KR20130108167A - Composition for transparent adhesive sheet - Google Patents

Abstract

PURPOSE: A composition for a transparent adhesive sheet provides a transparent adhesive sheet with excellent curing property and excellent transparency without the collision of a conductive layer even by being directly attached to the conductive layer of a transparent conductive film. CONSTITUTION: A composition for a transparent adhesive sheet comprises a (meth)acrylic copolymer with a structure unit represented by chemical formula 1, a crosslinking agent, and a tin-based catalyst. The acid value of the composition is 5 mgKOH/g or less. In chemical formula 1, R^1 is a hydrogen atom or a methyl group; R^2 is a C1-6 alkylene group; and R^3 is the urethane residue of polyolefinpolyol or hydrogen-added polyolefinpolyol. A transparent adhesive sheet is obtained by curing the composition for a transparent adhesive sheet, and the gel fraction thereof is 40-80%.

Description

Technical Field [0001] The present invention relates to a composition for a transparent adhesive sheet,

The present invention is a transparent pressure-sensitive adhesive sheet for fixing a transparent conductive film and a transparent conductive film, wherein the transparent pressure-sensitive adhesive sheet and the transparent pressure-sensitive adhesive sheet comprising the composition for a transparent pressure-sensitive adhesive sheet and the composition for a transparent pressure-sensitive adhesive sheet are used for bonding a transparent conductive film. The fixing transparent adhesive sheet is adhere | attached on the conductive layer surface of a transparent conductive film, It is related with the laminated body characterized by the above-mentioned.

BACKGROUND ART [0002] Recently, touch panels are beginning to be mounted in fields such as mobile phones and game devices. A touch panel is an optical transparent adhesive sheet which uses optical members, such as display materials, such as a transparent base material and glass which have transparent conductive films, such as silver and indium tin oxide (ITO), in a surface layer, a transparent protective sheet which protects it, and also a liquid crystal display. It is the laminated body bonded using.

There exist a resistive touch panel which detects mainly by the pressure at the time of input, and the capacitive touch panel which detects an input location by the static electricity from a human body at the time of input. In the capacitive touch panel, the conductive layer surface of the transparent conductive film is fixed to be in contact with the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet. Therefore, when an adhesive layer contacts a conductive layer surface of a transparent conductive film, there exists a problem that the oxidation reaction of a metal arises by the acid component contained in an adhesive, and the fall of electrically conductive function occurs. For this reason, the adhesive sheet for fixing a transparent conductive film does not contain an acid component, and high metal corrosion prevention property and favorable adhesiveness are calculated | required.

As a pressure-sensitive adhesive sheet having metal corrosion-preventive properties, a pressure-sensitive adhesive sheet (for example, Patent Document 1) containing a metal corrosion inhibitor has been proposed. Moreover, the adhesive sheet (for example, patent document 2) which reduced the corrosiveness with respect to a transparent conductive film by containing a specific amount of nitrogen atom containing component with respect to the acid component of an adhesive layer is proposed.

However, the adhesive sheet containing a metal corrosion inhibitor has a problem that a metal corrosion inhibitor discolors in an endurance test, and lowers an optical characteristic. In addition, the pressure-sensitive adhesive sheet containing a specific amount of the nitrogen atom-containing component 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 touch panel etc., the touch panel etc. which have a member in which the rod-shaped printed part was given are included, for example, including the member which has a level | step difference, such as a metal wiring and a printing step. In such a use, the adhesive sheet is required to have the performance of attaching and fixing the member and the capability of embedding the step, that is, excellent step tracking performance. If the transparent adhesive sheet cannot absorb such a step, the floating adhesive (bubble or void) of the transparent adhesive sheet is generated around the step, and the reflection loss of the light due to the lifting (bubble or void) occurs and the visibility of the liquid crystal display is increased. This may fall.

In order to obtain the excellent step-following ability, it is advantageous that the transparent adhesive sheet is flexible and has high adhesive force. However, for the above reason, it is required to have high adhesiveness without containing an acid component. To this demand, the pressure-sensitive adhesive composition comprising an acrylic polymer having a specific molecular weight containing no alkoxyalkyl acrylate as the main monomer and a crosslinking agent can achieve both good adhesion and metal corrosion resistance. To provide (for example, patent document 3) is disclosed.

However, since the adhesive composition which consists of the acrylic polymer of the specific molecular weight which does not contain the acid component which uses an alkoxyalkyl acrylate as a main monomer, and a crosslinking agent does not contain an acid component, hardening by an isocyanate crosslinking agent will become slow and a transparent adhesive sheet There was a problem that takes time to cure. In order to solve the problem, the addition of an amine compound containing a plurality of hydroxyl groups is also disclosed, but the amine compound may yellow the transparent adhesive sheet over time.

In short, it is a present situation that the outstanding adhesive composition which made all the characteristics, such as metal corrosion prevention property, a step | step traceability, transparency, curability, and the like compatible with high level, is not obtained.

Japanese Patent Laid-Open No. 2006-45315 Japanese Patent Publication No. 2010-144002 Japanese Patent Application Laid-Open No. 2010-77287

A problem to be solved by the present invention is to provide a transparent adhesive sheet which is excellent in curability and which is obtained by directly bonding to a conductive layer surface of a transparent conductive film without corroding the conductive layer, , And a composition for a transparent pressure-sensitive adhesive sheet.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined on the background of the said problem which the transparent adhesive sheet for touch panels has, and as a result, (A) the (meth) acryl copolymer which has a specific structural unit, (B) crosslinking agent, and (C) The composition for a transparent adhesive sheet containing a tin-type catalyst and whose acid content is less than predetermined amount finds that it is excellent in sclerosis | hardenability, and the transparency, adhesiveness of the obtained transparent adhesive sheet, the metal corrosion prevention property of a transparent conductive film, and the step | following traceability are favorable. The present invention was completed based on this knowledge.

