JP6097132B2 - Photocurable composition for transparent adhesive sheet, adhesive sheet using the same, and use thereof - Google Patents

Description

  The present invention relates to an acrylic photocurable composition for a transparent adhesive sheet, a transparent adhesive sheet formed by curing the photocurable composition, and a laminate formed by adhering the transparent adhesive sheet to a conductive layer surface of a transparent conductive film. About the body.

  In recent years, touch panels have begun to be mounted in fields such as mobile phones and game machines. The touch panel is a transparent substrate for optical use, such as a transparent base material such as glass having a transparent conductive film such as ITO (indium tin oxide) and the like, a transparent protective sheet for protecting it, and a display device such as a liquid crystal display. It is the laminated body bonded together using the adhesive sheet.

  There are two types of touch panels: a resistance film type touch panel that detects mainly by pressure at the time of input and a capacitance type touch panel that detects an input location by static electricity from the human body at the time of input. In the capacitive touch panel, the conductive layer surface of the transparent conductive film is fixed so as to be in contact with the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive used in this application generally contains an acid component for the purpose of improving adhesion, but when such a pressure-sensitive adhesive is used, when the pressure-sensitive adhesive layer contacts the conductive layer surface of the transparent conductive film, There is a problem that an oxidation reaction of the metal occurs due to the acid component contained in the pressure-sensitive adhesive, and the conductive function is lowered. For this reason, the adhesive sheet for fixing a transparent conductive film is required to have high metal corrosion prevention properties.

  As a pressure-sensitive adhesive sheet having metal corrosion prevention properties, a pressure-sensitive adhesive sheet containing a metal corrosion inhibitor (for example, Patent Document 1) has been proposed. Moreover, the adhesive sheet (for example, patent document 2) which reduced the corrosivity with respect to a transparent conductive film by containing a specific amount of nitrogen atom containing components with respect to the acid component of an adhesive layer is proposed. However, the pressure-sensitive adhesive sheet containing the metal corrosion inhibitor described in Patent Document 1 has problems such as that the metal corrosion inhibitor is likely to cause discoloration and optical properties are deteriorated. In addition, the pressure-sensitive adhesive sheet containing a specific amount of a nitrogen atom-containing component described in Patent Document 2 cannot sufficiently suppress an increase in the electrical resistance value of ITO due to the acid component contained in the pressure-sensitive adhesive layer. There was a problem.

  On the other hand, in some optical components such as touch panels, multi-layer ink printing may be applied to provide design and decorativeness, and at that time, there is a printing step between the printing part and the non-printing part. There is a problem that arises. For example, a touch panel having a member provided with a frame-like printed portion is used in a mobile phone or the like. In such an application, the pressure-sensitive adhesive sheet is required to have the ability to fill a printing step at the same time as the ability to stick and fix a member, that is, excellent step absorbability. If the transparent adhesive sheet cannot absorb the step, the transparent adhesive sheet floats (bubbles and voids) around the edge of the printed layer, causing light reflection loss due to the float and reducing the visibility of the liquid crystal display. There is a risk.

  In order to obtain excellent level difference absorbability, it is advantageous that the transparent pressure-sensitive adhesive sheet is soft and has high adhesive force, but as described above, it does not contain an acid component from the viewpoint of metal corrosion prevention. Is required. In response to this requirement, an alkoxyalkyl acrylate is the main monomer, and it comprises an acrylic polymer having a weight average molecular weight of 400,000 to 1.6 million and no acid component, and a crosslinking agent such as a polyfunctional epoxy compound or a polyfunctional isocyanate compound. A pressure-sensitive adhesive composition has been proposed, and it is disclosed to provide a transparent pressure-sensitive adhesive sheet that can achieve both good adhesion and metal corrosion prevention (for example, Patent Document 3).

  However, the composition in which a crosslinking agent is added to the polymer is not sufficiently stable after mixing the two, and the acrylic polymer has a high molecular weight, so that it is diluted with a solvent when the composition is applied. Therefore, it is very difficult to produce a thick adhesive sheet having a thickness of 100 μm or more.

JP 2006-45315 A JP 2010-144002 A JP 2009-079203 A1

  The problem to be solved by the present invention is that the conductive layer is not corroded even if directly bonded to the conductive layer surface of the transparent conductive film, the pressure-sensitive adhesive layer is excellent in transparency, adhesive strength, and step absorbability. To provide a liquid-type photocurable composition for a transparent adhesive sheet, a transparent adhesive sheet obtained by curing the photocurable composition, and a laminate obtained by adhering the transparent adhesive sheet to a conductive layer surface of a transparent conductive film. It is in.

  As a result of intensive studies on the background of the above-mentioned problems of the photocurable transparent adhesive sheet used for optical components such as touch panels, the present inventors have a molecular weight in a specific range, and at the end. A polyoxyalkylene urethane acrylate compound having a (meth) acryloyl group introduced is combined with a (meth) acrylic acid ester having a hydroxy group and a photopolymerizable monomer other than the (meth) acrylic acid ester having a hydroxy group. When used as a photo-curable composition for a transparent adhesive sheet by blending a photopolymerization initiator, it has excellent transparency, adhesiveness, excellent performance in metal corrosion prevention and step absorbency of transparent conductive films. Based on this finding, the present invention has been completed.

Thus, according to the present invention, the photocurable composition for transparent adhesive sheets shown in the following (1) to (3), the optical adhesive sheet shown in (4) to (5), and (6). A transparent conductive film laminate, a touch panel shown in (7), and an image display device shown in (8) are provided.
(1) Polyurethane (A) having a polyoxyalkylene polyol as a skeleton and having a (meth) acryloyl group at the terminal and a weight average molecular weight of 10,000 to 300,000, a (meth) acrylic acid ester (B) having a hydroxy group, A photocurable composition for a transparent pressure-sensitive adhesive sheet, which contains another photopolymerizable monomer (C) and a photopolymerization initiator (D) and has an acid value of 0 to 5 mgKOH / g.

