JP2023135469A - Polarizing plate, display member, method of manufacturing polarizing plate - Google Patents

Abstract

To provide a polarizing plate thinner than before, a display member using the polarizing plate, and a method of manufacturing the polarizing plate.SOLUTION: A polarizing plate provided herein comprises a polarizer, and a cured resin layer formed of a curable composition containing (A) a cationic polymerizable compound, (B) a radical polymerizable compound, and (C) a photopolymerization initiator and laminated directly on one surface of the polarizer without other layers in between, where content ratio of the cationic polymerizable compound and the radical polymerizable compound is in a range of 95:5 to 70:30 by mass.SELECTED DRAWING: Figure 1

Description

The present invention relates to a polarizing plate, a display member, and a method for manufacturing a polarizing plate.

Polarizing plates are used in liquid crystal displays (LCDs) and organic EL displays (OLEDs) to prevent reflection of external light. The polarizing plate is provided with a protective film for protecting the polarizer. A protective film for a polarizing plate generally has a structure in which a hard coat layer is provided on a transparent base material. As the material of the transparent base material, triacetyl cellulose (TAC), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), etc. are used in consideration of adhesion with PVA. Since the transparent base material has a thickness of 20 to 40 μm, it has been difficult to meet the demand for further thinning of the polarizing plate.

Therefore, as a thinner polarizing plate, the transparent base material is omitted and two layers are laminated on the polarizer: an intervening layer made of a thermosetting resin and a hard coat layer made of a photocurable resin. This is being considered (see Patent Document 1).

Patent No. 4680165

In the polarizing plate described in Patent Document 1, an intervening layer made of a thermosetting resin is interposed in order to improve the adhesion between the polarizer and the hard coat layer. However, the configuration described in Patent Document 1 has room for further thinning.

Therefore, an object of the present invention is to provide a polarizing plate that is thinner than conventional ones, a display member using the polarizing plate, and a method for manufacturing the polarizing plate.

The polarizing plate according to the present invention includes a polarizer and a cured resin layer, and the cured resin layer contains (A) a cationically polymerizable compound, (B) a radically polymerizable compound, and (C) a photopolymerization initiator. is laminated on one side of the polarizer without intervening other layers, and the content ratio of the cationically polymerizable compound and the radically polymerizable compound is 95:5 to 70 in mass ratio. :30.

The method for manufacturing a polarizing plate according to the present invention is for manufacturing a polarizing plate comprising a polarizer and a cured resin layer, the method comprising: (A) a cationically polymerizable compound; (B) a radically polymerizable compound; , (C) A curable composition containing a photopolymerization initiator is coated on one side of a polarizer without intervening other layers, and the coating film is cured to form a cured resin layer. It is characterized in that the content ratio of the polymerizable compound and the radically polymerizable compound is 95:5 to 70:30 in terms of mass ratio.

The present invention can provide a polarizing plate that is thinner than conventional ones, a display member using the polarizing plate, and a method for manufacturing the polarizing plate.

Cross-sectional view showing a polarizing plate according to an embodiment

FIG. 1 is a sectional view showing a polarizing plate according to an embodiment.

The polarizing plate 1 includes a polarizer 2 and a hard coat layer 3 provided on one side of the polarizer 2.

The polarizer 2 is made by adsorbing iodine or dye to a hydrophilic resin film such as polyvinyl alcohol (PVA), and uniaxially stretching the film to orient the iodine or dye. Since the hydrophilic resin film constituting the polarizer 2 has poor strength and water resistance, a hard coat layer 3 serving as a protective layer is provided on at least one surface of the polarizer 2.

The hard coat layer 3 is a functional layer that provides hardness to the polarizing plate 1 and protects the polarizer 2. Hard coat layer 3 is formed directly on the surface of polarizer 2 without using any other layer. The hard coat layer 3 can be formed by applying a coating liquid containing a polymerizable compound to the surface of the polarizer 2 and curing the coating film.

