Adhesive sheet

Abstract

The present invention relates to an adhesive sheet having a base layer and an adhesive layer disposed on at least one side of the base layer, wherein the peeling force when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min is A, and the peeling force when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min is B, and the value calculated by (AB) / A is 90% or more. The adhesive sheet of the present invention has excellent tackiness at room temperature and can be easily peeled off at high temperatures without causing deformation or damage to the adherend.

Description

【Technical Field】 【0001】 Cross - reference to Related related applications This invention claims the rights and priorities based on Chinese Patent Application No. 202310266393.X filed in China on March 17, 2023, and the entire disclosure thereof is incorporated herein by reference. 【0002】 This invention relates to an adhesive sheet, and particularly to an adhesive sheet that has excellent adhesiveness and heat - releasability, can be easily peeled off by heating after use, and does not cause deformation or damage to the adherend. 【Background Art】 【0003】 Generally, an adhesive exhibits a soft solid (viscoelastic body) state in the temperature range near room temperature and has the property of easily adhering to an adherend under pressure. Utilizing such properties, adhesives are widely used in the form of adhesive sheets with a substrate having an adhesive layer provided on at least one side of the substrate for purposes such as fixing various articles, surface protection of various articles, or decoration to obtain a desired appearance. 【0004】 In the above - mentioned applications, problems such as poor adhesiveness and re - peelability of the adhesive sheet may occur. Also, when the adhesive sheet becomes unnecessary and is peeled off, the adherend may be damaged or deformed. 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 This invention is made to solve the above - mentioned existing problems, and aims to provide an adhesive sheet that has excellent adhesiveness and heat - releasability, can be easily peeled off by heating after use, and does not cause deformation or damage to the adherend. 【Means for Solving the Problems】 【0006】 In order to solve the above-mentioned existing problems, the inventors of the present invention conducted diligent research and found that the above problems can be solved by controlling the difference between the peeling force A when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min and the peeling force B when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min to a specific range, thus completing the present invention. 【0007】 In other words, the present invention is as follows. [1] An adhesive sheet having a base layer and an adhesive layer disposed on at least one side of the base layer, wherein the peeling force when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min is A, and the peeling force when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min is B, and the value calculated by (AB) / A is 90% or more. [2] The adhesive sheet according to [1], wherein the peel force when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min is 2 to 40 N / 20 mm, and the peel force when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min is 0.01 to 4 N / 20 mm. [3] The adhesive sheet according to [1] or [2], wherein the adhesive layer comprises rubber and a tackifying resin, and the content of the tackifying resin is 5 to 120 parts by weight per 100 parts by weight of rubber. [4] The adhesive sheet according to [3], wherein the rubber is one or more selected from styrene-ethylene-butylene-styrene rubber, styrene-butadiene-styrene rubber, styrene-butadiene rubber, and styrene-isoprene-styrene rubber. [5] The adhesive sheet according to [3], wherein the styrene content in the rubber is 5 to 25% by weight. [6] The adhesive sheet according to [3], wherein the tackifying resin is one or more selected from rosin resin, modified rosin resin, terpene resin, and C5 / C9 tackifying resin, and the tackifying resin has a softening point of 50 to 85°C or a viscosity of 1000 to 20000 cP at 23°C. [7] The base material layer has a foaming ratio of 1.1 to 20 cm 3 The adhesive sheet according to [1] or [2], wherein the weight is / g, the thickness is 0.06 to 2.0 mm, the 50% compressive strength is 100 kPa to 10000 kPa, and the thickness of the adhesive layer is 1 to 200 μm. [Effects of the Invention] 【0008】 The adhesive sheet according to the present invention has excellent adhesive properties and heat-removable properties, and can be easily peeled off by heating after use without causing deformation or damage to the adherend. [Brief explanation of the drawing] 【0009】 [Figure 1] Figure 1 is a schematic cross-sectional view showing the structure of an adhesive sheet according to one embodiment of the present invention. [Explanation of Symbols] 【0010】 1 Adhesive sheet 10 Base material layer 20 Adhesive layer [Modes for carrying out the invention] 【0011】 Preferred embodiments of the present invention will be described below. Matters necessary for carrying out the present invention other than those specifically mentioned herein will be understood by those skilled in the art based on the teachings on carrying out the invention described herein and the common technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed herein and the common technical knowledge in the art. 