WO2022191246A1

WO2022191246A1 - Polarizing plate, and method for producing same

Info

Publication number: WO2022191246A1
Application number: PCT/JP2022/010354
Authority: WO
Inventors: 浩司久門; 智之山口; 智岩田
Original assignee: 住友化学株式会社
Priority date: 2021-03-11
Filing date: 2022-03-09
Publication date: 2022-09-15
Also published as: KR20230156723A; TW202243896A

Abstract

[Problem] To provide a polarizing plate provided with a polarizer in which a polarizer gap part is not formed in an end region, and cracks are suppressed in a heat shock test. [Solution] A polarizing plate has thermoplastic resin films on both surfaces of a polarizer containing iodine and boron, wherein the ends of the polarizer in the direction parallel to the direction of the polarizer transmission axis are at the same position in the plane direction rather than the ends of at least one of the thermoplastic resin films in the direction parallel to the direction of the polarizer transmission axis or are located on the outside in the plane direction, and the ends of the polarizer in the direction parallel to the direction of the polarizer transmission axis satisfy formula (I) below. Boric acid cross-linking index ≦0.9 (I) [The boric acid cross-linking index is defined by the Raman scattered light intensity at a wavenumber of 780 cm^-1/the Raman scattered light intensity at a wavenumber of 850 cm^-1.]

Description

Polarizing plate and manufacturing method thereof

The present invention relates to a polarizing plate and a manufacturing method thereof.

Patent Document 1 below discloses a polarizer having a lower concentration of boric acid at the ends of the through holes than other portions, and the polarized light, as a polarizing plate having good durability even when through holes are formed in the polarizing plate. Discloses a polarizing plate having protective films on both sides of the element.

JP 2016-206641 A

However, the polarizing plate described in Patent Document 1 has polarizer voids formed at the ends thereof. The polarizer gap means a gap between the protective films formed by the edge of the polarizer existing (or positioned) inside the edge of the protective film in the plane direction. If the polarizer gap is formed at the end of the polarizing plate, light may leak from the polarizer gap when the polarizing plate is incorporated in a display device or the like.

An object of the present invention is to prevent the polarizer gap from being formed in the end portion of the polarizing plate (especially the end portion in the direction parallel to the transmission axis direction of the polarizer), and after exposure to a high temperature (85 ° C.), An object of the present invention is to provide a polarizing plate equipped with a polarizer that suppresses the occurrence of cracks in a heat shock test in which the polarizer is repeatedly exposed to a low temperature (−40° C.) by cooling, and a method for producing the polarizer.

The present invention provides the following polarizing plate and manufacturing method thereof.
[1] A polarizing plate having thermoplastic resin films on both sides of a polarizer containing iodine and boron,
Is the end of the polarizer in the direction parallel to the polarizer transmission axis direction the same position in the plane direction as the end of at least one of the thermoplastic resin films in the direction parallel to the polarizer transmission axis direction? or located on the outside in the plane direction,
A polarizing plate in which an end portion of the polarizer in a direction parallel to a polarizer transmission axis direction satisfies the following formula (I).
Boric acid cross-linking index ≤ 0.9 (I)
[The boric acid cross-linking index is defined as Raman scattered light intensity at a wavenumber of 780 cm ^-1 /Raman scattered light intensity at a wavenumber of 850 cm ^-1 . ]
[2] a lamination step of obtaining a polarizing plate by laminating thermoplastic resin films on both sides of a polarizer containing iodine and boron;
and an edge treatment step of contacting the edge of the polarizing plate in a direction parallel to the polarizer transmission axis direction with a treatment liquid at 20° C. or higher for 3 to 150 seconds.
[3] The method according to [2], further comprising an end portion forming step of forming an end portion of the polarizing plate in a direction parallel to the polarizer transmission axis direction by cutting and/or punching the polarizing plate. A method for manufacturing a polarizing plate.
[4] In the polarizing plate, further comprising a surface protecting step of laminating a surface protecting film for a polarizing plate on the surface of the thermoplastic resin film opposite to the side on which the polarizer is arranged, [2]
Or the manufacturing method of the polarizing plate as described in [3].
[5] The method for producing a polarizing plate according to any one of [2] to [4], wherein the treatment liquid contains water.
[6] The method for producing a polarizing plate according to any one of [2] to [5], wherein the treatment liquid is water.
[7] The method for producing a polarizing plate according to any one of [2] to [6], wherein the treatment liquid has a pH of 3 to 9.
[8] A polarizing plate having a thermoplastic resin film on at least one surface of a polarizer containing iodine and boron,
The end portion of the polarizer in the direction parallel to the polarizer transmission axis direction is at the same position in the plane direction as the end portion of the thermoplastic resin film in the direction parallel to the polarizer transmission axis direction, or located outside the
A polarizing plate in which an end portion of the polarizer in a direction parallel to a polarizer transmission axis direction satisfies the following formula (I).
Boric acid cross-linking index ≤ 0.9 (I)
[The boric acid cross-linking index is defined as Raman scattered light intensity at a wavenumber of 780 cm ^-1 /Raman scattered light intensity at a wavenumber of 850 cm ^-1 . ]
[9] a lamination step of obtaining a polarizing plate by laminating a thermoplastic resin film on at least one surface of a polarizer containing iodine and boron;
and an edge treatment step of contacting an edge of the polarizer in a direction parallel to the polarizer transmission axis direction with a treatment liquid at 20° C. or higher for 3 to 150 seconds.

According to the present invention, the polarizer gap is not formed in the end portion of the polarizing plate (especially the end portion in the direction parallel to the transmission axis direction of the polarizer), and after exposure to a high temperature (85° C.), It is possible to provide a polarizing plate having a polarizer that suppresses the occurrence of cracks in a heat shock test in which cooling causes repeated exposure to a low temperature (−40° C.), and a method for producing the same. Further, according to the present invention, light leakage is improved because no polarizer gap is formed.

FIG. 1 is a schematic cross-sectional view showing a polarizing plate according to this embodiment. FIG. 2 is an explanatory diagram for explaining the polarizer that constitutes the polarizing plate according to this embodiment. FIG. 3 is an explanatory view explaining the aspect of the end portion of the polarizing plate in the direction parallel to the polarizer transmission axis direction, and (a) to (e) are included in the scope of the present embodiment. FIG. 11 is an explanatory diagram illustrating a mode of an end portion in a direction parallel to the polarizer transmission axis direction, and (f) is an end portion in a direction parallel to the polarizer transmission axis direction of a polarizing plate outside the scope of this embodiment; It is an explanatory view explaining a mode. FIG. 4 is an explanatory diagram for explaining microscopic Raman spectroscopic analysis for the polarizing plate according to this embodiment. FIG. 5 is a schematic cross-sectional view showing a polarizing plate according to another embodiment.

An embodiment of the present invention (hereinafter also referred to as "this embodiment") 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, the scale of each component is adjusted appropriately to facilitate understanding, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component. In the drawings, similar components are provided with similar reference numerals. X, Y and Z shown in FIGS. 1 and 5 mean three coordinate axes orthogonal to each other. The directions indicated by the XYZ coordinate axes in FIGS. 1 and 5 are common to each figure. In addition, in this specification, "planar view" means viewing the polarizing plate and the polarizer from the thickness direction.

