CN113474690A - Resin composition for protecting polarizer and polarizing plate comprising protective layer formed from the same - Google Patents

Resin composition for protecting polarizer and polarizing plate comprising protective layer formed from the same Download PDF

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CN113474690A
CN113474690A CN201980093131.XA CN201980093131A CN113474690A CN 113474690 A CN113474690 A CN 113474690A CN 201980093131 A CN201980093131 A CN 201980093131A CN 113474690 A CN113474690 A CN 113474690A
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group
polarizer
weight
polarizing plate
resin composition
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Inventor
姜太艳
长瀬纯一
三田聪司
泽田浩明
中西贞裕
池田哲朗
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Nitto Denko Corp
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Nitto Denko Corp
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F230/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal
    • C08F230/04—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing a metal
    • C08F230/06—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing a metal containing boron
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/10—Homopolymers or copolymers of methacrylic acid esters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D143/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing boron, silicon, phosphorus, selenium, tellurium, or a metal; Coating compositions based on derivatives of such polymers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid

Abstract

The purpose of the present invention is to provide a resin composition for protecting a polarizer, which has excellent adhesion to a polarizer and can prevent defects such as discoloration from the end, and a polarizer comprising a protective layer comprising the resin composition. The resin composition for protecting a polarizer of the present invention comprises a polymer obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 part by weight and less than 50 parts by weight of a comonomer represented by formula (1), and the polymer has a glass transition temperature of 50 ℃ or higher. [ formula 1](wherein X represents a group containing a monomer selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, and vinyl groupA functional group of at least 1 reactive group of the group consisting of an ether group, an epoxy group, an oxetanyl group, a hydroxyl group, an amino group, an aldehyde group and a carboxyl group; r1And R2Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group, R1And R2Optionally linked to each other to form a ring).

Description

Resin composition for protecting polarizer and polarizing plate comprising protective layer formed from the same
Technical Field
The present invention relates to a resin composition for protecting a polarizer and a polarizing plate having a protective layer formed from the composition.
Background
Typically, a polarizer is produced by dyeing a polyvinyl alcohol (PVA) -based resin film with a dichroic substance such as iodine (for example, patent documents 1 and 2). It is known that: in a polarizing plate, moisture is absorbed in a hot and humid environment, and the iodine complex is broken, and iodine is eluted, whereby the degree of polarization is reduced and the transmittance is increased (discolored). Since moisture enters from the end of the polarizing plate, discoloration at the end of the polarizer tends to be significant.
Typically, the polarizer is used in the form of a polarizing plate including a polarizer and protective layers provided on both sides of the polarizer. In recent years, in order to meet the demand for thinner polarizing plates, there have been proposed a polarizer and a protective layer, and a polarizing plate including a protective layer only on one side of the polarizer. In such a constitution, the absorption of moisture from the end portion becomes faster, and the discoloration of the end portion may become more remarkable. Further, when the protective layer is thin, the durability may be reduced, and the polarizer may not be appropriately protected.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 5048120
Patent document 2: japanese patent laid-open publication No. 2013-156391
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above conventional problems, and a main object thereof is to provide a resin composition for protecting a polarizer, which has excellent adhesion to a polarizer and can prevent defects such as discoloration from an end portion, and a polarizer including a protective layer formed of the resin composition.
Means for solving the problems
The resin composition for protecting a polarizer of the present invention comprises a polymer obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 part by weight and less than 50 parts by weight of a comonomer represented by formula (1), wherein the polymer has a glass transition temperature of 50 ℃ or higher,
Figure BDA0003231392040000021
(wherein X represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group and carboxyl group; R1And R2Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group, R1And R2Optionally linked to each other to form a ring).
In one embodiment, the weight average molecular weight of the polymer is 10,000 or more.
In one embodiment, the reactive group is at least 1 selected from the group consisting of a (meth) acryloyl group and a (meth) acrylamide group.
In another aspect of the present invention, a polarizing plate is provided. The polarizing plate comprises a polarizer and a protective layer formed of the polarizer-protecting resin composition on at least one surface of the polarizer.
In one embodiment, the protective layer has a thickness of 0.1 to 8 μm.
In one embodiment, the polarizer has an iodine content of 2 to 25 wt%.
In one embodiment, the polarizer has a thickness of 8 μm or less.
ADVANTAGEOUS EFFECTS OF INVENTION
The present invention provides a resin composition for protecting a polarizer, which has excellent adhesion to a polarizer and can prevent defects such as discoloration from the edge, and a polarizer comprising a protective layer formed from the resin composition. Specifically, the resin composition for protecting a polarizer of the present invention comprises a polymer obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 part by weight and less than 50 parts by weight of a comonomer represented by formula (1), and the polymer has a glass transition temperature of 50 ℃ or higher.
Figure BDA0003231392040000031
(wherein X represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group and carboxyl group; R1And R2Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group, R1And R2Optionally linked to each other to form a ring).
The layer (protective layer) formed from the resin composition for protecting a polarizer of the present invention can be sufficiently adhered to a polarizer, and appearance defects such as lifting and peeling can be prevented. In addition, moisture can be prevented from entering from the end portion, and discoloration from the end portion of the polarizer can be prevented. Further, the protective layer formed from the resin composition has excellent crack resistance. Therefore, even when the protective layer is thin, the polarizer can be appropriately protected. Further, since the protective layer and the adhesive layer are excellent in anchoring force, a laminated state with other components of the image display device, for example, can be maintained satisfactorily.
Drawings
Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.
A. Resin composition for protecting polarizer
The resin composition for protecting a polarizer of the present invention comprises a polymer obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 part by weight and less than 50 parts by weight of a comonomer represented by formula (1), and the polymer has a glass transition temperature of 50 ℃ or higher.
Figure BDA0003231392040000041
(wherein X represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group and carboxyl group; R1And R2Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group, R1And R2Optionally linked to each other to form a ring).
The layer (typically, a protective layer) formed using the resin composition for protecting a polarizer of the present invention has excellent adhesion to a polarizer, and even when the protective layer is formed to have a small thickness, appearance defects such as lifting and peeling of the protective layer can be prevented. Further, the layer formed using the resin composition for protecting a polarizer of the present invention can prevent discoloration from the end of the polarizer. Further, the protective layer formed using the resin composition for protecting a polarizer of the present invention is also excellent in crack resistance. Therefore, even when the thickness is small, the polarizing plate can be appropriately protected.
A-1. Polymer
The above polymer can be obtained by polymerizing more than 50 parts by weight of an acrylic monomer with more than 0 part by weight and less than 50 parts by weight of a comonomer represented by formula (1).
