Adhesive composition, adhesive tape, method for affixing electronic equipment component or vehicle-borne equipment component, and method for producing electronic equipment or vehicle-borne equipment

Abstract

The purpose of the present invention is to provide an adhesive composition to be a material of an adhesive tape capable of achieving both high shear adhesion strength and light-pressure adhesiveness. The present invention is an adhesive composition containing an acrylic copolymer that contains more than 30% by mass of a constituent unit derived from 1-methylheptyl (meth)acrylate and contains 0.01%-50% by mass of a constituent unit derived from n-heptyl (meth)acrylate.

Description

Adhesive composition, adhesive tape, method for fixing electronic device components or vehicle-mounted device components, and method for manufacturing electronic device or vehicle-mounted device

[0001] The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive tape, a method for fixing an electronic device component or an in-vehicle device component, and a method for manufacturing an electronic device or an in-vehicle device.

[0002] Conventionally, adhesive tapes having an adhesive layer containing an adhesive have been widely used to fix components in electronic components, vehicles, houses, and building materials (e.g., Patent Documents 1 to 3). Specifically, adhesive tapes have been used to adhere a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to adhere a touch panel module to a display panel module.

[0003] JP 2015-052050 A JP 2015-021067 A JP 2015-120876 A

[0004] Adhesive tapes used to secure the front and rear panels of displays and devices require high shear adhesive strength, and acrylic adhesives containing acrylic copolymers are widely used as adhesives with such high shear adhesive strength. Meanwhile, with the recent trend toward thinner devices, adhesive tapes used to secure components are required to have lighter pressure-sensitive adhesive properties, allowing them to be applied with less force to prevent damage to the components. However, there is a trade-off between high shear adhesive strength and light pressure-sensitive adhesive properties, and it is difficult for conventional acrylic adhesives to achieve both high shear adhesive strength and light pressure-sensitive adhesive properties.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive composition that can be used as a material for a pressure-sensitive adhesive tape that can achieve both high shear adhesive strength and light pressure-sensitive adhesiveness. Another object of the present invention is to provide a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition, a method for fixing electronic device components or in-vehicle device components using the pressure-sensitive adhesive tape, and a method for manufacturing an electronic device or in-vehicle device.

[0006] Disclosure 1 is a pressure-sensitive adhesive composition containing an acrylic copolymer containing more than 30% by mass of structural units derived from 1-methylheptyl(meth)acrylate and 0.01% by mass to 50% by mass of structural units derived from n-heptyl(meth)acrylate. Disclosure 2 is the pressure-sensitive adhesive composition according to Disclosure 1, wherein the acrylic copolymer has a ratio of structural units derived from 1-methylheptyl(meth)acrylate to structural units derived from n-heptyl(meth)acrylate (proportion (mass%) of structural units derived from 1-methylheptyl(meth)acrylate / proportion (mass%) of structural units derived from n-heptyl(meth)acrylate) of 1 or more. Disclosure 3 is the pressure-sensitive adhesive composition according to Disclosure 1 or 2, wherein the acrylic copolymer contains 50% by mass or more of structural units derived from 1-methylheptyl(meth)acrylate. Disclosure 4 relates to the pressure-sensitive adhesive composition according to Disclosure 1 or 2, wherein the acrylic copolymer contains more than 30% by mass and not more than 50% by mass of structural units derived from 1-methylheptyl (meth)acrylate. Disclosure 5 relates to the pressure-sensitive adhesive composition according to Disclosure 1 or 2, wherein the acrylic copolymer contains 50% by mass or more of structural units derived from a (meth)acrylic acid alkyl ester, including structural units derived from 1-methylheptyl (meth)acrylate and structural units derived from n-heptyl (meth)acrylate. Disclosure 6 relates to the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 5, wherein the acrylic copolymer further contains structural units derived from a monomer having a glass transition temperature of −35° C. or higher. Disclosure 7 relates to the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 6, wherein the acrylic copolymer further contains structural units derived from a monomer having no crosslinkable functional group and having a glass transition temperature of 0° C. or higher. Disclosure 8 relates to the pressure-sensitive adhesive composition according to Disclosure 7, wherein the content of structural units derived from a monomer having a glass transition temperature of 0° C. or higher is 0.1% by mass or more and 70% by mass or less. Disclosure 9 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 8, wherein the acrylic copolymer further contains a structural unit derived from a monomer having a crosslinkable functional group. Disclosure 10 is the pressure-sensitive adhesive composition according to Disclosure 9, wherein the acrylic copolymer contains 0.01% by mass or more and 20% by mass or less of the structural unit derived from the monomer having a crosslinkable functional group.Disclosure 11 is the pressure-sensitive adhesive composition according to Disclosures 9 or 10, wherein the monomer having a crosslinkable functional group contains a monomer having a hydroxyl group. Disclosure 12 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 11, wherein the acrylic copolymer contains at least one structural unit selected from the group consisting of structural units derived from a monomer having a cyclic ether structure other than an epoxy structure or an oxetane structure, and structural units derived from a monomer having an acyclic ether structure. Disclosure 13 is the pressure-sensitive adhesive composition according to Disclosure 12, wherein the content of the at least one structural unit selected from the group consisting of structural units derived from a monomer having a cyclic ether structure other than an epoxy structure or an oxetane structure, and structural units derived from a monomer having an acyclic ether structure is 0.01% by mass or more and 50% by mass or less. Disclosure 14 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 13, wherein the acrylic copolymer has a weight-average molecular weight of 200,000 or more and 2,000,000 or less. Disclosure 15 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 14, further containing a crosslinking agent. Disclosure 16 is the pressure-sensitive adhesive composition according to Disclosure 15, wherein the crosslinking agent contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. Disclosure 17 is the pressure-sensitive adhesive composition according to Disclosure 16, wherein the crosslinking agent contains an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. Disclosure 18 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 17, further containing a tackifier resin. Disclosure 19 is the pressure-sensitive adhesive composition according to Disclosure 18, wherein the tackifier resin contains at least one selected from the group consisting of a rosin ester-based tackifier resin, a terpene-based tackifier resin, and an acrylic tackifier resin composed of a (meth)acrylic compound. Disclosure 20 is the pressure-sensitive adhesive composition according to Disclosure 19, wherein the tackifier resin contains a rosin ester-based tackifier resin and a terpene-based tackifier resin. Disclosure 21 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 20, which does not contain a surfactant. Disclosure 22 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 21, further containing a black pigment. Disclosure 23 is the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 22, wherein the content of bio-derived carbon is 10% by mass or more.Disclosure 24 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition according to any one of Disclosures 1 to 23. Disclosure 25 is the pressure-sensitive adhesive tape according to Disclosure 24, wherein the pressure-sensitive adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less. Disclosure 26 is the pressure-sensitive adhesive tape according to Disclosure 24 or 25, used to fix electronic equipment components or on-vehicle equipment components. Disclosure 27 is a method for fixing electronic equipment components or on-vehicle equipment components using the pressure-sensitive adhesive tape according to Disclosure 24 or 25. Disclosure 28 is a method for producing electronic equipment or on-vehicle equipment, comprising a step of fixing electronic equipment components or on-vehicle equipment components using the pressure-sensitive adhesive tape according to Disclosure 24 or 25. In this specification, (meth)acrylate means acrylate or methacrylate, and (meth)acrylic means acrylic or methacrylic. The acrylic copolymer may be a methacrylic copolymer. The present invention will be described in detail below.

[0007] As a result of extensive research, the present inventors have found that by using a pressure-sensitive adhesive composition containing an acrylic copolymer containing specific amounts of structural units derived from 1-methylheptyl (meth)acrylate and structural units derived from n-heptyl (meth)acrylate, the resulting pressure-sensitive adhesive tape can achieve both high shear adhesive strength and light pressure-sensitive adhesiveness, and have thus completed the present invention.

[0008] The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer, and the acrylic copolymer contains more than 30% by mass of structural units derived from 1-methylheptyl (meth)acrylate and 0.01% by mass to 50% by mass of structural units derived from n-heptyl (meth)acrylate. This allows a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition of the present invention to achieve both high shear adhesive strength and light pressure-sensitive adhesiveness. The reason why high shear adhesive strength and light pressure-sensitive adhesiveness can be achieved by containing structural units derived from 1-methylheptyl (meth)acrylate and structural units derived from n-heptyl (meth)acrylate in the above ranges is unclear, but it can be considered as follows. First, the 1-methylheptyl group of 1-methylheptyl (meth)acrylate forms a branched chain structure near the main chain, which results in a higher main chain rigidity than typical linear monomers. When the acrylic copolymer is formed, the glass transition temperature is improved, making it easier to exhibit high shear adhesive strength. On the other hand, due to the high rigidity of the main chain, it is difficult to achieve sufficient adhesive strength unless a strong force is applied, and there are limitations to light pressure-sensitive adhesiveness. Meanwhile, n-heptyl (meth)acrylate has a structure very similar to 1-methylheptyl (meth)acrylate, but the n-heptyl group has relatively little steric hindrance near the main chain. Therefore, n-heptyl (meth)acrylate improves the flexibility of the main chain when made into an acrylic copolymer, making the adhesive more easily deformable under external forces and therefore easier to apply with lighter force. Thus, it is surprising that the acrylic copolymer contains a small amount of the n-heptyl (meth)acrylate-derived structural unit in addition to the 1-methylheptyl (meth)acrylate-derived structural unit, and thus the resulting adhesive tape exhibits a good balance of high shear adhesive strength and light pressure-sensitive adhesiveness.

[0009] The 1-methylheptyl (meth)acrylate in the structural unit derived from 1-methylheptyl (meth)acrylate may be 1-methylheptyl acrylate or 1-methylheptyl methacrylate, but is more preferably 1-methylheptyl acrylate. The 1-methylheptyl (meth)acrylate in the structural unit derived from 1-methylheptyl (meth)acrylate may consist solely of petroleum-derived 1-methylheptyl (meth)acrylate, but preferably contains bio-derived 1-methylheptyl (meth)acrylate. If the 1-methylheptyl (meth)acrylate contains bio-derived 1-methylheptyl (meth)acrylate, this is preferable from the viewpoint of saving petroleum resources and also from the viewpoint of reducing carbon dioxide emissions.

