KR20160117205A - Adhesive composition and adhesive sheet - Google Patents

Abstract

According to the present invention, an adhesive composition comprises: a (meth)acrylic-based copolymer of which acid value is 2.5 mg KOH/g or less, and which includes 0.01-1 wt% of a constituent unit derived from a monomer having a hydroxyl group, based on the entire constituent units; 5-30 parts by weight of a tolylene diisocyanate-based compound based on 100 parts by weight of the (meth)acrylic-based copolymer; and an imidazole compound.

Description

[0001] ADHESIVE COMPOSITION AND ADHESIVE SHEET [0002]

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

BACKGROUND ART [0002] In many image display units such as mobile phones and portable terminals, liquid crystal display devices are incorporated.

In general, a liquid crystal display device is provided with a liquid crystal cell, and optical films such as a polarizing plate, a retardation film, and a brightness enhancement film. In recent years, a liquid crystal display device provided with a touch panel has been increasing. The liquid crystal cell, the optical film, the optical films, or the optical film and the touch panel are bonded through a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition.

An optical film such as a polarizing plate is generally constituted by laminating members having different shrinkage ratios. As a result, the optical film may be warped due to changes in temperature or humidity, and peeling, peeling or foaming may occur at the interface between the pressure-sensitive adhesive layer and the optical film. In addition, there is a problem that a so-called white void phenomenon occurs in which the adhesive layer can not alleviate the stress generated when the optical film shrinks or expands due to changes in temperature or humidity, the residual stress applied to the adhesive layer is uneven, May occur. Therefore, there is a demand for a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer capable of achieving durability capable of restraining lifting and peeling and suppression of gray hair.

A method has been proposed in which the cohesive force of the pressure-sensitive adhesive layer is increased to suppress the dimensional change of the optical film in order to achieve both of the durability of the pressure-sensitive adhesive layer and the suppression of the gray hair. For example, International Publication No. WO06 / 06127 discloses a pressure-sensitive adhesive which does not cause lifting or peeling off of the adhered interface between an adherend and a pressure-sensitive adhesive layer even after long-term exposure under high temperature and high humidity after being adhered to an adherend, wherein 1 to 10% by mass of a carboxyl- 100 parts by mass of an acryl-based polymer obtained by copolymerizing an isocyanurate compound and 4 to 20 parts by mass of a tolylene diisocyanate compound having an isocyanurate structure.

Recently, the input method of the touch panel has become the mainstream of the capacitance type. In the electrostatic capacity type, an indium tin oxide (ITO) film constituting the touch panel is in contact with the pressure-sensitive adhesive layer. For this reason, the pressure-sensitive adhesive composition used in a liquid crystal display device is required to be difficult to corrode ITO.

However, in the pressure-sensitive adhesive composition for a polarizing plate described in International Publication No. 2011/062127, since an acrylic polymer has an acid group derived from a carboxyl group-containing monomer, there arises a problem that ITO is corroded.

Generally, when the amount of the acidic group contained in the pressure-sensitive adhesive composition is small, the corrosion of ITO can be suppressed.

However, in the conventional pressure-sensitive adhesive composition for a polarizing plate, an acrylic copolymer having a large number of acidic groups is used as described in the above-mentioned International Publication No. 2011/062127 in order to make the pressure-sensitive adhesive layer sufficiently soft and hard to cause peeling. When an acrylic copolymer having a small number of acid groups is used for the pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer becomes too hard when being used as a pressure-sensitive adhesive layer, and peeling easily occurs due to changes in temperature or humidity. Therefore, a pressure-sensitive adhesive composition that combines both durability and suppression of white streaks when an acrylic copolymer having a small number of acid groups is used and a pressure-sensitive adhesive layer is used is not known.

Furthermore, when an acrylic copolymer having a small number of acid groups is used in the pressure-sensitive adhesive composition, there is a problem that the curing period is prolonged due to a slow reaction rate when the pressure-sensitive adhesive composition is crosslinked to form a pressure-sensitive adhesive layer.

Here, a method of using a tin compound as a cross-linking catalyst may be considered in order to increase the reaction rate and shorten the curing time. However, when a tin compound is used as a crosslinking catalyst, durability may be deteriorated. Therefore, a method for shortening the curing period without using a tin compound is required.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet capable of both durability and suppression of gray hair while using an acrylic copolymer having a small amount of acid groups and shortening curing time.

Means for solving the above-mentioned problems include the following embodiments.

(1) a (meth) acrylic copolymer having an acid value of 2.5 mgKOH / g or less and a structural unit derived from a monomer having a hydroxyl group in a range of 0.01% by mass to 1% Sensitive adhesive composition comprising a tolylene diisocyanate compound in an amount of 5 parts by mass to 30 parts by mass based on 100 parts by mass of an acrylic copolymer and an imidazole compound.

<2> The pressure-sensitive adhesive composition according to <1>, wherein the content of the imidazole compound ranges from 0.01 part by mass to 1.5 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.

<3> The pressure-sensitive adhesive composition according to <1> or <2>, further comprising a silane coupling agent in an amount of 0.05 part by mass to 1 part by mass based on 100 parts by mass of the (meth) acrylic copolymer.

<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein the acid value of the (meth) acrylic copolymer is 0 mgKOH / g.

<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the tolylene diisocyanate compound is an adduct of tolylene diisocyanate and a polyol.

<6> The pressure-sensitive adhesive composition according to any one of <1> to <5>, wherein a storage elastic modulus (G ') value at 30 ° C. after crosslinking is in the range of 2.0 × 10 ⁵ Pa to 1.0 × 10 ⁷ Pa.

<7> A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of <1> to <6>.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet which can both reduce durability and suppress grayish white while using an acrylic copolymer having a small number of acid groups and shorten curing time.

Hereinafter, embodiments of the present invention will be described. In the present specification, the numerical range indicated by &quot; ~ &quot; indicates a range including the numerical values described before and after &quot; ~ &quot; as the minimum value and the maximum value, respectively. In addition, in the present specification, the amount of each component in the composition means a total amount of plural kinds of substances corresponding to the component, unless otherwise mentioned, when plural kinds of substances corresponding to each component are used together in the pressure-sensitive adhesive composition.

Further, (meth) acryl means at least one of acrylic and methacrylic, and (meth) acrylate means at least one of acrylate and methacrylate.

Further, the pressure-sensitive adhesive composition means a composition before the completion of the crosslinking reaction between the (meth) acrylic copolymer and the tolylene diisocyanate compound, for example, a liquid, paste or powdery composition.

Further, the pressure-sensitive adhesive layer means a layer after completion of the crosslinking reaction between the (meth) acrylic copolymer and the tolylene diisocyanate compound, for example, a solid or gel-like layer.