(2) The photocurable composition is 20 to 50% by mass of polyurethane (A), 5 to 20% by mass of (meth) acrylic acid ester (B) having a hydroxy group, and a photopolymerizable monomer other than (B). The photocurable composition for a transparent adhesive sheet according to (1), which contains 30 to 74.8% by mass of the monomer (C) and 0.2 to 5% by mass of the photopolymerization initiator (D). object.
(3) The photopolymerizable monomer (C) is a (meth) acrylic ester of a hydrocarbon monoalcohol having 6 to 18 carbon atoms, wherein the theoretical glass transition temperature (Tg) of the homopolymer is −5 ° C. or higher. The photocurable composition for transparent adhesive sheets according to claim 1 or 2, wherein
(4) An optical pressure-sensitive adhesive sheet obtained by curing the photocurable composition for a transparent pressure-sensitive adhesive sheet according to any one of (1) to (3).
(5) The optical pressure-sensitive adhesive sheet according to (4), which is a transparent conductive film fixing sheet for bonding to the conductive layer surface of the transparent conductive film.
(6) The transparent conductive film laminated body which bonded together the adhesive sheet for optics of said (5) to the conductive layer surface of a transparent conductive film.
(7) A touch panel having the transparent conductive film laminate according to (6).
(8) An image display device comprising the touch panel according to (7).

  The photocurable composition for a transparent 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. By photocuring, a transparent adhesive sheet excellent in adhesiveness, transparency, and step absorbability can be obtained. Moreover, since the acid value of the composition is at most 5 mgKOH / g, when the transparent adhesive sheet is bonded to the conductive layer surface of the transparent conductive film, corrosion of the transparent conductive film due to the acid component can be suppressed, By including a (meth) acrylic acid ester having a hydroxy group, high cohesive force and adhesion to a substrate can be obtained. In addition, when the photocurable composition for transparent adhesive sheets of the present invention is used, a sheet having a thickness of 100 μm or more can be easily produced. Moreover, since the transparent adhesive sheet of this invention is excellent in level | step difference absorbability, the floating (bubble or space | gap) of the transparent adhesive sheet in the edge part periphery of a printing layer can be suppressed, and the touch panel excellent in visibility is obtained. be able to.

Next, the form for implementing this invention is demonstrated. In the specification and claims of the present application, the (meth) acryloyl group means
Is meant a chemical formula CH ₂ = CH-CO-, a group represented by or formula _{CH 2 = C (CH 3)} -CO- , a group represented by,
Isocyanato group is
This means a group represented by the chemical formula -N = C = O.

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

<Polyurethane (A) having (meth) acryloyl group>
As the polyoxyalkylene polyol used for the production of the polyurethane (A), those having an alkylene chain having 2 to 4 carbon atoms are preferable, and specific examples thereof include, for example, polyethylene polyol, polypropylene polyol, polybutylene polyol, polytetraalkylene. And methylene polyol. Moreover, the copolymer of 2 or more types of oxyalkylene polyols can also be used, and 2 or more types of polyoxyalkylene polyols can also be blended and used. Of these, polyoxyalkylene diol is 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 adhesive sheet may be reduced. On the other hand, when the number average molecular weight of the polyoxyalkylene polyol is excessively increased, there is a concern that the cohesive force of the transparent pressure-sensitive adhesive sheet is lowered because urethane bonds in the polyurethane are reduced.

  The polyisocyanate used in the polyurethane (A) of the present invention is not particularly limited, but tolylene diisocyanate and hydrogenated product thereof, xylylene diisocyanate and hydrogenated product thereof, diphenylmethane diisocyanate and hydrogenated product thereof, 1,5- Naphthylene diisocyanate and its hydrogenated product, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexyl diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, norbornane diisocyanate, etc. A diisocyanate is mentioned, You may use 2 or more types together. Among these, from the viewpoint of controlling light resistance and reactivity, hydrogenated products of isophorone diisocyanate or diphenylmethane diisocyanate are preferable.

  The polyurethane (A) used in the present invention can be produced according to a conventional method using polyoxyalkylene and polyisocyanate. A preferred first synthesis method is as follows. First, a polyoxyalkylene and a polyisocyanate are reacted at a ratio in which the amount of isocyanato groups is larger than the amount of hydroxy groups to synthesize a polyurethane having an isocyanato group. At this time, the molecular weight can be adjusted by adjusting the ratio of the amount of isocyanato groups to the amount of hydroxy groups. Specifically, the smaller the ratio of the amount of isocyanate groups to the amount of hydroxy groups, the greater the molecular weight of the polyurethane having isocyanate groups, and the larger the ratio of the amount of isocyanate groups to hydroxyl groups, the greater the amount of polyurethane compounds having isocyanate groups. The molecular weight is small. Next, the polyurethane (A) is synthesized by reacting a polyurethane having an isocyanato group with a compound having a hydroxy group and a (meth) acryloyl group.

  Although it does not specifically limit as a compound which has a hydroxy group and a (meth) acryloyl group, Hydroxyalkyl (2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate) ( 1,3-butanediol mono (meth) acrylate, 1,4-butanediol mono (meth) acrylate, 1,6-hexanediol mono (meth) acrylate, 3-methylpentanediol mono (meth) acrylate And monools having a (meth) acryloyl group derived from various polyols such as Two or more of these may be used in combination. Among these, 2-hydroxyethyl (meth) acrylate is preferable in terms of reactivity with the isocyanato group and photocurability.

