Adhesive sheets and articles

Abstract

This adhesive sheet provides excellent handling and adhesion during bonding, even when the adherend is a porous material, as the heated and melted adhesive does not easily penetrate into the pores of the porous material. [Solution] An adhesive sheet having a base material and an adhesive layer provided on the base material, wherein the adhesive layer is formed from a resin composition comprising an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler, and the epoxy resin comprises an epoxy resin that is solid at 23°C and an epoxy resin that is liquid at 23°C.

Description

[Technical Field]

[0001] This invention relates to an adhesive sheet and an article on which the adhesive sheet is used. [Background technology]

[0002] For use in fixing applications, thermosetting adhesive sheets have been proposed, which have an adhesive layer on a substrate that hardens upon heating. The adhesive layer of these thermosetting adhesive sheets contains various components, including adhesive components, depending on the performance required for the adhesive sheet, such as heat resistance and adhesion. As adhesive components, epoxy resins are used that, in addition to adhesion, also have excellent properties such as insulation, heat resistance, mechanical strength, and chemical resistance.

[0003] Studies are underway to develop these thermosetting adhesive sheets to achieve the appropriate level of adhesion and heat resistance depending on the substrate and application. For example, Patent Document 1 discloses an adhesive sheet having an adhesive layer formed from a thermosetting adhesive composition containing 100 parts by weight of an acrylic polymer having a specific structure and 5 to 30 parts by weight of an epoxy resin. The objective is to provide an adhesive sheet that exhibits excellent adhesive strength to polyimide films, has heat resistance to withstand solder reflow during mounting in the semiconductor device manufacturing process, and does not have any appearance abnormalities such as resin leakage during bonding. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2002-12841 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, conventional thermosetting adhesive sheets, which have an adhesive layer on a substrate, had room for improvement, particularly in the following respects.

[0006] Generally, to achieve adhesive properties in an epoxy resin-containing adhesive layer, it is heated to a predetermined temperature to induce resin flow, softening and melting the adhesive layer. Subsequently, as the epoxy resin hardens, the adhesive layer adheres to the substrate. However, the inventors have revealed that thermosetting adhesive sheets using epoxy resin have the following problems. In other words, when the adherend is a porous material, the adhesive softens and melts during heating, seeping into the pores of the porous material. As a result, the adhesive is absorbed by the porous material, and during subsequent heat curing, interfacial delamination occurs between the adhesive layer and the substrate, leading to poor handling during the bonding process and reduced adhesion after heat curing (after bonding).

[0007] Furthermore, if a thermosetting adhesive sheet using epoxy resin is kept in a high-temperature environment for a long period of time after being bonded to an object (after heat curing), its adhesive properties will decrease and it will become more prone to peeling.

[0008] The object of the present invention is to solve the problems seen in view of the above circumstances, and in particular to provide an adhesive sheet and an article using the adhesive sheet that, even when the adherend is a porous member, does not easily penetrate into the pores of the porous member when heated and melted, and has excellent handling properties and adhesion during the bonding process. Furthermore, a further object of the present invention is to provide an adhesive sheet and an article using the adhesive sheet that, even when the adherend is a porous member, has excellent handling properties and adhesion during the bonding process, and also has excellent long-term stability of adhesive strength in high-temperature environments after the bonding process. [Means for solving the problem]

[0009] The inventors of the present invention focused on the fact that when an adhesive sheet having an adhesive layer made of epoxy resin is used to fix porous members, the handling properties during the bonding process (heat curing) become poor and the adhesive properties after heat curing decrease. Furthermore, they also focused on the long-term stability of adhesive strength in high-temperature environments and conducted diligent research. As a result, they found that the above problems can be solved by forming the adhesive layer with a specific resin composition, and thus completed the present invention.

[0010] The present invention has the following aspects. [1] An adhesive sheet having a base material and an adhesive layer provided on the base material, The adhesive layer is formed from a resin composition comprising an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler. The epoxy resin in the adhesive sheet comprises an epoxy resin that is solid at 23°C and an epoxy resin that is liquid at 23°C. [2] The adhesive sheet according to [1], comprising an epoxy resin that is liquid at 23°C and having a fluorene skeleton. [3] The adhesive sheet according to [2], wherein the epoxy resin having a fluorene skeleton is a bifunctional epoxy resin having a 9,9-bisphenylfluorene skeleton. [4] The adhesive sheet according to [1], wherein the epoxy resin that is solid at 23°C is at least one of a bisphenol-type epoxy resin and a novolac-type epoxy resin. [5] The adhesive sheet according to any one of [1] to [4], wherein the latent curing agent for epoxy resin is dicyandiamide. [6] The adhesive sheet according to any one of [1] to [5], wherein the elastomer is acrylonitrile butadiene rubber. [7] The adhesive sheet according to any one of [1] to [6], wherein the curing accelerator is an imidazole compound. [8] The adhesive sheet according to any one of items [1] to [7], wherein the aspect ratio of the filler is 2 or more and 30 or less. [9] The adhesive sheet according to any one of [1] to [8], wherein the minimum melt viscosity (dynamic viscoelasticity measurement: frequency 10 Hz, heating rate 10 °C / min) at 110 °C to 150 °C before curing of the adhesive layer is 5 Pa·s or more.

[10] The adhesive sheet according to any one of [1] to [9], wherein the storage elastic modulus G' (dynamic viscoelasticity measurement: frequency 10 Hz, heating rate 10 °C / min) before curing of the adhesive layer is 300 Pa or more and 3000 Pa or less at 120 °C.

[11] The adhesive sheet according to any one of [1] to

[10] , wherein the holding force (displacement distance) against SUS measured under the following measurement conditions based on JIS Z 0237:2000 is 3.0 mm or less. Pasting area: 20 mm × 20 mm Temperature: 23 °C Load: 100 gf (1.0 N) Time: 15 minutes

[12] The probe tack before curing measured in accordance with ASTM D2979:2016 is 1.0 N / cm 2 or more and 15 N / cm 2 or less. The adhesive sheet according to any one of [1] to

[11] .

[13] An article including the adhesive sheet according to any one of [1] to

[12] adhered to a porous member.

Advantages of the Invention

[0011] According to an embodiment of the present invention, even when the adherend is a porous member, an adhesive sheet excellent in handling properties and adhesiveness during the adhesion process, in which the heated and melted adhesive hardly penetrates into the pores of the porous member, and an article using the adhesive sheet can be provided. Further, according to another embodiment of the present invention, even when the adherend is a porous member, an adhesive sheet excellent in handling properties and adhesiveness during the adhesion process, and further excellent in the long-term stability of the adhesive strength in a high-temperature environment after the adhesion process, and an article using the adhesive sheet can be provided.

Brief Description of the Drawings

[0012] [Figure 1]This is a schematic cross-sectional view showing an example of the layer structure of an adhesive sheet according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view showing an example of the layer structure of an adhesive sheet according to another embodiment of the present invention. [Figure 3] This is a schematic plan view showing an example of the adhesive portion of an adhesive sheet (where an adhesive portion is provided on an adhesive layer) according to another embodiment of the present invention. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described below.

[0014] An adhesive sheet according to one embodiment of the present invention comprises a substrate and an adhesive layer provided on the substrate, wherein the adhesive layer is formed from a resin composition comprising an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler, and the epoxy resin comprises an epoxy resin that is solid at 23°C and an epoxy resin that is liquid at 23°C. An adhesive sheet of another embodiment of the present invention comprises a substrate and an adhesive layer provided on the substrate, wherein the adhesive layer is formed from a resin composition comprising an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler having an aspect ratio of 2 to 30, and the epoxy resin comprises an epoxy resin that is solid at 23°C and an epoxy resin that is liquid at 23°C.

[0015] The adhesive layer comprises an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler. By including both a solid epoxy resin at 23°C and a liquid epoxy resin at 23°C as the epoxy resin, the penetration of the adhesive into the porous material during heating can be controlled when bonding adhesive sheets. This suppresses a decrease in handling properties during the bonding process (heat curing) and allows for sufficient adhesion after heat curing. Furthermore, the presence of such an adhesive layer in the adhesive sheet can suppress peeling at the ends after the adhesive sheet has been attached. For example, when an adhesive sheet is wrapped around a cylindrical substrate, peeling at the ends between the adhesive layer and the back of the adhesive sheet (the back of the substrate on the side without the adhesive layer) during heating can be suppressed. In another embodiment, the adhesive layer includes a filler with an aspect ratio of 2 to 30 as the filler, which further improves the long-term stability of the adhesive strength of the adhesive sheet in high-temperature environments.