【0012】 Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numeral and described accordingly, and redundant explanations may be omitted or simplified. Also, the embodiments shown in the drawings are schematic for the purpose of clearly illustrating the present invention and do not necessarily accurately represent the size or scale of the actual product provided. 【0013】 <Adhesive sheet> The adhesive sheet of the present invention has a base material layer and an adhesive layer disposed on at least one side of the base material layer. The peel strength when the adhesive layer is peeled at a peeling rate of 300 mm / min in the 180° direction at 23°C is designated as A, the adhesive layer is heated at 80°C for 5 minutes, and the peel strength when peeled at a peeling rate of 300 mm / min in the 180° direction at 80°C is designated as B. The numerical value calculated by (A - B) / A is 90% or more. 【0014】 Preferably, the numerical value calculated by (A - B) / A is 91% or more, more preferably 94% or more, and even more preferably 97% or more. The upper limit of this numerical value is not particularly limited and may be 100%, preferably 99.8%, more preferably 99.6%, and even more preferably 99.3%. 【0015】 In the present invention, by controlling the numerical value calculated by (A - B) / A within the above range, an adhesive sheet can be obtained that has excellent adhesiveness at normal temperature and can be easily peeled at a high temperature state without causing deformation or damage to the adherend. 【0016】 FIG. 1 is a cross-sectional view schematically showing the structure of an adhesive sheet according to an embodiment of the present invention. As shown in FIG. 1, the adhesive sheet 1 includes a base material layer 10 and an adhesive layer 20 provided on one side of the base material layer 10. The adhesive layer 20 is preferably provided over the entire surface of the base material layer 10. 【0017】 Although not shown, in the present invention, the adhesive layer of the present invention can be provided on both sides of the base material layer, that is, it can be made into a double-sided adhesive tape. In the case of a double-sided adhesive tape, both of the adhesive layers on both sides of the base material layer have the characteristics of the adhesive layer required in the present invention. 【0018】 Alternatively, in the present invention, the adhesive layer of the present invention may be provided on one side of the base material layer, and another adhesive layer different from the adhesive layer of the present invention may be provided on the other side. Examples of the other adhesive layer include an acrylic-based adhesive layer, a silicone resin-based adhesive layer, a urethane-based adhesive layer, a polyacrylamide-based adhesive layer, and the like. 【0019】 Also, although not shown, the adhesive sheet of the present invention may be provided with a release liner on the outside of the adhesive layer for the purpose of protecting the adhesive surface before being put into use. 【0020】 The concept of the adhesive sheet in this specification may include those referred to as adhesive tapes, adhesive labels, adhesive films, etc. Note that the adhesive sheet disclosed in this specification may be in sheet form or may be an adhesive sheet processed into various shapes. In some preferred embodiments, the adhesive sheet of the present invention may be provided in a long strip shape. 【0021】 [Adhesive layer] The adhesive layer of the present invention has a peel strength of 2 to 40 N / 20 mm when peeled at a tensile speed of 300 mm / min in the 180° direction at 23°C. The lower limit is preferably 5 N / 20 mm, more preferably 7 N / 20 mm, still more preferably 8 N / 20 mm, and even more preferably 9 N / 20 mm, and the upper limit is preferably 35 N / 20 mm, more preferably 30 N / 20 mm, still more preferably 20 N / 20 mm, and even more preferably 16 N / 20 mm. 