Adhesive tape and electronic device

Abstract

The purpose of the present invention is to provide an adhesive tape that achieves both excellent impact absorption and excellent thermal stability and to provide an electronic device that includes the adhesive tape.　The present invention is an adhesive tape having an adhesive layer. The adhesive layer is configured from a continuous phase and a dispersed phase. The continuous phase contains an acrylic copolymer having a constituent unit derived from an acrylic acid ester. The dispersed layer contains an aromatic block copolymer (X) having at least two blocks having a constituent unit derived from a vinyl aromatic compound and at least one of a block having a constituent unit derived from a conjugated diene compound and a hydrogenated block having a constituent unit derived from a conjugated diene compound. In a heating test in which the dispersed phase is heated at 150°C for 2 days, the average area of the dispersed phase in a cross-section in the thickness direction before the heating test is 10 μm2 or less, and the area change rate of the dispersed phase in a cross-section in the thickness direction before and after the heating test is 2.0 or less.

Description

Adhesive tape, and electronic devices

[0001] This invention relates to an adhesive tape. Furthermore, this invention relates to an electronic device including the adhesive tape.

[0002] Adhesive tapes having an adhesive layer containing an adhesive have been widely used for fixing components in various industrial applications such as electronic equipment, vehicles, housing, and building materials (for example, Patent Documents 1 to 3). Specifically, for example, adhesive tapes are used to adhere a cover panel for protecting the surface of portable electronic devices to a touch panel module or display panel module, or to adhere a touch panel module to a display panel module.

[0003] Japanese Patent Publication No. 2015-052050, Japanese Patent Publication No. 2015-021067, Japanese Patent Publication No. 2015-120876

[0004] Adhesive tapes used to secure panels to the casings of smartphones, tablets, and other devices require adhesive tapes with excellent shock absorption properties to prevent damage to components from impact during drops. Furthermore, with the recent trend towards thinner electronic devices, the demand for adhesive tapes with superior shock absorption is increasing even further.

[0005] Conventionally, mixing rubber with resin is known as a method to improve the shock absorption properties of resin. However, when rubber is mixed with adhesive tape to further enhance its shock absorption, the compatibility between acrylic copolymers, which are widely used as adhesives, and rubber is poor. Furthermore, even if acrylic copolymers and rubber are compatible, the resulting adhesive tends to have poor thermal stability. Therefore, it is difficult to obtain an adhesive tape that exhibits excellent shock absorption at both room temperature and high-temperature environments, achieving both excellent shock absorption and excellent thermal stability.

[0006] The present invention aims to provide an adhesive tape that achieves both excellent shock absorption and excellent thermal stability. Furthermore, the present invention aims to provide an electronic device containing the adhesive tape.

[0007] Disclosure 1 is an adhesive tape having an adhesive layer, wherein the adhesive layer is composed of a continuous phase and a dispersed phase, the continuous phase includes an acrylic copolymer having structural units derived from an acrylic acid ester, and the dispersed phase includes an aromatic block copolymer (X) having at least two blocks having structural units derived from a vinyl aromatic compound, and at least one of a block having structural units derived from a conjugated diene compound and a hydrogenated form of a block having structural units derived from a conjugated diene compound, and when the dispersed phase is heated at 150°C for two days, the average area of ​​the cross-section in the thickness direction of the dispersed phase before the heating test is 10 μm ２ The following is an adhesive tape wherein the area change rate in the cross-section in the thickness direction before and after the heating test of the dispersed phase is 2.0 or less. Disclosure 2 is an adhesive tape wherein the dispersed phase has an average area of ​​1.00 μm in the cross-section in the thickness direction. ２The following is an adhesive tape according to Disclosure 1. Disclosure 3 is an adhesive tape according to Disclosure 1 or 2, wherein the dispersed phase has an aspect ratio of 1.0 or more and 2.0 or less in the cross-section in the thickness direction. Disclosure 4 is an adhesive tape according to Disclosure 1, 2 or 3, wherein the acrylic copolymer has constituent units derived from monomers having crosslinkable functional groups. Disclosure 5 is an adhesive tape according to Disclosure 1, 2, 3 or 4, wherein the acrylic copolymer has constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends. Disclosure 6 is an adhesive tape according to Disclosure 5, wherein the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends in the acrylic copolymer is 5% by mass or more and 50% by mass or less. Disclosure 7 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5 or 6, wherein the acrylic copolymer has blocks containing at least one or more constituent units derived from (meth)acrylate alkyl esters and blocks containing at least one or more constituent units derived from vinyl aromatic compounds. Disclosure 8 is an adhesive tape of Disclosure 7, wherein the acrylic copolymer has a content of 2.5% by mass or more and 20% by mass or less of constituent units derived from the vinyl aromatic compound. Disclosure 9 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the acrylic copolymer has constituent units derived from isobornyl (meth)acrylate. Disclosure 10 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the acrylic copolymer has a weight-average molecular weight of 700,000 or more and 1,500,000 or less. Disclosure 11 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the content of the aromatic block copolymer (X) per 100 parts by mass of the acrylic copolymer is 60 parts by mass or less. Disclosure 12 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the adhesive layer contains a coloring agent. Disclosure 13 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the adhesive layer contains a tackifying resin. Disclosure 14 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the adhesive layer does not contain a tackifying resin.Disclosure 15 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the adhesive layer has a structure derived from a crosslinking agent. Disclosure 16 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the adhesive layer has a shear storage modulus of 0.30 MPa or more at 23°C as measured in a dynamic viscoelastic measurement at a measurement frequency of 1 Hz. Disclosure 17 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the adhesive layer has a shear storage modulus of 0.02 MPa or more at 65°C as measured in a dynamic viscoelastic measurement at a measurement frequency of 1 Hz. Disclosure 18 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the adhesive layer has a loss tangent of 0.5 or more at 23°C as measured in a dynamic viscoelasticity measurement at a measurement frequency of 100 Hz. Disclosure 19 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, wherein the adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less. Disclosure 20 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, wherein the adhesive layer has a foamed structure. Disclosure 21 states that the adhesive layer has a deemed density of 0.59 g / cm³. ３ 1.15g / cm or more ３The following is the adhesive tape of the present disclosure 20. The present disclosure 22 is an adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or 21 without a base material. The present disclosure 23 is an adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or 21 with a base material. The present disclosure 24 is an adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 or 23 used for fixing electronic device components or vehicle-mounted components. The present disclosure 25 is an electronic device including the adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24. Hereinafter, the present invention will be described in detail. Hereinafter, an embodiment of the present invention or one thereof will be described as "this embodiment".

[0008] The inventors assumed that an adhesive tape having an adhesive layer has a structure composed of a continuous phase containing an acrylic copolymer and a dispersed phase containing an aromatic block copolymer having a specific structure in the adhesive layer. Then, for an adhesive tape having such an adhesive layer, a heating test under specific conditions was conducted, and it was considered to make the average area in the cross section in the thickness direction of the dispersed phase before the heating test and the change rate of the average area in the cross section in the thickness direction of the dispersed phase before and after the heating test below specific values. As a result, it was found that an adhesive tape having both excellent shock absorption and excellent thermal stability can be obtained, and the present invention was completed.

[0009] The adhesive tape of this embodiment has an adhesive layer. The adhesive layer is composed of a continuous phase and a dispersed phase. The continuous phase includes an acrylic copolymer (hereinafter sometimes simply referred to as "acrylic copolymer") having constituent units derived from (meth)acrylic acid esters, and the dispersed phase includes an aromatic block copolymer (X) having at least two blocks having constituent units derived from vinyl aromatic compounds, and at least one of a block having constituent units derived from a conjugated diene compound and a hydrogenated form of said block. The adhesive tape of this embodiment has a structure in which the adhesive layer is composed of the continuous phase and the dispersed phase, and the average area of ​​the dispersed phase before the heating test and the rate of change of area of ​​the dispersed phase before and after the heating test, described later, satisfy the range described later, thereby achieving both excellent shock absorption and excellent thermal stability. Although this is an optional feature of the adhesive tape of this embodiment, the adhesive tape of this embodiment has excellent shock absorption and tends to have sufficient adhesive strength for bonding parts and materials. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0010] Furthermore, in the adhesive tape of this embodiment, the fact that the adhesive layer has a structure composed of a continuous phase and a dispersed phase can be confirmed by cutting the adhesive layer into a plane parallel to the thickness direction using a cryomicrotome (e.g., Leica) to prepare a section with a thickness of 1.0 μm. Next, after placing the prepared section on glass, the section is stained with ruthenium tetroxide aqueous solution, and then images are taken at a magnification of 1500x using a simple SEM (e.g., Hitachi High-Tech "TM4000Plus"). In addition, the fact that the continuous phase contains an acrylic copolymer and the dispersed phase contains the above-mentioned aromatic block copolymer (X) can be confirmed by nano-IR measurement. Note that a method of confirmation when confirmation by nano-IR measurement is difficult is shown below. First, the fact that the adhesive layer contains an acrylic copolymer and an aromatic block copolymer (X) can be confirmed. １It is confirmed by means of 1H-NMR, thermal decomposition GC / MS, etc. Further, the ruthenium-stained adhesive layer is observed using a simple SEM, and it is confirmed that the continuous phase is more strongly stained than the dispersed phase, or the osmium-stained adhesive layer is observed using a simple SEM, and it is confirmed that the dispersed phase is more strongly stained than the continuous phase, whereby it can be confirmed that the continuous phase contains an acrylic copolymer and the dispersed phase contains the aromatic block copolymer (X).

[0011] When conducting a heating test in which the above-mentioned dispersed phase is heated at 150°C for 2 days, the upper limit of the average area in the cross-section in the thickness direction of the dispersed phase before the heating test (hereinafter, may also be simply referred to as "the average area of the dispersed phase before the heating test") is 10 μm ２ and the upper limit of the area change rate in the cross-section in the thickness direction of the dispersed phase before and after the heating test (hereinafter, may also be simply referred to as "the area change rate of the dispersed phase before and after the heating test") is 2.0. By the average area of the dispersed phase before the heating test and the area change rate of the dispersed phase before and after the heating test satisfying the above ranges, the adhesive tape of the present embodiment having an adhesive layer having a structure composed of the continuous phase and the dispersed phase becomes an adhesive tape that achieves both excellent shock absorption and excellent thermal stability.

[0012] The upper limit of the average area of the dispersed phase before the heating test is 10 μm ２ is. When the average area of the dispersed phase before the heating test is 10 μm ２ or less, when the adhesive layer has a structure composed of the continuous phase and the dispersed phase, the adhesive tape of the present embodiment is excellent in shock absorption. At this time, since the average area of the dispersed phase before the heating test is small and the decrease in the adhesive force exhibited by the continuous phase can be suppressed, the adhesive tape of the present embodiment can maintain the adhesive force required for bonding parts and members. The preferable upper limit of the average area of the dispersed phase before the heating test is 5.00 μm ２ more preferably the upper limit is 3.00 μm ２ even more preferably the upper limit is 1.00 μm ２ even more preferably the upper limit is 0.70 μm ２ particularly preferably the upper limit is 0.50 μm ２ especially preferably the upper limit is 0.30 μm ２A very preferred upper limit is 0.20 μm ２ Furthermore, while the lower limit of the average area of ​​the dispersed phase is not particularly limited, from the viewpoint of further improving the shock absorption performance of the adhesive tape of this embodiment, a preferred lower limit for the average area of ​​the dispersed phase is 0.01 μm. ２ A more preferable lower limit is 0.03 μm ２ The average area of ​​the dispersed phase is, for example, 0.01 μm. ２ 10 μm or more ２ Below, 0.03 μm ２ 5.00 μm or more ２ Below, 0.03 μm ２ 3.00 μm or more ２ Below, 0.03 μm ２ 1.00 μm or more ２ Below, 0.03 μm ２ 0.70 μm or more ２ Below, 0.03 μm ２ 0.50 μm or more ２ Below, 0.03 μm ２ 0.30 μm or more ２ Below, 0.03 μm ２ 0.20 μm or more ２ The following are some examples.

[0013] The average area of ​​the dispersed phase before the heating test described above can be measured by the following method. Specifically, first, the adhesive layer of the adhesive tape of this embodiment is cut from the adhesive tape using a cryomicrotome (e.g., Leica) to a plane parallel to the thickness direction, and a section with a thickness (length direction or width direction in the adhesive tape) of 1.0 μm is prepared. Next, the prepared section is placed on glass, and after staining the section with ruthenium using an aqueous ruthenium tetroxide solution, an image of 84.6 μm × 63.4 μm is taken at a magnification of 1500x using a simple SEM (e.g., Hitachi High-Tech "TM4000Plus"). Then, the average area of ​​the dispersed phase present in the image is measured by performing image analysis (analysis range: 63.4 μm × 47.6 μm) on the acquired image using the open-source image analysis software Fiji (ImageJ). Furthermore, sections are prepared so that the cutting direction is shifted by 30° from the direction in which the section was cut immediately before, and the average area of ​​the dispersed phase is measured in the same manner as described above. The above measurement is repeated until the cutting direction returns to that of the first measurement, and the average of the average areas of the dispersed phase in the total of six sections measured is taken as the average area of ​​the dispersed phase in the entire adhesive layer (the average area of ​​the dispersed phase described above).

[0014] Methods for adjusting the average area of ​​the dispersed phase before the heating test include, for example, adjusting the composition of the adhesive layer described later, and adjusting the conditions for making the adhesive tape. Specifically, methods for adjusting the composition of the adhesive layer include, for example, adjusting the content of the aromatic block copolymer (X) per 100 parts by mass of the acrylic copolymer, changing the composition of the aromatic block copolymer (X) (for example, adjusting the type and content of constituent units derived from vinyl aromatic compounds, adjusting the diblock ratio, changing whether or not hydrogenation of the conjugated diene polymer block is performed, etc.), adjusting the weight-average molecular weight of the aromatic block copolymer (X), changing the composition of the acrylic copolymer (for example, adjusting the type and content of constituent units derived from (meth)acrylate alkyl esters, constituent units derived from monomers having crosslinkable functional groups, olefin polymers having polymerizable unsaturated double bonds at the terminals, constituent units derived from vinyl aromatic compounds, and other monomers copolymerized, etc.), adjusting the weight-average molecular weight, polydispersity, etc. of the acrylic copolymer, and adjusting the content of the crosslinking agent contained in the adhesive composition. Specific methods for adjusting the manufacturing conditions of adhesive tape include, for example, changing the coating method, adjusting the heating temperature and heating time after coating, and adjusting the type and amount of solvent added.

[0015] The upper limit of the area change rate of the dispersed phase before and after the heating test is 2.0. By having an area change rate of 2.0 or less, the adhesive tape of this embodiment exhibits excellent thermal stability and maintains excellent shock absorption even in high-temperature environments. A preferred upper limit for the area change rate of the dispersed phase before and after the heating test is 1.8, a more preferred upper limit is 1.6, an even more preferred upper limit is 1.4, and an even more preferred upper limit is 1.2. Furthermore, there is no particular lower limit for the area change rate of the dispersed phase before and after the heating test, but the practical lower limit is 0.1. Examples of suitable area change rates for the dispersed phase before and after the heating test include 0.1 to 2.0, 0.1 to 1.8, 0.1 to 1.6, 0.1 to 1.4, and 0.1 to 1.2.

