JP6969226B2 - Adhesive composition, adhesive sheet and laminate - Google Patents

Description

The present invention relates to pressure-sensitive adhesive compositions, pressure-sensitive adhesive sheets and laminates.

In recent years, a display device such as a liquid crystal display (LCD) and a device combining a display device such as a touch panel and an input device have been widely used in various fields. Above all, the capacitive touch panel is rapidly becoming widespread because of its functionality. In the manufacture of these display devices and input devices, adhesive sheets are used for bonding optical members, and adhesive sheets are also used for bonding display devices and input devices.

In the capacitance touch panel, when a finger is brought close to the surface, the capacitance between a plurality of electrodes changes at the same time, and it is possible to detect the position with high accuracy by measuring the ratio of the amount of current. However, if this method is increased in size, the touch panel will malfunction more often. In order to deal with such a problem, it is conceivable to use an adhesive sheet having a low relative permittivity.

On the other hand, a pressure-sensitive adhesive capable of realizing a pressure-sensitive adhesive layer having a low relative permittivity is known (see Patent Documents 1 to 3).
Patent Document 1 includes a (meth) acrylic polymer obtained by polymerizing a monomer component containing 19 to 96% by weight of an alkyl (meth) acrylate having an alkyl (meth) acrylate at the end of a branched alkyl group having 12 to 24 carbon atoms. Adhesives are listed. Further, Patent Document 2 describes an alkyl (meth) acrylate (a1) having a branched alkyl group having 10 to 24 carbon atoms at the ester terminal and an alkyl (meth) acrylate having a linear alkyl group having 8 to 24 carbon atoms at the ester terminal. A pressure-sensitive adhesive containing a (meth) acrylic polymer obtained by polymerizing a monomer component containing (a2) is described. Further, Patent Document 3 is 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 end of the ester group (meth). Adhesives containing acrylic polymers are described.

Japanese Patent No. 5923857 Japanese Patent No. 6038469 Japanese Unexamined Patent Publication No. 2016-172865 Japanese Unexamined Patent Publication No. 2016-50255

However, it has been found that when the present inventors form an adhesive layer on an adherend having a stepped portion by using the adhesives described in Patent Documents 1 to 3, air remains in the entire stepped portion. ..
On the other hand, there is known a sheet-like adhesive having improved step followability with respect to an adherend having a step portion by imparting appropriate rigidity (see, for example, Patent Document 4). Specifically, Patent Document 4 provides a sheet-like adhesive for fixing a transparent hard plate provided with a stepped portion to the surface of an image display device, and is a (meth) acrylic acid as a component (A). A pressure-sensitive adhesive composition containing an ester polymer, a polymer-type silane coupling agent as a component (B), and a cross-linking agent as a component (C), and a polymer-type silane coupling agent as a component (B). Is a polymer-type silane coupling agent in which a plurality of alkoxysilyl groups and a plurality of organic functional groups are bonded to a polymer chain, and the film thickness is set to a value within the range of 30 to 200 μm, soda. The adhesive strength measured after being attached to lime glass and pressurized and then left in an environment of 23 ° C. and 50% RH for 24 hours has a value of 10 N / 25 mm or more, and the gel content is 50 to 80%. Sheet-like adhesives having a value within the range are described. However, Patent Document 4 does not describe controlling the relative permittivity of the sheet-like pressure-sensitive adhesive by using components other than the components (A) to (C).

An object to be solved by the present invention is to provide a pressure-sensitive adhesive composition capable of lowering the relative permittivity when the pressure-sensitive adhesive layer is formed and improving step followability and durability.

Here, when forming a pressure-sensitive adhesive sheet used for optical applications as in Patent Documents 1 to 3, an active energy ray-curable pressure-sensitive adhesive composition or a thermosetting pressure-sensitive adhesive composition containing a base polymer is used. Has been done. As a base polymer, acrylic monomer units such as alkyl (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate, etc., are excellent in transparency and the like. Acrylate-based base polymers containing the above are used.
However, the present inventors, as in Patent Documents 1 to 3, copolymerize an alkyl (meth) acrylate having an alkyl group having a long-chain branched structure such as 10 to 24 carbon atoms at the end of the ester group. By simply changing the structure of the base polymer, the relative permittivity can be lowered when the pressure-sensitive adhesive layer is formed, but the step followability is inferior, and conversely, the number of carbon atoms is 10 to 24 in order to improve the step followability. If the copolymerization component of the alkyl (meth) acrylate having an alkyl group having a long-chain branched structure at the end of the ester group is reduced, the relative permittivity becomes high, and the relative permittivity is kept low while maintaining the step followability. We have found it difficult to improve durability.
As a result of diligent studies to solve the above problems, the present inventors have obtained a polymer having a number average molecular weight of 250 to 15,000 and a liquid or oily unsaturated hydrocarbon at 20 ° C. and a weight average molecular weight. By using an alkoxysilyl group-containing acrylic polymer liquid or oily at 400 to 5000 and at 20 ° C. in combination with a crosslinkable acrylic polymer, the specific dielectric constant when the pressure-sensitive adhesive layer is formed can be reduced and the step followability can be reduced. We have found that the durability can be improved, and have completed the present invention.

