Adhesive sheet and method for producing adhesive sheet

Abstract

The purpose of the present invention is to provide: an adhesive sheet that is suitable for use even when a transmission signal has a higher frequency, and that has an excellent appearance in high-temperature environments and after peeling off a separator; and a method for producing the adhesive sheet. The present invention is an adhesive sheet including an adhesive layer and a separator on at least one of the surfaces of the adhesive layer. The adhesive layer has a dielectric loss tangent of 0.003 or less and a gel fraction of 30 mass% or more at a frequency of 10 GHz. When the separator is present on only one surface of the adhesive layer, the 180º peel strength of the separator with respect to the adhesive layer is 1.0 N / 25 mm or less. When the separator is present on both surfaces of the adhesive layer, the 180º peel strength of the separator on both surfaces with respect to the adhesive layer is 1.0 N / 25 mm or less.

Description

Adhesive sheet and method for manufacturing the adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a method for producing the pressure-sensitive adhesive sheet.

[0002] BACKGROUND ART Pressure-sensitive adhesive tapes or pressure-sensitive adhesive sheets are widely used in a variety of fields, for example, for assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), or for fixing in-vehicle electronic device components such as in-vehicle panels to vehicle bodies (e.g., Patent Documents 1 and 2).

[0003] JP 2009-242541 A JP 2009-258274 A

[0004] In recent years, in the field of electronic devices, there has been a demand for transmitting and receiving larger amounts of data at higher speeds, and the practical application of so-called fifth-generation mobile communication systems (5G) has been progressing, which has led to an increase in the frequency of transmission signals. However, the increase in frequency has caused a problem of increased attenuation of transmission signals (referred to as "transmission loss"). As adhesive tapes or sheets used in electronic devices, there is a demand for adhesive tapes or sheets that can suppress such transmission loss. In particular, in recent years, film-based antennas have been increasingly used for antennas such as small antenna base stations and vehicle-mounted antennas. As adhesive tapes or sheets used for bonding internal components of such antenna films, bonding antenna films to other components, etc., there is a demand for adhesive tapes or sheets that can suppress transmission loss and can be used suitably even when the transmission signal frequency is increased.

[0005] The present invention aims to provide an adhesive sheet that can be suitably used even when transmission signals are at high frequencies and that has excellent appearance in high-temperature environments and after the separator has been peeled off, and a method for producing the adhesive sheet.

[0006] The present disclosure 1 is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a separator on at least one side of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz and a gel fraction of 30 mass% or more, and when a separator is present on only one side of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less, and when separators are present on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. The present disclosure 2 is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a separator on at least one side of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz and a shear storage modulus at 150°C measured by dynamic viscoelasticity measurement at a frequency of 1 Hz of 1.0 x 10 ４Pa or more, and when a separator is provided on only one side of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less, and when separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less.

[0010] The present disclosure 3 is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a separator on at least one surface of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer having a dielectric dissipation factor of 0.003 or less at a frequency of 10 GHz and a gel fraction of 30 mass% or more, all of the separators having a silicon atom-containing release layer, and when a separator is present on only one surface of the pressure-sensitive adhesive layer, XPS measurement of the pressure-sensitive adhesive layer surface after peeling off the separator reveals a silicon atom concentration of 5 at% or less on the pressure-sensitive adhesive layer surface after peeling off the separator, and when separators are present on both surfaces of the pressure-sensitive adhesive layer, XPS measurement of the pressure-sensitive adhesive layer surface after peeling off the separator reveals a silicon atom concentration of 5 at% or less on both surfaces of the pressure-sensitive adhesive layer after peeling off the separator.

[0011] The present disclosure 4 is a pressure-sensitive adhesive sheet according to the present disclosure 1 or 2, wherein the separator has a silicon atom-containing release layer.

[0013] Disclosure 5 is the pressure-sensitive adhesive sheet of Disclosure 3, wherein when a separator is present on only one side of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less, and when separators are present on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. Disclosure 6 is the pressure-sensitive adhesive sheet of Disclosure 1, 2, 3, 4, or 5, wherein the separator is present on both sides of the pressure-sensitive adhesive layer, and the 180° peel strength of one separator from the pressure-sensitive adhesive layer is at least twice the 180° peel strength of the other separator from the pressure-sensitive adhesive layer. Disclosure 7 is the pressure-sensitive adhesive sheet of Disclosure 1, 2, 3, 4, 5, or 6, wherein the pressure-sensitive adhesive layer contains a rubber-based elastomer. Disclosure 8 is the pressure-sensitive adhesive sheet of Disclosure 7, wherein the rubber-based elastomer contains a hydrogenated styrene-based elastomer. Disclosure 9 is the pressure-sensitive adhesive sheet of Disclosure 8, wherein the hydrogenated styrene-based elastomer comprises a branched styrene-ethylene-butylene-styrene (SEBS) block copolymer.Disclosure 10 is the pressure-sensitive adhesive sheet of Disclosure 7, 8, or 9, wherein the pressure-sensitive adhesive layer contains a cross-linking aid, and the content of the cross-linking aid is 2 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the rubber-based elastomer. Disclosure 11 is the pressure-sensitive adhesive sheet of Disclosure 7, 8, 9, or 10, wherein the pressure-sensitive adhesive layer contains a tackifier resin, and the tackifier resin contains an alicyclic petroleum resin. Disclosure 12 is the pressure-sensitive adhesive sheet of Disclosure 7, 8, 9, 10, or 11, wherein the pressure-sensitive adhesive layer contains an antioxidant. Disclosure 13 is the pressure-sensitive adhesive sheet of Disclosure 12, wherein the antioxidant contains at least one selected from the group consisting of hindered phenols and hindered amines. Disclosure 14 is the pressure-sensitive adhesive sheet of claim 12 or 13, wherein the content of the antioxidant is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber-based elastomer. Disclosure 15 is the PSA sheet of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the PSA layer has a gel fraction of 50% by mass or less. Disclosure 16 is the PSA sheet of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, which does not have a substrate. Disclosure 17 is the PSA sheet of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, which has a PSA layer and a separator on at least one surface of the PSA layer, wherein the PSA layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz, a gel fraction of 30% by mass or more, and a shear storage modulus of 1.0 x 10 at 150°C as measured by dynamic viscoelasticity measurement at a frequency of 1 Hz. ４and when a separator is present on only one surface of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; when separators are present on both surfaces of the pressure-sensitive adhesive layer, the separators on both surfaces have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; all of the separators have a silicon atom-containing release layer; when a separator is present on only one surface of the pressure-sensitive adhesive layer, in XPS measurement of the surface of the pressure-sensitive adhesive layer after peeling of the separator, the silicon atom concentration of the surface of the pressure-sensitive adhesive layer after peeling of the separator is 5 at % or less; and when separators are present on both surfaces of the pressure-sensitive adhesive layer after peeling of the separator, in XPS measurement of the surface of the pressure-sensitive adhesive layer after peeling of the separator, the silicon atom concentration of both surfaces of the pressure-sensitive adhesive layer after peeling of the separator is 5 at % or less.

[0032] Disclosure 18 is a method for producing a pressure-sensitive adhesive sheet according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, comprising the step of irradiating a laminate having the pressure-sensitive adhesive layer and the separator on one side of the pressure-sensitive adhesive layer with energy rays from the separator side. Disclosure 19 is a method for producing a pressure-sensitive adhesive sheet according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, comprising the step of irradiating a laminate having the pressure-sensitive adhesive layer and the separator on both sides of the pressure-sensitive adhesive layer with energy rays from the separator sides on both sides. The present invention will be described in detail below. The pressure-sensitive adhesive sheet of Disclosure 1 will also be referred to as the "pressure-sensitive adhesive sheet of Invention 1," the pressure-sensitive adhesive sheet of Disclosure 2 will also be referred to as the "pressure-sensitive adhesive sheet of Invention 2," the pressure-sensitive adhesive sheet of Disclosure 3 will also be referred to as the "pressure-sensitive adhesive sheet of Invention 3," and the pressure-sensitive adhesive sheet of Disclosure 17 will also be referred to as the "pressure-sensitive adhesive sheet of Invention 17." Furthermore, matters common to the pressure-sensitive adhesive sheet of Invention 1, the pressure-sensitive adhesive sheet of Invention 2, the pressure-sensitive adhesive sheet of Invention 3, and the pressure-sensitive adhesive sheet of Invention 17 will not be specified in particular, or will be described as the "pressure-sensitive adhesive sheet of the present invention."

[0007] Since transmission loss increases in proportion to frequency, it is an unavoidable problem that transmission loss increases as the frequency of a transmission signal increases. Since transmission loss is affected not only by frequency but also by the "dielectric constant" and "dielectric loss tangent" of insulating parts present around conductive parts, in order to reduce transmission loss in high frequency bands (e.g., around 1 to 80 GHz), it is expected that transmission loss can be reduced, for example, by using a pressure-sensitive adhesive sheet that has a small dielectric loss tangent and excellent low dielectric properties in high frequency bands.

[0008] On the other hand, for example, antennas such as small antenna base stations and vehicle-mounted antennas are often used outdoors, so the pressure-sensitive adhesive sheets used for bonding internal components of the antenna film or bonding the antenna film to other components are exposed to high temperatures (about 120°C). When the pressure-sensitive adhesive sheet is exposed to high temperatures, outgassing may occur from the adherend, or microbubbles that have entered between the adherend and the pressure-sensitive adhesive sheet due to insufficient adhesion to the adherend may grow larger at high temperatures, causing foaming at the interface between the adherend and the pressure-sensitive adhesive sheet, resulting in a problem of impaired appearance. When foaming occurs at the interface between the adherend and the pressure-sensitive adhesive sheet, the dielectric properties in the high-frequency band may change, adversely affecting signal transmission.

[0009] In addition, a method for crosslinking the pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet includes irradiation with energy rays such as electron beams (EB). Energy ray irradiation allows crosslinking to proceed without introducing polar groups into the resin contained in the pressure-sensitive adhesive layer, thereby improving the low dielectric properties and heat resistance of the pressure-sensitive adhesive sheet. However, when a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer has been crosslinked by energy ray irradiation is used, the separator protecting the pressure-sensitive adhesive layer becomes hard and difficult to peel, which reduces the workability of the pressure-sensitive adhesive sheet and causes interface breakdown between the pressure-sensitive adhesive layer and the separator, resulting in a damaged appearance and a decrease in adhesive strength. On the other hand, when the separator is peeled off and the pressure-sensitive adhesive layer is crosslinked by energy ray irradiation, radicals derived from the resin contained in the pressure-sensitive adhesive layer, generated by energy ray irradiation, combine with oxygen in the air, oxidizing the resin contained in the pressure-sensitive adhesive layer, which can deteriorate the low dielectric properties.