Figure BDA0003231392040000042
(wherein X represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group and carboxyl group; R1And R2Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group, R1And R2Optionally linked to each other to form a ring).
Typically, the polymer has a structure represented by the following formula. The polymer has a boron-containing substituent (for example, a repeating unit of k in the following formula) in a side chain thereof by polymerizing the comonomer represented by formula (1) with an acrylic monomer component. This improves the adhesion between the polarizer and the layer (protective layer) formed using the polarizer-protecting resin composition. The boron-containing substituent may be contained in the polymer by bonding or may be contained randomly.
Figure BDA0003231392040000051
(in the formula, R4Represents an arbitrary functional group; j and k represent an integer of 1 or more).
The weight average molecular weight of the polymer is preferably 10,000 or more, more preferably 20,000 or more, further preferably 35,000 or more, and particularly preferably 50,000 or more. The weight average molecular weight of the polymer is preferably 250,000 or less, more preferably 200,000 or less, and still more preferably 150,000 or less. By setting the weight average molecular weight of the polymer to the above range, the crack resistance of the layer (protective layer) formed using the resin composition for protecting a polarizer can be improved. The weight average molecular weight can be determined by, for example, GPC (solvent: Dimethylformamide (DMF)).
The glass transition temperature of the polymer is 50 ℃ or higher, preferably 60 ℃ or higher, and more preferably 80 ℃ or higher. The glass transition temperature of the polymer is preferably 300 ℃ or lower, more preferably 200 ℃ or lower, and still more preferably 120 ℃ or lower. When the glass transition temperature is in the above range, the crack resistance of a layer (protective layer) formed using the resin composition for protecting a polarizer can be improved.
The above-mentioned polymer can be obtained by polymerizing a monomer composition comprising more than 50 parts by weight of an acrylic monomer, more than 0 part by weight and less than 50 parts by weight of a comonomer represented by formula (1), a polymerization initiator, and any other monomer, by using any and appropriate polymerization method. As the polymerization method, solution polymerization is preferably used. By polymerizing the above polymer by solution polymerization, a polymer having a higher molecular weight can be obtained.
A-1-1. acrylic acid series monomer
As the acrylic monomer, any and suitable acrylic monomer can be used. Examples thereof include (meth) acrylate monomers having a linear or branched structure and (meth) acrylate monomers having a cyclic structure. In the present specification, (meth) acrylic acid means acrylic acid and/or methacrylic acid.
Examples of the (meth) acrylate monomer having a linear or branched structure include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, methyl 2-ethylhexyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. Methyl (meth) acrylate is preferably used. The (meth) acrylate monomer may be used in a single amount of 1 kind, or may be used in combination of 2 or more kinds.
Examples of the (meth) acrylate-based monomer having a cyclic structure include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, biphenyl (meth) acrylate, o-diphenoxyethyl (meth) acrylate, o-diphenoxyethoxyethyl (meth) acrylate, m-diphenoxyethyl acrylate, p-diphenoxyethyl (meth) acrylate, o-diphenoxy-2-hydroxypropyl (meth) acrylate, p-diphenoxy-2-hydroxypropyl (meth) acrylate, m-diphenoxy-2-hydroxypropyl (meth) acrylate, and mixtures thereof, Biphenyl group-containing monomers such as N- (meth) acryloyloxyethyl o-biphenyl ═ carbamate, N- (meth) acryloyloxyethyl p-biphenyl ═ carbamate, N- (meth) acryloyloxyethyl m-biphenyl ═ carbamate, and o-phenylphenol glycidyl ether acrylate; tribiphenyl (meth) acrylate, o-terphenoxyethyl (meth) acrylate, and the like. 1-adamantyl (meth) acrylate and dicyclopentyl (meth) acrylate are preferably used. By using these monomers, a polymer having a high glass transition temperature can be obtained. These monomers may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
In addition, a silsesquioxane compound having a (meth) acryloyl group may be used instead of the (meth) acrylate monomer. By using the silsesquioxane compound, an acrylic polymer having a high glass transition temperature can be obtained. Silsesquioxane compounds are known to have various skeleton structures such as a cage structure, a ladder structure, a random structure, and the like. The silsesquioxane compound may have only 1 of these structures, or may have 2 or more of these structures. The silsesquioxane compound may be used in 1 kind alone, or in combination of 2 or more kinds.
As the (meth) acryloyl group-containing silsesquioxane compound, for example, SQ series MAC grade and AC grade of east asian synthesis company can be used. The MAC grade is a silsesquioxane compound containing a methacryloyl group, and specific examples thereof include MAC-SQ TM-100, MAC-SQ SI-20, and MAC-SQ HDM. The AC grade is a silsesquioxane compound containing an acryloyl group, and specific examples thereof include AC-SQ TA-100 and AC-SQ SI-20.
More than 50 parts by weight of an acrylic monomer is used. The acrylic monomer is used so that the total amount thereof and a comonomer described later is 100 parts by weight.
A-1-2. comonomer
As the comonomer, a comonomer represented by the formula (1) is used. By using such a comonomer, a substituent containing boron is introduced into the side chain of the resulting polymer. Therefore, typically, the adhesiveness between a polarizer made of a PVA-based resin and a layer (protective layer) formed using a polarizer protective resin composition can be improved. Further, the layer itself formed using the resin composition for polarizer protection can also have improved water resistance, and discoloration from the end of the polarizer can be prevented. Only 1 kind of the comonomer may be used, or 2 or more kinds may be used in combination.
Figure BDA0003231392040000071
(wherein X represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group and carboxyl group; R1And R2Each independently of the otherR represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group1And R2Optionally linked to each other to form a ring).
The aliphatic hydrocarbon group includes a C1-20 linear or branched alkyl group optionally having a substituent, a C3-20 cyclic alkyl group optionally having a substituent, and a C2-20 alkenyl group. Examples of the aryl group include a phenyl group having 6 to 20 carbon atoms which may have a substituent, a naphthyl group having 10 to 20 carbon atoms which may have a substituent, and the like. As the heterocyclic group, a five-membered ring group or a six-membered ring group which may be substituted and which contains at least 1 hetero atom is exemplified. In addition, R is1And R2Optionally joined to each other to form a ring. R1And R2Preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom.
The reactive group contained in the functional group represented by X is at least 1 selected from the group consisting of a vinyl group, a (meth) acryloyl group, a styryl group, a (meth) acrylamide group, a vinyl ether group, an epoxy group, an oxetanyl group, a hydroxyl group, an amino group, an aldehyde group, and a carboxyl group. The reactive group is preferably a (meth) acryloyl group and/or a (meth) acrylamide group. By having these reactive groups, the adhesiveness between the polarizer and a layer (protective layer) formed using the polarizer-protecting resin composition can be improved.
