JP2015174907A - Adhesive composition, adhesive layer and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition capable of forming an adhesive layer excellent in step followability which can follow to an adhesive body having steps without generating air bubble or the like during laminating and processability which no adhesive adhere to a cutting blade during cutting and no cobwebbed situation is generated.SOLUTION: There is provided an adhesive composition containing (A) (meth)acrylic copolymer and (B) an isocyanate compound and forming an adhesive layer having storage elastic modulus at 25°C of 0.8×10Pa or more and that at 80°C of 5.0×10Pa or less.

Description

  The present invention relates to a pressure-sensitive adhesive composition excellent in step followability and processability, a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition, and a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer.

  In recent years, an image display device such as a liquid crystal display device and an input device such as a touch panel used in combination with the image display device have been widely used. In manufacturing these image display devices and input devices, an adhesive sheet having an adhesive layer is used when the constituent members are bonded together.

  For example, in a liquid crystal display device, a front transparent plate such as a glass plate is provided on the viewing side of the display panel via an adhesive layer. On the other hand, a printed layer may be formed on the peripheral edge of the front transparent plate in order to display a specific frame or figure around the screen and enhance the design. For example, in a touch panel, a transparent plate such as a glass plate and a transparent conductive film having a transparent conductive thin film such as indium tin oxide (ITO) formed on the surface thereof are laminated via an adhesive layer.

  As described above, an increasing number of liquid crystal display devices, touch panels, and the like include a member having a step based on a printed layer, a conductive thin film, or the like. For this reason, the pressure-sensitive adhesive layer used for sticking / fixing the member is required to have excellent step followability so that no gap is generated.

  In order to provide the pressure-sensitive adhesive layer with step following ability, for example, it is conceivable to form a relatively thick pressure-sensitive adhesive layer using a flexible pressure-sensitive adhesive made of a polymer having a low glass transition temperature (Tg). . However, such a pressure-sensitive adhesive layer has problems such as adhesion of the pressure-sensitive adhesive to the cutting blade at the time of cutting or stringing, and is inferior in workability. For this reason, it has been difficult to achieve both step followability and processability of the pressure-sensitive adhesive layer.

Patent Document 1 discloses a laminate used for an image display device such as a touch panel, a liquid crystal display, and electronic paper. Specifically, it is a laminate in which an adhesive layer is formed on a transparent substrate on which a printing ink layer is formed, and the adhesive layer is a cured product of a specific adhesive composition, A laminate having a storage elastic modulus at 25 ° C. of 1.0 × 10 ⁵ Pa or more and less than 1.0 × 10 ⁷ Pa is disclosed.

  Patent Document 2 discloses an adhesive layer used for bonding an image display panel and a front transparent plate having a raised portion on the surface on the image display panel side, and a storage elastic modulus at 23 ° C. is 0.12 MPa. An adhesive layer that is ˜1 MPa is disclosed.

  In the above patent documents, although the storage elastic modulus of the pressure-sensitive adhesive layer near normal temperature is specified, if it has the storage elastic modulus in the above range at normal temperature (around 25 ° C.), the storage elastic modulus is high even at high temperature (around 80 ° C.). Further improvement is desired in terms of compatibility between the step following ability and workability.

JP2013-142132A JP 2012-237965 A

  The problem of the present invention is that the step following ability can follow an adherend having a step without causing bubbles or the like at the time of sticking, and the adhesive does not adhere to the cutting blade at the time of cutting, or stringing occurs. An object of the present invention is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent processability.

  The present inventors diligently studied to solve the above problems. As a result, it has been found that the above problems can be solved by using a pressure-sensitive adhesive composition having the following specific configuration, and the present invention has been completed.

The present invention includes, for example, the following [1] to [11].
[1] A pressure-sensitive adhesive composition containing (A) a (meth) acrylic copolymer and (B) an isocyanate compound, and storage of a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition at 25 ° C. An adhesive composition having an elastic modulus of 0.8 × 10 ⁵ Pa or more and a storage elastic modulus at 80 ° C. of 5.0 × 10 ⁴ Pa or less.

  [2] A monomer component in which the (meth) acrylic copolymer (A) includes an acrylic acid alkyl ester (a-1), a methacrylic acid alkyl ester (a-2), and a polar group-containing monomer (a-3). The pressure-sensitive adhesive composition according to the above [1], which is a copolymer obtained by copolymerization of

  [3] The (meth) acrylic copolymer (A) is an acrylic acid alkyl ester having 8 or more alkyl groups as the acrylic acid alkyl ester (a-1). The pressure-sensitive adhesive composition according to the above [2], which is a copolymer obtained by using a methacrylic acid alkyl ester having 8 or more carbon atoms in the alkyl group as a-2).

  [4] In the monomer component forming the copolymer (A), the use ratio (a-1: a-2) of the acrylic acid alkyl ester (a-1) and the methacrylic acid alkyl ester (a-2) is The pressure-sensitive adhesive composition according to [2] or [3], wherein the mass ratio is 1: 0.5 to 1: 5.

  [5] The monomer component forming the copolymer (A), wherein the polar group-containing monomer (a-3) includes a hydroxyl group-containing monomer, according to any one of [2] to [4]. Adhesive composition.

[6] The pressure-sensitive adhesive according to any one of [1] to [5], wherein the amount of the acid group-containing monomer used in the copolymerization is 0.1% by mass or less in 100% by mass of the monomer component. Composition.
[7] The weight average molecular weight (Mw) measured by a gel permeation chromatography method of the (meth) acrylic copolymer (A) is 50000 to 450,000 in terms of polystyrene, [1] to [6] The pressure-sensitive adhesive composition according to any one of [6].

[8] The pressure-sensitive adhesive composition according to any one of [1] to [7] above is formed, the storage elastic modulus at 25 ° C. is 0.8 × 10 ⁵ Pa or more, and the storage at 80 ° C. An adhesive layer having an elastic modulus of 5.0 × 10 ⁴ Pa or less.

  [9] The pressure-sensitive adhesive layer according to [8], wherein the gel fraction is 10 to 80% by mass.

