JP2018035226A - Adhesive composition, and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition which is excellent in an effect for reducing a dielectric loss, and is effective for reduction in power consumption of a high-frequency device and a device having a distribution panel with a small distance between wires, and to provide an adhesive sheet having an adhesive layer formed from the adhesive composition.SOLUTION: An adhesive composition contains an acrylic copolymer (A) having 25-90 mass% of a constitutional unit (a1) derived from a monomer (a1') represented by general formula (1), where a dielectric loss tangent (tanδ) at a frequency of 1 GHz is 4.80×10or less, and is used for a device that transmits or receives an electromagnetic wave at a frequency of 10 MHz or more, or a device having an integrated circuit with a distance between wires of 3 μm or less. In general formula (1), Ris a hydrogen atom or a methyl group. Rand Rare each independently alkyl groups having 4 to 18 carbon atoms.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, and an apparatus using the pressure-sensitive adhesive sheet.

In an electronic device, an adhesive is used to fix various members.
For example, Patent Document 1 includes a polymer obtained by polymerizing a monomer mixture containing three predetermined monomers as an adhesive used in a low frequency device such as a capacitive touch panel, and a dielectric at a frequency of 100 kHz. An adhesive capable of forming an adhesive layer having a rate of 3.5 or less is disclosed.

Japanese Patent Laying-Open No. 2015-183179

By the way, in recent years, development of high-frequency devices that transmit or receive high-frequency electromagnetic waves has progressed.
For example, devices such as mobile phones, high-speed wireless LANs, non-contact type IC card systems, dangerous object detection sensors, collision avoidance systems built into automobiles, GPS (Global Positioning System) positioning systems, industrial scientific medical equipment, etc. are 10 MHz. This is a high frequency device that transmits or receives the above high frequency.
In these high-frequency devices, a dielectric is used as a member such as a substrate, a resonator, a filter, and an antenna, and an adhesive is used to fix these members.

In such a high-frequency device, power consumption becomes one of the problems, and a material that contributes to reduction in power consumption is required for a dielectric material for the high-frequency device.
In addition, the problem related to power consumption is a matter that occurs even in a device having an integrated circuit with a small distance between wires, and a dielectric material constituting the integrated circuit is also required to reduce power consumption.

In Patent Document 1, a pressure-sensitive adhesive used for a low-frequency device such as a capacitive touch panel is studied. However, the low-frequency device has low power consumption and often does not cause a problem. In fact, in Patent Document 1, no study has been made on reducing the power consumption of a device.
In general, propagation loss that affects the amount of power consumption depends on frequency. When a suitable adhesive for low-frequency devices is applied to a high-frequency device or a semiconductor integrated circuit, the propagation of the adhesive Since the loss is large, it often does not contribute to a reduction in power consumption or causes an increase in power consumption.
Therefore, there is a demand for an adhesive that is effective in reducing power consumption in high-frequency devices and semiconductor integrated circuits.

  The present invention relates to a pressure-sensitive adhesive composition effective for reducing power consumption of a device including a semiconductor integrated circuit having a small distance between high-frequency devices and wiring, and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition The purpose is to provide.

  The present inventors provide an adhesive composition comprising an acrylic copolymer having a predetermined amount of a structural unit derived from a monomer having a specific structure, and having a dielectric loss tangent (tan δ) at a frequency of 1 GHz adjusted to a predetermined value or less. We found that the problem could be solved.

That is, the present invention provides the following [1] to [15].
[1] A pressure-sensitive adhesive composition comprising an acrylic copolymer (A) having 25 to 90% by mass of a structural unit (a1) derived from a monomer (a1 ′) represented by the following general formula (1): ,
The dielectric loss tangent (tan δ) at a frequency of 1 GHz is 4.80 × 10 ⁻³ or less,
A pressure-sensitive adhesive composition used for a device that transmits or receives an electromagnetic wave having a frequency of 10 MHz or more, or a device having an integrated circuit with a distance between wirings of 3 μm or less.

[In the general formula (1), R ¹ is a hydrogen atom or a methyl group. R ² and R ³ are each independently an alkyl group having 4 to 18 carbon atoms. ]
[2] The pressure-sensitive adhesive composition according to the above [1], wherein the relative dielectric constant at a frequency of 1 GHz is 1.5 to 3.2.
[3] The pressure-sensitive adhesive composition according to the above [1] or [2], wherein R ² and R ³ in the general formula (1) are each independently a linear alkyl group having 4 to 18 carbon atoms. .
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the monomer (a1 ′) includes a monomer (a11 ′) represented by the following general formula (1-1). .

[In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group. ]
[5] The above [1] to [1], wherein the acrylic copolymer (A) further has a structural unit (a2) derived from an alkyl (meth) acrylate (a2 ′) having an alkyl group having 1 to 12 carbon atoms. [4] The pressure-sensitive adhesive composition according to any one of [4].
[6] The pressure-sensitive adhesive composition according to the above [5], wherein the acrylic copolymer (A) further has a structural unit (a3) derived from the functional group-containing monomer (a3 ′).
[7] The pressure-sensitive adhesive composition according to [6], further including a crosslinking agent (C).
[8] The pressure-sensitive adhesive composition according to any one of [1] to [7], wherein the acrylic copolymer (A) has a mass average molecular weight of 50,000 to 800,000.
[9] The pressure-sensitive adhesive composition according to any one of the above [1] to [8], wherein the acrylic copolymer (A) has a glass transition temperature of −70 ° C. to 5 ° C.
[10] The pressure-sensitive adhesive composition according to any one of [1] to [9], further including a tackifier (B).
[11] The pressure-sensitive adhesive composition according to any one of [1] to [10], wherein a haze value measured in accordance with JIS K7136 is 1% or more.
[12] The pressure-sensitive adhesive composition according to any one of [1] to [11], further including a colorant.
[13] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to [12].
[14] An apparatus for transmitting or receiving an electromagnetic wave having a frequency of 10 MHz or higher, using the adhesive sheet according to [13].
[15] A device having an integrated circuit using the adhesive sheet according to the above [13] and having a wiring distance of 3 μm or less.

  The pressure-sensitive adhesive composition of the present invention is effective for reducing the power consumption of these devices when used for fixing members of devices having a high-frequency device or a power distribution plate having a small distance between wires.