In one embodiment, the functional group represented by X is preferably a functional group represented by the following formula.
Z-Y-
(wherein Z represents a functional group containing at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group and carboxyl group; Y represents phenylene or alkylene).
As the comonomer represented by the general formula (1), specifically, the following compounds can be used.
Figure BDA0003231392040000081
Figure BDA0003231392040000091
The comonomer represented by formula (1) is used in a content of more than 0 part by weight and less than 50 parts by weight. Preferably 0.01 to less than 50 parts by weight, more preferably 0.05 to 20 parts by weight, still more preferably 0.1 to 10 parts by weight, and particularly preferably 0.5 to 5 parts by weight. If the content of the comonomer exceeds 50 parts by weight, discoloration from the terminal portions is likely to occur.
A-1-3 polymerization initiator
As the polymerization initiator, any and suitable polymerization initiator can be used. Examples thereof include peroxides such as benzoyl peroxide, lauroyl peroxide and sodium peroxide; hydrogen peroxide such as t-butyl hydroperoxide and cumene hydroperoxide; azo compounds such as azobisisobutyronitrile and the like. Only 1 kind of them may be used, or 2 or more kinds may be used.
The content of the polymerization initiator may be used in any and appropriate amount. The content of the polymerization initiator is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 2 parts by weight.
As mentioned above, the polymer is preferably obtained by solution polymerization of the above-mentioned monomers and comonomers. As the solvent usable in the solution polymerization, any and appropriate solvent can be used. Examples thereof include water; alcohols such as methanol, ethanol, and isopropanol; aromatic hydrocarbons or aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane, and n-hexane; ester compounds such as ethyl acetate; ketone compounds such as acetone and methyl ethyl ketone; cyclic ether compounds such as tetrahydrofuran and dioxane. These solvents may be used alone in 1 kind, or may be used in combination in 2 or more kinds. In addition, an organic solvent may be used in combination with water.
The polymerization reaction may be carried out at any and suitable temperature and time. For example, the polymerization reaction can be carried out at 50 to 100 ℃ and preferably at 60 to 80 ℃. The reaction time is, for example, 1 hour to 8 hours, preferably 3 hours to 5 hours.
The resin composition for protecting a polarizer of the present invention contains, for example, the above-mentioned polymer and a solvent. The content of the polymer in the resin composition for polarizer protection is preferably 1 to 30% by weight, more preferably 5 to 20% by weight. When the polymer content in the resin composition for protecting a polarizer is in the above range, a desired protective layer can be formed well by coating.
A-2. preparation method of resin composition for protecting polarizer
In one embodiment, the resin composition for protecting a polarizer of the present invention is a polymerization solution obtained by solution polymerization of a monomer and a comonomer. In other embodiments of the present invention, the polymer may be obtained by mixing the above-mentioned polymer with an arbitrary and appropriate solvent by an arbitrary and appropriate method. As the solvent, the solvent used in the above solution polymerization may be used, and other solvents may also be used. As the solvent, ethyl acetate, toluene, methyl ethyl ketone, and cyclopentanone are preferably used. These solvents may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
The resin composition for protecting a polarizer may further contain any appropriate additive, if necessary, in addition to the polymer and the solvent. The additive may be used in a single amount of 1 kind, or may be used in combination of 2 or more kinds. These additives may be used in any and suitable amount.
B. Polarizing plate
The polarizing plate of the present invention comprises a polarizer and a protective layer formed of the polarizer-protecting resin composition on at least one surface of the polarizer. The protective layer formed from the resin composition for protecting a polarizer has excellent adhesion to a polarizer. Therefore, even when the polarizer is thin, the protective layer can be prevented from being lifted from the polarizer, peeling off, or the like. Further, discoloration of the end portion of the self-polarizing member can be prevented. Further, the protective layer is also excellent in crack resistance. Therefore, even when the thickness is small, the polarizing plate can be appropriately protected.
B-1 summary of polarizing plate
Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The polarizing plate 100 illustrated in the drawing includes a polarizer 10 and a protective layer 20 formed on at least one surface of the polarizer. The protective layer 20 is a layer formed of the resin composition for protecting a polarizer. By forming the protective layer from the resin composition for protecting a polarizer, the adhesion between the protective layer and the polarizer is improved. Therefore, moisture can be prevented from entering from the end of the polarizing plate, and discoloration from the end can be prevented. Further, the protective layer 20 is also excellent in crack resistance, and therefore, the polarizer 10 can be appropriately protected. Further, even when the protective layer 20 is formed only on one side of the polarizer 10, it is possible to prevent the occurrence of discoloration of the polarizer from the end portion. Therefore, the polarizing plate 100 can be thinned. In the illustrated example, the protective layer 20 is formed only on one surface of the polarizer 10, and the protective layers 20 may be formed on both sides of the polarizer 10. Further, a protective layer 20 may be formed on one surface of the polarizer 10, and another protective layer may be formed on the other surface of the polarizer 10. Typically, the protective layer 20 may be formed directly (without an adhesive layer or an adhesive layer) on the polarizer 10. The protective layer is formed directly on the polarizer, which contributes to the thinning of the polarizing plate. Further, by directly forming the protective layer, the adhesion between the polarizer and the protective layer can be improved.
The polarizing plate 100 may further include any and appropriate functional layers other than the protective layer 20 according to purposes. Examples of the functional layer include a retardation layer, a light diffusion layer, an antireflection layer, and a reflective polarizer. The functional layer may be laminated on the polarizer 10 side or on the protective layer 20 side. Further, a plurality of functional layers may be included.
B-2. polarizer
Typically, the polarizing element is a resin film containing a dichroic material. Examples of the dichroic substance include iodine and an organic dye. The dichroic substance may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Preferably comprising iodine.
In one embodiment, the iodine content of the polarizer 10 is preferably 2 to 25 wt%. In another embodiment of the present invention, the iodine content of the polarizer 10 is preferably 10 to 25% by weight, and more preferably 15 to 25% by weight. The discoloration of polarizers with high iodine content in hot and humid environments can become more pronounced. Therefore, the effect achieved by forming the protective layer using the resin composition for protecting a polarizer can be further exhibited. In the present specification, the "iodine content" refers to the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, in the polarizer, iodine is represented by iodide ion (I)-) Iodine molecule (I)2) Polyiodide (I)3 -、I5 -) The iodine content in the present specification means the amount of iodine including all of these forms. The iodine content can be calculated by standard curve methods such as fluorescent X-ray analysis. The polyiodide exists in the polarizer in a state where a PVA-iodine complex is formed. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, a complex of PVA and triiodide ion (PVA. I)3 -) A complex of PVA and a pentaiodide ion (PVA. I) having an absorption peak at about 470nm5 -) Has an absorption peak around 600 nm. As a result, the polyiodide ions can absorb light in a wide range of visible light according to their forms. On the other hand, iodide ion (I)-) Has an absorption peak around 230nm and does not substantially interfere with the absorption of visible light. Thus, polyiodide ions present in the state of a complex with PVA can primarily interfere with the absorption properties of the pre-polarizer.