<Polarizing plate>
The polarizing plate according to the present embodiment is a polarizing plate having a thermoplastic resin film on at least one surface of a polarizer containing iodine and boron, preferably a polarizing plate having a thermoplastic resin film on both sides of the polarizer. is. In the polarizing plate according to the present embodiment, the end portion of the polarizer in the direction parallel to the polarizer transmission axis direction is closer than the end portion of at least one of the thermoplastic resin films in the direction parallel to the polarizer transmission axis direction. They are at the same position in the plane direction, or they are located outside in the plane direction. Further, the end portion of the polarizer in the direction parallel to the polarizer transmission axis direction satisfies the following formula (I).
Boric acid cross-linking index ≤ 0.9 (I)
[The boric acid cross-linking index is defined as Raman scattered light intensity at a wavenumber of 780 cm ^-1 /Raman scattered light intensity at a wavenumber of 850 cm ^-1 . ].

FIG. 1 is a schematic cross-sectional view showing a polarizing plate according to this embodiment. As shown in FIG. 1, polarizing plate 1 has thermoplastic resin films (first thermoplastic resin film 3 and second thermoplastic resin film 4) on both sides of polarizer 2 containing iodine and boron. The polarizing plate 1 is formed by laminating thermoplastic resin films (a first thermoplastic resin film 3 and a second thermoplastic resin film 4) on both sides of a polarizer 2 using an adhesive or pressure-sensitive adhesive. . Hereinafter, in this specification, the "first thermoplastic resin film" and the "second thermoplastic resin film" may be collectively referred to as protective films.

As used herein, the term "polarizer" refers to a member that has the function of converting light such as natural light into linearly polarized light. The polarizer has a transmission axis and an absorption axis. The "transmission axis direction" and "absorption axis direction" of the polarizer will be described below with reference to FIG. FIG. 2 is an explanatory diagram for explaining the polarizer that constitutes the polarizing plate according to this embodiment. As shown in FIG. 2, the transmission axis direction (TD direction) of the polarizer is understood as the vibration direction of transmitted light when natural light is transmitted through the polarizer. On the other hand, the absorption axis direction (MD direction) of the polarizer is orthogonal to the transmission axis of the polarizer. In addition, the polarizer may be a stretched film, the absorption axis direction of the polarizer may coincide with the stretching direction (MD direction), and the transmission axis direction of the polarizer may coincide with the width direction (TD direction).

The polarizing plate according to this embodiment has no polarizer gap. That is, in the polarizing plate, the end portion of the polarizer in the direction parallel to the polarizer transmission axis direction is more in the plane direction than the end portion of at least one of the thermoplastic resin films in the direction parallel to the polarizer transmission axis direction. at the same position or on the outside in the plane direction. In the present specification, "the end of the polarizer in the direction parallel to the polarizer transmission axis direction is at the same position in the plane direction as the end of at least one of the thermoplastic resin films in the direction parallel to the polarizer transmission axis direction. or located on the outer side in the plane direction" means excluding the structure of the polarizing plate as shown in FIG. 3(f). That is, in the polarizing plate shown in FIG. 3( f ), the end portion 21 of the polarizer in the direction parallel to the polarizer transmission axis direction is the end portion of the thermoplastic resin film on both sides in the direction parallel to the polarizer transmission axis direction. A polarizer gap portion 2a is formed because it is located on the inner side of 31 and 41 in the plane direction. On the other hand, in the present embodiment, the end portion 21 of the polarizer in the direction parallel to the polarizer transmission axis direction is more likely than the

end portions

31 and 41 of at least one of the thermoplastic resin films in the direction parallel to the polarizer transmission axis direction. The structure is not particularly limited as long as it is located at the same position in the plane direction or located outside in the plane direction. For example, in the end portion 10 of the polarizing plate shown in FIG. It may be located at the same position in the plane direction as the

ends

31 and 41 of the film in the direction parallel to the polarizer transmission axis direction. Further, as shown in FIGS. 3B and 3C, the end portion 21 of the polarizer in the direction parallel to the polarizer transmission axis direction is parallel to the polarizer transmission axis direction of one of the thermoplastic resin films. Even if it is located at the same position in the plane direction as the

ends

31 and 41 in the other direction, and is positioned outside the

ends

31 and 41 in the direction parallel to the polarizer transmission axis direction in the other thermoplastic resin film in the plane direction. good. Furthermore, as shown in FIGS. 3(d) and 3(e), the end portion 21 of the polarizer in the direction parallel to the polarizer transmission axis direction is parallel to the polarizer transmission axis direction of one of the thermoplastic resin films. , and is located outside the

ends

31 and 41 of the other thermoplastic resin film in the direction parallel to the polarizer transmission axis direction in the plane direction. good too. In this specification, as shown in FIGS. 3(d) and 3(e), the end 21 of the polarizer in the direction parallel to the polarizer transmission axis direction and the

ends

31 and 41 of the thermoplastic resin film are When having an inclination, the ends 31 and 41 of the thermoplastic resin film represent the center position in the thickness direction of the thermoplastic resin film, and the end portion 21 of the polarizer represents the center position in the thickness direction of the polarizer as the "polarizer transmission axis. shall be expressed as "the edge in the direction parallel to the direction". In the specification of the present application, the term “plane direction” refers to a direction parallel to the plane of the polarizer 2 .

In the polarizing plate according to this embodiment, the end portion of the polarizer in the direction parallel to the polarizer transmission axis direction satisfies the following formula (I).
Boric acid cross-linking index ≤ 0.9 (I)
[Boric acid crosslinking index=Raman scattered light intensity at wavenumber 780 cm ⁻¹ /Raman scattered light intensity at wavenumber 850 cm ⁻¹ ].

The value of the boric acid cross-linking index may be 0 or more, or may be greater than 0. Also, it is preferably greater than 0 and 0.9 or less, more preferably 0.1 or more and 0.85 or less, and even more preferably 0.15 or more and 0.80 or less. As used herein, the term “boric acid cross-linking index” means an index that indicates how much polyvinyl alcohol molecular chains are cross-linked with boric acid in a polarizer made of a polyvinyl alcohol-based resin film or the like. It can be said that the higher the value of the boric acid cross-linking degree index, the more advanced the boric acid cross-linking between the polyvinyl alcohol molecular chains is in the polarizer, and the polarizer can be provided with the property that iodine escape hardly occurs. On the other hand, if the value of the boric acid cross-linking degree index is too high at the ends of the polarizer (especially the ends parallel to the transmission axis direction of the polarizer), cracks tend to occur in the polarizing plate in the heat shock test. . By satisfying the above formula (I), it is possible to suppress the occurrence of cracks in the polarizing plate in the heat shock test.

In addition, the polarizing plate according to the present embodiment has a boric acid cross-linking index (hereinafter, sometimes referred to as "boric acid cross-linking index (1)") at the end of the polarizer in the direction parallel to the polarizer transmission axis direction. ) and a boric acid cross-linking index (hereinafter sometimes referred to as “boric acid cross-linking index (2)”) at 100 μm inward in the plane direction from the end of the polarizer in the direction parallel to the polarizer transmission axis direction. (Boric acid cross-linking index (1)/Boric acid cross-linking index (2)) is preferably 0.95 or less. The ratio of boric acid cross-linking index (1)/boric acid cross-linking index (2) is more preferably 0.90 or less, and may be 0 or more.