[0016] The rate of change in area of ​​the dispersed phase before and after the heating test can be measured by the following method. First, the average area of ​​the dispersed phase before the heating test is measured using the method described above. Next, the adhesive layer is heated for two days by being left in a constant temperature oven set to 150°C, and then air-cooled to approximately 25°C in a 25°C environment. Then, sections are prepared using the same method as described above for measuring the average area of ​​the dispersed phase before the heating test, and the average area of ​​the dispersed phase is measured to determine the average area of ​​the dispersed phase after the heating test. Using the obtained average area of ​​the dispersed phase before and after the heating test, the rate of change in area of ​​the dispersed phase before and after the heating test can be calculated using the following formula (I): Rate of change in area of ​​the dispersed phase before and after the heating test = (Average area of ​​the dispersed phase after the heating test) ÷ (Average area of ​​the dispersed phase before the heating test) (I)

[0017] Methods for adjusting the rate of change in area of ​​the dispersed phase before and after the heating test include, for example, adjusting the composition of the adhesive layer described later, and adjusting the conditions for making the adhesive tape. Specifically, methods for adjusting the composition of the adhesive layer include, for example, adjusting the content of the aromatic block copolymer (X) per 100 parts by mass of the acrylic copolymer, changing the composition of the aromatic block copolymer (X) (for example, adjusting the type and content of constituent units derived from vinyl aromatic compounds, adjusting the diblock ratio, changing whether or not hydrogenation of the conjugated diene polymer block is performed, etc.), adjusting the weight-average molecular weight of the aromatic block copolymer (X), changing the composition of the acrylic copolymer (for example, adjusting the type and content of constituent units derived from (meth)acrylate alkyl esters, constituent units derived from monomers having crosslinkable functional groups, olefin polymers having polymerizable unsaturated double bonds at the terminals, constituent units derived from vinyl aromatic compounds, and other monomers copolymerized, etc.), adjusting the weight-average molecular weight, polydispersity, etc. of the acrylic copolymer, and adjusting the content of the crosslinking agent contained in the adhesive composition. Specific methods for adjusting the manufacturing conditions of adhesive tape include, for example, changing the coating method, adjusting the heating temperature and heating time after coating, and adjusting the type and amount of solvent added.

[0018] The aspect ratio of the dispersed phase in the thickness direction (hereinafter sometimes simply referred to as "aspect ratio of the dispersed phase") has a preferred upper limit of 2.0. By having an aspect ratio of 2.0 or less, the isotropy of the adhesive layer against tension is further improved, allowing the adhesive tape of this embodiment to be manufactured in a way that exhibits excellent shock absorption regardless of the manufacturing direction, thus making it easier to produce an adhesive tape with superior manufacturing efficiency. A more preferred upper limit for the aspect ratio of the dispersed phase is 1.8, and an even more preferred upper limit is 1.5. In this specification, "aspect ratio of the dispersed phase" refers to the average of the values ​​obtained by dividing the major axis of each dispersed phase by its minor axis (major axis of the dispersed phase / minor axis of the dispersed phase). Therefore, the aspect ratio of the dispersed phase should be 1.0 or greater. Examples of aspect ratios for the dispersed phase include 1.0 to 2.0, 1.0 to 1.8, and 1.0 to 1.5.

[0019] The aspect ratio of the dispersed phase described above can be measured by the following method. Specifically, sections of the adhesive layer are prepared using the same method as the method for measuring the average area of ​​the dispersed phase described above, and image analysis is performed on the prepared sections to measure the aspect ratio of the dispersed phase in the sections present in the image. Furthermore, sections are prepared so that the cutting direction is shifted by 30° from the direction in which the section was cut immediately before, and the average aspect ratio of the dispersed phase is measured in the same manner as described above. The above measurement is repeated until the cutting direction returns to that of the first measurement, and the average value of the average aspect ratio of the dispersed phase in a total of six measured sections is taken as the average aspect ratio of the dispersed phase of the entire adhesive layer (average aspect ratio of the dispersed phase described above).

[0020] Methods for adjusting the aspect ratio of the dispersed phase include, for example, adjusting the composition of the adhesive layer described later, and adjusting the manufacturing conditions of the adhesive tape. Specifically, methods for adjusting the composition of the adhesive layer include, for example, adjusting the content of the aromatic block copolymer (X) per 100 parts by mass of the acrylic copolymer, changing the composition of the aromatic block copolymer (X) (for example, adjusting the type and content of constituent units derived from vinyl aromatic compounds, adjusting the diblock ratio, changing whether or not hydrogenation of the conjugated diene polymer block is performed, etc.), adjusting the weight-average molecular weight of the aromatic block copolymer (X), changing the composition of the acrylic copolymer (for example, adjusting the type and content of constituent units derived from (meth)acrylate alkyl esters, constituent units derived from monomers having crosslinkable functional groups, olefin polymers having polymerizable unsaturated double bonds at the terminals, constituent units derived from vinyl aromatic compounds, and other monomers copolymerized, etc.), adjusting the weight-average molecular weight, polydispersity, etc. of the acrylic copolymer, and adjusting the content of the crosslinking agent contained in the adhesive composition. Specific methods for adjusting the manufacturing conditions of adhesive tape include, for example, changing the coating method, adjusting the heating temperature and heating time after coating, and adjusting the type and amount of solvent added.

[0021] The above adhesive layer contains an acrylic copolymer having constituent units derived from (meth)acrylic acid ester.

[0022] In recent years, the depletion of petroleum resources and the emission of carbon dioxide from the combustion of petroleum-derived products have become serious concerns. Therefore, attempts are being made to conserve petroleum resources by using bio-derived materials instead of petroleum-derived materials. For this reason, the (meth)acrylate alkyl ester in the constituent unit derived from the above-mentioned alkyl (meth)acrylate ester may consist only of petroleum-derived materials, but it is preferable that it also contains bio-derived materials that include bio-derived carbon. The inclusion of bio-derived materials in the above-mentioned alkyl (meth)acrylate ester is preferable from the viewpoint of conserving petroleum resources, and furthermore, since bio-derived materials are originally produced by taking in carbon dioxide from the atmosphere, it is thought that burning them will not increase the total amount of carbon dioxide in the atmosphere, which is also preferable from the viewpoint of reducing carbon dioxide emissions.

[0023] When the alkyl (meth)acrylate in the constituent unit derived from the above alkyl (meth)acrylate contains a bio-derived material, it is preferable that the alkyl (meth)acrylate is synthesized by esterification of an alcohol, which is a bio-derived material, with (meth)acrylic acid.

[0024] The above acrylic copolymer has at least one constituent unit selected from the group consisting of constituent units derived from (meth)acrylate n-hexyl, (meth)acrylate n-heptyl, and (meth)acrylate 1-methylheptyl (hereinafter sometimes simply referred to as "constituent unit derived from (meth)acrylate alkyl ester (a)"). By including the constituent unit derived from (meth)acrylate alkyl ester (a), the adhesive layer tends to have appropriate adhesive strength and appropriate flexibility, making it easier to produce an adhesive tape with superior adhesive properties in this embodiment. Furthermore, it becomes easier to adjust the content of bio-derived carbon, as described later, to a suitable range, thereby further reducing the environmental impact of the adhesive tape in this embodiment. Note that the above acrylic copolymer may have only one type of constituent unit derived from (meth)acrylate alkyl ester (a), or it may have two or more types.

[0025] The total content of constituent units derived from the above-mentioned alkyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, and 1-methylheptyl (meth)acrylate in relation to the above-mentioned alkyl (meth)acrylate (hereinafter sometimes simply referred to as "total content of constituent units derived from alkyl (meth)acrylate (a)") has a preferred lower limit of 20% by mass. A total content of constituent units derived from alkyl (meth)acrylate (a) of 20% by mass or more makes it easier to produce an adhesive tape with superior tackiness. Furthermore, it becomes easier to adjust the content of bio-derived carbon, as described later, to a suitable range, thereby further reducing the environmental impact of the adhesive tape of this embodiment. A more preferred lower limit for the total content of constituent units derived from alkyl (meth)acrylate (a) is 40% by mass, and an even more preferred lower limit is 60% by mass. Also, a higher total content of constituent units derived from alkyl (meth)acrylate (a) is preferable, with 100% by mass being the most preferable. The total content percentage of constituent units derived from the above-mentioned alkyl (meth)acrylate (a) can be, for example, 20% by mass or more and 100% by mass or less, 40% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, etc.

[0026] The above acrylic copolymer preferably further contains a structural unit derived from isobornyl (meth)acrylate as a structural unit derived from the above alkyl (meth)acrylate. By including the structural unit derived from isobornyl (meth)acrylate in the structural unit derived from the above alkyl (meth)acrylate, the resulting adhesive tape can be given excellent bending resistance.

[0027] The preferred lower limit for the content of constituent units derived from isobornyl (meth)acrylate in relation to the alkyl (meth)acrylate is 1% by mass, and the preferred upper limit is 60% by mass. A content of 1% by mass or more of constituent units derived from isobornyl (meth)acrylate provides the resulting adhesive tape with superior bending resistance. A content of 60% by mass or less of constituent units derived from isobornyl (meth)acrylate makes the adhesive layer more flexible, resulting in the adhesive tape of this embodiment having superior shock absorption. A more preferred lower limit for the content of constituent units derived from isobornyl (meth)acrylate is 5% by mass, a more preferred upper limit is 50% by mass, an even more preferred lower limit is 10% by mass, an even more preferred upper limit is 40% by mass, an even more preferred upper limit is 30% by mass, and a particularly preferred upper limit is 25% by mass. Examples of the content ratio of the constituent units derived from isobornyl (meth)acrylate include 1% by mass or more and 60% by mass or less, 5% by mass or more and 50% by mass or less, 10% by mass or more and 40% by mass or less, 10% by mass or more and 30% by mass or less, and 10% by mass or more and 25% by mass or less.

[0028] The above acrylic copolymer may have, as constituent units derived from the above alkyl (meth)acrylate, a constituent unit derived from the above alkyl (meth)acrylate (a) and a constituent unit derived from the above alkyl (meth)acrylate (b), which is a constituent unit other than the constituent unit derived from the above isobornyl (meth)acrylate.

[0029] Examples of constituent units derived from the above alkyl (meth)acrylate (b) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, isohexyl (meth)acrylate, cyclohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ( Examples of constituent units derived from alkyl esters of (meth)acrylate include n-octyl meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, etc. Furthermore, if the above acrylic copolymer has constituent units derived from the above alkyl ester (b), it may have only one type of constituent unit derived from the above alkyl ester (b), or it may have two or more types.

[0030] The preferred lower limit and preferred upper limit of the content of the constituent units derived from the alkyl (meth)acrylate in the above acrylic copolymer is 50% by mass. By having the content of the constituent units derived from the alkyl (meth)acrylate within the above range, the adhesive layer will have superior adhesive strength. A more preferred lower limit for the content of the constituent units derived from the alkyl (meth)acrylate is 60% by mass, a more preferred upper limit is 90% by mass, an even more preferred lower limit is 65% by mass, an even more preferred upper limit is 85% by mass, and an even more preferred upper limit is 80% by mass. Examples of the content of the constituent units derived from the alkyl (meth)acrylate include 50% by mass or more and 95% by mass or less, 60% by mass or more and 90% by mass or less, 65% by mass or more and 85% by mass or less, and 65% by mass or more and 80% by mass or less.

[0031] The above acrylic copolymer preferably has structural units derived from monomers having crosslinkable functional groups. Because the above acrylic copolymer has structural units derived from monomers having crosslinkable functional groups, the acrylic copolymer can sufficiently form a crosslinked structure through chemical crosslinking via a crosslinking agent between molecules, and the polar functional groups in the acrylic copolymer interact with each other, thereby increasing the cohesive force of the adhesive layer. As a result, the adhesive layer has a more appropriate hardness, thus improving the bending resistance of the resulting adhesive tape. Furthermore, the increased cohesive force of the adhesive layer improves the high-temperature holding performance of the resulting adhesive tape.

[0032] Examples of constituent units derived from monomers having the above-mentioned crosslinkable functional group include constituent units derived from carboxyl group-containing monomers, constituent units derived from hydroxyl group-containing monomers, constituent units derived from amide group-containing monomers, and constituent units derived from amino group-containing monomers. In particular, from the viewpoint of further increasing the cohesive force of the adhesive layer, it is preferable that the constituent units derived from monomers having the above-mentioned crosslinkable functional group include at least one selected from the group consisting of constituent units derived from carboxyl group-containing monomers and constituent units derived from hydroxyl group-containing monomers.

[0033] Specific examples of constituent units derived from the above carboxyl group-containing monomers include unsaturated monocarboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, and crotonic acid, as well as dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Specific examples of constituent units derived from the above hydroxyl group-containing monomers include constituent units derived from 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Specific examples of constituent units derived from the above amide group-containing monomers include constituent units derived from N-vinyl-2-pyrrolidone, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide. Specific examples of constituent units derived from the above amino group-containing monomers include constituent units derived from (meth)acryloylmorpholine, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. Furthermore, the constituent units derived from monomers having these crosslinkable functional groups may consist of only one type, or two or more types.

[0034] In the above acrylic copolymer, the total content of constituent units derived from the monomer having the crosslinkable functional group is preferably 0.1% by mass and preferably 10% by mass. When the content of constituent units derived from the monomer having the crosslinkable functional group is 0.1% by mass or more, the cohesive force of the adhesive layer is increased, and the adhesive layer has a more appropriate hardness, thereby improving the bending resistance and high-temperature holding performance of the resulting adhesive tape. When the content of constituent units derived from the monomer having the crosslinkable functional group is 10% by mass or less, the adhesive layer has an appropriate flexibility, thereby improving the shock absorption of the resulting adhesive tape. A more preferable lower limit for the content of constituent units derived from the monomer having the crosslinkable functional group is 0.5% by mass, a more preferable upper limit is 9.0% by mass, an even more preferable lower limit is 1.0% by mass, an even more preferable upper limit is 8.0% by mass, an even more preferable lower limit is 3.0% by mass, an even more preferable upper limit is 7.0% by mass, and a particularly preferable lower limit is 5.0% by mass. Examples of the total content of constituent units derived from monomers having the above-mentioned crosslinkable functional groups include 0.1% by mass or more and 10% by mass or less, 0.5% by mass or more and 9.0% by mass or less, 1.0% by mass or more and 8.0% by mass or less, 3.0% by mass or more and 7.0% by mass or less, 5.0% by mass or more and 7.0% by mass or less.

[0035] The above acrylic copolymer preferably has structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals. By having structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals, the resulting adhesive tape exhibits improved shock absorption and high bending resistance.

[0036] When the above-mentioned acrylic copolymer has constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals, the acrylic copolymer has a structure in which constituent units derived from an alkyl (meth)acrylate ester are used as the main chain and constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals are used as side chains. In this structure, the constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its terminals, located in the side chains of the acrylic copolymer, aggregate through interaction, forming a pseudo-crosslink. Therefore, when the adhesive layer is subjected to impact and the strain increases, the pseudo-crosslink breaks, and the molecules of the acrylic copolymer stretch, resulting in increased flexibility of the adhesive layer and excellent stress relaxation properties. As a result, the resulting adhesive tape has superior shock absorption properties.

[0037] Furthermore, when the acrylic copolymer has the above-mentioned structure, if the strain is small, the molecules of the acrylic copolymer become hard as if they were in a cross-linked structure due to the above-mentioned pseudo-crosslinking, and the adhesive layer has appropriate hardness. As a result, the resulting adhesive tape has better bending resistance. Also, when the strain applied to the adhesive layer is small, the cohesive force of the adhesive layer is further improved, and the adhesive tape of this embodiment has better holding performance at high temperatures.

[0038] The olefin polymer having a polymerizable unsaturated double bond at one end may have a polymerizable unsaturated double bond at one end, or it may have polymerizable unsaturated double bonds at both ends. Among these, an olefin polymer having a polymerizable unsaturated double bond at one end is preferred because it is less prone to intramolecular chemical crosslinking, the cohesive force of the adhesive layer is increased, and it has a moderate hardness, thereby further improving the bending resistance of the resulting adhesive tape.

[0039] Examples of olefin polymers having a polymerizable unsaturated double bond at one or both ends include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, and butene polymers, which have a group containing a polymerizable unsaturated carbon-carbon double bond at one or both ends. Examples of the group containing a polymerizable unsaturated carbon-carbon double bond include (meth)acryloyl groups, vinyl ether groups, and styryl groups. Among these, (meth)acryloyl groups are preferred because they exhibit excellent copolymerization with the alkyl (meth)acrylate esters. In this specification, "(meth)acryloyl" means acryloyl or methacryloyl.

[0040] Examples of olefin polymers having polymerizable unsaturated double bonds at their ends include ethylene macromonomers having a (meth)acryloyl group at one end, propylene macromonomers having a (meth)acryloyl group at one end, ethylene-butylene macromonomers having a (meth)acryloyl group at one end, and ethylene-propylene macromonomers having a (meth)acryloyl group at one end. Among these, ethylene-butylene macromonomers having a (meth)acryloyl group at one end and ethylene-propylene macromonomers having a (meth)acryloyl group at one end are preferred from the viewpoint of improving the adhesive strength of the adhesive layer. These olefin polymers having polymerizable unsaturated double bonds at their ends may be used individually or in combination of two or more. In this specification, "macromonomer" refers to a monomer having polymerizable functional groups with a weight-average molecular weight of about 1,000 to 100,000.