In detail, the hard coat layer 3 is a cured resin layer formed by curing a curable composition containing (A) a cationically polymerizable compound, (B) a radically polymerizable compound, and (C) a photopolymerization initiator. It is. In this specification, the term "polymerizable compound" is a general term for monomers, oligomers, prepolymers, and polymers having a polymerizable functional group.

(A) Cationically polymerizable compound The cationically polymerizable compound is preferably a compound having one or both of an epoxy group and an oxetanyl group as a polymerizable functional group. Examples of cationic polymerizable compounds include 3-ethyl-3-hydroxyethyloxetane, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 3,3-dimethyloxetane, 3,3-bis( chloromethyl)oxetane, 2-hydroxymethyloxetane, 3-methyl-3-oxetanemethanol, 3-methyl-3-methoxymethyloxetane, 3-ethyl-3-phenoxymethyloxetane, 3-ethyl-3{[(3- Oxetanes such as ethyloxetan-3-yl)methoxy]methyl}oxetane, resorcinol bis(3-methyl-3-oxetanylethyl) ether, xylylene bisoxetane, m-xylylene bis(3-ethyl-3-oxetanylethyl ether) ;Cyclohexene oxide, 1,13-tetradecadiene dioxide, limonene dioxide, (3,4,3',4'-diepoxy)bicyclohexyl, 3,4-epoxycyclohexylmethyl (3',4'-epoxy) Examples include alicyclic epoxies such as cyclohexane carboxylate, bis(3,4-epoxycyclohexyl) adipate, and bis(3,4-epoxycyclohexyl) sebacate.

Among these, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, (3,3',4,4'-diepoxy)bicyclohexyl and 3,4-epoxycyclohexylmethyl One or more selected from (3',4'-epoxy)cyclohexanecarboxylate is preferred.

(B) Radical polymerizable compound As the radical polymerizable compound, (meth)acrylate having one or both of an acryloyl group and a methacryloyl group can be used as a polymerizable functional group. It is preferable to use a polyfunctional (meth)acrylate having multiple polymerizable functional groups. In this specification, "(meth)acrylate" is a generic term for both acrylate and methacrylate, and "(meth)acryloyl" is a generic term for both acryloyl and methacryloyl.

Examples of the bifunctional (meth)acrylate include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxy diacrylate, bisphenol A tetrapropoxy diacrylate, and 1,6-hexanediol diacrylate.

Examples of trifunctional or higher functional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and dipentaerythritol. Examples include tetra(meth)acrylate, isocyanuric acid-modified tri(meth)acrylate, and the like.

Further, the above (meth)acrylate monomer may have a part of its molecular skeleton modified, such as ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. can also be used.

Furthermore, the polyfunctional (meth)acrylate oligomer is not particularly limited as long as it is a difunctional or higher (meth)acrylate oligomer, such as urethane (meth)acrylate oligomer, epoxy (meth)acrylate oligomer, polyester (meth)acrylate oligomer, etc. Various (meth)acrylate oligomers such as acrylate oligomers and polyether (meth)acrylate oligomers can be used.

Urethane (meth)acrylate oligomers are obtained, for example, by reacting polyhydric alcohols and organic diisocyanates with hydroxy (meth)acrylates.

Further, preferred epoxy (meth)acrylate oligomers include (meth)acrylate obtained by reacting trifunctional or higher functional aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, etc. with (meth)acrylic acid; (Meth)acrylate obtained by reacting a functional or higher functional aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, etc. with a polybasic acid and (meth)acrylic acid, and a difunctional or higher functional aromatic epoxy resin It is a (meth)acrylate obtained by reacting an alicyclic epoxy resin, an aliphatic epoxy resin, etc., a phenol, and (meth)acrylic acid.

In the hard coat layer forming cured composition, (A) the cationic polymerizable compound has a role of improving the adhesion between the hard coat layer 3 and the polarizer 2. The cationically polymerizable compound has a cationically polymerizable functional group such as an epoxy group or an oxetanyl group, and generates an ether bond derived from the cationically polymerizable group through cationic polymerization. The ether bond derived from the cationic polymerizable compound forms a hydrogen bond with a hydroxyl group possessed by a hydrophilic resin such as PVA, which is the base material of the polarizer 2. It is thought that this improves the adhesion between the hard coat layer 3 and the polarizer 2. On the other hand, the radically polymerizable compound (B) has a role of improving the hardness of the hard coat layer 3.

