JP7397755B2 - Polarizer - Google Patents

Description

The present invention relates to a polarizing plate.

In recent years, the designs of image display devices have been diversifying. Influenced by this trend, polarizing plates are required to accommodate a variety of shapes.

JP 2017-182017 Publication

A polarizing plate that has a concave portion on its outer edge and/or a through hole in its plane is exposed to a high temperature environment and left in the air at room temperature, and then light leaks around the concave portion and the through hole. may occur.

An object of the present invention is to provide a polarizing plate that has a concave portion on the outer edge and/or has a through hole in the plane when viewed from above, and that after being exposed to a high temperature environment and left in the air at room temperature. An object of the present invention is to provide a polarizing plate that suppresses light leakage.

The present invention provides the following polarizing plate, image display device, and method for manufacturing a polarizing plate.
[1] Including a polyvinyl alcohol resin polarizer and a first thermoplastic resin film provided on one surface thereof,
The water absorption rate of the first thermoplastic resin film is 0.1% or less,
In a plan view, a polarizing plate having a concave portion at the outer edge or a through hole in the plane,
A polarizing plate having a shrinkage force of 1.3 N or less per 2 mm width in the absorption axis direction of the polyvinyl alcohol resin polarizer.
[2] The polarizing plate according to [1], wherein the first thermoplastic resin film is an acrylic resin film or a cyclic polyolefin (COP) resin film.
[3] The polarizing plate according to [1] or [2], further including a second thermoplastic resin film provided on the other surface of the polyvinyl alcohol resin polarizer.
[4] A polarizing plate with an adhesive layer, comprising the polarizing plate according to any one of [1] to [3], and an adhesive layer provided on the first thermoplastic resin film side of the polarizing plate.
[5] The polarizing plate with an adhesive layer according to [4] , wherein the adhesive layer is for bonding the polarizing plate to an image display element.
[6] An image display device comprising the polarizing plate according to any one of [1] to [3].
[7] A method for manufacturing a polarizing plate according to any one of [1] to [3], comprising:
A preparation step for preparing a polyvinyl alcohol resin polarizer;
a laminating step of laminating the polyvinyl alcohol resin polarizer and a first thermoplastic resin film;
A profile processing step in which a concave portion is provided at the outer edge of the polarizing plate or a through hole is provided in the plane;
including;
The manufacturing method, wherein the preparation step includes an annealing step.

According to the present invention, there is provided a polarizing plate that includes a polyvinyl alcohol resin polarizer and also includes a first thermoplastic resin film having a water absorption rate of 0.1% or less on one surface thereof, wherein the outer edge portion in a plan view Even if the polarizing plate has a concave part or a through hole in the plane, the shrinkage force in the absorption axis direction of the polyvinyl alcohol resin polarizer is within the above range, so it will not work after being exposed to a high temperature environment. , light leakage that occurs after being left in the air at room temperature can be suppressed.

FIG. 1 is a schematic plan view showing a polarizing plate according to one embodiment of the present invention. FIG. 3 is a schematic plan view showing an example of a concave portion. FIG. 1 is a schematic plan view showing a polarizing plate according to one embodiment of the present invention. FIG. 3 is a schematic plan view showing an example of a through hole. FIG. 2 is a schematic plan view showing an example of the relationship between the direction of shrinkage and the direction of the stretching axis of a polarizing plate. It is a schematic plan view which shows an example of the relationship between the depth direction of a recessed part, and an extending|stretching direction. FIG. 1 is a schematic cross-sectional view showing a polarizing plate according to one embodiment of the present invention. It is a flow chart showing a method for manufacturing a polarizer. FIG. 2 is a schematic diagram for explaining a method for evaluating light leakage through a polarizing plate. It is a schematic diagram showing a polarizing plate produced in an example.

<Polarizing plate>
The polarizing plate according to the present invention is a polarizing plate that includes a polarizer and a first thermoplastic resin film provided on one surface thereof, and the polarizer is a polyvinyl alcohol resin polarizer that is a polyvinyl alcohol resin film. It is. The polarizing plate is a polarizing plate that has a concave portion on the outer edge, a through hole in the plane, or both when viewed in plan. The concave portion of the outer edge portion and the in-plane through hole may be collectively referred to as the irregularly shaped portion hereinafter. In this specification, planar view means viewing from the thickness direction of the layer.

The polarizing plate of the present invention may have a rectangular shape or a rounded rectangular shape in plan view. A rectangular shape with rounded corners refers to a shape in which one or more of the corners of a rectangular shape is a curve.In other words, one or more of the corners of a rectangular shape is rounded. A shape in which none of the corners are rounded. Moreover, in this specification, a square shape shall mean a rectangular shape or a square shape. When the polarizing plate has a rectangular shape with rounded corners, one or more of the four corners of the polarizing plate may be rounded.

The radius of curvature of the rounded corner portion may be, for example, 1 mm or more and 10 mm or less, and preferably 2 mm or more and 8 mm or less.

As shown in FIG. 1, a polarizing plate according to an embodiment of the present invention is a rectangular polarizing plate 10 with rounded corners having concave portions 11 and 12 on the outer edge. In the polarizing plate 10, three of the four corners of the rectangle are rounded.

The recessed portion 11 is recessed inward from the outer edge in plan view, and the depth of the recess may be, for example, 0.1 mm or more, preferably 0.5 mm or more, and more preferably 1 mm or more. It is. On the other hand, the depth of the recess is usually 7 mm or less.

The outer corner portion 13 constituting the concave portion 11 may or may not be a right angle. Further, the outer corner portion 13 may or may not have rounded corners. When the outer corner portion 13 has a rounded corner, the radius of curvature may be, for example, 0.1 mm or more and 10 mm or less, and preferably 0.5 mm or more and 5 mm or less.

The inner corner portion 14 constituting the concave portion 11 may or may not be a right angle. Further, the inner corner portion 14 may or may not have rounded corners. When the outer corner portion 14 has a rounded corner, the radius of curvature may be, for example, 0.1 mm or more and 1 mm or less, and preferably 0.5 mm or more and 5 mm or less.

The concave portion 12 has a U-shaped concave shape in a plan view, and the depth of the concave portion may be, for example, 0.5 mm or more and 10 mm or less, and preferably 1 mm or more and 8 mm or less.

The radius of curvature of the inner corner portion 15 constituting the concave portion 12 may be, for example, 0.5 mm or more and 15 mm or less, and preferably 1 mm or more and 10 mm or less.

The shape of the concave portion 11 is not particularly limited, and may be, for example, as shown in FIGS. 2(a) to 2(d).

As shown in FIG. 3, a polarizing plate according to another embodiment of the present invention is a rounded rectangular polarizing plate 20 having through holes 21 in the plane when viewed from above. In the polarizing plate 20, four of the four corners of the rectangle are rounded.

Although the through hole 21 is shown as a circular through hole in FIG. 3, it is not limited to this, and may be, for example, an ellipse, a square, a rounded rectangle, or a combination thereof.

The radius of the through hole 21 may be, for example, 0.5 mm or more and 30 mm or less, and preferably 1 mm or more and 10 mm or less.

