TWI842838B - Polarizing plate - Google Patents

Abstract

An objective of the present invention is to provide a polarizing plate that is less likely to crack due to temperature changes. The solution of the present invention is a polarizing plate 100, which includes: a polarizer layer 30; a first optical resin film 10 which is provided on one surface of the polarizer layer 30; and a second optical resin film 50 which is provided on the other surface of the polarizer layer 30. When the polarizing plate 100 is viewed from the thickness direction, the shape of the outer periphery of the polarizing plate 100 has at least one of a concave portion, a convex portion and a curved portion. The arithmetic mean height Sa of an end face of the polarizer layer 30 is 0.3 to 0.7 μm, or the quadratic root mean square height Sq of an end face of the polarizer layer is 0.4 to 0.8 μm.

Description

Polarizing plate

The present invention relates to a polarizing plate.

Polarizing plates usually include: a polarizing layer containing a pigment, and a pair of optical resin films disposed on both sides of the polarizing layer, and are used by bonding to a display panel such as a liquid crystal cell or an organic electroluminescent element. The periphery of the polarizing plate is usually configured to match the shape of the periphery of the display portion of the display panel.

When the outer periphery of the display portion of the display panel is not rectangular in a plan view but has at least one of a concave portion, a convex portion and a curved portion, the outer periphery of the polarizing plate used in the display portion is also correspondingly not rectangular but has at least one of a concave portion, a convex portion and a curved portion (for example, refer to Patent Document 1).

[Prior Art Literature]

[Patent Literature]

Patent document 1: Japanese Patent Publication No. 2018-92119

After review, the inventors of the present invention determined that the outer periphery of a polarizing plate that is not rectangular but has at least one of a concave portion, a convex portion, and a curved portion is more likely to cause discoloration of the polarized layer in a wet and hot environment than a rectangular polarizing plate, or the optical resin film is more likely to peel off from the polarizing plate in the end face. Such a phenomenon is more likely to occur in concave portions, convex portions, and curved portions or their vicinities than in straight portions.

The present invention is completed in view of the above-mentioned problems, and its purpose is to provide a polarizing plate having at least one of a concave portion, a convex portion and a curved portion at the outer periphery, the polarizing plate is not easy to discolor in a humid and hot environment, and the optical resin film is not easy to peel off from the polarizing layer on the end surface.

The polarizing plate of the present invention comprises: a polarizing layer; a first optical resin film disposed on the surface of one side of the polarizing layer; and a second optical resin film disposed on the surface of the other side of the polarizing layer. Furthermore, when the polarizing plate is viewed from the thickness direction, the shape of the outer periphery of the polarizing plate has at least one of a concave portion, a convex portion, and a curved portion, and the arithmetic mean height Sa of the end face of the polarizing layer is 0.3 to 0.7 μm.

In addition, another polarizing plate of the present invention comprises: a polarizer layer; a first optical resin film disposed on the surface of one side of the polarizer layer; and a second optical resin film disposed on the surface of the other side of the polarizer layer. Furthermore, the square root mean square height Sq of the end face of the polarizer layer is 0.4 to 0.8 μm. The arithmetic mean height Sa of the end face can be 0.3 to 0.7 μm.

In the polarizing plate of the present invention, the maximum height Sz of the end face of the aforementioned polarizer layer can be less than 5.0μm.

According to the present invention, a polarizing plate is provided, which has at least one of a concave portion, a convex portion and a curved portion on the outer periphery. The polarizing plate is not easy to discolor in a humid and hot environment, and the optical resin film is not easy to peel off from the polarizing layer on the end surface.

10: First optical resin film

20, 40: Next is the agent layer

30: Polarizer layer

31: Absorption axis

30A: Two-dimensional measurement area

50: Second optical resin film

80: Blade

80t: Blade tip

80d: Noodles

100: Polarizing plate

AB: Straight line

AX: Rotation axis

C: Rotation direction

dX: distance

dZ: maximum value

P: Periphery

PL: Straight line part

PP: convex part

PD: concave part

PR, PDR, PPR: Chamfered curve part

Q: Straight line

T: Cutting material

Figure 1 is a schematic cross-sectional view of a polarizing plate in one embodiment of the present invention.