Specifically, the present invention and the configurations of preferred embodiments of the present invention are as follows.
[1] A crosslinkable acrylic polymer, a crosslinking agent, a polymer having an unsaturated hydrocarbon in the molecule (in the present specification, it may be abbreviated as "a polymer having an unsaturated hydrocarbon"; the polymer itself. A pressure-sensitive adhesive composition containing a polymer having a structure having double bonds, triple bonds, unsaturated hydrocarbons constituting an aromatic ring, etc.) and an alkoxysilyl group-containing acrylic polymer in the molecule.
The crosslinkable acrylic polymer is contained in an amount of 50% by mass or more based on the pressure-sensitive adhesive composition.
The number average molecular weight of the polymer having unsaturated hydrocarbons is 250 to 15000, the polymer having unsaturated hydrocarbons is liquid or oily at 20 ° C., and the weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000. Yes, the alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C.
A pressure-sensitive adhesive composition in which the relative permittivity of the pressure-sensitive adhesive layer at a frequency of 1 MHz is 3.5 or less when the pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, is formed.
[2] The crosslinkable functional group of the crosslinkable acrylic polymer is one or more selected from any one of a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group and an isocyanate group [1]. ] The pressure-sensitive adhesive composition according to.
[3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the cross-linking agent is one or more selected from one of a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound. ..
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the polymer having an unsaturated hydrocarbon is a styrene-based polymer, polyisoprene or polybutadiene.
[5] The pressure-sensitive adhesive composition according to any one of [1] to [4], which contains 1 to 20 parts by mass of a polymer having unsaturated hydrocarbons with respect to 100 parts by mass of a crosslinkable acrylic polymer.
[6] The pressure-sensitive adhesive composition according to any one of [1] to [5], which contains 5 to 15 parts by mass of a polymer having unsaturated hydrocarbons with respect to 100 parts by mass of a crosslinkable acrylic polymer.
[7] The pressure-sensitive adhesive composition according to any one of [1] to [6], which contains 1 to 20 parts by mass of an alkoxysilyl group-containing acrylic polymer with respect to 100 parts by mass of a crosslinkable acrylic polymer.
[8] The pressure-sensitive adhesive composition according to any one of [1] to [7], which contains 4 to 15 parts by mass of an alkoxysilyl group-containing acrylic polymer with respect to 100 parts by mass of a crosslinkable acrylic polymer.
[9] It has an adhesive layer and has an adhesive layer.
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition according to any one of [1] to [8].
[10] 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 adhesive layer,
The adhesive sheet according to [9], wherein the first release sheet and the second release sheet have different release forces.
[11] A laminated body having an adherend on at least one surface of the pressure-sensitive adhesive sheet according to [9] or [10], and the adherend having a stepped portion.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition capable of reducing the relative permittivity when the pressure-sensitive adhesive layer is formed and improving the step followability.
According to the present invention, it is possible to provide an adhesive sheet having a low relative permittivity and excellent step followability and durability.

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

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments and specific examples, but the present invention is not limited to such embodiments. The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value. In addition, the term "(meth) acrylic acid" includes both acrylic acid and methacrylic acid. The same applies to derivatives such as salts, esters, amides and copolymers of (meth) acrylic acid.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a cross-linking acrylic polymer, a cross-linking agent, a polymer having an unsaturated hydrocarbon in the molecule, and an alkoxysilyl group-containing acrylic polymer, and is a cross-linking acrylic. The polymer containing 50% by mass or more of the pressure-sensitive adhesive composition, the number average molecular weight of the polymer having unsaturated hydrocarbons is 250 to 15,000, and the polymer having unsaturated hydrocarbons is liquid or oily at 20 ° C. The alkoxysilyl group-containing acrylic polymer has a weight average molecular weight of 400 to 5000, and the alkoxysilyl group-containing acrylic polymer is liquid or oily at 20 ° C. to form a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive composition. In some cases, the specific 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 reduce the relative permittivity when the pressure-sensitive adhesive layer is formed, can improve the step followability, and is less likely to cause air bubbles or peeling, and has excellent durability. Can be. That is, in the pressure-sensitive adhesive composition of the present invention, the component that lowers the relative permittivity and the component that improves the durability are not used as a copolymerization component of the crosslinkable acrylic polymer, but as a separate material having a small molecular weight. By including it in the composition, each of the component that lowers the relative permittivity and the component that improves the durability can also have the role of a plasticizer that improves the step followability. This makes it possible to form a pressure-sensitive adhesive layer that has both a low relative permittivity, step followability, and durability.
When the pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, is formed, the relative permittivity of the pressure-sensitive adhesive layer at a frequency of 1 MHz is preferably 3.1 or less, more preferably 3.0 or less. It is particularly preferable that it is 2.9 or less.
The pressure-sensitive adhesive composition preferably has a solid content concentration of 20 to 60% by mass, more preferably 30 to 50% by mass, in a state containing a solvent described later.
Hereinafter, preferred embodiments of the pressure-sensitive adhesive composition of the present invention will be described.

<Crosslinkable acrylic polymer>
The crosslinkable acrylic polymer is not particularly limited, and a known crosslinkable acrylic polymer can be used.
The crosslinkable acrylic polymer is a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 or more and 9 or less carbon atoms and a (meth) acrylic monomer having 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 or more and 9 or less 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 specific dielectric constant can be formed from the pressure-sensitive adhesive composition containing the crosslinkable acrylic polymer. A pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer having a low relative permittivity is preferably used for bonding optical members 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 or more and 9 or less carbon atoms contained in the crosslinkable acrylic polymer has an alkyl group having 5 or more carbon atoms. Moreover, since such an alkyl group has a branched structure, it has a large molar volume and a low density. Therefore, the molar volume of the crosslinkable acrylic polymer can be increased and the density can be reduced. Further, since the unit (a1) has an alkyl group having 9 or less carbon atoms, the volume shrinkage when made into a polymer can be suppressed, and the molar volume of the crosslinkable acrylic polymer can be maintained large. Conceivable. As a result, a pressure-sensitive adhesive layer having a low relative permittivity can be formed.
The crosslinkable acrylic polymer is preferably one having transparency to the extent that the visibility of the display device is not deteriorated.
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 or more and 9 or less carbon atoms. Examples of such (meth) acrylic acid alkyl esters include (meth) acrylic acid isopentyl, (meth) acrylic acid isohexyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid isoheptyl, and (meth) acrylic acid isooctyl. (Meta) Isononyl acrylate and the like can be mentioned. One of these may be used alone, or two or more thereof may be used in combination. Among them, it is preferable to use 2-ethylhexyl (meth) acrylic acid as the non-crosslinkable (meth) acrylic acid ester unit (a1), and 2-ethylhexyl acrylate (2-EHA) and 2-ethylhexyl methacrylate (2-EHMA). Is more preferable to use.