[Pressure sensitive adhesive composition]

The pressure-sensitive adhesive composition according to the present invention comprises a (meth) acrylic copolymer having an acid value of 2.5 mgKOH / g or less and having a structural unit derived from a monomer having a hydroxyl group in a range of 0.01 to 1 mass% A tolylene diisocyanate compound in an amount of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer, and an imidazole compound.

Since the acid value of the (meth) acrylic copolymer is as low as 2.5 mgKOH / g or less in the pressure-sensitive adhesive composition of the present invention, it is difficult to corrode ITO when it is used, for example, for adhesion of a capacitive touch panel.

Further, the pressure-sensitive adhesive composition of the present invention is excellent in both durability and suppression of white streaks when an optical film such as a polarizing plate or a touch panel is attached to an adherend such as a liquid crystal cell as a pressure-sensitive adhesive layer.

In the pressure-sensitive adhesive composition of the present invention, there is a condensate of a crosslinked product in which the (meth) acrylic copolymer is chemically crosslinked with a tolylene diisocyanate compound and a tolylene diisocyanate formed by the reaction of the tolylene diisocyanate compound.

It is considered that the condensation product of tolylene diisocyanate is relatively hard, so that the occurrence of stress can be suppressed, and the crosslinked product is relatively soft, so that adhesion with an adherend becomes good.

Therefore, it is considered that both the durability and the suppression of the gray hair are excellent by setting the hardness due to the condensate and the partial softness due to the cross-linked body to an appropriate range. More specifically, it is assumed as follows.

The pressure-sensitive adhesive composition of the present invention is a (meth) acrylic copolymer having a structural unit derived from a monomer having a hydroxyl group in a range of 0.01 mass% to 1 mass% with respect to the total structural units, that is, a (meth) It is partially softened when formed into a pressure-sensitive adhesive layer, so that the pressure-sensitive adhesive layer is excellent in adhesion to an adherend such as a touch panel, an optical film, and a liquid crystal cell, and is difficult to peel off. (Meth) acrylic copolymer has a hydroxyl group content of not less than 0.01% by mass, so that the pressure-sensitive adhesive layer is not so soft, gas generation (foaming) can be suppressed from the optical film, and the amount of hydroxyl groups is 1.0% Peeling from the adherend is suppressed because the film is hard and not rigid.

The pressure-sensitive adhesive composition of the present invention contains a tolylene diisocyanate compound in a range of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer, so that it becomes harder to suppress the occurrence of stress Do. In detail, by containing not less than 5 parts by mass of a tolylene diisocyanate compound as a crosslinking agent, it is possible to suppress foaming and peeling due to excellent durability (particularly, heat resistance), and by containing not more than 30 parts by mass of a tolylene diisocyanate compound, It is possible to suppress whitening at the time of use, and can be suitably used for bonding an article such as a touch panel or an optical film that requires transparency.

Further, since the pressure-sensitive adhesive composition of the present invention contains a tolylene diisocyanate compound as a crosslinking agent, it can be suitably used for bonding of a touch panel or an optical film, and both durability and suppression of gray hair can be achieved. On the other hand, when the crosslinking agent is a xylylene diisocyanate compound, the compatibility of the (meth) acrylic copolymer and the xylylene diisocyanate compound is poor and the pressure-sensitive adhesive layer is whitened and can not be used for bonding an article such as a touch panel or an optical film that requires transparency . If the cross-linking agent is a hexamethylene diisocyanate-based compound, hardness sufficient to inhibit the occurrence of stress can not be obtained when the pressure-sensitive adhesive layer is used, so that white flakes are generated, and both durability and suppression of white streaks are impossible.

Generally, the (meth) acrylic copolymer having a hydroxyl group without an acidic group as a crosslinkable functional group tends to have a long curing time because of poor reactivity with the crosslinking agent. Therefore, when only a hydroxyl group is used as the crosslinkable functional group, the curing time is prolonged and the crosslinking reaction may not be completed.

On the other hand, in the pressure-sensitive adhesive composition of the present invention, by using a tolylene diisocyanate compound as a cross-linking agent and using an imidazole compound as a cross-linking catalyst, curing time can be shortened while both durability and suppression of white streak are suppressed.

[(Meth) acrylic copolymer]

The pressure-sensitive adhesive composition of the present invention includes a (meth) acrylic copolymer having an acid value of 2.5 mgKOH / g or less and a structural unit derived from a monomer having a hydroxyl group in a range of 0.01 mass% to 1 mass% do. The above (meth) acrylic copolymer is preferably a copolymer containing an alkyl (meth) acrylate as a main component, and if necessary, a monomer having a carboxyl group, other monomers, or the like may be used as a copolymerization component. Here, the copolymer mainly composed of alkyl (meth) acrylate is a copolymer having a constituent unit derived from alkyl (meth) acrylate in an amount of 50% by mass or more based on 100% by mass of the constituent unit in the copolymer.

Since the (meth) acrylic copolymer has an acid value of 2.5 mgKOH / g or less, it is difficult to corrode ITO when it is used, for example, for bonding a capacitive touch panel. The acid value of the (meth) acrylic copolymer is preferably 2.0 mgKOH / g or less, more preferably 1.0 mgKOH / g or less, still more preferably 0.5 mgKOH / g or less, and more preferably 0 mgKOH / / g is particularly preferable. The acid value is a value calculated by the following equation.

Acid value (mgKOH / g) = (A / B) x 56.1 x 10 x C

A = content (% by mass) of monomers having a carboxyl group in all monomers used in the (meth) acrylic copolymer

B = molecular weight of the monomer having a carboxyl group used in the (meth) acrylic copolymer

56.1 is the molecular weight of KOH.

C = number of carboxyl groups in one molecule of a monomer having a carboxyl group used in the (meth) acrylic copolymer

When two or more kinds of monomers having carboxyl groups used in the (meth) acrylic copolymer are used, the acid value is determined for each monomer by the above-mentioned calculation formula, and the obtained values are totaled to obtain the acid value.

The (meth) acrylic copolymer has a constituent unit derived from a monomer having a hydroxyl group, and the hydroxyl group and the tolylene diisocyanate compound undergo a crosslinking reaction. Therefore, the cohesive force of the pressure-sensitive adhesive composition is increased, so that the adhesive force is excellent and the foaming can be suppressed in the durability test.

Examples of the alkyl (meth) acrylate which is the main component of the (meth) acrylic copolymer used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, n- butyl (meth) acrylate, Acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n (Meth) acrylate, n-decyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, , And isobonyl (meth) acrylate. The alkyl group of the alkyl (meth) acrylate may be linear, branched or cyclic. The alkyl group preferably has 1 to 18 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 4 carbon atoms.