The present invention is described in the following (1) to (7).

(1) (A) Formula (I):

Having a structural unit represented by (wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 6 carbon atoms, and R ³ represents a urethane bond residue of a polyolefin polyol or a hydrogenated polyolefin polyol) It is a composition for transparent adhesive sheets containing a (meth) acryl copolymer, (B) crosslinking agent, and (C) tin type catalysts, The acid value is 5 mgKOH / g or less, The composition for transparent adhesive sheets characterized by the above-mentioned.

(2) (A) (meth) acryl copolymer which has a structural unit represented by General formula (I) contains a (meth) acryloyl group in presence of a polyolefin polyol and / or hydrogenated polyolefin polyol and a tin-type catalyst. The composition for transparent adhesive sheets as described in said (1) obtained by copolymerizing a monomer (except having an isocyanate group) and (meth) acryloyloxyalkyl isocyanate.

(3) (A) The (meth) acryl copolymer having a structural unit represented by the formula (I) has 1 to 18 carbon atoms in the alkyl group in the presence of a polyolefin polyol and / or a hydrogenated polyolefin polyol and a tin catalyst. 90 to 99.5 mol% of (meth) acrylic acid alkoxyalkyl esters having 2 to 20 carbon atoms of phosphorus (meth) acrylic acid alkyl ester and / or alkoxyalkyl group, 0 to 9.5 mol% of (meth) acryloyl group-containing polar monomer, and 2- The composition for transparent adhesive sheets as described in said (2) obtained by copolymerizing 0.5-10 mol% of (meth) acryloyloxyethyl isocyanate.

(4) The transparent adhesive sheet obtained by hardening | curing the composition for transparent adhesive sheets in any one of said (1)-(3).

(5) The transparent adhesive sheet as described in said (4) whose gel fraction is 40 to 80%.

(6) The transparent adhesive sheet for fixing a transparent conductive film, wherein the transparent adhesive sheet according to (4) or (5) is used for bonding a transparent conductive film.

(7) The transparent adhesive sheet for fixing a transparent conductive film as described in said (6) is adhere | attached on the conductive layer surface of a transparent conductive film, The laminated body characterized by the above-mentioned.

By including the (meth) acryl copolymer which has a specific structural unit, ie, a polyolefin frame | skeleton, in the composition, the composition for transparent adhesive sheets of this invention becomes favorable for the step | following followability of the obtained transparent adhesive sheet and adhesive force with respect to a base material. In addition, by including a tin catalyst, the crosslinking agent is curable, and the curing time of the transparent adhesive sheet can be shortened. Moreover, since it is a composition for transparent adhesive sheets which does not contain an acid substantially, corrosion of the electrically conductive layer surface of the transparent conductive film by an acid component can be suppressed.

Hereinafter, the present invention will be described in detail.

Further, in the present in the (meth) acrylate herein means the group is CH ₂ = CH-CO- or _{CH 2 = C (CH 3)} -CO-.

(Composition for transparent adhesive sheet)

The composition for transparent adhesive sheets of this invention, (A) Formula (I):

(, R ¹ in the formula is also known as a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 6, R ³ is a polyolefin polyol and / or a hydrogenated polyolefin polyol (referred to as "polyolefin polyols and the like") It is a composition for transparent adhesive sheets containing the (meth) acryl copolymer, (B) crosslinking agent, and (C) tin-type catalyst which have a structural unit represented by the urethane bond residue of the thing, The acid value is 5 mgKOH / g or less, It is characterized by the above-mentioned. It is a composition for transparent adhesive sheets.

((Meth) acrylic copolymer having a structural unit represented by formula (I))

(A) Although it does not specifically limit as a method of synthesize | combining the (meth) acryl copolymer which has a structural unit represented by General formula (I), In the presence of polyolefin polyol etc. and a tin-type catalyst, 1 or more types of (meth) acryloyl groups The method of copolymerizing a containing monomer (except having an isocyanate group) and the (meth) acryloyl group containing monomer which has an isocyanate group as a functional group, and simultaneously adding a polyolefin polyol etc. to this isocyanate group is preferable. In this method, the polymerization of the (meth) acryloyl group-containing monomer and the addition reaction of the isocyanate and the polyolefin polyol are simultaneously carried out, thereby preventing the phase separation of the (meth) acrylic polymer and the polyolefin polyol, which are heteropolymers, while branching the polyolefin skeleton. It becomes possible to synthesize | combine the (meth) acryl copolymer which has in the. Furthermore, in the presence of a tin catalyst, the air obtained after copolymerizing one or more (meth) acryloyl group containing monomers (except having an isocyanate group) and the (meth) acryloyl group containing monomer which has an isocyanate group in the functional group beforehand is obtained Polyolefin polyol etc. can also be added to the isocyanate group of copolymer.

R ¹ in formula (I) is a hydrogen atom or a methyl group. R <^2> of general formula (I) is a C1-C6 alkylene group, and may be not only a linear alkylene group but an alkylene group which has a branch. R ² preferably has 2 to 4 carbon atoms. Urethane bond residues, such as a polyolefin polyol in description of R <^3> , mean the group except the atom derived from the hydroxyl group which reacts with an isocyanate group and forms a urethane bond in polyolefin polyol.