It is sectional drawing of the adhesive sheet which shows an example of a structure of the adhesive sheet of this invention.

  In this specification, for example, “(meth) acrylate” is used as a term indicating both “acrylate” and “methacrylate”, and the same applies to other similar terms.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention includes an acrylic copolymer (A) having 25 to 90% by mass of a structural unit (a1) derived from the monomer (a1 ′) represented by the general formula (1), and having a frequency. The dielectric loss tangent (tan δ) at 1 GHz is 4.80 × 10 ⁻³ or less.
The pressure-sensitive adhesive composition of one embodiment of the present invention preferably further contains a tackifier (B) and a crosslinking agent (C) from the viewpoint of improving the tackiness, and within a range not impairing the effects of the present invention. You may contain additives other than a component (B) and (C).

In general, the amount of power consumption can be indicated by the value of the attenuation constant a indicating the degree of attenuation of the propagation signal. The pressure-sensitive adhesive composition having a smaller attenuation constant a has lower power consumption and lower power consumption. It can be said that the reduction effect is excellent.
The attenuation constant a is known to be related to the frequency f, the relative dielectric constant ε ′, and the dielectric loss tangent tan δ, as shown in the following formula (i).

(In the above formula (i), a represents an attenuation constant, f represents a frequency, ε ′ represents a relative dielectric constant, tan δ represents a dielectric loss tangent, and C represents a constant (light speed in vacuum: 299972458 m / s).)

As can be seen from the above formula (i), in a low-frequency device such as a capacitive touch panel, since f is small, the attenuation constant a is not so large, and power consumption is not a problem. On the other hand, in a high frequency device, since f is large, the attenuation constant a becomes large, and an increase in power consumption becomes a problem.
Here, in order to reduce the attenuation constant a, it is necessary to reduce the values of the relative permittivity ε ′ and the dielectric loss tangent tan δ.

The pressure-sensitive adhesive composition of the present invention is a material having a low dielectric loss by adjusting the contained components so that the dielectric loss tangent (tan δ) at a frequency of 1 GHz is 4.80 × 10 ⁻³ or less.
That is, when the adhesive composition having a dielectric loss tangent (tan δ) at 1 GHz exceeding 4.80 × 10 ⁻³ is used for fixing a member of an apparatus provided with a high-frequency device or a distribution board having a small inter-wiring distance, An increase in power consumption of the apparatus is caused, and the effect of suppressing power consumption tends to be insufficient.
From the above viewpoint, in the pressure-sensitive adhesive composition of one embodiment of the present invention, the dielectric loss tangent (tan δ) at a frequency of 1 GHz is preferably 4.40 × 10 ⁻³ or less, more preferably 4.20 × 10 ⁻³ or less, More preferably, it is 4.00 * 10 <^-3> or less, More preferably, it is 3.70 * 10 < ^-3 > or less, More preferably, it is 3.30 * 10 <^-3> or less.
In the pressure-sensitive adhesive composition of one embodiment of the present invention, the dielectric loss tangent (tan δ) at a frequency of 1 GHz is preferably 0.01 × 10 ⁻³ or more, more preferably 0.05 × 10 ⁻³ or more, and ^still more preferably. It is 0.10 × 10 ⁻³ or more.

In the pressure-sensitive adhesive composition of one embodiment of the present invention, the relative dielectric constant at a frequency of 1 GHz is preferably 1.50 to 3.20, more preferably 1.60 to 3.10, and still more preferably 1.70 to 3. 00.
An adhesive composition having a relative dielectric constant of 1.50 or more at 1 GHz can efficiently transmit and receive radio waves when applied to a high frequency device.
On the other hand, when the pressure-sensitive adhesive composition having a relative dielectric constant of 1.20 or less at 1 GHz is used for fixing a member of a device having a distribution board with a smaller dielectric loss and a high-frequency device or a smaller distance between wirings, The power consumption of these devices can be effectively reduced. Moreover, when it uses for the apparatus which receives electromagnetic waves, it contributes also to size reduction of the said apparatus. Furthermore, when used in a semiconductor integrated circuit having a small distance between wirings, leakage (leakage) when an alternating current is passed can be prevented.

  In the present specification, the dielectric loss tangent (tan δ) and relative dielectric constant at a frequency of 1 GHz of the pressure-sensitive adhesive composition mean values measured by the methods described in Examples.

In the pressure-sensitive adhesive composition of the present invention, the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz are adjusted to the above ranges by adjusting the types and contents of the components to be contained.
Hereinafter, each component contained in the pressure-sensitive adhesive composition of the present invention will be described with a focus on the adjustment of dielectric loss tangent (tan δ) and relative dielectric constant.

<Acrylic copolymer (A)>
The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer (A) having 25 to 90% by mass of a structural unit (a1) derived from a monomer (a1 ′) represented by the following general formula (1).
In the present invention, a pressure-sensitive adhesive composition containing the acrylic copolymer (A) having the structural unit (a1) derived from the monomer (a1 ′), in particular, a dielectric loss tangent (tan δ) at 1 GHz and It becomes easy to adjust the relative dielectric constant low.

[In the general formula (1), R ¹ is a hydrogen atom or a methyl group. R ² and R ³ are each independently an alkyl group having 4 to 18 carbon atoms. ]

In addition, a monomer (a1 ') may be used independently and may use 2 or more types together.
Examples of the alkyl group that can be selected as R ² and R ³ include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, octadecyl, and the like. Groups and the like.
These alkyl groups may be straight chain alkyl groups or branched chain alkyl groups.
However, R ² and R ³ are preferably straight-chain alkyl groups having 4 to 18 carbon atoms from the viewpoint of forming a pressure-sensitive adhesive composition having a low dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz.

The number of carbon atoms of the alkyl group that can be selected as R ² and R ³ is preferably from 5 to 16, more preferably from the viewpoint of a pressure-sensitive adhesive composition in which the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz are adjusted low. It is 6-14, More preferably, it is 8-12, More preferably, it is 10-12.

In consideration of the above matters, in one embodiment of the present invention, from the viewpoint of forming a pressure-sensitive adhesive composition in which the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz are adjusted low, the monomer (a1 ′) is represented by the following general formula (1- It is preferable that the monomer (a11 ') represented by 1) is included.

