JP2024009307A - polarizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer in which the occurrence of crack is suppressed in a dew condensation heat shock test in which a low-temperature (-40°C) dew condensation condition and a high temperature (85°C) condition are repeated, and a portion where iodine loss occurs in an end region of the polarizer does not become prominent.

SOLUTION: A polarizer composed of a resin film containing boric acid and iodine is provided in which: a boric acid low density-portion where the concentration of boric acid is lower than the concentration of boric acid in an inside region inward 500 μm or more from the edge thereof is formed in a region that includes the edge in a plan view; an iodine low-density portion where the concentration of iodine is lower than the concentration of iodine in the inside region is formed in the region that includes the edge; and the length of the iodine low-density portion from the edge thereof is 19 μm or more and 100 μm or less.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a polarizer, and also relates to a polarizing plate equipped with the same, a method for manufacturing them, and an image display device.

Patent Document 1 proposes a polarizer in which a portion where the concentration of boric acid is lower than other portions is formed at the end portion.

JP2016-206641A

In the polarizer described in Patent Document 1, in addition to a region with a low boric acid concentration being formed at the end, iodine loss occurs in a width exceeding 300 μm from the end in plan view (see FIG. 4). b)).

The purpose of the present invention is to perform a dew condensation heat shock test in which the operation is repeated by exposing to low temperature (-40°C) drying conditions, cooling, exposing to 25°C outside air to form a dew state, and then exposing to high temperature (85°C) drying conditions. It is an object of the present invention to provide a polarizer in which the occurrence of cracks is suppressed and in which portions of iodine loss are not noticeable in the end regions, a polarizing plate equipped with the same, and a method for manufacturing the same.

The present invention provides the following polarizer, polarizing plate, image display device, and manufacturing method.
[1] A polarizer that is a resin film containing boric acid and iodine,
A low boric acid concentration region is formed in a region including the end in plan view, the concentration of boric acid being lower than the concentration of boric acid in the inner region 500 μm or more inside from the end,
A low iodine concentration region having a lower iodine concentration than the iodine concentration in the inner region is formed in a region including the end portion,
A polarizer, wherein the length of the low iodine concentration region from the end is 19 μm or more and 100 μm or less. [2] The polarizer according to [1], wherein the concentration of boric acid in the low boric acid concentration region decreases as it approaches the end in a direction from the inside to the end in a plan view of the polarizer.
[3] The polarizer according to [1] or [2], wherein the length of the low boric acid concentration region from the end is 15 μm or more.
[4] The polarizer according to any one of [1] to [3], wherein the boric acid low concentration region and the iodine low concentration region are formed along an outer edge of the polarizer.
[5] The polarizer has an irregularly shaped portion in a plan view, and the boric acid low concentration region and the iodine low concentration region are formed in an end region included in the irregularly shaped portion, [1] The polarizer according to any one of [4].
[6] The polarizer according to [5], wherein the irregularly shaped portion is a concave portion provided in the peripheral portion or a through hole provided within the plane of the polarizer.
[7] A polarizing plate comprising the polarizer according to any one of [1] to [6] and an optical film disposed on one or both sides of the polarizer.
[8] An image display device comprising the polarizing plate according to [7].
[9] The image display device according to [8], having a camera hole.
[10] A method for producing a polarizing plate comprising a polarizer that is a resin film containing boric acid and iodine, and an optical film disposed on one or both sides of the polarizer,
A method for manufacturing a polarizing plate, comprising a base treatment step of bringing a basic solution at a temperature of 50° C. or lower into contact with an end of the resin film containing boric acid and iodine for a period of 6 minutes or less.
[11] The method for producing a polarizing plate according to [10], wherein the basic solution contains water.
[12] The method for producing a polarizing plate according to [10] or [11], wherein the basic solution is a solution in which a strong basic compound is dissolved in a solvent.
[13] The method for producing a polarizing plate according to [12], wherein the strong basic compound contains sodium hydroxide and/or potassium hydroxide.
[14] The method further includes a molding step of molding the resin film containing boric acid and iodine into a predetermined shape by cutting and/or punching, and the resin film subjected to the molding step is subjected to the base treatment step. The method for producing a polarizing plate according to any one of [10] to [13].

According to the present invention, a condensation heat shock test (condensation heat shock test) in which the operation of exposing to low temperature (-40°C) drying conditions, cooling, exposing to 25°C outside air to form a dew state, and then repeating the operation of exposing to high temperature (85°C) drying conditions ( A polarizer that suppresses the occurrence of cracks in a condensation heat shock test (hereinafter referred to simply as a condensation heat shock test for the sake of brevity) and in which iodine loss is not noticeable in the edge region, a polarizing plate equipped with the polarizer, and a polarizing plate equipped with the same, A manufacturing method can be provided.

FIG. 1 is a schematic cross-sectional view showing a polarizer according to an embodiment of the present invention. FIG. 2 is a schematic top view of a polarizer for explaining a low boric acid concentration region. FIG. 2 is a schematic top view of a polarizer for explaining a low iodine concentration region. 1 is a schematic cross-sectional view showing an example of an image display device having a camera hole. FIG. 1 is a schematic top view showing a polarizer according to an embodiment of the present invention. FIG. 1 is a schematic plan view showing a polarizing plate according to an embodiment of the present invention. FIG. 1 is a schematic plan view showing a polarizing plate according to an embodiment of the present invention. FIG. 1 is a schematic plan view showing a polarizing plate according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing a polarizing plate according to an embodiment of the present invention. It is a schematic diagram showing an example of a first laminate. It is a schematic diagram showing an example of a second laminate and an end mill. It is a schematic diagram showing an example of a cutting process. It is a schematic diagram for explaining a measurement sample in an example. It is a schematic sectional view showing the first laminated body in an example. FIG. 3 is a schematic top view showing a polarizing plate in an example. The TOF-SIMS analysis results and end observation results of Example 1 are shown. The TOF-SIMS analysis results and end observation results of Comparative Example 1 are shown. The TOF-SIMS analysis results and end observation results of Comparative Example 2 are shown.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, each component is shown adjusted to an appropriate scale to make it easier to understand, and the scale of each component shown in the drawings does not necessarily match the actual scale of the component. In the drawings, equivalent components are given the same reference numerals. X, Y, and Z shown in each figure mean three coordinate axes that are orthogonal to each other. The directions indicated by the XYZ coordinate axes in each figure are common to each figure.