In the synthesis of the (meth) acrylic copolymer, 1.5 to 3 mol of the polyolefin polyol or the like is preferably added to 1 mol of the (meth) acryloyl group-containing monomer having an isocyanate group as a functional group, and more preferably 1.8 to 2.8 such as the polyolefin polyol. The mol amount is added, more preferably from 2.0 to 2.5 mol. When the amount of polyolefin polyol or the like is less than 1.5 mol with respect to 1 mol of the (meth) acryloyl group-containing monomer having an isocyanate group, the polyolefin polyol or the like is gelled by crosslinking (meth) acrylic polymer during synthesis, which is not preferable. not. When the amount of polyolefin polyol or the like is more than 3 mol, many polyolefin polyols and the like contained in the composition for transparent pressure sensitive adhesive sheets are present, and the cohesion force of the sheet obtained from the composition for transparent pressure sensitive adhesive sheet is not preferable. Moreover, since the polyolefin polyol etc. which remain | survived without introducing into a (meth) acryl copolymer can be made to react by adding a crosslinking agent, there is no problem even if the residual polyolefin polyol etc. exist in the composition for transparent adhesive sheets.

As a method of copolymerizing the (meth) acryloyl-group containing monomer (except having an isocyanate group) and (meth) acryloyloxyalkyl isocyanate, it can manufacture by a well-known polymerization method, As a polymerization method, it is, for example, , A solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a polymerization method by ultraviolet irradiation, and the like. In terms of transparency, water resistance, cost, and the like, a solution polymerization method and a UV polymerization method are suitable, and a solution polymerization method can be particularly suitably used.

The polymerization initiator used at the time of copolymerization of a (meth) acryloyl-group containing monomer (except having an isocyanate group) and (meth) acryloyloxyalkyl isocyanate is not specifically limited, It can select from a well-known thing suitably, and can use it. have. For example, 2,2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4 -Dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis (2, Azo polymerization initiators such as 4,4-trimethylpentane) and dimethyl-2,2'-azobis (2-methylpropionate); Benzoyl peroxide, t-butylhydroperoxide, di-t-butylperoxide, t-butylperoxybenzoate, dicumylperoxide, 1,1-bis (t-butylperoxy) 3,3,5- Oil-soluble polymerization initiators, such as peroxide type polymerization initiators, such as a trimethyl cyclohexane and a 1, 1-bis (t-butyl peroxy) cyclo dodecane, are illustrated preferably. A polymerization initiator can be used individually or in combination of 2 or more types. What is necessary is just normal usage-amount of a polymerization initiator, for example, it is 0.01 with respect to a total of 100 mass parts of a (meth) acryloyl-group containing monomer (except having an isocyanate group) and a (meth) acryloyloxyalkyl isocyanate component. It can be selected from the range of about 5 mass parts, it is preferable that it is the range of 0.02-4 mass parts, and it is more preferable that it is 0.03-3 mass parts.

In addition, in solution polymerization, various general solvents can be used. As such a solvent, esters, such as ethyl acetate, n-propyl acetate, n-butyl acetate, aromatic hydrocarbons, such as toluene and benzene, aliphatic hydrocarbons, such as n-hexane and n-heptane, cyclohexane, methylcyclohexane, etc. And organic solvents such as ketones such as alicyclic hydrocarbons, methyl ethyl ketone, and methyl isobutyl ketone. A solvent can be used individually or in combination of 2 or more types.

As a polyolefin polyol used for manufacture of the (A) (meth) acryl copolymer of this invention, the polyol cargo of various saturated and unsaturated alkyl compounds commercially available can be used, for example, Polyethylene polyol, poly Propylene polyol, polybutadiene polyol, polyisoprene polyol, hydrogenated polybutadiene polyol, hydrogenated polyisoprene polyol and the like. Especially, hydrogenated 1,2- polybutadiene polyol or hydrogenated polyisoprene polyol is preferable from a viewpoint of the workability of the liquid transparent adhesive sheet composition, the light resistance of the transparent adhesive sheet obtained, and transparency (non-crystalline). In addition, hydrogenated 1,2-polybutadiene means what reacted hydrogen to the double bond part of 1,2-polybutadiene, and changed it into a single bond. The same applies to hydrogenated polyisoprene.

As number average molecular weights, such as the polyolefin polyol used by this invention, it is preferable that it is 500-5000, It is more preferable that it is 1000-4000, It is further more preferable that it is 1500-3500. When the number average molecular weight is smaller than 500, the step-following ability of the obtained transparent adhesive sheet deteriorates, which is not preferable. When the number average molecular weight is larger than 5000, the viscosity of the composition for transparent adhesive sheet becomes too high, which is not preferable. As a commercial item, such as the polyolefin polyol which can be used suitably for this invention, the hydrogenated 1,2- polybutadiene polyol by Nippon Soda Co., Ltd. product, product name: GI-1000, GI-2000, GI-3000 ( The number average molecular weight can respectively illustrate about 1500, about 2100, about 3000), hydrogenated polyisoprene polyol by product of Idemitsu Koyama Co., Ltd., and product name Epol (number average molecular weight is about 2500).