[0010] When the 1-methylheptyl (meth)acrylate in the structural unit derived from 1-methylheptyl (meth)acrylate contains bio-derived 1-methylheptyl (meth)acrylate, the 1-methylheptyl (meth)acrylate is preferably synthesized by esterification of bio-derived 1-methylheptyl alcohol with (meth)acrylic acid. The bio-derived 1-methylheptyl alcohol can be obtained, for example, by cracking a raw material collected from plants or animals (e.g., ricinoleic acid derived from castor oil).

[0011] The lower limit of the content of the structural units derived from the 1-methylheptyl (meth)acrylate in the acrylic copolymer is greater than 30% by mass. When the content of the structural units derived from the 1-methylheptyl (meth)acrylate is greater than 30% by mass, high shear adhesive strength and light pressure-sensitive adhesiveness can be achieved simultaneously. Furthermore, the content of the structural units derived from the 1-methylheptyl (meth)acrylate is preferably greater than 30% by mass and not greater than 50% by mass. When the content of the structural units derived from the 1-methylheptyl (meth)acrylate is within the above range, a good balance between light pressure-sensitive adhesiveness and shear adhesive strength can be achieved. Furthermore, it is also preferable that the content of the structural units derived from the 1-methylheptyl (meth)acrylate in the acrylic copolymer is 50% by mass or more. When the content of the structural units derived from the 1-methylheptyl (meth)acrylate in the acrylic copolymer is 50% by mass or more, higher shear adhesive strength can be obtained while maintaining light pressure-sensitive adhesiveness. From the same viewpoint, the content of the structural units derived from the 1-methylheptyl (meth)acrylate in the acrylic copolymer is more preferably 80% by mass or more, even more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. The upper limit of the content of the structural units derived from the 1-methylheptyl (meth)acrylate is not particularly limited, but is preferably 99% by mass or less from the viewpoint of obtaining a higher shear adhesive strength even when applied with a conventional pressure-bonding force. Examples of the content range of the structural units derived from the 1-methylheptyl (meth)acrylate include 80% by mass or more and 99% by mass or less, 85% by mass or more and 99% by mass or less, and 90% by mass or more and 99% by mass or less.

[0012] The content of the structural units derived from 1-methylheptyl (meth)acrylate in the acrylic copolymer can be calculated by pyrolysis GC-MS. More specifically, a standard sample having a known content of structural units derived from 1-methylheptyl (meth)acrylate is subjected to pyrolysis GC-MS measurement, a calibration curve is created from the measured 2-octene peak area, and the created calibration curve can be used to calculate the content of structural units derived from 1-methylheptyl (meth)acrylate. More specifically, the calibration curve can be created as follows: An acrylic copolymer (standard sample) having a known content of structural units derived from 1-methylheptyl (meth)acrylate is prepared by adjusting the blending ratio of n-heptyl (meth)acrylate and 1-methylheptyl (meth)acrylate. The standard sample is weighed out and subjected to pyrolysis GC-MS measurement under the conditions below, and each total ion current chromatogram is obtained. A calibration curve can be created by plotting the content of structural units derived from 1-methylheptyl (meth)acrylate on the horizontal axis and the peak area of ​​2-octene in a total ion current chromatogram on the vertical axis. Next, the acrylic copolymer to be measured is weighed out in the same amount as the standard sample used to create the calibration curve, and pyrolysis GC-MS measurement is performed under the following conditions. The content of structural units derived from 1-methylheptyl (meth)acrylate is calculated from the peak area of ​​2-octene in the obtained total ion current chromatogram and the created calibration curve. Using a similar method, the content of structural units derived from n-heptyl (meth)acrylate can be calculated from the peak area of ​​1-heptene.

[0013] <Pyrolysis GC-MS measurement conditions> Equipment: PY-3030D (manufactured by FRONTIER LAB) Pyrolysis temperature: 550°C GC-MS equipment: Agilent 7890B (manufactured by Agilent Technologies) & JMS-Q1500 (manufactured by JEOL Ltd.) Inlet temperature: 300℃ Sample amount: 0.2mg precision weighing Column: Ultra-ALLOY-1 (non-polar) 0.25mmφ x 30m x 0.25μm He flow rate: 1.0mL / min (split ratio 1:50) Column temperature: 40℃ (3min) → 10℃ / min → 300℃ (5min) MS temperature, ion source: 230°C, interface: 250°C MS measurement range: 35-600 Ionization method: EI method Measurement mode: Scan Ionization voltage: 70 eV

[0014] The n-heptyl(meth)acrylate in the structural unit derived from n-heptyl(meth)acrylate may be either n-heptyl acrylate or n-heptyl methacrylate, with n-heptyl acrylate being more preferred. The n-heptyl(meth)acrylate in the structural unit derived from n-heptyl(meth)acrylate may be petroleum-derived n-heptyl(meth)acrylate or bio-derived n-heptyl(meth)acrylate. If the n-heptyl(meth)acrylate in the structural unit derived from n-heptyl(meth)acrylate contains bio-derived n-heptyl(meth)acrylate, this is preferred from the viewpoints of saving petroleum resources and reducing carbon dioxide emissions.

[0015] The bio-derived n-heptyl (meth)acrylate can be synthesized by esterifying bio-derived n-heptyl alcohol with (meth)acrylic acid. The bio-derived n-heptyl alcohol can be obtained, for example, by cracking a raw material collected from plants or animals (e.g., ricinoleic acid derived from castor oil).

[0016] The content of the structural units derived from n-heptyl (meth)acrylate in the acrylic copolymer has a lower limit of 0.01 wt% and an upper limit of 50 wt%. When the content of the structural units derived from n-heptyl (meth)acrylate is within the above range, a pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition can be imparted with light pressure-bonding properties. Furthermore, the content of the structural units derived from n-heptyl (meth)acrylate is preferably 0.1 wt% or more. When the content of the structural units derived from n-heptyl (meth)acrylate is 0.1 wt% or more, a high shear adhesive strength can be exhibited even when applied with weak pressure-bonding force. The content of the structural units derived from n-heptyl (meth)acrylate is more preferably 0.5 wt% or more, even more preferably 1 wt% or more, even more preferably 5 wt% or more, very preferably 10 wt% or more, more preferably 40 wt% or less, and even more preferably 30 wt% or less. Examples of the range of the content of the structural unit derived from n-heptyl (meth)acrylate include 0.01% by mass or more and 50% by mass or less, 0.01% by mass or more and 40% by mass or less, 0.01% by mass or more and 30% by mass or less, 0.1% by mass or more and 50% by mass or less, 0.1% by mass or more and 40% by mass or less, 0.1% by mass or more and 30% by mass or less, 0.5% by mass or more and 50% by mass or less, 0.5% by mass or more and 40% by mass or less, 0.5% by mass or more and 30% by mass or less, 1% by mass or more and 50% by mass or less, 1% by mass or more and 40% by mass or less, 1% by mass or more and 30% by mass or less, 5% by mass or more and 40% by mass or less, 5% by mass or more and 30% by mass or less, 10% by mass or more and 40% by mass or less, and 10% by mass or more and 30% by mass or less.

[0017] The content of the structural unit derived from the n-heptyl (meth)acrylate in the acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The amount of hydrogen can be calculated from the integrated intensity ratio of the peak of hydrogen derived from n-heptyl (meth)acrylate by measurement using a C-NMR or the like.

[0018] In the acrylic copolymer, the ratio of structural units derived from 1-methylheptyl (meth)acrylate to structural units derived from n-heptyl (meth)acrylate (ratio (mass%) of structural units derived from 1-methylheptyl (meth)acrylate / ratio (mass%) of structural units derived from n-heptyl (meth)acrylate) is preferably 1 or more. When this ratio is 1 or more, that is, when the ratio of structural units derived from 1-methylheptyl (meth)acrylate in the acrylic copolymer is equal to or greater than the ratio of structural units derived from n-heptyl (meth)acrylate, a pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition can exhibit a certain level of shear adhesive strength when applied with weak pressure, while exhibiting extremely high shear adhesive strength when applied with normal pressure, making it applicable to a wide range of component fixing processes. This ratio is more preferably 5 or more, and even more preferably 10 or more. There are no particular limitations on the upper limit of this ratio, but from the viewpoint of maintaining a certain level of shear adhesive strength when applied with weak pressure. The range of the ratio may be, for example, 1 or more and 100 or less, 5 or more and 100 or less, or 10 or more and 100 or less.

[0019] The acrylic copolymer preferably further contains a structural unit derived from a monomer having a crosslinkable functional group. When the acrylic copolymer contains a structural unit derived from a monomer having a crosslinkable functional group, the cohesive strength of the pressure-sensitive adhesive layer increases, and the adhesive strength of the pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition to a rough surface increases. The glass transition temperature when the monomer having a crosslinkable functional group is made into a homopolymer is not particularly limited, and may be 0°C or higher.

[0020] The monomer having a crosslinkable functional group is not particularly limited, and examples thereof include a monomer having a hydroxyl group, a monomer having a carboxyl group, a monomer having a glycidyl group, a monomer having an amide group, and a monomer having a nitrile group. Among these, monomers having a hydroxyl group and monomers having a carboxyl group are preferred because they facilitate adjustment of the gel fraction, and monomers having a hydroxyl group are more preferred. Furthermore, the monomer having a crosslinkable functional group preferably has a (meth)acryloyl group. In this specification, the term "(meth)acryloyl" refers to acryloyl or methacryloyl. Examples of the monomer having a hydroxyl group include acrylic monomers having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1-methyl-2-hydroxypropyl (meth)acrylate, 1-methyl-3-hydroxypropyl (meth)acrylate, 1-ethyl-2-hydroxyethyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 9-hydroxynonyl (meth)acrylate, and polypropylene glycol mono(meth)acrylate. Examples of the monomer having a carboxyl group include unsaturated monocarboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Examples of the monomer having a glycidyl group include acrylic monomers having a glycidyl group such as glycidyl (meth)acrylate.Examples of the monomer having an amide group include acrylic monomers having an amide group, such as hydroxyethyl(meth)acrylamide, isopropyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide. Examples of the monomer having a nitrile group include acrylic monomers having a nitrile group, such as (meth)acrylonitrile. These monomers having a crosslinkable functional group may be used alone or in combination of two or more.

