KR20140126239A - Photo-curable composition for transparent adhesive sheet, adhesive sheet made of same and use thereof - Google Patents

Abstract

Provided is a photo-curable composition which includes polyurethane (A) which has polyoxyalkylene polyol as a backbone, has a (meth)acryloyl group on a terminal, and has a weight average molecular weight of 10,000 to 300,000; (meth)acrylate ester (B) having a hydroxy group; other photopolymerizable monomers (C), wherein the composition has an acid value of 0-5 mgKOH/g. A transparent conductive film laminate is obtained by forming an optical adhesive sheet by curing the photo-curable composition and bonding the optical adhesive sheet to the conductive layer of a transparent conductive film.

Description

[0001] PHOTO-CURABLE COMPOSITION FOR TRANSPARENT ADHESIVE SHEET, ADHESIVE SHEET MADE OF SAME AND USE THEREOF [0002]

The present invention relates to an acrylic photo-curable composition for a transparent adhesive sheet, a transparent adhesive sheet formed by curing the photo-curable composition, and a laminate obtained by adhering the transparent adhesive sheet to a conductive layer surface of a transparent conductive film.

2. Description of the Related Art In recent years, touch panels have begun to be installed in fields such as mobile phones and game machines. The touch panel is formed by using a transparent substrate such as glass having a transparent conductive film such as ITO (Indium Tin Oxide) as a surface layer, a transparent protective sheet for protecting the transparent substrate, or a display device such as a liquid crystal display, Laminated body.

The touch panel mainly has a resistance film type touch panel that detects an input portion with a pressure at the time of input, and a capacitance type touch panel that detects an input portion by static electricity from a human body at the time of input. In a capacitive touch panel, the conductive layer surface of the transparent conductive film is fixed so as to contact the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet. The pressure sensitive adhesive used for this purpose generally contains an acid component for the purpose of improving the adhesiveness. However, when such a pressure sensitive adhesive is used, when the pressure sensitive adhesive layer comes into contact with the conductive layer surface of the transparent conductive film, There is a problem in that the oxidation function of the conductive layer is deteriorated. For this reason, a high corrosion resistance of the metal is required for the pressure-sensitive adhesive sheet for fixing a transparent conductive film.

As a pressure-sensitive adhesive sheet having metal corrosion resistance, a pressure-sensitive adhesive sheet (for example, Patent Document 1) containing a metal corrosion inhibitor has been proposed. Further, there has been proposed a pressure-sensitive adhesive sheet (for example, Patent Document 2) in which the corrosiveness to the transparent conductive film is reduced by containing a specific amount of a nitrogen atom-containing component in the acid component of the pressure-sensitive adhesive layer. However, in the pressure-sensitive adhesive sheet containing the metal corrosion inhibitor described in Patent Document 1, there is a problem that the metal corrosion inhibitor tends to cause discoloration and the optical properties are lowered. In addition, the pressure-sensitive adhesive sheet containing a specific amount of the nitrogen atom-containing component described in Patent Document 2 has a problem that the increase of the electric resistance value of ITO can not be sufficiently suppressed due to the acid component contained in the pressure-sensitive adhesive layer.

On the other hand, in the case of an optical component such as a touch panel, multilayer ink printing is sometimes performed in order to give designability and decorative property, and there is a problem in that a printing step is generated between the printing portion (printing layer) and the non- . For example, a touch panel or the like having a member provided with a frame-shaped printing portion in a mobile phone or the like is used. In such applications, the pressure-sensitive adhesive sheet is required to have a capability of attaching and fixing a member, and at the same time, a capability of filling the printed steps, that is, excellent step difference absorbency. If the transparent pressure sensitive adhesive sheet can not absorb such a level difference, lifting (bubble or void) of the transparent pressure sensitive adhesive sheet around the end portion of the printed layer is generated, and reflection loss of light due to the lifting is caused and the visibility of the liquid crystal display is likely to decrease .

In order to obtain an excellent level difference absorbency, the transparent pressure-sensitive adhesive sheet is advantageous in that it is flexible and has high adhesive strength. On the other hand, from the viewpoint of metal corrosion inhibition as described above, it is required that it does not contain an acid component. With respect to this demand, a pressure-sensitive adhesive composition comprising an acrylic polymer having an alkoxyalkyl acrylate as a main monomer and an acid component-free weight average molecular weight of 400,000 to 1,600,000 and a crosslinking agent such as a polyfunctional epoxy compound or a polyfunctional isocyanate compound . This pressure-sensitive adhesive composition has been disclosed to supply a transparent pressure-sensitive adhesive sheet capable of satisfying both good adhesion and metal corrosion-preventive properties (for example, Patent Document 3).

However, since the pressure-sensitive adhesive composition has insufficient storage stability after mixing the acrylic polymer with a crosslinking agent and since the acrylic polymer has a high molecular weight, it is necessary to dilute the composition with a solvent, so that a thick pressure- There is a problem in that it is very difficult to produce such a structure.

Japanese Patent Application Laid-Open No. 2006-45315 Japanese Patent Application Laid-Open No. 2010-144002 Japanese Patent Application Laid-Open No. 2009-079203

A problem to be solved by the present invention is to provide a one-pack type photo-curing composition for a transparent pressure-sensitive adhesive sheet which does not corrode a conductive layer directly to a conductive layer surface of a transparent conductive film but has excellent transparency, adhesive strength, A transparent pressure-sensitive adhesive sheet obtained by curing the photo-curable composition, and a transparent pressure-sensitive adhesive sheet bonded to the surface of the conductive layer of the transparent conductive film.

The inventors of the present invention have conducted intensive investigations based on the above-mentioned problems in the light of the above-mentioned problems of a photocurable transparent pressure sensitive adhesive sheet used in an optical component such as a touch panel. As a result, it has been found out that a (meth) acryloyl group When the introduced polyoxyalkylene-based urethane acrylate compound is used in combination with a photopolymerizable monomer other than the (meth) acrylic acid ester having a hydroxy group and the (meth) acrylic acid ester having the hydroxy group, a photopolymerization initiator is blended, And exhibits excellent transparency, tackiness, metal corrosion resistance of the transparent conductive film, and excellent step-wise water absorbency when used in a chemical composition. Based on this finding, the present invention has been completed.

