WO2023002981A1

WO2023002981A1 - Adhesive composition, adhesive layer, and adhesive sheet

Info

Publication number: WO2023002981A1
Application number: PCT/JP2022/028057
Authority: WO
Inventors: 一輝笹原; 普史形見; 智一 ▲高▼橋
Original assignee: 日東電工株式会社
Priority date: 2021-07-21
Filing date: 2022-07-19
Publication date: 2023-01-26
Also published as: KR20240036065A; JP2023016419A; TW202313898A; CN117693571A

Abstract

The present invention provides: an adhesive composition which is capable of forming an adhesive layer that has a low dielectric constant and a low dielectric loss in a high frequency band, while having dielectric characteristics that are not susceptible to the influence of moisture and being suitable for bonding of members that constitute a millimeter wave antenna; and an adhesive sheet.　An adhesive composition according to the first aspect of the present invention has a dielectric constant of 2.0 to 5.0 at a frequency of 28 GHz, a dielectric loss of 0.0001 to 0.05 at a frequency of 28 GHz, a saturation moisture absorption of 2.8% or less at 65°C and 90% R. H., and an amount of dielectric loss change of 0.006 or less as calculated by the formula below.　(Amount of dielectric loss change) = Dfmax – Dfmin

Description

Adhesive composition, adhesive layer, and adhesive sheet

The present invention relates to an adhesive composition, an adhesive layer, and an adhesive sheet. More particularly, the present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet that are suitable for bonding components of a millimeter wave antenna.

In recent years, the speed and capacity of communication in portable communication devices such as smartphones are progressing year by year. It is expected to enable ultra-high-speed and large-capacity communication that is 100 times faster, 1/10 lower latency, and 10 times more simultaneous connections than ever before.

In order to enable ultra-high-speed, large-capacity communication, low latency, and multiple simultaneous connections in 5G, high-frequency electromagnetic waves with a frequency exceeding 24 GHz called millimeter waves are used, and the wavelength is shortened to the order of millimeters. This makes it possible to send a large amount of data at once.

On the other hand, compared to the frequency band used for 4G, millimeter waves tend to be attenuated due to resonance absorption with rain, oxygen in the air, and water molecules, etc., and have strong straightness and are easy to reflect. Antennas used for millimeter wave communications (hereinafter sometimes referred to as "millimeter wave antennas") are required to have a higher antenna gain than conventional 4G communications.

Patent Document 1 discloses a configuration in which a cover member is laminated on a base material provided with an antenna element as a millimeter wave antenna mounted on a portable communication device such as a smart phone. Adhesive is used for bonding.

As such an adhesive, for example, Patent Document 2 contains a polymer obtained by polymerizing a monomer mixture containing 2-ethylhexyl acrylate, a specific (meth)acrylic acid alkyl ester, and a hydroxyl group-containing monomer, A pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having a dielectric constant of 3.5 or less at a frequency of 100 kHz is disclosed.

Further, in Patent Document 3, a specific acrylic polymer, a vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a cross-linking agent are contained, and the dielectric constant at a frequency of 1 MHz is 3.5 or less. Certain adhesive layers are disclosed.

JP 2019-186942 A JP 2015-183178 A Japanese Patent Application Laid-Open No. 2020-007570

It is known that the materials that make up a millimeter wave antenna reduce millimeter waves due to the dielectric loss of the material. A characteristic of low dielectric loss is required. Low dielectric constant and low dielectric loss characteristics in high frequency bands are also required for adhesives used to bond members constituting millimeter wave antennas. In addition, since water tends to absorb and block millimeter waves in the high frequency band as described above, the dielectric properties are required to be less susceptible to moisture.

Although the adhesive of Patent Document 2 has a low dielectric constant at a low frequency (100 kHz), the dielectric loss in a high frequency band is not sufficiently low. Although it has a low dielectric constant, the dielectric loss in the high frequency band was not sufficiently low. In addition, it only describes the dielectric constant in the low frequency band and does not disclose information on the dielectric loss in the high frequency band, and it could not provide a solution to the problem to which the present application is directed.

The present invention was conceived under the circumstances as described above. An object of the present invention is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer suitable for bonding members constituting a millimeter wave antenna. Another object of the present invention is to provide a pressure-sensitive adhesive layer which has a low dielectric constant and dielectric loss in a high frequency band, whose dielectric properties are not easily affected by moisture, and which is suitable for bonding members constituting a millimeter wave antenna. That's what it is. Another object of the present invention is to provide an adhesive having a pressure-sensitive adhesive layer that has a low dielectric constant and dielectric loss in a high frequency band, is less susceptible to moisture in terms of dielectric properties, and is suitable for bonding members constituting a millimeter wave antenna. It is to provide a sheet.

That is, the present invention has a dielectric constant of 2.0 to 5.0 at a frequency of 28 GHz, a dielectric loss of 0.0001 to 0.05 at a frequency of 28 GHz, and a temperature of 65° C. and 90% R.D. H. Provided is a pressure-sensitive adhesive composition having a saturated moisture absorption at 2.8% or less and a change in dielectric loss calculated by the following formula of 0.006 or less.
Change in dielectric loss = D _fmax - D _fmin
D _fmax : 65° C., 90% R.I. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. , the maximum value D _fmin of the dielectric loss at a frequency of 28 GHz: 65° C., 90% R.E.M. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. The minimum value of dielectric loss at a frequency of 28 GHz while tracking the change in dielectric loss over time at

In the pressure-sensitive adhesive composition, the configuration in which the dielectric constant at a frequency of 28 GHz is 2.0 to 5.0 can improve the antenna gain of a millimeter wave antenna in which the constituent members are bonded using the pressure-sensitive adhesive composition. .

In the pressure-sensitive adhesive composition, the configuration that the dielectric loss at a frequency of 28 GHz is 0.0001 to 0.05 can improve the antenna gain of a millimeter wave antenna in which the constituent members are bonded using the pressure-sensitive adhesive composition. .

In the above adhesive composition, 65°C, 90% R.I. H. The saturated moisture absorption rate at 2.8% or less is excellent in water resistance when applied as an adhesive layer or the like to a millimeter wave antenna or the like at around room temperature, and can suppress the radiation loss of millimeter waves.

In the pressure-sensitive adhesive composition, the change in dielectric loss at a frequency of 28 GHz is 0.006 or less, the change in dielectric loss due to moisture absorption is controlled to be low, and millimeter-wave radiation loss can be suppressed. . In other words, it is possible to obtain a pressure-sensitive adhesive composition that is excellent in water resistance and capable of suppressing millimeter-wave radiation loss when the amount of change in dielectric loss is 0.006 or less.

In the pressure-sensitive adhesive composition, the dielectric constant at a frequency of 60 GHz is preferably 2.0 to 5.0. This configuration is preferable in that the antenna gain of a millimeter wave antenna in which constituent members are bonded using the pressure-sensitive adhesive composition can be improved.

The present invention also has a dielectric constant of 2.0 to 5.0 at a frequency of 60 GHz, a dielectric loss of 0.0001 to 0.05 at a frequency of 60 GHz, and a temperature of 65° C. and 90% R.D. H. Provided is a pressure-sensitive adhesive composition having a saturated moisture absorption rate of 2.8% or less and a change in dielectric loss calculated by the following formula of 0.003 or less.
Change in dielectric loss = D _fmax - D _fmin
D _fmax : 65° C., 90% R.I. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. , the maximum value D _fmin of the dielectric loss at a frequency of 60 GHz: 65° C., 90% R.E.M. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. The minimum value of dielectric loss at a frequency of 60 GHz while tracking the change in dielectric loss over time at

In the pressure-sensitive adhesive composition, the structure that the dielectric constant at a frequency of 60 GHz is 2.0 to 5.0 can improve the antenna gain of a millimeter wave antenna in which the constituent members are bonded using the pressure-sensitive adhesive composition. .

In the pressure-sensitive adhesive composition, the structure that the dielectric loss at a frequency of 60 GHz is 0.0001 to 0.05 can improve the antenna gain of a millimeter wave antenna in which the constituent members are bonded using the pressure-sensitive adhesive composition. .

In the pressure-sensitive adhesive composition, the change in dielectric loss at a frequency of 60 GHz is 0.003 or less, the change in dielectric loss due to moisture absorption is controlled to be low, and millimeter-wave radiation loss can be suppressed. . In other words, it is possible to obtain a pressure-sensitive adhesive composition that is excellent in water resistance and capable of suppressing millimeter-wave radiation loss when the amount of change in dielectric loss is 0.003 or less.

The adhesive composition preferably has a total light transmittance of 85% or more as measured on an adhesive layer with a thickness of 25 μm.

The adhesive composition preferably has a haze of 1.0% or less as measured on an adhesive layer with a thickness of 25 μm.

The present invention also provides a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

The present invention also provides an adhesive sheet having the adhesive layer.

The present invention also provides a millimeter wave antenna comprising at least the adhesive sheet and a substrate, wherein the substrate has an antenna element on at least one side thereof, and the adhesive sheet is adhered to the surface of the substrate having the antenna element. provide a millimeter-wave antenna that is

The pressure-sensitive adhesive composition and pressure-sensitive adhesive layer of the present invention exhibit low dielectric constant and dielectric loss in the high frequency band of millimeter waves, and can suppress radiation loss of millimeter waves. Therefore, by using the pressure-sensitive adhesive sheet of the present invention to bond constituent members of a millimeter wave antenna together, a millimeter wave antenna exhibiting high antenna gain can be efficiently manufactured. Also, the pressure-sensitive adhesive composition of the present invention is less susceptible to moisture with respect to its dielectric properties. Therefore, a millimeter wave antenna using the pressure-sensitive adhesive sheet of the present invention is less susceptible to moisture, and can stably suppress the radiation loss of millimeter waves to a low level.

FIG. 1 is a schematic diagram (sectional view) showing an embodiment of a millimeter wave antenna of the present invention. FIG. 2 is a schematic diagram (cross-sectional view) showing an embodiment of the millimeter wave antenna of the present invention. FIG. 3 is a schematic diagram (sectional view) showing an embodiment of the millimeter wave antenna of the present invention. FIG. 4 is a schematic diagram (cross-sectional view) showing an antenna laminate used in evaluation of transmission/reception characteristics. FIG. 4(a) is a side sectional view, and FIG. 4(b) is a top projection view.

[Adhesive composition]
The adhesive composition of the first aspect of the present invention has a dielectric constant of 2.0 to 5.0 at a frequency of 28 GHz and a dielectric loss of 0.0001 to 0.05 at a frequency of 28 GHz. % R.I. H. is 2.8% or less, and the amount of change in dielectric loss calculated by the following formula is 0.006 or less.
Change in dielectric loss = D _fmax - D _fmin
D _fmax : 65° C., 90% R.I. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. , the maximum value D _fmin of the dielectric loss at a frequency of 28 GHz: 65° C., 90% R.E.M. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. The minimum value of dielectric loss at a frequency of 28 GHz while tracking the change in dielectric loss over time at

The adhesive composition of the second aspect of the present invention has a dielectric constant of 2.0 to 5.0 at a frequency of 60 GHz and a dielectric loss of 0.0001 to 0.05 at a frequency of 60 GHz. % R.I. H. is 2.8% or less, and the amount of change in dielectric loss calculated by the following formula is 0.003 or less.
Change in dielectric loss = D _fmax - D _fmin
D _fmax : 65° C., 90% R.I. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. , the maximum value D _fmin of the dielectric loss at a frequency of 60 GHz: 65° C., 90% R.E.M. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. The minimum value of dielectric loss at a frequency of 60 GHz while tracking the change in dielectric loss over time at

The pressure-sensitive adhesive composition of the present invention may have any form, for example, solvent type, emulsion type, hot melt type (hot melt type), non-solvent type (active energy ray curable type, e.g. monomer mixtures, or monomer mixtures and partial polymers thereof, etc.).

As described above, the pressure-sensitive adhesive composition of the present invention may be solvent-based, that is, it may contain an organic solvent.

The organic solvent may be any organic compound that is used as a solvent. For example, hydrocarbon solvents such as cyclohexane, hexane, heptane, and methylcyclohexane; aromatic solvents such as toluene and xylene; butyl acetate, ethyl acetate, Ester solvents such as methyl acetate; Ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Alcohol solvents such as methanol, ethanol, propanol, butanol and isopropyl alcohol. The organic solvent may be a mixed solvent containing two or more organic solvents.

The adhesive composition of the first aspect of the present invention has a controlled low dielectric constant at 28 GHz, and can suppress radiation loss of millimeter waves. The dielectric constant at a frequency of 28 GHz of the pressure-sensitive adhesive composition of the first aspect of the present invention is 5.0 or less, preferably 4.5 or less, more preferably 4.0 or less, still more preferably 3.5 or less. It is more preferably 3.4 or less, particularly preferably 3.3 or less, and most preferably 3.2 or less, 3.1 or less, 3.0 or less, or 2.9 or less. Although the lower limit is not particularly limited, it is 2.0 or more, and may be 2.1 or more or 2.2 or more. Moreover, the adhesive composition of the second aspect preferably has a dielectric constant within the above range at a frequency of 28 GHz.

In this specification, the permittivity is measured by the method described in the examples below. The "relative permittivity" is a value obtained by dividing the "dielectric constant" by the "vacuum permittivity". "relative permittivity" shall be treated as synonymous. Moreover, the pressure-sensitive adhesive composition of the first aspect of the present invention and the pressure-sensitive adhesive composition of the second aspect of the present invention may be collectively referred to as "the pressure-sensitive adhesive composition of the present invention".

The pressure-sensitive adhesive composition of the first aspect of the present invention has controlled low dielectric loss at 28 GHz, and can suppress millimeter-wave radiation loss. The pressure-sensitive adhesive composition of the first aspect of the present invention has a dielectric loss of 0.050 or less, preferably 0.045 or less, more preferably 0.040 or less, still more preferably 0.035 or less, at a frequency of 28 GHz. It is more preferably 0.030 or less, particularly preferably 0.025 or less, and most preferably 0.020 or less. The lower limit is 0.0001 or more, and may be 0.0005 or more or 0.0010 or more. Moreover, the pressure-sensitive adhesive composition of the second aspect of the present invention preferably has a dielectric loss within the above range at a frequency of 28 GHz.

The adhesive composition of the second aspect of the present invention has a controlled low dielectric constant at 60 GHz, and can suppress radiation loss of millimeter waves. The dielectric constant of the pressure-sensitive adhesive composition of the second aspect of the present invention at a frequency of 60 GHz is 5.0 or less, preferably 4.5 or less, more preferably 4.0 or less, still more preferably 3.5 or less. It is more preferably 3.4 or less, particularly preferably 3.3 or less, and most preferably 3.2 or less, 3.1 or less, 3.0 or less, or 2.9 or less. Although the lower limit is not particularly limited, it is 2.0 or more, and may be 2.1 or more or 2.2 or more. Moreover, the pressure-sensitive adhesive composition of the first aspect of the present invention preferably has a dielectric constant within the above range at a frequency of 60 GHz.

The pressure-sensitive adhesive composition of the second aspect of the present invention has controlled low dielectric loss at 60 GHz, and can suppress millimeter-wave radiation loss. The dielectric loss of the adhesive composition of the second aspect of the present invention at a frequency of 60 GHz is 0.050 or less, preferably 0.045 or less, more preferably 0.040 or less, still more preferably 0.035 or less, Still more preferably 0.030 or less, particularly preferably 0.025 or less, most preferably 0.020 or less, 0.019 or less, 0.018 or less, 0.017 or less, 0.016 or less, 0.015 or less, It is 0.014 or less, 0.013 or less, or 0.012 or less. The lower limit of dielectric loss at a frequency of 60 GHz is 0.0001 or more, and may be 0.0005 or more or 0.0010 or more. Moreover, the pressure-sensitive adhesive composition of the first aspect of the present invention preferably has a dielectric loss within the above range at a frequency of 60 GHz.