[0021] The content of the structural unit derived from the monomer having a crosslinkable functional group in the acrylic copolymer is not particularly limited, but a preferred lower limit is 0.01% by mass, and a preferred upper limit is 20% by mass. If the content of the structural unit derived from the monomer having a crosslinkable functional group is within the above range, the adhesive strength of the pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition will be higher. A more preferred lower limit of the content of the structural unit derived from the monomer having a crosslinkable functional group is 0.1% by mass, a more preferred upper limit is 10% by mass, an even more preferred lower limit is 0.5% by mass, and an even more preferred upper limit is 5% by mass.

[0022] When the acrylic copolymer contains, among the structural units derived from the monomer having a crosslinkable functional group, particularly the structural unit derived from the monomer having a hydroxyl group, the content of the structural unit derived from the monomer having a hydroxyl group in the acrylic copolymer is not particularly limited, but a preferred lower limit is 0.01% by mass and a preferred upper limit is 20% by mass. When the content of the structural unit derived from the monomer having a hydroxyl group is within the above range, a pressure-sensitive adhesive tape using the obtained pressure-sensitive adhesive composition can exhibit higher shear adhesive strength whether it is applied with weak pressure-sensitive adhesive force or conventional pressure-sensitive adhesive force. A more preferred lower limit of the content of the structural unit derived from the monomer having a hydroxyl group is 0.1% by mass, a more preferred upper limit is 10% by mass, an even more preferred lower limit is 0.5% by mass, and an even more preferred upper limit is 5% by mass. Examples of the range of the content of the structural unit derived from the monomer having a hydroxyl group include 0.01% by mass or more and 10% by mass or less, 0.01% by mass or more and 5% by mass or less, 0.1% by mass or more and 20% by mass or less, 0.1% by mass or more and 10% by mass or less, 0.1% by mass or more and 5% by mass or less, 0.5% by mass or more and 20% by mass or less, 0.5% by mass or more and 10% by mass or less, and 0.5% by mass or more and 5% by mass or less.

[0023] The content of the structural unit derived from the monomer having the crosslinkable functional group in the acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The ratio can be calculated from the integrated intensity ratio of the hydrogen peaks derived from each monomer by measurement using a spectrometer (e.g., C-NMR).

[0024] When the acrylic copolymer contains, among the structural units derived from the monomer having a crosslinkable functional group, particularly a structural unit derived from the monomer having a hydroxyl group, it is also preferable that the content of the structural unit derived from the monomer having a hydroxyl group in the acrylic copolymer is 0.01% by mass or more and 2.0% by mass or less. When the content of the structural unit derived from the monomer having a hydroxyl group is within the above range, the pressure-sensitive adhesive layer is more likely to form a crosslinked structure and has appropriate bulk strength, thereby further improving the shear storage modulus at high temperatures, and therefore the heat resistance and high-temperature retention performance of the resulting pressure-sensitive adhesive tape are further improved. From the viewpoint of further improving the heat resistance and high-temperature retention performance of the resulting pressure-sensitive adhesive tape, the lower limit of the content of the structural unit derived from the monomer having a hydroxyl group is more preferably 0.05% by mass, more preferably 1.0% by mass, and even more preferably 0.1% by mass. The range of the content of the structural units derived from the monomer having a hydroxyl group can be, for example, 0.01% by mass or more and 1.0% by mass or less, 0.05% by mass or more and 2.0% by mass or less, 0.05% by mass or more and 1.0% by mass or less, 0.1% by mass or more and 2.0% by mass or less, 0.1% by mass or more and 1.0% by mass or less, etc. The content of the structural units derived from the monomer having a hydroxyl group in the acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The amount of hydrogen can be calculated from the integrated intensity ratio of the hydrogen peak derived from the monomer having a hydroxyl group by measurement using a spectrometer (e.g., C-NMR) or the like.

[0025] When the acrylic copolymer contains, among the structural units derived from the monomer having a crosslinkable functional group, particularly the structural unit derived from the monomer having a carboxyl group, the preferred lower limit of the content of the structural unit derived from the monomer having a carboxyl group in the acrylic copolymer is 0.1% by mass, and the preferred upper limit is 15% by mass.When the content of the structural unit derived from the monomer having a carboxyl group is within the above range, the pressure-sensitive adhesive layer is more likely to form a crosslinked structure and has appropriate bulk strength, thereby further improving the shear storage modulus at high temperatures, and therefore the heat resistance and high-temperature retention performance of the resulting pressure-sensitive adhesive tape are further improved.The more preferred lower limit of the content of the structural unit derived from the monomer having a carboxyl group is 1.0% by mass, and the more preferred upper limit is 10% by mass, and even more preferred lower limit is 3.0% by mass, and even more preferred upper limit is 8.0% by mass. The range of the content of the structural unit derived from the monomer having a carboxy group can be, for example, 0.1% by mass or more and 15% by mass or less, 0.1% by mass or more and 10% by mass or less, 0.1% by mass or more and 8.0% by mass or less, 1.0% by mass or more and 15% by mass or less, 1.0% by mass or more and 10% by mass or less, 1.0% by mass or more and 8.0% by mass or less, 3.0% by mass or more and 15% by mass or less, 3.0% by mass or more and 10% by mass or less, 3.0% by mass or more and 8.0% by mass or less, etc. The content of the structural unit derived from the monomer having a carboxy group in the acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The carbonyl group content can be calculated from the integrated intensity ratio of the hydrogen peak derived from the carboxyl group-containing monomer by measurement using a spectrometer (e.g., C-NMR) and the like.

[0026] The acrylic copolymer may have a structural unit derived from a monomer other than the structural unit derived from n-heptyl(meth)acrylate, the structural unit derived from 1-methylheptyl(meth)acrylate, and the structural unit derived from the monomer having a crosslinkable functional group. The other monomer is not particularly limited, and examples thereof include alkyl (meth)acrylate esters other than n-heptyl(meth)acrylate and 1-methylheptyl(meth)acrylate. Examples of the (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, esters of 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)octanol-1 with (meth)acrylic acid, esters of alcohols having a total of 18 carbon atoms and one or two methyl groups in the linear main chain with (meth)acrylic acid, behenyl (meth)acrylate, and arachidyl (meth)acrylate. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0027] In the acrylic copolymer, the content (total content) of structural units derived from a (meth)acrylic acid alkyl ester, including the structural units derived from 1-methylheptyl (meth)acrylate and the structural units derived from n-heptyl (meth)acrylate, is not particularly limited, but a preferred lower limit is 31% by mass, and a more preferred lower limit is 48% by mass. The content (total content) of structural units derived from a (meth)acrylic acid alkyl ester, including the structural units derived from 1-methylheptyl (meth)acrylate and the structural units derived from n-heptyl (meth)acrylate, is more preferably 50% by mass or more, with an even more preferred lower limit being 60% by mass, an even more preferred lower limit being 70% by mass, and an even more preferred lower limit being 80% by mass. The upper limit of the content (total content) of structural units derived from a (meth)acrylic acid alkyl ester is not particularly limited, but a preferred upper limit is 99% by mass, and a more preferred upper limit is 97% by mass. Examples of the range of the content (total content) of the structural units derived from the (meth)acrylic acid alkyl ester include 31% by mass or more and 99% by mass or less, 31% by mass or more and 97% by mass or less, 48% by mass or more and 99% by mass or less, 48% by mass or more and 97% by mass or less, 50% by mass or more and 99% by mass or less, 50% by mass or more and 97% by mass or less, 60% by mass or more and 99% by mass or less, 60% by mass or more and 97% by mass or less, 70% by mass or more and 99% by mass or less, 70% by mass or more and 97% by mass or less, 80% by mass or more and 99% by mass or less, and 80% by mass or more and 97% by mass or less.

[0028] Examples of the other monomers include benzyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and polypropylene glycol mono(meth)acrylate. Furthermore, examples of the other monomers that can be used include vinyl carboxylates such as vinyl acetate, and various monomers used in general acrylic polymers, such as styrene. These other monomers may be used alone, or two or more of them may be used in combination.

[0029] The acrylic copolymer may have a structural unit derived from a (meth)acrylate having an alkyl group having 8 or more carbon atoms. The (meth)acrylate having an alkyl group having 8 or more carbon atoms is not particularly limited, and examples thereof include, among those mentioned above, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, esters of 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)octanol-1 and (meth)acrylic acid, esters of alcohols having a total of 18 carbon atoms and one or two methyl groups in the linear main chain and (meth)acrylic acid, behenyl (meth)acrylate, and arachidyl (meth)acrylate.

[0030] The content of the structural units derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms in the acrylic copolymer is not particularly limited, but a preferred upper limit is 60% by mass. If the content of the structural units derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms is 60% by mass or less, the adhesive strength of the resulting pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition against rough surfaces will be higher. The upper limit of the content of the structural units derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms is more preferably 50% by mass, even more preferably 48.5% by mass, even more preferably 40% by mass, and particularly preferably 30% by mass. The lower limit of the content of the structural units derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms is not particularly limited, and may be 0% by mass. When the structural units derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms are contained, the lower limit of the content is preferably 1% by mass, more preferably 5% by mass. That is, the content of the structural unit derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms in the acrylic copolymer is preferably 1% by mass to 60% by mass. Examples of the content range of the structural unit derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms include 0% by mass to 60% by mass, 0% by mass to 50% by mass, 0% by mass to 48.5% by mass, 0% by mass to 40% by mass, 0% by mass to 30% by mass, 1% by mass to 60% by mass, 1% by mass to 50% by mass, 1% by mass to 48.5% by mass, 1% by mass to 40% by mass, 1% by mass to 30% by mass, 2% by mass to 60% by mass, 2% by mass to 50% by mass, 2% by mass to 48.5% by mass, 2% by mass to 40% by mass, and 2% by mass to 30% by mass.

[0031] The content of the structural unit derived from the (meth)acrylate having an alkyl group having 8 or more carbon atoms in the acrylic copolymer can also be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The ratio can be calculated from the integrated intensity ratio of the hydrogen peaks derived from each monomer by measurement using a spectrometer (e.g., C-NMR).

[0032] The acrylic copolymer preferably contains at least one constituent unit selected from the group consisting of constituent units derived from monomers having a cyclic ether structure other than an epoxy structure or an oxetane structure, and constituent units derived from monomers having an acyclic ether structure. When the acrylic copolymer contains at least one constituent unit selected from the group consisting of constituent units derived from monomers having a cyclic ether structure other than an epoxy structure or an oxetane structure, and constituent units derived from monomers having an acyclic ether structure (hereinafter sometimes simply referred to as "constituent units derived from monomers having an ether structure"), the resulting pressure-sensitive adhesive composition has improved adhesive strength and can exhibit better adhesion to adherends.