Among them, methyl (meth) acrylate and n-butyl (meth) acrylate are preferable as the alkyl (meth) acrylate, and methyl acrylate and n-butyl acrylate are more preferable.

The content of the constituent unit derived from the alkyl (meth) acrylate in the (meth) acrylic copolymer is preferably 80% by mass or more, more preferably 90% by mass or more based on the total constitutional units because the adhesive property and the viscoelastic property are easily adjusted More preferably 95% by mass or more.

Examples of the monomer having a hydroxyl group, which is one component of the (meth) acrylic copolymer used in the present invention, include a (meth) acrylic monomer having a hydroxyl group and an unsaturated alcohol.

Examples of the (meth) acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) (Meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-hydroxybutyl (Meth) acrylate represented by 2-ethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (Meth) acrylate, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly (ethylene glycol-propylene glycol) .

Among them, the (meth) acrylic monomer having a hydroxyl group is preferably a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 5 carbon atoms, in view of good compatibility with other monomers and copolymerization and good crosslinking reaction with a crosslinking agent Hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms is more preferable. Specifically, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are more preferable.

Examples of the unsaturated alcohols include allyl alcohol and methallyl alcohol.

The (meth) acrylic copolymer has a structural unit derived from a monomer having a hydroxyl group in a range of 0.01 mass% to 1 mass% with respect to the total structural units. (Meth) acrylic copolymer has a constituent unit derived from a monomer having a hydroxyl group in an amount of not less than 0.01% by mass, the pressure-sensitive adhesive layer is not so soft and gas generation (foaming) from the optical film can be suppressed, % Or less, so that the pressure-sensitive adhesive layer is hard and does not become soft and peeling from the adherend is suppressed.

The (meth) acrylic copolymer preferably has a constituent unit derived from a monomer having a hydroxyl group in a range of 0.02 mass% to 0.7 mass%, more preferably 0.03 mass% to 0.5 mass% And more preferably in the range of 0.05 mass% to 0.3 mass%.

The (meth) acrylic copolymer may contain a monomer having a carboxyl group as a copolymerizable component in the range that the acid value of the (meth) acrylic copolymer is 2.5 mgKOH / g or less. Examples of the monomer having a carboxyl group include (meth) acrylic monomers having a carboxyl group. Examples of the (meth) acrylic monomer having a carboxyl group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamic acid, monohydroxyethyl (meth) (Meth) acrylate, monohydroxyethyl (meth) acrylate, maleic acid monohydroxyethyl (meth) acrylate, fumaric acid monohydroxyethyl (meth) acrylate, phthalic acid monohydroxyethyl (Meth) acrylic acid dimer, and? -Carboxy-polycaprolactone mono (meth) acrylate.

The content of the constituent unit derived from the monomer having a carboxyl group in the (meth) acrylic copolymer is preferably 0.2% by mass or less, more preferably 0.05% by mass or less, based on the total constituent units, from the viewpoint of lowering the acid value and inhibiting the corrosion of ITO , More preferably 0 mass% or not.

The (meth) acrylic copolymer used in the present invention may be a copolymerizable component other than the aforementioned alkyl (meth) acrylate, a monomer having a hydroxyl group, and other monomers other than a monomer having a carboxyl group. Examples of other monomers include (meth) acrylic monomers having an aromatic ring, (meth) acrylic monomers having a nitrogen atom, and other copolymerizable monomers.

The (meth) acrylic copolymer used in the present invention may contain a (meth) acrylic monomer having an aromatic ring as a copolymer component. As a result, the pressure-sensitive adhesive composition of the present invention can easily inhibit white stains when used for polarizer adhesion.

Examples of the (meth) acrylic monomer having an aromatic ring include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide (EO) (EO) -modified nonylphenol (meth) acrylate, hydroxyethylated? -Naphthol acrylate, and biphenyl (meth) acrylate.

The (meth) acrylic copolymer used in the present invention may contain a (meth) acrylic monomer having a nitrogen atom as a copolymer component. As a result, the pressure-sensitive adhesive composition of the present invention can further shorten the curing time.

Examples of the (meth) acrylic monomer having a nitrogen atom include aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, N, N, N-diethylacrylamide, N-ethyl, N-methyl (meth) acrylamide and N-isopropyl (meth) acrylamide.

The (meth) acrylic copolymer used in the present invention may contain other copolymerizable monomers as copolymer components. Examples of such monomers include aromatic monovinyl monomers typified by styrene,? -Methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, vinyltoluene and vinylpyridine, acrylonitrile and methacrylonitrile Representative cyanide vinyl monomers, carboxylic vinyl monomers typified by vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate (trade name, vinyl neodecanoate), and various derivatives thereof can be given.

The weight average molecular weight (Mw) of the (meth) acrylic copolymer used in the present invention is not particularly limited, but is preferably in the range of 700,000 to 2,000,000, more preferably in the range of 1 million to 1,500,000. The weight average molecular weight can be adjusted by the polymerization reaction temperature, time, amount of organic solvent and the like. When the weight average molecular weight is in the range of 700,000 to 2,000,000, the pressure-sensitive adhesive composition of the present invention is preferably low in viscosity and good in coatability.

The weight average molecular weight (Mw) of the (meth) acrylic copolymer is a value measured by the following method.

(Method for measuring weight average molecular weight (Mw)) [

Measurements are made according to the following (1) to (3).

(1) A (meth) acrylic copolymer solution is applied to a release paper and dried at 100 DEG C for 2 minutes to obtain a film-like (meth) acrylic copolymer.

(2) The film-like (meth) acrylic copolymer obtained in the above (1) is dissolved in tetrahydrofuran so as to have a solid content of 0.2%.

(3) The weight average molecular weight (Mw) of the (meth) acrylic copolymer as a standard polystyrene reduced value is measured by gel permeation chromatography (GPC) under the following conditions.

<Condition>

GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]

Column: Using 4 TSK-GEL GMHXL

Mobile phase solvent: tetrahydrofuran

Flow rate: 0.6 ml / min

Column temperature: 40 DEG C

The glass transition temperature (Tg) of the (meth) acrylic copolymer used in the present invention is preferably -80 ° C or higher, more preferably -60 ° C or higher for the purpose of imparting sufficient cohesive strength to the pressure-sensitive adhesive composition and exhibiting sufficient durability Do. The glass transition temperature (Tg) of the (meth) acrylic copolymer is preferably -20 占 폚 or lower for the purpose of exhibiting sufficient adhesion to the support substrate to exhibit durability without causing peeling or the like, -40 DEG C or less is more preferable.