Thus, according to the present invention, there can be provided a photo-curable composition for a transparent pressure-sensitive adhesive sheet as shown in the following (1) to (4), an optical adhesive sheet shown in (5) to (8) Film laminate, a touch panel shown in (10), and an image display device shown in (11).

(1) a polyurethane (A) having a polyoxyalkylene polyol skeleton and having a (meth) acryloyl group at the terminal and a weight average molecular weight of 10,000 to 300,000, (meth) acrylic acid ester (B) having a hydroxy group, Other photopolymerizable monomer (C) and photopolymerization initiator (D), and having an acid value of 0 to 5 mgKOH / g.

(2) The photocurable composition contains 20 to 50% by mass of the polyurethane (A), 5 to 20% by mass of the (meth) acrylic acid ester (B) having a hydroxy group, the photopolymerizable monomer (C) To 74.8% by mass of the photopolymerization initiator (D) and 0.2 to 5% by mass of the photopolymerization initiator (D).

(3) The photopolymerizable monomer (C) contains a (meth) acrylic acid ester of a hydrocarbon monoalcohol having 6 to 18 carbon atoms whose theoretical glass transition temperature (Tg) of the homopolymer is not lower than -5 ° C. 2). ≪ / RTI >

(4) The photocurable composition for a transparent pressure-sensitive adhesive sheet according to (1) or (2), wherein the acid value is 0 to 0.5 mgKOH / g.

(5) An optical pressure-sensitive adhesive sheet obtained by curing the photo-curing composition for a transparent pressure-sensitive adhesive sheet according to any one of (1) to (4)

(6) The pressure-sensitive adhesive sheet for optical use according to (5), wherein the cured product has a glass transition temperature (Tg) of -10 ° C to -60 ° C.

(7) The pressure-sensitive adhesive sheet for optical use according to (6), which is a double-sided pressure-sensitive adhesive sheet.

(8) A pressure-sensitive adhesive sheet for optical use according to (5), which is a sheet for fixing a transparent conductive film for bonding to the surface of a conductive layer of a transparent conductive film.

(9) A transparent conductive film laminate obtained by bonding the optical adhesive sheet according to (8) above to a conductive layer surface of a transparent conductive film.

(10) A touch panel having the transparent conductive film laminate according to (9).

(11) An image display apparatus comprising the touch panel according to (10) above.

(Effects of the Invention)

The photo-curing composition for a transparent pressure-sensitive adhesive sheet of the present invention contains a polyurethane compound having a weight average molecular weight of 10,000 to 300,000, a polyoxyalkylene polyol skeleton and a (meth) acryloyl group, , A transparent pressure-sensitive adhesive sheet having excellent tackiness, transparency and level difference absorbency can be obtained. In addition, since the acid value of the composition is at most 5 mgKOH / g, corrosion of the transparent conductive film due to the acid component can be suppressed when the transparent adhesive sheet is bonded to the conductive layer surface of the transparent conductive film. Further, by including a (meth) acrylic acid ester having a hydroxy group, a high cohesive force and adhesion to a substrate can be obtained. Further, by using the photo-curing composition for a transparent pressure-sensitive adhesive sheet of the present invention, a sheet having a film thickness of 100 mu m or more can be easily produced. Further, since the transparent pressure-sensitive adhesive sheet of the present invention is excellent in level difference absorbency, it is possible to suppress lifting (bubbles and voids) of the transparent pressure-sensitive adhesive sheet around the end portion of the printed layer, thereby obtaining a touch panel excellent in visibility.

Next, embodiments for carrying out the present invention will be described. Further, in the specification and claims of the present application, the term " (meth) acryloyl group &

A group represented by the formula CH ₂ = CH-CO-, or

Means a group represented by the formula CH ₂ C (CH ₃ ) -CO-,

Isocyanato group,

Means a group represented by the formula: -N = C = O.

≪ Photosetting composition for transparent adhesive sheet >

The photo-curing composition for a transparent pressure-sensitive adhesive sheet of the present invention comprises a polyurethane (A) having a polyoxyalkylene polyol skeleton and a (meth) acryloyl group at the terminal and having a weight average molecular weight of 10,000 to 300,000, (C) other than the (meth) acrylic acid ester (B), (B) and the photopolymerization initiator (D).

<Polyurethane (A) having (meth) acryloyl group>

The polyoxyalkylene polyol used in the production of the polyurethane (A) is preferably one having an alkylene chain of 2 to 4 carbon atoms, and specific examples thereof include polyethylene polyol, polypropylene polyol, polybutylene polyol, poly Tetramethylene polyol and the like. Further, a copolymer of two or more oxyalkylene polyols may be used, or two or more polyoxyalkylene polyols may be blended and used. Among them, polyoxyalkylene diols are preferably used.

The number average molecular weight of the polyoxyalkylene polyol is usually 500 to 5,000, preferably 800 to 4,000. If the number average molecular weight of the polyoxyalkylene polyol is excessively small, the adhesive strength of the transparent pressure-sensitive adhesive sheet may decrease. On the other hand, if the number average molecular weight of the polyoxyalkylene polyol is excessively large, the urethane bond in the polyurethane decreases, and the cohesive force of the transparent pressure sensitive adhesive sheet may decrease.

The polyisocyanate used in the polyurethane (A) of the present invention is not particularly limited, and examples thereof include tolylene diisocyanate and its hydrogenated product, xylylene diisocyanate and its hydrogenated product, diphenylmethane diisocyanate and its hydrogenated product, 1,5- (Isocyanatoethyl) isocyanate and its hydrogenated product, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexyldiisocyanate, 1,3-bis ) Cyclohexane, and norbornadiisocyanate, and two or more of them may be used in combination. Among them, hydrogenated products of isophorone diisocyanate or diphenylmethane diisocyanate are preferable from the viewpoint of light resistance and reactivity control.

The polyurethane (A) used in the present invention can be produced by a general method using a polyoxyalkylene polyol and a polyisocyanate. A preferred first synthesis method is as follows. First, the polyoxyalkylene polyol and the polyisocyanate are reacted at a ratio in which the amount of the isocyanate group is larger than the amount of the hydroxyl group to synthesize a polyurethane having an isocyanato group. At this time, it is possible to adjust the molecular weight by adjusting the ratio of the amount of isocyanato groups to the amount of hydroxyl groups. Specifically, the smaller the ratio of the amount of isocyanato groups to the amount of hydroxy groups is, the larger the molecular weight of the isocyanato group-containing polyurethane is, and the larger the ratio of the isocyanato groups to the hydroxyl group amount, the larger the molecular weight of the polyisocyanate group- Becomes smaller. Then, polyurethane (A) is synthesized by reacting a polyurethane having an isocyanato group with a compound having a hydroxy group and a (meth) acryloyl group.