Figure 2 (a) to (c) are top views of a polarizing plate of one embodiment of the present invention.

Figure 3 is a cross-sectional view of the end milling cutter perpendicular to the axis near the tool tip.

Below, the preferred embodiment of the present invention is described with reference to the drawings. In the drawings, the same symbols are given to the same components. The present invention is not limited to the embodiment described below.

(Polarizing plate)

FIG. 1 shows an end view of a polarizing plate 100 of an example of the present embodiment. The polarizing plate 100 of the present embodiment sequentially comprises: a first optical resin film 10, an adhesive layer 20, a polarizer layer 30, an adhesive layer 40, and a second optical resin film 50.

An example of the polarizer layer 30 is a resin layer dyed with a dichroic pigment such as iodine or a dichroic dye, and may be stretched. The resin constituting the resin layer may be a hydrophobic resin, but is usually a hydrophilic resin. Examples of hydrophilic resins are polyvinyl alcohol resins, polyvinyl acetate resins, and ethylene/vinyl acetate copolymer resins (EVA resins). Examples of hydrophobic resins are polyamide resins and polyester resins. The polarizer layer 30 may be treated with boric acid after dyeing. A typical example of the polarizer layer 30 is a resin layer obtained by iodine adsorption and orientation on a polyvinyl alcohol film. When the resin layer as the polarizer layer is composed of a hydrophilic resin such as a polyvinyl alcohol resin, more water enters and leaves the layer than a hydrophobic resin. This is believed to be the cause of discoloration in a humid and hot environment and the peeling of the optical resin film from the polarizer layer located at the end surface. The structure of the present invention can suppress such discoloration and peeling.

The thickness of the polarizer layer 30 may be, for example, 2 to 30 μm, 2 to 15 μm, or 2 to 10 μm.

The first optical resin film 10 and the second optical resin film 50 are usually colorless and transparent resin films. Examples of such resin films are protective films, phase difference films, brightness enhancement (reflective polarizer) films, anti-glare films, surface anti-reflection films, reflective films, semi-transmissive reflective films, viewing angle compensation films, optical compensation films, touch sensor films, antistatic films, and anti-fouling films.

Examples of resins constituting each optical resin film may be cellulose resins (triacetyl cellulose, etc.), polyolefin resins (polypropylene resins, etc.), cycloolefin resins (norene resins, etc.), acrylic resins (polymethyl methacrylate resins, etc.), or polyester resins (polyethylene resins, etc.). The first optical resin film 10 and the second optical resin film 50 may be multi-layer films.

The thickness of the first optical resin film 10 and the second optical resin film 50 may be, for example, 5 to 200 μm.

The materials and thicknesses of the first optical resin film 10 and the second optical resin film 50 may be the same or different.

If the bonding agent layers 20 and 40 are transparent materials that can bond the polarizer layer 30 to the first optical resin film 10 or the second optical resin film 50, there is no particular limitation on the material. An example of a bonding agent is an epoxy resin. The epoxy resin can be, for example, a hydrogenated epoxy resin, an aliphatic epoxy resin, or an aliphatic epoxy resin. A polymerization initiator (photocationic polymerization initiator, thermal cationic polymerization initiator, photoradical polymerization initiator or thermal radical polymerization initiator, etc.) or other additives (sensitizer, etc.) can be added to the epoxy resin.

Other examples of adhesives are acrylic resins such as acrylamide, acrylate, urethane acrylate, and epoxy acrylate.

Other examples of adhesives include water-based adhesives such as polyvinyl alcohol resins.

Another example of an adhesive is a pressure-sensitive adhesive. Examples of pressure-sensitive adhesives include pressure-sensitive adhesives such as acrylic resins, silicone resins, polyesters, polyurethanes, or polyethers.