[0033] Examples of the monomer having a cyclic ether structure other than the epoxy structure and the oxetane structure include a monomer having a cyclic ether structure such as tetrahydrofurfuryl (meth)acrylate, etc. Examples of the monomer having an acyclic ether structure include a monomer having an acyclic ether structure such as 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and ethyl carbitol (meth)acrylate.

[0034] The content of the structural units derived from the monomer having an ether structure in the acrylic copolymer is preferably 50% by mass or less. When the content of the structural units derived from the monomer having an ether structure is 50% by mass or less, the resulting pressure-sensitive adhesive composition has improved adhesive strength and can exhibit superior adhesion to an adherend. The content of the structural units derived from the monomer having an ether structure is more preferably 30% by mass, and even more preferably 10% by mass. Furthermore, when the acrylic copolymer contains structural units derived from the monomer having an ether structure, the lower limit of the content of the structural units derived from the monomer having an ether structure in the acrylic copolymer is not particularly limited, and may be greater than 0% by mass. The lower limit is preferably 0.01% by mass, more preferably 0.1% by mass, and even more preferably 1.0% by mass. The acrylic copolymer may not contain structural units derived from the monomer having an ether structure, i.e., the content of the structural units derived from the monomer having an ether structure may be 0% by mass. The content of the structural units derived from the monomer having an ether structure can be, for example, in the ranges of 0% by mass or more and 50% by mass or less, 0% by mass or more and 30% by mass or less, 0% by mass or more and 10% by mass or less, more than 0% by mass or more and 50% by mass or less, more than 0% by mass or more and 30% by mass or less, more than 0% by mass or more and 10% by mass or less, 0.01% by mass or more and 50% by mass or less, 0.01% by mass or more and 30% by mass or less, 0.01% by mass or more and 10% by mass or less, 0.1% by mass or more and 50% by mass or less, 0.1% by mass or more and 30% by mass or less, 0.1% by mass or more and 10% by mass or less, 1.0% by mass or more and 50% by mass or less, 1.0% by mass or more and 30% by mass or less, and 1.0% by mass or more and 10% by mass or less. The content of the structural units derived from the monomer having an ether structure can be measured by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ C-NMR, etc.) and calculation can be performed from the integrated intensity ratio of the hydrogen peak derived from the structural unit derived from the monomer having the ether structure.

[0035] The acrylic copolymer may have a structural unit derived from a monomer having a glass transition temperature (Tg) of -35°C or higher. When the acrylic copolymer contains a structural unit derived from a monomer having a glass transition temperature (Tg) of -35°C or higher, the adhesive strength of a pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition is further increased. Note that the monomer having a glass transition temperature (Tg) of -35°C or higher and the monomer having a glass transition temperature (Tg) of 0°C or higher, which will be described later, are monomers that, when made into a homopolymer, give a homopolymer having a glass transition temperature (Tg) of -35°C or higher or 0°C or higher, and the glass transition temperature (Tg) of the homopolymer can be determined, for example, by differential scanning calorimetry.

[0036] The glass transition temperature (Tg) of the monomer having a glass transition temperature (Tg) of −35° C. or higher is more preferably −15° C. or higher. There is no particular limitation on the upper limit of the glass transition temperature (Tg), but the upper limit is preferably 180° C., and more preferably 150° C.

[0037] The monomer having a glass transition temperature (Tg) of −35° C. or higher is not particularly limited, but a monomer having no crosslinkable functional group is preferred, and specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, tert-butyl (meth)acrylate, n-butyl methacrylate, isobutyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, trimethylolpropane formal (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, acrylamide, dimethylacrylamide, diethylacrylamide, etc. Of these, isobornyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate are preferred.

[0038] The content of the structural units derived from monomers having a glass transition temperature (Tg) of -35°C or higher in the acrylic copolymer is not particularly limited, but is preferably 5% by mass or more and 70% by mass or less. When the content of the structural units derived from monomers having a glass transition temperature (Tg) of -35°C or higher is 70% by mass or less, the adhesive tape using the resulting adhesive composition has better conformability to irregularities. The upper limit of the content of the structural units derived from monomers having a glass transition temperature (Tg) of -35°C or higher is more preferably 65% ​​by mass, even more preferably 60% by mass, even more preferably 55% by mass, and particularly preferably 50% by mass. When the structural units derived from monomers having a glass transition temperature (Tg) of -35°C or higher are contained, the lower limit of the content is preferably 5% by mass, and more preferably 10% by mass. Examples of the range of the content of the structural units derived from monomers having a glass transition temperature (Tg) of −35° C. or higher include 5% by mass or more and 65% by mass or less, 5% by mass or more and 60% by mass or less, 5% by mass or more and 55% by mass or less, 5% by mass or more and 50% by mass or less, 10% by mass or more and 70% by mass or less, 10% by mass or more and 65% by mass or less, 10% by mass or more and 60% by mass or less, 10% by mass or more and 55% by mass or less, and 10% by mass or more and 50% by mass or less.

[0039] The acrylic copolymer may contain a structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher. When the acrylic copolymer contains a structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher, the copolymer can exhibit higher shear adhesive strength. The monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher may be one contained in the other alkyl (meth)acrylates or a monomer other than the alkyl (meth)acrylates. The monomer having a glass transition temperature of 0°C or higher may be one contained in the monomer having an acyclic ether structure or the monomer having a cyclic ether structure other than an epoxy structure or an oxetane structure.

[0040] Examples of the crosslinkable functional group in the monomer having no crosslinkable functional group and a glass transition temperature of 0° C. or higher include a carboxy group, a hydroxyl group, a glycidyl group, an amide group, and a nitrile group.

[0041] Specific examples of the monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher include n-hexyl methacrylate (glass transition temperature when made into a homopolymer: 0°C), t-butyl acrylate (glass transition temperature when made into a homopolymer: 14°C), t-butyl methacrylate (glass transition temperature when made into a homopolymer: 107°C), cyclohexyl acrylate (glass transition temperature when made into a homopolymer: 15°C), isobornyl acrylate (glass transition temperature when made into a homopolymer: 97°C), isobornyl methacrylate (glass transition temperature when made into a homopolymer: 110°C), tetrahydrofurfuryl methacrylate (glass transition temperature when made into a homopolymer: 35°C), vinyl acetate (glass transition temperature when made into a homopolymer: 29°C), and styrene (glass transition temperature when made into a homopolymer: 100°C).

[0042] The content of the structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher in the acrylic copolymer is preferably 0.1% by mass or more at the lower limit and 70% by mass at the upper limit. By having the content of the structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher be 0.1% by mass or more, higher shear adhesive strength can be exhibited. By having the content of the structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher be 70% by mass or less, higher adhesive strength can be exhibited. The content of the structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0°C or higher is more preferably 1% by mass at the lower limit and 50% by mass at the upper limit, and even more preferably 3% by mass at the lower limit and 30% by mass at the upper limit. Examples of the content of the structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0° C. or higher include 0.1% by mass to 70% by mass, 0.1% by mass to 50% by mass, 0.1% by mass to 30% by mass, 1% by mass to 70% by mass, 1% by mass to 50% by mass, 1% by mass to 30% by mass, 3% by mass to 70% by mass, 3% by mass to 50% by mass, and 3% by mass to 30% by mass. The content of the structural unit derived from a monomer having no crosslinkable functional group and a glass transition temperature of 0° C. or higher can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The degree of crosslinking can be calculated from the integrated intensity ratio of the hydrogen peak derived from the monomer having no crosslinkable functional group and having a glass transition temperature of 0° C. or higher.

[0043] The content of the structural units derived from the monomer having a glass transition temperature (Tg) of −35° C. or higher and the monomer having a glass transition temperature (Tg) of 0° C. or higher in the acrylic copolymer can also be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The ratio can be calculated from the integrated intensity ratio of the hydrogen peaks derived from each monomer by measurement using a spectrometer (e.g., C-NMR).

[0044] The acrylic copolymer preferably contains a structural unit derived from a monomer having a ring structure. When the acrylic copolymer contains a structural unit derived from a monomer having a ring structure, the resulting pressure-sensitive adhesive composition can be suitably used in optical pressure-sensitive adhesive tapes. The ring structure is not particularly limited, and examples thereof include an alicyclic structure, an aromatic ring structure, and a heterocyclic structure. Among the monomers having a ring structure, examples thereof include isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, trimethylolpropane formal (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate. Of these, isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and trimethylolpropane formal (meth)acrylate are preferred. Among these, bio-derived monomers are particularly preferred, and bio-derived isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and trimethylolpropane formal (meth)acrylate are more preferred.

[0045] The monomer having a crosslinkable functional group and the other monomer preferably contain a biologically derived monomer, but may consist solely of petroleum-derived monomers. Theoretically, it is also possible for all of the acrylic monomers constituting the acrylic copolymer to be biologically derived monomers. From the standpoint of cost and productivity of the PSA composition, a relatively inexpensive and easily available biologically derived monomer may be used in combination with a petroleum-derived monomer.

[0046] The glass transition temperature (Tg) of the acrylic copolymer is not particularly limited, but is preferably -20°C or lower. If the glass transition temperature (Tg) of the acrylic copolymer is -20°C or lower, the adhesive strength of the pressure-sensitive adhesive layer to rough surfaces is improved, and therefore the adhesive strength of the pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition to rough surfaces is increased. The glass transition temperature (Tg) of the acrylic copolymer is more preferably -30°C or lower, even more preferably -40°C or lower, and even more preferably -50°C or lower. The lower limit of the glass transition temperature (Tg) of the acrylic copolymer is not particularly limited, and is usually -90°C or higher, preferably -80°C or higher. The glass transition temperature (Tg) of the acrylic copolymer can be determined, for example, by differential scanning calorimetry.