  [10] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to [8] or [9].

  [11] A support, a pressure-sensitive adhesive layer according to [8] or [9], and a substrate with a conductive thin film in which a conductive thin film made of a metal or a metal oxide is formed on the surface of the substrate. A laminated body for a touch panel, which is laminated in this order.

  According to the present invention, it is possible to follow an adherend having a level difference without causing bubbles or the like at the time of sticking, and the adhesive does not adhere to the cutting blade at the time of cutting, or stringing occurs. It is possible to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer excellent in processability.

FIG. 1 is a viscoelastic spectrum of the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples.

Hereinafter, the pressure-sensitive adhesive composition, pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet of the present invention will be described.
[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer (A) and an isocyanate compound (B), and is a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. The storage elastic modulus (G′1) at 25 ° C. is 0.8 × 10 ⁵ Pa or more, and the storage elastic modulus (G′2) at 80 ° C. is 5.0 × 10 ⁴ Pa or less. And

  Here, as a characteristic of the pressure-sensitive adhesive composition of the present invention, an adhesive layer having a thickness of 1.0 mm formed under the following conditions was subjected to dynamic viscosity based on JIS K7244 using “Physica MCR300” manufactured by Anton Paar. Storage elastic modulus (G′1) and (G′2) are measured by measuring a viscoelastic spectrum by an elastic measurement method (temperature range of −40 to 160 ° C., temperature increase rate of 3.67 ° C./min, frequency of 10 Hz). ) Can be obtained.

  The pressure-sensitive adhesive layer in the dynamic viscoelasticity measurement is formed as follows. The pressure-sensitive adhesive composition is applied onto a release-treated polyethylene terephthalate film (PET film) so that the thickness after drying is 50 μm, and dried at 90 ° C. for 4 minutes to remove the solvent and form a coating film. To do. The peeled PET film is further bonded to the surface of the coating film opposite to the PET film, and aged for 7 days in a 23 ° C./65% RH environment to form a 50 μm thick adhesive layer. To do. After the aging is completed, the PET film on one side of the obtained pressure-sensitive adhesive sheet is peeled off, and the pressure-sensitive adhesive layers having a thickness of 50 μm are bonded to each other multiple times to form a pressure-sensitive adhesive layer having a final thickness of 1.0 mm. And the said viscoelastic spectrum is measured about this adhesive layer.

  In addition, the said formation conditions of an adhesive layer are described in order to measure the storage elastic modulus as a characteristic of the adhesive composition of this invention, and the adhesive formed using the adhesive composition of this invention Of course, the agent layer is not limited to the layer formed under the above conditions.

In the pressure-sensitive adhesive layer, the storage elastic modulus (G′1) at 25 ° C. is 0.8 × 10 ⁵ Pa or more, preferably 0.9 × 10 ^{5 to} 4.0 × 10 ⁵ Pa, particularly preferably 1. 0 × 10 ^{5 to} 3.0 × 10 ⁵ Pa; the storage elastic modulus (G ′ 2) at 80 ° C. is 5.0 × 10 ⁴ Pa or less, preferably 4.0 × 10 ^{4 to} 1.0 × 10 ³ Pa, particularly preferably 3.5 × 10 ^{4 to} 2.0 × 10 ³ Pa.

  When the storage elastic modulus (G′1) at 25 ° C. is in the above range, the pressure-sensitive adhesive layer is excellent in hardness at room temperature, and processability is improved. For example, when the pressure-sensitive adhesive layer is cut, adhesion of the pressure-sensitive adhesive to the cutting blade, stringing of the pressure-sensitive adhesive layer, and the like are prevented.

  When the storage elastic modulus (G′2) at 80 ° C. is in the above range, the pressure-sensitive adhesive layer is excellent in flexibility. Therefore, when applying the pressure-sensitive adhesive sheet to an adherend while heating and / or pressing (example) : Temperature 50 to 90 ° C., 2 to 10 atm), followability with respect to the level difference of the adherend is improved. For example, when a pressure-sensitive adhesive sheet is applied to an adherend having a step such as a support on which a printed layer is formed or a substrate on which a conductive thin film is formed, the pressure-sensitive adhesive layer has an excellent step following ability. Show. In addition, since the pressure-sensitive adhesive layer that has once followed the step has sufficient flexibility in a high-temperature environment, the pressure-sensitive adhesive layer is unlikely to sag or peel from the step portion even when exposed to a high-temperature environment.

  The gel fraction of the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of the present invention is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and further preferably 30 to 60% by mass. The said gel fraction is a value measured about the adhesive extract | collected, for example by the conditions of an Example description.

  Thus, the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of the present invention has a relatively high storage elastic modulus at room temperature (about 25 ° C.) and a storage elastic modulus at high temperature (about 80 ° C.). Because of the decrease, both step followability and workability are realized. In order to form a pressure-sensitive adhesive layer having storage elastic modulus (G′1) and (G′2) in the above range, for example, the (meth) acrylic copolymer described below as a component of the pressure-sensitive adhesive composition Examples thereof include use of the combination (A) and the isocyanate compound (B).

[(Meth) acrylic copolymer (A)]
As the (meth) acrylic copolymer (A), a monomer component including an acrylic acid alkyl ester (a-1), a methacrylic acid alkyl ester (a-2) and a polar group-containing monomer (a-3) is copolymerized. The resulting copolymer is preferred.

In this specification, acrylic and methacryl are collectively referred to as “(meth) acryl”. Moreover, the structural unit derived from a certain monomer A contained in the polymer is also referred to as “monomer A unit”.
Hereinafter, the monomer component will be described.

<< (Meth) acrylic acid alkyl ester (a-1), (a-2) >>
The acrylic acid alkyl ester (a-1) is preferably an acrylic acid alkyl ester having an alkyl group having 8 or more carbon atoms (CH ₂ ═CH—COOR ¹ ; R ¹ is an alkyl group having 8 or more carbon atoms). Here, as for carbon number of the said alkyl group, 8-18 are more preferable. When a (meth) acrylic copolymer containing such an acrylic acid alkyl ester unit having a long-chain alkyl group is used, appropriate elasticity can be imparted to the pressure-sensitive adhesive layer. For example, by using an alkyl acrylate ester having 8 or more carbon atoms in the alkyl group, a pressure-sensitive adhesive layer having a low storage elastic modulus (80 ° C.) and flexibility at a high temperature tends to be obtained. Moreover, it is preferable also from the point of the low dielectric constant of the adhesive layer obtained.