【0022】 When the adhesive layer is heated at 80°C for 5 minutes and then peeled at a tensile speed of 300 mm / min in the 180° direction at 80°C, the peel strength is 0.01 to 4 N / 20 mm. The lower limit is preferably 0.05 N / 20 mm, more preferably 0.5 N / 20 mm, still more preferably 1 N / 20 mm, and even more preferably 1.5 N / 20 mm, and the upper limit is preferably 3.5 N / 20 mm, more preferably 3 N / 20 mm, still more preferably 2.5 N / 20 mm, and even more preferably 2 N / 20 mm. 【0023】 When the peel strength of the adhesive layer at 23°C and the peel strength after heating at 80°C for 5 minutes are within the above ranges respectively, the adhesive sheet has excellent adhesiveness and heat re-peelability, and can be easily peeled by heating after use, without causing deformation or damage to the adherend. 【0024】 The above peeling force can be measured, for example, by the method described in the examples below. 【0025】 The adhesive layer of the present invention comprises rubber and a tackifying resin. The content of the tackifying resin is 5 to 120 parts by weight, preferably 10 to 100 parts by weight, more preferably 20 to 80 parts by weight, and even more preferably 30 to 50 parts by weight, per 100 parts by weight of rubber. 【0026】 By setting the content of the tackifying resin within the above range, it is possible to create an adhesive sheet that has excellent tackiness at room temperature and can be easily peeled off at high temperatures without causing deformation or damage to the adherend. 【0027】 The adhesive layer in the technology disclosed herein may be a layer formed from an adhesive composition comprising rubber and a tackifying resin. The form of the adhesive composition is not particularly limited and may be of various forms, such as water-dispersible, solvent-based, hot-melt, or active-energy ray-curable (e.g., photocurable). 【0028】 The components of the adhesive composition of the present invention will be described in detail below. 【0029】 (rubber) The adhesive composition of the present invention contains rubber. Examples of rubber include one or more selected from styrene-ethylene-butylene-styrene rubber (SEBS), styrene-butadiene-styrene rubber (SBS), styrene-butadiene rubber (SB), and styrene-isoprene-styrene rubber (SIS). From the viewpoint of the adhesive sheet having excellent tackiness and re-peelability, and being easily peeled off after use without causing contamination by adhesive residue, one or more selected from styrene-ethylene-butylene-styrene rubber (SEBS) and styrene-isoprene-styrene rubber (SIS) are preferred. Commercially available rubbers can be used as the rubber of the present invention. 【0030】 The weight-average molecular weight of the rubber is not particularly limited, but is preferably 50,000 to 500,000, and more preferably 100,000 to 300,000. This range is preferable because it tends to improve the rubber's cohesiveness, tackiness, and peel strength. 【0031】 In this specification, weight-average molecular weight refers to the weight-average molecular weight calculated for the region of the molecular weight distribution curve obtained by GPC measurement in which the molecular weight in terms of polystyrene is 10,000 or more. 【0032】 In the present invention, the styrene content in the rubber is 5 to 25% by weight, more preferably 8 to 24% by weight, even more preferably 10 to 15% by weight, and even more preferably 12 to 14% by weight. By setting the styrene content in the rubber within the above range, it is possible to maintain the cohesive force provided by the styrene portion while ensuring viscoelasticity provided by the soft segment, resulting in an adhesive sheet with excellent tackiness and re-peelability, which can be easily peeled off after use without contamination from adhesive residue. 【0033】 In this specification, "styrene content" in rubber refers to the weight ratio of the styrene component to the total weight of the rubber. The styrene content can be measured by NMR (nuclear magnetic resonance spectroscopy). 【0034】 (Adhesive-granting resin) In the present invention, the tackifying resin is one or more selected from rosin resin, modified rosin resin, terpene resin, and C5 / C9 tackifying resin, and the tackifying resin has a softening point of 50 to 85°C or a viscosity of 1000 to 20000 cP at 23°C. 【0035】 In the present invention, since the softening point or viscosity of the tackifying resin is within the above range, the adhesive sheet has excellent tackiness at room temperature and can be easily peeled off at high temperatures without causing deformation or damage to the adherend. 【0036】 The modified rosin resin is a modified rosin resin obtained by modifying rosin resin (phenol modification, styrene modification, hydrogenation modification, hydrocarbon modification, acid modification, etc.). 