Adhesive tapes, laminates, and electronic devices

Abstract

The purpose of the present invention is to provide an adhesive tape which is capable of exhibiting excellent adhesive force to a silicone-based adherend. An adhesive tape according to the present invention has an adhesive layer that contains a (meth)acrylic copolymer. A laminate which is obtained by bonding the adhesive tape to a silicone rubber that is affixed to an SUS304 plate is left to stand for 72 hours in an environment at 25°C and 50% RH, and is subsequently subjected to a peel test in which the adhesive tape in the laminate is peeled at 180° from the silicone rubber under conditions of 23°C, 50% RH, and a peeling rate of 300 mm / min using a tensile tester. If the surface, from which the adhesive tape has been separated, of the silicone rubber after the peel test is cleaned at least eight times with ethyl acetate and is subsequently subjected to TOF-SIMS measurement, the peak intensity (26 / total) of negative ions in a region where m / z is 26 with respect to the peak intensity (total) of all negative ions is 2.50 × 10-3 or more.

Description

[Technical Field]

[0001] This disclosure relates to adhesive tapes. Furthermore, this disclosure relates to laminates having a structure to which such adhesive tapes are attached, and to electronic devices including such adhesive tapes. [Background technology]

[0002] Adhesive tapes are widely used in a variety of fields, for example, for assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), or for fixing in-vehicle electronic device components such as in-vehicle panels to the vehicle body (for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-242541 [Patent Document 2] Japanese Patent Publication No. 2009-258274 [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, in response to the trend of PFAS (perfluoroalkyl and polyfluoroalkyl compounds) regulations, there has been a movement to reduce the use of fluororesins in the assembly and fixing of electronic devices. Silicone materials are cited as an alternative to fluorine-based materials, which are characterized by their low surface energy. When using adhesive tapes with adhesive layers of urethane-based adhesives, acrylic-based adhesives, or hydrocarbon-based adhesives, which have relatively high surface energy, the interfacial adhesion is insufficient when bonding silicone materials. Therefore, adhesive tapes with silicone-based adhesives as the adhesive layer have typically been used when bonding silicone materials.

[0005] However, in adhesive tapes using a silicone-based adhesive as the adhesive layer, it is currently necessary to use a separator that has a release layer containing fluororesin to facilitate peeling from the silicone-based adhesive, in order to protect the adhesive layer.

[0006] On the other hand, when using adhesive tapes with adhesives other than silicone-based adhesives as the adhesive layer to bond silicone materials, it is necessary to perform surface treatments such as corona treatment and primer treatment on the surface of the silicone material to be bonded. This presents challenges in terms of reduced work efficiency and the need for additional equipment. Based on the above, there was a challenge in designing an adhesive tape that does not contain fluororesin and can firmly bond silicone materials without prior surface treatment.

[0007] This disclosure aims to provide an adhesive tape that can exhibit excellent adhesion to silicone-based substrates without the use of silicone-based adhesives or prior surface treatment of the substrate. Furthermore, this disclosure aims to provide a laminate having a structure to which the adhesive tape is attached. Moreover, this disclosure aims to provide an electronic device including the adhesive tape. [Means for solving the problem]

[0008] Disclosure 1 relates to an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer. The adhesive tape is bonded to a silicone rubber fixed to a SUS304 plate. After standing the laminate at 23°C and 50%RH for 72 hours, a peel test is performed using a tensile testing machine to peel the adhesive tape from the silicone rubber at a 180° angle under the conditions of 23°C, 50%RH, and a peel speed of 300 mm / min. After the peel test, the surface of the silicone rubber on the side from which the adhesive tape was peeled is washed at least 8 times with ethyl acetate. TOF-SIMS measurement is then performed on the washed surface, and the peak intensity of negative ions in the region of m / z 26 (26 / total) relative to the total peak intensity of all negative ions (total) is 2.50 × 10⁻⁶. -3That's all for this adhesive tape. Disclosure 2 relates to an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer, wherein the adhesive layer contains component A, which comprises at least one selected from a silane coupling agent having an aliphatic amino group, a silane coupling agent having a skeleton with a protected aliphatic amino group, a compound having a structure derived from a silane coupling agent having an aliphatic amino group, and a compound having a structure derived from a silane coupling agent having a skeleton with a protected aliphatic amino group, and the content of component A per 100 parts by mass of the (meth)acrylic copolymer is 8.0 parts by mass or less. Disclosure 3 is an adhesive tape according to Disclosure 2, wherein the content of component A per 100 parts by mass of the (meth)acrylic copolymer is 1.5 parts by mass or more. Disclosure 4 is an adhesive tape of Disclosure 3 wherein the content of component A per 100 parts by mass of the (meth)acrylic copolymer is greater than 3.0 parts by mass. Disclosure 5 is an adhesive tape according to Disclosure 2, 3, or 4, wherein at least one of the aliphatic amino groups in component A is a primary aliphatic amino group or a secondary aliphatic amino group with an acyclic structure. Disclosure 6 is an adhesive tape according to Disclosure 1, 2, 3, 4, or 5, wherein the (meth)acrylic copolymer has structural units derived from an alkyl (meth)acrylate, and the structural units derived from the alkyl (meth)acrylate do not have structural units derived from an alkyl (meth)acrylate with 2 or fewer carbon atoms in the alkyl group at the ester terminus, or the structural units derived from the alkyl (meth)acrylate have structural units derived from an alkyl (meth)acrylate with 2 or fewer carbon atoms in the alkyl group at the ester terminus, and the content of structural units derived from the alkyl (meth)acrylate with 2 or fewer carbon atoms in the alkyl group at the ester terminus in the structural units derived from the alkyl (meth)acrylate is 25% by mass or less. Disclosure 7 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, or 6, which has a constituent unit derived from the alkyl (meth)acrylate, and a constituent unit derived from the alkyl (meth)acrylate having 7 carbon atoms in the alkyl group at the ester terminus. Disclosure 8 is an adhesive tape of 1, 2, 3, 4, 5, 6, or 7 in which the (meth)acrylic copolymer does not have constituent units derived from a carboxyl group-containing monomer. Disclosure 9 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet irradiation. Disclosure 10 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the adhesive layer contains a radical generator. Disclosure 11 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the adhesive layer has a gel fraction of 35% by mass or more. Disclosure 12 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet irradiation, and the gel fraction of the adhesive layer is 35% by mass or more. Disclosure 13 further comprises an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, wherein the release layer of the separator does not contain an organofluorine compound. Disclosure 14 further relates to an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the relative intensity of the peak at 103.9 eV is 0.170 or less when the surface of the peel interface between the separator and the adhesive layer is measured by XPS after peeling the separator 180° from the adhesive layer in an environment of 23°C and 50% RH. Disclosure 15 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 used for bonding silicone-based substrates. Disclosure 16 is an adhesive tape of Disclosure 15 in which the silicone-based adherend is an electronic device component, a vehicle component, a building component, or a medical component. Disclosure 17 is a laminate that includes a structure in which the adhesive tapes of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 are attached to a silicone-based substrate. Disclosure 18 is an electronic device that includes the adhesive tapes of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. Disclosure 19 relates to an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer and a separator, wherein the relative intensity of the peak at 103.9 eV is 0.170 or less when the surface of the peel interface between the separator and the adhesive layer is measured by XPS after peeling the separator 180° from the adhesive layer in an environment of 23°C and 50% RH. The details of this disclosure are described below.

[0009] The present inventors investigated the mass-to-charge ratio of the surface of a silicone-based adherend after peeling off an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer. As a result, they found that by satisfying a specific value for such a mass-to-charge ratio, it is possible to obtain an adhesive tape that exhibits excellent adhesion to a silicone-based adherend without using a silicone-based adhesive or performing any prior surface treatment of the adherend, thus completing this disclosure.

[0010] For the laminate obtained by laminating the adhesive tape of the present disclosure on silicone rubber fixed to a SUS304 plate, after leaving it standing in an environment of 23°C and 50% RH for 72 hours, using a tensile tester, under the conditions of 23°C, 50% RH, and a peeling rate of 300 mm / min, a peeling test is performed to peel the adhesive tape in the laminate from the silicone rubber at 180°. Regarding the surface of the silicone rubber on the side from which the adhesive tape has been peeled after the peeling test, after washing the surface with ethyl acetate at least 8 times, for the washed surface, the peak intensity of negative ions (26 / total) in the region of m / z = 26 with respect to the total peak intensity of all negative ions (total) when TOF-SIMS measurement is performed (hereinafter, may also be simply referred to as "relative intensity of the peak of negative ions in the region of m / z = 26 after peeling the adhesive tape"). The lower limit is 2.50×10 -3 is. By the relative intensity of the peak of negative ions in the region of m / z = 26 after peeling the adhesive tape being 2.50×10 -3 or more, the adhesive tape of the present disclosure can exhibit excellent adhesive strength to a silicone-based adherend without using a silicone-based adhesive and without performing pretreatment on the surface of the adherend in advance. The preferable lower limit of the relative intensity of the peak of negative ions in the region of m / z = 26 after peeling the adhesive tape is 2.60×10 -3 , and the more preferable lower limit is 2.70×10 -3 . Also, the preferable upper limit of the relative intensity of the peak of negative ions in the region of m / z = 26 after peeling the adhesive tape is 4.00×10 -2 . By the relative intensity of the peak of negative ions in the region of m / z = 26 after peeling the adhesive tape being 4.00×10 -2 or less, it becomes an adhesive force that can avoid cohesive failure where the adhesive remains on the adherend, and the bulk strength generally required for the adhesive tape can be ensured. The more preferable upper limit of the relative intensity of the peak of negative ions in the region of m / z = 26 after peeling the adhesive tape is 3.50×10 -2 , and the further preferable upper limit is 3.00×10 -2 . In this specification, "the negative ion peak in the m / z region of 26" refers to the peak detected in the m / z range of 25.986 to 26.050.