[0010] The present inventors investigated adjusting, within specific ranges, the dielectric loss tangent of the adhesive layer at a frequency of 10 GHz, the gel fraction of the adhesive layer, or the shear storage modulus at 150°C measured by dynamic viscoelasticity measurement of the adhesive layer at a frequency of 1 Hz, and the 180° peel force of the separator from the adhesive layer or the silicon atom concentration on the surface of the adhesive layer after separator peeling, in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a separator on at least one side thereof. As a result, the present inventors discovered that a pressure-sensitive adhesive sheet can be obtained that is suitable for use even when transmission signals are at high frequencies and has excellent heat resistance and workability, leading to the completion of the present invention. The pressure-sensitive adhesive sheet of the present invention has excellent heat resistance and workability, and therefore has excellent appearance in high-temperature environments and after separator peeling.

[0011] The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer has a dielectric loss tangent (Df) of 0.003 at a frequency of 10 GHz. Since the pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz, the pressure-sensitive adhesive sheet of the present invention can be suitably used even when the transmission signal is at a high frequency. The pressure-sensitive adhesive layer preferably has a dielectric loss tangent of 0.002 at a frequency of 10 GHz, more preferably 0.001 at a frequency of 10 GHz. The lower limit of the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz is not particularly limited, and the lower the better. The dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz can be measured in accordance with JIS C2565 using, for example, a dielectric constant measuring device (such as "ADMS01Nc" manufactured by AET Corporation) in a TM mode resonator measurement mode.

[0012] The method for adjusting the dielectric loss tangent at a frequency of 10 GHz of the pressure-sensitive adhesive layer to fall within the above range is not particularly limited, and examples thereof include a method of adjusting the composition or content of the resin contained in the pressure-sensitive adhesive layer (described below), a method of reducing the molecular polarizability (e.g., a method of introducing fluorine atoms, hydrocarbon groups, etc.), and a method of increasing the molecular volume (e.g., a method of introducing an alicyclic structure). Other examples include a method of incorporating a substance exhibiting a low dielectric loss tangent into the pressure-sensitive adhesive layer (e.g., a method of incorporating a filler such as hollow cells, a fluorine filler, a silica filler, or glass fiber). Other examples include a method of reducing the mobility of the molecules contained in the pressure-sensitive adhesive layer (e.g., a method of incorporating a crystalline polymer), a method of increasing the average molecular weight of the polymer contained in the pressure-sensitive adhesive layer, and a method of reducing the water absorption or moisture content of the polymer contained in the pressure-sensitive adhesive layer (e.g., a method of introducing fluorine atoms or substituents, a method of introducing hydrocarbon groups). Furthermore, when crosslinking the pressure-sensitive adhesive layer, irradiating the pressure-sensitive adhesive layer with energy rays without peeling off the separator suppresses oxidation of the resin contained in the pressure-sensitive adhesive layer, making it easier to adjust the dielectric loss tangent to fall within the above range.

[0013] The pressure-sensitive adhesive layer preferably contains a rubber-based elastomer. Examples of the rubber-based elastomer include non-hydrogenated styrene-based elastomers and hydrogenated styrene-based elastomers. Among these, it is preferable to include a hydrogenated styrene-based elastomer, which has a low double bond (unsaturated bond) content and therefore provides the pressure-sensitive adhesive sheet of the present invention with excellent heat resistance and is less susceptible to changes in optical properties in high-temperature environments. The hydrogenated styrene-based elastomer has a smaller dielectric constant and dielectric loss tangent in high-frequency bands than, for example, acrylic polymers. Therefore, by including the hydrogenated styrene-based elastomer in the pressure-sensitive adhesive layer, the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz is more likely to fall within an appropriate range, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when transmission signals are at higher frequencies. In this specification, "hydrogenated styrene elastomer" means a styrene elastomer in which preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and even more preferably 96% or more of the double bonds (unsaturated bonds) in the repeating units derived from a conjugated diene compound described below have been converted to saturated bonds by hydrogenation. The hydrogenated styrene elastomer may be a partially hydrogenated product or a completely hydrogenated product. The hydrogenation ratio (hydrogenation rate) is measured by using deuterated chloroform as a solvent and measuring the hydrogenation rate at 20 Hz. １ It can be calculated by measuring the H-NMR spectrum.

[0014] The hydrogenated styrene elastomer is not particularly limited, but is preferably a hydrogenated product of a block copolymer having an aromatic alkenyl polymer block and a conjugated diene polymer block.

[0015] The hydrogenated product of the block copolymer having the aromatic alkenyl polymer block and the conjugated diene polymer block is not particularly limited, and may be any hydrogenated product of a block copolymer having rubber elasticity at room temperature and having a hard segment portion and a soft segment portion. The aromatic alkenyl polymer block is the hard segment portion, and the conjugated diene polymer block is the soft segment portion. More specific examples of the hydrogenated product of the block copolymer having the aromatic alkenyl polymer block and the conjugated diene polymer block include a hydrogenated product of a block copolymer having a structure represented by the formula A-B-A, a hydrogenated product of the formula (A-B) ｎ A: aromatic alkenyl polymer block B: conjugated diene polymer block C: component derived from a coupling agent n: integer of 3 or more Among them, a hydrogenated product of a radial block copolymer having a structure represented by the above formula (A-B) is particularly preferred. ｎ A hydrogenated product of a radial block copolymer having a structure represented by the formula (A-B) is preferred. ｎ In the hydrogenated radial block copolymer having the structure represented by C, crosslinking proceeds well, so that the gel fraction of the pressure-sensitive adhesive layer described below and the shear storage modulus at 150°C measured by dynamic viscoelasticity measurement of the pressure-sensitive adhesive layer at a frequency of 1 Hz described below (hereinafter, sometimes simply referred to as "shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C") more easily fall within appropriate ranges, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention. ｎ By containing a hydrogenated product of the radial block copolymer having the structure represented by C, the adhesive strength of the pressure-sensitive adhesive sheet of the present invention is further improved, and foaming at the interface with the adherend in a high-temperature environment is more unlikely to occur. Furthermore, the improved adhesive strength of the pressure-sensitive adhesive layer makes it possible to reduce the amount of tackifier resin (particularly the tackifier resin (T2) that is prone to self-polymerization as described below). As a result, the amount of tackifier resin (T2) that is easily self-polymerized as described below) that is contained in the pressure-sensitive adhesive sheet of the present invention is reduced. ｎCrosslinking of the hydrogenated radial block copolymer having a structure represented by C proceeds well, making it easier for the gel fraction of the pressure-sensitive adhesive layer described below and the shear storage modulus of the pressure-sensitive adhesive layer described below at a frequency of 1 Hz and 150°C to satisfy appropriate ranges, and further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention.

[0016] The aromatic alkenyl polymer block represented by A means a block having repeating units derived from an aromatic alkenyl compound. The aromatic alkenyl polymer block represented by A may be any block having repeating units derived from an aromatic alkenyl compound, and may also contain repeating units derived from other compounds such as ethylene and 1,3-butadiene (which is converted to an ethylene-butylene structure by hydrogenation). Examples of the aromatic alkenyl compound include alkylstyrenes, halogenated styrenes, halogen-substituted alkylstyrenes, alkoxystyrenes, carboxyalkylstyrenes, alkyl ether styrenes, alkylsilylstyrenes, vinylbenzyl dimethoxyphosphide, vinylnaphthalene, vinylanthracene, N,N-diethyl-p-aminoethylstyrene, and vinylpyridine.

[0017] Examples of the alkylstyrene include styrene, methylstyrene, dimethylstyrene, and t-butylstyrene. Examples of the halogenated styrene include chlorostyrene, bromostyrene, and fluorostyrene. Examples of the halogen-substituted alkylstyrene include chloromethylstyrene. Examples of the alkoxystyrene include methoxystyrene and ethoxystyrene. Examples of the carboxyalkylstyrene include carboxymethylstyrene. Examples of the alkyl etherstyrene include vinylbenzyl propyl ether. Examples of the alkylsilylstyrene include trimethylsilylstyrene. These aromatic alkenyl compounds may be used alone or in combination of two or more. Among these, styrene, methylstyrene, and dimethylstyrene are preferred, with styrene being more preferred due to its industrial availability.

[0018] The conjugated diene polymer block represented by B has a repeating unit derived from a conjugated diene compound. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene. These conjugated diene compounds may be used alone or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferred because of their high polymerization reactivity and industrial availability. In addition to the conjugated diene compounds, other usable compounds include, for example, 2,5-dihydrofuran-2,5-dione.

[0019] Examples of hydrogenated block copolymers having a structure represented by the above formula A-B-A include styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-ethylene-propylene-styrene (SEPS) block copolymer, styrene-ethylene-ethylene-propylene-styrene (SEEPS) block copolymer, and styrene-isobutylene-styrene (SIBS) block copolymer. Among these, SEBS block copolymers are preferred because crosslinking proceeds well and the gel fraction of the pressure-sensitive adhesive layer described below and the shear storage modulus of the pressure-sensitive adhesive layer described below at a frequency of 1 Hz and 150°C more easily fall within appropriate ranges, and branched SEBS block copolymers are more preferred. The number of branches in the branched SEBS block copolymer is preferably 2 or more, from the viewpoint of proceeding crosslinking well.

[0020] The above formula (A-B) ｎThe hydrogenated product of the radial block copolymer having the structure represented by C is a branched styrene block copolymer having a structure in which a plurality of styrene block copolymers (A-B) having a diblock structure in which one hard segment and one soft segment are bonded to each other project radially from component (C) derived from a coupling agent at the center. n may be an integer of 3 or more, but is preferably 4 or more in order to further improve the adhesive strength of the pressure-sensitive adhesive sheet of the present invention. There is no particular upper limit for n, but it is preferable that n is 4 or more as represented by the formula (A-B) above. ｎ From the viewpoint of preventing the hydrogenated product of the radial block copolymer having the structure represented by C from becoming too hard, it is usually 8 or less.

[0021] The coupling agent, which is the raw material for the component derived from the coupling agent represented by C, is a polyfunctional compound that radially bonds the diblock styrene-based block copolymer (A-B). Examples of the coupling agent include silane compounds such as halogenated silanes and alkoxysilanes, tin compounds such as tin halides, epoxy compounds such as polycarboxylic acid esters and epoxidized soybean oil, acrylic esters such as pentaerythritol tetraacrylate, and divinyl compounds such as epoxysilanes and divinylbenzene. More specific examples include trichlorosilane, tribromosilane, tetrachlorosilane, tetrabromosilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrachlorotin, and diethyl adipate.

[0022] The above formula (A-B) ｎ The preferred lower limit of the content of the aromatic alkenyl polymer block represented by A in the hydrogenated product of the radial block copolymer having the structure represented by C is 5% by mass, and the preferred upper limit is 30% by mass. When the content of the aromatic alkenyl polymer block represented by A is within the above range, the adhesive strength of the pressure-sensitive adhesive sheet of the present invention is further improved. ｎThe content of the aromatic alkenyl polymer block represented by A in the hydrogenated product of the radial block copolymer having the structure represented by C is more preferably 8% by mass, even more preferably 9% by mass, and more preferably 25% by mass, even more preferably 20% by mass.