  Examples of the acrylic acid alkyl ester having an alkyl group having 8 or more carbon atoms include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, undecaacrylate, Examples include lauryl acrylate, stearyl acrylate, and isostearyl acrylate. These may be used alone or in combination of two or more.

As the methacrylic acid alkyl ester (a-2), a methacrylic acid alkyl ester having 8 or more carbon atoms in the alkyl group (CH ₂ ═C (CH ₃ ) —COOR ² ; R ² is an alkyl group having 8 or more carbon atoms. ), Wherein the alkyl group preferably has 8 to 18 carbon atoms. When a (meth) acrylic copolymer including such a methacrylic acid alkyl ester unit having a long-chain alkyl group is used, appropriate elasticity can be imparted to the pressure-sensitive adhesive layer. For example, by using a methacrylic acid alkyl ester having 8 or more carbon atoms in the alkyl group, a pressure-sensitive adhesive layer having a high storage elastic modulus (25 ° C.) and being hard at room temperature tends to be obtained. Moreover, it is preferable also from the point of the low dielectric constant of the adhesive layer obtained.

  Examples of the methacrylic acid alkyl ester having 8 or more carbon atoms in the alkyl group include, for example, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undeca methacrylate, Examples include lauryl methacrylate, stearyl methacrylate, and isostearyl methacrylate. These may be used alone or in combination of two or more.

(Meth) as a monomer component of the acrylic copolymer (A), the number of carbon atoms in the alkyl group of 1 to 7 (meth) acrylic acid alkyl ester _{^{(CH 2 = CR 3 -COOR 4}} ; R 3 is a hydrogen atom or methyl Group, and R ⁴ is an alkyl group having 1 to 7 carbon atoms). However, the amount of alkyl group (meth) acrylic acid alkyl ester having 1 to 7 carbon atoms in the alkyl group is a (meth) acrylic acid alkyl ester having 8 or more carbon atoms in the alkyl group from the viewpoint of storage modulus and dielectric constant. 30 parts by mass or less is preferable with respect to 100 parts by mass in total, more preferably 25 parts by mass or less, and still more preferably 20 parts by mass or less.

  Examples of the alkyl (meth) acrylate having 1 to 7 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl ( Examples include meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and heptyl (meth) acrylate. These may be used alone or in combination of two or more.

  Among 100% by mass of the monomer component forming the (meth) acrylic copolymer (A), an alkyl acrylate having an alkyl group with 8 or more carbon atoms and an alkyl methacrylate having an alkyl group with 8 or more carbon atoms. The total amount is preferably 50 to 99% by mass, more preferably 60 to 97% by mass, and still more preferably 70 to 95% by mass. When the total amount of (meth) acrylic acid alkyl ester having 8 or more carbon atoms in the alkyl group is within the above range, the storage elastic modulus of the resulting pressure-sensitive adhesive layer can be adjusted within the above range (flexibility and hardness From the standpoint of a balance of properties) and a low dielectric constant.

  The use ratio (a-1: a-2) of the acrylic acid alkyl ester (a-1) and the methacrylic acid alkyl ester (a-2) is a mass ratio, preferably 1: 0.5 to 1: 5. Yes, more preferably 1: 0.7 to 1: 4. When the usage rate of (a-2) increases, the storage elastic modulus of the pressure-sensitive adhesive layer tends to increase, and when the usage rate of (a-2) decreases, the storage elastic modulus of the pressure-sensitive adhesive layer decreases. There is a tendency. Moreover, when the usage ratio is in the above range, it is preferable in terms of reducing the dielectric constant of the adhesive layer.

<< Polar group-containing monomer (a-3) >>
Examples of the polar group-containing monomer (a-3) include a hydroxyl group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, a nitrogen-based heterocyclic ring-containing monomer, and a cyano group-containing monomer. However, the acid group-containing monomer is excluded from the polar group-containing monomer (a-3).

  Examples of the hydroxyl group-containing monomer include a hydroxyl group-containing (meth) acrylate, specifically, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate. , Hydroxyalkyl (meth) acrylates such as 6-hydroxyhexyl (meth) acrylate and 8-hydroxyoctyl (meth) acrylate. Carbon number of the hydroxyalkyl group in hydroxyalkyl (meth) acrylate is 2-8 normally, Preferably it is 2-6.

  The polar group-containing monomer (a-3) is preferably a hydroxyl group-containing monomer from the viewpoint of crosslinkability between the (meth) acrylic copolymer (A) and the isocyanate compound (B). The hydroxyl group functions as a crosslinkable functional group with an isocyanate group contained in the isocyanate compound (B).

  The use amount of the hydroxyl group-containing monomer is preferably 0.1 to 25% by mass, more preferably 0.5 to 15% by mass, and further preferably 1 to 10% by mass in 100% by mass of the monomer component. When the use amount of the hydroxyl group-containing monomer is not more than the above upper limit, the viscosity of the (meth) acrylic copolymer (A) does not become too high, and the coating property is good. Further, the relative dielectric constant of the pressure-sensitive adhesive layer does not become too high. When the amount of the hydroxyl group-containing monomer used is equal to or more than the lower limit, a crosslinked structure is effectively formed, and a pressure-sensitive adhesive layer having an appropriate cohesive force can be obtained. Moreover, it is excellent in wet heat whitening resistance.

  Examples of the amino group-containing monomer include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

  Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and N-hexyl (meth) acrylamide.

  Examples of the nitrogen heterocycle-containing monomer include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The total use amount of the polar group-containing monomer (a-3) is preferably 0.1 to 25% by mass, more preferably 0.5 to 15% by mass, and further preferably 1 to 10% by mass in 100% by mass of the monomer component. %.
A polar group containing monomer (a-3) may be used individually by 1 type, and may use 2 or more types.