In order to obtain the (meth) acryl copolymer which has a structural unit represented by General formula (I) of this invention, addition reaction, such as a polyolefin polyol, to a isocyanate group is performed, ie, a urethanization reaction. A well-known urethanization catalyst can be used for the urethanation reaction, and a tin-type catalyst is especially preferable. Examples of the tin catalyst include dibutyltin dilaurate, dibutyltin diethylhexate, dioctyltin dilaurate, and the like. The amount of the urethanization catalyst used may be based on the total mass of the raw materials provided in the reaction (that is, (meth) acryloyl group-containing monomers (except having an isocyanate group), (meth) acryloyloxyalkyl isocyanate and polyolefin polyol, and the like. Based on the sum of mass), it is 10-300 ppm normally, It is preferable that it is 30-250 ppm, and it is more preferable that it is 50-200 ppm. This urethanization catalyst can be used also as a hardening | curing agent of the crosslinking agent added when producing a transparent adhesive sheet. In addition, it is preferable to carry out reaction conditions of addition reaction normally at 30-100 degreeC continuously for about 1 to 5 hours.

There is no restriction | limiting in particular as a (meth) acryloyl-group containing monomer (except having an isocyanate group) used for superposition | polymerization of the (meth) acryl copolymer of this invention, It can be used individually or in combination of 2 or more types, It is preferable not to contain a carboxyl group (formula: -COOH). For example methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylic Isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, isodecyl (meth) Alkyl (meth) acrylates, such as acrylate, stearyl (meth) acrylate, tridecyl (meth) acrylate, and isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, and norbornyl (meth) Acrylate, isobornyl (meth) acrylate, norbornanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylic Elate, dicyclopentanyl jade Cyclic alkyl (meth) acrylates, such as ethyl (meth) acrylate and tricyclodecane dimethylol di (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth Alkoxyalkyl (meth) acrylates, such as acrylate, 2-methoxyethoxyethyl (meth) acrylate and 2-ethoxyethoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, ethoxy Fluorinated alkyl (meth) acryl, such as alkoxy (poly) alkylene glycol (meth) acrylate and octafluoro pentyl (meth) acrylate, such as a cd ethylene glycol (meth) acrylate and a methoxy dipropylene glycol (meth) acrylate Dialkylaminoalkyl (meth) acrylates, such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate, (meth) acrylamide, diacetone (meth) ) Amide group-containing (meth) acrylates, such as krillamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,3- Hydroxyl-containing (meth) acrylate, Gly, such as butanediol (meth) acrylate, 1,4-butanediol (meth) acrylate, 1,6-hexanediol (meth) acrylate, 3-methylpentanediol (meth) acrylate Epoxy-group containing (meth) acrylates, such as cylyl (meth) acrylate, silicone modified (meth) acrylate, polyethyleneglycol di (meth) acrylate, diethyleneglycol di (meth) acrylate, neopentylglycol di (meth) Polyfunctional (meth) acrylates, such as a) acrylate, a triethylene diclicol di (meth) acrylate, and a tripropylene glycol di (meth) acrylate, etc. are mentioned.

As a (meth) acryloyl group containing monomer which has an isocyanate group suitably used for superposition | polymerization of the (meth) acryl copolymer of this invention as a functional group, it is 2- (meth) acryloyloxyethyl isocyanate, 3- (meth), for example. ) Acryloyloxypropyl isocyanate, 4- (meth) acryloyloxybutyl isocyanate, 6- (meth) acryloyloxyhexyl isocyanate, etc. are mentioned. Especially, 2- (meth) acryloyloxyethyl isocyanate is preferable at the point of the reactivity with a hydroxyl group.

One or more (meth) acryloyl-group containing monomers (except having an isocyanate group) and (meth) acryloyloxyalkyl isocyanate used suitably for the superposition | polymerization of the (meth) acryl copolymer of this invention are carbon number of an alkyl group. (Meth) acrylic acid alkyl ester having 1 to 18 and / or 90 to 99.5 mol% (meth) acrylic acid alkoxyalkyl ester having 2 to 20 carbon atoms of the alkoxyalkyl group, and (meth) acryloyl group-containing polar monomer 0 to 9.5 mol% And copolymerized in a composition of 0.5 to 10 mol% of 2- (meth) acryloyloxyethyl isocyanate. More preferably, (meth) acrylic-acid alkylester of 1-18 carbon atoms of an alkyl group and / or 92-99.5 mol% of (meth) acrylic-acid alkoxyalkyl ester of 2-20 carbon atoms of an alkoxyalkyl group, and (meth) acryloyl group It is 0-7.5 mol% of containing polar monomer and 0.5-5 mol% of 2- (meth) acryloyloxyethyl isocyanate. More preferably, 94.5-99.5 mol% of (meth) acrylic-acid alkylester and / or (meth) acrylic-acid alkoxyalkyl ester whose carbon number of alkoxyalkyl group has 2-20 carbon atoms of an alkyl group, and (meth) acryloyl group It is 0-5.0 mol% of containing polar monomer and 0.5-4.0 mol% of 2- (meth) acryloyloxyethyl isocyanate. Here, as a (meth) acryloyl group containing polar monomer, the (meth) acryloyl group containing monomer which has polar groups, such as an amino group, an amide group, or a hydroxyl group, is mentioned in the molecule | numerator. More specifically, monomers, such as a dialkyl aminoalkyl (meth) acrylate, an amide group containing (meth) acrylate, and a hydroxyl group containing (meth) acrylate, are mentioned. Especially, diacetone acrylamide is preferable at the point of heat yellowing resistance and cohesion force.