[0023] The preferred upper limit of the styrene (St) content of the hydrogenated styrene-based elastomer is 30% by mass. If the styrene content is 30% by mass or less, the pressure-sensitive adhesive layer has appropriate adhesive strength, and the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz is more likely to fall within an appropriate range, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when transmission signals are at higher frequencies. A more preferred upper limit of the styrene content is 20% by mass. Furthermore, a preferred lower limit of the styrene content is 8% by mass, from the viewpoint of maintaining the cohesive strength of the pressure-sensitive adhesive layer. In this specification, the "styrene content" refers to the mass ratio (r １ That is, the styrene content (R1) (mass%) is derived from the mass ratio (r １ ): (monomer mass of aromatic alkenyl compound before polymerization) / (monomer mass of aromatic alkenyl compound before polymerization+monomer mass of conjugated diene compound before polymerization), and １ In addition, when the mass ratio of the aromatic alkenyl compound monomers before polymerization is unknown, the block copolymer can be calculated as １ The molar ratio (r ２ That is, the styrene content (R2) (mol%) can be predicted from the molar ratio (r ２ ): (molar ratio of aromatic alkenyl polymer block) / (molar ratio of aromatic alkenyl polymer block+molar ratio of conjugated diene polymer block), and ２(mol %). The styrene content (R2) is different from the styrene content (R1), but in the case of the SEBS block copolymer, for example, there are the following trends: When the styrene content (R1) is 10% by mass, the styrene content (R2) is 4 mol % or more and 7.9 mol % or less When the styrene content (R1) is 15% by mass, the styrene content (R2) is 8 mol % or more and 9.9 mol % or less When the styrene content (R1) is 20% by mass, the styrene content (R2) is 10 mol % or more and 15 mol % or less When the styrene content (R1) is 30% by mass, the styrene content (R2) is 15 mol % or more and 20 mol % or less When a commercially available product whose catalog lists the styrene content is used, that value is used as the styrene content.

[0024] The content of the styrene-based elastomer is not particularly limited, but a preferred lower limit of the content of the styrene-based elastomer relative to 100% by mass of the rubber-based elastomer is 80% by mass. If the content of the styrene-based elastomer is 80% by mass or more, foaming is less likely to occur at the interface between the pressure-sensitive adhesive sheet and the adherend in a high-temperature environment, and the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz is more likely to satisfy the range, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when transmission signals are at higher frequencies. A more preferred lower limit of the content of the styrene-based elastomer is 90% by mass. There is no particular preferred upper limit to the content of the rubber-based elastomer, and it may be 100% by mass. In other words, the rubber-based elastomer may be the styrene-based elastomer alone.

[0025] The preferred lower limit of the weight-average molecular weight (Mw) of the rubber-based elastomer is 100,000. If the weight-average molecular weight (Mw) is 100,000 or more, the adhesive strength of the pressure-sensitive adhesive layer is further improved, and the dielectric loss tangent at a frequency of 10 GHz of the pressure-sensitive adhesive layer is more likely to fall within the appropriate range, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when transmission signals are at higher frequencies. A more preferred lower limit of the weight-average molecular weight of the rubber-based elastomer is 200,000, and an even more preferred lower limit is 250,000. There is no particular preferred upper limit for the weight-average molecular weight of the rubber-based elastomer, but the higher the weight-average molecular weight of the rubber-based elastomer, the higher the adhesive strength of the pressure-sensitive adhesive sheet of the present invention. However, the viscosity of the pressure-sensitive adhesive increases, resulting in reduced processability. Therefore, from the perspective of pressure-sensitive adhesive sheet production, the limit is essentially around 700,000.

[0026] In this specification, the term "weight average molecular weight" refers to a weight average molecular weight measured as a polystyrene equivalent molecular weight by gel permeation chromatography (GPC). Measurement of the weight average molecular weight by GPC can be carried out, for example, by the following method. A solution of a rubber elastomer dissolved in tetrahydrofuran (THF) is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to obtain a GPC test solution. The GPC system used is "ACQUITY" manufactured by Waters Corporation. ＴＭ Advanced Polymer Chromatography ＴＭ The "HSPgel" manufactured by Waters was used as the GPC column. ＴＭGPC measurements are performed using a HR MB-M (6.0 mm x 150 mm) and a differential refractive index detector (Waters, "2414") as a detector. The sample injection volume is 20 mg / mL, the solution is 10 μL, the flow rate is 0.5 mL / min, and the column temperature is 40 ° C. The analysis software used is Empower 3, which is included with the device. Polystyrene (peak top molecular weight: 2,110,000, 1,090,000, 427,000, 190,000, 37,900, 18,100, 5,970, 2,420, 500) (manufactured by Tosoh Corporation) is used as a standard. Polystyrene is measured as a standard, and a calibration curve is created using analysis software to convert the elution volume to polystyrene molecular weight, and the weight average molecular weight is converted from the GPC elution volume using this calibration curve.

[0027] The preferred lower limit of the rubber elastomer content in the pressure-sensitive adhesive layer is 50% by mass, and the preferred upper limit is 95% by mass. A rubber elastomer content of 50% by mass or more makes it less likely for the pressure-sensitive adhesive sheet to foam at the interface with the adherend in high-temperature environments, and the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz is more likely to meet the range, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when transmission signals are at higher frequencies. A rubber elastomer content of 95% by mass or less makes the pressure-sensitive adhesive have an appropriately soft shear storage modulus at room temperature, allowing it to exhibit higher adhesive strength. A more preferred lower limit of the rubber elastomer is 53% by mass, a more preferred upper limit is 92% by mass, an even more preferred lower limit is 55% by mass, and an even more preferred upper limit is 90% by mass.

[0028] The pressure-sensitive adhesive layer preferably further contains a cross-linking aid. By including a cross-linking aid in the pressure-sensitive adhesive layer, cross-linking of the rubber-based elastomer proceeds smoothly, making it easier for the gel fraction of the pressure-sensitive adhesive layer described below and the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C to satisfy the appropriate ranges, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention. Examples of the cross-linking aid include (meth)acrylic monomers and triallyl isocyanurate. These cross-linking aids are easily radicalized, so by including these cross-linking aids in the pressure-sensitive adhesive layer, cross-linking of the rubber-based elastomer by energy ray irradiation proceeds smoothly. As a result, it is easier for the gel fraction of the pressure-sensitive adhesive layer described below and the shear storage modulus of the pressure-sensitive adhesive layer described below at a frequency of 1 Hz and 150°C to satisfy the appropriate ranges, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention. In this specification, "(meth)acrylic" refers to acrylic or methacrylic.

[0029] Examples of the (meth)acrylic monomer include (meth)acrylic acid esters, which are commonly used as monomers constituting (meth)acrylic copolymers. The number of functional groups in the (meth)acrylic monomer is not particularly limited, and may be bifunctional, trifunctional, tetrafunctional, pentafunctional, hexafunctional, or the like. Specific examples of the (meth)acrylic monomer 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, and dipentaerythritol hexa(meth)acrylate. These (meth)acrylic monomers may be used alone or in combination of two or more. Among these, methacrylic acid esters are preferred from the viewpoint of efficient crosslinking. Furthermore, when the base polymer contains the rubber-based elastomer, it is preferable that the base polymer has good compatibility with the rubber-based elastomer, facilitates more efficient crosslinking of the rubber-based elastomer, and has little effect on the dielectric properties of the PSA sheet of the present invention. Therefore, among methacrylic acid esters, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, and trimethylolpropane trimethacrylate are preferred.

[0030] The content of the cross-linking aid is preferably 2 parts by mass or more, and preferably 15 parts by mass or more, per 100 parts by mass of the rubber-based elastomer. When the content of the cross-linking aid is 2 parts by mass or more, cross-linking of the rubber-based elastomer proceeds well, making it easier for the gel fraction of the pressure-sensitive adhesive layer described below and the shear storage modulus of the pressure-sensitive adhesive layer described below at a frequency of 1 Hz and 150°C to fall within appropriate ranges, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention. When the content of the cross-linking aid is 15 parts by mass or less, the cross-linking aid does not bleed out, and the adhesive strength of the pressure-sensitive adhesive sheet of the present invention is further improved. A more preferred lower limit of the content of the cross-linking aid is 3 parts by mass, and even more preferred is 4 parts by mass, and a more preferred upper limit is 12 parts by mass, and even more preferred is 10 parts by mass.

[0031] The pressure-sensitive adhesive layer preferably further contains a tackifier resin, which further improves the adhesive strength of the pressure-sensitive adhesive layer and also reduces the likelihood of foaming at the interface with the adherend in a high-temperature environment, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention.

[0032] The tackifier resin is not particularly limited and may be a tackifier resin (T1) having no carbon-carbon double bond (unsaturated bond), or a tackifier resin (T2) having at least one selected from the group consisting of a carbon-carbon double bond and an aromatic ring. These tackifier resins may be used alone or in combination of two or more. Among these, it is preferable to contain the tackifier resin (T1), and the content of the tackifier resin (T1) in the tackifier resin is more preferably 80% by mass or more, and even more preferably 90% by mass or more. It is particularly preferable that the tackifier resin consists solely of the tackifier resin (T1) having no double bond. Since the tackifier resin (T1) has a smaller dielectric constant and dielectric loss tangent in the high-frequency band, by including the tackifier resin (T1) in the pressure-sensitive adhesive layer, the dielectric loss tangent at a frequency of 10 GHz of the pressure-sensitive adhesive layer is more likely to fall within the appropriate range, and the pressure-sensitive adhesive sheet of the present invention can be more suitably used even when the transmission signal frequency increases. Furthermore, the tackifier resin (T1) is less susceptible to self-polymerization than the tackifier resin (T2). Therefore, when the pressure-sensitive adhesive layer contains the tackifier resin (T1), crosslinking of the base polymer proceeds favorably, making it easier for the gel fraction of the pressure-sensitive adhesive layer, described below, and the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C, described below, to fall within appropriate ranges. As a result, the heat resistance of the pressure-sensitive adhesive sheet of the present invention is further improved.

[0033] The SP value of the tackifier resin (T1) is not particularly limited, but since the dielectric constant and dielectric loss tangent become even smaller in the high frequency band, a preferred upper limit is 9.0, and a more preferred upper limit is 8.5. The lower limit of the SP value of the tackifier resin (T1) is not particularly limited, but considering the SP values ​​of general tackifier resins, the substantial lower limit is about 7.5. In this specification, the "SP value" refers to a parameter that determines the activity of each component in a multi-component system, determined based on Hildebrand's regular solution theory, and is calculated by Small's method using Hoy's constant according to the following formula (I): SP value (δ) = d * (ΣG) / M (I) (d: density (g / mL), G: Hoy's molecular attraction constant of each functional group, M: molecular weight (g / mol))

[0034] The method for calculating the SP value is described in the following references: K. L. Hoy, New values ​​of the solubility parameters from vapor pressure data, J. Paint Techn., Vol. 42, No. 541, p. 76 (1970); K. L. Hoy, The Hoy tables of solubility parameters, Union Carbide Corp., 1985; Hoy, Solubility Parameters as a design parameter for water borne polymers and coatings. Preprints 14th Int. Conf. Athene, 1988. ;K. L. Hoy, J. Coated Fabrics, 19, p. 53 (1989).