The number of carbon atoms of the branched alkyl group of the unit (a1) derived from the non-crosslinkable (meth) acrylic acid 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 permittivity can be formed. Further, by setting the carbon number of the branched alkyl group within the above range, the degree of polymerization of the crosslinkable acrylic polymer can be easily controlled, and a pressure-sensitive adhesive composition having excellent 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, preferably 80% by mass, based on the total mass of the crosslinkable acrylic polymer. It is more preferably 90% by mass or more, and further preferably 90% by mass or more. By setting the content of the unit (a1) within the above range, the relative permittivity of the pressure-sensitive adhesive layer can be sufficiently reduced, and the durability of the pressure-sensitive adhesive layer can be further enhanced.

(Unit (a2) derived from (meth) acrylic monomer having a crosslinkable functional group)
In the present invention, the crosslinkable functional group of the crosslinkable acrylic polymer is selected from one of a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group (preferably a glycidyl group), and an isocyanate group. It is preferable that there is at least one type. In this case, the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group includes a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, and 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.
Further, as the (meth) acrylic acid monomer having a crosslinkable functional group, a methacrylic acid monomer is preferable to an acrylic acid monomer from the viewpoint of not increasing the relative permittivity.
The unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group includes a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, and a glycidyl group. The monomer unit is preferable, and the hydroxy group-containing monomer unit is more preferable. 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. Examples thereof include (meth) acrylic acid [(mono, di or poly) alkylene glycol] such as mono (meth) acrylic acid mono (diethylene glycol), and (meth) acrylic acid lactone such as (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 a glycidyl group-containing monomer 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 with respect to the total mass of the crosslinkable acrylic polymer. It is preferably present, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. The content of the unit (a2) is preferably 40% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. If the content of the unit (a2) is at least the lower limit of the above range, it has sufficient crosslinkability, and if it is at least the upper limit of the above range, the required adhesive physical properties can be maintained and the relative permittivity. Can form a sufficiently low pressure-sensitive adhesive layer.

(Other monomer unit)
The crosslinkable acrylic polymer is simply a unit other than the unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester and the (meth) acrylic monomer unit (a2) having a crosslinkable functional group, if necessary. It may have a polymer unit. Examples of the other monomer 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. , (Meta) stearyl acrylate and the like can be mentioned. Further, the other (meth) acrylic acid ester unit may include a (meth) acrylic acid ester unit having a linear alkyl group having 5 or more and 9 or less carbon atoms. 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. Further, as other (meth) acrylic acid ester units, (meth) acrylic acid ester units having a cyclic group such as cyclohexyl (meth) acrylate and benzyl (meth) acrylate, (meth) acrylonitrile, vinyl acetate, etc. Examples thereof include styrene, vinyl chloride, vinylpyrrolidone and vinylpyridine. The content of the other monomer unit 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 characteristics of crosslinkable acrylic polymer)
The weight average molecular weight of the crosslinkable acrylic polymer is preferably 100,000 or more and 2 million or less, and more preferably 300,000 or more and 1.5 million or less. By setting the weight average molecular weight within the above range, sufficient step followability can be ensured. The weight average molecular weight of the crosslinkable acrylic polymer is a value before cross-linking with a cross-linking agent. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and determined based on 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 −90 ° C. or higher and −15 ° C. or lower, more preferably −80 ° C. or higher and −18 ° C. or lower, and −75 ° C. or higher and −18 ° C. or lower. The following is more preferable. By setting the glass transition temperature (Tg) of the crosslinkable acrylic polymer within the above range, the cohesive force when the pressure-sensitive adhesive layer is formed can be further enhanced. As a result, a pressure-sensitive adhesive layer having excellent durability and adhesive strength can be obtained.

<Relative permittivity of crosslinkable acrylic polymer>
The relative permittivity of the crosslinkable acrylic polymer alone is preferably 4.0 or less, preferably 3.8 or less.

<Polymer having unsaturated hydrocarbons in the molecule>
In the present invention, the polymer having unsaturated hydrocarbons has a number average molecular weight of 250 to 15,000, and the polymer having unsaturated hydrocarbons is liquid or oily at 20 ° C.
A polymer having unsaturated hydrocarbons is liquid or oily at 20 ° C. means that the viscosity measured at 20 ° C. by a B-type viscometer is 10,000 mPa · s or less.

The polymer having unsaturated hydrocarbons may be composed only of unsaturated hydrocarbons or may contain other structures, but it is preferably composed only of unsaturated hydrocarbons.
The unsaturated bond contained in the unsaturated hydrocarbon may be a double bond or a triple bond, but is preferably a double bond. The number of unsaturated bonds in each constituent unit of the polymer having unsaturated hydrocarbons is preferably 1 to 5, and more preferably 1 to 4. Further, it is more preferable that the number of carbon atoms of each constituent unit is 1 to 3.
Further, it is preferable that the polymer having an unsaturated hydrocarbon does not have a polar group from the viewpoint of lowering the relative permittivity. On the other hand, when the polymer having unsaturated hydrocarbons is incompatible with the crosslinkable acrylic polymer, polar groups may be introduced at a content of 20% or less of the weight of the polymer having unsaturated hydrocarbons.
The polymer having unsaturated hydrocarbons may be linear, may have a branched structure or a cyclic structure, but the linearity is a step from the viewpoint of lowering the relative permittivity. It is preferable from the viewpoint of improving the followability.

Examples of the polymer having unsaturated hydrocarbons include polybutadiene, polyisoprene, and styrene-based polymers.

(Styrene polymer)
As the polymer having unsaturated hydrocarbons, one type of styrene-based polymer may be contained alone, or two or more types having different compositions, number average molecular weights, etc. of the styrene-based polymers may be contained.

Examples of the styrene-based monomer that can constitute the styrene-based polymer include styrene and alkyl styrene (methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, and octyl styrene. ), Halogenized styrene (chlorostyrene, bromostyrene) and other monomers having a styrene skeleton. Above all, as the styrene-based monomer, it is preferable to use styrene from the viewpoint that it does not have a functional group capable of reacting with a cross-linking agent and is easily available.

As the styrene-based polymer, a commercially available product can be used. Examples of commercially available products include Piccolastic A5 (trade name, styrene homopolymer, number average molecular weight 300) manufactured by EASTMAN CHEMICAL.