Examples of the compound having a hydroxyl group and (meth) acryloyl group include, but are not limited to, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl Hydroxyalkyl (meth) acrylate; Acrylate such as 1,3-butanediol mono (meth) acrylate, 1,4-butanediol mono (meth) acrylate, 1,6-hexanediol mono (meth) acrylate and 3-methylpentanediol mono And monools having (meth) acryloyl groups derived from various polyols. These may be used in combination of two or more. Among them, 2-hydroxyethyl (meth) acrylate is preferable in view of reactivity with an isocyanato group and photocurability.

At this time, the introduction amount of the (meth) acryloyl group can be adjusted by reacting one alkyl alcohol with a polyurethane having an isocyanato group in the hydroxy group. Examples of the alkyl alcohol include, but are not limited to, linear, branched, and alicyclic alkyl alcohols. These alkyl alcohols may be used in combination of two or more kinds.

The amount of the (meth) acryloyl group to be introduced is usually from 50 to 100 mol%, preferably from 80 to 100 mol%, and more preferably 100 mol% with respect to the isocyanato group. When the amount of the (meth) acryloyl group introduced is less than 50 mol% with respect to the isocyanato group, the cohesive force of the transparent pressure sensitive adhesive sheet may be lowered.

Next, a preferable second synthetic method of the polyurethane (A) will be described. First, a polyoxyalkylene polyol and a polyisocyanate are reacted in such a ratio that the amount of the hydroxy group is larger than the amount of the isocyanate group, thereby synthesizing a polyurethane having a hydroxy group. At this time, it is possible to adjust the molecular weight by adjusting the ratio of the amount of hydroxy groups to the amount of isocyanato groups. Specifically, the smaller the ratio of the amount of hydroxyl groups to the amount of isocyanato groups, the larger the molecular weight of the polyurethane having a hydroxy group. The larger the ratio of the amount of hydroxy groups to the amount of isocyanato groups, the smaller the molecular weight of the polyurethane compound having a hydroxy group. Then, the polyurethane (A) is synthesized by reacting a polyurethane having a hydroxy group with a compound having an isocyanato group and a (meth) acryloyl group.

At this time, the content of the (meth) acryloyl group can be adjusted by adjusting the amount of the compound having an isocyanato group and a (meth) acryloyl group. The amount of the (meth) acryloyl group to be introduced is usually from 50 to 100 mol%, more preferably from 80 to 100 mol%, and still more preferably 100 mol% with respect to the hydroxyl group. When the amount of the (meth) acryloyl group introduced is less than 50 mol% with respect to the hydroxyl group, the cohesive force of the transparent pressure sensitive adhesive sheet may decrease.

Examples of the compound having an isocyanato group and (meth) acryloyl group include, but are not limited to, 2- (meth) acryloyloxyethyl isocyanate, 2- (meth) acryloyloxypropyl isocyanate, Acryloyloxymethyl) ethyl isocyanate, and the like. Examples of commercial products of compounds having an isocyanato group and (meth) acryloyl group include car lens MOI (registered trademark) and car lens AOI (registered trademark) manufactured by Showa Denko K.K. can do. These may be used in combination of two or more. Among them, 2- (meth) acryloyloxyethyl isocyanate is preferable in view of reactivity with a hydroxy group and photocurability.

In the synthesis of the polyurethane (A), the reaction between the hydroxyl group and the isocyanato group is carried out in the presence of an organic solvent which is inert to the isocyanato group, in the presence of dibutyltin dilaurate, dibutyltin diethylhexoate, Laurate or the like at a temperature of usually from 30 to 100 DEG C for about 1 to 5 hours. The amount of the urethanization catalyst used is usually 50 to 500 mass ppm relative to the total mass of the reactants.

The weight average molecular weight of the polyurethane (A) used in the present invention is 10,000 to 300,000, preferably 20,000 to 200,000, and more preferably 30,000 to 100,000. When the weight average molecular weight of the polyurethane (A) is less than 10,000, the adhesive strength of the transparent pressure sensitive adhesive sheet is lowered. On the contrary, when the weight average molecular weight exceeds 300,000, handling becomes difficult and workability is lowered.

The weight average molecular weight is a molecular weight in terms of polystyrene measured by gel permeation chromatography Shodex GPC-101 (manufactured by Showa Denko KK).

The content of the polyurethane (A) in the photo-curable composition for a transparent pressure-sensitive adhesive sheet may be appropriately selected, but is preferably 20 to 50 mass%, more preferably 25 to 45 mass%, still more preferably 30 to 40 mass% Mass%. If the content of the polyurethane (A) is excessively small, the cohesive force at the time of use as the transparent pressure sensitive adhesive sheet tends to deteriorate. On the contrary, if the content is excessively large, the adhesive force at the time of use as the transparent pressure sensitive adhesive sheet tends to deteriorate.

<(Meth) acrylic acid ester (B) having a hydroxy group>

The (meth) acrylic acid ester (B) having a hydroxy group used in the present invention preferably has no carboxyl group (-COOH), and examples thereof include hydroxyalkyl (meth) acrylate and the like have. Specific examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (Meth) acrylate, 1,4-butanediol (meth) acrylate, 1,6-hexanediol (meth) acrylate and 3-methylpentanediol (meth) acrylate, Two or more of them may be used in combination. The number of carbon atoms of the alkyl group of the (meth) acrylic acid ester (B) having a hydroxy group is usually 2 to 10, preferably 2 to 6, and more preferably 2 to 4. Particularly, 2-hydroxyethyl (meth) acrylate is most commonly used in view of the adhesive force of the resulting pressure-sensitive adhesive sheet.

The content of the (meth) acrylic acid ester (B) having a hydroxy group is usually 5 to 20% by mass, preferably 6 to 18% by mass, and more preferably 7 to 15% by mass in the photocurable composition for a transparent pressure- . If the content of the (meth) acrylic acid ester (B) having a hydroxy group in the photocurable composition for a transparent pressure-sensitive adhesive sheet is excessively small, the adhesion property of the resultant pressure-sensitive adhesive sheet to a substrate may become insufficient. Conversely, The water resistance of the sheet may deteriorate.

