JP6969481B2 - 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, in various fields, 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. 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 considered to use an adhesive sheet having a controlled relative permittivity. Among them, in the capacitive touch panel having an image display device and a touch panel, the touch panel is liable to malfunction due to electrical noise from the image display device. It is being considered to use an adhesive sheet having a low dielectric constant.

For example, Patent Documents 1 and 2 disclose a pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having a low relative permittivity. Patent Document 1 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 disclosed. Further, Patent Document 2 describes 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 single amount of (meth) acrylic having a crosslinkable functional group. A base polymer (A) containing a body-derived unit (a2), a monomer (B) containing at least one polymerizable unsaturated group, and a cross-linking agent (A) that reacts with the base polymer (A) by heat. A pressure-sensitive adhesive composition containing C) and a polymerization initiator (D) that initiates a polymerization reaction of the monomer (B) by irradiation with active energy rays is disclosed.

Japanese Unexamined Patent Publication No. 2016-172865 International Publication WO2017 / 159788 Gazette

However, when the present inventors attach the pressure-sensitive adhesive layer in Patent Document 1 to an adherend having a stepped portion, air may remain in the stepped portion and the step-following property may not be sufficient. all right. Further, when the present inventors want to obtain a pressure-sensitive adhesive layer having a low dielectric constant, it is necessary to mix a material having a low dielectric constant with the pressure-sensitive adhesive, but these materials are compatible with the pressure-sensitive adhesive. It was also found that it may be bad and the transparency of the adhesive layer may be deteriorated.
Since the pressure-sensitive adhesive composition of Patent Document 2 is a dual-curing type pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer is semi-cured, then bonded to an adherend, and then post-cured. However, depending on the bonding method with the adherend and the application, an adhesive layer having no post-curing ability is required due to adverse effects such as energy ray irradiation for post-curing and yellowing of the adherend in the heating process. In some cases, the development of a pressure-sensitive adhesive layer that does not have post-curing ability has also been required.

Therefore, in order to solve the problems of the prior art, the present inventors have a pressure-sensitive adhesive layer having no post-curing ability, a low relative permittivity, and excellent step followability and transparency. Studies have been carried out for the purpose of providing a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer.

As a result of diligent studies to solve the above problems, the present inventors have obtained a diene polymer having a number average molecular weight of 250 to 15,000 and a linear saturated hydrocarbon compound having a number average molecular weight of 250 to 5000. It has been found that, when used in combination with a crosslinkable acrylic polymer, a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having a low relative permittivity and excellent step followability and transparency can be obtained.
Specifically, the present invention has the following configurations.

[1] A pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer, a crosslinking agent, a diene-based polymer, and a linear saturated hydrocarbon compound.
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 diene polymer is 250 to 15,000, and the diene polymer has a number average molecular weight of 250 to 15,000.
The number average molecular weight of the linear saturated hydrocarbon compound is 250 to 5000, and the number average molecular weight is 250 to 5000.
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 pressure-sensitive adhesive composition according to [1], wherein the diene-based polymer is a polymer having a non-conjugated diene structure in the molecule.
[3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the diene-based polymer is a butadiene-based polymer.
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the diene-based polymer has a 1,2-vinyl group.
[5] The pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the linear saturated hydrocarbon compound is a polyolefin-based polymer.
[6] The crosslinkable functional group of the crosslinkable acrylic polymer is one or more selected from a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group and an isocyanate group [1] to [ 5] The pressure-sensitive adhesive composition according to any one of.
[7] The pressure-sensitive adhesive according to any one of [1] to [6], wherein the cross-linking agent is one or more selected from a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound. Composition.
[8] The pressure-sensitive adhesive composition according to any one of [1] to [7], which contains 1 to 20 parts by mass of a diene-based polymer with respect to 100 parts by mass of a crosslinkable acrylic polymer.
[9] The pressure-sensitive adhesive composition according to any one of [1] to [8], which contains 0.5 to 20 parts by mass of a linear saturated hydrocarbon compound with respect to 100 parts by mass of a crosslinkable acrylic polymer.
[10] It has an adhesive layer and has an adhesive layer.
A pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition according to any one of [1] to [9].
[11] 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 adhesive sheet according to [10], wherein the first release sheet and the second release sheet have different release forces.
[12] It has a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive composition according to any one of [1] to [9], and an adherend on at least one surface side of the pressure-sensitive adhesive layer.
A laminated body in which the adherend has a stepped portion.