[0035] Examples of the tackifier resin (T1) include hydrogenated C5 petroleum resins, alicyclic saturated hydrocarbon resins, hydrogenated C9 petroleum resins, hydrogenated C9 aromatic resins, hydrogenated α-methylstyrene resins, and ultra-light-colored rosin esters. Among these, the tackifier resin (T1) is preferably an alicyclic saturated hydrocarbon resin, which has excellent low dielectric properties.

[0036] Examples of the tackifier resin (T2) include terpenes, aromatic-modified terpenes, aromatic-modified hydrogenated terpenes, terpene phenols, hydrogenated terpene phenols, rosin esters, rosin phenols, styrene copolymer tackifier resins, C5 petroleum resins, alicyclic petroleum resins, C9 petroleum resins, C5 aliphatic resins, C9 aromatic resins, and pure C9 monomer resins. Among these, terpenes, aromatic-modified terpenes, and rosin esters are preferred, and terpenes are more preferred, from the viewpoint of being easily compatible with the rubber elastomer and further improving the adhesive strength of the pressure-sensitive adhesive sheet of the present invention. Furthermore, alicyclic petroleum resins are preferred, from the viewpoint of excellent low dielectric properties.

[0037] The preferred lower limit of the softening point of the tackifier resin is 80°C. If the softening point is 80°C or higher, the adhesive strength of the pressure-sensitive adhesive sheet of the present invention at high temperatures is further improved, and foaming at the interface with the adherend in a high-temperature environment is less likely to occur, resulting in better heat resistance. A more preferred lower limit of the softening point is 90°C, and an even more preferred lower limit is 100°C. There is no particular preferred upper limit of the softening point, but taking into account the temperature used, 140°C is preferred. The softening point can be measured by a method in accordance with JIS K2207.

[0038] The preferred lower limit of the content of the tackifier resin is 20 parts by mass, and the preferred upper limit is 80 parts by mass, relative to 100 parts by mass of the rubber-based elastomer. When the content of the tackifier resin is 20 parts by mass or more, the adhesive strength of the PSA layer is further improved. When the content of the tackifier resin is 80 parts by mass or less, even if the PSA layer contains the tackifier resin, crosslinking of the rubber-based elastomer proceeds well, making it easier for the gel fraction of the PSA layer described below and the shear storage modulus of the PSA layer at a frequency of 1 Hz and 150°C described below to fall within appropriate ranges, thereby further improving the heat resistance of the PSA sheet of the present invention. A more preferred lower limit of the content of the tackifier resin is 30 parts by mass, and a more preferred upper limit is 70 parts by mass.

[0039] The pressure-sensitive adhesive layer preferably further contains an antioxidant. By containing the antioxidant in the pressure-sensitive adhesive layer, oxygen radicals generated when the pressure-sensitive adhesive layer is crosslinked by energy ray irradiation can be trapped, and oxidation of the resin contained in the pressure-sensitive adhesive layer can be further suppressed, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when the transmission signal has a high frequency. Furthermore, by containing the antioxidant in the pressure-sensitive adhesive layer, radicals derived from the release layer generated in the separator described below can be trapped when the pressure-sensitive adhesive layer is crosslinked by energy ray irradiation from the separator side described below, and hardening of the separator can be further suppressed, thereby further improving the workability of the pressure-sensitive adhesive sheet of the present invention.

[0040] The antioxidant is not particularly limited, but from the viewpoints of heat resistance, minimal discoloration, and excellent optical properties, it is preferable that the antioxidant contains at least one selected from the group consisting of hindered phenols and hindered amines. Examples of the hindered phenols include Adekastab AO-60 (manufactured by ADEKA Corporation). Examples of the hindered amines include Tinuvin 123 (manufactured by BASF Corporation).

[0041] The antioxidant content, relative to 100 parts by mass of the rubber-based elastomer, preferably has a lower limit of 0.1% by mass and an upper limit of 10% by mass. By having the antioxidant content of 0.1% by mass or more, oxidation of the rubber-based elastomer can be further suppressed, making the pressure-sensitive adhesive sheet of the present invention more suitable for use even when transmission signals are at higher frequencies. Furthermore, hardening of the separator (described below) can be further suppressed, thereby improving the workability of the pressure-sensitive adhesive sheet of the present invention. By having the antioxidant content of 10% by mass or less, crosslinking of the rubber-based elastomer proceeds well, making it easier for the gel fraction of the pressure-sensitive adhesive layer (described below) and the shear storage modulus of the pressure-sensitive adhesive layer (described below) at a frequency of 1 Hz and 150°C to fall within appropriate ranges, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention. A more preferred lower limit of the antioxidant content is 0.5% by mass, an even more preferred lower limit is 1.0% by mass, and a more preferred upper limit is 8% by mass, an even more preferred upper limit is 5% by mass.

[0042] The pressure-sensitive adhesive layer may further contain a softener. The inclusion of a softener in the pressure-sensitive adhesive layer further improves the adhesive strength of the pressure-sensitive adhesive layer. Examples of softeners include polybutene, n-butene-isobutylene copolymer, polyisoprene, and paraffin-based oil. When the pressure-sensitive adhesive layer contains the rubber-based elastomer, polybutene is preferred due to its high compatibility with the rubber-based elastomer. On the other hand, the use of a softener reduces the adhesive strength of the pressure-sensitive adhesive sheet of the present invention at high temperatures. Therefore, the amount of the softener must be adjusted depending on the performance and degree of crosslinking of the rubber-based elastomer used. When using a rubber-based elastomer that can exhibit adhesive strength at room temperature even by itself, it is preferable to use a smaller amount of the softener. In other words, the lower limit of the amount of the softener is not particularly limited and may be 0 parts by mass.

[0043] The pressure-sensitive adhesive layer may contain other additives as long as the effects of the present invention are not impaired.

[0044] The preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 1 μm, and the preferred upper limit is 300 μm. When the thickness of the pressure-sensitive adhesive layer is within this range, the pressure-sensitive adhesive sheet of the present invention can achieve both sufficient adhesive strength and ease of handling. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 2.5 μm, and the more preferred upper limit is 200 μm.

[0045] In the pressure-sensitive adhesive sheet of Invention 1 and the pressure-sensitive adhesive sheet of Invention 3, the pressure-sensitive adhesive layer has a lower limit of gel fraction of 30% by mass. When the pressure-sensitive adhesive layer has a gel fraction of 30% by mass or more, the pressure-sensitive adhesive sheet of the present invention is less likely to foam at the interface with the adherend even in a high-temperature environment, thereby improving its heat resistance. A preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 35% by mass, and a more preferred lower limit is 40% by mass. Furthermore, in the pressure-sensitive adhesive sheet of Invention 2, the pressure-sensitive adhesive layer has a lower limit of gel fraction of 30% by mass. When the pressure-sensitive adhesive layer has a gel fraction of 30% by mass or more, the pressure-sensitive adhesive sheet of the present invention is less likely to foam at the interface with the adherend even in a high-temperature environment, thereby improving its heat resistance. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 35% by mass, and an even more preferred lower limit is 40% by mass. There is no particular upper limit to the gel fraction of the pressure-sensitive adhesive layer, but if it is too high, the adhesive strength of the pressure-sensitive adhesive sheet of the present invention will decrease and foaming will easily occur at the interface with the adherend in a high-temperature environment, so the upper limit is preferably 70% by mass, more preferably 50% by mass. The gel fraction of the pressure-sensitive adhesive layer can be measured, for example, as follows. That is, by peeling off the separator from the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer W ０ After collecting (g), the collected pressure-sensitive adhesive layer is immersed in 50 mL of toluene and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. After shaking, the pressure-sensitive adhesive layer is passed through a metal mesh (opening #200 mesh, mass: W １ The pressure-sensitive adhesive layer that has absorbed toluene and swollen is filtered using a filter (g). The separated pressure-sensitive adhesive layer is dried at 110°C for 1 hour, and then the mass W of the pressure-sensitive adhesive layer including the metal mesh is measured. ２ (g) is measured. ０ , W １ , and W ２ The gel fraction can be measured by a method of calculating the gel fraction from the following formula (1) using the above formula: Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (1) (W ０ : initial pressure-sensitive adhesive layer mass, W １ : initial mass of the metal mesh, W ２ : mass of adhesive layer including metal mesh after drying)

[0046] In the pressure-sensitive adhesive sheet of invention 2, the lower limit of the shear storage modulus at 150°C measured by dynamic viscoelasticity measurement at a frequency of 1 Hz of the pressure-sensitive adhesive layer is 1.0 x 10 ４ The pressure-sensitive adhesive layer has a shear storage modulus of 1.0×10 Pa at a frequency of 1 Hz and 150° C. ４ When the shear storage modulus of the pressure-sensitive adhesive layer is 1.5×10 Pa or more, the pressure-sensitive adhesive sheet of the present invention is less likely to foam at the interface with the adherend even in a high-temperature environment, and the heat resistance is improved. ４ Pa, and a more preferable lower limit is 2.0 × 10 ４ In the pressure-sensitive adhesive sheet of invention 1 and the pressure-sensitive adhesive sheet of invention 3, the preferred lower limit of the shear storage modulus at 150°C measured by dynamic viscoelasticity measurement at a frequency of 1 Hz of the pressure-sensitive adhesive layer is 1.0 x 10 ４ The pressure-sensitive adhesive layer has a shear storage modulus of 1.0×10 Pa at a frequency of 1 Hz and 150° C. ４ When the shear storage modulus of the pressure-sensitive adhesive layer is 1.5×10 Pa or more, the pressure-sensitive adhesive sheet of the present invention is less likely to develop bubbles at the interface with the adherend even in a high-temperature environment, and the heat resistance is further improved. ４ Pa, and a more preferable lower limit is 2.0 × 10 ４ Although there is no particular upper limit to the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C, if it is too high, the adhesive strength of the pressure-sensitive adhesive sheet of the present invention will decrease, and therefore a preferred upper limit is 1.0 × 10 ５Pa. The shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C can be measured by dynamic viscoelasticity measurement (DMA), for example, as follows. That is, the pressure-sensitive adhesive sheet of the present invention is cut into a 10 mm x 5 mm planar shape, and the separator and film are peeled off to prepare a measurement sample of the pressure-sensitive adhesive layer. Using a dynamic viscoelasticity measuring device (such as the "DVA-200" manufactured by IT Measurement Control Co., Ltd.), the dynamic viscoelasticity spectrum is measured from -50°C to 200°C under conditions of a slow heating rate shear deformation mode of 5°C / min and a measurement frequency of 1 Hz. By obtaining the shear storage modulus at 150°C in this measurement, the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C can be measured.

