present invention can significantly reduce the difference (absolute value) between the amount of shift of the 1 st polarizer and the amount of shift of the 2 nd polarizer, compared to the comparative example. Therefore, the polarizer set of the embodiment of the present invention has a significant advantage in design when applied to an image display device.

Industrial applicability

The polarizing plate set of the present invention is suitably used for an image display device, and particularly, is suitably used for an image display device having a camera unit, such as a smart phone, a tablet PC, or a smart watch.

Claims

1. A polarizing plate group comprising a rectangular 1 st polarizing plate disposed on the visible side of an image display unit and a rectangular 2 nd polarizing plate disposed on the back side of the image display unit,

wherein the 1 st polarizer comprises a 1 st polarizer, a protective layer disposed on at least one side of the 1 st polarizer, and a 1 st adhesive layer disposed on the image display unit side,

the 2 nd polarizing plate has a 2 nd polarizer, a protective layer disposed on at least one side of the 2 nd polarizer, a reflective polarizer disposed on the side opposite to the image display unit of the 2 nd polarizer, and a 2 nd adhesive layer disposed on the side of the image display unit,

the thicknesses of the 1 st polarizer and the 2 nd polarizer are respectively less than 20 μm,

the 1 st polarizer has an absorption axis in a short side direction, the 2 nd polarizer has an absorption axis in a long side direction,

the 1 st polarizing plate and the 2 nd polarizing plate have through holes at respective ends or at positions near the ends that correspond to each other.

2. The set of polarizers according to claim 1,

a distance A from an outermost portion of the 1 st adhesive layer on the image display unit side to a thickness direction center portion of the 1 st polarizer₁(mum) and thickness T of the 1 st polarizer_pol1(mum) creep value C of the 1 st adhesive layer_psa1(μm/hr) and the thickness T of the 1 st adhesive layer_psa1(mum) and thickness T of protective layer in the 1 st polarizing plate_pro1(μm) satisfies the following relationship,

(A₁×T_pol1)×(C_psa1×T_psa1)/T_pro1＝K₁≤300×10²(μm³/hr)

a distance A from an outermost portion of the 2 nd adhesive layer on the image display unit side to a thickness direction center portion of the 2 nd polarizer₂(mum) and the thickness T of the 2 nd polarizer_pol2(mum), creep value C of the 2 nd adhesive layer_psa2(μm/hr), thickness T of the 2 nd adhesive layer_psa2(mum) and a thickness T of a protective layer in the 2 nd polarizing plate_pro2(μm) satisfies the following relationship,

(A₂×T_pol2)×(C_psa2×T_psa2)/T_pro2＝K₂≤300×10²(μm³/hr)。

3. the set of polarizers according to claim 2,

said K₁And K₂Are respectively 200X 10²(μm³Hr) below.

4. The set of polarizers according to claim 2 or 3,

creep value C of the No. 1 adhesive layer_psa1Is 100(μm/hr) or less.

5. A set of polarizers according to any one of claims 1 to 4,

thickness T of the 2 nd polarizer_pol2Is 10 μm or less.

6. A set of polarizers according to any one of claims 2 to 5,

said K₁And K₂Are respectively 150X 10²(μm³Hr) below.

7. A set of polarizers according to any one of claims 1 to 6,

thickness T of the 1 st polarizer_pol1Is 10 μm or less.

8. A set of polarizers according to any one of claims 1 to 7,

thickness T of the 1 st adhesive layer_psa1And the thickness T of the 2 nd adhesive layer_psa2Respectively 10 to 22 mu m.

9. A set of polarizers according to any one of claims 1 to 8,

the through-hole is formed in each corner of the 1 st polarizing plate and the 2 nd polarizing plate.

10. The set of polarizers according to claim 9,

l represents a distance from a center in a longitudinal direction to an end in the longitudinal direction when the 1 st polarizer and the 2 nd polarizer are viewed in plan₁And L is a distance from the center of the 1 st polarizer and the 2 nd polarizer in the longitudinal direction to the center of the through hole in the longitudinal direction₂W represents a distance from the center of the 1 st polarizer and the 2 nd polarizer in the short side direction to the end of the short side direction₁And the distance in the short side direction from the center in the short side direction of the 1 st polarizer and the 2 nd polarizer to the center of the through hole is W₂Then, the through hole is formed in the 1 st polarizer and the 2 nd polarizer respectively at L of 0.85 ≤₂/L₁W is not less than 0.99 and not less than 0.50₂/W₁Less than or equal to 0.99.

11. A set of polarizers according to any one of claims 1 to 10,

the diameter of the through hole is 10mm or less.

12. A set of polarizers according to any one of claims 1 to 11,

the length-width ratio of the 1 st polaroid and the 2 nd polaroid is 1.3-2.5 respectively.

13. An image display device comprising an image display unit and the polarizer set according to any one of claims 1 to 12, wherein the 1 st polarizer is disposed on a visible side of the image display unit, and the 2 nd polarizer is disposed on a back side of the image display unit.