According to the present invention, there is provided a pressure-sensitive adhesive composition which is a pressure-sensitive adhesive layer having no post-curing ability and can form a pressure-sensitive adhesive layer having a low relative permittivity and excellent step followability and transparency. be able to.

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. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

As used herein, "(meth) acrylic acid" represents both acrylic acid and / or methacrylic acid. Further, in the present specification, "monomer" and "monomer" are synonymous.

(Adhesive composition)
The present invention relates to a pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer, a crosslinker, a diene polymer and a linear saturated hydrocarbon compound. Here, the number average molecular weight of the diene-based polymer is 250 to 15,000, and the number average molecular weight of the linear saturated hydrocarbon compound is 250 to 5,000. Further, the pressure-sensitive adhesive composition of the present invention contains a crosslinkable acrylic polymer in an amount of 50% by mass or more based on the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive composition. The relative permittivity of the layer at a frequency of 1 MHz is 3.5 or less.

By having the above-mentioned structure, the pressure-sensitive adhesive composition of the present invention can reduce the relative permittivity when the pressure-sensitive adhesive layer is formed, and forms the pressure-sensitive adhesive layer having excellent step followability and transparency. be able to.
Usually, when forming an adhesive sheet used for optical applications, a crosslinkable acrylic polymer (base polymer) having excellent transparency is used. In order to lower the relative permittivity, it is considered to change the structure of such a crosslinkable acrylic polymer (base polymer), but if the relative permittivity is lowered, the step followability and transparency are inferior. On the contrary, it is difficult to reduce the relative permittivity and to have excellent step followability and transparency, for example, the relative permittivity increases when the step followability and transparency are improved. However, after diligent studies, the present inventors did not change the structure of the crosslinkable acrylic polymer (base polymer), but instead used a diene polymer and a linear saturated hydrocarbon compound as the crosslinkable acrylic polymer. It has been found that the relative dielectric constant of the pressure-sensitive adhesive layer can be lowered, and the step followability and transparency can be improved by using in combination with. As described above, the present invention has a low relative permittivity and excellent step followability in the pressure-sensitive adhesive layer having no post-curing ability by using the compound having a predetermined structure in combination with the crosslinkable acrylic polymer. And succeeded in combining transparency.

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 may be 3.5 or less, preferably 3.1 or less. It is more preferably 0 or less, and further preferably 2.9 or less. By setting the relative permittivity of the pressure-sensitive adhesive layer within the above range, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer is preferably used for adhering an optical member constituting a display device equipped with a touch panel.
The relative permittivity of the pressure-sensitive adhesive layer is a relative permittivity at a frequency of 1 MHz, and a value calculated by a method specified in JIS C 2138 is used.

The haze of the pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, is preferably 2.0% or less, more preferably 1.5% or less, still more preferably 1.0% or less. Here, the haze of the pressure-sensitive adhesive layer is a value measured by a method according to JIS K 7136 with slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd. bonded to both sides of the pressure-sensitive adhesive layer. Specifically, the adhesive layer is attached to a slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd., and the slide glass is also attached to the opposite surface of the adhesive layer so that air and foreign matter do not enter. , Glass / adhesive layer / glass are laminated in this order to prepare a laminated body. This laminate is subjected to autoclave (pressure defoaming) treatment at 0.5 MPa and 40 ° C. for 30 minutes, and the haze value is measured using NDH4000 manufactured by Nippon Denshoku Kogyo Co., Ltd.