[0047] Examples of methods for adjusting the gel fraction and shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C within the above ranges include crosslinking resins contained in the pressure-sensitive adhesive layer, such as the rubber elastomer and the tackifier resin (if necessary). Other examples include adjusting the type and amount of the rubber elastomer and the tackifier resin (if necessary) involved in the crosslinking. Other examples include adjusting the type and amount of a crosslinking initiator that triggers the crosslinking reaction or a crosslinking aid that promotes crosslinking, adjusting the irradiation intensity and irradiation time of UV light, which is an energy ray that promotes crosslinking, adjusting the irradiation intensity, irradiation time, and acceleration voltage of electron beam irradiation, and adjusting the type and amount of a crosslinking inhibitor. Examples of crosslinking methods include crosslinking the rubber elastomer resin and the tackifier resin (if necessary) by irradiating them with UV light. Other examples include a method of crosslinking the rubber elastomer or the tackifier resin, etc., blended as needed, by electron beam irradiation, and a method of introducing crosslinkable functional groups into the rubber elastomer or the tackifier resin, etc., blended as needed, grafting them by electron beam irradiation, and then crosslinking them by heat. Crosslinking by irradiation with energy rays such as UV light or electron beams allows crosslinking to proceed without introducing polar groups into the resin contained in the pressure-sensitive adhesive layer, making it easier for the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz to fall within an appropriate range, and the pressure-sensitive adhesive sheet of the present invention can be more suitably used even when the transmission signal frequency increases. Furthermore, the pressure-sensitive adhesive sheet of the present invention has better heat resistance. Among these, the method of crosslinking by electron beam irradiation is more preferred from the viewpoint of increasing the production speed of the pressure-sensitive adhesive sheet.

[0048] The pressure-sensitive adhesive sheet of the present invention has a separator on at least one surface of the pressure-sensitive adhesive layer. That is, the pressure-sensitive adhesive sheet of the present invention may be a pressure-sensitive adhesive sheet having a separator on one surface of the pressure-sensitive adhesive layer, or a pressure-sensitive adhesive sheet having separators on both surfaces of the pressure-sensitive adhesive layer.

[0049] Examples of materials for the separator include polyester and kraft paper, with polyester being preferred from the viewpoint of preventing the inclusion of foreign matter from the separator.

[0050] The preferred upper limit of the thickness of the separator is 188 μm. By making the thickness of the separator 188 μm or less, the 180° peel strength of the separator from the pressure-sensitive adhesive layer is further reduced, and the workability of the pressure-sensitive adhesive sheet of the present invention is further improved. The more preferred upper limit of the thickness of the separator is 75 μm, and the even more preferred upper limit is 50 μm. There is no particular preferred lower limit of the thickness of the separator, but the lower limit is about 25 μm.

[0051] In the pressure-sensitive adhesive sheet of Invention 1 and the pressure-sensitive adhesive sheet of Invention 2, the separator has an upper limit of 1.0 N / 25 mm for its 180° peel strength from the pressure-sensitive adhesive layer. That is, when a separator is provided on only one side of the pressure-sensitive adhesive layer, the separator has an 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less, and when separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides have an 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. By ensuring that the 180° peel strengths of all of the separators from the pressure-sensitive adhesive layer are 1.0 N / 25 mm or less, the workability of the pressure-sensitive adhesive sheet of the present invention is improved. A preferred upper limit of the 180° peel strength of the separator from the pressure-sensitive adhesive layer is 0.8 N / 25 mm, and a more preferred upper limit is 0.5 N / 25 mm. In the pressure-sensitive adhesive sheet of invention 3, the separators preferably all have an upper limit of 1.0 N / 25 mm for their 180° peel strength from the pressure-sensitive adhesive layer. That is, when a separator is provided on only one side of the pressure-sensitive adhesive layer, the separator preferably has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. When separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides preferably have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. By having all of the separators have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less, the workability of the pressure-sensitive adhesive sheet of the invention is further improved. The upper limit of the 180° peel strength of the separator from the pressure-sensitive adhesive layer is more preferably 0.8 N / 25 mm, and even more preferably 0.5 N / 25 mm. Furthermore, there is no particular preferred lower limit for the 180° peel strength of the separator from the pressure-sensitive adhesive layer, but the lower limit is substantially about 0.01 N / 25 mm. The 180° peel strength of the separator from the pressure-sensitive adhesive layer can be measured, for example, as follows: The pressure-sensitive adhesive sheet is cut to have a planar shape of 25 mm x 70 mm, one separator (the side not to be measured) is peeled from the cut pressure-sensitive adhesive sheet, and the sheet is bonded to SUS by moving a rubber roller back and forth at a speed of 300 mm / min.After standing at 23°C for 24 hours, the other separator of the bonded PSA sheet is subjected to a 180° peel test at a peel rate of 300 mm / min using a tensile tester (manufactured by Shimadzu Corporation, "AG-IS"), whereby the 180° peel strength of the separator to the PSA layer can be measured.

[0052] When the pressure-sensitive adhesive sheet of the present invention has the separators on both sides of the pressure-sensitive adhesive layer, the 180° peel strength of one separator from the pressure-sensitive adhesive layer is preferably at least twice the 180° peel strength of the other separator from the pressure-sensitive adhesive layer. By having the 180° peel strength of one separator from the pressure-sensitive adhesive layer at least twice the 180° peel strength of the other separator from the pressure-sensitive adhesive layer, one separator can be peeled off without peeling off the other separator, thereby further improving the workability of the pressure-sensitive adhesive sheet of the present invention.

[0053] In the pressure-sensitive adhesive sheet of invention 3, all of the separators have a silicon atom-containing release layer. When the separator has a silicon atom-containing release layer, the 180° peel strength of the separator from the pressure-sensitive adhesive layer, as described below, is reduced, improving the workability of the pressure-sensitive adhesive sheet of the present invention. Furthermore, the separators in the pressure-sensitive adhesive sheets of invention 1 and invention 2 preferably have a silicon atom-containing release layer. When the separator has a silicon atom-containing release layer, the 180° peel strength of the separator from the pressure-sensitive adhesive layer is further reduced, improving the workability of the pressure-sensitive adhesive sheet of the present invention. Note that when the pressure-sensitive adhesive sheet of invention 1 and invention 2 have separators on both sides, only one separator may have a silicon atom-containing release layer, or both separators may have silicon atom-containing release layers.

[0054] The pressure-sensitive adhesive sheet of the present invention is preferably produced by irradiating the separator with energy rays to crosslink the resin contained in the pressure-sensitive adhesive layer, as described below. However, when the separator has the silicon atom-containing release layer, radicals derived from the release layer are generated in the separator by energy ray irradiation, and the pressure-sensitive adhesive layer and the separator are crosslinked, so that the separator becomes hard and the workability of the pressure-sensitive adhesive sheet of the present invention is reduced. In this case, when the separator is peeled from the pressure-sensitive adhesive layer, silicon atoms are transferred to the pressure-sensitive adhesive layer through crosslinking between the separator and the pressure-sensitive adhesive layer by radicals derived from the release layer. Therefore, by measuring the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled, the amount of silicon atoms transferred to the pressure-sensitive adhesive layer and, consequently, the degree of crosslinking between the separator and the pressure-sensitive adhesive layer by radicals derived from the release layer can be predicted, and the workability of the pressure-sensitive adhesive sheet of the present invention can be evaluated. In the pressure-sensitive adhesive sheet of the third invention, in XPS measurement of the pressure-sensitive adhesive layer surface after the separator is peeled off, the upper limit of the silicon atom concentration on the pressure-sensitive adhesive layer surface after the separator is peeled off is 5 at% in all cases. That is, when a separator is present on only one side of the pressure-sensitive adhesive layer, in XPS measurement of the pressure-sensitive adhesive layer surface after the separator is peeled off, the silicon atom concentration on the pressure-sensitive adhesive layer surface after the separator is peeled off is 5 at% or less. When separators are present on both sides of the pressure-sensitive adhesive layer, in XPS measurement of both surfaces of the pressure-sensitive adhesive layer after the separator is peeled off, the silicon atom concentration on the pressure-sensitive adhesive layer surface after the separator is peeled off is 5 at% or less. By having the silicon atom concentrations on the pressure-sensitive adhesive layer surface after the separator is peeled off be 5 at% or less in all cases, crosslinking between the pressure-sensitive adhesive layer and the separator due to radicals derived from the release layer in the separator can be suppressed, improving the workability of the pressure-sensitive adhesive sheet of the present invention. A preferred upper limit of the silicon atom concentration on the pressure-sensitive adhesive layer surface after the separator is peeled off is 3 at%. In the pressure-sensitive adhesive sheet of invention 1 and the pressure-sensitive adhesive sheet of invention 2, the preferred upper limit of the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after peeling off the separator is 5 at % in XPS measurement of the surface of the pressure-sensitive adhesive layer after peeling off the separator.By having a silicon atom concentration of 5 at% or less on the surface of the pressure-sensitive adhesive layer after the separator is peeled off, crosslinking between the pressure-sensitive adhesive layer and the separator due to radicals derived from the release layer in the separator can be further suppressed, further improving the workability of the pressure-sensitive adhesive sheet of the present invention. A more preferred upper limit of the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off is 3 at%. There is no particular preferred lower limit for the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off, but the closer to 0 at% it is, the more preferred. Note that when the pressure-sensitive adhesive sheet of the first invention and the pressure-sensitive adhesive sheet of the second invention have separators with silicon atom-containing release layers on both sides of the pressure-sensitive adhesive layer, it is more preferred that the silicon atom concentrations on both surfaces of the pressure-sensitive adhesive layer after the separator is peeled off satisfy the above-mentioned range.

[0055] The silicon atom concentration in XPS measurement of the pressure-sensitive adhesive layer surface after the separator has been peeled off can be obtained, for example, by the following method. That is, wide-scan analysis of XPS measurement is performed on the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet after the separator has been peeled off using a PHI5000 VersaProbe II (manufactured by ULVAC-PHI) or the like. Next, the concentrations of atoms other than silicon, such as the carbon atom concentration, nitrogen atom concentration, and oxygen atom concentration, and the silicon atom concentration are each derived by considering the RSF (relative sensitivity factor S) for the integrated value analyzed from the obtained spectral data. The silicon atom concentration relative to the total of all the derived atomic concentrations (100 at%) can then be calculated to obtain the silicon atom concentration on the pressure-sensitive adhesive layer surface after the separator has been peeled off. The XPS measurement is performed under the following conditions: X-ray source: Al Kα radiation; Photoelectron take-off angle: 45 degrees; Step width: 1 eV

[0056] In this specification, "the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off" means, in the case where the pressure-sensitive adhesive layer contains a component having a silicon atom, the concentration does not include the silicon atom concentration derived from that component. The silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off and the silicon atom concentration derived from the component contained in the pressure-sensitive adhesive layer can be distinguished as follows. That is, the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off is subtracted from the silicon atom concentration on the surface of a pressure-sensitive adhesive layer of the same composition prepared without using a separator, thereby distinguishing between the silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off and the silicon atom concentration derived from the component contained in the pressure-sensitive adhesive layer.