The thickness of the polarizer is preferably 8 μm or less, and more preferably 0.6 μm or more and less than 8 μm. In one embodiment, the thickness of the polarizer is preferably 30 μm or less, more preferably 25 μm or less, even more preferably 18 μm or less, particularly preferably 12 μm or less, and even more particularly preferably less than 8 μm. The thickness of the polarizer is preferably 1 μm or more. In another embodiment, the thickness of the polarizer is preferably 5 μm or less, more preferably 2.5 μm or less, even more preferably 2 μm or less, and particularly preferably 1.5 μm or less. On the other hand, the thickness of the polarizer is preferably 0.6 μm or more, and more preferably 1.0 μm or more.
The single transmittance of the polarizer is, for example, 30% or more. The theoretical upper limit of the monomer transmittance is 50%, and the practical upper limit is 46%. The monomer transmittance (Ts) is a Y value obtained by measuring and correcting visibility with a 2-degree field of view (C light source) according to JIS Z8701, and is measured, for example, with a spectrophotometer with an integrating sphere (product name: V7100, manufactured by JASCO corporation).
The degree of polarization of the polarizer is, for example, 99.0% or more, preferably 99.5% or more, and more preferably 99.9% or more. As described above, the polarizing plate of the present invention can prevent discoloration from the end portion. Therefore, even when the degree of polarization of the polarizer is high, the degree of polarization can be maintained well.
B-2-1. method for manufacturing polarizing piece
The polarizer can be manufactured using any and suitable method. For example, the PVA-based resin film may be subjected to a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step. In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on a substrate. The laminate of the substrate and the resin layer can be obtained, for example, by a method of applying a coating solution containing the PVA-based resin to the substrate, a method of laminating a PVA-based resin film on the substrate, or the like. As the substrate, any and appropriate resin substrate can be used, and for example, a thermoplastic resin substrate can be used.
B-2-1. PVA resin film
Examples of the PVA resin forming the PVA resin film include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA resin is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.99 mol%, and more preferably 99.0 mol% to 99.99 mol%. The degree of saponification can be determined in accordance with JIS K6726-. By using the PVA-based resin having such a saponification degree, a polarizing plate having excellent durability can be obtained.
The average polymerization degree of the PVA-based resin can be appropriately selected according to the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average polymerization degree can be determined in accordance with JIS K6726-.
The thickness of the PVA-based resin film may be set according to a desired thickness of the polarizer. The thickness of the PVA resin film is, for example, 0.5 to 200. mu.m. By using the dyeing solution described later, for example, even if the PVA-based resin film is less than 10 μm, sufficient dyeing can be performed in a short time, and a property capable of sufficiently functioning as a polarizer can be provided.
As described above, the polarizer can be produced by subjecting the PVA-based resin film to, for example, a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step. Each step may be performed at an arbitrary and appropriate timing. Further, any step other than the dyeing step may be omitted, or a plurality of steps may be performed simultaneously, or each step may be performed a plurality of times, as necessary. Hereinafter, each step will be described.
B-2-1-2 stretching
Typically, the PVA-based resin film is uniaxially stretched 3 to 7 times the original length in the stretching treatment. The PVA-based resin film is subjected to dry stretching. Dry stretching is preferable because the stretching treatment can be performed in a wider temperature range. The temperature for dry drawing is, for example, 50 to 200 ℃, preferably 80 to 180 ℃, and more preferably 90 to 160 ℃. The stretching direction may be the longitudinal direction (MD direction) of the film or the width direction (TD direction) of the film. It should be noted that the stretching direction may correspond to the absorption axis direction of the resulting polarizer.
B-2-1-3. dyeing
The dyeing step is a step of dyeing the PVA-based resin film with a dichroic substance. Preferably, the adsorption is performed by adsorbing a dichroic substance. Examples of the adsorption method include a method of immersing the PVA-based resin film in a dyeing solution containing a dichroic substance, a method of applying the dyeing solution to the PVA-based resin film, and a method of spraying the dyeing solution onto the PVA-based resin film. The PVA-based resin film is preferably immersed in a dyeing solution. This is because a dichroic material can be adsorbed well.
As the above-mentioned dichroic substance, iodine and dichroic dyes are exemplified as described above. Iodine is preferred. When iodine is used as the dichroic material, an aqueous iodine solution is preferably used as the dyeing liquid. The iodine content of the aqueous iodine solution is preferably 0.04 parts by weight to 5.0 parts by weight with respect to 100 parts by weight of water. In one embodiment, the iodine content in the aqueous iodine solution is preferably 0.3 parts by weight or more relative to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to blend an iodide into the aqueous iodine solution. As iodide, potassium iodide is preferably used. The content of the iodide is preferably 0.3 to 15 parts by weight with respect to 100 parts by weight of water.
The liquid temperature of the dyeing solution during dyeing can be set to any and appropriate value. For example, 20 ℃ to 50 ℃. When the PVA-based resin film is immersed in the dyeing solution, the immersion time is, for example, 1 second to 1 minute.
In one embodiment, the dyeing bath is a solution containing an oxidizing agent that oxidizes iodide and iodide ions. The oxidizing agent is an ionic compound comprising a cation and an anion. In the staining solution, polyiodide is formed by oxidation of iodide ions. As a result, the content of polyiodide ions contained in the dyeing solution becomes high, and the PVA-based resin film can be efficiently dyed. Further, the content of polyiodide ions in the dyeing solution can be increased with a small amount of iodine compared to the case where the dyeing solution is prepared by adding iodine to an aqueous solution containing water or iodide. In this embodiment, the iodine content in the dyeing solution can be adjusted by adding an oxidizing agent that oxidizes iodide ions to the dyeing solution. Therefore, the content of polyiodide ions in the dyeing solution can be adjusted more easily.
The content of the iodide contained in the dyeing solution is preferably 1 to 40 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of the solvent. If the content of iodide is in the above range, a sufficient amount of polyiodide can be formed in the dyeing solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Potassium iodide is preferred.