[In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group. ]

Incidentally, the monomer (a11 ') may be used alone wherein R ¹ is hydrogen atom or a methyl group, R ¹ is a hydrogen atom, may be used in combination of two or a methyl group.

  In one embodiment of the present invention, the proportion of the monomer (a11 ′) in 100% by mass of the monomer (a1 ′) is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, further from the above viewpoint. Preferably it is 90-100 mass%, More preferably, it is 95-100 mass%.

In the acrylic copolymer (A) used in the present invention, the content of the structural unit (a1) derived from the monomer (a1 ′) is the total structural unit (100% by mass) of the acrylic copolymer (A). On the other hand, it is 25-90 mass%, Preferably it is 27-80 mass%, More preferably, it is 30-75 mass%, More preferably, it is 32-70 mass%, More preferably, it is 35-60 mass%.
When the content of the structural unit (a1) is less than 25% by mass, the resulting adhesive composition tends to increase the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz, which is not preferable.
On the other hand, if the content of the structural unit (a1) is more than 90% by mass, the tackiness tends to be insufficient.

The acrylic copolymer (A) used in one embodiment of the present invention includes an alkyl (meth) acrylate (a2 ′) having a C 1-12 alkyl group (hereinafter referred to as “monomer (a2)) together with the structural unit (a1). It is preferable to have the structural unit (a2) derived from “)”.
While making the acrylic copolymer having the structural unit (a2) together with the structural unit (a1), the dielectric loss tangent (tan δ) at 1 GHz and the relative dielectric constant of the obtained pressure-sensitive adhesive composition are kept low. , The adhesiveness can be improved.

As carbon number of the alkyl group which a monomer (a2 ') has, it is 1-12, Preferably it is 1-9, More preferably, it is 4-9, More preferably, it is 6-8.
The alkyl group may be a linear alkyl group or a branched alkyl group.

Examples of the monomer (a2 ′) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, Examples include t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isooctyl (meth) acrylate.
These monomers (a2 ′) may be used alone or in combination of two or more.

  In the acrylic copolymer (A) used in one embodiment of the present invention, the content of the structural unit (a2) derived from the monomer (a2 ′) is the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz of the pressure-sensitive adhesive composition. From the viewpoint of improving the adhesiveness while maintaining the value of the rate low, it is preferably 5 to 70% by mass, more preferably based on the total structural unit (100% by mass) of the acrylic copolymer (A). It is 7-65 mass%, More preferably, it is 10-60 mass%, More preferably, it is 15-55 mass%.

Moreover, from the viewpoint of making the pressure-sensitive adhesive composition further improved in tackiness, the acrylic copolymer (A) used in one embodiment of the present invention further contains a functional group together with the structural units (a1) and (a2). It is more preferable to have the structural unit (a3) derived from the monomer (a3 ′) (hereinafter also referred to as “monomer (a3 ′)”).
The functional group possessed by the monomer (a3 ′) may be any one that can react with the crosslinking agent (C) described later.

Specific examples of the monomer (a3 ′) include a hydroxy group-containing monomer, a carboxy group-containing monomer, and an epoxy group-containing monomer.
These monomers (a3 ′) may be used alone or in combination of two or more.

Examples of the hydroxy-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl (meth) ) Hydroxyalkyl (meth) acrylates such as acrylate and 4-hydroxybutyl (meth) acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.
In addition, as carbon number of the alkyl group which hydroxyalkyl (meth) acrylate has, Preferably it is 1-10, More preferably, it is 1-8, More preferably, it is 1-6, More preferably, it is 2-4, The said alkyl The group may be a straight chain alkyl group or a branched chain alkyl group.

  Examples of the carboxy group-containing monomer include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid and the like.

  Examples of the epoxy-containing monomer include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, (3,4-epoxycyclohexyl) methyl (meth) acrylate, and 3-epoxycyclo-2-hydroxypropyl (meth) acrylate. Epoxy group-containing (meth) acrylic acid esters such as glycidyl crotonate and allyl glycidyl ether.

  In one embodiment of the present invention, the monomer (a3 ′) is a hydroxy group from the viewpoint of improving the adhesiveness while maintaining the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz of the pressure-sensitive adhesive composition low. Containing monomers are preferred, hydroxyalkyl (meth) acrylates are more preferred, and 2-hydroxyethyl (meth) acrylates are even more preferred.

Note that when the acrylic copolymer (A) used in one embodiment of the present invention includes the structural unit (a3), the functional group present in the structural unit (a3) is a polymerization of a (meth) acryloyl group or a vinyl group. A part thereof may be modified with a polymerizable compound having a functional group, but it is modified with a polymerizable compound from the viewpoint of adjusting the dielectric loss tangent (tan δ) and relative dielectric constant of the pressure-sensitive adhesive composition at 1 GHz. Preferably not.
In the acrylic copolymer (A) used in one embodiment of the present invention, the proportion of the functional group modified by the polymerizable compound is the functionality present in the structural unit (a3) of the acrylic copolymer (A). Preferably it is 0-30 mol% with respect to the whole quantity (100 mol%) of group, More preferably, it is 0-10 mol%, More preferably, it is 0-5 mol%, More preferably, it is 0 mol%.

  In the acrylic copolymer (A) used in one embodiment of the present invention, the content of the structural unit (a2) derived from the monomer (a2 ′) is the dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz of the pressure-sensitive adhesive composition. From the viewpoint of improving the adhesiveness while maintaining a low value of the rate, it is preferably 1 to 30% by mass, more preferably based on the total structural unit (100% by mass) of the acrylic copolymer (A). It is 1.5-25 mass%, More preferably, it is 2-20 mass%, More preferably, it is 2.5-15 mass%.

The acrylic copolymer (A) used in one embodiment of the present invention includes structural units derived from monomers other than the above-described monomers (a1 ′) to (a3 ′) within a range not impairing the effects of the present invention. You may have.
Such other monomers can be selected from, for example, monomers copolymerizable with the above-described monomers (a1 ′) to (a3 ′), and olefins such as ethylene, propylene, isobutylene; vinyl chloride, vinylidene Halogenated olefins such as chloride; diene monomers such as butadiene, isoprene and chloroprene; styrene, α-methylstyrene, vinyl toluene, vinyl formate, vinyl acetate, acrylonitrile, (meth) acrylamide, (meth) acrylonitrile, (meta ) Acryloylmorpholine, N-vinylpyrrolidone and the like.

