Adhesive tape, electrical connection member, and structure

Abstract

One purpose of the present invention is to provide an adhesive tape capable of exhibiting both excellent heat resistance and excellent applicability to rigid bodies. Another purpose of the present invention is to provide an electrical connection member that makes it possible to rigidly hold an electroconductive member on a connection target member and to maintain a state in which the electroconductive member is rigidly held on the connection target member even at high temperatures, and also makes it possible to establish a stable electrical connection at normal temperatures and at high temperatures. Still another purpose is to provide a structure which makes it possible to establish a stable electrical connection at normal temperatures and at high temperatures. The present invention is an adhesive tape including an adhesive layer formed from an adhesive composition, wherein the adhesive composition includes an acrylic copolymer, the acrylic copolymer comprises a constituent unit derived from an alkyl (meth)acrylate and a constituent unit derived from an olefin-based polymer having a polymerizable unsaturated double bond at an end, and the adhesive layer has a groove in at least one surface thereof.

Description

Adhesive tape, electrical connection components, and structural components

[0001] This invention relates to adhesive tapes. Furthermore, this invention relates to electrical connection members. Moreover, this invention relates to structures.

[0002] Adhesive tape is used for assembly in portable electronic devices such as mobile phones and personal digital assistants (PDAs) (for example, Patent Documents 1 and 2). Adhesive tape is also used for bonding optical components (for example, Patent Document 3).

[0003] On the other hand, in automotive windows, for example, to provide a defroster or defogger, it is necessary to form a power supply section on the glass plate and electrically connect terminals made of metal plates or the like to the power supply section using a conductive material. Conventionally, solder has been widely used as the conductive material, but due to recent lead regulations and the poor adhesion of lead-free solder, for example, Patent Document 4 discloses the use of conductive rubber as an alternative to solder. In Patent Document 4, conductive rubber is bonded to the glass plate so that it is in contact with both the power supply section and the terminals and is held in a compressed state.

[0004] Furthermore, Patent Document 5 discloses a connector sheet comprising a sheet portion having electrical insulating properties and a conductive portion provided on the sheet portion. The connector sheet is used to electrically connect a metal portion constituting the housing of an electrical device to a ground connection portion of a circuit board built into the housing, and is fixed to the circuit board via an adhesive portion or the like.

[0005] Japanese Patent Publication No. 2009-242541, Japanese Patent Publication No. 2009-258274, Japanese Patent Publication No. 2012-214544, Japanese Patent Publication No. 2012-043690, Japanese Patent Publication No. 2007-227111

[0006] Adhesive tapes used to secure electronic equipment components or automotive parts are increasingly required to have adhesive strength at high temperatures approaching 100°C, and the demand for heat resistance in adhesive tapes is increasing year by year. Typically, a method used to improve the heat resistance of adhesive tapes is to incorporate a high modulus adhesive into the adhesive layer of the tape. However, adhesive tapes containing a high modulus adhesive in the adhesive layer have the problem of reduced adhesive strength.

[0007] Furthermore, adhesive tapes used to fix automotive parts and the like are expected to be bonded to rigid bodies. However, adhesive tapes containing high-modulus adhesives in the adhesive layer have a hard adhesive layer, and when bonding rigid bodies (especially when bonding large-area rigid bodies), air bubbles can get trapped at the bonding surface, resulting in insufficient adhesive strength. Therefore, obtaining an adhesive tape that achieves both excellent heat resistance and excellent adhesion to rigid bodies is a difficult challenge.

[0008] Furthermore, when using conductive rubber as a conductive material to electrically connect components such as glass plates and metal terminals, it is necessary to maintain the conductivity of the conductive rubber by keeping it in a compressed state. However, when the conductive rubber is compressed, there is a problem that the elastic force of the rubber can cause peeling at the adhesive part that fixes the metal terminal. Moreover, as the compressive strain of the conductive rubber increases, the conductive material becomes less able to adhere to the components to be connected, and the electrical resistance of the contact surface increases, which also causes the temperature of the electrical connection part to rise when a large current is passed through it. For this reason, Patent Document 4 employs a method of bonding the components to be connected using a thermosetting adhesive, but this requires heating and time for curing, resulting in poor workability, and a bonding method that does not use a thermosetting adhesive is desired.

[0009] On the other hand, the connector sheet shown in Patent Document 5 is fixed to the circuit board by screwing metal screws into mounting holes provided on the circuit board in order to connect the metal part of the housing to the circuit board. While such a fixing method is effective for components that can be provided with mounting holes into which metal screws can be screwed, it is not particularly effective for glass plates and metal terminals, for which it is difficult to provide mounting holes into which metal screws can be screwed. Therefore, it is difficult to fix the components to be connected while simultaneously making an electrical connection to them via a conductive member using such a fixing method.

[0010] The present invention aims to provide an adhesive tape that can achieve both excellent heat resistance and excellent adhesion to rigid bodies. Furthermore, the present invention aims to provide an electrical connection member that can firmly hold a conductive member to a connection target member, maintain a state of firm holding of the conductive member to the connection target member even at high temperatures, and enable stable electrical connections at both room temperature and high temperatures. Moreover, the present invention aims to provide a structure that can enable stable electrical connections at both room temperature and high temperatures.

[0011] Disclosure 1 is an adhesive tape having an adhesive layer formed using an adhesive composition, wherein the adhesive composition includes an acrylic copolymer, the acrylic copolymer having constituent units derived from an alkyl (meth)acrylate and constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals, and the adhesive layer is an adhesive tape having grooves on at least one surface. Disclosure 2 is the adhesive tape of Disclosure 1, wherein the grooves are bubble-removing grooves for removing air bubbles. Disclosure 3 is the adhesive tape of Disclosure 1 or 2, wherein the depth of the grooves is 15% or more and 80% or less relative to the thickness of the adhesive layer. Disclosure 4 is the adhesive tape of Disclosure 1, 2 or 3, wherein the constituent units derived from the alkyl (meth)acrylate include constituent units having an alkyl group having 1 to 4 carbon atoms, and the content ratio of the constituent units derived from the alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms in the constituent units derived from the alkyl (meth)acrylate is 50% by mass or more and 100% by mass or less. Disclosure 5 is an adhesive tape according to Disclosure 1, 2, 3, or 4, wherein the constituent units derived from the alkyl (meth)acrylate include constituent units derived from the alkyl (meth)acrylate having an alkyl group having 1 to 2 carbon atoms, and the content of the constituent units derived from the alkyl (meth)acrylate having an alkyl group having 1 to 2 carbon atoms in the constituent units derived from the alkyl (meth)acrylate is 10% by mass or more and 80% by mass or less. Disclosure 6 is an adhesive tape according to Disclosure 1, 2, 3, 4, or 5, wherein the content of the constituent units derived from the olefin polymer having a polymerizable unsaturated double bond at its end in the acrylic copolymer is 10% by mass or more and 30% 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 constituent units derived from polar functional group-containing monomers, and the total content of the constituent units derived from polar functional group-containing monomers in the acrylic copolymer is 3.0% by mass or more and 15% by mass or less.Disclosure 8 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the acrylic copolymer has a weight-average molecular weight of 750,000 or more and 1,500,000 or less. Disclosure 9 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the adhesive composition contains at least one selected from the group consisting of a tackifying resin and a silane coupling agent. Disclosure 10 is an adhesive tape according to Disclosure 9, wherein the adhesive composition contains the tackifying resin, and the content of the tackifying resin is 5.0 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the acrylic copolymer. Disclosure 11 is an adhesive tape according to Disclosure 9 or 10, wherein the adhesive composition contains the silane coupling agent, and the content of the silane coupling agent is 0.1 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the acrylic copolymer. Disclosure 12 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the gel fraction of the adhesive layer is 10% by mass or more and 90% by mass or less. Disclosure 13 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the thickness of the adhesive layer is 20 μm or more and 100 μm or less. Disclosure 14 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, which has a substrate. Disclosure 15 is an adhesive tape according to Disclosure 14, wherein the total thickness of the adhesive layer and the substrate is 50 μm or more and 500 μm or less. Disclosure 16 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein a release sheet with a textured surface on the adhesive layer side is laminated on the surface of the adhesive layer, and the surface of the adhesive layer is formed with a textured shape that fits into the texture of the release sheet. Disclosure 17 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 used for fixing electronic equipment components or automotive components. 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 used for electrical connection members.Disclosure 19 is an electrical connection member having a conductive member and an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. Disclosure 20 is a structure in which a conductive member is held to a member to be connected by an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. Disclosure 21 is an electrical connection member having a conductive member and an adhesive tape, wherein the adhesive tape has an adhesive layer formed using an adhesive composition, the adhesive composition includes an acrylic copolymer, and the acrylic copolymer is an electrical connection member having constituent units derived from an alkyl (meth)acrylate ester and constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal. Disclosure 22 is an electrical connection member of Disclosure 21 having a structure in which the adhesive tape holds the conductive member to the member to be connected. Disclosure 23 is an electrical connection member of Disclosure 21 or 22 having a structure in which the conductive member penetrates the adhesive tape. Disclosure 24 is an electrical connection member of Disclosure 21, 22 or 23 in which the constituent unit derived from the alkyl (meth)acrylate includes a constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms, and the content ratio of the constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms in the constituent unit derived from the alkyl (meth)acrylate is 50% by mass or more and 100% by mass or less. Disclosure 25 is an electrical connection member of Disclosure 21, 22, 23, or 24, wherein the constituent units derived from the alkyl (meth)acrylate include constituent units derived from the alkyl (meth)acrylate having an alkyl group having 1 to 2 carbon atoms, and the content ratio of the constituent units derived from the alkyl (meth)acrylate having an alkyl group having 1 to 2 carbon atoms in the constituent units derived from the alkyl (meth)acrylate is 10% by mass or more and 80% by mass or less.Disclosure 26 is an electrical connection member of Disclosure 21, 22, 23, 24, or 25, 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 10% by mass or more and 30% by mass or less. Disclosure 27 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, or 26, wherein the acrylic copolymer has constituent units derived from a polar functional group-containing monomer, and the total content of constituent units derived from the polar functional group-containing monomer in the acrylic copolymer is 3.0% by mass or more and 15% by mass or less. Disclosure 28 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, or 27, wherein the acrylic copolymer has a weight-average molecular weight of 750,000 or more and 1,500,000 or less. Disclosure 29 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, 27, or 28, wherein the adhesive composition contains at least one selected from the group consisting of a tackifying resin and a silane coupling agent. Disclosure 30 is an electrical connection member of Disclosure 29, wherein the adhesive composition contains the tackifying resin, and the content of the tackifying resin is 5.0 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the acrylic copolymer. Disclosure 31 is an electrical connection member of Disclosure 29 or 30, wherein the adhesive composition contains the silane coupling agent, and the content of the silane coupling agent is 0.1 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the acrylic copolymer. Disclosure 32 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or 31, wherein the adhesive layer has grooves. Disclosure 33 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32, wherein the gel fraction of the adhesive layer is 10% by mass or more and 90% by mass or less. Disclosure 34 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, or 33, wherein the thickness of the adhesive layer is 20 μm or more and 100 μm or less. Disclosure 35 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, or 34, wherein the adhesive tape has a base material.Disclosure 36 is an electrical connection member of Disclosure 35, wherein the total thickness of the adhesive layer and the substrate is 50 μm or more and 500 μm or less. Disclosure 37 is an electrical connection member of Disclosure 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or 36, further having a connecting member for connecting the conductive member and the adhesive tape. Disclosure 38 includes an electrical connection member and a member to be connected, wherein the electrical connection member has a conductive member and an adhesive tape, the adhesive tape has an adhesive layer formed using an adhesive composition, the adhesive composition includes an acrylic copolymer, and the acrylic copolymer is a structure having constituent units derived from (meth)acrylate alkyl ester and constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals. Hereinafter, embodiments of the present invention or one thereof will be described as "this embodiment". Furthermore, the electrical connection member of Disclosure 19 will also be referred to as the "electrical connection member of Embodiment 1," and the electrical connection member of Disclosure 21 will also be referred to as the "electrical connection member of Embodiment 2." In addition, matters common to the electrical connection member of Embodiment 1 and the electrical connection member of Embodiment 2 will not be specifically specified, or will be described as "the electrical connection member of this embodiment." Furthermore, the structure of Disclosure 20 will also be referred to as the "structure of Embodiment 1," and the electrical connection member of Disclosure 37 will also be referred to as the "structure of Embodiment 2." Furthermore, matters common to the structure of Embodiment 1 and the structure of Embodiment 2 will not be specifically specified, or will be described as "the structure of this embodiment."

[0012] The inventors of the present invention investigated the use of an acrylic copolymer having a specific structural unit as the adhesive in an adhesive tape having an adhesive layer, and found that they could obtain an adhesive tape that could maintain adhesive strength at room temperature while improving heat resistance. Furthermore, the inventors investigated the addition of grooves to the adhesive layer containing such an acrylic copolymer having a specific structural unit, and as a result found that they could obtain an adhesive tape that achieved both excellent heat resistance and excellent adhesion to rigid bodies, thus completing the present invention.

[0013] Furthermore, the inventors considered using adhesive tape to firmly hold the conductive member to the connection target member in an electrical connection member having a conductive member, from the viewpoint of workability. As a result, they found that by using an adhesive tape that combines excellent heat resistance and high adhesive strength, the conductive member can be firmly held to the connection target member, and peeling of the adhesive tape from the conductive member and the connection target member can be suppressed even at high temperatures. Therefore, they found that it is possible to obtain an electrical connection member that can make a stable electrical connection at both room temperature and high temperatures, and thus completed the present invention.

[0014] The adhesive tape of this embodiment has an adhesive layer formed using an adhesive composition. A method for forming the adhesive layer using the adhesive composition includes, for example, applying the adhesive composition to a release sheet or the like, and then heating and drying the adhesive composition.

[0015] The adhesive layer described above has grooves on at least one surface. Having grooves on at least one surface of the adhesive layer prevents air bubbles from entering the bonding surface when bonding rigid bodies, thus the adhesive tape of this embodiment has excellent adhesion to rigid bodies. For this reason, since the grooves are usually formed to remove air bubbles, it is preferable that the grooves are air bubble removal grooves for removing air bubbles.

[0016] Preferably, at least one end of the groove extends to the side surface. Because at least one end of the groove extends to the side surface, air bubbles attempting to enter the bonding surface are more easily pushed out from the side, resulting in superior adhesion of the adhesive tape of this embodiment to rigid bodies.

[0017] When the surface of the adhesive layer is observed from the thickness direction, the shape of the grooves can be, for example, linear (straight, curved, grid-like, etc.), circular, etc., but is not particularly limited, and in any shape, it is preferable that at least a portion of the grooves extend to the side surface. When the adhesive layer is cut by a plane parallel to the thickness direction, the cross-sectional shape of the grooves can be, for example, a square, a triangle, a U-shape, etc.

