Adhesive tape, laminate, and electronic device

Abstract

An object of the present disclosure is to provide an adhesive tape capable of exerting excellent adhesive force on a silicone-based adherend. The present disclosure relates to an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer, for which, when the adhesive tape is attached to a laminate of a silicone rubber fixed to a SUS 304 plate, after standing for 72 hours in an environment of 23°C, 50% RH, a peeling test of peeling the adhesive tape from the silicone rubber at 180° is performed on the laminate using a tensile testing machine under conditions of 23°C, 50% RH, and a peeling speed of 300 mm / min, and after the peeling test, the surface of the side of the silicone rubber from which the adhesive tape was peeled is cleaned with ethyl acetate at least 8 times, and then TOF-SIMS measurement is performed on the cleaned surface, the peak intensity of negative ions in the region of m / z 26 relative to the total peak intensity of all negative ions (26 / total) at this time is 2.50 x 10 ‑3 or less. The above.

Description

Technical Field

[0001] This disclosure relates to adhesive tape. Furthermore, this disclosure relates to laminates having a structure to which the adhesive tape is attached and to electronic devices comprising the adhesive tape. Background Technology

[0002] Adhesive tape is widely used in a variety of fields, such as for assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), or for fixing automotive electronic device components such as automotive panels to the vehicle body (e.g., Patent Documents 1 and 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-242541

[0006] Patent Document 2: Japanese Patent Application Publication No. 2009-258274 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In recent years, influenced by the trend of PFAS (perfluoroalkyl and polyfluoroalkyl compounds) restrictions, there has been a movement to reduce the use of fluoropolymers in the assembly and fixing of electronic devices. Organosilicon materials can be cited as an alternative to fluorinated materials characterized by low surface energy. For low-surface-energy organosilicon materials, when using adhesive tapes with high-surface-energy urethane adhesives, acrylic adhesives, hydrocarbon adhesives, etc., as the adhesive layer, insufficient interfacial adhesion is a common reason for using silicone adhesive tapes as the adhesive layer when bonding organosilicon materials.

[0009] However, the current situation is that in adhesive tapes with silicone-based adhesives as the adhesive layer, spacers that protect the adhesive layer must be used to facilitate peeling from the silicone-based adhesive. These spacers have a release layer containing fluororesin.

[0010] On the other hand, when bonding silicone materials, if an adhesive tape with an adhesive other than silicone-based adhesive is used as the adhesive layer, the surface of the silicone material to be bonded needs to be treated with corona treatment, primer treatment, etc. From the point of view, there are problems such as reduced work efficiency and the need for additional equipment.

[0011] Therefore, there is a challenge in designing adhesive tapes that do not contain fluorine resins and can firmly bond silicone materials without prior surface treatment.

[0012] The purpose of this disclosure is to provide an adhesive tape that exhibits excellent adhesion to silicone-based substrates without prior surface treatment, even without the use of silicone-based adhesives. Furthermore, the purpose of this disclosure is to provide a laminate having the adhesive tape attached to it. Additionally, the purpose of this disclosure is to provide an electronic device incorporating the adhesive tape.

[0013] Methods for solving problems

[0014] This disclosure 1 relates to an adhesive tape having an adhesive layer containing a (meth)acrylic acid copolymer. For a laminate formed by bonding the adhesive tape to a silicone rubber substrate fixed to an SUS304 board, after standing for 72 hours at 23°C and 50% RH, a peel test is performed using a tensile testing machine at 23°C, 50% RH, and a peel speed of 300 mm / min, peeling the adhesive tape from the silicone rubber substrate at 180°. After the peel test, the surface of the silicone rubber substrate on the side where the adhesive tape was peeled off is cleaned with ethyl acetate at least eight times. TOF-SIMS analysis is then performed on the cleaned surface. The peak intensity (26 / total) of the negative ions in the region with m / z of 26 relative to the total peak intensity of all negative ions is 2.50 × 10⁻⁶. -3 above.

[0015] This disclosure 2 relates to an adhesive tape having an adhesive layer containing a (meth)acrylic acid copolymer, the adhesive layer containing component A, said component A comprising at least one selected from a silane coupling agent having an aliphatic amino group, a silane coupling agent having a backbone protected by an 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 backbone protected by an aliphatic amino group, wherein the content of said component A is 8.0 parts by weight or less relative to 100 parts by weight of the (meth)acrylic acid copolymer.

[0016] This disclosure 3 relates to the adhesive tape of this disclosure 2, wherein the content of component A is 1.5 parts by mass or more relative to 100 parts by mass of the (meth)acrylic copolymer.

[0017] This disclosure 4 relates to the adhesive tape of this disclosure 3, wherein the content of component A is greater than 3.0 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer.

[0018] This disclosure 5 relates to adhesive tapes of disclosures 2, 3 or 4, wherein, in component A, at least one of the aliphatic amino groups is an aliphatic primary amino group or an aliphatic secondary amino group with a non-cyclic structure.

[0019] This disclosure 6 relates to adhesive tapes of disclosures 1, 2, 3, 4 or 5, wherein the aforementioned (meth)acrylate copolymers have structural units derived from alkyl (meth)acrylates, wherein the structural units derived from alkyl (meth)acrylates do not have structural units derived from alkyl (meth)acrylates with 2 or fewer carbon atoms in the alkyl group at the ester terminus, or wherein the structural units derived from alkyl (meth)acrylates have structural units derived from alkyl (meth)acrylates with 2 or fewer carbon atoms in the alkyl (meth)acrylates, and the content of the structural units derived from alkyl (meth)acrylates with 2 or fewer carbon atoms in the alkyl (meth)acrylates is 25% by mass or less.

[0020] This disclosure 7 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5 or 6, wherein the aforementioned structural units derived from alkyl (meth)acrylates have structural units derived from alkyl (meth)acrylates and have structural units of alkyl (meth)acrylates with 7 carbon atoms derived from the alkyl group at the ester terminus.

[0021] This disclosure 8 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5, 6 or 7, wherein the aforementioned (meth)acrylic acid copolymers do not have structural units derived from carboxyl-containing monomers.

[0022] This disclosure 9 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5, 6, 7 or 8, wherein the adhesive layer contains components that are cross-linked by electron beam irradiation or ultraviolet irradiation.

[0023] This disclosure 10 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein the adhesive layer contains a free radical generating agent.

[0024] This disclosure 11 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the gel content of the adhesive layer is 35% by mass or more.

[0025] This disclosure 12 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the adhesive layer contains a component that is cross-linked by electron beam irradiation or ultraviolet irradiation, and the gel content of the adhesive layer is 35% by mass or more.

[0026] This disclosure 13 relates to an adhesive tape of disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, which further comprises a spacer, wherein the release layer of the spacer is free of organofluorine compounds.

[0027] This disclosure 14 relates to an adhesive tape of disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13, which further comprises a spacer obtained by peeling the spacer from the adhesive layer at 180° in an environment of 23°C and 50%RH. XPS measurement is performed on the surface of the peel interface between the spacer and the adhesive layer, and the relative intensity of the peak at 103.9 eV is 0.170 or less.

[0028] This disclosure 15 relates to adhesive tapes of disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, for bonding silicone-based substrates.

[0029] This disclosure 16 relates to the adhesive tape of this disclosure 15, wherein the aforementioned silicone-based adherend is an electronic device component, a vehicle component, a building component, or a medical component.

[0030] This disclosure 17 relates to a laminate comprising a structure formed by attaching an adhesive tape of disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16 to a silicone-based adherend.

[0031] This disclosure 18 relates to an electronic device comprising the adhesive tape of disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16.

[0032] This disclosure 19 relates to an adhesive tape having a spacer and an adhesive layer containing a (meth)acrylic acid copolymer. The spacer is obtained by peeling it 180° from the adhesive layer at 23°C and 50%RH. XPS measurement is performed on the surface of the peel interface between the spacer and the adhesive layer, and the relative intensity of the peak at 103.9 eV is 0.170 or less.

[0033] The following is a detailed description of this disclosure.

[0034] The inventors investigated the mass-to-charge ratio of the surface of a silicone-based adherend after it was peeled off from an adhesive tape containing an adhesive layer of (meth)acrylic acid copolymer. The results showed that by achieving a specific mass-to-charge ratio, an adhesive tape exhibiting excellent adhesion to silicone-based adherends without prior surface treatment could be obtained, even without the use of a silicone-based adhesive. This led to the completion of this disclosure.

[0035] Regarding the adhesive tape of the present disclosure, for the laminate formed by attaching the above-mentioned adhesive tape to the silicone rubber fixed to the SUS304 plate, after standing for 72 hours in an environment of 23°C and 50% RH, using a tensile testing machine, under the conditions of 23°C, 50% RH, and a peeling speed of 300 mm / min, a peeling test is performed to peel the above-mentioned adhesive tape in the laminate from the silicone rubber at 180°. For the surface of the silicone rubber on the side from which the adhesive tape has been peeled after the peeling test, the surface is washed at least 8 times with ethyl acetate, and then TOF-SIMS measurement is performed on the washed surface. At this time, the peak intensity of the negative ions in the region where m / z is 26 with respect to the peak intensity (total) of all negative ions (26 / total) (hereinafter, sometimes simply referred to as "the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape.") has a lower limit of 2.50×10 -3 . By making the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape 2.50×10 -3 or more, the adhesive tape of the present disclosure can exhibit excellent adhesive force to the silicone-based adherend without using a silicone-based adhesive and without pre-treating the surface of the adherend. The preferred lower limit of the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape is 2.60×10 -3 , and the more preferred lower limit is 2.70×10 -3 .

[0036] In addition, the preferred upper limit of the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape is 4.00×10 -2 . By making the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape 4.00×10 -2 or less, it becomes possible to avoid the cohesive failure of the adhesive remaining on the adherend and ensure the bulk strength (Japanese: バルク強度) generally required for the adhesive tape. The more preferred upper limit of the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape is 3.50×10 -2 , and the further preferred upper limit is 3.00×10 -2 .

[0037] It should be noted that in this specification, the "peak of the negative ions in the region where m / z is 26" refers to the peak detected within the range of m / z from 25.986 to 26.050.

[0038] It should be noted that the relative intensity of the peak of the negative ions in the region where m / z is 26 after peeling the adhesive tape can be measured by the following method.

[0039] First, the surface of a 50mm × 125mm SUS304 board is cleaned with ethanol and then dry-rubbed. A film adhesive tape (manufactured by Teraoka Seisakusho, "767") with a silicone adhesive layer on one side and a non-silicone adhesive layer on the other side is cut to a size of 30mm wide and 70mm long. After peeling off the spacers on the non-silicone adhesive layer side, the adhesive layer is attached to the SUS304 board. The spacers on the silicone adhesive layer side are then further peeled off to expose the silicone adhesive layer. A piece of silicone rubber ("manufactured by Togawa Rubber Co., Ltd., K-125 (50)") cut to a size of 30mm wide and 70mm long and 1mm thick is attached to the silicone adhesive layer to create a silicone-based adhesive.