The shape of the through hole 21 is not particularly limited, and may be, for example, the shape shown in FIGS. 4(a) to 4(d). The number of through holes 21 may be one, or two or more.

According to the present inventors, it has been found that when a polarizing plate has an irregularly shaped portion as described above, light leakage is likely to occur around the irregularly shaped portion. Light leakage in the present invention can be observed after the polarizing plate is exposed to a high temperature environment and then left in the air at room temperature. The high-temperature environmental conditions and observation method are those described in the Examples section below.

The principle of light leakage is estimated to be as follows, but the present invention is not limited thereto. First, when the polarizing plate is heated, the polarizer contracts along the stretching axis, that is, along the absorption axis, and this contraction applies stress to the first thermoplastic resin film. As shown in FIG. 5(a), when the polarizing plate does not have irregularly shaped parts, the contraction of the polarizer occurs in the direction of the absorption axis, and even if stress is applied to the first thermoplastic resin film, the absorption axis of the polarizer No disturbance occurs, and no light leakage occurs. However, as shown in FIG. 5(b), when a polarizing plate has an irregularly shaped part, contraction occurs near the irregularly shaped part along the shape of the irregularly shaped part, and the direction of contraction of the polarizer is different from the absorption axis. There will be places where the directions are different. At such locations, the direction of stress applied to the first thermoplastic resin film is in a direction different from the absorption axis. It is estimated that when the first thermoplastic resin film receives stress in a direction different from the absorption axis, light leakage occurs at this location.

The direction of the stretching axis (absorption axis) of the polarizer with respect to the polarizing plate is not particularly limited, but for example, if the polarizing plate is rectangular in plan view, it may be parallel to the long side direction, or parallel to the short side direction. It may be a direction in which the angle with the long side direction (or short side direction) is 45±5 degrees, preferably 45±2 degrees.

Further, according to the present inventor, light leakage tends to occur around the irregularly shaped part when the shortest distance between the irregularly shaped part and the center of gravity of the polarizing plate is, for example, 40 mm or more, preferably 50 mm or more, and more preferably 60 mm or more. I found out. This is because the farther the position where the irregularly shaped part is provided is from the center of gravity, the greater the amount of shrinkage of the polarizer in the irregularly shaped part, and the greater the stress that the first thermoplastic resin film receives in a direction different from the absorption axis, resulting in light leakage. It is presumed that this is because it tends to occur more easily. For example, when the polarizing plate is rectangular, the center of gravity of the polarizing plate can be defined as the intersection of diagonals. When the polarizing plate has a rectangular shape with rounded corners or when corners are lost due to concave portions, the rounded portions can be replaced with corner portions and diagonals can be formed from the corner portions to form the intersection points.

Furthermore, it has been found that light leakage is likely to occur around the irregularly shaped part when the irregularly shaped part is located in a region exceeding a diameter equivalent to 20% of the area from the center of gravity of the polarizing plate. This is because the farther the position where the irregularly shaped part is provided is from the center of gravity, the greater the amount of shrinkage of the polarizer in the irregularly shaped part, and the greater the stress that the first thermoplastic resin film receives in a direction different from the absorption axis, resulting in light leakage. It is presumed that this is because it tends to occur more easily. The diameter equivalent to 20% of the area from the center of gravity means the radius of a circle whose area is equivalent to 20% of the area of the entire polarizing plate when a circle centered on the center of gravity is superimposed on the polarizing plate in plan view. do.

The polarizing plate may have an irregularly shaped portion in a region exceeding a 30% area equivalent diameter from the center of gravity of the polarizing plate, or may have an irregularly shaped portion in a region exceeding a 40% equivalent diameter.

Furthermore, the present inventors have also found that light leakage tends to occur when the depth direction of the concave portion at the outer edge of the polarizing plate is orthogonal to the direction of the stretching axis (shrinkage direction). For example, such a polarizing plate is a polarizing plate having a rectangular shape with rounded corners and a concave portion 41 in plan view, as shown in FIG. Examples include a polarizing plate in which the portion 41 includes the center point 43 of the long side 42 and the direction of the long side 42 is the absorption axis direction.

The thickness of the polarizing plate can usually be 5 μm or more and 200 μm or less, and may be 150 μm or less, or 120 μm or less.

The polarizing plate includes a polarizer and a first thermoplastic resin film provided on one surface of the polarizer. A polarizing plate 100 shown in FIG. 7 includes a polarizer 101 and a first thermoplastic resin film 102 on one surface of the polarizer 101. Further, the polarizing plate 100 may further include a second thermoplastic resin film 103 on the other surface of the polarizer 101. Hereinafter, the first thermoplastic resin film 102 and the second thermoplastic resin film 103 will also be collectively referred to as thermoplastic resin films.

[Polarizer]
The polarizer 101 is a polyvinyl alcohol resin polarizer that is a polyvinyl alcohol resin film, and specifically, is a polarizer in which, for example, a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film. It's fine. Such a polarizer can be manufactured according to a polarizer manufacturing method described below. The polarizer 101 is an absorption type polarizer that has the property of absorbing linearly polarized light having a vibration plane parallel to the absorption axis and transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to the transmission axis). Something can happen. The polarizer 101 can be used as the polarizing plate 100 by pasting the first thermoplastic resin film 102 on one surface with an adhesive or adhesive.

The shrinkage force (hereinafter also simply referred to as "shrinkage force") per 2 mm width of the polarizer 101 in the absorption axis direction is 1.3 N or less. When the shrinkage force of the polarizer 101 is 1.3 N or less, light leakage tends to be less likely to occur around the irregularly shaped portion of the polarizing plate 100. As described above, it is presumed that the light leakage is caused by depolarization caused by distortion of the first thermoplastic resin film having a low water absorption rate due to shrinkage of the polarizer. The inventors of the present invention have focused on this and found that light leakage can be suppressed by lowering the shrinkage force of the polarizer. The shrinkage force of the polarizer 101 is measured according to the measurement method described in the Examples section below.

The shrinkage force of the polarizer 101 is preferably 1.2 N or less, more preferably 0.9 N or less, even more preferably 0.8 N or less, particularly preferably 0.7 N or less, from the viewpoint of suppressing light leakage. It is. On the other hand, the shrinkage force of the polarizer 101 is usually 0.1N or more. Examples of methods for reducing the shrinkage force of the polarizer 101 to 1.3 N or less include adjusting the boric acid concentration in the crosslinking step described below and performing an annealing treatment.

The thickness of the polarizer 101 is usually 20 μm or less, preferably 18 μm or less, and more preferably 15 μm or less. Reducing the thickness of the polarizer 101 is advantageous for making the polarizing plate 100 thin. The thickness of the polarizer 101 is usually 1 μm or more, and may be, for example, 5 μm or more.

The thickness of the polarizer 101 can be controlled, for example, by selecting a polyvinyl alcohol resin film, adjusting the stretching ratio, and the like.