【0037】 The terpene resins are not particularly limited and include, for example, terpene resins; and modified terpene resins obtained by modifying these terpene resins (phenol modification, styrene modification, hydrogenation modification, hydrocarbon modification, etc.). 【0038】 Examples include α-pinene polymers, β-pinene polymers, diterpene polymers, terpene phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins. 【0039】 A commercially available product can be used as the tackifying resin of the present invention. 【0040】 In this specification, the softening point of the tackifying resin is defined as the value measured based on the softening point test method (ring-ball method) specified in JIS K5902 and JIS K2207. The viscosity can be measured by a conventional viscosity measurement method. 【0041】 (Antistatic agent) In the present invention, the adhesive composition preferably further contains an antistatic agent. 【0042】 Examples of antistatic agents included in the above-mentioned adhesive layer-forming composition include conductive polymers, conductive inorganic fine particles, metal fine particles or fibers, ionic compounds, and ionic surfactants. These antistatic agents may be used individually or in combination of two or more. 【0043】 <Conductive polymer> Examples of the conductive polymers mentioned above include polyaniline, polypyrrole, polythiophene, polyquinoxaline, polyacetylene, polyethyleneimine, and allylamine polymers. Among these, polyaniline, polythiophene, and others that readily form water-soluble or water-dispersible conductive polymers are preferred. These conductive polymers may be used individually or in combination of two or more. 【0044】 <Conductive inorganic particles> Examples of the above-mentioned conductive inorganic fine particles include conductive metal oxides, carbon nanotubes, graphene, fullerenes, acetylene black, Ketjenblack, natural graphite, artificial graphite, and titanium black. These conductive inorganic fine particles may be used individually or in mixtures of two or more types. 【0045】 Examples of conductive metal oxides include tin oxide-based, antimony oxide-based, indium oxide-based, and zinc oxide-based metal oxides. Examples of tin oxide-based conductive fine particles include tin oxide, as well as antimony-doped tin oxide, indium-doped tin oxide, aluminum-doped tin oxide, tungsten-doped tin oxide, titanium oxide-cerium oxide-tin oxide composite, and titanium oxide-tin oxide composite. The average particle size of the fine particles is 1 to 100 nm, preferably 2 to 50 nm. 【0046】 <Metal particles or fibers> Any suitable polymer can be used as the metal nanoparticles or fibers mentioned above, as long as the effects of the present invention are obtained. Examples include nanoparticles or nanowires made of gold, silver, copper, aluminum, nickel, or alloys thereof. These metal nanoparticles or fibers can be used individually or in mixtures of two or more types. 【0047】 <Ionic compounds> Examples of ionic compounds include alkali metal salts and / or organic cation-anionic salts. In this invention, "organic cation-anionic salt" refers to an organic salt in which the cation portion is composed of organic matter, while the anion portion may be organic or inorganic. "Organic cation-anionic salts" are also called ionic liquids and ionic solids. These ionic compounds can be used individually or in mixtures of two or more. As alkali metal salts, organic and inorganic salts of alkali metals can be used. 【0048】 <Ionic surfactants> Examples of the above-mentioned ionic surfactants include cationic surfactants (e.g., quaternary ammonium salt type, phosphonium salt type, sulfonium salt type, etc.), anionic surfactants (e.g., carboxylic acid type, sulfonate type, sulfate type, phosphate type, phosphite type, etc.), amphoteric surfactants (e.g., sulfobetaine type, alkylbetaine type, alkylimidazolium betaine type, etc.), and nonionic surfactants (e.g., polyol derivatives, β-cyclodextrin inclusion compounds, sorbitan fatty acid monoesters / diesters, polyoxyalkylene derivatives, amine oxides, etc.). These ionic surfactants may be used individually or in combination of two or more types. 【0049】 In some preferred embodiments, the content of the antistatic agent is preferably 0.01 to 15 parts by weight, more preferably 0.02 to 10 parts by weight, per 100 parts by weight of the rubber. In some preferred embodiments, the content of the antistatic agent is preferably 0.01 parts by weight, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 5 parts by weight, 10 parts by weight, or 15 parts by weight, per 100 parts by weight of the rubber. When the content of the antistatic agent is within the above range, a sufficient antistatic effect can be obtained, the static electricity generated during peeling can be sufficiently suppressed, and damage to the adherend can be avoided or reduced. 