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

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

  Next, a preferable second synthesis method of the polyurethane (A) will be described. First, a polyoxyalkylene polyol and a polyisocyanate are reacted at a ratio in which the amount of hydroxy groups is greater than the amount of isocyanato groups to synthesize a polyurethane having hydroxy groups. 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 hydroxy groups to the amount of isocyanato groups, the greater the molecular weight of the polyurethane having hydroxy groups, and the larger the ratio of the amount of hydroxy groups to the amount of isocyanate groups, the greater the molecular weight of the polyurethane compound having hydroxy groups. Becomes smaller. Next, 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 introduction amount of the (meth) acryloyl group is usually 50 to 100 mol%, more preferably 80 to 100 mol%, still more preferably 100 mol% with respect to the hydroxy group. When the introduction amount of the (meth) acryloyl group is less than 50 mol% with respect to the hydroxy group, the cohesive force of the transparent adhesive sheet may be lowered.

  The compound having an isocyanato group and (meth) acryloyl group is not particularly limited, but 2- (meth) acryloyloxyethyl isocyanate, 2- (meth) acryloyloxypropyl isocyanate, 1,1-bis (acryloyloxymethyl) ethyl An isocyanate etc. are mentioned. Examples of commercially available compounds having an isocyanato group and a (meth) acryloyl group include Karenz MOI (registered trademark) and Karenz AOI (registered trademark) manufactured by Showa Denko KK. Two or more of these may be used in combination. Among these, 2- (meth) acryloyloxyethyl isocyanate is preferable from the viewpoint of reactivity with a hydroxy group and photocurability.

  In the synthesis of the polyurethane (A), the reaction between the hydroxy group and the isocyanato group is carried out using a urethanization catalyst such as dibutyltin dilaurate, dibutyltin diethylhexoate, dioctyltin dilaurate in the presence of an organic solvent inert to the isocyanato group. Usually, it is continuously performed at 30 to 100 ° C. for about 1 to 5 hours. The use amount of the urethanization catalyst is usually 50 to 500 ppm by mass with respect to the total mass of the reaction product.

  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 decreases, and conversely, when the weight average molecular weight exceeds 300,000, handling becomes difficult and workability decreases. .

  In addition, a weight average molecular weight is a molecular weight of polystyrene conversion measured using gel permeation chromatography Shodex GPC-101 (made by Showa Denko KK).

  The content of the polyurethane (A) in the photocurable composition for a transparent adhesive sheet may be appropriately selected, but is preferably 20 to 50% by mass, more preferably 25 to 45% by mass, and still more preferably. Is 30-40 mass%. When the content of polyurethane (A) is excessively small, the cohesive force when used as a transparent adhesive sheet tends to decrease, and conversely when it is excessively large, the adhesive force when used as a transparent adhesive sheet tends to decrease.

<(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 carboxy group (chemical formula: —COOH), and examples thereof include hydroxyalkyl (meth) acrylate and the like. It is done. Specific examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,3-butanediol (meth) acrylate, Examples include 1,4-butanediol (meth) acrylate, 1,6-hexanediol (meth) acrylate, and 3-methylpentanediol (meth) acrylate, and these may be used alone or in combination of two or more. it can. Carbon number of the alkyl group of the (meth) acrylic acid ester (B) having a hydroxy group is usually 2 to 10, particularly 2 to 6 is preferable, and 2 to 4 is more preferable. In particular, 2-hydroxyethyl (meth) acrylate is most often used in terms of the adhesive strength of the resulting adhesive sheet.

  Content of (meth) acrylic acid ester (B) which has a hydroxyl group is 5-20 mass% normally in the photocurable composition for transparent adhesive sheets, Preferably it is 6-18 mass%, More Preferably it is 7-15 mass%. If the content of the (meth) acrylic acid ester (B) having a hydroxy group in the photocurable composition for a transparent adhesive sheet is too small, the adhesiveness of the resulting adhesive sheet to the substrate may be insufficient. On the contrary, if the amount is excessively large, the water resistance of the pressure-sensitive adhesive sheet may deteriorate.

<Other photopolymerizable monomer (C)>
The other photopolymerizable monomer (C) refers to a photopolymerizable monomer other than the (meth) acrylic acid ester having a hydroxy group as the component (B). The photopolymerizable monomer (C) is preferably a monomer that does not contain a carboxy group. The monomer is not particularly limited, and may be monofunctional or polyfunctional as long as it has a photopolymerizable functional group such as a vinyl group or a (meth) acryloyl group. A photopolymerizable monomer can be used individually or in combination of 2 or more types. The monofunctional or polyfunctional functional group mentioned here refers to a functional group involved in polymerization such as a vinyl group or 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-butyl (meth) acrylate, and tert-butyl (meth). Alkyl such as acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, n-hexyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate (Meth) acrylate;
Cyclohexyl (meth) acrylate, norbornyl (meth) acrylate, isobornyl (meth) acrylate, norbornanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate Cyclic alkyl (meth) acrylates such as dicyclopentanyloxyethyl (meth) acrylate and tricyclodecane dimethylol di (meth) acrylate;

Alkoxyalkyl (meth) acrylates such as ethoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, 2-methoxyethoxyethyl (meth) acrylate, 2-ethoxyethoxyethyl (meth) acrylate;
Alkoxy (poly) alkylene glycol (meth) acrylates such as methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, 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;

Polyethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, hydroxypivalate ester neopentyl glycol di (Meth) acrylate, 1,3-bis (hydroxyethyl) -5,5-dimethylhydantoin di (meth) acrylate, α, ω-di (meth) acrylbisdiethylene glycol phthalate, trimethylolpropane tri (meth) acrylate, ethylene Glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) Multifunctional (meth) acrylates such as acrylate, 1,6-hexanediol di (meth) acrylate, diacryloxyethyl phosphate, dipentaerythritol trihydroxy (meth) acrylate, pentaerythritol tetra (meth) acrylate;
Acrylamide derivatives such as acrylamide, dimethylacrylamide, diethylacrylamide, (meth) acryloylmorpholine;
Examples thereof include epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate.