In one embodiment, an ionic compound containing a cation and an anion is used as the oxidizing agent for oxidizing iodide ions. Examples of the anion or cation include Fe3+、Ag+、Ag2+、Au+、Au3+、Co3+、Cu2 +、Mn3+、Pt2+An isocationic acid; br3-、ClO3 -、ClO2 -、ClO-、Cr2O7 2-、NO3 -、MnO4 -And (4) plasma. Preferably ferric ion (Fe)3+). The ferric ions are present in the dyeing solution in the form of ferrous ions after oxidation of the iodide ions. Ferric ions and ferrous ions may enter the PVA-based resin film during the dyeing process. These iron ions have the effect of dehydrating PVA. Therefore, the action of polyiodide ions being released from the PVA-based resin film can be suppressed in the subsequent steps. As a result, the dyeability of the PVA-based resin film can be further improved, which is preferable.
As the oxidizing agent, any and appropriate compound may be used as long as it is an ionic compound that causes a desired electrode reaction in the dyeing solution. Examples thereof include iron sulfate, iron chloride, iron nitrate and the like containing Fe3+A compound as a cation; potassium permanganate and the like containing MnO4 -A compound as an anion; copper chloride, copper sulfate, etc. contain Cu2+A compound as a cation, and the like. From the inclusion of Fe3+From the aspect of (1), it is preferable to use at least 1 compound selected from the group consisting of iron sulfate, iron chloride and iron nitrate. The oxidizing agent may be used alone1 or more than 2 kinds may be used in combination.
The content of the oxidizing agent in the dyeing solution is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 10 parts by weight, and still more preferably 0.5 to 4 parts by weight, based on 100 parts by weight of the solvent. The content of the oxidizing agent in the dyeing solution may be determined according to the content of the iodide contained in the dyeing solution.
The molar ratio of the iodide to the oxidant can be set to any and suitable value, for example, 2/1 to 50/1, preferably 10/1 to 50/1. If the molar ratio of the iodide to the oxidizing agent is within the above range, the oxidizing agent can sufficiently function as an oxidizing agent for oxidizing iodide ions.
The iodide and oxidant may be used in any and suitable combination. For example, from the viewpoint of obtaining a polarizer having excellent characteristics such as durability, a combination of using potassium iodide as an iodide and using iron sulfate as an oxidizing agent is preferable.
As the solvent of the dyeing solution, any and appropriate solvent can be used, and water is usually used.
The above-mentioned dyeing solution may also contain any and suitable other compounds in addition to the iodide and the oxidizing agent. For example, the staining solution may further comprise iodine. When the dyeing solution further contains iodine, the iodine content in the dyeing solution is, for example, 1 part by weight or less with respect to 100 parts by weight of the solvent.
B-2-1-4 swelling
The swelling step is usually performed before the dyeing step. In one embodiment, the swelling step may be performed in the same immersion bath as the dyeing step. The swelling step is performed by, for example, immersing the PVA-based resin film in a swelling bath. As the swelling bath, any and appropriate liquid can be used, and water such as distilled water or pure water can be used. The swelling bath may comprise any and suitable other ingredients besides water. Examples of the other components include a solvent such as alcohol, an additive such as a surfactant, and an iodide. The iodide may be exemplified as above. Potassium iodide is preferably used. The temperature of the swelling bath is, for example, 20 ℃ to 45 ℃. The immersion time is, for example, 10 seconds to 300 seconds.
B-2-1-5. Cross-linking
In the crosslinking step, a boron compound is generally used as a crosslinking agent. Examples of the boron compound include boric acid and borax. Boric acid is preferred. In the crosslinking step, the boron compound is usually used in the form of an aqueous solution.
When the aqueous boric acid solution is used, the boric acid concentration of the aqueous boric acid solution is, for example, 2 to 15% by weight, preferably 3 to 13% by weight. The aqueous boric acid solution may further contain an iodide such as potassium iodide, and a zinc compound such as zinc sulfate or zinc chloride.
The crosslinking step can be carried out by any suitable method. Examples of the method include a method of immersing the PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to the PVA-based resin film, and a method of spraying an aqueous solution containing a boron compound onto the PVA-based resin film. Preferably in an aqueous solution containing a boron compound.
The temperature of the solution used for crosslinking is, for example, 25 ℃ or higher, preferably 30 to 85 ℃, and more preferably 40 to 70 ℃. The immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.
B-2-1-6. cleaning
The washing step may be performed using an aqueous solution containing water or the iodide. Typically, the PVA-based resin film is immersed in an aqueous potassium iodide solution. The temperature of the aqueous solution in the cleaning step is, for example, 5 to 50 ℃. The immersion time is, for example, 1 to 300 seconds.
B-2-1-7, drying
The drying step can be performed by any suitable method. Examples thereof include natural drying, air-blowing drying, drying under reduced pressure, and heat drying is preferably used. When the heating and drying are performed, the heating temperature is, for example, 30 to 100 ℃. The drying time is, for example, 10 seconds to 10 minutes.
B-3 protective layer
The protective layer 20 is formed on at least one surface of the polarizer 10. The protective layer 20 is formed using the above-described polarizer-protecting resin composition.
The thickness of the protective layer 20 may be set to an arbitrary and appropriate value according to the thickness of the polarizer and the glass transition temperature of the above-described polymer. In one embodiment, the thickness of the protective layer is preferably 0.1 to 8 μm, more preferably 0.2 to 3 μm, and still more preferably 0.5 to 1 μm. By setting the thickness of the protective layer to the above range, it is possible to contribute to thinning of the polarizing plate. As described above, the protective layer 20 can appropriately protect the polarizer 10 even when the thickness is small, and can prevent discoloration from the end portion. If the thickness of the protective layer 20 exceeds 8 μm, the adhesiveness between the polarizer and the protective layer may be reduced.
The elastic modulus of the cross section of the protective layer 20 is preferably 4GPa to 8GPa, and more preferably 5GPa to 6 GPa. By setting the elastic modulus to the above range, the occurrence of cracks in the protective layer can be prevented. Therefore, even when the thickness is small, the polarizing plate can be appropriately protected. In the present specification, the elastic modulus of the cross section of the protective layer can be measured by the method described in the examples described below.
The moisture permeability of the protective layer is preferably 10g/m2·24h～2000g/m224h, more preferably 100g/m2·24h～1800g/m224h, more preferably 150g/m2·24h～1500g/m224 h. By setting the moisture permeability within the above range, it is possible to prevent moisture from entering and the polarizer from being discolored.
The protective layer may be formed by any suitable method. For example, the polarizing plate can be formed by applying the resin composition for protecting a polarizing plate to the polarizing plate. As the coating method, various methods such as bar coater coating, air knife coating, gravure coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexo printing, screen printing, and the like can be used. In addition, the surface of the polarizer to be coated with the polarizer-protecting resin composition may be subjected to an arbitrary and appropriate surface modification treatment.