[0018] The grooves may be multiple on the surface of the adhesive layer, and may be patterned with a specific shape. When there are multiple grooves in the adhesive layer, it is preferable that at least some of the grooves satisfy the range described later for width, depth, depth ratio, etc., and it is more preferable that all of the grooves satisfy the range described later for width, depth, depth ratio, etc. Furthermore, when there are multiple grooves in the adhesive layer, the depth and width of the grooves do not all need to be the same, and the depth and width of the grooves may differ.

[0019] In this specification, examples of methods for forming the grooves in the adhesive layer include, for example, a method of directly applying an adhesive to a release sheet that has been given an uneven decorative finish to form an adhesive layer, a method of laminating a release sheet that has been given an uneven decorative finish onto the surface of the adhesive layer to form an uneven shape that fits into the unevenness of the release sheet, and a method of performing sandblasting or laser processing on the surface of the adhesive layer.

[0020] The ratio of the groove depth to the thickness of the adhesive layer (hereinafter sometimes simply referred to as "the ratio of the groove depth") has a preferred lower limit of 15% and a preferred upper limit of 80%. When the ratio of the groove depth is 15% or more, air bubbles that try to enter the bonding surface are more easily pushed out from the sides, so that the adhesive tape of this embodiment has better adhesion to rigid bodies. When the ratio of the groove depth is 80% or less, adhesive residue due to the adhesive tearing when the adhesive tape is peeled off can be better prevented. The ratio of the groove depth has a more preferred lower limit of 30%, a more preferred upper limit of 70%, an even more preferred lower limit of 40%, and an even more preferred upper limit of 60%. Examples of the ratio of the groove depth include 15% to 80%, 30% to 70%, 40% to 60%, etc.

[0021] As described above, the adhesive layer is preferably such that the ratio of the groove depths satisfies the range described above, but it is more preferable that the grooves in the adhesive layer have a specific depth. Specifically, the preferred lower limit for the groove depth is 5 μm, and the preferred upper limit is 150 μm. When the groove depth is 5 μm or more, air bubbles that try to enter the bonding surface are more easily pushed out from the sides, so that the adhesive tape of this embodiment has better adhesion to rigid bodies. When the groove depth is 150 μm or less, adhesive residue due to the adhesive tearing when the adhesive tape is peeled off can be better prevented. A more preferred lower limit for the groove depth is 10 μm, a more preferred upper limit is 100 μm, an even more preferred lower limit is 15 μm, and an even more preferred upper limit is 50 μm. Examples of groove depths include 5 μm to 150 μm, 10 μm to 100 μm, 15 μm to 50 μm, etc.

[0022] In this specification, the "groove depth" refers to the groove depth measured from the surface of the adhesive layer (Figure 1, d １This refers to the average value of (equivalent to). Furthermore, in this specification, the groove depth can be obtained by the following method. That is, first, a sample is prepared by cutting the adhesive tape with a cutter or the like so as to cross the groove of the adhesive layer with a plane parallel to the thickness direction of the adhesive tape, and the groove depth is measured by observing it from a direction parallel to the groove using an optical microscope (such as Keyence Corporation's "VHX-6000") at a magnification of, for example, 200x. Then, this measurement is performed at five locations, and the average value of the five measured groove depths is taken as the groove depth of the adhesive layer. If the adhesive tape to be measured is an adhesive tape with a release sheet as described later, the release sheet is not peeled off from the adhesive tape, and the above sample is prepared and the groove depth is measured. Furthermore, the ratio of the groove depth is the obtained groove depth of the adhesive layer and the thickness of the adhesive layer (d shown in Figure 1). ２ Using the above formula (i), it can be calculated by the following equation: Percentage of groove depth (%) = {(Depth of groove in adhesive layer) / d ２} × 100 (i)

[0023] Methods for adjusting the depth of the grooves in the adhesive layer as described herein include, for example, using a release sheet with a large uneven surface as a release sheet, as described later, and adjusting the groove depth by sandblasting or laser processing.

[0024] When the groove is linear, the preferred lower limit of the groove width is 10 μm, and the preferred upper limit is 300 μm. A width of 10 μm or more makes it easier for air bubbles attempting to enter the bonding surface to be pushed out from the sides, resulting in superior adhesion of the adhesive tape of this embodiment to rigid bodies. A groove width of 300 μm or less ensures sufficient bonding area, resulting in superior adhesive strength for the adhesive tape of this embodiment. A more preferred lower limit of the groove width is 25 μm, a more preferred upper limit is 200 μm, an even more preferred lower limit is 50 μm, and an even more preferred upper limit is 150 μm. Examples of groove widths include 10 μm to 300 μm, 25 μm to 200 μm, and 50 μm to 150 μm.

[0025] In this specification, "groove width" means the width of the groove at a point where the height of the adhesive layer with grooves is 5%, with the height of the surface of the groove being 0% and the height of the deepest part of the groove being 100%. In this specification, the groove width can be measured by observing the portion of the groove in the adhesive layer at a height of 5%, for example, at a magnification of 200x, using an optical microscope (such as the Keyence VHX-6000).

[0026] The above adhesive composition contains an acrylic copolymer having structural units derived from an alkyl (meth)acrylate ester and structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals. In this specification, "(meth)acrylic" means acrylic or methacrylic. The above acrylic copolymer has a structure in which structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals aggregate through interaction, forming pseudo-crosslinking points. Because the above acrylic copolymer adopts such a structure, the above adhesive composition exhibits hard properties like a crosslinked adhesive composition when the strain is small, and the holding power is further improved. On the other hand, when peel stress is applied and the strain becomes large, the pseudo-crosslinking breaks, and the molecules of the above acrylic copolymer stretch, so the above adhesive composition exhibits high flexibility and the adhesive strength is improved. In other words, the presence of the above acrylic copolymer in the above adhesive composition improves the adhesive strength of the adhesive composition and further improves the holding power. Furthermore, because the acrylic copolymer adopts such a structure, the cohesive force of the adhesive layer formed using the adhesive composition is improved, thus improving the heat resistance of the adhesive tape of this embodiment.

[0027] Examples of constituent units derived from the above alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, n-heptyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate. Examples of constituent units include those derived from 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. In particular, from the viewpoint of further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape of this embodiment by increasing the polarity of the above acrylic copolymer and improving the cohesive force of the adhesive layer formed using the above adhesive composition, it is preferable that the constituent units derived from the alkyl (meth)acrylate include constituent units derived from alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms. These alkyl (meth)acrylates may be used individually or in combination of two or more.

[0028] When the above-mentioned alkyl (meth)acrylate-derived structural units include structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms, the preferred lower limit of the content of structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms in the above-mentioned alkyl (meth)acrylate-derived structural units is 50% by mass. By having a content of 50% by mass or more of structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms, the polarity of the acrylic copolymer increases, and the cohesive force of the adhesive layer formed using the adhesive composition is improved, thereby further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape of this embodiment. A more preferred lower limit for the content of structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms is 60% by mass, and an even more preferred lower limit is 70% by mass. Furthermore, from the viewpoint of further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape of this embodiment, it is preferable that the content of the constituent units derived from the alkyl (meth)acrylate ester having an alkyl group having 1 to 4 carbon atoms is higher. Therefore, from this viewpoint, it is most preferable that the content of the constituent units derived from the alkyl (meth)acrylate ester having an alkyl group having 1 to 4 carbon atoms is 100% by mass, that is, that the constituent units derived from the alkyl (meth)acrylate ester consist only of constituent units derived from the alkyl (meth)acrylate ester having an alkyl group having 1 to 4 carbon atoms. On the other hand, from the viewpoint of further improving the adhesion of the adhesive tape of this embodiment to a rigid body by making the adhesive layer formed using the above adhesive composition more flexible, the preferred upper limit of the content of the constituent units derived from the alkyl (meth)acrylate ester having an alkyl group having 1 to 4 carbon atoms is 98% by mass, and the more preferred upper limit is 95% by mass. Examples of the content of constituent units derived from alkyl (meth)acrylate esters having an alkyl group with 1 to 4 carbon atoms include 50% to 100% by mass, 60% to 98% by mass, 70% to 95% by mass, and so on.

[0029] From the viewpoint of the adhesive strength of the above adhesive composition, it is preferable that the constituent units derived from the (meth)acrylate alkyl ester include constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms. When the constituent units derived from the (meth)acrylate alkyl ester include constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms, the preferred lower limit of the content of the constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms in the constituent units derived from the (meth)acrylate alkyl ester is 10% by mass, and the preferred upper limit is 80% by mass. By having a content of 10% by mass or more of the constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms, the polarity of the acrylic copolymer becomes greater, and the cohesive force of the adhesive layer formed using the above adhesive composition is improved, thereby further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape of this embodiment. In addition, it is possible to suppress the adhesive layer formed using the above adhesive composition from becoming too flexible and the grooves in the adhesive layer disappearing. By having a content of 80% by mass or less of the constituent units derived from the alkyl (meth)acrylate ester having one to two C1 alkyl groups, it becomes easier to adjust the glass transition temperature of the acrylic copolymer, as described later, within an appropriate range, and the adhesive strength of the adhesive layer formed using the adhesive composition is further improved. A more preferable lower limit for the content of the constituent units derived from the alkyl (meth)acrylate ester having one to two C1 alkyl groups is 15% by mass, a more preferable upper limit is 50% by mass, an even more preferable lower limit is 20% by mass, and an even more preferable upper limit is 30% by mass. Examples of the content of the constituent units derived from the alkyl (meth)acrylate ester having one to two C1 alkyl groups include 10% by mass or more and 80% by mass or less, 15% by mass or more and 50% by mass or less, and 20% by mass or more and 30% by mass or less.

[0030] In the above acrylic copolymer, the preferable lower limit of the content ratio of the structural unit derived from the above alkyl (meth)acrylate is 50% by mass, and the preferable upper limit is 90% by mass. When the content ratio of the structural unit derived from the above alkyl (meth)acrylate is within the above range, the adhesive strength and the holding power of the adhesive tape of the present embodiment are further improved. The more preferable lower limit of the content ratio of the structural unit derived from the above alkyl (meth)acrylate is 60% by mass, the more preferable upper limit is 80% by mass, the still more preferable lower limit is 65% by mass, and the still more preferable upper limit is 75% by mass. Note that examples of the content ratio of the structural unit derived from the above alkyl (meth)acrylate include 50% by mass or more and 90% by mass or less, 60% by mass or more and 80% by mass or less, 65% by mass or more and 75% by mass or less, and the like.

[0031] The olefin polymer having a polymerizable unsaturated double bond at the above terminal may have a polymerizable unsaturated double bond at one terminal or may have polymerizable unsaturated double bonds at both terminals. Among them, from the viewpoint that an appropriate number of pseudo-crosslinks are likely to be formed, an olefin polymer having a polymerizable unsaturated double bond at one terminal is preferable.

[0032] Examples of the olefin polymer having a polymerizable unsaturated double bond at the above terminal include an ethylene-butylene copolymer, an ethylene-propylene copolymer, an ethylene polymer, a propylene polymer, a butylene polymer, etc., which have a group having a polymerizable unsaturated double bond at one terminal or both terminals. Note that these olefin polymers having a polymerizable unsaturated double bond at the terminal may be used alone or in combination of two or more.

[0033] Examples of the group having a polymerizable unsaturated double bond include a (meth)acryloyl group, a vinyl ether group, a styryl group, etc. Among them, the (meth)acryloyl group is preferable because of its excellent copolymerizability with the above alkyl (meth)acrylate.

[0034] Examples of olefin polymers having a (meth)acryloyl group at one end 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 making it easier to adjust the glass transition temperature of the acrylic copolymer described later to an appropriate range and further improving the adhesive strength of the adhesive layer formed using the above adhesive composition. In this specification, "macromonomer" means a monomer having polymerizable functional groups and a weight-average molecular weight of about 1,000 to 100,000.

[0035] In the above acrylic copolymer, the preferable lower limit of the content ratio of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 5% by mass, and the preferable upper limit is 30% by mass. When the content ratio of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 5% by mass or more, an appropriate number of pseudo-crosslinks are formed in the above acrylic copolymer, and the adhesive strength, holding power, and heat resistance of the adhesive tape of the present embodiment are further improved. When the content ratio of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 30% by mass or less, the cohesive failure of the adhesive layer formed using the above adhesive composition can be further suppressed. Further, since the adhesive layer formed using the above adhesive composition becomes more flexible, the adhesion property of the adhesive tape of the present embodiment to a rigid body is further improved. The more preferable lower limit of the content ratio of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 10% by mass, the more preferable upper limit is 27% by mass, the further preferable lower limit is 15% by mass, and the further preferable upper limit is 25% by mass. Note that examples of the content ratio of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal include 5% by mass or more and 30% by mass or less, 10% by mass or more and 27% by mass or less, 15% by mass or more and 25% by mass or less, and the like.

[0036] The above acrylic copolymer preferably has a structural unit derived from a polar functional group-containing monomer. Since the above acrylic copolymer is likely to form a crosslinked structure when it has a structural unit derived from a polar functional group-containing monomer, the cohesive force of the adhesive layer formed using the above adhesive composition is further improved, and the adhesive strength, holding power, and heat resistance of the adhesive tape of the present embodiment are further improved.

[0037] Examples of constituent units derived from the above-mentioned polar functional group-containing monomers 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 improving the cohesive force of the adhesive layer formed using the above-mentioned adhesive composition and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape of this embodiment, it is preferable that the constituent units derived from the above-mentioned polar functional group-containing monomers 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. These polar functional group-containing monomers may be used individually or in combination of two or more.

[0038] Examples of the above carboxyl group-containing monomers include unsaturated carboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Examples of the above hydroxyl group-containing monomers include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of the above amide group-containing monomers include N-vinyl-2-pyrrolidone, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide. Examples of the above amino group-containing monomers include (meth)acryloylmorpholine, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate.

[0039] In the above acrylic copolymer, the preferred lower limit of the total content of constituent units derived from the polar functional group-containing monomer is 3.0% by mass, and the preferred upper limit is 15% by mass. A total content of 3.0% by mass or more of constituent units derived from the polar functional group-containing monomer makes it easier for the acrylic copolymer to form a crosslinked structure, thereby improving the cohesive force of the adhesive layer formed using the adhesive composition, and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape of this embodiment. Furthermore, it is possible to prevent the adhesive layer formed using the adhesive composition from becoming too flexible, causing the grooves in the adhesive layer to disappear. A total content of 15% by mass or less of constituent units derived from the polar functional group-containing monomer makes the adhesive layer formed using the adhesive composition more flexible, thereby further improving the adhesion of the adhesive tape of this embodiment to a rigid body. A more preferred lower limit of 4.0% by mass, a more preferred upper limit of 10% by mass, an even more preferred lower limit of 5.0% by mass, and an even more preferred upper limit of 7.0% by mass for the total content of constituent units derived from the polar functional group-containing monomer. Examples of the total content of constituent units derived from the above polar functional group-containing monomers include 3.0% by mass or more and 15% by mass or less, 4.0% by mass or more and 10% by mass or less, and 5.0% by mass or more and 7.0% by mass or less.