[0011] Furthermore, the relative intensity of the negative ion peak in the m / z 26 region after peeling off the adhesive tape can be measured by the following method. Specifically, first, the surface of a 50mm x 125mm SUS304 plate was cleaned with ethanol and then wiped dry. A film adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767"), which has a silicone-based adhesive layer on one side and a non-silicone-based adhesive layer on the other side, was cut to a size of 30mm in width and 70mm in length. After peeling off the separator on the side with the non-silicone-based adhesive layer, this adhesive layer was attached to the SUS304 plate. Furthermore, the separator on the silicone-based adhesive layer side was peeled off, exposing the silicone-based adhesive layer. A 1mm thick silicone rubber (manufactured by Togawa Rubber Co., Ltd., "K-125(50)") cut to a size of 30mm in width and 70mm in length was attached to the silicone-based adhesive layer to create a silicone-based adherend. The adhesive tape of the present disclosure was cut into a size of 25 mm in width and 70 mm in length. The separator on one surface of the cut adhesive tape was peeled off, and one surface of the adhesive tape was lined with the corona-treated surface of a polyethylene terephthalate (PET) film having a thickness of 23 μm. The separator on the other surface of the lined adhesive tape was peeled off, and after being bonded to the silicone rubber surface of the above silicone-based adherend, a 2 kg roller was reciprocated once at a speed of 300 mm / min for pressure bonding, and left standing for 72 hours in an atmosphere of 23°C and 50% RH to produce a laminate. Regarding the produced laminate, in accordance with JIS Z0237, using a tensile tester (manufactured by Shimadzu Corporation, "AG-IS"), under the conditions of 23°C, a tensile speed of 300 mm / min, and a peeling angle of 180°, a peeling test was performed to peel the adhesive tape from the above silicone-based adherend. Then, regarding the silicone rubber in the above silicone-based adherend after the peeling test, the surface on the side where the adhesive tape was peeled was washed with ethyl acetate at least 8 times, and then TOF-SIMS measurement was performed on the washed surface, and by analyzing the obtained spectral data, the peak intensity of negative ions (26 / total) in the region where m / z is 26 was obtained with respect to the peak intensity (total) of all negative ions.

[0012] The washing operation with ethyl acetate and the TOF-SIMS measurement can be specifically performed by the following methods and the like. Note that during the following operations, take care not to contaminate the silicone rubber surface from which the adhesive tape has been peeled. Also, when peeling the adhesive tape from the silicone-based adherend in the peeling test using a tensile tester, the area where the adhesive and the silicone-based adherend are visually interface-peeled is set as the target area for TOF-SIMS measurement. In the case where the adhesive layer has cohesive failure over the entire peeling surface of the adhesive tape, expose the cohesive failure area to liquid nitrogen to cool and solidify it, and the cohesive failure adhesive layer can be removed with metal tweezers or a spatula. Repeat the above removal operation until the silicone rubber surface of the silicone-based adherend is visually exposed, and set it as the target area for TOF-SIMS measurement.

[0013] (Washing operation) First, peel off a film adhesive tape having a silicone-based adhesive layer from silicone rubber. The peeling method is not limited, but it is adjusted so that the speed is approximately 300 mm / min and the peeling angle is approximately 90°, and it can be peeled off by hand. After peeling off the film adhesive tape having a silicone-based adhesive layer from the above silicone rubber, a measurement sample is prepared by cutting out the obtained silicone rubber into a square of about 1 cm using a cutter or scissors. After placing the surface of the measurement sample that was in contact with the adhesive tape of the present disclosure on the ethyl acetate liquid surface of an aluminum cup with an inner diameter of 5 cm into which 2 mL of ethyl acetate has been poured, it is washed with ethyl acetate by shaking back and forth 80 times at an interval of 1 cm per minute (i). At that time, it can be shaken by piercing the back surface of a portion not related to the measurement with a needle or the like, or by using tweezers. Also, when it is difficult to operate because the sample to be washed touches the bottom of the aluminum cup during shaking, ethyl acetate may be added. Prepare another aluminum cup with an inner diameter of 5 cm into which 2 mL of ethyl acetate has been poured, perform the same washing again, and then heat the measurement sample in an atmospheric pressure oven at 80 °C for 10 minutes (ii). The operations of (i) and (ii) above are regarded as one set, and a total of 4 sets or more are performed. Note that new aluminum cups and ethyl acetate are used each time the operations of (i) and (ii) are performed.

[0014] (TOF-SIMS measurement) TOF-SIMS measurement can be performed using a time-of-flight secondary ion mass spectrometer (manufactured by ION-TOF, such as "TOF.SIMS5"), and the measurement can be performed under the following conditions. From the obtained secondary ion spectrum, a value obtained by dividing the total sum (area) of the negative ion peaks in the region where m / z is 26 by the total sum (area) of all the negative ion peaks is calculated. <Measurement conditions for TOF-SIMS measurement> · Primary ion species: Bi3+ + · Acceleration voltage: 25 kV · Detected ion polarity: negative (negative ion) · Measurement range: 500 μm × 500 μm · Number of pixels: 128 × 128 (pixels) · Number of scans: 25 scan ·Mass range (m / z): 0~850

[0015] The negative ion peak in the m / z 26 region is mainly CN ― This is a peak containing the mass of [the substance]. Therefore, methods for adjusting the relative intensity of the negative ion peak in the m / z region of 26 after peeling off the adhesive tape include, for example, adding component A (described later) to the adhesive layer, changing the amount or structure of component A, adding an amine-modified silicone compound, or changing the composition of the (meth)acrylic copolymer in the adhesive layer.

[0016] The adhesive tape of this disclosure has an adhesive layer containing an acrylic copolymer. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0017] The above (meth)acrylic copolymer preferably has a constituent unit derived from an alkyl (meth)acrylate ester (hereinafter sometimes simply referred to as "constituent unit (a)"). Examples of the alkyl (meth)acrylate esters mentioned above include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, isoheptyl (meth)acrylate, and 2- Examples include ethylhexyl, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, isobolonyl (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, and behenyl (meth)acrylate. In particular, from the viewpoint of improving wettability to silicone-based substrates with low surface energy, constituent units derived from alkyl (meth)acrylate esters with 3 or more carbon atoms in the alkyl group at the ester terminal are preferred. From the viewpoint of avoiding a decrease in cohesive force that leads to a decrease in adhesive strength and the occurrence of crystalline interactions, constituent units derived from alkyl (meth)acrylate esters with 22 or fewer carbon atoms in the alkyl group at the ester terminal are preferred. A more preferred lower limit for the number of carbon atoms in the alkyl group at the ester terminal is 4, a more preferred upper limit is 18, an even more preferred upper limit is 16, an even more preferred upper limit is 12, a particularly preferred upper limit is 10, and the most preferred upper limit is 8. Among these, from the viewpoint of easily ensuring a balance between adhesive strength and cohesive force to silicone substrates, the above (meth)acrylic copolymer preferably has constituent units derived from alkyl (meth)acrylate esters with 7 carbon atoms in the alkyl group at the ester terminal. These alkyl (meth)acrylates may be used individually or in combination of two or more. Furthermore, in this specification, "ester-terminated alkyl group" refers to an alkyl group that is directly bonded to the oxygen atom of the ester bond.

[0018] The above-mentioned structural unit (a) does not have a structural unit derived from an alkyl (meth)acrylate ester with 2 or fewer carbon atoms in the alkyl group at the ester terminus (hereinafter sometimes simply referred to as "structural unit (a-1)"), or the above-mentioned structural unit (a) has the above-mentioned structural unit (a) and the content ratio of the above-mentioned structural unit (a) in the above-mentioned structural unit (a) is preferably 25% by mass or less. The adhesion strength of the adhesive tape of this disclosure to the silicone-based adherend is further improved by the above-mentioned structural unit (a) not having the above-mentioned structural unit (a), or by the above-mentioned structural unit (a) having the above-mentioned structural unit (a) and the content ratio of the above-mentioned structural unit (a) in the above-mentioned structural unit (a) being 25% by mass or less. A more preferable upper limit for the content of the above-mentioned constituent unit (a-1) in 100% by mass of the above-mentioned constituent unit (a) is 20% by mass, an even more preferable upper limit is 15% by mass, and an even more preferable upper limit is 10% by mass, and it is most preferable that the above-mentioned constituent unit (a) does not contain the above-mentioned constituent unit (a-1).

[0019] The preferred lower limit of the content of the above-mentioned constituent unit (a) in the above-mentioned (meth)acrylic copolymer is 50% by mass. By having a content of 50% by mass or more of the above-mentioned constituent unit (a), the adhesive strength of the adhesive tape of this disclosure to the silicone-based adherend is further improved. Furthermore, the content of the above-mentioned structural unit (a) may be 100% by mass, that is, the above-mentioned (meth)acrylic copolymer may consist only of the above-mentioned structural unit (a). However, from the viewpoint of preferring to include structural units derived from polar group-containing monomers described later in order to improve adhesiveness and retention, the preferred upper limit is 99.9% by mass.

[0020] The (meth)acrylic copolymer described above may have at least one constituent unit selected from the group consisting of constituent units derived from hydroxyl group-containing monomers, constituent units derived from amino group-containing monomers, constituent units derived from amide group-containing monomers (excluding N,N-disubstituted amide skeletons), constituent units derived from alkenyl group-containing monomers, and constituent units derived from alkynyl group-containing monomers (hereinafter, these constituent units may simply be referred to as "constituent unit (b)"), to the extent that it does not impair the effects of the present disclosure. The (meth)acrylic copolymer having the above constituent unit (b) increases the polarity of the adhesive layer and further increases the cohesive force, thereby improving the adhesive strength and high-temperature retention strength. Furthermore, if a crosslinked structure is formed by chemically crosslinking the functional groups such as hydroxyl groups, amino groups, amide groups, alkenyl groups, and alkynyl groups, the cohesive force of the adhesive layer is further increased, further improving the adhesive strength and retention strength. In particular, from the viewpoint of avoiding reactions with silane coupling agents having aliphatic amino groups or silane coupling agents having a skeleton with protected aliphatic amino groups, and ensuring the coatability of the adhesive solution and the stability of the adhesive layer's performance over time, it is preferable that the (meth)acrylic copolymer has constituent units derived from hydroxyl group-containing monomers, amino group-containing monomers, and amide group-containing monomers (excluding N,N-disubstituted amide skeletons).

[0021] Examples of the hydroxyl group-containing monomers mentioned above include 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the above-mentioned amino group-containing monomers include 2-dimethylaminoethyl (meth)acrylate and N-{3-(dimethylamino)propyl}acrylamide. Examples of the above amide group-containing monomers (excluding the N,N-disubstituted amide skeleton) include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, N-heptyl(meth)acrylamide, N-octyl(meth)acrylamide, and N-(2-ethylhexyl)(meth)acrylamide.

[0022] When the above (meth)acrylic copolymer contains the above constituent unit (b), the preferred upper limit of the total content of the above constituent unit (b) in the above (meth)acrylic copolymer is 20% by mass. By having a total content of the above constituent unit (b) of 20% by mass or less, the polarity of the adhesive layer is further reduced, which lowers the surface energy of the adhesive layer and further improves the adhesion to silicone-based substrates. In addition, reactions with silane coupling agents having aliphatic amino groups or silane coupling agents having a skeleton with protected aliphatic amino groups are minimized, ensuring the coatability of the adhesive solution and the stability of the adhesive layer's performance over time. A more preferred upper limit of the total content of the above constituent unit (b) is 15% by mass, an even more preferred upper limit is 10% by mass, an even more preferred upper limit is 5.0% by mass, and a particularly preferred upper limit is 1.0% by mass. Furthermore, the lower limit of the total content of the constituent unit (b) in the (meth)acrylic copolymer is not particularly limited and may be 0% by mass or greater than 0% by mass. If the lower limit of the total content of the constituent unit (b) is greater than 0% by mass, it is, for example, 0.1% by mass. In addition, the total content of the above-mentioned constituent unit (b) in the above-mentioned (meth)acrylic copolymer can be specifically included in the following ranges: 0% by mass or more and 20% by mass or less, 0% by mass or more and 15% by mass or less, 0% by mass or more and 10% by mass or less, 0% by mass or more and 5.0% by mass or less, 0% by mass or more and 1.0% by mass or less, 0.1% by mass or more and 20% by mass or less, 0.1% by mass or more and 15% by mass or less, 0.1% by mass or more and 10% by mass or less, 0.1% by mass or more and 5.0% by mass or less, 0.1% by mass or more and 1.0% by mass or less.