Examples
The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
Production example 1 production of polarizing plate 1
As the thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ℃ was used. One surface of the substrate was subjected to corona treatment, and an aqueous solution containing polyvinyl alcohol (polymerization degree of 4200 and saponification degree of 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree of 1200, acetoacetyl-modified degree of 4.6% and saponification degree of 99.0 mol% or more, manufactured by japan synthetic chemical industries, product name "GOHSEFIMER Z200") at a ratio of 9:1 was applied to the corona-treated surface at 25 ℃.
The resulting laminate was stretched in air at 140 ℃ by 4.5 times in a direction orthogonal to the longitudinal direction of the laminate using a tenter stretcher (stretching treatment).
Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by adding 4 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment).
Subsequently, the laminate was immersed for 6 seconds in a dyeing solution (aqueous solution prepared by adding 24.0 parts by weight of potassium iodide and 2.8 parts by weight of iron sulfate n-hydrate to 100 parts by weight of water, molar ratio of iodide to oxidizing agent: 21.0/1) at 30 ℃ to dye (dyeing treatment).
Next, the substrate was immersed in a crosslinking bath (an aqueous boric acid solution prepared by adding 3 parts by weight of potassium iodide and 3 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 60 ℃ for 35 seconds (crosslinking treatment).
Thereafter, the laminate was immersed in a cleaning bath (aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a liquid temperature of 25 ℃ for 10 seconds (cleaning treatment).
Thereafter, the laminate was dried in an oven at 60 ℃ for 60 seconds to obtain a laminate 1 having a PVA resin layer (polarizer) with a thickness of 1.2. mu.m.
Production example 2 production of polarizing plate 2
As the substrate, a long-sized amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of 75 ℃ was used. One surface of the substrate was subjected to corona treatment, and an aqueous solution containing polyvinyl alcohol (polymerization degree of 4200 and saponification degree of 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree of 1200, acetoacetyl-modified degree of 4.6% and saponification degree of 99.0 mol% or more, manufactured by japan synthetic chemical industries, product name "GOHSEFIMERZ 200") at a ratio of 9:1 was applied to the corona-treated surface at 25 ℃.
The resulting laminate was uniaxially stretched to 2.0 times along the longitudinal (longitudinal) free end between rolls having different peripheral speeds in an oven at 120 ℃ (in-air auxiliary stretching).
Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by adding 4 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment).
Then, the polarizing plate was immersed in a dyeing bath at a liquid temperature of 30 ℃ while adjusting the iodine concentration and the immersion time so as to achieve a predetermined transmittance. In this example, an aqueous iodine solution containing 100 parts by weight of water and 0.2 part by weight of iodine and 1.5 parts by weight of potassium iodide was immersed for 60 seconds (dyeing treatment).
Next, the substrate was immersed in a crosslinking bath (aqueous boric acid solution prepared by adding 3 parts by weight of potassium iodide to 100 parts by weight of water and 3 parts by weight of boric acid) at a liquid temperature of 30 ℃ for 30 seconds (crosslinking treatment).
Thereafter, the laminate was uniaxially stretched (underwater stretching) so that the total stretching ratio became 5.5 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds while being immersed in an aqueous boric acid solution (aqueous solution prepared by adding 4 parts by weight of boric acid and 5 parts by weight of potassium iodide to 100 parts by weight of water) having a liquid temperature of 70 ℃.
Thereafter, the laminate was immersed in a cleaning bath (aqueous solution prepared by adding 4 parts by weight of potassium iodide to 100 parts by weight of water) at a liquid temperature of 30 ℃.
Subsequently, the laminate was dried in an oven at 60 ℃ for 60 seconds to obtain a laminate 2 having a PVA resin layer (polarizer) with a thickness of 5 μm.
Production example 3 preparation of acrylic adhesive
A monomer mixture containing 99 parts by weight of butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate was put into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser. Further, 0.1 part by weight of 2, 2' -azobisisobutyronitrile as a polymerization initiator was charged together with ethyl acetate per 100 parts by weight of the monomer mixture (solid content), nitrogen gas was introduced while slowly stirring the mixture, the nitrogen gas was replaced, and then the liquid temperature in the flask was maintained at about 60 ℃ to conduct a polymerization reaction for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%. In this manner, a solution of an acrylic polymer (base polymer) having a weight average molecular weight of 140 ten thousand was prepared.
An acrylic adhesive (solution) was obtained by blending 0.095 parts by weight of trimethylolpropane xylylene diisocyanate (trade name: TAKENATE D110N, manufactured by Mitsui chemical Co., Ltd.) and 0.3 part by weight of dibenzoyl peroxide as crosslinking agents, 0.2 parts by weight of organosilane (trade name: A100, manufactured by Sukikai chemical Co., Ltd.) and 0.2 parts by weight of a thiol group-containing silane coupling agent (trade name: X41-1810, manufactured by shin-Etsu chemical Co., Ltd.) and 0.3 parts by weight of an antioxidant (trade name: Irganox1010, manufactured by BASF Co., Ltd.) with respect to 100 parts by weight of the solid content of the acrylic polymer solution.
Example 1 production of polarizing plate 1
99.9 parts by weight of methyl methacrylate (MMA, Fuji film and Wako pure chemical industries, Ltd.; trade name: methyl methacrylate monomer), 0.1 part by weight of a comonomer represented by the general formula (1e), and 0.2 part by weight of a polymerization initiator (Fuji film and Wako pure chemical industries, Ltd.; trade name: 2, 2' -azobis (isobutyronitrile)) were dissolved in 100 parts by weight of toluene. Then, the resulting mixture was heated to 70 ℃ under a nitrogen atmosphere and subjected to polymerization reaction for 5 hours to obtain an acrylic polymer solution (resin composition for polarizer protection) 1 (solid content concentration: 50% by weight). The weight average molecular weight of the acrylic polymer obtained was 50,000, and the glass transition temperature was 80 ℃.
The obtained acrylic polymer solution was applied to the polarizer side of the laminate obtained in production example 1 so that the thickness after drying became 1 μm, to form a protective layer. Next, the thermoplastic resin substrate was peeled off from the polarizer, and the polarizing plate 1 was obtained.
EXAMPLE 2 preparation of polarizing plate 2
An acrylic polymer solution (resin composition for polarizer protection) 2 (solid content concentration: 50 wt%) was obtained in the same manner as in example 1, except that the content of MMA was 99 wt%, the content of comonomer was 1 wt%, and 2 wt% of a polymerization initiator was used (polymerization conditions were changed by changing the set weight average molecular weight). The weight average molecular weight of the acrylic polymer obtained was 10,000, and the glass transition temperature was 50 ℃.
A polarizing plate 2 was obtained in the same manner as in example 1, except that the acrylic polymer solution 2 was used.