Since the pressure-sensitive adhesive composition of the present invention has a controlled low saturated moisture absorption rate, it is possible to suppress radiation loss of millimeter waves. 25° C., 90% R.I. of the pressure-sensitive adhesive composition of the present invention. H. is preferably 2.8% or less, more preferably 2.7% or less, still more preferably 2.6% or less, even more preferably 2.5% or less, and particularly preferably 2.4% or less. , most preferably 2.3% or less, 2.2% or less, 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, It is 0.7% or less, or 0.6% or less. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.3% or more, 0.4% or more, or 0.5% or more.

65°C, 90% R.I. of the adhesive composition of the present invention. H. is 2.8% or less, preferably 2.6% or less, more preferably 2.4% or less, even more preferably 2.3% or less, and even more preferably 2.2% or less, Especially preferably 2.1% or less, most preferably 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1. 4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, or 0.7% or less. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.4% or more, or may be 0.5% or 0.6% or more. 65°C, 90% R.I. H. When the saturated moisture absorption rate in is low, the radiation loss of millimeter waves can be suppressed even when the pressure-sensitive adhesive layer or the like is applied and placed in a high-temperature environment.

　85°C, 85% R.I. of the pressure-sensitive adhesive composition of the present invention. H. is preferably 5.0% or less, more preferably 4.0% or less, still more preferably 3.5% or less, even more preferably 3.0% or less, and particularly preferably 2.8% or less. , most preferably 2.6% or less, 2.4% or less, 2.2% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% 1.0% or less or 0.8% or less. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.4% or more, 0.5% or more, or 0.6% or more. 85°C, 85% R.I. H. When the saturated moisture absorption rate in is low, the radiation loss of millimeter waves can be suppressed even when the pressure-sensitive adhesive layer or the like is applied and placed in a high-temperature environment.

The saturated moisture absorption rate under each temperature and humidity environment is, for example, the dry sample weight (w1) and the sample at 65° C. and 90% RH. H. It can be obtained from the weight (w2) at the time when the weight is no longer changed (when the moisture absorption rate is saturated) by leaving it in the atmosphere of , by the following formula. 25°C, 90% R.I. H. , and 85° C., 85% R.I. H. can also be obtained under the conditions of Note that the values of w1 and w2 are assumed to be measured at the same temperature and humidity.
Saturated moisture absorption rate (%) = {(w2-w1)/w1} x 100

Since the pressure-sensitive adhesive composition of the present invention controls the amount of change in dielectric loss due to moisture absorption to a low level, it is possible to suppress millimeter-wave radiation loss and its change over time. The amount of change in dielectric loss due to moisture absorption at a frequency of 28 GHz of the adhesive composition of the first aspect of the present invention is 0.006 or less, preferably 0.005 or less, more preferably 0.004 or less. The lower limit of the amount of change in dielectric loss due to moisture absorption at a frequency of 28 GHz is not particularly limited, but may be, for example, 0.0001 or more, 0.0002 or more, or 0.0003 or more. When the amount of change in dielectric loss is within the above range, the radiation loss of millimeter waves can be stably suppressed in an environment of room temperature to high temperature in a state where the pressure-sensitive adhesive layer or the like is applied. Moreover, it is preferable that the pressure-sensitive adhesive composition of the second aspect of the present invention has an amount of change in dielectric loss due to moisture absorption at a frequency of 28 GHz within the above range.

The amount of change in dielectric loss due to moisture absorption at a frequency of 60 GHz of the adhesive composition of the second aspect of the present invention is 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. The lower limit of the saturated moisture absorption rate is not particularly limited. It may be 0.0007 or more, 0.0008 or more, or 0.0009 or more. When the amount of change is within the above range, the radiation loss of millimeter waves can be stably suppressed in an environment of room temperature to high temperature in the state where the pressure-sensitive adhesive layer or the like is applied. Moreover, it is preferable that the pressure-sensitive adhesive composition of the first aspect of the present invention has an amount of change in dielectric loss due to moisture absorption at a frequency of 60 GHz within the above range.

The amount of change in dielectric loss at the above frequencies of 28 GHz and 60 GHz was measured at 65° C. and 90% RH. H. 23±1° C., 52±1%R. H. (elapsed time = 0 minutes), measure the dielectric loss at each frequency every 10 minutes from 4 minutes to 180 minutes, the maximum value (D _fmax ) and the minimum value among them It can be obtained from (D _fmin ) by the following formula.
Change in dielectric loss = D _fmax - D _fmin

Since the pressure-sensitive adhesive composition of the present invention is controlled to have a low water vapor transmission rate, it is possible to suppress the movement of water molecules in the pressure-sensitive adhesive composition, thereby suppressing variations in the radiation loss of millimeter waves. 40° C., 92% R.I. of the pressure-sensitive adhesive composition of the present invention. H. is preferably 430 g/m ² /day or less, more preferably 300 g/m ² /day or less, still more preferably 250 g/m ² /day or less, still more preferably 200 g/m ² /day Below, it is particularly preferably 150 g/m ² /day or less, most preferably 100 g/m ² /day or less, 50 g/m ² /day or less, or 30 g/m ² /day or less. The lower limit of water vapor permeability is not particularly limited, but may be, for example, 10 g/m ² /day or more, 20 g/m ² /day or more, or 25 g/m ² /day or more.

The water vapor transmission rate (WVTR) is a value measured based on the cup method. The dry weight (w1) of calcium chloride isolated from the outside by an adhesive layer, and the sample was heated at 40° C. and 92% R.I. H. Measure the weight (w2) after a predetermined time (when the moisture absorption rate is saturated) after leaving it in the atmosphere of , and measure the weight change per unit time (1 day), unit area of the adhesive layer (1 m ² ) can be obtained by converting

The dielectric constant or dielectric loss at 28 GHz or 60 GHz of the adhesive composition of the present invention, the saturated moisture absorption rate, the water vapor permeability, and the amount of change in dielectric loss due to moisture absorption are adjusted by adjusting the monomer composition, the type and content of additives, etc. can be adjusted accordingly. In the present specification, the dielectric constant or dielectric loss at 28 GHz or 60 GHz, the saturated moisture absorption rate, the water vapor permeability, and the amount of change in dielectric loss due to moisture absorption are measured by the methods described in Examples below. .

The dielectric constant, dielectric loss, saturated moisture absorption rate and water vapor permeability of the pressure-sensitive adhesive composition of the present invention are the dielectric constant, dielectric loss, saturated moisture absorption rate and It refers to water vapor permeability.

The base polymer that constitutes the pressure-sensitive adhesive composition of the present invention is not particularly limited. composition, synthetic rubber pressure-sensitive adhesive composition, etc.) contains as a base polymer, a silicone-based polymer contained as a base polymer in a silicone-based pressure-sensitive adhesive composition, and a polyester-based pressure-sensitive adhesive composition contains as a base polymer Polyester-based polymer, urethane-based polymer contained as a base polymer in a urethane-based pressure-sensitive adhesive composition, polyamide-based polymer contained as a base polymer in a polyamide-based pressure-sensitive adhesive composition, epoxy-based polymer contained in an epoxy-based pressure-sensitive adhesive composition as a base polymer Examples include polymers, vinyl alkyl ether polymers contained as base polymers in vinyl alkyl ether pressure-sensitive adhesive compositions, and fluoropolymers contained as base polymers in fluorine pressure-sensitive adhesive compositions. Among them, acrylic polymers and rubber polymers are preferred. In addition, the base polymer can be used alone or in combination of two or more.

Examples of the rubber-based polymer include natural rubber, styrene-butadiene rubber (SBR), polyisoprene (PIP), polyisobutylene (PIB), butene-based polymer (butene (1-butene, and cis- or trans-2-butene) and / or 2-methylpropene (isobutylene) as the main monomer), ABA type block copolymer rubber and its hydride, styrene-butadiene-styrene block copolymer rubber (SBS), styrene-isoprene- Styrene Block Copolymer Rubber (SIS), Styrene-Isobutylene-Styrene Block Copolymer Rubber (SIBS), Styrene-Vinyl Isoprene-Styrene Block Copolymer Rubber (SVIS), SBS Hydrogenated Styrene-Ethylene- Examples include butylene-styrene block copolymer rubber (SEBS) and styrene-ethylene-propylene-styrene block copolymer rubber (SEPS), which is a hydrogenated product of SIS. Among them, polyisobutylene is preferred. These rubber-based polymers can be used alone or in combination of two or more.

In the above acrylic polymer, by containing a mixture, partial polymer or copolymer thereof of a methacrylate compound and a (meth)acrylate compound, the dielectric constant and dielectric loss in a high frequency band are controlled to be low, and the dielectric loss is exacerbated. Moisture absorption, which is the cause, can be suppressed. As a result, the rate of change in dielectric loss due to moisture absorption can be suppressed. The "mixture, partial polymer or copolymer" of the above methacrylate compound and (meth)acrylate compound may be referred to as a methacrylic copolymer. Further, a "methacrylate compound" is a compound having a "methacryloyl group", and a "(meth)acrylate compound" is a compound having at least one of an "acryloyl group" and a "methacryloyl group". Moreover, "(meth)acryl" represents either one or both of "acryl" and "methacryl".

The partially polymerized product means a composition in which one or more of the monomer components constituting the mixture is partially polymerized.

As used herein, the term "base polymer" refers to the main component (the component with the highest compounding ratio; the same shall apply hereinafter) among the polymer components contained in the pressure-sensitive adhesive composition. It refers to a component that accounts for a proportion greater than % by mass. In the present specification, the term "base polymer" includes "a mixture of monomer components constituting the base polymer or a partially polymerized product of a mixture of monomer components constituting the base polymer". In this specification, the above-mentioned "mixture of monomer components" includes the case of being composed of a single monomer component and the case of being composed of two or more monomer components. In addition, the above-mentioned "partially polymerized mixture of monomer components" means a composition in which one or more of the constituent monomer components of the above-mentioned "mixture of monomer components" is partially polymerized. do.

The content of the base polymer in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably 75% by mass or more (eg 75 to 99.9% by mass), more preferably 85% by mass or more (eg 85 to 99.9% by mass).

The content of the methacrylic copolymer in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably 75% by mass or more (eg 75 to 99.9% by mass), more preferably 85% by mass or more (eg 85 to 99.9% by mass).

[Mixture, its partial polymer or copolymer (methacrylic copolymer)]
The pressure-sensitive adhesive composition of the present invention is a methacrylic pressure-sensitive adhesive composition having a mixture, a partial polymer thereof, or a copolymer thereof (methacrylic copolymer) as a base polymer. The content of the methacrylic copolymer is not particularly limited to 100% by mass of the total amount of the adhesive composition of the present invention, but is preferably 75% by mass or more (for example, 75 to 99.9% by mass). , preferably 85% by mass or more (for example, 85 to 99.9% by mass).

The pressure-sensitive adhesive composition of the present invention includes, for example, a water-dispersible composition (emulsion type composition) containing the above copolymer as an essential component, and an active energy ray containing the above mixture or a partial polymer thereof as an essential component. Examples include curable compositions, among which compositions containing a mixture or a partially polymerized product thereof as an essential component are preferred.

The methacrylic copolymer according to the present invention contains, as constituent monomers, a methacrylate compound having a hydrocarbon group with 6 or more carbon atoms and a (meth)acrylate compound having a crosslinkable functional group.

<Methacrylate compound having a hydrocarbon group with 6 or more carbon atoms>
The methacrylate compound used in the methacrylic copolymer contains a hydrocarbon group having 6 or more carbon atoms. The hydrocarbon group having 6 or more carbon atoms in the methacrylate compound preferably has an aliphatic group, an alicyclic-containing group, or an aromatic ring-containing group. These hydrocarbon group-containing methacrylate compounds may be used alone or in combination of two or more.

In the methacrylic copolymer, the main structural unit is derived from a methacrylate compound and has an α-methyl group, so the polarization near the main chain is reduced compared to the case of acrylate compounds, and as a result, the dielectric loss is reduced. it is conceivable that. In addition, since the methacryloyl group is more hydrophobic than the acryloyl group and suppresses moisture absorption, it is possible to suppress deterioration of dielectric loss in a high frequency band caused by moisture absorption and the amount of change in dielectric loss.

When the methacrylate compound has an alicyclic group or an aromatic group, the methacrylic copolymer can easily obtain an appropriate cohesive force and strong adhesiveness. Also, by increasing the gel fraction, it becomes easier to obtain excellent anti-foaming and peeling properties. Furthermore, it becomes easy to obtain appropriate flexibility in the pressure-sensitive adhesive layer, and it becomes easy to obtain excellent stress relaxation properties and excellent step followability.

When the hydrocarbon group having 6 or more carbon atoms is an aliphatic group, the number of carbon atoms in the hydrocarbon group is preferably 8 or more, more preferably 9 or more, and still more preferably 10 or more. The number of carbon atoms in the hydrocarbon group is preferably 22 or less, more preferably 20 or less, still more preferably 16 or less.

Examples of methacrylate compounds in which the hydrocarbon group having 6 or more carbon atoms is an aliphatic group include hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, and methacrylic acid. isononyl, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, isostearyl methacrylate, stearyl methacrylate , nonadecyl methacrylate, eicosyl methacrylate, and the like. Among them, lauryl methacrylate, tridecyl methacrylate, and isodecyl methacrylate are preferred.

The content of the methacrylate compound in which the hydrocarbon group having 6 or more carbon atoms is an aliphatic group in the methacrylic copolymer according to the present invention is not particularly limited, but is 25% per 100% by mass of all structural units. % by mass or more, more preferably 25.0 to 99.5 mass %, still more preferably 30.0 to 99.3 mass %, still more preferably 40.0 to 99.0 mass %. It is preferable to use 25% by mass or more from the viewpoint of low dielectric constant and low dielectric loss in a high frequency band.

When the hydrocarbon group having 6 or more carbon atoms is an alicyclic-containing group, the number of carbon atoms in the hydrocarbon group is preferably 6 or more, more preferably 8 or more. The number of carbon atoms in the hydrocarbon group is preferably 22 or less, more preferably 16 or less.

Examples of methacrylate compounds in which the hydrocarbon group having 6 or more carbon atoms is an alicyclic group include methacrylic acid cycloalkyl esters having a cycloalkane ring (cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, etc.) , a methacrylic acid ester having a bicyclic hydrocarbon ring (pinane, pinene, bornane, norbornane, norbornene, etc.), and a tricyclic or higher aliphatic hydrocarbon ring (dicyclopentane ring, dicyclopentene ring, adamantane ring, tricyclic methacrylic acid esters having a cyclopentane ring, tricyclopentene ring, etc.).

Examples of the methacrylic acid cycloalkyl esters include cyclohexyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, cycloheptyl methacrylate, and cyclooctyl methacrylate.

Examples of methacrylic acid esters having a bicyclic hydrocarbon ring include bornyl methacrylate and isobornyl methacrylate.

Examples of the methacrylic acid ester having a hydrocarbon ring of three or more rings include dicyclopentanyl methacrylate, dicyclopentanyloxyethyl methacrylate, tricyclopentanyl methacrylate, 1-adamantyl methacrylate, and methacrylic acid 2. -methyl-2-adamantyl, 2-ethyl-2-adamantyl methacrylate and the like.

When the hydrocarbon group having 6 or more carbon atoms is an aromatic ring-containing group, the number of carbon atoms in the hydrocarbon group is preferably 6-14, more preferably 6-10.

