JP2019014778A - Adhesive composition, adhesive sheet and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition capable of improving step followability and durability without increasing the relative permittivity when an adhesive layer is formed. A pressure-sensitive adhesive composition containing a cross-linking acrylic polymer, a cross-linking agent, and an alkoxysilyl group-containing acrylic polymer, wherein the cross-linking acrylic polymer is contained in an amount of 50% by mass or more based on the pressure-sensitive adhesive composition. When the weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000, the alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C., and a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive composition is formed. A pressure-sensitive adhesive composition; a pressure-sensitive adhesive sheet; a laminate having a pressure-sensitive adhesive layer having a specific dielectric constant of 3.5 or less at a frequency of 1 MHz. [Selection diagram] None

Description

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

  In recent years, in various fields, a display device such as a liquid crystal display (LCD), a display device such as a touch panel, and an input device are widely used. In particular, capacitive touch panels are rapidly spreading due to their functionality. In the production of these display devices and input devices, an adhesive sheet is used for the purpose of bonding optical members, and the adhesive sheet is also used for bonding between the display device and the input device.

  In a capacitive touch panel, when a finger is brought close to the surface, the capacitance between a plurality of electrodes changes simultaneously, and the position can be detected with high accuracy by measuring the ratio of the amount of current. However, when this method is enlarged, the malfunction of the touch panel increases. In order to cope with such a problem, it is conceivable to use an adhesive sheet having a low relative dielectric constant.

On the other hand, an adhesive capable of realizing an adhesive layer with a low relative dielectric constant is known (see Patent Document 1).
Patent Document 1 was obtained by polymerizing a monomer component containing 19 to 99.5% by weight of an alkyl (meth) acrylate having a branched alkyl group having 10 to 24 carbon atoms at the terminal of the ester group (meth). A pressure-sensitive adhesive containing an acrylic polymer is described.

JP, 2006-172865, A JP, 2006-50255, A

However, it has been found that when the pressure-sensitive adhesive layer is formed on the adherend having a stepped portion using the pressure-sensitive adhesive described in Patent Document 1, air remains in the entire stepped portion.
On the other hand, there is known a method of imparting appropriate rigidity while enhancing the step following property when an adhesive layer is formed on an adherend having a step portion (for example, Patent Document 2). Patent Document 2 discloses a sheet-like pressure-sensitive adhesive for fixing a transparent hard plate provided with a step portion to the surface of an image display device, and a (meth) acrylic acid ester polymer as a component (A), (B) It consists of an adhesive composition containing a polymer-type silane coupling agent as a component and a crosslinking agent as a component (C), and the polymer-type silane coupling agent as a component (B) is added to the polymer chain. On the other hand, it is a polymer type silane coupling agent formed by bonding a plurality of alkoxysilyl groups and a plurality of organic functional groups, and the film thickness is set to a value within the range of 30 to 200 μm. After pressurization, the adhesive strength measured after being left in an environment of 23 ° C. and 50% RH for 24 hours is set to a value of 10 N / 25 mm or more, and the gel fraction is set to a value within the range of 50 to 80%. Do Over preparative shaped adhesive agent. However, Patent Document 2 has no description regarding the relative dielectric constant.

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive composition that can improve the step following ability and durability without increasing the relative dielectric constant when a pressure-sensitive adhesive layer is formed.

Here, when forming the adhesive sheet used for optical uses like patent document 1, etc., the active energy ray hardening-type adhesive composition or thermosetting-type adhesive composition containing a base polymer is used. Yes. As the base polymer, acrylic monomer units such as alkyl (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, polyether (meth) acrylate and the like are excellent in transparency. An acrylic base polymer containing is used.
However, the inventors of the present invention simply changed the structure of the base polymer, and when the pressure-sensitive adhesive layer was formed, the step following ability was inferior when the relative dielectric constant was lowered, and conversely, when the step following ability was improved, the relative dielectric constant was reduced. It has been found that it is difficult to improve both the relative permittivity and the step following ability, such as increasing.
As a result of intensive studies to solve the above-mentioned problems, the present inventors obtained a crosslinkable acrylic polymer from an alkoxysilyl group-containing acrylic polymer having a weight average molecular weight of 400 to 5000 and liquid or oily at 20 ° C. By using together, it has been found that the step followability and durability can be improved without increasing the relative dielectric constant when the pressure-sensitive adhesive layer is formed, and the present invention has been completed.

Specifically, the configurations of the present invention and preferred embodiments of the present invention are as follows.
[1] A pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer, a crosslinking agent, and an alkoxysilyl group-containing acrylic polymer,
Containing 50% by mass or more of the crosslinkable acrylic polymer with respect to the pressure-sensitive adhesive composition,
The weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000,
The alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C.,
A pressure-sensitive adhesive composition having a relative dielectric constant of 3.5 or less at a frequency of 1 MHz when a pressure-sensitive adhesive layer that is a cured product of the pressure-sensitive adhesive composition is formed.
[2] The crosslinkable functional group of the crosslinkable acrylic polymer is one type or one or more types selected from any of a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group, and an isocyanate group. ] The adhesive composition of description.
[3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the crosslinking agent is one or more types selected from any one of a bifunctional or higher functional epoxy compound and a bifunctional or higher functional isocyanate compound. .
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the alkoxysilyl group-containing acrylic polymer is contained in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the crosslinkable acrylic polymer.
[5] The pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the alkoxysilyl group-containing acrylic polymer is contained in an amount of 4 to 15 parts by mass with respect to 100 parts by mass of the crosslinkable acrylic polymer.
[6] having an adhesive layer;
The adhesive sheet whose adhesive layer is a hardened | cured material of the adhesive composition as described in any one of [1]-[5].
[7] The first release sheet is provided on one surface of the pressure-sensitive adhesive layer,
A second release sheet is provided on the other surface of the pressure-sensitive adhesive layer,
The adhesive sheet according to [6], wherein the first release sheet and the second release sheet have different release forces.
[8] An adherend is provided on at least one surface of the pressure-sensitive adhesive sheet according to [6] or [7],
A laminate in which the adherend has a stepped portion.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive composition which can make level | step difference followability and durability favorable can be provided, without raising the dielectric constant at the time of forming an adhesive layer.
ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet excellent in level | step difference followability and durability can be provided, without raising a dielectric constant.