  The total content of the structural units (a1), (a2), and (a3) in the acrylic copolymer (A) used in one embodiment of the present invention is the total content in the acrylic copolymer (A1). Preferably it is 70-100 mass% with respect to a structural unit (100 mass%), More preferably, it is 80-100 mass%, More preferably, it is 90-100 mass%, More preferably, it is 95-100 mass%.

In one embodiment of the present invention, the mass average molecular weight (Mw) of the acrylic copolymer (A) is usually 20,000 or more, preferably 50,000, from the viewpoint of making a pressure-sensitive adhesive composition with improved adhesiveness. To 800,000, more preferably 80,000 to 600,000, still more preferably 100,000 to 500,000, and still more preferably 120,000 to 450,000.
The molecular weight distribution (Mw / Mn) (Mn: number average molecular weight) of the acrylic copolymer (A) is preferably 1.1 to 10.0, more preferably 1.3 to 6.0, and more preferably Preferably it is 1.7-5.0, More preferably, it is 2.0-4.5.
In the present specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) are values in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method. It is the value measured based on the described method.

In one aspect of the present invention, the glass transition temperature (Tg) of the acrylic copolymer (A) is preferably −70 ° C. to 5 ° C. from the viewpoint of a pressure-sensitive adhesive composition with improved adhesiveness. More preferably, it is -60 to 0 degreeC, More preferably, it is -55 to -5 degreeC.
In the present specification, the value of glass transition temperature (Tg) of the acrylic copolymer (A), the absolute temperature calculated by the following formula (ii) (Unit: K) a glass transition temperature (Tg _K) of It is a value converted to Celsius temperature (unit: ° C.).

[W ₁ , W ₂ , W ₃ , W ₄ ... In the above formula (ii) indicate the mass fraction (mass%) of the monomer component constituting the acrylic copolymer (A), and Tg ₁ , Tg ₂ , Tg ₃ , Tg ₄ ... Indicate the glass transition temperature (unit: K) of the homopolymer of the monomer component constituting the acrylic copolymer (A). ]

  In the pressure-sensitive adhesive composition of one embodiment of the present invention, the content of the acrylic copolymer (A) is preferably 40 to 100% by mass with respect to the total amount (100% by mass) of the pressure-sensitive adhesive composition. Preferably it is 50-99.9 mass%, More preferably, it is 55-99 mass%, More preferably, it is 60-95 mass%.

<Tackifier (B)>
The pressure-sensitive adhesive composition of one embodiment of the present invention preferably further contains a tackifier (B) from the viewpoint of further improving the tackiness.
In particular, an adherend containing a polyolefin such as polyethylene or polypropylene has a relatively low polarity of polyolefin, and therefore it may be difficult to adhere the acrylic copolymer (A) with high adhesive strength. However, by forming a pressure-sensitive adhesive composition containing the tackifier (B) together with the acrylic copolymer (A), good adhesiveness can be expressed even on an adherend having such a low polarity. be able to.

In the present specification, the tackifier is a component that assists in improving the adhesive properties of the acrylic copolymer (A), and an oligomer having a mass average molecular weight (Mw) of usually less than 20,000. Point to.
The weight average molecular weight (Mw) of the tackifier (B) is usually less than 20,000, preferably 400 to 10,000, more preferably 500 to 8,000.

Examples of the tackifier (B) include rosin tackifiers, terpene tackifiers, styrene tackifiers, petroleum-derived tackifiers, and the like.
In addition, you may use these tackifiers (B) individually or in combination of 2 or more types from which a softening point and a structure differ.

  Examples of the rosin tackifier include rosin resins such as rosin resins, rosin ester resins and rosin-modified phenol resins, and hydrogenated rosin resins obtained by hydrogenating these rosin resins.

  Examples of the terpene tackifier include terpene resins such as terpene resins, aromatic modified terpene resins, terpene phenol resins, and hydrogenated terpene resins obtained by hydrogenating these terpene resins.

  Examples of styrenic tackifiers include styrene resins obtained by copolymerizing styrene monomers such as α-methylstyrene or β-methylstyrene and aliphatic monomers, and hydrogenating these styrene resins. And hydrogenated styrene resins.

  Examples of petroleum-derived tackifiers include C5 petroleum resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperine, 1.3-pentadiene produced by thermal decomposition of petroleum naphtha and the C5 Hydrogenated petroleum resin of petroleum resin; C9 petroleum resin obtained by copolymerizing C9 fractions such as indene and vinyltoluene produced by thermal decomposition of petroleum naphtha, and hydrogenated petroleum resin of this C9 petroleum resin; Can be mentioned.

The softening point of the tackifier (B) is preferably 80 ° C or higher, more preferably 90 to 180 ° C, still more preferably 100 to 170 ° C, from the viewpoint of making the pressure-sensitive adhesive composition further improved in tackiness. More preferably, it is 110-150 degreeC.
In the present specification, the “softening point” of the tackifier means a value measured according to JIS K 2207: 1996.
In addition, when two or more types of tackifiers are used, the content ratio of the plurality of tackifiers is adjusted so that the weighted average of the softening points of the plurality of tackifiers belongs to the above range. Is preferred.

  In the pressure-sensitive adhesive composition of one embodiment of the present invention, the content of the tackifier (B) is preferably 1 to 100 parts by mass of the acrylic copolymer (A) contained in the pressure-sensitive adhesive composition. 200 mass parts, More preferably, it is 3-100 mass parts, More preferably, it is 5-80 mass parts, More preferably, it is 10-60 mass parts.

<Crosslinking agent (C)>
The pressure-sensitive adhesive composition of one embodiment of the present invention preferably further contains a crosslinking agent (C) from the viewpoint of further improving the pressure-sensitive adhesiveness.
When the functional group is present in the structural unit of the acrylic copolymer (A), the crosslinking agent (C) reacts with the functional group to crosslink the acrylic copolymers (A). .