If the copolymerization ratio of the (meth) acrylic acid alkyl ester having 1 to 18 carbon atoms of the alkyl group and / or the (meth) acrylic acid alkoxyalkyl ester having 2 to 20 carbon atoms of the alkoxyalkyl group is less than 90 mol%, the adhesiveness is deteriorated and is not preferable. In the case of more than 99.5 mol%, since the copolymerization ratio of 2- (meth) acryloyloxyethyl isocyanate becomes too small, the addition to polyolefin polyol and the like is small as a result, and the desired adhesive force is not obtained, which is not preferable. When the copolymerization ratio of a polar monomer is more than 9.5 mol%, the water resistance of a transparent adhesive sheet worsens and it is unpreferable. When the copolymerization ratio of 2- (meth) acryloyloxyethyl isocyanate is less than 0.5 mol%, the addition to the polyolefin polyol and the like is less, and the desired adhesive force is not obtained, which is not preferable. The amount of polyolefin polyol, etc. to say increases, and the cohesion force of a transparent adhesive sheet falls, and it is unpreferable.

As molecular weight of the (A) (meth) acryl copolymer in this invention, it is preferable that it is the weight average molecular weights 50,000-1 million, It is more preferable that it is 80,000-800,000, It is further more preferable that it is 100,000-500,000. When weight average molecular weight is less than 50,000, the cohesion force of a polymer becomes small and adhesiveness becomes low. When the weight average molecular weight is larger than 1 million, since the viscosity of the composition for transparent adhesive sheets becomes too high, it is not preferable.

In addition, the value of the weight average molecular weight in this invention is measured at normal temperature on the following conditions using gel permeation chromatography (The Showa Denko Co., Ltd. make, Shodex GPC-101), and polystyrene conversion. Is calculated.

Column: Showa Denko Kabushiki Kaisha LF-804

Column temperature: 40 DEG C

Sample: 0.2 mass% tetrahydrofuran solution of copolymer

Flow rate: 1ml / min

Eluent: tetrahydrofuran

It is preferable that the glass transition temperature of the (A) (meth) acryl copolymer of this invention is -5-70 degreeC from a viewpoint of the intensity | strength and adhesive force of a transparent adhesive sheet. More preferably, it is -10-60 degreeC. (A) When the glass transition temperature of a (meth) acryl copolymer is lower than -70 degreeC, since the obtained transparent adhesive sheet becomes soft too much, the adhesive force of a transparent adhesive sheet becomes low and it is unpreferable. Moreover, when the glass transition temperature of (A) (meth) acryl copolymer is higher than -5 degreeC, since the transparent adhesive sheet becomes hard too much by low temperature, it is not preferable. Here, glass transition temperature (Tg) points out what was calculated | required from the following method. A 10 mg sample was taken from the (meth) acrylic copolymer, and differential scanning calorimetry was measured by using a differential scanning calorimeter (DSC) to vary the temperature from -80 ° C to 200 ° C at a heating rate of 10 ° C / min, The endothermic start temperature due to the glass transition is set to Tg. In addition, when two Tg is observed, the average value of two Tg shall be taken.

(Crosslinking agent)

As (B) crosslinking agent used for the composition for transparent adhesive sheets of this invention, if it is a polyfunctional compound which has at least 2 or more groups couple | bonded with hydroxyl groups, such as a polyolefin polyol, it can use without a restriction | limiting. (B) A crosslinking agent can be used individually or in mixture of 2 or more types. In this invention, when using the (B) crosslinking agent, when forming an acrylic adhesive layer, an acrylic polymer is bridge | crosslinked and the durability of a transparent adhesive sheet improves. As (B) crosslinking agent which can be used by this invention, a polyfunctional melamine compound, a polyfunctional epoxy compound, a polyfunctional isocyanate compound, etc. can be illustrated, for example.

As said polyfunctional melamine compound, methylated trimethylol melamine, butylated hexamethylol melamine, etc. are mentioned, for example. Moreover, as a polyfunctional epoxy compound, diglycidyl aniline, glycerin diglycidyl ether, etc. are mentioned, for example. As the polyfunctional isocyanate compound, for example, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 2-methyl-1,5-pentane diisocyanate, 3-methyl-1, 5-pentane diisocyanate, isophorone diisocyanate, cyclohexyl diisocyanate, tolylene diisocyanate (TDI), hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, trimethylolpropane and tolylene diisocyanate And reaction products of trimethylolpropane and hexamethylene diisocyanate, polyether polyisocyanate, polyester polyisocyanate, hydrogenated xylene diisocyanate, hydrogenated tetramethyl xylene diisocyanate and the like. Especially, it is preferable to use a polyfunctional isocyanate compound (isocyanate crosslinking agent) as a crosslinking agent from the viewpoint of the reactivity with hydroxyl groups, such as a polyolefin polyol, and 1,6-hexamethylene diisocyanate (HDI) of aliphatic isocyanate from a yellowing resistance, It is preferable to use isophorone diisocyanate (IPDI) and hydrogenated diphenylmethane diisocyanate.

Although there is no restriction | limiting in particular as a usage-amount of (B) crosslinking agent, For example, 0.1-10 mass parts is preferable normally with respect to 100 mass parts of (meth) acryl copolymers, More preferably, it is 0.2-9 mass parts, More preferably, Is 0.5 to 8 parts by mass. When the amount of the crosslinking agent used is less than 0.1 part by mass, the cohesive force of the transparent pressure sensitive adhesive sheet is insufficient, and when the amount of the crosslinking agent used is greater than 10 parts by mass, the transparent pressure sensitive adhesive sheet becomes too hard. , Not preferred.