(Polybutadiene)
As the polymer having unsaturated hydrocarbons, one kind of polybutadiene may be contained alone, or two or more kinds having different composition, number average molecular weight and the like of polybutadiene may be contained.

As the polybutadiene, a commercially available product can be used. Examples of commercially available products are those manufactured by Kuraray (product numbers: "LBR-302" and "LBR-307") and Total Cray Valley (trade names "Ricon 130", "Ricon 131", "Ricon 142" and "Ricon 156"). "Ricon 157") and the like.

(Number average molecular weight of polymers with unsaturated hydrocarbons)
The number average molecular weight of the polymer having unsaturated hydrocarbons is 15,000 or less, preferably 10,000 or less, more preferably 7,000 or less, and particularly preferably 5,000 or less. The number average molecular weight of the polymer having unsaturated hydrocarbons is 250 or more, preferably 280 or more, and more preferably 300 or more. By setting the number average molecular weight of the polymer having unsaturated hydrocarbons within the above range, the compatibility with the above-mentioned (meth) acrylic polymer becomes better, and when it is used for an optical member, it does not become cloudy and is transparently adhered. An agent layer can be formed. Further, by setting the number average molecular weight of the polymer having unsaturated hydrocarbons within the above range, it is possible to form a pressure-sensitive adhesive layer having excellent step followability.

The number average molecular weight of the polymer having unsaturated hydrocarbons is a value measured by gel permeation chromatography (GPC) and determined based on polystyrene. However, for a polymer having an unsaturated hydrocarbon whose number average molecular weight cannot be measured by GPC, the value obtained from the measured value by the vapor pressure osmotic method is used as the number average molecular weight.

(Contents of polymer having unsaturated hydrocarbons)
In the present invention, it is preferable to contain 1 to 20 parts by mass of the polymer having unsaturated hydrocarbons with respect to 100 parts by mass of the crosslinkable acrylic polymer.
The content of the polymer having unsaturated hydrocarbons is more preferably 3% by mass or more, and particularly preferably 5% by mass or more, based on the total mass of the crosslinkable acrylic polymer. Further, the content of the polymer having unsaturated hydrocarbons is more preferably 15% by mass or less, and particularly preferably 12% by mass or less, based on the total mass of the crosslinkable acrylic polymer. By setting the content of unsaturated hydrocarbons within the above range, the relative permittivity of the pressure-sensitive adhesive layer can be lowered more effectively, and a pressure-sensitive adhesive layer having excellent durability can be formed.

When a polymer having unsaturated hydrocarbons 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 a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method.

<Alkoxysilyl group-containing acrylic polymer>
In the present invention, the alkoxysilyl group-containing acrylic polymer has a weight average molecular weight of 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 at 20 ° C. by a B-type viscometer 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, more preferably −40 ° C. or lower.
Here, the glass transition temperature (Tg) is a value calculated from the composition or a value measured by a method using a calorimeter such as a differential scanning calorimeter (DSC).
As a calculation method, it can be calculated from the monomer unit and its content ratio by the Fox formula.
Fox formula: 1 / Tg = (W1 / Tg1) + (W2 / Tg2) + ... + (Wm / Tgm)
W1 + W2 + ... + Wm = 1
In the formula, Tg is the glass transition point of the alkoxysilyl group-containing acrylic polymer, and Tg1, Tg2, ..., Tgm are the glass transition points of the constituent units derived from each monomer in the alkoxysilyl group-containing acrylic polymer, and W1. , W2 ... Wm is the weight fraction of the structural unit derived from each monomer in the above-mentioned alkoxysilyl group-containing acrylic polymer.

The alkoxysilyl group-containing acrylic polymer is not particularly limited. The alkoxysilyl group-containing acrylic polymer is preferably a copolymer of a (meth) acrylic acid ester monomer and a vinyl monomer having a trialkoxysilyl group or a (meth) acrylic monomer.
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 of the (meth) acrylic acid-derived structure of the alkoxysilyl group-containing acrylic polymer to the Si atom of the alkoxysilyl group, that is,-(CH _2- C (R ⁰ ) (COO-))-. The linking group from the oxygen atom to the alkoxysilyl group of the skeleton (R ⁰ represents a hydrogen atom or a methyl group) preferably has a long linking chain length from the viewpoint of lowering the specific dielectric constant.
The oxygen atom at the terminal 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 of the structure derived from (meth) acrylic acid is preferably, for example, 30 atoms or less.
The main clavicle may have one type of acrylate-derived repeating unit or a methacrylate-derived repeating unit, or may have two or more types of acrylate-derived repeating units or methacrylate-derived repeating units. The main clavicle skeleton preferably has two or more acrylate-derived repeating units or methacrylate-derived repeating units.
Preferred 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. 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 lowering the relative permittivity.
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 represent an alkyl group.
The upper limit of the number of carbon atoms 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 setting 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 the adhesive is transparent without becoming cloudy when used in an optical member. An agent layer can be formed. Further, by setting the weight average molecular weight of the alkoxysilyl group-containing acrylic polymer within the above range, it is possible to form a pressure-sensitive adhesive layer having excellent step followability and durability.
Here, the weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is a value measured by gel permeation chromatography (GPC) and determined based on polystyrene. However, for those that cannot be measured by GPC, the value obtained from the measured value by the vapor pressure osmotic pressure method is used as the weight average molecular weight.

As the alkoxysilyl group-containing acrylic polymer, a commercially available product can be used. Examples of commercially available products include the ARUFON (registered trademark) US series manufactured by Toagosei Co., Ltd., specifically, the product name "ARUFON US-6100" (weight average molecular weight 2500) and the product name "ARUFON US". -6170 ”(weight average molecular weight 3000) and the like.
Further, as the alkoxysilyl group-containing acrylic polymer, Actflow (registered trademark) NE-1000 manufactured by Soken Chemical Co., Ltd. can also be preferably used.