&Lt; Other photopolymerizable monomer (C) >

The other photopolymerizable monomer (C) refers to a photopolymerizable monomer other than the (meth) acrylate ester having a hydroxyl group as the component (B). The photopolymerizable monomer (C) is preferably a monomer that does not contain a carboxyl group. The monomer is not particularly limited and may be either monofunctional or multifunctional, provided that it has a photopolymerizable functional group such as vinyl group and (meth) acryloyl group. The photopolymerizable monomers may be used alone or in combination of two or more. The term "monofunctional or polyfunctional functional group" as used herein refers to a functional group involved in polymerization such as a vinyl group and a (meth) acryloyl group.

Specific examples of the photopolymerizable monomer (C) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n- (Meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (Meth) acrylate, and tridecyl (meth) acrylate;

(Meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, norbornyl (meth) acrylate, isobornyl (Meth) acrylate such as dicyclopentanyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate and tricyclodecane dimethylol (meth) acrylate;

Ethoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, 2- methoxyethoxyethyl Alkoxyalkyl (meth) acrylates such as acrylate;

Alkoxy (poly) alkylene glycol (meth) acrylates such as methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate and methoxydipropylene glycol (meth) acrylate;

Fluorinated alkyl (meth) acrylates such as octafluoropentyl (meth) acrylate;

Dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate;

Acrylates such as polyethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di Di (meth) acrylate di (meth) acrylate, 1,3-bis (hydroxyethyl) -5,5-dimethylhydantoin (Meth) acrylate, ethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, diacryloxyethyl phosphate, dipentaerythritol trihydroxy (meth) acrylate, pentaerythritol tetra Polyfunctional (meth) acrylate;

Acrylamide derivatives such as acrylamide, dimethylacrylamide, diethylacrylamide and (meth) acryloylmorpholine;

(Meth) acrylate containing an epoxy group such as glycidyl (meth) acrylate.

The content of the photopolymerizable monomer (C) can be appropriately selected so that the glass transition temperature of the cured product obtained by curing the photocurable composition falls within a desired range. As described later, in the present invention, it is preferable to adjust the glass transition temperature of the pressure-sensitive adhesive sheet obtained by curing to a range of -10 to -60 占 폚. To this end, the content of the photopolymerizable monomer (C) Is usually 30 to 74.8 mass%, preferably 40 to 65 mass%, and more preferably 45 to 60 mass%. If the content of the photopolymerizable monomer (C) in the photocurable composition for transparent adhesive sheet is excessively small, the adhesion property of the obtained pressure sensitive adhesive sheet to the substrate may become insufficient. When the content of the photopolymerizable monomer (C) in the photocurable composition for a transparent pressure sensitive adhesive sheet is excessively large, the cohesive force of the obtained pressure sensitive adhesive sheet becomes small, and the adhesive force of the pressure sensitive adhesive sheet tends to deteriorate.

In the present invention, the monomer (C-1) having a theoretical glass transition temperature (Tg) of less than -5 캜 of the homopolymer as the photopolymerizable monomer (C) and the monomer (C-1) having a theoretical Tg of the homopolymer ) Can be used in combination. Specific examples of the monomer (C-1) include n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isostearyl acrylate, Specific examples of the monomer (C-2) include esters of a (meth) acrylic acid with an alcohol having a hydrocarbon group having 6 to 18 carbon atoms such as lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, (Meth) acrylate. The ratio of the monomer (C-1) to the monomer (C-2) can be appropriately selected, but the proportion of the monomer (C-2) in the total amount of the monomer (C) is preferably 30 to 60% More preferably from 35 to 50% by mass, and in this range, a pressure-sensitive adhesive sheet rich in adhesiveness and flexibility can be obtained.

Here, the theoretical glass transition temperature (Tg) is the glass transition temperature (Tg) of the homopolymer (homopolymer of the monomer). The Tg of various homopolymers can be calculated from the known data in "Adhesion Technology Handbook" (issued March, 1997) by Nikkan Kogyo Shinbun Co., Ltd. and "Wiley-Interscience Polymer Handbook 4th Edition" The Tg of the homopolymer of the monomer which is not described in the above known data is determined by the following method: Namely, the homopolymer solution obtained by solution polymerization of the target monomer is applied to the release liner The differential scanning calorimetry (DSC) was carried out on this test sample by changing the temperature from -80 ° C to 280 ° C at a heating rate of 10 ° C / min, The endothermic initiation temperature due to the glass transition is defined as the Tg of the homopolymer.

&Lt; Photopolymerization initiator (D) >

The photopolymerization initiator (D) of the present invention is not particularly limited. Specific examples thereof include benzophenone, benzyl, benzoin, omega -bromoacetophenone, chloroacetone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, p- Acetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzoin methyl ether, Butyl ether, benzoin-n-butyl ether, benzyl methyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy- 2-methylpropan-1-one, methyl benzoyl formate, 2,2-diethoxyacetophenone, 4-N, N'-dimethylacetophenone, 2- - (methylthio) phenyl] -2-morpholinopropane-1-one;

A sulfide-based photopolymerization initiator such as diphenyl disulfide, dibenzyl disulfide, tetraethyl thiol disulfide, tetramethyl ammonium monosulfide and the like;

Acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide;

Quinone-based photopolymerization initiators such as benzoquinone and anthraquinone;

Azo-based photopolymerization initiators such as azobisisobutylonitrile and 2,2'-azobispropane;

A sulfochloride-based photopolymerization initiator;

Thioxanthone photopolymerization initiators such as thioxanthone, 2-chlorothioxanthone and 2-methylthioxanthone;

And peroxide-based photopolymerization initiators such as benzoyl peroxide and di-t-butyl peroxide. These may be used alone or in combination of two or more. Among them, 1-hydroxycyclohexyl phenyl ketone and / or 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferable from the viewpoint of solubility in the transparent pressure-sensitive adhesive sheet photo-curable composition.

The content of the photopolymerization initiator (D) is preferably from 0.2 to 5% by mass, more preferably from 0.5 to 3% by mass, in view of the photocurability and the balance of the strength and tackiness of the obtained pressure-sensitive adhesive sheet %to be. If the content of the photopolymerization initiator (D) is too small, the photocuring tends to be insufficient. On the other hand, if the content is too large, the tackiness of the obtained pressure sensitive adhesive sheet tends to be lowered.