[0016] Embodiments of the present invention will be described in further detail below. (adhesive layer) The adhesive sheet according to an embodiment of the present invention has an adhesive layer provided on a substrate. The adhesive layer is formed from a resin composition comprising an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler. The thickness of the adhesive layer is not particularly limited, but in order to obtain sufficient adhesion, a thickness of 10 μm or more after drying is preferred, more preferably 15 μm or more, and even more preferably 20 μm or more. In order to avoid excessive thickness and keep material costs down, a thickness of 100 μm or less is preferred, more preferably 75 μm or less, and even more preferably 50 μm or less.

[0017] <Epoxy resin> The adhesive layer of the adhesive sheet according to an embodiment of the present invention contains an epoxy resin that is solid at 23°C and an epoxy resin that is liquid at 23°C. By including the epoxy resin that is solid at 23°C and the epoxy resin that is liquid at 23°C together with an elastomer, a tackifier, and a filler in the adhesive layer, the penetration into the porous material during heating can be controlled, thereby suppressing a decrease in handling properties during the bonding process (heat curing) and obtaining sufficient adhesion after heat curing. The epoxy resin content relative to the total mass of the resin composition of the adhesive layer is preferably 30% by mass or more, more preferably 40% by mass or more, from the viewpoint of adhesion. Furthermore, from the viewpoint of adding elastomers, tackifiers, and fillers to improve various physical properties, it is preferably 60% by mass or less, and more preferably 50% by mass or less.

[0018] The epoxy resin that is solid at 23°C is not particularly limited as long as it is solid at 23°C. Examples include bisphenol-type epoxy resin, novolac-type epoxy resin, tetraphenylethane-type epoxy resin, bixylenol-type epoxy resin, naphthalene-type epoxy resin, naphthalene-type tetrafunctional epoxy resin, dicyclopentadiene-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, biphenyl aralkyl-type epoxy resin, naphthylene ether-type epoxy resin, anthracene-type epoxy resin, epoxy resin having a naphthol aralkyl skeleton, epoxy having a fluorene skeleton, etc. From the viewpoint of heat resistance and ease of handling, the epoxy resin that is solid at 23°C is preferably at least one of bisphenol-type epoxy resin and novolac-type epoxy resin. The epoxy resin that is solid at 23°C may be used alone or in combination of two or more types. When there are two or more epoxy resins that are solid at 23°C, their combination and ratio can be arbitrarily selected.

[0019] The epoxy resin that is liquid at 23°C is not particularly limited as long as it is liquid at 23°C. Examples include bisphenol-type epoxy resins, novolac-type epoxy resins, naphthalene-type epoxy resins, glycidyl ester-type epoxy resins, glycidylamine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane-type epoxy resins, cyclohexanedimethanol-type epoxy resins, glycidylamine-type epoxy resins, epoxy resins having a butadiene structure, epoxy resins having a phenylene skeleton, epoxy resins having a fluorene skeleton, etc. One type of epoxy resin that is liquid at 23°C may be used alone, or two or more types may be used in combination. When there are two or more types of epoxy resins that are liquid at 23°C, their combination and ratio can be arbitrarily selected.

[0020] The mixing ratio (mass ratio) L / S of epoxy resin (L) that is liquid at 23°C to epoxy resin (S) that is solid at 23°C is preferably 0.5 / 1.0 or more and 1.2 / 1.0 or less, more preferably 0.5 / 1.0 or more and 1.0 / 1.0 or less, and even more preferably 0.6 / 1.0 or more and 0.9 / 1.0 or less. When the proportion of liquid epoxy resin (L) at 23°C is high, there is a tendency for the penetration to increase and the tackiness of the adhesive layer to become stronger. Also, when the proportion of liquid epoxy resin (L) at 23°C is high, there is a tendency for the cohesive force of the adhesive layer to decrease and for cohesive failure to occur, which can cause the adhesive sheet to shift or peel off easily from the adherend. By incorporating a liquid epoxy resin (L) at 23°C in a specific ratio to a solid epoxy resin (S) at 23°C, an adhesive layer with appropriate penetrating properties, tackiness, and cohesive strength can be formed. From the viewpoint of forming an adhesive layer with appropriate penetrating properties, tackiness, and cohesive strength, the mixing ratio (mass ratio) L / S is preferably within the above range.

[0021] Using a combination of bisphenol-type epoxy resin (bifunctional epoxy resin) and novolac-type epoxy resin (polyfunctional epoxy resin) as the epoxy resin is preferable from the viewpoint of penetration and reactivity during bonding, suppression of peeling after bonding, and heat resistance. The mixing ratio (mass ratio) B / N of bisphenol-type epoxy resin (B) to novolac-type epoxy resin (N) is preferably set appropriately within the range of 1.0 / 9.0 to 9.0 / 1.0, and more preferably 2.0 / 8.0 to 8.0 / 2.0. From the viewpoint of peeling suppression (peel strength), it is preferable to include bisphenol-type epoxy resin (B), and from the viewpoint of reactivity, elastic modulus, and heat resistance, it is preferable to include novolac-type epoxy resin (N). From these viewpoints, it is preferable that the mixture is well-balanced within the above mixing ratio range. For example, from the viewpoint of storage modulus and probe tack, B / N is preferably 2.0 / 1.0 to 5.0 / 1.0, more preferably 3.0 / 1.0 to 4.5 / 1.0, and even more preferably 3.5 / 1.0 to 4.0 / 1.0.

[0022] Examples of bisphenol-type epoxy resins include bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol AF type epoxy resin, fatty acid-modified (dimer acid-modified, aliphatic monocarboxylic acid-modified) bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin. Examples of novolac-type epoxy resins include phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, resol novolac-type epoxy resins, α-naphthol novolac-type epoxy resins, brominated phenol novolac-type epoxy resins, and orthocresol novolac-type epoxy resins.

[0023] The epoxy resin preferably further contains an epoxy resin (F) having a fluorene skeleton, from the viewpoint of long-term stability of adhesive strength in high-temperature environments. Examples of epoxy resins include bifunctional epoxy resins having a 9,9-bisphenylfluorene skeleton, such as epoxy resins with bisphenol fluorene (BPF) as the diol component and epoxy resins with bisphenoxyethanol fluorene (BPEF) as the diol component. Of the epoxy resins having a fluorene skeleton, bifunctional epoxy resins having a 9,9-bisphenylfluorene skeleton are preferred, particularly from the viewpoint of excellent heat resistance. Furthermore, if the adhesive layer contains an epoxy resin having a fluorene skeleton as a liquid epoxy resin at 23°C, the long-term heat resistance of the cured product itself is improved, and the stress caused by the deterioration and shrinkage of the adhesive layer is alleviated, making it less likely to peel off, thus improving the long-term stability of the adhesive strength in high-temperature environments. For this reason, from the viewpoint of the long-term stability of the adhesive strength in high-temperature environments, it is preferable to include a liquid epoxy resin (L) having a fluorene skeleton at 23°C in the above blending ratio (mass ratio) range of L / S.

[0024] The content of epoxy resin having a fluorene skeleton is preferably 20 parts by mass or more and 60 parts by mass or less, more preferably 25 parts by mass or more and 55 parts by mass or less, and even more preferably 30 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of epoxy resin. An epoxy resin having a fluorene skeleton may be used as a liquid epoxy resin at 23°C, and one or both of the bisphenol-type epoxy resin and the novolac-type epoxy resin may be used as a solid epoxy resin at 23°C. By incorporating an epoxy resin having a fluorene skeleton into the adhesive layer at the above blending ratio, it is possible to obtain sufficient tack, heat resistance, and long-term stability of adhesive strength in high-temperature environments while fully obtaining the combined effect with bisphenol-type epoxy resin and / or novolac-type epoxy resin. Note that "100 parts by mass of epoxy resin" means a total epoxy resin content of 100 parts by mass.