FIG. 1 is a cross-sectional view illustrating an example of the configuration of the pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a cross-sectional view illustrating an example of the configuration of the laminate of the present invention.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Adhesive composition)
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer, a crosslinking agent and an alkoxysilyl group-containing acrylic polymer,
Containing 50% by mass or more of the crosslinkable acrylic polymer with respect to the pressure-sensitive adhesive composition,
The weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000,
The alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C.,
When a pressure-sensitive adhesive layer that is a cured product of the pressure-sensitive adhesive composition is formed, the relative dielectric constant of the pressure-sensitive adhesive layer at a frequency of 1 MHz is 3.5 or less.
With this configuration, the pressure-sensitive adhesive composition of the present invention can improve the step following ability and durability without increasing the relative dielectric constant when the pressure-sensitive adhesive layer is formed. By including the pressure-sensitive adhesive composition as a separate material having a low molecular weight and having an alkoxysilyl group, not a copolymer component of the crosslinkable acrylic polymer, the step followability and durability are improved without increasing the relative dielectric constant. It can also play the role of a plasticizer.
When a pressure-sensitive adhesive layer that is a cured product of the pressure-sensitive adhesive composition is formed, the relative dielectric constant of the pressure-sensitive adhesive layer at a frequency of 1 MHz is preferably 3.3 or less.
The pressure-sensitive adhesive composition preferably has a solid content concentration of 20 to 60% by mass, and more preferably 30 to 50% by mass in a state containing the solvent described later.
Hereinafter, the preferable aspect of the adhesive composition of this invention is demonstrated.

<Crosslinkable acrylic polymer>
There is no restriction | limiting in particular as a crosslinkable acrylic polymer, A well-known crosslinkable acrylic polymer can be used.
The crosslinkable acrylic polymer is a (meth) acrylic monomer having a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms and a crosslinkable functional group It is preferable to contain the unit (a2) derived from.
The crosslinkable acrylic polymer has a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms and a (meth) acrylic monomer having a crosslinkable functional group. When the derived unit (a2) is contained, a pressure-sensitive adhesive layer having a sufficiently low relative dielectric constant can be formed from a pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a low relative dielectric constant is preferably used for adhesion of an optical member constituting a display device equipped with a touch panel.

The unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms contained in the crosslinkable acrylic polymer has an alkyl group having 5 or more carbon atoms, And since such an alkyl group is a branched structure, its molar volume is large and its density is low. For this reason, the molar volume of the crosslinkable acrylic polymer can be increased and the density can be decreased. In addition, since the unit (a1) has an alkyl group having 9 or less carbon atoms, the volume shrinkage when the polymer is used can be suppressed, and the molar volume of the crosslinkable acrylic polymer can be maintained large. Conceivable. As a result, an adhesive layer having a low relative dielectric constant can be formed.
The crosslinkable acrylic polymer is preferably one having transparency that does not deteriorate the visibility of the display device.
In the present specification, the “unit” is a repeating unit (monomer unit) constituting the polymer.

<Unit derived from non-crosslinkable (meth) acrylic acid ester (a1)>
The unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester is a repeating unit derived from the (meth) acrylic acid alkyl ester having a branched alkyl group having 5 to 9 carbon atoms. Examples of such (meth) acrylic acid alkyl ester include isopentyl (meth) acrylate, isohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isoheptyl (meth) acrylate, isooctyl (meth) acrylate, Examples thereof include isononyl (meth) acrylate. These may be used alone or in combination of two or more. Among these, as the non-crosslinkable (meth) acrylic acid ester unit (a1), 2-ethylhexyl (meth) acrylate is preferably used, and 2-ethylhexyl acrylate (2-EHA) and 2-ethylhexyl methacrylate (2-EHMA) are preferably used. It is more preferable to use

  The number of carbon atoms of the branched alkyl group contained in the unit (a1) derived from the non-crosslinkable (meth) acrylic ester may be 5 or more and 9 or less, but is preferably 7 or more and 9 or less. By setting the number of carbon atoms of the branched alkyl group within the above range, a pressure-sensitive adhesive layer having a sufficiently low relative dielectric constant can be formed. Moreover, by setting the carbon number of the branched alkyl group within the above range, it is easy to control the degree of polymerization of the crosslinkable acrylic polymer, and a pressure-sensitive adhesive composition excellent in processability can be obtained.

  The content of the unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester in the crosslinkable acrylic polymer is preferably 60% by mass or more based on the total mass of the crosslinkable acrylic polymer, 80 More preferably, the content is at least 90% by mass, even more preferably at least 90% by mass. When the content of the unit (a1) is within the above range, the relative dielectric constant of the pressure-sensitive adhesive layer can be sufficiently lowered, and the durability of the pressure-sensitive adhesive layer can be further increased.

