JP6622450B2 - Adhesive for polarizing plate and display device using the same - Google Patents

Description

  The present invention relates to a polarizing plate adhesive for bonding a polarizer (polarizing film) and a protective film used when manufacturing a polarizing plate, and a display device using the same.

  In recent years, flat displays such as liquid crystal displays and plasma displays have been widely used as display devices because they are space-saving and have high definition. Among these, liquid crystal displays are attracting attention and are being developed because they are more power-saving and have higher definition.

  In a liquid crystal display panel, a polarizing plate serving as an optical shutter is used in combination with liquid crystal. Here, although the polarizing plate is equipped with a polarizer, since the polarizer is usually produced by uniaxially stretching a polyvinyl alcohol resin to a length of 5 to 6 times in a water tank, it is easy to tear in the stretching direction, There is a drawback of being brittle. Therefore, the polarizer is configured to adhere a protective film to the front surface and / or the back surface.

  Here, conventionally, a polyvinyl alcohol-based water-based adhesive has been used as an adhesive for bonding a polarizer and a protective film. For example, with a difficult-to-adhere film formed from a cycloolefin polymer. There are problems that adhesion is difficult and productivity is difficult to improve.

  Therefore, in order to solve these disadvantages, an adhesive made of a composition containing an active energy ray-curable compound has been proposed. More specifically, an adhesive comprising an epoxy resin containing no aromatic ring as a main component and a photocationic polymerization initiator, which is cured by cationic polymerization by irradiation with active energy rays. Has been proposed. And even if it is a case where a resin film with low moisture permeability is used as a protective film by using such an adhesive, one side of the polarizer can be used with sufficient adhesive strength without causing problems such as poor appearance. Or it is described that the polarizing plate by which the protective film was bonded on both surfaces can be provided (for example, refer patent document 1).

  Further, 100 parts by mass of an epoxy resin (A) having two or more epoxy groups in the molecule and at least one of the epoxy groups being an alicyclic epoxy group, and two or more epoxy groups in the molecule A photocurable adhesive comprising 5 to 1000 parts by mass of an epoxy resin (B) having substantially no alicyclic epoxy group and 0.5 to 20 parts by mass of a cationic photopolymerization initiator (C). Agents have been proposed. And by using such an adhesive, it is excellent in storage stability, can suppress discoloration of the adhesive itself and the object to be bonded at the time of curing, has a high curing speed and gives good adhesiveness. It is described that a curable adhesive can be provided (see, for example, Patent Document 2).

Japanese Patent No. 4306270 JP 2008-257199 A

  However, the adhesives described in Patent Documents 1 and 2 are difficult to achieve both adhesiveness to both the polarizer and the protective film, and because of poor heat resistance, the polarizer has cracks. There was a problem that it was likely to occur.

  Accordingly, the present invention has been made in view of the above-described problems, and has excellent adhesion to the polarizer and the protective film, and has excellent heat resistance and can suppress generation of cracks in the polarizer. An object of the present invention is to provide a plate adhesive and a display device using the same.

  In order to achieve the above object, a polarizing plate of the present invention is attached to at least one surface of a polarizer via a polarizer, an adhesive layer provided on the surface of the polarizer, and an adhesive layer. And a protective film, and the adhesive layer includes an aromatic epoxy resin having an epoxy group having three or more functional groups, a branched structure, and at least one functional epoxy group in the branched structure. It is characterized by being formed of a cured product.

  According to the present invention, there is provided a polarizing plate provided with an adhesive layer for a polarizing plate that has good adhesion to a polarizer and a protective film, has excellent heat resistance, and can suppress generation of cracks in the polarizer. Can be provided.

It is sectional drawing which shows the polarizing plate which concerns on embodiment of this invention. It is a figure for demonstrating the manufacturing method of the polarizing plate which concerns on embodiment of this invention. It is a figure for demonstrating the initial stage sclerosis | hardenability test of the polarizing plate which concerns on the Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a polarizing plate according to an embodiment of the present invention.

  As shown in FIG. 1, the polarizing plate 1 is attached to both sides of the polarizer 2 through the polarizer 2, the adhesive layer 9 provided on the surface of the polarizer 2, and the adhesive layer 9. A polarizing plate protective film (hereinafter, sometimes simply referred to as “protective film”) 3 is provided.