[0025] The number-average molecular weight of the epoxy resin is not particularly limited, but epoxy resins with a number-average molecular weight of 100 to 60,000 in standard polystyrene equivalent according to GPC can be used. The epoxy equivalent of the epoxy resin is not particularly limited, but is generally 50 g / eq to 30,000 g / eq, preferably 50 g / eq to 5,000 g / eq, more preferably 50 g / eq to 3,000 g / eq, and even more preferably 100 g / eq to 2,000 g / eq. "Epoxy equivalent" is defined as the molecular weight of epoxy resin per epoxy group, and can be determined by methods such as the perchloric acid-tetraethylammonium bromide method described in JIS K7236, Method for Determining the Epoxy Equivalent of Epoxy Resin (2001). Furthermore, if the epoxy resin of the present invention is composed of multiple types of epoxy resins, the number-average molecular weight and epoxy equivalent can be calculated using the weighted average value of the number-average molecular weights and epoxy equivalents of these multiple types of epoxy resins.

[0026] <Latent curing agent> The adhesive layer of the adhesive sheet according to the embodiment of the present invention contains a latent curing agent for epoxy resins. A latent curing agent for epoxy resins is a compound that, when mixed with epoxy resin, is inert and does not react at room temperature (e.g., 20°C), but becomes activated by heating and reacts with the epoxy groups of the epoxy resin to cause curing. As such latent curing agents for epoxy resins, compounds that are substantially inert at room temperature and can be activated and cured at temperatures of, for example, 70°C or higher depending on the heating temperature during the bonding treatment (heat curing) of the adhesive sheet can be used, and general latent curing agents can be used. Examples of latent curing agents for epoxy resins include dicyandiamide, imidazole compounds, polyamine compounds, and microencapsulated curing agents. Among these, dicyandiamide is preferred due to its availability and storage stability. These latent curing agents for epoxy resins may be used individually or in combination of two or more. The content of the latent curing agent for epoxy resin is preferably 0.5 parts by mass to 15 parts by mass, and more preferably 1 part by mass to 10 parts by mass, per 100 parts by mass of epoxy resin in the adhesive layer.

[0027] <Curing accelerator> The adhesive layer of the adhesive sheet according to the embodiment of the present invention contains a curing accelerator. By including a curing accelerator in the adhesive layer, the curing time can be shortened and the curing reaction can be carried out sufficiently, depending on the combination with the latent curing agent for epoxy resin described above. The curing accelerator used in the adhesive layer is not particularly limited, but examples include imidazole compounds and phosphorus compounds (such as triphenylphosphine). These curing accelerators may be used individually or in combination of two or more. Imidazole compounds are preferred because they can form an adhesive layer with a high glass transition temperature and excellent heat resistance. Specific examples of imidazole compounds include imidazole derivatives such as 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, and 2-phenyl-4-methyl-5-hydroxyimidazole. Among these, 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine isocyanurate adduct is preferred, and the product name: 2MAOK-PW manufactured by Shikoku Chemicals, Inc. can be used.

[0028] The curing accelerator content is preferably 0.1 parts by mass to 15 parts by mass, and more preferably 0.3 parts by mass to 10 parts by mass, per 100 parts by mass of epoxy resin in the adhesive layer. If the curing accelerator content is 0.1 parts by mass or more, a sufficient additive effect can be obtained, and if it is 15 parts by mass or less, the excess amount can be suppressed, reducing material costs and allowing the additive effect to be obtained without impairing other desired effects. In this invention, depending on the combination, imidazole compounds can function as both latent curing agents and curing accelerators for epoxy resins. When the latent curing agent for epoxy resins contains compounds other than imidazole compounds, the imidazole compound is used as a curing accelerator when adding it results in improved curability, such as a reduction in curing time, a lower curing temperature, or an improvement in the strength of the cured product. Furthermore, when two or more imidazole compounds are included, the imidazole compound with the smaller contribution per part to improved curability, such as a reduction in curing time, a lower curing temperature, or an improvement in the strength of the resin composition, is used as the curing accelerator.

[0029] <Elastomer> The adhesive layer of the adhesive sheet according to the embodiment of the present invention contains an elastomer. By including an elastomer in the adhesive layer, adhesion to the substrate and flexibility can be improved. Furthermore, by including an elastomer, it is possible to form an adhesive layer that has sufficient storage modulus and appropriate penetrability. The elastomer content is preferably 5 parts by mass or more and 20 parts by mass or less, and more preferably 7 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of epoxy resin in the adhesive layer. If the elastomer content is 5 parts by mass or more, a sufficient additive effect can be obtained, and if it is 20 parts by mass or less, the excess amount can be suppressed, the material cost can be reduced, and the additive effect can be obtained without impairing other desired effects.

[0030] Specific examples of elastomers include, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber (EPM, EPDM), chloroprene rubber (CR), acrylic rubber (ACR), urethane rubber (PUR), silicone rubber (Q), fluororubber (FKM, FPM), ethylene-acrylic rubber (AEM), ethylene vinyl acetate rubber (EVA), epichlorohydrin rubber (ECO), polyolefin-based thermoplastic elastomer (TPO), polystyrene-based thermoplastic elastomer (TPS), polyvinyl chloride-based thermoplastic elastomer (TPVC), polyurethane-based thermoplastic elastomer (TPU), polyester-based thermoplastic elastomer (TPEE), and polyamide-based thermoplastic elastomer (TPAE). Among these, highly polar elastomers such as acrylonitrile butadiene rubber and ethylene acrylic rubber are preferred in terms of flexibility, adhesion, and heat resistance. Furthermore, acrylonitrile butadiene rubber such as carboxylated nitrile rubber is more preferred in terms of superior heat resistance. As for carboxylated nitrile rubber, carboxylated acrylonitrile rubber into which acrylic acid, methacrylic acid, maleic anhydride, etc., have been introduced is preferred. Examples of commercially available carboxylated acrylonitrile rubbers include Nipol® NX775 and Nipol® 1072CGJ manufactured by Nippon Zeon Co., Ltd.

[0031] <Adhesion agent> The adhesive layer of the adhesive sheet according to the embodiment of the present invention includes a tackifier. By including a tackifier, the tack and adhesion of the adhesive layer can be improved, and it can also contribute to the control of penetration during adhesion and the storage modulus. Specific examples of tackifiers include natural resins such as rosin resins and terpene resins, and synthetic resins such as petroleum resins. Examples of synthetic resins include C5 (aliphatic) resins, C9 (aromatic) resins, C5 / C9 (aliphatic / aromatic copolymer) resins, alkylphenol resins, and xylene resins. Among these, aromatic tackifiers such as C9 resins, xylene resins, and alkylphenol resins are preferred from the viewpoint of heat resistance, and xylene resins are particularly preferred.

[0032] The tackifier content is preferably 10 to 25 parts by mass, and more preferably 15 to 20 parts by mass, per 100 parts by mass of epoxy resin in the adhesive layer. If the tackifier content is 10 parts by mass or more, a sufficient additive effect can be obtained, and if it is 25 parts by mass or less, the excess amount can be suppressed, reducing material costs and allowing the additive effect to be obtained without impairing other desired effects.

[0033] <Filler> The adhesive layer of the adhesive sheet according to an embodiment of the present invention includes a filler. The inclusion of a filler improves the long-term stability of the adhesive force in high-temperature environments and also suppresses penetration. The filler can be spherical or non-spherical (for example, fibrous, plate-like, flake-like, needle-like, etc.), but from the viewpoint of long-term stability of the adhesive force in high-temperature environments, a non-spherical shape is preferred, and a fibrous shape is even more preferred. Examples of fillers used in the adhesive layer include inorganic fillers such as silicon carbide, silicon nitride, wollastonite, xonotlite, aluminum borate, zinc oxide, talc (magnesium silicate mineral), mica (aluminum silicate mineral), gypsum fiber, glass fiber, and carbon fiber, as well as organic fillers such as aramid fiber and poly(p-oxybenzoyl) (POB). Two or more fillers may be used in combination. Among these, inorganic fillers are preferred in terms of long-term stability of adhesive strength in high-temperature environments, silicates such as talc (magnesium silicate) and wollastonite are more preferred, and wollastonite is particularly preferred in terms of heat resistance. Wollastonite is a fibrous silicate mineral, and commercially available products such as "SH-1800" (aspect ratio 8) manufactured by Kinsei Matec Co., Ltd. can be used.