  The content of the photopolymerizable monomer (C) can be appropriately selected so that the glass transition temperature of a cured product obtained by curing the photocurable composition falls within a desired range. As will be described later, in the present invention, it is desirable to adjust the glass transition temperature of the pressure-sensitive adhesive sheet obtained by curing in the range of −10 to −60 ° C. For that purpose, photopolymerization in the photocurable composition is performed. The content of the functional monomer (C) is usually 30 to 74.8% by mass, preferably 40 to 65% by mass, and more preferably 45 to 60% by mass. When there is too little content of the photopolymerizable monomer (C) in the photocurable composition for transparent adhesive sheets, the adhesiveness to the base material of the obtained adhesive sheet may become inadequate. In addition, when the content of the photopolymerizable monomer (C) in the photocurable composition for a transparent adhesive sheet is excessively large, the cohesive force of the obtained adhesive sheet is reduced and the adhesive force of the adhesive sheet is reduced. It becomes easy to do.

  In the present invention, as the photopolymerizable monomer (C), a monomer (C-1) having a theoretical glass transition temperature (Tg) of homopolymer lower than −5 ° C. and a theoretical Tg of homopolymer of −5 ° C. These monomers (C-2) 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, and the like. Specific examples of C-2) include esters of (meth) acrylic acid with alcohols having a hydrocarbon group having 6 to 18 carbon atoms such as lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, etc. And hydrocarbon (meth) acrylates. Although the usage ratio of the monomer (C-1) and the monomer (C-2) can be appropriately selected, the ratio of the monomer (C-2) to the total amount of the monomer (C) is 30 to 60 mass. %, And preferably 35 to 50% by mass. Within this range, a pressure-sensitive adhesive sheet rich in adhesiveness and flexibility can be obtained.

  Here, the theoretical glass transition temperature (Tg) is a glass transition temperature (Tg) of a homopolymer (a homopolymer of monomers). The Tg of various homopolymers is a publicly known document, “Non-Kogyo Kogyo Shimbun Co., Ltd.” “Adhesive Technology Handbook” (issued in March 1997) and Wiley-Interscience “Polymer Handbook 4th Edition” (issued) Date: 1999). For the Tg of a homopolymer of a monomer not described in the above-mentioned publicly known material, the value obtained by the following method is adopted. That is, a test sample is prepared by casting and drying a homopolymer solution obtained by solution polymerization of a target monomer on a release liner. With respect to this test sample, a differential scanning calorimeter (DSC) was used to perform differential scanning calorimetry at a temperature rising rate of 10 ° C./min from −80 ° C. to 280 ° C., and an endothermic start temperature due to glass transition. Is the Tg of the homopolymer.

<Photopolymerization initiator (D)>
The photopolymerization initiator (D) of the present invention is not particularly limited, but benzophenone, benzyl, benzoin, ω-bromoacetophenone, chloroacetone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2- Phenylacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzoin methyl ether, benzoin isobutyl ether, benzoin -N-butyl ether, benzyl methyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4-isopropylpheny ) -2-hydroxy-2-methylpropan-1-one, methylbenzoylformate, 2,2-diethoxyacetophenone, 4-N, N′-dimethylacetophenone, 2-methyl-1- [4- (methylthio) ) Carbonyl photopolymerization initiators such as phenyl] -2-morpholinopropan-1-one;

Sulfide photopolymerization initiators such as diphenyl disulfide, dibenzyl disulfide, tetraethylthiuram disulfide, tetramethylammonium monosulfide;
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 photopolymerization initiators such as azobisisobutyronitrile and 2,2′-azobispropane;
Sulfochloride-based photopolymerization initiators;
Thioxanthone photopolymerization initiators such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone;
Examples thereof include peroxide photopolymerization initiators such as benzoyl peroxide and di-t-butyl peroxide. These may be used alone or in combination of two or more. Among these, 1-hydroxycyclohexyl phenyl ketone and / or 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferable from the viewpoint of solubility in the transparent adhesive sheet photocurable composition.

  Content of a photoinitiator (D) shall be 0.2-5 mass% in the photocurable composition for transparent adhesive sheets from the point of balance of photocurability, the intensity | strength of the adhesive sheet obtained, and adhesiveness. It is preferably 0.5 to 3% by mass. When the content of the photopolymerization initiator (D) is excessively small, photocuring tends to be insufficient, and conversely, when the content is excessively large, the adhesiveness of the resulting pressure-sensitive adhesive sheet tends to decrease.

  The acid value of the photocurable composition for a transparent adhesive sheet of the present invention is 0 to 5 mgKOH / g, preferably 0 to 0.5 mgKOH / g, more preferably 0 to 0.1 mgKOH / g. When the acid value is higher than 5 mgKOH / g, it becomes difficult to suppress corrosion of the conductive layer surface of the transparent conductive film. The acid value of the composition is a value measured according to JIS K0070, and is measured as follows.