  And in this invention, while the adhesive bond layer 9 has a tri- or more functional epoxy group, it has a branched structure, The resin composition containing the aromatic epoxy resin in which at least 1 functional epoxy group exists in a branched structure It is characterized in that it is formed of a cured product.

<Polarizer>
There is no restriction | limiting in particular as the polarizer 2, A conventionally well-known thing can be used. For example, dichroic materials such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product.

  Among these, a polarizer produced by dyeing a polyvinyl alcohol film having an average polymerization degree of 2000 to 2800 and a saponification degree of 90 to 100 mol% with iodine and uniaxially stretching it 5 to 6 times is particularly preferable. More specifically, such a polarizer is obtained by, for example, immersing and stretching a polyvinyl alcohol film by immersing it in an aqueous solution of iodine. As an aqueous solution of iodine, for example, it is preferable to immerse in an aqueous solution of 0.1 to 1.0% by mass of iodine / potassium iodide. If necessary, it may be immersed in an aqueous solution such as boric acid or potassium iodide at 50 to 70 ° C., or may be immersed in water at 25 to 35 ° C. in order to prevent washing or uneven dyeing. Stretching may be performed after dyeing with iodine, may be stretched while dyeing, or may be dyed with iodine after stretching. After dyeing and stretching, it may be washed with water and dried at 35 to 55 ° C. for about 1 to 10 minutes.

<Protective film>
The protective film 3 is preferably a material that is excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropic properties, and the like. For example, cellulose resins such as cellulose diacetate and cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) Resin, polycarbonate resin, polyethylene, polypropylene, polyolefin having cyclo or norbornene structure, polyolefin resin such as ethylene / propylene copolymer, vinyl chloride resin, amide resin such as nylon and aromatic polyamide, imide resin Resin, sulfone resin, polyether sulfone resin, polyether ether ketone resin, polyphenylene sulfide resin, vinyl alcohol resin, vinylidene chloride Resins, vinyl butyral resins, arylate resins, polyoxymethylene resins, such as epoxy resin or a mixture of the resin, and the like.

  Among these, the protective film 3 is preferably a cellulose resin that is an ester of cellulose and a fatty acid, a cycloolefin polymer (COP film), or polyethylene terephthalate (PET film). Examples of the cellulose resin include cellulose triacetate (TAC film), cellulose diacetate, cellulose tripropionate, and cellulose dipropionate.

  Among these, cellulose triacetate, polyethylene terephthalate and cycloolefin polymer are particularly preferable from the viewpoint of availability and cost. Cellulose triacetate may be saponified, but is preferably unsaponified. Examples of the cycloolefin polymer include polymers having as a constituent a polymer obtained by hydrogenating a ring-opening polymer of tetracyclododecene described in JP-B-2-9619.

  Examples of commercially available TAC films include UV-50, UV-80, SH-80, TD-80U, TD-TAC, UZ-TAC, and Kika series manufactured by Konica Minolta Opto, Inc. It is done. Examples of commercially available COP films include Arton (registered trademark) manufactured by JSR Corporation, ZEONEX (registered trademark) series, and ZEONOR (registered trademark) series manufactured by ZEON Corporation. Examples of commercially available PET film include the Cosmo Shine (registered trademark) series manufactured by Toyobo Co., Ltd.

  The surface of the protective film 3 is preferably modified by corona discharge treatment. There is no restriction | limiting in particular as a method of a corona discharge treatment, It can process using a common corona discharge treatment apparatus (for example, Kasuga Electric Co., Ltd. product). By performing the corona discharge treatment, for example, an active group such as a hydroxyl group is formed on the surface of the protective film 3, and this is considered to contribute to the improvement of the adhesiveness. When saponified cellulose triacetate is used as the protective film 3, the effect of improving the adhesion similar to that of the corona discharge treatment can be expected, and therefore the corona discharge treatment is not always necessary. However, since the saponification process is complicated and expensive, it is preferable in the production process to use unsaponified cellulose triacetate after corona discharge treatment.