[Manufacturing method of polarizer]
A method for manufacturing polarizer 101 will be described with reference to the drawings. The manufacturing method shown in FIG. 8 includes the following steps:
a swelling step S10 in which the polyvinyl alcohol resin film is immersed in a swelling tank containing a treatment liquid containing water;
a dyeing step S20 of dyeing the polyvinyl alcohol resin film by immersing it in a dyeing tank containing a treatment liquid containing a dichroic dye;
a crosslinking step S30 in which the polyvinyl alcohol resin film is immersed in a crosslinking tank containing a treatment liquid containing a crosslinking agent for crosslinking treatment;
a cleaning step S40 of immersing the polyvinyl alcohol resin film in a cleaning tank;
Drying step S50,
can include.
The polyvinyl alcohol resin film is uniaxially stretched (stretched) at any one or more stages of the polarizer manufacturing process, more specifically, at any one or more stages from before the swelling step S10 to the crosslinking step S30. process).

The manufacturing method may further include steps other than those described above, and a specific example thereof may be an annealing step S60 as shown in FIG. 8.

The various processing steps included in the manufacturing method according to the present invention can be carried out continuously by continuously transporting the polyvinyl alcohol resin film, which is the original film, along the film transport path of the polarizer manufacturing device. I can do it. The film transport path is equipped with equipment (processing tanks, furnaces, etc.) for implementing the various processing steps described above in the order in which they are performed.

The film transport path can be constructed by arranging guide rolls, nip rolls, etc. at appropriate positions in addition to the above equipment. For example, guide rolls can be placed before and after each processing tank or in the processing tank, thereby allowing the film to be introduced into and immersed in the processing tank and pulled out from the processing tank. More specifically, by providing two or more guide rolls in each processing tank and transporting the film along these guide rolls, the film can be immersed in each processing tank.

As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film that is the raw film, a saponified polyvinyl acetate resin can be used. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. The degree of saponification of the polyvinyl alcohol resin is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. In this specification, "(meth)acrylic" means at least one selected from acrylic and methacryl. The same applies to "(meth)acryloyl".

The polyvinyl alcohol resin may be modified; for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes may also be used.

The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 or more and 10,000 or less, more preferably 1,500 or more and 8,000 or less, and even more preferably 2,000 or more and 5,000 or less. The average degree of polymerization of polyvinyl alcohol resin can be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain preferable polarizing performance, and if it exceeds 10,000, film processability may be poor.

The thickness of the polyvinyl alcohol resin film is, for example, about 10 μm or more and 50 μm or less, and from the viewpoint of setting the polarizer thickness to 15 μm or less, it is preferably 40 μm or less, more preferably 30 μm or less.

The polyvinyl alcohol resin film that is the raw film can be prepared, for example, as a roll (wound product) of a long unstretched or stretched polyvinyl alcohol resin film. In this case, the polarizer is also obtained as a long object. Each step will be explained in detail below.

(1) Swelling step S10
The swelling treatment in this step is a treatment carried out as necessary for the purpose of removing foreign substances from the polyvinyl alcohol resin film, which is the original film, removing plasticizers, imparting dyeability, plasticizing the film, etc. Specifically, it can be a treatment in which the polyvinyl alcohol resin film is immersed in a swelling tank containing a treatment liquid containing water. The film may be immersed in one swelling tank, or may be immersed in two or more swelling tanks in sequence. The film may be uniaxially stretched before the swelling treatment, during the swelling treatment, or before and during the swelling treatment.

The processing liquid contained in the swelling tank may be water (for example, pure water), or may be an aqueous solution containing a water-soluble organic solvent such as alcohol.

The temperature of the processing liquid stored in the swelling tank when dipping the film is usually about 10°C or more and 70°C or less, preferably about 15°C or more and 50°C or less, and the immersion time of the film is usually about 10 seconds or more and 600°C or more. It is about seconds or less, preferably about 20 seconds or more and 300 seconds or less.

(2) Dyeing process S20
The dyeing process in this process is a process performed for the purpose of adsorbing and orienting the dichroic dye to the polyvinyl alcohol resin film. This can be a treatment in which the polyvinyl alcohol resin film is immersed. The film may be immersed in one dyeing tank or may be sequentially immersed in two or more dyeing tanks. In order to improve the dyeability of the dichroic dye, the film to be subjected to the dyeing process may be subjected to at least some uniaxial stretching treatment. In place of the uniaxial stretching treatment before the dyeing treatment, or in addition to the uniaxial stretching treatment before the dyeing treatment, the uniaxial stretching treatment may be performed during the dyeing treatment.

The dichroic dye can be iodine or a dichroic organic dye. Specific examples of dichroic organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Splat Blue G, Splat Blue GL, Splat Orange GL, Direct Includes Sky Blue, Direct First Orange S, and First Black. One type of dichroic dye may be used alone, or two or more types may be used in combination.

When using iodine as the dichroic dye, the treatment liquid contained in the dyeing tank may be an aqueous solution containing iodine and potassium iodide. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used together. Further, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc., may be coexisting. When boric acid is added, it is distinguished from the crosslinking treatment described below in that it contains iodine. The content of iodine in the aqueous solution is usually 0.01 parts by mass or more and 1 part by mass or less per 100 parts by mass of water. Further, the content of iodide such as potassium iodide is usually 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of water. As mentioned above, the treatment liquid contained in the dyeing bath can contain zinc salts.

The temperature of the treatment liquid stored in the dyeing tank when dipping the film is usually 10°C or more and 45°C or less, preferably 10°C or more and 40°C or less, more preferably 20°C or more and 35°C or less, and The immersion time is usually 30 seconds or more and 600 seconds or less, preferably 60 seconds or more and 300 seconds or less.

When using a dichroic organic dye as the dichroic dye, an aqueous solution containing the dichroic organic dye can be used as the treatment liquid stored in the dyeing bath. The content of the dichroic organic dye in the aqueous solution is usually 1 x 10 ^-4 parts by mass or more and 10 parts by mass or less, preferably 1 x 10 ^-3 parts by mass or more and 1 part by mass or less per 100 parts by mass of water. . The dyeing tank may contain a dyeing aid, for example, an inorganic salt such as sodium sulfate, a surfactant, and the like. One type of dichroic organic dye may be used alone, or two or more types may be used in combination. The temperature of the treatment liquid stored in the dyeing tank when dipping the film is, for example, 20°C or more and 80°C or less, preferably 30°C or more and 70°C or less, and the immersion time of the film is usually 30 seconds or more and 600 seconds or less. , preferably 60 seconds or more and 300 seconds or less.

(3) Crosslinking step S30
Cross-linking treatment, in which the polyvinyl alcohol resin film is treated with a cross-linking agent after the dyeing process, is a treatment performed for the purpose of making the polyvinyl alcohol resin film waterproof by cross-linking and adjusting the hue. After the dyeing process, the film may be immersed in a treatment solution. The film may be immersed in one crosslinking tank, or may be sequentially immersed in two or more crosslinking tanks. A uniaxial stretching process may be performed during the crosslinking process.