[0040] The adhesive tape of this disclosure is cut into pieces 25 mm wide and 70 mm long. The spacer on one side of the cut adhesive tape is peeled off, and one side of the adhesive tape is backed with a corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film. The spacer on the other side of the backed adhesive tape is peeled off, and the tape is adhered to the silicone rubber surface of the aforementioned silicone-based substrate. A 2 kg roller is used to press the tape back and forth once at a speed of 300 mm / min. The laminate is then left to stand at 23°C and 50% RH for 72 hours to produce a laminate. The laminate is then subjected to a peel test according to JIS Z0237 using a tensile testing machine (Shimadzu Corporation, "AG-IS") at 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°, to test the peeling of the adhesive tape from the aforementioned silicone-based substrate. Then, for the silicone rubber in the above-mentioned organosilicon adhesive after the peel test, the surface of the side from which the adhesive tape was peeled off was cleaned with ethyl acetate at least 8 times, and the cleaned surface was subjected to TOF-SIMS measurement. The obtained spectral data was analyzed to obtain the peak intensity of negative ions in the region of m / z 26 relative to the total peak intensity of all negative ions (26 / total).

[0041] The washing process using ethyl acetate and the TOF-SIMS determination can be carried out using the following methods.

[0042] It should be noted that during the following operations, care should be taken not to contaminate the silicone rubber surface after the adhesive tape has been peeled off. Additionally, in peel tests using a tensile testing machine, when peeling the adhesive tape from the silicone-based adherend, the area where the adhesive and silicone-based adherend show a visible interface separation is designated as the area to be measured by TOF-SIMS. It should be noted that if cohesive failure occurs in the adhesive layer across the entire peeled surface, the area of ​​cohesive failure can be exposed to liquid nitrogen to allow it to cool and solidify. The cohesive failure adhesive layer can then be removed using metal tweezers or a spatula. This removal process is repeated until the silicone-based adherend rubber surface is visually exposed; this area is designated as the area to be measured by TOF-SIMS.

[0043] (Cleaning operation)

[0044] First, peel the membrane adhesive tape with the silicone adhesive layer from the silicone rubber. There are no restrictions on the peeling method; a speed of approximately 300 mm / min and a peeling angle of approximately 90° can be adjusted, and the peeling can be done by hand. After peeling the membrane adhesive tape with the silicone adhesive layer from the silicone rubber, cut the obtained silicone rubber into approximately 1 cm squares using a cutter or scissors to prepare the test sample. Place the test sample against the adhesive tape of this disclosure on the surface of the ethyl acetate solution in an aluminum cup with an inner diameter of 5 cm containing 2 mL of ethyl acetate. Shake the sample 80 times at a distance of 1 cm within 1 minute, thereby cleaning it with ethyl acetate (i). At this time, you can insert a needle into the back of an area unrelated to the test and shake it, or use tweezers. Alternatively, if it is difficult to handle the sample while shaking because it is in contact with the bottom of the aluminum cup, additional ethyl acetate can be added. Prepare another aluminum cup with an inner diameter of 5 cm containing 2 mL of ethyl acetate, perform the same cleaning again, and then heat the test sample in an oven at 80°C for 10 minutes (ii). Set up operations (i) and (ii) above as one group, and perform a total of four or more groups. It should be noted that a new aluminum cup and ethyl acetate should be used each time operations (i) and (ii) are performed.

[0045] (TOF-SIMS measurement)

[0046] TOF-SIMS measurements can be performed using a time-of-flight secondary ion mass spectrometer (ION-TOF, "TOF.SIMS5", etc.), under the following conditions. The value is obtained by calculating the sum (area) of the peaks of negative ions in the region with m / z 26, divided by the sum (area) of all negative ion peaks, based on the obtained secondary ion spectrum.

[0047] <Measurement conditions for TOF-SIMS>

[0048] Primary ion types: Bi3++

[0049] Accelerating voltage: 25kV

[0050] • Detection of ion polarity: negative (negative ion)

[0051] • Measurement range: 500μm × 500μm

[0052] • Pixel count: 128×128 (pixels)

[0053] • Number of scans: 25

[0054] • Mass range (m / z): 0~850

[0055] The peak of negative ions in the region of m / z 26 mainly contains CN. ― The peak of the quality. Therefore, as a method to adjust the relative intensity of the negative ion peak in the region of m / z 26 after the adhesive tape is peeled off, for example, the following methods can be used: adding component A, etc., as described later, to the adhesive layer; changing the amount or structure of component A; adding an amine-modified organosilicon compound; changing the composition of the (meth)acrylic copolymer of the adhesive layer, etc.

[0056] The adhesive tape disclosed herein has an adhesive layer containing an acrylic copolymer. It should be noted that, in this specification, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.

[0057] The above-mentioned (meth)acrylic acid copolymers preferably have structural units derived from alkyl (meth)acrylic acid esters (hereinafter, sometimes simply referred to as "structural unit (a)").

[0058] Examples of the aforementioned alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, cyclohexyl methacrylate, n-heptyl methacrylate, isoheptyl methacrylate, and 2-ethylhexyl methacrylate. Octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, isobornyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, stearyl methacrylate, isostearyl methacrylate, docosyl methacrylate, etc. Among these, from the viewpoint of improving the wettability of low surface energy organosilicon-based adhesives, structural units of alkyl methacrylates with 3 or more carbon atoms derived from the ester terminus are preferred. From the viewpoint of avoiding reduced cohesive strength and crystallinity interactions that lead to decreased adhesive strength, structural units of alkyl methacrylates with 22 or fewer carbon atoms derived from the ester terminus are preferred. The more preferred lower limit for the number of carbon atoms in the alkyl group at the ester terminus is 4, the more preferred upper limit is 18, the further preferred upper limit is 16, the even more preferred upper limit is 12, the particularly preferred upper limit is 10, and the most preferred upper limit is 8. From the viewpoint of easily ensuring a balance between adhesive force and cohesive force on the silicone adherend, the above-mentioned (meth)acrylate copolymer preferably has a structural unit derived from an alkyl (meth)acrylate with 7 carbon atoms in the alkyl group at the ester terminus.

[0059] It should be noted that these (meth)acrylate alkyl esters can be used alone or in combination of two or more.

[0060] In addition, "ester-terminal alkyl" in this specification refers to an alkyl group that is directly bonded to the oxygen atom of the ester bond.

[0061] Preferably, the structural unit (a) does not have a structural unit of an alkyl methacrylate (hereinafter sometimes simply referred to as "structural unit (a-1)") derived from an alkyl group at the ester terminus, having 2 or fewer carbon atoms; or, the structural unit (a) has the structural unit (a-1), and the content of the structural unit (a-1) in the structural unit (a) is 25% by mass or less. By making the structural unit (a) not have the structural unit (a-1), or having the structural unit (a-1) and the content of the structural unit (a-1) in the structural unit (a) is 25% by mass or less, the adhesive strength of the adhesive tape of this disclosure to silicone-based adherends is further improved.

[0062] The preferred upper limit of the proportion of the above structural unit (a-1) in 100% by mass of the above structural unit (a) is 20% by mass, the further preferred upper limit is 15% by mass, the even more preferred upper limit is 10% by mass, and the most preferred upper limit is that the above structural unit (a) does not have the above structural unit (a-1).

[0063] The preferred lower limit for the content of the above-mentioned structural unit (a) in the (meth)acrylic copolymer is 50% by mass. By making the content of the above-mentioned structural unit (a) 50% by mass or more, the adhesive force of the adhesive tape of this disclosure on silicone-based substrates is further improved.

[0064] In addition, the content of the above structural unit (a) can be 100% by mass, that is, the above (meth)acrylic acid copolymer can be composed only of the above structural unit (a), but from the viewpoint that it is preferable to include structural units derived from monomers containing polar groups described later in order to improve adhesion and holding power, the preferred upper limit is 99.9% by mass.

[0065] The aforementioned (meth)acrylic acid copolymers may, without impairing the effects of this disclosure, have at least one structural unit selected from structural units derived from hydroxyl-containing monomers, structural units derived from amino-containing monomers, structural units derived from amide-containing monomers (excluding N,N-disubstituted amide skeletons), structural units derived from alkenyl-containing monomers, and structural units derived from alkynyl-containing monomers (hereinafter, these structural units are sometimes simply referred to as "structural unit (b)"). By giving the aforementioned (meth)acrylic acid copolymers the aforementioned structural unit (b), the polarity of the aforementioned adhesive layer is increased, the cohesive force is further increased, and therefore the adhesive force is improved, as is the high-temperature retention force. Furthermore, when a cross-linked structure is formed by chemically cross-linking the aforementioned functional groups such as hydroxyl, amino, amide, alkenyl, and alkynyl groups, the cohesive force of the aforementioned adhesive layer is further increased, thereby further improving the adhesive force and retention force. From the viewpoints of avoiding reactions with silane coupling agents containing aliphatic amino groups or silane coupling agents with a backbone of aliphatic amino groups protected, ensuring the coatability of the adhesive solution, and the stability of the adhesive layer over time, the above-mentioned (meth)acrylic acid copolymers preferably have structural units derived from monomers containing hydroxyl groups, monomers containing amino groups, and monomers containing amide groups (except for N,N-disubstituted amide backbones).

[0066] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxyisopropyl methacrylate, and 4-hydroxybutyl methacrylate.

[0067] Examples of amino-containing monomers include 2-dimethylaminoethyl (meth)acrylate and N-{3-(dimethylamino)propyl}acrylamide.

[0068] Examples of monomers containing amide groups (excluding N,N-disubstituted amide skeletons) 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.

[0069] When the aforementioned (meth)acrylic acid copolymer has the aforementioned structural unit (b), the preferred upper limit for the total content of the aforementioned structural unit (b) in the aforementioned (meth)acrylic acid copolymer is 20% by mass. By making the total content of the aforementioned structural unit (b) 20% by mass or less, the polarity of the aforementioned adhesive layer is further reduced, thereby reducing the surface energy of the adhesive layer and further improving the adhesion to the silicone-based adhesive. In addition, the reaction with silane coupling agents having aliphatic amino groups or silane coupling agents having a backbone protected by aliphatic amino groups can be suppressed to a minimum, ensuring the coatability of the adhesive solution and the stability of the adhesive layer over time. The more preferred upper limit for the total content of the aforementioned structural unit (b) is 15% by mass, the more preferred upper limit is 10% by mass, the even more preferred upper limit is 5.0% by mass, and the particularly preferred upper limit is 1.0% by mass.

[0070] Furthermore, there is no particular limitation on the lower limit of the total content of the above-mentioned structural unit (b) in the (meth)acrylic copolymer; it can be 0% by mass or greater than 0% by mass. When the lower limit of the total content of the above-mentioned structural unit (b) is greater than 0% by mass, it is, for example, 0.1% by mass.