[0040] The glass transition temperature (Tg) of the above acrylic copolymer is preferably in the range of -100°C to 200°C, and a more preferable upper limit is -20°C. A glass transition temperature of -20°C or lower allows the molecules of the acrylic copolymer to stretch more easily, thus improving the adhesive strength of the adhesive tape in this embodiment. A further preferable upper limit for the glass transition temperature of the acrylic copolymer is -30°C, and an even more preferable upper limit is -35°C. Furthermore, if the acrylic copolymer has multiple glass transition temperatures, it is more preferable that all of the glass transition temperatures of the acrylic copolymer are -20°C or lower. Examples of glass transition temperatures (Tg) of the acrylic copolymer include -100°C to 200°C, -100°C to -30°C, and -100°C to -35°C. In this specification, the glass transition temperature of the acrylic copolymer can be measured by differential scanning calorimetry. More specifically, the glass transition temperature of the above-mentioned acrylic copolymer can be measured by performing measurements under conditions of a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min), using a differential scanning calorimeter (Seiko Instruments, "220C", etc.), in accordance with JIS K6240:2011, with a measurement temperature of -100°C to 200°C and a heating rate of 10°C / min.

[0041] In this specification, methods for adjusting the glass transition temperature of an acrylic copolymer include, for example, adjusting it by changing the type and amount of monomers used as materials for the acrylic copolymer.

[0042] The weight-average molecular weight (Mw) of the above acrylic copolymer is preferably 750,000 or more and 1,500,000 or less. A weight-average molecular weight of 750,000 or more increases the bulk cohesive force of the adhesive layer formed using the adhesive composition, further improving the adhesive strength and heat resistance of the adhesive tape of this embodiment. Furthermore, it prevents the adhesive layer formed using the adhesive composition from becoming too flexible, thus suppressing the disappearance of the grooves in the adhesive layer. A weight-average molecular weight of 1,500,000 or less prevents the adhesive layer formed using the adhesive composition from becoming too hard, further improving the adhesive strength of the adhesive tape of this embodiment. Additionally, the greater flexibility of the adhesive layer formed using the adhesive composition further improves the adhesion of the adhesive tape of this embodiment to rigid bodies. The weight-average molecular weight of the above acrylic copolymer is more preferably 800,000 or more, and even more preferably 900,000 or more. Furthermore, the weight-average molecular weight of the above acrylic copolymer is more preferably less than 1,500,000, even more preferably 1,400,000 or less, and even more preferably 1,200,000 or less. Examples of weight-average molecular weights (Mw) of the above-mentioned acrylic copolymers include 750,000 to 1,500,000, 800,000 to less than 1,500,000, 900,000 to 1,400,000, and 900,000 to 1,200,000.

[0043] The preferred lower limit for the polydispersity of the above acrylic copolymer is 1.0, and the preferred upper limit is 6.0. Having the polydispersity of the above acrylic copolymer within this range further improves the adhesive strength and holding power of the adhesive tape of this embodiment. A more preferred lower limit for the polydispersity of the above acrylic copolymer is 1.5, and a more preferred upper limit is 4.5. Note that the polydispersity of the above acrylic copolymer refers to the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn). Examples of polydispersity of the above acrylic copolymer include 1.0 to 6.0, 1.5 to 4.5, etc.

[0044] In this specification, the weight-average molecular weight and the number-average molecular weight of an acrylic copolymer can be determined from the molecular weight distribution in polystyrene terms measured using gel permeation chromatography (GPC). Specifically, for example, they can be determined by measuring under the following conditions using gel permeation chromatography (Waters, "2690 Separations Module," etc.): Solvent: Tetrahydrofuran Sample flow rate: 1 mL / min Detector: Differential refractometer RI Column: GPC KF-806L (Showa Denko Corporation) Column temperature (measurement temperature): 40°C Injection volume: 20 μL Furthermore, the polydispersity of the acrylic copolymer can be calculated using the weight-average molecular weight and the number-average molecular weight of the acrylic copolymer measured by the GPC method.

[0045] Methods for adjusting the weight-average molecular weight of an acrylic copolymer as described herein include, for example, changing the polymerization temperature, changing the polymerization time, changing the type of solvent used for polymerization, changing the type of monomer, changing the concentration of monomer, and adding a chain transfer agent.

[0046] The polymerization method for synthesizing the above-mentioned acrylic copolymer can be a conventionally known method in which a mixture of monomer raw materials is subjected to 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.

[0047] 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.

[0048] 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.

[0049] The content of the acrylic copolymer in the above adhesive composition is not particularly limited, but it is preferably 70% by mass or more. A content of 70% by mass or more of the acrylic copolymer further improves the heat resistance of the adhesive tape of this embodiment. A content of 70% by mass or more of the acrylic copolymer is more preferable. Furthermore, the content of the acrylic copolymer may be 100% by mass, but from the viewpoint of further increasing the cohesive force of the adhesive layer by including a silane coupling agent or crosslinking agent described later in the adhesive layer, a preferred upper limit is 99% by mass, and a more preferred upper limit is 98% by mass. Examples of the content of the acrylic copolymer include 70% by mass or more and 100% by mass or less, more than 70% by mass and 99% by mass or less, and more than 70% by mass and 98% by mass or less.

[0050] The above adhesive composition preferably contains at least one selected from the group consisting of a tackifying resin and a silane coupling agent. By containing at least one selected from the group consisting of a tackifying resin and a silane coupling agent, the adhesive strength of the adhesive tape of this embodiment is further improved.

[0051] Examples of the tackifying resins mentioned above include terpene phenol resins, rosin resins, xylene resins, terpene resins, and petroleum resins. In particular, from the viewpoint of compatibility, it is preferable that at least one of the group consisting of terpene phenol resins, rosin resins, and terpene resins be selected as the tackifying resin. These tackifying resins may be used individually or in combination of two or more types.

[0052] Examples of the above terpene phenol resins include YS Polystar G150 and YS Polystar G125 (both manufactured by Yasuhara Chemical Co., Ltd.). Examples of the above rosin resins include Super Ester A-125 (manufactured by Arakawa Chemical Industries, Ltd.). Examples of the above terpene resins include YS Resin PX1250 (manufactured by Yasuhara Chemical Co., Ltd.).

[0053] When the above adhesive composition contains the above tackifying resin, the preferred lower limit of the content of the tackifying resin per 100 parts by mass of the acrylic copolymer in the above adhesive composition is 5.0 parts by mass, and the preferred upper limit is 40 parts by mass. A content of 5.0 parts by mass or more of the tackifying resin further improves the adhesive strength of the adhesive tape of this embodiment. A content of 40 parts by mass or less of the tackifying resin makes the adhesive layer more flexible, further improving the adhesion of the adhesive tape of this embodiment to a rigid body. A more preferred lower limit of the content of the tackifying resin is 10 parts by mass, a more preferred upper limit is 35 parts by mass, an even more preferred lower limit is 15 parts by mass, and an even more preferred upper limit is 30 parts by mass. Examples of the content of the tackifying resin include 5.0 parts by mass or more and 40 parts by mass or less, 10 parts by mass or more and 35 parts by mass or less, 15 parts by mass or more and 30 parts by mass or less, etc.

[0054] The presence of a silane coupling agent in the adhesive layer allows for the formation of a chemical bond between the adherend and the adhesive layer through a condensation reaction between hydroxyl groups and silanol groups on the adherend surface, thereby maintaining sufficient interfacial interaction for the adhesive layer to exhibit adhesive strength even in high-temperature environments. As a result, the adhesive strength of the adhesive tape of this embodiment is further improved in high-temperature environments. Therefore, from the viewpoint of desirablely forming a chemical bond with the acrylic copolymer, the silane coupling agent preferably has a reactive site that forms a chemical bond with the acrylic copolymer. Examples of the reactive site include epoxy groups, functional groups having carbon-carbon double bonds (vinyl groups, (meth)acryloyl groups, etc.), amino groups, mercapto groups, etc. Among these, epoxy groups are preferred from the viewpoint of excellent reactivity. In this specification, carbon-carbon double bonds contained in aromatic rings are not included in the carbon-carbon double bonds in the functional groups having carbon-carbon double bonds.

[0055] Examples of silane coupling agents having the above-mentioned reactive site include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethylmethoxysilane, N-(2-aminoethyl)3-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, and γ-mercaptopropylmethyldimethoxysilane. In particular, γ-glycidoxypropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane are preferred from the viewpoint of easily improving the adhesive strength of the resulting adhesive tape. These silane coupling agents may be used individually or in combination of two or more.

[0056] When the above adhesive composition contains the above silane coupling agent, the preferred lower limit of the content of the silane coupling agent per 100 parts by mass of the acrylic copolymer in the above adhesive composition is 0.1 parts by mass, and the preferred upper limit is 3.0 parts by mass. By having a silane coupling agent content of 0.1 parts by mass or more, an appropriate number of chemical bonds are formed between the adherend and the adhesive layer, and in particular, sufficient interfacial interaction can be maintained for the adhesive layer to exhibit adhesive strength even in high-temperature environments, thereby further improving the adhesive strength of the adhesive tape of this embodiment in high-temperature environments. By having a silane coupling agent content of 3.0 parts by mass or less, the adhesive layer becomes more flexible, thereby further improving the adhesion of the adhesive tape of this embodiment to rigid bodies. Furthermore, the peelability of the adhesive tape of this embodiment is further improved, and it becomes easier to peel it off from the adherend while suppressing adhesive residue, so the resulting adhesive tape can be more suitably used for temporary fixing of parts. A more preferable lower limit for the content of the silane coupling agent is 0.3 parts by mass, a more preferable upper limit is 2.0 parts by mass, an even more preferable lower limit is 0.5 parts by mass, and an even more preferable upper limit is 1.5 parts by mass. Examples of the content of the silane coupling agent include 0.1 parts by mass or more and 3.0 parts by mass or less, 0.3 parts by mass or more and 2.0 parts by mass or less, 0.5 parts by mass or more and 1.5 parts by mass or less.

[0057] The above adhesive composition preferably contains a crosslinking agent. The inclusion of a crosslinking agent in the adhesive composition facilitates the formation of a crosslinked structure in the acrylic copolymer, thereby improving the cohesive strength of the adhesive layer formed using the adhesive composition, and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape of this embodiment. By adjusting the degree of crosslinking, the gel fraction of the adhesive layer, described later, can be adjusted to an appropriate range. Furthermore, for the acrylic copolymer to be crosslinked via the crosslinking agent, it is preferable that the acrylic copolymer has constituent units derived from the polar functional group-containing monomer.

[0058] Examples of the crosslinking agents mentioned above include epoxy crosslinking agents and isocyanate crosslinking agents. Among these, isocyanate crosslinking agents are preferred because they make it easier to adjust the gel fraction of the adhesive layer (described later) to an appropriate range, and thus improve the adhesive strength and holding power of the adhesive tape having the adhesive layer.

[0059] 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. Having the crosslinking agent content within these ranges makes it easier to adjust the gel fraction of the adhesive layer (described later) to an appropriate range, thereby further improving the adhesive strength, holding power, and heat resistance of the adhesive tape having the adhesive layer. A more preferred lower limit of the crosslinking agent content is 0.1 parts by mass, and a more preferred upper limit is 3.0 parts by mass. Examples of crosslinking agent content include 0.05 parts by mass or more and 5.0 parts by mass or less, and 0.1 parts by mass or more and 3.0 parts by mass or less.

[0060] The above adhesive composition may optionally contain conventionally known fine particles such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as well as other additives.

[0061] The preferable lower limit of the gel fraction of the above adhesive layer is 10% by mass, and the preferable upper limit is 90% by mass. When the gel fraction of the above adhesive layer is 10% by mass or more, the above adhesive layer becomes hard, and the holding power of the above adhesive tape is further improved. Also, the cohesive force of the bulk of the above adhesive layer becomes larger, and the heat resistance of the adhesive tape of the present embodiment is further improved. Furthermore, it is possible to suppress the case where the adhesive layer becomes too flexible and the grooves of the adhesive layer disappear. In addition, the peelability of the adhesive tape of the present embodiment is further improved, and it becomes easier to peel while suppressing adhesive residue from the adherend. Therefore, the obtained adhesive tape can be more suitably used for temporarily fixing parts. When the gel fraction of the above adhesive layer is 90% by mass or less, the above adhesive layer becomes more stretchable, and the adhesive force of the adhesive tape of the present embodiment is further improved. Also, since the above adhesive layer becomes more flexible, the adhesion property of the adhesive tape of the present embodiment to a rigid body is further improved. The more preferable lower limit of the gel fraction of the above adhesive layer is 30% by mass, and the more preferable upper limit is 70% by mass. Note that examples of the gel fraction of the above adhesive layer include 10% by mass or more and 90% by mass or less, 30% by mass or more and 70% by mass or less, and the like. Also, in this specification, the gel fraction of the adhesive layer can be measured by the following method. That is, an adhesive tape is cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece. After immersing the test piece in tetrahydrofuran (THF) at 23°C for 24 hours, it is taken out from the tetrahydrofuran and dried under the condition of 110°C for 1 hour. The mass of the dried test piece is measured, and the gel fraction is calculated using the following formula (ii). Note that the test piece is not laminated with a release film for protecting the adhesive layer. Also, when the adhesive tape does not have a base material, W ０ is set to 0. Gel fraction (% by mass) = 100 × (W ２ −W ０ ) / (W １ −W ０ ) (ii) (W ０ : mass of the base material, W １ : mass of the test piece before immersion, W ２ : mass of the test piece after immersion and drying)

[0062] Methods for adjusting the gel fraction of the adhesive layer as described herein include adjusting the content ratio of constituent units derived from polar functional group-containing monomers in the acrylic copolymer, and adjusting the type and content of tackifying resins and crosslinking agents included in the adhesive composition.

[0063] The thickness of the adhesive layer described above has a preferred lower limit of 20 μm and a preferred upper limit of 100 μm. A thickness of 20 μm or more in the adhesive layer provides sufficient adhesive strength and adhesion for the adhesive tape of this embodiment. A thickness of 100 μm or less provides superior heat resistance for the adhesive tape of this embodiment. A more preferred lower limit for the thickness of the adhesive layer is 25 μm, a more preferred upper limit is 90 μm, and an even more preferred lower limit is 35 μm. An even more preferred upper limit is 75 μm. Examples of suitable adhesive layer thicknesses include 20 μm to 100 μm, 25 μm to 90 μm, and 35 μm to 75 μm.

[0064] The adhesive tape of this embodiment may be a non-support type adhesive tape without a base material, or a support type adhesive tape in which the adhesive layer is formed on a base material. In particular, from the viewpoint of heat resistance, it is preferable that the adhesive tape of this embodiment has a base material. If the adhesive tape of this embodiment has a base material, it may be a single-sided adhesive tape with the adhesive layer on one side of the base material, or a double-sided adhesive tape with the adhesive layer on both sides.

[0065] Examples of the above-mentioned substrates include resin films such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, and polyimide, as well as nonwoven fabrics and foam substrates.