Examples of the crosslinking agent include boric acid, glyoxal, glutaraldehyde, etc., and boric acid is preferably used. Two or more types of crosslinking agents can also be used in combination. The content of boric acid in the treatment solution stored in the crosslinking tank is usually 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of water, and preferably 1 part by mass or more and 10 parts by mass or less from the viewpoint of shrinkage force of the polarizer. Parts by mass or less.

When the dichroic dye is iodine, the treatment liquid stored in the crosslinking tank preferably contains iodide in addition to boric acid. The content of iodide in the treatment liquid stored in the crosslinking tank is usually 0.1 parts by mass or more and 15 parts by mass or less, preferably 5 parts by mass or more and 12 parts by mass or less per 100 parts by mass of water. Examples of iodides include potassium iodide and zinc iodide. Further, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may be allowed to coexist in the crosslinking tank.

The temperature of the processing liquid stored in the crosslinking tank when dipping the film is usually 50°C or more and 85°C or less, preferably 50°C or more and 70°C or less, and the immersion time of the film is usually 10 seconds or more and 600 seconds or less. , preferably 20 seconds or more and 300 seconds or less.

In the crosslinking step S30, there may be two or more crosslinking tanks. In this case, the composition and temperature of the treatment liquid stored in each crosslinking tank may be the same or different. The treatment liquid stored in the crosslinking tank may have a concentration of a crosslinking agent, an iodide, etc., and a temperature depending on the purpose of immersing the polyvinyl alcohol resin film. The crosslinking treatment for water resistance by crosslinking and the crosslinking treatment for hue adjustment (complementary color) may be performed in a plurality of steps (for example, in a plurality of tanks).
Generally, when performing both cross-linking treatment for water resistance and hue adjustment (complementary color), the tank (complementary color tank) that performs the cross-linking treatment for hue adjustment (complementary color) is placed in the latter stage. Placed. The temperature of the processing liquid stored in the complementary color tank is, for example, 10°C or more and 55°C or less, preferably 20°C or more and 50°C or less. The content of the crosslinking agent in the processing liquid stored in the complementary color tank is, for example, 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of water. The content of iodide in the processing liquid stored in the complementary color tank is, for example, 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of water.

As described above, in manufacturing a polarizer, a polyvinyl alcohol resin film is uniaxially stretched in one or more stages from before the swelling step S10 to the crosslinking step S30 (stretching step, FIG. 1). . From the viewpoint of improving the dyeability of the dichroic dye, the film to be subjected to the dyeing process is preferably a film that has been subjected to at least some uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, or In addition to the uniaxial stretching process before the dyeing process, it is preferable to perform the uniaxial stretching process during the dyeing process.

The uniaxial stretching process may be either dry stretching in which stretching is performed in air or wet stretching in which stretching is performed in a bath, or both of these may be performed. The uniaxial stretching process can be inter-roll stretching, hot roll stretching, tenter stretching, etc., in which longitudinal uniaxial stretching is performed with a peripheral speed difference between two nip rolls, but preferably includes inter-roll stretching. The stretching ratio (when stretching is performed in two or more stages, the cumulative stretching ratio) based on the original film is about 3 times or more and 8 times or less. In order to provide good polarizing properties, the stretching ratio is preferably 4 times or more, more preferably 5 times or more.

By passing through the crosslinking step S30, the polarizer obtained contains a boron component. There is a tendency that the smaller the content of this boron component, the smaller the shrinkage force can be. In order to reduce the content of the boron component, the boric acid content in the treatment liquid in the crosslinking tank may be lowered or the immersion time in the crosslinking tank may be shortened.

(4) Cleaning step S40
The cleaning treatment in this process is a treatment carried out as necessary for the purpose of removing chemicals such as excess crosslinking agent and dichroic dyes attached to the polyvinyl alcohol resin film, and uses a cleaning solution containing water. This is a process for cleaning the polyvinyl alcohol resin film after the crosslinking process. Specifically, it can be a process in which the polyvinyl alcohol resin film after the crosslinking process is immersed in a processing liquid (cleaning liquid) contained in a cleaning tank. The film may be immersed in one cleaning tank, or may be immersed in two or more cleaning tanks sequentially. Alternatively, the cleaning treatment may be a treatment in which a cleaning liquid is sprayed as a shower onto the polyvinyl alcohol resin film after the crosslinking step, or the above-mentioned dipping and spraying may be combined.

The cleaning liquid may be water (for example, pure water), or may be an aqueous solution containing a water-soluble organic solvent such as alcohol. The temperature of the cleaning liquid can be, for example, about 5° C. or higher and 40° C. or lower.

The cleaning step S40 is an optional step and may be omitted. Preferably, the film after the cleaning step S40 is subjected to a drying step S50.

(5) Drying step S50
The drying step S50 is a zone for drying the polyvinyl alcohol resin film after the cleaning step S40. A drying process can be performed by introducing the polyvinyl alcohol resin film after the washing step S40 into the drying step S50 while continuing to transport the polyvinyl alcohol resin film, thereby obtaining a polarizer.

The drying process is performed using a film drying means (heating means). A suitable example of the drying means is a drying oven. The drying oven is preferably one in which the temperature inside the oven can be controlled. The drying oven is, for example, a hot air oven that can increase the temperature inside the oven by supplying hot air or the like. Further, the drying process by the drying means may be a process in which the polyvinyl alcohol resin film after the cleaning step S40 is brought into close contact with one or more heating bodies having a convex curved surface, or a process in which the film is heated using a heater. good.

Examples of the heating body include a roll (for example, a guide roll that also serves as a heat roll) that is equipped with a heat source (for example, a heat medium such as hot water or an infrared heater) and can increase the surface temperature. Examples of the heater include an infrared heater, a halogen heater, and a panel heater.

The temperature of the drying process (for example, the temperature inside the drying oven, the surface temperature of the heat roll, etc.) is usually 30°C or more and 100°C or less, preferably 50°C or more and 90°C or less. The drying time is not particularly limited, but is, for example, 30 seconds or more and 600 seconds or less.

(6) Annealing step S60
For the purpose of reducing the shrinkage force of the polarizer, an annealing step S60 may be performed after the temperature of the polarizer is brought to room temperature after the drying step S50.

In the annealing step, for example, a first base film is attached to one side of the polarizer via a pure water layer using its surface tension, and a second base film is attached to the other side via a pure water layer due to its surface tension. By pasting and heating, drying is performed to remove moisture from the pure water layer. The drying temperature is usually 70°C to 90°C or less, and the drying time is usually 0.5 to 2 minutes. By drying, a three-layer laminate is obtained in which the first base film is attached to one side of the polarizer, and the second base film is attached to the other side of the polarizer in a releasable manner. Next, the second base film is peeled off from this three-layer laminate to obtain a laminate in which the first base film is adhered to only one side of the polarizer, and this two-layer laminate is separated into two blank sheets. The annealing process is performed by sandwiching between dust paper and heating in this state. The heating temperature is usually 70°C to 110°C, preferably 80°C to 100°C, and the heating time is usually 0.5 to 24 hours, preferably 2 to 12 hours. Since the polarizer is heated while being held between the first base film that is peelably attached and the dust-free paper that is not attached, the stress on the polarizer is easily relieved. Therefore, the contractile force can be reduced.