The polarizer layer 30 and the first optical resin film 10 may be laminated only with the adhesive layer 20 interposed therebetween, and an easy-adhesion layer (not shown) may be provided between the polarizer layer 30 and the adhesive layer 20, or between the adhesive layer 20 and the first optical resin film 10. In addition, the polarizer layer 30 and the second optical resin film 50 may be laminated only with the adhesive layer 40 interposed therebetween, and an easy-adhesion layer (not shown) may be provided between the polarizer layer 30 and the adhesive layer 40, or between the adhesive layer 40 and the second optical resin film 50. The easy-to-bond layer is a layer that can enhance the bonding strength between the adhesive layer 20, 40 and the polarizer layer 30, the first optical resin film 10 or the second optical resin film 50.

The thickness of the adhesive layer 20 may be, for example, 0.01 μm to 5 μm, 0.05 μm to 3 μm, or 0.1 μm to 1 μm. When a pressure-sensitive adhesive is used, the thickness of the adhesive layer 20 may be, for example, 2 to 500 μm, 2 to 200 μm, or 2 to 50 μm.

The overall thickness of the polarizing plate 100 may be, for example, 10 to 500 μm, 10 to 300 μm, or 10 to 200 μm.

A pressure-sensitive adhesive layer (adhesive layer) and an isolation film may be further provided under the first optical resin film 10 or on the second optical resin film 50. In addition, a protective film may also be further provided under the first optical resin film 10 or on the second optical resin film 50.

The isolation film is a film that can be peeled off from the pressure-sensitive adhesive layer and is a film that prevents foreign matter from adhering to the pressure-sensitive adhesive layer. For example, when the polarizing plate 100 is adhered to the image display element, the isolation film is peeled off to expose the pressure-sensitive adhesive layer. The resin constituting the isolation film can be, for example, a polyethylene resin, a polypropylene resin, or a polyester resin (polyethylene terephthalate, etc.).

The protective film is a film used to prevent damage to the first optical resin film 10 or the second optical resin film 50. For example, it can be a self-adhesive resin film alone or a multilayer film composed of a resin film and a pressure-sensitive adhesive layered on the resin film. The protective film can be peeled off from the first optical resin film 10 or the second optical resin film 50 provided with the protective film. When the protective film is a multilayer film formed by a pressure-sensitive adhesive layered on the resin film, the protective film is peeled off from the first optical resin film 10 or the second optical resin film 50 according to the pressure-sensitive adhesive. The resin of the protective film can also be set to be the same as that of the isolation film.

The thickness of the isolation film and the protective film may be, for example, 2 to 500 μm, 2 to 200 μm, or 2 to 100 μm.

When the polarizing plate 100 of this embodiment is viewed from its thickness direction, the outer periphery P of the polarizing plate 100 is not formed by only straight lines (e.g., a rectangle), but has at least one selected from a group consisting of a concave portion, a convex portion, and a curved portion.

For example, the outer periphery P of the polarizing plate 100 shown in FIG. 2 (a) may have four adjacent straight line portions PL orthogonal to each other; and chamfered curved line portions PR respectively disposed between two straight line portions PL. In other words, the outer periphery P of the polarizing plate 100 is provided with chamfered curved line portions PR at the four corners of the rectangle.

Furthermore, as shown in FIG. 2(b) of the polarizing plate 100, a concave portion PD may be further provided for one of the straight line portions PL in the outer periphery P of the polarizing plate 100 in FIG. 2(a). The shape of the concave portion PD is not limited, but for example, as shown in FIG. 2(b), it may be a substantially rectangular shape having three adjacent straight line portions PDL orthogonal to each other, with a chamfered curved portion PDR between the straight line portions PDL, and a chamfered curved portion PDR between the straight line portion PDL and the straight line portion PL. The curved portion PDR between the two straight line portions PDL is concave toward the inside of the surface of the polarizing plate 100. The chamfered curved portion PDR between the straight line portion PDL and the straight line portion PL is convex toward the outside of the surface of the polarizing plate 100.