<Polarizer>
The polarizer is a resin film containing boric acid and iodine. The resin film containing boric acid and iodine may be, for example, a resin film in which iodine is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film, and the polyvinyl alcohol molecular chains are crosslinked with boric acid. A polarizer is an absorption type polarizer that has the property of absorbing linearly polarized light with a vibration plane parallel to the absorption axis and transmitting linearly polarized light with a vibration plane perpendicular to the absorption axis (parallel to the transmission axis). be able to. A polarizer can be used as a polarizing plate by laminating an optical film on one or both sides with an adhesive or a pressure-sensitive adhesive.

As shown in FIG. 1, the polarizer 2 can constitute a polarizing plate 1 by being disposed between a first optical film 3 and a second optical film 4. Hereinafter, the first optical film and the second optical film may be collectively referred to as an optical film.

In the polarizer, in a region including the end in plan view, there is a low boric acid concentration region that has a lower boric acid concentration than the boric acid concentration in the inner region (hereinafter also referred to as the inner region) located 500 μm or more inside from the end. It is formed. In the inner region, both the concentration of boric acid and the concentration of iodine can be approximately uniform. As shown in FIG. 2, the polarizer 2 has a boric acid low concentration region 30 in a region including the end in a plan view, and can have an inner region 32 at least 500 μm inward from the end. Inner region 32 may include an area for displaying images when incorporated into a liquid crystal display. The boric acid concentration in the intermediate region 31 between the low boric acid concentration region 30 and the inner region 32 is usually approximately the same boric acid concentration as the inner region 32 . In this specification, planar view means viewing from the thickness direction of the polarizer. The concentration of boric acid is the concentration of boric acid per unit area including the thickness direction of the polarizer. ) is measured by As used herein, boric acid includes, for example, boric acid molecules (H ₃ BO ₃ ) and borate ions (BO ₃ ³⁻ ).

The polarizer tends to be more likely to be inhibited from cracking in a dew condensation heat shock test due to the formation of low boric acid concentration regions. The condensation heat shock test can be conducted according to the method described in the Examples section below.

The concentration of boric acid in the low boric acid concentration area is preferably close to the end in the direction from the inside to the end in plan view of the polarizer, from the viewpoint of suppressing cracks and making color loss less noticeable in the polarizer's appearance. It's about as low as it gets. The ends of the polarizer preferably do not contain boric acid.

The length from the end of the low boric acid concentration region may be, for example, 15 μm or more, from the viewpoint of crack suppression, preferably 15 μm or more and less than 200 μm, more preferably 15 μm or more and less than 150 μm, and even more preferably 15 μm or more and less than 100 μm. Particularly preferably, the thickness may be 15 μm or more and less than 50 μm.

The boundary between the area where the boric acid low concentration site is formed and the other area is determined from the edge obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS), which will be explained in the Examples section below. It can be determined from the boric acid concentration profile versus distance. For example, if an area where the borate ion intensity is constant can be read in the boric acid concentration profile, calculate the average value of the borate ion intensity in that area, and calculate the position from the end where the borate ion intensity is the above average value. The area up to the area can be designated as a low boric acid concentration site. If the region where the borate ion intensity is constant is difficult to read in the boric acid concentration profile, the average borate ion intensity in a range of 30 μm inward from the point where the borate ion intensity is maximum in the boric acid concentration profile. The value can be determined, and the region from the end to the position where the boric acid ion intensity becomes the above average value can be defined as a low boric acid concentration region.

In the polarizer, a low iodine concentration region is formed in a region including the end portion, the iodine concentration being lower than the iodine concentration in the inner region located 500 μm or more inside from the end portion. The length of the low iodine concentration region from the end is 19 μm or more and 100 μm or less. As shown in FIG. 3, the polarizer 2 has a low iodine concentration region 33 in a region including the end portion in plan view. The iodine concentration in the intermediate region 34 between the low iodine concentration region 33 and the inner region 32 is usually approximately the same as that in the inner region 32 . The low iodine concentration region is a region formed in a region through which light passes when observing a polarizer in planar view using an optical microscope. Iodine includes, for example, iodine molecules (I ₂ ), polyiodine complexes (I ₃ ⁻ , I ₅ ⁻ ), and iodine ions (I ⁻ ).

When the length of the low iodine concentration region from the end is 100 μm or less, the low iodine concentration region tends to be less noticeable in the appearance of the polarizer. Furthermore, if the length of the low iodine concentration region from the end is 19 μm or more, cracks tend to be easily suppressed. The length of the low iodine concentration region from the end is preferably 19 μm or more and 50 μm or less, from the viewpoint of making iodine loss less noticeable.

The low iodine concentration area and the high iodine concentration area are determined according to the method described in the Examples section below. In an optical microscope image imported into a personal computer and subjected to image processing, the brightness of the low iodine concentration area is usually 180 or more, and the brightness of the inner area is 100 or more and 140 or less, and the brightness of the iodine low concentration area and the inner area are The brightness of the iodine concentration in the intermediate region between is usually less than 180.

The boric acid low concentration site and the iodine low concentration site may be sites that partially overlap each other, or either one may be a site that completely overlaps the other. From the viewpoint of suppressing cracks and making iodine loss less noticeable, preferably the low iodine concentration region completely includes the low boric acid concentration region.
A plurality of boric acid low concentration sites and a plurality of iodine low concentration sites may be formed in a plurality of regions of the polarizer.

The low boric acid concentration region and the low iodine concentration region are preferably formed along the outer edge of the polarizer from the viewpoint of suppressing cracks. The boric acid low concentration region and the iodine low concentration region may be formed along the entire outer edge of the polarizer, or may be formed along a portion of the outer edge of the polarizer.

The polarizer may have an irregularly shaped portion. The irregularly shaped portion may be a concave portion formed on the outer edge of the polarizer and a through hole formed within the plane of the polarizer. Further, the irregularly shaped portion may have a tangential direction discontinuous, for example, a shape in which two straight lines intersect, and the radius of curvature at the intersection may be 0 mm. The crack prevention effect of the present invention is remarkable when the tangent direction is discontinuous or when the radius of curvature at the intersection is small (usually 3 mm or less, preferably 2 mm or less, more preferably 1 mm or less). The polarizer may have two or more irregularly shaped portions on the outer edge and/or within the plane. As for specific examples of the shape of the irregularly shaped portion and the position where it is formed, the examples of the shape of the irregularly shaped portion and the position where it is formed in the description of the polarizing plate to be described later are applied.