Examples of methacrylate compounds in which the hydrocarbon group having 6 or more carbon atoms is an aromatic ring-containing group include, for example, aromatic carbocyclic rings (e.g., monocyclic carbocyclic rings such as benzene ring, condensed carbocyclic rings such as naphthalene ring, etc.) Specific examples include benzyl methacrylate, phenyl methacrylate, naphthyl methacrylate, 6-(1,1′-biphenyl-4-yloxy)hexyl methacrylate, and the like.

The total content of the methacrylate compound in which the hydrocarbon group having 6 or more carbon atoms is an alicyclic-containing group or an aromatic ring-containing group in the methacrylic copolymer according to the present invention is not particularly limited, but all structural units It is preferably 1.0 to 60.0% by mass, more preferably 5.0 to 55.0% by mass, and still more preferably 10.0 to 50.0% by mass with respect to 100% by mass.

The methacrylate compound may have a (poly)oxyalkylene chain. In the case of having a (poly)oxyalkylene chain, the hydrocarbon group having 6 or more carbon atoms is preferably at the end of the ester moiety in the methacrylate compound. The number of oxygen atoms in the (poly)oxyalkylene chain (that is, the number of repeating oxyalkylene groups) is preferably 1-10, more preferably 1-3. The hydrocarbon group having 6 or more carbon atoms at the terminal may be any of an aliphatic group, an alicyclic group, and an aromatic group, but is preferably an alicyclic group or an aromatic group, particularly Aromatic groups are preferred.

Among the methacrylate compounds having a (poly)oxyalkylene chain, those having an aromatic group at the end thereof have a reduced polarizability in the entire repeating unit, which is effective in reducing dielectric loss in a high frequency band.

The content of the methacrylate compound having the (poly)oxyalkylene chain in the methacrylic copolymer according to the present invention is not particularly limited, but is 1.0 to 30.0% by mass with respect to 100% by mass of all structural units. %, more preferably 5.0 to 25.0 mass %, still more preferably 10.0 to 20.0 mass %.

The total content of the methacrylate compound having a hydrocarbon group having 6 or more carbon atoms in the methacrylic copolymer is preferably 25% by mass or more, more preferably 25% by mass, based on 100% by mass of all structural units. 0 to 99.5% by mass, more preferably 30.0 to 99.3% by mass, particularly preferably 40.0 to 99.0% by mass. Using 25.0% by mass or more is preferable from the viewpoint of low dielectric constant and low dielectric loss in a high frequency band.

<Crosslinkable functional group-containing (meth)acrylate compound>
Since the methacrylic copolymer contains a crosslinkable functional group-containing (meth)acrylate compound having a crosslinkable functional group in the ester portion, it is crosslinked to increase the gel fraction when a crosslinking agent is used, It becomes easier to obtain excellent anti-foaming and peeling properties. Moreover, since it becomes easy to obtain favorable cohesive force, it becomes easy to obtain strong adhesiveness. Furthermore, it becomes easy to suppress the whitening of the adhesive sheet that occurs in a high-humidity environment.

The crosslinkable functional group possessed by the (meth)acrylate compound containing the crosslinkable functional group is, for example, a hydroxyl group, a carboxyl group, an acid anhydride group, an epoxy group such as a glycidyl group, since the gel fraction can be easily adjusted. containing groups, isocyanate groups, aziridyl groups, and the like. Among them, a hydroxyl group is preferable because the gel fraction can be easily adjusted. The crosslinkable functional group-containing (meth)acrylate compound can be used alone or in combination of two or more.

Examples of the (meth)acrylate compound containing a crosslinkable functional group having a hydroxyl group include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, ( 3-hydroxypropyl meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, (meth)acrylic acid hydroxylauryl, 4-hydroxymethylcyclohexyl (meth)acrylate and the like. Among them, 2-hydroxyethyl (meth)acrylate is preferable from the viewpoint that good cohesive force can be easily obtained and adhesion reliability at high temperatures can be easily obtained.

The content of the crosslinkable functional group-containing (meth)acrylate compound in the methacrylic copolymer according to the present invention is preferably 0.1 to 30.0% by mass with respect to 100% by mass of all structural units, More preferably 0.2 to 20.0% by mass, still more preferably 0.3 to 10.0% by mass, and particularly preferably 0.5 to 5.0% by mass. It is preferable to use 0.1% by mass or more from the viewpoint of adjusting the gel fraction, and to use 30.0% by mass or less is preferable from the viewpoint of low dielectric constant and low dielectric loss in a high frequency band.

<Copolymerizable Monomer>
The methacrylic copolymer may contain a copolymerizable monomer in addition to the methacrylate compound having a hydrocarbon group of 6 or more carbon atoms and the crosslinkable functional group-containing (meth)acrylate compound. A copolymerizable monomer can be used individually or in combination of 2 or more types.

Examples of the copolymerizable monomer include, for example, an acrylate compound having a hydrocarbon group having 1 to 24 carbon atoms, a methacrylate compound having a hydrocarbon group having 1 to 5 carbon atoms, and a repeating unit of the main chain in which all carbon atoms are side chains. a substituted methylene compound having a heterocyclic ring-containing monomer, a carboxyl group-containing monomer, a nitrile group-containing monomer, an isocyanate group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, an alkoxy group having 5 or less carbon atoms (meth) acrylic Acid alkoxyalkyl esters, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, vinyl esters (vinyl acetate, vinyl propionate, etc.), aromatic vinyl compounds (styrene, vinyltoluene, etc.), olefins or dienes (ethylene, propylene, butadiene, isoprene, isobutylene, etc.), vinyl ethers (vinyl alkyl ether, etc.), vinyl chloride, vinyl alcohol, macromonomers having a weight average molecular weight of 30,000 or less, and polyfunctional monomers having two or more polymerizable functional groups. be done. These can be used individually or in combination of 2 or more types.

The adhesive composition of the present invention preferably does not contain or substantially does not contain acidic group-containing monomers (eg, carboxyl group-containing monomers, sulfo group-containing monomers, phosphoric acid group-containing monomers, etc.). This configuration is preferable in that an excellent anti-corrosion effect can be obtained for the antenna element or wiring. The content of the acidic group-containing monomer is preferably 0.05% by weight or less (for example, 0 to 0.05% by weight), more preferably 0.01% by weight or less, relative to the total amount of the adhesive composition. (for example, 0 to 0.01% by weight), more preferably 0.001% by weight or less (for example, 0 to 0.001% by weight), can be said to be substantially free.

Among the above copolymerizable monomers, heterocyclic-containing monomers, carboxyl group-containing monomers, amide group-containing monomers, amino group-containing monomers, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers have an appropriate cohesive force for the adhesive layer. It is preferable in that it is easy to obtain and the 180° peeling adhesive force to a glass plate or an acrylic plate is increased to easily obtain strong adhesiveness, and from the viewpoint of metal corrosion prevention, heterocyclic-containing monomers are more preferable.

Examples of the methacrylate compounds having a hydrocarbon group having 1 to 5 carbon atoms include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, methacrylate s -butyl, t-butyl methacrylate, isopentyl methacrylate and the like.

Examples of the acrylate compound having a hydrocarbon group having 1 to 24 carbon atoms include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, s-butyl acrylate, acrylic t-butyl acrylate, pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate , dodecyl acrylate, lauryl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, octadecyl acrylate, isostearyl acrylate, stearyl acrylate, nonadecyl acrylate, eicosyl acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate, bornyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, dicyclopentanyloxyethyl acrylate, acrylic tricyclopentanyl acrylate, 1-adamantyl acrylate, 2-methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl acrylate, phenyl acrylate, naphthyl acrylate, 6-(1,1'- biphenyl-4-yloxy)hexyl and the like.

The heterocycle-containing monomers include heterocycles having only nitrogen atoms as heteroatoms (pyrrolidine, pyrrole, imidazole, pyrazole, piperidine, pyridine, pyrimidine, pyrroline, piperazine, pyrazine, etc.), heterocycles having nitrogen and oxygen atoms ( pyrrolidone, oxazole, isoxazole, morpholine, morpholinone, piperidone, lactam, oxazine, morpholinedione, succinimide, itaconimide, etc.), heterocycles containing nitrogen and sulfur atoms (thiazole, isothiazole, thiazine), heterocycles containing oxygen atoms (lactone, tetrahydrofuran, furan, tetrahydropyran, dioxane, etc.), and a heterocyclic ring having a sulfur atom (tetrahydrothiophene, thiophene, tetrahydrothiopyran, thiopyran, etc.).

When the methacrylic copolymer according to the present invention contains a heterocyclic ring-containing monomer, the pressure-sensitive adhesive layer can have appropriate flexibility, and excellent stress relaxation and step conformability can be easily obtained. .

Examples of heterocyclic-containing monomers having a heterocyclic ring having only a nitrogen atom as the heteroatom include N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, and N-vinylpyrrole. , N-vinylimidazole, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylpyrazole and the like.

Examples of the heterocyclic ring-containing monomer having a heterocyclic ring having a nitrogen atom and an oxygen atom as the heteroatom include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-(meth)acryloyl-2-pyrrolidone, N -vinyloxazole, N-vinylisoxazole, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide , N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyhexamethylenesuccinimide, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N- cyclohexyl itaconimide, N-lauryl itaconimide and the like.

Examples of the heterocyclic-containing monomer having a heterocyclic ring containing a nitrogen atom and a sulfur atom as the heteroatom include N-vinylthiazole and N-vinylisothiazole.

Among these, N-vinyl-2-pyrrolidone is particularly preferred.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. The carboxyl group-containing monomers also include, for example, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride. Alternatively, it may be a derivative formed by ester bonding with, for example, itaconic acid.

Examples of the nitrile group-containing monomer include (meth)acrylonitrile.

Examples of the isocyanate group-containing monomer include 2-isocyanatoethyl (meth)acrylate.

Examples of the amide group-containing monomer include (meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl N,N-dialkyl (meth)acrylamides such as (meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-di(t-butyl)(meth)acrylamide; N-ethyl ( N-alkyl(meth)acrylamides such as meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, Nn-butyl(meth)acrylamide; N-vinylcarboxylic acids such as N-vinylacetamide Amides; monomers having a hydroxyl group and an amide group, such as N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth) ) acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, N-(4-hydroxybutyl) N-hydroxyalkyl (meth)acrylamides such as (meth)acrylamide; monomers having an alkoxy group and an amide group, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-butoxymethyl ( N-alkoxyalkyl(meth)acrylamides such as meth)acrylamide; other examples include N,N-dimethylaminopropyl(meth)acrylamide, N-(meth)acryloylmorpholine and the like.

The (meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides, such as N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and the like. .

Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, and the like.

Examples of the (meth)acrylic acid alkoxyalkyl ester having an alkoxy group having 5 or less carbon atoms include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and methoxy (meth)acrylate. triethylene glycol, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate and the like.

Examples of the sulfonic acid group-containing monomer include sodium vinyl sulfonate.

The above macromonomer is a high-molecular-weight monomer obtained by polymerizing a plurality of the above monomer components. When a macromonomer is used, structural units derived from monomer components constituting the macromonomer are present continuously to some extent in the base polymer. Therefore, by using a macromonomer, it is possible to introduce a higher-order structure derived from the macromonomer into the base polymer, and the properties required for adhesives (adhesive strength, cohesive strength, step conformability, etc.) can be easily achieved. can be adjusted. The weight average molecular weight of the macromonomer is preferably 3,000 to 35,000, more preferably 4,000 to 30,000, even more preferably 5,000 to 25,000, still more preferably 6,000 to 20,000.

Examples of the polyfunctional monomer having two or more polymerizable functional groups include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, Tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, polyester acrylate, urethane acrylate and the like. A polyfunctional monomer can be used individually or in combination of 2 or more types.

The content of the polyfunctional monomer in the methacrylic copolymer according to the present invention is not particularly limited, but is 0.5% by mass or less (for example, 0 to 0.5 % by mass), more preferably 0 to 0.35 mass %, still more preferably 0 to 0.2 mass %. When the content of the polyfunctional monomer is 0.5% by mass or less, the pressure-sensitive adhesive layer has appropriate cohesive strength, and the pressure-sensitive adhesive strength and step absorbability are easily improved, which is preferable. When using a cross-linking agent, the polyfunctional monomer may not be used, but the content of the polyfunctional monomer when the cross-linking agent is not used is preferably 0.001 to 0.5% by mass. , more preferably 0.001 to 0.35% by mass, more preferably 0.002 to 0.2% by mass.

The total content of the copolymerizable monomers in the methacrylic copolymer is not particularly limited, but is preferably 30.0% by mass or less, more preferably 15.0% by mass, based on 100% by mass of all structural units. It is 0% by mass or less.

The methacrylic copolymer is obtained by mixing the methacrylate compound having a hydrocarbon group with 6 or more carbon atoms, the crosslinkable functional group-containing (meth)acrylate compound and the copolymerizable monomer, or by a known or conventional polymerization method. It can be obtained by polymerizing with Examples of the polymerization method include a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a polymerization method using active energy ray irradiation (active energy ray polymerization method). Among them, the solution polymerization method and the active energy ray polymerization method are preferable, and the active energy ray polymerization method is more preferable, from the viewpoints of the transparency, water resistance, cost, etc. of the pressure-sensitive adhesive layer.

Examples of the active energy ray irradiated during the active energy ray polymerization (photopolymerization) include ionizing radiation such as α-ray, β-ray, γ-ray, neutron beam, and electron beam, and ultraviolet rays, particularly ultraviolet rays. is preferred. Moreover, the irradiation energy, irradiation time, irradiation method, and the like of the active energy ray are not particularly limited as long as the photopolymerization initiator can be activated to cause the reaction of the monomer components.

Various general solvents may be used in the polymerization of the methacrylic copolymer. Examples of such solvents include esters (ethyl acetate, n-butyl acetate, etc.), aromatic hydrocarbons (toluene, benzene, etc.), aliphatic hydrocarbons (n-hexane, n-heptane, etc.), Organic solvents such as alicyclic hydrocarbons (cyclohexane, methylcyclohexane, etc.) and ketones (methyl ethyl ketone, methyl isobutyl ketone, etc.) can be mentioned. A solvent can be used individually or in combination of 2 or more types.

In addition, when polymerizing the methacrylic copolymer, a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) may be used depending on the type of polymerization reaction. A polymerization initiator can be used individually or in combination of 2 or more types.

The photopolymerization initiator is not particularly limited. Active oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and the like can be mentioned. A photoinitiator can be used individually or in combination of 2 or more types.

Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, anisole methyl ether and the like. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, 4-(t-butyl ) and dichloroacetophenone. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. be done. Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and the like. Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

The amount of the photopolymerization initiator used is not particularly limited. 0.01 to 5.0 parts by mass.

Examples of the thermal polymerization initiator include azo polymerization initiators, peroxide polymerization initiators (eg, dibenzoyl peroxide, tert-butyl permaleate, etc.), redox polymerization initiators, and the like. . Among them, the azo polymerization initiator disclosed in JP-A-2002-69411 is preferable. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile (AMBN), 2,2'-azobis (2- methyl propionate), 4,4′-azobis-4-cyanovaleric acid and the like.

The amount of the thermal polymerization initiator used, for example, in the case of the azo polymerization initiator, is preferably 0.05 to 0.5 parts by mass with respect to 100 parts by mass of all structural units of the methacrylic copolymer. More preferably, it is 0.1 to 0.3 parts by mass.

The weight average molecular weight (Mw) of the copolymer forming the adhesive layer of the present invention is preferably 100,000 to 5,000,000, more preferably 200,000 to 4,000,000, and still more preferably 300,000 to 3,000,000. A configuration in which the weight-average molecular weight is 100,000 or more is preferable in terms of improving adhesive strength and holding properties, and improving resistance to foaming and peeling. A configuration in which the weight-average molecular weight is 5,000,000 or less is preferable in terms of easily increasing adhesive strength and improving resistance to foaming and peeling.