(Tin-based catalyst)

Examples of the (C) tin catalyst used in the present invention include dibutyltin dilaurate, dibutyltin diethylhexate, dioctyltin dilaurate, and the like. Especially, the curability of (B) crosslinking agent is favorable and dioctyl tin dilaurate is preferable from a viewpoint of safety. (C) It is preferable to use a tin catalyst in 0.001-0.10 mass part with respect to 100 mass parts of (A) (meth) acryl copolymers, It is more preferable that it is 0.003-0.080 mass part, It is 0.005-0.050 mass More preferably denial. When (C) tin-based catalyst is less than 0.001 mass part with respect to 100 mass parts of (A) (meth) acryl copolymers, sclerosis | hardenability of the composition for transparent adhesive sheets is not enough, there exists a tendency for cohesion force to become small, and 0.100 When more than mass part, there exists a tendency for the usable time at the time of transparent adhesive sheet preparation to become short.

(Composition for transparent adhesive sheet)

It is preferable that the composition for transparent adhesive sheets of this invention is 0-5 mgKOH / g, More preferably, it is 0-1 mgKOH / g, More preferably, it is 0-0.3 mgKOH / g, Especially 0-0.1 mgKOH / g is preferred. If the acid value is higher than 5 mgKOH / g, it is difficult to suppress corrosion of the conductive layer surface of the transparent conductive film. The acid value of the composition for a transparent pressure-sensitive adhesive sheet is a value measured in accordance with JIS K0070. For example, it measures as follows.

About 2 g of a sample is precisely weighed in a 100 ml Erlenmeyer flask by precision balance, and 10 ml of a mixed solvent of ethanol / diethyl ether = 1/1 (mass ratio) is added and dissolved in it. In addition, 1-3 drops of a phenolphthalein ethanol solution is added to this container as an indicator, and it fully stirs until a sample becomes uniform. This is titrated with a 0.1 N potassium hydroxide-ethanol solution, and when the light pink of the indicator is continued for 30 seconds, it is used as the end point of neutralization. From the result, the value obtained using the following formula (1) is made into the acid value of the composition for transparent adhesive sheets.

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

f: factor of 0.1N potassium hydroxide-ethanol solution

S: sampling amount (g)

You may add tackifying resin to the composition for transparent adhesive sheets of this invention in the range which does not reduce transparency, in order to improve the adhesive force of the transparent adhesive sheet obtained as needed. Examples of the tackifying resin include rosin-based resins such as rosin and rosin esters; Terpene resins such as diterpene polymers and α-pinene-phenol copolymers; Petroleum resins such as aliphatic (C5) and aromatic (C9); In addition, styrene resin, phenol resin, xylene resin, etc. are mentioned. It is preferable to add the hydrogenated rosin or the disproportionate rosin esterified thing, aliphatic, aromatic petroleum resin, acrylic resin which has high Tg, etc. to a transparent adhesive sheet from a light-resistant viewpoint. As addition amount of tackifying resin, it is preferable to add 1-10 mass parts with respect to 100 mass parts of compositions for transparent adhesive sheets.

Moreover, the composition for transparent adhesive sheets of this invention may contain various well-known additives as needed in the range which does not impair transparency. As additives, charging such as plasticizers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, light stabilizers, ultraviolet absorbers, polymerization inhibitors, light stabilizers such as benzotriazoles, phosphate esters and other flame retardants, and surfactants An inhibitor etc. are mentioned.

In addition, you may dilute the composition for transparent adhesive sheets of this invention using an organic solvent for the purpose of viscosity adjustment at the time of application | coating. As an organic solvent used, methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol, isopropanol, n-propyl acetate, etc. are mentioned, for example. Can be. These organic solvents may be used singly or in combination of two or more kinds. Especially, n-propyl acetate is preferable from the viewpoint of solubility, such as a polyolefin polyol.

(Transparent adhesive sheet)

The transparent pressure sensitive adhesive sheet of the present invention is obtained by curing the composition for a transparent pressure sensitive adhesive sheet. More specifically, it is used for the purpose of joining optical members (for joining optical members) and for manufacturing optical products. In addition, the transparent adhesive sheet of this invention may have a base material, and may be a double-sided adhesive sheet which consists only of an adhesive layer, without a base material. The optical member is not particularly limited as long as it is a member having optical characteristics, and examples thereof include an image display device, a member constituting a touch panel, and a member used in these devices. More specifically, for example, a polarizing plate, a retardation film, 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.

A transparent adhesive sheet can be obtained by apply | coating the solution which melt | dissolved the composition for transparent adhesive sheets in the solvent to a peeling film, and heat-drying and crosslinking the apply | coated solution. The thickness of the transparent pressure sensitive adhesive sheet is preferably 5 to 200 占 퐉, more preferably 10 to 150 占 퐉, and further preferably 15 to 100 占 퐉. If the thickness of the transparent pressure sensitive adhesive sheet is smaller than 5 占 퐉, bonding of the transparent pressure sensitive adhesive sheet tends to become difficult. When the film thickness of a transparent adhesive sheet becomes thicker than 200 micrometers, a solvent may remain in a sheet and the problem of a bad smell may arise. Moreover, although the well-known coating method can be used for the application | coating (coating application) in the formation method of the optical adhesive sheet of this invention, a conventional coater, for example, a gravure roll coater, a reverse roll coater, and a kiss roll coater , Dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, direct coaters and the like.