《Acid group-containing monomer》
In this specification, examples of the acid group include a carboxyl group, an acid anhydride group, a phosphoric acid group, and a sulfuric acid group. Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, mono (meth) acryloyloxyethyl ester succinate, and ω-carboxypolycaprolactone mono (meth) acrylate. Carboxyl group-containing (meth) acrylates such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid. Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride. Examples of the phosphate group-containing monomer include (meth) acrylic monomers having a phosphate group in the side chain, and examples of the sulfate group-containing monomer include (meth) acrylic monomers having a sulfate group in the side chain.

  The total amount of the acid group-containing monomer used in the copolymerization is preferably 0.1% by mass or less, more preferably 0% by mass with respect to 100% by mass of the monomer component. If the total amount of the acid group-containing monomer is within the above range, the (meth) acrylic copolymer (A) will corrode even if it is in direct contact with the electrode / wiring pattern made of metal or metal oxide. There is no. For this reason, the adhesive composition of this invention can be used suitably for a touchscreen use, for example. For example, the acid value of the (meth) acrylic copolymer (A) is preferably 0.5 mgKOH / g or less, more preferably 0.1 mgKOH / g or less.

《Other monomers》
The monomer that forms the (meth) acrylic copolymer (A) is, for example, an alkoxyalkyl (meth) acrylate or an alkoxypolyalkylene glycol as long as the physical properties of the (meth) acrylic copolymer (A) are not impaired. Other (meth) acrylic acid esters such as mono (meth) acrylate, alicyclic group or aromatic ring-containing (meth) acrylate can also be used.

  Examples of the alkoxyalkyl (meth) acrylate include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl ( Examples include meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

  Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, ethoxydiethylene glycol mono (meth) acrylate, And methoxytriethylene glycol mono (meth) acrylate.

  Examples of the alicyclic group or aromatic ring-containing (meth) acrylate include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate.

  Further, within the range where the physical properties of the (meth) acrylic copolymer (A) are not impaired, for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene and octylstyrene. Styrenic monomers such as alkyl styrene, fluoro styrene, chloro styrene, bromo styrene, dibromo styrene, iodinated styrene, nitro styrene, acetyl styrene and methoxy styrene, etc .; copolymerizable monomers such as vinyl acetate can also be used it can.

  In the above copolymerization, the total amount of other monomers used is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, in 100% by mass of the monomer component. Other monomers may be used alone or in combination of two or more.

<< Production conditions for (meth) acrylic copolymer (A) >>
Although the manufacturing conditions of a (meth) acrylic-type copolymer (A) are not specifically limited, For example, it can manufacture by a solution polymerization method. Specifically, a polymerization solvent and a monomer component are charged into a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas, and the reaction start temperature is usually 40 to 100 ° C., preferably 50 to 80 ° C. The reaction system is maintained at a temperature of usually 50 to 90 ° C., preferably 70 to 90 ° C., and allowed to react for 4 to 20 hours.

  The copolymer (A) is obtained, for example, by copolymerizing monomer components including the above-described acrylic acid alkyl ester (a-1), methacrylic acid alkyl ester (a-2), and polar group-containing monomer (a-3). However, it may be a random copolymer or a block copolymer. Among these, a random copolymer is preferable.

  Examples of the polymerization solvent used for the solution polymerization include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; cyclopentane, Cycloaliphatic hydrocarbons such as cyclohexane, cycloheptane, cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether; chloroform, Halogenated hydrocarbons such as carbon tetrachloride, 1,2-dichloroethane, chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, methyl propionate; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone Ketones such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide and sulfolane Etc. These polymerization solvents may be used alone or in combination of two or more.

  Examples of the polymerization initiator used for solution polymerization include azo initiators and peroxide initiators. Specific examples include azo compounds such as 2,2'-isobisisobutyronitrile and peroxides such as benzoyl peroxide and laurium peroxide. Among these, an azo compound is preferable. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2′-azobis (2-cyclopropyl). Propionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile) 2- (carbamoylazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis ( N, N′-dimethyleneisobutylamidine), 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2 2'-azobis (isobutyramide) dihydrate, 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpro Pionate), 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide]. These polymerization initiators may be used alone or in combination of two or more.

  A polymerization initiator is 0.01-5 mass parts normally with respect to 100 mass parts of monomer components which form a (meth) acrylic-type copolymer (A), Preferably it exists in the range of 0.1-3 mass parts. Used in quantity. Moreover, you may add suitably a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent during the said polymerization reaction.

<< Physical properties and content of (meth) acrylic copolymer (A) >>
The weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) method of the (meth) acrylic copolymer (A) is a polystyrene conversion value, and is usually 50000-450,000, preferably 100000-430,000. More preferably, it is 150,000-400000, Most preferably, it is 150,000-380000. By using the copolymer (A) having Mw in the above range and having the above monomer unit, it is easy to balance the adhesive force (the balance of storage elastic modulus (G′1) and (G′2)), It can be set as the adhesive composition of the viscosity suitable for coating.

The molecular weight distribution (Mw / Mn) measured by the GPC method of the (meth) acrylic copolymer (A) is usually 10 or less, preferably 9 or less, more preferably 8 or less.
The glass transition temperature (Tg) of the (meth) acrylic copolymer (A) can be calculated by, for example, the Fox formula from the monomer units constituting the copolymer and the content ratio thereof. For example, the (meth) acrylic copolymer (A) is synthesized so that the glass transition temperature (Tg) determined by the Fox equation is usually −70 to −20 ° C., preferably −60 to −30 ° C. be able to. By using the (meth) acrylic copolymer (A) having such a glass transition temperature (Tg), a pressure-sensitive adhesive composition having excellent pressure-sensitive adhesive properties at room temperature can be obtained.
Fox formula: 1 / Tg = (W ₁ / Tg ₁ ) + (W ₂ / Tg ₂ ) +... + (W _m / Tg _m )
W ₁ + W ₂ + ... + W _m = 1
In the formula, Tg is a glass transition temperature of the (meth) acrylic copolymer (A), Tg ₁ , Tg ₂ ,..., Tg _m are glass transition temperatures of homopolymers composed of the respective monomers, W ₁ , W ₂ ,..., W _m are weight fractions of the structural units derived from the respective monomers in the copolymer (A).