The weight-average molecular weight (Mw) of the copolymer can be determined by GPC in terms of polystyrene. For example, it can be measured under the following conditions using a high-speed GPC device (product name “HPLC-8120GPC” manufactured by Tosoh Corporation).
・Column: TSKgel Super HZM-H/HZ4000/HZ3000/HZ2000
・Solvent: Tetrahydrofuran ・Flow rate: 0.6 ml/min

The glass transition temperature (Tg) of the copolymer is preferably -70 to 100°C, more preferably -65 to 50°C, still more preferably -60 to 10°C. When the glass transition temperature of the methacrylic copolymer is −70° C. or higher, the cohesive force is improved, and the resistance to foaming and peeling is easily improved, which is preferable. Further, when the glass transition temperature is 100 ° C. or less, the pressure-sensitive adhesive composition has moderate flexibility, and it becomes easy to obtain good adhesive strength and good step absorbability, and it is easy to obtain excellent adhesion reliability. Therefore, it is preferable.

The glass transition temperature (Tg) of the above copolymer is the glass transition temperature (theoretical value) represented by the following FOX formula. In the following formula, Tg is the glass transition temperature (unit: K) of the copolymer, Tg is the glass transition temperature (unit: K) when monomer _i forms a homopolymer, and W is the monomer component of monomer _i . Represents the mass fraction in the total amount (i=1, 2, . . . n).
₁ /Tg ₌ W1 _/ Tg1 ₊ W2/Tg2+...+ _Wn / _Tgn

As the Tg of the homopolymer of the monomers constituting the above copolymer, the following values can be adopted.
・Lauryl methacrylate -65℃
・2-Ethylhexyl methacrylate -10°C
・ Lauryl acrylate 0℃
・2-Ethylhexyl acrylate -70°C
・Isodecyl methacrylate -41°C
・2-Hydroxyethyl methacrylate 55°C
・Methyl methacrylate 105°C
・Cyclohexyl methacrylate 66°C
・Isobornyl methacrylate 173°C
・Dicyclopentanyl methacrylate 175°C
・Methacrylic acid 228°C
・N-vinylpyrrolidone 86°C
・2-Phenoxyethyl methacrylate 5°C
・Benzyl methacrylate 54°C
・2-(2-methoxyethoxy)ethyl methacrylate -3°C

Also, as the Tg of homopolymers of monomers not described above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. Furthermore, as the Tg of a homopolymer of a monomer not described in the above literature, the value obtained by the above-described measuring method (tan δ peak top temperature by viscoelasticity test) can be employed.

A chain transfer agent may be used in the polymerization of the methacrylic copolymer to adjust the molecular weight. Examples of the chain transfer agent include 2-mercaptoethanol, α-thioglycerol, 2,3-dimercapto-1-propanol, octyl mercaptan, t-nonyl mercaptan, dodecyl mercaptan (lauryl mercaptan), t-dodecyl mercaptan, glycidyl mercaptan, thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, ethylene glycol thioglycolate, neopentyl glycol thioglycolate, pentaerythritol thioglycolate, α-methylstyrene dimer and the like. Among them, α-thioglycerol and methyl thioglycolate are preferable, and α-thioglycerol is particularly preferable, from the viewpoint of suppressing whitening of the adhesive sheet due to humidification. A chain transfer agent can be used individually or in combination of 2 or more types.

The content of the chain transfer agent is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, and still more preferably 100 parts by mass of the total structural units of the methacrylic copolymer. 0.3 to 10 parts by mass. A methacrylic copolymer having a weight-average molecular weight controlled to 1,000 to 30,000 can be easily obtained by setting the content (the amount used) of the chain transfer agent within the above range.

The adhesive composition of the present invention preferably contains a cross-linking agent. When the pressure-sensitive adhesive composition contains a cross-linking agent, the base polymer is cross-linked to increase the gel fraction, thereby making it easier to improve the resistance to foaming and peeling. Examples of the cross-linking agent include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, melamine-based cross-linking agents, peroxide-based cross-linking agents, urea-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, metal Examples include salt-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, and amine-based cross-linking agents. Among them, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferable, and isocyanate-based cross-linking agents are more preferable, from the viewpoint of improving resistance to foaming and peeling. A crosslinking agent can be used individually or in combination of 2 or more types.

Examples of the isocyanate-based crosslinking agent (polyfunctional isocyanate compound) include lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate; cyclopentylene diisocyanate; , cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate and other alicyclic polyisocyanates; 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate , xylylene diisocyanate and other aromatic polyisocyanates. Examples of the isocyanate-based cross-linking agent include trimethylolpropane/tolylene diisocyanate adduct (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane/hexamethylene diisocyanate adduct (trade name Commercially available products such as "Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd." and trimethylolpropane/xylylene diisocyanate adduct (trade name "Takenate D-110N" manufactured by Mitsui Chemicals, Inc.) can also be used.

Examples of the epoxy-based cross-linking agent (polyfunctional epoxy compound) include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidyl aminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether , glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipate diglycidyl ester, o-phthalate diglycidyl ester, triglycidyl-tris(2 -hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Further, examples of the epoxy-based cross-linking agent include commercially available products such as trade name "Tetrad C" (manufactured by Mitsubishi Gas Chemical Company, Inc.).

The content of the cross-linking agent in the adhesive composition is, for example, preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the methacrylic copolymer. be. When the content of the cross-linking agent is 0.001 parts by mass or more, the resistance to foaming and peeling is easily improved, which is preferable. On the other hand, when the content of the cross-linking agent is 10 parts by mass or less, the pressure-sensitive adhesive layer has appropriate flexibility and the pressure-sensitive adhesive strength is easily improved, which is preferable.

The adhesive composition of the present invention contains inorganic fine particles, organic fine particles, and polymer materials other than the base polymer, in addition to the above-mentioned base polymer, from the viewpoint of further lowering the dielectric constant and the dielectric loss in a high frequency band. You can stay. These can be used individually or in combination of 2 or more types. From the viewpoint of low dielectric constant and low dielectric loss in a high frequency band, the above inorganic fine particles and organic fine particles are preferably those exhibiting insulating properties (insulating filler).

(Inorganic fine particles)
Examples of inorganic fine particles that can be blended in the pressure-sensitive adhesive composition of the present invention include metal oxides such as silica, alumina, zirconia, and titania; metal salts such as aluminum borate and aluminum hydroxide; minerals such as mica; and hollow nanosilica. and inorganic fine particles having a hollow structure. These can be used individually or in combination of 2 or more types.

The inorganic fine particles may be surface-treated from the viewpoint of dispersibility in the base polymer. As the surface treatment agent, known or commonly used agents can be used without limitation, and examples thereof include silane coupling agents, titanium coupling agents, organic acids, polyols, and silicones, with silane coupling agents being preferred. Silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, dimethylvinylmethoxysilane, dimethylvinylethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, vinyl-tris(2-methoxy)silane, vinyltri Acetoxysilane, 2-methacryloxyethyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxy-propylmethyldimethoxysilane, triethoxyphenylsilane, trimethoxyphenylsilane, dimethoxysilane diphenylsilane, methyldiethoxyphenylsilane, dimethoxymethylphenylsilane and the like.

The particle diameter (D50) of the inorganic fine particles is preferably 1 to 100 nm, more preferably 5 to 80 nm, and more preferably 5 to 80 nm, from the viewpoints of low dielectric constant, low dielectric loss, and transparency in a high frequency band of the pressure-sensitive adhesive composition. It is preferably 10 to 50 nm. The median particle size means the particle size (median size) at 50% of the integrated value in the particle size distribution measured by the laser diffraction/scattering method.

When the pressure-sensitive adhesive composition of the present invention contains inorganic fine particles, the content thereof is 100 parts by mass of the above-mentioned base polymer from the viewpoints of low dielectric constant, low dielectric loss and transparency in a high frequency band of the pressure-sensitive adhesive composition. is preferably 0.01 to 30 parts by mass, more preferably 0.05 to 25 parts by mass, still more preferably 0.10 to 20 parts by mass, even more preferably 0.15 to 10 parts by mass, particularly preferably is 0.2 to 5 parts by mass.

(organic fine particles)
Examples of organic fine particles that can be blended in the adhesive composition of the present invention include styrene resins, acrylic resins, silicone resins, acrylic-styrene resins, vinyl chloride resins, vinylidene chloride resins, amide resins, and urethane. Polymers such as resins, phenolic resins, styrene-conjugated diene-based resins, acrylic-conjugated diene-based resins, olefinic resins, and fluorine-based resins, or fine particles composed of crosslinked products of these polymers, and further these polymers, Examples thereof include fine particles configured to have a hollow structure by means of a crosslinked polymer. These can be used individually or in combination of 2 or more types.

The particle size (D50) of the organic fine particles is preferably 1 to 100 nm, more preferably 5 to 80 nm, and more preferably 5 to 80 nm, from the viewpoints of low dielectric constant, low dielectric loss, and transparency in the high frequency band of the pressure-sensitive adhesive composition. It is preferably 10 to 50 nm. The above median particle diameter means the particle diameter (median diameter) at an integrated value of 50% in the particle size distribution measured by the laser diffraction/scattering method.

When the pressure-sensitive adhesive composition of the present invention contains organic fine particles, the content thereof is 100 parts by mass of the above-mentioned base polymer from the viewpoint of low dielectric constant, low dielectric loss and transparency in a high frequency band of the pressure-sensitive adhesive composition. is usually 0.01 to 30 parts by mass, preferably 0.05 to 25 parts by mass, more preferably 0.1 to 20 parts by mass, more preferably 0.15 to 10 parts by mass, particularly preferably is 0.2 to 5 parts by mass.

(polymer material)
As the polymer material that can be blended in the pressure-sensitive adhesive composition of the present invention, those having low dielectric constant and dielectric loss and compatibility with the base polymer are preferable. , polyethylene, polypropylene, polystyrene, polycarbonate, norbornene resin or addition copolymer resin with olefins, polyphenylene ether, bismaleimide/triazine/resin, polyetherimide, polyimide, polyetheretherketone (PEEK), liquid crystal polymer, Rubber/elastomers, hydrogenated polyolefin resins, terpenes, isoprenes, terpene phenol resins, aromatic modified terpene resins and their hydrogenated resins, and the like. These can be used individually or in combination of 2 or more types.

When the pressure-sensitive adhesive composition of the present invention contains a polymer material, its content is not particularly limited. It is usually 0.01 to 50 parts by mass, preferably 0.05 to 40 parts by mass, and more preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the base polymer.

(anti-rust)
The pressure-sensitive adhesive composition of the present invention may further contain an antirust agent. If the pressure-sensitive adhesive composition contains a rust inhibitor, it is preferable in that an excellent anti-corrosion effect can be obtained for the antenna element and metal wiring.

A rust inhibitor is a compound that prevents metal from rusting and corroding. Examples of rust inhibitors include amine compounds, benzotriazole compounds, and nitrites. Others include ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropine, thiourea, phenyl carbamate, cyclohexylammonium-N-cyclohexyl. carbamate (CHC) and the like. A rust inhibitor can be used individually or in combination of 2 or more types.

Examples of the amine compound include hydroxy group-containing amine compounds such as 2-amino-2-methyl-1-propanol, monoethanolamine, monoisopropanolamine, diethylethanolamine, ammonia and ammonia water; cyclic amines such as morpholine; cyclohexyl Cyclic alkylamine compounds such as amines; linear alkylamines such as 3-methoxypropylamine; Examples of nitrites include dicyclohexylammonium nitrite (DICHAN), diisopropylammonium nitrite (DIPAN), sodium nitrite, potassium nitrite, and calcium nitrite.

The content of the rust inhibitor is preferably 0.02 to 15 parts by mass with respect to 100 parts by mass of the base polymer. When the content is 0.02 parts by mass or more, good corrosion prevention performance can be easily obtained, which is preferable. On the other hand, when the content is 15 parts by mass or less, transparency is easily ensured, and adhesion reliability such as resistance to foaming and peeling is easily ensured, which is preferable.

Among them, the anticorrosive agent is benzodiazepine because it can obtain adhesion reliability to the base polymer, transparency, and corrosion resistance properties in a well-balanced manner at a high level, and can obtain excellent appearance. A triazole compound is preferred.

The benzotriazole-based compound is not particularly limited as long as it is a compound having a benzotriazole skeleton, but from the viewpoint that having a structure represented by the following formula (1) provides a more excellent anti-corrosion effect. preferable.

(In formula (1) above, R ¹ and R ² are the same or different, and R ¹ is a substituent on the benzene ring, which is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, aryl group having 6 to 14 carbon atoms, amino group, mono- or di-C _1-10 alkylamino group, amino-C _1-6 alkyl group, mono- or di-C _1-10 alkylamino-C _1-6 alkyl group , a mercapto group, an alkoxycarbonyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n R ¹ may be the same or different, and R ² is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms. group, amino group, mono- or di-C _1-10 alkylamino group, amino-C _1-6 alkyl group, mono- or di-C _1-10 alkylamino-C _1-6 alkyl group, mercapto group, carbon number 1-12 or a substituent such as an alkoxy group having 1 to 12 carbon atoms.)

From the viewpoint of obtaining a better anti-corrosion effect, R ¹ is preferably an alkyl group having 1 to 3 carbon atoms, an alkoxycarbonyl group, or the like, and more preferably a methyl group or the like. Also, n is preferably 0 or 1. From the same viewpoint, R ² is preferably a hydrogen atom, a mono- or di-C _1-10 alkylamino-C _1-6 alkyl group, etc., a hydrogen atom, a di-C _1-8 alkylamino-C _1-4 alkyl group, etc. is more preferred.

The content of the benzotriazole-based compound is preferably 0.02 to 3 parts by mass, more preferably 0.02 to 2.5 parts by mass, and still more preferably 0.02 to 0.02 parts by mass with respect to 100 parts by mass of the base polymer. 2 parts by mass. When the amount of the benzotriazole-based compound is within a certain range, adhesion reliability such as resistance to foaming and peeling can be reliably secured, and an increase in haze of the adhesive sheet can be reliably prevented.

(Silane coupling agent)
The pressure-sensitive adhesive composition of the invention may further contain a silane coupling agent. When the pressure-sensitive adhesive composition contains a silane coupling agent, it is preferable because excellent adhesion to glass (especially, excellent adhesion reliability to glass at high temperature and high humidity) can be easily obtained.

Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-aminopropyltrimethoxysilane, and the like. Among them, γ-glycidoxypropyltrimethoxysilane is preferred. Examples of the silane coupling agent include commercially available products such as the product name "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.). A silane coupling agent can be used individually or in combination of 2 or more types.

The content of the silane coupling agent is preferably 0.01 to 1 part by mass, more preferably 0.03 to 0.5 parts by mass with respect to 100 parts by mass of the base polymer, from the viewpoint of improving adhesion reliability to glass. part by mass.

(Other additives)
The pressure-sensitive adhesive composition of the present invention may optionally contain antioxidants, cross-linking accelerators, tackifying resins (rosin derivatives, polyterpene resins, oil-soluble phenols, etc.), aging Known additives such as inhibitors, colorants (pigments, dyes, etc.), ultraviolet absorbers, chain transfer agents, plasticizers, softeners, surfactants, and antistatic agents may be included. These can be used individually or in combination of 2 or more types.