【0050】 In addition to the above components, the adhesive composition of the present invention may optionally contain various additives commonly used in the field of adhesives, such as photoinitiators, plasticizers, softeners, anti-aging agents, and antioxidants, to the extent that they do not impair the effects of the present invention. Such additives can be conventionally used by conventional methods. 【0051】 (Formation of the adhesive layer) The adhesive layer disclosed herein can be formed by conventionally known methods. For example, a direct method can be employed in which an adhesive layer is formed by directly applying (typically coating) an adhesive composition to a substrate layer and drying it. Alternatively, a transfer method can be employed in which an adhesive layer is formed on a peelable surface (release surface) by applying an adhesive composition to the surface and drying it, and then the adhesive layer is transferred to the substrate layer. From the viewpoint of productivity, the transfer method is preferred. The release surface can be the surface of a release liner, the back surface of a peeled substrate layer, etc. The adhesive layer disclosed herein is typically formed continuously, but is not limited to this form, and may be formed in a regular or irregular pattern such as dots or stripes. 【0052】 The adhesive composition can be applied using conventionally known coaters such as gravure roll coaters, die coaters, and bar coaters. Alternatively, the adhesive composition can be applied by impregnation or curtain coating methods. 【0053】 From the viewpoint of improving manufacturing efficiency, it is preferable to dry the adhesive composition under heating. The drying temperature can be, for example, around 40 to 150°C, and is usually preferably around 60 to 130°C. After drying the adhesive composition, further aging can be performed for purposes such as adjusting the migration of components in the adhesive layer, promoting the crosslinking reaction, and relieving any strain that may be present in the substrate film or adhesive layer. 【0054】 The thickness of the adhesive layer is not particularly limited, but considering the balance between adhesion to the adherend and cohesiveness, the thickness of the adhesive layer is preferably 1 to 200 μm, more preferably 10 to 150 μm, even more preferably 30 to 100 μm, and even more preferably 40 to 80 μm. By setting the thickness of the adhesive layer within the above range, good adhesion can be obtained. 【0055】 [Base material layer] The material of the base layer constituting the adhesive sheet disclosed herein is not particularly limited and can be appropriately selected according to the purpose and form of use of the adhesive sheet. Non-limited examples of usable base layers include plastic films such as polyolefin films mainly composed of polyolefins such as polyethylene, polypropylene, polybutene, and ethylene propylene copolymer, polyvinyl chloride films mainly composed of polyvinyl chloride, films mainly composed of cast polypropylene, and thermoplastic polyurethane films; foam sheets formed from foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and nonwoven fabrics obtained by using various fibrous materials (which may be natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate) alone or in blends; papers such as Japanese paper, fine paper, kraft paper, and crepe paper; and metal foils such as aluminum foil and copper foil. Of these, the base layer preferably contains at least one selected from the group consisting of thermoplastic polyurethane, polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and polyvinyl chloride. A base material may also be a composite of these. Examples of such composite substrates include, for instance, a substrate having a structure in which metal foil and the above-mentioned plastic film are laminated, and a plastic substrate reinforced with inorganic fibers such as glass cloth. 【0056】 The surface of the substrate layer of the present invention may be subjected to any surface treatment in order to improve adhesion and retention with adjacent layers. Examples of such surface treatments include chemical and physical treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, and ionization radiation treatment, as well as coating treatments. 【0057】 In the present invention, the base layer has a foaming ratio of 1.1 to 20 cm². 3 The weight is per gram, the thickness is 0.06 to 2.0 mm, and the 50% compressive strength is 100 kPa to 10000 kPa. 【0058】 The foaming ratio of the substrate layer is preferably 1.3 to 15 cm². 3 / g, more preferably 1.4-8cm 3 / g, more preferably 1.5-4cm 3 It is / g. 【0059】 In accordance with JIS K 7222, the foaming ratio of the base material layer can be calculated from the reciprocal of the density of the base material layer. 