(Content of acrylic polymer containing alkoxysilyl group)
In the present invention, it is preferable that 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 content of the alkoxysilyl group-containing acrylic polymer is more preferably 3% by mass or more, particularly preferably 4% by mass or more, and 5% by mass or more, based on the total mass of the crosslinkable acrylic polymer. It is more preferable to have. 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, based on the total mass of the crosslinkable acrylic polymer. Further, it is preferable that the relationship between the content (C1) of the linear saturated hydrocarbon polymer and the content (C2) of the alkoxysilylki group-containing acrylic polymer is C1 + C2 ≦ 20 parts by mass and C1> C2. 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 having excellent step followability and durability without increasing the relative permittivity of the pressure-sensitive adhesive layer.
The alkoxysilyl group-containing acrylic polymer may contain one type alone, or may contain two or more types having different compositions, weight average molecular weights, and the like.

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 a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method. Among these, the solution polymerization method is preferable as the polymerization method because the production can be performed relatively easily.

<Crosslinking agent>
The cross-linking agent is preferably a cross-linking agent that reacts with the cross-linking acrylic polymer by heat.
As the cross-linking agent, for example, among known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds, cross-linking functional groups possessed by the cross-linking acrylic polymer can be used. It can be appropriately selected in consideration of reactivity. For example, when a hydroxy group is contained as a crosslinkable functional group, an isocyanate compound can be used because of 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 cross-linking agent is preferably one or more selected from any of a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound, and is a bifunctional or higher isocyanate compound. Is more preferable.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like.
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 di. Glycyzyl 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.
As the cross-linking agent, a commercially available product can be used. Examples of commercially available products include xylylene diisocyanate compounds (Mitsui Chemicals, Inc., Takenate D-110N) and the like.

As the cross-linking agent, one type may be used alone or two or more types may be used in combination. The content of the cross-linking agent in the pressure-sensitive adhesive composition is appropriately selected depending on the desired adhesive characteristics 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 cross-linking acrylic polymer. It can be less than or equal to 0.03 parts by mass, and can be 0.03 parts by mass or more and 3 parts by mass or less.
The content of the cross-linking agent can be 0.01% by mass or more and 5.0% by mass or less, and 0.02% by mass or more and 2.0% by mass or less, based on the total mass of the pressure-sensitive adhesive composition. can do.

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

One type of solvent may be used alone, or two or more types may be used in combination. The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, but can be 25 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the crosslinkable acrylic polymer, and 30 parts by mass or more and 400 parts by mass or less. Can be.
Further, the content of the solvent can be 10% by mass or more and 90% by mass or less, and can be 20% by mass or more and 80% by mass or less, based on the total mass of the pressure-sensitive adhesive composition.

<Plasticizer>
The pressure-sensitive adhesive composition of the present invention may contain a plasticizer other than the polymer having an unsaturated hydrocarbon and the alkoxysilyl group-containing acrylic polymer. When a plasticizer is contained, the content of the plasticizer can be 50 parts by mass or less, 30 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. A plasticizer other than the content of the linear saturated hydrocarbon polymer (C1), the content of the alkoxysilyl group-containing acrylic polymer (C2), the linear saturated hydrocarbon polymer and the alkoxysilyl group-containing acrylic polymer. The relationship of the content (C3) is preferably C1 + C2 + C3 ≦ 20 parts by mass and C1>C2> C3.

As the plasticizer, a non-functional acrylic polymer can be used. The 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 having no functional group. It means a polymer composed of a non-acrylic monomer unit.
Examples of the acrylic monomer unit having no functional group other than the acrylate group include those similar to the non-crosslinkable (meth) acrylic acid ester unit (a1).
Examples of the non-acrylic monomer unit having no functional group include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caproate, vinyl laurate, vinyl myristate, vinyl palmitate, and stearer. Examples thereof include vinyl carboxylic acid esters such as vinyl acetate, vinyl cyclohexanecarboxylate, vinyl benzoate, and styrene.

<Arbitrary ingredient>
The pressure-sensitive adhesive composition may contain other components other than the 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, and light stabilizers such as hindered amine compounds. You can select from among them as needed.
Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. One type of these antioxidants may be used alone, or two or more types may be used in combination.
Examples of the metal corrosion inhibitor include benzoriazole-based resins.
Examples of the tackifier include rosin-based resin, terpene-based resin, terpene phenol-based resin, Kumaron inden-based resin, styrene-based resin, xylene-based resin, phenol-based resin, petroleum resin and the like.
Examples of the silane coupling agent include a mercaptoalkoxysilane compound (for example, a mercapto group-substituted alkoxy oligomer) and the like.
Examples of the ultraviolet absorber include benzotriazole-based compounds and benzophenone-based compounds.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition that substantially does not contain a polymer monomer or a polymerization initiator in addition to a polymer having a cross-linking agent and an unsaturated hydrocarbon and an acrylic polymer containing an alkoxysilyl group. It is preferable that there is (aftercureless). After-cure is a semi-cured adhesive layer which is a cured product of the pressure-sensitive adhesive composition, and after the pressure-sensitive adhesive layer is provided on the surface of the adherend, the semi-cured adhesive layer is further formed. Say how to completely cure. Aftercure-less means that aftercure is not required after the adhesive layer is provided on the surface of the adherend.

[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.
Since the adhesive sheet of the present invention has a low relative permittivity and is excellent in step followability and durability, it is preferably used for adhering optical members constituting a display device equipped with a touch panel.

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 of only the pressure-sensitive adhesive layer. Further, 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.
Examples of the single-sided adhesive sheet include a multi-layer sheet in which an adhesive layer is laminated on a support. Further, another layer may be provided between the support and the pressure-sensitive adhesive layer.
The double-sided pressure-sensitive adhesive sheet includes a single-layer pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, a multi-layered pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated, and a multi-layered pressure-sensitive adhesive in which another pressure-sensitive adhesive layer is laminated between the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer. Examples thereof include a sheet and a multi-layered pressure-sensitive adhesive sheet in which a support is laminated between the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer. When the double-sided adhesive sheet has a support, it is preferable to use a transparent support as the support. Since such a double-sided pressure-sensitive adhesive sheet is also excellent in transparency of the pressure-sensitive adhesive sheet as a whole, it can be suitably used for bonding optical members to each other.
Among the above-mentioned adhesive sheets, the pressure-sensitive adhesive sheet of the present invention is preferably a non-carrier type, preferably a single-layer adhesive sheet composed of an adhesive layer, or a multilayer pressure-sensitive adhesive sheet in which a plurality of adhesive layers are laminated, and is a single layer composed of an adhesive layer. Double-sided adhesive sheets are 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. Film; Examples thereof include an optical film such as an antireflection film and an electromagnetic wave shielding film.