When the pressure-sensitive adhesive composition of the present invention contains a tackifier, the content thereof is preferably 0.01 parts by mass or more, more preferably 0.01 part by mass or more based on 100 parts by mass of the base polymer, from the viewpoint of imparting appropriate adhesiveness. is 0.05 parts by mass or more. Also, from the point of avoiding excessively high peel strength, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less.

[Adhesive layer]
Since the pressure-sensitive adhesive layer of the present invention is formed from the pressure-sensitive adhesive composition of the present invention, it exhibits a low dielectric constant and low dielectric loss in millimeter waves in a high frequency band (28 to 60 GHz). That is, the pressure-sensitive adhesive layer of the present invention can suppress radiation loss of millimeter waves.

The pressure-sensitive adhesive layer of the present invention is preferable in that it has a low dielectric constant at 28 GHz and can suppress radiation loss of millimeter waves. The dielectric constant of the adhesive layer of the present invention at a frequency of 28 GHz is preferably 2.0 to 5.0, more preferably 2.05 to 4.5, still more preferably 2.1 to 4.0, still more preferably 2 .15-3.5, particularly preferably 2.2-3.4, most preferably 2.2-3.3, 2.2-3.2, 2.2-3.1, 2.2-3 .0 or 2.2 to 2.9.

The dielectric constant at 28 GHz of the pressure-sensitive adhesive layer of the present invention can be adjusted by adjusting the type of base polymer, monomer composition, type and content of additives, etc. that constitute the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer. , can be adjusted.

The pressure-sensitive adhesive layer of the present invention is preferable in that the dielectric loss at 28 GHz is controlled to be low and the radiation loss of millimeter waves can be suppressed. The dielectric loss of the adhesive layer of the present invention at a frequency of 28 GHz is preferably 0.050 or less, more preferably 0.045 or less, still more preferably 0.040 or less, even more preferably 0.035 or less, and particularly preferably 0.045 or less. 030 or less, most preferably 0.025 or less or 0.020 or less. Although the lower limit is not particularly limited, it is preferably 0.0001 or more, and may be 0.0005 or more or 0.0010 or more.

The dielectric loss at 28 GHz in the pressure-sensitive adhesive layer of the present invention can be adjusted by adjusting the type of base polymer, monomer composition, type and content of additives, etc. that constitute the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer. , can be adjusted.

The adhesive layer of the present invention is preferable in that it has a low dielectric constant at 60 GHz and can suppress radiation loss of millimeter waves. The dielectric constant of the adhesive layer of the present invention at a frequency of 60 GHz is preferably 2.0 to 5.0, more preferably 2.1 to 4.5, still more preferably 2.2 to 4.0, still more preferably 2.2-3.5, particularly preferably 2.2-3.4, most preferably 2.2-3.3, 2.2-3.2, 2.2-3.1, 2.2- 3.0 or 2.2 to 2.9.

The dielectric constant at 60 GHz in the pressure-sensitive adhesive layer of the present invention can be adjusted by adjusting the type of base polymer, monomer composition, type and content of additives, etc. that constitute the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer. , can be adjusted.

The pressure-sensitive adhesive layer of the present invention preferably has a controlled low dielectric loss at 60 GHz, which is preferable in that it can suppress the radiation loss of millimeter waves. The dielectric loss of the pressure-sensitive adhesive layer of the present invention at a frequency of 60 GHz is preferably 0.050 or less, more preferably 0.045 or less, still more preferably 0.040 or less, even more preferably 0.035 or less, and particularly preferably 0. 0.030 or less, most preferably 0.025 or less or 0.020 or less. The lower limit of dielectric loss at a frequency of 60 GHz is preferably 0.0001 or more, and may be 0.0005 or more or 0.0010 or more.

The dielectric loss at 60 GHz in the pressure-sensitive adhesive layer of the present invention can be determined by adjusting the type of base polymer, monomer composition, type and content of additives, etc. that constitute the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer. , can be adjusted.

The adhesive layer of the present invention is transparent or has transparency. Therefore, the visibility and appearance through the pressure-sensitive adhesive composition are excellent. Thus, the pressure-sensitive adhesive layer of the present invention is suitable for optical applications.

The haze (according to JIS K7136) of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is preferably 1.2% or less, more preferably 1.1% or less, still more preferably 1.0% or less, and even more preferably is 0.9% or less, especially 0.8% or less. When the haze is, for example, 1.2% or less, excellent transparency and excellent appearance are likely to be obtained. The haze is measured, for example, by setting the pressure-sensitive adhesive layer to a thickness of 25 μm, allowing it to stand in a normal state (23° C., 50% RH) for at least 24 hours, and then using a slide glass (for example, total light transmittance of 91.8%, Haze 0.4%) can be used as a sample and measured using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory).

The total light transmittance (according to JIS K7361-1) in the visible light wavelength region of the adhesive layer of the present invention is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, and even more preferably 90%. % or more, particularly preferably 91% or more, most preferably 92% or more. When the total light transmittance is 85% or more, excellent transparency and excellent appearance are likely to be obtained. For the total light transmittance, for example, the pressure-sensitive adhesive layer thickness is 25 μm, and this is allowed to stand in a normal state (23° C., 50% RH) for at least 24 hours. A haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory) is used as a sample, which is laminated on a slide glass (for example, total light transmittance 91.8%, haze 0.4%). can be measured using

The haze and total light transmittance of the pressure-sensitive adhesive layer of the present invention can be adjusted by adjusting the monomer composition, the type and content of additives, and the like.

The gel fraction (percentage of insoluble components) of the pressure-sensitive adhesive layer of the present invention is preferably 30 to 95%, more preferably 35 to 90%, still more preferably 40 to 85%, still more preferably 45 to 80%, Especially preferred is 50 to 75%. When the gel fraction is 30% or more, the cohesive force of the pressure-sensitive adhesive layer is improved, dents are less likely to occur during handling, and foaming or peeling occurs at the interface with the adherend in a high-temperature environment. is suppressed, and excellent anti-foaming and peeling resistance is easily obtained, which is preferable. When the gel fraction is 95% or less, it is preferable because a suitable flexibility can be obtained, the adhesiveness and step followability are further improved, and foreign substances are hardly absorbed.

The gel fraction (ratio of solvent-insoluble components) can be calculated, for example, as follows.

About 0.1 g was collected from the adhesive layer, wrapped in a porous tetrafluoroethylene sheet (trade name “NTF1122”, manufactured by Nitto Denko Corporation) having an average pore size of 0.2 μm, and then tied with a kite string. Measure the mass, and let the mass be the mass before immersion (Z). The weight before immersion is the total weight of the adhesive layer, the tetrafluoroethylene sheet and the kite string. Also, the total mass of the tetrafluoroethylene sheet and the kite string is measured, and this mass is taken as the package mass (Y). Next, the adhesive layer wrapped with a tetrafluoroethylene sheet and tied with kite string (referred to as a "sample") is placed in a 50 ml container filled with ethyl acetate or toluene and allowed to stand at 23°C for 7 days. Then, the sample (after ethyl acetate treatment) is taken out from the container, transferred to an aluminum cup, dried at 130 ° C. for 2 hours in a dryer to remove ethyl acetate or toluene, and then weighed. is the mass after immersion (X). Then, the gel fraction is calculated from the following formula.
Gel fraction (%) = {(XY)/(ZY)} x 100

The gel fraction of the pressure-sensitive adhesive layer of the present invention can be controlled by, for example, monomer composition, weight average molecular weight, amount of cross-linking agent used, types and amounts of other additives used, and the like.

The storage elastic modulus of the pressure-sensitive adhesive layer of the present invention at 25° C. is preferably 0.01 MPa or more, more preferably 0.02 MPa or more, still more preferably 0.03 MPa or more, still more preferably 0.04 MPa or more, and particularly preferably 0.05 MPa or more, most preferably 0.10 MPa or more. When the storage elastic modulus is 0.01 MPa or more, dents are less likely to occur during handling, and good adhesion reliability can be easily obtained, which is preferable. In terms of step followability and foreign matter absorption, the storage elastic modulus of the pressure-sensitive adhesive layer at 25° C. is preferably 5 MPa or less, more preferably 4.5 MPa or less, still more preferably 4.0 MPa or less, and even more preferably. 3.5 MPa or less, particularly preferably 3.0 MPa or less, most preferably 2.5 MPa or less or 2.0 MPa or less. The storage modulus of the pressure-sensitive adhesive layer is measured when dynamic viscoelasticity is performed at a frequency of 1 Hz. The above storage modulus is the real part of the shear modulus represented by a complex number, and the tensile modulus can be converted in consideration of the Poisson's ratio of the sample.

The storage elastic modulus of the pressure-sensitive adhesive layer of the present invention can be controlled by the monomer composition, weight-average molecular weight, amount of cross-linking agent used (added amount), types and amounts of other additives used, and the like.

The 300% tensile residual stress of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is preferably 2 to 24 N/cm ² , more preferably 2.5 to 20 N/cm ² , still more preferably 3 to 16 N/cm 2 . ^cm2 . When the 300% tensile residual stress is 2 N/cm ² or more, good resistance to foaming and peeling is likely to be obtained, and when it is 24 N/cm ² or less, good stress relaxation is obtained and good conformability to unevenness is obtained. is easy to obtain, which is preferable.

When the 300% tensile residual stress is within the above range, the pressure-sensitive adhesive layer of the present invention can easily obtain excellent stress relaxation properties and can easily exhibit excellent step conformability. , for example, a height of 20 to 50 μm).

The 300% tensile residual stress was measured at 23°C and 50%R. H. Under the environment of , pull the adhesive layer in the length direction to 300% elongation (strain), hold the elongation, and determine the tensile load applied to the adhesive layer 300 seconds after the end of pulling, It is the value (N/cm ² ) obtained by dividing the tensile load by the initial cross-sectional area (cross-sectional area before pulling) of the pressure-sensitive adhesive layer. The initial elongation of the adhesive layer is 100%.

The 300% tensile residual stress of the pressure-sensitive adhesive layer of the present invention can be controlled by the monomer composition of the base polymer, the weight average molecular weight, the amount (addition amount) of the cross-linking agent used, and the type and amount of other additives used. .

Since the pressure-sensitive adhesive layer of the present invention has a controlled low saturated moisture absorption rate, it is possible to suppress the radiation loss of millimeter waves. 25° C., 90% R.I. of the pressure-sensitive adhesive layer of the present invention. H. is preferably 2.8% or less, more preferably 2.7% or less, still more preferably 2.6% or less, even more preferably 2.5% or less, particularly preferably 2.4% or less, Most preferably 2.3% or less, 2.2% or less, 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less , 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0 .7% or less or 0.6% or less. 25°C, 90% R.I. H. If the saturated moisture absorption rate at is low, the radiation loss of millimeter waves can be suppressed near room temperature. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.3% or more, 0.4% or more, or 0.5% or more.

65 ° C., 90% R.I. of the pressure-sensitive adhesive layer of the present invention. H. is preferably 2.8% or less, more preferably 2.6% or less, still more preferably 2.4% or less, even more preferably 2.3% or less, particularly preferably 2.2% or less, Most preferably 2.1% or less, 2.0% or less, 1.9% or less, 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less , 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, or 0.7% or less. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.4% or more, 0.5% or more, or 0.6% or more. 65°C, 90% R.I. H. If the saturated moisture absorption rate of is low, the radiation loss of millimeter waves can be suppressed even when exposed to a high-temperature environment.

　85°C, 85% R.I. of the pressure-sensitive adhesive layer of the present invention. H. is preferably 5.0% or less, more preferably 4.0% or less, still more preferably 3.5% or less, even more preferably 3.0% or less, particularly preferably 2.8% or less, Most preferably 2.6% or less, 2.4% or less, 2.2% or less, 2.0% or less, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less , 1.0% or less, or 0.8% or less. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.4% or more, 0.5% or more, or 0.6% or more. 85°C, 85% R.I. H. If the saturated moisture absorption rate of is low, the radiation loss of millimeter waves can be suppressed even when exposed to a high-temperature environment.

The saturated moisture absorption rate under each temperature and humidity environment is, for example, the dry sample weight (w1) and the sample at 65° C. and 90% RH. H. It can be obtained from the weight (w2) at the time when there is no change in the weight (when the moisture absorption is saturated) by leaving it in the atmosphere of , by the following formula. 25°C, 90% R.I. H. , and 85° C., 85% R.I. H. can also be obtained under the conditions of Note that the values of w1 and w2 are assumed to be measured at the same temperature and humidity.
Saturated moisture absorption rate (%) = {(w2-w1)/w1} x 100

The pressure-sensitive adhesive layer of the present invention controls the amount of change in dielectric loss due to moisture absorption to be low, so it is possible to suppress the radiation loss of millimeter waves. The amount of change in dielectric loss due to moisture absorption at a frequency of 28 GHz of the pressure-sensitive adhesive layer of the present invention is preferably 0.006 or less, more preferably 0.005 or less, and still more preferably 0.004 or less. The lower limit of the saturated moisture absorption rate is not particularly limited, but may be, for example, 0.0001 or more, 0.0002 or more, or 0.0003 or more.

The change in dielectric loss of the pressure-sensitive adhesive layer of the present invention due to moisture absorption at a frequency of 60 GHz is preferably 0.003 or less, more preferably 0.002 or less, and still more preferably 0.001 or less. The lower limit of the saturated moisture absorption rate is not particularly limited. It may be 0.0007 or more, 0.0008 or more, or 0.0009 or more.

Since the pressure-sensitive adhesive layer of the present invention is controlled to have a low water vapor permeability, it is possible to suppress radiation loss of millimeter waves. 40° C., 92% R.I. of the pressure-sensitive adhesive layer of the present invention. H. is preferably 430 g/m ² /day or less, more preferably 300 g/m ² /day or less, still more preferably 250 g/m ² /day or less, even more preferably 200 g/m ² /day or less, It is preferably 150 g/m ² /day or less, most preferably 100 g/m ² /day or less, 50 g/m ² /day or less, or 30 g/m ² /day or less. 40°C, 92% R.I. H. When the water vapor transmission rate in is low, the water resistance of the pressure-sensitive adhesive layer is improved, and the radiation loss of millimeter waves in the pressure-sensitive adhesive layer can be suppressed. The lower limit of water vapor permeability is not particularly limited, but may be, for example, 10 g/m ² /day or more, 20 g/m ² /day or more, or 25 g/m ² /day or more.

The water vapor transmission rate (WVTR) is a value measured based on the cup method. The dry weight (w1) of calcium chloride isolated from the outside by an adhesive layer, and the sample was heated at 40° C. and 92% R.I. H. Measure the weight (w2) after a predetermined time (when the moisture absorption rate is saturated) after leaving it in the atmosphere of , and convert the weight change amount to unit time (1 day) and unit area (1 m ² ). can be obtained by

The dielectric constant or dielectric loss at 28 GHz or 60 GHz of the pressure-sensitive adhesive layer of the present invention, the saturated moisture absorption rate, the water vapor permeability, and the amount of change in dielectric loss due to moisture absorption can be adjusted by adjusting the monomer composition, the type and content of additives, etc. can be adjusted by

Although the thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, it is preferably 10 to 500 μm, more preferably 11 to 400 μm, still more preferably 12 to 350 μm and 12 to 300 μm. When the thickness is at least a certain value, the conformability to irregularities and the adhesion reliability are likely to be improved. Moreover, when the thickness is below a certain value, foreign matter is less likely to be absorbed during handling, and there is a tendency for excellent manufacturability.

The method for producing the pressure-sensitive adhesive layer is not particularly limited. It is mentioned that Curing can be performed by irradiation with active energy rays, drying by heating, or the like.

A known coating method may be used for applying (coating) the pressure-sensitive adhesive composition. For example, coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, and direct coaters may be used.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it has the pressure-sensitive adhesive layer of the present invention.