【0060】 The thickness of the base material layer is preferably 0.06 to 1.8 mm, more preferably 0.1 to 1.0 mm, and even more preferably 0.15 to 0.50 mm. 【0061】 The 50% compressive strength of the base material layer is preferably 200 kPa to 8000 kPa, more preferably 400 kPa to 4000 kPa, and even more preferably 1000 kPa to 3000 kPa. 【0062】 (Method of manufacturing adhesive sheets) The adhesive sheet of the present invention can be manufactured by any suitable method. For example, this could involve applying an adhesive composition onto a substrate layer, or transferring a coating layer formed by applying an adhesive composition onto any suitable substrate to the substrate layer. 【0063】 Any suitable coating method can be used to apply the above-mentioned adhesive composition. For example, each layer can be formed by drying after coating. Examples of coating methods include those using a multi-coater, die coater, gravure coater, applicator, rod coater, air knife coat, reverse roll coat, lip coat, dip coat, offset printing, flexographic printing, and screen printing. Examples of drying methods include natural drying and heat drying. In the case of heat drying, the heating temperature can be set to any suitable temperature depending on the properties of the substance to be dried. 【0064】 (Application) The adhesive sheets disclosed herein can be attached to various components and devices for protective and other purposes. In particular, when used in the manufacture of electronic product components, the adhesive sheets of the present invention provide excellent adhesion between electronic product components and other components, and exhibit good heat-peelability when defects occur or when product components are repaired. [Examples] 【0065】 The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. In the examples, unless otherwise specified, "parts" are based on weight. If specific conditions are not specified in the examples, the process will be carried out according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all materials and equipment used are common products that are available commercially. 【0066】 Example 1 A PE foam with a thickness of 0.15 mm was used as the base layer. 【0067】 30 parts by weight of rosin resin (softening point: 80°C) and 100 parts by weight of styrene-ethylene-butylene-styrene rubber (SEBS) (styrene content: 12% by weight) were dissolved in toluene, and 2 parts by weight of antioxidant (product name: I168) and 1 part by weight of antioxidant (product name: I565) were added and mixed to obtain a mixed solution. 【0068】 Next, the mixed solution is applied to the corona-treated side of the substrate layer at a sizing amount (coating amount) of 80 g / m². 2 The adhesive was applied under drying conditions of 110°C for 2 minutes and at a production speed of 15 m / min to form an adhesive layer with a thickness of 25 μm, thereby obtaining an adhesive sheet. 【0069】 Examples 2-10 An adhesive sheet was prepared in the same manner as in Example 1, except that the base layer and adhesive layer shown in Table 1 were used. 【0070】 Comparative Examples 1-6 An adhesive sheet was prepared in the same manner as in Example 1, except that the base layer and adhesive layer shown in Table 1 were used. In Comparative Example 6, the adhesive layer was formed using a commercially available silane-based adhesive. 【0071】 The adhesive sheets obtained in the examples and comparative examples were evaluated. The results are shown in Tables 1 to 4. 【0072】 In the table below, "peel force at 23°C" refers to the peel force when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min, and "peel force at 80°C" refers to the peel force when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min. 【0073】 In the table below, PE represents polyethylene, and PET represents polyethylene terephthalate. 【0074】 [Table 1] 【0075】 [Table 2] 【0076】 [Table 3] 【0077】 [Table 4] 【0078】 <Evaluation Test> (1) Expansion ratio The foaming ratio of the above-mentioned base material layer can be calculated from the reciprocal of the density of the base material layer. For example, it can be measured in accordance with JIS K 7222. 【0079】 (2) 50% compressive strength The 50% compressive strength was calculated in accordance with JIS K-6767. 【0080】 (3) Peeling force at 23°C A 20mm wide x 150mm long piece was cut from the adhesive sheet of each example and comparative example to serve as a test specimen. A SUS plate (SUS430BA plate) washed with toluene was used as the adherend. Under standard conditions of 23°C and 50% RH, the test specimen was pressed onto the adherend by moving a 2kg roller back and forth once. After leaving the test specimen pressed onto the adherend in the above standard conditions for 30 minutes, it was peeled off at a tensile speed of 300mm / min and a peel angle of 180° using a tensile testing machine (Shimadzu Corporation, product name "Tensilon") in accordance with JIS Z 0237, and the 180° peel force (N / 20mm) was measured. 