[0034] In the aspect ratio (major axis / minor axis) of a filler, the major axis represents the longest length (major axis diameter) in the longest direction of the filler, and the minor axis represents the longest length in the direction perpendicular to the major axis. The aspect ratio of the filler is preferably 2 or higher, more preferably 5 or higher, and even more preferably 7 or higher, from the viewpoint of long-term stability of adhesive strength in high-temperature environments, and fibrous fillers can be suitably used. Furthermore, the aspect ratio of the filler is preferably 30 or lower, more preferably 20 or lower, and even more preferably 10 or lower, from the viewpoint of processability during the manufacture of the adhesive sheet (prevention of dispersion defects, etc.). The aspect ratio of a filler can be determined by capturing an image of the filler using a scanning electron microscope (SEM) and measuring and analyzing the particle shape. For example, in the case of a plate-shaped filler, the aspect ratio represents the ratio of the face length to the thickness, while in the case of a fibrous filler, the aspect ratio represents the ratio of the fiber length to the fiber diameter. The filler size can be any filler having the average particle size of a general-purpose filler. For example, a filler with an average particle size of 1 μm to 200 μm, preferably 1 μm to 100 μm, can be used.

[0035] The filler content is preferably 2 to 15 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of epoxy resin in the adhesive layer. If the filler content is 5 parts by mass or more, a sufficient additive effect can be obtained, and if it is 20 parts by mass or less, the excess amount can be suppressed, reducing material costs and allowing the additive effect to be obtained without impairing other desired effects.

[0036] <Other additives> The adhesive layer may contain, as necessary, one or more additives such as colorants, antioxidants, weathering agents, softeners, stabilizers, fillers, bulking agents, and reinforcing agents, in a range that does not impair the desired effects of the present invention.

[0037] (base material) An adhesive sheet according to an embodiment of the present invention has a substrate as a support for the adhesive layer. The base material is not particularly limited, but examples include resin films, cloths (woven fabrics, nonwoven fabrics), and paper, with heat-resistant insulating base materials being preferred. Examples of woven fabrics constituting the base material include glass cloth, acetate cloth, and polyester cloth. Examples of nonwoven fabrics constituting the base material include those whose constituent fibers are heat-resistant fibers selected from polybenzazole (PBO) fibers, polyphenylene sulfide (PPS) fibers, polyimide (PI) fibers, fluorine fibers, and polyetheretherketone (PEEK) fibers. Examples of paper constituting the base material include cellulose paper and aramid paper. The substrate may be a single-layer substrate or a laminated substrate consisting of two or more layers. When the substrate is a laminated substrate, examples include substrates in which different resin materials are laminated, or substrates in which paper, woven fabric, nonwoven fabric, etc., are laminated onto a resin film with adhesive or bonding agents. Among these, a substrate made of a resin film is preferred.

[0038] Examples of materials for the resin film constituting the base material include polyester resins such as polyethylene naphthalate (PEN) and aromatic polyester; polyamide resins such as polyamide and polyetheramide; polyimide resins such as polyimide (PI) and polyamideimide; polysulfone resins such as polysulfone and polyethersulfone; polyetherketone resins such as polyetherketone and polyetheretherketone; and polyphenylene sulfide (PPS). Among these, PEN, PI, and PPS are preferred from the viewpoint of heat resistance, and PI and PPS are more preferred.

[0039] As the substrate made of resin film, a substrate made of a resin material having a 5% weight loss temperature of preferably 300°C or higher, more preferably 350°C or higher, can be suitably used. For example, a substrate made of a resin having a 5% weight loss temperature of 300°C to 500°C, or a substrate made of a resin having a 5% weight loss temperature of 350°C to 400°C can be used. The 5% weight loss temperature is the temperature at which, when heated from room temperature at a constant heating rate (10°C / min) using differential thermal-thermogravimetric analysis (TG-DTA) in air, the weight retention rate becomes 95%, i.e., a 5% weight loss is observed.

[0040] The thickness of the substrate is not particularly limited, but depending on the application, a substrate with a thickness of, for example, 2 μm to 200 μm, preferably 5 μm to 100 μm, and more preferably 10 μm to 50 μm can be used.

[0041] (Removable liner) The adhesive sheet according to the embodiment of the present invention may optionally have a release liner on the adhesive layer. The release liner functions as a protective material for the adhesive layer and is peeled off from the adhesive layer when it is attached to the adherend. As the release liner, various resin films (e.g., PET film), paper, cloth, etc., surface-treated with release agents such as silicone-based, long-chain alkyl-based, or fluorine-based materials can be used. Alternatively, low-adhesion films made of non-polar polymers such as fluorine-based resins (e.g., polytetrafluoroethylene) or olefin-based resins (e.g., polyethylene, polypropylene, etc.) may be used.

[0042] If the adhesive layer is formed on only one side of the substrate and no release liner is provided, it is preferable that at least the outermost layer on the side of the substrate opposite to the side on which the adhesive layer is provided is made of a resin material. Furthermore, it is preferable that the surface of the substrate or the surface of the outermost layer (the back surface where the adhesive layer is not provided) is treated with a mold release agent. By applying a release agent, the adhesive sheet, which is wound in a roll, can be easily pulled out and used. Preferred release agents include silicone-based release agents, long-chain alkyl group-containing release agents, fluorine-based release agents, release agents consisting of copolymers of silicone-based or fluorine-based materials and organic materials, and release agents consisting of mixtures of organic resins and release agents. Examples of organic resins include polyester resins, epoxy resins, acrylic resins, urethane resins, phenolic resins, alkyd resins, aminoalkyd resins, polyolefin resins (polyethylene, polypropylene, cyclic polyolefins, etc.), polyvinyl alcohol, cellulose-based resins, and melamine resins.

[0043] (Layer structure of adhesive sheets) An adhesive sheet according to an embodiment of the present invention has an adhesive layer provided on at least one surface of a substrate. The adhesive layer may be formed on only one surface of the substrate or on both surfaces. Furthermore, the adhesive layer may be formed in direct contact with the substrate, or an easy-adhesion treatment layer may be provided between the substrate and the adhesive layer. The easy-adhesion treatment layer can be formed by performing an easy-adhesion treatment on the surface of the substrate on which the adhesive layer is to be applied. Examples of easy-adhesion treatments include surface treatments such as primer treatment, corona treatment, etching treatment, plasma treatment, and sandblasting, as well as application of an easy-adhesion treatment agent. One or more of these treatments may be selected and performed in combination.

[0044] Figure 1 shows a schematic cross-sectional view of a single-sided adhesive sheet in which an adhesive layer 12 is provided on one side of a base material 11. Figure 2 shows a schematic cross-sectional view of a double-sided adhesive sheet in which adhesive layers 22 and 23 are provided on both sides of a base material 21. In a single-sided adhesive sheet, the base material 11 may have a laminated structure, and it is preferable that the layer on the side of surface 11B (the outermost layer) is a resin layer. In a single-sided adhesive sheet, the surface 11A of the substrate 11 may be subjected to surface treatment such as an easy-adhesion treatment, for example, corona discharge treatment, or a primer layer may be provided by applying an easy-adhesion treatment agent, as needed. By performing an easy-adhesion treatment, the adhesion of the adhesive layer 12 to the substrate 11 can be improved. If necessary, a release agent treatment, such as a release layer, is applied to the surface 11B of the base material 11. This prevents the resin composition of the adhesive layer 12 from adhering to the surface 11B of the base material 11 when the single-sided adhesive sheet is wound into a roll, while also maintaining ease of unwinding (pulling out). A release liner can be provided on the surface of the adhesive layer 12 (the side opposite to the substrate 11).

[0045] In the double-sided adhesive sheet shown in Figure 2, the above-mentioned easy-adhesion treatment may be applied to both sides (21A and 21B) or either one of the sides of the substrate 21. By performing the easy-adhesion treatment, the adhesion between the adhesive layer 22 and / or the adhesive layer 23 and the substrate 21 can be improved. A release liner can be provided on the surface of the adhesive layer 22 and / or adhesive layer 23 (the surface opposite to the substrate 21 side).