[0071] It should be noted that the total proportion of the above-mentioned structural unit (b) in the above-mentioned (meth)acrylic acid copolymer can be specifically categorized as follows: 0% or more and 20% or less by mass, 0% or more and 15% or less by mass, 0% or more and 10% or less by mass, 0% or more and 5.0% or less by mass, 0% or more and 1.0% or less by mass, 0.1% or more and 20% or less by mass, 0.1% or more and 15% or less by mass, 0.1% or more and 10% or less by mass, 0.1% or more and 5.0% or less by mass, 0.1% or more and 1.0% or less by mass, etc.

[0072] The aforementioned (meth)acrylic acid copolymers can have structural units derived from carboxyl-containing monomers without impairing the effects of this disclosure. By giving the aforementioned (meth)acrylic acid copolymers structural units derived from carboxyl-containing monomers, the polarity of the adhesive layer is increased, the cohesive force is further increased, and therefore the adhesive strength and high-temperature retention strength are also improved. Furthermore, when a cross-linked structure is formed by chemically cross-linking the aforementioned functional groups, the cohesive force of the adhesive is further increased, thereby further improving the adhesive strength and retention strength.

[0073] Examples of the aforementioned carboxyl-containing monomers include (meth)acrylic acid and 2-acryloyloxyethyl succinate.

[0074] When the aforementioned (meth)acrylic acid copolymers contain structural units derived from carboxyl-containing monomers, the proportion of these structural units in the (meth)acrylic acid copolymer is preferably less than 1.0% by mass. By keeping the proportion of these structural units less than 1.0% by mass, the reaction with silane coupling agents containing aliphatic amino groups or silane coupling agents with a backbone protected by aliphatic amino groups can be minimized, ensuring the coatability of the adhesive solution and the stability of the adhesive layer over time. It should be noted that when acrylic acid is 1.0% by mass, the viscosity increases rapidly when a silane coupling agent containing aliphatic amino groups is added to the acrylic acid copolymer solution, making it substantially difficult to form an adhesive layer suitable for evaluation. A more preferred upper limit for the proportion of structural units derived from carboxyl-containing monomers is 0.5% by mass, a more preferred upper limit is 0.3% by mass, a more preferably upper limit is 0.1% by mass, a particularly preferred upper limit is 0.05% by mass, and most preferably, the aforementioned (meth)acrylic acid copolymer does not contain any structural units derived from carboxyl-containing monomers.

[0075] The aforementioned (meth)acrylic acid copolymers may have structural units derived from monomers containing N,N-disubstituted amide groups, to a extent that does not impair the effects of this disclosure. By giving the aforementioned (meth)acrylic acid copolymers structural units derived from monomers containing N,N-disubstituted amide groups, the polarity of the aforementioned adhesive layer is increased, the cohesive force is further increased, and therefore the adhesive strength and high-temperature retention strength are also improved.

[0076] Examples of monomers containing N,N-disubstituted amide groups 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.

[0077] The preferred lower limit for the total content of structural units derived from monomers containing N,N-disubstituted amide groups in the above-mentioned (meth)acrylic acid copolymers is 3.0% by mass, and the preferred upper limit is 50% by mass. By making the content of structural units derived from monomers containing N,N-disubstituted amide groups 3.0% by mass or more, the cohesive strength of the above-mentioned adhesive can be further improved, and the adhesive strength and high-temperature holding strength of the adhesive tape disclosed herein can be further improved. By making the content of structural units derived from monomers containing N,N-disubstituted amide groups 50% by mass or less, the decrease in initial adhesion and adhesive strength due to excessive increase in cohesive strength can be suppressed. The more preferred lower limit for structural units derived from monomers containing N,N-disubstituted amide groups is 5.0% by mass, the more preferred lower limit is 10% by mass, the even more preferred lower limit is 15% by mass, the more preferred upper limit is 45% by mass, the even more preferred upper limit is 40% by mass, and the even more preferred upper limit is 35% by mass.

[0078] The aforementioned (meth)acrylic acid copolymers may have structural units other than the aforementioned structural unit (a), the aforementioned structural unit (b), the aforementioned structural unit derived from a carboxyl-containing monomer, and the aforementioned structural unit derived from a monomer containing an N,N-disubstituted amide group, without impairing the effects of this disclosure.

[0079] The preferred lower limit for the weight-average molecular weight (Mw) of the aforementioned (meth)acrylic acid copolymer is 400,000, and the preferred upper limit is 2,000,000. By making the weight-average molecular weight (Mw) of the aforementioned (meth)acrylic acid copolymer 400,000 or more, the adhesive strength and holding power of the adhesive tape of this disclosure are further improved. By making the weight-average molecular weight (Mw) of the aforementioned (meth)acrylic acid copolymer 2,000,000 or less, the aforementioned adhesive layer does not become too hard, and the adhesive strength of the adhesive tape of this disclosure becomes higher. The more preferred lower limit for the weight-average molecular weight (Mw) of the aforementioned (meth)acrylic acid copolymer is 500,000, the further preferred lower limit is 600,000, the more preferred upper limit is 1,600,000, and the further preferred upper limit is 1,200,000.

[0080] Specifically, the weight-average molecular weight (Mw) of the aforementioned (meth)acrylic acid copolymers can be categorized into the following ranges: 400,000 or more and 2,000,000 or less; 400,000 or more and 1,600,000 or less; 400,000 or more and 1,200,000 or less; 500,000 or more and 2,000,000 or more and 1,600,000 or less; 500,000 or more and 1,200,000 or less; 600,000 or more and 2,000,000 or more; 600,000 or more and 1,600,000 or less; and 600,000 or more and 1,200,000 or less.

[0081] It should be noted that, in this specification, "weight-average molecular weight" refers to the weight-average molecular weight determined by gel permeation chromatography (GPC) in the form of polystyrene-converted molecular weight.

[0082] As a method for determining the weight-average molecular weight of the above-mentioned (meth)acrylic acid copolymers, specifically, for example, a Waters "2690 Separations Module" can be used as the measuring device, a Showa Denko "GPCKF-806L" can be used as the column, ethyl acetate can be used as the solvent, and the determination can be carried out at a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0083] The preferred lower limit for the content of the aforementioned (meth)acrylic acid copolymer in the adhesive layer is 50% by mass, and the preferred upper limit is 99.5% by mass. By making the content of the aforementioned (meth)acrylic acid copolymer 50% by mass or more, the general physical properties required by adhesives, such as adhesion and holding power, can be achieved. By making the content of the aforementioned (meth)acrylic acid copolymer 99.5% by mass or less, the amount of the component required for silicone bonding can be ensured, and sufficient silicone adhesive force can be achieved. The more preferred lower limit for the content of the aforementioned (meth)acrylic acid copolymer is 60% by mass, the more preferred upper limit is 99% by mass, the further preferred lower limit is 70% by mass, the further preferred upper limit is 98.5% by mass, the even more preferred lower limit is 75%, the even more preferred upper limit is 98% by mass, the particularly preferred lower limit is 80% by mass, and the particularly preferred upper limit is 97.5% by mass.

[0084] As a polymerization method for synthesizing the above-mentioned (meth)acrylic acid copolymers, conventionally known methods can be used, which involve subjecting the monomers that are the source of the above-mentioned structural units to a free radical reaction in the presence of a polymerization initiator. Examples include solution polymerization (boiling point polymerization or isothermal polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization is preferred from the perspective of ease of synthesis.

[0085] 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 can be used alone or in combination of two or more.

[0086] Examples of polymerization initiators include organic peroxides and azo compounds.

[0087] Examples of the aforementioned organic peroxides include: 1,1-bis(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, tert-hexyl peroxypentanoate, tert-butyl peroxypentanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, tert-butyl peroxy-3,5,5-trimethylhexanoate, and tert-butyl peroxylaurate.

[0088] Examples of the aforementioned azo compounds include azobisisobutyronitrile and azobiscyclohexaneformitrile.

[0089] These polymerization initiators can be used alone or in combination of two or more.

[0090] The adhesive layer described above preferably contains component A, which comprises at least one selected from the following: a silane coupling agent having an aliphatic amino group (hereinafter, sometimes also referred to as "component A-1"); a silane coupling agent having an aliphatic amino-protected backbone (hereinafter, sometimes also referred to as "component A-2"); a compound having a structure derived from a silane coupling agent having an aliphatic amino group (hereinafter, sometimes also referred to as "component A-3"); and a compound having a structure derived from a silane coupling agent having an aliphatic amino-protected backbone (hereinafter, sometimes also referred to as "component A-4"). By including component A in the adhesive layer described above, the adhesive strength of the adhesive tape of this disclosure to silicone-based adherends is further improved.

[0091] The degree of the aliphatic amino group in component A is not particularly limited. From the viewpoint that it is easy to exhibit adhesive force to silicone-based adhesives, at least one of the aliphatic amino groups in component A is preferably an aliphatic primary amino group or an aliphatic secondary amino group, more preferably an aliphatic primary amino group or an acyclic aliphatic secondary amino group, and even more preferably an aliphatic primary amino group.

[0092] It should be noted that in this specification, "aliphatic secondary amino group with non-cyclic structure" refers to aliphatic secondary amino groups in which the nitrogen atom in the amino group is not included in the cyclic structure.

[0093] In addition, the structure of the hydrocarbon chain that constitutes the aliphatic amino group is not particularly limited; it can be a straight chain, a branched chain, or a cyclic structure.

[0094] Furthermore, the alkoxysilyl group in component A can be one or more, and the alkoxysilyl group can be a monoalkoxysilyl group, a dialkoxysilyl group, or a trialkoxy group.

[0095] There are no particular limitations on the above-mentioned component A-1 as long as it is a silane coupling agent containing aliphatic amino groups. It can contain one or more aliphatic amino groups.

[0096] Furthermore, the degree of aliphatic amino groups in the above-mentioned component A-1 is not particularly limited. As mentioned above, from the viewpoint of easily exhibiting adhesive strength to silicone-based adhesives, it is preferable to include at least one aliphatic primary amino group and aliphatic secondary amino group, more preferably to include at least one aliphatic primary amino group and aliphatic secondary amino group with a non-cyclic structure, and even more preferably to include aliphatic primary amino group.

[0097] In addition, as mentioned above, the structure of the hydrocarbon chain constituting the aliphatic amino group is not particularly limited; it can be a straight chain, a branched chain, or a cyclic structure.

[0098] Furthermore, the structure of the hydrocarbon chain between the amino group and the alkoxysilyl group is not particularly limited. However, if the number of carbon atoms in the hydrocarbon chain is too small, the steric hindrance between the amino group and the alkoxysilyl group becomes large, making it difficult to exhibit organosilicon adhesive force. Therefore, the number of carbon atoms between the amino group and the alkoxysilyl group is preferably 3 or more. Additionally, there is no particular upper limit to the number of carbon atoms between the amino group and the alkoxysilyl group, but a preferred upper limit is 8. Specifically, propylene or octylene are preferred, and propylene is more preferred.

[0099] Furthermore, in the above-mentioned component A-1, the alkoxysilyl group described above can be one or more, and the alkoxysilyl group can be a monoalkoxysilyl group, a dialkoxysilyl group, or a trialkoxy group.