<Unit (a2) derived from (meth) acrylic monomer having crosslinkable functional group>
In the present invention, the crosslinkable functional group of the crosslinkable acrylic polymer is one kind selected from a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group (preferably a glycidyl group), and an isocyanate group. One or more types are preferred. In this case, as the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group, a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, Examples thereof include an amide group-containing monomer unit, an epoxy group (preferably glycidyl group) -containing monomer unit, and an isocyanate group-containing monomer unit.
The (meth) acrylic acid monomer having a crosslinkable functional group is preferably a methacrylic acid monomer rather than an acrylic acid monomer from the viewpoint of not increasing the relative dielectric constant.
As the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group, a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, a glycidyl group-containing Monomer units are preferred, and hydroxy group-containing monomer units are more preferred. These monomer units may be one type or two or more types.
The hydroxy group-containing monomer unit is a repeating unit derived from the hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate, (Meth) acrylic acid lactones such as (meth) acrylic acid mono (diethylene glycol) (meth) acrylic acid [(mono, di or poly) alkylene glycol] and (meth) acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include repeating units derived from amino group-containing monomers such as (meth) acrylamide and allylamine.
Examples of the glycidyl group-containing monomer unit include repeating units derived from glycidyl group-containing monomers such as glycidyl (meth) acrylate.
Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.

  The content of the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group in the crosslinkable acrylic polymer is 0.01% by mass or more based on the total mass of the crosslinkable acrylic polymer. Preferably, it is 0.5% by mass or more, more preferably 1% by mass or more. The content of the unit (a2) is preferably 40% by mass or less, more preferably 35% by mass or less, and particularly preferably 15% by mass or less. If the content of the unit (a2) is not less than the lower limit value of the above range, it has sufficient crosslinkability, and if it is not more than the upper limit value of the above range, the necessary adhesive properties can be maintained and the relative dielectric constant can be maintained. Can form a sufficiently low pressure-sensitive adhesive layer.

<Other monomer units>
The crosslinkable acrylic polymer may be a unit other than the unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester and the (meth) acrylic monomer unit (a2) having a crosslinkable functional group, if necessary. It may have a monomer unit. Examples of other monomers include (meth) acrylic acid ester units having 4 or less carbon atoms or 10 or more carbon atoms. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-decyl (meth) acrylate, lauryl (meth) acrylate , Stearyl (meth) acrylate, and the like. Moreover, as another (meth) acrylic acid ester unit, the (meth) acrylic acid ester unit which has a C5-C9 linear alkyl group may be included. Specifically, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, etc. Can be mentioned. Furthermore, as other (meth) acrylic acid ester units, (meth) acrylic acid ester units having a cyclic group such as (meth) acrylic acid cyclohexyl, (meth) acrylic acid benzyl, (meth) acrylonitrile, vinyl acetate, Examples include styrene, vinyl chloride, vinyl pyrrolidone, vinyl pyridine and the like. The content of other monomer units in the crosslinkable acrylic polymer is preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 1% by mass or less.

<Physical properties of crosslinkable acrylic polymer>
The weight average molecular weight of the crosslinkable acrylic polymer is preferably from 100,000 to 2,000,000, more preferably from 300,000 to 1,500,000. By setting the weight average molecular weight within the above range, sufficient step following ability can be ensured. In addition, the weight average molecular weight of a crosslinkable acrylic polymer is a value before bridge | crosslinking with a crosslinking agent. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and obtained on the basis of polystyrene. As the crosslinkable acrylic polymer, a commercially available one may be used, or one synthesized by a known method may be used.

  The glass transition temperature (Tg) of the crosslinkable acrylic polymer is preferably -80 ° C or higher and -15 ° C or lower, more preferably -75 ° C or higher and -18 ° C or lower, and -70 ° C or higher and -18 ° C. More preferably, it is as follows. By setting the glass transition temperature (Tg) of the crosslinkable acrylic polymer within the above range, the cohesive force when used as the pressure-sensitive adhesive layer can be further increased. Thereby, the adhesive layer excellent in durability and excellent in adhesive force is obtained.

<Alkoxysilyl group-containing acrylic polymer>
In the present invention, the weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000, and the alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C.
The fact that the alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C. means that the viscosity measured by a B-type viscometer measured at 20 ° C. is 10,000 mPa · s or less.
The glass transition temperature (Tg) of the alkoxysilyl group-containing acrylic polymer is preferably −30 ° C. or lower, and more preferably −40 ° C. or lower.

There is no restriction | limiting in particular as an alkoxy silyl group containing acrylic polymer. The alkoxysilyl group-containing acrylic polymer is preferably a copolymer of an acrylate monomer and a vinyl monomer or acrylic monomer having a trialkoxysilyl group.
The alkoxysilyl group-containing acrylic polymer preferably has a repeating unit derived from acrylate or a repeating unit derived from methacrylate as the main chain skeleton.
The linking group from the terminal oxygen atom to the Si atom of the alkoxysilyl group in the (meth) acrylic acid-derived structure of the alkoxysilyl group-containing acrylic polymer, that is, — (CH ₂ —C (R ⁰ ) (COO —)) — The linking group from the oxygen atom of the skeleton to the alkoxysilyl group preferably has a long linking chain length from the viewpoint of reducing the relative dielectric constant.
The terminal oxygen atom of the structure derived from (meth) acrylic acid and the Si atom of the alkoxysilyl group may be directly bonded. The upper limit of the linking chain length of the linking group from the terminal oxygen atom to the Si atom of the alkoxysilyl group in the structure derived from (meth) acrylic acid is preferably 30 atoms or less, for example.
The main chain skeleton may have a repeating unit derived from one type of acrylate or a repeating unit derived from methacrylate, or may have a repeating unit derived from two or more types of acrylate or a repeating unit derived from methacrylate. The main chain skeleton preferably has two or more kinds of acrylate-derived repeating units or methacrylate-derived repeating units.
Preferable examples of the main chain skeleton include a copolymer of 2-ethylhexyl acrylate and methyl methacrylate, a copolymer of methyl acrylate and n-butyl acrylate, and a copolymer of ethyl acrylate and n-butyl acrylate. it can. Among these, a copolymer of 2-ethylhexyl acrylate and methyl methacrylate and a copolymer of ethyl acrylate and n-butyl acrylate are preferable.