The boric acid cross-linking index can be determined by microscopic Raman spectroscopic analysis. In the microscopic Raman spectroscopic analysis, by using a laser Raman spectrophotometer (trade name: "NRS-5100", manufactured by JASCO Corporation), the Raman scattered light intensity at the wave number of 780 cm ^-1 of the polarizer and the wave number of 850 cm ^-1 , and then dividing the Raman scattered light intensities at these wavenumbers (Raman scattered light intensity at a wavenumber of 780 cm ^-1 /Raman scattered light intensity at a wavenumber of 850 cm ^-1 ) to obtain the boric acid crosslinking degree index can be calculated.

Here, FIG. 4 is an explanatory diagram for explaining microscopic Raman spectroscopic analysis for the polarizing plate according to the present embodiment. As shown in FIG. 4, in the laser Raman spectrophotometer, the laser light X and the absorption axis direction of the polarizer are made to enter at right angles. Note that the laser light X is polarized in the thickness direction of the polarizer. Moreover, let the measurement position of a laser beam be the position of the thickness direction center of a polarizer. In addition, it is preferable to actually machine the cross section of the polarizing plate using a microtome before the Raman spectroscopic measurement. The Raman scattered light intensity at a wavenumber of 780 cm ^-1 means the Raman scattered light intensity caused by the bonding of polyvinyl alcohol and boron, and the Raman scattered light intensity at a wavenumber of 850 cm ^-1 means the Raman scattered light caused by polyvinyl alcohol. means strength.

Various conditions used for the microscopic Raman spectroscopic analysis are as follows.
Excitation wavelength: 532 nm
Grating: 600 l/mm
Slit width: 100×1000 μm
Aperture: φ40 μm
Objective lens: 100x.

The polarizing plate may be in the shape of a long strip or in the shape of a sheet. When the polarizing plate is sheet-shaped, the overall shape of the polarizing plate may be square or square with rounded corners in plan view. A square with rounded corners refers to a shape in which one or more of the corners of the square are curved. A shape in which none of the corners are rounded. Moreover, in this specification, a rectangular shape means a rectangular shape or a square shape. When the polarizing plate has a square shape with rounded corners, one or more of the four corners of the polarizing plate may be rounded. The polarizing plate may have a polygonal, circular, or elliptical overall shape in plan view.

The polarizing plate can also have a deformed portion in plan view. The deformed portion can be formed on at least one of the outer edge portion and the in-plane portion of the polarizing plate. When the polarizing plate has a deformed portion on its outer edge, the shape of the deformed portion may be, for example, a substantially U-shaped or substantially V-shaped convex inward from the outer edge in a plan view of the polarizing plate. Further, when the polarizing plate has a deformed portion in its plane, the deformed portion may be a through hole. Here, in the case where the polarizing plate has a deformed portion on the outer edge, if at least one of the end of the portion of the polarizing plate that is not the deformed portion and the end of the deformed portion satisfies the above formula (I), the present invention It belongs to the scope of the invention. Furthermore, it is more preferable that both the edge of the portion of the polarizing plate that is not the deformed portion and the edge of the deformed portion satisfy the above formula (I). The specific example of the overall shape of the polarizing plate in plan view described above is also applied as an example of the overall shape of the polarizer in the item (Polarizer) described later.

Hereinafter, the polarizing plate according to this embodiment will be described in more detail through its manufacturing method. First, each component of the polarizing plate will be described.

(Polarizer)
Polarizers contain boric acid and iodine. Specifically, 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 in a uniaxially stretched polyvinyl alcohol resin film and the polyvinyl alcohol molecular chains are crosslinked with boric acid. Such a polarizer can be obtained, for example, by carrying out a polarizer manufacturing process in a method for manufacturing a polarizing plate, which will be described later.

The thickness of the polarizer may be, for example, 3 μm or more and 30 μm or less, 5 μm or more and 25 μm or less, 15 μm or more and 25 μm or less, or 16 μm or more and 24 μm or less. The thicker the polarizer, the greater the contraction force of the polarizer due to temperature changes. For example, when the polarizer is stored in a harsh environment such as a heat shock test, cracks tend to occur in the polarizer. It is in. Further, when the polarizing plate is stored in a high-temperature environment, the polarizing plate tends to be greatly deformed. According to the present embodiment, even if the polarizer is thick and easily shrinkable, cracking of the polarizer in the heat shock test and deformation of the polarizing plate in the heat resistance test tend to be suppressed. .

(Thermoplastic resin film)
Since the thermoplastic resin film physically and chemically protects the polarizer, it can be a protective film for the polarizer. The thermoplastic resin film is preferably made of a translucent thermoplastic resin. Resins constituting the thermoplastic resin film include, for example, linear polyolefin resins, cyclic olefin polymer resins (COP resins), cellulose ester resins, polyester resins, polycarbonate resins, (meth)acrylic resins, polystyrene. based resins, or mixtures or copolymers thereof.

As used herein, the term “protective film” refers to a thermoplastic resin film that overlaps a polarizer directly or indirectly via a pressure-sensitive adhesive or adhesive, and after bonding the polarizing plate to a display device. is defined as the film that remains laminated to protect the polarizer. On the other hand, the "surface protective film for polarizing plate" described later is a film placed on the outermost surface of one of the polarizing plates, and is defined as a film that is peeled off after the polarizing plate is attached to the display device. shall be

As shown in FIG. 1, the first thermoplastic resin film 3 and the second thermoplastic resin film 4 may be films formed from the same type of resin, or films formed from different types of resin. may Also, the first thermoplastic resin film 3 and the second thermoplastic resin film 4 may be the same or different in thickness, retardation properties, optical properties, mechanical properties, and the like.

When the resin constituting the thermoplastic resin film is a chain polyolefin resin, the chain polyolefin resin may be, for example, a homopolymer of chain olefin such as polyethylene resin or polypropylene resin. The chain polyolefin-based resin may be a copolymer composed of two or more chain olefins.

When the resin constituting the thermoplastic resin film is a cyclic olefin polymer-based resin (cyclic polyolefin-based resin), the cyclic olefin polymer-based resin is, for example, a ring-opening (co)polymer of a cyclic olefin, or an addition polymerization of a cyclic olefin. May be coalesced. The cyclic olefin polymer-based resin may be, for example, a copolymer (for example, a random copolymer) of a cyclic olefin and a chain olefin. A chain olefin constituting the copolymer may be, for example, ethylene or propylene. The cyclic olefin polymer-based resin may be a graft polymer modified with an unsaturated carboxylic acid or a derivative thereof, or a hydride thereof. The cyclic olefin polymer-based resin may be, for example, a norbornene-based resin using norbornene-based monomers such as norbornene or polycyclic norbornene-based monomers.

When the resin constituting the thermoplastic resin film is a cellulose ester resin, the cellulose ester resin is, for example, cellulose triacetate (triacetyl cellulose (TAC)), cellulose diacetate, cellulose tripropionate, or cellulose dipropionate. It's okay. Copolymers of these may also be used. A cellulose ester-based resin in which a portion of hydroxyl groups is modified with other substituents may also be used.