[0023] The (meth)acrylic copolymer described above may have structural units derived from carboxyl group-containing monomers, to the extent that it does not impair the effects of the present disclosure. The presence of structural units derived from carboxyl group-containing monomers in the (meth)acrylic copolymer increases the polarity of the adhesive layer, thereby increasing its cohesive force, improving both its adhesiveness and its high-temperature retention. Furthermore, if a crosslinked structure is formed by chemically crosslinking the functional groups, the cohesive force of the adhesive increases further, resulting in even greater improvements in adhesiveness and retention.

[0024] Examples of the above-mentioned carboxyl group-containing monomers include (meth)acrylic acid and 2-acryloyloxyethyl succinate.

[0025] When the (meth)acrylic copolymer contains structural units derived from the carboxyl group-containing monomer, it is preferable that the content of structural units derived from the carboxyl group-containing monomer in the (meth)acrylic copolymer is less than 1.0% by mass. By having a content of structural units derived from the carboxyl group-containing monomer of less than 1.0% by mass, reactions with silane coupling agents having aliphatic amino groups or silane coupling agents having a skeleton with protected aliphatic amino groups are minimized, ensuring the coatability of the adhesive solution and the stability of the adhesive layer's performance over time. When the acrylic acid content was 1.0% by mass, a rapid increase in viscosity was observed when a silane coupling agent having aliphatic amino groups was added to the acrylic copolymer solution, making it substantially difficult to form an adhesive layer suitable for evaluation. A more preferable upper limit for the content of structural units derived from the carboxyl group-containing monomer is 0.5% by mass, an even more preferable upper limit is 0.3% by mass, an even more preferable upper limit is 0.1% by mass, and a particularly preferable upper limit is 0.05% by mass. It is most preferable that the (meth)acrylic copolymer does not contain structural units derived from the carboxyl group-containing monomer.

[0026] The (meth)acrylic copolymer described above may have constituent units derived from an N,N-disubstituted amide group-containing monomer, to the extent that it does not impair the effects of the present disclosure. The presence of constituent units derived from an N,N-disubstituted amide group-containing monomer in the (meth)acrylic copolymer increases the polarity of the adhesive layer and further increases the cohesive force, thereby improving the adhesive strength and also improving the high-temperature retention strength.

[0027] Examples of the above-mentioned N,N-disubstituted amide group-containing monomers include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dibutyl(meth)acrylamide, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, N-methyl-N-vinylacetamide, and N-vinylpyrrolidone.

[0028] In the above (meth)acrylic copolymer, the preferred lower limit for the total content of constituent units derived from N,N-disubstituted amide group-containing monomers is 3.0% by mass, and the preferred upper limit is 50% by mass. When the content of constituent units derived from N,N-disubstituted amide group-containing monomers is 3.0% by mass or more, the cohesive force of the adhesive is more easily improved, and the adhesive strength and high-temperature retention force of the adhesive tape of this disclosure are further improved. When the content of constituent units derived from N,N-disubstituted amide group-containing monomers is 50% by mass or less, it is possible to suppress the decrease in initial adhesion and adhesive strength due to an excessive increase in cohesive force. A more preferred lower limit for constituent units derived from N,N-disubstituted amide group-containing monomers is 5.0% by mass, an even more preferred lower limit is 10% by mass, an even more preferred lower limit is 15% by mass, a more preferred upper limit is 45% by mass, an even more preferred upper limit is 40% by mass, and an even more preferred upper limit is 35% by mass.

[0029] The (meth)acrylic copolymer described above may have structural units other than the structural unit (a), the structural unit (b), the structural unit derived from the carboxyl group-containing monomer, and the structural unit derived from the N,N-disubstituted amide group-containing monomer, to the extent that the effects of the present disclosure are not impaired.

[0030] The above (meth)acrylic copolymer has a preferred lower limit of 400,000 and a preferred upper limit of 2,000,000 in its weight-average molecular weight (Mw). A weight-average molecular weight (Mw) of 400,000 or more improves the adhesive strength and holding power of the adhesive tape of this disclosure. A weight-average molecular weight (Mw) of 2,000,000 or less prevents the adhesive layer from becoming too hard, resulting in higher adhesive strength for the adhesive tape of this disclosure. A more preferred lower limit of 500,000 for the weight-average molecular weight (Mw) of the above (meth)acrylic copolymer is 600,000, a more preferred upper limit is 1,600,000, and a still more preferred upper limit is 1,200,000. The weight-average molecular weight (Mw) of the above (meth)acrylic copolymer can be specifically categorized into ranges such as 400,000 to 2,000,000, 400,000 to 1,600,000, 400,000 to 1,200,000, 500,000 to 2,000,000, 500,000 to 1,600,000, 500,000 to 1,200,000, 600,000 to 2,000,000, 600,000 to 1,600,000, and 600,000 to 1,200,000. In this specification, "weight-average molecular weight" refers to the weight-average molecular weight measured as polystyrene-equivalent molecular weight by gel permeation chromatography (GPC). Specifically, the weight-average molecular weight of the above (meth)acrylic copolymer can be measured using, for example, a Waters 2690 Separations Module as the measuring instrument, a Showa Denko GPC KF-806L as the column, and ethyl acetate as the solvent, under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0031] The preferred lower limit for the content of the (meth)acrylic copolymer in the adhesive layer is 50% by mass, and the preferred upper limit is 99.5% by mass. A content of 50% by mass or more of the (meth)acrylic copolymer allows the adhesive to exhibit general physical properties required of adhesives, including tackiness and holding power. A content of 99.5% by mass or less of the (meth)acrylic copolymer ensures the addition of the necessary components for silicone bonding, resulting in sufficient silicone adhesive strength. A more preferred lower limit for the content of the (meth)acrylic copolymer is 60% by mass, a more preferred upper limit is 99% by mass, an even more preferred lower limit is 70% by mass, an even more preferred upper limit is 98.5% by mass, an even more preferred lower limit is 75%, an even more preferred upper limit is 98% by mass, a particularly preferred lower limit is 80% by mass, and a particularly preferred upper limit is 97.5% by mass.

[0032] As polymerization methods for synthesizing the above-mentioned (meth)acrylic copolymer, conventionally known methods can be used in which monomers from which the above-mentioned constituent units are derived are 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.

[0033] 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.

[0034] Examples of polymerization initiators include organic peroxides and azo compounds. Examples of the above-mentioned organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the above-mentioned azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitride. These polymerization initiators may be used individually or in combination of two or more.

[0035] The adhesive layer preferably contains component A, which includes at least one selected from a silane coupling agent having an aliphatic amino group (hereinafter sometimes referred to as "component A-1"), a silane coupling agent having a skeleton with a protected aliphatic amino group (hereinafter sometimes referred to as "component A-2"), a compound having a structure derived from a silane coupling agent having an aliphatic amino group (hereinafter sometimes referred to as "component A-3"), and a compound having a structure derived from a silane coupling agent having a skeleton with a protected aliphatic amino group (hereinafter sometimes referred to as "component A-4"). The inclusion of component A in the adhesive layer further improves the adhesion of the adhesive tape of this disclosure to silicone-based adherends.

[0036] The grade of the aliphatic amino group in component A is not particularly limited, but from the viewpoint of easily exhibiting adhesive strength to silicone substrates, it is preferable that at least one of the aliphatic amino groups in component A is a primary aliphatic amino group or a secondary aliphatic amino group, more preferably a primary aliphatic amino group or a secondary aliphatic amino group with an acyclic structure, and even more preferably a primary aliphatic amino group. In this specification, "acyclic secondary aliphatic amino group" means a secondary aliphatic amino group in which the nitrogen atom in the amino group is not included in the cyclic structure. Furthermore, the structure of the hydrocarbon chain constituting the aliphatic amino group is not particularly limited and may be linear, branched, or cyclic. Furthermore, component A may have one or more alkoxysilyl groups, and these alkoxysilyl groups may be monoalkoxysilyl groups, dialoxysilyl groups, or trialkoxy groups.

[0037] The above component A-1 is not particularly limited as long as it is a silane coupling agent having an aliphatic amino group, and may have one or more aliphatic amino groups. Furthermore, while the grade of the aliphatic amino group in component A-1 is not particularly limited, as described above, from the viewpoint of easily exhibiting adhesive strength to silicone substrates, it is preferable to include at least one selected from the group consisting of primary aliphatic amino groups and secondary aliphatic amino groups, more preferably to include at least one selected from the group consisting of primary aliphatic amino groups and acyclic secondary aliphatic amino groups, and even more preferably to include primary aliphatic amino groups. Furthermore, as mentioned above, the structure of the hydrocarbon chain constituting the aliphatic amino group is not particularly limited and may be linear, branched, or cyclic. Furthermore, while the structure of the hydrocarbon chain between the amino group and the alkoxysilyl group is not particularly limited, if the number of carbon atoms in the hydrocarbon chain is too small, steric hindrance between the amino group and the alkoxysilyl group increases, making it difficult to achieve silicone adhesion. Therefore, it is preferable that the number of carbon atoms between the amino group and the alkoxysilyl group be 3 or more. Also, while the upper limit of the number of carbon atoms between the amino group and the alkoxysilyl group is not particularly limited, a preferred upper limit is 8. Specifically, propylene groups and octylene groups are preferred, with propylene groups being more preferred. In addition, as described above, component A-1 may have one or more alkoxysilyl groups, and these alkoxysilyl groups may be monoalkoxysilyl groups, dialoxysilyl groups, or trialkoxy groups.

[0038] Examples of component A-1 include N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-8-aminooctyltrimethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinylbenzylaminoethylaminopropyltrimethoxysilane, N,N'-bis[3-(trimethoxysilyl)propyl]-1,2-ethanediamine, and X-12-972F manufactured by Shin-Etsu Chemical Co., Ltd.

[0039] The aliphatic amino group-protected skeleton in component A-2 described above may have aliphatic groups or aromatic groups as protecting groups, to the extent that it does not impair the effects of this disclosure. Examples of the aliphatic amino group-protected skeleton include ketimine skeletons and aldimine skeletons. Furthermore, component A-2 may have one or more aliphatic amino group-protected skeletons. Furthermore, component A-2 may have one or more alkoxysilyl groups, and these alkoxysilyl groups may be monoalkoxysilyl groups, dialoxysilyl groups, or trialkoxy groups.