The acid value of the photo-curable composition for a transparent pressure-sensitive adhesive sheet of the present invention is 0 to 5 mgKOH / g, preferably 0 to 0.5 mgKOH / g, and more preferably 0 to 0.1 mgKOH / g. When the acid value is higher than 5 mgKOH / g, it is difficult to suppress the corrosion of the conductive layer surface of the transparent conductive film. The acid value of the composition is a value measured in accordance with JIS K0070 and is measured as follows.

About 2 g of the sample is precisely weighed in a 100 ml Erlenmeyer flask with a precision balance, and 10 ml of a mixed solvent of ethanol / diethyl ether = 1/1 (weight ratio) is added and dissolved. Further, 1 to 3 drops of a phenolphthalein ethanol solution as an indicator is added to the container, and sufficiently stirred until the sample becomes uniform. This is titrated with a 0.1 N potassium hydroxide-ethanol solution, and the point where the pale red color of the indicator continues for 30 seconds is set as the end point of neutralization. From the result, the value obtained by using the following equation (1) is the acid value of the composition.

Acid value (mgKOH / g) = [B x f x 5.661] / S (1)

B, f and S in the calculation formula (1) are as follows.

B: Amount (ml) of 0.1 N potassium hydroxide-ethanol solution

f: Factor of 0.1N potassium hydroxide-ethanol solution (correction of shaking due to reagent lot)

S: Weight of sample (g)

To the photo-curable composition for a transparent pressure-sensitive adhesive sheet of the present invention, a tackifier resin may be added within a range not lowering transparency in order to improve the adhesive force of the pressure-sensitive adhesive sheet obtained as required. Examples of the tackifier resin include rosin-based resins such as rosin and esters of rosin; Terpene resins such as diterpene polymers and? -Pinene-phenol copolymers; Petroleum resins such as aliphatic (C5) and aromatic (C9); Other examples include styrene resins, phenol resins, and xylene resins. From the viewpoint of light resistance, it is preferable to add an esterified product of hydrogenated rosin or disproportionated rosin having a low unsaturated double bond, an aliphatic or aromatic petroleum resin, or a high Tg acrylic resin to the adhesive sheet. The amount of the tackifier resin to be added is preferably from 1 to 10 parts by mass per 100 parts by mass of the total amount of the component (A), the component (B), the component (C) and the component (D) relative to 100 parts by mass of the photocurable composition for a transparent pressure- It is the extent of wealth.

In addition, the photo-curable composition for a transparent pressure-sensitive adhesive sheet of the present invention may contain various known additives as needed within a range that does not impair transparency. Examples of additives include antistatic agents such as plasticizers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, light stabilizers, ultraviolet absorbers, light stabilizers such as polymerization inhibitors and benzotriazole, phosphate esters and other flame retardants, Dye and the like.

Since the photocurable composition for a transparent pressure-sensitive adhesive sheet of the present invention contains a (meth) acrylic acid ester (B) having a hydroxy group and other photopolymerizable monomer (C), it can be adjusted to a coatable viscosity without addition of an organic solvent, An organic solvent may be added for the purpose of adjusting the viscosity of the solution. Examples of the organic solvent to be used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol and isopropanol. These organic solvents may be used alone or in combination of two or more kinds.

&Lt; Optical adhesive sheet >

The optical adhesive sheet of the present invention is an optical adhesive sheet for optical use obtained by curing the photo-curing composition for a transparent adhesive sheet. More specifically, the present invention relates to a pressure-sensitive adhesive sheet for use in bonding an optical member (for bonding an optical member). The Tg of the cured product forming the adhesive sheet is preferably -10 to -60 캜, more preferably -20 to -50 캜. As the Tg of the cured product becomes higher, the pressure-sensitive adhesive sheet tends to be hardened, so that the level difference absorbency tends to decrease. On the contrary, if the Tg of the cured product is excessively low, the adhesive tends to become too soft. This optical pressure sensitive adhesive sheet may have a base material formed of a transparent resin sheet such as PET, or a double-sided pressure sensitive adhesive sheet having no base material and composed of a pressure sensitive adhesive layer only. Further, the pressure-sensitive adhesive layer may be composed of a single layer or a plurality of layers may be laminated. As a specific example of the laminated sheets of a plurality of layers, for example, a laminated sheet having a three-layer structure and a balance between the cohesive force and the adhesive force by changing the composition of the both layers and the center layer is exemplified.

The optical member to be bonded is not particularly limited as long as it is a member having optical characteristics, and examples thereof include an image display apparatus, a member constituting a touch panel or a member used in these apparatuses. More specifically, for example, a polarizing plate, a retardation plate, an optical compensation film, a luminance enhancement film, a light guide plate, a reflective film, an antireflection film, a transparent conductive film, a decorative film, , A transparent substrate, and a member in which these are laminated.

The optical adhesive sheet can be obtained by applying a photo-curing composition for a transparent pressure-sensitive adhesive sheet to a release film and irradiating ultraviolet rays to the applied composition using an ultraviolet irradiation device or the like. The thickness of the optical adhesive sheet is usually from 5 to 1,000 탆, preferably from 10 to 400 탆, more preferably from 15 to 300 탆. If the thickness of the optical pressure-sensitive adhesive sheet is excessively thin, bonding of the pressure-sensitive adhesive sheet tends to become difficult. If the thickness of the optical adhesive sheet is excessively increased, control of the film thickness tends to become difficult. In the method for forming an optical pressure-sensitive adhesive sheet of the present invention, a known coating method can be used for coating (coating), and a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, A roll coater, a bar coater, a knife coater, a spray coater, a comma coater, and a direct coater.

The surface (adhesive surface) of the optical pressure-sensitive adhesive sheet of the present invention may be protected by a release film (separator) until use. Each of the pressure-sensitive adhesive surfaces (both surfaces) of the pressure-sensitive adhesive sheet may be protected by two pieces of the release film, or may be protected in the form of being wound in a roll shape by a single release film whose both surfaces are separated. The release film is used as a protective material for the pressure-sensitive adhesive layer and is peeled off when adhered to the adherend. Further, the release film may not necessarily be provided. As the release film, a commonly used release film can be used. Although not particularly limited, for example, a plastic film surface-treated with a release agent such as a silicone type, a long chain alkyl type or a fluorine type can be used. The release film can be formed by a known method. The thickness of the release film is not particularly limited, and the thickness of the two release films may be the same or different. Further, the release film may be of different kind, and it is also possible to control the peelability by changing the rigidity thereof.