[0041] In the above acrylic copolymer, the preferred lower limit of the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 5% by mass, and the preferred upper limit is 50% by mass. When the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 5% by mass or more, an appropriate number of pseudo-crosslinks are formed. As a result, the adhesive layer has an appropriate hardness, and the bending resistance of the resulting adhesive tape is further improved. In addition, the cohesive force of the adhesive layer is further improved, and the resulting adhesive tape has superior holding performance at high temperatures. When the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 50% by mass or less, the adhesive layer has an appropriate flexibility, and the shock absorption of the resulting adhesive tape is further improved. A more preferable lower limit for the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends is 8% by mass, a more preferable upper limit is 45% by mass, an even more preferable lower limit is 10% by mass, an even more preferable upper limit is 40% by mass, an even more preferable lower limit is 15% by mass, and an even more preferable upper limit is 30% by mass. Examples of the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends include 5% by mass or more and 50% by mass or less, 8% by mass or more and 45% by mass or less, 10% by mass or more and 40% by mass or less, 15% by mass or more and 30% by mass or less, etc.

[0042] The above-mentioned acrylic copolymer preferably has structural units derived from vinyl aromatic compounds. Having structural units derived from vinyl aromatic compounds in the acrylic copolymer results in an adhesive tape with superior holding performance at high temperatures.

[0043] Examples of constituent units derived from the above-mentioned vinyl aromatic compounds include constituent units derived from styrene, constituent units derived from α-methylstyrene, and constituent units derived from hydrogenated versions thereof. Among these, constituent units derived from styrene are preferred from the viewpoint of producing an adhesive tape that is superior in shock absorption, bending resistance, and high-temperature holding performance. Note that the constituent units derived from these vinyl aromatic compounds may consist of only one type, or two or more types may coexist.

[0044] When the above acrylic copolymer has structural units derived from a vinyl aromatic compound, the above acrylic copolymer may be a random copolymer, or it may be a block copolymer (hereinafter sometimes simply referred to as "block copolymer (A)") of a block having structural units derived from the above (meth)acrylate alkyl ester (hereinafter sometimes simply referred to as "block (A-2)") and a block having structural units derived from the above vinyl aromatic compound (hereinafter sometimes simply referred to as "block (A-1)"). In the above block copolymer (A), block (A-1) becomes a hard segment and block (A-2) becomes a soft segment, providing shock absorption. In particular, from the viewpoint of obtaining an adhesive tape with superior shock absorption, it is preferable that the above acrylic copolymer has structural units derived from a vinyl aromatic compound and includes block copolymer (A).

[0045] The block copolymer (A) described above may be a diblock copolymer or a triblock copolymer. Among these, a triblock copolymer is preferred from the viewpoint that the resulting adhesive tape will have superior shock absorption, as well as superior bending resistance and high-temperature holding performance. Among triblock copolymers, a triblock copolymer having the structure of the hard block - soft block - hard block described above is more preferred.

[0046] The preferred lower limit for the content of block (A-1) in the block copolymer (A) is 3% by mass, and the preferred upper limit is 15% by mass. When the content of block (A-1) is 3% by mass or more, the adhesive tape of this embodiment has superior shock absorption properties. When the content of block (A-1) is 15% by mass or less, the adhesive tape of this embodiment has superior conformability and strong adhesion properties. The more preferred lower limit for the content of block (A-1) is 5% by mass, and the more preferred upper limit is 12% by mass. Examples of the content of block (A-1) include 3% by mass or more and 15% by mass or less, and 5% by mass or more and 12% by mass or less.

[0047] In the above acrylic copolymer, the preferred lower limit for the content of constituent units derived from the vinyl aromatic compound is 2.5% by mass, and the preferred upper limit for the content of constituent units derived from the vinyl aromatic compound is 20% by mass. When the content of constituent units derived from the vinyl aromatic compound is 2.5% by mass or more, the resulting adhesive tape will have superior holding performance at high temperatures. When the content of constituent units derived from the vinyl aromatic compound is 20% by mass or less, the resulting adhesive tape will have superior shock absorption properties. A more preferred lower limit for the content of constituent units derived from the vinyl aromatic compound is 3.0% by mass, a more preferred upper limit is 18% by mass, an even more preferred lower limit is 3.5% by mass, an even more preferred upper limit is 15% by mass, an even more preferred lower limit is 4.5% by mass, an even more preferred upper limit is 12% by mass, a particularly preferred lower limit is 6.0% by mass, a particularly preferred upper limit is 10% by mass, and a particularly preferred upper limit is 8.0% by mass. Examples of the content ratio of constituent units derived from the vinyl aromatic compound include 2.5% by mass or more and 20% by mass or less, 3.0% by mass or more and 18% by mass or less, 3.5% by mass or more and 15% by mass or less, 4.5% by mass or more and 12% by mass or less, 6.0% by mass or more and 10% by mass or less, and 6.0% by mass or more and 8.0% by mass or less.

[0048] The weight-average molecular weight (Mw) of the above acrylic copolymer has a preferred lower limit of 300,000 and a preferred upper limit of 1,500,000. When the weight-average molecular weight (Mw) of the above acrylic copolymer is within this range, the cohesive force of the adhesive layer is further increased, and the adhesive tape of this embodiment exhibits improved high-temperature retention performance. A more preferred lower limit for the weight-average molecular weight (Mw) of the above acrylic copolymer is 500,000, a more preferred upper limit is 1,200,000, and an even more preferred lower limit is 700,000. Examples of weight-average molecular weight (Mw) of the above acrylic copolymer include 300,000 to 1,500,000, 500,000 to 1,200,000, and 700,000 to 1,200,000.

[0049] The polydispersity (weight-average molecular weight / number-average molecular weight, Mw / Mn) of the above acrylic copolymer has a preferred lower limit of 1.0 and a preferred upper limit of 8.0. When the polydispersity (Mw / Mn) of the above acrylic copolymer is within the above range, the cohesive force of the adhesive layer is further increased, and the adhesive tape of this embodiment exhibits improved retention performance at high temperatures. A more preferred lower limit for the polydispersity (Mw / Mn) of the above acrylic copolymer is 1.5, and a more preferred upper limit is 7.5. Examples of polydispersity (weight-average molecular weight / number-average molecular weight, Mw / Mn) of the above acrylic copolymer include 1.0 to 8.0 and 1.5 to 7.5.

[0050] In this specification, the weight-average molecular weight and number-average molecular weight are those obtained by GPC (Gel Permeation Chromatography) measurement on a standard polystyrene basis. Specifically, an acrylic copolymer is diluted 50-fold with an organic solvent such as ethyl acetate, and the resulting dilution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a sample for measurement. Next, this sample for measurement is supplied to a gel permeation chromatograph, 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-based molecular weight of the acrylic copolymer is measured, and the obtained values ​​are defined as the weight-average molecular weight and number-average molecular weight. Examples of gel permeation chromatographs include the 2690 Separations Module (manufactured by Waters), and examples of columns include the GPC KF-806L (manufactured by Showa Denko).

[0051] Methods for adjusting the weight-average molecular weight of the above-mentioned acrylic copolymer include, for example, changing the type and amount of polymerization initiator and monomer concentration during the polymerization reaction, adding a small amount of chain transfer agent such as dodecyl mercaptan, controlling chain transfer to the solvent by changing the type of polymerization reaction solvent, and changing the temperature and time during polymerization.

[0052] The preferred lower limit for the content of the acrylic copolymer in the adhesive layer is 30% by mass, and the preferred upper limit is 95% by mass. By having the acrylic copolymer content within the above range, the adhesive layer can more easily form a structure composed of the continuous phase and the dispersed phase, thereby further improving the shock absorption of the adhesive tape of this embodiment. A more preferred lower limit for the acrylic copolymer content is 40% by mass, a more preferred upper limit is 90% by mass, an even more preferred lower limit is 45% by mass, and an even more preferred upper limit is 85% by mass. Examples of polydispersity (weight-average molecular weight / number-average molecular weight, Mw / Mn) of the acrylic copolymer include 30% by mass or more and 95% by mass or less, 40% by mass or more and 90% by mass or less, and 45% by mass or more and 85% by mass or less.

[0053] As polymerization methods for synthesizing the above-mentioned acrylic copolymer, conventionally known methods can be used in which a mixture of constituent monomers that serve as raw materials undergoes a radical reaction in the presence of a polymerization initiator. Examples include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization is preferred because it is easy to synthesize.

[0054] When solution polymerization is used as the polymerization method described above, examples of reaction solvents include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, and diethyl ether. These reaction solvents may be used individually or in combination of two or more.

[0055] Examples of polymerization initiators include organic peroxides and azo compounds. Examples of 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 azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonilonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0056] Furthermore, even when the acrylic copolymer is the block copolymer (A), the method for producing the block copolymer (A) is not particularly limited, and conventionally known methods can be used. Specifically, for example, a vinyl aromatic compound may be added to the soft block synthesized in the same manner as the acrylic copolymer described above, and copolymerized. Alternatively, the hard block and soft block synthesized in advance may be copolymerized.

[0057] Furthermore, if the block copolymer is a triblock copolymer having the structure of the hard block - soft block - hard block, the block copolymer can be obtained, for example, by living polymerization. Examples of living polymerization include living anionic polymerization and RAFT polymerization, but RAFT polymerization is particularly preferred. When producing the block copolymer (A) having the hard block - soft block - hard block by RAFT polymerization, the hard block is obtained using a chain transfer agent (RAFT agent), and then the constituent unit monomers of the soft block are polymerized or copolymerized in the presence of the obtained hard block to produce the triblock copolymer.

[0058] The above adhesive layer contains an aromatic block copolymer (X) having at least two blocks having structural units derived from vinyl aromatic compounds (hereinafter sometimes simply referred to as "vinyl aromatic polymer blocks"), and at least one of a block having structural units derived from a conjugated diene compound (hereinafter sometimes simply referred to as "conjugated diene polymer blocks") or a hydrogenated product of a block having structural units derived from a conjugated diene compound (hereinafter sometimes simply referred to as "hydrogenated product of conjugated diene polymer blocks"). Since the above aromatic block copolymer (X) has rubber elasticity, the inclusion of the above aromatic block copolymer (X) in the adhesive layer improves the flexibility of the adhesive layer, and the resulting adhesive tape has excellent shock absorption properties.

[0059] The vinyl aromatic polymer block described above may be any block having 5% by mass or more of constituent units derived from a vinyl aromatic compound, and may also contain constituent units derived from other compounds such as ethylene and 1,3-butadiene (which is converted to an ethylene-butylene structure by hydrogenation). Examples of the vinyl aromatic compound in the vinyl aromatic polymer block include alkylstyrene, halogenated styrene, halogen-substituted alkylstyrene, alkoxystyrene, carboxyalkylstyrene, alkyl ether styrene, alkylsilyl styrene, vinyl benzyl dimethoxy phosphide, vinyl naphthalene, vinyl anthracene, N,N-diethyl-p-aminoethylstyrene, and vinylpyridine.

[0060] Examples of alkylstyrenes include styrene, methylstyrene, dimethylstyrene, and t-butylstyrene. Examples of halogenated styrenes include chlorostyrene, bromostyrene, and fluorostyrene. Examples of halogen-substituted alkylstyrenes include chloromethylstyrene. Examples of alkoxystyrenes include methoxystyrene and ethoxystyrene. Examples of carboxyalkylstyrenes include carboxymethylstyrene. Examples of alkyl ether styrenes include vinyl benzyl propyl ether. Examples of alkylsilyl styrenes include trimethylsilyl styrene. Among these, styrene, methylstyrene, and dimethylstyrene are preferred, and styrene is more preferred because it is readily available industrially. These vinyl aromatic compounds may be used individually or in combination of two or more.

[0061] The preferred lower limit for the content of constituent units derived from the vinyl aromatic compound in the vinyl aromatic polymer block is 7% by mass. When the constituent units derived from the vinyl aromatic compound are 7% by mass or more, the bending rigidity of the adhesive layer is further improved, and the resulting adhesive tape has excellent shock absorption and superior bending resistance. A more preferred lower limit for the constituent units derived from the vinyl aromatic compound is 10% by mass. Furthermore, from the viewpoint of further improving the flexibility of the adhesive layer and resulting in an adhesive tape with superior shock absorption, a preferred upper limit for the constituent units derived from the vinyl aromatic compound is 35% by mass.

[0062] Examples of the above-mentioned conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene. In addition to the above-mentioned conjugated diene compounds, other usable compounds include, for example, 2,5-dihydrofuran-2,5-dione. Among these, 1,3-butadiene and isoprene are preferred due to their high polymerization reactivity and ease of industrial availability. These conjugated diene compounds may be used individually or in combination of two or more.

[0063] The hydrogenated form of the above-mentioned conjugated diene polymer block refers to a block in which the carbon-carbon double bonds (unsaturated bonds) in the constituent units derived from the above-mentioned conjugated diene compound are converted to saturated bonds by hydrogenation. From the viewpoint of preventing degradation due to heat, ultraviolet rays, etc., it is preferable that 80% or more of the carbon-carbon double bonds (unsaturated bonds) in the constituent units derived from the above-mentioned conjugated diene compound of the aromatic block copolymer (X) are converted to saturated bonds by hydrogenation, more preferably 90% or more, even more preferably 95% or more, and even more preferably 96% or more. Furthermore, it is most preferable that 100% of the unsaturated bonds are converted to saturated bonds by hydrogenation (i.e., it is a fully hydrogenated form). That is, it is preferable that 80% to 100% of the carbon-carbon double bonds (unsaturated bonds) in the constituent units derived from the above-mentioned conjugated diene compound are converted to saturated bonds by hydrogenation, more preferably 90% to 100%, even more preferably 95% to 100%, and even more preferably 96% to 100%.

[0064] The preferred lower limit for the content of constituent units derived from the conjugated diene compound in the above-mentioned conjugated diene polymer block is 80% by mass. When the content of constituent units derived from the conjugated diene compound is 80% by mass or more, the flexibility of the adhesive layer is further improved, and the shock absorption of the resulting adhesive tape is further improved. In addition, the adhesive strength of the adhesive layer is further improved. A more preferred lower limit for the content of constituent units derived from the conjugated diene compound is 90% by mass, and an even more preferred lower limit is 95% by mass. Furthermore, there is no particular upper limit for the content of constituent units derived from the conjugated diene compound, and it may be 100% by mass. Examples of the content of constituent units derived from the conjugated diene compound in the above-mentioned conjugated diene polymer block include 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, etc.

[0065] Examples of the structure of the above aromatic block copolymer (X) include, when the vinyl aromatic polymer block is B and the hydrogenated product of the block having constituent units derived from the conjugated diene polymer block and the conjugated diene compound is C, a triblock copolymer represented by formula B-C-B, a diblock copolymer represented by formula B-C, a pentablock copolymer represented by formula C-B-C-B-C, and the like.

[0066] Examples of aromatic block copolymers (X) having the structure represented by the above formula B-C-B include styrene-isoprene-styrene (SIS) block copolymer, styrene-butylene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-ethylene-propylene-styrene (SEPS) block copolymer, styrene-ethylene-ethylene-propylene-styrene (SEEPS) block copolymer, styrene-isobutylene-styrene (SIBS) block copolymer, and ethylene-styrene-butylene block copolymer. Among these, SIS block copolymer and SEBS block copolymer are preferred from the viewpoint of compatibility with the above acrylic copolymer.

[0067] The preferred lower limit for the weight-average molecular weight (Mw) of the aromatic block copolymer (X) is 50,000. A weight-average molecular weight (Mw) of 50,000 or more results in a more shock-absorbing adhesive tape. A more preferred lower limit for the weight-average molecular weight of the aromatic block copolymer (X) is 100,000, and an even more preferred lower limit is 150,000. While there is no particular upper limit for the weight-average molecular weight of the aromatic block copolymer (X), a preferred upper limit is 500,000 from the viewpoint of compatibility with the acrylic copolymer. Examples of weight-average molecular weight (Mw) for the aromatic block copolymer (X) include 50,000 to 500,000, 100,000 to 500,000, and 150,000 to 500,000.