A polyester-based resin other than a cellulose ester-based resin may be used as the resin that constitutes the thermoplastic resin film. The polyester-based resin may be, for example, a polycondensate of a polyhydric carboxylic acid or its derivative and a polyhydric alcohol. A polycarboxylic acid or derivative thereof may be a dicarboxylic acid or derivative thereof. Polycarboxylic acids or derivatives thereof can be, for example, terephthalic acid, isophthalic acid, dimethyl terephthalate, or dimethyl naphthalenedicarboxylate. Polyhydric alcohols may be, for example, diols. Polyhydric alcohols 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, polycyclohexanedimethylterephthalate, or polycyclohexanedimethylnaphthalate. .

When the resin constituting the thermoplastic resin film is a polycarbonate-based resin, the polycarbonate-based resin is a polymer in which polymerized units (monomers) are bonded via carbonate groups. The polycarbonate-based resin may be a modified polycarbonate having a modified polymer backbone, or may be a copolymerized polycarbonate.

When the resin constituting the thermoplastic resin film is a (meth)acrylic resin, the (meth)acrylic resin is, for example, poly(meth)acrylic acid ester (e.g., polymethyl methacrylate (PMMA)); methacrylic acid Methyl-(meth)acrylic acid copolymer; Methyl methacrylate-(meth)acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer; Methyl (meth)acrylate-styrene Copolymer (e.g., MS resin); copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid norbornyl copolymers, etc.).

Each of the first thermoplastic resin film and the second thermoplastic resin film is selected from the group consisting of lubricants, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidants. may contain at least one additive. Each of the first thermoplastic resin film and the second thermoplastic resin film has a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, and a charging A surface treatment layer (coating layer) such as an antifouling layer, an antifouling layer, and a conductive layer may be provided.

The thickness of the first thermoplastic resin film may be, for example, 5 μm or more and 110 μm or less, or 10 μm or more and 100 μm or less. The thickness of the second thermoplastic resin film may also be, for example, 5 μm or more and 110 μm or less, or 10 μm or more and 100 μm or less.

The first thermoplastic resin film and the second thermoplastic resin film may have retardation values. 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 thermoplastic resin film is preferably attached to the polarizer via an adhesive layer. The second thermoplastic resin film is also preferably bonded to the polarizer via an adhesive layer. The adhesive layer may contain a polyvinyl alcohol-based resin or the like. The adhesive layer may contain an active energy ray-curable resin, which will be described later.

An active energy ray-curable resin is a resin that cures when exposed to active energy rays. The active energy rays may be, for example, ultraviolet rays, 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 contain a cationic 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 for initiating the curing reaction of the curable compound.

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

If necessary, the active energy ray-curable resin may contain a cationic polymerization accelerator, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow control agent, a plasticizer, and an antifoaming agent. agents, antistatic agents, leveling agents, solvents, or the like.

The thickness of the adhesive layer is usually 0.01-10 μm. When the adhesive layer contains an active energy ray-curable resin, the thickness of the adhesive layer is preferably 0.1 to 8 μm, and when the adhesive layer contains a polyvinyl alcohol-based resin, the thickness of the adhesive layer is preferably 0.03 to 1 μm.

(Surface protective film for polarizing plate)
FIG. 5 is a schematic cross-sectional view showing a polarizing plate according to another embodiment. In the polarizing plate according to this embodiment, as shown in FIG. 5, a surface protective film for polarizing plate is further provided on the surface of the first thermoplastic resin film 3 or the second thermoplastic resin film 4 opposite to the polarizer 2. 5 may be provided. The polarizing plate surface protective film 5 is usually composed of a base film and an adhesive layer laminated thereon. , the pressure-sensitive adhesive layer and the substrate film are integrated. The base film is composed of, for example, polyolefin resins such as polyethylene resins and polypropylene resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate resins, and thermoplastic resins such as (meth)acrylic resins. be able to. The thickness of the polarizing plate surface protective film 5 may be, for example, 5 μm or more and 200 μm or less. The polarizing plate surface protective film 5 is a film used for the purpose of protecting the surface of the polarizing plate from scratches and stains. removed.

The polarizing plate may further include an adhesive layer on the surface of the first thermoplastic resin film 3 or the second thermoplastic resin film 4 opposite to the polarizer 2 . When the polarizing plate surface protective film 5 is provided, the adhesive layer is usually laminated on a thermoplastic resin film on which the polarizing plate surface protective film 5 is not laminated. For the purpose of protecting the adhesive layer, a release film may be laminated on the surface of the adhesive layer opposite to the thermoplastic resin film.

<Method for manufacturing polarizing plate>
The method for producing a polarizing plate according to the present embodiment includes a lamination step of obtaining a polarizing plate by laminating a thermoplastic resin film on at least one surface (preferably both surfaces) of a polarizer containing iodine and boron; An edge treatment step is included in which the edge of the plate in the direction parallel to the transmission axis direction of the polarizer is brought into contact with a treatment liquid at 20° C. or higher for 3 to 150 seconds. By the method for manufacturing a polarizing plate having such characteristics, iodine leakage is less likely to occur at the end portion in the direction parallel to the transmission axis direction of the polarizer, curling is suppressed, and cracking is suppressed in a heat shock test. A polarizing plate with a polarizer can be obtained.

The method for manufacturing the polarizing plate can include a polarizer manufacturing step (a step of manufacturing a polarizer containing boric acid and iodine) in the lamination step. The method for manufacturing the polarizing plate may further include an end portion forming step of forming an end portion of the polarizing plate in a direction parallel to the polarizer transmission axis direction by cutting and/or punching the polarizing plate. can. That is, the end portion of the polarizing plate in the direction parallel to the polarizer transmission axis direction may be formed by cutting and/or punching the polarizing plate. The edge forming step can be performed between the stacking step and the edge processing step.

The method for producing a polarizing plate further includes a surface protection step of laminating a surface protection film for a polarizing plate on the surface of the thermoplastic resin film opposite to the side on which the polarizer is arranged in the polarizing plate. can be done. The surface protection step may be performed before the lamination step or after the lamination step. Further, in the method for manufacturing the polarizing plate, the lamination step may be performed after the edge processing step. When the lamination step is performed after the edge treatment step, only the polarizer is subjected to contact with the treatment liquid at 20° C. or higher for 3 to 150 seconds in the edge treatment step. One aspect of the method for manufacturing a polarizing plate according to this embodiment will be specifically described below.

(Lamination process)
(1) Polarizer manufacturing process A polarizer manufacturing process is a process of manufacturing a polarizer containing boric acid and iodine. Specifically, a polarizer containing boric acid and iodine can be produced, for example, by subjecting a polyvinyl alcohol-based resin film (PVA film) to stretching treatment, dyeing treatment and cross-linking treatment. Stretching treatment, dyeing treatment and cross-linking treatment can be performed by known methods.

As the polyvinyl alcohol-based resin, saponified polyvinyl acetate-based resin can be used. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol resin may be in the range of 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more. The polyvinyl alcohol-based resin may be modified polyvinyl alcohol that is partially modified, for example, the polyvinyl alcohol-based resin may be modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; ; modified with unsaturated carboxylic acid alkyl esters and acrylamides; The average degree of polymerization of the polyvinyl alcohol resin is preferably 100-10000, more preferably 1500-8000, still more preferably 2000-5000.

For example, a polarizer is made by uniaxially stretching a raw film made of a polyvinyl alcohol resin, swelling it with water (swelling process), dyeing it with a dichroic dye (dyeing process), and cross-linking it with an aqueous boric acid solution ( crosslinking step), washing with water (washing step), and finally drying (drying step).