The pressure-sensitive adhesive sheet of the present invention may be a double-sided pressure-sensitive adhesive sheet in which both sides are pressure-sensitive adhesive layer surfaces, or may be a single-sided pressure-sensitive adhesive sheet in which only one side is pressure-sensitive adhesive layer surfaces. Among them, a double-sided pressure-sensitive adhesive sheet is preferable from the viewpoint of bonding two members together. In this specification, the term "adhesive sheet" includes a tape-like one, that is, "adhesive tape". Moreover, in this specification, the adhesive layer surface may be called an "adhesive surface."

The pressure-sensitive adhesive sheet of the present invention may have a separator (release liner) provided on the pressure-sensitive adhesive surface until use.

The pressure-sensitive adhesive sheet of the present invention may be a so-called "base-less type" pressure-sensitive adhesive sheet (hereinafter sometimes referred to as "base-less pressure-sensitive adhesive sheet") that does not have a base material (base layer). , a pressure-sensitive adhesive sheet having a substrate (hereinafter sometimes referred to as a "substrate-attached pressure-sensitive adhesive sheet"). Examples of the substrate-less pressure-sensitive adhesive sheet include, for example, a double-sided pressure-sensitive adhesive sheet consisting only of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer (sometimes referred to as "another pressure-sensitive adhesive layer"). ) and the like. On the other hand, the pressure-sensitive adhesive sheet with a substrate includes a pressure-sensitive adhesive sheet having the above pressure-sensitive adhesive layer on at least one side of a substrate. Among them, a substrate-less pressure-sensitive adhesive sheet (substrate-less double-sided pressure-sensitive adhesive sheet) is preferable, and a substrate-less double-sided pressure-sensitive adhesive sheet consisting only of the above pressure-sensitive adhesive layer is more preferable. A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer on both sides of a substrate (double-sided pressure-sensitive adhesive sheet with substrate) is also preferable. The pressure-sensitive adhesive layers on both sides of the double-sided pressure-sensitive adhesive sheet with a substrate may be the pressure-sensitive adhesive layers of the present invention, or one side may be the pressure-sensitive adhesive layer of the present invention and the other side may be another pressure-sensitive adhesive layer. good too. The above-mentioned "base material (base material layer)" does not include the separator that is peeled off when the adhesive sheet is used (pasted).

The pressure-sensitive adhesive sheet of the present invention is preferably a base-less pressure-sensitive adhesive sheet in order to avoid radiation loss of millimeter waves due to the base material. However, if the base material is made of a material with a low dielectric constant and low dielectric loss, it may be a pressure-sensitive adhesive sheet with a base material. Since it is desirable that the base material can be used regardless of the polarization state of millimeter waves, non-stretched base materials, particularly isotropic base materials, are preferred.

The 180° peeling adhesive strength of the adhesive sheet of the present invention to a glass plate at a tensile speed of 300 mm / min (especially, the 180° peeling adhesive strength of the adhesive surface provided by the adhesive layer of the present invention to a glass plate) is Although it is not limited, it is preferably 3 N/20 mm or more, more preferably 3.5 N/20 mm or more, still more preferably 4 N/20 mm or more, and still more preferably 3 N/20 mm or more, because sufficient adhesion to the antenna element can be obtained if the adhesive strength is high. It is preferably 5 N/20 mm, particularly preferably 6 N/20 mm or more, most preferably 7 N/20 mm or more, 8 N/20 mm or more, 9 N/20 mm or more or 10 N/20 mm or more. If the above-mentioned peeling adhesive force is at least a certain value, the adhesiveness to glass and the ability to prevent floating on steps will be more excellent. The upper limit of the 180° peeling adhesive strength of the pressure-sensitive adhesive sheet of the present invention to a glass plate at a tensile speed of 300 mm/min is not particularly limited, but for example, it is preferably 30 N/20 mm or less, more preferably 25 N/20 mm or less. , more preferably 22 N/20 mm or less, even more preferably 20 N/20 mm or less, particularly preferably 19 N/20 mm or less, most preferably 18 N/20 mm or less, 17 N/20 mm or less, 16 N/20 mm or less, 15 N/20 mm or less, 14 N /20 mm or less, 13 N/20 mm or less, 12 N/20 mm or less, or 11 N/20 mm or less. The 180° peeling adhesive strength against a glass plate at a tensile speed of 300 mm/min is determined by the following method for measuring 180° peeling adhesive strength.

Examples of the glass plate include the product name "Soda Lime Glass #0050" (manufactured by Matsunami Glass Industry Co., Ltd.). In addition, non-alkali glass, chemically strengthened glass, and the like can also be used.

　The 180° peeling adhesive strength at a tensile speed of 300 mm/min against the glass plate is obtained by the following measurement method. The adhesive surface of the adhesive sheet was adhered to the adherend and pressed under the conditions of one reciprocating press with a 2 kg roller, and the adhesive sheet was pressed at 23° C. and 50% R.I. H. After aging for 30 minutes in an atmosphere of 23°C, 50% R.I. H. The pressure-sensitive adhesive sheet is peeled off from the adherend under conditions of a peeling speed of 300 mm/min and a peeling angle of 180° in an atmosphere of , and the 180° peeling adhesive strength (N/20 mm) is measured.

The 180° peeling adhesive strength of the adhesive sheet of the present invention depends on the monomer composition of the base polymer (acrylic polymer), the weight average molecular weight, the amount of cross-linking agent used (addition amount), the type and amount of other additives used, etc. can be controlled.

Although the thickness (total thickness) of the adhesive sheet of the present invention is not particularly limited, it is preferably 10 to 500 μm, more preferably 11 to 400 μm, even more preferably 12 to 350 μm, still more preferably 12 to 300 μm. When the thickness is equal to or greater than a certain value, peeling at the step portion is less likely to occur. Further, when the thickness is below a certain level, it becomes easier to maintain an excellent appearance during production. Note that the thickness of the pressure-sensitive adhesive sheet of the present invention does not include the thickness of the separator.

The haze (according to JIS K7136) of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but is preferably 1.2% or less, more preferably 1.1% or less, still more preferably 1.0% or less, and even more preferably It is 0.9% or less, particularly preferably 0.8% or less. When the haze is 1.2% or less, excellent transparency and excellent appearance are likely to be obtained. The haze is measured, for example, by setting the pressure-sensitive adhesive layer to a thickness of 25 μm, allowing it to stand in a normal state (23° C., 50% RH) for at least 24 hours, and then using a slide glass (for example, total light transmittance of 91.8%, Haze 0.4%) can be used as a sample and measured using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory).

The total light transmittance (according to JIS K7361-1) in the visible light wavelength region of the adhesive sheet of the present invention is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, and even more preferably 90%. % or more, particularly preferably 91% or more, most preferably 92% or more. When the total light transmittance is 85% or more, excellent transparency and excellent appearance are likely to be obtained. For the total light transmittance, for example, the pressure-sensitive adhesive layer thickness is 25 μm, and this is allowed to stand in a normal state (23° C., 50% RH) for at least 24 hours. A haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory) is used as a sample, which is laminated on a slide glass (for example, total light transmittance 91.8%, haze 0.4%). can be measured using

Although the pressure-sensitive adhesive sheet of the present invention is not particularly limited, it is preferably manufactured according to a known or commonly used manufacturing method. For example, when the pressure-sensitive adhesive sheet of the present invention is a substrate-less pressure-sensitive adhesive sheet, it can be obtained by forming the pressure-sensitive adhesive layer on a separator by the method described above. Further, when the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet with a substrate, it may be obtained by directly forming the pressure-sensitive adhesive layer on the surface of the substrate (direct transfer method), or once the pressure-sensitive adhesive layer is formed on the separator. After forming the adhesive layer, the pressure-sensitive adhesive layer may be provided on the substrate by transferring (bonding) to the substrate (transfer method).

The adhesive sheet of the present invention may have other layers in addition to the adhesive layer. Examples of other layers include other adhesive layers (adhesive layers other than the above adhesive layer (adhesive layers other than the adhesive layer formed from the adhesive composition of the present invention)), intermediate layers, and undercoats. layers and the like. In addition, the pressure-sensitive adhesive sheet of the present invention may have two or more other layers.

When the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet with a substrate, examples of the substrate include various optical films such as plastic films, antireflection (AR) films, polarizing plates, and retardation plates. Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), (meth)acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, and polyarylate. , polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, trade name "Arton (cyclic olefin polymer, manufactured by JSR Corporation)", trade name "Zeonor (cyclic olefin polymer, Nippon Zeon Co., Ltd.)” and other plastic materials such as cyclic olefin-based polymers and fluorine-based polymers. In addition, these plastic materials can be used individually or in combination of 2 or more types. Further, the above-mentioned "base material" is a part that is attached to the adherend together with the adhesive layer when the pressure-sensitive adhesive sheet is applied to the adherend. A separator (release liner) that is peeled off when the adhesive sheet is used (attached) is not included in the "base material".

The base material is preferably transparent. The total light transmittance (according to JIS K7361-1) in the visible light wavelength region of the substrate is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, and even more preferably 90% or more. , particularly preferably 91% or more, most preferably 92% or more. In addition, the haze of the substrate (according to JIS K7136) is preferably 1.0% or less, more preferably 0.8% or less. Examples of such transparent substrates include PET films and non-oriented films such as the trade name "Arton" and the trade name "Zeonor". In particular, a non-oriented film is preferable because its properties do not depend on the direction of the millimeter-wave electric field.

Although the thickness of the base material is not particularly limited, it is preferably 12 to 500 μm, for example. In addition, the substrate may have either a single-layer structure or a multilayer structure. In addition, the surface of the substrate may be appropriately subjected to known and commonly used surface treatments such as physical treatments such as corona discharge treatment, plasma treatment and electron beam treatment, and chemical treatments such as undercoating treatment. .

The pressure-sensitive adhesive sheet of the present invention may have a separator (release liner) provided on the pressure-sensitive adhesive surface until use. In the case where the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, each pressure-sensitive adhesive surface may be protected by two separators, or a separator having release surfaces on both sides may be used to form a roll. It may be protected in a wound form. The separator is used as a protective material for the pressure-sensitive adhesive layer, and is peeled off when applied to an adherend. Moreover, when the pressure-sensitive adhesive sheet of the present invention is a substrate-less pressure-sensitive adhesive sheet, the separator also serves as a support for the pressure-sensitive adhesive layer. Note that the separator does not necessarily have to be provided.

As the separator, a commonly used release paper or the like can be used, and is not particularly limited. For example, a base material having a release treatment layer, a low-adhesive base material composed of a fluoropolymer, a low-adhesive base material composed of a non-polar polymer, and the like can be mentioned. Examples of substrates having a release treatment layer include plastic films and papers surface-treated with release agents such as silicone, long-chain alkyl, fluorine, and molybdenum sulfide. Examples of the fluorine-based polymer in the low-adhesive substrate made of the fluorine polymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chloro Examples include fluoroethylene-vinylidene fluoride copolymers. Examples of the non-polar polymer include olefin resins (e.g., polyethylene, polypropylene, etc.), and polyester base materials (polyethylene terephthalate base material, polyethylene naphthalate base material, polybutylene terephthalate base material, polybutylene terephthalate base material, etc.). materials, etc.) are also used. Note that the separator can be formed by a known or commonly used method. Also, the thickness of the separator is not particularly limited.

Since the pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer of the present invention, it has excellent adhesiveness and resistance to foaming and peeling, and furthermore has excellent stress relaxation properties and excellent conformability to unevenness. Therefore, the adhesion reliability, especially at high temperatures, is excellent. Moreover, it is excellent in external appearance.

For this reason, the pressure-sensitive adhesive sheet of the present invention is useful for bonding members that are prone to foaming at the interface at high temperatures. For example, polymethyl methacrylate (PMMA) may contain unreacted monomers, and foaming due to foreign matter is likely to occur at high temperatures. Polycarbonate (PC) also tends to outgas water and carbon dioxide at high temperatures. Since the pressure-sensitive adhesive sheet of the present invention is excellent in resistance to foaming and peeling, it is also useful for plastic adherends containing such resins.

Moreover, the pressure-sensitive adhesive sheet of the present invention is useful not only for adherends with a small coefficient of linear expansion, but also for adherends with a large coefficient of linear expansion. Examples of the adherend having a small linear expansion coefficient include a glass plate (linear expansion coefficient of 0.3×10 ⁻⁵ to 0.8×10 ⁻⁵ /° C.), polyethylene terephthalate substrate (PET film, wire expansion coefficient of 1.5×10 ⁻⁵ to 2×10 ⁻⁵ /° C.). Examples of the ^adherend having a large coefficient of linear expansion include resin substrates having a large coefficient of linear expansion. 8×10 ⁻⁵ /° C.), polymethyl methacrylate resin substrate (PMMA, linear expansion coefficient 7×10 ⁻⁵ to 8×10 ⁻⁵ /° C.), cycloolefin polymer substrate (COP, linear expansion coefficient 6× 10 ⁻⁵ to 7×10 ⁻⁵ /° C.), trade name “Zeonor” (manufactured by Nippon Zeon Co., Ltd.), trade name “Arton” (manufactured by JSR Corporation), and the like.

The pressure-sensitive adhesive sheet of the present invention is useful for bonding an adherend with a small coefficient of linear expansion and an adherend with a large coefficient of linear expansion. Specifically, the pressure-sensitive adhesive sheet of the present invention is preferably used for bonding a glass adherend (for example, a glass plate, chemically strengthened glass, glass lens, etc.) to the resin substrate having a large coefficient of linear expansion.

Thus, the pressure-sensitive adhesive sheet of the present invention is useful for bonding adherends made of various materials, and is particularly useful for bonding glass adherends and plastic adherends. The plastic adherend may be an optical film such as a plastic film having an ITO (indium tin oxide) layer on its surface.

Furthermore, the pressure-sensitive adhesive sheet of the present invention is useful not only for adherends with smooth surfaces, but also for adherends with uneven surfaces. In particular, the pressure-sensitive adhesive sheet of the present invention can be used even if at least one of the glass adherend and the resin substrate having a large coefficient of linear expansion has steps on the surface. It is useful for lamination with large resin substrates.

The adhesive sheet of the present invention is preferably used for manufacturing portable electronic devices. Examples of the portable electronic devices include mobile phones, PHS, smartphones, tablets (tablet computers), mobile computers (mobile PCs), personal digital assistants (PDA), electronic notebooks, portable televisions, portable radios, and the like. Broadcast receivers, portable game machines, portable audio players, portable DVD players, cameras such as digital cameras, and camcorder-type video cameras.

The pressure-sensitive adhesive sheet of the present invention is preferably used, for example, for attaching members or modules constituting a portable electronic device to each other, fixing members or modules constituting a portable electronic device to a housing, or the like. More specifically, bonding cover glass and lenses (especially glass lenses) with touch panels, touch sensors, and antenna modules, fixing cover glass and lenses (especially glass lenses) to housings, and attaching display panel housings. fixing the antenna module to the housing, fixing input devices such as sheet keyboards and touch panels to the housing, bonding the protective panel of the information display unit to the housing, bonding the housings together, housing Bonding between a body and a decorative sheet, fixing and bonding of various members and modules constituting a mobile electronic device, and the like can be mentioned. In this specification, the display panel refers to a structure composed of at least a lens (particularly a glass lens) and a touch panel. Further, the term "lens" used herein is a concept that includes both a transparent body that exhibits light refraction and a transparent body that does not have light refraction. In other words, a lens in this specification also includes a mere window panel that has no refractive effect.

Furthermore, the adhesive sheet of the present invention is preferably used for optical applications. That is, the pressure-sensitive adhesive sheet of the present invention is preferably an optical pressure-sensitive adhesive sheet for optical applications. More specifically, for example, it is preferably used for bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the optical member.