Examples of the crosslinking agent (C) include isocyanate-based crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; hexa [1- (2-methyl ) -Aziridinyl] aziridine-based cross-linking agents such as triphosphatriazine; chelate-based cross-linking agents such as aluminum chelates;
These crosslinking agents (C) may be used alone or in combination of two or more.
As the crosslinking agent (C) used in one embodiment of the present invention, an isocyanate-based crosslinking agent is preferable from the viewpoint of obtaining a pressure-sensitive adhesive composition in which cohesive force is increased and adhesiveness is further improved.

  In the pressure-sensitive adhesive composition of one embodiment of the present invention, the content of the crosslinking agent (C) is appropriately adjusted depending on the number of functional groups of the acrylic copolymer (A) contained in the pressure-sensitive adhesive composition. The amount is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and still more preferably 0.05 to 4 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A).

<Other additives>
The pressure-sensitive adhesive composition of one embodiment of the present invention may contain additives other than the tackifier (B) and the crosslinking agent (C) as long as the effects of the present invention are not impaired.
Examples of such other additives include ultraviolet absorbers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, surfactants, anti-aging agents, thickeners, antifoaming agents, A coloring agent etc. are mentioned.
Each of these additives may be used alone or in combination of two or more.

  In the pressure-sensitive adhesive composition of one embodiment of the present invention, the total content of components (A), (B) and (C) is preferably 80 to the total amount (100% by mass) of the pressure-sensitive adhesive composition. 100 mass%, More preferably, it is 90-100 mass%, More preferably, it is 95-100 mass%, More preferably, it is 98-100 mass%.

Note that, as described above, the acrylic copolymer (A) contained in the pressure-sensitive adhesive composition of one embodiment of the present invention adjusts the dielectric loss tangent (tan δ) and relative dielectric constant of the pressure-sensitive adhesive composition at 1 GHz. From the viewpoint, it is preferably not modified with a polymerizable compound.
Therefore, the pressure-sensitive adhesive composition of one embodiment of the present invention may contain a photopolymerization initiator, but the content is preferably as small as possible.
In the pressure-sensitive adhesive composition of one embodiment of the present invention, the content of the photopolymerization initiator is preferably 0 to 5 mass with respect to 100 parts by mass of the acrylic copolymer (A) contained in the pressure-sensitive adhesive composition. Part, more preferably 0 to 1 part by weight, still more preferably 0 to 0.1 part by weight, still more preferably 0 part by weight.

The pressure-sensitive adhesive composition of one embodiment of the present invention contains a pressure-sensitive adhesive resin having a mass average molecular weight (Mw) other than the acrylic copolymer (A) of 20,000 or more as long as the effects of the present invention are not impaired. May be.
However, in the pressure-sensitive adhesive composition of one embodiment of the present invention, in addition to the acrylic copolymer (A), the pressure-sensitive adhesive composition has a low dielectric loss tangent (tan δ) and relative dielectric constant at 1 GHz. The smaller the content of the adhesive resin, the better.
In the pressure-sensitive adhesive composition of one embodiment of the present invention, the content of the pressure-sensitive adhesive resin other than the acrylic copolymer (A) is 100 mass of the total amount of the acrylic copolymer (A1) in the pressure-sensitive adhesive composition. The amount is preferably 0 to 30 parts by mass, more preferably 0 to 10 parts by mass, still more preferably 0 to 5 parts by mass, and still more preferably 0 parts by mass.

In the pressure-sensitive adhesive composition of one embodiment of the present invention, the haze value measured according to JIS K7136 is preferably 1% or more, more preferably 1.5% or more, still more preferably 3% or more, and still more preferably. Is 5% or more, preferably 20% or less, more preferably 15% or less, and still more preferably 10% or less.
By setting the haze value to 1% or more, the pressure-sensitive adhesive sheet using the resulting pressure-sensitive adhesive composition can be easily checked for the presence or absence of sticking at the time of sticking, which is preferable in terms of workability.
In addition, by setting the haze value to 20% or less, the adherend surface can be seen through the pressure sensitive adhesive sheet when the pressure sensitive adhesive sheet is pasted, and it is easy to align the position of the adherend. Is preferable.
In addition, in this specification, the haze value of an adhesive composition is a value measured based on JISK7136, and is a value specifically measured based on the method as described in an Example.

The pressure-sensitive adhesive composition of one embodiment of the present invention preferably contains a colorant from the viewpoint of adjusting the haze value to the above range.
Examples of the colorant include inorganic pigments such as titanium white, zinc white, petal, vermilion, ultramarine, cobalt blue, titanium yellow, yellow lead, and carbon black; isoindolinone, Hansa yellow A, quinacridone, permanent red 4R, Organic pigments (including dyes) such as phthalocyanine blue, indanthrene blue RS, and aniline black; metal pigments such as aluminum and brass; pearlescent (pearl) pigments made of foil powder such as titanium dioxide-coated mica and basic lead carbonate; Etc.

  When the pressure-sensitive adhesive composition of one embodiment of the present invention contains a colorant, the content of the colorant is appropriately adjusted so that the haze value of the obtained pressure-sensitive adhesive composition falls within the above range. Preferably it is 0.01-10 mass parts with respect to 100 mass parts of acrylic copolymers (A) contained in a composition, More preferably, it is 0.05-5 mass parts, More preferably, it is 0.10-3 masses. Part.

[Configuration of adhesive sheet]
If the adhesive sheet of this invention has an adhesive layer formed from the above-mentioned adhesive composition of this invention, there will be no restriction | limiting in particular.
FIG. 1 is a cross-sectional view of an adhesive sheet showing an example of the configuration of the adhesive sheet of the present invention.
As an adhesive sheet of 1 aspect of this invention, as shown to Fig.1 (a), the adhesive sheet 1a with a base material which has the adhesive layer 12 on the at least one surface of the base material 11 is mentioned, for example.
In addition, in the structure of the adhesive sheet 1a with a base material, as shown in FIG.1 (b), it is good also as the adhesive sheet 1b with a base material which laminated | stacked the peeling material 13 on the adhesive layer 12. FIG.

  Moreover, as an adhesive sheet of 1 aspect of this invention, as shown in FIG.1 (c), the structure like the double-sided adhesive sheet 1c with a base material which has the adhesive layers 12a and 12b on both surfaces of the base material 11, respectively. It is good. In addition, the double-sided pressure-sensitive adhesive sheet 1c shown in FIG. 1C may have a configuration in which a release material is further laminated on the pressure-sensitive adhesive layers 12a and 12b.