[0068] The preferred upper limit of the content of the aromatic block copolymer (X) per 100 parts by mass of the acrylic copolymer is 60 parts by mass. When the content of the aromatic block copolymer (X) is 60 parts by mass or less, the adhesive layer is more easily formed to consist of the continuous phase and the dispersed phase, and the shock absorption of the adhesive tape of this embodiment is further improved. In addition, the bending rigidity of the adhesive layer is further improved, and the resulting adhesive tape has superior bending resistance. Furthermore, the adhesive strength of the adhesive layer is further improved. The more preferred upper limit of the content of the aromatic block copolymer (X) is 55 parts by mass, an even more preferred upper limit is 50 parts by mass, and an even more preferred upper limit is 45 parts by mass. In addition, the preferred lower limit of the content of the aromatic block copolymer (X) is 10 parts by mass. When the content of the aromatic block copolymer (X) is 10 parts by mass or more, the flexibility of the adhesive layer is further improved, and the resulting adhesive tape has superior shock absorption. A more preferable lower limit for the content of the aromatic block copolymer (X) is 15 parts by mass, an even more preferable lower limit is 20 parts by mass, and an even more preferable lower limit is 30 parts by mass. Examples of the content of the aromatic block copolymer (X) include 10 parts by mass or more and 60 parts by mass or less, 15 parts by mass or more and 55 parts by mass or less, 20 parts by mass or more and 50 parts by mass or less, 30 parts by mass or more and 45 parts by mass or less, etc.

[0069] The adhesive layer may be colored. When the adhesive layer is colored, light-shielding properties can be imparted to the adhesive layer, thereby suppressing deterioration of the substrate to which the adhesive tape is attached due to light and ultraviolet rays. As a result, the resulting adhesive tape can be more suitably used for fixing electronic equipment components or automotive components.

[0070] If the adhesive layer is colored, it is preferable that the adhesive layer contains a coloring agent. Examples of the coloring agent include pigments and dyes. Among these, pigments are preferred because they have excellent holding performance at high temperatures and the resulting adhesive tape can be more suitably used for fixing electronic equipment components or automotive components. Examples of the pigments include carbon black, aniline black, and titanium dioxide. Among these, carbon black is preferred because it is relatively inexpensive and chemically stable. Examples of the dyes include azo dyes, anthraquinone dyes, and phthalocyanine dyes.

[0071] The preferred upper limit of the coloring agent content per 100 parts by mass of the acrylic copolymer is 5.0 parts by mass. A coloring agent content of 5.0 parts by mass or less results in more sufficient adhesive strength for the adhesive layer. A more preferred upper limit for the coloring agent content is 4.0 parts by mass, an even more preferred upper limit is 3.5 parts by mass, and an even more preferred upper limit is 2.0 parts by mass. Furthermore, if the adhesive layer contains a coloring agent, the preferred lower limit is 0.2 parts by mass. A coloring agent content of 0.2 parts by mass or more provides sufficient light-shielding properties to the adhesive layer. A more preferred lower limit for the coloring agent content is 0.5 parts by mass, an even more preferred lower limit is 0.8 parts by mass, and an even more preferred lower limit is 1.0 part by mass. Note that the adhesive layer does not necessarily have to contain a coloring agent, and from the viewpoint of further improving the shock absorption properties of the resulting adhesive tape, it is preferable that the adhesive layer does not contain a coloring agent. Examples of the coloring agent content include 0 parts by mass or more and 5.0 parts by mass or less, 0.2 parts by mass or more and 5.0 parts by mass or less, 0.5 parts by mass or more and 4.0 parts by mass or less, 0.8 parts by mass or more and 3.5 parts by mass or less, 1.0 part by mass or more and 2.0 parts by mass or less.

[0072] The adhesive layer may or may not contain a tackifying resin. The inclusion of a tackifying resin in the adhesive layer improves its adhesive strength (especially on rough surfaces). Conversely, the absence of a tackifying resin in the adhesive layer allows for superior shock absorption in the resulting adhesive tape.

[0073] Examples of the tackifying resins mentioned above include rosin resins, rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, and C5-C9 copolymer petroleum resins. Among these, rosin ester resins or terpene phenol resins are preferred from the viewpoint of compatibility with the acrylic copolymer, and among these, rosin ester resins or terpene phenol resins having hydroxyl groups are more preferred. These tackifying resins may be used alone or in combination of two or more.

[0074] Examples of rosin ester resins having the hydroxyl group mentioned above include Pencel D-135 and Super Ester A-75 (both manufactured by Arakawa Chemical Industries, Ltd.). Examples of terpene phenol resins include YS Polystar G150 and YS Polystar T160 (both manufactured by Yasuhara Chemical Co., Ltd.).

[0075] When the adhesive layer contains the tackifying resin, it is preferable that the tackifying resin contains bio-derived carbon. By including a bio-derived carbon in the tackifying resin, the content of bio-derived carbon in the adhesive layer described later can be increased, and the environmental burden of the adhesive tape can be further reduced. Specific examples of bio-derived carbon-containing tackifying resins include Pine Crystal KE-604, Pine Crystal KR-140 (all rosin-based resins, manufactured by Arakawa Chemical Industries), Pine Crystal KE-100, Pine Crystal KE-359, Super Ester A-75 (all rosin ester-based resins, manufactured by Arakawa Chemical Industries), and Tamanol 803L (terpene phenol-based resin, manufactured by Arakawa Chemical Industries).

[0076] If the adhesive layer contains the tackifying resin, it is preferable that the tackifying resin has a softening point of 70°C or higher and 170°C or lower. Including a tackifying resin with a softening point of 70°C or higher further improves the high-temperature holding performance of the resulting adhesive tape. Including a tackifying resin with a softening point of 170°C or lower improves the wettability of the interface of the adhesive layer, thus further improving the adhesive strength of the adhesive layer. It is more preferable that the tackifying resin contains a tackifying resin with a softening point of 100°C or higher and 160°C or lower, even more preferable that it contains a tackifying resin with a softening point of 120°C or higher and 150°C or lower, and even more preferable that it contains a tackifying resin with a softening point of 130°C or higher and 140°C or lower. In this specification, "softening point of tackifying resin" means the softening temperature measured by JIS K2207 (ring-ball method).

[0077] If the adhesive layer contains the tackifying resin, it is preferable that the tackifying resin has a hydroxyl value of 25 mg KOH / g or more. By including a tackifying resin with a hydroxyl value of 25 mg KOH / g or more, the wettability of the interface of the adhesive layer is improved, and thus the adhesive strength of the adhesive layer is further improved. It is more preferable that the tackifying resin contains a hydroxyl value of 30 mg KOH / g or more, and even more preferable that it contains a hydroxyl value of 35 mg KOH / g or more. Furthermore, there is no particular upper limit to the hydroxyl value of the tackifying resin, but from the viewpoint of compatibility with the aromatic block copolymer (X), a preferred upper limit is 50 mg KOH / g. Examples of the hydroxyl value of the tackifying resin include 25 mg KOH / g or more and 50 mg KOH / g or less, 30 mg KOH / g or more and 50 mg KOH / g or less, 35 mg KOH / g or more and 50 mg KOH / g or less, etc. Furthermore, within this specification, the hydroxyl value of the tackifying resin can be measured by JIS K1557 (phthalic anhydride method).

[0078] When the adhesive layer contains the tackifying resin, the preferred upper limit of the tackifying resin content per 100 parts by mass of the acrylic copolymer is 50 parts by mass. A tackifying resin content of 50 parts by mass or less prevents the adhesive layer from becoming too hard, further improves the adhesive strength of the adhesive layer, and results in a more shock-absorbing adhesive tape. A more preferred upper limit for the tackifying resin content is 40 parts by mass, an even more preferred upper limit is 30 parts by mass, an even more preferred upper limit is 20 parts by mass, and a particularly preferred upper limit is 10 parts by mass. Furthermore, when the adhesive layer contains the tackifying resin, from the viewpoint of further improving the adhesive strength of the adhesive layer, a preferred lower limit for the tackifying resin content is 0.1 parts by mass, and a more preferred lower limit is 1.0 part by mass. Note that the adhesive layer does not necessarily have to contain the tackifying resin, and from the viewpoint of further improving the shock absorption of the resulting adhesive tape, it is preferable that the adhesive layer does not contain the tackifying resin. Examples of the content of the tackifying resin include 0 parts by mass or more and 50 parts by mass or less, more than 0 parts by mass and 40 parts by mass or less, 0.1 parts by mass or more and 30 parts by mass or less, 1.0 part by mass or more and 20 parts by mass or less, 1.0 part by mass or more and 10 parts by mass or less.

[0079] Preferably, the adhesive layer has a structure derived from a crosslinking agent. Because the adhesive layer has a structure derived from a crosslinking agent, its cohesive force is increased, resulting in an adhesive tape with better bending resistance and better holding performance at high temperatures. A method for providing the adhesive layer with a structure derived from a crosslinking agent includes, for example, applying an adhesive composition containing a crosslinking agent to a release film or the like, and then heating and drying it.

[0080] The above adhesive composition preferably contains a crosslinking agent. The inclusion of a crosslinking agent in the adhesive composition makes it easier to create an adhesive layer with a structure derived from the crosslinking agent. Therefore, the adhesive layer has increased cohesive strength, resulting in an adhesive tape with superior bending resistance and better retention performance at high temperatures. From the viewpoint of storage stability of the adhesive composition, the crosslinking agent may be added to the adhesive composition immediately before forming the adhesive layer.

[0081] Examples of the crosslinking agents include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of further improving the cohesive strength of the adhesive layer.

[0082] The preferred lower limit of the crosslinking agent content per 100 parts by mass of the acrylic copolymer is 0.05 parts by mass, and the preferred upper limit is 5.0 parts by mass. By having the crosslinking agent content within the above range, the degree of crosslinking of the adhesive layer is appropriately adjusted, and the balance between the bending rigidity and flexibility of the adhesive layer is improved, so that the resulting adhesive tape is more likely to achieve both bending resistance and shock absorption. A more preferred lower limit for the crosslinking agent content is 0.10 parts by mass, a more preferred upper limit is 3.0 parts by mass, an even more preferred lower limit is 0.15 parts by mass, an even more preferred upper limit is 2.0 parts by mass, an even more preferred upper limit is 1.0 part by mass, and a particularly preferred upper limit is 0.5 parts by mass. Examples of the crosslinking agent content include 0.05 parts by mass or more and 5.0 parts by mass or less, 0.10 parts by mass or more and 3.0 parts by mass or less, 0.15 parts by mass or more and 2.0 parts by mass or less, 0.15 parts by mass or more and 1.0 part by mass or less, 0.15 parts by mass or more and 0.5 parts by mass or less.

[0083] The adhesive layer described above may contain conventionally known additives such as antioxidants, organic fillers, inorganic fillers, surfactants, stabilizers, and softeners, as needed.

[0084] The preferred lower limit for the bio-derived carbon content in the adhesive layer is 10%. A bio-derived carbon content of 10% or more in the adhesive layer results in an adhesive tape that is superior in terms of conserving petroleum resources and reducing carbon dioxide emissions, thereby reducing environmental impact. A more preferred lower limit for the bio-derived carbon content in the adhesive layer is 15%, an even more preferred lower limit is 18%, and an even more preferred lower limit is 20%. Furthermore, there is no particular upper limit for the bio-derived carbon content in the adhesive layer, and it may be 100%. Examples of bio-derived carbon content in the adhesive layer include 10% to 100%, 15% to 100%, 18% to 100%, and 20% to 100%.

[0085] While bio-derived carbon contains a certain percentage of the radioactive isotope C-14, petroleum-derived carbon contains almost no C-14. Therefore, the "biologically derived carbon content" as used herein can be calculated by measuring the concentration of C-14 contained in the adhesive layer. Specifically, it can be measured in accordance with ASTM D6866-24, a standard widely used in the bioplastics industry.

[0086] The content of bio-derived carbon in the adhesive layer can be adjusted by adjusting the composition of the adhesive layer. Specifically, examples include a method of synthesizing the acrylic copolymer using an alkyl (meth)acrylate ester containing bio-derived carbon or a monomer having a crosslinkable functional group, or a method of incorporating a tackifying resin containing bio-derived carbon into the adhesive layer.

[0087] The shear storage modulus of the adhesive layer at 23°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz (hereinafter sometimes simply referred to as "shear storage modulus of the adhesive layer at 23°C"), has a preferred lower limit of 0.30 MPa and a preferred upper limit of 5.00 MPa. Having the shear storage modulus of the adhesive layer at 23°C within the above range further improves the bending resistance of the resulting adhesive tape. A more preferred lower limit for the shear storage modulus of the adhesive layer at 23°C is 0.40 MPa, a more preferred upper limit is 4.00 MPa, an even more preferred lower limit is 0.50 MPa, an even more preferred upper limit is 3.50 MPa, an even more preferred lower limit is 0.80 MPa, an even more preferred upper limit is 2.00 MPa, and a particularly preferred lower limit is 0.90 MPa. Examples of the shear storage modulus of the adhesive layer at 23°C include 0.30 MPa to 5.00 MPa, 0.40 MPa to 4.00 MPa, 0.50 MPa to 3.50 MPa, 0.80 MPa to 2.00 MPa, 0.90 MPa to 2.00 MPa, and so on.

[0088] The shear storage modulus of the adhesive layer at 65°C, measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz (hereinafter sometimes simply referred to as "shear storage modulus at 65°C"), has a preferred lower limit of 0.02 MPa. A shear storage modulus of 0.02 MPa or higher for the adhesive layer at 65°C further improves the high-temperature holding performance of the resulting adhesive tape. A more preferred lower limit for the shear storage modulus of 0.03 MPa, an even more preferred lower limit of 0.04 MPa, an even more preferred lower limit of 0.10 MPa, and a particularly preferred lower limit of 0.20 MPa. Furthermore, a preferred upper limit for the shear storage modulus of 0.60 MPa for the adhesive layer at 65°C is 0.60 MPa or lower. A shear storage modulus of 0.60 MPa or lower for the adhesive layer further improves the flexibility of the adhesive layer and enhances the shock absorption of the resulting adhesive tape. A more preferable upper limit for the shear storage modulus of the adhesive layer at 65°C is 0.45 MPa, and an even more preferable upper limit is 0.30 MPa. Examples of the shear storage modulus of the adhesive layer at 65°C include 0.02 MPa to 0.60 MPa, 0.03 MPa to 0.45 MPa, 0.04 MPa to 0.30 MPa, 0.10 MPa to 0.30 MPa, 0.20 MPa to 0.30 MPa, and so on.

[0089] The shear storage modulus of the adhesive layer at 23°C and the shear storage modulus of the adhesive layer at 65°C can be measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz. Specifically, a test specimen is prepared by laminating only the adhesive layer to a thickness of approximately 500 μm, and the measurement can be performed on the prepared test specimen using a dynamic viscoelasticity measuring device (for example, "DVA-200" manufactured by IT Measurement Control Co., Ltd.) under the following conditions: shear mode, measurement temperature -50°C to 300°C, heating rate 10°C / min, measurement frequency 1 Hz, and strain 0.10%.

[0090] Methods for adjusting the shear storage modulus of the adhesive layer at 23°C and the shear storage modulus of the adhesive layer at 65°C include, for example, adjusting the composition of the acrylic copolymer contained in the adhesive layer (for example, adjusting the type and content of constituent units derived from alkyl (meth)acrylate, constituent units derived from monomers having crosslinkable functional groups, constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their terminals, and constituent units derived from vinyl aromatic compounds, introducing blocks having constituent units derived from vinyl aromatic compounds, copolymerizing constituent units derived from isobornyl (meth)acrylate, etc.), weight-average molecular weight, polydispersity, etc., adjusting the type and content of tackifying resins and crosslinking agents contained in the adhesive layer, and adjusting the type and content of constituent units derived from vinyl aromatic compounds in the aromatic block copolymer (X).