[0100] Examples of the aforementioned 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-ethylenediamine, and X-12-972F manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0101] The protected skeleton of the aliphatic amino group in component A-2 may have aliphatic or aromatic groups as protecting groups, without impairing the effects of this disclosure. Examples of protected skeletons for the aliphatic amino group include ketimine skeletons and aldehyde imine skeletons. Furthermore, component A-2 may have one or more protected aliphatic amino groups.

[0102] Furthermore, the alkoxysilyl group in component A-2 can be one or more, and the alkoxysilyl group can be a monoalkoxysilyl group, a dialkoxysilyl group, or a trialkoxy group.

[0103] Examples of the aforementioned component A-2 include 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine and N-[3-(triethoxysilylpropyl)]benzaldehyde imine.

[0104] Examples of components A-3 include polymers of components A-1.

[0105] Examples of components A-4 include polymers of component A-2.

[0106] The preferred upper limit for the content of component A relative to 100 parts by weight of the aforementioned (meth)acrylic acid copolymer is 8.0 parts by weight. By keeping the content of component A at 8.0 parts by weight or less, the precipitation of the silane coupling agent in the adhesive layer can be prevented, and the reduction in the adhesive strength of the adhesive tape of this disclosure can be further suppressed. A more preferred upper limit for the content of component A is 7.0 parts by weight, a further preferred upper limit is 6.0 parts by weight, and an even more preferred upper limit is 5.0 parts by weight.

[0107] Furthermore, the preferred lower limit for the content of component A is 1.5 parts by mass. By making the content of component A 1.5 parts by mass or more, the adhesive strength of the adhesive tape of this disclosure to silicone-based adherents is further improved. The content of component A is more preferably 2.0 parts by mass or more, more preferably 2.5 parts by mass or more, even more preferably greater than 3.0 parts by mass, particularly preferably 3.2 parts by mass or more, particularly more preferably 3.5 parts by mass or more, and particularly more preferably 4.0 parts by mass or more.

[0108] It should be noted that the content of component A relative to 100 parts by weight of the (meth)acrylic acid copolymer can be specifically exemplified by the following amounts: 1.5 parts by weight or more and 8.0 parts by weight, 1.5 parts by weight or more and 7.0 parts by weight, 1.5 parts by weight or more and 6.0 parts by weight, 1.5 parts by weight or more and 5.0 parts by weight, 2.0 parts by weight or more and 8.0 parts by weight, 2.0 parts by weight or more and 7.0 parts by weight, 2.0 parts by weight or more and 6.0 parts by weight, 2.0 parts by weight or more and 5.0 parts by weight, 2.5 parts by weight or more and 8.0 parts by weight, 2.5 parts by weight or more and 7.0 parts by weight, 2.5 parts by weight or more and 6.0 parts by weight, 2.5 parts by weight or more and 5.0 parts by weight, and greater than 3.0 parts by weight and 8.0 parts by weight. Less than 0 parts by weight, more than 3.0 parts by weight and less than 7.0 parts by weight, more than 3.0 parts by weight and less than 6.0 parts by weight, more than 3.0 parts by weight and less than 5.0 parts by weight, more than 3.2 parts by weight and less than 8.0 parts by weight, more than 3.2 parts by weight and less than 7.0 parts by weight, more than 3.2 parts by weight and less than 6.0 parts by weight, more than 3.2 parts by weight and less than 5.0 parts by weight, more than 3.5 parts by weight and less than 8.0 parts by weight, more than 3.5 parts by weight and less than 7.0 parts by weight, more than 3.5 parts by weight and less than 6.0 parts by weight, more than 3.5 parts by weight and less than 5.0 parts by weight, more than 4.0 parts by weight and less than 8.0 parts by weight, more than 4.0 parts by weight and less than 7.0 parts by weight, more than 4.0 parts by weight and less than 6.0 parts by weight, more than 4.0 parts by weight and less than 5.0 parts by weight, etc.

[0109] The adhesive layer described above may contain tackifying resins, softeners, inorganic fillers, and other additives as needed, without impairing the effects of this disclosure.

[0110] Typically, device materials are sometimes exposed to high-temperature environments during use. Therefore, adhesive tapes for bonding silicone materials preferably have high-temperature retention strength. From this perspective, the components in the adhesive layer preferably have a cross-linked structure. By forming a cross-linked structure in the components of the adhesive layer, the gel fraction of the adhesive layer (described later) can be easily adjusted to an appropriate range, thereby further improving the cohesive strength of the adhesive layer and further improving the high-temperature retention strength of the adhesive tape of this disclosure.

[0111] 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, chemical crosslinking, and physical crosslinking. Among these, since crosslinking can be carried out without introducing polar functional groups into the adhesive layer, a low-polarity adhesive layer can be produced. From the viewpoints of further improving the adhesion to silicone-based adherends, improving the high-temperature retention of the adhesive layer, and ensuring the long-term stability of the adhesive solution, electron beam irradiation and ultraviolet irradiation are preferred. From the viewpoint of minimizing the amount of co-components, electron beam irradiation is more preferred.

[0112] As a method for crosslinking the components in the adhesive layer by using electron beam irradiation, examples include irradiating the adhesive tape with an electron beam using an electron beam irradiation device (such as "EBC-200" manufactured by NHV Corporation).

[0113] As a method of crosslinking the components in the adhesive layer by using ultraviolet irradiation, for example, a chemical lamp (manufactured by Toshiba, "FL20S·BL", etc.) can be used to irradiate the adhesive tape having an adhesive layer containing a free radical generator with ultraviolet light of a wavelength of 365 nm.

[0114] Examples of free radical generating agents contained in the adhesive layer include benzophenone and 4,4'-bis(dimethylamino)benzophenone.

[0115] The adhesive layer preferably contains a component that is cross-linked by electron beam irradiation or ultraviolet irradiation (hereinafter, sometimes simply referred to as "electron beam cross-linking component"). By containing the aforementioned electron beam cross-linking component, the adhesive layer is more easily cross-linked based on electron beam irradiation or ultraviolet irradiation, thus making the high-temperature retention of the adhesive layer more excellent.

[0116] Examples of components that are cross-linked by electron beam irradiation include (meth)acrylic acid monomers and allyl-containing compounds (excluding the aforementioned (meth)acrylic acid 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, triallyl isocyanurate, etc.

[0117] Examples of components that crosslink under ultraviolet light include (meth)acrylic acid monomers and allyl-containing compounds (excluding the aforementioned (meth)acrylic acid 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, triallyl isocyanurate, etc.

[0118] When the adhesive layer contains the aforementioned crosslinking components such as electron beam crosslinkers, the preferred lower limit of the content of the electron beam crosslinking components relative to 100 parts by weight of the (meth)acrylic acid copolymer is 0.1 parts by weight, and the preferred upper limit is 15 parts by weight. By making the content of the electron beam crosslinking components 0.1 parts by weight or more, it is easier to achieve better high-temperature retention of the adhesive layer. By making the content of the electron beam crosslinking components 15 parts by weight or less, it is possible to suppress the reduction in adhesive strength caused by the exudation of the electron beam crosslinking components and excessive crosslinking. The more preferred lower limit of the content of the electron beam crosslinking components is 0.5 parts by weight, the more preferred upper limit is 12 parts by weight, the even more preferred lower limit is 1.0 parts by weight, and the even more preferred upper limit is 10 parts by weight.

[0119] It should be noted that the adhesive layer can still exhibit excellent high-temperature retention even without the aforementioned cross-linking components such as electron beams. Therefore, the adhesive layer may also be free of the aforementioned cross-linking components such as electron beams.

[0120] Examples of the content of the aforementioned crosslinking components such as electron beams include: 0 parts by mass and 15 parts by mass, 0 parts by mass and 12 parts by mass, 0 parts by mass and 10 parts by mass, 0.1 parts by mass and 15 parts by mass, 0.1 parts by mass and 12 parts by mass, 0.1 parts by mass and 10 parts by mass, 0.5 parts by mass and 15 parts by mass, 0.5 parts by mass and 12 parts by mass, 0.5 parts by mass and 10 parts by mass, 1.0 parts by mass and 15 parts by mass, 1.0 parts by mass and 12 parts by mass, and 1.0 parts by mass and 10 parts by mass.

[0121] It should be noted that, from the viewpoint that it is easier to crosslink the adhesive layer based on electron beam irradiation or ultraviolet irradiation, the above-mentioned (meth)acrylic copolymers can contain vinyl, allyl, styrene and other alkenyl groups, and (meth)acryloyl groups.

[0122] Additionally, in this specification, "(meth)acryloyl" refers to acryloyl or methacryloyl.

[0123] The adhesive layer described above preferably contains a free radical generator. By containing a free radical generator, the adhesive layer is more easily cross-linked based on ultraviolet irradiation.

[0124] Examples of free radical generating agents include benzophenone-based, benzoyl ketal-based, α-hydroxy ketone-based, α-amino ketone-based, and α-acylphosphine oxide-based photoradioactive materials, with benzophenone-based materials being preferred. Specifically, examples of benzophenone-based photoradioactive materials include benzophenone and 4,4'-bis(dimethylamino)benzophenone.

[0125] The preferred lower limit for the content of the free radical generator relative to 100 parts by weight of the (meth)acrylic acid copolymer is 0.1 parts by weight, and the preferred upper limit is 10 parts by weight. By making the content of the free radical generator 0.1 parts by weight or more, the high-temperature retention strength of the adhesive layer is more easily improved. By making the content of the free radical generator 10 parts by weight or less, the reduction in adhesive strength caused by the exudation of the free radical generator and excessive crosslinking can be suppressed. The more preferred lower limit for the content of the free radical generator is 0.5 parts by weight, the more preferred upper limit is 8 parts by weight, the further preferred lower limit is 1 part by weight, and the further preferred upper limit is 5 parts by weight.

[0126] Furthermore, preferred contents of the aforementioned free radical generator include, for example, the following ranges: 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.

[0127] The preferred lower limit for the gel content of the adhesive layer is 35% by mass. By making the gel content of the adhesive layer 35% by mass or more, the cohesive force of the adhesive layer is further improved, and the high-temperature retention force of the adhesive tape disclosed herein is further improved. A more preferred lower limit for the gel content of the adhesive layer is 40% by mass, a further preferred lower limit is 45% by mass, and an even more preferred lower limit is 50% by mass.

[0128] Furthermore, the preferred upper limit for the gel content of the aforementioned adhesive layer is 90% by mass. By keeping the gel content of the aforementioned adhesive layer below 90% by mass, high holding power and the required adhesive strength can be achieved. A more preferred upper limit for the gel content of the aforementioned adhesive layer is 85% by mass, a further preferred upper limit is 80% by mass, and an even more preferred upper limit is 75% by mass.

[0129] It should be noted that the preferred gel fraction for the aforementioned adhesive layer can be, for example, 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, and 50% by mass or more and 75% by mass or less.

[0130] It should be noted that the gel fraction of the above-mentioned adhesive layer can be determined by the following method.