Although there is no restriction | limiting in particular as a discharge amount in the case of a corona treatment, 30-300 W * min / m < ² > is preferable, More preferably, it is 50-250 W * min / m < ² >. Within such a range, the adhesiveness between the protective film 3 and the adhesive layer 9 can be improved without deteriorating the protective film 3 itself, which is preferable. Here, the discharge amount is a work amount to an object by corona discharge obtained by the following calculation, and corona discharge power is determined based on this.
(Discharge amount) = (discharge power) ÷ {(target object processing speed) × (electrode length)}
<Adhesive layer>
As described above, the adhesive layer 9 in this embodiment has a tri- or higher functional epoxy group, a branched structure, and a resin containing an aromatic epoxy resin in which at least one functional epoxy group exists in the branched structure. It is formed of an adhesive made of a cured product of the composition.

  By using such an aromatic epoxy resin, the adhesiveness is good, the heat resistance is excellent, and it is possible to suppress the occurrence of cracks in the polarizer 2 in a thermal shock test such as a thermal cycle. Become.

(1) Aromatic epoxy resin As an aromatic epoxy resin having a trifunctional or higher functional epoxy group and a branched structure, and having a monofunctional epoxy group in the branched structure, for example, three glycidyl molecules in the molecule And a trifunctional aromatic epoxy resin having a group and a tetrafunctional aromatic epoxy resin having four glycidyl groups in the molecule.

  A trifunctional aromatic epoxy resin having a branched structure and having a monofunctional epoxy group in the branched structure is represented by the following general formula (1).

（式中、Ｒ^１〜Ｒ^４は、各々独立して水素原子、ハロゲン原子またはメチル基を表し、Ｙは、下記一般式（２）、または下記一般式（３）から選択される基を示す。）

Wherein R ^{1 to} R ⁴ each independently represent a hydrogen atom, a halogen atom or a methyl group, and Y represents a group selected from the following general formula (2) or the following general formula (3) .)

（式中、Ｒ^５〜Ｒ^２４は、各々独立して水素原子、ハロゲン原子またはメチル基を示し、Ｒ^０１〜Ｒ^０３は、各々独立して水素原子またはメチル基を示す。）

(In the formula, R ^{5 to} R ²⁴ each independently represent a hydrogen atom, a halogen atom or a methyl group, and R ^{01 to} R ⁰³ each independently represent a hydrogen atom or a methyl group.)

  In addition, * in the said General formula (2), (3) shows a coupling | bond part.

  Specific examples of the aromatic epoxy resin having a trifunctional epoxy group are shown below.

  The tetrafunctional aromatic epoxy resin is represented by the following general formulas (8) and (9).

（式中、Ｒ^２５〜Ｒ^６０は、各々独立して水素原子、ハロゲン原子またはメチル基を示し、Ｒ^０４〜Ｒ^０５は、各々独立して水素原子またはメチル基を示す。）

(In the formula, R ^{25 to} R ⁶⁰ each independently represent a hydrogen atom, a halogen atom or a methyl group, and R ^{04 to} R ⁰⁵ each independently represent a hydrogen atom or a methyl group.)

  Specific examples of the aromatic epoxy resin having a tetrafunctional epoxy group are shown below.

  Thus, as the aromatic epoxy resin in the present embodiment, an aromatic epoxy resin having an epoxy group having three or more functional groups and having at least one functional epoxy group in the branched structure is used. Moreover, the trisphenol glycidyl ether resin shown by said Formula (5)-Formula (7) is especially preferable from a viewpoint of suppressing further generation | occurrence | production of the crack of the polarizer in thermal shock tests, such as a thermal cycle.

  Moreover, while improving reliability and adhesiveness, from the viewpoint of avoiding an excessive increase in viscosity, the content of the aromatic epoxy resin is 5 to 5 with respect to the entire resin composition forming the adhesive layer 9. 40 mass% is preferable, 5-35 mass% is more preferable, and 8-30 mass% is especially preferable.

  In addition, the resin composition forming the adhesive layer 9 of the present embodiment has an aromatic skeleton in addition to the above-described aromatic epoxy resin from the viewpoint of improving photoreactivity and diluting the viscosity of the resin composition. Does not contain epoxy resin. Moreover, the resin composition which forms the contact bonding layer 9 of this embodiment contains the photo-acid generator (photoinitiator) and the photosensitizer.

(2) Epoxy resin not having an aromatic skeleton The epoxy resin not having an aromatic skeleton is not particularly limited, and examples thereof include an aliphatic epoxy resin and an alicyclic epoxy resin.