[0047] The weight-average molecular weight of the acrylic copolymer is not particularly limited, but may be, for example, in the range of approximately 30,000 to 2,000,000. The preferred lower limit of the weight-average molecular weight of the acrylic copolymer is 200,000, and the preferred upper limit is 2,000,000. When the weight-average molecular weight of the acrylic copolymer is within the above range, a pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition can achieve both high shear adhesive strength and light compression bonding at a higher level. The more preferred lower limit of the weight-average molecular weight of the acrylic copolymer is 300,000, an even more preferred lower limit is 400,000, an even more preferred lower limit is 500,000, a very preferred lower limit is 700,000, and a particularly preferred lower limit is 800,000, and a more preferred upper limit is 1,800,000, an even more preferred upper limit is 1,500,000, an even more preferred upper limit is 1,400,000, and a very preferred upper limit is 1,300,000. When the weight-average molecular weight of the acrylic copolymer is 500,000 or more, the adhesive strength of a pressure-sensitive adhesive tape using the resulting pressure-sensitive adhesive composition, particularly the holding power when a load is applied in the shear direction at high temperatures, is increased. The range of the weight average molecular weight of the acrylic copolymer is, for example, 200,000 to 1,800,000, 200,000 to 1,500,000, 200,000 to 1,400,000, 200,000 to 1,300,000, 300,000 to 2,000,000, 300,000 to 1,800,000, 300,000 to 1,500,000, 300,000 to 1,400,000, 300,000 to 1,300,000, 400,000 to 2,000,000, 400,000 to 1,800,000, 400,000 to 1,500,000, 400,000 to 1,400,000, and 400,000 to 1,500,000. Examples include 300,000 or less, 500,000 to 2,000,000, 500,000 to 1,800,000, 500,000 to 1,500,000, 500,000 to 1,400,000, 500,000 to 1,300,000, 700,000 to 2,000,000, 700,000 to 1,800,000, 700,000 to 1,500,000, 700,000 to 1,400,000, 700,000 to 1,300,000, 800,000 to 2,000,000, 800,000 to 1,800,000, 800,000 to 1,500,000, 800,000 to 1,400,000, and 800,000 to 1,300,000.

[0048] Examples of methods for adjusting the weight-average molecular weight of the acrylic copolymer include a method of changing the type or amount of a polymerization initiator or the monomer concentration during the polymerization reaction, a method of adding a small amount of a chain transfer agent such as dodecyl mercaptan, a method of changing the type of polymerization reaction solvent to control chain transfer to the solvent, and a method of changing the temperature or time during the reaction.

[0049] In this specification, the weight average molecular weight is the weight average molecular weight converted into standard polystyrene by GPC (Gel Permeation Chromatography). Specifically, the acrylic copolymer is diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. Next, this measurement sample is supplied to a gel permeation chromatograph (manufactured by Waters, trade name "2690 Separations Module" or its equivalent), and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C. The polystyrene-converted molecular weight of the acrylic copolymer is measured, and this value is taken as the weight average molecular weight of the acrylic copolymer.

[0050] The acrylic copolymer can be obtained by radical reaction of a raw material monomer mixture in the presence of a polymerization initiator. The radical reaction method is not particularly limited, and examples include living radical polymerization and free radical polymerization. Living radical polymerization produces copolymers with more uniform molecular weight and composition than free radical polymerization, and can suppress the generation of low-molecular-weight components, etc., thereby increasing the cohesive strength of the PSA composition and enhancing the adhesive strength of a PSA tape using the resulting PSA composition against rough surfaces. The polymerization method is not particularly limited, and conventionally known methods can be used. Examples of polymerization methods include solution polymerization (boiling point polymerization or constant temperature polymerization), UV polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization and UV polymerization are preferred because the PSA tape using the resulting PSA composition can achieve both high shear adhesive strength and light pressure-sensitive adhesiveness at a higher level. Furthermore, solution polymerization is more preferred because it allows for easier mixing of a tackifier resin with the resulting acrylic copolymer, further enhancing the adhesive strength of the PSA composition.

[0051] When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, dimethyl sulfoxide, ethanol, acetone, diethyl ether, etc. These reaction solvents may be used alone or in combination of two or more.

[0052] The polymerization initiator is not particularly limited, and examples thereof include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more. In the case of living radical polymerization, examples of the polymerization initiator include organotellurium polymerization initiators. The organotellurium polymerization initiator is not particularly limited as long as it is one that is generally used in living radical polymerization, and examples thereof include organotellurium compounds, organotelluride compounds, etc. In addition to the organotellurium polymerization initiator, an azo compound may also be used as the polymerization initiator in living radical polymerization in order to accelerate the polymerization rate.

[0053] The pressure-sensitive adhesive composition of the present invention preferably does not contain a surfactant. The absence of a surfactant in the pressure-sensitive adhesive composition of the present invention increases the adhesive strength of the pressure-sensitive adhesive composition, particularly at high temperatures. The absence of a surfactant in the pressure-sensitive adhesive composition means that the surfactant content in the pressure-sensitive adhesive composition is 3 wt% or less. A more preferred upper limit for the surfactant content is 1 wt%. The lower limit for the surfactant content is not particularly limited, but it is preferable to use 0 wt%, i.e., no surfactant at all. Examples of the surfactant content range include 0 wt% or more and 3 wt% or less, and 0 wt% or more and 1 wt% or less. The surfactant-free pressure-sensitive adhesive layer can be obtained, for example, by producing the acrylic copolymer without using a surfactant by solution polymerization, UV polymerization, or the like.

[0054] The surfactant content can be determined, for example, by measuring the pressure-sensitive adhesive layer using a liquid chromatography mass spectrometer (e.g., NEXCERA manufactured by Shimadzu Corporation, Exactive manufactured by Thermo Fisher Scientific, etc.). More specifically, an ethyl acetate solution of the pressure-sensitive adhesive composition is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). Approximately 10 μL of the obtained filtrate is injected into a liquid chromatography mass spectrometer and analyzed under the following conditions. The surfactant content can be determined from the area ratio of the peak corresponding to the surfactant in the pressure-sensitive adhesive composition. It is preferable to prepare samples of each surfactant type with a known surfactant content in the pressure-sensitive adhesive composition, and create a calibration curve showing the relationship between the surfactant content and the peak area ratio for analysis. Column: Hypersil GOLD (2.1 x 150 mm) manufactured by Thermo Fisher Scientific Mobile phase: acetonitrile Column temperature: 40°C Flow rate: 1.0 mL / min Ionization method: ESI Capillary temperature: 350°C

[0055] The pressure-sensitive adhesive composition of the present invention preferably further contains a crosslinking agent from the viewpoint of appropriately adjusting the gel fraction. The crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents. Among these, at least one selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents is preferred because of their excellent adhesion to the adherend, and it is more preferred to contain both an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. The molecular weight of the crosslinking agent is not particularly limited, but from the viewpoint of manufacturing, the molecular weight is preferably less than 2000 and preferably 100 or more.

[0056] The content of the crosslinking agent is not particularly limited, but a preferred lower limit is 0.05 parts by mass and a preferred upper limit is 7 parts by mass relative to 100 parts by mass of the acrylic copolymer. If the content of the crosslinking agent is within the above range, the gel fraction of the pressure-sensitive adhesive composition can be appropriately adjusted, and high shear adhesive strength and light pressure-sensitive adhesiveness can be achieved at a higher level. A more preferred lower limit of the content of the crosslinking agent is 0.1 parts by mass and a more preferred upper limit is 5 parts by mass. The content of the crosslinking agent indicates the amount of solids of the crosslinking agent.

[0057] The PSA composition of the present invention preferably further contains a tackifier resin. By including the tackifier resin in the PSA layer, the adhesive strength of the PSA composition is further enhanced. The tackifier resin is not particularly limited, and examples thereof include rosin-based tackifier resins, rosin ester-based tackifier resins, terpene-based tackifier resins, coumarone-indene-based tackifier resins, alicyclic saturated hydrocarbon-based tackifier resins, C5-based petroleum tackifier resins, C9-based petroleum tackifier resins, C5-C9 copolymer-based petroleum tackifier resins, and acrylic tackifier resins composed of (meth)acrylic compounds having a weight-average molecular weight of less than 30,000. These tackifier resins may be used alone or in combination of two or more. Among these, the PSA composition preferably contains at least one selected from the group consisting of rosin ester-based tackifier resins, terpene-based tackifier resins, and acrylic tackifier resins composed of (meth)acrylic compounds having a weight-average molecular weight of less than 30,000. A rosin ester-based tackifier resin and a terpene-based tackifier resin are more preferred.

[0058] Examples of the rosin-based tackifying resin include rosin-based resins and rosin polyol-based resins. Examples of the rosin ester-based tackifying resin include rosin ester-based resins, polymerized rosin ester-based resins, and hydrogenated rosin ester-based resins. Examples of the terpene-based tackifying resin include terpene-based resins and terpene phenol-based resins. The rosin ester-based tackifying resins and terpene-based tackifying resins are preferably derived from living organisms. Examples of the rosin ester-based tackifying resins derived from living organisms include rosin ester-based tackifying resins derived from natural resins such as pine resin. Examples of the terpene-based tackifying resins derived from living organisms include terpene-based tackifying resins derived from plant essential oils.

[0059] Specific examples of the rosin ester-based tackifying resin include Pencel D-135, Pine Crystal KE-359, Ester Gum AA-V, and Ester Gum H (all manufactured by Arakawa Chemical Industries, Ltd.). Specific examples of the terpene-based tackifying resin include YS Resin PX1250 and YS Polystar G150 (all manufactured by Yasuhara Chemical Co., Ltd.).

[0060] The acrylic tackifier resin is composed of a (meth)acrylic compound having a weight-average molecular weight of less than 30,000, and examples of the (meth)acrylic compound having a weight-average molecular weight of less than 30,000 include an acrylic oligomer having a weight-average molecular weight of less than 3,100,000 and an acrylic monomer having a weight-average molecular weight of less than 30,000, and among these, an acrylic oligomer having a weight-average molecular weight of less than 30,000 is preferred. Note that, in this specification, "acrylic tackifier resin" does not include the "acrylic isocyanate prepolymer" described below.

[0061] The weight-average molecular weight of the acrylic oligomer used as the acrylic tackifier resin is less than 30,000. The weight-average molecular weight of the acrylic oligomer is preferably 1,000 or more and less than 30,000. When the weight-average molecular weight of the acrylic oligomer is within the above range, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved. The weight-average molecular weight of the acrylic oligomer is more preferably 1,500 or more and less than 20,000, and even more preferably 2,000 or more and less than 10,000. The weight-average molecular weight of the acrylic oligomer can be measured by the same method as the method for measuring the weight-average molecular weight of the acrylic copolymer described above.