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

The release sheet is a removable laminated sheet having a release sheet base material and a release agent layer provided on one side of the release sheet base material, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity base material. Can be mentioned.
Papers and polymer films are used as the base material for the release sheet in the releaseable laminated sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone-based release agent or a long-chain alkyl group-containing compound is used. In particular, a highly reactive additive silicone-based release agent is preferably used.
Specific examples of the silicone-based release agent include BY24-4527, SD-7220, etc. manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3600, KS-774, X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd., etc. Can be mentioned. Further, the silicone-based release agent may contain a silicone resin which is an organic silicon compound having ₂ units of SiO and (CH ₃ ) ₃ SiO _1/2 units or CH ₂ = CH (CH ₃ ) SiO _{1/2 units.} preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3800, X92-183 manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

In the present invention, one surface of the pressure-sensitive adhesive layer is provided with a first release sheet, the other surface of the pressure-sensitive adhesive layer is provided with a second release sheet, and the release force of the first release sheet and the second release sheet. Is preferably different. In the example of FIG. 1, in the release sheet 12, it is preferable that the release sheet 12a and the release sheet 12b have different peelability in order to facilitate the release. That is, if the peelability from one side and the peelability from the other side are different, it becomes easy to peel off only the peeling sheet 12 having the higher peeling property first. In that case, the peelability of the release sheet 12a and the release sheet 12b may be adjusted according to the bonding method and the bonding order.

The thickness of the pressure-sensitive adhesive layer can be appropriately set according to the intended use, and is not particularly limited, but is usually preferably in the range of 10 μm or more and 500 μm or less, more preferably 20 μm or more and 450 μm or less, and 30 μm or more and 450 μm or less. It is more preferably 40 μm or more and 400 μm or less, further 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, it is possible to sufficiently secure the step-following property and further improve the durability. Further, by setting the thickness of the pressure-sensitive adhesive layer within the above range, it becomes easy to manufacture a double-sided pressure-sensitive adhesive sheet.

The relative permittivity is the relative permittivity at a specific frequency. In the present invention, the relative permittivity at a frequency of 1 MHz, which is a value calculated by the method specified in JIS C 2138, is used.

The adhesive strength of the pressure-sensitive adhesive sheet is preferably 8 N / 25 mm or more, and more preferably 10 N / 25 mm or more.

The adhesive force of the adhesive sheet to the adherend described above is a value measured by peeling 180 ° to each adherend and the adhesive force is measured according to JIS Z 0237.

(Manufacturing method of adhesive sheet)
The method for manufacturing the adhesive sheet is not particularly limited.
The pressure-sensitive adhesive sheet of the present invention may be composed of a pressure-sensitive adhesive layer and another layer, but it is preferably composed of only the pressure-sensitive adhesive layer. Examples of the other layer 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, polyether ether ketone, and triacetyl cellulose; optical films such as antireflection film and electromagnetic wave shielding film; and the like. Can be mentioned.

The process for manufacturing the pressure-sensitive adhesive sheet preferably includes a step of applying the pressure-sensitive adhesive composition on the release sheet to form a coating film and a step of heating the coating film to form a cured product.

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

The coating of the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet can be carried out using a known coating device. Examples of the coating device 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, a curtain coater and the like.
Further, the coating film can be heated by using a known heating device such as a heating furnace or an infrared lamp.

(How to use the adhesive sheet)
In the method of 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 surface of the adherend.

Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet contains a polymer having an unsaturated hydrocarbon having a small relative permittivity and an alkoxysilyl group-containing acrylic polymer, the pressure-sensitive adhesive layer can be formed even if the adherend has a stepped portion. It is possible to follow the unevenness of the step portion.

[Laminate]
The laminated body of the present invention has an adherend on at least one surface of the pressure-sensitive adhesive sheet, and the adherend has a stepped 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 surface of the adherend.

FIG. 2 is a cross-sectional view showing an example of the configuration of the laminated body 20 in which the 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 only one of 27c and 27d may be used). In FIG. 2, the adherend 22 has a stepped portion (27a, 27b), and the adherend 24 has a stepped portion (27c, 27d). The thickness of the stepped portion (27a, 27b, 27c, 27d) is usually 5 μm or more and 60 μm or less. As described above, the adhesive sheet 21 of the present invention can be attached to a member having a stepped portion, and can follow the unevenness of the stepped portion.

The adherend is preferably an optical member. Examples of the optical member include each constituent member in an optical product such as a touch panel and an image display device.
As the constituent members of the touch panel, for example, an ITO film having an ITO (indium tin oxide) film provided on a transparent resin film, ITO glass having an ITO film provided on the surface of a glass plate, and a transparent resin film coated with a conductive polymer. Examples thereof include transparent conductive films, hard coat films, and fingerprint resistant films. The adhesive sheet of the present invention is preferably for stacking sensors on a touch panel, and more preferably for stacking sensors on a touch panel using a touch pen. From this point of view, 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 a transparent resin film. A transparent conductive film coated with is preferable.
Examples of the constituent members of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a luminance improving film used in a liquid crystal display device.
Examples of the material used for these members include glass, polycarbonate, polyethylene terephthalate, polymethylmethacrylate, polyethylene naphthalate, cycloolefin polymer, triacetylcellulose, 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 adhesive sheet of the present invention is used to bond ITO films to each other inside a touch panel, to bond an ITO film to an ITO glass, to bond an ITO film to a liquid crystal panel of a touch panel, and to bond a cover glass to an ITO film. It is used for bonding, bonding between cover glass and decorative film, etc.