Moreover, as an adhesive sheet of 1 aspect of this invention, as shown in FIG.1 (d), the base | substrate which has the structure by which the adhesive layer 12 was pinched | interposed into two peeling materials 13a and 13b, without using a base material. The materialless adhesive sheet 1d may be used.
The release materials 13a and 13b of the adhesive sheet without base material 1d may be the same type of material or different types of materials, but the release force between the release material 13a and the release material 13b is different. It is preferable that the material is adjusted as described above.
In addition, as an adhesive sheet without a base material, the adhesive sheet which has the structure which wound what provided the adhesive layer on one side of the peeling material by which the peeling process was given to both surfaces was rolled is mentioned.

As thickness of the adhesive layer which the adhesive sheet of 1 aspect of this invention has, Preferably it is 0.5-100 micrometers, More preferably, it is 1-60 micrometers, More preferably, it is 3-40 micrometers.
If it is 0.5 μm or more, good adhesive force can be obtained for the adherend. On the other hand, if it is 100 micrometers or less, it is advantageous in terms of productivity and can be an easy-to-handle pressure-sensitive adhesive sheet.

<Base material>
As a base material which the adhesive sheet of 1 aspect of this invention has is selected suitably according to the use of the said adhesive sheet, an electroconductive base material may be used and an insulating base material may be used.

Examples of the conductive substrate include a metal substrate made of iron, aluminum, gold, silver, copper, or the like.
Examples of the insulating base material include various types of paper such as fine paper, art paper, coated paper, glassine paper, and laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials; Materials: Plastic film containing one or more resins selected from polyolefin resins such as polyethylene resins and polypropylene resins, polyester resins such as polybutylene terephthalate resins and polyethylene terephthalate resins, acetate resins, ABS resins, polystyrene resins and vinyl chloride resins Or a sheet; Glass substrate; etc. are mentioned.
Note that the substrate used in one embodiment of the present invention may be a single-layer film or a sheet, or may be a multilayer film or sheet that is a laminate of two or more layers.

The plastic film or sheet may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral.
The plastic film or sheet may further contain an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a slip agent, an antiblocking agent, a colorant, and the like.

When the base material is a plastic film or sheet, from the viewpoint of improving the adhesion between the base material and the pressure-sensitive adhesive layer, the surface of the base material is subjected to a surface treatment such as an oxidation method or an unevenness method as necessary. It is preferable.
Examples of the oxidation method include a corona discharge treatment method, a plasma treatment method, chromic acid oxidation (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and the like.
Examples of the unevenness method include a sand blast method and a solvent treatment method.
These surface treatments are appropriately selected according to the type of the substrate, but the corona discharge treatment method is preferred from the viewpoint of improving the adhesion with the pressure-sensitive adhesive layer and operability. Moreover, you may give a primer process to the surface of a base material.

  Although the thickness of a base material is suitably selected according to the use of an adhesive sheet, From a viewpoint of handleability, Preferably it is 10-250 micrometers, More preferably, it is 15-200 micrometers, More preferably, it is 20-150 micrometers.

<Release material>
As the release material included in the pressure-sensitive adhesive sheet of one embodiment of the present invention, a release sheet that has been subjected to a release process on both surfaces or a release sheet that has been subjected to a release process only on one surface is used.
Examples of the release treatment applied to such a release material include a method in which a release agent is applied to form a coating film made of the release agent on the surface of the release material substrate to be released.

Examples of the base material for the release material include paper base materials such as glassine paper, coated paper, high-quality paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials, or polyethylene terephthalate resin, polybutylene terephthalate. Examples thereof include plastic films such as resins, polyester resin films such as polyethylene naphthalate resin, and polyolefin resin films such as polypropylene resin and polyethylene resin.
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long chain alkyl resins, alkyd resins, and fluorine resins.
The thickness of the release material is preferably 10 to 200 μm, more preferably 25 to 150 μm.

[Method for producing adhesive sheet]
There is no restriction | limiting in particular as a manufacturing method of the adhesive sheet of this invention, The adhesive composition of this invention is apply | coated on a base material or a peeling material, a coating film is formed, the said coating film is dried, and adhesion is carried out. The manufacturing method which has the process of forming an agent layer is mentioned.
In addition, in order to improve the workability | operativity of the application | coating on the surface of the base material or a peeling material to a base material or a peeling material, the adhesive composition of this invention which is a forming material of an adhesive layer is further with an organic solvent. It is preferable to dilute to form a solution.

Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol and the like.
As these organic solvents, for example, the organic solvent used in the synthesis of the adhesive resin contained in the adhesive (A) may be used as it is, or one kind other than that used in the synthesis of the adhesive resin. You may add the above organic solvent.

  As solid content concentration of the solution of an adhesive composition, Preferably it is 5-60 mass%, More preferably, it is 10-45 mass%, More preferably, it is 15-30 mass%.

  Examples of the method for applying the solution of the pressure-sensitive adhesive composition on the substrate or release material include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure. Examples thereof include a coating method.

As a specific manufacturing method, as a manufacturing method of the pressure-sensitive adhesive sheet 1a with a substrate as shown in FIG. 1A, for example, a solution of the pressure-sensitive adhesive composition is directly applied to one surface of the substrate 11 and dried. Then, the method of forming the pressure-sensitive adhesive layer 12 and producing it can be mentioned.
Moreover, as a manufacturing method of the adhesive sheet 1b with a base material like FIG.1 (b), the solution of an adhesive composition is directly apply | coated on the peeling process surface of the peeling material 13, for example, it dries and it is an adhesive. Examples include a method in which the surface of the pressure-sensitive adhesive layer 12 exposed and the base material 11 are bonded together after the layer 12 is formed.
Furthermore, as a manufacturing method of the double-sided pressure-sensitive adhesive sheet 1c with a substrate as shown in FIG. 1C, for example, a solution of the pressure-sensitive adhesive composition is directly applied to each of both surfaces of the substrate and dried to be a pressure-sensitive adhesive layer. A method for producing 12, 12 ′ and two release materials are prepared, and a solution of the adhesive composition is directly applied onto the release-treated surface of each release material, followed by drying to provide an adhesive layer The method of bonding the adhesive layers 12a and 12b formed on the two release materials to both surfaces of the base material 11 and the like, etc., after the formation of the substrate, can be mentioned.
And as a manufacturing method of the adhesive sheet 1d without a base material like FIG.1 (d), for example, the solution of an adhesive composition is directly apply | coated to the peeling process surface of the one peeling material 13a, it dries by drying. Examples include a method in which another release material 13b is bonded to the surface of the pressure-sensitive adhesive layer 12 that is exposed after the layer 12 is formed.