[0046] (Adhesive portion / acrylic dots provided on the adhesive layer) In the adhesive sheet according to an embodiment of the present invention, a plurality of adhesive portions (A2R) made of adhesive material may be provided at intervals from each other on the surface of the adhesive layer opposite to the substrate side. Each adhesive portion (A2R) is formed in an island-like shape, surrounded by an area (A1LR) where the adhesive layer without adhesive portions (A2R) is exposed. It is preferable that multiple adhesive portions (A2R) are spaced apart across the entire surface of the adhesive layer opposite to the substrate side. By providing multiple adhesive portions (A2R) in the adhesive layer in this way, it is possible to provide an adhesive sheet with excellent temporary fixing properties (adhesion required for temporary fixing before the heat curing treatment of the adhesive layer) to the adherend. The adhesive portion (A2R) can be formed with various adhesives, but the adhesive portion formed with an acrylic adhesive is appropriately referred to as an "acrylic dot."

[0047] Figures 3(a) and 3(b) show examples of the shape and arrangement patterns of multiple adhesive portions (A2R) provided in the adhesive layer. In the figures, the symbol A2R indicates an adhesive portion, and the symbol A1LR indicates a region where no adhesive portions (A2R) are provided and the surface of the adhesive layer is exposed. Figure 3(a) shows a dot pattern in which circular adhesive areas (A2R) are regularly arranged in horizontal rows with a half-shifted position. Figure 3(b) shows a dot pattern in which square adhesive areas (A2R) are regularly arranged at equal intervals. The adhesive portion (A2R) preferably forms a regularly arranged pattern, but it may also be arranged randomly. The shape of the adhesive portion (A2R) may be a circle such as an ellipse or a perfect circle, a square, a triangle or other polygon.

[0048] The width (maximum and minimum width) of the adhesive portion (A2R) is not particularly limited, but is preferably in the range of 0.5 mm to 5 mm, and more preferably in the range of 0.5 mm to 3 mm. Similarly, the spacing between the adhesive portions (A2R), i.e., the width of the adhesive layer exposed area (A1LR), is not particularly limited, but is preferably in the range of 0.1 mm to 3.0 mm, and more preferably in the range of 0.1 mm to 1 mm. The thickness of the adhesive portion (A2R) is preferably in the range of 1 μm to 10 μm, and more preferably in the range of 1 μm to 5 μm. The upper surface of the adhesive portion (A2R) may protrude in the thickness direction from the upper surface of the adhesive layer in the adhesive layer exposed area (A1LR), or it may be in substantially the same plane. The ratio of the area of ​​the adhesive portion (A2R) to the total area (100%) of the adhesive portion (A2R) and the adhesive layer exposed area (A1LR) is preferably 1% to 70%, more preferably 20% to 70%, and particularly preferably 55% to 65%. By providing the adhesive portion (A2R) in such a ratio, temporary fixation (a characteristic exhibiting the adhesive strength necessary for temporary fixation) can be obtained without hindering the fluidity of the adhesive during heat curing.

[0049] In the adhesive sheet according to the embodiment of the present invention, the adhesive (A2) constituting the adhesive portion (A2R) can be, for example, an acrylic adhesive, a rubber adhesive, or a silicone adhesive. Two or more of these may be mixed and used. The type and mixing ratio of the adhesive (A2) can be appropriately adopted by referring to, for example, the contents described in International Publication No. 2022 / 176161.

[0050] (Porous material) An article according to an embodiment of the present invention includes an adhesive sheet according to the present invention attached to a porous member. The porous member has numerous voids, and these voids may be in a completely closed structure or in a structure in which each void is continuously connected to one another. The porous member preferably has a thickness of 10 μm or more and 5 mm or less. The porous member may consist of a single member or of multiple members. From the viewpoint of flexibility and workability, the porous member preferably has a void ratio of 10% or more and 95% or less. The voids of the porous member preferably have a diameter of 0.1 μm or more and 10 μm or less. As such a porous member, a resin sheet or a fibrous substrate having numerous voids can be used.

[0051] While there are no particular restrictions on the materials that make up the resin sheet, examples include polytetrafluoroethylene, polyethylene, polypropylene, polysulfone, polyvinylidene fluoride, polyester, polycarbonate, cellulose acetate, polyacrylonitrile, polybutadiene, polyimide, and polyamide.

[0052] The materials constituting the fibrous base material are not particularly restricted, but examples include rayon, polypropylene, polyethylene, acrylonitrile, polyester, polyphenylene sulfide, polytetrafluoroethylene, polyamide, wool, carbon fiber, and glass fiber. Conductive fibers such as steel wool and ceramic fibers such as aluminum nitride fibers can also be used. The fibrous base material can take the form of woven fabric or nonwoven fabric.

[0053] (Characteristics of adhesive sheets) <Storage modulus (G')> The storage modulus (G') of the adhesive layer of the adhesive sheet according to the embodiment of the present invention before curing is preferably 300 Pa or more and 4500 Pa or less at 120°C, more preferably 300 Pa or more and 3500 Pa or less, and even more preferably 300 Pa or more and 3000 Pa or less. If the storage modulus is too low, it may penetrate excessively into the porous material, and conversely, if the storage modulus is too high, the adhesive strength may decrease.

[0054] The storage modulus (G') was measured using a commercially available dynamic viscoelasticity analyzer (TA Instrument Japan Co., Ltd., product name: ARES-G2) under the following conditions (continuous strain of the adhesive layer at 0.1% and measurement of the temperature dependence at constant rate). Load: 20gf (0.20N) Frequency: 10Hz Temperature range: 25~250℃ Heating rate: 10°C / min Strain amount: 0.1%

[0055] <Holding force against SUS (slip distance (mm))> The holding force (slip distance (mm)) of the adhesive sheet against SUS according to the embodiment of the present invention is preferably 3.0 or less, more preferably 1.0 or less, even more preferably 0.7 or less, and particularly preferably 0.5 or less.

[0056] The holding force against SUS was measured based on JIS Z 0237:2000, specifically the holding force (slip distance (mm) when a load is applied in the shear direction) against the SUS plate. The measurement conditions were as follows. SUS plate: SUS304 steel plate as specified in JIS G4305, polished thoroughly in the length direction with 360-grit waterproof abrasive paper as specified in JIS R6253. Application area: 20mm x 20mm Temperature: 23℃ Load: 100gf (1.0N) Time: 15 minutes

[0057] <Minimum melt viscosity (Pa·s)> The minimum melt viscosity (Pa·s) of the adhesive layer of the adhesive sheet according to the embodiment of the present invention at 110°C to 150°C before curing is preferably 5 Pa·s or more, preferably 200 Pa·s or less, more preferably 150 Pa·s or less, and even more preferably 100 Pa·s or less. If the minimum melt viscosity of the adhesive layer before curing is too low, the portion of the adhesive layer adhering to the edges of the adhesive sheet is prone to shifting and peeling due to melting during heating (adhesion treatment). Having a sufficiently high minimum melt viscosity of the adhesive layer can suppress shifting and peeling during heating. Conversely, if the minimum melt viscosity of the adhesive layer before curing is too high, the adhesive properties may decrease, so it is preferable for the adhesive layer to have an appropriate minimum melt viscosity.

[0058] The minimum melt viscosity of the adhesive layer is thought to affect its ability to penetrate porous materials. A lower minimum melt viscosity results in faster resin flow, making it easier for the resin to penetrate the porous material. Conversely, a higher minimum melt viscosity results in slower resin flow toward the adherend, making it more difficult for the resin to penetrate the porous material. By having an adhesive layer with an appropriate minimum melt viscosity, good adhesion to adherends with uneven surfaces or voids (especially porous materials) can be achieved, while also preventing problems caused by excessive penetration into the porous material.