  As the glass transition temperature of the homopolymer composed of each monomer in the Fox formula, for example, the value described in Polymer Handbook Third Edition (Wiley-Interscience 1989) can be used.

  The content of the (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is usually from 60 to 99.99% by mass in 100% by mass of the solid content excluding the organic solvent in the composition. Preferably it is 70-99.95 mass%, Most preferably, it is 80-99.90 mass%. When the content of the (meth) acrylic copolymer (A) is in the above range, the performance as an adhesive is balanced and the adhesive properties are excellent.

[Isocyanate compound (B)]
As the isocyanate compound (B), an isocyanate compound having two or more isocyanate groups in one molecule is usually used. A crosslinked body (network polymer) can be formed by crosslinking the (meth) acrylic copolymer (A) with the isocyanate compound (B).

  The number of isocyanate groups in the isocyanate compound (B) is usually 2 or more, preferably 2 to 10, and more preferably 2 to 5. When the number of isocyanate groups is within the above range, it is preferable from the viewpoint of the crosslinking reaction efficiency between the (meth) acrylic copolymer (A) and the isocyanate compound (B) and the flexibility of the pressure-sensitive adhesive layer.

  Examples of the diisocyanate compound having 2 isocyanate groups in one molecule include aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl. Examples include aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. As the alicyclic diisocyanate, an alicyclic group having 7 to 30 carbon atoms such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, etc. Diisocyanate is mentioned. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

  Examples of the diisocyanate compound having 3 or more isocyanate groups in one molecule include aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4 ', 4 "-triphenylmethane triisocyanate.

  Examples of the isocyanate compound (B) include multimers (for example, dimers or trimers, biurets, isocyanurates) and derivatives (for example, polyhydric alcohols) of difunctional or trifunctional isocyanate compounds. And an addition reaction product of two or more molecules of a diisocyanate compound) and a polymer. Examples of the polyhydric alcohol in the derivative include trivalent or higher alcohols such as trimethylolpropane, glycerin and pentaerythritol as low molecular weight polyhydric alcohols; high molecular weight polyhydric alcohols such as polyether polyols, Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

  Examples of such an isocyanate compound include diphenylmethane diisocyanate trimer, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate biuret or isocyanurate, and a reaction product of trimethylolpropane and tolylene diisocyanate (for example, triethylene diisocyanate). A trimer adduct of diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a trimer adduct of hexamethylene diisocyanate), a polyether polyisocyanate, and a polyester polyisocyanate.

  Among the isocyanate compounds (B), hexamethylene diisocyanate and its trimethylolpropane adduct, isocyanurate of hexamethylene diisocyanate, and biuret of hexamethylene diisocyanate are preferable because of excellent weather resistance.

An isocyanate compound (B) may be used individually by 1 type, and may use 2 or more types.
In the pressure-sensitive adhesive composition of the present invention, the content of the isocyanate compound (B) is usually 0.01 to 10 parts by mass, more preferably 0 with respect to 100 parts by mass of the (meth) acrylic copolymer (A). 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass. When the content is in the above range, it is preferable in that appropriate adhesive force and cohesive force are expressed. When this content exceeds the above range, the resulting pressure-sensitive adhesive layer has too high cohesive force, so that sufficient adhesive force cannot be expressed on the adherend, resulting in poor bonding reliability. There is. When this content is less than the above range, the cohesive force of the pressure-sensitive adhesive layer becomes too low, which may cause adhesive residue or contamination during rework.

[Organic solvent (C)]
The pressure-sensitive adhesive composition of the present invention preferably contains an organic solvent (C) in order to adjust its coatability. As an organic solvent, the polymerization solvent demonstrated in the column of the (meth) acrylic-type copolymer (A) is mentioned. For example, the pressure-sensitive adhesive composition can be prepared by mixing the solution containing the (meth) acrylic copolymer (A) and the polymerization solvent obtained by the above copolymerization and the isocyanate compound (B). . In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent is usually 20 to 90% by mass, preferably 30 to 70% by mass.

[Additive]
In addition to the above components, the pressure-sensitive adhesive composition of the present invention includes an antioxidant, a light stabilizer, a metal corrosion inhibitor, a tackifier, a plasticizer, an antistatic agent, and a silane cup as long as the effects of the present invention are not impaired. You may contain 1 type, or 2 or more types selected from a ring agent, a crosslinking accelerator, and a rework agent.

[Preparation of pressure-sensitive adhesive composition]
The pressure-sensitive adhesive composition of the present invention is prepared by mixing the (meth) acrylic copolymer (A), the isocyanate compound (B), and other components as required by a conventionally known method. Can do. For example, an isocyanate compound (B) and, if necessary, other components are blended in a solution containing the copolymer and a polymerization solvent obtained when the (meth) acrylic copolymer (A) is synthesized. To do.

(Adhesive layer)
The pressure-sensitive adhesive layer of the present invention is formed from the above-mentioned pressure-sensitive adhesive composition.
The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a storage elastic modulus (G′1) at 25 ° C. of 0.8 × 10 ⁵ Pa or more, preferably 0.9 × 10 ^{5 to} 4.0. × 10 ⁵ Pa, particularly preferably 1.0 × 10 ^{5 to} 3.0 × 10 ⁵ Pa; the storage elastic modulus (G ′ 2) at 80 ° C. is 5.0 × 10 ⁴ Pa or less, preferably 4 0.0 × 10 ^{4 to} 1.0 × 10 ³ Pa, particularly preferably 3.5 × 10 ^{4 to} 2.0 × 10 ³ Pa.

  The storage elastic modulus is, for example, a value calculated from a dynamic viscoelastic spectrum measured for the laminate by laminating the adhesive layers a plurality of times to produce a laminate having a thickness of about 1.0 mm. .