Furthermore, as shown in FIG. 2 (c), the polarizing plate 100 may be provided with a convex portion PP on a straight portion PL of the outer periphery P of the polarizing plate 100 in FIG. 2 (a). The shape of the convex portion PP is not limited, but for example, as shown in FIG. 2 (c), it may be a generally rectangular shape having three adjacent straight portions PPL orthogonal to each other, with chamfered curved portions PPR respectively between the straight portions PPL, and with chamfered curved portions PPR respectively between the straight portions PPL and the straight portions PL. The chamfered curved portion PPR between the two straight portions PPL is concave toward the inside of the surface of the polarizing plate 100. The chamfered curved portion PPR between the straight portions PPL and the straight portions PL is convex toward the outside of the surface of the polarizing plate 100.

The depth of the concave portion PD from the straight portion PL and the height of the convex portion PP from the straight portion PL are not particularly limited, but are typically 1.0 mm or more. In addition, the width of the concave portion PD and the width of the convex portion PP are not particularly limited, but are typically 3.0 mm or more.

The shapes of the concave portion PD and the convex portion PP are not limited to the rectangles with the four corners rounded by the chamfered curves as shown in Figure 2 (b) and (c), but can also be simply rectangles, semicircles, polygons, etc.

The curve of each chamfered curve portion can be a circular arc, an elliptical arc, or a spline curve. The radius of curvature of each chamfered curve portion can be set to 1.0 to 40 mm.

Furthermore, in the outer periphery P of FIG. 2 (a), one to three of the four chamfered curve portions PR may be simple corner portions of non-chamfered curves. In the outer periphery P of FIG. 2 (b) and (c), one to four of the four chamfered curve portions PR may be simple corner portions of non-chamfered curves. Moreover, the outer periphery P may be a shape other than a rectangle as shown in FIG. 2 (a) to (c), and may be a shape based on a polygon such as a triangle or a hexagon.

Furthermore, the absorption axis of the polarizer layer 30 can be oriented in any direction of the polarizer 100 in accordance with the image display device used.

(Arithmetic mean height Sa)

Returning to FIG. 1, in the polarizing plate 100 of the embodiment of the present invention, the arithmetic mean height Sa of the end surface of the polarizing layer 30 of the polarizing plate 100 is 0.3 to 0.7 μm. Sa can be greater than 0.4 μm or less than 0.6 μm.

The arithmetic mean height Sa of the end face of the polarizer layer 30 is defined as follows in an arbitrary two-dimensional measurement area 30A on the end face. Define an XYZ coordinate system, wherein the plane parallel to the end face of the polarizer layer 30 is set as the XY plane, the height direction perpendicular to the end face is set as the Z direction, the position of the average height of the two-dimensional measurement area 30A on the end face is set as Z=0, and when the height in each x-coordinate and y-coordinate of the two-dimensional measurement area 30A is set as Z(x, y), the arithmetic mean height Sa is expressed by the following formula. Here, A is the area of the two-dimensional measurement area 30A.

The height Z(x, y) of each x and y in the two-dimensional measurement area 30A can be obtained by a scanning interference microscope, an atomic force microscope, etc. The size of the two-dimensional measurement area 30A can be set to, for example, a rectangular area with a side of 5 to 1000 μm.

(square root mean square height Sq)

Furthermore, the square root mean square height Sq of the end surface of the polarizer layer 30 can be 0.4 to 0.8 μm. Sq can be greater than 0.5 μm or less than 0.7 μm.

The square root mean square height Sq in any two-dimensional measurement area 30A is defined by the following formula.

(Maximum height Sz)

Furthermore, the maximum height Sz of the end surface of the polarizer layer 30 can be less than 5.0μm. Sz can also be less than 4.0μm.

The maximum height Sz is the sum of the absolute values of the maximum mountain height and the maximum valley depth in the two-dimensional measurement area 30A.

The measurement of three-dimensional surface roughness in the two-dimensional measurement area 30A can be based on ISO25178.

The two-dimensional measurement area 30A is preferably any straight line portion of the outer periphery P, that is, a plane portion in the end surface, or a plane portion inside the concave portion PD and the convex portion PP, or a plane portion outside the concave portion PD and the convex portion PP, such as a plane portion on four adjacent orthogonal straight line portions PL.