(Manufacturing method of laminated body)
The present invention also relates to a method for producing a laminate. The method for producing the laminate preferably includes a step of bringing the above-mentioned pressure-sensitive adhesive sheet into contact with the surface of the adherend.

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.
In addition, Example 1 is a reference example.

[Example 1]
<Preparation of adhesive composition>
2-Ethylhexyl acrylate (2-EHA), 2-ethylhexyl methacrylate (2-EHMA), and 2-hydroxyethyl acrylate (2-HEA) are blended in a mass ratio of 30:60:10, and a radical polymerization initiator is added. 2,2'-Azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain a crosslinkable acrylic polymer (A). The crosslinkable acrylic polymer (A) had a weight average molecular weight of 500,000.
The number average molecular weight or the weight average molecular weight is a value measured by gel permeation chromatography (GPC) and determined based on polystyrene. Those that could not be measured by GPC were measured by the vapor pressure osmotic pressure method.
The measurement conditions of gel permeation chromatographie (GPC) are as follows.
Solvent: Tetrahydrofuran Column: Shodex KF801, KF803L, KF800L, KF800D (4 units manufactured by Showa Denko KK were connected and used)
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 velocity): 0.8 ml / min Injection amount: 10 μl
Calibration curve: Standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko KK) A calibration curve with 10 samples from Mw = 1320 to 2,500,000 was used.
A polystyrene compound (Piccolastic A5 manufactured by EASTMAN CHEMICAL, number average molecular weight) as a polymer having unsaturated hydrocarbons with respect to 100 parts by mass of the solid content of the acrylic polymer of the crosslinkable acrylic polymer (A) obtained above. 300) in 10 parts by mass, an acrylic polymer containing an alkoxysilyl group (manufactured by Toa Synthetic Co., Ltd., trade name "ARUFON US-6100", weight average molecular weight 2500, Tg-58 ° C., having a trimethoxysilyl group and a main chain skeleton. Is a copolymer of 2-ethylhexyl acrylate and methyl methacrylate), and 0.15 part by mass of a xylylene diisocyanate compound (Takenate D-110N, manufactured by Mitsui Chemicals, Inc.) as a cross-linking agent is added to solidify. Ethyl acetate was added so that the component concentration was 40% by mass to obtain a pressure-sensitive adhesive composition.
A polystyrene compound (Piccolastic A5 manufactured by EASTMAN CHEMICAL, number average molecular weight 300) and an alkoxysilyl group-containing acrylic polymer (manufactured by Toa Synthetic Co., Ltd., trade name "ARUFON US-6100") used as a polymer having unsaturated hydrocarbons. ) Was oily at 20 ° C.

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

<Preparation of laminated body (1)>
Ultraviolet curable ink was applied to the surface of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm) and screen-printed in a frame shape (length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was 5 μm. Then, the ultraviolet curable ink printed by irradiating with ultraviolet rays was cured. This step was repeated three times to obtain a printed stepped glass having a stepped portion of 15 μm.
The obtained adhesive sheet is cut into a shape of 90 mm in length × 50 mm in width, the first release sheet is peeled off, and the adhesive layer is printed on a stepped glass using a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT). It was pasted together so as to cover the entire surface of the frame-shaped print. Then, the second release sheet was peeled off, and a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm) was attached to the surface of the exposed pressure-sensitive adhesive layer with the above laminator, and autoclaved (40 ° C., 0. 5 MPa, 30 minutes) was carried out to obtain a laminated body (1).

<Preparation of laminated body (2)>
The obtained adhesive sheet is cut into a shape of 90 mm in length × 50 mm in width, the first release sheet is peeled off, and a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT) is used to prepare the laminated body (1). The printed stepped glass having a stepped portion of 15 μm used was bonded so as to cover the entire surface of the frame-shaped print.
As an adherend, a polarizing plate (SKN-18243T manufactured by Polatechno Co., Ltd.) was cut out in advance to the same dimensions as one side of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm), and central grains were formed on the surface of the polarizing plate. About 0.05 mg of glass beads having a diameter of 30 μm was sprayed to prepare a product.
The second release sheet of the laminated body integrated with the printed step glass was peeled off, and the glass beads of the polarizing plate of the adherend were bonded to the sprayed surface with a laminator. Then, an autoclave treatment (40 ° C., 0.5 MPa, 30 minutes) was carried out to obtain a laminated body (2).

[Example 2]
As a polymer having unsaturated hydrocarbons, a polybutadiene compound (manufactured by Claret (product number: "LBR-302", number average molecular weight 5500)) is used instead of the polystyrene compound (Piccolastic A5 manufactured by EASTMAN CHEMICAL, number average molecular weight 300). , Alkoxysilyl group-containing acrylic polymer (manufactured by Toa Synthetic Co., Ltd., trade name "ARUFON US-6100") instead of alkoxysilyl group-containing acrylic polymer (manufactured by Toa Synthetic Co., Ltd., trade name "ARUFON US-6170"), weight average molecular weight 3000 The pressure-sensitive adhesive composition, the pressure-sensitive sheet, and the laminate are the same as in Example 1 except that they have a trimethoxysilyl group and the main chain skeleton is a copolymer of ethyl acrylate and n-butyl acrylate). I got a body.
The polybutadiene compound used as the polymer having unsaturated hydrocarbons (manufactured by Kuraray Co., Ltd. (product number: "LBR-302, number average molecular weight 5500") is oily at 20 ° C. and is an alkoxysilyl group-containing acrylic polymer (Toa). The trade name "ARUFON US-6170") manufactured by Synthetic Co., Ltd. was liquid at 20 ° C.

[Example 3]
As a polymer having unsaturated hydrocarbons, a polyisoprene / maleic anhydride copolymer (manufactured by Claret (product number: "MIP-004", manufactured by Claret), instead of a polystyrene compound (Piccolastic A5 manufactured by EASTMAN CHEMICAL, number average molecular weight 300)). 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 number average molecular weight was 9400)).

[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 a polymer having an unsaturated hydrocarbon and an acrylic polymer containing an alkoxysilyl group were 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-linking acrylic polymer (B) was used instead of the cross-linking acrylic polymer (A).
The crosslinkable 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 crosslinkable acrylic polymer (B) had a weight average molecular weight of 700,000.