The pressure-sensitive adhesive composition may contain a solvent, and in a state containing a solvent as described later, the solid content concentration is preferably 20 to 60% by mass, more preferably 25 to 50% by mass. ..

<Crosslinkable acrylic polymer>
As the crosslinkable acrylic polymer, a known crosslinkable acrylic polymer can be used. The crosslinkable acrylic polymer preferably has transparency to the extent that the visibility of the display device is not deteriorated.

The crosslinkable acrylic polymer preferably contains a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester and a unit (a2) derived from a (meth) acrylic monomer having a crosslinkable functional group. .. In this case, the unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester is 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. Is preferable. 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, it becomes easy to form a pressure-sensitive adhesive layer having a sufficiently low specific dielectric constant from the pressure-sensitive adhesive composition containing the crosslinkable acrylic polymer.
In the present specification, the "unit" is a repeating unit (monomer unit) constituting the polymer.

The 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 has an alkyl group having 5 or more carbon atoms, and such an alkyl group is branched. Due to the structure, the molar volume is large and the density is small. Therefore, when the crosslinkable acrylic polymer contains 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, the molarity of the crosslinkable acrylic polymer is obtained. The volume 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, it becomes easy to form a pressure-sensitive adhesive layer having a low relative permittivity.

The content of the crosslinkable acrylic polymer may be 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and 80% by mass, based on the pressure-sensitive adhesive composition. The above is more preferable. The content of the crosslinkable acrylic polymer is preferably 98% by mass or less with respect to the pressure-sensitive adhesive composition. In the present specification, when the content of the crosslinkable acrylic polymer is 50% by mass or more with respect to the total mass of the pressure-sensitive adhesive composition, the crosslinkable acrylic polymer is the main component of the pressure-sensitive adhesive composition. I can say.

<Unit derived from non-crosslinkable (meth) acrylic acid ester (a1)>
The unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester is preferably 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. Above all, it is preferable to use 2-ethylhexyl (meth) acrylic acid as the non-crosslinkable (meth) acrylic acid ester unit (a1).

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, it becomes easy to form a pressure-sensitive adhesive layer having a sufficiently low relative permittivity. 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 lowered, 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 one or more 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. Is preferable. In this case, the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group is a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, or an amide. It is preferably one or more selected from a group-containing monomer unit, an epoxy group (preferably glycidyl group) -containing monomer unit, and an isocyanate group-containing monomer unit.

Among them, the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group is a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, and glycidyl. It is preferably one kind or two or more kinds selected from the group-containing monomer unit, and particularly preferably the hydroxy group-containing monomer unit.
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.

Further, the (meth) acrylic 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 permittivity of the pressure-sensitive adhesive composition.

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 units>
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. Other monomers may be copolymerizable with a non-crosslinkable (meth) acrylic acid ester and an acrylic monomer having a crosslinkable functional group, for example, (meth) acrylonitrile, vinyl acetate, styrene, etc. Examples thereof include 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 further 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 measurement conditions of gel permeation chromatography (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 volume: 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.

The glass transition temperature (Tg) of the crosslinkable acrylic polymer is preferably −80 ° C. or higher and −10 ° C. or lower, more preferably −75 ° C. or higher and −15 ° C. or lower, and −70 ° 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.

The relative permittivity of the crosslinkable acrylic polymer is preferably 4.0 or less, and more preferably 3.8 or less. The relative permittivity of the above-mentioned crosslinkable acrylic polymer is the relative permittivity of only the crosslinkable acrylic polymer.

<Diene polymer>
The pressure-sensitive adhesive composition of the present invention contains a diene-based polymer. Here, the number average molecular weight of the diene polymer is 250 to 15,000. The diene-based polymer is preferably a polymer of alkaziene. Among them, the diene-based polymer is preferably a polymer having a non-conjugated diene structure in the molecule, and particularly preferably a polymer having a non-conjugated alkadiene structure in the molecule.