When the polarizer has an irregularly shaped part, from the viewpoint of suppressing cracks and making the low iodine concentration part less noticeable, it is preferable that the low boric acid concentration part and the low iodine concentration part be formed in the end region included in the irregular part. has been done.
In a polarizer having an irregularly shaped part, stress tends to be concentrated in the irregularly shaped part in a dew condensation heat shock test, and cracks tend to occur easily. Since the boric acid low concentration portion is formed in the end region included in the irregularly shaped portion, the occurrence of cracks tends to be easily suppressed in the dew condensation heat shock test.
In addition, as shown in FIG. 4, a polarizing plate 21 including a polarizer having an irregularly shaped part is connected to a camera hole 22, a cover glass 24, an adhesive layer 25, a liquid crystal panel 23, a polarizing plate 26, a camera 27, and a light-shielding tape. When used in the image display device 20 having the polarizer 28, since the circled portion in FIG. The dark areas become more noticeable, which may result in deterioration of design quality. However, even when the polarizer of the present invention is used in an image display device having a camera hole as described above, the low iodine concentration portion is less noticeable and tends to be excellent in design.

When the irregularly shaped portion is a concave portion, from the viewpoint of crack suppression, it is preferably formed such that the depth direction of the concave portion and the absorption axis (stretching direction) are perpendicular to each other, for example. Further, they may be formed so as to intersect at an angle of 30 degrees or more and usually 60 degrees or less.

The polarizer may be in the form of a long strip or in the form of a sheet. When the polarizer is sheet-shaped, the overall shape of the polarizer may be a rectangular shape or a rounded rectangular shape in a 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 polarizer may have a polygonal, circular, or elliptical overall shape in plan view. As a specific example of the overall shape of the polarizer in plan view, the example of the overall shape of the polarizing plate in the description of the polarizing plate described later is applied.

The thickness of the polarizer may be, for example, 1 μm or more and 50 μm or less, or 3 μm or more and 15 μm or less. The thinner the polarizer is, the easier it is to suppress contraction or expansion of the polarizer itself due to temperature changes, and the easier it is to suppress changes in the dimensions of the polarizer itself. As a result, stress is less likely to act on the polarizer, and cracks in the polarizer tend to be more easily suppressed.

FIG. 5 shows the overall shape of the polarizer 2 in plan view. The polarizer 2 has a rounded rectangular overall shape and has a concave portion as an irregularly shaped portion. The concave portion is formed so that the depth direction and the absorption axis (stretching direction) are parallel to each other. In the polarizer 2, a region I (11) and a region II (12) are partially formed along a part of the outer periphery including the concave portion, and are formed at the outer edge including the concave portion. Region I (11) is a region in which both a low boric acid concentration site and a low iodine concentration site are formed. Region II (12) can be a region in which either a low boric acid concentration site or a low iodine concentration site is formed.

<Polarizing plate>
A polarizing plate according to another aspect of the present invention includes the above-described polarizer and an optical film provided on one or both sides of the polarizer. The optical film can be bonded to the polarizer via an adhesive layer made of an adhesive or a pressure-sensitive adhesive.

As shown in FIG. 1, a polarizing plate 1 according to the present embodiment includes at least a pair of optical films (3, 4) and a film-shaped polarizer 2 located between the pair of optical films (3, 4). Equipped with. Below, for convenience of explanation, the polarizing plate 1 composed of a polarizer 2 and a pair of optical films (3, 4) will be mainly explained. However, as described later, the number of optical films included in the polarizing plate is not limited to two.

The optical film means a film-like member (excluding the polarizer 2 itself) that constitutes the polarizing plate 1. For example, optical film includes a protective film and a release film. Each optical film does not need to have a specific optical function by itself. A "film" (optical film) may be translated into a "layer" (optical layer). Each of the pair of optical films (3, 4) contains resin. However, the compositions of the optical films (3, 4) are not limited.

The polarizer 2 directly or indirectly overlaps the optical films (3, 4). For example, there may be another optical film between the polarizer 2 and the optical film (3, 4). The polarizer 2 may overlap the optical films (3, 4) through an adhesive layer.

FIG. 6 is a top view showing the surface of the polarizing plate 1 according to this embodiment. The cross section of the polarizing plate 1 shown in FIG. 6 is perpendicular to the surface of the polarizing plate 1. Further, the cross section of the polarizing plate 1 is orthogonal to the outer circumference 1p of the polarizing plate 1 located inside the recess 13 formed in the polarizing plate 1.

As shown in FIG. 6, a recess 13 is formed on the outer periphery 1p of the polarizing plate 1. In other words, there is a recess 13 on the outer periphery 1p of the polarizing plate 1. The recess 13 may be translated as a depression, a cutout, or a notch. The recess 13 may penetrate the polarizing plate 1 in a direction (Z-axis direction) perpendicular to the surface (light receiving surface) of the polarizing plate 1. The outer periphery 1p of the polarizing plate 1 may be referred to as the outer edge or outline of the polarizing plate 1 (light receiving surface) as viewed from a direction perpendicular to the light receiving surface of the polarizing plate 1 (planar view direction).

The inner corner 13c of the recessed portion 13 may be a right angle when viewed from above, or may be a curved line. That is, the end surface of the polarizing plate 1 located at the inner corner 13c of the recess 13 may be a curved surface. That is, the inner corner 13c of the recess may be chamfered. Since the inner corner 13c of the recess 13 is curved when viewed from above, cracks at the inner corner 13c of the recess 13 are more easily suppressed than when the inner corner 13c is a right angle. As shown in FIG. 4, the corners located at both ends of the recess 13 and the corners located at the four corners of the polarizing plate 1 may also be chamfered.

The width of the recess 13 (width of the recess 13 in the X-axis direction) is not particularly limited, but may be, for example, 3 mm or more and 160 mm or less. The depth of the recess 13 (width of the recess 13 in the Y-axis direction) is not particularly limited, but may be, for example, 0.5 mm or more and 160 mm or less. The length of the side (short side) of the polarizing plate 1 on which the recessed portion 13 is formed is not particularly limited, but may be, for example, 30 mm or more and 90 mm or less. The length of the side (long side) of the polarizing plate 1 on which the concave portion 13 is not formed is not particularly limited, but may be, for example, 30 mm or more and 170 mm or less. The thickness of the entire polarizing plate 1 is not particularly limited, but may be, for example, 30 μm or more and 300 μm or less.

The recess 13 shown in FIG. 6 has a square shape (rectangular shape) with rounded corners. However, the shape of the recess 13 is not limited. For example, the recess 13 may have a square shape. The recess 13 may be a polygon other than a quadrangle or a triangle. As shown in (a) to (h) in FIG. 7, the shape of the recess 13 is a rounded rectangle, a rectangle, a semicircle, a V-shape, a combination of a straight line and a curved line, and a curved shape. It may be. Although the shapes of the polarizing plate 1 shown in (a) to (h) in FIG. 7 all have symmetry, the shape of the polarizing plate 1 may be asymmetrical. A plurality of recesses 13 may be formed on the outer periphery 1p of the polarizing plate 1. A plurality of recesses 13 may be formed on one side constituting the outer periphery 1p of the polarizing plate 1. The recess 13 may be formed by cutting out at least one of the four corners of the square polarizing plate 1.