In the cured composition for forming a hard coat layer, the solid content ratio of (A) the cationically polymerizable compound and (B) the radically polymerizable resin is preferably 95:5 to 70:30 in terms of mass ratio. If the blending ratio of the cationically polymerizable compound exceeds 95% by mass, the ratio of the radically polymerizable group decreases, which is undesirable because the hardness of the hard coat layer 3 decreases. Moreover, if the blending ratio of the cationically polymerizable compound is less than 70%, the adhesion between the hard coat layer 3 and the polarizer 2 will decrease, which is not preferable.

(C) Photopolymerization initiator A photocationic polymerization initiator and a radical polymerization initiator are used as the photopolymerization initiator. Since a photocationic polymerization initiator and a radical polymerization initiator are used in combination, the cationic polymerization reaction and the radical polymerization reaction can proceed simultaneously by ultraviolet irradiation.

Examples of photocationic polymerization initiators include aryldiazonium salts such as p-methoxybenzenediazonium hexafluorophosphate; diaryliodonium salts such as diphenyliodonium hexafluorophosphate and diphenyliodonium hexafluoroantimonate; triphenylsulfonium hexafluorophosphate and triphenylsulfonium. Hexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium pentafluorohydroxyantimonate , diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate, and triarylsulfonium salts such as 4,4-bis(thianthrenium-9-yl)-diphenyl ether dihexafluorophosphate; Triarylselenonium salts such as phenylselenonium hexafluorophosphate, triphenylselenonium tetrafluoroborate, triphenylselenonium hexafluoroantimonate; such as dimethylphenacylsulfonium hexafluoroantimonate, diethylphenacylsulfonium hexafluoroantimonate, etc. Dialkyl phenacylsulfonium salts; dialkyl-4-hydroxy salts such as 4-hydroxyphenyldimethylsulfonium hexafluoroantimonate, 4-hydroxyphenylbenzylmethylsulfonium hexafluoroantimonate; α-hydroxymethylbenzoin sulfonic acid ester, N-hydroxyimide Examples include sulfonate esters such as sulfonate, α-sulfonyloxyketone, and β-sulfonyloxyketone.

Commercially available triarylsulfonium salts include "AT-6992" and "AT-6976" (trade names, both manufactured by ACETO); "ADEKA OPTOMER SP-150", "ADEKA OPTOMER SP-170", "ADEKA OPTOMER SP-170", "Optomer SP-171" (product name, all manufactured by ADEKA Co., Ltd.); "CPI-100P", "CPI-110P", "CPI-110A", "CPI-210S" (product name, all manufactured by Sun-Apro ( Co., Ltd.); “TS-91”, “TS-01” (trade names, both manufactured by Sanwa Chemical Co., Ltd.); “Esacure 1187”, “Esacure 1188” (trade names, both manufactured by Lamberti), “ "Omnicat550" and "Omnicat650" (product names, both manufactured by IGM RESIN) can be used.

Among the above, from the viewpoint of curability and transparency, the cationic polymerization initiator is preferably a triarylsulfonium salt, such as diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium salt, etc. At least one selected from the group consisting of phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate and 4,4-bis(thianthrenium-9-yl)-diphenyl ether dihexafluorophosphate is more preferred; ) phenyl]sulfonium hexafluorophosphate is more preferred.

Examples of the radical polymerization initiator include acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyl methyl ketal, benzoyl benzoate, α-acyl oxime ester, thioxanthone, and the like. Among them, α-hydroxyalkylphenone is preferably used from the viewpoint of curability and transparency. Radical polymerization initiators can be used alone or in combination of two or more.