About 2 g of a 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 to dissolve it. Further, 1 to 3 drops of phenolphthalein ethanol solution is added to this container as an indicator, and the mixture is sufficiently stirred until the sample becomes uniform. This is titrated with a 0.1N potassium hydroxide-ethanol solution, and the end point of neutralization is taken when the indicator is light red for 30 seconds. The value obtained from the result using the following calculation formula (1) is defined as the acid value of the composition.
Acid value (mgKOH / g) = [B × f × 5.661] / S (1)
In addition, B, f, and S in the calculation formula (1) are as follows.
B: Amount of 0.1N potassium hydroxide-ethanol solution used (ml)
f: Factor of 0.1N potassium hydroxide-ethanol solution (blur correction by reagent lot)
S: Sample collection amount (g)

  In order to improve the adhesive force of the obtained pressure-sensitive adhesive sheet, a tackifier resin may be added to the photocurable composition for a transparent pressure-sensitive adhesive sheet of the present invention as long as the transparency is not lowered. Examples of tackifier resins include rosin resins such as rosin and rosin esterified products; terpene resins such as diterpene polymers and α-pinene-phenol copolymers; aliphatic (C5) and aromatic ( Petroleum resin such as C9); styrene resin, phenol resin, xylene resin and the like. From the viewpoint of light resistance, it is preferable to add an esterified product of hydrogenated rosin or disproportionated rosin with few unsaturated double bonds, aliphatic or aromatic petroleum resin, high Tg acrylic resin, or the like to the adhesive sheet. As addition amount of tackifying resin, 100 mass parts of total amount of (A) component, (B) component, (C) component, and (D) component with respect to 100 mass parts of photocurable composition for transparent adhesive sheets 1) to 10 parts by mass.

  Moreover, the photocurable composition for transparent adhesive sheets of this invention may contain various well-known additives in the range which does not impair transparency as needed. Additives include plasticizers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, light stabilizers, UV absorbers, polymerization inhibitors, benzotriazole-based light stabilizers, phosphate esters System and other flame retardants, antistatic agents such as surfactants, dyes and the like.

  Since the photocurable composition for transparent adhesive sheets of the present invention contains (meth) acrylic acid ester (B) having a hydroxy group and other photopolymerizable monomer (C), no organic solvent is added. Both can be adjusted to a viscosity that can be applied, but an organic solvent may be added for the purpose of adjusting the viscosity during coating. Examples of the organic solvent 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.

<Optical pressure-sensitive adhesive sheet>
The optical pressure-sensitive adhesive sheet of the present invention is an optical pressure-sensitive adhesive sheet used for optical applications obtained by curing the above-described photocurable composition for transparent pressure-sensitive adhesive sheets. More specifically, the pressure-sensitive adhesive sheet is used for an application for bonding an optical member (for optical member bonding). The Tg of the cured product forming the pressure-sensitive adhesive sheet is preferably −10 to −60 ° C., more preferably −20 to −50 ° C. As the Tg of the cured product becomes higher, the pressure-sensitive adhesive sheet becomes harder and the step absorbability tends to decrease. Conversely, when the Tg of the cured product becomes excessively low, the adhesive force tends to decrease. This optical pressure-sensitive adhesive sheet may have a base material formed of a transparent resin sheet such as PET, or may be a double-sided pressure-sensitive adhesive sheet having only a pressure-sensitive adhesive layer without having a base material. Moreover, even if the adhesive layer consists of a single layer, multiple layers may be laminated | stacked. Specific examples of the multi-layer laminated sheet include, for example, a laminated sheet having a three-layer structure and changing the composition of both layers and the central layer to balance cohesive force and adhesive force.

  Although it will not specifically limit as an optical member used as the object of bonding if it is a member which has an optical characteristic, For example, the member used for an image display apparatus, a touchscreen, or these apparatuses etc. are mentioned. More specifically, for example, a polarizing plate, a retardation plate, an optical compensation film, a brightness enhancement film, a light guide plate, a reflection film, an antireflection film, a transparent conductive film, a design film, a decorative film, a surface protection film, a prism, a lens , A color filter, a transparent substrate, and a member in which these are laminated.

  The optical pressure-sensitive adhesive sheet can be obtained by applying a photocurable composition for a transparent pressure-sensitive adhesive sheet to a release film, and irradiating the applied composition with ultraviolet rays using an ultraviolet irradiation device or the like to cause photocuring. The film thickness of the optical pressure-sensitive adhesive sheet is usually 5 to 1,000 μm, preferably 10 to 400 μm, and more preferably 15 to 300 μm. When the film thickness of the optical pressure-sensitive adhesive sheet becomes excessively thin, it tends to be difficult to bond the pressure-sensitive adhesive sheet. When the film thickness of the optical pressure-sensitive adhesive sheet becomes excessively thick, it tends to be difficult to control the film thickness. In addition, for coating (coating) in the method for forming an optical pressure-sensitive adhesive sheet of the present invention, a known coating method can be used. Conventional coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters Dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, direct coaters and the like can be used.

  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. In addition, each adhesive surface (both surfaces) of the adhesive sheet may be protected by two release films, respectively, or is wound into a roll by one release film having both surfaces as release surfaces. It may be protected with. The release film is used as a protective material for the pressure-sensitive adhesive layer, and is peeled off when attached to an adherend. Note that the release film is not necessarily provided. As the release film, a commonly used release film can be used, and is not particularly limited. Examples thereof include a plastic film surface-treated with a release agent such as silicone, long-chain alkyl, or fluorine. The release film can be formed by a known method. Also, the thickness of the release film is not particularly limited, and the thicknesses of the two release films may be the same or different. Also, different types of release films may be used, and the releasability can be controlled by changing the rigidity.

<Laminated body of transparent conductive film and optical pressure-sensitive adhesive sheet>
The optical pressure-sensitive adhesive sheet of the present invention is suitably used as a sheet for fixing a transparent conductive film (hereinafter sometimes referred to as a pressure-sensitive adhesive sheet for fixing a transparent conductive film). A laminated body is formed by sticking this transparent conductive film fixing pressure-sensitive adhesive sheet to the conductive layer surface of the transparent conductive film according to a conventional method. This laminate is excellent in adhesive strength and has little corrosion of the conductive layer, and can be suitably used for touch panels. Moreover, the sheet for fixing a transparent conductive film of the present invention may have a base material or a double-sided pressure-sensitive adhesive sheet having only a pressure-sensitive adhesive layer without having a base material. Moreover, even if the adhesive layer consists of a single layer, multiple layers may be laminated | stacked. Among these, a double-sided pressure-sensitive adhesive sheet having only a pressure-sensitive adhesive layer without a substrate is preferable from the viewpoint of ensuring transparency and shape followability (step absorbability).