[0059] The minimum melt viscosity (Pa·s) at 110°C to 150°C before curing was measured using a commercially available dynamic viscoelasticity analyzer (TA Instrument Japan Co., Ltd., product name: ARES-G2) under the following conditions (continuous straining of the adhesive layer by 0.1% and measurement of the temperature dependence of constant-rate heating and cooling). Load: 20gf (0.20N) Frequency: 10Hz Temperature range: 25~250℃ Heating rate: 10°C / min Strain amount: 0.1%

[0060] <Probe tack (N / cm 2 )> The probe tack (N / cm 2 ) of the adhesive layer of the adhesive sheet according to an embodiment of the present invention before curing is preferably 1.0 or more and 15 or less, more preferably 1.5 or more and 10 or less, and even more preferably 2.0 or more and 10 or less. Since the uncured adhesive layer has sufficient tack, it is possible to suppress displacement during temporary fixing of the adhesive sheet and obtain good workability. If the tack is too high, the adhesive layer tends to flow or the cohesive force tends to be low, so it is preferably within an appropriate range.

[0061] The measurement of the probe tack was carried out in accordance with ASTM D2979:2016 except under the following conditions. Using a probe tack tester (manufactured by Tester Sangyo Co., Ltd., product name: TE-6001 Probe Tack Tester), with a probe diameter of 5 mmφ (circular), a contact time (pressing time) of 5 seconds, and a contact pressure (applying pressure) of 1000 gf / cm 2 (9.8 N / cm 2 ) ) was measured.

[0062] (Biomass content) The adhesive sheet according to an embodiment of the present invention can contain biomass-derived components, and the biomass content thereof can be a predetermined value or more. The "biomass content" refers to the value of the radiocarbon ( 14 C) content obtained by the measurement method, that is, the carbon concentration derived from biomass. The biomass content of the adhesive sheet according to an embodiment of the present invention is, for example, 1% or more, may be 5% or more, and is preferably 10% or more. The biomass content of the adhesive sheet refers to the mass ratio of the biomass-derived components in the total mass of the adhesive sheet, and is defined in accordance with ASTM D6866. The biomass content is determined in accordance with ASTM D6866 for all carbon atoms in the adhesive sheet containing biomass-derived components 14 ​​The proportion of carbon derived from biomass can be calculated by measuring the percentage of C (content: pMC). pMC stands for Percent Modern Carbon. The higher the biomass content, the more effective the reduction in carbon dioxide emissions becomes.

[0063] (Uses of adhesive sheets) The adhesive sheet according to the embodiment of the present invention can be used in various fields such as electrical, electronic, office automation equipment, home appliances, aircraft, ships, vehicles, indoor and outdoor supplies, and batteries. The adhesive sheet according to the embodiment of the present invention can be suitably used on porous materials of the adherend because the adhesive layer has appropriate penetrating properties when it is heated and cured. For example, it can be used for attaching adhesive sheets to porous materials in electrical and electronic equipment, joining porous materials (such as particleboard or wood) to metal panels in countertops, sinks, and stovetops of system kitchens, and joining porous materials to metal plates in components of batteries (such as internal pressure relief valves). Furthermore, the adhesive sheet according to the embodiment of the present invention has sufficient adhesive strength even to materials that are difficult to bond with ordinary adhesive sheets, such as PEEK, and can therefore be used to bond and fix various difficult-to-bond members.

[0064] (Method of manufacturing adhesive sheets) The method for manufacturing an adhesive sheet according to embodiments of the present invention is not particularly limited, but for example, a single-sided adhesive sheet can be manufactured by forming an adhesive layer on at least one surface of a substrate. The adhesive layer can be formed by a general method, such as a coating method in which it is directly applied to the substrate as described later, or by a transfer method in which the adhesive layer is formed on the surface of a release liner and the adhesive layer side of the release liner is bonded to the substrate. A double-sided adhesive sheet can be manufactured, for example, by bonding the adhesive layer formed on the release liner to one side of the substrate as described above, and then similarly bonding the adhesive layer formed on the release liner to the other side of the substrate.

[0065] Forming the adhesive layer can be achieved by coating a resin composition containing predetermined components, such as the epoxy resin mentioned above, onto the surface of a substrate (or release liner). To adjust the viscosity of the resin composition during coating, a solvent may be added. Specific examples of solvents include aromatic solvents such as toluene and xylene; aliphatic solvents such as hexane, octane, and isoparaffin; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and isobutyl acetate; and ether solvents such as diisopropyl ether and 1,4-dioxane. Methods for mixing resin compositions during preparation include mechanical kneading and dispersion, and solvent dispersion. Equipment used for dispersion includes mixers, ball mills, planetary mixers, paint conditioners, and three-roll mills. Two or more of these devices may be used in combination. Methods for coating the surface of a resin composition onto a substrate (or release liner) include, for example, using a roll coater or a reverse coater. By the above coating method, one or more layers of the resin composition can be applied to the surface of the substrate (or release liner), and by heating as necessary, an adhesive layer can be formed on the surface of the substrate (or release liner). [Examples]

[0066] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0067] The constituent materials of the adhesive layer of the fabricated adhesive sheet and the explanations of the abbreviations in the table are as follows: (Epoxy resin) YD014 (Bisphenol A type): Manufactured by Nippon Steel Chemical & Material Co., Ltd., Product name: Epotote YD-014, Solid at 23°C EOCN104s (phenol novolac type): Manufactured by Nippon Kayaku Co., Ltd., Product name: EOCN104S, Solid at 23°C EG-280 (Fluorene skeleton): Manufactured by Osaka Gas Chemical Co., Ltd., Product name: OGSOL EG-280, Liquid at 23°C (Hardening agent) DICY7 (Dicyandiamide): Manufactured by Mitsubishi Chemical Corporation, Product name (grade): DICY7 (Curing accelerator) 2MAOK-PW (Imidazole): Manufactured by Shikoku Chemicals Co., Ltd., Product name: Cureazole 2MAOK-PW (Elastomer) NX-775 (Carboxylated Nitrile Rubber): Manufactured by Zeon Corporation, Product Name: Nipol NX775 D-540 (urethane resin): Manufactured by Sumika Covestro Urethane Co., Ltd., Product name: DESMOCOLL 540 / 4 (Adhesion agent) Xylene resin: Manufactured by Fudo Co., Ltd., Product name: Nikanol L (Filler) P3 (spherical): Manufactured by Nippon Talc Co., Ltd., talc, product name: Micro Ace P3 SH-1800 (fibrous): Manufactured by Kinsei Matec Co., Ltd., Wollastonite, Product name: SH-1800 (average particle size 4 μm, aspect ratio 8)

[0068] (Example 1) A resin composition for forming an adhesive layer was obtained by mixing epoxy resin, latent curing agent for epoxy resin, curing accelerator, elastomer, tackifier, filler, and solvent (methyl ethyl ketone) in the proportions shown in Table 1. The units of the proportions of each component in Table 1 are parts by mass. Although the proportion of the solvent is not shown in Table 1, the solvent was added so that the total proportion of each component in the resin composition for forming the adhesive layer (total including the solvent) was 100 parts by mass. The obtained resin composition was coated onto a polyimide film (substrate), then heated at 90°C for 2 minutes to remove the solvent, and dried to form an adhesive layer, thereby obtaining an adhesive sheet. In this process, the resin composition was coated so that the adhesive layer after drying was 25 μm thick.

[0069] (Example 2) After forming an adhesive layer on a polyimide film (substrate) in the same manner as in Example 1, acrylic dots (adhesive parts) were formed on the adhesive layer as described below. First, an acrylic adhesive composition containing an acrylic copolymer, rosin ester, and aluminum chelate A(a) was prepared in the proportions shown in Table 1. The obtained acrylic adhesive composition was then applied by gravure printing to a release agent-treated PET film (release film) in a pattern of multiple round island-shaped dots. The mixture was then cured and dried to form an acrylic dot transfer sheet on the PET film (release film) with acrylic dots 1 μm thick. For aluminum chelate A(a), an aluminum chelate compound manufactured by Kawaken Fine Chemicals Co., Ltd. (product name: aluminum chelate A(a), chemical name: aluminum tris(acetylacetonate)) was used. For the rosin ester, a product manufactured by Harima Chemicals Co., Ltd. (product name: Haritac PCJ) was used. Next, the acrylic dot transfer sheet was laminated onto the adhesive layer, and the acrylic dots were transferred onto the adhesive layer by peeling off the PET film (release film). As a result, an acrylic dot pattern was formed on the adhesive layer, with multiple round, island-shaped acrylic dots (A2R) arranged on it, as shown in Figure 3(a). The areas where no acrylic dots (A2R) were formed were the adhesive layer exposed areas (A1LR). The diameter of the acrylic dots (A2R) was 1 mm, the spacing between the acrylic dots (A2R) was 0.25 mm, and the ratio of the area of ​​the acrylic dots (A2R) to the total area (100%) of the acrylic dots (A2R) and the adhesive layer exposed areas (A1LR) was 58%.