  Examples of aliphatic epoxy resins include aliphatic polyhydric alcohols and polyglycidyl ether compounds of alkylene oxide adducts thereof, such as 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, Diethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane diglycidyl ether, polyethylene glycol diglycidyl ether Etc.

  Examples of alicyclic epoxy resins include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1,2: 8,9 diepoxy limonene, 1,2-epoxy-4-vinylcyclohexane, and the like. Can be mentioned.

  In addition, from the viewpoint of improving curability and flexibility, the content of the epoxy resin having no aromatic skeleton is 60 to 95% by mass with respect to the entire resin composition forming the adhesive layer 9. Preferably, 65-95 mass% is more preferable, and 70-92 mass% is especially preferable.

(3) Photoacid generator As the photoacid generator, a conventionally known photoacid generator can be used without particular limitation. Specific examples include aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. These may be used alone or in combination of two or more.

  Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

  Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

  Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium hexafluoroantimonate, 4,4′-bis [diphenylsulfonio] diphenylsulfide bishexafluorophosphate, 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluoroantimonate, 4,4′-bis [Di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluorophosphate, 7- [di (p-toluyl) sulfonio] -2-iso Propylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate, 4 -(P-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenylsulfide Examples include tetrakis (pentafluorophenyl) borate and diphenyl [4- (phenylthio) phenyl] sulfonium phosphate.

  Examples of iron-allene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris. And (trifluoromethylsulfonyl) methanide.

  Commercially available photoacid generators may be used, for example, CPI-100P, 101A, 200K, 210S (manufactured by Sun Apro Co., Ltd.), Kayarad (registered trademark) PCI-220, PCI-620 (manufactured by Nippon Kayaku Co., Ltd.). ), UVI-6990 (manufactured by Union Carbide), Adeka optomer SP-150, SP-170 (manufactured by ADEKA), CI-5102, CIT-1370, 1682, CIP-1866S, 2048S, 2064S, (Nippon Soda) Co., Ltd.), DPI-101, 102, 103, 105, MPI-103, 105, BBI-101, 102, 103, 105, TPS-101, 102, 103, 105, MDS-103, 105, DTS-102 103 (Midori Chemical Co., Ltd.), PI-2074 (Rhodia Japan Co., Ltd.) Company, Ltd.) and the like.

  In addition, from the viewpoint of preventing a decrease in curability of the resin composition after irradiation with active energy rays and a decrease in durability, the content of the photoacid generator is in the entire resin composition forming the adhesive layer 9. On the other hand, 0.1-10 mass% is preferable, 0.5-8 mass% is more preferable, and 1-5 mass% is especially preferable.

(4) Photosensitizer The resin composition forming the adhesive layer 9 of this embodiment further contains a photosensitizer. By using a photosensitizer, the reactivity of cationic polymerization is improved, and the mechanical strength and adhesiveness of the resin composition of this embodiment can be improved.

  Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreducible dyes. More specifically, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4′- Benzophenone derivatives such as bis (dimethylamino) benzophenone and 4,4′-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone; Acridone derivatives such as N-methylacridone and N-butylacridone; and α, α-diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compounds, halogens Compounds, and the like.

  In addition, from a viewpoint of improving curability and weather resistance, 0-5 mass% is preferable with respect to the whole resin composition which forms content of the photosensitizer, and 0-2. Mass% is particularly preferred.

(5) Acrylic resin The resin composition which forms the adhesive bond layer 9 of this embodiment can contain an acrylic resin further. By using an acrylic resin that is a radical polymerizable compound, photoreactivity can be further improved and the viscosity of the resin composition can be easily diluted.

  As the acrylic resin, conventionally known acrylic resins can be used without particular limitation as long as they exhibit radical polymerizability. Typical examples include monomers having a (meth) acryloyl group, a (meth) acrylamide group, and the like, such as (meth) acrylic acid and derivatives thereof, (meth) acrylonitrile, (meth) acrylamide and derivatives thereof, and the like. It is done. These monomers may be used alone or in combination of two or more.