The optical member is an optical member having at least the pressure-sensitive adhesive sheet and a substrate, wherein the substrate has metal electrodes and wiring (e.g., copper, silver, ITO wiring, etc.) on at least one side thereof, and the metal electrodes and wiring of the substrate are The pressure-sensitive adhesive layer of the present invention is attached on the side having the The pressure-sensitive adhesive sheet may have a separator on the pressure-sensitive adhesive surface until use.　

Furthermore, the optical member preferably has the pressure-sensitive adhesive layer on the side of the substrate opposite to the side having the metal electrodes and wiring, and the surface of the substrate opposite to the side having the metal electrodes and wiring. More preferably, the pressure-sensitive adhesive layer is adhered thereon.

Examples of materials constituting the metal electrodes and wiring include titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, Examples include metals such as zirconium, tantalum, and hafnium, and metal oxides such as ITO (oxide of indium and tin), zinc oxide, and tin oxide. Furthermore, those containing two or more of these metals and metal oxides, and alloys containing these metals as main components are also included. Among them, gold, silver, copper and ITO are preferred from the viewpoint of conductivity, silver, copper and ITO are more preferred from the viewpoint of conductivity and cost, and ITO is further preferred from the viewpoint of transparency. That is, the metal electrodes and wiring are preferably silver, copper or ITO wiring, and particularly preferably ITO wiring. It should be noted that the same applies to the materials constituting the millimeter wave antenna elements described later. The metal electrodes and wiring are formed by forming a film of nitride, oxide, sulfide, etc. of the metal for the purpose of hiding the electrodes and / or wiring in order to prevent deterioration of visibility due to reflection of the metal. Blackening treatment may be applied.

An optical member has optical properties (for example, polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, optical rotation, visibility, electromagnetic wave permeability, etc.). It means a member that has Examples of the substrate constituting the optical member include a display device (image display device), equipment such as an input device (optical equipment), a substrate constituting an antenna module, or a substrate used in these equipment. Polarizing plate, wavelength plate, retardation plate, optical compensation film, brightness enhancement film, light guide plate, reflective film, antireflection film, antenna substrate, hard coat film (hard coat treatment applied to at least one side of plastic film such as PET film) film), transparent conductive film (e.g., plastic film having an ITO layer on its surface (preferably ITO film such as PET-ITO, polycarbonate, cycloolefin polymer), etc.), design film, decorative film, surface protection plate, Prisms, lenses, color filters, transparent substrates (glass sensors, glass display panels (LCD, etc.), glass substrates such as glass plates with transparent electrodes, etc.), and substrates on which these are laminated (these are collectively referred to as may be referred to as a "functional film") and the like. Moreover, these films may have a metal nanowire layer, a conductive polymer layer, or the like. Further, these films may be mesh-printed with thin metal wires. These films may also have antenna elements. The above-mentioned "plate" and "film" include forms such as plate-like, film-like, and sheet-like, respectively. For example, "polarizing film" includes "polarizing plate" and "polarizing sheet". . In addition, "film" shall include film sensors and the like.

The fine metal wire is blackened by forming a film of a nitride, oxide, sulfide, or the like of the metal for the purpose of concealing the deterioration of the visibility due to the reflection of the metal. good too.

Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), electronic paper, and the like. Moreover, a touch panel etc. are mentioned as said input device. Further, examples of the antenna module include a millimeter wave antenna, etc., which will be described later.

Examples of substrates constituting the optical member include substrates made of glass, (meth)acrylic resin, polycarbonate, polyethylene terephthalate, cycloolefin polymer, metal thin film, etc. (for example, sheet-shaped, film-shaped, plate-shaped substrates, etc.). etc. As described above, the "optical member" in the present invention includes members (design films, decorative films, surface protective films, etc.) that play a role of decoration and protection while maintaining the visibility of display devices and input devices. shall be taken.

If the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet with a substrate and the pressure-sensitive adhesive sheet constitutes a member having optical properties, the substrate can be regarded as the substrate, and the pressure-sensitive adhesive sheet is the optical member of the present invention. It can be said that it is.

When the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet with a substrate and the functional film is used as the substrate, the pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer on at least one side of the functional film. It can also be used as an "adhesive functional film".

[millimeter wave antenna]
Since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer (the pressure-sensitive adhesive layer of the present invention) having a low dielectric constant and dielectric loss in a high frequency band such as millimeter waves, it is possible to suppress the radiation loss of millimeter waves. Therefore, the pressure-sensitive adhesive sheet of the present invention is useful for bonding members constituting an antenna (millimeter wave antenna) used for millimeter wave communication.

In this specification, "millimeter wave communication" means communication in the frequency band of 20 GHz to 300 GHz.

As a member constituting a millimeter wave antenna, a substrate (hereinafter referred to as a “millimeter wave antenna substrate”) having an antenna element (hereinafter sometimes referred to as “millimeter wave antenna element”) for transmitting and receiving millimeter waves on at least one side may be called).

Examples of the millimeter-wave antenna substrate include the plastic film used as the base material of the above-mentioned adhesive sheet, and a material with a low dielectric constant and low dielectric loss is preferable in that it can suppress the radiation loss of millimeter waves. Cyclic olefin polymers such as "Arton" (manufactured by JSR Corporation) and trade name "Zeonor" (manufactured by Zeon Corporation) are preferred.

The dielectric constant of the millimeter wave antenna substrate at 28 GHz and/or 60 GHz is preferably 2.0 to 5.0, more preferably 2.1 to 4.5, and still more preferably 2, from the viewpoint of suppressing radiation loss of millimeter waves. .2 to 4.0, even more preferably 2.2 to 3.5, particularly preferably 2.2 to 3.4, most preferably 2.2 to 3.3, 2.2 to 3.2, 2 .2 to 3.1 or 2.2 to 3.0. In addition, the dielectric loss of the millimeter wave antenna substrate at 28 GHz and/or 60 GHz is preferably 0.0001 to 0.05, more preferably 0.001 to 0.029, and still more preferably 0.001 to 0.029, from the viewpoint of suppressing the radiation loss of millimeter waves. is 0.002 to 0.028, still more preferably 0.003 to 0.027, particularly preferably 0.004 to 0.026, most preferably 0.005 to 0.025, 0.006 to 0.024 , 0.007-0.023, 0.008-0.022, 0.009-0.021, 0.010-0.020, 0.011-0.019, 0.012-0.018, 0 0.013-0.017, 0.014-0.016 or 0.014-0.015.

The millimeter wave antenna substrate is preferably transparent. The total light transmittance (according to JIS K7361-1) in the visible light wavelength region of the millimeter wave antenna substrate is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, and even more preferably 90%. above, particularly preferably 91% or more, most preferably 92% or more. In addition, the haze (according to JIS K7136) of the millimeter wave antenna substrate is not particularly limited, but is preferably 1.2% or less, more preferably 1.1% or less, still more preferably 1.0% or less, and even more preferably. is 0.9% or less, particularly preferably 0.8% or less.

The thickness of the millimeter wave antenna substrate is preferably 5 to 250 μm from the viewpoint of suppressing radiation loss of millimeter waves while mounting the millimeter wave antenna element. Note that the millimeter wave antenna substrate may have either a single-layer structure or a multilayer structure. In addition, the surface of the millimeter wave antenna substrate is appropriately subjected to known and commonly used surface treatments such as physical treatments such as corona discharge treatment and plasma treatment, chemical treatments such as undercoat treatment, and coating layers such as hard coating. may be

The millimeter wave antenna element provided on the millimeter wave antenna substrate is not particularly limited as long as it can transmit and receive millimeter waves, but a phased array antenna is preferably used from the viewpoint of efficiently receiving millimeter waves with mobile communication devices such as smartphones. can be done. A phased array antenna is an antenna that enables transmission and reception in a desired direction by arranging a plurality of antenna elements in an array and controlling the phase of each antenna element. In other words, a phased array antenna can transmit and receive radio waves in a desired direction by electronically controlling the phase of each antenna element (beam steering) regardless of the direction of the antenna. It becomes possible.

As the millimeter wave antenna element, known antennas can be used without particular limitation. From antenna structures, slot antenna structures, planar inverted-F antenna structures, monopoles, dipoles, helical antenna structures, Yagi (Yagi-Uda) antenna structures, surface integrated waveguide structures, hybrids of these designs, etc. Antenna elements having resonating elements formed thereon may be mentioned. Different types of mm-wave antenna elements may be used for different frequency band combinations. A phased array antenna in which patch antenna elements are arranged in an array is preferable from the viewpoint of efficient reception of millimeter waves by mobile communication devices such as smartphones.

The material constituting the millimeter wave antenna element is not particularly limited, and examples include titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, and platinum. , tungsten, zirconium, tantalum, hafnium, and the like, ITO (indium-tin oxide), zinc oxide, tin oxide, and other metal oxides. Furthermore, materials containing two or more of these metals or metal oxides, and alloys containing these metals as main components are also included. Among them, silver, copper, and ITO are preferred from the viewpoint of conductivity, and ITO is more preferred from the viewpoint of transparency and visibility. That is, it is preferable that the millimeter wave antenna element is made of ITO.

When the antenna element is made of a metal such as silver or copper, a nitride, oxide, sulfide, or the like of the metal is added for the purpose of concealing the antenna element in order to prevent deterioration of visibility due to reflection of the metal. A blackening treatment may be performed by forming a film of.

In addition, the millimeter wave antenna substrate may include a transmission line path for transferring signals transmitted and received by the millimeter wave antenna elements to the transmitter/receiver circuit. Transmission line paths include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, waveguide structures (e.g. , coplanar waveguides or grounded coplanar waveguides), transmission lines formed from combinations of these types of transmission lines, and the like. The material that constitutes the transmission line path is also not particularly limited, and the material that constitutes the millimeter wave antenna element can be used.

Examples of members that make up the millimeter wave antenna include a cover member laminated on the millimeter wave antenna substrate to protect the millimeter wave antenna elements arranged on the millimeter wave antenna substrate. As the cover member, for example, optical films such as glass and plastic films can be used.

Examples of materials for plastic films include polyester resins such as polyethylene terephthalate (PET); (meth)acrylic resins such as polymethyl methacrylate (PMMA); polycarbonate; triacetyl cellulose (TAC); Polyimide; Transparent polyimide; Polyvinyl chloride; Polyvinyl acetate; Fluorine resin; Polyolefin resin such as polyethylene, polypropylene, ethylene-propylene copolymer; (manufactured by Nippon Zeon Co., Ltd.) and other plastic materials such as cyclic olefin polymers. These plastic materials can be used alone or in combination of two or more.

The dielectric constant of the cover member at 28 GHz and/or 60 GHz is preferably 2.0 to 5.0, more preferably 2.1 to 4.5, and still more preferably 2.2 in order to suppress radiation loss of millimeter waves. ~4.0, even more preferably 2.2-3.5, particularly preferably 2.2-3.4, most preferably 2.2-3.3, 2.2-3.2, 2.2 ~3.1 or 2.2-3.0. In addition, the dielectric loss of the cover member at 28 GHz and/or 60 GHz is preferably 0.0001 to 0.050, more preferably 0.001 to 0.02, still more preferably 0.001 to 0.02, from the viewpoint of suppressing millimeter wave radiation loss. 0.002 to 0.019, even more preferably 0.003 to 0.018, particularly preferably 0.004 to 0.017, most preferably 0.005 to 0.016, 0.006 to 0.015, 0.007 to 0.014, 0.008 to 0.013, 0.009 to 0.012 or 0.010 to 0.011.

The cover member is preferably transparent. The total light transmittance of the cover member in the visible light wavelength region (according to JIS K7361-1) is preferably 85% or more, more preferably 88% or more, still more preferably 89% or more, and even more preferably 90% or more, Especially preferably 91% or more, most preferably 92% or more. In addition, the haze (according to JIS K7136) of the cover member is preferably 1.2% or less, more preferably 1.1% or less, still more preferably 1.0% or less, and even more preferably 0.9% or less. Particularly preferably, it is 0.8% or less.

The thickness of the cover member is preferably 0.025 to 1.5 mm from the viewpoint of suppressing radiation loss of millimeter waves. In addition, the cover member may have either a single-layer structure or a multilayer structure. The surface of the cover member is appropriately subjected to known and commonly used surface treatments such as physical treatments such as corona discharge treatment and plasma treatment, chemical treatments such as undercoating, and coating layers such as hard coating. good too.

The adhesive sheet of the present invention is preferably used for manufacturing millimeter wave antennas used in mobile communication devices. Examples of the mobile communication devices include mobile phones, PHS, smart phones, tablets (tablet computers), mobile computers (mobile PCs), and personal digital assistants (PDAs).

The millimeter wave antenna may have members other than the millimeter wave antenna substrate, the cover member, and the adhesive sheet described above. , reflective film, anti-reflection film, hard coat film, transparent conductive film, design film, decorative film, surface protection plate, prism, lens, color filter, transparent substrate, image display panel (e.g. liquid crystal display panel, organic EL panel , plasma display panel, etc.). The image display panel may have a touch sensor.

The millimeter wave antenna may be placed at any position on the mobile communication device, and specifically, may be placed on the front, back, or side of the mobile communication device. The front surface of the mobile communication device is the surface that faces the user when the user uses the mobile communication device. do. Note that the display panel refers to a structure composed of at least a lens (especially a glass lens) and a touch panel.

The size (width) of the millimeter wave antenna is not limited either, and it may be formed on the entire surface of each surface of the mobile communication device, or may be arranged partially. Also, the shape of the millimeter wave antenna is not particularly limited, and may be rectangular, circular, or wire-shaped, for example. Alternatively, they may be arranged in a frame shape. Furthermore, the number of millimeter wave antennas arranged in the mobile communication device is not limited, and may be one, or a plurality may be arranged at arbitrary positions. When a plurality of millimeter wave antennas are arranged, the size (width) may be the same or different. A dummy pattern without a millimeter wave antenna may be placed in a portion of the mobile communication device where the millimeter wave antenna is not placed in order to improve visibility.

A millimeter-wave antenna of the present invention is a millimeter-wave antenna comprising at least the adhesive sheet and a substrate, wherein the substrate has an antenna element (millimeter-wave antenna element) on one side, and the substrate (millimeter-wave antenna substrate) of the antenna It is sufficient that the pressure-sensitive adhesive sheet is adhered to the side having the element, and other points are not particularly limited. Since the adhesive sheet in the millimeter wave antenna of the present invention is an adhesive sheet for use, it does not have a separator.

As the millimeter wave antenna, a millimeter wave antenna substrate may or may not have a separate optical member (the adhesive sheet may or may not be included, but having the millimeter wave antenna substrate is further advantageous in that the millimeter wave is radiated. It is preferable from the viewpoint of suppressing loss.). Further, the separate optical member may be singular or plural.

In the case of the above-described mode, the mode of bonding the millimeter wave antenna of the present invention and the another optical member includes, for example, (1) the millimeter wave antenna substrate of the present invention and the another optical member via the pressure-sensitive adhesive sheet of the present invention; (2) A mode in which the pressure-sensitive adhesive sheet of the present invention, which includes or constitutes a millimeter wave antenna substrate, is bonded to another optical member described above; Examples include a mode in which the antenna substrate is bonded to a member other than the millimeter wave antenna substrate, and (4) a mode in which the adhesive tape of the present invention including or constituting the millimeter wave antenna substrate is bonded to a member other than the millimeter wave antenna substrate. In the above aspect (2), the pressure-sensitive adhesive sheet of the present invention is preferably a double-sided pressure-sensitive adhesive sheet whose substrate is a millimeter wave antenna substrate.