  The transparent conductive film used in the present invention only needs to have a conductive layer on at least one surface layer, and a transparent conductive film in which a conductive material is provided on the surface layer of the transparent substrate by vapor deposition or coating can be suitably used. Among these, a transparent conductive film having a conductive layer in which a conductive material is formed by vapor deposition has an advantage that it can be easily manufactured. The conductive material deposited or coated in the conductive layer of the transparent conductive film is not particularly limited, and specific examples include indium tin oxide, indium oxide, tin oxide, zinc oxide, cadmium oxide, gallium oxide, and titanium oxide. It is done. In particular, indium tin oxide, which is excellent in transparency and conductivity, is preferable.

  In the transparent conductive film, the substrate on which the conductive material is deposited or coated is not particularly limited, and examples thereof include glass and resin films. Examples of the resin film include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, and polyvinylidene chloride film. , Polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, polyimide film, fluorine resin film , Nylon film, acrylic resin film, poly Black olefin films and the like. Of these, polyethylene terephthalate having excellent transparency and durability is preferable.

  Regarding the transparency of the transparent conductive film, the total light transmittance is preferably 80% or more, and the total light transmittance is more preferably 90% or more. When the transparency of the transparent conductive film is within the above range, the transparency of the touch panel device-mounted display using the transparent conductive film is easily maintained. Moreover, the thickness of a transparent conductive film laminated body is 0.1 mm-2.0 mm normally.

In the transparent conductive film laminate of the present invention, the rate of increase in the electric resistance value of the conductive film layer after standing for 500 hours at 60 ° C. and 90% RH is 20% or less, more preferably 10% or less, especially 5 % Or less is preferable. The smaller the increase rate, the more the corrosion of the metal forming the transparent conductive film is suppressed, and the performance when incorporated in a touch panel or the like is improved. Note that the rate of increase in the electrical resistance value can be calculated by the following equation (2).
Rate of increase in electric resistance value of conductive film layer (%) = [(electric resistance value after standing at 60 ° C., 90% RH for 500 hours) − (initial electric resistance value)] / (initial electric resistance value) × 100 (2)

<Touch panel>
The touch panel of this invention has a transparent conductive film laminated body formed by bonding the said adhesive sheet for transparent conductive film fixation to a transparent conductive film. The configuration of the touch panel is not particularly limited. For example, the configuration described in Patent Document 2 can be used. Especially, it is preferable that it is the structure of a capacitive touch panel.

  As a specific configuration example, a transparent conductive film laminate in which a transparent conductive film is provided on one side of a double-sided pressure-sensitive adhesive sheet has a capacitance provided in two layers between a display panel (transparent panel) and an image display module. A touch panel device of the type can be exemplified. Of the two transparent conductive films with pressure-sensitive adhesive layers, at least one layer may be the transparent conductive film laminate, and the transparent conductive film with pressure-sensitive adhesive layer on the image display module side is the transparent conductive film laminate. A structure or a structure in which each of the two transparent conductive films with an adhesive layer is the transparent conductive film laminate can be used as a preferable structure. As another preferred configuration example, a transparent conductive film laminate in which a transparent conductive film is provided on both sides of a double-sided pressure-sensitive adhesive sheet is fixed between a display panel and an image display module with a fixing tape or a fixing adhesive. An electrostatic capacity type touch panel can be exemplified. In the said structure, since a touch panel can be manufactured by fixing a display panel, a transparent conductive film laminated body, and an image display module using a fixing tape or a fixing adhesive, an assembly process becomes easy.

  The protective panel for 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. Of these, a (meth) acrylic resin excellent in transparency and lightness 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 characters and figures visually recognized around the image display part of the portable electronic terminal, or a black or white background provided on the back face thereof. By providing these decorative portions, design properties can be imparted 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 an electronic device incorporating the touch panel thinner.

  In addition, when making the transparent conductive film with the adhesive layer by the side of an image display module into a transparent conductive film laminated body, it is preferable that the thickness of the double-sided adhesive sheet of the said transparent conductive film laminated body shall be 5-300 micrometers. It is especially preferable to set it to -200 micrometers. Moreover, when the transparent conductive film with an adhesive layer on the side to be bonded to the display panel is used as a transparent conductive film laminate, the thickness of the double-sided pressure-sensitive adhesive sheet is 15 to 15 when a decorative part is provided on the display panel. 300 μm is preferable, and 25 to 200 μm is more preferable. Within the above range, the double-sided PSA sheet easily follows the decorative part of the display panel.

  The touch panel of the present invention can be incorporated into various image display devices according to a conventional method. The target image display device is not particularly limited, and examples thereof include an LCD display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), and electronic paper that are usually used for small electronic terminals. Can be used.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Synthesis of polyurethane (A-1)>
In a four-necked flask equipped with a thermometer, a stirrer, a dropping funnel, and a condenser tube with a drying tube, polypropylene glycol D-2000 (manufactured by Mitsui Chemicals) having an isophorone diisocyanate and a hydroxyl group having a hydroxyl value of 56 mgKOH / g at the end is used. The former was charged at a ratio of 15 mol and the latter at 14 mol, and then heated to 60 ° C. and reacted for 4 hours to obtain a polyurethane having isocyanato groups at both ends. Next, after adding 2 mol of 2-hydroxyethyl acrylate to 1 mol of the obtained polyurethane, the temperature was raised to 70 ° C. and reacted for 2 hours to obtain a polyurethane (A-1) having an acryloyl group at the terminal. Obtained. At this time, after confirming that the peak derived from the isocyanato group disappeared by IR, the reaction was terminated. The weight average molecular weight of the obtained polyurethane (A-1) was 70,000.