  More specifically, examples of the acrylic monomer include (meth) acrylic acid and salts thereof. That is, methyl (meth) acrylate, ethyl (meth) acrylate, methylphenoxyethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) Acrylate, pentyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylate, 2-methoxyethyl (meth) acrylate, (meth) acrylate, 2-hydroxy Ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate 3-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethylene glycol di (meth) acrylate, phenoxyethylene glycol di (meth) acrylate, diethylene glycol di (meth) ) Acrylate, phenoxydiethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, phenoxytriethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, nonaethylene glycol di (meth) acrylate, polypropylene glycol di ( (Meth) acrylate, dipropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butanediol (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1.6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (Meth) acrylate, trimethylolmethane tri (meth) acrylate, isobornyl (meth) acrylate, N-vinylpyrrolidone, acryloylmorpholine, urethane (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, mono-ε of tetrahydrofurfuryl alcohol -(Meth) acrylate of caprolactone adduct, di-ε-caprolactone adduct of tetrahydrofurfuryl alcohol, mono-β of caprolactone adduct, tetrahydrofurfuryl alcohol (Meth) acrylates such as (meth) acrylate of methyl-δ-valerolactone adduct, (meth) acrylate of diβ-methyl-δ-valerolactone adduct of tetrahydrofurfuryl alcohol, ω-carboxy-polycaprolactone monoacrylate, etc. Acrylic ester compounds; nitrile group-containing vinyl compounds such as acrylonitrile and methacrylonitrile; and (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N -Isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N- ( Hydroxy Chill) acrylamide, N- isopropyl (meth) acrylamide, N- methylol (meth) acrylamide, diacetone (meth) acrylamide, N, etc. N- methylenebis (meth) amide group-containing vinyl compound such as acrylamide.

  Among these, from the viewpoint of being excellent in initial curability as a resin composition for forming the adhesive layer 9 and improving the adhesion between the polarizer 2 and the protective film 3, a hydroxy group-containing acrylic monomer and a phenoxy group are contained. At least one of acrylic monomers is more preferable, and in particular, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, methylphenoxyethyl (meth) acrylate and phenoxydiethylene glycol (meth) acrylate, 2-hydroxy-3 -More preferred is phenoxypropyl acrylate.

  In addition, from the viewpoint of improving curability and weather resistance, the content of the acrylic resin is preferably 0 to 50% by mass, and 0 to 30% by mass with respect to the entire resin composition forming the adhesive layer 9. Is particularly preferred.

<Production method of polarizing plate>
(1) Method for Producing Resin Composition for Adhesive Layer The method for producing the resin composition for the adhesive layer 9 of the present invention is not particularly limited. Usually, the above-described aromatic epoxy resin and aromatic skeleton are used. A resin composition can be obtained by mixing an epoxy resin, a photoacid generator, a photosensitizer, and an acrylic resin that are not included. In addition, you may use an organic solvent suitably for viscosity adjustment. Moreover, there is no restriction | limiting in particular also in the mixing method, What is necessary is just to stir and mix sufficiently at room temperature (25 degreeC) until a mixture becomes uniform.
(2) Manufacturing method of polarizing plate As shown in FIG. 2, for example, the polarizer 2 is sandwiched between the protective films 3, and the obtained resin composition 6 for the adhesive layer is replaced with the protective film 3 and the polarizer 2. In between, an appropriate amount is dropped by a dropper and bonded by roll presses 7 and 8.

Next, 300 to 3000 mJ / cm ² , preferably 500 to 2000 mJ / cm ² , more preferably 800 to 1500 mJ / cm ² (365 nm reference, The polarizing plate 1 shown in FIG. 1 is manufactured by irradiating from both sides with the irradiation amount of ultraviolet rays (using a metal halide lamp).

  In FIG. 1, the adhesive layer 9 is provided on both surfaces of the polarizer 2 and the polarizer 2 is sandwiched between the protective film 3 and the adhesive layer 9, but the protective film 3 is provided only on one surface of the polarizer 2. The adhesive layer 9 may be provided.