[0070] The acrylic copolymer used was prepared as follows. <Preparation of acrylic copolymers> In a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 13 parts by mass of methyl acrylate, 70 parts by mass of 2-ethylhexyl acrylate, 4.9 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, 2 parts by mass of vinyl acetate, ethyl acetate as a solvent, n-dodecanethiol as a chain transfer agent, and lauryl peroxide as a polymerization initiator were charged. Nitrogen gas was sealed into the reactor, and the polymerization reaction was carried out under a nitrogen gas stream with stirring at 68°C for 3 hours, followed by 78°C for 3 hours. After cooling to room temperature, ethyl acetate was added. This yielded an acrylic copolymer solution with a solid content of 30%. The weight-average molecular weight (Mw) of the acrylic copolymer was 1,000,000, and the theoretical Tg was -62°C. The weight-average molecular weight (Mw) was measured by the GPC method (converted to standard polystyrene), and the theoretical Tg was calculated using the FOX formula.

[0071] (Example 3) An adhesive sheet was prepared in the same manner as in Example 1, except that the mixing ratio of each component of the resin composition for forming the adhesive layer was changed as shown in Table 1.

[0072] (Examples 4 and 5) An adhesive sheet was prepared in the same manner as in Example 1, except that the formulation of each component of the resin composition for forming the adhesive layer was changed as shown in Table 1.

[0073] (Examples 6 and 7) An adhesive sheet was prepared in the same manner as in Example 2, except that the formulation of each component of the resin composition for forming the adhesive layer was changed as shown in Table 1.

[0074] (Example 8) An adhesive sheet was prepared in the same manner as in Example 1, except that the mixing ratio of each component of the resin composition for forming the adhesive layer was changed as shown in Table 1.

[0075] (Comparative Examples 1-3) An adhesive sheet was prepared in the same manner as in Example 1, except that the formulation of each component of the resin composition for forming the adhesive layer was changed as shown in Table 1.

[0076] The adhesive sheets obtained in the examples and comparative examples were evaluated using the following method. The results are shown in Table 1.

[0077] <Storage modulus (G')> The storage modulus (G') before curing was measured using a commercially available dynamic viscoelasticity analyzer (TA Instrument Japan Co., Ltd., product name: ARES-G2) under the following conditions (continuous strain of the adhesive layer at 0.1% and constant-rate temperature rise / fall measurement). The test specimens used for measurement were prepared as follows. The resin compositions prepared in the above examples and comparative examples were applied to the release surface of a 25 μm thick PET release liner (product name: NS Separator (Si, light release, MA formulation), manufactured by Nakamoto Pax Co., Ltd.) so that the thickness after drying was approximately 2 mm, and dried at 90°C for 2 minutes to form an adhesive layer. Next, the specimen was processed to the predetermined size, and the PET release liner was peeled off and removed to obtain a test specimen (baseless adhesive layer). The dimensions of the test specimen were approximately 20 mm × 20 mm and approximately 2 mm thick. The storage modulus (G') values ​​at 120°C (Pa) are shown in Table 1. Load: 20gf (0.20N) Frequency: 10Hz Temperature range: 25~250℃ Heating rate: 10°C / min Strain amount: 0.1% The evaluation of the storage modulus (G') was based on the following criteria. G'(Pa) is greater than 4500: × G'(Pa) is greater than 3500 and less than or equal to 4500: △ G'(Pa) is greater than 3000 and less than or equal to 3500: ○ G'(Pa) is between 300 and 3000: ◎ G'(Pa) is less than 300: ×

[0078] <Staining Test> On a stainless steel plate (BA SUS), an anodized aluminum plate (length: 125mm, width: 50mm, thickness: 1.0mm) was placed, and a porous sheet (glass fiber fabric, manufactured by Nitto Boseki Co., Ltd., product number: KS1210, weave density warp: 53 threads / 25mm, weft: 48 threads / 25mm, plain weave, 1m) was used as the substrate. 2 Mass per unit: 92g / m 2 A porous sheet (glass fiber fabric) with a thickness of 0.09 mm was installed. To prevent the porous sheet from lifting, its upper and lower ends were secured with commercially available single-sided adhesive tape (manufactured by Teraoka Seisakusho, product name: Circuit Tape No. 647 Green, silicone-based adhesive). Test pieces, which were processed to a predetermined size (test piece length: 100 mm, width: 10 mm) from the adhesive sheets obtained in the examples and comparative examples, were attached to this porous sheet (glass fiber fabric). After heating at 180°C for 30 minutes, we checked whether the molten adhesive resin had seeped into the adherend (porous sheet) and reached the anodized aluminum plate beneath it (whether or not it had seeped around to the back). Furthermore, the degree of penetration (area ratio) of the adhesive resin into the adherend (porous sheet) was measured using a digital microscope. During this process, the adherend was observed from the side without the test piece (adhesive sheet) attached, and the areas where the color changed were identified as the areas where the adhesive resin had penetrated. The degree of penetration (area ratio) was defined as the ratio (%) of the area of ​​the adhesive resin that had penetrated the adherend to the area of ​​the test piece (adhesive sheet) attached to the adherend. The evaluation of permeability was based on the following criteria. If there is a reverse side or the degree of soak-in is greater than 15%: × No backing, and the degree of penetration is greater than 10% but less than 15%: △ No backing, and the degree of penetration is greater than 5% but less than 10%: ○ No staining on the reverse side, and less than 5% penetration: ◎

[0079] <Holding force against SUS (slip distance (mm))> The holding force against SUS was measured based on JIS Z 0237:2000, by measuring the holding force (slip distance (mm) when a load was applied in the shear direction) of the adhesive sheets obtained in the examples and comparative examples against the SUS plate. The measurement conditions were as follows. SUS plate: SUS304 steel plate as specified in JIS G4305, polished thoroughly in the length direction with 360-grit waterproof abrasive paper as specified in JIS R6253. Application area: 20mm x 20mm Temperature: 23℃ Load: 100gf (1.0N) Time: 15 minutes The evaluation of the holding power against SUS was performed based on the following criteria. Displacement distance (mm) is greater than 3.0: × Displacement distance (mm) greater than 1.0 and less than or equal to 3.0: △ Displacement distance (mm) greater than 0.5 and less than or equal to 1.0: ○ Displacement distance (mm) is 0.5 or less: ◎

[0080] <Minimum melt viscosity> The minimum melt viscosity (Pa·s) at 110°C to 150°C before curing was measured using a commercially available dynamic viscoelasticity analyzer (TA Instrument Japan Co., Ltd., product name: ARES-G2) under the following conditions (continuous strain of the adhesive layer at 0.1% and measurement of constant-rate heating and cooling dependence). The test specimens used for measurement were prepared as follows. The resin compositions prepared in the above examples and comparative examples were applied to the release surface of a 25 μm thick PET release liner (product name: NS Separator (Si, light release, MA formulation), manufactured by Nakamoto Pax Co., Ltd.) so that the thickness after drying was approximately 2 mm, and dried at 90°C for 2 minutes to form an adhesive layer. Next, the specimens were processed to the predetermined size, and the PET release liner was peeled off and removed to obtain a test specimen (baseless adhesive layer). The dimensions of the test specimens were approximately 20 mm × 20 mm and approximately 2 mm thick. Load: 20gf (0.20N) Frequency: 10Hz Temperature range: 25~250℃ Heating rate: 10°C / min Strain amount: 0.1% The evaluation of the minimum melt viscosity was performed based on the following criteria. Minimum melt viscosity (Pa·s) is greater than 200: × Minimum melt viscosity (Pa·s) greater than 150 and 200 or less: ○ Minimum melt viscosity (Pa·s) of 5 to 150: ◎ Minimum melt viscosity (Pa·s) is less than 5: ×