[0131] That is, the adhesive of W0 (g) adhesive layer was scraped and impregnated in 50 mL of ethyl acetate, and shaken for 24 hours at 23 °C and 200 rpm using a shaker. After shaking, the ethyl acetate was separated from the adhesive that had swollen due to absorbing ethyl acetate using a metal mesh (mesh #200). The separated adhesive was then dried at 110 °C for 1 hour. The mass of the dried adhesive containing the metal mesh was determined, and the gel fraction (mass %) was calculated using the following formula (1).

[0132] Gel fraction (mass%) = 100 × (W1 - W2) / W0 (1)

[0133] (W0: Initial adhesive mass, W1: Adhesive mass containing metal mesh after drying, W2: Initial mass of metal mesh)

[0134] In addition, the gel fraction of the adhesive layer can also be determined using the prepared test piece after preparing a test piece consisting only of the adhesive layer, or a test piece having both a substrate and an adhesive layer. Specifically, the test piece is immersed in 50 mL of ethyl acetate and shaken for 24 hours at 23°C and 200 rpm using a shaker. After shaking, the ethyl acetate and the test piece swollen by absorbing ethyl acetate are separated using a metal mesh (mesh #200). The separated test piece is dried at 110°C for 1 hour. The mass of the dried test piece containing the metal mesh is measured, and the gel fraction (mass %) is calculated using the following formula (2). It should be noted that the test piece does not have spacers. In addition, when the test piece does not have a substrate, W0 in the following formula (2) is calculated as 0.

[0135] Gel fraction (mass%) = 100 × (W2 - W0) / (W1 - W0) (2)

[0136] (W0: quality of the substrate layer, W1: quality of the test piece before impregnation, W2: quality of the test piece after impregnation and drying)

[0137] Methods for adjusting the gel fraction of the adhesive layer to the aforementioned range include, for example, adjusting the composition of the (meth)acrylic acid 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.

[0138] As methods for adjusting the aforementioned crosslinking conditions, for example, in electron beam irradiation-based crosslinking, methods such as adjusting the irradiation intensity, irradiation time, and accelerating voltage of the electron beam irradiation can be used. In ultraviolet irradiation-based crosslinking, methods such as adjusting the irradiation intensity and irradiation time of the ultraviolet light, which serves as the energy line promoting crosslinking, and methods for removing oxygen that hinders the reaction can be used. In the case of chemical crosslinking, methods such as adjusting the reactivity and amount of the crosslinking agent, and the reactivity and amount of the functional groups in the (meth)acrylic acid copolymer that react with the crosslinking agent can be used.

[0139] The preferred lower limit for the thickness of the adhesive layer is 5 μm, and the preferred upper limit is 200 μm. By keeping the thickness of the adhesive layer within this range, the resulting adhesive tape can achieve both sufficient adhesion and processability. A more preferred lower limit for the thickness of the adhesive layer is 10 μm, a further preferred lower limit is 15 μm, a more preferred upper limit is 150 μm, a further preferred upper limit is 125 μm, and an even more preferred upper limit is 100 μm.

[0140] It should be noted that the thickness of the aforementioned adhesive layer can be specifically categorized as follows: 5μm or more and 200μm or less, 5μm or more and 150μm or less, 5μm or more and 125μm or less, 5μm or more and 100μm or less, 10μm or more and 200μm or less, 10μm or more and 150μm or less, 10μm or more and 125μm or less, 10μm or more and 100μm or less, 15μm or more and 200μm or less, 15μm or more and 150μm or less, 15μm or more and 125μm or less, 15μm or more and 100μm or less, etc.

[0141] The adhesive tape of this disclosure may have layers other than the adhesive layer, such as a substrate, without impairing the effects of this disclosure. Additionally, it may have one or more adhesive layers of a different type than the aforementioned adhesive layers.

[0142] The adhesive tape of this disclosure may have spacers on at least one side of the adhesive layer. That is, the adhesive tape of this disclosure may be an adhesive tape with spacers on one side of the adhesive layer, or an adhesive tape with spacers on both sides of the adhesive layer.

[0143] There are no particular limitations on the substrate used for the spacers described above; any suitable substrate can be selected from those conventionally used as spacer substrates. Examples include plastic films such as polyester, polyethylene, polypropylene, polymethylpentene, and polycarbonate; metal foils such as aluminum and stainless steel; cellophane, woodfree paper, coated paper, impregnated paper, synthetic paper, and kraft paper. From the viewpoint of suppressing the ingress of foreign matter originating from the spacer, polyester is preferred.

[0144] Examples of the aforementioned polyesters include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).

[0145] The spacer preferably has a release layer. By including a release layer in the spacer, the spacer can be easily peeled off from the adhesive layer, preventing damage to the function and appearance of the adhesive tape of this disclosure after the spacer has been peeled off.

[0146] It should be noted that, in the case where the adhesive tape of this disclosure has the above-mentioned spacers on both sides, the spacers on only one side may have the above-mentioned release layer, or the spacers on both sides may have the above-mentioned release layer.

[0147] There are no particular limitations on the release layer used, but a release layer free of organic fluorine compounds is preferred. In this specification, "free of organic fluorine compounds" means that, in measurements of the surface of the release layer side of the spacer using XPS, TOF-SIMS, etc., the content of organic fluorine compounds is below the detection limit. By ensuring that the release layer is free of organic fluorine compounds, an adhesive tape with further suppressed organic fluorine compound content can be produced.

[0148] It should be noted that, conventionally, for adhesive tapes used to bond with silicone-based adhesives, it is difficult to peel the spacer from the adhesive layer protected by the spacer when the release layer of the spacer does not contain organofluorine compounds. Therefore, the release layer of the spacer in such adhesive tapes must contain fluorine compounds, which has become a problem. On the other hand, in the adhesive tape of this disclosure, the spacer can be easily peeled from the adhesive layer even when the release layer of the spacer does not contain organofluorine compounds. Therefore, from this point of view, the adhesive tape of this disclosure is also ideal.

[0149] For the aforementioned spacer, the spacer is obtained by peeling it 180° from the adhesive layer at 23°C and 50%RH. XPS measurements are performed on the surface of the peel interface between the spacer and the adhesive layer. The preferred upper limit for the relative intensity of the peak at 103.9 eV (hereinafter sometimes simply referred to as "relative intensity in the XPS measurement of the spacer") is 0.170. By setting the relative intensity in the XPS measurement of the spacer to 0.170 or less, the spacer becomes more suitable for protecting the adhesive layer, and peeling is easier when using the adhesive tape of this disclosure. As a result, the adhesive tape of this disclosure can be used more appropriately in practical applications. A more preferred upper limit for the relative intensity in the XPS measurement of the spacer is 0.160, and a further preferred upper limit is 0.150.

[0150] In addition, there is no particular limitation on the lower limit of the relative strength in the XPS measurement of the spacer, but the preferred lower limit is 0.010, the more preferred lower limit is 0.020, and the even more preferred lower limit is 0.030.

[0151] It should be noted that the relative intensity in the XPS measurement of the aforementioned spacer can specifically be, for example, ranges such as: 0.010 or higher and 0.170 or lower, 0.010 or higher and 0.160 or lower, 0.010 or higher and 0.150 or lower, 0.020 or higher and 0.170 or lower, 0.020 or higher and 0.160 or lower, 0.020 or higher and 0.150 or lower, 0.030 or higher and 0.170 or lower, 0.030 or higher and 0.160 or lower, 0.030 or higher and 0.150 or lower.

[0152] The relative strength of the spacer in the XPS test can be determined by the following method.

[0153] That is, firstly, as needed, the spacers on the side of the adhesive tape that have not been subjected to XPS testing are peeled off from the adhesive layer. Then, using a 2kg rubber roller, the tape is reciprocated once at a speed of 300mm / min to create a test piece backed onto a 23μm thick polyethylene terephthalate (PET) film or similar material. It should be noted that this step is not necessary if the adhesive tape has the spacers on only one side.

[0154] Next, for the test piece, according to JIS Z0237, a tensile testing machine (Shimadzu Corporation, "AG-IS") was used to peel the spacer from the adhesive tape at 23°C, tensile speed of 300 mm / min, and peel angle of 180°.

[0155] Then, for the peeling interface between the spacer and the adhesive layer in the spacer peeled from the adhesive tape, narrow scan analysis of C1s, O1s, and Si2p was performed by XPS under the following conditions: the peak of C1s was calibrated to 284.8 eV, the maximum value of Si2p in the measurement range was set to 1, and the minimum value was set to 0. The relative intensity of the peak at 103.9 eV was calculated, thereby obtaining the relative intensity in the XPS measurement of the spacer.

[0156] <XPS Measurement Conditions>

[0157] Measurement apparatus: PHI5000 VersaProbeII (manufactured by ULVAC-PHI)

[0158] X-ray source: Al Kα rays (1486.6 eV)

[0159] Photoelectron extraction angle: 45 degrees

[0160] Energy per unit volume: 23.5 eV (Si2p), 58.7 eV (C1s, O1s)

[0161] Measurement range settings: 94.0 eV~114.0 eV (Si2p), 278.0 eV~298.0 eV (C1s), 298.0 eV~523.0 eV (O1s)

[0162] STEP width: 0.1eV (Si2p), 0.125eV (C1s, O1s)

[0163] Number of scans: 3 (Si2p), 2 (C1s), 1 (O1s)

[0164] Number of cycles: 10

[0165] It should be noted that the adhesive tape described below is also one of the present disclosures. The adhesive tape has a spacer and an adhesive layer containing a (meth)acrylic copolymer. The spacer is obtained by peeling it 180° from the adhesive layer at 23°C and 50%RH. XPS measurement is performed on the surface of the peel interface between the obtained spacer and the adhesive layer. The relative intensity of the peak at 103.9 eV is less than 0.17.

[0166] When the adhesive tape has spacers on both sides, the relative strength of the spacers in the XPS measurement of the adhesive tape may meet the above range in only one spacer or in both spacers. When the adhesive tape has spacers on both sides, it is more preferable that the relative strength of the spacers in the XPS measurement meets the above range in both spacers.

[0167] The preferred lower limit for the thickness of the aforementioned spacer (the combined thickness of the substrate and the release layer used for the spacer) is 12 μm. By ensuring the thickness of the spacer is 12 μm or more, damage caused by unintentional bending, impact, etc., during the processing of the adhesive tape can be suppressed, and damage to the appearance and function of the resulting adhesive tape after the spacer is peeled off can be further suppressed. A more preferred lower limit for the thickness of the aforementioned spacer is 19 μm, and a more preferred lower limit is 25 μm.

[0168] In addition, there is no specific upper limit to the thickness of the aforementioned spacer; in practice, the upper limit is 200 μm.

[0169] The adhesive tape disclosed herein may be a support-type adhesive tape having a substrate other than the aforementioned spacer substrate, or a non-support-type adhesive tape not having a substrate other than the aforementioned spacer substrate. Furthermore, the adhesive tape disclosed herein may also be a double-sided tape comprising an adhesive layer other than an adhesive layer capable of exhibiting excellent adhesion to silicone-based substrates.