The diene-based polymer is preferably a polymer of alkaziene, and the diene-based polymer preferably contains a monomer unit derived from alkaziene having 4 to 12 carbon atoms. Examples of the alkaziene having 4 to 12 carbon atoms include butadiene, isoprene, pentadiene, hexadiene, cyclopentadiene, cyclohexadiene, and isobutylene. Among them, the alkaziene is preferably an alkaziene having 4 to 8 carbon atoms, and particularly preferably butadiene. That is, the diene-based polymer is preferably a butadiene-based polymer.

The butadiene-based polymer may be a polymer composed of a monomer unit derived from butadiene, or may be a copolymer containing another monomer unit. When the butadiene polymer is a copolymer, other monomer units constituting the butadiene polymer include, for example, styrene, (meth) acrylic acid, (meth) acrylic acid derivative, vinyl monomer, and non-butadiene polymer. Examples thereof include units derived from saturated carboxylic acid, unsaturated carboxylic acid derivative and the like.

The number average molecular weight of the diene polymer may be 250 or more, preferably 500 or more, and more preferably 800 or more. The number average molecular weight of the diene polymer may be 15,000 or less, preferably 10,000 or less, more preferably 8,000 or less, and even more preferably 5,000 or less. By setting the number average molecular weight of the diene polymer within the above range, the compatibility with the above-mentioned crosslinkable acrylic polymer becomes better, and a transparent pressure-sensitive adhesive layer is formed without becoming cloudy when used in an optical member. can do. Further, by setting the number average molecular weight of the diene polymer within the above range, it is possible to improve the step followability of the pressure-sensitive adhesive layer. The number average molecular weight of the diene polymer is a value obtained by measuring by gel permeation chromatography (GPC) or a vapor pressure type molecular weight measurement method (VPO method).

The diene-based polymer is preferably a polymer having a 1,2-vinyl group (1,2-vinyl structure). The 1,2-vinyl bond amount (1,2-vinyl group ratio) of the diene-based polymer is preferably 10% or more, more preferably 20% or more with respect to the diene-based polymer.
The 1,2-vinyl bond amount (1,2-vinyl group ratio) referred to here is the ratio of the 1,2-vinyl structure to the molecular weight (number average molecular weight) of the entire diene polymer. That is, the vinyl group ratio is calculated by the following formula when the number average molecular weight of the diene polymer is Md and the molecular weight of the 1,2-vinyl group-containing unit of the diene polymer is Mv.
(Vinyl group ratio%) = Mv ÷ Md × 100
Assuming that the molecular weight of the vinyl group-containing unit is Ms, the following relationship holds.
(Number of 1,2-vinyl groups per molecular chain of diene polymer) = Md × (1,2-vinyl group ratio) ÷ Ms

The diene polymer is preferably liquid or oily at 20 ° C. The fact that the diene polymer is liquid or oily at 20 ° C means that the viscosity measured by a B-type viscometer at 20 ° C is 30,000 mPa · s or less. The viscosity of the diene polymer is preferably 500 to 30,000 mPa · s, more preferably 800 to 20,000 mPa · s.

The content of the diene-based polymer is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and 3 to 12 parts by mass with respect to 100 parts by mass of the above-mentioned crosslinkable acrylic polymer. It is more preferably 3 to 10 parts by mass, and particularly preferably 3 to 10 parts by mass. By setting the content of the diene polymer within the above range, it becomes easy to form a pressure-sensitive adhesive layer having excellent step followability and transparency while exhibiting the effect of lowering the relative permittivity.
The diene-based polymer may contain one type alone, or may contain two or more types having different structures, number average molecular weights, and the like.

As the diene polymer, a commercially available product can be used. Examples of commercially available products include polybutadiene (manufactured by Total, Rikon 156, Rikon 157, Krasol LBH-P 2000, Krasol LBH-P 3000) and the like.
Further, the diene-based polymer can be 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.