The alkoxysilyl group-containing acrylic polymer preferably has a bulky side chain from the viewpoint of reducing the relative dielectric constant.
The alkoxysilyl group-containing acrylic polymer preferably has an alkoxysilyl group-containing side chain represented by —Si (OR ¹ ) (OR ² ) (OR ³ ) as a side chain. In the formula, R ¹ , R ² and R ³ each independently represents an alkyl group.
The upper limit of the carbon number of the alkyl group represented by R ¹ , R ² and R ³ is preferably 10 or less, for example.

(Weight average molecular weight of alkoxysilyl group-containing acrylic polymer)
The weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 5000 or less, preferably 4500 or less, and more preferably 4000 or less. The weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 or more, preferably 1000 or more, and more preferably 2000 or more. By making the weight average molecular weight of the alkoxysilyl group-containing acrylic polymer within the above range, the compatibility with the above-mentioned (meth) acrylic polymer becomes better, and it is a transparent adhesive without being clouded when used for an optical member. An agent layer can be formed. Moreover, the adhesive layer which is excellent in level | step difference followability and durability can be formed by making the weight average molecular weight of an alkoxysilyl group containing acrylic polymer into the said range.

A commercially available product can be used as the alkoxysilyl group-containing acrylic polymer. Examples of commercially available products include, for example, ARUFON (registered trademark) US series manufactured by Toagosei Co., Ltd., specifically, trade name “ARUFON US-6100” (weight average molecular weight 2500), trade name “ARUFON US”. -6170 "(weight average molecular weight 3000).
As an alkoxysilyl group-containing acrylic polymer, Actflow (registered trademark) NE-1000 manufactured by Soken Chemical Co., Ltd. can be suitably used.

(Content of alkoxysilyl group-containing acrylic polymer)
In the present invention, the alkoxysilyl group-containing acrylic polymer is preferably contained in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the crosslinkable acrylic polymer.
The content of the alkoxysilyl group-containing acrylic polymer is more preferably 3% by mass or more, particularly preferably 4% by mass or more, and more preferably 5% by mass or more with respect to the total mass of the crosslinkable acrylic polymer. More particularly preferred. Further, the content of the alkoxysilyl group-containing acrylic polymer is more preferably 15% by mass or less, and particularly preferably 12% by mass or less, with respect to the total mass of the crosslinkable acrylic polymer. By setting the content of the alkoxysilyl group-containing acrylic polymer within the above range, it is possible to form a pressure-sensitive adhesive layer excellent in step following ability and durability without increasing the relative dielectric constant of the pressure-sensitive adhesive layer.
One kind of alkoxysilyl group-containing acrylic polymer may be contained alone, or two or more kinds having different compositions and weight average molecular weights may be contained.

  When the alkoxysilyl group-containing acrylic polymer is produced by polymerization, the production method is not particularly limited and can be appropriately selected from commonly used polymerization methods. Examples of the polymerization method include solution polymerization, emulsion polymerization, and suspension polymerization. Among these, a solution polymerization method is preferable as the polymerization method because the production can be performed relatively easily.

<Crosslinking agent>
The crosslinking agent is preferably a crosslinking agent that reacts with the crosslinkable acrylic polymer by heat.
As the crosslinking agent, for example, among known crosslinking agents such as an isocyanate compound, an epoxy compound, an oxazoline compound, an aziridine compound, a metal chelate compound, a butylated melamine compound, a crosslinking functional group possessed by a crosslinking acrylic polymer It can be appropriately selected in consideration of reactivity. For example, when a hydroxy group is included as a crosslinkable functional group, an isocyanate compound can be used from the reactivity of the hydroxy group. From the viewpoint that the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group can be easily crosslinked, it is preferable to use an isocyanate compound or an epoxy compound. In the present invention, the crosslinking agent is preferably one or more types selected from any one of bifunctional or higher epoxy compounds and bifunctional or higher isocyanate compounds, and is a bifunctional or higher isocyanate compound. It is more preferable.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.
Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol diester. Glycidyl ether, tetraglycidyl xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. Can be mentioned.
A commercial item can be used as a crosslinking agent. As an example of a commercial item, a xylylene diisocyanate compound (Mitsui Chemicals, Takenate D-110N) etc. are mentioned.

As the crosslinking agent, one kind may be used alone, or two or more kinds may be used in combination. The content of the crosslinking agent in the pressure-sensitive adhesive composition is appropriately selected according to the desired adhesive properties and the like, and is not particularly limited, but is 0.01 parts by mass or more and 5 parts by mass with respect to 100 parts by mass of the crosslinkable acrylic polymer. Part or less, or 0.03 part by mass or more and 3 parts by mass or less.
Moreover, content of a crosslinking agent can be 0.01 mass% or more and 5.0 mass% or less with respect to the total mass of an adhesive composition, and is 0.02 mass% or more and 2.0 mass% or less. can do.

<Solvent>
The pressure-sensitive adhesive composition may further contain a solvent. The solvent is used for improving the coating suitability of the pressure-sensitive adhesive composition.
Examples of such solvents include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; methanol Alcohols such as ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone ; Methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate, etc. Ethers, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, polyols and derivatives thereof such as propylene glycol monomethyl ether acetate.

A solvent may be used individually by 1 type and may use 2 or more types together. Although content of a solvent is not specifically limited in an adhesive composition, It can be 25 mass parts or more and 500 mass parts or less with respect to 100 mass parts of crosslinkable acrylic polymers, and is 30 mass parts or more and 400 mass parts or less. It can be.
Moreover, content of a solvent can be 10 to 90 mass% with respect to the total mass of an adhesive composition, and can be 20 to 80 mass%.