[Comparative Example 3]
Similar to Comparative Example 1 except that the crosslinkable acrylic polymer (C) was used instead of the crosslinkable acrylic polymer (A) and the blending amount of the crosslinking agent was changed from 0.15 part by mass to 0.7 part by mass. A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a laminate were obtained.
The crosslinkable acrylic polymer (C) uses isostearyl acrylate (ISTA) instead of 2-EHMA and 4-hydroxybutyl acrylate (HBA) instead of 2-HEA to prepare ISTA, 2-EHA, and HBA. The mixture was blended so that the mass ratio was 90: 10: 1, and 2,2'-azobisisobutyronitrile was used as the radical polymerization initiator instead of 2,2'-azobis (2,4-dimethylvaleronitrile). A crosslinkable acrylic polymer (C) was obtained in the same manner as in Example 1 except that it was used. The crosslinkable acrylic polymer (C) had a weight average molecular weight of 700,000.

[Comparative Example 4]
An acrylic polymer that does not contain an alkoxysilyl group instead of an alkoxysilyl group-containing acrylic polymer (manufactured by Toa Synthetic Co., Ltd., trade name "ARUFON US-6100") without blending a polymer having unsaturated hydrocarbons (Toa Synthetic Co., Ltd.) 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 product, trade name “ARUFON UP-1110”, weight average molecular weight 2500) was used.

[evaluation]
<Relative permittivity>
The evaluation of the relative permittivity of the pressure-sensitive adhesive sheet was carried out by the following procedure. The pressure-sensitive adhesive layer (the first peeling sheet and the second peeling sheet peeled from the pressure-sensitive adhesive sheet) was sandwiched between two copper foils and autoclaved (40 ° C., 0.5 MPa, 30 minutes). .. Then, it was measured based on JIS C 2138 by a dielectric measurement system (manufactured by Toyo Corporation, type 1260). The frequency and measurement environment were measured under the following conditions.
Frequency: 1MHz
Measurement environment: 23 ° C, relative humidity 55%

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

<Durability>
The laminate (1) was treated in an environment of 85 ° C. and a relative humidity of 85% for 240 hours, and the entire sample was observed with a microscope (magnification: 25 times) for bubbles or peeling. evaluated.
⊚: No bubbles or peeling occurred.
◯: There are some bubbles.
X: Many bubbles are generated.

From Table 1 above, it was found that the pressure-sensitive adhesive compositions obtained in Examples 1 to 3 can reduce the relative permittivity when the pressure-sensitive adhesive layer is formed, and can improve the step followability and durability. The adhesive strength of the pressure-sensitive adhesive sheets of Examples 1 to 3 against glass was 18 N / 25 mm or more.
The pressure-sensitive adhesive sheet obtained in Comparative Example 1 of the embodiment in which the pressure-sensitive adhesive composition does not contain a polymer having an unsaturated hydrocarbon and an alkoxysilyl group-containing acrylic polymer can reduce the relative permittivity, but is inferior in step followability. , The relative permittivity and the step followability could not be achieved at the same time.
The pressure-sensitive adhesive sheet obtained in Comparative Example 2 in which the pressure-sensitive adhesive composition does not contain a polymer having an unsaturated hydrocarbon and an alkoxysilyl group-containing acrylic polymer has good step followability, but has a relative permittivity. It was too high to achieve both relative permittivity and step followability.
The pressure-sensitive adhesive sheet obtained in Comparative Example 3 of the embodiment in which the pressure-sensitive adhesive composition does not contain a polymer having an unsaturated hydrocarbon and an alkoxysilyl group-containing acrylic polymer can reduce the relative permittivity, but is inferior in step followability. , The relative permittivity and the step followability could not be achieved at the same time. In addition, Comparative Example 3 is an example referring to Example 4 of JP-A-2016-172865.
Although the pressure-sensitive adhesive sheet obtained in Comparative Example 4 using an acrylic polymer having no unsaturated hydrocarbon and no alkoxysilyl group in the pressure-sensitive adhesive composition had good step followability. , The relative dielectric constant was high.

1 Adhesive sheet with release sheet 11 Adhesive sheet (adhesive layer)
12a, 12b Peeling sheet 20 Laminated body 21 Adhesive sheet (adhesive layer)
22 Adhesive body 24 Adhesive body 27a, 27b, 27c, 27d Stepped portion

Claims (10)

A pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer, a crosslinking agent, a polymer having unsaturated hydrocarbons in the molecule, and an alkoxysilyl group-containing acrylic polymer.
The crosslinkable acrylic polymer is contained in an amount of 50% by mass or more based on the pressure-sensitive adhesive composition.
When the layer is formed only of the crosslinkable acrylic polymer, the relative permittivity of the layer at a frequency of 1 MHz is 3.8 or less.
The polymer having unsaturated hydrocarbons has a number average molecular weight of 250 to 15,000.
The polymer having unsaturated hydrocarbons is liquid or oily at 20 ° C.
The polymer having unsaturated hydrocarbons is polyisoprene, polybutadiene, or a copolymer containing these as a repeating unit.
The weight average molecular weight of the alkoxysilyl group-containing acrylic polymer is 400 to 5000, and the weight average molecular weight 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 the pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, is formed. Claim 1 in which the crosslinkable functional group of the crosslinkable acrylic polymer is one or more selected from any one of a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group and an isocyanate group. The pressure-sensitive adhesive composition according to. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the cross-linking agent is one or more selected from any of a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound. The pressure-sensitive adhesive composition according to any one of claims 1 to 3 , wherein the polymer having unsaturated hydrocarbons 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 polymer having unsaturated hydrocarbons is contained in an amount of 5 to 15 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 5 , 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 6 , 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. Has an adhesive layer,
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 7. 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 8 , wherein the first release sheet and the second release sheet have different release forces. Cover the surface of at least one of the adhesive sheets according to claim 8 or the surface of the adhesive sheet according to claim 9 excluding at least one of the first release sheet and the second release sheet. Have a body,
A laminated body in which the adherend has a stepped portion.

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