[0170] There are no particular limitations on the method for manufacturing the adhesive tape disclosed herein, and conventionally known methods may be used. Specifically, for example, it may be manufactured as follows: the above-mentioned (meth)acrylic acid copolymer and component A are added to a solvent, stirred thoroughly, the resulting adhesive solution is applied to the release layer of the spacer, and dried to form an adhesive layer, thereby manufacturing the tape.

[0171] The adhesive tape disclosed herein has no particular application and can be used for: assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), fixing automotive electronic device components such as automotive panels to the vehicle body, and manufacturing devices for transmitting or receiving electromagnetic waves. Among these applications, the adhesive tape of this disclosure is preferably used for bonding silicone-based substrates due to its excellent adhesion to such substrates.

[0172] Examples of silicone-based adhesives include silicone rubber, silicone foam, and objects with silicone coatings. More specifically, examples include electronic device components, vehicle components, building components, and medical components.

[0173] Examples of components for the aforementioned electronic devices include: heat dissipation pads, heat sinks, adhesives for fixing electrical and electronic components, sealing materials, potting compounds for protecting electrical and electronic components, coatings, semiconductor chip bonding materials, electronic circuit sealing and potting materials, rollers for OA equipment, anode caps, cable glass sheathing bundle materials, polymer insulators, and electrical insulating resin varnishes.

[0174] Examples of vehicle components include heat dissipation pads, heat sinks, heat dissipation foam, heat-resistant foam, heat-resistant hoses, O-rings, adhesives for fixing vehicle components, sealing materials, potting compounds for protecting vehicle accessories, and coatings.

[0175] Examples of such building components include building gaskets, vibration damping agents, heat-insulating rubber, heat-dissipating rubber, heat-insulating foam, heat-dissipating foam, adhesives for fixing building components, sealing materials, potting compounds for protecting building products, and coating agents.

[0176] Examples of such medical components include catheters, tubing, sealing materials for medical devices, gaskets, adhesives for securing medical components, and sealing materials.

[0177] This disclosure also includes laminates comprising a structure for attaching the adhesive tape of this disclosure to a silicone-based substrate. Laminates of this disclosure have a low content of fluorine resin and excellent environmental compatibility.

[0178] The laminate disclosed herein is not particularly limited as long as it has a structure in which the aforementioned adhesive tape is attached to an organosilicon-based substrate. For example, it can be described using the aforementioned adhesive tape 1 to... Figure 1 The laminate formed by bonding the component 2 containing silicone resin with other components 3 as shown.

[0179] In addition, examples include laminates made by bonding together components containing silicone resins.

[0180] Specifically, examples include structures formed by bonding silicone-based adhesives such as heat dissipation pads, heat sinks, adhesives for fixing electrical and electronic components, sealing materials, potting compounds for protecting electrical and electronic components, coatings, semiconductor chip bonding materials, electronic circuit sealing and potting materials, rollers for OA equipment, anode caps, glass sheathing bundle materials for cables, polymer insulators, and electrical insulating resin varnishes to electronic equipment components, as well as the aforementioned vehicle components, building components, and medical components.

[0181] Electronic devices incorporating the adhesive tape of this disclosure are also part of this disclosure. The electronic devices of this disclosure have low content of fluoropolymers and excellent environmental compatibility.

[0182] The electronic device disclosed herein is not particularly limited to any electronic device that includes the aforementioned adhesive tape; for example, electronic devices having the aforementioned adhesive tape can be cited. Figure 1 The electronic device shown is an electronic device with a laminate as a component, which is formed by bonding together components containing silicone resin.

[0183] Specifically, examples include mobile phones, smartphones, tablet computers, personal computers (PCs), laptops, game consoles, display terminals, electronic paper terminals, watches or watch-type electronic devices, eyeglass-type electronic devices, goggles-type electronic devices, etc., which include structures exemplified as stacked bodies of the present disclosure.

[0184] Invention Effects

[0185] According to this disclosure, an adhesive tape that exhibits excellent adhesion to silicone-based substrates without prior surface treatment can be provided, even without the use of silicone-based adhesives. Furthermore, according to this disclosure, a laminate having the adhesive tape attached to it can be provided. Additionally, according to this disclosure, an electronic device incorporating the adhesive tape can be provided. Attached Figure Description

[0186] Figure 1 This is a cross-sectional view schematically representing an example of a laminate of the present disclosure.

[0187] Figure 2 This is a schematic diagram illustrating the method for high-temperature retention testing. Detailed Implementation

[0188] The present disclosure is illustrated below with examples, but the present disclosure is not limited to these examples.

[0189] (Synthesis of (meth)acrylic acid copolymers a-k)

[0190] Ethyl acetate was added as a solvent to a reactor equipped with a thermometer, stirrer, and condenser. After nitrogen replacement, the reactor was heated and reflux was initiated. After the solvent boiled, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile (azobisisobutyronitrile) as a polymerization initiator 10 times with ethyl acetate was added. Then, an ethyl acetate solution containing the monomer mixtures shown in Table 1 (mass %) was added dropwise to the reactor over 2 hours to achieve a monomer concentration of 45% by mass. After the addition was completed, a polymerization reaction was carried out for 4 hours to obtain ethyl acetate solutions of (meth)acrylic acid copolymers a to k.

[0191] The ethyl acetate solutions of the obtained acrylic copolymers a to g were filtered through a filter, and the filtrate was fed into a gel permeation chromatograph (Waters Corporation, 2690 Separations Module). GPC analysis was performed at a sample flow rate of 1 mL / min and a column temperature of 40 °C to determine the polystyrene-converted molecular weight and weight-average molecular weight (Mw) of the acrylic copolymers. A GPC KF-806L column (Showa Denko Corporation) was used as the column, and a differential refractometer was used as the detector. The results are shown in Table 1.

[0192] (Synthesis of (meth)acrylic acid copolymer l)

[0193] Ethyl acetate, used as a solvent, was added to a reactor equipped with a thermometer, stirrer, and condenser. After nitrogen replacement, the reactor was heated and reflux was initiated. A polymerization initiator solution, prepared by diluting 0.1 parts by mass of azobisisobutyronitrile (azobisisobutyronitrile) as a polymerization initiator by ethyl acetate, was added to the reactor. Then, over 2 hours, 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. After the addition was complete, the polymerization initiator solution, prepared by diluting 0.1 parts by mass of azobisisobutyronitrile (azobisisobutyronitrile) as a polymerization initiator by ethyl acetate, was added back to the reactor, and the polymerization reaction was carried out for 4 hours to obtain an ethyl acetate solution of acrylic copolymer 1.

[0194] The ethyl acetate solution of the obtained acrylic copolymer l was filtered through a filter, and the filtrate was fed into a gel permeation chromatograph (Waters Corporation, 2690 Separations Module). GPC analysis was performed at a sample flow rate of 1 mL / min and a column temperature of 40 °C to determine the polystyrene equivalent molecular weight and weight-average molecular weight (Mw) of the acrylic copolymer. A GPC KF-806L column (Showa Denko Corporation) was used as the column, and a differential refractometer was used as the detector. The results are shown in Table 1.

[0195] The structural unit monomers of (meth)acrylic acid copolymers shown in Table 1 are as follows.

[0196] ·EA: Ethyl acrylate

[0197] ·BA: n-Butyl acrylate

[0198] HPA: n-Heptyl Acrylate

[0199] ·2OA: 2-Octyl Acrylate

[0200] ·2EHA: 2-Ethylhexyl acrylate

[0201] HEA: 2-Hydroxyethyl Acrylate

[0202] DMAA: N,N-dimethylacrylamide

[0203] • AAc: Acrylic acid

[0204] [Table 1]

[0205]

[0206] (Example 1)

[0207] (1) Making adhesive tape

[0208] KBM-602 (manufactured by Shin-Etsu Chemical Co., Ltd.), an aliphatic amine silane coupling agent, was added to an ethyl acetate solution of the obtained (meth)acrylic acid copolymer a, with a solid content of 3.0 parts by weight relative to 100 parts by weight of the solid content of (meth)acrylic acid copolymer a, so that the solid content was 30%. The mixture was then thoroughly mixed to prepare an adhesive solution.

[0209] The prepared adhesive solution was applied to the release layer of a 75 μm thick spacer (manufactured by TOYO CLOTH, "SP3000"), and then dried at 110°C for 3 minutes to form a 50 μm thick adhesive layer. Then, another 25 μm thick spacer (manufactured by TOYO CLOTH, "SP8001") was prepared, and the release layer was overlapped onto the formed adhesive layer in an opposing manner. The layer was then cured at 40°C for 48 hours to obtain the adhesive tape. It should be noted that the spacers used here do not contain fluorine components equivalent to PFAS.

[0210] (2) Determination of gel fraction of adhesive layer

[0211] The adhesive layer of W0 (g) was scraped and impregnated in 50 mL of ethyl acetate. The mixture was shaken for 24 hours at 23°C and 200 rpm. After shaking, the ethyl acetate was separated from the swollen adhesive by absorbing the ethyl acetate using a metal mesh (mesh size #200). The separated adhesive was then dried at 110°C for 1 hour. The mass of the dried adhesive containing the metal mesh was determined, and the gel fraction was calculated using the above formula (1). The results are shown in Table 2.

[0212] (3) Determination of the relative intensity of the negative ion peak in the region with m / z 26 after the adhesive tape is peeled off.

[0213] After cleaning the surface of a 50mm × 125mm SUS304 board with ethanol, it was dry-rubbed. A film adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767") with an organosilicon adhesive layer on one side was cut into a size of 30mm wide and 70mm long. After peeling off the spacers on the adhesive layer side that are not organosilicon adhesive layers, the adhesive layer was attached to the SUS304 board. The spacers on the organosilicon adhesive layer side were further peeled off to expose the organosilicon adhesive layer. A piece of silicone rubber ("manufactured by Togawa Rubber Co., Ltd., K-125 (50)") cut into a size of 30mm wide and 70mm long and 1mm thick was attached to the organosilicon adhesive layer to make an organosilicon adhesive.

[0214] The adhesive tape obtained in "(1) Preparation of Adhesive Tape" above was cut into pieces with a width of 25 mm and a length of 70 mm. The spacer on one side of the cut adhesive tape was peeled off, and one side of the adhesive tape was backed with the corona-treated side of a 23 μm thick polyethylene terephthalate (PET) film. The spacer on the other side of the backed adhesive tape was peeled off, and the tape was attached to the silicone rubber surface of the silicone-based substrate. A 2 kg roller was used to press the tape back and forth once at a speed of 300 mm / min. The tape was then left to stand for 72 hours at 23°C and 50% RH to produce a laminate. For the laminate produced, a peel test was performed on the silicone-based substrate using a tensile testing machine (manufactured by Shimadzu Corporation, "AG-IS") according to JIS Z0237, at 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°.