<Synthesis of polyurethane (A-2)>
In a four-necked flask equipped with a thermometer, a stirrer, a dropping funnel, and a condenser tube with a drying tube, polypropylene glycol D-2000 (manufactured by Mitsui Chemicals) having an isophorone diisocyanate and a hydroxyl group having a hydroxyl value of 56 mgKOH / g at the end is used. The former was charged at a ratio of 14 moles and the latter at a ratio of 15 moles, and then heated to 60 ° C. for reaction to obtain a polyurethane having hydroxy groups at both ends. At this time, when the remaining isocyanato group became 0.1% or less by IR measurement, 2 mol of 2-acryloyloxyethyl isocyanate was added to 1 mol of the obtained polyurethane, and the temperature was raised to 70 ° C. For 2 hours to obtain a polyurethane (A-2) having an acryloyl group at its terminal. At this time, after confirming that the peak derived from the isocyanato group disappeared by IR, the reaction was terminated. The obtained polyurethane (A-2) had a weight average molecular weight of 70,000.

<Synthesis of polyurethane (A-3)>
Polyurethane (A-2) except that the charge ratio of isophorone diisocyanate and polypropylene glycol D-2000 (made by Mitsui Chemicals) having a hydroxyl group of 56 mg KOH / g at the terminal is changed to 6 mol for the former and 7 mol for the latter ) To obtain a polyurethane (A-3) having an acryloyl group at the end. The obtained polyurethane (A-3) had a weight average molecular weight of 30,000.

<Synthesis of polyurethane (A-4)>
A polyurethane (A-4) having an acryloyl group at the terminal was obtained in the same manner as in the synthesis method of the polyurethane (A-1) except that a water additive of diphenylmethane diisocyanate was used instead of isophorone diisocyanate. The weight average molecular weight of the obtained polyurethane (A-4) was 70,000.

<Synthesis of polyurethane (A-5)>
In a four-necked flask equipped with a thermometer, a stirrer, a dropping funnel, and a condenser tube with a drying tube, polypropylene glycol D-2000 (manufactured by Mitsui Chemicals) having an isophorone diisocyanate and a hydroxyl group having a hydroxyl value of 56 mgKOH / g at the end is used. The former was charged at a ratio of 4 moles and the latter at 3 moles, then heated to 60 ° C. and reacted for 4 hours to obtain a polyurethane having isocyanato groups at both ends. Next, after adding 2 mol of 2-hydroxyethyl acrylate to 1 mol of the obtained polyurethane, the temperature was raised to 70 ° C. and reacted for 2 hours to obtain a polyurethane having an acryloyl group at the terminal (A-5). Obtained. At this time, after confirming that the peak derived from the isocyanato group disappeared by IR, the reaction was terminated. The weight average molecular weight of the obtained polyurethane (A-5) was 8,000.

<Weight average molecular weight>
The weight average molecular weight was measured under the following conditions using gel permeation chromatography Shodex GPC-101 (manufactured by Showa Denko KK).
Column: LF-804 (made by Showa Denko)
Column temperature: 40 ° C
Sample: 0.2 mass% tetrahydrofuran solution Flow rate: 1 ml / min
Eluent: Tetrahydrofuran Detector: RI detector

Examples 1-10 and Comparative Examples 1-3
Composition shown in Table 1 is polyurethane (A) shown in Table 1, (meth) acrylic acid ester (B) having a hydroxy group, other photopolymerizable monomer (C) and photopolymerization initiator (D). And a uniform photocurable composition for a transparent adhesive sheet was prepared by mixing with a disper at room temperature. The acid value of the obtained composition was as shown in Table 1. In addition, the composition of Table 1 is mass%, and Tg shown at the end of the other photopolymerizable monomer (C) described in the footnote is a value when each monomer is a homopolymer.

Next, the prepared photocurable composition for a transparent adhesive sheet was applied to a release PET film (100 mm × 100 mm × 75 μm) using an applicator so that the film thickness after curing was 150 μm, and the upper surface was peeled off to a thickness of 50 μm. After covering with a PET film, using an ultraviolet irradiation device (UV irradiation device 4 kw × 1, output: 160 W / cm, metal halide lamp manufactured by Nippon Battery Co., Ltd.), irradiation distance 12 cm, lamp moving speed 20 m / min, irradiation amount about 500 mJ The film was cured by irradiation with ultraviolet rays under the conditions of / cm ² to obtain a transparent adhesive sheet sandwiched between peeled PET films. About this transparent adhesive sheet, the increase rate of the electrical resistance of ITO film | membrane, adhesive force, total light transmittance, and level | step difference followability were evaluated by the method described below. The results are shown in Table 1.

<Evaluation method>
(Increase rate of electrical resistance of ITO film)
After the transparent adhesive sheet was cut out to a size of 50 mm × 50 mm, the peeled PET film having a thickness of 50 μm was peeled off. The transparent adhesive sheet from which the peeled PET film was peeled was attached to the center of the ITO film of the PET film on which the 100 mm × 100 mm ITO film was deposited to form a laminate.
Using resistivity meter Loresta GP (manufactured by Mitsubishi Chemical Corporation) to measure the electrical resistance R ₁ between both ends of the transparent adhesive sheet of the ITO film is stuck. Next, the laminated body, 60 ° C., allowed to stand for 500 hours in an environment of 90% RH, 23 ° C., allowed to stand for 1 hour under a 50% RH environment, in the same manner as the electric resistance _{R 1,} the electrical resistance It was measured R _2. Furthermore, the increase rate [%] of the electrical resistance of the ITO film was calculated from the following formula (3).
Rate of increase in electrical resistance [%] = (R ₂ −R ₁ ) / R ₁ × 100 (3)
It shows that the smaller the rate of increase in electrical resistance, the more the corrosion of the conductive film is suppressed. In addition, the case where the rate of increase in the electrical resistance of the ITO film was less than 5% was judged as ◯, the case where it was 5% or more and less than 10%, and the case where it was Δ or 10% or more was judged as x.