Next, preferred embodiments of the millimeter wave antenna of the present invention will be described with reference to the drawings.

FIG. 1 shows a millimeter wave antenna having at least a substrate that is an adhesive sheet 10 and a millimeter wave antenna substrate 11. The millimeter wave antenna substrate 11 has a millimeter wave antenna element 2 on one side, and the adhesive sheet 10 A millimeter wave antenna 1A attached to the surface of the antenna substrate 11 on the side having the millimeter wave antenna element 2 is shown.

FIG. 2 shows a millimeter wave antenna 1B having a cover member 12, an adhesive sheet 10, and a millimeter wave antenna substrate 11 in this order in contact with each other. The millimeter wave antenna substrate 11 has the millimeter wave antenna element 2 on the surface on the side of the adhesive sheet 10 , and the adhesive sheet 10 is attached to the surface of the millimeter wave antenna substrate 11 on the side having the millimeter wave antenna element 2 . ing. The cover member 12 is preferably glass, the millimeter wave antenna substrate 11 is preferably COP in terms of low dielectric constant and low dielectric loss, and the millimeter wave antenna element 2 is copper, silver, or ITO. is preferred.

FIG. 3 shows a millimeter wave antenna 1C having a cover member 12, an adhesive sheet 10a, a millimeter wave antenna substrate 11, an adhesive sheet 10b, and an image display panel 13 in this order in contact with each other. The millimeter wave antenna substrate 11 has the millimeter wave antenna element 2 on the surface on the side of the adhesive sheet 10a, and the adhesive sheet 10a is adhered to the surface of the millimeter wave antenna substrate 11 on the side having the millimeter wave antenna element 2. ing. The cover member 12 is preferably made of glass, the millimeter wave antenna substrate 11 is preferably made of COP in terms of low dielectric constant and low dielectric loss, and the millimeter wave antenna element 2 is preferably made of COP in terms of transparency and visibility. Therefore, it is preferably ITO, or silver or copper blackened with a film of nitride, oxide, sulfide, or the like. The adhesive sheet 10b may be the adhesive sheet of the present invention or may not be the adhesive sheet of the present invention, but is preferably the adhesive sheet of the present invention. The image display panel 13 may have a touch sensor (not shown).

In the millimeter wave antennas 1A to 1C of FIGS. 1 to 3, the

adhesive sheets

10, 10a, and preferably the adhesive sheet 10b are composed of the adhesive layer of the present invention with low dielectric constant and dielectric loss in the high frequency band. The radiation loss of millimeter waves is suppressed, and millimeter wave communication can be performed efficiently. In addition, since millimeter wave communication can be performed efficiently, the antenna area can be reduced, and the antenna can be miniaturized.

The present invention will be described in more detail below based on examples, but the present invention is not limited by these examples.

(Example 1)
100 parts by mass of polyisobutylene (trade name “OPPANOL N80”, Mw: 1050000, Mn: 440000, Mw/Mn: 2.4, manufactured by BASF) and fully hydrogenated terpene phenol as a tackifier (softening point: 135 ° C. , hydroxyl value: 160) were blended in toluene to prepare an adhesive composition (solution) having a solid content of 13% by mass. The obtained adhesive composition (solution) was applied onto a PET separator (trade name “MRF50”, manufactured by Mitsubishi Chemical Corporation) so that the final thickness (thickness of the adhesive layer) was 75 μm, A coating layer (adhesive composition layer) was formed. Next, the coating layer was dried at 130° C. for 5 minutes to form an adhesive layer, thereby producing an adhesive sheet having an adhesive layer thickness of 75 μm. A PET separator (trade name “MRF38”, manufactured by Mitsubishi Chemical Corporation) was attached to the adhesive surface of the adhesive sheet so that the release-treated surface and the adhesive layer were in contact with each other. A substrate-less double-sided PSA sheet in which both sides of the PSA layer are protected by separators was obtained.

(Example 2)
A mixture of 99 parts by weight of lauryl methacrylate (LMA), 1 part by weight of hydroxyethyl methacrylate (HEMA), and 2,2 as a thermal polymerization initiator are placed in a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring device. 0.2 parts by mass of '-azobisisobutyronitrile (AIBN) and ethyl acetate as a polymerization solvent are added so that the monomer component becomes 70% by mass, nitrogen gas is flowed, and the mixture is replaced with nitrogen for about 1 hour while stirring. did After that, the reactor was heated to 70° C. and reacted for 6 hours. Further, the reactor was heated to 80° C. and reacted for 3 hours to obtain a (meth)acrylic polymer having a weight average molecular weight (Mw) of 400,000. To this (meth)acrylic polymer solution (solid content: 100 parts by mass), an isocyanate-based cross-linking agent (trade name: "Coronate HX", manufactured by Tosoh Corporation, solid content concentration: 100%) was added in an amount of 0.1 on a solid content basis. Parts by weight, 0.01 parts by weight of dioctyltin dilaurate (trade name "Envillizer OL-1", manufactured by Tokyo Fine Chemical Co., Ltd.) as a cross-linking accelerator, and 5 parts by weight of acetylacetone as a cross-linking retarder are added and mixed uniformly. , to prepare a pressure-sensitive adhesive composition according to this example.

The pressure-sensitive adhesive composition is applied onto a polyethylene terephthalate (PET) separator (trade name “MRF38”, manufactured by Mitsubishi Chemical Corporation) so that the final thickness (thickness of the pressure-sensitive adhesive layer) is 25 μm. A layer (adhesive composition layer) was formed. Then, a drying treatment was performed for 120 minutes in a drier at 130° C. to volatilize residual monomers. Furthermore, a PET separator (trade name “MRE38”, manufactured by Mitsubishi Chemical Corporation) is provided on the above coating layer, and consists of only an adhesive layer, and both sides of the adhesive layer are protected by separators. A sticky sheet was obtained.

(Example 3)
A substrate-less double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2, except that a monomer mixture composed of 80 parts by mass of lauryl methacrylate (LMA) and 20 parts by mass of hydroxyethyl methacrylate (HEMA) was used.

(Comparative example 1)
100 parts by mass of butyl acrylate (BA), 5 parts by mass of acrylic acid (AA), and 4-hydroxybutyl acrylate (4-HBA) were placed in a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring device. A monomer mixture was obtained by charging 1 part by mass. Furthermore, with respect to 100 parts by mass of the total monomer mixture, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator and ethyl acetate as a polymerization solvent are used to make the monomer component 40% by mass. Nitrogen gas was flowed into the flask to replace with nitrogen while gently stirring. After that, the reactor was heated to 60° C. and reacted for 8 hours to obtain an acrylic polymer having a weight average molecular weight (Mw) of 1,800,000. To this acrylic polymer solution (solid content: 100 parts by mass), as an epoxy-based cross-linking agent (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd., solid content concentration: 100%), 0.25% on a solid content basis. Parts by mass were added and uniformly mixed to prepare a pressure-sensitive adhesive composition according to this example.

The pressure-sensitive adhesive composition is applied onto a polyethylene terephthalate (PET) separator (trade name “MRF38”, manufactured by Mitsubishi Chemical Corporation) so that the final thickness (thickness of the pressure-sensitive adhesive layer) is 25 μm. A layer (adhesive composition layer) was formed. Then, drying treatment was performed for 120 minutes in a drier at 130° C. to volatilize residual monomers. Furthermore, a PET separator (trade name “MRE38”, manufactured by Mitsubishi Chemical Corporation) is provided on the above coating layer, and consists of only an adhesive layer, and both sides of the adhesive layer are protected by separators. A sticky sheet was obtained.

[Characteristic evaluation]
The following measurements or evaluations were performed on the substrate-less double-sided pressure-sensitive adhesive sheets of Examples and Comparative Examples. The evaluation results are shown in Table 1.

(1) Evaluation of dielectric constant and dielectric loss The pressure-sensitive adhesive layer alone obtained in Examples or Comparative Examples (a PET separator subjected to silicone treatment was peeled from the double-sided pressure-sensitive adhesive sheet) was measured using the following equipment at a frequency of 28 GHz and Dielectric constant and dielectric loss were measured at 60 GHz. Measurements were performed on a circular area with a diameter of 8 cm for 28 GHz and on a circular area with a diameter of 4 cm for 60 GHz. At least three samples were prepared for each specimen, and after excluding the maximum and minimum values of the measured values of those three samples, the average values were taken as the dielectric constant and dielectric loss at each frequency.
・Measurement method: Open resonator method JIS R1660-2
Apparatus: Keycom Co., Ltd., interference type resonator method permittivity measurement system Measurement environment: 23±1° C., 52±1% RH H.

(2) Saturated Moisture Absorption A 10 mg sample was collected from the pressure-sensitive adhesive layer obtained in Examples or Comparative Examples. The sample is placed in a micro-thermogravimetry device with a humidifying function (IGA Sorp: model IG-SA-116, manufactured by Heiden), and a detector capable of measuring 0.001 mg order is used to measure the weight change. Heating at 130° C. was continued until no more was observed. Next, the inside of the same apparatus was heated at 65° C. and 0% R.I. H. and maintained for at least 1 hour, and the weight (w1) of the sample was measured when no weight change was observed (dry state). Furthermore, the inside of the same apparatus was heated at 65° C. and 90% R.I. H. and monitored for weight change for at least 10 hours. The weight (w2) of the sample was measured when there was no change in the weight of the sample (when the moisture absorption rate was saturated). From the above results, the saturated moisture absorption rate was determined by the following formula.
Saturated moisture absorption rate (%) = {(w2-w1)/w1} x 100

(3) Variation in Dielectric Loss Each pressure-sensitive adhesive layer alone obtained in Examples or Comparative Examples (a PET separator treated with silicone was peeled off from a double-sided pressure-sensitive adhesive sheet) was measured at 65° C. and 90% R.E. H. was humidified for at least 5 days in an atmosphere of 23±1° C., 52±1% R.I. H. (elapsed time = 0 minutes), and the dielectric constant and dielectric loss at frequencies of 28 GHz and 60 GHz are measured every 10 minutes from 4 minutes to 180 minutes according to the above open resonator method (JIS R1660- 2), it was measured using an interferometric resonator method permittivity measurement system (manufactured by Keycom Co., Ltd.). The dielectric loss of each sample was obtained as the average value of 3 specimens.

Using the maximum value (D _fmax ) and the minimum value (D _fmin ) among the dielectric losses obtained for each adhesive layer after humidification (elapsed time = 4 to 180 minutes), according to the following formula, The amount of change in dielectric loss was calculated.
Change in dielectric loss = D _fmax - D _fmin

(4) Total Light Transmittance and Haze One separator was peeled off from the double-sided pressure-sensitive adhesive sheet obtained in Examples or Comparative Examples, and the double-sided pressure-sensitive adhesive sheet was applied to a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., "White polishing No. .1", thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.2%), and the other separator is peeled off, double-sided adhesive sheet (adhesive layer) / slide glass A test piece having a layer structure of The total light transmittance and haze of the above test piece in the visible light region were measured at 23 ± 1 ° C. and 52 ± 1% RH using a haze meter (product name “HM-150”, manufactured by Murakami Color Laboratory Co., Ltd.). Measured under environmental conditions. Three samples were prepared for each specimen, and the average of the measured values of these three samples was taken as the total light transmittance and haze in the visible light region. As the thickness of the test piece increases, the value of total light transmittance decreases and the value of haze increases.

(5) Water vapor transmission rate (WVTR)
The water vapor permeability of the pressure-sensitive adhesive layers obtained in Examples and Comparative Examples was evaluated based on the cup method. The dry weight (w1) of calcium chloride isolated from the outside by an adhesive layer, and the sample was heated at 40° C. and 92% R.I. H. Measure the weight (w2) after a predetermined time (when the moisture absorption rate is saturated) after leaving it in the atmosphere of , and convert the weight change amount to unit time (1 day) and unit area (1 m ² ). The water vapor transmission rate (g/m ² /day) was obtained by this. The measurement of w2 was calculated from the value 24 to 48 hours after the start of humidification.

(6) Transmission and reception characteristics The transmission and reception characteristics of the pressure-sensitive adhesive layer obtained in Examples or Comparative Examples (a PET separator treated with silicone from a double-sided pressure-sensitive adhesive sheet) were evaluated as shown in FIG. The evaluation was made according to the Information Society of Japan, 4th Group 2, Chapter 5 “Planar Antenna”, URL: http://www.ieicehbkb.org/files/04/04gun — 02hen — 05.pdf). Specifically, a millimeter-wave patch antenna 43 having the shape shown in FIG. An antenna film 46 with a copper ground layer 45 formed thereon was produced. The size of the millimeter wave patch antenna 43 was adjusted so that it would be optimal when laminated with the adhesives of the respective examples and comparative examples (length A: 2.8 to 3.2 mm, width B: 4.13 mm). The adhesive layer 42 of each example or comparative example was attached to the patch antenna 43 side of the antenna film 46 so as not to contain air bubbles or foreign matter. ) to prepare an antenna laminate 4 of cover glass 41 /adhesive layer 42 /antenna film 46 . Feeding from the microstrip line 43a connected to the millimeter-wave patch antenna 43 of various antenna laminates 4, the transmission and reception characteristics in the frequency band of 30 GHz were evaluated. were placed close to each other).

1A, 1B, 1C

millimeter wave antenna

10, 10a, 10b adhesive sheet 11 millimeter wave antenna substrate 12 cover member 2 millimeter wave antenna element 13 image display panel 4 antenna laminate 41 cover glass 42 adhesive layer 43 millimeter wave patch antenna 43a Microstrip line 44 Antenna substrate 45 Copper ground layer 46 Antenna film

Claims

a dielectric constant of 2.0 to 5.0 at a frequency of 28 GHz;
Dielectric loss at a frequency of 28 GHz is 0.0001 to 0.05,
65°C, 90% R.I. H. The saturated moisture absorption rate in is 2.8% or less,
A pressure-sensitive adhesive composition having a dielectric loss change of 0.006 or less as calculated by the following formula.
Change in dielectric loss = D fmax - D fmin
D fmax : 65° C., 90% R.I. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. , the maximum value D fmin of the dielectric loss at a frequency of 28 GHz: 65° C., 90% R.E.M. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. The minimum value of dielectric loss at a frequency of 28 GHz while tracking the change in dielectric loss over time at
The adhesive composition according to claim 1, which has a dielectric constant of 2.0 to 5.0 at a frequency of 60 GHz.
a dielectric constant of 2.0 to 5.0 at a frequency of 60 GHz,
Dielectric loss at a frequency of 60 GHz is 0.0001 to 0.05,
65°C, 90% R.I. H. The saturated moisture absorption rate in is 2.8% or less,
A pressure-sensitive adhesive composition having a dielectric loss change of 0.003 or less as calculated by the following formula.
Change in dielectric loss = D fmax - D fmin
D fmax : 65° C., 90% R.I. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. , the maximum value D fmin of the dielectric loss at a frequency of 60 GHz: 65° C., 90% R.E.M. H. After humidifying to saturation at 23°C ± 1°C, 52 ± 1% R.I. H. The minimum value of dielectric loss at a frequency of 60 GHz while tracking the change in dielectric loss over time at
The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the total light transmittance measured for the pressure-sensitive adhesive layer with a thickness of 25 µm is 85% or more.
The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the haze measured for the pressure-sensitive adhesive layer having a thickness of 25 µm is 1.0% or less.
A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5.
A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer according to claim 6.
8. A millimeter-wave antenna having at least the adhesive sheet according to claim 7 and a substrate, wherein the substrate has an antenna element on at least one side thereof, and the adhesive sheet is attached to the surface of the substrate on the side having the antenna element. millimeter wave antenna.