The glass transition temperature (Tg) of the (meth) acrylic copolymer is a value obtained by converting the absolute temperature (K) obtained by the calculation of the following equation into the temperature in degrees Celsius.

In the formula, Tg ₁ , Tg ₂ , ... ... And Tg _n are monomer 1, monomer 2, ... ... And the absolute temperature (K) when the monomer of each of the monomers n is a homopolymer. m ₁ , m ₂ , ... ... And m _n is the mole fraction of each monomer.

The "glass transition temperature expressed by the absolute temperature (K) when the homopolymer is used" refers to the glass transition temperature, which is expressed by the absolute temperature (K) of the homopolymer produced by polymerizing the monomer alone. The glass transition temperature of the homopolymer was obtained by measuring the homopolymer using a differential scanning calorimeter (DSC) (EXSTAR6000, manufactured by Seiko Instruments Inc.) under the conditions of a measurement sample of 10 mg and a temperature raising rate of 10 캜 / min in a nitrogen stream The inflection point of the DSC curve is the glass transition temperature of the homopolymer.

Representative monomers "glass transition temperature expressed in degrees Celsius (C) of the homopolymer" are 5 ° C for methyl acrylate, -27 ° C for ethyl acrylate, -57 ° C for n-butyl acrylate and 2-ethylhexyl acrylate -76 ° C, 2-hydroxyethyl acrylate is -15 ° C, 4-hydroxybutyl acrylate is -39 ° C, t-butyl acrylate is 41 ° C and acrylic acid is 163 ° C. For example, by using these representative monomers, it is possible to appropriately adjust the glass transition temperature (Tg) of the (meth) acrylic copolymer.

Further, the absolute temperature K can be converted to the Celsius temperature (C) by subtracting 273 from the absolute temperature (K), and 273 is added to the Celsius temperature (C) Conversion is possible.

The method for producing the (meth) acrylic copolymer used in the present invention is not particularly limited, and can be produced by polymerizing monomers by solution polymerization, emulsion polymerization, suspension polymerization and the like. In addition, solution polymerization is preferable in that the pressure-sensitive adhesive composition of the present invention is prepared after production, since the treatment process is relatively simple and can be performed in a short time.

The solution polymerization is generally carried out by adding a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent, if necessary, in a polymerization vessel and heating the mixture for several hours while stirring at a reflux temperature of an organic solvent or in a nitrogen stream . The weight average molecular weight of the (meth) acrylic copolymer can be adjusted to a desired value by adjusting the reaction temperature, time, amount of solvent, type and amount of the catalyst.

Examples of the organic solvent for polymerization used in the production of the (meth) acrylic copolymer include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds and alcohol compounds. Each of these organic solvents may be used alone or in combination of two or more. Examples of the polymerization initiator include organic peroxides and azo compounds that can be used in ordinary polymerization methods.

[Tolylene diisocyanate compound]

The pressure-sensitive adhesive composition of the present invention contains a tolylene diisocyanate compound in an amount ranging from 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.

The tolylene diisocyanate compound functions as a crosslinking agent.

Examples of the tolylene diisocyanate compound include tolylene diisocyanate, dimer of tolylene diisocyanate, adduct of tolylene diisocyanate and polyol, isocyanurate of trimers or pentamers of tolylene diisocyanate, And tolylene diisocyanate compounds derived from various tolylene diisocyanates such as diisocyanate and burette. Among them, an isomer of tolylene diisocyanate and a polyol is preferable from the viewpoint of excellent reactivity and high crosslinking density and compatibility with the (meth) acrylic copolymer, and it is preferable to use a mixture of tolylene diisocyanate and trimethylol propane Is particularly preferable.

The content of the tolylene diisocyanate compound in the pressure-sensitive adhesive composition is in the range of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. By containing not less than 5 parts by mass of the tolylene diisocyanate compound, foaming and peeling can be suppressed, and durability (particularly, heat resistance) is excellent. By incorporating the tolylene diisocyanate compound in an amount of 30 parts by mass or less, whitening can be suppressed when the pressure-sensitive adhesive layer is formed, and it can be suitably used for bonding articles requiring transparency, such as touch panels and optical films.

The content of the tolylene diisocyanate compound in the pressure-sensitive adhesive composition is preferably from 10 parts by mass to 30 parts by mass, more preferably from 12 parts by mass to 30 parts by mass, per 100 parts by mass of the (meth) acrylic copolymer. As a result, the pressure-sensitive adhesive layer is more excellent in both durability and suppression of white spots.

The tolylene diisocyanate compound may be commercially available. As a commercially available product, "Coronate L" (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd. as an adduct of tolylene diisocyanate and trimethylol propane, and isocyanurate of tolylene diisocyanate, Nippon Polyurethane Industry Co., Ltd. &Quot; Colonate 2030 &quot;, etc. can be suitably used.

[Other Crosslinking Agent]

The pressure-sensitive adhesive composition of the present invention may contain other cross-linking agents other than the tolylene diisocyanate compound within the range not impairing the object of the present invention. Other crosslinking agents are not particularly limited, and polyisocyanate compounds other than tolylene diisocyanate compounds, polyepoxy compounds, polyaziridine compounds, metal chelate compounds and the like can be given. These other crosslinking agents may be used singly or in combination with a tolylene diisocyanate compound.

[Imidazole compound]

The pressure-sensitive adhesive composition in the present invention includes an imidazole compound. The imidazole compound functions as, for example, a crosslinking catalyst in the pressure-sensitive adhesive composition. By including the imidazole compound in the pressure-sensitive adhesive composition, the curing time can be further shortened while maintaining excellent durability.

The imidazole compound is not particularly limited as long as it is a compound having at least one imidazole ring in the molecule, but an N-substituted imidazole compound is preferable from the viewpoint of shortening the curing time and lengthening the pot life. The N-substituted imidazole compound is not particularly limited as long as it has at least one imidazole ring in the molecule and does not have a hydrogen atom on the nitrogen atom of the imidazole ring.

Concrete examples of the N-substituted imidazole compound include the compounds represented by the following general formula (I).

In formula (I), R ₁ , R ₂ and R ₄ each independently represent a hydrogen atom or a substituent, and R ₃ represents a substituent. Preferably, R ₁ , R ₂ and R ₄ in the general formula (I) each independently represent a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, and R ₃ represents an alkyl group, an aryl group or an aralkyl group. R ₁ and R ₂ or R ₃ and R ₄ may be connected to each other to form a cyclic structure.