[0066] The preferred lower limit for the thickness of the above-mentioned base material is 12 μm, and the preferred upper limit is 150 μm. When the thickness of the above-mentioned base material is 12 μm or more, the adhesive tape has appropriate stiffness and is easier to handle. When the thickness of the above-mentioned base material is 150 μm or less, the adhesive tape of this embodiment is easier to adhere to rigid bodies. A more preferred lower limit for the thickness of the above-mentioned base material is 50 μm, a more preferred upper limit is 125 μm, an even more preferred lower limit is 75 μm, and an even more preferred upper limit is 100 μm. Examples of the thickness of the above-mentioned base material include 12 μm to 150 μm, 50 μm to 125 μm, 75 μm to 100 μm, etc.

[0067] When the adhesive tape of this embodiment has a base material, the total thickness of the base material and the adhesive layer is preferably 50 μm at the lower limit and preferably 500 μm at the upper limit. By having the total thickness of the base material and the adhesive layer within the above range, deformation of the adhesive tape of this embodiment is suppressed and the heat resistance at high temperatures is further improved. A more preferable lower limit for the total thickness of the base material and the adhesive layer is 100 μm, a more preferable upper limit is 300 μm, and an even more preferable lower limit is 150 μm. An even more preferable upper limit is 250 μm. Examples of the total thickness of the base material and the adhesive layer include 50 μm or more and 500 μm or less, 100 μm or more and 300 μm or less, 150 μm or more and 250 μm or less, etc. Furthermore, when the adhesive tape of this embodiment has two or more adhesive layers, "total thickness of the base material and the adhesive layer" means the sum of the thickness of the base material and the thickness of all the adhesive layers of the adhesive tape.

[0068] The adhesive tape of this embodiment may be an adhesive tape with a release sheet, which has a release sheet to protect the adhesive layer.

[0069] The base material used for the above-mentioned release sheet is not particularly limited, but examples include resin films such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, and polyimide, as well as release paper, nonwoven fabrics, foamed base materials, etc.

[0070] Preferably, the release sheet has a textured surface. By having a textured surface on the release sheet, when the textured surface of the release sheet is laminated onto the adhesive layer, the surface of the adhesive layer is formed into a textured shape that fits into the texture of the release sheet, making it easier for the adhesive layer to have grooves. In other words, in the adhesive tape of this embodiment, it is preferable that a release sheet with a textured surface on the adhesive layer side is laminated onto the surface of the adhesive layer, and that the surface of the adhesive layer is formed into a textured shape that fits into the texture of the release sheet.

[0071] Examples of decorative textures on the surface of the release sheet include embossing and chemical etching.

[0072] If the surface of the release sheet is not decorated with embossed patterns, the preferred lower limit of the thickness of the release sheet is 20 μm, and the preferred upper limit is 300 μm. A thickness of 20 μm or more for the release sheet results in the adhesive tape of this embodiment having appropriate stiffness and superior handling properties. A thickness of 300 μm or less results in the release sheet having superior peelability from the adhesive tape. A more preferred lower limit for the thickness of the release sheet is 30 μm, a more preferred upper limit is 200 μm, an even more preferred lower limit is 50 μm, and an even more preferred upper limit is 100 μm. If the surface of the release sheet is not decorated with embossed patterns, examples of the thickness of the release sheet include 20 μm to 300 μm, 30 μm to 200 μm, 50 μm to 100 μm, etc.

[0073] When the surface of the release sheet is treated with a textured finish, the preferred lower limit of the thickness of the release sheet is 50 μm, and the preferred upper limit is 300 μm. When the thickness of the release sheet is 50 μm or more, the adhesive tape of this embodiment is formed with an uneven shape on the surface of the adhesive layer that fits into the unevenness of the release sheet, and the adhesive layer is more likely to have grooves. When the thickness of the release sheet is 300 μm or less, the release sheet has better peelability from the adhesive tape. When the surface of the release sheet is treated with a textured finish, the more preferred lower limit of the thickness of the release sheet is 75 μm, the more preferred upper limit is 200 μm, the still more preferred lower limit is 100 μm, and the still more preferred upper limit is 175 μm. If the surface of the release sheet described above is treated with an uneven decorative finish, the thickness of the release sheet can be, for example, 50 μm to 300 μm, 75 μm to 200 μm, 100 μm to 175 μm, etc.

[0074] The adhesive tape of this embodiment may have other layers, as long as they do not impair the effects of the present invention.

[0075] The method for manufacturing the adhesive tape of this embodiment is not particularly limited, and conventionally known methods can be used. For example, first, the alkyl (meth)acrylate, the olefin polymer having a polymerizable unsaturated double bond at its terminus, and optionally the polar functional group-containing monomer are copolymerized by a conventional method to obtain the acrylic copolymer. Next, a solution is prepared containing an adhesive composition obtained by blending the obtained acrylic copolymer with, optionally, the tackifying resin, the silane coupling agent, the crosslinking agent, and other additives. Then, the solution containing the adhesive composition is coated onto a release sheet and dried to form an adhesive layer, thereby producing an adhesive tape without a substrate. Alternatively, an adhesive tape with a substrate can be obtained by laminating the adhesive layer formed by the above method to a substrate.

[0076] The use of the adhesive tape of this embodiment is not particularly limited, but because it has excellent heat resistance, it is suitably used for fixing electronic equipment components or automotive components. In particular, because the adhesive tape of this embodiment also has excellent adhesion to rigid bodies, it is more preferably used as an electrical connection member. Examples of such electrical connection members include those that fix and electrically connect electronic equipment components to each other, specifically, members that fix and electrically connect components such as battery packs, automotive displays, and display front panels. An example of an electrical connection member using the adhesive tape of this embodiment is an electrical connection member having a conductive member and adhesive tape. In this case, it is preferable that the adhesive tape of this embodiment has the role of holding the conductive member to the component to be connected. Note that an electrical connection member having a conductive member and the adhesive tape of this embodiment is also one of this embodiment (electrical connection member of this embodiment 1). Furthermore, if the adhesive tape of this embodiment also has excellent peelability, it can be suitably used for temporary fixing of components manufactured in the manufacturing process of electronic equipment components, and in particular, it is preferable to use it for temporary fixing in the semiconductor manufacturing process.

[0077] A structure in which a conductive member is held to a member to be connected by the adhesive tape of this embodiment 1 is also one of this embodiment (structure of this embodiment 1). In the structure of this embodiment 1, the conductive member is firmly held to the member to be connected by the adhesive tape, and the adhesive tape does not peel off even when current is passed through it and it becomes hot, thus enabling a stable electrical connection.

[0078] An example of the structure of this embodiment 1 is shown in Figure 2. In the structure 2 shown in Figure 2, the conductive member 51 is held to the connection target members 61 and 62 by adhesive tape 41 in the electrical connection member 31. In this embodiment 1, "held to the connection target members by the adhesive tape of this embodiment" includes not only a structure in which the conductive member and the connection target members are bonded together by adhesive tape, but also a structure in which the conductive member penetrates the adhesive tape and is fixed adjacent to the connection target members, as shown in Figure 2.

[0079] An electrical connection member having a conductive member and an adhesive tape, wherein the adhesive tape has an adhesive layer formed using an adhesive composition, the adhesive composition includes an acrylic copolymer, and the acrylic copolymer has constituent units derived from alkyl (meth)acrylate and constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals, is also one of the embodiments (the electrical connection member of embodiment 2).

[0080] The electrical connection member of this second embodiment comprises a conductive member and an adhesive tape. In the electrical connection member of this second embodiment, the adhesive tape can achieve both excellent heat resistance and high adhesive strength. Therefore, the electrical connection member of this second embodiment can firmly hold the conductive member to the member to be connected, and can also suppress peeling of the adhesive tape from the conductive member and the member to be connected even when high temperatures are reached (for example, when a large current is flowing). Thus, stable electrical connections can be made at both room temperature and high temperatures. For this reason, it is preferable that the electrical connection member of this second embodiment has a structure in which the adhesive tape holds the conductive member to the member to be connected.

[0081] Figure 3 shows an example of how a conductive member is held on a member to be connected using the electrical connection member of this second embodiment. In Figure 3, the conductive member 52 is held on the members to be connected 61 and 62 by adhesive tape 42 using the electrical connection member 32. In the electrical connection member of this second embodiment, "held on the member to be connected" includes not only bonding the conductive member and the member to be connected with adhesive tape, but also structures in which the conductive member penetrates a portion of the adhesive tape, as in the electrical connection member shown in Figure 3. Furthermore, an electrical connection member having a structure in which the conductive member penetrates a portion of the adhesive tape also includes cases in which the electrical connection member is used to bring the conductive member and the member to be connected into contact, and the electrical connection member is fixed by the portion of the adhesive tape other than the portion that penetrates the conductive member. In particular, from the viewpoint of securely holding the conductive member by surrounding its entire side with adhesive tape, it is preferable that the electrical connection member of this second embodiment has a structure in which the conductive member penetrates the adhesive tape (i.e., a structure in which the conductive member penetrates the adhesive tape). Furthermore, because the conductive member is thicker than the upper surface of the adhesive tape, it can be brought into contact with the member to be connected in a compressed state.

[0082] Furthermore, a structure comprising an electrical connection member and a member to be connected, wherein the electrical connection member comprises a conductive member and an adhesive tape, the adhesive tape having an adhesive layer formed using an adhesive composition, the adhesive composition comprising an acrylic copolymer, and the acrylic copolymer comprising constituent units derived from alkyl (meth)acrylate and constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its ends, is also one of the embodiments (structure of embodiment 2). In the structure of embodiment 2, the conductive member is firmly held to the member to be connected at both room temperature and high temperature, thus enabling stable electrical connection at both room temperature and high temperature. In addition, examples of the electrical connection member in the structure of embodiment 2 include the electrical connection member of this embodiment, and examples of the adhesive tape in the structure of embodiment 2 include the adhesive tape of this embodiment described above and the adhesive tape in the electrical connection member of embodiment 2.

[0083] Examples of conductive members in the electrical connection member of this embodiment include a member having conductive rubber, a member having a metal spring, and a member in which the surface of a soft elastic body made of foam or the like is covered with a conductive layer such as metal foil. Among these, a member having conductive rubber is preferred from the viewpoint of integral formation with adhesive tape.

[0084] Examples of the conductive rubbers mentioned above include thermosetting rubbers and thermoplastic elastomers that are conductive. Specifically, examples of the thermosetting rubbers include silicone rubber, natural rubber, isoprene rubber, butadiene rubber, acrylonitrile butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylic rubber, fluororubber, and urethane rubber. Among these, silicone rubber is preferred from the viewpoint of having small compression set at room temperature and high temperature. Specifically, examples of the thermoplastic elastomers mentioned above include styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, ester-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, fluorine-based thermoplastic elastomers, and ion-crosslinked thermoplastic elastomers.

[0085] The above-mentioned conductive member may contain an inorganic filler from the viewpoint of improving conductivity. Examples of the inorganic filler include conductive fine particles and fibers of gold, silver, copper, carbon, graphite, etc. Furthermore, examples of conductive members containing the above-mentioned inorganic filler include those in which the surface of fine particles and fibers made of metal, ceramic, resin, etc. is coated with a conductive layer made of gold, silver, copper, etc., or those in which the surface of fine particles and fibers made of nickel, cobalt, iron, ferrite, or alloys containing these is coated with a conductive layer made of gold, silver, copper, etc.

[0086] The shape of the conductive member described above is not particularly limited, but examples include polygonal prism shape, cylindrical shape, etc. Among these, a cylindrical shape is preferred from the viewpoint of moldability.

[0087] The method for manufacturing the above-mentioned conductive member is not particularly limited, but examples include the following: a mold is prepared in which ferromagnetic pins are embedded, and a conductive filler and silicone rubber as a liquid rubber are poured into the mold to form a conductive member having a conductive part made of a conductive rubber-like elastic body and an insulating part surrounding it.

[0088] Examples of the members to be connected in the structure of this embodiment include metal tabs, metal wiring, and glass plates on which metal circuits are printed. Specifically, examples include metal terminals for installing defrosters and defoggers on automobile windows, and metal terminals for electronic components such as antennas, sensors, LED lights, heaters, and batteries.

[0089] The electrical connection member of this embodiment may have multiple conductive members, and if the electrical connection member of this embodiment has multiple conductive members, only one type of conductive member may be used, or two or more types may be used in combination.

[0090] The conductive connecting member of this second embodiment has an adhesive tape. The adhesive tape in the conductive connecting member of this second embodiment will be described in detail below. The adhesive tape has an adhesive layer formed using an adhesive composition. A method for forming the adhesive layer using the adhesive composition includes, for example, applying the adhesive composition to a release sheet or the like, and then heating and drying the adhesive composition.

[0091] The above adhesive composition contains an acrylic copolymer having structural units derived from an alkyl (meth)acrylate ester and structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals. The above acrylic copolymer has a structure in which structural units derived from the olefin polymer having polymerizable unsaturated double bonds at its terminals aggregate through interaction, forming pseudo-crosslinking points. Because the above acrylic copolymer adopts such a structure, the above adhesive composition exhibits hard properties like a crosslinked adhesive composition when the strain is small, and the holding power is further improved. On the other hand, when peel stress is applied and the strain becomes large, the pseudo-crosslinking breaks, and the molecules of the above acrylic copolymer stretch, so the above adhesive composition exhibits high flexibility and the adhesive strength is improved. In other words, because the above adhesive composition contains the above acrylic copolymer, the adhesive strength of the adhesive layer formed using the above adhesive composition is improved, and the electrical connection member of this embodiment 2 can firmly hold the conductive member to the member to be connected. Furthermore, the holding power of the above adhesive layer is further improved. Furthermore, because the acrylic copolymer adopts such a structure, the cohesive force of the adhesive layer formed using the adhesive composition is improved, resulting in improved heat resistance of the adhesive tape. Thus, the electrical connection member of this second embodiment can suppress the peeling of the adhesive tape from conductive members and connected members even when high temperatures are reached (for example, when a large current is flowing).

[0092] Examples of constituent units derived from the above alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, n-heptyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate. Examples of constituent units include those derived from 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. In particular, from the viewpoint of increasing the polarity of the acrylic copolymer and improving the cohesive force of the adhesive layer formed using the adhesive composition, thereby further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape, it is preferable that the constituent units derived from the alkyl (meth)acrylate include constituent units derived from alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms. These alkyl (meth)acrylates may be used individually or in combination of two or more.