The overall shape of the polarizing plate 1 excluding the recesses 13 is approximately square (rectangular). However, the shape of the polarizing plate 1 is not limited. For example, the shape of the polarizing plate 1 may be square. The shape of the polarizing plate 1 may be a polygon other than a quadrangle, a circle, or an ellipse. The overall shapes of the polarizer 2 and the optical films (3, 4) may be substantially the same as the shape of the polarizing plate 1. In the case of the rectangular polarizing plate 1 shown in FIG. 4, the recesses 13 are formed on the short sides of the polarizing plate 1, but the recesses 13 may be formed on the long sides of the polarizing plate 1.

As shown in FIG. 8, the polarizer 1 may have through holes in the plane when viewed from above. The diameter of the through hole 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.

(Other embodiments of polarizing plate)
For example, in addition to a pair of optical films consisting of a first optical film and a second optical film, the polarizing plate may further include another optical film containing resin. That is, the polarizing plate may include three or more optical films. For example, as shown in FIG. 9, the polarizing plate includes a first optical film 3 and a second optical film 4; a polarizer 2 located between the first optical film 3 and the second optical film 4; A third optical film 15 overlapping the optical film 3 may be provided. The third optical film 15 may be stacked on the first optical film 3 via the above-mentioned adhesive layer. The resin contained in the third optical film 15 may be at least one of the resins listed above as resins contained in the first optical film 3 and the second optical film 4, respectively. The composition of the third optical film 15 may be the same as the composition of the first optical film 3. The composition of the third optical film 15 may be different from the composition of the first optical film 3. The composition of the third optical film 15 may be the same as the composition of the second optical film 4. The composition of the third optical film 15 may be different from the composition of the second optical film 4. The thickness of the third optical film 15 may be, for example, 5 μm or more and 200 μm or less. The third optical film 15 may be peeled off and removed from the polarizing plate during the manufacturing process of the image display device. That is, the third optical film 15 may be a temporary optical film.

The polarizing plate may further include an adhesive layer overlapping one of the pair of optical films, and a release film overlapping the adhesive layer. For example, the polarizing plate shown in FIG. 9 may further include an adhesive layer overlapping the second optical film 4 and a release film overlapping the adhesive layer. The adhesive layer may include, for example, a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, or a urethane-based pressure-sensitive adhesive. The thickness of the adhesive layer may be, for example, 2 μm or more and 100 μm or less. The resin contained in the release film may be at least one of the resins listed above as resins contained in the first optical film 3 and the second optical film 4, respectively. The composition of the release film may be the same as the composition of the first optical film 3. The composition of the release film may be different from the composition of the first optical film 3. The composition of the release film may be the same as the composition of the second optical film 4. The composition of the release film may be different from the composition of the second optical film 4. The thickness of the release film may be, for example, 10 μm or more and 100 μm or less. The release film may be peeled off and removed from the polarizing plate during the manufacturing process of the image display device. A release film may be placed on both sides of the polarizing plate via an adhesive layer.

A polarizing plate can be used as an optical film or layer such as a reflective polarizing film, an anti-glare film, a surface anti-reflection film, a reflective film, a transflective film, a viewing angle compensation film, a window film, an antistatic layer, and a hard coat. It may further include at least one selected from the group consisting of a layer, an optical compensation layer, a touch sensor layer, and an antifouling layer.

The polarizing plate can have an irregularly shaped portion in a plan view. Further, the polarizing plate may have a rectangular shape or a rounded rectangular shape in plan view.

(optical film)
The optical film may be a thermoplastic resin having translucency. The optical film may be an optically transparent thermoplastic resin. Examples of resins constituting the optical film include chain polyolefin resins, cyclic olefin polymer resins (COP resins), cellulose ester resins, polyester resins, polycarbonate resins, (meth)acrylic resins, and polystyrene resins. , or a mixture or copolymer thereof.

When the polarizing plate has a first optical film and a second optical film, the composition of the first optical film may be exactly the same as the composition of the second optical film. For example, both the first optical film and the second optical film may contain a cyclic olefin polymer resin (COP resin). Even if the first optical film and the second optical film contain a cyclic olefin polymer resin (COP resin), cracks can be easily suppressed and color loss can be less noticeable in the present invention. When the polarizing plate has a first optical film and a second optical film, the composition of the first optical film may be different from the composition of the second optical film.

The glass transition temperature of the first optical film and the second optical film is preferably 100°C or more and 200°C or less, or 120°C or more and 150°C or less. When the glass transition temperature of each of the first optical film and the second optical film is within the above range, the first optical film and the second optical film are fused to each other due to the heat generated by polishing the edges of each optical film. easy.

The chain polyolefin resin may be, for example, a chain olefin homopolymer such as polyethylene resin or polypropylene resin. The chain polyolefin resin may be a copolymer of two or more types of chain olefins.

The cyclic olefin polymer resin (cyclic polyolefin resin) may be, for example, a ring-opening (co)polymer of cyclic olefins or an addition polymer of cyclic olefins. The cyclic olefin polymer resin may be, for example, a copolymer (for example, a random copolymer) of a cyclic olefin and a chain olefin. The chain olefin constituting the copolymer may be, for example, ethylene or propylene. The cyclic olefin polymer resin may be a graft polymer obtained by modifying the above polymer with an unsaturated carboxylic acid or a derivative thereof, or a hydrogenated product thereof. The cyclic olefin polymer resin may be, for example, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer.

The cellulose ester resin may be, for example, cellulose triacetate (triacetylcellulose (TAC)), cellulose diacetate, cellulose tripropionate or cellulose dipropionate. Copolymers of these may also be used. A cellulose ester resin in which some of the hydroxyl groups are modified with other substituents may also be used.

Polyester resins other than cellulose ester resins may be used. The polyester resin may be, for example, a polycondensate of a polycarboxylic acid or a derivative thereof and a polyhydric alcohol. The polyhydric carboxylic acid or its derivative may be a dicarboxylic acid or its derivative. The polyhydric carboxylic acid or derivative thereof may be, for example, terephthalic acid, isophthalic acid, dimethyl terephthalate, or dimethyl naphthalene dicarboxylate. The polyhydric alcohol may be, for example, a diol. The polyhydric alcohol may be, for example, ethylene glycol, propanediol, butanediol, neopentyl glycol, or cyclohexanedimethanol.