The alkyl group (R ₁ to R ₄ ) in the general formula (I) may be straight-chain or branched. The number of carbon atoms in the alkyl group is preferably 1 to 2. In the general formula (I), the aryl group (R ₁ to R ₄ ) preferably has 6 to 10 carbon atoms, and more preferably a phenyl group or a naphthyl group. In the general formula (I), the aralkyl group (R ₁ to R ₄ ) is preferably composed of an alkylene group having 1 to 2 carbon atoms and an aryl group having 6 to 10 carbon atoms, more preferably a benzyl group or a phenylethyl group.

The N-substituted imidazole compound represented by the general formula (I) is a compound wherein R ₃ is an alkyl group or an aralkyl group and R ₁ , R ₂ and R ₄ are each independently a hydrogen atom, an alkyl group or an aryl group, from the viewpoint of lengthening pot life while shortening the curing time. An aryl group is preferred. Among them, the N-substituted imidazole compound represented by the general formula (I) is selected from the group consisting of 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl- At least one paper is more preferable. It is also preferable that R ₃ and R ₄ are connected to each other to form a 5- to 6-membered saturated aliphatic ring and R ₁ and R ₂ are connected to each other to form a 6-membered aromatic ring. From the viewpoint of shortening the curing time 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole is more preferable.

The content of the imidazole compound in the pressure-sensitive adhesive composition is preferably 0.01 to 1.5 parts by mass, more preferably 0.05 to 1.2 parts by mass, per 100 parts by mass of the (meth) acrylic copolymer from the viewpoint of lengthening the pot life while shortening the curing time. More preferably in a range of 0.1 part by mass to 1.0 part by mass, and particularly preferably in a range of 0.3 part by mass to 0.7 part by mass.

Examples of the N-substituted imidazole compound used in the present invention include commercially available products such as "Cueazole 1, 2DMZ", "Cueazole 1B2MZ", "Cueazole 1B2PZ", and "Cueazole TBZ" available from Shikoku Chemical Industry Co., .

[Silane coupling agent]

The pressure-sensitive adhesive composition of the present invention preferably further comprises a silane coupling agent. When the pressure-sensitive adhesive composition contains a silane coupling agent, the pressure-sensitive adhesive layer exhibits better adhesion to glass, and even when the liquid crystal display device in which the polarizing plate is embedded is exposed in a high temperature environment or under a high temperature and high humidity environment, It is more likely that peeling is less likely to occur.

As the silane coupling agent, for example, a coupling agent having a mercapto group, a coupling agent having an epoxy group, a coupling agent having a carboxyl group, a coupling agent having an amino group, a coupling agent having a hydroxyl group, a coupling agent having an amido group, A coupling agent having an isocyanurate skeleton, and a coupling agent having an isocyanurate skeleton. These silane coupling agents may be used alone or in combination of two or more.

KBM-403, KBM-303, KBM-402, KBE-402, KBE-402, and KBE-402 manufactured by Shin-Etsu Chemical Industry Co., Ltd. may be used as commercially available products, Quot; -403 &quot; (trade name), may be suitably used as the silane coupling agent having an epoxy group.

When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, the content of the silane coupling agent in the pressure-sensitive adhesive composition is preferably in the range of 0.01 to 1.0 part by mass with respect to 100 parts by mass of the (meth) acrylic copolymer, By mass to 0.7 part by mass, and more preferably 0.1 part by mass to 0.5 part by mass.

[solvent]

In addition, the pressure-sensitive adhesive composition of the present invention may contain a solvent for the purpose of improving the coating property of an optical film such as a polarizing plate or a touch panel or a liquid crystal cell.

Examples of the solvent include hydrocarbons typified by hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, methylcyclohexane, dichloromethane, trichloroethane, trichlorethylene, tetrachlorethylene and dichloropropane Halogenated hydrocarbons, alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol and diacetone alcohol, ethers such as diethyl ether, diisopropyl ether, dioxane and tetrahydrofuran, Ketones represented by acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone and cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate and ethyl acetate, ethylene glycol monomethyl Ether, ethylene glycol monoethyl ether, propylene glycol monome A polyol represented by the ether acetates, and organic solvents and the like and derivatives thereof.

[Other components]

The pressure-sensitive adhesive composition of the present invention may contain, in addition to the (meth) acrylic copolymer, the tolylene diisocyanate compound and the imidazole compound, a silane coupling agent, a solvent and other crosslinking agents, weather resistance stabilizers, tackifiers, plasticizers, A light stabilizer such as a release agent, a dye, a pigment, an inorganic filler, a surfactant, an antioxidant, a metal corrosion inhibitor, an ultraviolet absorber, and a hindered amine compound may be appropriately contained.

The pressure-sensitive adhesive composition of the present invention preferably has a storage elastic modulus (G ') at 30 ° C after crosslinking in the range of 2.0 × 10 ⁵ Pa to 1.0 × 10 ⁷ Pa in order to further increase durability and further inhibit gray hair, More preferably from 10 ⁵ Pa to 1.0 × 10 ⁷ Pa, and still more preferably from 3.0 × 10 ⁵ Pa to 5.0 × 10 ⁶ Pa. The storage modulus of the pressure-sensitive adhesive composition is a value measured by the method described in the examples.

[Adhesive sheet]

The pressure-sensitive adhesive sheet in the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition described above. The pressure-sensitive adhesive sheet of the present invention may be a non-base type pressure-sensitive adhesive sheet which does not have a base material and may be an adhesive sheet of an ink-jet type which has a pressure-sensitive adhesive layer on at least one side of a base material such as an optical film . The pressure-sensitive adhesive sheet of the present invention is excellent in durability because the pressure-sensitive adhesive layer is hardly lifted or peeled from the interface with the adherend even when exposed to a high temperature environment or a high temperature and high humidity environment.

In the pressure-sensitive adhesive sheet of the present invention, the thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be appropriately selected depending on the application and required performance. The thickness of the pressure-sensitive adhesive layer is, for example, in the range of 1 占 퐉 to 100 占 퐉.

When the pressure-sensitive adhesive sheet of the present invention is used for optical use, it is preferable that the pressure-sensitive adhesive layer has high transparency. Specifically, the total light transmittance of the pressure-sensitive adhesive layer in the visible light wavelength region measured according to JIS K 7361 (1997) is preferably 85% or more, more preferably 90% or more.

The haze of the pressure-sensitive adhesive layer measured according to JIS K 7136 (2000) is preferably 2.5% or less, more preferably 2.0% or less, and further preferably 1.5% or less.

The exposed pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet in the present invention may be protected by a release film. The release film is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer, and for example, a resin film which has been easily peeled off at least on one side by using a peeling agent can be given. As the resin film, for example, a polyester film typified by a polyethylene terephthalate film can be mentioned. As the peeling agent, for example, fluorine resin, paraffin wax, silicone, and long chain alkyl group compound can be given. The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is provided for practical use, and is peeled off during use.