<Linear saturated hydrocarbon compound>
The pressure-sensitive adhesive composition of the present invention contains a linear saturated hydrocarbon compound. Here, the number average molecular weight of the linear saturated hydrocarbon compound is 250 to 5000. The linear saturated hydrocarbon compound is preferably a polymer of linear saturated hydrocarbon, and more preferably a polyolefin-based polymer.

Examples of the polyolefin-based polymer include polyethylene, polypropylene, polybutene and the like. Above all, the polyolefin-based polymer is more preferably polybutene. Polybutene is preferably used because it has excellent compatibility with the above-mentioned crosslinkable acrylic polymer. As the polyolefin-based polymer, a copolymer having ethylene and propylene as a monomer unit or a copolymer having ethylene and butene as a monomer unit can also be used.

The number average molecular weight of the linear saturated hydrocarbon compound may be 250 or more, preferably 280 or more, and more preferably 300 or more. The number average molecular weight of the linear saturated hydrocarbon compound may be 5000 or less, preferably 3000 or less, more preferably 2000 or less, and further preferably 1000 or less. By setting the number average molecular weight of the linear saturated hydrocarbon compound within the above range, the compatibility with the above-mentioned crosslinkable acrylic polymer becomes better, and a transparent pressure-sensitive adhesive that does not become cloudy when used in an optical member. Layers can be formed. Further, by setting the number average molecular weight of the linear saturated hydrocarbon compound within the above range, it is possible to improve the step followability of the pressure-sensitive adhesive layer. The number average molecular weight of the linear saturated hydrocarbon compound is a value measured by gel permeation chromatography (GPC) or a vapor pressure type molecular weight measurement method (VPO method).

The linear saturated hydrocarbon compound is preferably liquid or oily at 20 ° C. The fact that the linear saturated hydrocarbon compound is liquid or oily at 20 ° C means that the viscosity measured at 20 ° C by a B-type viscometer is 30,000 mPa · s or less.

The content of the linear saturated hydrocarbon compound is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass with respect to 100 parts by mass of the above-mentioned crosslinkable acrylic polymer. It is more preferably 2 to 10 parts by mass. By setting the content of the linear saturated hydrocarbon compound within the above range, it becomes easy to form a pressure-sensitive adhesive layer having excellent step followability and transparency while exhibiting the effect of lowering the relative permittivity.
The linear saturated hydrocarbon compound may be contained alone or may contain two or more types having different structures, number average molecular weights and the like.

<Crosslinking agent>
The pressure-sensitive adhesive composition of the present invention contains a cross-linking 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 its reactivity with 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 a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound, and more preferably a bifunctional or higher isocyanate compound. preferable.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. The diicyanate may be used as it is bifunctional, or may be used as a trifunctional derivative such as adduct, nurate, or burette.
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. The amount is preferably 0.03 part by mass or more, and more preferably 3 parts by mass or less.
The content of the cross-linking agent is preferably 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. It is more preferable to have.

<Solvent>
The pressure-sensitive adhesive composition of the present invention may further contain a solvent. In this case, the solvent can 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 is preferably 25 parts by mass or more and 500 parts by mass or less, and 30 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the crosslinkable acrylic polymer. Is more preferable.
The content of the solvent is preferably 10% by mass or more and 90% by mass or less, and more preferably 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, and when the pressure-sensitive adhesive composition contains a plasticizer, it is added within a range that does not impair the processability of the pressure-sensitive adhesive sheet and the protrusion of glue. For example, the content of the plasticizer is preferably 50 parts by mass or less, more preferably 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 is more preferable to do so.

As the plasticizer, for example, 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 of the present invention may contain any component other than the above-mentioned compounds. Optional 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. Can be selected as needed from.
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 layer formed from the pressure-sensitive adhesive composition of the present invention is preferably a pressure-sensitive adhesive layer having no post-curing ability. Here, the post-curing is a semi-cured product in which the pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, is used, and the pressure-sensitive adhesive layer is provided on the surface of the adherend. A method of completely curing the adhesive layer. Having no post-curing ability means that post-curing (after-cure) is not required after the pressure-sensitive adhesive layer is provided on the surface of the adherend.