The polyester resin may be, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, or polycyclohexane dimethyl naphthalate. .

Polycarbonate resin is a polymer in which polymerized units (monomers) are bonded via carbonate groups. The polycarbonate resin may be a modified polycarbonate having a modified polymer skeleton, or may be a copolymerized polycarbonate.

(Meth)acrylic resins include, for example, poly(meth)acrylic esters (for example, polymethyl methacrylate (PMMA)); methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-(meth)acrylic acid Acid ester copolymer; Methyl methacrylate-acrylic ester-(meth)acrylic acid copolymer; Methyl (meth)acrylate-styrene copolymer (for example, MS resin); Methyl methacrylate and alicyclic hydrocarbon It may be a copolymer with a compound having a group (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.).

The first optical film or the second optical film each contains at least one kind selected from the group consisting of a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. May contain additives.

The thickness of the first optical film may be, for example, 5 μm or more and 90 μm or less, or 10 μm or more and 60 μm or less. The thickness of the second optical film may also be, for example, 5 μm or more and 90 μm or less, or 10 μm or more and 60 μm or less.

At least one of the first optical film and the second optical film may be a film having an optical function. The film having an optical function may be, for example, a retardation film or a brightness enhancement film. For example, a retardation film imparted with an arbitrary retardation value can be obtained by stretching a film made of the thermoplastic resin or forming a liquid crystal layer or the like on the film.

The first optical film may be stacked on the polarizer via an adhesive layer. The second optical film may also be stacked on the polarizer via an adhesive layer. The adhesive layer may include a water-based adhesive such as polyvinyl alcohol. The adhesive layer may include an active energy ray-curable resin described below.

Active energy ray curable resin is a resin that hardens when irradiated with active energy rays. The active energy rays may be, for example, ultraviolet light, visible light, electron beams, or X-rays. For example, the active energy ray curable resin may be an ultraviolet curable resin.

The active energy ray-curable resin may be one type of resin or may contain multiple types of resins. For example, the active energy ray-curable resin may include a cationically polymerizable curable compound or a radically polymerizable curable compound. The active energy ray-curable resin may contain a cationic polymerization initiator or a radical polymerization initiator to initiate the curing reaction of the curable compound.

The cationically polymerizable curable compound may be, for example, an epoxy compound (a compound having at least one epoxy group in the molecule) or an oxetane compound (a compound having at least one oxetane ring in the molecule). The radically polymerizable curable compound may be, for example, a (meth)acrylic compound (a compound having at least one (meth)acryloyloxy group in the molecule). The radically polymerizable curable compound may be a vinyl compound having a radically polymerizable double bond.

The active energy ray-curable resin may contain cationic polymerization accelerators, ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, fluidity regulators, plasticizers, and antifoaming agents, as necessary. agent, antistatic agent, leveling agent, or solvent.

In order to improve the adhesion between the polarizer and the optical film, the bonding surface of the polarizer and/or the optical film is subjected to corona treatment, flame treatment, plasma treatment, or ultraviolet rays prior to lamination of the polarizer and optical film. Surface treatments such as irradiation treatment, primer coating treatment, and saponification treatment may also be performed.

(Other layers)
The polarizing plate includes a front plate, a retardation film (for example, a layer giving a retardation of λ/2, a layer giving a retardation of λ/4, a positive C layer, and a combination of at least two layers selected from these). It may further include a layer obtained by using the above method), a protect film, a touch sensor panel, an adhesive layer, etc. The polarizing plate can also be used as a circularly polarizing plate by laminating layers that provide a phase difference of λ/4. The polarizing plate may be a polarizing plate with an adhesive layer.

<Manufacturing method of polarizing plate>
A method for producing a polarizing plate is a method for producing a polarizing plate having a polarizer which is a resin film containing boric acid and iodine, and an optical film disposed on one or both sides of the polarizer, This manufacturing method includes a base treatment step of bringing a basic solution at a temperature of 50° C. or lower into contact with an end portion of a resin film containing iodine and iodine for a period of 6 minutes or less. This method for manufacturing a polarizing plate includes, before this base treatment step, a polarizer manufacturing step (a manufacturing step for a resin film containing boric acid and iodine), a lamination step, a molding step, and a cutting step, which will be described later, in this order. can be included.

(Polarizer manufacturing process)
A resin film containing boric acid and iodine (hereinafter also referred to as an unbase-treated polarizer) can be produced, for example, by subjecting a polyvinyl alcohol-based resin film (PVA film) to stretching treatment, dyeing treatment, and crosslinking treatment. can. The stretching treatment, dyeing treatment, and crosslinking treatment can be performed by known methods.

For example, first, a PVA film is stretched uniaxially or biaxially. Polarizers stretched in a uniaxial direction tend to have a high dichroic ratio. Following stretching, the PVA film is dyed with iodine, dichroic dyes (polyiodine) or organic dyes using a dyeing solution. The staining solution may contain boric acid, zinc sulfate, or zinc chloride. The PVA film may be washed with water before dyeing. Washing with water removes dirt and antiblocking agent from the surface of the PVA film. Furthermore, as a result of the PVA film swelling due to washing with water, uneven staining (uneven staining) is likely to be suppressed. The PVA film after dyeing is treated for crosslinking with a solution of a crosslinking agent containing boric acid (for example an aqueous solution of boric acid). After treatment with the crosslinking agent, the PVA film is washed with water and subsequently dried. Through the above steps, a resin film containing boric acid and iodine is obtained. Polyvinyl alcohol (PVA) resin is obtained by saponifying polyvinyl acetate resin. The polyvinyl acetate resin may be, for example, polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers (e.g., ethylene-vinyl acetate copolymer). . Other monomers copolymerized with vinyl acetate may be, in addition to ethylene, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, or acrylamides having ammonium groups. The polyvinyl alcohol resin may be modified with aldehydes. The modified polyvinyl alcohol resin may be, for example, partially formalized polyvinyl alcohol, polyvinyl acetal, or polyvinyl butyral. The polyvinyl alcohol resin may be a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochloric acid-treated polyvinyl chloride. Dyeing may be performed before stretching, or stretching may be performed in a dyeing solution. The length of the stretched resin film may be, for example, 3 to 7 times the length before stretching. The polyvinyl alcohol resin film may be in the form of a long strip or in the form of a sheet.