[0215] For the silicone rubber with the adhesive tape removed after the peel test, the peeling speed was adjusted to approximately 300 mm / min and the peeling angle to approximately 90°, and the silicone rubber was peeled off by hand, thereby peeling it off from the film adhesive tape with the silicone adhesive layer. After peeling off the silicone adhesive, the peeled silicone rubber was cut into approximately 1 cm squares using a cutter or scissors to prepare the test sample. The test sample was placed against the surface of the adhesive tape in an aluminum cup with 2 mL of ethyl acetate in its 5 cm inner diameter container, and the surface was shaken back and forth 80 times at a distance of 1 cm within 1 minute, thereby cleaning with ethyl acetate (i). Further, another aluminum cup with 2 mL of ethyl acetate in its 5 cm inner diameter container was prepared, and the same cleaning was performed again. The test sample was then heated in an oven at 80°C under normal pressure for 10 minutes (ii). The above operations (i) and (ii) were considered as one group, and a total of 4 groups were performed, with a total of 8 cleanings with ethyl acetate. It should be noted that a new aluminum cup and ethyl acetate are used each time operations (i) and (ii) are performed.

[0216] The surface cleaned with ethyl acetate was subjected to TOF-SIMS analysis. The obtained spectral data were analyzed using analytical software (ION-TOF, "SurfaceLab 7"), thus obtaining the relative intensities of the negative ion peaks in the region with m / z 26 after the adhesive tape was peeled off. The results are shown in Table 1. It should be noted that the TOF-SIMS analysis was performed as follows.

[0217] (TOF-SIMS measurement)

[0218] TOF-SIMS measurements were performed using a time-of-flight secondary ion mass spectrometer (ION-TOF, “TOF.SIMS5”), under the conditions described below. The value was obtained by dividing the sum (area) of the negative ion peaks in the region with m / z 26 by the sum (area) of all negative ion peaks, based on the obtained secondary ion spectrum.

[0219] <Measurement conditions for TOF-SIMS>

[0220] Primary ion types: Bi3++

[0221] Accelerating voltage: 25kV

[0222] • Detection of ion polarity: negative (negative ion)

[0223] • Measurement range: 500μm × 500μm

[0224] • Pixel count: 128×128 (pixels)

[0225] • Number of scans: 25

[0226] • Mass range (m / z): 0~850

[0227] (Examples 2-27, Comparative Examples 1-4, 6-9)

[0228] Except for the changes in the composition of the adhesive layer as shown in Tables 2-5 and 9, the adhesive tape was prepared in the same manner as in Example 1. After the adhesive tape was prepared, it was subjected to electron beam irradiation using an electron beam irradiation device (manufactured by NHV Corporation, "EBC-200") under the electron beam irradiation conditions shown in Tables 2-5 and 9 to crosslink the adhesive components, thereby forming an adhesive layer and obtaining the adhesive tape. Half of the total dose of electron beam was applied to each side of the adhesive tape.

[0229] The determination of the gel fraction of the adhesive layer was performed in the same manner as in Example 1. The results are shown in Tables 2-5 and 9.

[0230] (Examples 28-29)

[0231] The composition of the adhesive layer was modified as shown in Table 5. Furthermore, benzophenone, a free radical generator in UV crosslinking, was added to the adhesive layer only in the amounts shown in Table 5. Otherwise, the process was the same as in Example 1. After producing the adhesive tape, the resulting adhesive tape was subjected to UV irradiation with a chemical lamp (Toshiba, "FL20S·BL") at a wavelength of 365 nm under the UV irradiation conditions shown in Table 5 to crosslink the adhesive components, thereby forming an adhesive layer and obtaining the adhesive tape. The UV irradiation was performed from both sides of the adhesive tape, with each side irradiating with half the cumulative light intensity.

[0232] The gel fraction of the adhesive layer was determined in the same manner as in Example 1. The results are shown in Table 5.

[0233] (Comparative Example 5)

[0234] 100 parts by weight of styrene-ethylene / butene-styrene (SEBS) triblock copolymer (manufactured by ENEOS Materials, "DYNARON 8300") and 30 parts by weight of tackifying resin (manufactured by Arakawa Chemical Industry Co., Ltd., "ARKON P-125") were dissolved in toluene to prepare an adhesive solution with a solid content of 30%. Using this adhesive solution, an adhesive tape was prepared in the same manner as in Example 1.

[0235] The determination 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.

[0236] (Example 30)

[0237] (1) Making adhesive tape

[0238] First, the composition of the adhesive layer was changed as shown in Tables 6-8. Otherwise, the same procedure as in Example 1 was followed to prepare an adhesive solution (a) that will form the adhesive layer (A) and an adhesive solution (b) that will form the adhesive layer (B) with 0.2 parts by weight of isocyanate crosslinking agent (Covestro, Desmodur L75) relative to 100 parts by weight of the (meth)acrylic copolymer (solid content ratio).

[0239] Next, the prepared adhesive solution (a) was applied to the release layer of a 75 μm thick spacer (manufactured by TOYO CLOTH, "SP3000") and dried at 110°C for 3 minutes to form an adhesive layer. A laminate was fabricated by overlapping the adhesive layer formed on one side of a 23 μm thick PET film (manufactured by Futamura Chemical, "FE2002-23"). The laminate was then irradiated with an electron beam irradiation device (manufactured by NHV Corporation, "EBC-200") to crosslink the adhesive components, thereby forming a 75 μm thick adhesive layer (A). It should be noted that half of the total dose was irradiated from each side of the laminate.

[0240] Further, after applying the prepared adhesive solution (b) to the release layer of the spacer (B) as described in Table 6, it was dried at 110°C for 3 minutes, thereby forming an adhesive layer (B) with a thickness of 42 μm. Then, the adhesive layer (B) was overlapped on the side of the substrate without the adhesive layer (A) in the laminate to form the adhesive layer (A), and then the laminate was cured at 40°C for 48 hours. Then, the spacer on the adhesive layer (A) side was peeled off, and the spacer (A) shown in Table 6 was laminated. The adhesive tape with the spacer replaced was placed in an oven set at 60°C and 50%RH and left to stand for 168 hours at 60°C and 50%RH, thereby obtaining an adhesive tape having a substrate and adhesive layers and spacers on both sides of the substrate.

[0241] (2) Determination of gel fraction of adhesive layer

[0242] First, the laminate containing the adhesive layer (A) formed in "(1) Preparation of the adhesive tape" above was cut into pieces 25 mm wide and 60 mm long. The spacer (A) was then peeled off from the cut laminate to prepare a test piece for gel fraction determination. Next, the prepared test piece for gel fraction determination was immersed in 50 mL of ethyl acetate and shaken for 24 hours at 23°C and 200 rpm using a shaker. Then, the ethyl acetate was separated from the swollen test piece by absorbing the ethyl acetate using a metal mesh (mesh #200). The separated test piece was then dried at 110°C for 1 hour. The mass of the dried test piece containing the metal mesh was measured, and the gel fraction (mass %) was calculated using the above formula (2). The results are shown in Table 6.

[0243] (3) Determination of the relative intensity of the negative ion peak in the region with m / z 26 after the adhesive tape is peeled off.

[0244] The adhesive layer (B) was backed with the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film. The adhesive layer (A) was then bonded to the silicone rubber surface of the aforementioned silicone-based substrate. Otherwise, the procedure was the same as in Example 1, and the relative intensities of the negative ion peaks in the region with m / z 26 after the adhesive tape was peeled off were measured. The results are shown in Table 6.

[0245] (4) Determination of relative strength in XPS test after the spacer has been placed in a high temperature and high humidity environment

[0246] First, after peeling the spacer (B) from the adhesive layer (B) in the obtained adhesive tape, a test piece is made by pressing the adhesive layer (B) against the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film once using a 2 kg rubber roller at a speed of 300 mm / min.

[0247] Next, the prepared test piece was placed in a constant temperature and humidity oven set at 60°C and 50%RH. After standing for 168 hours at 60°C and 50%RH, the test piece was removed from the oven and air-cooled at 23°C for 30 minutes. Further, for the air-cooled test piece, according to JIS Z0237, a tensile testing machine (manufactured by Shimadzu Corporation, "AG-IS") was used to peel the spacer (A) from the adhesive layer (A) at 23°C, tensile speed of 300 mm / min, and peel angle of 180°.

[0248] Then, for the peeling interface between the spacer (A) and the adhesive layer (A) in the spacer (A) peeled from the adhesive layer (A), narrow scan analysis of C1s, O1s, and Si2p was performed by XPS under the following conditions: the peak value of C1s was set to 284.8 eV for calibration, the maximum value of Si2p in the measurement range was set to 1, and the minimum value was set to 0. The relative intensity of the peak at 103.9 eV was calculated, thus obtaining the relative intensity in the XPS measurement of the aforementioned spacer. The results are shown in Table 6.

[0249] <XPS Measurement Conditions>

[0250] Measurement apparatus: PHI5000 VersaProbeII (manufactured by ULVAC-PHI)

[0251] X-ray source: Al Kα rays (1486.6 eV)

[0252] Photoelectron extraction angle: 45 degrees

[0253] Energy per unit volume: 23.5 eV (Si2p), 58.7 eV (C1s, O1s)

[0254] Measurement range settings: 94.0 eV~114.0 eV (Si2p), 278.0 eV~298.0 eV (C1s), 298.0 eV~523.0 eV (O1s)

[0255] STEP width: 0.1eV (Si2p), 0.125eV (C1s, O1s)

[0256] Number of scans: 3 (Si2p), 2 (C1s), 1 (O1s)

[0257] Number of cycles: 10

[0258] (Examples 31-34, 38-44)

[0259] In the above-mentioned "(1) Fabrication of adhesive tape", the types of spacer (A), substrate and spacer (B), as well as the composition and thickness of adhesive layer (A) and adhesive layer (B) are as shown in Tables 6 to 8. Otherwise, the adhesive tape was fabricated and various measurements were performed in the same manner as in Example 30. The results are shown in Tables 6 to 8.

[0260] (Examples 35-37, 45-46)

[0261] In the above-mentioned "(1) Fabrication of Adhesive Tape", the types of spacers (A), substrates and spacers (B), as well as the composition and thickness of adhesive layers (A) and (B) are shown in Tables 6-8. Furthermore, after laminating the spacers (A) shown in Tables 6-8, the adhesive tape with the spacers replaced was placed in an oven set at 23°C and 50%RH and left to stand for 168 hours at 23°C and 50%RH. Otherwise, the adhesive tape was fabricated and various measurements were performed in the same manner as in Example 30. The results are shown in Tables 6-8.

[0262] (Example 47)

[0263] In the above-mentioned "(1) Fabrication of adhesive tape", the types of spacers (A), substrates and spacers (B), as well as the composition and thickness of adhesive layers (A) and (B) were changed as shown in Table 8. Furthermore, adhesive layer (A) was formed without electron beam irradiation. Otherwise, the adhesive tape was fabricated and various measurements were performed in the same manner as in Example 30. The results are shown in Table 8.

[0264] The types of spacers shown in Tables 6-8 are as follows.

[0265] • Spacer A: SP8001 (manufactured by TOYO CLOTH)

[0266] • Spacer B: SP3030 (manufactured by TOYO CLOTH)

[0267] • Spacer C: RF2 PET50cs14EX (Made by I'm Company)

[0268] • Spacer D: Cerapeel MDA (manufactured by Toray Industries, Inc.)