[0057] The pressure-sensitive adhesive sheet of the present invention may be a supported type having a substrate or a non-supported type having no substrate, as long as it has the pressure-sensitive adhesive layer and the separator on at least one side thereof. Among these, the non-supported type having no substrate is preferred from the viewpoints of cost, thinness, optical properties, and keeping the dielectric loss tangent low.

[0058] The pressure-sensitive adhesive sheet of the present invention has a preferred lower limit of transmission loss at a frequency of 40 GHz for a polyimide substrate of -10 dB. When the pressure-sensitive adhesive sheet of the present invention has a transmission loss of -10 dB or more for a polyimide substrate at a frequency of 40 GHz, the pressure-sensitive adhesive sheet of the present invention can be more suitably used even when the transmission signal is at a higher frequency. A more preferred lower limit of transmission loss at a frequency of 40 GHz for a polyimide substrate of the pressure-sensitive adhesive sheet of the present invention is -9 dB, and an even more preferred lower limit is -8 dB. There is no particular upper limit to the transmission loss at a frequency of 40 GHz for a polyimide substrate of the pressure-sensitive adhesive sheet of the present invention, but the closer to 0 dB, the more preferable. The transmission loss at a frequency of 40 GHz for a polyimide substrate of the pressure-sensitive adhesive sheet of the present invention can be obtained, for example, by measuring the transmission loss of a measurement sample at a frequency of 40 GHz and an impedance value of 50 Ω using a vector network analyzer (manufactured by Agilent Technologies, "N523OA") and a measurement probe (manufactured by SUSS MicroTec, "B90-122391"). The evaluation sample can be prepared by laminating polyimide and copper, etching the polyimide substrate to form a microstrip line, and then laminating an adhesive sheet on top of the copper wiring.

[0059] The preferred lower limit of the 90° peel strength of the pressure-sensitive adhesive sheet of the present invention from PC (polycarbonate) at 23°C is 10 N / 25 mm. When the pressure-sensitive adhesive sheet of the present invention has a 90° peel strength of 10 N / 25 mm or more from PC at 23°C, the pressure-sensitive adhesive sheet of the present invention has superior adhesive strength, exhibits high adhesive strength even to adherends that are prone to outgassing in high-temperature environments, and is less likely to develop bubbles at the interface with the adherend even in high-temperature environments. Examples of adherends that are prone to outgassing in high-temperature environments include adherends made of polycarbonate (PC), cycloolefin polymer (COP), polyimide (PI), etc. The more preferred lower limit of the 90° peel strength of the pressure-sensitive adhesive sheet of the present invention from PC at 23°C is 12 N / 25 mm, and even more preferred is 15 N / 25 mm. There is no particular preferred upper limit of the 90° peel strength of the pressure-sensitive adhesive sheet of the present invention from PC at 23°C, but from the viewpoint of workability, the upper limit is essentially about 50 N / 25 mm. The 90° peel strength of the pressure-sensitive adhesive sheet of the present invention against PC at 23°C can be measured, for example, by conducting a 90° peel test in an environment of 25°C at a peel rate of 50 mm / min.

[0060] The method for adjusting the 90° peel strength from PC at 23°C of the pressure-sensitive adhesive sheet of the present invention within the above range is not particularly limited, and examples include a method of adjusting the type and amount of resin contained in the pressure-sensitive adhesive layer, such as the rubber-based elastomer and the tackifier resin blended as needed, a method of adjusting the gel fraction of the pressure-sensitive adhesive layer and the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C, a method of modifying the surface of the pressure-sensitive adhesive layer by plasma treatment or corona treatment, etc. Other examples include a method of reducing the styrene content of the rubber-based elastomer, a method of increasing the diblock amount of the rubber-based elastomer, a method of increasing the thickness of the pressure-sensitive adhesive layer, a method of blending a filler into the pressure-sensitive adhesive layer to increase deformation resistance, etc.

[0061] The haze of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but is preferably 5.0% or less, and more preferably less than 1.0%. ＊The pressure-sensitive adhesive sheet of the present invention is resistant to changes in optical properties such as yellowing even in a high-temperature environment, and the haze and yellowing b value are preferably 0.5 or less, and more preferably 0.3 or less. ＊ It is preferable that the haze and yellowing index b (value b) of the pressure-sensitive adhesive sheet of the present invention satisfy the above range. ＊ The (b value) can be measured using, for example, a spectrophotometer (such as "CM3700A" manufactured by Konica Minolta, Inc.).

[0062] The pressure-sensitive adhesive sheet of the seventeenth invention has a pressure-sensitive adhesive layer and a separator on at least one surface of the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz, a gel fraction of 30 mass% or more, and a shear storage modulus of 1.0×10 at 150° C. as measured by dynamic viscoelasticity measurement at a frequency of 1 Hz. ４ Pa or more, and when a separator is present on only one side of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less, and when separators are present on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; all of the separators have a silicon atom-containing release layer, and when a separator is present on only one side of the pressure-sensitive adhesive layer, in XPS measurement of the surface of the pressure-sensitive adhesive layer after peeling the separator, the silicon atom concentration of the surface of the pressure-sensitive adhesive layer after peeling the separator is 5 at % or less, and when separators are present on both sides of the pressure-sensitive adhesive layer, in XPS measurement of the surface of the pressure-sensitive adhesive layer after peeling the separator, the silicon atom concentration of both surfaces of the pressure-sensitive adhesive layer after peeling the separator is 5 at % or less. Because of this configuration, the adhesive sheet of invention 17 can be suitably used even when the transmission signal is at a higher frequency, and has excellent appearance in high-temperature environments and after the separator is peeled off.

[0063] The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and any conventionally known method can be used. For example, the pressure-sensitive adhesive sheet can be produced by applying a pressure-sensitive adhesive solution containing the styrene-based elastomer and, if necessary, other additives such as the tackifier resin, onto a separator that has been subjected to a release treatment, drying the resulting mixture to form a pressure-sensitive adhesive layer, and then overlaying a base film or a separator that has been subjected to a release treatment on the pressure-sensitive adhesive layer.

[0064] The method for applying the pressure-sensitive adhesive solution to the separator is not particularly limited, but application using a comma coater is preferred from the viewpoints of making it easier to adjust the 180° peel strength of the separator from the pressure-sensitive adhesive layer within the above range and further improving the workability of the pressure-sensitive adhesive sheet of the present invention.

[0065] The present invention also provides a method for producing a pressure-sensitive adhesive sheet, comprising the step of irradiating a laminate having the pressure-sensitive adhesive layer and the separator on one side of the pressure-sensitive adhesive layer with energy rays from the separator side. By including the step of irradiating with energy rays from the separator side, oxidation of the resin contained in the pressure-sensitive adhesive layer due to association of oxygen in the atmosphere with radicals derived from the resin contained in the pressure-sensitive adhesive layer generated by energy ray irradiation can be further suppressed, making it easier for the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz to fall within an appropriate range. As a result, the pressure-sensitive adhesive sheet of the present invention can be more suitably used even when transmission signals are at higher frequencies.

[0066] When the pressure-sensitive adhesive sheet of the present invention has separators on both sides of the pressure-sensitive adhesive layer, a method for producing a pressure-sensitive adhesive sheet of the present invention also includes a step of irradiating a laminate having the pressure-sensitive adhesive layer and the separators on both sides of the pressure-sensitive adhesive layer with energy rays from the separator sides on both sides. By including a step of irradiating with energy rays from the separator sides on both sides, oxidation of the resin contained in the pressure-sensitive adhesive layer due to association of oxygen in the air with radicals derived from the resin contained in the pressure-sensitive adhesive layer generated by energy ray irradiation can be further suppressed, making it easier to adjust the dielectric loss tangent of the pressure-sensitive adhesive layer at a frequency of 10 GHz within the above range. As a result, the pressure-sensitive adhesive sheet of the present invention can be more suitably used even when transmission signals are at higher frequencies. Furthermore, generation of radicals derived from the release layer in one of the separators can be further suppressed, thereby reducing the 180° peel force of the separator from the pressure-sensitive adhesive layer, thereby further improving the workability of the pressure-sensitive adhesive sheet of the present invention. In the step of irradiating energy rays from the separator side of both surfaces, the 180° peel force of the separator from the pressure-sensitive adhesive layer on each surface can be adjusted by adjusting the irradiation intensity, irradiation time, and acceleration voltage of the energy rays irradiated from the separator side on each surface.

[0067] When the production of the pressure-sensitive adhesive sheet of the present invention includes a step of irradiating with energy rays, the preferred lower limit of the energy ray irradiation intensity is 5 kGy, and the preferred upper limit is 300 kGy. When the energy ray irradiation intensity is 5 kGy or more, the crosslinking of the pressure-sensitive adhesive layer proceeds more, making it easier to adjust the gel fraction of the pressure-sensitive adhesive layer and the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C within the above ranges, thereby further improving the heat resistance of the pressure-sensitive adhesive sheet of the present invention. When the energy ray irradiation intensity is 300 kGy or less, the generation of radicals derived from the release layer can be further suppressed, and the 180° peel force of the separator from the pressure-sensitive adhesive layer can be further reduced, thereby further improving the workability of the pressure-sensitive adhesive sheet of the present invention. The more preferred lower limit of the energy ray irradiation intensity is 10 kGy, and even more preferred is 20 kGy, and the more preferred upper limit is 250 kGy, and even more preferred is 200 kGy.

[0068] The use of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but it is preferably used in a device that transmits or receives electromagnetic waves. The device that transmits or receives electromagnetic waves preferably includes a laminate containing the pressure-sensitive adhesive sheet of the present invention and a film on which a conductive pattern is formed. The pressure-sensitive adhesive sheet of the present invention can be suitably used even when the transmission signal is at a high frequency, so it is more preferably used in a device that transmits or receives electromagnetic waves with a frequency of 1 GHz or more. More specifically, the pressure-sensitive adhesive sheet of the present invention is preferably used in a device that transmits or receives electromagnetic waves with a frequency of 1 GHz or more, for bonding internal components of a laminate (e.g., an antenna film, a substrate, etc.) containing a film on which a conductive pattern is formed, or for bonding a laminate containing the film on which a conductive pattern is formed to another component, in a device that transmits or receives electromagnetic waves with a frequency of 1 GHz or more. The device that transmits or receives electromagnetic waves with a frequency of 1 GHz or more is not particularly limited, and examples thereof include small antenna base stations, antennas such as in-vehicle antennas, smartphones, tablet terminals, other portable electronic devices, in-vehicle electronic devices, smart glasses, etc.