  When the storage elastic modulus (G′1) at 25 ° C. is in the above range, the pressure-sensitive adhesive layer of the present invention is excellent in hardness at room temperature and has improved workability. For example, when the pressure-sensitive adhesive layer is cut, adhesion of the pressure-sensitive adhesive to the cutting blade, stringing of the pressure-sensitive adhesive layer, and the like are prevented.

  When the storage elastic modulus (G′2) at 80 ° C. is in the above range, the pressure-sensitive adhesive layer of the present invention is excellent in flexibility. Therefore, when the pressure-sensitive adhesive sheet is applied to an adherend while heating and / or pressing. (Example: temperature 50 to 90 ° C., 2 to 10 atm), the followability to the level difference of the adherend is improved. For example, when a pressure-sensitive adhesive sheet is applied to an adherend having a step such as a support on which a printed layer is formed or a substrate on which a conductive thin film is formed, the pressure-sensitive adhesive layer of the present invention has excellent step following. Showing gender. In addition, since the pressure-sensitive adhesive layer that has once followed the step has sufficient flexibility in a high-temperature environment, the pressure-sensitive adhesive layer is unlikely to sag or peel from the step portion even when exposed to a high-temperature environment.

Thus, the pressure-sensitive adhesive layer of the present invention has both workability and step following ability.
The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a gel fraction of preferably 10 to 80% by mass, more preferably 20 to 70% by mass, from the viewpoints of cohesive strength, adhesive strength, and removability. More preferably, it is 30-60 mass%.

  The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a relative dielectric constant at a frequency of 100 Hz, preferably 5.0 or less, more preferably 2.0 to 4.5, still more preferably 2.5 to 4. .0. An adhesive layer having a relative dielectric constant in the above range can be suitably used for, for example, touch panel applications.

  The pressure-sensitive adhesive layer having a thickness of 50 μm formed from the pressure-sensitive adhesive composition of the present invention is the absolute value of the difference in haze values before and after standing even after standing in a 60 ° C./90% RH environment for 500 hours. Is usually 5.0% or less, more preferably 2.0% or less, and is excellent in whitening prevention. Here, “%” is a unit of haze value. For this reason, also when the said adhesive layer is used for an image display apparatus or an input device, it is excellent in the visibility of an image display part.

Details of the measurement conditions of the relative dielectric constant and haze value are as described in the examples.
The pressure-sensitive adhesive layer of the present invention specifically crosslinks the (meth) acrylic copolymer (A) with the isocyanate compound (B) by, for example, advancing the crosslinking reaction in the above-mentioned pressure-sensitive adhesive composition. Is obtained.

  The conditions for forming the pressure-sensitive adhesive layer are, for example, as follows. The pressure-sensitive adhesive composition of the present invention is applied on a support and varies depending on the type of solvent, but is usually 50 to 150 ° C., preferably 60 to 100 ° C., usually 1 to 5 minutes, preferably 3 to 5 minutes. Then, the solvent is removed and a coating film is formed. The film thickness of the dried coating film is usually 10 to 300 μm, preferably 20 to 180 μm.

  The pressure-sensitive adhesive layer is preferably formed under the following conditions. After apply | coating the adhesive composition of this invention on a support body and sticking a cover film on the coating film formed on the said conditions, normally 3 days or more, Preferably it is 7-10 days, Usually 5-60 degreeC, It is preferably cured under an environment of 15 to 40 ° C., usually 20 to 80% RH, preferably 30 to 70% RH. When crosslinking is performed under the aging conditions as described above, a crosslinked body (network polymer) can be efficiently formed.

  As a method for applying the pressure-sensitive adhesive composition, a predetermined thickness is obtained by a known method such as spin coating, knife coating, roll coating, bar coating, blade coating, die coating, or gravure coating. Thus, a method of applying and drying can be used.

  Examples of the support and cover film include polyester films such as polyethylene terephthalate (PET); and plastic films such as polyolefin films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. Examples of the pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet having only the pressure-sensitive adhesive layer, a base material, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on both surfaces of the base material, the base material, and one of the base materials. Examples thereof include a single-sided pressure-sensitive adhesive sheet having the above-mentioned pressure-sensitive adhesive layer formed on the surface, and a pressure-sensitive adhesive sheet having a peel-treated cover film attached to the surface of the pressure-sensitive adhesive sheet that is not in contact with the base material.

  Examples of the substrate and the cover film include polyester films such as polyethylene terephthalate (PET); and plastic films such as polyolefin films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer.

  The film thickness of the pressure-sensitive adhesive layer can be determined in consideration of, for example, a step (step following property) on the adherend surface and transparency. The thickness of the pressure-sensitive adhesive layer is usually 10 to 300 μm, preferably 20 to 180 μm. Although the film thickness of a base material and a cover film is not specifically limited, Usually, 5-150 micrometers, Preferably it is 10-100 micrometers.

[Application]
The pressure-sensitive adhesive composition, pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet of the present invention has a use for manufacturing an image display device such as a liquid crystal display device or electronic paper, an optical method, an ultrasonic method, a capacitance method, a resistance film method, or the like. It can use suitably for the manufacture use of input devices, such as a touch panel. In particular, it is suitably used for manufacturing a capacitive touch panel.

  The pressure-sensitive adhesive composition, pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet of the present invention is a conductive thin film in which a support and a conductive thin film (eg, electrode, wiring pattern) made of metal or metal oxide are formed on the surface of the substrate. It can use suitably for a lamination use with an attached base material.

  Examples of the support include glass plates; transparent plastic films such as polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA). The thickness of the support is usually 25 to 2000 μm.

  The support may have a printing layer in order to improve the design properties of a liquid crystal display device, a touch panel, and the like on the peripheral portion of the surface that comes into contact with the pressure-sensitive adhesive layer. The thickness of the print layer is usually 10 to 50 μm, and the cross section of the print layer is, for example, rectangular.