  Further, from the viewpoint of improving reliability and flexibility, the resin composition is preferably applied so that the thickness of the adhesive layer 9 after curing is preferably 20 μm or less, more preferably 10 μm or less, and more preferably 5 μm. The following are particularly preferred:

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

(Example 1)
<Preparation of resin composition for adhesive layer>
Trisphenol type glycidyl ether resin (trade name: VG-3101L, 10 parts by mass), an aromatic epoxy resin having a tri- or higher functional epoxy group, aliphatic epoxy resin (Yokkaichi Synthesis Co., Ltd.) , Neopentyl glycol diglycidyl ether, trade name: NP-E) 65 parts by mass, alicyclic epoxy resin (manufactured by Daicel Corporation, trade name: Celoxide 2021P), 25 parts by mass, photoacid generator (San Apro Co., Ltd.) Product, CPI210S) 3 parts by mass, and photosensitizer (Nippon Kayaku Co., Ltd., trade name: DETX-S) 1 part by mass in a thermostatic chamber at room temperature (25 ° C.) and humidity 50% RH. The mixture was stirred and mixed until uniform, to obtain a resin composition for the adhesive layer. The materials used and their blending ratios are as shown in Table 1 below.

<Production of polarizer>
The polarizer was produced by the following method. A polyvinyl alcohol film having an average polymerization degree of 2400 and a saponification degree of 99.9% and a thickness of 75 μm was immersed in warm water at 28 ° C. for 90 seconds to swell, and then the iodine / potassium iodide (weight ratio 2/3) concentration was 0. A polyvinyl alcohol film was dyed while being immersed in a 6% by weight aqueous solution and stretched 2.1 times. Then, it extended | stretched so that the total draw ratio might be 5.8 times in 60 degreeC boric-acid-ester aqueous solution, washed with water, and dried for 3 minutes at 45 degreeC, and produced the polarizer (25 micrometers in thickness).

<Manufacture of polarizing plate>
Next, the polarizing plate was manufactured by said method using the produced polarizer and the prepared resin composition within the temperature-controlled room | chamber temperature of room temperature (25 degreeC) and humidity 50% RH. As the protective film, a PET film (manufactured by Toyobo Co., Ltd., trade name: Cosmo Shine A4300, thickness 100 μm) and a COP film (manufactured by Nippon Zeon Co., Ltd., thickness 50 μm) were used. Further, the ultraviolet irradiation conditions are 1000 mJ / cm ² (365 nm standard, using a metal halide lamp) from both sides, and after the ultraviolet irradiation, the polarizing plate is stored in the above-mentioned constant temperature room for 24 hours, and the resin composition is aged and cured, A polarizing plate was completed. In addition, the thickness of one surface of the adhesive layer was 2 to 3 μm.

<Initial curability test>
As shown in FIG. 3, the produced polarizing plate immediately after irradiation with ultraviolet rays was bent so that the interval between the bent polarizing plates 1 was 10 mm (R10 mm), and it was visually determined whether or not the protective film was peeled off. When peeling was not observed, it was set as (circle), and when observed, it was set as x. The results are shown in Table 1.

<Peel strength test>
The produced polarizing plate was fixed to the SUS board with a double-sided tape. Next, a knife was inserted into the end face of the polarizing plate so as to be peeled off at the interface between the polarizer and the protective film (that is, the adhesive layer) of the polarizing plate, thereby creating a peeling allowance. Next, the peeling allowance portion was directed to a direction of 90 degrees and peeled at a predetermined peeling speed (300 mm / min), and the peel strengths of the PET film and the COP film as protective films were measured. The results are shown in Table 1.

<Cutting test>
The produced polarizing plate was cut into 50 mm × 50 mm with a Thomson blade, and the state of peeling off at the end of the cutting was visually observed. As evaluation criteria, 0.5 mm or less was set as the pass. The results are shown in Table 1.

<Hot water immersion test>
The produced polarizing plate was cut into a size of 50 mm × 50 mm with a Thomson blade, and then immersed in a water bath at 60 ° C. and held for 2 hours. Then, the sample was taken out from the water tank and the magnitude | size of the shrinkage | contraction of a polarizer was measured. As an evaluation standard, the shrinkage was less than 1.0 mm from the viewpoint that the shrinkage is small if the adhesiveness of the adhesive is high. The results are shown in Table 1.

<Thermal shock test>
The produced polarizing plate was cut into a size of 50 mm × 50 mm with a Thomson blade and then bonded to glass via a pressure sensitive adhesive. Next, after leaving the polarizing plate with glass in an environment of a cycle of -40 to 85 ° C. (30 minutes, 100 cycles), the length of cracking of the polarizer (the longest length) was visually measured. The crack length of less than 3.0 mm was accepted. The results are shown in Table 1.