<Plasticizer>
The pressure-sensitive adhesive composition of the present invention may contain a plasticizer other than the alkoxysilyl group-containing acrylic polymer. When a plasticizer is included, the content of the plasticizer can be 50 parts by mass or less, 100 parts by mass or less, and 10 parts by mass or less with respect to 100 parts by mass of the crosslinkable acrylic polymer. It can also be.

As the plasticizer, a non-functional acrylic polymer can be used. A non-functional acrylic polymer is a polymer consisting only of an acrylic monomer unit having no functional group other than an acrylate group, or an acrylic monomer unit having no functional group other than an acrylate group and no functional group. It means a polymer composed of non-acrylic monomer units.
As an acrylic monomer unit which does not have functional groups other than an acrylate group, the thing similar to a non-crosslinkable (meth) acrylic acid ester unit (a1) is mentioned, for example.
Non-acrylic monomer units having no functional group include, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, stearin. Examples thereof include carboxylic acid vinyl esters such as vinyl acid vinyl, vinyl cyclohexanecarboxylate, and vinyl benzoate, and styrene.

<Optional component>
The pressure-sensitive adhesive composition may contain components other than those described above as long as the effects of the present invention are not impaired. Other components include components known as additives for pressure-sensitive adhesives, such as antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, ultraviolet absorbers, light stabilizers such as hindered amine compounds, etc. You can select from among them as needed.
Examples of the antioxidant include phenolic antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. These antioxidants may be used alone or in combination of two or more.
Examples of the metal corrosion inhibitor include benzoriazol resins.
Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin.
Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers).
Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds.

  The pressure-sensitive adhesive composition of the present invention is preferably a pressure-sensitive adhesive composition that does not substantially contain a polymer monomer or a polymerization initiator in addition to the crosslinking agent and the alkoxysilyl group-containing acrylic polymer (after-curing less). . After-curing is a semi-cured pressure-sensitive adhesive layer after a pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, is used as a semi-cured material. Says how to fully cure. After-curing means that after-curing after providing an adhesive layer on the surface of the adherend is unnecessary.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition of the present invention.
The pressure-sensitive adhesive sheet of the present invention is preferably used for bonding an optical member constituting a display device on which a touch panel is mounted because it is excellent in step followability and durability without increasing the relative dielectric constant.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet composed only of a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet of the present invention may be a single-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive sheet.
As a single-sided adhesive sheet, the multilayer sheet | seat which the adhesive layer laminated | stacked on the support body is mentioned. Moreover, another layer may be provided between the support and the pressure-sensitive adhesive layer.
Double-sided pressure-sensitive adhesive sheets include single-layer pressure-sensitive adhesive sheets composed of pressure-sensitive adhesive layers, multilayer pressure-sensitive adhesive sheets in which a plurality of pressure-sensitive adhesive layers are laminated, and multilayer pressure-sensitive adhesives in which another pressure-sensitive adhesive layer is laminated between pressure-sensitive adhesive layers. A multilayer pressure-sensitive adhesive sheet in which a support is laminated between the sheet, the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer can be used. When the double-sided pressure-sensitive adhesive sheet has a support, those using a transparent support as the support are preferred. Such a double-sided pressure-sensitive adhesive sheet is excellent in transparency as a whole pressure-sensitive adhesive sheet, and therefore can be suitably used for bonding optical members.
Among the above-mentioned, the pressure-sensitive adhesive sheet of the present invention is preferably a non-carrier type, preferably a single-layer pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, or a multilayer pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated. A double-sided PSA sheet is particularly preferred.

  When the pressure-sensitive adhesive sheet of the present invention has a support, examples of the support include plastics such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyether ether ketone, and triacetyl cellulose. Films: Optical films such as antireflection films and electromagnetic wave shielding films.

The surface of the pressure-sensitive adhesive layer is preferably covered with a release sheet. That is, the pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet with a release sheet.
Drawing 1 is a sectional view showing an example of composition of an adhesive sheet with a release sheet. The pressure-sensitive adhesive sheet 11 shown in FIG. 1 has release sheets (12a, 12b). In addition, the adhesive sheet 11 of FIG. 1 is a non-carrier type single-layer adhesive sheet, and is a double-sided adhesive sheet.

As a release sheet, a peelable laminated sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low polarity substrate Is mentioned.
Papers and polymer films are used as the release sheet substrate in the peelable laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. Further, the silicone release agent may contain a silicone resin which is an organosilicon compound having a SiO ₂ unit and a (CH ₃ ) ₃ SiO _1/2 unit or CH ₂ ═CH (CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone, KS-3800, X92-183, manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

  In the present invention, the first release sheet is provided on one surface of the pressure-sensitive adhesive layer, the second release sheet is provided on the other surface of the pressure-sensitive adhesive layer, and the peeling force of the first release sheet and the second release sheet is provided. Are preferably different. In the example of FIG. 1, in the release sheet 12, in order to make it easy to peel, it is preferable that the release sheet 12a and the release sheet 12b have different peelability. That is, when the peelability from one side and the peelability from the other are different, it becomes easy to peel only the release sheet 12 having the higher peelability first. In that case, what is necessary is just to adjust the peelability of the peeling sheet 12 of the peeling sheet 12a and the peeling sheet 12b according to the bonding method and the bonding order.

  The thickness of the pressure-sensitive adhesive layer can be appropriately set depending on the application and is not particularly limited, but is usually preferably in the range of 10 μm to 500 μm, more preferably 20 μm to 450 μm, and more preferably 30 μm to 450 μm. Is more preferably 40 μm or more and 400 μm or less, still more preferably 40 μm or more and 350 μm or less, and particularly preferably 40 μm or more and 300 μm or less. By setting the thickness of the pressure-sensitive adhesive layer within the above range, the step following ability can be sufficiently secured, and the durability can be further enhanced. Moreover, manufacture of a double-sided adhesive sheet becomes easy by making thickness of an adhesive layer into the said range.