[0091] The adhesive layer described above has a preferred lower limit of 0.5 for the loss tangent at 23°C (hereinafter sometimes simply referred to as "the loss tangent of the adhesive layer at 23°C"), as measured by dynamic viscoelasticity measurement at a measurement frequency of 100 Hz. A loss tangent of the adhesive layer at 23°C of 0.5 or higher allows the adhesive tape of this embodiment to have superior shock absorption. A more preferred lower limit for the loss tangent of the adhesive layer at 23°C is 0.7, and an even more preferred lower limit is 1.0. Furthermore, a preferred upper limit for the loss tangent of the adhesive layer at 23°C is 2.5. A loss tangent of the adhesive layer at 23°C of 2.5 or lower further improves the bending resistance of the adhesive tape of this embodiment. A more preferred upper limit for the loss tangent of the adhesive layer at 23°C is 2.0, an even more preferred upper limit is 1.8, and an even more preferred upper limit is 1.5. The loss tangent of the adhesive layer at 23°C can be, for example, 0.5 to 2.5, 0.7 to 2.0, 1.0 to 1.8, 1.0 to 1.5, etc.

[0092] The loss tangent of the adhesive layer at 23°C can be measured by dynamic viscoelasticity measurement at a measurement frequency of 100 Hz. Specifically, a test specimen is prepared by laminating only the adhesive layer to a thickness of approximately 500 μm. Dynamic viscoelasticity measurement is then performed on the prepared test specimen using a dynamic viscoelasticity measuring device (for example, "DVA-200" manufactured by IT Measurement Control Co., Ltd.) under the conditions of shear mode, measurement temperature -100°C to 300°C, heating rate 10°C / min, measurement frequency 100 Hz, and strain 0.10%. The loss tangent of the adhesive layer at 23°C can be obtained from the resulting dynamic viscoelastic spectrum.

[0093] Methods for adjusting the loss tangent of the adhesive layer at 23°C include, for example, adjusting the composition of the acrylic copolymer contained in the adhesive layer (for example, adjusting the types and content of constituent units derived from alkyl (meth)acrylates, monomers having crosslinkable functional groups, olefin polymers having polymerizable unsaturated double bonds at their terminals, and vinyl aromatic compounds; introducing blocks having constituent units derived from vinyl aromatic compounds; copolymerizing constituent units derived from isobornyl (meth)acrylate, etc.), weight-average molecular weight, polydispersity, etc.; adjusting the types and content of tackifying resins and crosslinking agents contained in the adhesive layer; and adjusting the types and content of constituent units derived from vinyl aromatic compounds in the aromatic block copolymer (X).

[0094] The preferred lower limit for the gel fraction of the adhesive layer is 10% by mass, and the preferred upper limit is 70% by mass. When the gel fraction of the adhesive layer is 10% by mass or more, the cohesive force of the adhesive layer is increased, and the adhesive tape of this embodiment has superior holding performance at high temperatures. When the gel fraction of the adhesive layer is 70% by mass or less, the flexibility of the adhesive layer is further improved, and the shock absorption performance of the resulting adhesive tape is further improved. A more preferred lower limit for the gel fraction of the adhesive layer is 20% by mass, a more preferred upper limit is 60% by mass, an even more preferred lower limit is 30% by mass, and an even more preferred upper limit is 50% by mass. Examples of the gel fraction of the adhesive layer include 10% by mass or more and 70% by mass or less, 20% by mass or more and 60% by mass or less, 30% by mass or more and 50% by mass or less, etc.

[0095] The gel fraction of the adhesive layer described above can be measured by the following method. Specifically, first, a test specimen is prepared by cutting the adhesive tape having the adhesive layer into a planar rectangular shape with a width of 20 mm and a length of 40 mm. The test specimen 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 specimen is measured, and the gel fraction is calculated using the following formula (II). Note that the test specimen does not have a release film laminated on it to protect the adhesive layer. Furthermore, if the adhesive tape is a non-support type adhesive tape without a base material, the measurement can be performed using a test specimen obtained by attaching it to a base material and then cutting it, or without using a base material, W in the following formula (II) can be calculated. ０ Calculate by setting to 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (II) (W ０ : Mass of the base material, W １ : Mass of the test specimen before immersion, W ２ (Mass of the test specimen after immersion and drying)

[0096] Methods for adjusting the gel fraction of the adhesive layer include, for example, adjusting the type and content ratio of constituent units derived from monomers having crosslinkable functional groups contained in the acrylic copolymer in the adhesive layer, adjusting the type and content of the crosslinking agent contained in the adhesive layer, and adjusting the irradiance and irradiation time of electron beams or ultraviolet rays used when electron beam irradiation or ultraviolet irradiation is performed to form the adhesive layer. Specifically, methods for adjusting the degree of crosslinking of the adhesive layer include, for example, adjusting the type and content ratio of constituent units derived from monomers having crosslinkable functional groups, and adjusting the type and content of the crosslinking agent contained in the adhesive layer.

[0097] The preferred lower limit for the thickness of the adhesive layer is 50 μm, and the preferred upper limit is 500 μm. A thickness of 50 μm or more improves the adhesive strength of the adhesive layer. A thickness of 500 μm or less allows the adhesive layer to have appropriate flexibility, thereby improving the stress relaxation properties of the adhesive layer and resulting in superior shock absorption. A more preferred lower limit for the thickness of the adhesive layer is 80 μm, a more preferred upper limit is 400 μm, an even more preferred lower limit is 100 μm, an even more preferred upper limit is 300 μm, an even more preferred upper limit is 250 μm, and a particularly preferred upper limit is 200 μm. Examples of the thickness of the adhesive layer include 50 μm to 500 μm, 80 μm to 400 μm, 100 μm to 300 μm, 100 μm to 250 μm, 100 μm to 200 μm, and so on.

[0098] In this specification, thickness can be measured using a dial thickness gauge (for example, Mitutoyo's "ABS Digimatic Indicator").

[0099] Preferably, the adhesive layer has a foamed structure. Having a foamed structure in the adhesive layer improves the stress relaxation properties of the adhesive layer, and the adhesive tape of this embodiment has superior shock absorption properties.

[0100] Methods for forming a foamed structure in the adhesive layer include, for example, a method in which foaming particles are included in the adhesive composition and the adhesive composition is applied to a release film or the like and heated and dried to form a foamed structure; a method in which a gas is forcibly mixed and dispersed in the adhesive composition to form a foamed structure; and a method in which liquefied gas is mixed in the adhesive composition to form a foamed structure. Among these, from the viewpoint of the ease with which bubbles formed in the adhesive layer are dispersed when the adhesive composition is dried at high temperature, the method of including foaming particles in the adhesive composition and applying the adhesive composition to a release film or the like and heating and drying it is preferred.

[0101] The above adhesive composition preferably contains foaming particles. The inclusion of foaming particles in the adhesive composition improves the dispersibility of bubbles in the formed adhesive layer, resulting in a more stress-relaxing adhesive layer. Consequently, the shock absorption of the resulting adhesive tape is further improved.

[0102] Preferably, the adhesive layer has bubbles derived from foaming particles. A method for forming an adhesive layer having bubbles derived from foaming particles is, for example, to heat an adhesive composition containing foaming particles to cause foaming in the resulting layer.

[0103] Examples of the foaming particles mentioned above include those that foam when heated, and may also be thermally expanded particles. Specifically, examples include thermally decomposed foaming agents and thermally expandable microcapsules, and among these, it is preferable that the foaming particles include thermally expandable microcapsules.

[0104] The above-mentioned thermally expandable microcapsules are particles in which a volatile substance such as a low-boiling point solvent is encapsulated inside an outer resin shell. When heated, the outer resin shell softens, and the encapsulated volatile substance volatilizes or expands. As a result, the outer shell expands due to the resulting pressure, increasing the particle size. Therefore, when heated, the thermally expandable microcapsules become hollow particles with air bubbles inside the outer shell. Consequently, in the adhesive layer, the inclusion of thermally expandable microcapsules in the foaming particles prevents gas generated from the foaming particles from escaping to the outside of the adhesive layer, making it easier to maintain an appropriate amount of air bubbles within the adhesive layer and thus improving the foaming ratio of the adhesive layer. As a result, the adhesive layer has appropriate flexibility and superior stress relaxation properties, and the resulting adhesive tape has better shock absorption.

[0105] The outer shell resin of the above-mentioned heat-expandable microcapsules is preferably a thermoplastic resin. Examples of the thermoplastic resin include one or more resins selected from the group consisting of polymers and copolymers thereof of vinyl compounds such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene, and chloroprene, polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate. Among these, copolymers of acrylonitrile are preferred from the viewpoint that the encapsulated volatile substances do not easily permeate and the average particle size of the foamed particles, described later, can be easily adjusted to a suitable range.

[0106] Examples of volatile substances encapsulated inside the above-mentioned thermally expandable microcapsules include one or more low-boiling point liquids selected from the group consisting of C3-C7 hydrocarbons such as propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, hexane, and heptane; methane halides such as methyl chloride and methylene chloride; chlorofluorocarbons such as trichlorofluoromethane and dichlorodifluoromethane; tetraalkylsilanes such as tetramethylsilane and trimethylethylsilane; and petroleum ether. Among these, C3-C7 hydrocarbons are preferred.

[0107] The average particle size of the foamed particles described above has a preferred lower limit of 15 μm and a preferred upper limit of 60 μm. By having the average particle size of the foamed particles within the above range, the balance between the bending resistance and shock absorption of the resulting adhesive tape can be further improved. A more preferred lower limit for the average particle size of the foamed particles is 20 μm, a more preferred upper limit is 55 μm, an even more preferred lower limit is 25 μm, and an even more preferred upper limit is 50 μm. Examples of the average particle size of the foamed particles include 15 μm to 60 μm, 20 μm to 55 μm, 25 μm to 50 μm, etc. In this specification, the "average particle size of the foamed particles" refers to the average particle diameter of the foamed particles in an unfoamed state obtained by observing the adhesive composition containing the foamed particles. The average particle size of the foamed particles can also be obtained by randomly selecting particles using an optical microscope or the like and calculating the average of 10 points.

[0108] Furthermore, the expansion initiation temperature of the foaming particles (also called the "foaming initiation temperature") is not particularly limited, but for example, a temperature range of 95°C to 150°C is possible. The "expansion initiation temperature of foaming particles" refers to the temperature at which the foaming particles begin to expand, and can be measured using a thermomechanical analyzer (TMA) or the like.

[0109] Examples of commercially available foaming particles include Expancel 920DU40 (manufactured by Nippon Philite Co., Ltd., average particle size 40 μm), Expancel 920DU80 (manufactured by Nippon Philite Co., Ltd., average particle size 80 μm), EMC-20(B)R (manufactured by Nippon Philite Co., Ltd., average particle size 20 μm), and Advancel EML101 (manufactured by Sekisui Chemical Co., Ltd., average particle size 50 μm).

[0110] If the adhesive layer has a foamed structure, it may have an open-cell structure or a closed-cell structure, but it is preferable to have a closed-cell structure. Having a closed-cell structure in the adhesive layer improves the bending rigidity of the adhesive layer, and the resulting adhesive tape has improved bending resistance. In addition, the increased tensile strength of the adhesive layer suppresses cohesive failure of the adhesive layer, thus improving the adhesive strength of the adhesive layer. The cell structure can be confirmed, for example, by observing it at a magnification of 150 to 200 times using an optical microscope (for example, Keyence's "VHX-6000").

[0111] If the adhesive layer has a foamed structure, the deemed density of the adhesive layer has a preferred lower limit of 0.59 g / cm³. ３ Therefore, a preferred upper limit is 1.15 g / cm³. ３ Therefore, by having the deemed density of the adhesive layer within the above range, the resulting adhesive tape will have better shock absorption and excellent adhesion to rough surfaces. A more preferable lower limit for the deemed density of the adhesive layer is 0.65 g / cm³. ３ A more preferable upper limit is 1.12 g / cm³. ３ A more preferable lower limit is 0.70 g / cm³. ３ A more preferable upper limit is 1.10 g / cm³. ３ A more preferable lower limit is 0.75 g / cm³. ３ A more preferable upper limit is 1.05 g / cm³. ３ A particularly preferred lower limit is 0.80 g / cm³. ３ A particularly preferred upper limit is 1.00 g / cm³. ３ A very preferable upper limit is 0.90 g / cm³. ３ The deemed density of the above adhesive is, for example, 0.59 g / cm³. ３ 1.15g / cm or more ３ Below, 0.65g / cm ３ 1.12g / cm or more ３ Below, 0.70g / cm ３ 1.10g / cm or more ３ Below, 0.75g / cm ３ 1.05g / cm or more ３ Below, 0.80g / cm３ 1.00g / cm or more ３ Below, 0.80g / cm ３ 0.90g / cm or more ３ The following are some examples.

[0112] The deemed density of the adhesive layer described above can be measured using an electronic hydrometer (for example, Mirage's "ED120T") in accordance with JIS K 7222, etc.

[0113] Methods for adjusting the deemed density of the adhesive layer include, for example, adjusting the type and content of foaming agents such as foaming particles, and changing the composition of the adhesive layer.

[0114] When the adhesive layer has a foamed structure, the preferred lower limit for the average major diameter of the bubbles in the adhesive layer is 10 μm, and the preferred upper limit is 80 μm. When the average major diameter of the bubbles in the adhesive layer is 10 μm or more, the adhesive layer has appropriate flexibility, and the stress relaxation properties of the adhesive layer are further improved, resulting in an adhesive tape with better shock absorption. When the average major diameter of the bubbles in the adhesive layer is 80 μm or less, the bending rigidity of the adhesive layer is further improved, and the adhesive tape with improved bending resistance is further improved. In addition, the fracture strength of the adhesive layer is increased, which further suppresses cohesive failure of the adhesive layer, resulting in improved adhesive strength. A more preferred lower limit for the average major diameter of the bubbles in the adhesive layer is 15 μm, a more preferred upper limit is 70 μm, an even more preferred lower limit is 20 μm, an even more preferred upper limit is 65 μm, an even more preferred upper limit is 60 μm, a particularly preferred upper limit is 55 μm, and a very preferred upper limit is 50 μm. The average major diameter of the bubbles in the adhesive layer can be, for example, 10 μm to 80 μm, 15 μm to 70 μm, 20 μm to 65 μm, 20 μm to 60 μm, 20 μm to 55 μm, 20 μm to 50 μm, etc.

[0115] When the adhesive layer has a foamed structure, the preferred lower limit for the average minor diameter of the bubbles in the adhesive layer is 10 μm, and the preferred upper limit is 75 μm. When the average minor diameter of the bubbles in the adhesive layer is 10 μm or more, the adhesive layer has appropriate flexibility, and the stress relaxation properties of the adhesive layer are further improved, resulting in an adhesive tape with better shock absorption. When the average minor diameter of the bubbles in the adhesive layer is 75 μm or less, the bending rigidity of the adhesive layer is further improved, and the adhesive tape with improved bending resistance is further improved. In addition, the fracture strength of the adhesive layer is increased, which further suppresses cohesive failure of the adhesive layer, resulting in improved adhesive strength. A more preferred lower limit for the average minor diameter of the bubbles in the adhesive layer is 15 μm, a more preferred upper limit is 70 μm, an even more preferred lower limit is 20 μm, an even more preferred upper limit is 65 μm, an even more preferred upper limit is 60 μm, a particularly preferred upper limit is 55 μm, and a very preferred upper limit is 50 μm. The average short diameter of the bubbles in the adhesive layer can be, for example, 10 μm to 75 μm, 15 μm to 70 μm, 20 μm to 65 μm, 20 μm to 60 μm, 20 μm to 55 μm, 20 μm to 50 μm, etc.