The content of the monomer in the pressure-sensitive adhesive composition of the present invention is preferably 5% by mass or less, and more preferably 3% by mass or less. Further, the content of the polymerization initiator in the pressure-sensitive adhesive composition of the present invention is preferably 0.05% by mass or less, more preferably 0.01% by mass or less. In the present specification, if the content of the monomer and the polymerization initiator in the pressure-sensitive adhesive composition is within the above range, it can be said that the monomer and the polymerization initiator are not substantially contained, and the post-curing It can form an ineffective pressure-sensitive adhesive layer.

(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 above-mentioned pressure-sensitive adhesive composition. Since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer having a low relative permittivity and excellent step followability and transparency, it is preferably used for bonding optical members constituting a display device equipped with a touch panel.

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 base material-less type, preferably a single-layer pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, or a multi-layered pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated, and a single layer composed of a pressure-sensitive adhesive layer. Double-sided adhesive sheet is particularly preferable.

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 the pressure-sensitive adhesive sheet 1 with a release sheet. The adhesive sheet 11 shown in FIG. 1 has a release sheet (12a, 12b). The pressure-sensitive adhesive sheet 11 in FIG. 1 is a single-layer pressure-sensitive adhesive sheet without a base material, and is a double-sided pressure-sensitive 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 provided. Is preferably different. In the example of FIG. 1, it is preferable that the release sheets 12a and 12b have different peelability between the release sheet 12a and the release sheet 12b 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 haze of the pressure-sensitive adhesive sheet is preferably 2.0% or less, more preferably 1.5% or less, still more preferably 1.0% or less. Here, the haze of the pressure-sensitive adhesive sheet is a value measured by a method in accordance with JIS K 7136 with slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd. bonded to both sides of the pressure-sensitive adhesive sheet. Specifically, the adhesive sheet is attached to a slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd., and the slide glass is also attached to the opposite surface of the adhesive sheet so that air and foreign matter do not enter. A laminate in the order of / adhesive sheet / glass is produced. This laminate is subjected to autoclave (pressure defoaming) treatment at 0.5 MPa and 40 ° C. for 30 minutes, and the haze value is measured using NDH4000 manufactured by Nippon Denshoku Kogyo Co., Ltd.

The adhesive strength of the pressure-sensitive adhesive sheet to glass is preferably 10 N / 25 mm or more, and more preferably 15 N / 25 mm or more. The adhesive strength of the adhesive sheet to the adherend described above is a value measured by peeling 180 ° to the glass and the adhesive strength 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.

In the above-mentioned step, the reaction between the crosslinkable acrylic polymer and the crosslinker proceeds by heating the coating film 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)
When the pressure-sensitive adhesive sheet of the present invention is used, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend in an exposed state. Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a pressure-sensitive adhesive composition containing a diene-based polymer and a linear saturated hydrocarbon compound, even if the adherend has a stepped portion, the pressure-sensitive adhesive is used. The layer can follow the unevenness of the step portion.

(Laminated body)
The laminate of the present invention has a pressure-sensitive adhesive layer which is a cured product of the above-mentioned pressure-sensitive adhesive composition, and an adherend on at least one surface side of the pressure-sensitive adhesive layer. Here, the adherend may have a stepped portion or unevenness derived from the 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.
Examples of the constituent members of the touch panel include 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, and a transparent conductive film in which a transparent resin film is coated with a conductive polymer. Examples include hard coat films and fingerprint resistant films. The adhesive sheet of the present invention is preferably for laminating a touch panel and an image display device, and more preferably for laminating a touch panel using a touch pen and an image display device. 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 the above is preferable, and an adhesive sheet is preferably attached to the back surface (the surface without the conductive layer) of these glasses or films.
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, triacetyl cellulose, polyimide, and cellulose acylate. A functional layer such as a hard coat layer may be provided on the side of these films in contact with the pressure-sensitive adhesive layer.