EXAMPLE 3 preparation of polarizing plate 3
An acrylic polymer solution (polarizer-protecting resin composition) 3 (solid content concentration: 50 wt%) was obtained in the same manner as in example 1, except that the content of MMA was 99 wt% and the content of the comonomer was 1 wt%. The weight average molecular weight of the acrylic polymer obtained was 50,000, and the glass transition temperature was 80 ℃.
A polarizing plate 3 was obtained in the same manner as in example 1, except that the acrylic polymer solution 3 was used.
EXAMPLE 4 production of polarizing plate 4
An acrylic polymer solution (resin composition for polarizer protection) 4 (solid content concentration: 50 wt%) was obtained in the same manner as in example 1 except that the content of MMA was 99 wt%, the content of the comonomer was 1 wt%, and the content of the polymerization initiator was 0.1 wt%. The weight average molecular weight of the resulting acrylic polymer was 100,000, and the glass transition temperature was 90 ℃.
A polarizing plate 4 was obtained in the same manner as in example 1, except that the acrylic polymer solution 4 was used.
EXAMPLE 5 preparation of polarizing plate 5
A polarizing plate 5 was obtained in the same manner as in example 3, except that the acrylic polymer solution 3 was applied so that the thickness after drying became 0.2 μm.
EXAMPLE 6 production of polarizing plate 6
A polarizing plate 6 was obtained in the same manner as in example 3, except that the acrylic polymer solution 3 was applied so that the thickness after drying became 5 μm.
EXAMPLE 7 production of polarizing plate 7
An acrylic polymer solution (polarizer-protecting resin composition) 5 (solid content concentration: 10% by weight) was obtained in the same manner as in example 1, except that the amount of MMA was 70 parts by weight and the comonomer content was 30 parts by weight. The weight average molecular weight of the acrylic polymer obtained was 50,000, and the glass transition temperature was 80 ℃.
A polarizing plate 7 was obtained in the same manner as in example 1, except that the acrylic polymer solution 5 was used.
EXAMPLE 8 preparation of polarizing plate 8
An acrylic polymer solution (resin composition for protecting a polarizer) 6 (solid content concentration: 30 wt%) was obtained in the same manner AS in example 3 except that 99 parts by weight of dicyclopentyl acrylate (DCPA, trade name: FA-513AS, manufactured by Hitachi chemical Co., Ltd.) was used AS a monomer. The weight average molecular weight of the resulting acrylic polymer was 50,000, and the glass transition temperature was 150 ℃.
A polarizing plate 8 was obtained in the same manner as in example 3, except that the acrylic polymer solution 6 was used.
EXAMPLE 9 preparation of polarizing plate 9
An acrylic polymer solution 7 (a resin composition for polarizer protection) (solid content concentration: 30 wt%) was obtained in the same manner as in example 3, except that 99 parts by weight of an adamantyl monomer (product name: MADA, manufactured by osaka organic chemical industries, inc.) was used as the monomer. The weight average molecular weight of the resulting acrylic polymer was 50,000, and the glass transition temperature was 150 ℃.
A polarizing plate 9 was obtained in the same manner as in example 3, except that the acrylic polymer solution 7 was used.
EXAMPLE 10 production of polarizing plate 10
A polarizing plate 10 was obtained in the same manner as in example 3, except that the laminate 2 obtained in production example 2 was used as a polarizing material.
EXAMPLE 11 preparation of polarizing plate 11
Polarizing plate 11 was obtained in the same manner as in example 3, except that acrylic polymer solution 3 was applied to a thickness of 10 μm after drying to form a protective layer.
Comparative example 1 production of polarizing plate C1
An acrylic polymer solution (resin composition for protecting a polarizer) C1 (solid content concentration: 50 wt%) was obtained in the same manner as in example 1, except that no comonomer was added. The weight average molecular weight of the acrylic polymer obtained was 50,000, and the glass transition temperature was 80 ℃.
A polarizing plate C1 was obtained in the same manner as in example 1, except that the acrylic polymer solution C1 was used.
Comparative example 2 production of polarizing plate C2
An acrylic polymer solution (polarizer-protecting resin composition) C2 (solid content concentration: 1 wt%) was obtained in the same manner as in example 1, except that the content of MMA was 50 wt% and the content of the comonomer was 50 wt%. The weight average molecular weight of the acrylic polymer obtained was 50,000, and the glass transition temperature was 80 ℃.
A polarizing plate C2 was obtained in the same manner as in example 1, except that the acrylic polymer solution C2 was used.
Comparative example 3 production of polarizing plate C3
An acrylic polymer solution (polarizer-protecting resin composition) C3 (solid content concentration: 30 wt%) was obtained in the same manner as in example 1, except that methacrylic acid (product name: methyl acrylate, manufactured by Fuji photo-film and Wako pure chemical industries, Ltd.) was used as the monomer. The weight average molecular weight of the acrylic polymer obtained was 50,000, and the glass transition temperature was 10 ℃.
A polarizing plate C3 was obtained in the same manner as in example 1, except that the acrylic polymer solution C3 was used.
Comparative example 4 production of polarizing plate C4
A resin composition for polarizer protection (solid content concentration: 5 wt%) was prepared by dissolving a cycloolefin-based film (product name: ZEONOR, thickness: 25 μm, manufactured by ZEON Co., Ltd., Japan) in cyclohexane.
The obtained resin composition for protecting a polarizer was applied to the polarizer of the laminate obtained in production example 1 so that the thickness after drying became 1 μm, to form a protective layer, thereby obtaining a polarizing plate C4.
Comparative example 5 production of polarizing plate C5
A triacetyl cellulose (TAC) film (product name: KC4UYW, thickness 40 μm, manufactured by KONICA) was dissolved in methylene chloride to prepare a resin composition for polarizer protection (solid content concentration: 5 wt%).
The obtained resin composition for protecting a polarizer was applied to the polarizer of the laminate obtained in production example 1 so that the thickness after drying became 1 μm, to form a protective layer, thereby obtaining a polarizing plate C5.
The resin compositions for protecting polarizers used in examples and comparative examples and the obtained polarizing plates were used to perform the following evaluations. The results are shown in Table 1.
1. Moisture permeability (MOCON determination method)
The resin composition for protecting a polarizer used in each example or comparative example was applied to a TAC film having a thickness of 25 μm so that the dried thickness thereof became 1 μm, to prepare a laminate for evaluation. The laminate was measured for moisture permeability in accordance with JIS K7129-2:2019 at a temperature of 40 ℃ and a humidity of 90%. For the measurement, MOCON water vapor transmission rate measuring apparatus (product name: PERMATRAN-W, product name, manufactured by MOCON corporation) was used.