It is preferable that it is 40 to 80%, as for the gel fraction of the transparent adhesive sheet of this invention, it is more preferable that it is 45 to 70%, and it is still more preferable that it is 50 to 65%. Although the use is possible even when the gel fraction is smaller than 40%, the cohesive force of the transparent adhesive sheet becomes too small. Moreover, when gel fraction is larger than 80%, the step | following followability of a transparent adhesive sheet worsens and it is unpreferable.

In addition, the gel fraction of a transparent adhesive sheet is calculated | required by following formula (2) based on the mass of the sample before toluene immersion and toluene for 24 hours at room temperature, and drying at 80 degreeC for 5 hours.

(Transparent adhesive sheet for fixing a transparent conductive film)

The transparent adhesive sheet for fixing a transparent conductive film of this invention is a transparent adhesive sheet for fixing a transparent conductive film formed by hardening | curing said composition for transparent adhesive sheets, can adhere | attach with the conductive layer surface of a transparent conductive film suitably, and also a conductive layer Corrosion is unlikely to occur. Therefore, a laminate obtained by bonding a sheet for fixing a transparent conductive film to a conductive layer surface of a transparent conductive film can be suitably used as a touch panel. Moreover, the transparent adhesive sheet for fixing a transparent conductive film of this invention may have a base material, and may be a double-sided adhesive sheet which consists only of an adhesive layer, without a base material. In addition, an adhesive layer may consist of a single layer or multiple layers may be laminated | stacked. Especially, it is preferable that it is a double-sided adhesive sheet which does not have a base material and contains only an adhesive layer from a viewpoint of ensuring transparency and step | step difference followability.

As a transparent conductive film in which the transparent adhesive sheet for fixing the transparent conductive film of this invention is used, what is necessary is just to have a conductive layer in the surface layer of at least one surface, The transparent conductive film in which the conductive material formed by vapor deposition or coating in the surface layer of a transparent base material is mentioned. have. Specific examples of the conductive material to be deposited or coated on the conductive layer of the transparent conductive film include silver, indium tin oxide, indium oxide, tin oxide, zinc oxide, cadmium oxide, . Of these, silver, indium tin oxide, which is excellent in transparency and conductivity, is suitably used. In the transparent conductive film, the substrate on which the conductive material is deposited or coated is not particularly limited, but glass and a resin film may be mentioned.

In addition, the transparent adhesive sheet for fixing a transparent conductive film of this invention can be obtained by the method similar to the above-mentioned transparent adhesive sheet.

<Examples>

Although an Example and a comparative example demonstrate this invention more concretely below, this invention is not limited at all by these examples.

<Synthesis of (meth) acryl copolymers (A-1) to (A-12)>

500 parts of acetic acid n-propyl, hydrogenated polyolefindiol (made by Nippon Soda Chemical Co., Ltd., GI-3000, hydroxyl value 29.5 mgKOH / g, number average) to the reaction container provided with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring apparatus. Molecular weight 3800) 299 parts (0.08 mol), dioctyl tin dilaurate 0.03 parts (0.05 mmol), 2-ethylhexyl acrylate 126 parts (0.65 mol), isobornyl acrylate 69 parts (0.32 mol), 2- 4.7 parts (0.03 mol) of methacryloyl oxyethyl isocyanate (made by Showa Denko Co., Ltd., Karens MOI (registered trademark)) and 0.1 part of 2, 2- azoisobutylnitrile are put, and it is 8 at 95 degreeC in nitrogen stream. It time-processed and obtained the (meth) acryl copolymer (A-1) of glass transition temperature of -40 degreeC, and the weight average molecular weight 150,000. In addition, the measurement of the glass transition temperature of a (meth) acryl copolymer and the weight average molecular weight was performed by the method mentioned above. In addition, except having made into the composition of the (meth) acryloyl-group containing monomer (except having an isocyanate group) of Table 1, (meth) acryloyloxyalkyl isocyanate, polyolefin polyol, etc., and a tin-type catalyst, In the same manner as the acrylic copolymer (A-1), (meth) acryl copolymers (A-2) to (A-12) were obtained. In addition, the glass transition temperature and the weight average molecular weight were measured also about (meth) acryl copolymer (A-2)-(A-12) similarly to (meth) acryl copolymer (A-1). The results are shown in Table 1.

(Examples 1 to 10 and Comparative Examples 1 and 2)

A crosslinking agent, a polyolefin polyol, etc. are mix | blended with the composition shown in Table 2, Furthermore, solid content concentration is adjusted with acetic acid = n-propyl, the adhesive composition solution (solid content concentration: 50 mass%) is obtained, and the obtained adhesive composition solution is carried out at room temperature. The composition solution for transparent adhesive sheets was manufactured by mixing using a disper. This solution was casted (coating layer thickness 150 µm) so that the thickness after drying was 50 µm on the peeling treatment surface of the separator on which one side of the polyethylene terephthalate (PET) film having a thickness of 50 µm was subjected to the peeling treatment. It heat-drys for 5 minutes at 110 degreeC, and 3 minutes at 110 degreeC, The peeling process surface side of the separator in which the peeling process is given to the single side | surface of 50-micrometer-thick PET film is covered on an adhesive side. And it aged at 40 degreeC for 72 hours, and produced the double-sided adhesive sheet (inorganic material type).

(Acid value)

The acid value of each composition for transparent adhesive sheets was measured by said method. The results are shown in Table 2.