The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by applying the pressure-sensitive adhesive composition according to the present invention to a release film or a base material and then curing for a certain period of time after drying to form a pressure-sensitive adhesive layer. The curing condition can be, for example, 1 to 10 days under an environment of 23 ° C and 50% RH (relative humidity). By curing the pressure-sensitive adhesive layer, the (meth) acrylic copolymer can be sufficiently crosslinked with the tolylene diisocyanate compound.

The base sheet-free adhesive sheet can be produced, for example, by applying a pressure-sensitive adhesive composition on a release-treated surface of a release film and drying it to form a layer of the pressure-sensitive adhesive composition, separating the exposed surface of the layer, And then the film is overlapped and cured so that the peeling-treated surface is in contact with the film to form a pressure-sensitive adhesive layer.

The pressure-sensitive adhesive sheet of the present invention may be produced by applying the pressure-sensitive adhesive composition to a base material such as an optical film, or by applying the pressure-sensitive adhesive composition to a release film. In this method, for example, a pressure-sensitive adhesive composition is coated on a release surface of a release film and dried to form a layer of a pressure-sensitive adhesive composition, a base material is applied to an exposed surface of the layer obtained, A method of forming a layer can be mentioned.

The base material of the pressure-sensitive adhesive sheet of the present invention may be an optical film. Specific examples of the optical film include optical films used in liquid crystal display devices. More specifically, optical films such as a polarizing plate, a retardation film, an antireflection film, a viewing angle increasing film, a luminance improving film, and an ITO film can be mentioned. Among them, an optical film is preferable as the base material of the pressure-sensitive adhesive sheet of the present invention, and a polarizing plate is more preferable.

The polarizing plate may have at least a polarizer, for example, a polarizing plate having a protective film on one side of a polarizer or a polarizing plate having a protective film on both sides of the polarizing plate. As the polarizer of the polarizing plate, for example, a polyvinyl alcohol (PVA) film in which iodine is adsorbed is used, and a triacetylcellulose (TAC) film is used as a protective film of the polarizer.

When the polarizing plate is used as the base material, the pressure-sensitive adhesive layer may be formed on the PVA film or on the TAC film.

Examples of a method of applying the pressure-sensitive adhesive composition to a release film or a base material include a known method using a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater and a spray coater.

The pressure-sensitive adhesive sheet in the present invention can be suitably used for bonding an optical film or the like of a liquid crystal display device. That is, in the pressure-sensitive adhesive sheet of the present invention, the adhesion of optical films such as a polarizing plate, a retardation film, an antireflection film, a viewing angle expansion film, a brightness enhancement film, and an ITO film and a bonding between the optical film and the liquid crystal cell, Can be used suitably. Further, the pressure-sensitive adhesive sheet in the present invention can be suitably used for bonding a touch panel to a liquid crystal cell, a glass substrate, a protective film and the like.

Examples of the pressure-sensitive adhesive sheet in the present invention include a pressure-sensitive adhesive sheet of a no-base material type having a structure (release film / pressure-sensitive adhesive layer / release film) in which a release film is adhered to both surfaces of a pressure-sensitive adhesive layer, And an adhesive base sheet type adhesive sheet provided with a structure (optical film / pressure-sensitive adhesive layer / release film) in which a release film is stuck on one side.

Example

Hereinafter, the present invention will be described concretely with reference to Examples, but the present invention is not limited to these Examples.

&Lt; Preparation of (meth) acrylic copolymer >

(Production Example 1)

99.99 parts by mass of butyl acrylate (BA) as an alkyl (meth) acrylate and 0.01 mass parts of 2-hydroxyethyl acrylate (2HEA) as a monomer having a hydroxyl group were placed in a reactor equipped with a thermometer, a stirrer, And 110 parts by mass of ethyl acetate as a solvent were mixed and replaced with nitrogen in the reactor. Thereafter, the mixture in the reactor was heated to 70 DEG C with stirring, and then 0.04 parts by mass of azobisdimethylvaleronitrile (ABVN) as a polymerization initiator and 40 parts by mass of ethyl acetate as a solvent were added in this order, and polymerization reaction was maintained for 6 hours . After completion of the polymerization reaction, the reaction product was diluted with ethyl acetate as a solvent to give a solid content of 24.0% by mass. Thus, a solution of the BA / 2HEA copolymer ((meth) acrylic copolymer) was obtained.

(Production Example 2 to Production Example 13)

In Production Examples 2 to 13, a solution of a (meth) acrylic copolymer was obtained in the same manner as in Production Example 1, except that the monomer composition shown in Table 1 was used when the (meth) acrylic copolymer was produced. In Table 1, MA represents methyl acrylate, AA represents acrylic acid, and 4HBA represents 4-hydroxybutyl acrylate.

Table 1 shows the monomer composition (mass part), acid value, glass transition temperature (Tg) and weight average molecular weight (Mw) in the (meth) acrylic copolymers prepared in Production Examples 1 to 13. The acid value, Tg and Mw of the (meth) acrylic copolymer were calculated and measured as described above.

Specifically, the acid value of the (meth) acrylic copolymer of Production Example 7 was calculated as follows.

(1 / 72.1) x 56.1 x 10 x 1 = 7.8

The molecular weight of AA is 72.1, and the number of carboxyl groups in the AA1 molecule is 1.

&Lt; Preparation of pressure-sensitive adhesive composition &

(Example 1)

416.7 parts by mass (100.0 parts by mass as solid content) of the solution of the (meth) acrylic copolymer obtained in Production Example 1 and 20.0 parts by mass of Kolonate L as a tolylene diisocyanate compound (manufactured by Nippon Polyurethane Industry Co., 15.0 parts by mass as an active ingredient of isocyanate and trimethylol propane) and 0.3 parts by mass of imidazole compound (manufactured by Shikoku Chemical Industry Co., Ltd., 2,3-dihydro-1H-pyrolo [ 1,2-a] benzimidazole) and 0.4 mass parts of KBM-403 as a silane coupling agent (SC) (3-glycidoxypropyltrimethoxysilane manufactured by Shin-Etsu Chemical Co., Ltd., 0.4 mass Ltd.) were thoroughly stirred and mixed to obtain a pressure-sensitive adhesive composition.

(Examples 2 to 17)

In Examples 2 to 17, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the composition of the pressure-sensitive adhesive composition shown in Table 2 below was used.