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.

[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 weight average molecular weight of the crosslinkable acrylic polymer (A) was measured by gel permeation chromatography (GPC) and determined based on polystyrene.
The measurement conditions of gel permeation chromatography (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.

5 parts by mass of a diene polymer (“Ricon 156” manufactured by Total) with respect to 100 parts by mass of the solid content of the crosslinkable acrylic polymer (A) obtained above, a linear saturated hydrocarbon compound (Japan). Add 5 parts by mass of "Polybutene Grade 0N" manufactured by Yu Co., Ltd. and 0.2 parts by mass of a xylylene diisocyanate compound (Takenate D-110N manufactured by Mitsui Chemicals Co., Ltd.) as a cross-linking agent, and the solid content concentration is 40% by mass. Ethyl acetate was added so as to be%, and a pressure-sensitive adhesive composition was obtained.
The number average molecular weight of the diene polymer was 1400, and the number average molecular weight of the linear saturated hydrocarbon compound was 370.

<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 thickness after drying was 150 μm. 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 (manufactured by Oji Ftex Co., Ltd .: 38RL-07 (L)) having a thickness of 38 μm was attached to the surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was 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%.

<Manufacturing of laminated body>
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 8 times to obtain a printed stepped glass having a stepped portion of 40 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.

[Example 2]
Adhesion is carried out in the same manner as in Example 1 except that the amount of the diene polymer charged is changed from 5 parts by mass to 8 parts by mass and the amount of the linear saturated hydrocarbon compound is changed from 5 parts by mass to 2 parts by mass. An agent composition, an adhesive sheet and a laminate were obtained.

[Example 3]
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 diene-based polymer compound was changed from Rikon 156 to Rikon 154 manufactured by Total.

[Example 4]
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 linear saturated hydrocarbon compound was changed from "polybutene grade 0N" manufactured by NOF Corporation to polybutene 30N.

[Example 5]
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate were obtained in the same manner as in Example 2 except that the amount of the diene-based polymer added was changed from 8 parts by mass to 12 parts by mass.

[Example 6]
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 amount of the linear saturated hydrocarbon compound added was changed from 5 parts by mass to 12 parts by mass.

[Example 7]
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 amount of the diene-based polymer charged was changed from 5 parts by mass to 22 parts by mass.

[Comparative Example 1]
The pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet and laminate were the same as in Example 1 except that the amount of the diene-based polymer charged was changed from 5 parts by mass to 10 parts by mass and no linear saturated hydrocarbon compound was added. Got

[Comparative Example 2]
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 diene-based polymer and the linear saturated hydrocarbon compound were not added.

[evaluation]
<Relative permittivity>
The evaluation of the relative permittivity of the pressure-sensitive adhesive layer 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). .. After that, the relative permittivity was measured based on JIS C 2138 by a dielectric measurement system (manufactured by Toyo Corporation, 1260 type). The frequency and measurement environment were measured under the following conditions.
Frequency: 1MHz
Measurement environment: 23 ° C, relative humidity 55%

<Step followability>
The printed step portion of the laminated body 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 in the laminated body.
◯: In the laminated body, air bubbles of less than 0.5 mmΦ remain in a part of the stepped portion.
X: In the laminated body, bubbles of 0.5 mmΦ or more remain in the entire stepped portion.