(Measurement of Electric Resistance of Indium Tin Oxide Film)

The double-sided adhesive sheet obtained above is cut out to the size of 50 mm x 50 mm, the peeling PET film of 38 micrometers thickness on one side is peeled off, and it is bonded to the indium tin oxide film surface of an indium tin oxide vapor deposition PET film of 100 mm x 100 mm. Electricity at both ends of the bonded pressure sensitive adhesive double coated sheet resistance meter using (Mitsubishi Chemical "reseuta GP as" the manufactured sikki, Ltd.) was measured for initial electrical resistance value (R _1). After leaving the indium tin oxide-deposited PET film bonded the double-sided adhesive sheet for 500 hours at 60 ° C. and 90% RH conditions, and leaving it at 23 ° C. and 50% RH conditions for 1 hour, the electrical resistance value at the same location as the initial stage ( R ₂ ) was measured. The electrical resistance value increase rate of the indium tin oxide film was computed by following formula (3).

Evaluation of the electrical resistance value increase rate was performed based on the following reference | standard. The results are shown in Table 2.

○; Electric resistance increase rate less than 5%

?; Electrical resistance increase rate less than 5 to 10%

×; 10% or more increase in electrical resistance

(Total light transmittance measurement)

The adhesive sheet obtained above was cut out to the size of 30 mm x 30 mm, the peeling PET film of one side was peeled among the peeling PET films which exist on both surfaces of an adhesive sheet, and what bonded to the glass plate was used as the sample for a measurement. About the measurement sample, total light transmittance (%) was measured using "HR-100 type" by Murakami Color Technology Research Institute. The results are shown in Table 2.

(Measurement of Adhesive Strength of Adhesive Sheet)

The double-sided adhesive sheet obtained above was cut out to the size of 25 mm x 100 mm, the peeled PET film of one side of the double-sided adhesive sheet was peeled off, and the back side of the 50-micrometer-thick PET film subjected to the corona treatment was then attached to the adhesive side. (Measurement surface) was attached to the test plate, and a 2 kg rubber roller (width: about 50 mm) was reciprocated once, and the sample for a measurement was produced. A glass plate was used as a trial plate. The obtained sample for measurement was left to stand for 24 hours in an environment of 23 ° C. and a humidity of 50%, and subjected to a tensile test in a 180 ° direction at a peeling rate of 300 mm / min in accordance with JIS ZO237, and to the adhesive force against the glass plate of the double-sided adhesive sheet ( N / 25mm) was measured. The obtained measured value was regarded as adhesive force. The results are shown in Table 2.

(Evaluation of Step Followability)

The peeling PET film of the one side of the double-sided adhesive sheet obtained above was peeled to the glass plate with printing of thickness 0.5mm, length 50mm, width 40mm, and the window frame shape of thickness 15micrometer, and width 5mm, the double-sided adhesive sheet was bonded together, and the single side | side again After peeling off the PET film, the adhesive layer of the stepped portion was formed by bonding to a glass plate having a thickness of 0.5 mm, a length of 50 mm, and a width of 40 mm, performing a heat press treatment under conditions of 5 atmospheres, 70 ° C., and 10 minutes. Was observed with the naked eye.

Evaluation of step followability was performed based on the following criteria. The results are shown in Table 2.

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

?; The state of slight lifting of the adhesion layer in the part with a step difference is confirmed

×; The state where clear lifting of the adhesive layer was confirmed in the part with a step

(Measurement of gel fraction)

The gel fraction was measured by the method mentioned above using the obtained transparent adhesive sheet. The results are shown in Table 2.

Claims (7)

(A) Formula (I)

Having a structural unit represented by (wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 6 carbon atoms, and R ³ represents a urethane bond residue of a polyolefin polyol or a hydrogenated polyolefin polyol) It is a composition for transparent adhesive sheets containing a (meth) acryl copolymer, (B) crosslinking agent, and (C) tin-type catalyst, The acid value is 5 mgKOH / g or less, The composition for transparent adhesive sheets. (A) The (meth) acryl copolymer which has a structural unit represented by general formula (I) is a (meth) acryl in presence of a polyolefin polyol and / or hydrogenated polyolefin polyol, and a tin-type catalyst. The composition for transparent adhesive sheets obtained by copolymerizing a loyl-group containing monomer (except having an isocyanate group) and (meth) acryloyloxyalkyl isocyanate. (A) The (meth) acryl copolymer which has a structural unit represented by general formula (I) is carbon number of an alkyl group in presence of a polyolefin polyol and / or hydrogenated polyolefin polyol, and a tin-type catalyst. 90 to 99.5 mol% of (meth) acrylic acid alkoxyalkyl esters having 1 to 18 (meth) acrylic acid alkyl esters and / or alkoxyalkyl groups having 2 to 20 carbon atoms, 0 to 9.5 mol% of (meth) acryloyl group-containing polar monomers, And the composition for transparent adhesive sheets obtained by copolymerizing 0.5-10 mol% of 2- (meth) acryloyloxyethyl isocyanate. The transparent adhesive sheet obtained by hardening | curing the composition for transparent adhesive sheets in any one of Claims 1-3. The transparent adhesive sheet of Claim 4 whose gel fraction is 40 to 80%. The transparent adhesive sheet of Claim 4 is used for joining of a transparent conductive film, The transparent adhesive sheet for transparent conductive film fixing characterized by the above-mentioned. The transparent adhesive sheet for fixing a transparent conductive film of Claim 6 is adhere | attached on the conductive layer surface of a transparent conductive film, The laminated body characterized by the above-mentioned.