The first base film and the second base film can be easily peeled off. The first base film and the second base film can be peeled off immediately before bonding the thermoplastic resin film in the thermoplastic resin film bonding step described below.

The first base film may be, for example, a TAC film, and the second base film may be, for example, a PMMA film.

Heating can be performed using, for example, a common heating furnace. Examples of the heating furnace include a temperature-controllable hot air oven, an infrared heater, and the like.

Through the above steps, it is possible to obtain a polarizer in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film.

The obtained polarizer can also be transported as it is, for example, to the next polarizing plate production step (step of laminating a thermoplastic resin film on one or both sides of the polarizer).

[First thermoplastic resin film]
The first thermoplastic resin film 102 has a water absorption rate (hereinafter also simply referred to as "water absorption rate") of 0.1% or less. Generally, the higher the water absorption rate of the first thermoplastic resin film 102, the less light leakage tends to occur. This is because when the first thermoplastic resin film 102 has a high water absorption rate, moisture in the atmosphere is absorbed by the first thermoplastic resin film and the polarizer when it is left in the air at room temperature after being exposed to a high temperature environment. It is presumed that this is because the first thermoplastic resin film and the polarizer expand and the stress is relaxed. However, according to the present invention, even if the water absorption rate of the first thermoplastic resin film 102 is 0.1% or less, the occurrence of light leakage can be prevented by lowering the shrinkage rate of the polarizer 101 as described above. It can be easily suppressed. Water absorption refers to the amount of water contained in a film, and is expressed as the ratio of the mass of water to the mass of the film. The water absorption rate of the first thermoplastic resin film 102 is determined by the measuring method described in the Examples section below. The water absorption rate of the first thermoplastic resin film 102 may be, for example, 0.05% or less, while the water absorption rate of the first thermoplastic resin film 102 is usually 0% or more, for example, 0.0001% or more. or 0.001% or more.

As the first thermoplastic resin film 102, polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.) and cyclic polyolefin resins (norbornene resins, etc.); Examples include transparent resin films made of meth)acrylic resins and the like. Among these, preferred are (meth)acrylic resin films or cyclic polyolefin (COP) resin films from the viewpoint of optical light resistance and dimensional stability. In particular, since a cyclic polyolefin (COP) resin film has a low water absorption rate, when a cyclic polyolefin (COP) resin film is used as the first thermoplastic resin film 102, the polarizing plate of the present invention tends to be effective. In general, films made of cyclic polyolefin resin (COP) have a low water absorption rate, so polarizing plates containing this film will still experience light leakage around irregularly shaped parts even after being left at room temperature after being exposed to high temperatures. It tends to be easy. However, according to the present invention, even if the first thermoplastic resin film 102 is a film made of such a cyclic polyolefin resin, light leakage tends not to occur around the irregularly shaped portion.

The thickness of the first thermoplastic resin film 102 is preferably thin from the viewpoint of making the polarizing plate 100 thin, but if it is too thin, the strength tends to decrease and workability tends to be poor, so it is preferably 5 μm or more and 150 μm or less. , more preferably 5 μm or more and 100 μm or less, still more preferably 10 μm or more and 50 μm or less.

The first thermoplastic resin film 102 may have a function as a protective film. Further, either one or both of the first thermoplastic resin film 102 and the second thermoplastic resin film 103 described below can also be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film is provided with an arbitrary retardation value by stretching (uniaxially or biaxially stretching, etc.) a transparent resin film made of the above material or by forming a liquid crystal layer or the like on the film. It can be done.
When the polarizing plate 100 is placed in an image display device, the polarizing plate 100 can be bonded to the image display device so that the first thermoplastic resin film 102 is on the image display device side. Moreover, the polarizing plate 100 can also be bonded to an image display device so that the first thermoplastic resin film 102 is on the outside of the image display device. The polarizing plate 100 is preferably bonded to the image display device so that the first thermoplastic resin film 102 faces the image display device side.

The first thermoplastic resin film 102 and the second thermoplastic resin film 103 described later may have a hard coat layer formed thereon. The hard coat layer may be formed on one surface or both surfaces of the thermoplastic resin film. By providing a hard coat layer, it is possible to obtain a thermoplastic resin film with improved hardness and scratch resistance. The hard coat layer is, for example, a cured layer of ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resin, silicone resin, polyester resin, urethane resin, amide resin, and epoxy resin. The hard coat layer may contain additives to improve strength. The additive is not limited, and may include inorganic fine particles, organic fine particles, or a mixture thereof.

[Second thermoplastic resin film]
The second thermoplastic resin film 103 may be of the same type as the film exemplified in the description of the first thermoplastic resin film 102, or may be of a different type. The second thermoplastic resin film 103 may have a water absorption rate of 0.1% or less or more than 0.1%.

As the second thermoplastic resin film 103, thermoplastic resins such as polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.); triacetyl cellulose, diacetyl Cellulose ester resins such as cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate resins; (meth)acrylic resins such as polymethyl methacrylate resins; or mixtures thereof. It can be a transparent resin film made of , copolymer, or the like.

The second thermoplastic resin film 103 may have a function as a protective film. When the polarizing plate 100 is placed in an image display device, the polarizing plate 100 can be bonded to the image display device so that the second thermoplastic resin film 103 is on the outside of the image display device. Moreover, the polarizing plate 100 can also be bonded to an image display device so that the second thermoplastic resin film 103 is on the image display device side. The polarizing plate 100 is preferably attached to the image display device so that the second thermoplastic resin film 103 is on the outside of the image display device.

[Other components of polarizing plate]
(1) Optical Functional Film The polarizing plate 100 can include an optically functional film other than the polarizer 101 to impart a desired optical function, and a suitable example thereof is a retardation film.
As described above, the first thermoplastic resin film 102 and/or the second thermoplastic resin film 103 can also serve as a retardation film, but a retardation film can also be laminated separately from these films. In the latter case, the retardation film can be laminated on the outer surface of the first thermoplastic resin film 102 and/or the second thermoplastic resin film 103 via a pressure-sensitive adhesive layer or an adhesive layer.

As a retardation film, a birefringent film composed of a stretched film of a thermoplastic resin having translucency; a film in which discotic liquid crystal or nematic liquid crystal is aligned; the above liquid crystal layer is formed on a base film; Examples include those that were
The base film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester resin such as triacetylcellulose.

Examples of other optically functional films (optical members) that may be included in the polarizing plate 100 include a light condensing plate, a brightness enhancement film, a reflective layer (reflective film), a semi-transparent reflective layer (semi-transparent reflective film), and a light diffusing layer ( light diffusion film), etc. These are generally provided when the polarizing plate is a polarizing plate placed on the back side (backlight side) of the liquid crystal cell.