[0069] FIG. 1 is a cross-sectional view schematically illustrating the state in which internal members of a laminate including a film on which a conductive pattern is formed are bonded together using the pressure-sensitive adhesive sheet of the present invention. In FIG. 1, internal members 21 and 22 are bonded together using the pressure-sensitive adhesive sheet 1 of the present invention in a laminate 2 including a film on which a conductive pattern is formed. The laminate 2 including a film on which a conductive pattern is formed may have further members (for example, members 23 and 24 as shown in FIG. 1) in addition to the pressure-sensitive adhesive sheet 1 of the present invention and members 21 and 22. FIG. 2 is a cross-sectional view schematically illustrating the state in which a laminate including a film on which a conductive pattern is formed is bonded to another member using the pressure-sensitive adhesive sheet of the present invention. In FIG. 2, a laminate 2 including a film on which a conductive pattern is formed is bonded to another member 3 using the pressure-sensitive adhesive sheet 1 of the present invention.

[0070] According to the present invention, it is possible to provide an adhesive sheet that can be suitably used even when the transmission signal is at a high frequency and that has excellent appearance in high-temperature environments and after the separator has been peeled off, and a method for manufacturing the adhesive sheet.

[0071] 1 is a cross-sectional view schematically showing a state in which the pressure-sensitive adhesive sheet of the present invention is used to bond internal members of a laminate including a film on which a conductive pattern is formed, and a cross-sectional view schematically showing a state in which the pressure-sensitive adhesive sheet of the present invention is used to bond a laminate including a film on which a conductive pattern is formed and another member.

[0072] The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples.

[0073] (Synthesis of Radial Hydrogenated Styrenic Elastomer A (Mw: 300,000)) 4,000 g of degassed and dehydrated cyclohexane, 200 g of 1,3-butadiene monomer, 3.0 g of n-butyllithium (n-BuLi), and tetrahydrofuran (THF) were added to an autoclave at a molar ratio of n-BuLi / THF = 40. Polymerization was then carried out for 40 minutes at the polymerization initiation temperature of 40°C, followed by addition of 100 g of styrene monomer and polymerization for 60 minutes (aromatic alkenyl polymer block (A)). 700 g of 1,3-butadiene monomer was then added and polymerization was carried out for 150 minutes (diblock structured styrene-based block copolymer (A-B)). Tetrachlorosilane (SiCl ) was added as a coupling agent. ４ 0.25 moles of 2,4-dimethylaminobenzoate (A-B) was added to the copolymer to carry out a coupling reaction of the diblock styrene-based block copolymer (A-B), thereby obtaining a styrene-based block copolymer having a styrene content of 10% by weight. This copolymer was diluted with purified and dried cyclohexane to adjust the polymer concentration to 5% by mass, and then subjected to a hydrogenation reaction.

[0074] In the hydrogenation reaction, 1000 g of the copolymer solution was first charged into a thoroughly dried 2 L autoclave equipped with a stirrer, degassed under reduced pressure, substituted with hydrogen, and maintained at 90°C with stirring. Next, 50 ml of a cyclohexane solution containing 0.2 mmol of di-p-tolylbis(η-cyclopentadienyl)titanium and 10 ml of a cyclohexane solution containing 0.108 mmol of n-butyllithium (n-BuLi) were added at 0°C and 2.0 kg / cm ２ The mixture was mixed under a hydrogen pressure of 0.7 MPa and added to the copolymer solution in the autoclave. The hydrogenation reaction was initiated under stirring at a hydrogen gas supply pressure of 0.7 MPa-Gauge and a reaction temperature of 80°C. When hydrogen absorption was complete, the reaction solution was returned to room temperature and pressure and extracted from the reaction vessel to obtain radial hydrogenated styrene elastomer A (radial block copolymer (A-B) ４ The resulting radial hydrogenated styrene elastomer A was １ H-NMR analysis revealed that 95% or more of the butadiene units and less than 5% of the styrene units were hydrogenated.

[0075] (Preparation of Pressure-Sensitive Adhesive (A to R) Solutions) According to the compositions shown in Table 1, each material was added to 350 parts by mass of toluene and stirred to obtain pressure-sensitive adhesive solutions containing Pressure-Sensitive Adhesives A to R.

[0076]

[0077] (Examples 1 to 16, Comparative Examples 1, 4 to 6, 8 to 10) (1) Preparation of Pressure-Sensitive Adhesive Sheets A pressure-sensitive adhesive solution was applied to the silicon atom-containing release layer of a 75 μm-thick separator ("SP8001" manufactured by Toyo Cross Co., Ltd.) so that the thickness after drying would be 50 μm, and then dried at 110° C. for 5 minutes to form a pressure-sensitive adhesive layer. A 50 μm-thick separator ("SP8001" manufactured by Toyo Cross Co., Ltd.) was then laminated on the side of the pressure-sensitive adhesive layer where the separator was not laminated, with the silicon atom-containing release layer facing the pressure-sensitive adhesive layer, to prepare a laminate. The surface of the pressure-sensitive adhesive layer that was in contact with the 50 μm-thick separator was designated the front surface, and the surface that was in contact with the 75 μm-thick separator was designated the back surface. Furthermore, according to the electron beam irradiation conditions shown in Tables 2 to 4, the front and back surfaces of the pressure-sensitive adhesive layer of the prepared laminate were irradiated with electron beams from the separator side at an acceleration voltage of 150 kV using an electron beam irradiation apparatus EBC-200 (manufactured by NHV Corporation), thereby crosslinking the pressure-sensitive adhesive layer and obtaining a pressure-sensitive adhesive sheet.

[0078] (2) Measurement of the dielectric loss tangent of the adhesive layer at a frequency of 10 GHz. Multiple sheets of the resulting adhesive sheet were laminated to a thickness of 100 μm. The separators on both sides of the laminated adhesive sheet were peeled off, and 50 μm-thick polyethylene terephthalate (PET) films were attached to the top and bottom surfaces. The resulting laminate of PET film and adhesive layer was cut into a width of 3 mm and a length of 80 mm, and the dielectric loss tangent was measured in the TM mode resonator measurement mode using a dielectric constant measurement device (manufactured by AET Corporation, "ADMS01Nc") in accordance with JIS C2565. The dielectric loss tangent of the PET film alone was also measured using the above method, and the value of the adhesive layer alone was calculated using the measured value of the laminate of the PET film and adhesive layer and the measured value of the PET film alone. The results are shown in Tables 2 to 4.

[0079] (3) Measurement of gel fraction of pressure-sensitive adhesive layer The separator of the pressure-sensitive adhesive sheet was peeled off, and the pressure-sensitive adhesive layer W ０ After collecting (g), the collected pressure-sensitive adhesive layer was immersed in 50 mL of toluene and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. After shaking, the pressure-sensitive adhesive layer was passed through a metal mesh (opening #200 mesh, mass: W １The pressure-sensitive adhesive layer that had absorbed toluene and swollen was filtered using a filter (g). The separated pressure-sensitive adhesive layer was dried at 110°C for 1 hour, and then the mass W ２ The measured W (g) was ０ , W １ , and W ２ The gel fraction was calculated from the following formula (1) using the above formula. The results are shown in Tables 2 to 4. Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (1) (W ０ : initial pressure-sensitive adhesive layer mass, W １ : initial mass of the metal mesh, W ２ : mass of adhesive layer including metal mesh after drying)

[0080] (4) Measurement of Shear Storage Modulus of Pressure-Sensitive Adhesive Layer at a Frequency of 1 Hz and 150°C The obtained pressure-sensitive adhesive sheet was cut into a 10 mm x 5 mm planar shape, and the separators on both sides were peeled off to prepare a measurement sample of only the pressure-sensitive adhesive layer. Then, using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200"), the dynamic viscoelasticity spectrum was measured from -50°C to 200°C under conditions of a slow heating rate shear deformation mode of 5°C / min and a measurement frequency of 1 Hz. The shear storage modulus at 150°C in this measurement was obtained, and the shear storage modulus of the pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C was measured. The results are shown in Tables 2 to 4.

[0081] (Comparative Example 2) A pressure-sensitive adhesive sheet was obtained in the same manner as in "(1) Preparation of pressure-sensitive adhesive sheet" above, except that electron beam irradiation was not performed. In addition, measurements were performed using the same methods as in "(2) Measurement of dielectric loss tangent of pressure-sensitive adhesive layer at a frequency of 10 GHz", "(3) Measurement of gel fraction of pressure-sensitive adhesive layer", and "(4) Measurement of shear storage modulus of pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C" above. The results are shown in Table 4.

[0082] (Comparative Example 3) A pressure-sensitive adhesive sheet was obtained in the same manner as in "(1) Preparation of pressure-sensitive adhesive sheet" above, except that the pressure-sensitive adhesive layer was crosslinked by heating at 40°C for 72 hours instead of crosslinking the pressure-sensitive adhesive layer by electron beam irradiation. In addition, measurements were performed in the same manner as in "(2) Measurement of dielectric loss tangent of pressure-sensitive adhesive layer at a frequency of 10 GHz", "(3) Measurement of gel fraction of pressure-sensitive adhesive layer", and "(4) Measurement of shear storage modulus of pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C" above. The results are shown in Table 4.

[0083] (Comparative Example 7) A pressure-sensitive adhesive sheet was obtained in the same manner as in "(1) Preparation of pressure-sensitive adhesive sheet" above, except that the separator was peeled off when irradiating with electron beams. Measurements were also carried out in the same manner as in Example 1, and by the same methods as in "(2) Measurement of dielectric loss tangent of pressure-sensitive adhesive layer at a frequency of 10 GHz", "(3) Measurement of gel fraction of pressure-sensitive adhesive layer", and "(4) Measurement of shear storage modulus of pressure-sensitive adhesive layer at a frequency of 1 Hz and 150°C". The results are shown in Table 4.

[0084]

[0085]

[0086]

[0087] <Evaluation> The pressure-sensitive adhesive sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 5 to 7.

[0088] (Low Dielectric Properties) A ​​polyimide substrate was prepared by laminating polyimide and copper and etching the laminate to form a microstrip line. The resulting pressure-sensitive adhesive sheet was cut to match the shape of the prepared polyimide substrate. The separator on one side of the cut pressure-sensitive adhesive sheet was peeled off, and a 2.0 kg rubber roller was placed on the sheet and rolled back and forth at a speed of 300 mm / min to bond the sheet to the copper wiring of the prepared polyimide substrate. The sheet was then left to stand at 23°C for 24 hours to prepare a test sample. The transmission loss of the prepared test sample was measured at a frequency of 40 GHz and an impedance value of 50Ω using a vector network analyzer (Agilent Technologies, "N523OA") and a measurement probe (SUSS MicroTec, "B90-122391"), and the transmission loss at a frequency of 40 GHz relative to the polyimide substrate was obtained. The low dielectric properties of the adhesive sheet were judged as follows: if the transmission loss at a frequency of 40 GHz for the obtained polyimide substrate was -8 dB or more, it was marked "◎"; if it was -10 dB or more but less than -8 dB, it was marked "○"; if it was less than -10 dB, it was marked "×".