As will be described later, unlike a polarizing plate whose outer periphery P is formed only by straight lines, it is impossible to use a plane grinding device to cut the end surface of a polarizing plate with concave, convex or curved parts for size adjustment. Therefore, the end surface of such a polarizing plate is usually cut by an end milling cutter in a manner that covers the entire periphery. Therefore, any part of the end surface has roughly the same surface roughness.

The surface with an average height of 0 at the diameter portion of the outer periphery P, that is, at the flat surface portion of the end surface, becomes a plane. Since it is easy to determine the surface with Z=0, it is suitable as the two-dimensional measurement area 30A.

It is also preferable that the two-dimensional measurement area 30A is located at the end of the absorption axis (extension direction) of the polarizer layer 30. In addition, when the two-dimensional measurement area 30A is located at the end of the absorption axis direction, the area 30A is in a state of intersecting with the absorption axis of the polarizer layer 30.

When the arithmetic mean height Sa of the end face of the polarizer layer 30 is larger, the surface area of the end face will become larger, so there will be a tendency for discoloration to increase in a humid and hot environment. In contrast, when the arithmetic mean height Sa of the end face of the polarizer layer 30 is smaller, the amount of the first optical resin film 10 and/or the second optical resin film 50 peeled off from the polarizer layer 30 will tend to increase. Among them, the smaller Sa corresponds to the state where the end face is kept as it is after punching with a Thompson knife without grinding, and it can be inferred that the reason is the peeling of the optical resin film caused by the impact of punching.

When the square root mean square height Sq of the end face of the polarizer layer 30 is larger, the surface area of the end face becomes larger, so there is a tendency for discoloration to increase in a humid and hot environment. In contrast, when the square root mean square height Sq of the end face of the polarizer layer 30 is smaller, the amount of the first optical resin film 10 and/or the second optical resin film 50 peeling off from the polarizer layer 30 tends to increase easily.

When the maximum height Sz of the end face of the polarizer layer 30 is larger, the surface area of the end face becomes larger, so there is a tendency for greater discoloration in a humid and hot environment.

This polarizing plate is bonded to a display panel such as a liquid crystal unit or an organic EL element, and can be used in an image display device such as a liquid crystal display device or an organic EL display device. A liquid crystal display device may include a liquid crystal unit and the above-mentioned polarizing plate bonded to one side or both surfaces of the liquid crystal unit. An organic EL display device may include, for example, an organic EL element and the above-mentioned polarizing plate bonded to one side or both surfaces of the liquid crystal unit. A liquid crystal unit is usually equipped with two polarizing plates.

(Polarizing plate manufacturing method)

Next, the manufacturing method of the polarizing plate 100 described above is described.

First, a raw sheet of the polarizing plate 100 having the above-mentioned layer structure is manufactured by a known method. Then, a cutting tool such as a Thompson knife is used to punch out the raw sheet film, and a polarizing plate having a concave portion, a convex portion or a curved portion at the outer periphery P is obtained. It is explained here that it is difficult to ensure sufficient dimensional accuracy at the outer periphery P by cutting only with a Thompson knife, so a grinding process of the end surface is required.

When the outer periphery P has a concave portion, a convex portion or a curved portion, it is impossible to use the plane grinding device used for grinding the end face of a rectangular polarizing plate, that is, it is impossible to use a rotating circular plate with a plurality of cutters arranged along the circumferential direction on the main surface of one side to contact the end face of the polarizing plate in a manner parallel to the end face of the polarizing plate to grind the entire end face. Therefore, an end milling cutter is used to cut the end face of the polarizing plate. More specifically, the axial direction of the end milling cutter is parallel to the thickness direction of the polarizing plate, and the end milling cutter and the polarizing plate are moved relative to each other along the end face of the polarizing plate, thereby cutting the end face of the polarizing plate to meet the desired size.

Here, it is better to use an end milling cutter with a spiral-shaped cutter. In particular, in terms of the cross-sectional shape of the cutter, it is better to use an end milling cutter with a smaller dZ and dZ/dX as shown in Figure 3.