(2) Adhesive layer The polarizing plate 100 can be made into a polarizing plate with an adhesive layer by providing an adhesive layer. Examples of the adhesive layer include an adhesive layer for bonding the polarizing plate 100 to a liquid crystal cell, an image display element such as an organic EL display element, or other optical member. The adhesive layer can be laminated on the outer surface of the first thermoplastic resin film 102 in the polarizing plate 100 having the configuration shown in FIG. The adhesive layer can also be laminated on the outer surface of the second thermoplastic resin film 103 in the polarizing plate 100 having the configuration shown in FIG. The adhesive layer is preferably laminated on the outer surface of the first thermoplastic resin film 102.

As the adhesive used in the adhesive layer, those having base polymers such as (meth)acrylic resins, silicone resins, polyester resins, polyurethane resins, and polyether resins can be used. Among these, (meth)acrylic adhesives are preferred from the viewpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability, and the like.
The (meth)acrylic adhesive contains a (meth)acrylic acid alkyl ester having an alkyl group having 20 or less carbon atoms, such as a methyl group, an ethyl group, or an n-, i-, or t-butyl group; A weight average molecular weight compound containing a functional group-containing (meth)acrylic monomer such as acrylic acid or hydroxyethyl (meth)acrylate so that the glass transition temperature is preferably 25°C or lower, more preferably 0°C or lower. (Meth)acrylic resins having a carbon content of 100,000 or more are useful as base polymers.

To form an adhesive layer on a polarizing plate, for example, an adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, and this is directly applied to the target surface of the polarizing plate. A method of forming an adhesive layer on a separate film that has been subjected to a release treatment, or a method of forming an adhesive layer in the form of a sheet on a separate film that has been subjected to a release treatment, and then transferring it to the target surface of a polarizing plate. I can do it.
The thickness of the adhesive layer is determined depending on its adhesive strength, etc., but is suitably in the range of 1 μm or more and 50 μm or less, preferably 2 μm or more and 40 μm or less.

The polarizing plate may include the above-described separate film. The separate film can be a film made of a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate, or the like. Among these, a stretched film of polyethylene terephthalate is preferred.

The adhesive layer contains glass fibers, glass beads, resin beads, fillers made of metal powder and other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, etc., as necessary. be able to.

Examples of the antistatic agent include ionic compounds, conductive fine particles, conductive polymers, etc., and ionic compounds are preferably used.
The cation component constituting the ionic compound may be an inorganic cation or an organic cation.
Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, phosphonium cations, piperidinium cations, and pyrrolidinium cations, and examples of inorganic cations include lithium ions and potassium ions.
On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but an anion component containing a fluorine atom is preferred since it provides an ionic compound with excellent antistatic performance. Examples of anion components containing a fluorine atom include hexafluorophosphate anion [(PF ₆ ⁻ )], bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ] anion, and bis(fluorosulfonyl)imide anion [ (FSO ₂ ) ₂ N ⁻ ] anion and the like.

(3) Protect Film The polarizing plate 100 can include a protect film for protecting its surface (typically, the surface of the first thermoplastic resin film 102 or the second thermoplastic resin film 103). For example, after a polarizing plate is bonded to an image display element or other optical member, the protect film is peeled off together with the adhesive layer it has.

The protect film is composed of, for example, a base film and an adhesive layer laminated thereon. Regarding the adhesive layer, the above description is cited.
The resin constituting the base film is, for example, a thermoplastic resin such as a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate resin. be able to. Preferably, it is a polyester resin such as polyethylene terephthalate.

<Manufacturing method of polarizing plate>
The method for manufacturing the polarizing plate 100 includes a preparation step of preparing the polarizer 101, a bonding step of bonding the polarizer 101 and the first thermoplastic resin film 102, and a step of providing a concave portion at the outer edge of the polarizing plate. , or a profile processing step of providing a through hole in the plane, and the preparation step can include an annealing step. Further, the irregular shape processing step may be a step of providing both a concave portion and an in-plane through hole at the outer edge of the polarizing plate.

When the polarizing plate 100 further includes a second thermoplastic resin film 103, the manufacturing method further includes a second bonding step of bonding the second thermoplastic resin film 103 to the other surface of the polarizer 101. be able to.

[Preparation process]
The preparation step can include the steps described above for the polarizer manufacturing method. In the method for manufacturing a polarizing plate of the present invention, the preparation step can include an annealing step.

[Lamination process]
In the bonding step, thermoplastic resin films can be bonded (laminated) on both sides of the polarizer 101 via an adhesive. The adhesive used to bond the polarizer 101 and the thermoplastic resin film may be an active energy ray-curable adhesive such as an ultraviolet curable adhesive, an aqueous solution of polyvinyl alcohol resin, or a crosslinking agent mixed therein. Examples include aqueous adhesives such as aqueous solutions and urethane emulsion adhesives. When pasting thermoplastic resin films on both sides of the polarizer 101, the adhesives forming the two adhesive layers may be the same type or different types. For example, when laminating thermoplastic resin films on both sides, one side may be laminated using a water-based adhesive, and the other side may be laminated using an active energy ray-curable adhesive. The ultraviolet curable adhesive may be a mixture of a radically polymerizable (meth)acrylic compound and a radical photopolymerization initiator, a mixture of a cationically polymerizable epoxy compound and a cationic photopolymerization initiator, or the like. Furthermore, a cationically polymerizable epoxy compound and a radically polymerizable (meth)acrylic compound can be used together, and a photocationic polymerization initiator and a photoradical polymerization initiator can also be used together as an initiator.

When using an active energy ray-curable adhesive, the adhesive is cured by irradiating active energy rays after lamination. The light source of active energy rays is not particularly limited, but active energy rays (ultraviolet rays) having an emission distribution at a wavelength of 400 nm or less are preferable, and specifically, low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultrahigh pressure mercury lamps, chemical lamps, Black light lamps, microwave-excited mercury lamps, metal halide lamps, etc. are preferably used.

In order to improve the adhesiveness between the polarizer 101 and the thermoplastic resin film, corona is applied to the bonding surface of the polarizer 101 and/or the thermoplastic resin film prior to bonding the polarizer 101 and the thermoplastic resin film. Surface treatments such as flame treatment, plasma treatment, ultraviolet irradiation treatment, primer coating treatment, and saponification treatment may be performed.

As described above, the polarizing plate 100 of the present invention can also be produced by laminating a thermoplastic resin film to the polarizer 101, which is a single-layer film, but is not limited to this method. For example, it can also be produced by a method using a base film as described in JP-A No. 2009-98653. The latter method is advantageous for obtaining a polarizing plate having a thin film polarizer (polarizer layer) and can include, for example, the following steps.

A resin layer forming step of forming a polyvinyl alcohol resin layer by applying a coating solution containing a polyvinyl alcohol resin to at least one surface of the base film and drying it to obtain a laminated film;
A stretching step of stretching the laminated film to obtain a stretched film;
A dyeing process for obtaining a polarizing laminated film by dyeing the polyvinyl alcohol resin layer of the stretched film with a dichroic dye to form a polarizer layer (equivalent to a polarizer);
A first laminating step of laminating a thermoplastic resin film onto the polarizer layer of the polarizing laminated film using an adhesive to obtain a laminated film;
Peeling step of peeling and removing the base film from the bonded film to obtain a polarizing plate with a single-sided thermoplastic resin film.