  The relative dielectric constant is a relative dielectric constant at a specific frequency. In the present invention, a relative dielectric constant at a frequency of 1 MHz and a value calculated by a method defined in JIS C 2138 is used.

  The adhesive strength of the pressure-sensitive adhesive sheet is preferably 10 N / 25 mm or more, and more preferably 15 N / 25 mm or more.

  In addition, the adhesive force of the adhesive sheet with respect to the adherend described above is a value measured by peeling 180 ° with respect to each adherend and measuring the adhesive force according to JIS Z 0237.

<Method for producing adhesive sheet>
The manufacturing method of an adhesive sheet is not specifically limited.
Although the adhesive sheet of this invention may be comprised from an adhesive layer and another layer, it is preferable that it is comprised only from an adhesive layer. Examples of other layers include a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition other than the above, a support, a release sheet, and the like. Examples of the support include plastic films such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyetheretherketone, and triacetyl cellulose; optical films such as antireflection films and electromagnetic wave shielding films; Is mentioned.

  It is preferable that the manufacturing process of an adhesive sheet includes the process of apply | coating an adhesive composition on a peeling sheet and forming a coating film, and the process of making this coating film into a hardened | cured material by heating.

Hereinafter, the step of coating the pressure-sensitive adhesive composition on the release sheet to form a coating film and the step of heating the coating film to obtain a cured product will be described as a representative.
By the heating of the coating film, the reaction of the crosslinkable acrylic polymer and the crosslinking agent proceeds to form a cured product (adhesive sheet). In order to make the pressure-sensitive adhesive composition into a cured state, after removing the solvent after coating, an aging treatment may be performed in which the pressure-sensitive adhesive sheet is allowed to stand for a certain period at a certain temperature. The aging treatment can be performed, for example, by standing at 23 ° C. for 7 days.

Application of the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet can be carried out using a known coating apparatus. Examples of the coating apparatus include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a micro gravure coater, a rod blade coater, a lip coater, a die coater, and a curtain coater.
The coating film can be heated using a known heating device such as a heating furnace or an infrared lamp.

<How to use the adhesive sheet>
In the method for using the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the adherend surface.

  Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet contains an alkoxysilyl group-containing acrylic polymer having a small relative dielectric constant, even if the adherend has a stepped portion, the pressure-sensitive adhesive layer follows the unevenness of the stepped portion. Can do.

[Laminate]
The laminate of the present invention has an adherend on at least one surface of the pressure-sensitive adhesive sheet of the present invention, and the adherend has a step portion.
The adherend is preferably an optical member constituting an image display device having a liquid crystal module or an optical member constituting a touch panel. The laminate is preferably obtained through a step of bringing the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet into contact with the adherend surface.

  FIG. 2 is a cross-sectional view illustrating an example of the configuration of the laminate 20 in which the pressure-sensitive adhesive sheet 21 of the present invention is bonded to the adherend 22 and the adherend 24. As shown in FIG. 2, the adherends 22 and 24 have stepped portions (27a, 27b, 27c, 27d or 27a and 27b or 27c and 27d may be provided on only one side). In FIG. 2, the adherend 22 has stepped portions (27a, 27b), and the adherend 24 has stepped portions (27c, 27d). The thickness of the stepped portions (27a, 27b, 27c, 27d) is usually 5 μm or more and 60 μm or less. Thus, the adhesive sheet 21 of this invention can be bonded to the member which has a level difference part, and can follow the unevenness | corrugation of a level difference part.

The adherend is preferably an optical member. As an optical member, each structural member in optical products, such as a touch panel and an image display apparatus, can be mentioned.
As a constituent member of the touch panel, for example, an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on the surface of a glass plate, a transparent conductive film in which a transparent polymer film is coated with a conductive polymer, Examples thereof include a hard coat film and an anti-fingerprint film. The pressure-sensitive adhesive sheet of the present invention is preferably for touch panel sensor lamination, and more preferably for touch panel sensor lamination using a touch pen. From this viewpoint, the adherend of the pressure-sensitive adhesive sheet of the present invention includes an ITO film having an ITO film provided on a transparent resin film, an ITO glass having an ITO film provided on the surface of a glass plate, and a conductive polymer on the transparent resin film. A transparent conductive film coated with is preferred.
Examples of the constituent member of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a brightness enhancement film used in a liquid crystal display device.
Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

  When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, it can be used for bonding two adherends. In this case, the pressure-sensitive adhesive sheet of the present invention is formed by bonding between ITO films inside the touch panel, bonding between the ITO film and ITO glass, bonding between the ITO film of the touch panel and the liquid crystal panel, and the cover glass and the ITO film. Used for bonding, bonding between a cover glass and a decorative film.