【0081】 (4) Peeling force at 80°C Test specimens measuring 20 mm in width and 150 mm in length were cut from the adhesive sheets of each example and comparative example. A SUS plate (SUS430BA plate) washed with toluene was used as the adherend. Under standard conditions of 23°C and 50% RH, the test specimens were pressed onto the adherend by passing a 2 kg roller back and forth once. After the test specimens pressed onto the adherend were heated at 80°C for 5 minutes, they were peeled at 80°C at a tensile speed of 300 mm / min and a peel angle of 180° using a tensile testing machine (Shimadzu Corporation, product name "Tensilon") in accordance with JIS Z 0237, and the 180° peel force (N / 20 mm) was measured. 【0082】 (5) Reworkability of flexible composite foam One end of a 20mm wide, 150mm long Nitto SCF400 foam sheet was fixed to a SUS steel plate with Nitto NO.5000NS tape (same size as the SCF foam), and the other end of the SCF400 foam was attached to Nitto NO.5000NS tape (same size as the SCF foam) which had a 0.05mm thick PET film composite on one side. The adhesive sheet was applied to the PET surface, which was a composite of the SUS steel plate, SCF400, and PET sheet, using a 2kg roller at a speed of 300mm / min. After leaving it at room temperature (23°C) for 30 minutes, it was peeled off at room temperature using a tensile testing machine (Shimadzu Corporation, product name "Tensilon") at 180° and a tensile speed of 300mm / min to check for damage to the SCF400. The same experiment was also performed at 80°C to check for damage to the SCF400. If damage occurs when the SCF is peeled off at 23°C but not when it is peeled off at 80°C, it means that the adhesive sheet has high tackiness at 23°C and is easy to peel off at 80°C, so the reworkability is judged to be "OK". If no damage occurs when the SCF400 is peeled off at 23°C or damage occurs when the SCF400 is peeled off at 80°C, it means that the adhesive sheet has low tackiness at 23°C or is not easily peeled off at 80°C, so the reworkability is judged to be "NG". 【0083】 As shown in the table above, the adhesive sheets of Examples 1 to 10 had excellent adhesion and heat-removable properties, and could be easily peeled off by heating after use without causing deformation or damage to the adherend. On the other hand, the adhesive sheets of Comparative Examples 1 to 6 did not provide excellent adhesion or were prone to deformation or damage to the adherend.

Claims

[Claim 1] An adhesive sheet having a base layer and an adhesive layer disposed on at least one side of the base layer, An adhesive sheet characterized in that, A is the peeling force when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min, B is the peeling force when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min, and the value calculated by (A - B) / A is 90% or more. [Claim 2] The adhesive sheet according to claim 1, characterized in that the peeling force when the adhesive layer is peeled off at 23°C in a 180° direction at a tensile speed of 300 mm / min is 2 to 40 N / 20 mm, and the peeling force when the adhesive layer is heated at 80°C for 5 minutes and peeled off at 80°C in a 180° direction at a tensile speed of 300 mm / min is 0.01 to 4 N / 20 mm. [Claim 3] The adhesive sheet according to claim 1 or 2, characterized in that the adhesive layer comprises rubber and a tackifying resin, wherein the content of the tackifying resin is 5 to 120 parts by weight per 100 parts by weight of rubber. [Claim 4] The adhesive sheet according to claim 3, characterized in that the rubber is one or more selected from styrene-ethylene-butylene-styrene rubber, styrene-butadiene-styrene rubber, styrene-butadiene rubber, and styrene-isoprene-styrene rubber. [Claim 5] The adhesive sheet according to claim 3, characterized in that the styrene content in the rubber is 5 to 25% by weight. [Claim 6] The adhesive sheet according to claim 3, wherein the tackifying resin is one or more selected from rosin resin, modified rosin resin, terpene resin, and C5 / C9 tackifying resin, and the tackifying resin has a softening point of 50 to 85°C or a viscosity of 1,000 to 20,000 cP at 23°C. [Claim 7] The aforementioned substrate layer has a foaming ratio of 1.1 to 20 cm ３ The adhesive sheet according to claim 1 or 2, characterized in that it has a strength of 0.06 to 2.0 mm, a 50% compressive strength of 100 kPa to 10000 kPa, and the thickness of the adhesive layer is 1 to 200 μm.

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