&Lt; Layered product of transparent conductive film and optical adhesive sheet &

The optical pressure-sensitive adhesive sheet of the present invention is suitably used as a fixing sheet for a transparent conductive film (hereinafter sometimes referred to as a pressure-sensitive adhesive sheet for fixing a transparent conductive film). The laminate is formed by bonding the adhesive sheet for fixing a transparent conductive film to the conductive layer surface of the transparent conductive film according to a general method. This laminate is excellent in adhesion force and less in corrosion of the conductive layer, and can be suitably used for a touch panel. The sheet for fixing a transparent conductive film of the present invention may have a substrate, or may be a double-sided pressure-sensitive adhesive sheet comprising only a pressure-sensitive adhesive layer having no substrate. Further, the pressure-sensitive adhesive layer may be composed of a single layer or a plurality of layers may be laminated. Among these, from the viewpoint of ensuring transparency and shape-conformability (step difference absorbency), it is preferable that the double-sided pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet which does not have a substrate and is composed of only a pressure-sensitive adhesive layer.

The transparent conductive film used in the present invention may have at least a conductive layer on the surface layer of one side or a transparent conductive film in which a conductive material is provided on the surface layer of the transparent substrate by vapor deposition or coating. Among them, there is an advantage that a transparent conductive film having a conductive layer in which a conductive material is formed by vapor deposition can be easily manufactured. The conductive material to be vapor-deposited or coated on the conductive layer of the transparent conductive film is not particularly limited, and specific examples thereof include indium tin oxide, indium oxide, tin oxide, zinc oxide, cadmium oxide, titanium oxide and the like. Among them, indium tin oxide having excellent transparency and conductivity is particularly suitable.

As the transparent conductive film, a substrate on which a conductive material is deposited or coated is not particularly limited, and examples thereof include glass and resin film. Examples of the resin film include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetylcellulose film, triacetylcellulose film, acetylcellulose butyrate film, polyvinyl chloride film, A polyvinyl alcohol film, an ethylene-vinyl acetate copolymer film, a polystyrene film, a polycarbonate film, a polymethylpentene film, a polysulfone film, a polyetheretherketone film, a polyethersulfone film, a polyetherimide film , A polyimide film, a fluororesin film, a nylon film, an acrylic resin film, and a polycycloolefin film. Among them, polyethylene terephthalate excellent in transparency and durability is preferable.

The transparent conductive film preferably has a total light transmittance of 80% or more, and more preferably 90% or more of total light transmittance. If the transparency of the transparent conductive film is within the above range, the transparency of the display mounted with the touch panel device using the transparent conductive film tends to be maintained. The thickness of the transparent conductive film laminate is usually 0.1 mm to 2.0 mm.

The transparent conductive film laminate of the present invention preferably has an increase rate of the electrical resistance value of the conductive film layer after leaving for 500 hours under the conditions of 60 DEG C and 90% RH, preferably not more than 20%, more preferably not more than 10% % Or less. As the rate of increase is smaller, the corrosion of the metal forming the transparent conductive film is suppressed, and the performance when introduced into a touch panel or the like is improved. The rate of increase of the electric resistance value can be calculated by the following formula (2).

(Initial electrical resistance value) / (initial electrical resistance value) x 100 [0060] The electric resistance value of the conductive film layer is expressed by the following formula: ·(2)

<Touch panel>

The touch panel of the present invention has a transparent conductive film laminate formed by bonding the adhesive sheet for fixing a transparent conductive film to a transparent conductive film. The configuration of the touch panel is not particularly limited, and for example, the configuration disclosed in Patent Document 2 can be used. Among them, it is preferable that the touch panel is of a capacitive type.

As a specific constructional example, a capacitive touch panel device in which a transparent conductive film laminate provided with a transparent conductive film on one surface of a double-sided pressure sensitive adhesive sheet is provided in two layers between a display panel (transparent panel) and an image display module can be exemplified. At least one of the transparent conductive films having the two-layered pressure-sensitive adhesive layer may be the transparent conductive film laminate, and the transparent conductive film having the pressure-sensitive adhesive layer at the side of the image display module may be a laminate structure of the transparent conductive film, Can be used as a preferable constitution of the transparent conductive film laminated structure. Further, as another preferable configuration example, an example of a capacitive touch panel in which a transparent conductive film laminate provided with transparent conductive films on both sides of a double-sided adhesive sheet is fixed between a display panel and an image display module by a fixing tape or fixing adhesive can do. In the above configuration, since the touch panel can be manufactured by fixing the display panel, the transparent conductive film laminate, and the image display module using the fixing tape or the fixing adhesive, the assembling process is facilitated.

The protective panel of the touch panel of the present invention is not particularly limited, and examples thereof include (meth) acrylic resin, polycarbonate resin, glass, and polyethylene terephthalate resin. Among them, a (meth) acrylic resin superior in transparency and light weight is preferable.

The display panel of the touch panel of the present invention may have a decorative portion. Specific examples of the decorative part include letters and figures visually recognized around the image display part of the portable electronic terminal or black or white backgrounds provided on the back of these parts. By providing these decorative portions, designability can be given to the portable electronic terminal.

The thickness of the touch panel excluding the image display module is preferably 0.3 mm to 3.0 mm. Within the above range, it is easy to make the electronic device equipped with the touch panel thin.

When the transparent conductive film having the pressure-sensitive adhesive layer on the side of the image display module is a transparent conductive film laminate, the thickness of the double-sided pressure-sensitive adhesive sheet of the transparent conductive film laminate is preferably 5 to 300 탆, Is particularly preferable. In the case where the transparent conductive film having the pressure-sensitive adhesive layer on the side to be bonded to the display panel is formed as a transparent conductive film laminate, the thickness of the double-sided pressure-sensitive adhesive sheet is preferably 15 to 300 m, more preferably 25 to 200 Mu m is more preferable. Within this range, the double-faced pressure-sensitive adhesive sheet is likely to follow the decorative part of the display panel.

The touch panel of the present invention can be mounted on various image display devices according to a general method. The object image display device is not particularly limited. For example, an LCD display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), an electronic paper, or the like .