(Laminate manufacturing method)
The present invention also relates to a method for producing a laminate. It is preferable that the manufacturing method of a laminated body includes the process which makes the adhesive sheet mentioned above contact the surface of a to-be-adhered body.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
<Preparation of pressure-sensitive adhesive composition>
2-ethylhexyl acrylate (2-EHA), 2-ethylhexyl methacrylate (2-EHMA), 2-hydroxyethyl acrylate (2-HEA) were blended in a mass ratio of 30:60:10 to produce a radical polymerization initiator. 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and random copolymerized to obtain a crosslinkable acrylic polymer (A). The weight average molecular weight of the crosslinkable acrylic polymer (A) was 500,000.
In addition, a weight average molecular weight is the value calculated | required on the basis of polystyrene, measured by gel permeation chromatography (GPC).
The measurement conditions of gel permeation chromatography (GPC) are as follows.
Solvent: Tetrahydrofuran Column: Shodex KF801, KF803L, KF800L, KF800D (used by connecting four Showa Denko Co., Ltd.)
Column temperature: 40 ° C
Sample concentration: 0.5% by mass
Detector: RI-2031plus (manufactured by JASCO)
Pump: RI-2080plus (manufactured by JASCO)
Flow rate (flow rate): 0.8 ml / min Injection volume: 10 μl
Calibration curve: Standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko KK) Mw = 1320 to 2500,000 calibration curves with 10 samples were used.
With respect to 100 mass parts of the solid content of the acrylic polymer of the crosslinkable acrylic polymer (A) obtained above, an alkoxysilyl group-containing acrylic polymer (manufactured by Toagosei Co., Ltd., trade name “ARUFON US-6100”, weight average) 10 parts by mass of molecular weight 2500, Tg-58 ° C., trimethoxysilyl group and main chain skeleton is a copolymer of 2-ethylhexyl acrylate and methyl methacrylate, xylylene diisocyanate compound as a crosslinking agent (Mitsui Chemicals) 0.15 parts by mass of Takenate D-110N (manufactured by Co., Ltd.) was added, and ethyl acetate was added so that the solid content concentration was 40% by mass to obtain a pressure-sensitive adhesive composition.
The alkoxysilyl group-containing acrylic polymer (trade name “ARUFON US-6100” manufactured by Toagosei Co., Ltd.) was liquid at 20 ° C.

<Production of adhesive sheet>
A 38 μm-thick polyethylene terephthalate film (first release sheet) provided with a release agent layer treated with a silicone release agent was prepared from the pressure-sensitive adhesive composition produced as described above (manufactured by Oji F-Tex Co., Ltd .: 38RL-07). The surface of (2)) was uniformly coated with an applicator so that the coating amount after drying was 150 μm / m ² . Then, it dried for 3 minutes with a 100 degreeC air circulation type thermostat oven, and formed the adhesive layer on the surface of a 1st peeling sheet. Next, a pair of 38 μm thick second release sheet (Oji F-Tex Co., Ltd .: 38RL-07 (L)) is bonded to the surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer has a pair of peel strength differences. A pressure-sensitive adhesive sheet having a configuration of a first release sheet / pressure-sensitive adhesive layer / second release sheet sandwiched between release sheets was obtained. The pressure-sensitive adhesive sheet was subjected to an aging treatment that was allowed to stand for 7 days at 23 ° C. and a relative humidity of 50%.

<Preparation of laminate (1)>
On the surface of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm), ultraviolet curable ink was screen-printed in a frame shape (length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was 5 μm. Next, the ultraviolet curable ink printed by irradiating with ultraviolet rays was cured. This process was repeated 8 times to obtain a printed step glass having a step portion of 40 μm.
The obtained pressure-sensitive adhesive sheet was cut into a shape of 90 mm in length and 50 mm in width, the first release sheet was peeled off, and the pressure-sensitive adhesive layer was made of a printed step glass using a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT). Bonding was performed so as to cover the entire frame-shaped print. Thereafter, the second release sheet was peeled off, and a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm) was bonded to the surface of the exposed pressure-sensitive adhesive layer with the laminator, followed by autoclaving (40 ° C., 0. 5 MPa, 30 minutes) was implemented, and the laminated body (1) was obtained.

<Preparation of laminate (2)>
The obtained pressure-sensitive adhesive sheet was cut into a shape of 90 mm in length and 50 mm in width, the first release sheet was peeled off, and a laminate (1) was produced using a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT). Bonding was performed so as to cover the entire printing surface in the frame shape of the printed stepped glass having the used 40 μm stepped portion.
As an adherend, a polarizing plate (manufactured by Polatechno Co., Ltd., SKN-18243T) is cut in advance to the same dimensions as one side of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm), and the center particle is formed on the surface of the polarizing plate. What sprinkled about 0.05 mg of glass beads with a diameter of 30 μm was prepared.
The 2nd peeling sheet of the laminated body integrated with the printing level | step difference glass was peeled, and it bonded with the surface where the glass bead of the polarizing plate of the said to-be-adhered body was disperse | distributed with the laminator. Then, the autoclave process (40 degreeC, 0.5 Mpa, 30 minutes) was implemented, and the laminated body (2) was obtained.

[Example 2]
Instead of an alkoxysilyl group-containing acrylic polymer (trade name “ARUFON US-6100” manufactured by Toagosei Co., Ltd.), an alkoxysilyl group-containing acrylic polymer (trade name “ARUFON US-6170” manufactured by Toagosei Co., Ltd., weight average molecular weight 3000; A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate in the same manner as in Example 1 except that the trimethoxysilyl group and the main chain skeleton are copolymers of ethyl acrylate and n-butyl acrylate) Got.
The alkoxysilyl group-containing acrylic polymer (trade name “ARUFON US-6170” manufactured by Toagosei Co., Ltd.) was liquid at 20 ° C.

[Comparative Example 1]
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate were obtained in the same manner as in Example 1 except that the alkoxysilyl group-containing acrylic polymer was not blended.

[Comparative Example 2]
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate were obtained in the same manner as in Comparative Example 1 except that the cross-linkable acrylic polymer (B) was used instead of the cross-linkable acrylic polymer (A).
The cross-linkable acrylic polymer (B) uses n-butyl acrylate (BA) instead of 2-EHMA so that the mass ratio of BA, 2-EHA, and 2-HEA is 70:20:10. A crosslinkable acrylic polymer (B) was obtained in the same manner as in Example 1 except that it was blended. The weight average molecular weight of the crosslinkable acrylic polymer (B) was 700,000.