When laminating thermoplastic resin films on both sides of the polarizer 101 layer (polarizer), a second thermoplastic resin film is further applied to the polarizer surface of the polarizing plate with the first thermoplastic resin film on one side using an adhesive. A second bonding step of bonding is included.

In the above method using a base film, an annealing step and a drying step may be included in the dyeing step to obtain the polarizing laminate film (for example, after the crosslinking step or washing step during the dyeing step to obtain the polarizing laminate film). I can do it. The polarizer contained in the polarizing laminated film, the polarizing plate with one-sided thermoplastic resin film, and the polarizing plate with double-sided thermoplastic resin film obtained through the second lamination step, or the polarizer isolated from these can also be used. , is a polarizer belonging to the present invention.

The bonding step may further include a step of forming an adhesive layer on the first thermoplastic resin film 102 side. Adhesives constituting the adhesive layer include (meth)acrylic adhesives, styrene adhesives, silicone adhesives, rubber adhesives, urethane adhesives, polyester adhesives, and epoxy copolymer adhesives. Agents etc. can be used.

[Irregular shape processing process]
The polarizing plate 100 is obtained by cutting a long polarizing plate into sheets to obtain a sheet polarizing plate, and providing a concave portion at the outer edge of the sheet polarizing plate or providing a through hole in the plane. be able to. Further, it is also possible to provide both a concave portion and an in-plane through hole at the outer edge of the polarizing plate. As a specific example of a method of providing a concave portion on the outer edge of a sheet polarizing plate or a method of providing a through hole in the plane, for example, a sheet polarizing plate is formed so that the outer edge has a concave portion using a Thomson blade. Examples include a punching method, a method of cutting the end face of a sheet polarizing plate using a router, and a method of perforating using a rotary cutting tool such as a drill. When performing the irregular shape processing, the single sheet polarizing plate may be used alone, or may be a laminate in which a plurality of sheets are stacked one on top of the other.

<Image display device>
Polarizing plates can be used in image display devices. Examples of the image display element used in the image display device include a liquid crystal display element, an organic EL display element, and the like. In constructing a liquid crystal display device, a polarizing plate may be used as a polarizing plate placed on the viewing side, a polarizing plate placed on the backlight side, or a polarizing plate placed on the viewing side and backlight side. It may be used for both polarizing plates. The polarizing plate can be bonded to an image display device via an adhesive layer.

The present invention will be explained in more detail below using Examples, but the present invention is not limited to these Examples. "%" and "parts" in the examples are mass % and parts by mass unless otherwise specified. Tests and measurements were performed as follows.

[Measurement of contraction force]
The polarizing plates obtained in each example and comparative example were cut into small pieces of 10 cm x 5 cm, immersed in 600 mL of solvent, and subjected to ultrasonic treatment at room temperature for 30 minutes to dissolve the pasted thermoplastic resin film. Removed.
In addition, when the thermoplastic resin films on both sides of the polarizer were both films made of cyclic polyolefin resin (COP film), they were dissolved and removed using cyclohexane as a solvent.
When the thermoplastic resin films on both sides of the polarizer were both films made of triacetyl cellulose resin (TAC films), methylene dichloride was used as a solvent to dissolve and remove them.
When one thermoplastic resin film is a COP film and the other thermoplastic resin film is a TAC film, after dissolving and removing the TAC film using methylene dichloride as a solvent, use cyclohexane as a solvent to remove the COP film. The thermoplastic resin film was dissolved and removed by dissolving and removing the film.
A sample for MD shrinkage force measurement having a width of 2 mm and a length of 10 mm with the long side in the absorption axis direction (stretching direction) was cut from the polarizing film from which the thermoplastic resin film had been removed. This sample was set in a thermomechanical analyzer (TMA) "TMA7100" (manufactured by Hitachi High-Tech Science Co., Ltd.) and kept at 80°C for 4 hours while keeping its dimensions constant. The contraction force in the axial direction (MD) was measured.

[Heating test]
The polarizing plate obtained in each example and comparative example was laminated on the surface of alkali-free glass (Eagle XG manufactured by Corning, 120 x 200 x 0.7 mm) that had been cleaned with ethanol, and then Autoclave treatment was performed at ℃. This was used as an evaluation sample.

The evaluation sample was placed in a dry constant temperature bath at 85° C. and continued to be heated as it was for 250 hours. Thereafter, the sample was taken out from the tank and allowed to stand overnight (12 hours) at a temperature of 22° C. and a humidity of 55%.

[Light leakage measurement]
As shown in FIG. 9, a polarizing plate 202 that had not been subjected to a heating test was placed on a backlight 203, and a sample polarizing plate 201 that had been subjected to a heating test was placed on top of it. At this time, the two polarizing plates 201 and the polarizing plate (unheated test) 202 were installed so that they were crossed nicols (the brightness was the darkest). From above, a mask made of black drawing paper cut into the irregular shape of the polarizing plate 201 of the evaluation sample is placed over the irregularly shaped part of the polarizing plate 201 of the evaluation sample. Heating test) The light directly emitted from the backlight 203 without passing through 202 was blocked to make it easier to see the light leakage. The illumination light from the backlight 203 was 12,000 candela/ ^m2 , and in this state, the photo was taken with a camera (Nikon D5600) from 50 cm directly above (the conditions were constant: shutter speed 1 s, aperture F5.6, ISO 100, lens AF- P NIKKOR, zoom 18-55mm (55mm) and compared the degree of light leakage.

In order to quantify and compare the degree of light leakage, the degree of light leakage L was determined according to the following procedure. 1) A photograph of the sample for evaluation in a crossed nicol state was taken into a personal computer.
2) Load the image into image processing software (Microsoft Paint), and calculate the 8-bit RGB color values (0 to 255 each) of the areas where the "brightness" value is the highest in the areas where light has escaped on the outer edge of the polarizing plate. _E , G _E , and B _E , and the RGB values near the center where no light passes within the plane of the polarizing plate are R _C , G _C , and B _C, respectively.
3) At this time, the light penetration degree L was determined according to the following formula.
L = [(R _E - R _C ) ² + (G _E - G _C ) ² + (B _E - B _C ) ² ] ^1/2
[E=Edge (light passing part), C=Center (center part)]
The smaller the value of L, the smaller the degree of light leakage.

[Measurement of water absorption rate of thermoplastic resin film]
The water absorption rate of the thermoplastic resin film used in each example was measured according to the following procedure.
A sample film (approximately 50 mg) was prepared by cutting out a thermoplastic resin film.
Set it in the moisture adsorption/desorption measuring device (Dynamic Vapor Sorption Analyzer) “IGA Sorp” (manufactured by HIDEN ISOCHEMA (UK)),
While measuring the mass of the sample film, maintain it under dry conditions at 25 ° C., measure the mass after 24 hours and use it as the reference mass,
Subsequently, while measuring the mass of the sample film, it was held under conditions of 25 ° C. and relative humidity of 55%, and the mass after 6 hours was measured and considered as the mass after moisturization,
Water absorption (%) was determined using the following formula.
Water absorption rate = (mass after moisturizing - standard mass) / standard mass x 100 (%)

[Preparation of polarizing plate]
A polarizing plate is produced through 1) a preparation process in which the polarizer is cut into a sheet shape and some samples are annealed to reduce shrinkage; 2) the polarizer and a protective film are laminated with an adhesive, and (for image display panel); 3) processing step of punching out a polarizing plate sheet into an irregular shape and polishing the edges, in this order.