[0040] Examples of component A-2 include 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine and N-[3-(triethoxysilylpropyl)]benzaldehydeimine.

[0041] Examples of component A-3 include a polymer of component A-1.

[0042] Examples of component A-4 include a polymer of component A-2.

[0043] A preferred upper limit for the content of component A per 100 parts by mass of the (meth)acrylic copolymer is 8.0 parts by mass. By having a content of component A of 8.0 parts by mass or less, it is possible to prevent the silane coupling agent from precipitating in the adhesive layer, and to further suppress the decrease in the adhesive strength of the adhesive tape of this disclosure. A more preferred upper limit for the content of component A is 7.0 parts by mass, an even more preferred upper limit is 6.0 parts by mass, and an even more preferred upper limit is 5.0 parts by mass. Furthermore, the preferred lower limit of the content of component A is 1.5 parts by mass. A content of 1.5 parts by mass or more of component A further improves the adhesive strength of the adhesive tape of this disclosure to silicone-based substrates. A content of 2.0 parts by mass or more is more preferable, 2.5 parts by mass or more is even more preferable, greater than 3.0 parts by mass is even more preferable, 3.2 parts by mass or more is particularly preferable, 3.5 parts by mass or more is particularly preferable, and 4.0 parts by mass or more is especially preferable. Specifically, the content of component A per 100 parts by mass of the (meth)acrylic copolymer is, for example, 1.5 parts by mass or more and 8.0 parts by mass or less, 1.5 parts by mass or more and 7.0 parts by mass or less, 1.5 parts by mass or more and 6.0 parts by mass or less, 1.5 parts by mass or more and 5.0 parts by mass or less, 2.0 parts by mass or more and 8.0 parts by mass or less, 2.0 parts by mass or more and 7.0 parts by mass or less, 2.0 parts by mass or more and 6.0 parts by mass or less, 2.0 parts by mass or more and 5.0 parts by mass or less, 2.5 parts by mass or more and 7.0 parts by mass or less, 2.5 parts by mass or more and 6.0 parts by mass or less, 2.5 parts by mass or more and 5.0 parts by mass or less, and greater than 3.0 parts by mass and 8.0 parts by mass or less. Lower, more than 3.0 parts by mass and less than or equal to 7.0 parts by mass, more than 3.0 parts by mass and less than or equal to 6.0 parts by mass, more than 3.0 parts by mass and less than or equal to 5.0 parts by mass, more than 3.2 parts by mass and less than or equal to 8.0 parts by mass, more than 3.2 parts by mass and less than or equal to 7.0 parts by mass, more than 3.2 parts by mass and less than or equal to 5.0 parts by mass, 3.5 parts by mass 8.0 parts by mass or more, 3.5 parts by mass or more and 7.0 parts by mass or less, 3.5 parts by mass or more and 5.0 parts by mass or less, 4.0 parts by mass or more and 8.0 parts by mass or less, 4.0 parts by mass or more and 7.0 parts by mass or less, 4.0 parts by mass or more and 5.0 parts by mass or less, etc.

[0044] The adhesive layer described above may contain other additives such as tackifying resins, softeners, and inorganic fillers, as necessary, to the extent that it does not impair the effects of the present disclosure.

[0045] Since device materials are typically exposed to high-temperature environments during use, it is preferable that the adhesive tape used to bond silicone materials has high-temperature retention capabilities. From this perspective, it is preferable that the components in the adhesive layer have a cross-linked structure. By forming a cross-linked structure in the components of the adhesive layer, it becomes easier to adjust the gel fraction of the adhesive layer to an appropriate range, as described later, thereby improving the cohesive force of the adhesive layer and further improving the high-temperature retention capabilities of the adhesive tape of this disclosure.

[0046] Methods for crosslinking the components in the adhesive layer include, for example, radiation crosslinking such as electron beam irradiation, ultraviolet irradiation, and gamma ray irradiation, as well as chemical crosslinking and physical crosslinking. Among these, electron beam irradiation and ultraviolet irradiation are preferred from the viewpoint of improving adhesion to silicone substrates, providing superior high-temperature retention of the adhesive layer, and ensuring the long-term stability of the adhesive solution, as they allow for crosslinking without introducing polar functional groups into the adhesive layer. Electron beam irradiation is more preferred from the viewpoint of minimizing the amount of components used.

[0047] One method for crosslinking the components in the adhesive layer by electron beam irradiation is to irradiate the adhesive tape with an electron beam using an electron beam irradiation device (such as the "EBC-200" manufactured by NHV Corporation).

[0048] One method for crosslinking the components in the adhesive layer by ultraviolet irradiation is to irradiate an adhesive tape having an adhesive layer containing a radical generator with ultraviolet light at a wavelength of 365 nm using a chemical lamp (such as Toshiba's "FL20S-BL"). Examples of radical-generating agents to be included in the adhesive layer include benzophenone and 4,4'-bis(dimethylamino)benzophenone.

[0049] The adhesive layer described above preferably contains a component that crosslinks upon electron beam irradiation or ultraviolet irradiation (hereinafter sometimes simply referred to as "electron beam or other crosslinking component"). By containing the electron beam or other crosslinking component, the crosslinking of the adhesive layer by electron beam irradiation or ultraviolet irradiation progresses more easily, making it easier to obtain an adhesive layer with superior high-temperature retention.

[0050] Examples of components that can be crosslinked by the above electron beam irradiation include (meth)acrylic monomers and allyl group-containing compounds (excluding the above (meth)acrylic copolymers). Specifically, examples include ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and triallyl isocyanurate. Examples of components that crosslink upon UV irradiation include (meth)acrylic monomers and allyl group-containing compounds (excluding the (meth)acrylic copolymers mentioned above). Specifically, examples include ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and triallyl isocyanurate.

[0051] When the adhesive layer contains the electron beam or other crosslinking component, the preferred lower limit of the content of the electron beam or other crosslinking component per 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 15 parts by mass. A content of 0.1 parts by mass or more of the electron beam or other crosslinking component makes it easier to achieve superior high-temperature retention in the adhesive layer. A content of 15 parts by mass or less of the electron beam or other crosslinking component suppresses bleed-out of the electron beam or other crosslinking component and reduces adhesive strength due to excessive crosslinking. A more preferred lower limit of the content of the electron beam or other crosslinking component is 0.5 parts by mass, a more preferred upper limit is 12 parts by mass, an even more preferred lower limit is 1.0 part by mass, and an even more preferred upper limit is 10 parts by mass. Furthermore, since the adhesive layer can exhibit excellent high-temperature retention even without containing the electron beam or other crosslinking component, the adhesive layer does not need to contain the electron beam or other crosslinking component. Examples of the content of the electron beam or other crosslinking component include ranges such as 0 parts by mass to 15 parts by mass, 0 parts by mass to 12 parts by mass, 0 parts by mass to 10 parts by mass, 0.1 parts by mass to 15 parts by mass, 0.1 parts by mass to 12 parts by mass, 0.1 parts by mass to 10 parts by mass, 0.5 parts by mass to 15 parts by mass, 0.5 parts by mass to 12 parts by mass, 0.5 parts by mass to 10 parts by mass, 1.0 part by mass to 15 parts by mass, 1.0 part by mass to 12 parts by mass, and 1.0 part by mass to 10 parts by mass.

[0052] Furthermore, from the viewpoint of facilitating the crosslinking of the adhesive layer by electron beam irradiation or ultraviolet irradiation, the (meth)acrylic copolymer may contain alkenyl groups such as vinyl groups, allyl groups, and styryl groups, or (meth)acryloyl groups. Furthermore, in this specification, "(meth)acryloyl group" means an acryloyl group or a methacryloyl group.

[0053] The adhesive layer preferably contains a radical generator. By containing a radical generator, the crosslinking of the adhesive layer by ultraviolet irradiation is made more likely to occur.

[0054] Examples of the radical generating agents mentioned above include benzophenone-based, benzyl ketal-based, α-hydroxyketone-based, α-aminoketone-based, and α-acylphosphinoxide-based photoradical generating agents, with benzophenone-based agents being preferred. Specific examples of benzophenone-based photoradical generating agents include benzophenone and 4,4'-bis(dimethylamino)benzophenone.

[0055] The preferred lower limit for the content of the radical generator per 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 10 parts by mass. A content of 0.1 parts by mass or more of the radical generator makes it easier to achieve superior high-temperature retention in the adhesive layer. A content of 10 parts by mass or less of the radical generator suppresses the reduction in adhesive strength due to excessive bleed-out or crosslinking of the radical generator. A more preferred lower limit for the content of the radical generator is 0.5 parts by mass, a more preferred upper limit is 8 parts by mass, an even more preferred lower limit is 1 part by mass, and an even more preferred upper limit is 5 parts by mass. Furthermore, preferred content of the radical generator includes, for example, ranges such as 0.1 parts by mass or more and 10 parts by mass or less, 0.1 parts by mass or more and 8 parts by mass or less, 0.1 parts by mass or more and 5 parts by mass or less, 0.5 parts by mass or more and 10 parts by mass or less, 0.5 parts by mass or more and 8 parts by mass or less, 0.5 parts by mass or more and 5 parts by mass or less, 1 part by mass or more and 10 parts by mass or less, 1 part by mass or more and 8 parts by mass or less, and 1 part by mass or more and 5 parts by mass or less.

[0056] The adhesive layer described above has a preferred lower limit of 35% by mass for its gel fraction. A gel fraction of 35% by mass or higher in the adhesive layer further improves the cohesive force of the adhesive layer and enhances the high-temperature retention of the adhesive tape of this disclosure. A more preferred lower limit for the gel fraction of the adhesive layer is 40% by mass, an even more preferred lower limit is 45% by mass, and an even more preferred lower limit is 50% by mass. Furthermore, the preferred upper limit for the gel fraction of the adhesive layer is 90% by mass. By having a gel fraction of 90% by mass or less in the adhesive layer, high holding power and the necessary adhesive strength can be achieved. A more preferred upper limit for the gel fraction of the adhesive layer is 85% by mass, an even more preferred upper limit is 80% by mass, and an even more preferred upper limit is 75% by mass. The preferred gel fraction of the adhesive layer mentioned above can be found in the following ranges: 35% by mass or more and 90% by mass or less, 35% by mass or more and 85% by mass or less, 35% by mass or more and 80% by mass or less, 35% by mass or more and 75% by mass or less, 40% by mass or more and 90% by mass or less, 40% by mass or more and 85% by mass or less, 40% by mass or more and 80% by mass or less, 40% by mass or more and 75% by mass or less, 45% by mass or more and 90% by mass or less, 45% by mass or more and 85% by mass or less, 45% by mass or more and 80% by mass or less, 45% by mass or more and 75% by mass or less, 50% by mass or more and 90% by mass or less, 50% by mass or more and 85% by mass or less, 50% by mass or more and 80% by mass or less, 50% by mass or more and 75% by mass or less.