The uniaxial stretching of the polyvinyl alcohol resin film may be either dry stretching in air or wet stretching in a bath, or both. In the wet stretching, for example, the polyvinyl alcohol resin film may be stretched while being immersed in a treatment bath during and/or before and/or after the dyeing step and/or the cross-linking step. The final draw ratio of the polyvinyl alcohol resin film is usually about 4 to 8 times.

In the swelling process, the polyvinyl alcohol resin film is swollen with water. The swelling treatment can be performed by immersing the polyvinyl alcohol-based resin film in water. The water temperature is, for example, 10 to 70° C., and the immersion time is, for example, about 10 to 600 seconds.

In the dyeing process, the polyvinyl alcohol-based resin film is dyed with a dichroic dye, and the dichroic dye is adsorbed on the film. For the dyeing treatment, for example, a polyvinyl alcohol-based resin film may be immersed in an aqueous solution containing a dichroic dye. Specifically, iodine or dichroic dyes are used as dichroic dyes.

When iodine is used as a dichroic dye, a method of dyeing by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually adopted. The content of iodine in the aqueous solution can usually be about 0.003 to 1 part by mass per 100 parts by mass of water. The content of potassium iodide in the aqueous solution is usually 0.1 per 100 parts by mass of water.
It is about 20 parts by mass. The temperature of this aqueous solution is usually about 10 to 45° C., and the immersion time is usually about 30 to 600 seconds.

The cross-linking step is performed, for example, by immersing the dyed polyvinyl alcohol-based resin film in an aqueous boric acid solution. The content of boric acid in the boric acid aqueous solution is usually about 1 to 15 parts by mass, preferably 2 to 10 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, the boric acid aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 1 to 20 parts by mass, preferably 5 to 15 parts by mass, per 100 parts by mass of water. The immersion time of the film in the aqueous boric acid solution is usually about 10 to 600 seconds, preferably 20 seconds or more, and preferably 300 seconds or less. The temperature of the boric acid aqueous solution is usually 50°C or higher, preferably 50 to 70°C.

A polyvinyl alcohol-based resin film that has undergone a cross-linking process is usually subjected to a washing process with water. The washing treatment is performed, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in water. The temperature of water in the cleaning treatment is usually about 5 to 40° C., and the immersion time is usually about 2 to 120 seconds.

After that, a polarizer is obtained through a drying process. Drying is usually performed using a hot air dryer or a far-infrared heater. The drying temperature is usually 40-100° C., and the drying time is usually about 30-600 seconds.

(2) Lamination step The lamination step is a step of obtaining a polarizing plate by laminating a thermoplastic resin film on at least one side (preferably both sides) of the polarizer. Specifically, a polarizing plate (hereinafter, a polarizing plate that has not undergone the edge treatment step is also referred to as an “untreated polarizing plate” for convenience of explanation) by stacking a polarizer and a thermoplastic resin film and bonding them to each other. described) can be manufactured. The polarizer and the thermoplastic resin film may be long strips. The thermoplastic resin film can be attached to a polarizer via an adhesive layer.

In the lamination step, in order to improve the adhesiveness between the polarizer and the thermoplastic resin film, prior to laminating the polarizer and the thermoplastic resin film, the bonding surface of the polarizer and/or the thermoplastic resin film is may be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation treatment, primer coating treatment, saponification treatment and the like.

(3) Surface protection step The surface protection step is a step of laminating a surface protection film for a polarizing plate on the surface of the polarizing plate opposite to the side on which the polarizer of the thermoplastic resin film is arranged. The surface protection step may be performed before the edge forming step of forming the edge of the polarizing plate in the direction parallel to the polarizer transmission axis direction, or may be performed after the edge forming step and the edge treatment step. However, it can be preferably performed after the lamination step and before the edge formation step.

(End forming step)
In the edge forming step, the polarizer of the polarizing plate is formed by cutting and/or punching the untreated polarizing plate in order to form an edge in the direction parallel to the polarizer transmission axis direction in the untreated polarizing plate. This is the step of forming the end portion in the direction parallel to the transmission axis direction. This process can also adjust the dimensions of the untreated polarizing plate to dimensions that are easy to process. Specifically, cutting and/or punching can be performed by using a cutting blade, using a punching blade, or by irradiating laser light. The laser light may be a _CO2 laser. Thereby, a long untreated polarizing plate can be processed into a sheet-like untreated polarizing plate. In the edge forming step, the untreated polarizing plate can be cut and/or punched singly or in a state of being stacked. After cutting, the cut surface of the polarizing plate may be finished by cutting.

(End processing process)
The edge treatment step is a step of bringing the edge of the polarizing plate in the direction parallel to the polarizer transmission axis direction into contact with a treatment liquid at 20° C. or higher for 3 to 150 seconds. By the edge treatment step, the edge of the polarizer constituting the polarizing plate in the direction parallel to the polarizer transmission axis direction can satisfy the value of the boric acid cross-linking degree index of 0.9 or less, and the heat shock can be reduced. It is possible to obtain a polarizing plate having a polarizer that suppresses the occurrence of cracks in a test.

The edge treatment step may be performed on one untreated polarizing plate, or may be performed in a state where a plurality of untreated polarizing plates are laminated. When performing the edge treatment on a plurality of sheets, for example, 5 or more and 3000 or less untreated polarizing plates can be superimposed. The number of untreated polarizing plates to be stacked is preferably 7 or more, for example, 2000 or 1000. When performing edge treatment on a plurality of stacked untreated polarizing plates, it is preferable to press the untreated polarizing plates from the top and bottom surfaces of the stacked polarizing plates and/or from the left and right side portions. When performing the edge treatment on one untreated polarizing plate, the edge treatment may be performed on the untreated polarizing plate only, or the untreated polarizing plate is attached to the substrate and these are attached. In this state, the end portion of the polarizing plate in the direction parallel to the transmission axis direction of the polarizer may be treated.

In the edge treatment step, the treatment liquid preferably contains water. More preferably, the treatment liquid may be water, and the treatment liquid may be an aqueous boric acid solution. Further, the pH of the treatment liquid is preferably 3-9, more preferably 4-8, and even more preferably 5-7. Moreover, the treatment liquid may contain a water-soluble resin or a water-dispersible resin. Examples of water-soluble resins or water-dispersible resins include (meth)acrylic resins; polyvinyl alcohol-based resins; polyvinyl acetal-based resins; ethylene-vinyl alcohol copolymer-based resins; polyvinylpyrrolidone-based resins; melamine-based resin; urea-based resin; polyamide-based resin; polyester-based resin; polyurethane-based resin; cellulose-based resin; Among these, hydroxyl group-containing resins such as (meth)acrylic resins; polyvinyl alcohol resins; and polyvinyl acetal resins are preferred, and polyvinyl alcohol resins are more preferred.

In the edge treatment step, the temperature of the treatment liquid that is brought into contact with the edge of the polarizing plate in the direction parallel to the polarizer transmission axis direction is 20° C. or higher as described above. From the viewpoint of appropriately controlling the boric acid cross-linking degree index, the temperature of the treatment liquid is preferably 25° C. or higher and 90° C. or lower.
C. to 85.degree. C., more preferably 40.degree. C. to 85.degree. C., and particularly preferably 55.degree.