(Measurement of adhesive strength of adhesive sheet)
The adhesive sheet is cut into a size of 25 mm × 100 mm, the 50 μm release PET film on one side of the adhesive sheet is peeled off, the corona treatment is applied on one side, and the 50 μm thick PET film is applied again. 75 μm of peeled PET was peeled off, the adhesive surface (measurement surface) was attached to a glass plate, and a 2 kg rubber roller (width: about 50 mm) was reciprocated once to prepare a measurement sample. The obtained sample for measurement is allowed to stand for 24 hours in an environment of 23 ° C. and 50% humidity, and subjected to a tensile test in the 180 ° direction at a peeling rate of 300 mm / min in accordance with JIS Z0237. The adhesive force (N / 25 mm) to was measured. The obtained measured value was defined as adhesive strength.

(Total light transmittance)
After the transparent adhesive sheet was cut into a size of 30 mm × 30 mm, the peeled PET film having a thickness of 50 μm was peeled off. The transparent pressure-sensitive adhesive sheet from which the peeled PET film was peeled was attached to a glass plate to obtain a measurement sample. Using a haze / transmittance / reflectometer HR-100 (manufactured by Murakami Color Research Laboratory Co., Ltd.), the total light transmittance of the measurement sample was measured.

(Evaluation of step absorbency)
Remove the double-sided PSA sheet from the double-sided PSA sheet obtained above onto a glass plate with a thickness of 0.5mm, a length of 50mm, and a width of 40mm. After sticking the adhesive sheet and peeling off the 75 μm release PET film on one side, it was attached to a glass plate having a thickness of 0.5 mm, a length of 50 mm, and a width of 40 mm, and 5 atmospheres, 70 ° C., 10 minutes. It fixed by performing the heating-pressing process on condition. Immediately after fixing, the floating of the pressure-sensitive adhesive layer at the stepped portion after 24 hours in an atmosphere of temperature 85 ° C. and humidity 85% was visually observed, and the step absorbability was evaluated according to the following criteria.
○: A state in which the adhesion layer is not lifted at a stepped portion △; A state in which a slight lift of the adhesive layer is confirmed at a stepped portion ×; Confirmed state

  From the results shown in Table 1, it can be seen that the transparent adhesive sheets (Examples 1 to 10) of the present invention have low corrosiveness of the transparent conductive film and are excellent in transparency, adhesiveness and step absorbability. In particular, as a photopolymerizable monomer (C), when a homopolymer includes an acrylate having a theoretical glass transition temperature of −5 ° C. or higher (Examples 1 to 6 and 8 to 10), Compared with Example 7), the effect of improving the step absorbability is greater. On the other hand, when a polyurethane having a weight average molecular weight of 8,000 is used (Comparative Example 1), the step absorbability is inferior and the (meth) acrylic acid ester (B) having a hydroxy group is not used ( Comparative Example 2) is inferior in transparency and adhesive strength. Furthermore, when using polyurethane with a large acid value (Comparative Example 3), the rate of increase in the electrical resistance value of the conductive film is large, and corrosion of the conductive metal is inevitable.

  According to the present invention, a liquid that does not corrode the conductive layer even when directly bonded to the conductive layer surface of the transparent conductive film, is excellent in the transparency, cohesive strength, and adhesive strength of the pressure-sensitive adhesive layer, and is excellent in step absorbability. A photocurable composition for a transparent adhesive sheet of a mold can be provided. In addition, by using a transparent adhesive sheet formed by curing the composition, a high-quality touch panel in which corrosion of the conductive layer is suppressed and an image display device equipped with the touch panel can be obtained.

Claims (7)

(Meth) acrylic acid ester having 20-50 mass% of polyurethane (A) having a polyoxyalkylene polyol as a skeleton and having a (meth) acryloyl group at the terminal and a weight average molecular weight of 10,000 to 300,000 and hydroxy group B) is contained in an amount of 5 to 20% by mass , the other photopolymerizable monomer (C) is contained in an amount of 30 to 74.8% by mass and the photopolymerization initiator (D) is contained in an amount of 0.2 to 5% by mass. A photocurable composition for a transparent adhesive sheet having a value of 0 to 5 mgKOH / g,
The photocurable composition for a transparent pressure-sensitive adhesive sheet, wherein the polyurethane (A) has 80 to 100 mol% of (meth) acryloyl groups introduced to isocyanato groups or hydroxy groups at both ends thereof. The other photopolymerizable monomer (C) is a hydrocarbon monoalcohol (meth) acrylic acid ester having 6 to 18 carbon atoms having a theoretical glass transition temperature (Tg) of the homopolymer of -5 ° C or higher. The photocurable composition for a transparent adhesive sheet according to claim 1, which is contained. The optical adhesive sheet obtained by hardening the photocurable composition for transparent adhesive sheets of Claim 1 or 2 . The optical pressure-sensitive adhesive sheet according to claim 3, which is a transparent conductive film fixing sheet for bonding to a conductive layer surface of the transparent conductive film. The transparent conductive film laminated body which bonded together the adhesive sheet for optics of Claim 4 to the conductive layer surface of the transparent conductive film. A touch panel having the transparent conductive film laminate according to claim 5 . An image display device comprising the touch panel according to claim 6 .