[0093] When the above-mentioned alkyl (meth)acrylate-derived structural units include structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms, the preferred lower limit of the content of structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms in the above-mentioned alkyl (meth)acrylate-derived structural units is 50% by mass. By having a content of 50% by mass or more of structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms, the polarity of the acrylic copolymer increases, improving the cohesive force of the adhesive layer formed using the adhesive composition, thereby further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape. A more preferred lower limit for the content of structural units derived from alkyl (meth)acrylate-derived structural units having an alkyl group with 1 to 4 carbon atoms is 60% by mass, and an even more preferred lower limit is 70% by mass. Furthermore, from the viewpoint of further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape, a higher content of the constituent units derived from the alkyl (meth)acrylate ester having an alkyl group with 1 to 4 carbon atoms is preferable. Therefore, from this viewpoint, it is most preferable that the content of the constituent units derived from the alkyl (meth)acrylate ester having an alkyl group with 1 to 4 carbon atoms is 100% by mass, that is, that the constituent units derived from the alkyl (meth)acrylate ester consist only of constituent units derived from the alkyl (meth)acrylate ester having an alkyl group with 1 to 4 carbon atoms. On the other hand, from the viewpoint of improving the adhesion of the adhesive tape to a rigid body by making the adhesive layer formed using the adhesive composition more flexible, and making it easier to firmly hold the conductive member to the connected member, the preferred upper limit of the content of the constituent units derived from the alkyl (meth)acrylate ester having an alkyl group with 1 to 4 carbon atoms is 98% by mass, and the more preferred upper limit is 95% by mass.Examples of the content of constituent units derived from alkyl (meth)acrylate esters having an alkyl group with 1 to 4 carbon atoms include 50% to 100% by mass, 60% to 98% by mass, 70% to 95% by mass, and so on.

[0094] From the viewpoint of the adhesive strength of the above adhesive composition, it is preferable that the constituent units derived from the (meth)acrylate alkyl ester include constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms. When the constituent units derived from the (meth)acrylate alkyl ester include constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms, the preferred lower limit of the content of the constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms in the constituent units derived from the (meth)acrylate alkyl ester is 10% by mass, and the preferred upper limit is 80% by mass. By having a content of 10% by mass or more of the constituent units derived from the (meth)acrylate alkyl ester having an alkyl group having 1 to 2 carbon atoms, the polarity of the acrylic copolymer becomes greater, and the cohesive force of the adhesive layer formed using the above adhesive composition is improved, thereby further improving the adhesive strength (especially the adhesive strength at high temperatures) and heat resistance of the adhesive tape. Furthermore, if the adhesive layer has grooves as described later, it is possible to suppress the grooves in the adhesive layer from disappearing because the adhesive layer formed using the above adhesive composition becomes too flexible. By having a content of 80% by mass or less of the constituent units derived from the alkyl (meth)acrylate ester having one to two C1 alkyl groups, it becomes easier to adjust the glass transition temperature of the acrylic copolymer, as described later, within an appropriate range, and the adhesive strength of the adhesive layer formed using the adhesive composition is further improved. A more preferable lower limit for the content of the constituent units derived from the alkyl (meth)acrylate ester having one to two C1 alkyl groups is 15% by mass, a more preferable upper limit is 50% by mass, an even more preferable lower limit is 20% by mass, and an even more preferable upper limit is 30% by mass. Examples of the content of the constituent units derived from the alkyl (meth)acrylate ester having one to two C1 alkyl groups include 10% by mass or more and 80% by mass or less, 15% by mass or more and 50% by mass or less, and 20% by mass or more and 30% by mass or less.

[0095] In the above acrylic copolymer, the preferred lower limit of the content of constituent units derived from the above alkyl (meth)acrylate is 50% by mass, and the preferred upper limit is 90% by mass. By having the content of constituent units derived from the above alkyl (meth)acrylate within the above range, the adhesive strength and holding power of the adhesive tape are further improved. A more preferred lower limit of the content of constituent units derived from the above alkyl (meth)acrylate is 60% by mass, a more preferred upper limit is 80% by mass, an even more preferred lower limit is 65% by mass, and an even more preferred upper limit is 75% by mass. Examples of the content of constituent units derived from the above alkyl (meth)acrylate include 50% by mass or more and 90% by mass or less, 60% by mass or more and 80% by mass or less, 65% by mass or more and 75% by mass or less, etc.

[0096] 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, the olefin polymer having a polymerizable unsaturated double bond at one end is preferred from the viewpoint of easily forming an appropriate number of pseudo-crosslinks.

[0097] Examples of olefin polymers having polymerizable unsaturated double bonds at their ends include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, and butylene polymers, which have groups with polymerizable unsaturated double bonds at one or both ends. These olefin polymers having polymerizable unsaturated double bonds at their ends may be used individually or in combination of two or more types.

[0098] Examples of groups having the polymerizable unsaturated double bond mentioned above 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)acrylates mentioned above.

[0099] Examples of olefin polymers having a (meth)acryloyl group at one end 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 making it easier to adjust the glass transition temperature of the acrylic copolymer described later to an appropriate range and further improving the adhesive strength of the adhesive layer formed using the above adhesive composition.

[0100] In the above acrylic copolymer, the preferred lower limit of the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends is 5% by mass, and the preferred upper limit is 30% by mass. When the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends is 5% by mass or more, an appropriate number of pseudo-crosslinks are formed in the acrylic copolymer, further improving the adhesive strength, holding power, and heat resistance of the adhesive tape. When the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends is 30% by mass or less, cohesive failure of the adhesive layer formed using the adhesive composition can be further suppressed. In addition, the adhesive layer formed using the adhesive composition becomes more flexible, which further improves the adhesion of the adhesive tape to a rigid body, making it easier to firmly hold the conductive member to the connected member. A more preferable lower limit for the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends is 10% by mass, a more preferable upper limit is 27% by mass, an even more preferable lower limit is 15% by mass, and an even more preferable upper limit is 25% 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 30% by mass or less, 10% by mass or more and 27% by mass or less, 15% by mass or more and 25% by mass or less, etc.

[0101] The above acrylic copolymer preferably has structural units derived from a polar functional group-containing monomer. Having structural units derived from a polar functional group-containing monomer makes it easier for the acrylic copolymer to form a crosslinked structure, thereby improving the cohesive force of the adhesive layer formed using the adhesive composition, and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape.

[0102] Examples of constituent units derived from the above-mentioned polar functional group-containing monomers 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 improving the cohesive force of the adhesive layer formed using the above-mentioned adhesive composition and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape, it is preferable that the constituent units derived from the above-mentioned polar functional group-containing monomers 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. These polar functional group-containing monomers may be used individually or in combination of two or more.

[0103] Examples of the above carboxyl group-containing monomers include unsaturated carboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Examples of the above hydroxyl group-containing monomers include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of the above amide group-containing monomers include N-vinyl-2-pyrrolidone, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide. Examples of the above amino group-containing monomers include (meth)acryloylmorpholine, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate.

[0104] In the above acrylic copolymer, the preferred lower limit of the total content of constituent units derived from the polar functional group-containing monomer is 3.0% by mass, and the preferred upper limit is 15% by mass. When the total content of constituent units derived from the polar functional group-containing monomer is 3.0% by mass or more, the acrylic copolymer is more likely to form a crosslinked structure, thereby improving the cohesive force of the adhesive layer formed using the adhesive composition, and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape. Furthermore, if the adhesive layer has grooves as described later, it is possible to suppress the disappearance of the grooves in the adhesive layer due to the adhesive layer becoming too flexible when formed using the adhesive composition. When the total content of constituent units derived from the polar functional group-containing monomer is 15% by mass or less, the adhesive layer formed using the adhesive composition becomes more flexible, thereby further improving the adhesion of the adhesive tape to a rigid body. A more preferred lower limit of the total content of constituent units derived from the polar functional group-containing monomer is 4.0% by mass, a more preferred upper limit is 10% by mass, an even more preferred lower limit is 5.0% by mass, and an even more preferred upper limit is 7.0% by mass. Examples of the total content of constituent units derived from the above polar functional group-containing monomers include 3.0% by mass or more and 15% by mass or less, 4.0% by mass or more and 10% by mass or less, and 5.0% by mass or more and 7.0% by mass or less.

[0105] The glass transition temperature (Tg) of the above acrylic copolymer is preferably in the range of -100°C to 200°C, with a more preferable upper limit of -20°C. A glass transition temperature of -20°C or lower allows the molecules of the acrylic copolymer to stretch more easily, thereby improving the adhesive strength of the adhesive tape. A further preferable upper limit for the glass transition temperature of the acrylic copolymer is -30°C, with a particularly preferable upper limit of -35°C. Furthermore, if the acrylic copolymer has multiple glass transition temperatures, it is more preferable that all of the glass transition temperatures of the acrylic copolymer are -20°C or lower. Examples of glass transition temperatures (Tg) for the acrylic copolymer include -100°C to 200°C, -100°C to -30°C, and -100°C to -35°C.

[0106] The weight-average molecular weight (Mw) of the above acrylic copolymer is preferably 750,000 or more and less than 1,500,000. A weight-average molecular weight of 750,000 or more increases the bulk cohesive force of the adhesive layer formed using the adhesive composition, further improving the adhesive strength and heat resistance of the adhesive tape. Furthermore, if the adhesive layer has grooves described later, it is possible to prevent the adhesive layer formed using the adhesive composition from becoming too flexible and causing the grooves to disappear. A weight-average molecular weight of less than 1,500,000 prevents the adhesive layer formed using the adhesive composition from becoming too rigid, further improving the adhesive strength of the adhesive tape. Additionally, the greater flexibility of the adhesive layer formed using the adhesive composition improves the adhesion of the adhesive tape to rigid bodies, making it easier to more firmly hold the conductive member to the connected member. A more preferable lower limit for the weight-average molecular weight of the above acrylic copolymer is 800,000, a more preferable upper limit is 1,400,000, an even more preferable lower limit is 900,000, and an even more preferable upper limit is 1,200,000. Examples of weight-average molecular weights (Mw) of the above-mentioned acrylic copolymers include 750,000 to less than 1,500,000, 800,000 to less than 1,500,000, 900,000 to 1,400,000, and 900,000 to 1,200,000.

[0107] The preferred lower limit for the polydispersity of the above acrylic copolymer is 1.0, and the preferred upper limit is 6.0. When the polydispersity of the above acrylic copolymer is within the above range, the adhesive strength and holding power of the adhesive tape are further improved. A more preferred lower limit for the polydispersity of the above acrylic copolymer is 1.5, and a more preferred upper limit is 4.5. Note that the above polydispersity refers to the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn). Examples of polydispersity of the above acrylic copolymer include 1.0 to 6.0, 1.5 to 4.5, etc.

[0108] The polymerization method for synthesizing the above-mentioned acrylic copolymer can be a conventionally known method in which a mixture of monomer raw materials is subjected to 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.

[0109] 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.

[0110] 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.

[0111] The content of the acrylic copolymer in the above adhesive composition is not particularly limited, but it is preferably 70% by mass or more. A content of 70% by mass or more of the acrylic copolymer further improves the heat resistance of the adhesive tape. A content of 70% by mass or more of the acrylic copolymer is more preferable. Furthermore, the content of the acrylic copolymer may be 100% by mass, but from the viewpoint of further increasing the cohesive force of the adhesive layer by including a silane coupling agent or crosslinking agent described later in the adhesive layer, a preferred upper limit is 99% by mass, and a more preferred upper limit is 98% by mass. Examples of the content of the acrylic copolymer include 70% by mass or more and 100% by mass or less, more than 70% by mass and 99% by mass or less, and more than 70% by mass and 98% by mass or less.

[0112] The above adhesive composition preferably contains at least one selected from the group consisting of a tackifying resin and a silane coupling agent. By containing at least one selected from the group consisting of a tackifying resin and a silane coupling agent, the adhesive strength of the adhesive tape is further improved.

[0113] Examples of the tackifying resins mentioned above include terpene phenol resins, rosin resins, xylene resins, terpene resins, and petroleum resins. In particular, from the viewpoint of compatibility, it is preferable that at least one of the group consisting of terpene phenol resins, rosin resins, and terpene resins be selected as the tackifying resin. These tackifying resins may be used individually or in combination of two or more types.

[0114] Examples of the above terpene phenol resins include YS Polystar G150 and YS Polystar G125 (both manufactured by Yasuhara Chemical Co., Ltd.). Examples of the above rosin resins include Super Ester A-125 (manufactured by Arakawa Chemical Industries, Ltd.). Examples of the above terpene resins include YS Resin PX1250 (manufactured by Yasuhara Chemical Co., Ltd.).

[0115] When the above adhesive composition contains the above tackifying resin, the preferred lower limit of the content of the tackifying resin per 100 parts by mass of the acrylic copolymer in the above adhesive composition is 5.0 parts by mass, and the preferred upper limit is 40 parts by mass. When the content of the tackifying resin is 5.0 parts by mass or more, the adhesive strength of the adhesive tape is further improved. When the content of the tackifying resin is 40 parts by mass or less, the adhesive layer becomes more flexible, which further improves the adhesion of the adhesive tape to a rigid body, making it easier to firmly hold the conductive member to the member to be connected. A more preferred lower limit of the content of the tackifying resin is 10 parts by mass, a more preferred upper limit is 35 parts by mass, an even more preferred lower limit is 15 parts by mass, and an even more preferred upper limit is 30 parts by mass. Examples of the content of the tackifying resin include 5.0 parts by mass or more and 40 parts by mass or less, 10 parts by mass or more and 35 parts by mass or less, 15 parts by mass or more and 30 parts by mass or less, etc.

[0116] The presence of a silane coupling agent in the adhesive layer allows for the formation of a chemical bond between the adherend and the adhesive layer through a condensation reaction between hydroxyl groups and silanol groups on the adherend surface, thereby maintaining sufficient interfacial interaction for the adhesive layer to exhibit adhesive strength even in high-temperature environments. As a result, the adhesive strength of the adhesive tape in high-temperature environments is further improved. Therefore, from the viewpoint of desirablely forming a chemical bond with the acrylic copolymer, the silane coupling agent preferably has a reactive site that forms a chemical bond with the acrylic copolymer. Examples of such reactive sites include epoxy groups, functional groups having carbon-carbon double bonds (vinyl groups, (meth)acryloyl groups, etc.), amino groups, and mercapto groups. Among these, epoxy groups are preferred from the viewpoint of excellent reactivity. In this specification, carbon-carbon double bonds contained in aromatic rings are not included in the carbon-carbon double bonds in the functional groups having carbon-carbon double bonds.

[0117] Examples of silane coupling agents having the above-mentioned reactive site include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethylmethoxysilane, N-(2-aminoethyl)3-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, and γ-mercaptopropylmethyldimethoxysilane. In particular, γ-glycidoxypropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane are preferred from the viewpoint of easily improving the adhesive strength of the resulting adhesive tape. These silane coupling agents may be used individually or in combination of two or more.

[0118] When the above adhesive composition contains the above silane coupling agent, the preferred lower limit of the content of the silane coupling agent per 100 parts by mass of the acrylic copolymer in the above adhesive composition is 0.1 parts by mass, and the preferred upper limit is 3.0 parts by mass. When the content of the silane coupling agent is 0.1 parts by mass or more, an appropriate number of chemical bonds are formed between the adherend and the adhesive layer, and in particular, sufficient interfacial interaction can be maintained for the adhesive layer to exhibit adhesive force even in high-temperature environments, thereby further improving the adhesive force of the adhesive tape in high-temperature environments. When the content of the silane coupling agent is 3.0 parts by mass or less, the adhesive layer becomes more flexible, which further improves the adhesion of the adhesive tape to a rigid body, and makes it easier to firmly hold the conductive member to the connected member. The more preferred lower limit of the content of the silane coupling agent is 0.3 parts by mass, the more preferred upper limit is 2.0 parts by mass, the even more preferred lower limit is 0.5 parts by mass, and the even more preferred upper limit is 1.5 parts by mass. Examples of the silane coupling agent content include 0.1 parts by mass or more and 3.0 parts by mass or less, 0.3 parts by mass or more and 2.0 parts by mass or less, and 0.5 parts by mass or more and 1.5 parts by mass or less.