In the edge treatment step, the treatment liquid is brought into contact with the edge of the polarizing plate in the direction parallel to the transmission axis direction of the polarizer for 3 to 150 seconds as described above. The duration of the treatment liquid in contact with the edge suppresses iodine removal at the edge in the direction parallel to the polarizer transmission axis direction, suppresses curling of the polarizing plate, and reduces the optical performance of the polarizer in the polarizing plate. From the viewpoint of suppressing (decrease in polarization degree, hue change, etc.) and appropriately controlling the boric acid cross-linking degree index, the time is preferably within 140 seconds, more preferably within 120 seconds, A time of 30 seconds or less is particularly preferred. The time for which the treatment liquid is brought into contact with the edge may be 5 seconds or longer.

The range of the amount of iodine missing at the end may be 0 μm or more, or may be 0.1 μm or more. From the viewpoint of deterioration in optical performance and appearance quality at the ends, the upper limit of the amount of iodine removed at the ends is preferably 100 μm or less, preferably 50 μm or less, more preferably 30 μm or less, and particularly less than 19 μm. preferable. As used herein, the term “iodine escape amount” means the distance (μm) of light escape from the edge of the polarizer in the direction parallel to the polarizer transmission axis direction.

As a method of bringing the end portion of the polarizing plate in the direction parallel to the polarizer transmission axis direction into contact with the treatment liquid, for example, all or part of the untreated polarizing plate (at least parallel to the polarizer transmission axis direction of the polarizing plate) All or part of the untreated polarizing plate (at least the end in the direction parallel to the polarizer transmission axis direction of the polarizing plate) is immersed in a tank containing the treatment liquid. A method of spraying a part of the untreated polarizing plate (at least the end of the polarizing plate in a direction parallel to the polarizer transmission axis direction), a part of the untreated polarizing plate (at least the polarizing plate and a method of contacting an article (a fibrous material such as a cloth, a sponge, etc.) in which the treatment liquid is immersed. Alternatively, when the lamination step is performed after the edge treatment step, all or part of the polarizer containing iodine and boron (at least the edge of the polarizer in the direction parallel to the polarizer transmission axis direction) , a method of immersing in a bath containing a treatment liquid, a method of spraying the treatment liquid on all or part of the polarizer (at least the end of the polarizer in the direction parallel to the polarizer transmission axis direction), and the use of the polarizer. A method of contacting a portion (at least the end portion of the polarizer in the direction parallel to the transmission axis direction of the polarizer) with an article (fibrous material such as cloth, sponge, etc.) immersed in the treatment liquid may be used.

When the treatment liquid is an aqueous boric acid solution, the polarizing plate can be washed with water after the polarizing plate is brought into contact with the treatment liquid. Water washing can be performed, for example, by a method of immersing the polarizing plate in a tank containing water and/or a method of spraying water on the polarizing plate. By the above method, the polarizing plate according to this embodiment can be obtained.

(Drying process)
The method for manufacturing a polarizing plate according to the present embodiment may have a drying treatment step after the edge treatment step described above. In the drying treatment step, the drying temperature may be 20° C. or higher, 23° C. or higher, or 100° C. or lower. The drying treatment step may be performed on one polarizing plate, or may be performed with a plurality of polarizing plates laminated. Further, when the edge processing step is performed while the untreated polarizing plate is bonded to the substrate, the drying treatment may be performed in the bonded state.

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

The present invention will be described in more detail below with reference to examples. Unless otherwise specified, "%" and "parts" in the examples are % by mass and parts by mass.

<Example 1>
(Production Example 1: Polarizer production process)
A long polyvinyl alcohol film (average degree of polymerization: about 2400, degree of saponification: 99.9 mol% or more, thickness: 60 µm) was continuously conveyed and kept in a swelling bath made of pure water at 20°C for a residence time of 31 seconds. (swelling step). After that, the film pulled out from the swelling bath was immersed in a 30° C. dyeing bath containing iodine with a potassium iodide/water ratio of 2/100 (mass ratio) for a residence time of 122 seconds (dyeing step). The film pulled out from the dye bath was then immersed in a 56° C. crosslinking bath containing potassium iodide/boric acid/water at a ratio of 12/4.1/100 (weight ratio) for a residence time of 70 seconds, followed by It was immersed in a 40° C. crosslinking bath containing potassium chloride/boric acid/water at a ratio of 9/2.9/100 (mass ratio) for a residence time of 13 seconds (crosslinking step). In the dyeing process and the cross-linking process, longitudinal uniaxial stretching was performed by stretching between rolls in a bath. The total draw ratio based on the raw film was 5.5 times. Next, after the film pulled out from the cross-linking bath is immersed in a washing bath made of pure water at 5°C for a residence time of 3 seconds (washing step), it is introduced into a drying oven at 80°C for a residence time of 190 seconds for drying. Thus (drying step), a polarizer was obtained. The thickness of the polarizer thus obtained was 23.6 μm.

(Production Example 2: Lamination process)
As a first thermoplastic resin film, a protective film (trade name: “TG60UL”, manufactured by FUJIFILM Corporation) made of triacetyl cellulose resin and having a thickness of 60 μm was prepared. Further, a retardation film (trade name: “KC3XR-1”, manufactured by Konica Minolta, Inc.) made of triacetyl cellulose resin and having a thickness of 40 μm was prepared as a second thermoplastic resin film.

One surface of each of the protective film and the retardation film was subjected to corona treatment, and an epoxy-based UV-curable adhesive was applied to the corona-treated surface using an adhesive coating device. Next, the polarizer obtained in Production Example 1 was superimposed on the coating layer surface, followed by pressing and bonding using a bonding roll to obtain a polarizing plate precursor. This polarizing plate precursor was irradiated with an ultraviolet irradiation device with a belt conveyor from the side of the retardation film (for ultraviolet lamps, product name: "D Bulb", manufactured by Fusion UV Systems Co., Ltd. is used), and the cumulative amount of light is 200 mJ/. The polarizing plate was obtained by curing the adhesive by irradiating ultraviolet rays so as to obtain cm ² (UVB). On the other hand, on the protective film side of the polarizing plate, a surface protective film for polarizing plate (a film having an acrylic pressure-sensitive adhesive layer on one side of a PET substrate, product name "AY-638", manufactured by Fujimori Industry Co., Ltd.) is attached to the above polarizing plate. Laminated. As described above, a polarizing plate with a surface protective film for a polarizing plate having a surface protective film for a polarizing plate/protective film/adhesive layer/polarizer/adhesive layer/retardation film was obtained.

Next, a release film-attached pressure-sensitive adhesive layer having an acrylic pressure-sensitive adhesive layer (thickness of 20 µm) on the release-treated surface of the release film was prepared. A first laminate was obtained by laminating the pressure-sensitive adhesive layer with a release film on the retardation film side of the polarizing plate with a surface protective film for a polarizing plate after corona-treating the surface of the phase shifter film. The first laminate has a structure of surface protective film for polarizing plate/protective film/adhesive layer/polarizer/adhesive layer/retardation film/adhesive layer/release film.

(Manufacturing Example 3: Edge forming step)
The first laminate obtained in Production Example 2 was cut into sheets using a cutter. Then, after stacking a plurality of the sheets and polishing the outer periphery, the sheets were separated and collected to form a second laminate of 217 mm (MD direction) x 164 mm (TD direction). Here, the TD direction means a direction orthogonal to the stretching direction (MD direction) of the polarizer. The second laminate obtained here is called an untreated polarizing plate with a surface protective film for a polarizing plate.