[0057] The gel fraction of the adhesive layer can be measured by the following method. Specifically, W0 (g) of the adhesive layer is scraped off and immersed in 50 mL of ethyl acetate, and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the ethyl acetate and the adhesive that has absorbed the ethyl acetate and swollen are separated using a metal mesh (mesh size #200). The separated adhesive is dried at 110°C for 1 hour. The mass of the dried adhesive including the metal mesh is measured, and the gel fraction (mass%) is calculated using the following formula (1). Gel fraction (mass %) = 100 × (W1 - W2) / W0(1) (W0: initial adhesive mass, W1: adhesive mass including metal mesh after drying, W2: initial mass of metal mesh)

[0058] Furthermore, the gel fraction of the adhesive layer can also be measured using a test specimen consisting only of the adhesive layer, or a test specimen having both a substrate and an adhesive layer, after which the prepared test specimen is used. Specifically, the specimen is immersed in 50 mL of ethyl acetate and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the ethyl acetate and the swollen test specimen that has absorbed the ethyl acetate are separated using a metal mesh (mesh size #200). The separated test specimen is dried at 110°C for 1 hour. The mass of the dried test specimen including the metal mesh is measured, and the gel fraction (mass%) is calculated using the following formula (2). Note that the test specimen should not have a separator. If the test specimen does not have a substrate, W0 in the following formula (2) should be set to 0 for calculation. Gel fraction (mass %) = 100 × (W2 - W0) / (W1 - W0) (2) (W0: Mass of the substrate layer, W1: Mass of the test specimen before immersion, W2: Mass of the test specimen after immersion and drying)

[0059] Methods for adjusting the gel fraction of the adhesive layer to within the above range include, for example, adjusting the composition of the (meth)acrylic copolymer, adjusting the crosslinking conditions of the components in the adhesive layer, and adjusting the type and amount of additives such as silane coupling agents. Methods for adjusting the above crosslinking conditions include, for example, adjusting the irradiation intensity, irradiation time, and acceleration voltage of the electron beam in the case of crosslinking by electron beam irradiation, and adjusting the irradiation intensity and irradiation time of ultraviolet rays, which are energy rays that promote crosslinking, and removing oxygen that inhibits the reaction in the case of crosslinking by ultraviolet irradiation. When using chemical crosslinking, methods include adjusting the reactivity and amount of the crosslinking agent, and the reactivity and amount of the functional groups that react with the crosslinking agent in the (meth)acrylic copolymer.

[0060] The preferred lower limit for the thickness of the adhesive layer is 5 μm, and the preferred upper limit is 200 μm. By having the thickness of the adhesive layer within this range, the resulting adhesive tape can achieve both sufficient adhesive strength and ease of handling. A more preferred lower limit for the thickness of the adhesive layer is 10 μm, an even more preferred lower limit is 15 μm, an even more preferred upper limit is 150 μm, an even more preferred upper limit is 125 μm, and an even more preferred upper limit is 100 μm. Specifically, the thickness of the adhesive layer mentioned above can be, for example, 5 μm to 200 μm, 5 μm to 150 μm, 5 μm to 125 μm, 5 μm to 100 μm, 10 μm to 200 μm, 10 μm to 150 μm, 10 μm to 125 μm, 10 μm to 100 μm, 15 μm to 200 μm, 15 μm to 150 μm, 15 μm to 125 μm, 15 μm to 100 μm, etc.

[0061] The adhesive tape of this disclosure may have layers other than the adhesive layer, such as a substrate, to the extent that it does not impair the effects of this disclosure. It may also have one or more adhesive layers of a different type from the adhesive layer described above.

[0062] The adhesive tape of this disclosure may have a separator on at least one side of the adhesive layer. That is, the adhesive tape of this disclosure may have a separator on one side of the adhesive layer, or it may have separators on both sides of the adhesive layer.

[0063] The separator substrate used in the above-mentioned separator is not particularly limited, and any substrate that has been conventionally used as a separator substrate can be appropriately selected and used. Examples include plastic films such as polyester, polyethylene, polypropylene, polymethylpentene, and polycarbonate; metal foils such as aluminum and stainless steel; and paper substrates such as glassine paper, fine paper, coated paper, impregnated paper, synthetic paper, and kraft paper. Among these, polyester is preferred from the viewpoint of suppressing the inclusion of foreign matter originating from the separator. Examples of the above-mentioned polyesters include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).

[0064] The separator preferably has a release layer. By including a release layer in the separator, the separator can be easily peeled off the adhesive layer, and the function and appearance of the adhesive tape of this disclosure after the separator has been peeled off can be prevented. Furthermore, if the adhesive tape of this disclosure has the separator on both sides, the separator on one side may have the release layer, or the separators on both sides may have the release layer.

[0065] The above-mentioned release layer is not particularly limited, but a release layer that does not contain organic fluorine compounds is preferred. In this specification, "does not contain organic fluorine compounds" means that the content of organic fluorine compounds is below the detection limit when measured on the surface of the release layer side of the separator by XPS, TOF-SIMS, etc. By making the above-mentioned release layer free of organic fluorine compounds, it is possible to make an adhesive tape with an even lower content of organic fluorine compounds. Conventionally, with adhesive tapes used for bonding to silicone substrates, if the release layer of the separator does not contain an organic fluorine compound, it is difficult to peel the separator from the adhesive layer that the separator protects. Therefore, the release layer of the separator in such adhesive tapes must contain a fluorine compound, which has been a problem. On the other hand, with the adhesive tape of this disclosure, even if the release layer of the separator does not contain an organic fluorine compound, it is possible to easily peel the separator from the adhesive layer. Therefore, from this viewpoint as well, the adhesive tape of this disclosure is desirable.

[0066] The above separator has a preferred upper limit of 0.170 for the relative intensity of the peak at 103.9 eV (hereinafter sometimes simply referred to as "relative intensity of the separator in XPS measurement") when the surface of the peel interface between the separator and the adhesive layer is measured by XPS at 180° peel of the separator in an environment of 23°C and 50% RH. A relative intensity of 0.170 or less in XPS measurement of the above separator allows the separator to be used more suitably to protect the adhesive layer while being easier to peel off when using the adhesive tape of this disclosure. As a result, the adhesive tape of this disclosure becomes more suitably usable in practical applications. A more preferred upper limit for the relative intensity of the above separator in XPS measurement is 0.160, and an even more preferred upper limit is 0.150. Furthermore, while there are no particular limitations on the lower limit of the relative intensity in the XPS measurement of the above separator, a preferred lower limit is 0.010, a more preferred lower limit is 0.020, and an even more preferred lower limit is 0.030. Specifically, the relative intensity of the above separator in XPS measurement can be found in the following ranges: 0.010 to 0.170, 0.010 to 0.160, 0.010 to 0.150, 0.020 to 0.170, 0.020 to 0.160, 0.020 to 0.150, 0.030 to 0.170, 0.030 to 0.160, 0.030 to 0.150, etc.

[0067] The relative intensity of the above separator in XPS measurement can be measured by the following method. Specifically, first, if necessary, the separator on the side of the adhesive tape not to be subjected to XPS measurement is peeled off from the adhesive layer. Then, a test specimen is prepared by pressing and backing it onto a 23 μm thick polyethylene terephthalate (PET) film or the like using a 2 kg rubber roller at a speed of 300 mm / min for one back-and-forth motion. Note that this step is unnecessary if the adhesive tape has the separator on only one side. Next, for the test piece, in accordance with JIS Z0237, using a tensile testing machine (manufactured by Shimadzu Corporation, "AG-IS"), the separator is peeled from the adhesive tape under the conditions of 23°C, a tensile speed of 300 mm / min, and a peeling angle of 180°. Then, regarding the peeling interface with the adhesive layer in the separator peeled from the adhesive tape, narrow scan analysis of C1s, O1s, and Si2p in XPS measurement is performed under the following conditions. After calibration with the peak top of C1s set at 284.8 eV, among the measurement range of Si2p, with the maximum value set at 1 and the minimum value set at 0, the relative intensity of the peak at 103.9 eV is obtained, thereby obtaining the relative intensity in the XPS measurement of the above separator. <XPS measurement conditions> Measuring device: PHI5000 VersaProbe II (manufactured by ULVAC-PHI) X-ray source: Al Kα ray (1486.6 eV) Photoelectron extraction angle: 45 degrees Pass energy: 23.5 eV (Si2p), 58.7 eV (C1s, O1s) Setting range during measurement: 94.0 eV to 114.0 eV (Si2p), 278.0 eV to 298.0 eV (C1s), 298.0 eV to 523.0 eV (O1s) STEP width: 0.1 eV (Si2p), 0.125 eV (C1s, O1s) Number of sweeps: 3 times (Si2p), 2 times (C1s), 1 time (O1s) Number of cycles: 10 times

[0068] In addition, an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer and a separator, when the surface of the peeling interface with the adhesive layer in the separator peeled from the adhesive layer at 180° under the environment of 23°C and 50% RH is measured by XPS, an adhesive tape in which the relative intensity of the peak at 103.9 eV is 0.17 or less is also one of the present disclosures.

[0069] If the adhesive tape has separators on both sides, the relative strength of the separators in the XPS measurement may satisfy the above range with only one separator, or it may satisfy the above range with both separators. If the adhesive tape has separators on both sides, it is more preferable that the relative strength of the separators in the XPS measurement satisfies the above range with both separators.

[0070] The preferred lower limit for the thickness of the separator (the total thickness of the separator substrate and release layer) is 12 μm. A separator thickness of 12 μm or more helps to reduce damage from unintended bending or impact when handling the adhesive tape, and further suppresses deterioration of the appearance and function of the resulting adhesive tape after the separator is removed. A more preferred lower limit for the thickness of the separator is 19 μm, and an even more preferred lower limit is 25 μm. Furthermore, while there is no particular upper limit to the thickness of the separator mentioned above, the practical upper limit is 200 μm.

[0071] The adhesive tape of this disclosure may be a support-type adhesive tape having a substrate other than the separator substrate described above, or it may be a non-support-type adhesive tape that does not have a substrate other than the separator substrate described above. Furthermore, the adhesive tape of this disclosure may be a double-sided tape having a configuration that includes another adhesive layer other than the adhesive layer that can exhibit excellent adhesion to a silicone-based adherend.

[0072] The method for manufacturing the adhesive tape of this disclosure is not particularly limited, and conventionally known methods can be used. Specifically, for example, the adhesive tape can be manufactured by adding the (meth)acrylic copolymer, component A, etc., to a solvent, stirring thoroughly, and then coating the resulting adhesive solution onto the release layer of a separator, drying it, and forming an adhesive layer.