[Physical properties and uses of pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet]
The value of the attenuation constant at 1 GHz of the pressure-sensitive adhesive composition of one embodiment of the present invention is preferably 0.150 m ⁻¹ or less, more preferably 0.130 m ⁻ from the viewpoint of exerting the effect of reducing the power consumption of the applied device. ¹ or less, more preferably 0.120 m ⁻¹ or less, even more preferably 0.100 m ⁻¹ or less.
In the present specification, the value of the attenuation constant at 1 GHz of the pressure-sensitive adhesive composition means a value measured by the method described in Examples.

About the adhesive sheet of 1 aspect of this invention, as adhesive force with respect to the polypropylene board which is a to-be-adhered body, Preferably it is 3.0 N / 25mm or more, More preferably, it is 5.0 N / 25mm or more, More preferably, it is 7.0 N / 25mm As mentioned above, More preferably, it is 8.0 N / 25mm or more.
In the present specification, the adhesive strength of the adhesive sheet is a value measured in accordance with JIS Z0237: 2000 using an adherend as a polystyrene plate, and more specifically, according to the method described in the examples. Based on the measured value.

  The pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive sheet of the present invention having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition have a device for transmitting or receiving an electromagnetic wave having a frequency of 10 MHz or more, and a distance between wirings of 3 μm. Use for fixing members of devices having the following integrated circuits is effective in reducing power consumption of these devices.

In addition, this invention can also provide the following apparatus.
-The apparatus which transmits or receives the electromagnetic waves of the frequency of 10 MHz or more using the adhesive sheet of this invention.
-The apparatus which has an integrated circuit with the distance between wirings of 3 micrometers or less using the adhesive sheet of this invention.

In the present invention, as an apparatus for transmitting or receiving an electromagnetic wave having a frequency of 10 MHz or more, for example, a mobile phone, a high-speed wireless LAN, a non-contact type IC card system, a dangerous substance detection sensor, a collision avoidance system incorporated in an automobile, GPS (Global Positioning System) Immediate systems, industrial science and medical equipment, etc.
In an apparatus having an integrated circuit with an inter-wiring distance of 3 μm or less, the pressure-sensitive adhesive sheet of the present invention has a function as a cover lay, and can reduce power consumption and prevent leakage between wirings (leakage).

The various physical property values shown in the description of the following examples are values measured as follows.
(1) Mass average molecular weight (Mw), number average molecular weight (Mn)
Using a gel permeation chromatograph device (product name “HLC-8020” manufactured by Tosoh Corporation), the value measured under the following conditions and measured in terms of standard polystyrene was used.
(Measurement condition)
Column: “TSK guard column HXL-H”, “TSK gel GMHXL (× 2)” and “TSK gel G2000HXL” (both manufactured by Tosoh Corporation).
-Column temperature: 40 ° C
・ Developing solvent: Tetrahydrofuran ・ Flow rate: 1.0 mL / min
(2) Glass transition temperature (Tg)
It was calculated from the formula (ii).

Examples 1-4, Comparative Examples 1-3
To 100 parts by mass of any of the acrylic copolymers (α1) to (α6) shown in Table 2, various types and additives (solid content ratio) shown in Table 2 are added, and ethyl acetate is further added. Was added to dilute to prepare a pressure-sensitive adhesive composition having a solid content concentration of 40% by mass.
And the prepared adhesive composition was apply | coated on the peeling process surface of the peeling film (the product name "SP-PET381031" by Lintec Corporation), and it dried, and formed the 25-micrometer-thick adhesive layer.
Next, the release treatment surface of the same release film as described above was laminated on the surface of the formed pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive sheet without a substrate.
Separately from the above, an adhesive layer is formed on the release film, and a PET film (product name “Lumirror”, thickness 50 μm, manufactured by Toray Industries, Inc.) is laminated on the adhesive layer. Thus, a pressure-sensitive adhesive sheet with a substrate was also produced.

Each component used in the examples and comparative examples is as follows.
<Acrylic copolymer>
Acrylic copolymers (α1) to (α6) containing structural units derived from the types of monomers shown in Table 1 in the mass ratio shown in Table 1 were used. The weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and glass transition temperature (Tg) of each acrylic copolymer are as shown in Table 1.
In addition, about the abbreviation of the monomer in Table 1, it is as follows.
DTDMA: 2-decyltetradecanyl methacrylate (a compound in which R ¹ in the general formula (1-1) is a methyl group)
DTDA: 2-decyltetradecanyl acrylate (a compound in which R ¹ in the general formula (1-1) is a hydrogen atom)
HDA: hexadecyl acrylate (a compound in which R ¹ and R ² in the general formula (1) are hydrogen atoms and R ³ is — (CH ₂ ) ₁₃ CH ₃ )
2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate MA: methyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate AAc: acrylic acid

<Tackifier>
Alcon P-125: Product name, manufactured by Arakawa Chemical Industries, Ltd., softening point: 125 ° C., alicyclic saturated hydrocarbon resin.
<Crosslinking agent>
-Stabio D-370N: Product name, manufactured by Mitsui Chemicals, Inc., an organic polyvalent isocyanate-based crosslinking agent.
Coronate L: Product name, manufactured by Tosoh Corporation, an organic polyvalent isocyanate-based crosslinking agent.

  The following measurement was performed using the produced adhesive sheet without a base material and the adhesive sheet with a base material. These results are shown in Table 2.