(Lamination process)
In the lamination step, a first laminate is produced by stacking and bonding an unbase-treated polarizer and an optical film to each other. The unbase-treated polarizer and optical film may be in the form of a long strip. When unbase-treated polarizers are stacked so as to be disposed between a pair of optical films, in the first laminate 10, as shown in FIG. , 9).

The optical film can be bonded to the polarizer via an adhesive layer.

In the lamination process, an adhesive layer can be formed on the outermost surface of either one of the first laminates 10. For example, the adhesive layer is formed by applying an adhesive to the surface of one of the pair of optical films (5, 9) opposite to the unbase-treated polarizer 7, and applying an adhesive layer on the adhesive layer. It can be formed by laminating a separate film that can be peeled off from the agent layer. Moreover, in the lamination process, a protect film that can be peeled off from the optical film can be bonded to the outermost surface of either one of the first laminates 10.

(molding process)
In the molding process, the dimensions of the first laminate 10 may be adjusted to dimensions that are easy to process. Further, an irregularly shaped portion may be formed at the outer edge of the first laminate 10 by punching or cutting. Cutting and/or punching can be performed using a cutting blade, a punching blade, or irradiation with laser light. The laser light may be a _CO2 laser. The elongated first laminate can be made into a sheet-like first laminate in a molding process.
In the forming process, the first laminate can be cut or punched individually or in a stacked state.

(Cutting process)
The method for manufacturing a polarizing plate can further include a cutting step of bringing an end mill into contact with the outer periphery of the first laminate or a second laminate, which will be described later, and moving the end mill along the outer periphery of the laminate. As shown in FIG. 10, the positions of the ends of the unbase-treated polarizer 7 and the optical films (5, 9) may be aligned throughout the entire outer periphery of the first laminate 10 before the cutting process.

As shown in FIGS. 11 and 12, the end mill 50 used in the cutting process has a protruding blade (edge) 50e on a side surface substantially parallel to the rotation axis 50a. In the cutting process, the rotating end mill 50 is moved along the outer periphery of the first laminate 10 with the side surface of the end mill 50 in contact with the outer periphery (end surface) of the first laminate 10 . For example, the rotating end mill 50 may be moved along the path indicated by the arrow in FIG. As a result, the outer periphery (end surface) of the first laminate 10 is cut or polished by the blade 50e, the outer periphery (end surface) of the first laminate 10 becomes smooth, the recessed part 13 is formed, and the inside of the recessed part 13 is Corners are chamfered. As shown in FIG. 11, after a plurality of first laminates 10 are stacked to form a second laminate 100, the side surface of the end mill 50 is brought into contact with the outer periphery (end surface) of the second laminate 100, and the end mill 50 is rotated. The end mill 50 may be moved along the outer periphery of the second laminate 100. That is, in the cutting process, the outer periphery of the plurality of first laminates 10 constituting the second laminate 100 may be cut or polished at once using the end mill 50. In the cutting process, the corners located at both ends of the concave portion 13 and the corners located at the four corners of the first laminate 10 may be chamfered.

The cutting amount of the end mill in the cutting step may be, for example, 10 μm or more and 500 μm or less, preferably 50 μm or more and 150 μm or less.

The cutting process may be repeated three or more times. For example, in the third cutting process, the chips generated in the second cutting process may be removed from the end surface of the first laminate 10 without cutting the first laminate 10 at all. Multiple end mills may be used in each cutting step.

The feed rate of the end mill in the cutting process may be 100 mm/min or more and less than 3000 mm/min. The rotational speed of the end mill in the cutting process may be, for example, 500 rpm or more and 60,000 rpm or less, preferably 10,000 rpm or more and 60,000 rpm or less. The cutting angle in the cutting step may be, for example, 30° or more and 70° or less, preferably 45° or more and 65° or less. When the helix angle of the end mill 50 is α, the cutting angle β is defined as 90°−α. As shown in FIG. 11, the helix angle α of the end mill 50 is the angle between the direction d1 in which the blade 50e extends on the side surface of the end mill 50 and the rotational axis 50a of the end mill 50. The cutting angle β may be rephrased as the angle formed by the direction d1 in which the blade 50e extends and the direction d2 perpendicular to the rotation axis 50a. The diameter φ (thickness) of the end mill 50 used in the cutting process may be, for example, 3.0 mm or more and 6.0 mm or less.

(Base treatment step)
The base treatment can be performed by bringing a basic solution into contact with the end of the resin film containing boric acid and iodine contained in the first laminate. A low boric acid concentration region and a low iodine concentration region can be formed by subjecting the end portions of a resin film containing boric acid and iodine to a base treatment. The base treatment can be applied to a second laminate obtained by stacking, for example, 5 or more and 3000 or less first laminates. The number of stacked first laminates is preferably 7 or more, for example 2000 or 1000.

The basic solution used in the base treatment preferably contains water. The basic solution may be, for example, a solution in which a strong basic compound is dissolved in a solvent, and is preferably an aqueous solution of a strong basic compound. Strongly basic compounds preferably include sodium hydroxide and/or potassium hydroxide.

The temperature of the basic solution that is brought into contact with the edge of the resin film containing boric acid and iodine may be 50°C or lower, and the optical performance may deteriorate due to the disordered orientation of the polarizer in the polarizing plate (degree of polarization). The temperature is preferably 45° C. or lower, more preferably 40° C. or lower, and usually room temperature or higher, from the viewpoint of suppressing the deterioration (lowering, hue change, etc.) and lowering the boric acid concentration.

The time period for which the end portion of the resin film containing boric acid and iodine is brought into contact with the basic solution may be within 6 minutes, and the optical performance may deteriorate due to the disordered orientation of the polarizer in the polarizing plate (degree of polarization). From the viewpoint of reducing the boric acid concentration, the time may preferably be within 5 minutes, and usually exceeds 1 minute.

The concentration of the basic compound in the basic solution may be, for example, 0.1 mol/liter or more and 4 mol/liter or less, preferably 1 mol/liter or more and 3 mol/liter or less, and more preferably 1.5 mol/liter or more. It is mol/liter or more and 2.5 mol/liter or less.

As a method of bringing the end of the resin film containing boric acid and iodine into contact with a basic solution, for example, all or part of the first laminate or the second laminate is immersed in a tank containing a basic solution. and a method of spraying a basic solution onto all or part of the first laminate or the second laminate.

After contacting with the basic solution, the resin film containing boric acid and iodine can be washed with water. It is preferable to wash with water two or more times. Washing with water can be performed, for example, by immersing the first laminate or the second laminate in a tank containing water, and/or by spraying water onto the first laminate or the second laminate.

By the above method, a polarizing plate according to this embodiment can be obtained.