[0116] When the adhesive layer has a foamed structure, the aspect ratio of the bubbles in the adhesive layer has a preferred lower limit of 1.00 and a preferred upper limit of 3.50. When the aspect ratio of the bubbles in the adhesive layer is 1.00 or higher, the structure of the bubbles in the adhesive layer becomes flattened, and the adhesive layer has appropriate flexibility. As a result, the stress relaxation properties of the adhesive layer are further improved, and the resulting adhesive tape has better shock absorption properties. When the aspect ratio of the bubbles in the adhesive layer is 3.50 or lower, the bending rigidity of the adhesive layer is further improved, and the resulting adhesive tape has better bending resistance. In addition, since the fracture strength of the adhesive layer is increased, cohesive failure of the adhesive layer can be further suppressed, and the adhesive strength of the adhesive layer is further improved. A more preferred lower limit for the aspect ratio of the bubbles in the adhesive layer is 1.25, a more preferred upper limit is 3.00, an even more preferred lower limit is 1.50, and an even more preferred upper limit is 2.50. Examples of the average minor diameter of the bubbles in the adhesive layer mentioned above include 1.00 to 3.50, 1.25 to 3.00, 1.50 to 2.50, etc. In this specification, "bubble aspect ratio" means the value obtained by dividing the average major diameter of the bubbles by the average minor diameter of the bubbles (average major diameter of bubbles / average minor diameter of bubbles).

[0117] The average major diameter, average minor diameter, and aspect ratio of the bubbles in the adhesive layer can be determined, for example, as follows: Using a razor (Feather Corporation), the adhesive layer is sliced ​​with a plane parallel to the MD (Machine Direction) direction and the thickness direction to obtain an MD cut sample. The obtained MD cut sample is photographed using a digital microscope (for example, Keyence Corporation's "VHX-6000") under conditions such as a magnification of 200x and a measurement screen size of 1.8 mm × 1.3 mm. In the obtained photographed image, the bubble with the largest major diameter and the bubble with the second largest major diameter are selected, and the major and minor diameters of these bubbles are measured to calculate the aspect ratio. Perform this operation for three captured images. The average of the major axes of the six bubbles is taken as the average major axis of the bubbles in the adhesive layer, the average of the minor axes of the six bubbles is taken as the average minor axis of the bubbles in the adhesive layer, and the average of the aspect ratios of the six bubbles is taken as the aspect ratio of the bubbles in the adhesive layer. If the above MD direction is unknown, slice the adhesive layer with a plane parallel to the thickness direction to obtain a cut sample. Slice the sample so that the cutting direction is shifted by 30° from the direction from which the previous cut sample was cut, and measure the aspect ratio in the same manner as above. Repeat the above measurement until returning to the cutting direction of the first measurement. The average of the major axes of the twelve bubbles measured is taken as the average major axis of the bubbles in the adhesive layer, the average of the minor axes of the twelve bubbles is taken as the average minor axis of the bubbles in the adhesive layer, and the average of the aspect ratios of the twelve bubbles is taken as the aspect ratio of the bubbles in the adhesive layer.

[0118] Methods for adjusting the average major diameter of the bubbles in the adhesive layer, the average minor diameter of the bubbles in the adhesive layer, and the aspect ratio of the bubbles in the adhesive layer include, for example, a method of mechanically stretching and compressing the adhesive layer during its manufacture, and a method of including a surfactant or stabilizer in the resin composition that forms the adhesive layer.

[0119] Preferably, the average major diameter of the bubbles in the adhesive layer is 0.80 times or less the thickness of the adhesive layer. Having an average major diameter of 0.80 times or less the thickness of the adhesive layer improves the bending rigidity of the adhesive layer, resulting in improved bending resistance of the resulting adhesive tape. Furthermore, the increased tensile strength of the adhesive layer suppresses cohesive failure, thus improving the adhesive strength of the adhesive layer. More preferably, the average major diameter of the bubbles is 0.70 times or less the thickness of the adhesive layer, even more preferably 0.60 times or less, and even more preferably 0.30 times or less. Also, preferably, the average major diameter of the bubbles is 0.05 times or more the thickness of the adhesive layer. Having an average major diameter of 0.05 times or more the thickness of the adhesive layer provides the adhesive layer with appropriate flexibility, improving stress relaxation and resulting in superior shock absorption of the resulting adhesive tape. It is more preferable that the average major diameter of the bubbles is 0.10 times or more the thickness of the adhesive layer. That is, it is preferable that the average major diameter of the bubbles is 0.05 times or more and 0.80 times or less the thickness of the adhesive layer, more preferably 0.10 times or more and 0.70 times or less, even more preferably 0.1 times or more and 0.60 times or less, and even more preferably 0.10 times or more and 0.30 times or less.

[0120] If the adhesive layer has a foamed structure, it is preferable that the adhesive layer has a structure in which no air bubbles are exposed on the surface in the thickness direction. Because the adhesive layer does not have air bubbles exposed on the surface in the thickness direction, the area of ​​the adhesive interface between the adhesive layer and the adherend is increased, and the adhesive strength of the adhesive layer is further improved.

[0121] One method for creating a structure in which no air bubbles are exposed on the surface in the thickness direction of the adhesive layer is to use an adhesive composition containing large foaming particles, thereby suppressing the floating of foaming particles to the liquid surface during the solution coating of the adhesive composition in the adhesive layer formation process.

[0122] The adhesive tape of this embodiment may have other layers besides the adhesive layer as needed, but from the viewpoint of further improving the shock absorption and adhesion to rough surfaces of the resulting adhesive tape, it is preferable that the adhesive tape has only the adhesive layer. Furthermore, when the adhesive tape of this embodiment has only the adhesive layer, the resulting adhesive tape becomes thinner, making it more suitable for fixing electronic equipment components or automotive components.

[0123] The above adhesive tape may or may not have a base material. If the adhesive tape has a base material, the resulting adhesive tape can be given better reworkability. If the adhesive tape does not have a base material, the resulting adhesive tape will have improved shock absorption and adhesion to rough surfaces. In addition, since the resulting adhesive tape will be thinner, it can be used more suitably for fixing electronic equipment components or automotive components.

[0124] If the adhesive tape of this embodiment has a base material, it may be a single-sided adhesive tape having the adhesive layer on one side of the base material, or it may be a double-sided adhesive tape having adhesive layers on both sides of the base material. Furthermore, if the adhesive tape is a double-sided adhesive tape, at least one of the adhesive layers may be the adhesive layer, and the other adhesive layer may be the adhesive layer, or any adhesive layer as long as it does not impair the effects of the present invention.

[0125] If the adhesive tape described above has a base material, examples of the base material used for the base material include film, nonwoven fabric, and the like.

[0126] From the viewpoint of increasing the overall bio-derived carbon content of the adhesive tape, a substrate made from a bio-derived material is preferred for the substrate used in the above-mentioned substrate. Examples of the above-mentioned bio-derived materials include polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS), as well as polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetylcellulose (TAC), cellulose, and polyamide (PA), all of which are derived from plants.

[0127] Furthermore, from the perspective of reducing environmental impact by decreasing the use of new petroleum resources and suppressing carbon dioxide emissions, base materials made from recycled resources may be used. Methods for recycling resources include, for example, recovering waste from packaging containers, home appliances, automobiles, construction materials, food, etc., or waste generated in the manufacturing process, and using the extracted materials again as raw materials by washing, decontamination, or decomposition by heating or fermentation. Examples of base materials using the above recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., using recovered plastics that have been re-resinated as raw materials. Alternatively, the recovered waste may be burned and used as thermal energy for the manufacture of base materials and their raw materials, or the oils and fats contained in the recovered waste may be mixed with petroleum, fractionally distilled, and refined to be used as raw materials.

[0128] The type of base material used for the above-mentioned base material is preferably a film, from the viewpoint of the base material having excellent stiffness and further improving the bending resistance of the resulting adhesive tape, and preferably a film containing PES or a film containing PA. Examples of PA 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.

[0129] The preferred lower limit for the thickness of the above-mentioned substrate is 3.5 μm, and the preferred upper limit is 1000 μm. By having the thickness of the above-mentioned substrate within the above range, the balance between the flexibility and rigidity of the substrate is improved, and the bending resistance and shock absorption of the resulting adhesive tape are further improved. A more preferred lower limit for the thickness of the above-mentioned substrate is 5 μm, a more preferred upper limit is 500 μm, an even more preferred lower limit is 6.5 μm, an even more preferred upper limit is 300 μm, an even more preferred lower limit is 10 μm, an even more preferred upper limit is 200 μm, a particularly preferred lower limit is 30 μm, and a particularly more preferred upper limit is 100 μm. Examples of the thickness of the above-mentioned substrate include 3.5 μm to 1000 μm, 5 μm to 500 μm, 6.5 μm to 300 μm, 10 μm to 200 μm, 30 μm to 100 μm, etc.

[0130] The method for manufacturing the above-mentioned adhesive tape is not particularly limited, and conventionally known methods can be used. For example, the method for manufacturing an adhesive tape having only the above-mentioned adhesive layer is as follows. First, a solvent is added to the above-mentioned acrylic copolymer, the above-mentioned aromatic block copolymer (X), tackifying resin, foaming particles, etc., to prepare a solution of the adhesive composition. Next, the prepared solution of the adhesive composition is applied to the release treatment surface of a release PET film, and the solution of the adhesive composition is heated to dry and remove the solvent in the solution and form a foamed structure, thereby forming an adhesive layer. Then, by placing the release treatment surface of the release PET film on top of the formed adhesive layer, an adhesive tape can be obtained in which the surface of the adhesive layer is covered with the release PET film. Adhesive tapes can also be manufactured using an extruder for extrusion molding. Specifically, for example, the above-mentioned adhesive layer can be supplied to an extruder, melt-kneaded, and then a sheet-like raw material of the adhesive layer can be extruded.

[0131] Furthermore, the method for manufacturing an adhesive tape having the above-mentioned substrate and having the above-mentioned adhesive layer on at least one side of the substrate is as follows. That is, an adhesive layer formed in the same manner as the method for manufacturing an adhesive tape having only the above-mentioned adhesive layer is bonded to the substrate, pressed together using a rubber roller to create a laminated and integrated structure, and then cured for one hour in an environment of 23°C to obtain an adhesive tape having an adhesive layer on one side of the substrate. Alternatively, the adhesive composition may be directly applied to the substrate, dried to form an adhesive layer, and then the release treatment surface of a release film may be placed on top of the formed adhesive layer. Alternatively, an adhesive tape having the above-mentioned adhesive layer on one side of the substrate and an adhesive layer on the other side of the substrate can be obtained by placing an arbitrary adhesive layer prepared on the other side of the substrate and then laminating and integrating it.

[0132] The preferred lower limit for the 180° peel force of the above adhesive tape against SUS at 23°C is 10 N / 25 mm. A 180° peel force of 10 N / 25 mm or higher on SUS at 23°C results in superior adhesive strength. A more preferred lower limit for the 180° peel force of the above adhesive tape against SUS at 23°C is 12 N / 25 mm, an even more preferred lower limit is 15 N / 25 mm, and an even more preferred lower limit is 20 N / 25 mm. Furthermore, there is no particular upper limit for the 180° peel force of the above adhesive tape against SUS at 23°C, but approximately 50 N / 25 mm is a practical upper limit. Examples of the 180° peel force of the above adhesive tape on SUS at 23°C include 10N / 25mm to 50N / 25mm, 12N / 25mm to 50N / 25mm, 15N / 25mm to 50N / 25mm, 20N / 25mm to 50N / 25mm, etc.

[0133] The 180° peel force of the above adhesive tape against SUS at 23°C can be measured by the following method. First, one side of the adhesive tape (the side not to be measured) is pressed onto a 23 μm thick polyethylene terephthalate film by, if necessary, running a 2 kg rubber roller back and forth once at a speed of 300 mm / min to create a test piece. Then, it is cut to a width of 25 mm and a length of 75 mm to prepare a test piece. Next, the adhesive layer on the other side of the prepared test piece is attached to a SUS304 plate (a SUS304 plate that has been cleaned with ethanol and then wiped dry), and pressed by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Finally, it is cured at 23°C and 50% RH for 20 minutes to prepare a test sample. The obtained test samples can be measured by peeling the adhesive tape from the SUS304 plate in accordance with JIS Z 0237:2009, under conditions of 23°C, 50% RH, a tensile speed of 300 mm / min, and a peeling angle of 180°.

[0134] Methods for adjusting the 180° peel force of the above adhesive tape against SUS at 23°C include, for example, changing the composition of the acrylic copolymer contained in the adhesive layer (for example, increasing the content of constituent units derived from monomers having crosslinkable functional groups), adjusting the weight-average molecular weight, polydispersity, etc., of the acrylic copolymer, including a tackifying resin in the adhesive layer, adjusting the thickness of the adhesive layer, adjusting the content of the crosslinking agent contained in the adhesive composition, and adjusting the type and thickness of the substrate.

[0135] The thickness of the adhesive tape described above has a preferred lower limit of 50 μm and a preferred upper limit of 500 μm. A thickness of 50 μm or more in this embodiment further improves the shock absorption properties of the resulting adhesive tape. A thickness of 500 μm or less allows for more suitable use in fixing electronic equipment components or automotive components. A more preferred lower limit for the thickness of the adhesive tape is 80 μm, a more preferred upper limit is 400 μm, an even more preferred lower limit is 100 μm, an even more preferred upper limit is 300 μm, and an even more preferred upper limit is 250 μm. Examples of the overall thickness of the adhesive tape include 50 μm to 500 μm, 80 μm to 400 μm, 100 μm to 300 μm, 100 μm to 250 μm, etc. In this specification, "thickness of adhesive tape" does not include the thickness of the separator, such as a release film, that protects the outermost adhesive layer of the adhesive tape.

[0136] The adhesive tape of this embodiment has a preferred upper limit of 70% for light transmittance at a wavelength of 550 nm. By having a light transmittance of 70% or less at a wavelength of 550 nm, the adhesive tape of this embodiment can be more suitably used for fixing internal components of electrical and electronic equipment. A more preferred upper limit for the light transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm is 60%, an even more preferred upper limit is 50% by mass, an even more preferred upper limit is 40%, a particularly preferred upper limit is 30%, and a very preferred upper limit is 10%. There is no particular lower limit for the light transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm, with 0% being the most preferred. Examples of the light transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm include 0% to 70%, 0% to 60%, 0% to 50%, 0% to 40%, 0% to 30%, and 0% to 10%. Furthermore, the transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm can be measured using a spectrophotometer (such as the "V-670" manufactured by JASCO Corporation).

[0137] The applications of the above-mentioned adhesive tape are not particularly limited, but because it has excellent shock absorption properties, it can be suitably used for fixing parts, and because it also exhibits excellent thermal stability, it can be more suitably used for fixing electronic equipment components or automotive components exposed to high-temperature environments. Examples of the above-mentioned electronic equipment include televisions, monitors, and portable electronic devices, and examples of the above-mentioned automotive components include automotive electronic equipment.

[0138] Furthermore, it is preferable that the adhesive tape of this embodiment be further provided with bending resistance, high-temperature retention performance, light-shielding properties, etc., by various methods.

[0139] Adhesive tapes with excellent bending resistance can prevent damage to the adherend due to deformation of the adhesive tape when the adherend is bent, making them more suitable for bonding and fixing components of thin electronic devices. Specifically, examples include fixing components in foldable display devices such as thin televisions and thin monitors, and more specifically, using them to fix the surface cover panel of a display device to a housing with uneven surfaces.

[0140] Adhesive tapes with excellent high-temperature holding performance can be used to fix electronic device components that are often exposed to high-temperature environments, as they can exhibit excellent holding performance even in high-temperature environments.

[0141] Adhesive tapes with excellent light-blocking properties can further suppress light leakage from the adhesive interface, making them more suitable for fixing electronic equipment components or automotive components.

[0142] An electronic device including the adhesive tape of this embodiment is also one of these embodiments. The electronic device of this embodiment is not particularly limited as long as it includes the adhesive tape, but examples include electronic devices in which electronic components are bonded and fixed together with the adhesive tape, and specifically, for example, a display device in which a cover panel and a housing having irregularities are bonded and fixed together with the adhesive tape.

[0143] According to the present invention, it is possible to provide an adhesive tape that achieves both excellent shock absorption and excellent thermal stability. Furthermore, according to the present invention, it is possible to provide an electronic device that includes the adhesive tape.

[0144] This is a schematic diagram of a test specimen used to evaluate shock absorption. This is a schematic diagram illustrating the method for evaluating shock absorption. This is a schematic diagram illustrating the method for evaluating bending resistance. This is a schematic diagram illustrating a high-temperature holding test.