[0119] The above adhesive composition preferably contains a crosslinking agent. This facilitates the formation of a crosslinked structure in the acrylic copolymer, thereby improving the cohesive strength of the adhesive layer formed using the above adhesive composition, and further improving the adhesive strength, holding power, and heat resistance of the adhesive tape. By adjusting the degree of crosslinking at this time, the gel fraction of the adhesive layer, described later, can be adjusted to an appropriate range. In order for the acrylic copolymer to be crosslinked via the crosslinking agent, it is preferable that the acrylic copolymer has constituent units derived from the polar functional group-containing monomer.

[0120] Examples of the crosslinking agents mentioned above include epoxy crosslinking agents and isocyanate crosslinking agents. Among these, isocyanate crosslinking agents are preferred because they make it easier to adjust the gel fraction of the adhesive layer (described later) to an appropriate range, and thus improve the adhesive strength and holding power of the adhesive tape having the adhesive layer.

[0121] 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. Having the crosslinking agent content within these ranges makes it easier to adjust the gel fraction of the adhesive layer (described later) to an appropriate range, thereby further improving the adhesive strength, holding power, and heat resistance of the adhesive tape having the adhesive layer. A more preferred lower limit of the crosslinking agent content is 0.1 parts by mass, and a more preferred upper limit is 3.0 parts by mass. Examples of crosslinking agent content include 0.05 parts by mass or more and 5.0 parts by mass or less, and 0.1 parts by mass or more and 3.0 parts by mass or less.

[0122] The above adhesive composition may optionally contain conventionally known fine particles such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as well as other additives.

[0123] In the conductive connecting member of this second embodiment, it is preferable that the adhesive layer of the adhesive tape has grooves on at least one surface. Having grooves on at least one surface of the adhesive layer prevents air bubbles from entering the bonding surface when rigid bodies are bonded together, thereby improving the adhesive tape's ability to adhere to rigid bodies and making it easier to firmly hold the conductive member to the member to be connected. For this reason, since the grooves are usually formed to remove air bubbles, it is more preferable that the grooves are air bubble removal grooves for removing air bubbles.

[0124] Preferably, at least one end of the groove extends to the side surface. Because at least one end of the groove extends to the side surface, air bubbles attempting to enter the bonding surface are more easily pushed out from the side. This results in superior adhesion of the adhesive tape to rigid bodies, and makes it easier to hold the conductive member more firmly to the connected member.

[0125] When the surface of the adhesive layer is observed from the thickness direction, the shape of the grooves can be, for example, linear (straight, curved, grid-like, etc.), circular, etc., but is not particularly limited, and in any shape, it is preferable that at least a portion of the grooves extend to the side surface. When the adhesive layer is cut by a plane parallel to the thickness direction, the cross-sectional shape of the grooves can be, for example, a square, a triangle, a U-shape, etc.

[0126] The grooves may be multiple on the surface of the adhesive layer, and may be patterned with a specific shape. When there are multiple grooves in the adhesive layer, it is preferable that at least some of the grooves satisfy the range described later for width, depth, depth ratio, etc., and it is more preferable that all of the grooves satisfy the range described later for width, depth, depth ratio, etc. Furthermore, when there are multiple grooves in the adhesive layer, the depth and width of the grooves do not all need to be the same, and the depth and width of the grooves may differ.

[0127] The ratio of the groove depth to the thickness of the adhesive layer (hereinafter sometimes simply referred to as "groove depth ratio") has a preferred lower limit of 15% and a preferred upper limit of 80%. When the groove depth ratio is 15% or more, air bubbles that try to enter the bonding surface are more easily pushed out from the sides, so the adhesive tape has better adhesion to rigid bodies and the conductive member is more firmly held to the connected member. When the groove depth ratio is 80% or less, adhesive residue due to the adhesive tearing when the adhesive tape is peeled off can be prevented. The groove depth ratio has a more preferred lower limit of 30%, a more preferred upper limit of 70%, an even more preferred lower limit of 40%, and an even more preferred upper limit of 60%. Examples of groove depth ratios include 15% to 80%, 30% to 70%, 40% to 60%, etc.

[0128] As described above, the adhesive layer preferably has a groove depth ratio that satisfies the range described above, but it is more preferable that the grooves in the adhesive layer have a specific average depth. Specifically, the preferred lower limit of the groove depth is 5 μm, and the preferred upper limit is 150 μm. When the groove depth is 5 μm or more, air bubbles that try to enter the bonding surface are more easily pushed out from the sides, so that the adhesive tape of this embodiment has better adhesion to rigid bodies and the conductive member is more easily held firmly by the connected member. When the groove depth is 150 μm or less, adhesive residue due to the adhesive tearing when the adhesive tape is peeled off can be better prevented. The more preferred lower limit of the groove depth is 10 μm, the more preferred upper limit is 100 μm, the even more preferred lower limit is 15 μm, and the even more preferred upper limit is 50 μm. Examples of groove depths include 5 μm to 150 μm, 10 μm to 100 μm, 15 μm to 50 μm, and so on.

[0129] When the groove is linear, the preferred lower limit of the groove width is 10 μm, and the preferred upper limit is 300 μm. A width of 10 μm or more makes it easier for air bubbles attempting to enter the bonding surface to be pushed out from the sides, resulting in superior adhesion of the adhesive tape to rigid bodies and easier secure holding of the conductive member to the connected member. A groove width of 300 μm or less ensures sufficient bonding area, resulting in superior adhesive strength for the adhesive tape of this embodiment. A more preferred lower limit of the groove width is 25 μm, a more preferred upper limit is 200 μm, an even more preferred lower limit is 50 μm, and an even more preferred upper limit is 150 μm. Examples of groove widths include 10 μm to 300 μm, 25 μm to 200 μm, and 50 μm to 150 μm.

[0130] The preferred lower limit for the gel fraction of the adhesive layer is 10% by mass, and the preferred upper limit is 90% by mass. When the gel fraction of the adhesive layer is 10% by mass or more, the adhesive layer becomes harder, and the holding power of the adhesive tape is further improved. In addition, the bulk cohesive force of the adhesive layer becomes greater, and the heat resistance of the adhesive tape is further improved. Furthermore, it is possible to suppress the disappearance of the grooves in the adhesive layer due to the adhesive layer becoming too flexible. When the gel fraction of the adhesive layer is 90% by mass or less, the adhesive layer becomes more stretchable, and the adhesive strength of the adhesive tape is further improved. In addition, the greater flexibility of the adhesive layer improves the adhesion of the adhesive tape to a rigid body, making it easier to firmly hold the conductive member to the connected member. The more preferred lower limit for the gel fraction of the adhesive layer is 30% by mass, and the more preferred upper limit is 70% by mass. Examples of the gel fraction of the adhesive layer include 10% by mass or more and 90% by mass or less, 30% by mass or more and 70% by mass or less, etc.

[0131] The preferred lower limit for the thickness of the adhesive layer is 20 μm, and the preferred upper limit is 100 μm. A thickness of 20 μm or more ensures that the adhesive tape has sufficient adhesive strength. A thickness of 100 μm or less ensures that the adhesive tape has superior heat resistance. A more preferred lower limit for the thickness of the adhesive layer is 25 μm, a more preferred upper limit is 90 μm, and an even more preferred lower limit is 35 μm. An even more preferred upper limit is 75 μm. Examples of suitable adhesive layer thicknesses include 20 μm to 100 μm, 25 μm to 90 μm, and 35 μm to 75 μm.

[0132] The above-mentioned adhesive tape may be a non-support type adhesive tape without a base material, or a support type adhesive tape in which the adhesive layer is formed on a base material. In particular, from the viewpoint of heat resistance, it is preferable that the adhesive tape has a base material. If the adhesive tape has a base material, it may be a single-sided adhesive tape with the adhesive layer on one side of the base material, or a double-sided adhesive tape with the adhesive layer on both sides.

[0133] Examples of the above-mentioned substrates include resin films such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, and polyimide, as well as nonwoven fabrics and foam substrates.

[0134] The preferred lower limit for the thickness of the above-mentioned substrate is 12 μm, and the preferred upper limit is 150 μm. When the thickness of the above-mentioned substrate is 12 μm or more, the adhesive tape has appropriate stiffness and is easy to handle. When the thickness of the above-mentioned substrate is 150 μm or less, the adhesive tape has better adhesion to rigid bodies, making it easier to firmly hold the conductive member to the connected member. A more preferred lower limit for the thickness of the above-mentioned substrate is 50 μm, a more preferred upper limit is 125 μm, an even more preferred lower limit is 75 μm, and an even more preferred upper limit is 100 μm. Examples of the thickness of the above-mentioned substrate include 12 μm to 150 μm, 50 μm to 125 μm, 75 μm to 100 μm, etc.

[0135] When the adhesive tape of this embodiment has a base material, the total thickness of the base material and the adhesive layer is preferably 50 μm at the lower limit and preferably 500 μm at the upper limit. By having the total thickness of the base material and the adhesive layer within the above range, deformation of the adhesive tape is suppressed and heat resistance at high temperatures is further improved. A more preferable lower limit for the total thickness of the base material and the adhesive layer is 100 μm, a more preferable upper limit is 300 μm, and an even more preferable lower limit is 150 μm. An even more preferable upper limit is 250 μm. Examples of the total thickness of the base material and the adhesive layer include 50 μm or more and 500 μm or less, 100 μm or more and 300 μm or less, 150 μm or more and 250 μm or less, etc. Furthermore, when the adhesive tape has two or more adhesive layers, "total thickness of the base material and the adhesive layer" means the sum of the thickness of the base material and the thickness of all the adhesive layers of the adhesive tape.

[0136] The above adhesive tape may also be an adhesive tape with a release sheet, which has a release sheet to protect the adhesive layer.

[0137] The base material used for the above-mentioned release sheet is not particularly limited, but examples include resin films such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, and polyimide, as well as release paper, nonwoven fabrics, foamed base materials, etc.

[0138] Preferably, the release sheet has a textured surface. By having a textured surface on the release sheet, when the textured surface of the release sheet is laminated onto the adhesive layer, the surface of the adhesive layer is formed into a textured shape that fits into the texture of the release sheet, making it easier for the adhesive layer to have grooves. In other words, in the adhesive tape, it is preferable that a release sheet with a textured surface on the adhesive layer side is laminated onto the surface of the adhesive layer, and that the surface of the adhesive layer is formed into a textured shape that fits into the texture of the release sheet.

[0139] Examples of decorative textures on the surface of the release sheet include embossing.

[0140] If the surface of the release sheet is not decorated with embossed or uneven surfaces, the preferred lower limit for the thickness of the release sheet is 20 μm. A thickness of 20 μm or more results in the adhesive tape having appropriate stiffness and excellent handling properties. A thickness of 300 μm or less results in the release sheet having superior peelability from the adhesive tape. A more preferred lower limit for the thickness of the release sheet is 30 μm, a more preferred upper limit is 200 μm, an even more preferred lower limit is 50 μm, and an even more preferred upper limit is 100 μm. If the surface of the release sheet is not decorated with embossed or uneven surfaces, examples of the thickness of the release sheet include 20 μm to 300 μm, 30 μm to 200 μm, 50 μm to 100 μm, etc.

[0141] When the surface of the release sheet is treated with a textured finish, the preferred lower limit of the thickness of the release sheet is 50 μm, and the preferred upper limit is 300 μm. When the thickness of the release sheet is 50 μm or more, the adhesive tape is formed with an uneven shape on the surface of the adhesive layer that fits into the unevenness of the release sheet, and the adhesive layer is more likely to have grooves. When the thickness of the release sheet is 300 μm or less, the release sheet has better peelability from the adhesive tape. When the surface of the release sheet is treated with a textured finish, the more preferred lower limit of the thickness of the release sheet is 75 μm, the more preferred upper limit is 200 μm, the still more preferred lower limit is 100 μm, and the still more preferred upper limit is 175 μm. If the surface of the release sheet described above is treated with an uneven decorative finish, the thickness of the release sheet can be, for example, 50 μm to 300 μm, 75 μm to 200 μm, 100 μm to 175 μm, etc.

[0142] The above adhesive tape may have other layers, as long as they do not impair the effects of the present invention.

[0143] The method for producing the above-mentioned adhesive tape is not particularly limited, and conventionally known methods can be used. For example, first, the above-mentioned alkyl (meth)acrylate, the above-mentioned olefin polymer having a polymerizable unsaturated double bond at its terminus, and optionally the above-mentioned monomer containing a polar functional group are copolymerized by a conventional method to obtain the above-mentioned acrylic copolymer. Next, a solution is prepared containing the obtained acrylic copolymer and, optionally, the above-mentioned tackifying resin, the above-mentioned silane coupling agent, the above-mentioned crosslinking agent, and other additives to form an adhesive composition. Then, the solution containing the adhesive composition is coated onto a release sheet and dried to form an adhesive layer, thereby producing an adhesive tape without a substrate. Alternatively, an adhesive tape with a substrate can be obtained by laminating the adhesive layer formed by the above method to a substrate.

[0144] The electrical connection member of this embodiment may have multiple adhesive tapes. By having multiple adhesive tapes in the electrical connection member of this embodiment, the conductive member can be fixed more firmly, so that the conductive member is less likely to peel off the adhesive tape even at high temperatures, and a more stable electrical connection can be made at both room temperature and high temperatures. Furthermore, the electrical connection member of this embodiment can be configured to have a connecting member described later, making it possible to create an electrical connection member that is easy to introduce between members to be connected.

[0145] The electrical connection member of this embodiment may have members other than the conductive member and the adhesive tape, as long as the effects of the present invention are not impaired.

[0146] Preferably, the electrical connection member of this embodiment further includes a connecting member for connecting the conductive member and the adhesive tape. The presence of the connecting member in the electrical connection member of this embodiment facilitates the introduction of the electrical connection member between the members to be connected. Furthermore, it facilitates the positioning of the conductive member, as it becomes easier to position the conductive member at a desired location within the electrical connection member.

[0147] Examples of the connecting members include resin sheets, rubber sheets, and metal sheets. Among these, resin sheets are preferred from the viewpoint of the connecting member having appropriate strength and superior interlayer strength with the adhesive tape. Examples of the resin sheets include polyethylene terephthalate (PET) sheets, polyethylene naphthalate (PEN) sheets, polycarbonate (PC) sheets, polyetheretherketone (PEEK) sheets, polyimide (PI) sheets, polyamide (PA) sheets, polyethylene (PE) sheets, polypropylene (PP) sheets, and polyurethane (PU) sheets. Among these, PET sheets and PI sheets are preferred from the viewpoint of superior resin sheet strength and heat resistance.