For explanation, FIG. 3 is a cross-sectional view of the front end of the blade 80 in a cross section perpendicular to the axis of the end mill. The rotation direction of the end mill is C. The blade 80 has a cutting edge 80t and a surface 80d further to the rear than the cutting edge 80t. The surface 80d can contact the cutting object T immediately after cutting by the cutting edge 80t. In this embodiment, the cutting edge 80t is set as a starting point with the straight line Q connecting the cutting edge 80t and the rotation axis AX of the end mill as a reference, and is moved along a straight line AB that is orthogonal to the straight line Q and passes through the cutting edge 80t, while the height profile of the surface 80d based on the straight line AB is measured by a scanning interference microscope. Then, the maximum value of the height of the surface 80d, i.e. dZ [μm], and the distance dX [μm] from the tool tip 80t in the AB direction assigned to dZ are obtained from the contour.

At this time, it is better to use an end milling cutter with a blade tip of dZ ≤ 1.0 μm and dZ/dX ≤ 4. In this way, it is easy to set the surface roughness of the end face 20e of the polarizer layer 30 within the above range. Even if it is an end milling cutter with a spiral blade, if it is dZ> 1.0 μm or dZ/d> 4, there is a tendency for the surface roughness to become too large.

The above has been described with respect to the preferred implementation forms of the present invention, but the present invention is not limited to the above implementation forms at all.

For example, it can be implemented even without one or both of the adhesive layers 20 and 40.

(Implementation example)

Below, examples and comparative examples are given to more specifically illustrate the contents of the present invention. In addition, the present invention is not limited to the examples described below.

[Implementation Example 1]

株式會社(Zeon Corporation)製造，厚度為13μm)黏合於該偏光片層之一側的面。再者，將形成在剝離膜上的丙烯酸系黏著劑層A(厚度20μm)積層在COP膜上。將形成在剝離膜上的丙烯酸系黏著劑層B(厚度5μm)積層在偏光片之另一側的面。將上表面具有保護膜之亮度增進膜(3M分司製作，APF-V3，厚度30μm，反射型偏光片)黏合於已將剝離膜剝離而露出的丙烯酸系黏著劑層B上。 A 20 μm thick polyvinyl alcohol resin was stretched and dyed with iodine to produce a polarizer (8 μm thick) with iodine adsorbed and oriented on the polyvinyl alcohol film. A cyclic olefin resin (COP) film (Japan

Co., Ltd. (Zeon Corporation, thickness 13μm) is bonded to the surface of one side of the polarizer layer. Furthermore, the acrylic adhesive layer A (thickness 20μm) formed on the peeling film is laminated on the COP film. The acrylic adhesive layer B (thickness 5μm) formed on the peeling film is laminated on the surface of the other side of the polarizer. A brightness enhancement film (manufactured by 3M Branch, APF-V3, thickness 30μm, reflective polarizer) with a protective film on the upper surface is bonded to the acrylic adhesive layer B exposed by peeling off the peeling film.

In this way, a polarizer original sheet consisting of a peeling film/acrylic adhesive layer A/COP film/water-based adhesive/polarizer/acrylic adhesive layer B/brightness enhancement film/protective film is produced.

A polarizing plate 100 having a recess PD in the shape of FIG. 2 (b) is cut out from the original sheet by a Thompson knife. The length of the long side of the rectangle is set to 140 mm, the length of the short side of the rectangle is set to 70 mm, the depth of the recess is set to 5 mm, the width of the recess is set to 30 mm, the radius of curvature of the chamfered curve portion PR is about 10 to 12 mm, and the radius of curvature of the chamfered curve portion PDR is about 3 mm. In addition, the polarizing plate 100 has a recess PD. The recess PD is roughly rectangular. The recess PD has three adjacent straight line portions PDL that are orthogonal to each other. There is a chamfered curve portion PDR between each of the straight line portions PDL. There is a chamfered curve portion PDR between each of the straight line portions PDL and the straight line portion PL. The absorption axis 31 of the polarizing plate 100 is orthogonal to the depth direction of the recess PD and is in the left-right direction in FIG. 2(b).

Using an end milling cutter with a spiral diameter shape and an average dZ of 0.6μm and an average dZ/dX of 2.2, the entire circumference of the end surface was polished and the size was adjusted to obtain a polarizing plate of implementation 1.