(Manufacturing Example 4: Edge processing step)
A third laminate is formed by stacking seven second laminates obtained in Production Example 3 above, and the front and back surfaces of the third laminate are made of non-alkali glass (trade name: "Eagle") with a thickness of 0.7 mm. XG", manufactured by Corning) and fixed with a clip. Furthermore, the end portion including one side in the TD direction of the third laminate (the end portion in the direction parallel to the transmission axis direction of the polarizer) was immersed in water (pure water) at a temperature of 60° C. for 5 seconds. The immersion was performed by immersing the edge of the third laminate to a depth of 2 cm from the water surface. Then, the remaining three sides of the third laminate were also immersed in water (pure water) at a temperature of 60° C. for 5 seconds in the same manner to obtain a fourth laminate. After that, the fourth laminate was dried by leaving it at room temperature for one day while holding it with non-alkali glass and fixing it with a clip. After the fourth laminate was dried, the alkali-free glass and the clip were removed from the fourth laminate, seven polarizing plates were separated and collected, and a fifth laminate was obtained. As described above, a laminate (fifth laminate) including the polarizing plate of Example 1 was produced. The end of the manufactured fifth laminate in the direction parallel to the polarizer transmission axis direction is observed with a laser microscope, and the end of the polarizer in the direction parallel to the polarizer transmission axis direction is the thermoplastic resin film on both sides. It was confirmed that the end portion in the direction parallel to the transmission axis direction of the polarizer was at the same position in the surface direction.

<Example 2>
In the above production example 4 (end treatment step), the end including one side in the TD direction of the third laminate and the remaining three sides were immersed in water at a temperature of 80 ° C. (pure water) for 5 seconds. A laminate including the polarizing plate of Example 2 (fifth laminate) was produced in the same manner as in Example 1. The end of the manufactured fifth laminate in the direction parallel to the polarizer transmission axis direction is observed with a laser microscope, and the end of the polarizer in the direction parallel to the polarizer transmission axis direction is the thermoplastic resin film on both sides. It was confirmed that the end portion in the direction parallel to the transmission axis direction of the polarizer was at the same position in the surface direction.

<Example 3>
In the above Production Example 4 (end portion treatment step), the end portion including one side in the TD direction of the third laminate and the remaining three sides were immersed in water at a temperature of 50 ° C. (pure water) for 5 seconds. A laminate (fifth laminate) containing the polarizing plate of Example 3 was produced in the same manner as in Example 1. The end of the manufactured fifth laminate in the direction parallel to the polarizer transmission axis direction is observed with a laser microscope, and the end of the polarizer in the direction parallel to the polarizer transmission axis direction is the thermoplastic resin film on both sides. It was confirmed that the end portion in the direction parallel to the transmission axis direction of the polarizer was at the same position in the surface direction.

<Comparative Example 1>
In the above production example 4 (end portion treatment step), the end portion including one side in the TD direction of the third laminate and the remaining three sides were immersed in water (pure water) at a temperature of 80 ° C. for 16 minutes. A laminate including the polarizing plate of Comparative Example 1 (fifth laminate) was produced in the same manner as in Comparative Example 1. The end of the manufactured fifth laminate in the direction parallel to the polarizer transmission axis direction was observed with a laser microscope, and the in-plane inner side 250 μm from the end of the polarizer (protective film) in the direction parallel to the polarizer transmission axis direction. It was confirmed that the polarizer did not exist until the polarizer and that there was a polarizer void.

(1) Heat shock test (HS test)
A plurality of fifth laminates each including the polarizing plate of each of the examples and comparative examples described above were prepared, and a heat shock test was performed on the fifth laminates according to the following procedure.

First, the release film is peeled off from the fifth laminate, and a non-alkaline glass (trade name: “Eagle XG”, manufactured by Corning Incorporated) with a thickness of 0.7 mm is applied to the peeling surface of the fifth laminate using a laminator. pasted together. Subsequently, the fifth laminate to which the alkali-free glass was bonded was autoclaved (at a temperature of 50°C and a pressure of 5 kgf/cm ² (490.3 kPa) for 20 minutes) to obtain a polarizing plate surface. A sample for HS test evaluation of the fifth laminate was obtained by peeling off the protective film and then storing for one day in an environment with a temperature of 23° C. and a relative humidity of 55%.

A heat shock (HS ) was tested. After the test, it was visually observed whether or not a crack occurred at the end portion of the polarizer in the direction parallel to the polarizer transmission axis direction in the HS test evaluation sample. The number of HS test evaluation samples having cracks at the edges of the plurality of HS test evaluation samples subjected to the HS test was determined as the defective sample rate (%). A defective sample occurrence rate (%) of 35% or less can be evaluated as good. Table 1 shows the results.

(2) Measurement of Curl Amount A fifth laminate including the polarizing plate of each of the examples and comparative examples described above was prepared, and the amount of curl was measured for the fifth laminate. The amount of curl is such that the rectangular sheet of the fifth laminate (217 mm (MD direction) × 164 mm (TD direction)) is placed on a horizontal table, and the separate film is on the lower side (the side that contacts the table). Then, the height from the table to the four vertexes and the midpoints of the four sides of the sheet body was measured with a ruler. The curl amount (mm) was obtained by averaging the eight values obtained for each sheet. The curl amount (mm) can be evaluated to be better as the value is smaller. Table 1 shows the results.

(3) Appearance Evaluation Seven sheets of the fifth laminate including the polarizing plates of each of the Examples and Comparative Examples described above were visually confirmed and evaluated according to the following criteria. Table 1 shows the results.
[Evaluation criteria]
Good: No lifting or peeling is observed between the polarizing plate surface protective film and the protective film (thermoplastic resin film) for all seven sheets.
not good: Lifting or peeling is observed between the polarizing plate surface protective film and the protective film (thermoplastic resin film), even if only one.

(4) Measurement of triggering force of surface protective film for polarizing plate The pulling force of the surface protective film for polarizing plate was measured according to the following procedure. First, five test pieces of 50 mm (MD direction)×25 mm (TD direction) were cut out from the fifth laminate. The test piece was cut so that one side of the test piece in the TD direction was the edge-treated side.

Next, the separate film was peeled off from the above test piece, and a 0.7 mm-thick alkali-free glass (trade name: "Eagle XG", manufactured by Corning) was laminated to the peeled surface of the test piece using a laminator. At the same time, a release paper was attached to the non-alkali glass. At that time, the release paper and the test piece were bonded to the non-alkali glass so that the edge of the test piece up to 1 mm inside from the edge-treated side was positioned on the release paper. Furthermore, the area from the edge-treated side of the test piece including the above edge to the inner side of 5 mm was covered with cellophane tape (manufactured by Nichiban Co., Ltd.) with a width of 25 mm, and the long side of the test piece and the long side of the cellophane tape They were pasted so as to form a straight line, thereby preparing a sample for measuring the pulling force.

By using an autograph (product name (product number): "AGS-50NX", manufactured by Shimadzu Corporation) on the above-mentioned sample for measuring the triggering force, under an environment of a temperature of 23 ° C. and a relative humidity of 55%, the peel width: 25 mm, a peel angle of 180°, and a peel speed of 300 mm/min were used to measure the pulling force. In this case, one grip portion of the autograph gripped the non-alkali glass, and the other grip portion gripped the cellophane tape.