(Example 2)
The above-mentioned trisphenol-type glycidyl ether resin (trade name: VG-3101L, manufactured by Printec Co., Ltd.) was changed to 20 parts by mass, and an aliphatic epoxy resin (Yokkaichi Gosei Co., Ltd., Neopentyl glycol di) A resin composition for an adhesive layer was prepared in the same manner as in Example 1 except that the amount of glycidyl ether, trade name: NP-E) was changed to 55 parts by mass. In addition, the used material and its compounding ratio are as showing in Table 1 below. Then, the polarizing plate was manufactured similarly to the above-mentioned Example 1, and the above-mentioned various tests were done. The results are shown in Table 1.

Example 3
The above-mentioned trisphenol type glycidyl ether resin (trade name: VG-3101L, manufactured by Printec Co., Ltd.) was changed to 25 parts by mass, and an aliphatic epoxy resin (Yokkaichi Gosei Co., Ltd., neopentyl glycol di) was used. The amount of glycidyl ether, trade name: NP-E) was changed to 55 parts by mass, and the amount of alicyclic epoxy resin (manufactured by Daicel Corporation, trade name: Celoxide 2021P) was changed to 20 parts by weight. A resin composition for the adhesive layer was prepared in the same manner as in Example 1 except that. In addition, the used material and its compounding ratio are as showing in Table 1 below. Then, the polarizing plate was manufactured similarly to the above-mentioned Example 1, and the above-mentioned various tests were done. The results are shown in Table 1.

(Example 4)
Trisphenol type glycidyl ether resin (made by Printec Co., Ltd., trade name: VG-3101L) which is an aromatic epoxy resin having an epoxy group having 3 or more functional groups, aliphatic epoxy resin (manufactured by Yokkaichi Gosei Co., Ltd.) , Neopentyl glycol diglycidyl ether, trade name: NP-E) 42 parts by mass, alicyclic epoxy resin (manufactured by Daicel Corporation, trade name: Celoxide 2021P), 18 parts by weight, 4-hydroxybutyl acrylate which is an acrylic monomer (Osaka Organic Chemical Industry Co., Ltd., trade name: 4-HBA) 10 parts by mass, acrylic monomer phenoxyethyl acrylate (Osaka Organic Chemicals Co., Ltd., trade name: Biscote # 192, PEA) 10 masses Part, 3 parts by mass of a photoacid generator (manufactured by San Apro Co., Ltd., CPI210S), and a photoacid generator (BA SF Co., Ltd., trade name: Irgacure 907) 1 part by mass is stirred and mixed in a thermostatic chamber at room temperature (25 ° C.) and humidity 50% RH until it becomes uniform visually, and a resin composition for an adhesive layer Got. The materials used and their blending ratios are as shown in Table 1 below. Then, the polarizing plate was manufactured similarly to the above-mentioned Example 1, and the above-mentioned various tests were done. The results are shown in Table 1.

(Comparative Example 1)
The above-mentioned trisphenol-type glycidyl ether resin (trade name: VG-3101L, manufactured by Printec Co., Ltd.) is not blended, and an aliphatic epoxy resin (manufactured by Yokkaichi Gosei Co., Ltd., neopentyl glycol diglycidyl ether, trade name: NP-E) was changed to 70 parts by mass, and the above was changed except that the amount of alicyclic epoxy resin (manufactured by Daicel Corporation, trade name: Celoxide 2021P) was changed to 30 parts by mass. In the same manner as in Example 1, a resin composition for an adhesive layer was prepared. In addition, the used material and its compounding ratio are as showing in Table 1 below. Then, the polarizing plate was manufactured similarly to the above-mentioned Example 1, and the above-mentioned various tests were done. The results are shown in Table 1.

(Comparative Example 2)
The above-mentioned trisphenol-type glycidyl ether resin (trade name: VG-3101L, manufactured by Printec Co., Ltd.) is not blended, and an aliphatic epoxy resin (manufactured by Yokkaichi Gosei Co., Ltd., neopentyl glycol diglycidyl ether, trade name: NP-E) was changed to 20 parts by mass, and the alicyclic epoxy resin (manufactured by Daicel Corporation, trade name: Celoxide 2021P) was changed to 80 parts by mass, as described above. In the same manner as in Example 1, a resin composition for an adhesive layer was prepared. In addition, the used material and its compounding ratio are as showing in Table 1 below. Then, the polarizing plate was manufactured similarly to the above-mentioned Example 1, and the above-mentioned various tests were done. The results are shown in Table 1.