[0089] (Appearance in a high-temperature environment or after peeling off the separator) (1) Heat resistance The obtained pressure-sensitive adhesive sheet was cut into a 60 mm x 60 mm planar shape. The separator on one side of the cut pressure-sensitive adhesive sheet was peeled off, and the sheet was laminated onto a polyimide film (manufactured by DuPont-Toray Co., Ltd., "200H-50 μm"). The separator on the other side of the pressure-sensitive adhesive sheet was then peeled off, exposing the adhesive layer, and the exposed side of the pressure-sensitive adhesive sheet was placed on the same polyimide film. A 2.0 kg rubber roller was placed on the polyimide film, and the rubber roller was moved back and forth once at a speed of 300 mm / min to laminate the polyimide film and the pressure-sensitive adhesive sheet. The resulting test sample was then heat-treated at 85°C for 1 day in an 85% RH environment and then naturally cooled to 25°C. The pressure-sensitive adhesive sheet was then observed for foaming using an optical microscope from a direction perpendicular to the interface between the pressure-sensitive adhesive sheet and the polyimide film of the test sample. The foaming resistance (heat resistance) of the adhesive sheet in a high temperature environment was judged as follows: if no foaming was observed in the adhesive sheet, it was marked with "◎"; if foaming was observed but disappeared after leaving it for one week, it was marked with "○"; if foaming was observed but did not disappear even after leaving it for one week, it was marked with "×".

[0090] (2) Workability (A) Measurement of 180° Peel Force of Separator from Adhesive Layer The adhesive sheet was cut to a planar shape of 25 mm x 100 mm. One separator (the side not being measured) was peeled from the cut adhesive sheet, and the sheet was bonded to SUS by rolling a rubber roller back and forth at a speed of 300 mm / min. After leaving the sheet at 23°C for 24 hours, a 180° peel test was performed on the separator on the other side of the adhesive sheet at a peel speed of 300 mm / min using a tensile tester (Shimadzu Corporation, "AG-IS"), and the 180° peel force of the separator from the adhesive layer was measured.

[0091] (B) Measurement of silicon atom concentration on the pressure-sensitive adhesive layer surface after separator peeling: The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet from which the separator was peeled off in the measurement of the 180° peel force of the separator to the pressure-sensitive adhesive layer was subjected to wide-scan analysis of XPS measurement using a PHI5000VersaProbe II (manufactured by ULVAC-PHI). Next, the RSF (relative sensitivity factor S) was taken into account for the integrated value analyzed from the obtained spectral data to derive the concentration of each detected atom. The silicon atom concentration relative to the total of all derived atomic concentrations (100 at%) was then calculated to obtain the silicon atom concentration on the pressure-sensitive adhesive layer surface after separator peeling. The XPS measurement was performed under the following conditions: X-ray source: Al Kα radiation; Photoelectron take-off angle: 45 degrees; Step width: 1 eV

[0092] (C) Evaluation of Appearance of Pressure-Sensitive Adhesive Layer After Peeling Off of Separator The surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet from which the separator had been peeled off in the measurement of the 180° peel force from the separator to the pressure-sensitive adhesive layer was visually observed on both sides. The appearance of the pressure-sensitive adhesive layer after peeling off of the separator was judged as follows: "◎" if the surface of the pressure-sensitive adhesive layer had not peeled off, "◯" if only lifting was observed at the edge of the surface of the pressure-sensitive adhesive layer, and "×" if the surface of the pressure-sensitive adhesive layer had peeled off.

[0093] (3) Overall Judgment In the judgment of the above-mentioned "(1) Heat Resistance" and "(C) Evaluation of Appearance of Pressure-Sensitive Adhesive Layer After Peeling Off of Separator," if both judgments were "◎", it was judged as "◎", if at least one judgment was "×", it was judged as "×", and if otherwise, it was judged as "○", and an overall judgment of the appearance under a high temperature environment and after peeling off of the separator was made.

[0094] (Adhesion) The adhesive sheet was cut into a planar rectangular shape measuring 25 mm x 100 mm. The separator on one side of the cut adhesive sheet was peeled off and the sheet was laminated onto a 100 μm cycloolefin polymer (COP) film. The separator on the other side of the adhesive sheet was then peeled off and the sheet was laminated onto a polycarbonate (PC) plate. The surface of the PC plate was washed with ethanol, wiped dry, and visually confirmed to be free of scratches before use. A 2.0 kg rubber roller was placed on the COP film and rolled back and forth at a speed of 300 mm / min to bond the PC plate and adhesive sheet together. After leaving the mixture at 23°C for 24 hours, a test sample was prepared. The resulting test sample was subjected to a 90° peel test at 23°C and a peel rate of 50 mm / min using a tensile tester (Shimadzu Corporation, "AG-IS") to measure the 90° peel strength against the PC at 23°C. The adhesiveness (adhesive strength) of the pressure-sensitive adhesive sheet was judged as follows: if the resulting 90° peel strength against PC at 23°C was 15 N / 25 mm or more, it was marked "◎", if it was 10 N / 25 mm or more but less than 15 N / 25 mm, it was marked "◯", and if it was less than 10 N / 25 mm, it was marked "X". Even if the evaluation is "X", the pressure-sensitive adhesive sheet of the present invention can be suitably used even when the transmission signal is at a high frequency, and has excellent heat resistance and workability, so it can be used without problems depending on the application.

[0095]

[0096]

[0097]

[0098] According to the present invention, it is possible to provide an adhesive sheet that can be suitably used even when the transmission signal is at a high frequency and that has excellent appearance in high-temperature environments and after the separator has been peeled off, and a method for manufacturing the adhesive sheet.

[0099] REFERENCE SIGNS LIST 1 adhesive sheet 2 laminate including film on which conductive pattern is formed 21, 22, 23, 24 member (internal member) 3 other member

Claims

1. A pressure-sensitive adhesive layer and a separator on at least one surface of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz and a gel fraction of 30 mass% or more; when a separator is provided on only one surface of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; When separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. A pressure-sensitive adhesive sheet characterized by:

2. A pressure-sensitive adhesive layer and a separator on at least one surface of the pressure-sensitive adhesive layer, The pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz and a shear storage modulus of 1.0×10 at 150° C. measured by dynamic viscoelasticity measurement at a frequency of 1 Hz. ４ Pa or more, when a separator is provided on only one surface of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; When separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. A pressure-sensitive adhesive sheet characterized by:

3. A pressure-sensitive adhesive layer and a separator on at least one surface of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz and a gel fraction of 30 mass% or more; All of the separators have a silicon atom-containing release layer, when a separator is present on only one surface of the pressure-sensitive adhesive layer, a silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off is 5 at% or less, as determined by XPS measurement of the surface of the pressure-sensitive adhesive layer after the separator is peeled off; When the pressure-sensitive adhesive layer has separators on both sides, the silicon atom concentration on both surfaces of the pressure-sensitive adhesive layer after the separators are peeled off is 5 at % or less in an XPS measurement of the surface of the pressure-sensitive adhesive layer after the separators are peeled off. A pressure-sensitive adhesive sheet characterized by:

4. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the separator has a silicon atom-containing release layer.

5. when a separator is provided on only one surface of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; When separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less. The pressure-sensitive adhesive sheet according to claim 3 .

6. The separator is provided on both sides of the pressure-sensitive adhesive layer, The 180° peel strength of one of the separators from the pressure-sensitive adhesive layer is at least twice the 180° peel strength of the other of the separators from the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet according to claim 1, 2, 3 or 5.

7. 6. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer contains a rubber-based elastomer.

8. The pressure-sensitive adhesive sheet according to claim 7 , wherein the rubber-based elastomer includes a hydrogenated styrene-based elastomer.

9. 9. The pressure-sensitive adhesive sheet according to claim 8, wherein the hydrogenated styrene elastomer comprises a branched styrene-ethylene-butylene-styrene (SEBS) block copolymer.

10. the pressure-sensitive adhesive layer contains a crosslinking aid, The content of the crosslinking aid is 2 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the rubber-based elastomer. The pressure-sensitive adhesive sheet according to claim 7.

11. the pressure-sensitive adhesive layer contains a tackifying resin, The tackifier resin contains an alicyclic petroleum resin The pressure-sensitive adhesive sheet according to claim 7.

12. The pressure-sensitive adhesive sheet according to claim 7 , wherein the pressure-sensitive adhesive layer contains an antioxidant.

13. The pressure-sensitive adhesive sheet according to claim 12 , wherein the antioxidant comprises at least one selected from the group consisting of hindered phenols and hindered amines.

14. The pressure-sensitive adhesive sheet according to claim 12, wherein the content of the antioxidant is 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the rubber-based elastomer.

15. The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive layer has a gel fraction of 50% by mass or less.

16. The pressure-sensitive adhesive sheet according to claim 1, 2, 3 or 5, which does not have a substrate.

17. A pressure-sensitive adhesive layer and a separator on at least one surface of the pressure-sensitive adhesive layer, The pressure-sensitive adhesive layer has a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz, a gel fraction of 30 mass% or more, and a shear storage modulus of 1.0×10 at 150° C. measured by dynamic viscoelasticity measurement at a frequency of 1 Hz. ４ Pa or more, when a separator is provided on only one surface of the pressure-sensitive adhesive layer, the separator has a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; when separators are provided on both sides of the pressure-sensitive adhesive layer, the separators on both sides have a 180° peel strength from the pressure-sensitive adhesive layer of 1.0 N / 25 mm or less; All of the separators have a silicon atom-containing release layer, when a separator is present on only one surface of the pressure-sensitive adhesive layer, a silicon atom concentration on the surface of the pressure-sensitive adhesive layer after the separator is peeled off is 5 at% or less in an XPS measurement of the surface of the pressure-sensitive adhesive layer after the separator is peeled off; When the pressure-sensitive adhesive layer has separators on both sides, the silicon atom concentration on both surfaces of the pressure-sensitive adhesive layer after the separators are peeled off is 5 at % or less in an XPS measurement of the surface of the pressure-sensitive adhesive layer after the separators are peeled off. A pressure-sensitive adhesive sheet characterized by:

18. 18. The method for producing a pressure-sensitive adhesive sheet according to claim 1, further comprising a step of irradiating a laminate having the pressure-sensitive adhesive layer and the separator on one side of the pressure-sensitive adhesive layer with energy rays from the separator side.

19. 18. The method for producing a pressure-sensitive adhesive sheet according to claim 1, further comprising a step of irradiating a laminate having the pressure-sensitive adhesive layer and the separators on both sides of the pressure-sensitive adhesive layer with energy rays from the separator sides on both sides.