In the measurement of the triggering force, the maximum value of the peeling force measured when the surface protective film for polarizing plate was peeled off from the protective film was regarded as the triggering force. The triggering force (N/25 mm) was the average of the values obtained from five samples for measuring the triggering force. A triggering force (N/25 mm) of 0.1 or more can be evaluated as good. If the lifting force is too high, it will be difficult to peel off, and if it is less than 0.1, peeling will occur in an undesired step during the manufacturing process, and the protective function for the polarizing plate cannot be achieved, which is not preferable. Table 1 shows the results.

(5) Measurement of iodine removal amount Five fifth laminates each including the polarizing plate of each of the examples and comparative examples described above are prepared, and the fifth laminate is subjected to the following procedure to measure the polarizer transmission through the polarizer. The amount of iodine released at the end in the direction parallel to the axial direction was measured.

First, the separate film was peeled off from the fifth laminate, and a 0.7 mm-thick alkali-free glass (trade name: "Eagle XG", manufactured by Corning) was attached to the peeling surface of the fifth laminate using a laminator. Matched. Subsequently, the polarizing plate surface protective film was peeled off to obtain a sample for evaluating the amount of iodine removed from the fifth laminate.

Next, the sample for evaluating the amount of iodine removed is placed on a polarizing plate for inspection in a crossed Nicols state, and a light source is irradiated from the back of the sample for evaluating the amount of iodine removed, so that the polarizer transmission axis direction of each sample The presence or absence of light leakage at the end in the direction parallel to . Furthermore, by observing the end of the sample for evaluating the amount of iodine loss that has passed through with a digital microscope (trade name (product number): “VHX-1000”, manufactured by Keyence Corporation), the polarizer transmission in the sample The distance (μm) of light leakage from the end in the direction parallel to the axial direction was specified, and this was determined as the iodine escape amount. It can be evaluated that the larger the distance (μm), the larger the amount of iodine escaped, and thus the smaller the distance (μm), the better the evaluation. The amount of iodine removed was the average value of the distances obtained from the five samples for evaluating the amount of iodine removed. Table 1 shows the results. In Table 1, the value of the iodine escape amount (426 μm) in Comparative Example 1 indicates the amount of light escape from the edge of the polarizing plate. As described above, in Comparative Example 1, since there is no polarizer up to 250 μm inside the plane from the end of the polarizing plate (protective film) in the direction parallel to the polarizer transmission axis direction, the actual amount of iodine missing in the polarizer is 176 μm.

(6) Calculation of boric acid cross-linking degree index Five fifth laminates each containing the polarizing plate of each of the examples and comparative examples described above were prepared, and the fifth laminate was subjected to the above-described method for the polarizer. Boric acid cross-linking degree index (boric acid cross-linking degree index (1)) at the end in the direction parallel to the polarizer transmission axis direction, and the plane direction from the end of the polarizer in the direction parallel to the polarizer transmission axis direction Boric acid cross-linking index (boric acid cross-linking index (2)) at inner 100 μm, and ratio of boric acid cross-linking index (1) to boric acid cross-linking index (2) (boric acid cross-linking index (1) / boric acid cross-linking degree index (2)) was determined. The boric acid cross-linking degree index was the average value of the values obtained from the five fifth laminates. Table 1 shows the results.

<Discussion>
It is understood that the polarizing plates of Examples 1 to 3 are inhibited from cracking at the edges in the direction parallel to the transmission axis direction of the polarizer in the heat shock test. Further, the polarizing plates of Examples 1 to 3 are less prone to iodine loss and have good visibility. In addition, the polarizing plates of Examples 1 to 3 are suppressed from curling, and the surface protective film for polarizing plate has a good curling force.

On the other hand, in the polarizing plate of Comparative Example 1, cracks were suppressed at the edges in the direction parallel to the transmission axis of the polarizer in the heat shock test, but voids were present in the polarizer. In addition, iodine loss occurred, curling was likely to occur, and the curling force of the surface protective film for polarizing plate was lowered.

1 polarizing plate, 2 polarizer, 2a polarizer void, 3 first thermoplastic resin film, 4 second thermoplastic resin film, 5 surface protective film for polarizing plate, 10 parallel to the polarizer transmission axis direction of the polarizing plate 21 end of the polarizer in the direction parallel to the polarizer transmission axis direction, 31, 41 end of the thermoplastic resin film in the direction parallel to the polarizer transmission axis direction, TD the polarizer transmission axis direction , MD: absorption axis direction of polarizer, X: laser light.

Claims

A polarizing plate having thermoplastic resin films on both sides of a polarizer containing iodine and boron,
Is the end of the polarizer in the direction parallel to the polarizer transmission axis direction the same position in the plane direction as the end of at least one of the thermoplastic resin films in the direction parallel to the polarizer transmission axis direction? Or located on the outside in the plane direction,
A polarizing plate in which an end portion of the polarizer in a direction parallel to a polarizer transmission axis direction satisfies the following formula (I).
Boric acid cross-linking index ≤ 0.9 (I)
[The boric acid cross-linking index is defined as Raman scattered light intensity at a wavenumber of 780 cm -1 /Raman scattered light intensity at a wavenumber of 850 cm -1 . ]
A lamination step of obtaining a polarizing plate by laminating thermoplastic resin films on both sides of a polarizer containing iodine and boron;
and an edge treatment step of contacting the edge of the polarizing plate in a direction parallel to the polarizer transmission axis direction with a treatment liquid at 20° C. or higher for 3 to 150 seconds.
3. The polarizing plate according to claim 2, further comprising an edge forming step of forming an edge in a direction parallel to the polarizer transmission axis direction of the polarizing plate by cutting and/or punching the polarizing plate. Production method.
4. The method according to claim 2 or 3, further comprising a surface protection step of laminating a surface protection film for a polarizing plate on the surface of the thermoplastic resin film opposite to the side on which the polarizer is arranged in the polarizing plate. A method for producing the described polarizing plate.
The method for manufacturing a polarizing plate according to any one of claims 2 to 4, wherein the treatment liquid contains water.
The method for manufacturing a polarizing plate according to any one of claims 2 to 5, wherein the treatment liquid is water.
The method for producing a polarizing plate according to any one of claims 2 to 6, wherein the treatment liquid has a pH of 3 to 9.
A polarizing plate having a thermoplastic resin film on at least one surface of the polarizer containing iodine and boron,
The end portion of the polarizer in the direction parallel to the polarizer transmission axis direction is at the same position in the plane direction as the end portion of the thermoplastic resin film in the direction parallel to the polarizer transmission axis direction, or located outside the
A polarizing plate in which an end portion of the polarizer in a direction parallel to a polarizer transmission axis direction satisfies the following formula (I).
Boric acid cross-linking index ≤ 0.9 (I)
[The boric acid cross-linking index is defined as Raman scattered light intensity at a wavenumber of 780 cm -1 /Raman scattered light intensity at a wavenumber of 850 cm -1 . ]
A lamination step of obtaining a polarizing plate by laminating a thermoplastic resin film on at least one surface of a polarizer containing iodine and boron;
and an edge treatment step of contacting the edge of the polarizing plate in a direction parallel to the polarizer transmission axis direction with a treatment liquid at 20° C. or higher for 3 to 150 seconds.