[Comparative Example 3]
Similar to Example 1 except that the crosslinkable acrylic polymer (C) was used instead of the crosslinkable acrylic polymer (A), and the amount of the crosslinking agent was changed from 0.15 parts by mass to 0.7 parts by mass. Thus, a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate were obtained.
In addition, crosslinkable acrylic polymer (C) uses ISTA, 2-EHA, HBA by using isostearyl acrylate (ISTA) instead of 2-EHMA and 4-hydroxybutyl acrylate (HBA) instead of 2-EHA. The weight ratio was 90: 10: 1, and 2,2′-azobisisobutyronitrile was used instead of 2,2′-azobis (2,4-dimethylvaleronitrile) as a radical polymerization initiator. A crosslinkable acrylic polymer (C) was obtained in the same manner as in Example 1 except that it was used. The weight average molecular weight of the crosslinkable acrylic polymer (C) was 700,000.
[Comparative Example 4]
Instead of an alkoxysilyl group-containing acrylic polymer (trade name “ARUFON US-6100” manufactured by Toagosei Co., Ltd.), an acrylic polymer having no alkoxysilyl group (trade name “ARUFON UP-1110” manufactured by Toagosei Co., Ltd.), weight average A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a laminate were obtained in the same manner as in Example 1 except that the molecular weight was changed to 2500).

[Evaluation]
<Relative permittivity>
Evaluation of the dielectric constant of the pressure-sensitive adhesive sheet was performed according to the following procedure. The pressure-sensitive adhesive layer (from which the first release sheet and the second release sheet were peeled from the pressure-sensitive adhesive sheet) was sandwiched between two copper foils and autoclaved (40 ° C., 0.5 MPa, 30 minutes). . Then, it measured based on JISC2138 with the dielectric material measurement system (Corporation | KK Toyo technica make, 1260 type | mold). The frequency and measurement environment were measured under the following conditions.
Frequency: 1MHz
Measurement environment: 23 ° C, relative humidity 55%

<Step following capability>
The printed stepped portions of the laminate (1) and the laminate (2) were observed with a microscope (magnification: 25 times), and the step followability of the adhesive sheet was evaluated according to the following criteria.
○: The level difference is completely filled.
Δ: Air remains in a part of the stepped portion.
X: Air remains in the entire step portion.

<Durability>
The laminate (1) was treated for 240 hours in an environment of 85 ° C. and relative humidity of 85%, and the entire sample was observed with a microscope (magnification: 25 times) to see if there were any bubbles or peeling. evaluated.
(Double-circle): A bubble and peeling do not generate | occur | produce at all.
○: There are some bubbles.
×: Many bubbles are generated.

From Table 1 above, it was found that the pressure-sensitive adhesive compositions obtained in Examples 1 and 2 can improve the step following ability and durability without increasing the relative dielectric constant when the pressure-sensitive adhesive layer is formed. In addition, the adhesive force of the adhesive sheet of Example 1 and 2 was 18 N / 25mm or more.
The pressure-sensitive adhesive sheet obtained in Comparative Example 1 in a mode in which the pressure-sensitive adhesive composition does not contain an alkoxysilyl group-containing acrylic polymer has a sufficiently low relative dielectric constant, but has poor step following ability, and has a relative dielectric constant and step following ability. It was incompatible.
The pressure-sensitive adhesive sheet obtained in Comparative Example 2 in a mode in which the pressure-sensitive adhesive composition does not contain an alkoxysilyl group-containing acrylic polymer has good step following ability, but has a high relative dielectric constant, and has a high relative dielectric constant and step following ability. It was something that could not be compatible.
The pressure-sensitive adhesive sheet obtained in Comparative Example 3 in a mode in which the pressure-sensitive adhesive composition does not contain an alkoxysilyl group-containing acrylic polymer was able to reduce the relative permittivity, but the step following ability was poor, and the relative permittivity and the step following ability were reduced. It was incompatible. In addition, the comparative example 3 is an example which referred Example 4 of Unexamined-Japanese-Patent No. 2006-172865.
The pressure-sensitive adhesive sheet obtained in Comparative Example 4 using an acrylic oligomer having no alkoxysilyl group in the pressure-sensitive adhesive composition had good step followability, but had a high relative dielectric constant.

1 Adhesive sheet with release sheet 11 Adhesive sheet (adhesive layer)
12a, 12b Release sheet 20 Laminate 21 Adhesive sheet (adhesive layer)
22 adherend 24 adherend 27a, 27b, 27c, 27d stepped portion

Claims (8)

A pressure-sensitive adhesive composition comprising a crosslinkable acrylic polymer, a crosslinker and an alkoxysilyl group-containing acrylic polymer,
Containing 50% by mass or more of the crosslinkable acrylic polymer with respect to the pressure-sensitive adhesive composition,
The weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000,
The alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C.,
The adhesive composition whose relative dielectric constant in the frequency of 1 MHz of the said adhesive layer is 3.5 or less when the adhesive layer which is the hardened | cured material of the said adhesive composition is formed.   The crosslinkable functional group of the crosslinkable acrylic polymer is one or more selected from any of a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group, and an isocyanate group. 2. The pressure-sensitive adhesive composition according to 1.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the crosslinking agent is one type or at least one type selected from a bifunctional or higher functional epoxy compound and a bifunctional or higher functional isocyanate compound.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the alkoxysilyl group-containing acrylic polymer is contained in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the crosslinkable acrylic polymer.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the alkoxysilyl group-containing acrylic polymer is contained in an amount of 4 to 15 parts by mass with respect to 100 parts by mass of the crosslinkable acrylic polymer. Having an adhesive layer,
The adhesive sheet whose said adhesive layer is a hardened | cured material of the adhesive composition as described in any one of Claims 1-5. A first release sheet is provided on one surface of the pressure-sensitive adhesive layer,
A second release sheet is provided on the other surface of the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive sheet according to claim 6, wherein the first release sheet and the second release sheet have different peeling forces. An adherend is provided on at least one surface of the pressure-sensitive adhesive sheet according to claim 6 or 7,
A laminate in which the adherend has a stepped portion.

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