  Examples of the conductive thin film constituting the substrate with the conductive thin film include a thin film made of a metal, a metal oxide, or a mixture thereof, such as indium tin oxide (ITO), antimony tin oxide (ATO), and tin oxide. The transparent thin film which consists of is mentioned. The thickness of the conductive thin film is usually 10 to 200 nm. As a base material which comprises a base material with an electroconductive thin film, transparent plastic films, such as a polyethylene terephthalate film, are mentioned, for example. The thickness of the substrate is usually 25 to 1000 μm.

  The pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention is disposed so as to adhere the support and the substrate with the conductive thin film, and this pressure-sensitive adhesive layer is a conductive layer formed on the substrate with the conductive thin film. When the printed layer is formed on the support, it is also in direct contact with the printed layer.

  The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a specific storage elastic modulus as described above, and is excellent in step following ability, and therefore is based on an electrode / wiring pattern or a printed layer. Even if there is a step, no gap is formed. Further, in the present invention, since the pressure-sensitive adhesive layer can be substantially free of acid groups, even if the pressure-sensitive adhesive layer is in direct contact with a conductive thin film made of metal or metal oxide, Corrosion of the conductive thin film can be prevented, and an increase in the resistance value can be suppressed. For this reason, even in a capacitive touch panel, the pressure-sensitive adhesive layer directly contacts the conductive thin film forming the stepped electrode / wiring pattern, but the pressure-sensitive adhesive layer does not change the characteristics of the conductive thin film. Has the advantage.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. In the following description of Examples and the like, “part” means “part by mass” unless otherwise specified.
Each measured value in the examples was determined by the following method.

[Average molecular weight]
About the (meth) acrylic-type copolymer, the weight average molecular weight (Mw) and number average molecular weight (Mn) by standard polystyrene conversion were calculated | required by the gel permeation chromatography (GPC) method on the following conditions.
-Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)
-GPC column configuration: The following five columns (all manufactured by Tosoh Corporation)
(1) TSK-GEL HXL-H (guard column)
(2) TSK-GEL G7000HXL
(3) TSK-GEL GMHXL
(4) TSK-GEL GMHXL
(5) TSK-GEL G2500HXL
Sample concentration: 1.0 mg / cm ³ (diluted with tetrahydrofuran)
Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 cm ³ / min
-Column temperature: 40 ° C

[Gel fraction]
About 0.1 g of the pressure-sensitive adhesive was collected from the pressure-sensitive adhesive sheet obtained in the Examples and the like, added with 30 mL of ethyl acetate and shaken for 4 hours, and then the contents of the sample bottle were placed on a 200-mesh stainless steel wire mesh. After filtration, the residue on the wire mesh was dried at 100 ° C. for 2 hours, the dry weight was measured, and the gel fraction was determined by the following formula.
・ Gel fraction (%) = (weight after drying / weight collected of adhesive) × 100 (%)

[Storage modulus]
Adhesive layers having a thickness of 50 μm obtained in Examples and the like are bonded together several times in an environment of 23 ° C./50% RH, treated in an autoclave at 50 ° C./5 atm for 20 minutes, and adhesive having a thickness of 1.0 mm. An agent layer was prepared. For the pressure-sensitive adhesive layer having a thickness of 1.0 mm, a dynamic viscoelasticity measurement method (temperature range: −40 to 160 ° C., temperature rising rate: 3.67 ° C.) based on JIS K7244 using “Physica MCR300” manufactured by Anton Paar. / Min, conditions of frequency 10 Hz), the viscoelastic spectrum was measured, and the storage elastic modulus at temperatures of 25 ° C. and 80 ° C. was determined.

[Relative permittivity]
Prepare two PSA sheets obtained in Examples, etc., peel off the peeled PET film from each of them, and then bond the PSA layers together to prepare a PSA sheet with a thickness of 100 μm. The pressure-sensitive adhesive layer was transferred to a copper foil, and a copper foil having a thickness of 100 μm was further stuck on the pressure-sensitive adhesive layer to obtain a measurement sample. It connected to copper foil using Toyo Technica LCR meter 6440B, and calculated the dielectric constant (100 Hz) in 23 degreeC / 50% RH atmosphere.

[180 ° peeling strength (adhesive strength)]
The PET film on one side of the pressure-sensitive adhesive sheet obtained in Examples and the like was peeled off, the entire pressure-sensitive adhesive layer was bonded to a 100 μm-thick PET film, and cut into 25 mm × 150 mm to prepare test pieces. Subsequently, the other peeled PET film was peeled off, and the pressure-sensitive adhesive layer exposed was pasted on a glass plate and subjected to 3 reciprocating pressures with a roller having a weight of 2 kg. After the pressure bonding, the sample is left for 2 hours in an atmosphere of 23 ° C./50% RH, and then the short side of the test piece is peeled off and pulled in a 180 ° direction at a speed of 300 mm / min. It was.

[Wet heat whitening (haze)]
The PET film on one side of the pressure-sensitive adhesive sheet obtained in Examples and the like was peeled off, and the entire pressure-sensitive adhesive layer was bonded to a 100 μm-thick PET film and cut into a size of 50 mm × 50 mm. Next, the other peeled PET film was peeled off and the exposed adhesive layer was bonded to a glass plate, treated with an autoclave at 50 ° C./5 atm for 20 minutes, and then subjected to 1 in a 23 ° C./50% RH atmosphere. The test piece was created by allowing to stand for a period of time.

  After measuring the haze before the endurance test of the prepared test piece, the test piece was left in a 60 ° C./90% RH environment for 500 hours. The test piece was taken out and allowed to stand at room temperature for 1 hour, and then the haze was measured to determine the difference from the haze before the durability test. For the measurement of haze, MH-150 (manufactured by Murakami Color Research Laboratory Co., Ltd.) was used.

[Step following capability]
The PET film on one side of the pressure-sensitive adhesive sheet obtained in Examples and the like was peeled off, the entire pressure-sensitive adhesive layer was bonded to a 100 μm-thick PET film, and cut into 50 mm × 50 mm to prepare test pieces. Next, a 20 μm thick PET film cut to 15 mm × 15 mm is placed on a glass plate, and a test piece (50 mm × 50 mm) is formed so that the entire surface of the PET film (15 mm × 15 mm) on the glass plate is covered with an adhesive layer. After being treated with an autoclave at 50 ° C./5 atm for 20 minutes, it was allowed to stand at room temperature for 1 hour, and the appearance of the step portion was visually observed.
AA: Bubbles cannot be visually confirmed at the stepped portion.
BB: Bubbles can be clearly confirmed visually at the stepped portion.