[0148] The preferred lower limit for the thickness of the above-mentioned connecting member is 30 μm, and the preferred upper limit is 1000 μm. Having the thickness of the connecting member within this range makes it easier to determine the position of the conductive member within the electrical connection member. Furthermore, it allows for sufficient pressure to be applied to the conductive member. A more preferred lower limit for the thickness of the above-mentioned connecting member is 50 μm, and a more preferred upper limit is 350 μm. Examples of the thickness of the above-mentioned connecting member include 30 μm to 1000 μm, 50 μm to 350 μm, etc.

[0149] An example of an electrical connection member having the above-described connecting member is shown in Figure 4. In Figure 4, the electrical connection member 33 has a connecting member 7 with a through hole sized for the conductive member 52 to pass through, and the conductive member 52 is fixed by being inserted into the interior of the connecting member 7, as the connecting member 6 is positioned to be embedded in the conductive member 3. The conductive member 52 is firmly fixed by laminating and integrating a frame-shaped adhesive tape 42 sized for the conductive member to pass through onto both sides of the connecting member 7.

[0150] The shape of the through-hole in the connecting member 7 may be adjusted to match the shape of the conductive member 52. Examples of such shapes include circles and polygons such as squares, but a circle is preferred.

[0151] The connecting member 7 may have through holes other than the one through which the conductive member 52 passes. Furthermore, having through holes improves the airflow between the inner and outer circumferences of the adhesive tape, making it easier to secure the electrical connection member to the connected member. In addition, it can further suppress problems such as peeling of the adhesive tape and poor conductivity of the conductive member caused by air expansion in the space surrounding the conductive member.

[0152] The electrical connection member of this embodiment can be manufactured by the following methods, etc. Specifically, it can be manufactured by, for example, inserting a separately molded conductive member into an adhesive tape having a through hole and integrating them. Alternatively, it can be manufactured using an insert molding method in which an adhesive tape having a through hole is inserted into a mold for molding conductive members to form the conductive member. Or, it can be manufactured by integrally forming a conductive member in the through-hole portion of a connecting member such as a resin film having a through hole, and then attaching adhesive tape to both sides of the surrounding connecting member.

[0153] The electrical connection member of this embodiment is not particularly limited in its use, but it is preferably used to electrically connect terminals made of metal plates or the like to a glass plate in order to install a defroster or defogger on an automobile window glass, or to electrically connect to electronic components such as antennas, sensors, LED lights, heaters, and batteries. The electrical connection member of this embodiment can make a stable electrical connection at both room temperature and high temperature, and therefore can make an electrical connection without problems even when a large current is flowing.

[0154] Furthermore, a structure in which a glass plate and a terminal made of a metal plate or the like are connected using the electrical connection member of this embodiment, and a structure in which electronic components such as an antenna, sensor, LED light, heater, battery and a circuit board are connected using the electrical connection member of this embodiment, are preferred embodiments of the structure of this embodiment.

[0155] The present invention provides an adhesive tape that achieves both excellent heat resistance and excellent adhesion to rigid bodies. Furthermore, the present invention provides an electrical connection member that can firmly hold a conductive member to a connection target member, maintain a state of firm holding of the conductive member to the connection target member even at high temperatures, and enable stable electrical connections at both room temperature and high temperatures. Moreover, the present invention provides a structure that enables stable electrical connections at both room temperature and high temperatures.

[0156] This is a schematic diagram showing the depth of the grooves in the adhesive layer. This is a schematic cross-sectional view showing an example of the structure of this embodiment 1. This is a schematic cross-sectional view showing an example in which a conductive member is held to a member to be connected using the electrical connection member of this embodiment 2. This is a schematic cross-sectional view showing an example of the electrical connection member of this embodiment having a connecting member. This is a top view of the electrical connection member used for evaluation. This is a schematic cross-sectional view of the measurement sample used for evaluation.

[0157] 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.

[0158] (Synthesis of Acrylic Copolymer A) A reactor equipped with a thermometer, stirrer, and condenser was prepared. 73.9 parts by mass of n-butyl acrylate, 20.0 parts by mass of ethylene-butylene macromonomer, 6.0 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and ethyl acetate as a solvent 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. After that, 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 then 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 ethylene-butylene macromonomer shown in Table 1 was HPVM-L1253 (manufactured by Kraton Polymer Japan). Furthermore, the molecular weight distribution in polystyrene equivalent was measured for the obtained acrylic copolymer using gel permeation chromatography (GPC) (Waters, "2690 Separations Module") under the following conditions. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of acrylic copolymer A were measured from the obtained molecular weight distribution curve, and the polydispersity (Mw / Mn) was calculated. <GPC Measurement Conditions> Solvent: Tetrahydrofuran Sample flow rate: 1 mL / min Detector: Differential refractometer RI Column: GPC KF-806L (manufactured by Showa Denko) Column temperature (measurement temperature): 40°C Injection volume: 20 μL

[0159] (Acrylic copolymers B-F, K-M) Except for using the constituent monomers shown in Table 1, the acrylic copolymers were synthesized in the same manner as acrylic copolymer A. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the acrylic copolymers were measured, and the polydispersity (Mw / Mn) was obtained. The results are shown in Table 1.

[0160] (Acrylic copolymers G to J) Except for adjusting the amount of ethyl acetate added as a solvent to adjust the concentration of reaction solids in the polymerization reaction, acrylic copolymers were synthesized in the same manner as acrylic copolymer A. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the acrylic copolymers were measured, and the polydispersity (Mw / Mn) was obtained. The results are shown in Table 1.

[0161]

[0162] (Example 1-1) (1) Preparation of adhesive tape An adhesive composition was obtained by adding each material to an ethyl acetate solution containing the obtained acrylic copolymer A in the composition shown in Table 2. The obtained adhesive composition was applied to the textured surface of a 150 μm thick release sheet (Lintec Corporation, "R-284") with a textured surface on one side, and dried at 110°C for 5 minutes to form an adhesive layer with a thickness of 50 μm. A 100 μm thick PET film (Toyo Cloth Co., Ltd.) used as the base material was then placed on top. Furthermore, an adhesive layer of the same composition and thickness was formed on the other side of the base material, and cured at 40°C for 48 hours to obtain a double-sided adhesive tape having a base material and grooves in the adhesive layers on both sides.

[0163] (2) Ratio of groove depth to adhesive layer thickness First, a sample was prepared by cutting the adhesive tape with a cutter so as to cross the groove in the adhesive layer with a plane parallel to the thickness direction of the adhesive tape. On one side of the prepared sample (the side on which the groove depth in the adhesive layer is measured), the groove depth was measured using an optical microscope (Keyence Corporation, "VHX-6000"), and this measurement was performed at five locations. The average value of the five measured groove depths was taken as the groove depth of the adhesive layer. Then, using the obtained groove depth of the adhesive layer and the thickness of the adhesive layer, the ratio of the groove depth to the thickness of the adhesive layer was calculated using the above formula (i). The results are shown in Table 2. Note that when preparing the sample, the release liner on the adhesive tape was not removed, and when measuring the groove depth, the release liner on the adhesive tape was not removed.

[0164] (3) Gel fraction of the adhesive layer The obtained adhesive tape was cut into a 50 mm x 100 mm rectangular shape to prepare a test specimen. The test specimen was immersed in tetrahydrofuran (THF) at 23°C for 24 hours, then removed from the tetrahydrofuran and dried at 110°C for 1 hour. The mass of the dried test specimen was measured, and the gel fraction was calculated using the following formula (ii). The results are shown in Table 2. Note that no release sheet to protect the adhesive layer was laminated on the test specimen. 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)

[0165] (Examples 1-2 to 1-31, Comparative Examples 1 to 2) Except for the types and contents of each material in the adhesive composition, the thickness of the adhesive layer, and the type and thickness of the substrate being as shown in Tables 2 to 5, adhesive tapes having grooves in the adhesive layers on both sides were manufactured in the same manner as in Example 1-1, and the ratio of groove depth in the adhesive layer and the gel fraction of the adhesive layer were obtained. The results are shown in Tables 2 to 5.

[0166] (Example 1-32) Following the same procedure as in Example 1-1, an adhesive composition having the composition shown in Table 4 was prepared. Two laminated films were then prepared by forming a 100 μm thick adhesive layer on a 150 μm thick release sheet (Lintec Corporation, "R-284") with a textured surface on one side. The two laminated films were then laminated so that the adhesive layers overlapped, and cured at 40°C for 48 hours to obtain a double-sided adhesive tape without a substrate and with grooves on both sides. For the measurement, as described in "(2) Ratio of groove depth to adhesive layer thickness" above, the obtained adhesive tape was considered as a tape with 100 μm thick adhesive layers on both sides, and the groove depth in the 100 μm thick adhesive layer was measured. The ratio of the groove depth to the 100 μm thick adhesive layer was then calculated. The gel fraction of the adhesive layer was measured in the same procedure as in Example 1-1. The results are shown in Table 4.

[0167] (Comparative Example 3) Except that the types and contents of each material in the adhesive composition were as shown in Table 5, the types and thicknesses of the substrate were as shown in Table 5, and instead of a 150 m thick release sheet with a textured surface (Lintec Corporation, "R-284") with a textured surface, a 50 μm thick polyethylene terephthalate (PET) film with a release treatment on one side and no textured surface was used as the release sheet protecting the adhesive layers on both sides, an adhesive tape without grooves in the adhesive layers on both sides was manufactured in the same manner as in Example 1-1, and the ratio of groove depth in the adhesive layer and the gel fraction of the adhesive layer were obtained. The results are shown in Table 5.

[0168] The PET films 1 to 3, which are the base materials shown in Tables 2 to 5, are all PET films of different thicknesses manufactured by Toyo Cloth Co., Ltd.

[0169] <Evaluation> The adhesive tapes obtained in Examples 1-1 to 1-32 and Comparative Examples 1 to 3 were evaluated as follows. The results are shown in Tables 2 to 5.

[0170] (Heat Resistance) Test specimens were prepared by cutting the obtained adhesive tape to a size of 10 mm wide x 20 mm long. A shear creep test was performed on the prepared test specimens using a creep tester (Asahi Seiko Co., Ltd., "Micro-shear creep measuring device") at 110°C, applying a load of 50 g in the shear direction for 3 hours. The heat resistance of the adhesive tape was evaluated based on the following criteria: "A" if the shear deformation of the test specimen at the end of the shear creep test was less than 3.0 μm, "B" if it was 3.0 μm or more and less than 5.0 μm, "C" if it was 5.0 μm or more and less than 7.0 μm, and "D" if it was 7.0 μm or more.

[0171] (Adhesion to Rigid Bodies) Test pieces were prepared by cutting the obtained adhesive tape to a size of 25 mm square. These test pieces were then attached to a 2.5 cm square, 1.5 cm thick metal plate (SUS (stainless steel) plate that had been cleaned with ethanol and then wiped dry). After peeling off the release sheet from the other side of the adhesive tape that had been pressed onto the metal plate, the tape was attached to a 1.5 cm thick tempered glass plate and pressed at 1.5 MPa for 10 seconds to create a measurement sample. The measurement sample was visually inspected from the glass side of the sample to check for the presence or absence of air bubbles at the adhesive interface between the adhesive tape and the SUS plate, and the adhesion of the adhesive tape to rigid bodies was evaluated according to the following criteria: ・A: No air bubbles were present at the adhesive interface. ・B: Air bubbles were present at the adhesive interface, but the proportion of the adhesive area occupied by the air bubbles was within 20%. ・C: Air bubbles were present at the adhesive interface, and the proportion of the adhesive area occupied by the air bubbles was greater than 20%.

[0172] (Peelability) Using a tensile testing machine (A&D Corporation, "RTI-1310"), the adhesive tape was peeled from the metal plate in the planar direction at 23°C and a tensile speed of 50 mm / min. The peel interface on the glass plate after peeling the adhesive tape was observed, and the peelability of the adhesive tape was evaluated according to the following criteria: ・A: No adhesive residue at the peel interface. ・B: There was adhesive residue at the peel interface, but the residue was within 10% of the peel area. ・C: There was adhesive residue at the peel interface, and the residue was greater than 10% of the peel area. Even if the evaluation is "C", the adhesive tape of this embodiment can be used without problems depending on the application.

[0173]

[0174]

[0175]

[0176]

[0177] (Example 2-1) (1) Preparation of adhesive tape An adhesive composition was obtained by adding each material to an ethyl acetate solution containing the obtained acrylic copolymer A in the composition shown in Table 6. The obtained adhesive composition was applied to the release surface of a 100 μm thick PET film having a release surface on one side, and dried at 110°C for 5 minutes to form an adhesive layer with a thickness of 50 μm on the release surface of the PET film. The adhesive layer was bonded to one side of a 100 μm thick PET film (manufactured by Toyo Cross Co., Ltd.) used as a substrate. Furthermore, an adhesive layer of the same composition and thickness was formed on the release surface of a PET film having a release surface of the same thickness, and after bonding it to the other side of the substrate, it was cured at 40°C for 48 hours to obtain a double-sided adhesive tape with a substrate.

[0178] (2) Gel fraction of the adhesive layer The obtained adhesive tape was cut into a 50 mm x 100 mm rectangular shape to prepare a test specimen. The test specimen was immersed in tetrahydrofuran (THF) at 23°C for 24 hours, then removed from the tetrahydrofuran and dried at 110°C for 1 hour. The mass of the dried test specimen was measured, and the gel fraction was calculated using the following formula (ii). The results are shown in Table 6. Note that no release PET film to protect the adhesive layer was laminated on the test specimen. 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)

[0179] (Examples 2-2 to 2-23, Comparative Examples 4 to 6) Adhesive tapes were manufactured in the same manner as in Example 2-1, except that the types and contents of each material in the adhesive composition, as well as the types and thicknesses of the substrates, were as shown in Tables 6 to 9, and the gel fraction of the adhesive layer was obtained. The results are shown in Tables 6 to 9. In Comparative Example 6, the SCT101 (manufactured by Fujikura Chemical Co., Ltd.) used is an acrylic copolymer that does not have constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends.

[0180] (Examples 2-24 to 2-26) (1) Preparation of adhesive tape An adhesive composition was obtained in the same manner as in Example 1, except that the types and contents of each material in the adhesive composition were as shown in Table 8. The obtained adhesive composition was applied to the textured surface of a 150 μm thick release sheet (Lintec Corporation, "R-284") with a textured surface on one side, and dried at 110°C for 5 minutes to form an adhesive layer of the thickness shown in Table 8. A 100 μm thick PET film (Toyo Cloth Co., Ltd.) used as the base material was then placed on top. Furthermore, an adhesive layer of the same composition and thickness was formed on the other side of the base material, and cured at 40°C for 48 hours to obtain a double-sided adhesive tape having a base material and grooves in the adhesive layers on both sides.

[0181] (2) Gel fraction of the adhesive layer The gel fraction of the adhesive layer was obtained in the same manner as in Example 2-1. The results are shown in Table 8.