[0269] • Spacer E: MRQ75 (manufactured by Mitsubishi Chemical)

[0270] • Spacer F: SP3000 (manufactured by TOYO CLOTH)

[0271] • Spacer G: SP1007 (manufactured by TOYO CLOTH)

[0272] • Spacer H: SP4020 (manufactured by TOYO CLOTH)

[0273] • Spacer I: SP4030 (manufactured by TOYO CLOTH)

[0274] • Spacer J: MRV75 (V06) (manufactured by Mitsubishi Chemical Co.)

[0275] • Spacer K: MRV100 (VOC) (manufactured by Mitsubishi Chemical Co.)

[0276] It should be noted that the spacers shown in Tables 6 to 8 do not contain fluorine components equivalent to PFAS.

[0277] <Evaluation>

[0278] The adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 2 to 9.

[0279] (Adhesion strength to silicone-based substrates)

[0280] After cleaning the surface of a 50mm × 125mm SUS304 board with ethanol, it was dry-rubbed. A film adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767") with an organosilicon adhesive layer on one side was cut into a size of 30mm wide and 70mm long. After peeling off the spacers on the adhesive layer side that are not organosilicon adhesive layers, the adhesive layer (partial organosilicon adhesive layer) was attached to the SUS304 board. The spacers on the organosilicon adhesive layer side were further peeled off to expose the organosilicon adhesive layer. A piece of silicone rubber ("manufactured by Togawa Rubber Co., Ltd., K-125 (50)") cut into a size of 30mm wide and 70mm long and 1mm thick was attached to the organosilicon adhesive layer to make an organosilicon adhesive.

[0281] The obtained adhesive tape was cut into pieces 25 mm wide and 70 mm long. The spacer (spacer (B)) on one side of the cut adhesive tape was peeled off, and one side of the adhesive tape was backed onto the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film. The spacer (spacer (A)) on the other side of the backed adhesive tape was peeled off and bonded to the silicone rubber surface of the aforementioned silicone-based adhesive. A 2 kg roller was then used to press the tape together once at a speed of 300 mm / min. The mixture was then left to stand at 23°C and 50% RH for 72 hours to prepare the test sample.

[0282] For the prepared test samples, according to JIS Z0237, a tensile testing machine (Shimadzu Corporation, "AG-IS") was used to peel the adhesive tape from the silicone-based substrate at 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-based substrate was determined according to the following criteria.

[0283] ◎: Peel force of 3.0N / 25mm or more at 180°.

[0284] ○: The 180° peel force is greater than or equal to 2.0N / 25mm and less than 3.0N / 25mm.

[0285] ×: 180° peel force is less than 2.0N / 25mm.

[0286] It should be noted that, regarding Comparative Example 4, since the adhesive tape could not be adhered to the silicone-based substrate and the 180° peel force could not be measured, the 180° peel force (N / 25mm) against silicone rubber in Table 5 is recorded as "-".

[0287] (High-temperature retention)

[0288] exist Figure 2 The diagram below schematically illustrates the method for high-temperature retention testing.

[0289] First, according to JIS Z-1528, the obtained adhesive tape was cut into pieces 25 mm wide and 60 mm long to prepare test piece 5. After peeling off the spacer (spacer (B) for Examples 30-47) from one side of test piece 5, the exposed adhesive layer (adhesive layer (B) for Examples 30-47) was backed with polyethylene terephthalate (PET) film 4. After peeling off the spacer (spacer (A) for Examples 30-47) from the other side of test piece 5, the exposed adhesive layer (adhesive layer (A) for Examples 30-47) was bonded at 23°C to a cold-rolled stainless steel sheet (SUS304 sheet cleaned with ethanol and dry-rubbed) 6 with a thickness of 2.0 mm, a width of 50 mm, and a length of 75 mm. The length of the bond was 25 mm. After the test piece 5 was exposed from the end of the SUS304 sheet 6, the pieces were staggered in the length direction and bonded together. Then, a 2 kg roller was used to press the pieces together once to prepare the test sample. After the test sample was left to stand for 20 minutes at 23°C and 50%RH, a 1kg weight 7 was applied to the test sample in the shear direction at 80°C. The time of weight 7 application was taken as the start time (0 hours). A high-temperature retention test was conducted, in which the load applied by weight 7 was maintained for 1 hour. It was confirmed whether the test piece 5 fell off. If it did not fall off after 1 hour, the amount of movement (offset) from the starting position was measured using a scale and magnifying glass. The high-temperature retention force of the adhesive tape was evaluated according to the following criteria.

[0290] ◎: The offset of the test piece is less than 0.1 mm.

[0291] ○: The offset of the test piece is greater than 0.1mm and less than 0.5mm.

[0292] △: The test piece deviates by more than 0.5 mm and does not fall.

[0293] ×: The test piece fell during the high-temperature retention test.

[0294] It should be noted that even if the evaluation is “×”, the adhesive tape disclosed herein can still be used without problems depending on the application.

[0295] (Topical)

[0296] In the above "(1) Fabrication of adhesive tape", the coating performance is evaluated according to the following criteria, starting from the process of applying the obtained adhesive solution to the spacer (for Examples 30 to 47, it is the process of applying the adhesive solution that forms the adhesive layer (A) to the spacer (A)).

[0297] ○: Can be applied without problems.

[0298] △: It can be applied, but the applied layer produces whiteness, streaks, etc.

[0299] ×: Cannot be applied.

[0300] (Ease of spacer peeling)

[0301] For Examples 30-47 in Tables 6-8, the obtained adhesive tape was cut into pieces with a width of 25 mm and a length of 70 mm. The spacer (B) in the cut adhesive tape was peeled off, and the exposed adhesive surface was attached to a 50 mm × 125 mm SUS304 plate that had been cleaned with ethanol and then dry-rubbed. The plate was then left to stand for 72 hours at 23°C and 50% RH to prepare the test sample.

[0302] For the prepared test samples, according to JIS Z0237, a tensile testing machine (Shimadzu Corporation, "AG-IS") was used to peel the spacer (A) from the adhesive tape at 23°C, tensile speed of 300 mm / min, and 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 spacer of the adhesive tape was determined according to the following criteria.

[0303] ◎: Peel force at 180° is less than 0.50N / 25mm.

[0304] ○: 180° peel force greater than 0.50N / 25mm and less than 1.00N / 25mm.

[0305] ×: 180° peel force greater than 1.00N / 25mm.

[0306] It should be noted that even if the evaluation is “×”, the adhesive tape disclosed herein can still be used without problems depending on the application.

[0307] [Table 2]

[0308]

[0309] [Table 3]

[0310]

[0311] [Table 4]

[0312]

[0313] [Table 5]

[0314]

[0315] [Table 6]

[0316]

[0317] [Table 7]

[0318]

[0319] [Table 8]

[0320]

[0321] [Table 9]

[0322]

[0323] Industrial availability

[0324] According to this disclosure, an adhesive tape that exhibits excellent adhesion to silicone-based substrates without prior surface treatment can be provided, even without the use of silicone-based adhesives. Furthermore, according to this disclosure, a laminate having the adhesive tape attached to it can be provided. Additionally, according to this disclosure, an electronic device incorporating the adhesive tape can be provided.

[0325] Explanation of reference numerals in the attached figures

[0326] 1. Adhesive tape

[0327] 2. Components containing silicone resins

[0328] 3 Other components

[0329] 4. Polyethylene terephthalate (PET) film

[0330] 5 test pieces

[0331] 6 SUS304 boards

[0332] 7. Weight (1kg)

Claims

1. An adhesive tape, characterized in that, It has an adhesive layer containing (meth)acrylic acid copolymers. For a laminate formed by attaching the adhesive tape to silicone rubber fixed to a SUS304 board, after standing for 72 hours at 23°C and 50%RH, a peel test was performed using a tensile testing machine at 23°C, 50%RH, and a peel speed of 300 mm / min, peeling the adhesive tape from the silicone rubber in the laminate at 180°. The surface of the silicone rubber after the peel test, on the side where the adhesive tape was peeled off, was cleaned with ethyl acetate at least 8 times. TOF-SIMS analysis was then performed on the cleaned surface. The peak intensity of the negative ions in the region with m / z of 26 relative to the total peak intensity (total), i.e., 26 / total, was 2.50 × 10⁻⁶. -3 above.

2. The adhesive tape according to claim 1, wherein, The adhesive layer contains component A, which comprises at least one selected from the group consisting of a silane coupling agent having an aliphatic amino group, a silane coupling agent having a backbone with an aliphatic amino group protected, 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 backbone with an aliphatic amino group protected. The content of component A is less than 8.0 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer.

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

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

5. The adhesive tape according to claim 2, 3 or 4, wherein, In component A, at least one of the aliphatic amino groups is an aliphatic primary amino group or an aliphatic secondary amino group with a non-cyclic structure.

6. The adhesive tape according to claim 1, 2, 3, 4 or 5, wherein, The (meth)acrylic copolymer has structural units derived from alkyl (meth)acrylic esters. The structural unit derived from alkyl methacrylate does not have a structural unit of alkyl methacrylate derived from an ester terminus with 2 or fewer carbon atoms, or the structural unit derived from alkyl methacrylate has a structural unit of alkyl methacrylate derived from an ester terminus with 2 or fewer carbon atoms, and the content of the structural unit of alkyl methacrylate derived from an ester terminus with 2 or fewer carbon atoms is 25% by mass or less.

7. The adhesive tape according to claim 1, 2, 3, 4, 5 or 6, wherein, The structural unit derived from (meth)acrylate has a structural unit derived from (meth)acrylate and a structural unit of (meth)acrylate with 7 carbon atoms derived from the alkyl group at the ester terminus.

8. The adhesive tape according to claim 1, 2, 3, 4, 5, 6 or 7, wherein, The (meth)acrylic acid copolymers do not have structural units derived from carboxyl-containing monomers.

9. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein, The adhesive layer contains components that are cross-linked by electron beam irradiation or ultraviolet irradiation.

10. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein, The adhesive layer contains a free radical generating agent.

11. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein, The gel fraction of the adhesive layer is 35% by mass or more.

12. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein, The adhesive layer contains components that are cross-linked by electron beam irradiation or ultraviolet irradiation. The gel fraction of the adhesive layer is 35% by mass or more.

13. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, further comprising a spacer. The release layer of the spacer does not contain organic fluorine compounds.

14. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13, further comprising a spacer. The spacer was obtained by peeling the adhesive layer 180° at 23°C and 50%RH. XPS measurement was performed on the surface of the peel interface between the spacer and the adhesive layer. The relative intensity of the peak at 103.9 eV was below 0.

170.

15. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, for bonding silicone-based substrates.

16. The adhesive tape according to claim 15, wherein, The silicone-based adhesives are electronic device components, vehicle components, building components, and medical components.

17. A laminate comprising a structure formed by attaching the adhesive tape of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16 to a silicone-based substrate.

18. An electronic device comprising the adhesive tape as described in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16.

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