[0073] The applications of the adhesive tape of this disclosure are not particularly limited and can be used for assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), or for manufacturing devices that emit or receive electromagnetic waves to fix automotive electronic device components such as automotive panels to the vehicle body. In particular, the adhesive tape of this disclosure has excellent adhesive strength to silicone-based substrates, and is therefore preferably used for bonding silicone-based substrates. Examples of the silicone-based substrates mentioned above include silicone rubber, silicone foam, and objects having a silicone coating. Specifically, examples include electronic equipment components, vehicle components, building components, and medical components.

[0074] Examples of the above-mentioned electronic equipment components include heat dissipation pads and sheets, adhesives and sealants for fixing electrical and electronic components, potting agents and coatings for protecting electrical and electronic components, die bonding materials for semiconductors, potting materials for sealing electronic circuits, rolls for office automation equipment, anode caps, glass sleeve bundling materials for cables, polymer insulators, and electrical insulating resin varnishes. Examples of the above-mentioned vehicle components include heat dissipation pads and sheets, heat dissipation foam, heat-resistant foam, heat-resistant hoses, O-rings, adhesives and sealants for fixing vehicle components, and potting agents and coatings for protecting vehicle accessories. Examples of the above-mentioned building components include building gaskets, vibration dampers, heat insulating rubber, heat dissipating rubber, heat insulating foam, heat dissipating foam, adhesives and sealants for fixing building components, and potting agents and coatings for protecting building materials. Examples of the above-mentioned medical components include catheters and tubes, seals and gaskets for medical devices, and adhesives and sealants for fixing medical components.

[0075] A laminate containing the adhesive tape of this disclosure attached to a silicone-based substrate is also one of the disclosures. The laminate of this disclosure has a low content of organofluororesins and is environmentally friendly.

[0076] The laminate of this disclosure is not particularly limited as long as it has a structure in which the adhesive tape is attached to a silicone-based substrate, but for example, a laminate is obtained by bonding a member 2 containing a silicone-based resin and another member 3 using the adhesive tape 1, as shown in Figure 1. Other examples include laminates formed by bonding together components containing silicone resin. Specifically, examples include structures in which silicone-based adherends such as heat dissipation pads and sheets, adhesives and sealants for fixing electrical and electronic components, potting agents and coatings for protecting electrical and electronic components, die bonding materials for semiconductors, potting materials for sealing electronic circuits, rolls for office automation equipment, anode caps, glass sleeve bundling materials for cables, polymer insulators, electrical insulating resin varnishes, and other electronic equipment components, as well as the aforementioned vehicle components, building components, and medical components, are bonded together using the aforementioned adhesive tape.

[0077] Electronic devices including the adhesive tape of this disclosure are also part of this disclosure. The electronic devices of this disclosure have a low content of organic fluororesins and are environmentally friendly.

[0078] The electronic devices of this disclosure are not particularly limited as long as they include the adhesive tape described above, but examples include electronic devices having the laminate shown in Figure 1 as a component, and electronic devices having a laminate formed by bonding together members containing silicone resin as a component. Specifically, examples include mobile phones, smartphones, tablets, personal computers (PCs) and laptops, game consoles, display terminals, e-paper terminals, watches and watch-type electronic devices, eyeglass-type electronic devices, goggle-type electronic devices, etc., which include the structures exemplified as laminates in this disclosure described above. [Effects of the Invention]

[0079] According to this disclosure, it is possible to provide an adhesive tape that can exhibit excellent adhesion to silicone-based substrates without the use of silicone-based adhesives or prior surface treatment of the substrate. Furthermore, according to this disclosure, it is possible to provide a laminate having a structure to which the adhesive tape is attached. Moreover, according to this disclosure, it is possible to provide an electronic device including the adhesive tape. [Brief explanation of the drawing]

[0080] [Figure 1] This is a schematic cross-sectional view showing an example of the laminate of this disclosure. [Figure 2] This is a schematic diagram illustrating the method for high-temperature retention testing. [Modes for carrying out the invention]

[0081] The embodiments of this disclosure will be further described below with reference to examples, but this disclosure is not limited to these examples.

[0082] (Synthesis of (meth)acrylic copolymers a-k) Ethyl acetate was added as a solvent to a reactor equipped with a thermometer, stirrer, and condenser, and then nitrogen was purged. The reactor was then heated and reflux was started. After the solvent boiled, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10-fold with ethyl acetate was added as a polymerization initiator. Then, ethyl acetate solutions of monomer mixtures with the content ratios (by mass) shown in Table 1 were added dropwise to the reactor from a dropping funnel over 2 hours until the monomer concentration reached 45% by mass. After the dropwise addition was completed, the polymerization reaction was carried out for 4 hours to obtain ethyl acetate solutions of (meth)acrylic copolymers a to k. The ethyl acetate solutions of the obtained acrylic copolymers a-g were filtered, and the resulting filtrate was supplied to a gel permeation chromatograph (Waters 2690 Separations Module). GPC measurements were performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C to determine the polystyrene-equivalent molecular weight of the acrylic copolymers and to determine the weight-average molecular weight (Mw). A GPC KF-806L column (Showa Denko Corporation) was used, and a differential refractometer was used as the detector. The results are shown in Table 1.

[0083] (Synthesis of (meth)acrylic copolymer l) Ethyl acetate was added as a solvent to a reactor equipped with a thermometer, stirrer, and condenser, and the reactor was purged with nitrogen. The reactor was then heated and reflux was started. A polymerization initiator solution, prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10-fold with ethyl acetate, was added to the reactor as a polymerization initiator. Then, 96.6 parts by mass of n-heptyl acrylate, 2.9 parts by mass of acrylic acid, and 0.5 parts by mass of 2-hydroxyethyl acrylate were added dropwise over 2 hours. After the dropwise addition was complete, the polymerization initiator solution, prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10-fold with ethyl acetate, was added again to the reactor as a polymerization initiator, and the polymerization reaction was carried out for 4 hours to obtain an ethyl acetate solution of acrylic copolymer l. The ethyl acetate solution of the obtained acrylic copolymer was filtered, and the resulting filtrate was supplied to a gel permeation chromatograph (Waters 2690 Separations Module). GPC measurements were performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C to determine the polystyrene-equivalent molecular weight of the acrylic copolymer and then the weight-average molecular weight (Mw). A GPC KF-806L column (Showa Denko Corporation) was used, and a differential refractometer was used as the detector. The results are shown in Table 1.

[0084] The constituent monomers of the (meth)acrylic copolymers shown in Table 1 are as follows: • EA: Ethyl acrylate BA: n-butyl acrylate • HPA: n-heptyl acrylate 2OA: Octyl Acrylate • 2EHA: 2-ethylhexyl acrylate • HEA: 2-hydroxyethyl acrylate • DMAA: N,N-dimethylacrylamide AAc: Acrylic acid

[0085] [Table 1]

[0086] (Example 1) (1) Making adhesive tape To the obtained ethyl acetate solution of (meth)acrylic copolymer a, 3.0 parts by mass of KBM-602 (manufactured by Shin-Etsu Chemical Co., Ltd.) was added as an aliphatic amine silane coupling agent for every 100 parts by mass of the solid content of (meth)acrylic copolymer a. Ethyl acetate was then added to bring the solid content ratio to 30%, and the mixture was thoroughly mixed to prepare an adhesive solution. A 50 μm thick adhesive layer was formed by coating the release layer of a 75 μm thick separator (Toyo Cloth Co., Ltd., "SP3000") with the prepared adhesive solution and drying it at 110°C for 3 minutes. Then, another 25 μm thick separator (Toyo Cloth Co., Ltd., "SP8001") was prepared and placed on top of the formed adhesive layer with its release layer facing it, and cured at 40°C for 48 hours to obtain an adhesive tape. The separator used here does not contain any fluorine components that would qualify as PFAS.

[0087] (2) Measurement of the gel fraction of the adhesive layer W0 (g) of the adhesive layer was scraped off and immersed in 50 mL of ethyl acetate. The mixture was shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the ethyl acetate and the adhesive that had absorbed and swollen with ethyl acetate were separated using a metal mesh (mesh size #200). The separated adhesive was dried at 110°C for 1 hour. The mass of the dried adhesive, including the metal mesh, was measured, and the gel fraction was calculated using formula (1) above. The results are shown in Table 2.

[0088] (3) Measurement of the relative intensity of the negative ion peak in the m / z region of 26 after peeling off the adhesive tape. A 50mm x 125mm SUS304 plate surface was cleaned with ethanol and then wiped dry. A film adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767") having a silicone adhesive layer on one side was cut to a size of 30mm in width and 70mm in length. After peeling off the separator on the side with the adhesive layer that was not the silicone adhesive layer, this adhesive layer was attached to the SUS304 plate. Furthermore, the separator on the side with the silicone adhesive layer was peeled off to expose the silicone adhesive layer, and a 1mm thick piece of silicone rubber (manufactured by Togawa Rubber Co., Ltd., "K-125(50)") cut to a size of 30mm in width and 70mm in length was attached to the silicone adhesive layer to create a silicone-based adherend. The adhesive tape obtained in "(1) Preparation of adhesive tape" described above was cut to a size of 25 mm in width and 70 mm in length. The separator was peeled off one side of the cut adhesive tape, and one side of the adhesive tape was backed with the corona-treated side of a 23 μm thick polyethylene terephthalate (PET) film. The separator was peeled off the other side of the backed adhesive tape, and it was bonded to the silicone rubber surface of the silicone-based adherend. A 2 kg roller was then pressed down once back and forth at a speed of 300 mm / min, and the laminate was left to stand for 72 hours in an atmosphere of 23°C and 50% RH to produce a laminate. The produced laminate was subjected to a peel test in accordance with JIS Z0237, using a tensile testing machine (Shimadzu Corporation, "AG-IS"), under conditions of 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°, in order to peel the adhesive tape from the silicone-based adherend. For the silicone rubber from which the adhesive tape was peeled after the peel test, it was adjusted to a peeling speed of approximately 300 mm / min and a peeling angle of approximately 90°, and the silicone rubber was peeled from the film adhesive tape having a silicone-based adhesive layer by peeling it by hand. After peeling from the above silicone-based adherend, the peeled silicone rubber was cut into a square of about 1 cm using a cutter or scissors to prepare a measurement sample. The surface of the measurement sample that had been in contact with the adhesive tape was placed on the ethyl acetate liquid surface of an aluminum cup with an inner diameter of 5 cm into which 2 mL of ethyl acetate had been poured, and then it was washed with ethyl acetate by shaking it back and forth 80 times at an interval of 1 cm per minute for 1 minute (i). Further, an aluminum cup with an inner diameter of 5 cm into which another 2 mL of ethyl acetate had been poured was prepared, and after performing the same washing again, the measurement sample was heated in an atmospheric pressure oven at 80 °C for 10 minutes (ii). The operations (i) and (ii) described above were taken as one set, and a total of 4 sets were performed, and a total of 8 washings with ethyl acetate were carried out. In addition, new aluminum cups and ethyl acetate were used each time the operations (i) and (ii) were performed. For the surface washed with the above ethyl acetate, TOF-SIMS measurement was performed, and the obtained spectral data was analyzed using analysis software (manufactured by ION-TOF, "SurfaceLab 7") to obtain the relative intensity of the negative ion peak in the region where m / z is 26 after peeling the adhesive tape. The results are shown in Table 1. The TOF-SIMS measurement was specifically performed as follows. (TOF-SIMS Measurement) The TOF-SIMS measurement was performed using a time-of-flight secondary ion mass spectrometer (manufactured by ION-TOF, "TOF.SIMS5"), and the measurement conditions were as described below.. From the obtained secondary ion spectrum, a value obtained by dividing the sum (area) of the negative ion peaks in the region where m / z is 26 by the sum (area) of all the negative ion peaks was calculated. <Measurement Conditions for TOF-SIMS Measurement> · Primary ion species: Bi3+ + · Acceleration voltage: 25 kV · Detected ion polarity: negative (negative ion) · Measurement range: 500 μm × 500 μm • Pixel count: 128 x 128 (pixels) • Number of scans: 25 scans ·Mass range (m / z): 0~850