(Comparative Examples 1 to 4)

In Comparative Examples 1 to 4, a solution of the (meth) acrylic copolymer obtained in Production Examples 7, 8, 12 and 13 was used instead of the solution of the (meth) acrylic copolymer obtained in Production Example 1, To prepare a pressure-sensitive adhesive composition. The (meth) acrylic copolymer obtained in Production Examples 7 and 8 had an acid value of more than 2.5 mgKOH / g, and the (meth) acrylic copolymer obtained in Production Examples 12 and 13 contained 0.01% by mass of 2HEA as a copolymerization component. And 1% by mass.

(Comparative Example 5)

In Comparative Example 5, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 3 except that the amount of the tolylene diisocyanate compound was less than 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.

(Comparative Examples 6 and 7)

In Comparative Example 6, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 2 except that a tolylene diisocyanate-based compound, TAKENATE D-110N (manufactured by Takeda Chemical Industries, Ltd.) was used as a crosslinking agent instead of the tolylene diisocyanate compound. In Comparative Example 7, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 2, except that Sumidel N-75 (manufactured by Sumika Bayer Urethane Co., Ltd.), which is a hexamethylene diisocyanate compound, was used instead of the tolylene diisocyanate compound as a crosslinking agent.

(Comparative Example 8)

In Comparative Example 8, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 3, except that dibutyltin dilaurate was used as a crosslinking catalyst instead of the imidazole compound.

(Comparative Example 9)

In Comparative Example 9, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 2 except that the amount of the tolylene diisocyanate compound was changed to more than 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.

&Lt; Preparation of adhesive sheet sample >

Using the pressure-sensitive adhesive compositions of each of the examples and comparative examples obtained above, a pressure-sensitive adhesive sheet sample was prepared in the following procedure. First, a pressure-sensitive adhesive composition was coated on the surface-treated surface of a release film (100E-0010NO23, manufactured by Fujimori Kogyo Co., Ltd.) surface-treated with a silicone type releasing agent so that the applied amount after drying was 20 g / cm 2. Next, the release film after application of the pressure-sensitive adhesive composition was dried using a hot-air circulation type drier at 100 DEG C for 90 seconds to form a pressure-sensitive adhesive composition layer on the release film. Subsequently, one side of a polarizing plate of triacetyl cellulose (TAC) / polyvinyl alcohol (PVA) / TAC structure and a layer of a pressure sensitive adhesive composition on a release film were laminated and passed through a pressure nip roll. After pressure bonding, autoclave treatment (50 캜, 5 kg / cm 2, 20 minutes) was carried out and curing was carried out at 35 캜 and 45% RH for 96 hours to prepare a pressure sensitive adhesive sheet sample having a laminated structure of release film / pressure- Respectively.

Table 2 below shows the composition of the pressure-sensitive adhesive composition obtained in Examples 1 to 17 and Comparative Examples 1 to 9, the measurement results of the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet samples, and the evaluation results.

The crosslinking agents a to c and the crosslinking catalysts d to g shown in Table 2 are as follows.

Crosslinking agent a: Colonate L (manufactured by Nippon Polyurethane Industry Co., Ltd., adduct of tolylene diisocyanate and trimethylol propane)

Crosslinking agent b: Takenate D-110N (manufactured by Takeda Chemical Industries, Ltd., xylene diisocyanate compound)

Crosslinking agent c: Sumidule N-75 (a hexamethylene diisocyanate compound manufactured by Sumika Bayer Urethane Co., Ltd.)

Crosslinking catalyst d: cuazole TBZ (2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, product of Shikoku Chemical Industry Co., Ltd.)

Crosslinking catalyst e: cueazole 1B2MZ (1-benzyl-2-methylimidazole, manufactured by Shikoku Chemical Industry Co., Ltd.)

Crosslinking catalyst f: cueazole 1B2PZ (1-benzyl-2-phenylimidazole manufactured by Shikoku Chemical Industry Co., Ltd.)

Crosslinking catalyst g: Dibutyltin dilaurate

SC: KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane)

In Table 2, &quot; ND1 &quot; indicates that evaluation by the haze is impossible, and &quot; ND2 &quot;

[Evaluation of corrosion resistance of ITO]

A silver paste (trade name: DATE FA-401CA, manufactured by Fujikura Kasei Kogyo Co., Ltd.) was applied to both ends of a conductive surface of an ITO film (product name: Titerite TCF KB300N03-125-U3 / P, Ltd.) was thinly coated so as to have a width of 15 mm and baked at 140 占 폚 for 15 minutes.

The pressure-sensitive adhesive sheet samples obtained by using the pressure-sensitive adhesive compositions of Examples and Comparative Examples were cut to a size of 30 mm long × 75 mm wide, and the release film of the pressure-sensitive adhesive sheet sample was peeled off to expose the pressure-sensitive adhesive layer.

The adhesive sheet sample was attached to the electrically conductive surface of the ITO film so that the exposed pressure-sensitive adhesive layer filled between the silver paste and the silver paste, and then cut into a length of 20 mm and a width of 95 mm. After the cutting, autoclave treatment was performed under conditions of 0.5 MPa, 40 DEG C, and 30 minutes to obtain a corrosion inhibiting test sample.

Corrosion resistance test A lead wire of a tester was placed on the silver paste portions at both ends and the resistance value before the test was measured. Next, the corrosion inhibition test sample was subjected to a corrosion inhibition test in which the sample was allowed to stand at 60 DEG C and 90% RH for 250 hours. The corrosion resistance test sample after the test was taken out, and the resistance value after the test was measured by placing the lead rod of the tester on the silver paste portion at both ends of the corrosion inhibition test sample under the environment of 23 캜 and 50% RH. The change rate of the resistance value from the resistance value before the test and the resistance value after the test was calculated by the following equation.

(%) = [(Resistance value after test - resistance value before test) / resistance value before test] × 100

The corrosion resistance of the ITO was evaluated according to the rate of change (%) of the resistance value calculated by the above formula and the following evaluation criteria. When the evaluation result is A or B, the corrosion of ITO is small and there is no practical problem.

Evaluation standard

A: The change rate of the resistance value is less than 10%.

B: The change rate of the resistance value is 10% or more and less than 20%.

C: The change rate of the resistance value is 20% or more.

[Evaluation of durability (80 占 폚, 60 占 폚 占 90% RH)

A test piece having a size of 140 mm x 260 mm (long side) cut at a long side of 45 DEG with respect to the absorption axis was prepared as described above, and the release film of the test piece was peeled off to expose the pressure sensitive adhesive layer. Next, a sample for evaluation of durability was prepared by attaching the exposed surface of the pressure-sensitive adhesive layer by using a laminator so that the exposed surface was in contact with one side of a non-alkali glass plate &quot;# 1737 &quot; Next, this sample was subjected to an autoclave treatment (50 DEG C, 5 kg / cm2, 20 minutes), and left to stand at 23 DEG C and 50% RH for 24 hours. Thereafter, each sample was allowed to stand for 500 hours under a high-temperature environment of 80 ° C or a high-temperature and high-humidity environment of 60 ° C × 90% RH, and the foaming, peeling, and floating state were visually observed. If the evaluation result is A or B, the durability is excellent and there is no practical problem.