2. Modulus of elasticity
< method for producing sample >
The polarizing plates obtained in examples or comparative examples were embedded with an epoxy resin. Next, the embedded polarizing plate was cut with a microtome. Next, the cut sample was fixed to a predetermined support, and the elastic modulus of the cut surface (side surface) of the protective layer was measured. A nanoindenter (product name: Triboindenter, manufactured by Hysitron Inc.) was used for the measurement. The measurement was performed under the following conditions.
Using a pressure head: berkovich (triangular pyramid type)
The determination method comprises the following steps: single indentation determination
Measuring temperature: at room temperature
And (3) indentation depth setting: 50nm
3. Advance adhesion (checkerboard peel test)
The polarizing plates obtained in the examples and comparative examples were cut into a size of 50mm × 150mm to obtain evaluation samples.
Using an NT cutter and a jig for adhesion force test, 11 scratches were scribed vertically and horizontally at 1mm intervals in the center of the test specimen on the protective layer side. The scratch angle was set to 35 ° ± 10 °. Next, a water-deposited transparent tape (No.252, 24mm wide) was stuck so as to cover the entire scratch, and the portion to which the tape was stuck was rubbed 10 times in a balanced manner with a pressure-bonding blade to perform pressure bonding. Thereafter, the tape was peeled by hand at high speed in the 45 ° direction. The tape was repeatedly applied and peeled 2 times, and the presence or absence of peeling was visually checked.
The cases where no peeling was observed were evaluated as good, the cases where 1 to 5 peeling were observed were evaluated as Δ, and the cases where 6 or more peeling was observed were evaluated as x.
4. End decolorization
The acrylic pressure-sensitive adhesive composition obtained in production example 3 was uniformly applied to the surface of a polyethylene terephthalate film (separator) treated with a silicone release agent by a jet coater, and then dried in an air-circulating oven at 155 ℃ for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 20 μm on the separator surface. Next, the pressure-sensitive adhesive layer was transferred to the polarizer protective layer surface side of the polarizing plate obtained in example or comparative example. Further, an adhesive was applied to the polarizer-side surface of the polarizing plate, and a (meth) acrylic resin film A (thickness: 40 μm) having a lactone ring structure was bonded thereto to obtain a polarizing plate with an adhesive layer.
The resulting polarizing plate with an adhesive layer (optical film/(adhesive)/polarizer/protective layer/adhesive/separator) was cut into pieces (50mm × 50 mm). Next, the separator was peeled off and attached to the alkali-free glass via the adhesive layer. Subsequently, the mixture was left at 60 ℃ and 90% humidity for 72 hours. Then, whether or not the polarizer was discolored was confirmed by an optical microscope (product name: MX61L, manufactured by Olympus). The amount of discoloration was measured from an image obtained by imaging the length of discoloration from the end of the polarizer at 10 times the magnification of an optical microscope. The longest length among the decolored portions was defined as the length (μm) of the decolored portion of the polarizer.
The presence or absence of discoloration was also measured under the same conditions for the polarizer 1 obtained in production example 1 and the polarizer 2 obtained in production example 2. The results of the evaluation of the discoloration of the polarizing material alone (polarizing material 1: 450 μm, polarizing material 2: 150 μm) were evaluated as good, those with less than 45% discoloration, those with 45% or more and less than 60% as good, and those with more than 60% as good.
5. Weight average molecular weight of acrylic polymer
Using the acrylic polymers obtained in examples or comparative examples, a 0.5 wt% N, N-Dimethylformamide (DMF) (added salt) solution was prepared and allowed to stand at room temperature overnight. Subsequently, the preparation solution was filtered through a membrane filter (pore diameter: 0.45 μm), and GPC measurement was performed using the filtrate. For the measurement, the following apparatus was used and the measurement was performed under the following conditions.
GPC: agilent 1200 (manufactured by Agilent Technologies Co., Ltd.)
< measurement conditions >
Column temperature: 40 deg.C
Eluent: DMF (added salt)
Flow rate: 0.4 mL/min
Injection amount: 40 μ L
A detector: differential Refractometer (RI)
Standard sample: polystyrene conversion (PS)
6. Glass transition temperature
About 5mg of the acrylic polymer obtained in examples or comparative examples was collected, and DSC measurement was performed under the following conditions.
A measuring device: TA Instruments, product name: q-2000
< measurement conditions >
Temperature program: 0 ℃→ 150 ℃ → 0 ℃ → 150 ℃ C
Atmosphere gas: n is a radical of2(50 mL/min)
Measuring speed: 10 ℃/min
[ Table 1]
Figure BDA0003231392040000271
The polarizing plates obtained in examples 1 to 11 were able to prevent discoloration from occurring at the end of the polarizer even when the protective layer was thin. Further, the adhesive property to the polarizer is also excellent, and the polarizer can be protected from peeling.
Industrial applicability
The resin composition for protecting a polarizer of the present invention can provide a polarizing plate which has excellent adhesion to a polarizer and can prevent discoloration of an end portion even when the resin composition is thin. The polarizing plate of the present invention can be widely applied to liquid crystal panels of liquid crystal televisions, liquid crystal displays, cellular phones, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, facsimile machines, clocks, microwave ovens, and the like.
Description of the reference numerals
10 polarizer
20 protective layer
100 polarizing plate

Claims (7)

1. A resin composition for protecting a polarizer, comprising a polymer obtained by polymerizing more than 50 parts by weight of an acrylic monomer and more than 0 part by weight and less than 50 parts by weight of a comonomer represented by the formula (1), wherein the polymer has a glass transition temperature of 50 ℃ or higher,
Figure FDA0003231392030000011
in formula (1), X represents a functional group comprising at least 1 reactive group selected from the group consisting of a vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, hydroxyl group, amino group, aldehyde group, and carboxyl group; r1And R2Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group or an optionally substituted heterocyclic group, R1And R2Optionally joined to each other to form a ring.
2. The resin composition for protecting a polarizing plate according to claim 1, wherein the weight average molecular weight of the polymer is 10000 or more.
3. The resin composition for protecting a polarizer according to claim 1 or 2, wherein the reactive group is at least 1 selected from the group consisting of a (meth) acryloyl group and a (meth) acrylamide group.
4. A polarizing plate comprising:
a polarizing member; and
a protective layer comprising the resin composition for protecting a polarizing plate according to any one of claims 1 to 3 on at least one surface of the polarizing plate.
5. The polarizing plate according to claim 4, wherein the protective layer has a thickness of 0.1 to 8 μm.
6. The polarizing plate of claim 4 or 5, wherein the iodine content of the polarizing element is 2 to 25 wt%.
7. The polarizing plate according to any one of claims 4 to 6, wherein the polarizing element has a thickness of 8 μm or less.
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