<Durability>
The obtained adhesive sheet was cut into a shape having a length of 50 mm and a width of 25 mm, the first release sheet was peeled off, and the adhesive sheet was attached to a transparent PET film (product name: Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm.
A polarizing plate (SKN-18243T manufactured by Polatechno Co., Ltd.) was cut out to the same dimensions as a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm), and the polarizing plate was attached to the glass plate to form an adherend. Next, about 0.05 mg of glass beads having a central particle size of 30 μm was sprayed on the surface of the polarizing plate to prepare a product.
The second release sheet of the adhesive sheet integrated with the transparent PET film was peeled off and bonded to the surface on which the glass beads of the polarizing plate of the adherend were sprayed with a laminator. Then, an autoclave treatment (40 ° C., 0.5 MPa, 30 minutes) was carried out to obtain a laminated body.
The obtained laminate was treated for 24 hours in an environment of 85 ° C. and a relative humidity of less than 10%, and the treated glass bead sprayed portion was observed with a microscope (magnification: 25 times) to check the foreign matter embedding property of the adhesive sheet. It was evaluated according to the following criteria.
⊚: No new bubbles are generated around the glass beads.
◯: New bubbles of less than 0.5 mmΦ are generated from around the glass beads.
X: New bubbles of 0.5 mmΦ or more are generated from around the glass beads.

<Haze>
The first release sheet was peeled off from the pressure-sensitive adhesive sheet, and a slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd. was attached to one surface of the pressure-sensitive adhesive layer. Next, the second release sheet is peeled off from the adhesive sheet, a slide glass manufactured by Matsunami Glass Co., Ltd. (product number: S9112) is bonded to the other surface of the adhesive layer, and the glass / adhesive layer / glass is laminated in this order. The laminated body was prepared. This laminate was subjected to autoclave (pressure defoaming) treatment at 0.5 MPa and 40 ° C. for 30 minutes, and the haze value was measured using NDH4000 manufactured by Nippon Denshoku Kogyo Co., Ltd.

Polybutadiene A: Total, Ricon 156
Polybutadiene B: Total, Ricon 154
Polybutene A: Made by NOF Corporation, Polybutene Grade 0N
Polybutene B: Made by NOF Corporation, Polybutene 30N

From the above table, it was found that the pressure-sensitive adhesive composition obtained in the examples is a pressure-sensitive adhesive layer having a low relative permittivity and can form a pressure-sensitive adhesive layer having excellent step followability and transparency. rice field. Further, the pressure-sensitive adhesive composition obtained in the examples could form a pressure-sensitive adhesive layer having excellent durability. In Examples 1 to 6, which contained 1 to 20 parts by mass of the diene polymer with respect to 100 parts by mass of the crosslinkable acrylic polymer, the transparency of the pressure-sensitive adhesive layer was more excellent.

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 (12)

A pressure-sensitive adhesive composition containing a crosslinkable acrylic polymer, a crosslinking agent, a diene-based polymer, and a linear saturated hydrocarbon compound.
The crosslinkable acrylic polymer is contained in an amount of 50% by mass or more based on the pressure-sensitive adhesive composition.
The diene-based polymer has a number average molecular weight of 250 to 15,000, and has a number average molecular weight of 250 to 15,000.
The linear saturated hydrocarbon compound has a number average molecular weight of 250 to 5000.
A pressure-sensitive adhesive composition having a relative permittivity 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. The pressure-sensitive adhesive composition according to claim 1, wherein the diene-based polymer is a polymer having a non-conjugated diene structure in the molecule. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the diene-based polymer is a butadiene-based polymer. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the diene-based polymer has a 1,2-vinyl group. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the linear saturated hydrocarbon compound is a polyolefin-based polymer. Any of claims 1 to 5, wherein the crosslinkable functional group of the crosslinkable acrylic polymer is one or more selected from 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 item 1. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the cross-linking agent is one or more selected from 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 7, wherein the diene-based 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 8, which contains 0.5 to 20 parts by mass of the linear saturated hydrocarbon compound with respect to 100 parts by mass of the crosslinkable acrylic polymer. Has an adhesive layer,
A pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 9. 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 10, wherein the first release sheet and the second release sheet have different release forces. It has a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 9, and an adherend on at least one surface side of the pressure-sensitive adhesive layer.
A laminated body in which the adherend has a stepped portion.

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