(Comparative Example 3)
Trisphenol type glycidyl ether resin (trade name: VG-3101L, manufactured by Printec Co., Ltd.), aliphatic epoxy resin (manufactured by Yokkaichi Gosei Co., Ltd., neopentyl glycol diglycidyl ether, trade name: NP-E) And alicyclic epoxy resin (manufactured by Daicel Corporation, trade name: Celoxide 2021P), instead of 100 parts by mass of hydrogenated epoxy resin (trade name: YX8000, manufactured by Mitsubishi Chemical Corporation) A resin composition for the adhesive layer was prepared in the same manner as in Example 1 except that. In addition, the used material and its compounding ratio are as showing in Table 1 below. Then, the polarizing plate was manufactured similarly to the above-mentioned Example 1, and the above-mentioned various tests were done. The results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 4 containing an aromatic epoxy resin having a tri- or higher functional epoxy group, a branched structure, and at least one functional epoxy group in the branched structure, Compared with Comparative Examples 1 to 3 that do not contain an aromatic epoxy resin having a tri- or higher functional epoxy group, in the thermal shock test, almost no cracks occurred in the polarizer, and the adhesive layers of Examples 1 to 3 It can be seen that is excellent in heat resistance and can prevent the occurrence of cracks in the polarizer.

  Moreover, in Examples 1-4, compared with the comparative example 2, the peeling strength of PET film is high, compared with the comparative example 3, the peeling strength of PET film and a COP film is high, compared with the comparative examples 1-3. However, in the cutting test, peeling at the end is small. Moreover, in Examples 1-4, peeling of a protective film has not generate | occur | produced in the initial stage sclerosis | hardenability test. From the above, it can be seen that the adhesive layers of Examples 1 to 4 have good adhesion to the polarizer and the protective film.

  Moreover, in Examples 1-4, compared with Comparative Examples 1-3, even when it was a case where it was immersed in warm water, the shrinkage | contraction of a polarizer was very small and the adhesive bond layer was excellent with respect to the polarizer. It turns out that it has adhesiveness (adhesiveness).

  As described above, the present invention is particularly applicable to a polarizing plate adhesive for bonding a polarizer (polarizing film) and a protective film used in manufacturing a polarizing plate, and a display device using the same. Is useful.

DESCRIPTION OF SYMBOLS 1 Polarizing plate 2 Polarizer 3 Protective film 9 Adhesive layer

Claims (5)

A polarizer, an adhesive layer provided on the surface of the polarizer, and a protective film attached to at least one surface of the polarizer via the adhesive layer;
The adhesive layer has an epoxy group having three or more functional groups, has a branched structure, and an aromatic epoxy resin having at least one functional epoxy group in the branched structure, an epoxy resin having no aromatic skeleton, A polarizing plate formed of a cured product of a resin composition containing a photoacid generator and a photosensitizer,
As an epoxy resin having no aromatic skeleton, an aliphatic epoxy resin and an alicyclic epoxy resin are contained,
The content of the aromatic epoxy resin is 5 to 40% by mass with respect to the entire resin composition,
The aromatic epoxy resin is trisphenol glycidyl ether resin,
The aliphatic epoxy resin is one selected from the group consisting of neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and trimethylolpropane diglycidyl ether,
The polarizing plate was cut into a size of 50 mm × 50 mm with a Thomson blade, and then bonded to glass via a pressure-sensitive adhesive. The polarizing plate with glass was cycled between −40 to 85 ° C. (30 minutes) , 100 cycles), and after visually measuring the crack length (longest length) of the polarizer, the crack length is less than 3.0 mm. Polarizer. The polarizing plate according to claim 1, wherein the glycidyl ether resin of trisphenol is a resin represented by the following formula (1).

  The polarizing plate according to claim 1, wherein the adhesive layer has a thickness of 20 μm or less.   The polarizing plate according to claim 1, wherein the resin composition further contains an acrylic resin.   A display device comprising the polarizing plate according to claim 1.

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