[0089] (Examples 2-27, Comparative Examples 1-4, 6-9) Except for changing the composition of the adhesive layer as shown in Tables 2-5 and 9, an adhesive tape was prepared in the same manner as in Example 1. Then, the obtained adhesive tape was irradiated with an electron beam using an electron beam irradiation device (NHV Corporation, "EBC-200") according to the electron beam irradiation conditions shown in Tables 2-5 and 9, to crosslink the adhesive components and form an adhesive layer, thereby obtaining an adhesive tape. The electron beam was irradiated from both sides of the adhesive tape, with half of the total dose applied to each side. The gel fraction of the adhesive layer was measured in the same manner as in Example 1. The results are shown in Tables 2-5 and 9.

[0090] (Examples 28-29) An adhesive tape was prepared in the same manner as in Example 1, except that the composition of the adhesive layer was changed as shown in Table 5, and benzophenone was added to the adhesive layer in the amount shown in Table 5 as a radical generator for UV crosslinking. The obtained adhesive tape was then irradiated with UV light including a wavelength of 365 nm using a chemical lamp (Toshiba, "FL20S·BL") according to the UV irradiation conditions shown in Table 5, thereby crosslinking the adhesive components and forming an adhesive layer to obtain an adhesive tape. UV irradiation was performed from both sides of the adhesive tape, with half of the accumulated light intensity applied to each side. The gel fraction of the adhesive layer was measured in the same manner as in Example 1. The results are shown in Table 5.

[0091] (Comparative Example 5) An adhesive tape was prepared in the same manner as in Example 1, except that 100 parts by mass of styrene-ethylene-butylene-styrene (SEBS) triblock copolymer (manufactured by ENEOS Material, "DYNARON 8300") and 30 parts by weight of tackifying resin (manufactured by Arakawa Chemical Industries, "Alcon P-125") were dissolved in toluene to prepare an adhesive solution with a solid content of 30%, and an adhesive tape was prepared using this adhesive solution. The measurement of the gel fraction of the adhesive layer was performed in the same manner as in Example 1, except that ethyl acetate was replaced with toluene. The results are shown in Table 9.

[0092] (Example 30) (1) Making adhesive tape First, an adhesive solution (a) for forming adhesive layer (A) and an adhesive solution (b) for forming adhesive layer (B) were prepared in the same manner as in Example 1, except that the composition of the adhesive layer was changed as shown in Tables 6 to 8, so that the isocyanate crosslinking agent (Desmodule L75, manufactured by Covestro) was 0.2 parts by mass (solid content ratio) per 100 parts by mass of (meth)acrylic copolymer. Next, an adhesive solution (a) prepared for this purpose was applied to the release layer of a 75 μm thick separator (Toyo Cross Co., Ltd., "SP3000"), and then dried at 110°C for 3 minutes to form an adhesive layer. A laminate was created by stacking the adhesive layers formed on one side of a 23 μm thick PET film (Futamura Chemical Co., Ltd., "FE2002-23"), and the laminate was irradiated with an electron beam using an electron beam irradiation device (NHV Corporation, "EBC-200") to crosslink the adhesive components, thereby forming a 75 μm thick adhesive layer (A). The electron beam was irradiated from both sides of the laminate, with half of the total dose applied to each side. Furthermore, after applying the prepared adhesive solution (b) onto the release layer of separator (B) shown in Table 6, an adhesive layer (B) with a thickness of 42 μm was formed by drying at 110°C for 3 minutes. Then, adhesive layer (B) was superimposed on the side of the substrate that did not have adhesive layer (A) in the laminate with adhesive layer (A) formed on it, and the laminate was integrated, followed by curing at 40°C for 48 hours. After peeling off the separator on the adhesive layer (A) side and laminating with separator (A) as shown in Table 6, the adhesive tape with the replaced separator was placed in an oven set to 60°C and 50% RH and left to stand for 168 hours under 60°C and 50% RH conditions, thereby obtaining an adhesive tape having a substrate and adhesive layers and separators on both sides of the substrate.

[0093] (2) Measurement of the gel fraction of the adhesive layer First, in the "(1) Preparation of adhesive tape" described above, the laminate with the adhesive layer (A) was cut to a size of 25 mm in width and 60 mm in length. Then, the separator (A) was peeled off from the cut laminate to prepare a test piece for measuring the gel fraction. Next, the prepared test piece for measuring the gel fraction was immersed in 50 mL of ethyl acetate and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. Then, the ethyl acetate and the test piece that had absorbed the ethyl acetate and swollen were separated using a metal mesh (mesh size #200). The separated test piece was then dried at 110°C for 1 hour. The mass of the test piece including the metal mesh after drying was measured, and the gel fraction (mass %) was calculated using the above formula (2). The results are shown in Table 6.

[0094] (3) Measurement of the relative intensity of the negative ion peak in the m / z region of 26 after peeling off the adhesive tape. Except for backing the adhesive layer (B) with the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film and bonding the adhesive layer (A) to the silicone rubber surface of the silicone-based adherend, the relative intensity of the negative ion peak in the m / z region of 26 after peeling off the adhesive tape was measured in the same manner as in Example 1. The results are shown in Table 6.

[0095] (4) Measurement of relative intensity in XPS measurement after the separator has been left to stand in a high temperature and high humidity environment. First, the separator (B) in the obtained adhesive tape was peeled off from the adhesive layer (B). Then, a 2 kg rubber roller was used to press the adhesive layer (B) onto the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film by one back-and-forth motion at a speed of 300 mm / min to prepare a test specimen. Next, the prepared test specimens are placed in a constant temperature and humidity oven set to 60°C and 50%RH, and left to stand for 168 hours under these conditions. After that, the test specimens are removed from the constant temperature and humidity oven and air-cooled for 30 minutes in an environment of 23°C. Furthermore, the air-cooled test specimens are subjected to JIS standards. In accordance with Z0237, the separator (A) was peeled off from the adhesive layer (A) using a tensile testing machine (manufactured by Shimadzu Corporation, "AG-IS") under the conditions of 23°C, a tensile speed of 300 mm / min, and a peeling angle of 180°. Then, regarding the peeling interface with the adhesive layer (A) on the separator (A) peeled off from the adhesive layer (A), narrow scan analysis of C1s, O1s, and Si2p in XPS measurement was performed under the following conditions. After calibration with the peak top of C1s being 284.8 eV, among the measurement range of Si2p, with the maximum value being 1 and the minimum value being 0, the relative intensity of the peak at 103.9 eV was obtained to obtain the relative intensity in the XPS measurement of the above separator. The results are shown in Table 6. <XPS Measurement Conditions> Measuring device: PHI5000VersaProbeII (manufactured by ULVAC-PHI) X-ray source: Al Kα ray (1486.6 eV) Photoelectron extraction angle: 45 degrees Pass energy: 23.5 eV (Si2p), 58.7 eV (C1s, O1s) Measurement setting range: 94.0 eV to 114.0 eV (Si2p), 278.0 eV to 298.0 eV (C1s), 298.0 eV to 523.0 eV (O1s) STEP width: 0.1 eV (Si2p), 0.125 eV (C1s, O1s) Number of sweeps: 3 times (Si2p), 2 times (C1s), 1 time (O1s) Number of cycles: 10 times

[0096] (Examples 31 to 34, 38 to 44) In the above-mentioned "(1) Preparation of Adhesive Tape", except that the types of separator (A), base material, and separator (B), as well as the composition and thickness in the adhesive layer (A) and adhesive layer (B) were as shown in Tables 6 to 8, an adhesive tape was prepared and various measurements were performed in the same manner as in Example 30. The results are shown in Tables 6 to 8.

[0097] (Examples 35 to 37, 45 to 46) In the above-mentioned "(1) Preparation of adhesive tape," the types of separator (A), substrate, and separator (B), as well as the composition and thickness of the adhesive layers (A) and (B), were as shown in Tables 6-8. Furthermore, after laminating the separator (A) shown in Tables 6-8, the adhesive tape with the replaced separator was placed in an oven set to 23°C and 50%RH and left to stand for 168 hours under the conditions of 23°C and 50%RH. Except for these conditions, the adhesive tape was prepared in the same manner as in Example 30, and various measurements were performed. The results are shown in Tables 6-8.

[0098] (Example 47) In the above-described "(1) Preparation of adhesive tape," the separator (A), substrate, and type of separator (B), as well as the composition and thickness of the adhesive layer (A) and adhesive layer (B), were changed as shown in Table 8. Furthermore, the adhesive layer (A) was formed without electron beam irradiation. Except for these changes, the adhesive tape was prepared in the same manner as in Example 30, and various measurements were performed. The results are shown in Table 8.

[0099] The types of separators shown in Tables 6-8 are as follows: • Separator A: SP8001 (manufactured by Toyo Cloth Co., Ltd.) • Separator B: SP3030 (manufactured by Toyo Cross Co., Ltd.) • Separator C: RF2 PET50cs14EX (manufactured by I'm Co., Ltd.) • Separator D: Therapeuil MDA (manufactured by Toray Industries, Inc.) • Separator E: MRQ75 (manufactured by Mitsubishi Chemical Corporation) • Separator F: SP3000 (manufactured by Toyo Cross Co., Ltd.) • Separator G: SP1007 (manufactured by Toyo Cross Co., Ltd.) • Separator H: SP4020 (manufactured by Toyo Cross Co., Ltd.) • Separator I: SP4030 (manufactured by Toyo Cross Co., Ltd.) • Separator J: MRV75 (V06) (manufactured by Mitsubishi Chemical Corporation) • Separator K: MRV100 (VOC) (manufactured by Mitsubishi Chemical Corporation) Note that none of the separators shown in Tables 6-8 contain fluorine components that would qualify as PFAS.

[0100] <Rating> The adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 2 to 9.