<Image display device>
The above polarizing plate can be used in an image display device. Examples of the image display device include a liquid crystal display device and an organic EL display device. The polarizing plate may be used as a polarizing plate placed on the viewing side of the image display device, or may be used as a polarizing plate placed on the backlight side of the image display device, or may be used as a polarizing plate placed on the viewing side and the backlight side of the image display device. It may be used for both side polarizing plates. Since the polarizing plate of the present embodiment has color loss spots that are less noticeable, the design is less likely to be impaired even when used on the viewing side of an image display device. Therefore, the image display device is suitable as an image display device having a camera hole, for example, an image display device used in mobile devices such as smartphones and mobile phones, personal computers, and the like.

Hereinafter, the present invention will be explained in more detail with reference to Examples. "%" and "parts" in the examples are mass % and parts by mass unless otherwise specified.

[Condensation heat shock test]
For each example and comparative example, three polarizing plates were tested according to the following procedure.
(1) The optical film side surface of a polarizing plate with a thickness of 21 μm and the surface of a glass plate (manufactured by Corning Inc.) wiped with ethanol were laminated via an adhesive layer, and autoclaved (50°C, 0°C). .5 MPa for 20 minutes).
(2) After autoclaving, it was confirmed by optical microscopic observation that no cracks were generated in the two corners of the concave portion of the polarizing plate (circled in FIG. 15).
(3) The polarizing plate was placed in a condensation heat shock oven, and the following operation was repeated 10 times as one cycle.
First, the polarizing plate was cooled by holding it at -40°C for 30 minutes. Then, it was exposed to outside air at 25° C. for 5 minutes. Thereafter, it was heated to 85°C and kept under dry conditions at 85°C for 30 minutes. Thereafter, it was cooled to 25°C, held for 5 minutes, and then cooled to -40°C. Note that dew condensation formed on the surface of the polarizing plate when it was exposed to outside air at 25° C. for 5 minutes, and thereafter, it was heated to 85° C. in the dew-condensed state. After the polarizing plate was kept under dry conditions at 85° C., the dew condensation state had disappeared.
(4) Take out the polarizing plate from the condensation heat shock oven, and use an optical microscope to determine the number, average length, and maximum length of cracks that have occurred at the two concave corners that were observed using an optical microscope in (2) above. was measured. Further, using an optical microscope, the distance from the end of the polarizing plate to the region where the iodine low concentration region was formed was measured.

[Measurement of boric acid concentration]
The concentration distribution of borate ions (BO ₃ ³⁻ ) was determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS). As shown in FIG. 13, the protect film pasted on the optical film 5 (thickness 52 μm) side of the polarizing plate 110 is peeled off, and the separate film pasted on the adhesive layer on the optical film 9 (thickness 21 μm) side is removed. It was peeled off, and one end region including the corner of the concave portion was cut out to a length of 1 mm (1000 μm) with a width of 100 μm toward the inside of the polarizing plate to obtain measurement sample 200. The measurement sample 200 includes an optical film 201 (thickness: 52 μm), an adhesive layer 202 (thickness: 1 μm), a polarizer 203 (thickness: 8 μm), an adhesive layer 204 (thickness: 1 μm), an optical film 205 (thickness: 21 μm), an adhesive layer 206 ( The thickness was 20 μm) in this order. The ion beam scans and irradiates the measurement region 207 on the side surface in the length direction (1000 μm) of the measurement sample 200 to obtain a two-dimensional distribution of signal intensity of borate ions on this side surface, and from the obtained two-dimensional distribution A portion corresponding to the side surface of the polarizer was cut out, and the integrated value of signal intensity was plotted in the length direction of the measurement sample 200 to obtain a profile of boric acid concentration in the length direction. The conditions for time-of-flight secondary ion mass spectrometry (TOF-SIMS) are shown below.
Although the boric acid concentration was measured in a polarizing plate state, the obtained boric acid concentration can be regarded as the boric acid concentration of the polarizer.
Device name: Product name: PHI TRIFT V nano TOF (ULVAC-PHI Co., Ltd.)
Irradiated primary ions: Au ₃ ⁺
Primary ion acceleration voltage: 30kV
Spatial resolution of ion beam: 1μm x 1μm
Area of measurement area: 200μm x 200μm
From the obtained boric acid concentration profile, calculate the average value of boric acid ion intensity in the range of 30 μm or more and 60 μm or less from the end, and calculate the boric acid ion strength from the end to the position where the boric acid ion intensity has the above average value. The low acid concentration region was defined as the low acid concentration region, and the length of the region where the low boric acid concentration region was formed from the end of the polarizing plate (the length of the low boric acid concentration region) was measured.

[Evaluation of low iodine concentration areas]
The portion of the polarizing plate that has been treated with a base is observed using transmitted light using an optical microscope, and the optical microscope image is imported into a personal computer. The length (length of the low iodine concentration area) was measured.
In the optical microscope image captured on a personal computer, visually the low iodine concentration area appears bright and the inner area appears dark. Image processing was performed on the optical microscope image to create a 256-tone black and white image (brightness 255 is white) so that the brightness of the low iodine concentration area is 180 to 220 and the brightness of the inner area is 100 to 140. 0 is black), and the area (white) where the brightness is 180 or more was defined as a low iodine concentration area, and the average value of the length from the end was determined.

[Preparation of polarizing plate]
(First laminate)
The production of the first laminate 10 will be described with reference to FIG. 14. A first laminate 10 was formed by bonding a pair of optical films 5 and 9 to a polarizer 7 via adhesive layers 6 and 8. The first laminate 10 had a rectangular shape. In the first laminate 10, the polarizer 7 was placed between the pair of optical films 5 and 9. Both of the pair of optical films 5 and 9 were made of a cyclic olefin polymer resin. Polarizer 7 was a stretched and dyed film of polyvinyl alcohol.

An adhesive was applied to the optical film 9 side of the first laminate 10 to form an adhesive layer 41, and a separate film 42 was laminated thereon. This separate film was peelable from the adhesive layer. A protect film 43 was bonded to the optical film 5 side of the first laminate 10. This protection film 43 was peelable from the optical film 5.

The thickness of the optical film 5 bonded to one surface of the polarizer was 52 μm. The thickness of the optical film 9 bonded to the other surface of the polarizer was 21 μm. The thickness of polarizer 7 was 8 μm. The entire thickness of the first laminate 10 was 103 μm. The adhesive layer 6 interposed between the optical film 5 and the polarizer 7 having a thickness of 52 μm was a polyvinyl alcohol resin (water glue). The adhesive layer 8 interposed between the optical film 9 and the polarizer 7 having a thickness of 21 μm was a UV-curable epoxy resin.