An organic solvent may be appropriately added to the hard coat layer-forming cured composition. Examples of organic solvents include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropyl alcohol, and isobutanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone, and ketone alcohols such as diacetone alcohol. Aromatic hydrocarbons such as benzene, toluene, xylene, glycols such as ethylene glycol, propylene glycol, hexylene glycol, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, diethyl carbitol, propylene Glycol ethers such as glycol monomethyl ether, esters such as methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, amyl acetate, ethers such as dimethyl ether and diethyl ether, N-methylpyrrolidone, dimethylformamide, etc. Among them, one type or a mixture of two or more types can be used.

In addition, various additives such as antifoaming agents, leveling agents, antioxidants, ultraviolet absorbers, light stabilizers, polymerization inhibitors, photosensitizers, etc. may be added to the hard coat layer forming hardening composition as necessary. May be combined.

In the polarizing plate 1 according to the present embodiment, the above-mentioned hard coat layer forming hardening composition is applied to at least one surface of a polarizer 2 without intervening other layers, dried, and a coating film is formed by UV irradiation. It can be manufactured by curing. In the method for manufacturing the polarizing plate 1 according to the present embodiment, the hard coat layer 3 can be directly laminated on the polarizer 2 by applying the cured composition once and irradiating the ultraviolet rays once, so the manufacturing efficiency is excellent. Further, as the polymerizable compound in the hard coat layer forming hardening composition, a cationically polymerizable compound and a radically polymerizable compound are used in combination, and the blending ratio thereof is within the above-mentioned range. For this reason, although the hard coat layer 3 is formed on the polarizer 2 without intervening other layers, both the adhesion between the hard coat layer 3 and the polarizer 2 and the surface hardness of the hard coat layer 3 are Excellent in

The polarizing plate 1 according to the present embodiment can be used to configure an image display device by being bonded to an image display panel such as a liquid crystal panel or an organic EL panel. The image display device also includes a configuration equipped with a touch panel. The polarizing plate 1 according to this embodiment has a hard coat layer 3 formed on at least one side of a polarizer 2 without intervening another layer, and a transparent resin film is not provided on the at least one side. Omitting at least one transparent resin film contributes to making the image display device thinner. Since it has excellent one-sided stain resistance and scratch resistance, it is suitable as an optical film provided on the outermost surface of an image display device.

In addition, in this embodiment, the example in which the hard coat layer 3 was formed on one side of the polarizer 2 was explained. In this case, a protective film made of a resin film such as triacetyl cellulose, polymethyl methacrylate, or cycloolefin polymer may be attached to the other surface of the polarizer 2. Further, the hard coat layer 3 may be formed on the other side of the polarizer 2 without interposing any other layer.

Further, the polarizing plate 1 according to this embodiment may constitute a display member used in an image display device. Examples of display members include a configuration in which an adhesive layer is laminated on the polarizing plate 1, a configuration in which another resin film is laminated on the polarizing plate 1, a configuration in which a circularly polarizing plate is laminated on the polarizing plate 1, etc. .

Examples in which the present invention was specifically implemented will be described below.

The materials used in the examples and comparative examples are as follows.
<Radical polymerizable compound>
Pentaerythritol triacrylate <Cationic polymerizable compound>
3',4'-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (product name: Celoxide 2021P, Daicel Corporation)
<Radical polymerization initiator>
1-Hydroxycyclohexyl-phenylketone (trade name: Irgacure (registered trademark) 184)
<Cationic polymerization initiator>
Triarylsulfonium salt (product name: CPI-100P, San-Apro Co., Ltd.)
<Solvent>
Methyl ethyl ketone (MEK)
Methyl isobutyl ketone (MIBK)

A 25 μm thick triacetylcellulose film was attached to one side of the PVA film to create a laminated film with a total thickness of 40 μm. The hard coat layer forming hardening composition listed in Table 1 was applied to the other side of the PVA film using a wire bar coater, and after drying, the coating film was irradiated with ultraviolet rays at an exposure dose of 100 mJ/ ^cm2 . The film was cured to create a hard coat film. The coating amount of the cured composition for forming a hard coat layer was such that the thickness of the hard coat layer after curing was 5 μm.