[0101] (Adhesion strength to silicone-based substrates) A 50mm x 125mm SUS304 plate surface was cleaned with ethanol and then wiped dry. A film adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767") having a silicone adhesive layer on one side was cut to a size of 30mm in width and 70mm in length. After peeling off the separator on the side of the adhesive layer that was not the silicone adhesive layer, this adhesive layer (the adhesive layer that was not the silicone adhesive layer) was attached to the SUS304 plate. Furthermore, the separator on the side of the silicone adhesive layer was peeled off, exposing the silicone adhesive layer. A 1mm thick silicone rubber (manufactured by Togawa Rubber Co., Ltd., "K-125(50)") cut to a size of 30mm in width and 70mm in length was attached to the silicone adhesive layer to create a silicone-based adherend. The obtained adhesive tape was cut to a size of 25 mm in width and 70 mm in length. The separator (separator (B) in Examples 30-47) was peeled off from one side of the cut adhesive tape, and one side of the adhesive tape was bonded to the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film to form a backing. The separator (separator (A) in Examples 30-47) was peeled off from the other side of the backed adhesive tape, and it was bonded to the silicone rubber surface of the silicone-based adherend. A 2 kg roller was then used to press it down by making one back-and-forth motion at a speed of 300 mm / min, and the sample was left to stand for 72 hours in an atmosphere of 23°C and 50% RH to prepare the measurement sample. For the prepared measurement samples, the adhesive tape was peeled from the silicone substrate using a tensile testing machine (Shimadzu Corporation, "AG-IS") in accordance with JIS Z0237, under conditions of 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°, and the 180° peel force (N / 25 mm) was measured. Using the obtained 180° peel force, the adhesive strength of the adhesive tape to the silicone substrate was determined according to the following criteria. ◎: The 180° peeling force was 3.0 N / 25 mm or higher. ○: The 180° peeling force was 2.0 N / 25 mm or more, and less than 3.0 N / 25 mm. ×: The 180° peeling force was less than 2.0 N / 25 mm. In Comparative Example 4, the adhesive tape could not be adhered to the silicone substrate, and therefore the 180° peel force could not be measured. Consequently, the 180° peel force (N / 25mm) for silicone rubber in Table 5 is indicated as "-".

[0102] (High temperature holding power) Figure 2 shows a schematic diagram illustrating the method of the high-temperature retention test. First, in accordance with JIS Z-1528, the obtained adhesive tape was cut to a width of 25 mm and a length of 60 mm to prepare test piece 5. After peeling off the separator (separator (B) in Examples 30-47) from one side of test piece 5, the exposed adhesive layer (adhesive layer (B) in Examples 30-47) was backed with polyethylene terephthalate (PET) film 4. After peeling off the separator (separator (A) in Examples 30-47) from the other side of test piece 5, the exposed adhesive layer (adhesive layer (A) in Examples 30-47) was bonded at 23°C to a cold-rolled stainless steel plate (SUS304 plate cleaned with ethanol and wiped dry) 6 with a thickness of 2.0 mm, a width of 50 mm, and a length of 75 mm. The length of the bonded bond was 25 mm, and the test piece 5 was offset in the length direction so that it extended beyond the edge of the SUS304 plate 6. Then, a 2 kg roller was passed back and forth once to press the bond and prepare a measurement sample. The measurement sample was left to stand for 20 minutes in an atmosphere of 23°C and 50% RH. Then, a 1 kg weight 7 was attached to the measurement sample in an environment of 80°C so that a shear load was applied to the measurement sample. The time when the weight 7 was attached was taken as the start time (0 hours), and the load from the weight 7 was maintained for 1 hour to perform a high-temperature holding test. The presence or absence of test piece 5 was checked, and if it did not fall after 1 hour, the amount of displacement (scatter) from the starting position was measured using a scale magnifier. The high-temperature holding power of the adhesive tape was evaluated based on the following criteria. ◎: The displacement of the test specimen was 0.1 mm or less. ○: The displacement of the test specimen was greater than 0.1 mm and less than or equal to 0.5 mm. △: The test specimen did not fall if its displacement was greater than 0.5 mm. ×: The test specimen fell during the high-temperature retention test. Even if the evaluation is "×", the adhesive tape described herein can still be used without problems depending on the application.

[0103] (Coating properties) In the above-mentioned "(1) Preparation of adhesive tape," the coatability was evaluated according to the following criteria, starting from the step of applying the obtained adhesive solution to the separator (for Examples 30 to 47, the step of applying the adhesive solution that forms the adhesive layer (A) to the separator (A)). ○: The coating process was completed without any problems. △: Although coating was possible, clouding, streaks, etc., occurred in the coated layer. ×: It was not possible to apply the coating.

[0104] (Ease of separator removal) For Examples 30-47 in Tables 6-8, the obtained adhesive tape was cut to a size of 25 mm in width and 70 mm in length. The separator (B) was peeled off the cut adhesive tape, and the exposed adhesive surface was attached to a 50 mm x 125 mm SUS304 plate whose surface had been washed with ethanol and then wiped dry. The sample was then left to stand for 72 hours in an atmosphere of 23°C and 50% RH to prepare a measurement sample. For the prepared measurement samples, the separator (A) was peeled off the adhesive tape using a tensile testing machine (Shimadzu Corporation, "AG-IS") in accordance with JIS Z0237, under conditions of 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°, and the 180° peel force (N / 25 mm) was measured. Using the obtained 180° peel force, the ease of peeling the separator from the adhesive tape was determined according to the following criteria. ◎: The 180° peeling force was 0.50 N / 25 mm or less. ○: The 180° peeling force was greater than 0.50 N / 25 mm and less than or equal to 1.00 N / 25 mm. ×: The 180° peeling force was greater than 1.00 N / 25 mm. Even if the evaluation is "×", the adhesive tape described herein can still be used without problems depending on the application.

[0105] [Table 2]

[0106] [Table 3]

[0107] [Table 4]

[0108] [Table 5]

[0109] [Table 6]

[0110] [Table 7]

[0111] [Table 8]

[0112] [Table 9] [Industrial applicability]

[0113] According to this disclosure, it is possible to provide an adhesive tape that can exhibit excellent adhesion to silicone-based substrates without the use of silicone-based adhesives or prior surface treatment of the substrate. Furthermore, according to this disclosure, it is possible to provide a laminate having a structure to which the adhesive tape is attached. Moreover, according to this disclosure, it is possible to provide an electronic device including the adhesive tape. [Explanation of Symbols]

[0114] 1 Adhesive tape 2. Components containing silicone resin 3 Other components 4. Polyethylene terephthalate (PET) film 5 Test specimens 6 SUS304 plate 7 Weight (1kg)

Claims

1. An adhesive tape having an adhesive layer containing a (meth)acrylic copolymer and not containing a silicone-based adhesive, A laminate formed by bonding the aforementioned adhesive tape to silicone rubber fixed to a SUS304 plate was left standing for 72 hours in an environment of 23°C and 50% RH. Then, a peel test was performed using a tensile testing machine under the conditions of 23°C, 50% RH, and a peeling speed of 300 mm / min, in which the adhesive tape in the laminate was peeled 180° from the silicone rubber. After the peel test, the surface of the silicone rubber on the side from which the adhesive tape was peeled was washed at least eight times with ethyl acetate. Then, TOF-SIMS measurement was performed on the washed surface, and the peak intensity of negative ions in the region of m / z 26 (26 / total) relative to the total peak intensity of all negative ions (total) was found to be 2.50 × 10⁻⁶. －３ That's all. Used to bond silicone-based substrates. An adhesive tape characterized by the following features.

2. The adhesive layer contains component A, which comprises at least one selected from a silane coupling agent having an aliphatic amino group, a silane coupling agent having a skeleton with a protected aliphatic amino group, a compound having a structure derived from a silane coupling agent having an aliphatic amino group, and a compound having a structure derived from a silane coupling agent having a protected aliphatic amino group. The content of component A relative to 100 parts by mass of the (meth)acrylic copolymer is 8.0 parts by mass or less. The adhesive tape according to claim 1.

3. The adhesive tape according to claim 2, wherein the content of component A relative to 100 parts by mass of the (meth)acrylic copolymer is 1.5 parts by mass or more.

4. The adhesive tape according to claim 3, wherein the content of component A per 100 parts by mass of the (meth)acrylic copolymer is greater than 3.0 parts by mass.

5. The adhesive tape according to claim 2, 3, or 4, wherein at least one of the aliphatic amino groups in component A is a primary aliphatic amino group or a secondary aliphatic amino group having an acyclic structure.

6. The (meth)acrylic copolymer has constituent units derived from alkyl (meth)acrylate esters, The constituent units derived from the alkyl (meth)acrylate do not contain constituent units derived from alkyl (meth)acrylate with two or fewer carbon atoms in the alkyl group at the ester terminal, or the constituent units derived from alkyl (meth)acrylate have constituent units derived from alkyl (meth)acrylate with two or fewer carbon atoms in the alkyl group at the ester terminal, and the content of constituent units derived from alkyl (meth)acrylate with two or fewer carbon atoms in the alkyl group at the ester terminal in the constituent units derived from alkyl (meth)acrylate is 25% by mass or less. The adhesive tape according to claim 1, 2, 3, or 4.

7. The constituent unit derived from the alkyl (meth)acrylate has a constituent unit derived from the alkyl (meth)acrylate, The adhesive tape according to claim 1, 2, 3, or 4, having a constituent unit derived from an alkyl (meth)acrylate ester having 7 carbon atoms in the alkyl group at the ester terminus.

8. The adhesive tape according to claim 1, 2, 3, or 4, wherein the (meth)acrylic copolymer does not have constituent units derived from a carboxyl group-containing monomer.

9. The adhesive tape according to claim 1, 2, 3, or 4, wherein the adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet irradiation.

10. The adhesive tape according to claim 1, 2, 3, or 4, wherein the adhesive layer contains a radical generator.

11. The adhesive tape according to claim 1, 2, 3, or 4, wherein the adhesive layer has a gel fraction of 35% by mass or more.

12. The adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet irradiation. The adhesive layer has a gel fraction of 35% by mass or more. The adhesive tape according to claim 1, 2, 3, or 4.

13. Furthermore, it has a separator, The adhesive tape according to claim 1, 2, 3, or 4, wherein the release layer of the separator does not contain an organofluorine compound.

14. Furthermore, it has a separator, The adhesive tape according to claim 1, 2, 3, or 4, wherein the relative intensity of the peak at 103.9 eV is 0.170 or less when the surface of the peel interface between the separator and the adhesive layer is measured by XPS after peeling the separator 180° from the adhesive layer in an environment of 23°C and 50% RH.

15. The adhesive tape according to claim 1, 2, 3, or 4, wherein the silicone-based adherend is an electronic device component, a vehicle component, a building component, or a medical component.

16. A laminate comprising a structure in which the adhesive tape according to claim 1, 2, 3, or 4 is attached to a silicone-based substrate.

17. An electronic device comprising the adhesive tape described in claim 1, 2, 3, or 4.

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