(Currently shaped processing)
By the above procedure, 47 sheets of the first laminate 10 are prepared in which the adhesive layer 41 is formed on the optical film 9 side, the separate film 42 is laminated thereon, and the protect film 43 is laminated on the optical film 5 side. Then, a concave portion was formed on the short side of each first laminate by punching using a Thomson blade. The shape of this concave portion was the same in all 47 first laminates. A second laminate was produced by stacking 47 first laminates in which concave portions were formed. In this second laminate, the long sides and short sides of all 47 first laminates were aligned, and the concave portions were aligned.

After punching, the following three cutting steps were performed. In any cutting process, the second laminate is fixed with a clamp, the side surface of the end mill is in contact with the outer periphery (end face) of the second laminate, and the rotating end mill is inserted into the outer periphery (recessed part) of the second laminate. along the outer circumference). That is, the entire outer periphery of each of the 47 first laminates was cut at once with an end mill. The end mill used in each cutting process was DXL-4 manufactured by Nissin Tools Co., Ltd. The cutting angle β was the value shown in Table 1 below. The diameter φ of the end mill was 4 mm.

The amount of scraping in the first cutting process was the value shown in Table 1 below. The rotation speed (R) of the end mill in the first cutting step was 30,000 rpm. The feed rate (V) of the end mill in the first cutting process was 1000 mm/min.

The amount of scraping in the second cutting step was the value shown in Table 1 below. The rotation speed (R) of the end mill in the second cutting step was 30,000 rpm. The feed rate (V) of the end mill in the second cutting step was 1000 mm/min.

The amount of scraping in the third cutting process was the value shown in Table 1 below. The rotation speed (R) of the end mill in the third cutting step was 30,000 rpm. The feed rate (V) of the end mill in the third cutting step was 1000 mm/min.

By the above method, 47 polarizing plates were manufactured. The shape, dimensions, and laminated structure of each polarizing plate were the same. The overall shape of each polarizing plate was rectangular. FIG. 15 shows the shape of the obtained polarizing plate 110 in plan view. As shown in FIG. 15, the polarizing plate 110 had a rectangular concave portion 113 formed on the short side. The length of the short side of the polarizing plate 110 was 70 mm. The length of the long side of the polarizing plate 110 was 140 mm. The width 111 of the recessed portion 113 was 30 mm. The depth 112 of the recessed portion 113 was 5 mm. Further, the depth direction of the concave portion 113 was parallel to the absorption axis (stretching direction).

<Example 1>
The polarizing plate of Example 1 was obtained by stacking 10 polarizing plates processed into the above shape and subjecting the ends to base treatment under the following conditions and procedure.
(1) It was immersed in a NaOH aqueous solution at a concentration of 2 mol/liter and at 40°C for 5 minutes.
(2) Next, the laminated polarizing plates were washed in the order of washing tank 1 (20°C) and washing tank 2 (20°C) for 1 minute each.
After the above edge base treatment, the three polarizing plates were subjected to measurement of boric acid concentration and a condensation heat shock test. The results are shown in Table 1. Furthermore, FIG. 16 shows a TOF-SIMS analysis result (a) and an optical microscope observation image of the end region (b).
This polarizing plate had a low boric acid concentration region formed in a region including the end with a width of 20 μm from the end. Further, in this polarizing plate, an iodine low concentration region was also formed in a region including the end portion with a width of 50 μm from the end portion.

<Comparative example 1>
Regarding the three polarizing plates processed into the above shape, the boric acid concentration was measured and the dew condensation heat shock test was conducted without performing the edge base treatment of Example 1. The results are shown in Table 1. Further, FIG. 17 shows a TOF-SIMS analysis result (a) and an optical microscope observation image of the end region (b).
This polarizing plate had a low boric acid concentration region formed in a region including the end with a width of 12 μm from the end. Further, in this polarizing plate, no low iodine concentration region was formed in the region including the end portions.

<Comparative example 2>
A polarizing plate of Comparative Example 2 was obtained in the same manner as in Example 1, except that the polarizing plate was immersed in the NaOH aqueous solution for 1 minute instead of immersing it in the NaOH aqueous solution for 5 minutes in Example 1. Furthermore, FIG. 18 shows a TOF-SIMS analysis result (a) and an optical microscope observation image of the end region (b).
This polarizing plate had a low boric acid concentration region formed in a region including the end with a width of 14 μm from the end. Further, in this polarizing plate, an iodine low concentration region was also formed in a region including the end portion with a width of 18 μm from the end portion.

In Example 1, the number of cracks was small, the average crack length and maximum crack length were short, and the area where the low iodine concentration site was formed was very small.
In Comparative Example 1, the number of cracks was large, the average crack length and the maximum crack length were long, and crack generation was not suppressed.
In Comparative Example 2, although the number of cracks was reduced, the average crack length and maximum crack length were long, and cracks were not sufficiently suppressed.
It can be seen that according to the present invention, a polarizer can be obtained in which the occurrence of cracks is suppressed in the above-mentioned dew condensation heat shock test and in which iodine omission is not noticeable.

1 polarizing plate, 2 polarizer, 3 first optical film, 4 second optical film, 5, 9 optical film, 7 unbase treated polarizer, 10 first laminate, 11 region I, 12 region II, 13,113 recessed portion, 14 through hole, 15 third optical film, 20 image display device, 21 polarizing plate, 22 camera hole, 23 liquid crystal panel, 24 cover glass, 25 adhesive layer, 26 polarizing plate, 27 camera, 28 light shielding tape, 30 boric acid low concentration region, 31 intermediate region, 32 inner region, 33 iodine low concentration region, 34 intermediate region, 41 adhesive layer, 42 separate film, 43 protect film, 50 end mill, 50a rotation axis, 50e blade (edge) , 100 second laminate, 110 polarizing plate, 111 width, 112 depth, 200 measurement sample, 201, 205 optical film, 202, 204 adhesive layer, 203 polarizer, 206 adhesive layer, 207 measurement area, α torsion angle , β cutting angle

Claims (1)

A polarizer that is a resin film containing boric acid and iodine,
A low boric acid concentration region is formed in a region including the end in plan view, the concentration of boric acid being lower than the concentration of boric acid in the inner region 500 μm or more inside from the end,
A low iodine concentration region having a lower iodine concentration than the iodine concentration in the inner region is formed in a region including the end portion,
A polarizer, wherein the length of the low iodine concentration region from the end is 19 μm or more and 100 μm or less.

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