The mixing ratio of the cationically polymerizable compound and the radically polymerizable compound (mass of the cationically polymerizable compound:mass of the radically polymerizable compound) in each Example and each Comparative Example is as follows.
・Example 1 80:20
・Example 2 95: 5
・Example 3 70:30
・Comparative example 1 100: 0
・Comparative example 2 65:35
・Comparative example 3 50:50

The pencil hardness of the hard coat films of Examples and Comparative Examples and the adhesion of the hard coat layer were evaluated by the following method.

<Pencil hardness>
Pencil hardness was evaluated in accordance with JIS K5400-1900. The pencil hardness of the surface of the hard coat layer was measured using a pencil (uni, Mitsubishi Pencil Co., Ltd.) and a Clemens scratch tester (HA-301, Tester Sangyo Co., Ltd.). The test was repeated while changing the hardness of the pencil, and changes in appearance due to scratches were visually observed, and the maximum hardness at which no scratches were observed was taken as the evaluation value. Pencil hardness of 2H or higher was considered to be a pass.

<Adhesion>
The adhesion between the hard coat layer and the PVA film was evaluated in accordance with JIS K5600-5-6. 100 crosscuts of 1 mm ² were created in the hard coat layer of the hard coat films according to Examples and Comparative Examples using a checkerboard peel test jig. Adhesive tape (CT405AP-24, Nichiban Co., Ltd.) is pasted on the created cross-cut, and after pressing it uniformly using a spatula, the adhesive tape is peeled off in a 90° direction to determine the residual rate of the hard coat layer (1 mm ² The remaining number of regions) was taken as the evaluation value. A hard coat layer residual rate of 95% or more was considered a pass.

Table 1 shows the composition of the cured composition for forming a hard coat layer and the evaluation results of pencil hardness and adhesion.

The hard coat layer of the hard coat film according to Examples 1 to 3 was a curable composition containing a cationically polymerizable compound and a radically polymerizable compound such that the mass ratio was within the range of 95:5 to 70:30. It is formed by something. Therefore, both the adhesion of the hard coat layer to the PVA film and the pencil hardness of the surface of the hard coat layer were excellent.

In the hard coat film according to Comparative Example 1, the hard coat layer was formed from a curable composition that did not contain a radically polymerizable compound, so compared to Examples 1 to 3, the pencil hardness of the hard coat layer surface was lower. decreased.

In the hard coat films of Comparative Examples 2 and 3, the adhesion of the hard coat layer to the PVA film was lower than in Examples 1 to 3 because the blending ratio of the cationic polymerizable compound was less than the above range.

As described above, according to the present invention, by directly laminating a hard coat layer on a PVA film (polarizer), it is possible to reduce the overall thickness, and the hard coat layer has excellent adhesion and surface hardness to the PVA film. It was confirmed that a polarizing plate could be realized.

INDUSTRIAL APPLICATION This invention can be utilized for the polarizing plate used for an image display apparatus etc.

1 Polarizing plate 2 Polarizer 3 Hard coat layer

Claims (5)

A polarizer and
Equipped with a cured resin layer,
The cured resin layer is made of a curable composition containing (A) a cationically polymerizable compound, (B) a radically polymerizable compound, and (C) a photopolymerization initiator; are laminated without intervening layers,
A polarizing plate characterized in that the content ratio of the cationically polymerizable compound to the radically polymerizable compound is 95:5 to 70:30 in terms of mass ratio. The polarizing plate according to claim 1, wherein the cationically polymerizable compound has at least one cationically curable functional group selected from an epoxy group and an oxetanyl group. The polarizing plate according to claim 1 or 2, wherein the radically polymerizable compound has at least one radically curable functional group selected from an acryloyl group and a methacryloyl group. A display member comprising the polarizing plate according to any one of claims 1 to 3. A method for manufacturing a polarizing plate comprising a polarizer and a cured resin layer,
A curable composition containing (A) a cationically polymerizable compound, (B) a radically polymerizable compound, and (C) a photopolymerization initiator is applied onto one side of the polarizer without intervening another layer. forming the cured resin layer by processing and curing the coating film,
A method for producing a polarizing plate, characterized in that the content ratio of the cationically polymerizable compound to the radically polymerizable compound is 95:5 to 70:30 in terms of mass ratio.

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