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited at all by these examples.

&Lt; Synthesis of polyurethane (A-1) >

A polypropylene glycol D-2000 (manufactured by Mitsui Chemicals, Inc.) having isophorone diisocyanate and a hydroxy group having a hydroxyl value of 56 mgKOH / g at the end was added to a four-necked flask equipped with a thermometer, a stirrer, a dropping funnel, 15 mol of the former and 14 mol of the latter were charged, followed by heating to 60 DEG C for 4 hours to obtain a polyurethane having isocyanato groups at both terminals. Subsequently, 2 mol of 2-hydroxyethyl acrylate was added to 1 mol of the obtained polyurethane, and the temperature was raised to 70 DEG C and the reaction was carried out for 2 hours to obtain a polyurethane (A-1) having an acryloyl group at the terminal. At this time, it was confirmed by IR that the peak derived from the isocyanato group disappeared, and the reaction was terminated. The polyurethane (A-1) thus obtained had a weight average molecular weight of 70,000.

&Lt; Synthesis of polyurethane (A-2) >

A polypropylene glycol D-2000 (manufactured by Mitsui Chemicals, Inc.) having isophorone diisocyanate and a hydroxy group having a hydroxyl value of 56 mgKOH / g at the end was added to a four-necked flask equipped with a thermometer, a stirrer, a dropping funnel, 14 mol of the former and 15 mol of the latter were charged, followed by heating to 60 DEG C to effect the reaction to obtain polyurethane having hydroxyl groups at both terminals. At this time, 2 mol of 2-acryloyloxyethyl isocyanate was added to 1 mol of the polyurethane obtained when the remaining isocyanato group became 0.1% or less by IR measurement, the temperature was raised to 70 캜, and the reaction was carried out for 2 hours To obtain a polyurethane (A-2) having an acryloyl group at the terminal. At this time, it was confirmed by IR that the peak derived from the isocyanato group disappeared, and the reaction was terminated. The polyurethane (A-2) thus obtained had a weight average molecular weight of 70,000.

&Lt; Synthesis of polyurethane (A-3) >

Except that the charging ratio of polypropylene glycol D-2000 (manufactured by Mitsui Chemicals, Inc.) having isophorone diisocyanate and a hydroxy group having a hydroxyl value of 56 mgKOH / g at the end thereof was changed to 6 moles of the former and 7 moles of the latter, -2), a polyurethane (A-3) having an acryloyl group at the terminal thereof was obtained. The polyurethane (A-3) thus obtained had a weight average molecular weight of 30,000.

&Lt; Synthesis of polyurethane (A-4) >

A polyurethane (A-4) having an acryloyl group at the terminal thereof was obtained in the same manner as in the synthesis of polyurethane (A-1) except that a hydrogenated product of diphenylmethane diisocyanate was used instead of isophorone diisocyanate. The polyurethane (A-4) thus obtained had a weight average molecular weight of 70,000.

&Lt; Synthesis of polyurethane (A-5) >

A polypropylene glycol D-2000 (manufactured by Mitsui Chemicals, Inc.) having isophorone diisocyanate and a hydroxy group having a hydroxyl value of 56 mgKOH / g at the end was added to a four-necked flask equipped with a thermometer, a stirrer, a dropping funnel, 4 mol of the former and 3 mol of the latter were added thereto, and then the temperature was raised to 60 DEG C and reacted for 4 hours to obtain a polyurethane having isocyanato groups at both terminals. Subsequently, 2 mol of 2-hydroxyethyl acrylate was added to 1 mol of the obtained polyurethane, and the temperature was raised to 70 DEG C and reacted for 2 hours to obtain a polyurethane (A-5) having an acryloyl group at the terminal. At this time, it was confirmed by IR that the peak derived from the isocyanato group disappeared, and the reaction was terminated. The polyurethane (A-5) thus obtained had a weight average molecular weight of 8,000.

&Lt; Weight average molecular weight &

The weight average molecular weight was measured by gel permeation chromatography Shodex GPC-101 (manufactured by Showa Denko K.K.) under the following conditions.

Column: LF-804 (manufactured by Showa Denko Co., Ltd.)

Temperature of column: 40 ° C

Sample: 0.2 mass% tetrahydrofuran solution

Flow rate: 1 ml / min

Eluent: tetrahydrofuran

Detector: RI detector

Examples 1 to 10 and Comparative Examples 1 to 3

The polyurethane (A) shown in Table 1, the (meth) acrylic acid ester (B) having a hydroxy group, the other photopolymerizable monomer (C) and the photopolymerization initiator (D) To prepare a photo-curing composition for a uniform transparent pressure-sensitive adhesive sheet. The acid value of the obtained composition is as shown in Table 1. The composition in Table 1 is% by mass, and Tg at the end of other photopolymerizable monomer (C) described in the footnote is a value when each monomer is a homopolymer.

Subsequently, the photocurable composition for a transparent pressure-sensitive adhesive sheet prepared was applied to a peelable PET film (100 mm x 100 mm x 75 m) having a thickness of 150 mu m after curing using an applicator, And then irradiated with ultraviolet light (UV irradiator: 4 kw x 1, output: 160 W / cm, metal halide lamp, manufactured by Nippon Denshi K.K.) Under a condition of 500 mJ / cm &lt; 2 &gt; to obtain a transparent pressure-sensitive adhesive sheet sandwiched by the peelable PET film. With respect to this transparent pressure-sensitive adhesive sheet, the rate of increase of the electrical resistance of the ITO film, the adhesive force, the total light transmittance, and the stepwise followability were evaluated by the method described below. The results are shown in Table 1.

<Evaluation method>

(Rate of increase of electric resistance of ITO film)

The transparent pressure sensitive adhesive sheet was cut into a size of 50 mm x 50 mm and then peeled off the peelable PET film having a thickness of 50 m. A transparent pressure-sensitive adhesive sheet from which a peeled PET film was peeled off was attached to the center of an ITO film of a PET film on which a 100 mm x 100 mm ITO film was deposited to form a laminate.

Using a resistivity meter Loresta GP (manufactured by Mitsubishi Kagaku Co., Ltd.), the electrical resistance R ₁ between both ends of the transparent adhesive sheet of the ITO film was measured. Then, the laminate to 60 ℃, and then allowed to stand for 500 hours under a 90% RH environment for 1 h under 23 ℃, a 50% RH environment, and the same manner as the electric resistance R ₁ was measured electrical resistance R _2. Further, the rate of increase [%] of electrical resistance of the ITO film was calculated from the following equation (3).