[0062] The glass transition temperature of the acrylic oligomer used as the acrylic tackifier resin preferably has a lower limit of 0°C and an upper limit of 300°C. When the glass transition temperature of the acrylic oligomer is within the above range, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved. The lower limit of the glass transition temperature of the acrylic oligomer is more preferably 20°C, and even more preferably 40°C. Examples of the glass transition temperature of the acrylic oligomer include 0°C or higher and 300°C or lower, 20°C or higher and 300°C or lower, and 40°C or higher and 300°C or lower. The glass transition temperature of the acrylic oligomer can be measured, for example, by differential scanning calorimetry under a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) according to JIS K6240:2011, at a measurement temperature of -100°C to 200°C and a heating rate of 10°C / min.

[0063] Examples of the constituent monomers of the acrylic oligomer and the acrylic monomer include the same monomers as those used in the constituent units derived from the branched alkyl group-containing alkyl(meth)acrylate (A), the constituent units derived from the monomers having a crosslinkable functional group, and the constituent units derived from the other monomers in the acrylic copolymer described above. Examples of the constituent monomers of the acrylic oligomer and the acrylic monomer include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, t-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, heptyl(meth)acrylate, octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, isobutyl(meth)acrylate, ... Preferred examples include alkyl (meth)acrylates such as nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound-derived alcohols.The acrylic oligomer preferably contains, as a monomer unit, an acrylic monomer having a relatively bulky structure, such as an alkyl (meth)acrylate in which the alkyl group has a branched structure, such as isobutyl (meth)acrylate or t-butyl (meth)acrylate; an ester of (meth)acrylic acid with an alicyclic alcohol (alicyclic hydrocarbon group-containing (meth)acrylate), such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, or dicyclopentanyl (meth)acrylate; or a (meth)acrylate having a cyclic structure, such as an aryl (meth)acrylate, such as phenyl (meth)acrylate or benzyl (meth)acrylate, from the viewpoint of further improving the adhesiveness of the resulting pressure-sensitive adhesive tape. In addition to the above-mentioned (meth)acrylate monomer, a functional group-containing monomer can be used as a constituent monomer component of the acrylic oligomer. Suitable examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle), such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers, such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers, such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers, such as AA and MAA; and hydroxy group-containing monomers, such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used alone or in combination of two or more. Among these, carboxy group-containing monomers are preferred, with AA being particularly preferred. For example, using a carboxy group-containing monomer as the functional group-containing monomer can improve adhesive strength to highly polar adherends. Furthermore, including a structural unit derived from the monomer having the crosslinkable functional group as a constituent monomer of the acrylic oligomer can further improve the adhesive strength of the resulting pressure-sensitive adhesive composition.

[0064] The acrylic oligomer can be synthesized, for example, by the same method as that for the acrylic copolymer described above. Alternatively, a commercially available acrylic tackifier resin may be used.

[0065] The tackifier resin preferably contains a tackifier resin having a softening point of 80°C or higher and 170°C or lower. By containing a tackifier resin having a softening point of 80°C or higher and 170°C or lower, it becomes easier to adjust the glass transition temperature of the PSA layer to within the above-mentioned range, and the obtained PSA tape has better heat resistance. The softening point of the tackifier resin is more preferably 90°C in lower limit, more preferably 160°C in upper limit, even more preferably 100°C in lower limit, and even more preferably 150°C in upper limit. Examples of the softening point range of the tackifier resin include 80°C in lower limit and 170°C in lower limit, respectively, 80°C in lower limit and 160°C in lower limit, 80°C in lower limit and 150°C in lower limit, respectively, 90°C in lower limit and 170°C in lower limit, 90°C in lower limit and 160°C in lower limit, 90°C in lower limit and 150°C in lower limit, respectively, 100°C in lower limit and 150°C in lower limit. In this specification, the "softening point" refers to a softening point measured by a method in accordance with JIS K 2207 (ring and ball method).

[0066] The content of the tackifier resin is not particularly limited, but a preferred lower limit is 10 parts by mass and a preferred upper limit is 60 parts by mass per 100 parts by mass of the acrylic copolymer. If the content of the tackifier resin is within the above range, the adhesive strength of the resulting pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition against rough surfaces will be higher. The lower limit of the content of the tackifier resin is more preferably 15 parts by mass, even more preferably 20 parts by mass, even more preferably 30 parts by mass, more preferably 50 parts by mass, even more preferably 40 parts by mass, and even more preferably 35 parts by mass. The content range of the tackifying resin is, for example, 10 parts by mass or more and 50 parts by mass or less, 10 parts by mass or more and 40 parts by mass or less, 10 parts by mass or more and 35 parts by mass or less, 15 parts by mass or more and 60 parts by mass or less, 15 parts by mass or more and 50 parts by mass or less, 15 parts by mass or more and 35 parts by mass or less. , 20 parts by mass to 60 parts by mass, 20 parts by mass to 50 parts by mass, 20 parts by mass to 40 parts by mass, 20 parts by mass to 35 parts by mass, 30 parts by mass to 60 parts by mass, 30 parts by mass to 50 parts by mass, 30 parts by mass to 40 parts by mass, 30 parts by mass to 35 parts by mass, etc.

[0067] The pressure-sensitive adhesive layer may contain a black pigment. By containing the black pigment in the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition can be imparted with light-blocking properties, and when a pressure-sensitive adhesive tape using the obtained pressure-sensitive adhesive composition is used to fix electronic components such as displays, light leakage from the adhesive surface can be further suppressed. Examples of the black pigment include black fillers. Specific examples of the black filler include carbon black and titanium black.

[0068] The content of the black pigment is preferably 0.1 parts by mass or more and 5.0 parts by mass or less relative to 100 parts by mass of the acrylic copolymer. Having the content of the black pigment within this range can further enhance light-blocking properties. The content of the black pigment is more preferably 0.5 parts by mass or more and more preferably 3.0 parts by mass or less. Examples of the range of the content of the black pigment include 0.1 parts by mass or more and 3.0 parts by mass or less, 0.5 parts by mass or more and 5.0 parts by mass or less, and 0.5 parts by mass or more and 3.0 parts by mass or less.

[0069] The pressure-sensitive adhesive composition of the present invention may contain additives such as a silane coupling agent, a plasticizer, a softener, a filler, a dye, etc., as required.

[0070] The PSA composition of the present invention preferably has a bio-derived carbon content of 10% by mass or more. A bio-derived carbon content of 10% by mass or more is an indicator of a "bio-based product." A bio-derived carbon content of 10% by mass or more is preferred from the perspective of conserving petroleum resources and reducing carbon dioxide emissions. A more preferred lower limit of the bio-derived carbon content is 40% by mass, and an even more preferred lower limit is 60% by mass. The upper limit of the bio-derived carbon content is not particularly limited and may be 100% by mass. Examples of the range of the bio-derived carbon content include 10% by mass or more and 100% by mass or less, 40% by mass or more and 100% by mass or less, and 60% by mass or more and 100% by mass or less. Note that while bio-derived carbon contains a certain proportion of the radioactive isotope (C-14), petroleum-derived carbon contains almost no C-14. Therefore, the bio-derived carbon content can be calculated by measuring the concentration of C-14 contained in the PSA composition. Specifically, it can be measured in accordance with ASTM D6866-22, a standard used in many bioplastic industries.

[0071] The method for producing the pressure-sensitive adhesive composition of the present invention is not particularly limited. For example, the pressure-sensitive adhesive composition of the present invention can be obtained by synthesizing an acrylic copolymer by the above-mentioned method, and mixing, as necessary, additives such as the above-mentioned crosslinking agent and the above-mentioned tackifying resin together with a solvent.

[0072] By using the pressure-sensitive adhesive composition of the present invention in the pressure-sensitive adhesive layer, both high shear adhesive strength and light pressure-sensitive adhesiveness can be achieved. A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing such a pressure-sensitive adhesive composition of the present invention also constitutes one aspect of the present invention. The details of the composition of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the present invention are the same as those of the pressure-sensitive adhesive composition of the present invention.

[0073] The gel fraction of the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 10% by mass and a preferred upper limit is 70% by mass. When the gel fraction is within the above range, the pressure-sensitive adhesive layer's conformability to irregularities and cohesive strength are both increased, resulting in higher adhesive strength of the pressure-sensitive adhesive tape against rough surfaces. A more preferred lower limit of the gel fraction is 15% by mass and a more preferred upper limit is 60% by mass. Examples of gel fraction ranges for the pressure-sensitive adhesive layer include 10% by mass to 70% by mass, 10% by mass to 60% by mass, 15% by mass to 70% by mass, and 15% by mass to 60% by mass. The gel fraction is measured as follows: First, a pressure-sensitive adhesive tape is cut into a 20 mm x 40 mm planar rectangular shape to prepare a test piece. The test piece is immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate, and dried at 110°C for 1 hour. The mass of the dried test piece is measured, and the gel fraction is calculated using the following formula (1): The test piece was not laminated with a release film to protect the pressure-sensitive adhesive layer. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (1) (W ０ : Mass of substrate (PET film), W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0074] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 3 μm and a preferred upper limit is 300 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, high shear adhesive strength and light pressure-sensitive adhesiveness can be simultaneously achieved at a higher level. A more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm, and an even more preferred lower limit is 10 μm. A more preferred upper limit of the thickness of the pressure-sensitive adhesive layer is 200 μm, and an even more preferred upper limit is 100 μm. Examples of thickness ranges for the pressure-sensitive adhesive layer include 3 μm to 300 μm, 3 μm to 200 μm, 3 μm to 100 μm, 5 μm to 300 μm, 5 μm to 200 μm, 5 μm to 100 μm, 10 μm to 300 μm, 10 μm to 200 μm, and 10 μm to 100 μm.

[0075] The pressure-sensitive adhesive tape of the present invention may be a non-supported tape without a substrate, a single-sided pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer on one side of the substrate, or a double-sided pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer on both sides of the substrate. The substrate is not particularly limited, and conventionally known substrates can be used. However, to increase the content of biological materials in the entire pressure-sensitive adhesive tape, it is preferable to use a biological substrate. Examples of the biological substrate include films and nonwoven fabrics made of plant-derived polyesters (PES), such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). Other examples include films and nonwoven fabrics made of plant-derived polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetyl cellulose (TAC), cellulose, polyamide (PA), and the like.