[0182] (3) Ratio of groove depth to adhesive layer thickness First, a sample was prepared by cutting the adhesive tape with a cutter so as to cross the groove in the adhesive layer with a plane parallel to the thickness direction of the adhesive tape. On one side of the prepared sample (the side on which the groove depth in the adhesive layer is measured), the groove depth was measured using an optical microscope (Keyence Corporation, "VHX-6000"), and this measurement was performed at five locations. The average value of the five measured groove depths was taken as the groove depth of the adhesive layer. Then, using the obtained groove depth of the adhesive layer and the thickness of the adhesive layer, the ratio of the groove depth to the thickness of the adhesive layer was calculated using the above formula (i). The results are shown in Table 8. Note that when preparing the sample, the release liner on the adhesive tape was not removed, and when measuring the groove depth, the release liner on the adhesive tape was not removed.

[0183] (Example 2-27) Following the same procedure as in Example 2-1, an adhesive composition with the composition shown in Table 8 was prepared. Two laminated films were then prepared by forming a 100 μm thick adhesive layer on the release surface of a 100 μm thick PET film having a release surface on one side. The two prepared laminated films were then laminated so that the adhesive layers overlapped, and cured at 40°C for 48 hours to obtain a double-sided adhesive tape without a substrate and without grooves on both sides of the adhesive tape. The gel fraction of the adhesive layer was measured in the same procedure as in Example 2-1. The results are shown in Table 8.

[0184] (Example 2-28) Following the same procedure as in Examples 2-24 to 2-26, an adhesive composition with the composition shown in Table 8 was prepared. Two laminated films were then made by forming a 100 μm thick adhesive layer on a 150 μm thick release sheet (Lintec Corporation, "R-284") with a textured surface on one side. The two laminated films were then laminated so that the adhesive layers overlapped, and cured at 40°C for 48 hours to obtain a double-sided adhesive tape without a base material and with grooves on both sides. For the measurement, in "(3) Ratio of groove depth to adhesive layer thickness" in Examples 2-24 to 2-26 described above, the obtained adhesive tape was considered as a tape with 100 μm thick adhesive layers on both sides, and the groove depth in the 100 μm thick adhesive layer was measured to calculate the ratio of the groove depth to the 100 μm thick adhesive layer. The gel fraction of the adhesive layer was measured in the same manner as in Example 2-1. The results are shown in Table 8.

[0185] The PET films 1 to 3, which are the base materials shown in Tables 6 to 9, are all PET films of different thicknesses manufactured by Toyo Cloth Co., Ltd.

[0186] <Evaluation> The following evaluations were performed using the adhesive tapes obtained in Examples 2-1 to 2-28 and Comparative Examples 4 to 6. The results are shown in Tables 6 to 9.

[0187] (1) Preparation of measurement samples (1-1) Preparation of conductive members First, a mold with ferromagnetic pins embedded in it was prepared, and silicone rubber as a liquid rubber, which was compounded with silver-coated nickel particles with an average particle size of 35 μm as a conductive filler, was poured into the mold to form a conductive member having a conductive part made of a conductive rubber-like elastic body and an insulating part surrounding it. The obtained conductive member was circular with a diameter of 2.5 mm and a thickness of 700 μm. The conductive part of the conductive member was circular, and the conductive filler in the conductive part was arranged in a continuous line in the thickness direction, with a filling rate of conductive filler of 33 volume%. One molded conductive member and a PET sheet (thickness 100 μm) having one through hole with a diameter of 2.0 mm in the center of the sheet for inserting the conductive member were inserted into the mold, and a conductive member with a connecting member was obtained in which the conductive member was integrally molded inside the through hole of the PET sheet. The resulting conductive member with a connecting member had a structure in which the PET sheet, which served as the connecting member, was embedded in the insulating portion of the conductive member.

[0188] (1-2) Fabrication of electrical connection member A through hole measuring 4 mm in width and 4 mm in length was made in the obtained adhesive tape at a position overlapping with the conductive member, and then the tape was attached to both sides of the connecting member in the conductive member with the connecting member attached. The electrical connection member was then cut so that its outer dimensions were 14 mm in width and 14 mm in length, thereby obtaining an electrical connection member having a structure in which the conductive member penetrates the adhesive tape. A cross-sectional view of the fabricated electrical connection member is shown in Figure 4, and a top view of the fabricated electrical connection member is shown in Figure 5.

[0189] (1-3) Preparation of measurement sample A measurement sample was prepared by placing a glass plate on one side of the prepared electrical connection member and a copper plate on the other side, and then applying a force of 1.5 MPa from the copper plate side and pressing for 10 seconds, thereby sandwiching and bonding the electrical connection member between the glass plate and the copper plate. A cross-sectional view of the prepared measurement sample is shown in Figure 6.

[0190] (2) Surface peel strength at room temperature The measured samples obtained were subjected to a tensile testing machine (A&D Corporation, "RTI-1310") at 23°C and a tensile speed of 50 mm / min. The copper plate was pulled vertically (90° direction) to peel the adhesive tape from the connecting member (PET sheet), and the maximum stress at which peeling occurred was defined as the surface peel strength. If the obtained surface peel strength was 3.5 MPa or higher, it was classified as "A"; if it was 2.5 MPa or higher and less than 3.5 MPa, it was classified as "B"; if it was 1.5 MPa or higher and less than 2.5 MPa, it was classified as "C"; and if it was less than 1.5 MPa, it was classified as "D". The surface peel strength at room temperature was determined based on these criteria. The better the evaluation, the more firmly the conductive member is held to the connected member, and the more stable the electrical connection can be made at room temperature.

[0191] (3) Surface delamination strength at high temperatures The surface delamination strength was measured in the same manner as described in "(2) Surface delamination strength at room temperature" above, except that the measurement temperature for surface delamination strength was changed to 80°C. The surface delamination strength at high temperatures was judged as follows: "A" if the obtained surface delamination strength was 2.0 MPa or higher, "B" if it was 1.5 MPa or higher and less than 2.0 MPa, "C" if it was 0.75 MPa or higher and less than 1.5 MPa, and "D" if it was less than 0.75 MPa. The better the evaluation, the more firmly the conductive member is held to the connected member even at high temperatures, and the more stable the electrical connection can be made even at high temperatures.

[0192] From the results of "(2) Surface peel strength at room temperature" and "(3) Surface peel strength at high temperature" described above, it was found that the electrical connection members using adhesive tapes in Examples 2-1 to 2-28 can provide stable electrical connections at both room temperature and high temperature.

[0193] (Adhesion of adhesive tape to rigid body) Test pieces were prepared by cutting the obtained adhesive tape to a size of 25 mm square. These test pieces were attached to a 2.5 cm square, 1.5 cm thick metal plate (SUS (stainless steel) plate that had been washed with ethanol and then wiped dry). After peeling off the release sheet from the other side of the adhesive tape that had been pressed onto the metal plate, the tape was attached to a 1.5 cm thick tempered glass and pressed at 1.5 MPa for 10 seconds to create a measurement sample. The measurement sample was visually observed from the glass side of the measurement sample to check for the presence or absence of air bubbles at the adhesive interface between the adhesive tape and the SUS plate, and the adhesion of the adhesive tape to a rigid body was evaluated according to the following criteria: ・A: No air bubbles were present at the adhesive interface. ・B: Air bubbles were present at the adhesive interface, but the proportion of the adhesive area occupied by the air bubbles was within 20%. ・C: Air bubbles were present at the adhesive interface, and the proportion of the adhesive area occupied by the air bubbles was greater than 20%. Even if the evaluation is "×", the electrical connection member of this second embodiment can be used without any practical problems.

[0194]

[0195]

[0196]

[0197]

[0198] The present invention provides an adhesive tape that achieves both excellent heat resistance and excellent adhesion to rigid bodies. Furthermore, the present invention provides an electrical connection member that can firmly hold a conductive member to a connection target member, maintain a state of firm holding of the conductive member to the connection target member even at high temperatures, and enable stable electrical connections at both room temperature and high temperatures. Moreover, the present invention provides a structure that enables stable electrical connections at both room temperature and high temperatures.

[0199] 1. Adhesive layer 2. Structure 31, 32, 33. Electrical connection members 41, 42. Adhesive tape 51, 52. Conductive members 61, 62, 63, 64. Members to be connected 7. Connecting member 8. Copper plate 9. Glass plate

Claims

An adhesive tape having an adhesive layer formed using an adhesive composition, The adhesive composition comprises an acrylic copolymer. The acrylic copolymer comprises structural units derived from alkyl (meth)acrylate esters and structural units derived from olefin polymers having polymerizable unsaturated double bonds at their terminal ends. The adhesive layer has grooves on at least one surface. An adhesive tape characterized by the following features. The adhesive tape according to claim 1, wherein the groove is a bubble removal groove for removing air bubbles. The adhesive tape according to claim 1 or 2, wherein the depth of the groove is 15% or more and 80% or less relative to the thickness of the adhesive layer. The constituent unit derived from the alkyl (meth)acrylate includes a constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms. The content of the constituent units derived from the alkyl (meth)acrylate ester, which have an alkyl group having 1 to 4 carbon atoms, is 50% by mass or more and 100% by mass or less. The adhesive tape according to claim 1, 2, or 3. The constituent unit derived from the (meth)acrylate alkyl ester includes a constituent unit derived from the (meth)acrylate alkyl ester having an alkyl group having 1 or more carbon atoms and 2 or less carbon atoms. The content of the constituent units derived from the alkyl (meth)acrylate ester, which have an alkyl group having 1 to 2 carbon atoms, is 10% by mass or more and 80% by mass or less. The adhesive tape according to claim 1, 2, 3, or 4. The adhesive tape according to claim 1, 2, 3, 4, or 5, wherein the content of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal in the acrylic copolymer is 10% by mass or more and 30% by mass or less. The acrylic copolymer has constituent units derived from a monomer containing a polar functional group, The total content of constituent units derived from the polar functional group-containing monomer in the acrylic copolymer is 3.0% by mass or more and 15% by mass or less. The adhesive tape according to claim 1, 2, 3, 4, 5, or 6. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the acrylic copolymer has a weight-average molecular weight of 750,000 or more and 1,500,000 or less. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, or 8, wherein the adhesive composition contains at least one selected from the group consisting of a tackifying resin and a silane coupling agent. The adhesive composition contains the tackifying resin, The content of the tackifying resin relative to 100 parts by mass of the acrylic copolymer is 5.0 parts by mass or more and 40 parts by mass or less. The adhesive tape according to claim 9. The adhesive composition contains the silane coupling agent, The content of the silane coupling agent per 100 parts by mass of the acrylic copolymer is 0.1 parts by mass or more and 3.0 parts by mass or less. The adhesive tape according to claim 9 or 10. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the gel fraction of the adhesive layer is 10% by mass or more and 90% by mass or less. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the thickness of the adhesive layer is 20 μm or more and 100 μm or less. An adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, having a base material. The adhesive tape according to claim 14, wherein the total thickness of the adhesive layer and the substrate is 50 μm or more and 500 μm or less. A release sheet, which has a textured surface on the adhesive layer side, is laminated on the surface of the adhesive layer, and the surface of the adhesive layer is formed with a textured shape that fits into the texture of the release sheet. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, used for fixing electronic equipment components or in-vehicle components. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, used in electrical connection members. An electrical connection member having a conductive member and an adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. A structure in which a conductive member is held to a member to be connected by an adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. An electrical connection member having a conductive member and an adhesive tape, The aforementioned adhesive tape has an adhesive layer formed using an adhesive composition, The adhesive composition comprises an acrylic copolymer. The acrylic copolymer comprises structural units derived from alkyl (meth)acrylate esters and structural units derived from olefin polymers having polymerizable unsaturated double bonds at their terminal ends. An electrical connection member characterized by the following features. The electrical connection member according to claim 21, wherein the electrical connection member has a structure in which the adhesive tape holds the conductive member to the member to be connected. The electrical connection member according to claim 21 or 22, wherein the electrical connection member has a structure in which the conductive member penetrates the adhesive tape. The constituent unit derived from the alkyl (meth)acrylate includes a constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms. The electrical connection member according to claim 21, 22, or 23, wherein the content of a constituent unit derived from the alkyl (meth)acrylate ester having an alkyl group having 1 to 4 carbon atoms in the constituent unit derived from the alkyl (meth)acrylate ester is 50% by mass or more and 100% by mass or less. The constituent unit derived from the (meth)acrylate alkyl ester includes a constituent unit derived from the (meth)acrylate alkyl ester having an alkyl group having 1 or more carbon atoms and 2 or less carbon atoms. The content of the constituent units derived from the alkyl (meth)acrylate ester, which have an alkyl group having 1 to 2 carbon atoms, is 10% by mass or more and 80% by mass or less. The electrical connection member according to claim 21, 22, 23, or 24. The electrical connection member according to claim 21, 22, 23, 24, or 25, wherein the content of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal in the acrylic copolymer is 10% by mass or more and 30% by mass or less. The acrylic copolymer has constituent units derived from a monomer containing a polar functional group, The total content of constituent units derived from the polar functional group-containing monomer in the acrylic copolymer is 3.0% by mass or more and 15% by mass or less. The electrical connection member according to claim 21, 22, 23, 24, 25, or 26. The acrylic copolymer has a weight-average molecular weight of 750,000 or more and 1,500,000 or less, as described in claim 21, 22, 23, 24, 25, 26, or 27, which is the electrical connection member. The electrical connection member according to claim 21, 22, 23, 24, 25, 26, 27, or 28, wherein the adhesive composition contains at least one selected from the group consisting of a tackifying resin and a silane coupling agent. The adhesive composition contains the tackifying resin, The content of the tackifying resin relative to 100 parts by mass of the acrylic copolymer is 5.0 parts by mass or more and 40 parts by mass or less. The electrical connection member according to claim 29. The adhesive composition contains the silane coupling agent, The content of the silane coupling agent per 100 parts by mass of the acrylic copolymer is 0.1 parts by mass or more and 3.0 parts by mass or less. The electrical connection member according to claim 29 or 30. The electrical connection member according to claim 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or 31, wherein the adhesive layer has grooves. The electrical connection member according to claim 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32, wherein the gel fraction of the adhesive layer is 10% by mass or more and 90% by mass or less. The electrical connection member according to claim 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, or 33, wherein the thickness of the adhesive layer is 20 μm or more and 100 μm or less. The electrical connection member according to claim 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, or 34, wherein the adhesive tape has a base material. The electrical connection member according to claim 35, wherein the total thickness of the adhesive layer and the substrate is 50 μm or more and 500 μm or less. Furthermore, the electrical connection member according to claim 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, further comprising a connecting member for connecting the conductive member and the adhesive tape. Including electrical connection members and members to be connected, The electrical connection member comprises a conductive member and an adhesive tape. The aforementioned adhesive tape has an adhesive layer formed using an adhesive composition, The adhesive composition comprises an acrylic copolymer. The acrylic copolymer comprises structural units derived from alkyl (meth)acrylate esters and structural units derived from olefin polymers having polymerizable unsaturated double bonds at their terminal ends. A structure characterized by the following features.

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