1. Preparation of Polarizer A polarizer (thickness: 12 μm) was prepared by adsorbing and orienting iodine onto a uniaxially stretched polyvinyl alcohol film (PVA). A first base film (TAC film), a polarizer, and a second base film (PMMA film) were laminated in this order via a pure water layer, and then dried and attached to produce a laminated film. . The first base film and the second base film can be easily peeled off. This laminated film was cut into a certain size (250 mm x 330 mm). At this time, the polarizer was cut out so that the stretching direction of the sheet was parallel to the long side direction or the short side direction of the cut sheet. Next, the second base film was gently peeled off from the end, sandwiched between dust-free paper on both sides, and further sandwiched between acrylic plates from the outside to be fixed. Three sets of these were prepared, and each was subjected to the following conditions: (1) temperature 85℃, dry for 12 hours, (2) temperature 85℃, dry, 3.5 hours, (3) temperature 22℃, humidity 55%, overnight. The mixture was left standing or heated to obtain polarizers (1), (2), and (3). In (1) and (2), the mixture was left to stand overnight after heating. The contraction forces of polarizers (1), (2) and (3) were 0.8N, 1.1N and 1.5N, respectively.

2. Lamination A film made of a cyclic polyolefin resin (hereinafter also referred to as COP) and a film made of a triacetyl cellulose resin (hereinafter also referred to as TAC) were cut into the same size (250 x 330 mm) as the polarizing plate. The combination of two thermoplastic resin films (thermoplastic resin film on the side pasted to the glass surface/thermoplastic resin film on the opposite side from the side pasted to the glass surface) is pasted so that it has the following four configurations. The following combinations were performed: COP/COP (Configuration 1), COP/TAC (Configuration 2), TAC/COP (Configuration 3), TAC/TAC (Configuration 4). A TAC film that had been saponified in advance was used. The bonding surface of each thermoplastic resin film was subjected to corona treatment to improve adhesion. The thermoplastic resin film on the side to be bonded to the glass surface and the polarizer side of the polarizer to which the first base film is bonded are laminated via a UV curable adhesive, and UV light is applied to the first thermoplastic resin. The adhesive was cured by irradiating from the film side. Thereafter, the first base film attached to the polarizer was gently peeled off from the end, and the thermoplastic resin film on the side opposite to the side to be attached to the glass surface was similarly attached to that surface.
Note that the water absorption rate of the COP film was 0.01%, and the water absorption rate of the TAC film was 2.01%.

The thermoplastic resin film surface on the side to be bonded to the glass surface of the produced polarizing plate was subjected to corona treatment, and an adhesive film (toward the image display panel) was bonded.

3. Irregular Shape Processing The completed polarizing plate sheet (250 x 330 mm) was punched out into the shape of the polarizing plate 300 shown in FIG. 10 using a Thomson blade, and this was laminated to a thickness of about 10 mm. The top and bottom of this bundle of polarizing plates were sandwiched between two PS (polystyrene) sheets of the same shape, which were also punched out with a Thomson blade, and 300 μm from the end was polished using a router to obtain a polarizing plate with the shape shown in Figure 10. Ta. The radius of curvature of the rounded corner portions 302, 303, and 304 was 5.0 mm, 6.0 mm, and 4.0 mm, respectively, and the corner portion 305 was a right angle. The recessed portion 301 had a width of 32.0 mm and a depth of 5.3 mm. The radii of curvature of the outer rounded corners 306 and 307 and the inner rounded corners 308 and 309 were 2.5 mm, 2.0 mm, 2.3 mm, and 2.5 mm, respectively. The concave portion 310 has a width of 5.0 mm and a depth of 7.3 mm, the radius of curvature of the rounded corner portion 311 is 2.5 mm, and the shortest distance 313 between the concave portion 301 and the center of gravity 312 of the polarizing plate is 64.7 mm. The shortest distance 314 between the portion 310 and the center of gravity 312 of the polarizing plate was 62.7 mm.
Met.

<Examples and comparative examples>
After a heating test, light leakage measurements were performed on each of the obtained polarizing plates. Table 1 shows the results for the concave portion 301, and Table 2 shows the results for the concave portion 310, for each configuration of the thermoplastic resin film.

From the results in Tables 1 and 2, it can be seen that the polarizing plates according to the present invention all have low L values and light leakage is suppressed.

10, 20, 40, 100, 201, 300 Polarizing plate, 11, 12, 41, 301, 310 Concave upper part, 302, 303, 304, 305 Corner, 13, 306, 307 Outer corner portion 14, 15, 308, 309 , 311 inner corner portion, 312 center of gravity, 313, 314 shortest distance, 21 through hole, 42 long side, 43 center point, 101 polarizer, 102 first thermoplastic resin film, 103 second thermoplastic resin film, 202 polarizing plate (unheated test), 203 backlight

Claims (6)

including a polyvinyl alcohol-based resin polarizer and a first thermoplastic resin film provided on one surface thereof,
The water absorption rate of the first thermoplastic resin film is 0.1% or less,
In plan view, the outer edge has a concave portion,
The recessed portion has a shape recessed inward from the outer edge in a plan view, and the depth of the recess is 0.1 mm or more and 7 mm or less,
The outer corner portion constituting the concave portion has a rounded corner, and the radius of curvature thereof is 0.1 mm or more and 5 mm or less,
The inner corner portion constituting the recessed portion has a rounded corner, and the radius of curvature is 0.1 mm or more and 5 mm or less, or the recessed portion has a U-shaped recess shape in plan view, and the recess The depth is 0.5 mm or more and 8 mm or less,
The inner corner portion constituting the concave portion is a polarizing plate having a radius of curvature of 0.5 mm or more and 10 mm or less,
A polarizing plate having a shrinkage force of 1.3 N or less per 2 mm width in the absorption axis direction of the polyvinyl alcohol resin polarizer. The polarizing plate according to claim 1, wherein the first thermoplastic resin film is an acrylic resin film or a cyclic polyolefin (COP) resin film. The polarizing plate according to claim 1 or 2, further comprising a second thermoplastic resin film provided on the other surface of the polyvinyl alcohol resin polarizer. A polarizing plate with an adhesive layer, comprising the polarizing plate according to any one of claims 1 to 3, and an adhesive layer provided on the first thermoplastic resin film side of the polarizing plate. The polarizing plate with an adhesive layer according to claim 4, wherein the adhesive layer is for bonding the polarizing plate to an image display element. An image display device comprising the polarizing plate according to claim 1.

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