[0145] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0146] <Monomers containing bio-derived carbon> (1) Linoleic acid derived from castor oil was converted to linoleic acid hydroperoxide by lipoxygenase, and then a mixture containing n-hexylaldehyde was obtained by isomerase. By distillation of the obtained mixture, n-hexylaldehyde containing bio-derived carbon was obtained. Furthermore, by hydrogenation of the obtained n-hexylaldehyde containing bio-derived carbon, n-hexyl alcohol containing bio-derived carbon was obtained. By esterifying the obtained n-hexyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), n-hexyl acrylic acid containing bio-derived carbon was prepared.

[0147] (2) Ricinoleic acid derived from n-heptyl acrylate castor oil was cracked to obtain a mixture containing undecylenic acid and n-heptyl alcohol. Then, undecylenic acid was separated from the obtained mixture by distillation to obtain n-heptyl alcohol containing bio-derived carbon. By esterifying the obtained n-heptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), n-heptyl acrylate containing bio-derived carbon was prepared.

[0148] (3) Ricinoleic acid derived from 1-methylheptyl acrylate castor oil was dissolved in alkali to obtain a mixture containing sebacic acid and 1-methylheptyl alcohol. Then, sebacic 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.).

[0149] (4) Pinene extracted from pine resin was isomerized to obtain camphene containing bio-derived carbon. By reacting camphene containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), isobornyl acrylate containing bio-derived carbon was prepared.

[0150] (5) Pinene extracted from pine resin was isomerized to obtain camphene containing bio-derived carbon. By reacting camphene containing bio-derived carbon with methacrylic acid (manufactured by Mitsubishi Chemical Corporation), isobornyl methacrylate containing bio-derived carbon was prepared.

[0151] <Biologically derived, carbon-free monomers> ・n-butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・2-ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) ・methyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・methyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・ethylene-butylene macromonomer (ethylene-butylene macromonomer with an acryloyl group at one end, manufactured by Kraton Polymers, "HPVM-L1253") ・acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) ・2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) ・styrene (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0152] <Expandable Particles> - Thermally expandable microcapsules: Expancel 920DU40 (manufactured by Nippon Philite Co., Ltd., average particle size 40 μm)

[0153] <Aromatic Block Copolymers (X)> ・SIS Block Copolymer: Quintac 3620 (manufactured by Zeon Corporation, styrene ratio 14%) ・SEBS Block Copolymer: DYNARON 8300P (manufactured by ENEOS Material Corporation) ・SEPS Block Copolymer: SEPTON 2063 (manufactured by Kuraray Co., Ltd.)

[0154] <Coloring agent> ・Carbon black: Multi-rack A903 Black (manufactured by Toyo Color Co., Ltd.)

[0155] <Tackifying Resins> ・Terpene phenol resin: YS Polystar G150 (manufactured by Yasuhara Chemical Co., Ltd.) ・Rosin ester resin: Pine Crystal KE-359 (manufactured by Arakawa Chemical Industries, Ltd., softening point: 94-104°C, hydroxyl value: 38-47 mgKOH / g, tackifying resin containing bio-derived carbon)

[0156] <Crosslinking agents> - Isocyanate-based crosslinking agent: Desmodulo L-75 (manufactured by Covestro) - Epoxy-based crosslinking agent: Tetrad E-5C (manufactured by Mitsubishi Gas Chemical Company)

[0157] (Synthesis of Acrylic Copolymer) (Acrylic Copolymer A) A reactor equipped with a thermometer, stirrer, and condenser was prepared. A mixture of the constituent unit monomers shown in Table 1 and 80 parts by mass of ethyl acetate were added to the reactor, and the reactor was heated and reflux was started. Subsequently, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added to the reactor as a polymerization initiator, and polymerization was started under reflux. Next, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added 1 hour and 2 hours after the start of polymerization, and further, 0.05 parts by mass of t-hexylperoxypivalate was added 4 hours after the start of polymerization to continue the polymerization reaction. Eight hours after the start of polymerization, an ethyl acetate solution of acrylic copolymer A was obtained. The weight-average molecular weight of the obtained acrylic copolymer was measured using a 2690 Separations Module (Waters Co., Ltd.) as the measuring instrument, a GPC KF-806L column (Showa Denko Corporation), and ethyl acetate as the solvent, under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The results are shown in Table 1.

[0158] (Acrylic copolymers B-E, I-L, U-W) Except for the types and amounts of constituent monomers of the acrylic copolymers shown in Tables 1-2, ethyl acetate solutions of the acrylic copolymers were prepared in the same manner as for acrylic copolymer A, and the weight-average molecular weight of the acrylic copolymers was measured. The results are shown in Tables 1-2.

[0159] (Acrylic copolymer F) (1) Synthesis of RAFT agent 0.902 g of 1,6-hexanedithiol, 1.83 g of carbon disulfide, and 11 mL of dimethylformamide were placed in a two-necked flask and stirred at 25°C. 2.49 g of triethylammonium was added dropwise over 15 minutes and stirred at 25°C for 3 hours. Next, 2.75 g of methyl-α-bromophenylacetic acid was added dropwise over 15 minutes and stirred at 25°C for 4 hours. Then, 100 mL of extraction solvent (n-hexane:ethyl acetate = 50:50) and 50 mL of water were added to the reaction mixture and liquid-liquid extraction was performed. The organic layers obtained from the first and second liquid-liquid extractions were mixed and washed sequentially with 50 mL of 1 M hydrochloric acid, 50 mL of water, and 50 mL of saturated brine. Sodium sulfate was added to the organic layer after washing and dried, then the sodium sulfate was filtered off, and the filtrate was concentrated using an evaporator to remove the organic solvent. The obtained concentrate was purified by silica gel column chromatography to obtain the RAFT agent.

[0160] (2) Synthesis of a block having structural units derived from styrene 0.19 g of the obtained RAFT agent, 0.035 g of styrene and 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator, and 80 g of ethyl acetate as a solvent were placed in a two-necked flask, and the temperature was raised to 85°C while replacing the inside of the flask with nitrogen gas. The amount of styrene added was such that the content ratio in the acrylic copolymer is as shown in Table 1. Then, the polymerization reaction was carried out by stirring at 85°C for 6 hours (first stage reaction). After the first stage reaction was completed, 400 g of n-hexane was added to the flask, and the reactants were stirred to precipitate the product. Unreacted monomers (St) and the RAFT agent were filtered off, and the reactants were dried under reduced pressure at 70°C to obtain a hard block having structural units derived from styrene.

[0161] (3) Synthesis of Acrylic Copolymers Furthermore, a mixture of constituent unit monomers other than styrene in Table 1, 0.0027 g of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator, and 5 g of ethyl acetate as a solvent, along with the hard block having constituent units derived from styrene obtained earlier, were placed in a two-necked flask, and the flask was heated to 85°C while purging the inside of the flask with nitrogen gas. The polymerization reaction was then carried out by stirring at 85°C for 6 hours (second-stage reaction), and a reaction solution containing a block copolymer consisting of a hard block having constituent units derived from styrene and a soft block derived from constituent unit monomers other than styrene in Table 1 was obtained. A portion of the reaction solution was taken, 400 g of n-hexane was added thereto, and the reaction product was precipitated by stirring. Unreacted monomers and solvent were filtered off, and the reaction product was dried under reduced pressure at 70°C to remove the block copolymer from the reaction solution. An acrylic copolymer having a triblock copolymer structure was synthesized by the above method. Subsequently, an ethyl acetate solution of the acrylic copolymer was prepared. The weight-average molecular weight was measured using the same method as for acrylic copolymer A. The results are shown in Table 1.

[0162] (Acrylic copolymers G-H, M-T) Except for the types and amounts of constituent monomers of the acrylic copolymers shown in Tables 1-2, ethyl acetate solutions of acrylic copolymers having a triblock copolymer structure were prepared in the same manner as for acrylic copolymer F. For acrylic copolymers O-R, the types and amounts of constituent monomers of the acrylic copolymers were as shown in Table 2, and the amount of polymerization initiator added in "(3) Synthesis of acrylic copolymers" described above was appropriately changed, except for the same manner as for acrylic copolymer F, ethyl acetate solutions of acrylic copolymers having a triblock copolymer structure were prepared. The weight-average molecular weight of the acrylic copolymers was determined in the same manner as for acrylic copolymer A. The results are shown in Tables 1-2.

[0163]

[0164]

[0165] (Example 1) (1) Preparation of adhesive tape To the solution of acrylic copolymer A obtained in the above-described "(synthesis of acrylic copolymer)", 0.4 parts by mass of thermally expandable microcapsules as foaming particles, 30 parts by mass of SIS block copolymer dissolved in toluene as aromatic block copolymer (X), 0.2 parts by mass of isocyanate-based crosslinking agent as a crosslinking agent, and 30 parts by mass of ethyl acetate as a solvent were added to 100 parts by mass of the solid content of acrylic copolymer A, and the mixture was thoroughly stirred to prepare a solution containing an adhesive composition. The prepared solution containing the adhesive composition was applied to the release surface of a 50 μm thick release PET film, and then heated at 110°C for 5 minutes to dry the solvent and foam the layer of adhesive composition, thereby forming an 80 μm thick adhesive layer. After bonding the obtained adhesive layer to the release-treated surface of a 50 μm thick release PET film, and curing it in a 40°C environment for 48 hours, an adhesive tape with only an adhesive layer was obtained, and an adhesive tape with a release PET film, in which the surface of the adhesive layer was protected by the release PET film, was obtained.

[0166] (2) Measurement of the average area of ​​the dispersed phase (2-1) Section preparation and staining First, the adhesive layer obtained by peeling off the release PET film from both sides of the obtained adhesive tape was cooled to -60°C using a cryomicrotome (Leica, "ULTRACUT FC7"), and then cut into a plane parallel to the thickness direction with a glass knife, and the cut sections with a thickness of 1.0 μm were collected on a glass slide. In order to suppress the occurrence of wrinkles in the sections, water was dropped onto a hydrophilized glass slide, and the sections were collected in the part where the water froze (thin ice). The collected sections were then air-dried at room temperature and stained under the following conditions. Staining reagent: Ruthenium tetroxide Staining conditions: VSC1R1H vacuum electron staining apparatus manufactured by Philgen (Time: 10 min, concentration: 1)

[0167] (2-2) Acquisition of images for analysis Next, after staining the sections in "(2-1) Section preparation and staining" described above, images for analysis were acquired using a simple SEM (Hitachi High-Tech, "TM4000Plus") under the following conditions, and it was confirmed that the adhesive layer of the obtained adhesive tape had a continuous phase and a dispersed phase. Acceleration voltage: 5kV Detection signal: Backscattered electron Magnification: 1500x Image size: 84.6μm × 63.4μm

[0168] (2-3) Image Analysis The images obtained in "(2-2) Acquisition of Images for Analysis" described above were analyzed using the open-source image analysis software Fiji in the following steps (i) to (iii).

[0169] (i) Image cropping: Using "Rectangle" on the acquired image, the central area of ​​the image was selected. Then, "Duplicate" was applied to crop and duplicate the image. The conditions for the image cropping area were as follows: Width 63.4 (μm) × Height 47.6 (μm)

[0170] (ii) Extraction of the Dispersive Phase The image cropped in "(i) Image Cropping" above was given the "Threshold" function, and the threshold was adjusted so that the dispersed phase region would be extracted. Subsequently, "Binary Options (Close)", "Binary Options (Fill Holes)", and "Binary Options (Open)" were applied to remove noise from the extracted region and extract the dispersed phase region. The conditions for each analysis module are as follows, for example.・Threshold threshold method: MaxEntropy ・Binary Options (Close) iterations: 1 Count: 1 Black background: True Pad edges when eroding: True ・Binary Options (Fill Holes) iterations: 1 Count: 1 Black background: True Pad edges when eroding: True・Binary Options (Open) iterations: 1 Count: 1 Black background:True Pad edges when eroding:True

[0171] (iii) Analysis of the area of ​​the dispersed phase For the image from which the dispersed phase was extracted in "(ii) Extraction of the dispersed phase" described above, "Set Measurements" was applied to set the feature calculation items for the extracted region. Next, "Analyze Particles" was applied to analyze the area of ​​each dispersed phase. The conditions for each analysis module were as follows: • Set Measurements Area: True • Analyze Particles Size: 5-Infinity Circulation: 0-1

[0172] (2-4) Calculation of the average area of ​​the dispersed phase Using the area of ​​the dispersed phase analyzed in "(iii) Analysis of the area of ​​the dispersed phase" described above, the average area of ​​the dispersed phase was calculated using the following formula (III). Average area of ​​the dispersed phase (μm ２ ) = {Total actual exposed area of ​​the dispersed phase (μm²) ２)} / {Number of analysis} (III) Note that the actual exposed area of ​​the dispersed phase in equation (III) is (μm ２ The actual exposed area of ​​the dispersed phase (μm²) was calculated using the following formula (IV). ２ ) = {dispersed phase area (pixel ２ )} × {resolution ２ (μm / pixel) ２ (IV) Furthermore, sections were prepared so that the cutting direction was shifted by 30° from the direction in which the section was cut immediately before, and the average area of ​​the dispersed phase was measured in the same manner as above. The above measurement was repeated until the cutting direction returned to that of the first measurement, and the average of the average area of ​​the dispersed phase in a total of six sections was taken as the average area of ​​the dispersed phase in the entire adhesive layer. The results are shown in Table 3.

[0173] (3) Measurement of the aspect ratio of the dispersed phase (3-1) Analysis of the aspect ratio of the dispersed phase Sections were prepared by cutting out the adhesive layer using the same method as in "(2-1) Section preparation and staining" described above. Set Measurements was applied to the images in which the dispersed phase region was extracted using "(i) Image cropping" and "(ii) Extraction of the dispersed phase" described above to set the feature calculation items for the extracted region. Subsequently, Analyze Particles was applied to analyze the aspect ratio of the dispersed phase (major axis of the dispersed phase / minor axis of the dispersed phase). The conditions for each analysis module were as follows: Set Measurements Fit ellipse: True Analyze Particles Size: 5-Infinity Circularity: 0-1

[0174] (3-2) Calculation of the average aspect ratio of the dispersed phase Using the aspect ratio of the dispersed phase analyzed in "(3-1) Analysis of the aspect ratio of the dispersed phase" described above, the average aspect ratio of the dispersed phase was calculated using the following formula (V): Average aspect ratio of the dispersed phase = {Sum of aspect ratios of the dispersed phase} / {Number of analysis} (V) Furthermore, sections were prepared so that the cutting direction was shifted by 30° from the direction from which the section was cut immediately before, and the average area of ​​the dispersed phase was measured in the same manner as above. The above measurement was repeated until returning to the cutting direction of the first measurement, and the average aspect ratio of the dispersed phase in a total of six measured sections was measured, and the average value of the average aspect ratio of the dispersed phase in a total of six measured sections was taken as the average aspect ratio of the dispersed phase of the entire adhesive layer. The results are shown in Table 3.

[0175] (4) Calculation of the area change rate of the dispersed phase before and after the heating test First, the average area of ​​the dispersed phase measured using the same method as in "(2) Measurement of the average area of ​​the dispersed phase" described above was taken as the average area of ​​the dispersed phase before the heating test. Next, the obtained adhesive tape was placed in a constant temperature oven set to 150°C and heated for two days, then air-cooled to about 25°C in a 25°C environment. Then, using the same method as in "(2) Measurement of the average area of ​​the dispersed phase" described above, the average area of ​​the dispersed phase was measured on the prepared section and taken as the average area of ​​the dispersed phase after the heating test. Then, using the obtained average area of ​​the dispersed phase before the heating test and the average area of ​​the dispersed phase after the heating test, the area change rate of the dispersed phase before and after the heating test, which involved heating at 150°C for two days, was calculated using formula (I) above. The results are shown in Table 3.

[0176] (5) Measurement of the deemed density of the adhesive layer The release PET film on both sides is peeled off from the obtained adhesive tape, and the deemed density of the adhesive layer (g / cm³) is determined in accordance with JIS K 7222. ３ The following was measured. The results are shown in Table 3.