[Cutability]
30 pressure-sensitive adhesive sheets obtained in Examples and the like were cut using a Thomson punching machine with a 50 mm × 50 mm Thomson blade. Immediately after cutting, the shape of the end portion was observed, and it was determined that A was the case where no sticking out of the glue, the end portion was crushed, or one of the adhesive layer defects was found in 30 sheets, and B was seen.

[Example 1]
In a reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet pipe, 39 parts of 2-ethylhexyl methacrylate (2-EHMA), 35 parts of lauryl methacrylate (LMA), 2-ethylhexyl acrylate (2-EHA) 20 Parts, 2-hydroxyethyl acrylate (2-HEA) 5 parts, acrylamide (AM) 1 part, and ethyl acetate solvent 70 parts were heated to 80 ° C. while introducing nitrogen gas. Next, 0.3 part of azobisisobutyronitrile (AIBN) was added, and a polymerization reaction was performed at 80 ° C. for 8 hours in a nitrogen atmosphere. After completion of the reaction, it was diluted with ethyl acetate to prepare a polymer solution having a solid content concentration of 50% by mass. The obtained (meth) acrylic copolymer had a weight average molecular weight (Mw) of 380000 and a molecular weight distribution (Mw / Mn) of 7.5.

  With respect to the obtained (meth) acrylic copolymer solution (solid content concentration 50% by mass) and 100 parts (solid content) of the (meth) acrylic copolymer contained in the solution, an HDI isocyanate compound “ 0.4 parts of “TPA-100” (manufactured by Asahi Kasei Chemicals Corporation) was mixed to obtain an adhesive composition.

  The obtained pressure-sensitive adhesive composition was applied onto a peeled PET film having a thickness of 38 μm at a liquid temperature of 25 ° C. so that the thickness after drying was 50 μm, and dried at 90 ° C. for 4 minutes to obtain a solvent. Was removed to form a coating film. A PET film having a thickness of 38 μm was further bonded to the surface of the coating film opposite to the surface of the PET film, and aged for 7 days in a 23 ° C./65% RH environment, and an adhesive having a thickness of 50 μm. A pressure-sensitive adhesive sheet having an agent layer was obtained.

[Examples 2-7, Comparative Examples 1-4]
A (meth) acrylic copolymer solution was obtained in the same manner as in Example 1 except that the monomer components listed in Table 1 were used. Next, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 50 μm were obtained in the same manner as in Example 1 except that the (meth) acrylic copolymer solution was changed as shown in Table 1. .

As shown in Table 1, when the storage elastic modulus (25 ° C.) of the pressure-sensitive adhesive layer is 0.8 × 10 ⁵ Pa or more and the storage elastic modulus (80 ° C.) is 5.0 × 10 ⁴ Pa or less, Excellent step following ability and cutting ability. On the other hand, as shown in Comparative Examples 1 and 2, when the storage elastic modulus (80 ° C.) of the pressure-sensitive adhesive layer exceeds 5.0 × 10 ⁴ Pa, the step following ability is inferior. When the storage elastic modulus (25 ° C.) of the agent layer was less than 0.8 × 10 ⁵ Pa, the cutting property was inferior.

Claims (11)

(A) a (meth) acrylic copolymer;
(B) an adhesive composition containing an isocyanate compound,
Of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition,
A pressure-sensitive adhesive composition having a storage elastic modulus at 25 ° C. of 0.8 × 10 ⁵ Pa or more and a storage elastic modulus at 80 ° C. of 5.0 × 10 ⁴ Pa or less.   The (meth) acrylic copolymer (A) is a copolymer of monomer components including an acrylic acid alkyl ester (a-1), a methacrylic acid alkyl ester (a-2), and a polar group-containing monomer (a-3). The pressure-sensitive adhesive composition according to claim 1, which is a copolymer obtained as described above.   The (meth) acrylic copolymer (A) is an acrylic acid alkyl ester having 8 or more alkyl groups as the acrylic acid alkyl ester (a-1), and the methacrylic acid alkyl ester (a-2). The pressure-sensitive adhesive composition according to claim 2, which is a copolymer obtained by using a methacrylic acid alkyl ester having an alkyl group having 8 or more alkyl groups.   In the monomer component that forms the copolymer (A), the use ratio (a-1: a-2) of the alkyl acrylate ester (a-1) and the alkyl methacrylate ester (a-2) is a mass ratio. The pressure-sensitive adhesive composition according to claim 2 or 3, wherein the ratio is 1: 0.5 to 1: 5.   The pressure-sensitive adhesive composition according to any one of claims 2 to 4, wherein in the monomer component forming the copolymer (A), the polar group-containing monomer (a-3) includes a hydroxyl group-containing monomer.   The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the amount of the acid group-containing monomer used in the copolymerization is 0.1% by mass or less in 100% by mass of the monomer component.   The weight average molecular weight (Mw) measured by the gel permeation chromatography method of the said (meth) acrylic-type copolymer (A) is 50000-450,000 in polystyrene conversion, Any one of Claims 1-6. Item 1. The pressure-sensitive adhesive composition according to item 1. It is formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 7,
A pressure-sensitive adhesive layer having a storage elastic modulus at 25 ° C. of 0.8 × 10 ⁵ Pa or more and a storage elastic modulus at 80 ° C. of 5.0 × 10 ⁴ Pa or less.   The pressure-sensitive adhesive layer according to claim 8, wherein the gel fraction is 10 to 80% by mass.   A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to claim 8.   The support, the pressure-sensitive adhesive layer according to claim 8 or 9, and a substrate with a conductive thin film in which a conductive thin film made of metal or metal oxide is formed on the surface of the substrate are laminated in this order. A laminate for a touch panel characterized by the following.

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