[0076] From the viewpoint of substrate strength, the substrate is preferably a film made of PES or a film made of PA. Furthermore, from the viewpoint of heat resistance and oil resistance, a film made of PA is preferable. Examples of the constituent material of the PA film include nylon 11, nylon 1010, nylon 610, nylon 510, nylon 410, etc., which are made from castor oil, and nylon 56, etc., which are made from cellulose.

[0077] Furthermore, from the perspective of reducing the use of new petroleum resources and reducing carbon dioxide emissions to reduce the environmental impact, substrates made from recycled resources may be used. Examples of resource recycling methods include collecting waste materials such as packaging containers, home appliances, automobiles, construction materials, and food, as well as waste generated during manufacturing processes, and then cleaning, decontaminating, or decomposing the extracted materials by heating or fermentation to reuse them as raw materials. Examples of substrates made from recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., which are made from recycled plastics that have been re-resinized. Furthermore, the collected waste materials may be burned and used as thermal energy for the production of substrates and their raw materials, or the oils and fats contained in the collected waste materials may be mixed with petroleum, fractionated, and purified, and then used as raw materials.

[0078] The substrate may be a foam substrate from the viewpoint of improving compression characteristics. The foam substrate is preferably a foam substrate made of PE, PP and / or PU, and more preferably a foam substrate made of PE from the viewpoint of achieving a high degree of both flexibility and strength. Examples of the constituent material of the foam substrate made of PE include PE made from sugarcane.

[0079] The method for producing the foam base material is not particularly limited, but a preferred method is, for example, to prepare a foamable resin composition containing a PE resin containing PE derived from sugarcane and a foaming agent, and then foam the foaming agent when extruding the foamable resin composition into a sheet using an extruder, and optionally crosslink the resulting polyolefin foam.

[0080] The thickness of the foam substrate is not particularly limited, but a preferred lower limit is 50 μm and a preferred upper limit is 1000 μm. When the thickness of the foam substrate is within this range, it can exhibit high impact resistance while exhibiting high flexibility that allows it to be adhered to the shape of the adherend. A more preferred upper limit of the thickness of the foam substrate is 300 μm. Examples of the thickness range of the foam substrate include 50 μm to 1000 μm, and 50 μm to 300 μm.

[0081] The pressure-sensitive adhesive tape of the present invention has a total thickness (total thickness of the substrate and the pressure-sensitive adhesive layer) of preferably 3 μm as a lower limit and 1200 μm as an upper limit. If the total thickness of the pressure-sensitive adhesive tape is within the above range, the adhesive strength of the pressure-sensitive adhesive tape to rough surfaces will be higher. A more preferred upper limit of the total thickness of the pressure-sensitive adhesive tape of the present invention is 500 μm. Examples of the range of the total thickness of the pressure-sensitive adhesive tape include 3 μm or more and 1200 μm or less, and 3 μm or more and 500 μm or less.

[0082] The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited, and it can be produced by a conventionally known production method. For example, in the case of a double-sided pressure-sensitive adhesive tape having a substrate, the following method can be used. First, a solution of pressure-sensitive adhesive A is prepared by adding a solvent to the acrylic copolymer and, if necessary, the crosslinking agent and the tackifying resin, etc., and this solution of pressure-sensitive adhesive A is applied to the surface of the substrate. The solvent in the solution is completely dried and removed to form a pressure-sensitive adhesive layer A. Next, a release film is superimposed on the formed pressure-sensitive adhesive layer A with its release-treated surface facing the pressure-sensitive adhesive layer A. Next, a release film separate from the above release film is prepared, and a solution of pressure-sensitive adhesive B prepared in the same manner as above is applied to the release-treated surface of this release film. The solvent in the solution is completely dried and removed to produce a laminate film in which pressure-sensitive adhesive layer B is formed on the surface of the release film. The obtained laminate film is superimposed on the back surface of the substrate on which pressure-sensitive adhesive layer A has been formed, with the pressure-sensitive adhesive layer B facing the back surface of the substrate, to produce a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided adhesive tape can be obtained which has adhesive layers on both sides of the substrate and in which the surfaces of the adhesive layers are covered with release films.

[0083] Alternatively, two sets of laminate films may be prepared in a similar manner, and these laminate films may be superimposed on each of both surfaces of a substrate with the pressure-sensitive adhesive layers of the laminate films facing the substrate to prepare a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of the substrate and in which the surfaces of the pressure-sensitive adhesive layers are covered with release films.

[0084] Alternatively, a solution of adhesive prepared in a similar manner may be applied to the release-treated surface of a release film, the solvent in the solution is completely dried to remove it, forming an adhesive layer, and then this adhesive layer may be laminated on the release-treated surface of the release film to obtain a non-supported tape having no substrate.

[0085] The use of the pressure-sensitive adhesive tape of the present invention is not particularly limited, but since it can achieve both high shear adhesive strength and light pressure-sensitive adhesiveness, it is preferably used for fixing electronic equipment components or in-vehicle equipment components. Specifically, the pressure-sensitive adhesive tape of the present invention can be suitably used for adhesive fixing of electronic equipment components in large portable electronic devices, adhesive fixing of in-vehicle equipment components (e.g., in-vehicle panels), etc.

[0086] The present invention also includes a method for fixing an electronic device component or an in-vehicle device component using the pressure-sensitive adhesive tape of the present invention. The present invention also includes a method for manufacturing an electronic device or an in-vehicle device, which includes a step of fixing an electronic device component or an in-vehicle device component using the pressure-sensitive adhesive tape of the present invention. These methods enable the electronic device component or the in-vehicle device component to be firmly fixed even when attached with a light pressure.

[0087] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that can be used as a material for a pressure-sensitive adhesive tape that can achieve both high shear adhesive strength and light pressure-sensitive adhesiveness. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition, a method for fixing electronic equipment components or in-vehicle equipment components using the pressure-sensitive adhesive tape, and a method for manufacturing electronic equipment or in-vehicle equipment.

[0088] The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0089] <1-Methylheptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was alkali-fused to obtain a mixture containing sepacic acid and 1-methylheptyl alcohol. Next, sepacic acid was separated from the obtained mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. 1-Methylheptyl acrylate containing bio-derived carbon was prepared by esterifying the obtained 1-methylheptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0090] <n-heptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was cracked to obtain a mixture containing undecylenic acid and n-heptyl alcohol. Next, undecylenic acid was separated from the obtained mixture by distillation to obtain n-heptyl alcohol containing bio-derived carbon. The obtained n-heptyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-heptyl acrylate containing bio-derived carbon.

[0091] <Isobornyl acrylate containing bio-derived carbon> Camphene containing bio-derived carbon was obtained by isomerizing pinene extracted from pine resin. Camphene containing bio-derived carbon was reacted with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare isobornyl acrylate containing bio-derived carbon.

[0092] <Isobornyl methacrylate containing bio-derived carbon> Camphene containing bio-derived carbon was obtained by isomerizing pinene extracted from pine resin. Camphene containing bio-derived carbon was reacted with methacrylic acid (manufactured by Mitsubishi Chemical Corporation) to prepare isobornyl methacrylate containing bio-derived carbon.

[0093] <2-hydroxyethyl acrylate containing bio-derived carbon> Ethanol containing bio-derived carbon was obtained by fermenting sugar contained in sugarcane. The obtained ethanol containing bio-derived carbon was dehydrated to obtain ethylene, which was then oxidized to obtain ethylene oxide, to which water was added to obtain ethylene glycol containing bio-derived carbon. The obtained ethylene glycol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare 2-hydroxyethyl acrylate containing bio-derived carbon.

[0094] <n-Hexyl acrylate containing bio-derived carbon> Linoleic acid derived from castor oil was converted to linoleic acid hydroperoxide using lipoxygenase, and then a mixture containing n-hexylaldehyde was obtained using isomerase. The resulting mixture was distilled to obtain n-hexylaldehyde containing bio-derived carbon. The obtained n-hexylaldehyde containing bio-derived carbon was then hydrogenated to obtain n-hexyl alcohol containing bio-derived carbon. The obtained n-hexyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-hexyl acrylate containing bio-derived carbon.

[0095] <Bio-derived carbon-free monomers> Butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) 2-Methoxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Methyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Ethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Dimethylacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.) Cyclohexyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.)

[0096] <Tackifying resin> Rosin ester resin (manufactured by Arakawa Chemical Industries, Ltd., "KE359", softening temperature: 100°C) Terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., "YS Polystar G150", softening temperature: 145°C to 155°C)

[0097] <Crosslinking agent> Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, "Coronate L-45") Epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., "Tetrad X")

[0098] <Pigment> Carbon black (Toyo Color Co., Ltd., "Multilac A903 Black")

[0099] <Substrate> PET (polyethylene terephthalate film, manufactured by Futamura Chemical Co., Ltd., "FE2002", thickness 50 μm) PE foam (polyethylene foam, manufactured by Sekisui Chemical Co., Ltd., "WL02", thickness 150 μm) Nonwoven fabric (manufactured by Toray International Inc., "G2260-1S", thickness 610 μm) PEN (polyethylene naphthalate film, manufactured by Toyobo Co., Ltd., "Teonex Q5100", thickness 12 μm) PI (polyimide film, manufactured by PI Advanced Materials, "GF", thickness 12 μm) Colored substrate (manufactured by Toray Industries, Inc., "Lumirror #25X30", thickness 23 μm)

[0100] Example 1 (1) Production of Acrylic Copolymer Ethyl acetate was added as a polymerization solvent to a reaction vessel, and nitrogen was bubbled through. The reaction vessel was then heated while nitrogen was flowing in to initiate reflux. A polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10 times with ethyl acetate was added to the reaction vessel. 33.9 parts by mass of 1-methylheptyl acrylate, 1 part by mass of n-heptyl acrylate, 5 parts by mass of acrylic acid, and 0.1 parts by mass of 2-hydroxyethyl acrylate were added dropwise over a period of 2 hours. After completion of the dropwise addition, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10 times with ethyl acetate was added again to the reaction vessel, and a polymerization reaction was carried out for 4 hours to obtain an acrylic copolymer-containing solution. The ratio (mass%) of structural units derived from 1-methylheptyl acrylate to structural units derived from n-heptyl acrylate in the resulting acrylic copolymer was calculated to be 33.9.