[0177] (6) Measurement of the shear storage modulus of the adhesive layer at 23°C and at 65°C Multiple adhesive layers were prepared by peeling off the release PET films from both sides of the obtained adhesive tape, and test specimens were made by laminating only the adhesive layers to a thickness of 500 μm. Dynamic viscoelasticity measurements were performed on the prepared test specimens using a dynamic viscoelasticity measuring device (DVA-200, manufactured by IT Measurement Control Co., Ltd.) under the following conditions: shear mode, measurement temperature -50°C to 300°C, heating rate 10°C / min, measurement frequency 1 Hz, and strain 0.10%. The shear storage modulus (MPa) of the adhesive layer at 23°C and the shear storage modulus (MPa) of the adhesive layer at 65°C were measured. The results are shown in Table 3.

[0178] (7) Measurement of the loss tangent of the adhesive layer at 23°C Multiple adhesive layers were prepared by peeling off the release PET film from both sides of the obtained adhesive tape, and test specimens were made by laminating only the adhesive layers to a thickness of 500 μm. Dynamic viscoelasticity measurements were performed on the prepared test specimens using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd., "DVA-200") under the conditions of shear mode, measurement temperature -100°C to 300°C, heating rate 10°C / min, measurement frequency 100 Hz, and strain 0.10%, and the loss tangent of the adhesive layer at 23°C was obtained from the obtained dynamic viscoelasticity spectrum. The results are shown in Table 3.

[0179] (8) Measurement of the gel fraction of the adhesive layer The release PET film was peeled off one side of the obtained adhesive tape and bonded to a 23 μm thick base PET film (Futamura Chemical Co., Ltd., "FE2002"), and cut into a flat rectangular shape with a width of 20 mm and a length of 40 mm. The release PET film was then peeled off the other side of the adhesive tape 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 (mass %) was calculated using the above formula (II). The results are shown in Table 3.

[0180] (Examples 2-33, Comparative Examples 1, 3-5) Except for the composition and thickness of the adhesive layer being as shown in Tables 3-6 in "(1) Preparation of adhesive tape" described above, adhesive tapes were prepared and various measurements were performed in the same manner as in Example 1. The results are shown in Tables 3-6. For Comparative Examples 1, 3-4, in "(1) Preparation of adhesive tape" described above, ethyl acetate was used as the solvent to dissolve the aromatic block copolymer (X), and a solution containing the adhesive composition was prepared.

[0181] (Example 34) An adhesive layer was formed in the same manner as in Example 1, except that the composition and thickness of the adhesive layer were as shown in Table 5. The obtained adhesive layer was attached to one side of the substrate as shown in Table 5, and then pressed down by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Furthermore, an adhesive layer with the same composition and thickness was prepared and attached to the other side of the substrate, and then pressed down by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min to laminate and integrate it, and then cured in an environment of 23°C for 1 hour to obtain an adhesive tape having adhesive layers on both sides of the substrate. Note that "PET film" in Table 5 is Lumirror (thickness: 38 μm) manufactured by Toray Industries, Inc. For various measurements, only the adhesive layer was removed from the obtained adhesive tape using a cutter knife, and measurements were performed in the same manner as in Example 1. The results are shown in Table 5.

[0182] (Comparative Example 2) First, the ethyl acetate solution of the acrylic copolymer V prepared in "(Synthesis of Acrylic Copolymer)" described above was dried. Next, 30 parts by mass of the SIS block copolymer were melted in a planetary roller extruder using a solid weighing device. The acrylic copolymer V, which had been melted in a single-screw extruder, and the materials shown in Table 6 were supplied using an attached feeder and mixed with the SIS block copolymer. The mixture was stirred, and an adhesive layer having a foamed structure was laminated between two release polyethylene terephthalate (PET) films (thickness 50 μm) using a double-roll calender. This obtained an adhesive tape with the thickness shown in Table 6. Various measurements were performed in the same manner as in Example 1. The results are shown in Table 6.

[0183] <Evaluation> The adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 3 to 6.

[0184] (Impact Absorption) (1) Calculation of impact absorption energy in the test specimen before heating The obtained adhesive tape was cut to a size of 30 mm x 30 mm, and two SUS plates 3 with a size of 125 mm x 50 mm and a thickness of 2 mm were stacked on the cut adhesive tape 2 as shown in Figure 1 to create a test specimen 1. For the obtained test specimen 1, as shown in Figure 2, the test specimen was set up so that the pendulum 4 would hit only one of the SUS plates 3 when it passed the lowest point of the test specimen. Then, a pendulum 4 with a mass of 1.0 kg was dropped from a height of 0.2 m (H in Figure 2) and hit the test specimen, and the highest height h reached was measured. Using the obtained height h, the impact absorption energy in the test specimen before heating was calculated from the following formula. Note that the lowest point reached by the pendulum is set to 0 for height. Impact absorption energy in the test specimen before heating (J) = mg(0.2 - h) (m: mass of the pendulum (kg), g: acceleration due to gravity (9.80 m / s) ２ ), h: measured height (m)

[0185] (2) Evaluation of the shock absorption performance of the adhesive tape Based on the calculated shock absorption energy, the shock absorption performance of the adhesive tape was evaluated according to the following criteria: A: The shock absorption energy was 0.50 J or more. B: The shock absorption energy was 0.30 J or more and less than 0.50 J. C: The shock absorption energy was 0.15 J or more and less than 0.30 J. D: The shock absorption energy was less than 0.15 J.

[0186] (Thermal Stability) (1) Calculation of the rate of change of shock absorption energy before and after heating After preparing test specimens in the same manner as described above for "(Shock Absorption)", the prepared test specimens were placed in a constant temperature oven set to 120°C and left to stand for 48 hours to heat the test specimens. After the heated test specimens were air-cooled in an environment of 25°C, the shock absorption energy of the test specimens after heating was calculated in the same manner as described above for "(Shock Absorption)". Using the obtained shock absorption energy of the test specimens after heating and the shock absorption energy of the test specimens before heating obtained in "(Shock Absorption)" above, the rate of change of shock absorption energy before and after heating was calculated from the following formula: Rate of change of shock absorption energy before and after heating (%) = 100 × [{(Shock absorption energy of the test specimen after heating) - (Shock absorption energy of the test specimen before heating) / (Shock absorption energy of the test specimen after heating)}]

[0187] (2) Evaluation of the thermal stability of the adhesive tape Based on the calculated rate of change of shock absorption energy before and after heating, the thermal stability of the adhesive tape was evaluated according to the following criteria: A: The rate of change of shock absorption energy before and after heating was less than 20%. B: The rate of change of shock absorption energy before and after heating was 20% or more and less than 50%. C: The rate of change of shock absorption energy before and after heating was 50% or more.

[0188] (Isotropy under tension) Using a punching blade (High Polymer Instruments Co., Ltd., "Tensile Type 3 Dumbbell Shape"), the obtained adhesive tape was punched into a dumbbell shape, and test specimens were prepared by peeling off the release PET film from both sides. Next, a dumbbell tensile test was performed on the obtained test specimens using a tensile testing machine (Shimadzu Corporation, "Autograph AGS-X"), under the conditions of a grip distance of 40 mm and a tensile speed of 100 mm / min in accordance with JIS K 7161, by pulling the test specimen until it broke. In the tensile strength-strain curve (S-S curve) obtained from the dumbbell tensile test, the slope of the line was calculated from two points on the S-S curve: the point with a displacement strain of 1% and the point with a displacement strain of 3%, and this slope was defined as the tensile modulus (MPa). Subsequently, the tensile modulus was measured in the same manner as above, except that a test specimen was prepared so that the tensile direction was shifted by 30° from the tensile direction in the preceding dumbbell tensile test. The above measurements were repeated until returning to the tensile direction of the initial measurement. The tensile modulus with the highest value obtained was taken as the tensile modulus in the first direction, and the tensile modulus in the direction perpendicular to the first direction was taken as the tensile modulus in the second direction. The ratio of tensile moduli (first direction / second direction) was calculated from the tensile moduli of the first and second directions. Based on the obtained ratio of tensile moduli, the isotropy of the adhesive tape against tension was evaluated according to the following criteria: A: The ratio of tensile moduli was 1.2 or less. B: The ratio of tensile moduli was greater than 1.2. Even if the evaluation is "B", the adhesive tape of this embodiment can be used without problems depending on the application.

[0189] (Bending resistance) Aluminum alloy plates (SHAANXI SHWEW-E STEEL PIPE, "Aluminum 6061-T6", 1.6 mm thick, 25.4 mm wide, 203.2 mm long) were bonded to both sides of the obtained adhesive tape by applying a load of 1 MPa for 20 seconds at 65°C to create a laminated and integrated structure. The laminated structure was then left to cure at 23°C for 24 hours. The fabricated laminated structure 5 was set up in a Tensilon (A&D Company, Limited) measuring instrument in accordance with JIS K 7171 as shown in Figure 3 (distance between compression jigs: 57.15 mm, distance between fixing jigs: 177.8 mm). Subsequently, the laminated structure 5 was compressed at a constant speed of 0.05 mm / s in an environment of 23 ± 1°C and 50 ± 5% humidity until the load reached 50 N. In the obtained stress-deformation curve, the slope of the line (stress / deformation) was calculated from two points on the stress-deformation curve: one with a stress of 20 N and another with a stress of 50 N. Based on the obtained slope of the line, the bending resistance of the adhesive tape was evaluated according to the following criteria: A: The slope of the line was 17.0 N / mm or more. B: The slope of the line was 15.5 N / mm or more and less than 17.0 N / mm. C: The slope of the line was less than 15.5 N / mm. Even if the evaluation is "C", the adhesive tape of this embodiment can be used without problems depending on the application.

[0190] (High-temperature retention performance) A high-temperature retention test was conducted in accordance with JIS Z 0237:2009. Figure 4 shows a schematic representation of the high-temperature retention test. Specifically, one side of the adhesive tape 2 (the side not measured) was first backed with a 23 μm thick polyethylene terephthalate film 8 (Futamura Chemical Co., Ltd., "FE2002"), and then cut to a width of 25 mm x length of 75 mm to prepare a test piece. This test piece was placed so that its adhesive layer (the side being measured) faced a SUS304 plate 9 (SUS304 plate washed with ethanol and then wiped dry) with a thickness of 2 mm, a width of 50 mm, and a length of 80 mm. Then, a 2 kg rubber roller was passed back and forth over the test piece at a speed of 300 mm / min, so that a portion of the test piece extended beyond the SUS304 plate 9 (adhesion area: width 25 mm, length 25 mm). Subsequently, the sample was cured for 20 minutes at 23°C and 50% RH to prepare a test sample. The test sample was placed at 80°C and 50% RH and left to stand for 15 minutes. Then, in this environment, a 1 kg weight 10 was attached to the polyethylene terephthalate film 8 of the test sample so that a shear load (lengthwise direction) was applied, in accordance with JIS Z 0237:2009. One hour after attaching the weight 10, the amount of shear displacement from the position where the adhesive layer SUS304 plate 9 was bonded was measured. Based on the measured displacement, the high-temperature holding performance of the adhesive tape was evaluated according to the following criteria: A: Displacement was 0.5 mm or less. B: Displacement exceeded 0.5 mm but was 5 mm or less. C: Displacement exceeded 5 mm but was 10 mm or less. D: Displacement exceeded 10 mm, or the test piece fell off. Even if the evaluation is "D", the adhesive tape of this embodiment can still be used without problems depending on the application.

[0191] (Light-shielding properties) The obtained adhesive tape was cut to a width of 2 mm x length of 75 mm. Next, one adhesive layer of the cut adhesive tape was placed facing the polishing surface of water-resistant abrasive paper (Noritake Coated Abrasives, "C947H", grit size 360, surface roughness Ra = 10.8 μm), and then bonded to the test piece by passing a 2 kg rubber roller back and forth at a speed of 300 mm / min. After that, the other adhesive layer of the adhesive tape was placed facing the polishing surface of the water-resistant abrasive paper in the same manner, and then bonded to the test piece by passing a 2 kg rubber roller back and forth at a speed of 300 mm / min. After that, the test samples were prepared by curing for 20 minutes in an environment of 23°C and 50% RH. Using a floodlight, the luminous intensity of 3.0 × 10⁻¹⁰ was set on the surface of the adhesive tape bonded to the prepared test sample. ５ The light-blocking properties of the adhesive tape were evaluated by irradiating it with light from a CD and visually checking for light leakage, according to the following criteria: A: No light leakage was observed visually. B: Light leakage was observed visually. Even if the evaluation is "B", the adhesive tape of this embodiment can be used without problems depending on the application.

[0192]

[0193]

[0194]

[0195]

[0196] According to the present invention, it is possible to provide an adhesive tape that achieves both excellent shock absorption and excellent thermal stability. Furthermore, according to the present invention, it is possible to provide an electronic device that includes the adhesive tape.

[0197] 1. Test specimen 2. Adhesive tape 3. SUS plate 4. Pendulum 5. Laminate 6. Compression jig 7. Fixing jig 8. Polyethylene terephthalate (PET) film 9. SUS304 plate 10. Weight (1 kg)

Claims

1. An adhesive tape having an adhesive layer, wherein the adhesive layer is composed of a continuous phase and a dispersed phase, the continuous phase includes an acrylic copolymer having structural units derived from an acrylic acid ester, and the dispersed phase includes an aromatic block copolymer (X) having at least two blocks having structural units derived from a vinyl aromatic compound, and at least one of a block having structural units derived from a conjugated diene compound and a hydrogenated form of a block having structural units derived from a conjugated diene compound, and the average area of ​​the cross-section in the thickness direction of the dispersed phase before the heating test is 10 μm ２ The adhesive tape is characterized in that, furthermore, the area change rate in the cross-section in the thickness direction of the dispersed phase before and after the heating test is 2.0 or less.

2. The dispersed phase has an average area of ​​1.00 μm² in the cross-section in the thickness direction. ２ The adhesive tape according to claim 1, which is as follows:

3. The adhesive tape according to claim 1 or 2, wherein the dispersed phase has an aspect ratio of 1.0 or more and 2.0 or less in the cross-section in the thickness direction.

4. The adhesive tape according to claim 1, 2, or 3, wherein the acrylic copolymer has constituent units derived from monomers having crosslinkable functional groups.

5. The adhesive tape according to claim 1, 2, 3, or 4, wherein the acrylic copolymer has constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals.

6. The adhesive tape according to claim 5, wherein the content of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminals in the acrylic copolymer is 5% by mass or more and 50% by mass or less.

7. The adhesive tape according to claim 1, 2, 3, 4, 5, or 6, wherein the acrylic copolymer comprises a block containing a structural unit derived from at least one alkyl (meth)acrylate and a block containing a structural unit derived from at least one vinyl aromatic compound.

8. The adhesive tape according to claim 7, wherein the acrylic copolymer contains 2.5% by mass or more and 20% by mass or less of constituent units derived from the vinyl aromatic compound.

9. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, or 8, wherein the acrylic copolymer has constituent units derived from isobornyl (meth)acrylate.

10. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the acrylic copolymer has a weight-average molecular weight of 700,000 or more and 1,500,000 or less.

11. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the content of the aromatic block copolymer (X) is 60 parts by mass or less per 100 parts by mass of the acrylic copolymer.

12. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the adhesive layer contains a coloring agent.

13. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the adhesive layer contains a tackifying resin.

14. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the adhesive layer does not contain a tackifying resin.

15. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the adhesive layer has a structure derived from a crosslinking agent.

16. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the adhesive layer has a shear storage modulus of 0.30 MPa or more at 23°C as measured in a dynamic viscoelasticity measurement at a measurement frequency of 1 Hz.

17. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the adhesive layer has a shear storage modulus of 0.02 MPa or more at 65°C as measured in a dynamic viscoelasticity measurement at a measurement frequency of 1 Hz.

18. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the adhesive layer has a loss tangent of 0.5 or more at 23°C as measured in a dynamic viscoelasticity measurement at a measurement frequency of 100 Hz.

19. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, wherein the adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less.

20. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, wherein the adhesive layer has a foamed structure.

21. The adhesive layer has an assumed density of 0.59 g / cm³. ３ 1.15g / cm or more ３ The adhesive tape according to claim 20, which is as follows:

22. An adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, which does not have a base material.

23. An adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, having a base material.

24. An adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23, used for fixing electronic equipment components or in-vehicle components.

25. Electronic device comprising the adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24.

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