[0081] <ProbeTack> Probe tack measurements were performed in accordance with ASTM D2979:2016, except for the following conditions: A probe tack tester (manufactured by Tester Industries Co., Ltd., product name: TE-6001 Probe Tack Tester) was used, with a probe diameter of 5 mmφ (circular), a contact time (pressure time) of 5 seconds, and a contact pressure (adhesion pressure) of 1000 gf / cm². 2 (9.8 N / cm 2 The measurements were taken under the following conditions. The adhesive sheets obtained in the examples and comparative examples were processed to create test specimens measuring 20 mm in length and 20 mm in width. The evaluation of Tack was based on the following criteria. Probe tack (N / cm) 2 ) is greater than 15: × Probe tack (N / cm) 2 ) greater than 10 and 15 or less: ○ Probe tack (N / cm) 2 ) is between 2.0 and 10: ◎ Probe tack (N / cm) 2 ) is 1.0 or greater and less than 2.0: ○ Probe tack (N / cm) 2 ) is 0.5 or greater and less than 1.0: △ Probe tack (N / cm) 2 ) is less than 0.5: ×

[0082] <Test of long-term stability of adhesive strength under high-temperature conditions> Test pieces made from the adhesive sheets obtained in the examples and comparative examples, measuring 120 mm in length and 20 mm in width, were attached to stainless steel plates (SUS plates), placed in a drying oven (manufactured by Kusumoto Kasei Co., Ltd., product name: ETAC HISPEC HIGH TEMPERATURE CHAMBER EHT-2H), and heat-cured at 180°C for 30 minutes, after which they were left to stand at room temperature for 1 hour. Next, the SUS plate to which the heat-cured test piece (adhesive sheet) described above was attached was placed in a drying oven (manufactured by Kusumoto Kasei Co., Ltd., product name: ETAC HISPEC HIGH TEMPERATURE CHAMBER EHT-2H) set to 230°C and removed after 500 hours. It was then left to stand at room temperature for more than 2 hours. Subsequently, a 90° peel test was performed using a tensile testing machine (Tensile and compression testing machine manufactured by Toyo Seiki Seisakusho Co., Ltd., model: V1-C) and a separately prepared 90° peel jig, in accordance with the JIS Z0237:2000 test method for adhesive tapes and adhesive sheets. Heat resistance was evaluated based on whether or not the substrate fractured during peeling in a 90° peel test. Materials that fractured during peeling were considered to have superior heat resistance compared to those that did not fracture due to cohesive failure during peeling.

[0083] [Table 1]

[0084] From the evaluation results of Examples 1 to 8, it can be seen that, according to the embodiments of the present invention, when the adherend is a porous material, an adhesive sheet can be provided that has an adhesive layer with suppressed penetration during the bonding process (heat curing).

[0085] Furthermore, the evaluation results from Examples 1 to 3 and 8 show that, according to the embodiments of the present invention, when the adherend is a porous material, an adhesive sheet can be provided that has an adhesive layer with suppressed penetration during the bonding process (heat curing), and exhibits excellent long-term stability of adhesive strength in high-temperature environments (particularly excellent when the filler is fibrous). Comparing Example 1 and Example 4, it can be seen that Example 1, which uses fibrous fillers, exhibits superior long-term stability of adhesive strength in high-temperature environments compared to Example 4, which uses spherical fillers. Similarly, comparing Example 2 and Example 6, it can be seen that Example 2, which uses fibrous fillers, exhibits superior long-term stability of adhesive strength in high-temperature environments compared to Example 6, which uses spherical fillers.

[0086] Furthermore, as the evaluation results of Examples 1 to 8 show, sufficient SUS retention force and the minimum melt viscosity of the adhesive layer are obtained, indicating that according to the embodiments of the present invention, an adhesive sheet with suppressed terminal peeling can be provided. Furthermore, as the evaluation results of Examples 1 to 8 show, sufficient SUS retention force and tack of the adhesive layer are obtained, indicating that the embodiments of the present invention can provide an adhesive sheet with excellent workability during temporary fixing.

[0087] In Example 5, the storage modulus is higher and the probe tack is lower compared to Example 4 due to the higher proportion of novolac-type epoxy resin used. Similarly, in Example 7, the storage modulus is higher and the probe tack is lower compared to Example 6 due to the higher proportion of novolac-type epoxy resin used.

[0088] Example 8 has a higher content of liquid epoxy resin (EG280), which is thought to result in better penetration into porous materials compared to the other examples (there is no back-side penetration, but the degree of penetration is slightly greater). Furthermore, due to the high content of liquid epoxy resin (EG280), it can be seen that the SUS retention strength is lower and the tack is greater compared to the other examples.

[0089] Comparative Example 1, lacking a curing accelerator, did not cure sufficiently, resulting in a low minimum melt viscosity and high penetration into porous materials (due to a back-side penetration and greater degree of penetration). Furthermore, it contained a high amount of liquid tackifier (xylene resin) at room temperature, which likely resulted in low SUS adhesion. In measuring the storage modulus, the resin flowed out, making accurate measurement impossible. Long-term stability of the adhesive strength under high-temperature conditions could not be evaluated due to the resin flowing out of the adhesive layer.

[0090] Comparative Example 2, lacking an elastomer, is thought to have higher permeability into porous materials (due to the presence of a backing layer and a greater degree of permeability). Furthermore, the absence of an elastomer is thought to result in lower retention of SUS material. Additionally, the lack of an elastomer resulted in poor film formation, making it impossible to form a film on the release paper.

[0091] Comparative Example 3, lacking a tackifier (xylene resin), exhibits improved penetration into porous materials (although there is no back-side penetration, the degree of penetration is high). Furthermore, the absence of a tackifier (xylene resin) results in lower storage modulus and lower probe tack. [Explanation of symbols]

[0092] 11 Base material 12 Adhesive layer 21 Base material 22 Adhesive layer 23 Adhesive layer

Claims

1. An adhesive sheet comprising a base material and an adhesive layer provided on the base material, The adhesive layer is formed from a resin composition comprising an epoxy resin, a latent curing agent for epoxy resins, a curing accelerator, an elastomer, a tackifier, and a filler. The epoxy resin comprises an epoxy resin that is solid at 23°C and an epoxy resin that is liquid at 23°C, in the form of an adhesive sheet.

2. The adhesive sheet according to claim 1, wherein the epoxy resin that is liquid at 23°C comprises an epoxy resin having a fluorene skeleton.

3. The adhesive sheet according to claim 2, wherein the epoxy resin having a fluorene skeleton is a bifunctional epoxy resin having a 9,9-bisphenylfluorene skeleton.

4. The adhesive sheet according to claim 1, wherein the epoxy resin that is solid at 23°C is at least one of a bisphenol-type epoxy resin and a novolac-type epoxy resin.

5. The adhesive sheet according to any one of claims 1 to 4, wherein the latent curing agent for epoxy resin is dicyandiamide.

6. The adhesive sheet according to any one of claims 1 to 4, wherein the elastomer is acrylonitrile butadiene rubber.

7. The adhesive sheet according to any one of claims 1 to 4, wherein the curing accelerator is an imidazole compound.

8. The adhesive sheet according to any one of claims 1 to 4, wherein the aspect ratio of the filler is 2 or more and 30 or less.

9. The adhesive sheet according to any one of claims 1 to 4, wherein the minimum melt viscosity (dynamic viscoelasticity measurement: frequency 10 Hz, heating rate 10°C / min) of the adhesive layer before curing at 110°C to 150°C is 5 Pa·s or more.

10. The adhesive sheet according to any one of claims 1 to 4, wherein the storage modulus G' of the adhesive layer before curing (dynamic viscoelasticity measurement: frequency 10 Hz, heating rate 10°C / min) is 300 Pa or more and 3000 Pa or less at 120°C.

11. An adhesive sheet according to any one of claims 1 to 4, wherein the holding force (slip distance) against SUS measured under the following measurement conditions based on JIS Z 0237:2000 is 3.0 mm or less. Application area: 20mm x 20mm Temperature: 23℃ Load: 100 gf (1.0 N) Time: 15 minutes

12. The probe tack before curing, measured according to ASTM D2979:2016, was 1.0 N / cm. ２ More than 15N / cm ２ The adhesive sheet according to any one of claims 1 to 4, which is as follows:

13. An article comprising an adhesive sheet according to any one of claims 1 to 4, which is attached to a porous member.

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