[0101] The obtained acrylic copolymer was diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. This measurement sample was supplied to a gel permeation chromatograph (Waters, 2690 Separations Module) and subjected to GPC measurement under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C., and the polystyrene-equivalent molecular weight of the acrylic copolymer was measured to determine the weight average molecular weight.

[0102] (2) Preparation of Pressure-Sensitive Adhesive Tape An isocyanate-based crosslinking agent was added to the obtained acrylic copolymer-containing solution in an amount of 0.5 parts by mass of solids per 100 parts by mass of the acrylic copolymer to prepare a pressure-sensitive adhesive solution. This pressure-sensitive adhesive solution was applied to the release-treated surface of a 75 μm-thick release-treated PET film so that the thickness after drying would be 50 μm, and then dried at 110° C. for 5 minutes to form a pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was then placed on the release-treated surface of a 75 μm-thick release-treated PET film and aged at 40° C. for 48 hours to obtain a pressure-sensitive adhesive tape (non-support type).

[0103] (3) Measurement of gel fraction of adhesive layer The release film on one side of the obtained adhesive tape was peeled off, and the tape was attached to a 23 μm thick PET film (FE2002, manufactured by Futamura Chemical Co., Ltd.), and cut into a 20 mm x 40 mm flat rectangular shape. The release film on the other side of the adhesive tape was then peeled off to prepare a test piece, and its mass was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate, and dried at 110°C for 1 hour. The mass of the dried test piece was measured, and the gel fraction was calculated using the following formula (1): Gel fraction (mass%) = 100 x (W ２ -W ０ ) / (W １ -W ０ ) (1) (W ０ : Mass of substrate (PET film), W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0104] (Examples 2 to 40, Comparative Examples 1 to 7) Pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the types and blending amounts of the acrylic monomers constituting the acrylic copolymer, and the types and blending amounts of the tackifier resin, crosslinking agent, and additives were changed as shown in Tables 1 to 5. In Examples 28 to 31, pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the types and blending amounts of each component of the pressure-sensitive adhesive composition were changed as shown in Table 3, and further the amount of polymerization initiator added, etc. was changed as appropriate to adjust the weight average molecular weight.

[0105] Example 41 An acrylic copolymer-containing solution was obtained in the same manner as in Example 1, except that the types and blending amounts of the acrylic monomers constituting the acrylic copolymer, and the types and blending amounts of the tackifier resin, crosslinker, and additives were as shown in Table 4. For the obtained acrylic copolymer, the weight average molecular weight and the proportion (mass%) of structural units derived from 1-methylheptyl acrylate / proportion (mass%) of structural units derived from n-heptyl acrylate in the obtained acrylic copolymer were measured and calculated in the same manner as in Example 1. Next, two pressure-sensitive adhesive layers were formed in the same manner as in Example 1. The surfaces of the obtained pressure-sensitive adhesive layers not laminated with the release films were bonded to both sides of a 50 μm-thick PET substrate, respectively, to obtain a support-type pressure-sensitive adhesive tape.

[0106] Examples 42 to 46 Pressure-sensitive adhesive tapes were obtained in the same manner as in Example 41, except that the type of substrate was changed as shown in Table 4.

[0107] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated by the following methods. The results are shown in Tables 1 to 5.

[0108] (Evaluation of shear adhesive strength when lightly pressed) The obtained pressure-sensitive adhesive tape was cut into a flat square shape of 20 mm wide x 20 mm long, and one side (first side) of the pressure-sensitive adhesive tape was placed on the surface of a stainless steel plate (SUS304 plate washed with ethanol and then wiped dry), and a 0.5 kg rubber roller was moved back and forth once at a speed of 300 mm / min to press the tape. Further, in an environment of 23°C, the other side (second side) of the pressure-sensitive adhesive tape was pressed against the surface of a stainless steel plate (SUS304 plate washed with ethanol and then wiped dry) by moving a 0.5 kg rubber roller back and forth once at a speed of 300 mm / min, and the tape was left to stand at 23°C and 50% RH for 24 hours to obtain a test sample. For the obtained test samples, a tensile tester (Shimadzu Corporation, "Universal Testing Machine Autograph AGS-X") was used to measure the shear adhesive strength (MPa) of the first surface of the adhesive tape to SUS in an atmosphere of 23°C and 50% RH by peeling the first surface of the adhesive tape at a rate of 10 mm / min in the direction of shear stress. This was taken as the shear adhesive strength when lightly pressed. The obtained shear adhesive strength when lightly pressed was evaluated according to the following criteria: ☆: 1.8 MPa or more ◎: 1.5 MPa or more but less than 1.8 MPa ○: 1.2 MPa or more but less than 1.5 MPa △: 1 MPa or more but less than 1.2 MPa ×: Less than 1 MPa

[0109] (Evaluation of shear adhesive strength during normal compression) The shear adhesive strength was measured in the same manner as in the evaluation of shear adhesive strength during light compression, except that the weight of the rubber roller used to compress the adhesive tape during preparation of the test sample was set to 2.0 kg. This was taken as the shear adhesive strength during normal compression (shear adhesive strength at the compression strength of a conventional adhesive tape). The obtained shear adhesive strength during normal compression was evaluated according to the following criteria: ☆: 2.3 MPa or more ◎: 2 MPa or more and less than 2.3 MPa ○: 1.7 MPa or more and less than 2 MPa △: 1.5 MPa or more and less than 1.7 MPa ×: less than 1.5 MPa

[0110]

[0111]

[0112]

[0113]

[0114]

[0115] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that can be used as a material for a pressure-sensitive adhesive tape that can achieve both high shear adhesive strength and light pressure-sensitive adhesiveness. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition, a method for fixing electronic equipment components or in-vehicle equipment components using the pressure-sensitive adhesive tape, and a method for manufacturing electronic equipment or in-vehicle equipment.

Claims

1. A pressure-sensitive adhesive composition containing an acrylic copolymer containing more than 30% by mass of structural units derived from 1-methylheptyl (meth)acrylate and 0.01% by mass to 50% by mass of structural units derived from n-heptyl (meth)acrylate.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer has a ratio of structural units derived from 1-methylheptyl (meth)acrylate to structural units derived from n-heptyl (meth)acrylate (ratio (mass%) of structural units derived from 1-methylheptyl (meth)acrylate / ratio (mass%) of structural units derived from n-heptyl (meth)acrylate) of 1 or more.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the acrylic copolymer contains 50% by mass or more of structural units derived from 1-methylheptyl (meth)acrylate.

4. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the acrylic copolymer contains more than 30% by mass and not more than 50% by mass of structural units derived from 1-methylheptyl (meth)acrylate.

5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the acrylic copolymer contains 50 mass% or more of structural units derived from a (meth)acrylic acid alkyl ester, including structural units derived from the 1-methylheptyl (meth)acrylate and structural units derived from the n-heptyl (meth)acrylate.

6. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the acrylic copolymer further contains a structural unit derived from a monomer having a glass transition temperature of -35°C or higher.

7. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the acrylic copolymer further contains a structural unit derived from a monomer having no crosslinkable functional group and having a glass transition temperature of 0°C or higher.

8. The pressure-sensitive adhesive composition according to claim 7, wherein the content of the structural units derived from the monomer having a glass transition temperature of 0°C or higher is 0.1% by mass or more and 70% by mass or less.

9. The pressure-sensitive adhesive composition according to any one of claims 1 to 8, wherein the acrylic copolymer further contains a structural unit derived from a monomer having a crosslinkable functional group.

10. The pressure-sensitive adhesive composition according to claim 9, wherein the acrylic copolymer contains 0.01% by mass or more and 20% by mass or less of a structural unit derived from the monomer having a crosslinkable functional group.

11. The pressure-sensitive adhesive composition according to claim 9 or 10, wherein the monomer having a crosslinkable functional group contains a monomer having a hydroxyl group.

12. The pressure-sensitive adhesive composition according to any one of claims 1 to 11, wherein the acrylic copolymer comprises at least one structural unit selected from the group consisting of structural units derived from a monomer having a cyclic ether structure other than an epoxy structure or an oxetane structure, and at least one structural unit selected from the group consisting of structural units derived from a monomer having an acyclic ether structure.

13. The pressure-sensitive adhesive composition according to claim 12, wherein the content of at least one type of structural unit selected from the group consisting of structural units derived from a monomer having a cyclic ether structure other than an epoxy structure or an oxetane structure, and structural units derived from a monomer having an acyclic ether structure is 0.01% by mass or more and 50% by mass or less.

14. The pressure-sensitive adhesive composition according to any one of claims 1 to 13, wherein the acrylic copolymer has a weight-average molecular weight of 200,000 or more and 2,000,000 or less.

15. The pressure-sensitive adhesive composition according to any one of claims 1 to 14, further comprising a crosslinking agent.

16. The pressure-sensitive adhesive composition according to claim 15, wherein the crosslinking agent contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

17. The pressure-sensitive adhesive composition according to claim 16, wherein the crosslinking agent comprises an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

18. The pressure-sensitive adhesive composition according to any one of claims 1 to 17, further comprising a tackifying resin.

19. The pressure-sensitive adhesive composition according to claim 18, wherein the tackifying resin contains at least one selected from the group consisting of rosin ester-based tackifying resins, terpene-based tackifying resins, and acrylic tackifying resins made from (meth)acrylic compounds.

20. The pressure-sensitive adhesive composition according to claim 19, wherein the tackifying resin contains a rosin ester-based tackifying resin and a terpene-based tackifying resin.

21. The pressure-sensitive adhesive composition according to any one of claims 1 to 20, which does not contain a surfactant.

22. The pressure-sensitive adhesive composition according to any one of claims 1 to 21, further comprising a black pigment.

23. The adhesive composition according to any one of claims 1 to 22, wherein the content of bio-derived carbon is 10% by mass or more.

24. An adhesive tape having an adhesive layer containing the adhesive composition according to any one of claims 1 to 23.

25. The adhesive tape according to claim 24, wherein the adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less.

26. The adhesive tape according to claim 25, which is used to fasten electronic equipment parts or in-vehicle equipment parts.

27. A method for fixing electronic equipment components or vehicle-mounted equipment components, comprising using the adhesive tape of claim 24 to fix electronic equipment components or vehicle-mounted equipment components.

28. A method for manufacturing an electronic device or an in-vehicle device, comprising the step of fixing an electronic device part or an in-vehicle device part using the adhesive tape according to claim 24.

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