(1) Measurement of dielectric loss tangent and relative dielectric constant of pressure-sensitive adhesive composition A measurement sample was prepared by the following procedure.
First, 8 adhesive sheets without base materials prepared in Examples and Comparative Examples were used, and 8 adhesive layers of the adhesive sheets without base materials were overlapped to form an adhesive laminate composed of 8 adhesive layers. The body layer was sandwiched between two release films.
Next, the two release films present on both sides of this pressure-sensitive adhesive laminate were removed, and a 100 μm thick PET film (product name “Toyobo Co., Ltd., product name“ Cosmo Shine A4300 ") was affixed to obtain a measurement sample having a configuration of PET film / adhesive laminate / PET film.
A dielectric test fixture (manufactured by Agilent Technologies, product name “Agilent 16453A”) is connected to a material analyzer (manufactured by Agilent Technologies, product name “RF Impedance / Material Analyzer E4991A”), and 23 ° C. The relative permittivity ε ′ _all and dielectric loss ε ″ _all of the measurement sample at a frequency of 1 GHz were measured in an environment of 50% RH (relative humidity).
Even PET film dielectric constant epsilon _'0 and dielectric loss epsilon _"0 single measurement sample has, using the above device was measured separately.
Then, the relative dielectric constant ε ′, dielectric loss ε ″, and dielectric loss tangent (tan δ) of the pressure-sensitive adhesive laminate were calculated from the following formulas (a) to (c). ) And relative dielectric constant ε ′ are shown in Table 2 as dielectric loss tangent (tan δ) and relative dielectric constant ε ′ at 1 GHz of the pressure-sensitive adhesive composition.

[In the above formulas (a) to (c), d represents the thickness (μm) of the sample for measurement, and x represents the total thickness (μm) of the two PET films. ε ′ _all represents the relative dielectric constant of the measurement sample, ε ″ _all represents the dielectric loss of the measurement sample. ε ′ ₀ represents the relative dielectric constant of the PET film, and ε ″ ₀ represents the dielectric loss of the PET film. ε ′ is the relative dielectric constant of the adhesive laminate (adhesive composition), ε ″ is the dielectric loss of the adhesive laminate (adhesive composition), and tan δ is the dielectric loss tangent of the adhesive laminate (adhesive composition). Is shown.]
The thickness d of the measurement sample and the total thickness x of the PET film were measured using a constant pressure thickness meter (product name “PG-02” manufactured by Teclock Corporation).

(2) Measurement of haze value of pressure-sensitive adhesive composition A test sample was prepared by cutting the prepared pressure-sensitive adhesive sheet with a substrate into 50 mm x 50 mm.
The release sheet of the test sample was removed, and the haze value of the test sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name “NDH2000”) according to JIS K7136.
Separately, the haze value of only the base PET film was also measured, and the difference between the haze value of the test sample and the haze value of only the PET film was taken as the haze value of the target pressure-sensitive adhesive composition.

(3) Measurement of adhesive strength of pressure-sensitive adhesive sheet A test sample was prepared by cutting the prepared pressure-sensitive adhesive sheet with a base material into 25 mm × 200 mm.
The release sheet of the test sample was removed, and the exposed adhesive layer was attached to a polypropylene plate as an adherend in an environment of 23 ° C. and 50% RH (relative humidity).
Then, after being left for 24 hours in an environment of 23 ° C. and 50% RH, the adhesive strength of the adhesive sheet was measured at a pulling speed of 300 mm / min by a 180 ° peeling method based on JIS Z0237: 2000.

(4) Calculation of attenuation constant Using the values of the dielectric loss tangent (tan δ) and relative dielectric constant ε ′ of the pressure-sensitive adhesive composition obtained in the above (1), the calculation was performed from the formula (i).
It can be determined that the smaller the value of the attenuation constant, the better the effect of reducing power consumption.

  From Table 2, the pressure-sensitive adhesive compositions prepared in Examples 1 to 4 had lower attenuation constants at 1 GHz than those of Comparative Examples 1 to 3. Therefore, it is thought that the adhesive sheet produced in Examples 1-4 is a reduction effect of power consumption compared with Comparative Examples 1-3.

1a, 1b, 1c, 1d Adhesive sheet 11 Base material 12, 12a, 12b Adhesive layer 13, 13a, 13b Release material

Claims (15)

A pressure-sensitive adhesive composition comprising an acrylic copolymer (A) having 25 to 90% by mass of a structural unit (a1) derived from a monomer (a1 ′) represented by the following general formula (1),
The dielectric loss tangent (tan δ) at a frequency of 1 GHz is 4.80 × 10 ⁻³ or less,
A pressure-sensitive adhesive composition used for a device that transmits or receives an electromagnetic wave having a frequency of 10 MHz or more, or a device having an integrated circuit with a distance between wirings of 3 μm or less.

[In the general formula (1), R ¹ is a hydrogen atom or a methyl group. R ² and R ³ are each independently an alkyl group having 4 to 18 carbon atoms. ]   The pressure-sensitive adhesive composition according to claim 1, wherein the relative dielectric constant at a frequency of 1 GHz is 1.5 to 3.2. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein R ² and R ³ in the general formula (1) are each independently a linear alkyl group having 4 to 18 carbon atoms. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the monomer (a1 ') includes a monomer (a11') represented by the following general formula (1-1).

[In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group. ]   The acrylic copolymer (A) further has a structural unit (a2) derived from an alkyl (meth) acrylate (a2 ′) having an alkyl group having 1 to 12 carbon atoms. The pressure-sensitive adhesive composition according to item.   The pressure-sensitive adhesive composition according to claim 5, wherein the acrylic copolymer (A) further has a structural unit (a3) derived from the functional group-containing monomer (a3 ').   Furthermore, the adhesive composition of Claim 6 containing a crosslinking agent (C).   The pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the acrylic copolymer (A) has a mass average molecular weight of 50,000 to 800,000.   The pressure-sensitive adhesive composition according to any one of claims 1 to 8, wherein the acrylic copolymer (A) has a glass transition temperature of -70 ° C to 5 ° C.   Furthermore, the adhesive composition as described in any one of Claims 1-9 containing a tackifier (B).   The adhesive composition as described in any one of Claims 1-10 whose haze value measured based on JISK7136 is 1% or more.   Furthermore, the adhesive composition as described in any one of Claims 1-11 containing a coloring agent.   The adhesive sheet which has an adhesive layer formed from the adhesive composition as described in any one of Claims 1-12.   The apparatus which transmits or receives the electromagnetic waves of the frequency of 10 MHz or more using the adhesive sheet of Claim 13.   An apparatus having an integrated circuit using the adhesive sheet according to claim 13 and having an inter-wiring distance of 3 μm or less.