Evaluation standard

A: No foaming or peeling is seen at all.

B: Foaming is scarcely seen, and no peeling occurs at a position of 0.5 mm or more from the outer peripheral end at two sides.

C: The foaming is remarkable, or peeling occurs at a position of 0.5 mm or more from the outer peripheral end at two sides.

[Evaluation of gray hair]

A test piece having a size of 140 mm x 260 mm (long side) cut at a long side of 45 DEG with respect to the absorption axis was prepared as described above, and the release film of the test piece was peeled off to expose the pressure sensitive adhesive layer. Next, a sample of the pressure-sensitive adhesive sheet on which the pressure-sensitive adhesive layer was exposed was stuck to both sides of a 0.7 mm non-alkali glass plate "# 1737" made by Corning Inc. using a laminator so that the polarization axes of the polarizing plates were orthogonal to each other. Next, this sample was subjected to an autoclave treatment (50 DEG C, 5 kg / cm2, 20 minutes), and left to stand at 23 DEG C and 50% RH for 24 hours. Thereafter, it was left for 500 hours under the conditions of 70 ° C and 0% RH. After standing, the state of naked eyes was visually observed using a uniform light source under conditions of 23 캜 and 50% RH, and evaluated by the following evaluation criteria. When the evaluation result is A or B, the suppression of gray hair is excellent and there is no practical problem.

Evaluation standard

A: No gray hair is recognized at all.

B: The gray hair is hardly recognized.

C: A lot of gray hair is recognized.

[Evaluation of curing time]

The pressure-sensitive adhesive composition was coated on the surface-treated surface of a release film (100E-0010NO23, manufactured by Fujimori Kogyo Co., Ltd.) surface-treated with a silicone type releasing agent so that the thickness after drying was 20 占 퐉. Next, the release film after applying the pressure-sensitive adhesive composition was dried using a hot-air circulation type drier at 100 DEG C for 60 seconds to form a pressure-sensitive adhesive composition layer on the release film. A surface treated surface of a release film (25E-0010BD manufactured by Fujimori Kogyo Co., Ltd.) surface-treated with a silicone type releasing agent was adhered to the layer of the pressure-sensitive adhesive composition to prepare a pressure-sensitive adhesive composition sheet. The pressure-sensitive adhesive layer thus prepared was stored under the environment of 23 ° C × 50% RH, and the gel fraction was measured after 96 hours and 168 hours from the start of storage. If the evaluation result is A, the working efficiency is improved and there is no practical problem.

Evaluation standard

A: The difference in gel fraction between 96 hours and 168 hours after curing is within 3%.

B: The difference in gel fraction after 96 hours and after 168 hours of curing exceeds 3%.

[Evaluation of Portlife]

The shelf life of the pressure sensitive adhesive composition of each of the examples and comparative examples was confirmed to be a storage time in which the thickness of the coating film formed by applying the pressure sensitive adhesive composition could be uniformly applied without occurrence of stem-like defects such as turbidity and coating unevenness . Storage conditions were 23 캜 and 50% RH.

The coating was obtained by the following method.

The pressure-sensitive adhesive composition after storage was applied on a release film (100E-0010NO23 manufactured by Fujimori Kogyo Co., Ltd.) surface-treated with a silicone type releasing agent so that the applied amount after drying was 25 g / cm 2 and dried by a hot air circulating dryer at 100 캜 for 90 seconds, &Lt; / RTI &gt; The state of the dried film at each storage time was visually observed and evaluated according to the following evaluation criteria. If the evaluation result is A or B, there is no practical problem.

Evaluation standard

A: No stem-shaped defects were found in the coating film at the storage time of 48 hours.

B: Stain-like defects are not observed in the coating film at the storage time of 24 hours, but streak-like defects are seen in the coating film at 48 hours.

C: Defects in stem shape or gelation occurred in the coating film at the storage time of 24 hours.

[Measurement of storage elastic modulus (G ')]

The storage elastic modulus (G ') of each of the pressure-sensitive adhesive compositions of the examples and comparative examples was measured by the following method.

The pressure-sensitive adhesive composition thus prepared was applied, dried and cured under the same conditions as in the preparation of the above-mentioned pressure-sensitive adhesive sheet sample to form a pressure-sensitive adhesive layer of 20 m. The pressure-sensitive adhesive layer thus formed was bonded to each other so that the thickness of the pressure-sensitive adhesive layer was 600 占 퐉. Using a dynamic viscoelasticity measuring device (Physica MCR301 manufactured by Anton Paar Co., Ltd.) The storage elastic modulus (G ') (Pa) was measured while applying a shear stress at 1 Hz. The results are shown in Table 2.

[result]

In Examples 1 to 17, ITO corrosion resistance and durability (rated at 80 ° C and 60 ° C × 90% RH, respectively) and graying and curing periods were evaluated to be B or more and practically no problem.

On the other hand, in Comparative Examples 1 to 9, evaluation C or non-measurable (haze due to whitening or peeling) was observed in any of ITO corrosion inhibition and durability (80 ° C and 60 ° C × 90% RH, respectively) And there is a problem in practical use.

Claims (7)

(Meth) acrylic copolymer having an acid value of 2.5 mgKOH / g or less and having a structural unit derived from a monomer having a hydroxyl group in a range of 0.01% by mass to 1% by mass with respect to all the constitutional units,
A tolylene diisocyanate compound in an amount of 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer,
&Lt; / RTI &gt; imidazole compound. The method according to claim 1,
Wherein the content of the imidazole compound is in the range of 0.01 part by mass to 1.5 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. The method according to claim 1 or 2,
And a silane coupling agent in an amount of 0.05 part by mass to 1 part by mass based on 100 parts by mass of the (meth) acrylic copolymer. The method according to claim 1 or 2,
Wherein the acid value of the (meth) acrylic copolymer is 0 mgKOH / g. The method according to claim 1 or 2,
Wherein the tolylene diisocyanate compound is an adduct of tolylene diisocyanate and a polyol. The method according to claim 1 or 2,
And a storage elastic modulus (G ') value at 30 ° C after crosslinking is in the range of 2.0 × 10 ⁵ to 1.0 × 10 ⁷ Pa. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 or 2.