Increase rate of electric resistance [%] = (R ₂ -R ₁ ) / R ₁ × 100 (3)

It is shown that the corrosion rate of the conductive film is suppressed as the rate of increase of electric resistance is smaller. A case where the rate of increase of the electrical resistance of the ITO film is less than 5% is evaluated as &amp; cir &amp;, a case where the rate of increase of the electrical resistance of the ITO film is less than 10%

(Measurement of Adhesive Force of Adhesive Sheet)

The pressure-sensitive adhesive sheet was cut into a size of 25 mm x 100 mm, a 50 占 퐉 peelable PET film on one side of the pressure-sensitive adhesive sheet was peeled off, a PET film having a thickness of 50 占 퐉, Peeling PET of 75 占 퐉 on the other side was peeled off, adhered surface (measuring surface) was attached to the glass plate, and a 2 kg rubber roller (width: about 50 mm) was reciprocated one time to prepare a sample for measurement. The obtained measurement sample was allowed to stand for 24 hours under an environment of 23 ° C and a humidity of 50% and subjected to a tensile test in the 180 ° direction at a peeling speed of 300 mm / min in accordance with JIS Z0237 to determine the adhesive strength (N / 25 mm) was measured. The obtained measured value was regarded as adhesive force.

(Total light transmittance)

The transparent pressure sensitive adhesive sheet was cut into a size of 30 mm x 30 mm, and then a peelable PET film having a thickness of 50 m was peeled off. The peelable PET film was peeled off and the transparent pressure-sensitive adhesive sheet was attached to a glass plate to obtain a sample for measurement. The total light transmittance of the sample for measurement was measured using a haze, transmittance, and reflectance system HR-100 (manufactured by Murakami Shikisai Glass Co., Ltd.).

(Step difference absorbency evaluation)

The peelable PET film of the double-sided pressure-sensitive adhesive sheet obtained above was peeled off from a glass plate having a thickness of 0.5 mm, a length of 50 mm and a width of 40 mm printed on a 15 탆 thick and 5 mm wide, A 75 占 퐉 peel-off PET film on one side was peeled off, and then bonded to a glass plate having a thickness of 0.5 mm, a length of 50 mm and a width of 40 mm, and subjected to heating and pressing under conditions of 5 atm, 70 占 폚 for 10 minutes Fixed. Immediately after the fixation, and after 24 hours under the atmosphere of the temperature of 85 캜 and the humidity of 85%, lifting of the adhesive layer of the step difference portion was visually observed and the step difference absorbency was evaluated based on the following criteria.

○; In the state where the adhesive layer is not lifted from the stepped portion

?; A state in which the adhesive layer is observed to be slightly swollen at the stepped portion

×; It has been confirmed that the adhesive layer is clearly excited at the stepped portion

From the results shown in Table 1, it can be understood that the transparent pressure-sensitive adhesive sheet of the present invention (Examples 1 to 10) has small corrosivity of the transparent conductive film and excellent transparency, adhesiveness, and step difference absorbency. Particularly, in the case where the photopolymerizable monomer (C) contains an acrylate having a theoretical glass transition temperature of -5 占 폚 or higher (Examples 1 to 6 and 8 to 10) as a homopolymer (Example 7) The effect of improving the level difference absorbency is greater. On the other hand, in the case of using a polyurethane having a weight average molecular weight of 8,000 (Comparative Example 1), the step absorption was inferior and when the (meth) acrylic acid ester (B) having a hydroxy group was not used (Comparative Example 2) Adhesion is deteriorating. Further, in the case of using a polyurethane having a high acid value (Comparative Example 3), the rate of increase of the electric resistance value of the conductive film is large, and corrosion of the conductive metal can not be avoided.

&Lt; Industrial Availability >

According to the present invention, there is provided a one-pack type photo-curing composition for a transparent pressure-sensitive adhesive sheet which is excellent in transparency, cohesive strength and adhesive force of a pressure-sensitive adhesive layer and has excellent step difference absorbability without causing corrosion of the conductive layer even when directly bonded to the conductive layer side of the transparent conductive film can do. Further, by using the transparent pressure-sensitive adhesive sheet formed by curing the composition, the touch panel with high quality in which the corrosion of the conductive layer is suppressed and the image display apparatus equipped with the touch panel can be obtained.

Claims (11)

(A) having a weight average molecular weight of 10,000 to 300,000 and having a (meth) acryloyl group at the terminal and a polyoxyalkylene polyol skeleton, a (meth) acrylic acid ester (B) having a hydroxy group, A photocurable composition for a transparent pressure-sensitive adhesive sheet, which comprises a monomer (C) and a photopolymerization initiator (D) and has an acid value of 0 to 5 mgKOH / g. The method according to claim 1,
The photo-curable composition comprises 20 to 50% by mass of a polyurethane (A), 5 to 20% by mass of a (meth) acrylic ester (B) having a hydroxy group, 30 to 74.8% by mass of a photopolymerizable monomer (C) (D) in a proportion of 0.2 to 5% by mass. 3. The method according to claim 1 or 2,
And the other photopolymerizable monomer (C) contains a (meth) acrylic acid ester of a hydrocarbon monoalcohol having a carbon number of 6 to 18 whose theoretical glass transition temperature (Tg) of the homopolymer is not lower than -5 DEG C Photocurable composition. 3. The method according to claim 1 or 2,
And an acid value of 0 to 0.5 mgKOH / g. A pressure-sensitive adhesive sheet for optical use characterized by having as a pressure-sensitive adhesive layer a cured product of the photo-curable composition for a transparent pressure-sensitive adhesive sheet according to claim 1 or 2. 6. The method of claim 5,
Wherein the cured product has a glass transition temperature (Tg) of -10 ° C to -60 ° C. The method according to claim 6,
Wherein the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet. 6. The method of claim 5,
Wherein the sheet is a sheet for fixing a transparent conductive film to be bonded to a conductive layer surface of a transparent conductive film. A transparent conductive film laminate according to claim 8, wherein the adhesive sheet for optical is bonded to the surface of the conductive layer of the transparent conductive film. A touch panel having the transparent conductive film laminate according to claim 9. An image display apparatus comprising the touch panel according to claim 10.