(Comparison Example 1)

The polarizing plate of Comparative Example 1 was obtained in the same manner as Example 1, except that an end milling cutter with a spiral diameter shape having an average dZ of 1.4 μm and an average dZ/dX of 14 was used and the entire circumference of the end surface was ground.

(Comparison Example 2)

The polarizing plate of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the end surface was not ground with an end mill but cut with a Thompson cutter.

(Measurement of three-dimensional surface roughness Sa, Sq, Sz)

The height function Z(x, y) of the end face of the polarizer layer is obtained by using the following microscope.

(Hitachi High-Tech Science Corporation) Scanning white interference microscope VS1000 series Hitachi, Ltd.

(Hitachi High-Tech Science Corporation)

Measurement conditions: Objective lens: 50×

Two-dimensional measurement area: The vertical depth (thickness direction) in the straight line part (plane perpendicular to the absorption axis) of the end surface of the polarizer layer 30 (PVA layer) of the polarizing plate is 5 to 8 μm × the horizontal width (direction perpendicular to the thickness direction) is 150 to 300 μm

According to the obtained function Z, Sa, Sq and Sz are obtained according to the above formula. The end face after Sa, Sq and Sz are measured is located on the straight line part PL on the left and right of Figure 2 (b) and is orthogonal to the absorption axis 31. In addition, Sa, Sq and Sz in each polarizing plate 100 represent the same value throughout the entire circumference.

(Evaluation of iodine removal)

The polarizing plate obtained by the embodiment or comparative example is placed in an environment of 65°C and 90% relative humidity for 500 hours.

Then, two polarizing plates (one is the polarizing plate of the embodiment or comparative example, and the other is a commercially available common polarizing plate) are arranged in a crossed nicol state, and the ends are observed all around using an optical microscope, and the width of the ends away from the region where the light reduction (extinction) corresponding to the crossed polarization does not occur is measured. The extinction is caused by the removal of iodine, which has the function of showing polarization performance. In addition, the extinction occurs near the concave portion PD in Figure 2, and its maximum width is obtained as the iodine removal.

(Evaluation of the peeling amount of brightness enhancement film)

Evaluation was performed using a reflection microscope.

The conditions and results are shown in Table 1.

[Table 1]

The embodiment is capable of reducing the amount of iodine removal and also reducing the amount of peeling of the brightness enhancement film.

(Industrial applicability)

The polarizing plate of the present invention can be used, for example, as an optical component for bonding liquid crystal units or organic electroluminescent elements to form image display devices such as liquid crystal televisions, organic electroluminescent televisions or smart phones.

10: First optical resin film

20, 40: Next is the agent layer

30: Polarizer layer

30A: Measurement area

50: Second optical resin film

100: Polarizing plate

Claims (3)

A polarizing plate comprises: a polarizer layer; a first optical resin film disposed on a surface of one side of the polarizer layer; a second optical resin film disposed on a surface of the other side of the polarizer layer; and a protective film disposed on the second optical resin film; the polarizer layer and the first optical resin film are laminated only with an adhesive layer in between, and the adhesive layer is an adhesive containing epoxy resin, an adhesive containing acrylic resin, or a protective film disposed on the second optical resin film. Adhesive, or water-based adhesive; the polarizer layer and the second optical resin film are laminated only with an adhesive layer belonging to a pressure-sensitive adhesive between them; when the polarizer is viewed from the thickness direction, the shape of the outer periphery of the polarizer has a concave portion; the square root mean square height Sq of the end face of the polarizer layer is 0.4 to 0.8 μm; the arithmetic mean height Sa of the end face of the polarizer layer is 0.3 to 0.7 μm ; the protective film is a multi-layer film formed by laminating a pressure-sensitive adhesive on a resin film; the protective film can be peeled off from the second optical resin film according to the pressure-sensitive adhesive. As described in item 1 of the patent application scope, the maximum height Sz of the end face of the polarizer layer is less than 5.0μm. The polarizing plate as described in item 1 or 2 of the patent application, wherein the second optical resin film is a brightness enhancement film.

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