TW201718797A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

A pressure-sensitive adhesive sheet for fixing members for portable devices is provided, the sheet including a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition which comprises an acrylic polymer as a base polymer, a tackifier resin, and crosslinking agents. The acrylic polymer is constituted of monomer components which include more than 50 wt% C1-6 alkyl (meth)acrylate(s). The tackifier resin is contained in an amount exceeding 10 parts by weight per 100 parts by weight of the acrylic polymer. The crosslinking agents comprise an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent.

Description

Adhesive sheet

The present invention relates to an adhesive sheet. In detail, it relates to an adhesive sheet suitable for fixing a member constituting a portable device. The present application claims the priority of Japanese Patent Application No. 2015- 185 861, filed on Sep. It is incorporated herein by reference.

In general, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter) has the property of exhibiting a soft solid (viscoelastic) state in a temperature region near room temperature, which is simply followed by pressure. Being attached to the body. In this nature, the adhesive is typically used in the form of an adhesive sheet, which is widely used for the purpose of joining or fixing, protecting, and the like of components in mobile phones and other portable devices. Patent Documents 1 and 2 are cited as technical documents relating to double-sided tapes for fixing components for mobile electronic devices. [Prior Art Document] [Patent Document 1] Japanese Patent Application Publication No. 2009-215355 (Patent Document 2) Japanese Patent Application Publication No. 2013-100485

[Problems to be Solved by the Invention] The portable device carries the user, and thus it is easy to adhere to secretions such as sebum or hand scale, cosmetics or hair styling agents, moisturizers, sunscreens, and the like, or oils contained in foods and the like. In particular, in a portable device of a touch panel type that has been widely used in recent years, the display unit includes a display unit/input unit that also functions as an input unit, and the user directly contacts the display unit/input unit with a fingertip. The operation is performed on the surface, so there is a greater chance of attaching oil to the fingertip. Further, in a wearable device, the user is worn in a state of being in contact with the skin, and in such a use form, there are many opportunities for exposure to oil such as sebum or chemicals applied to the skin. When such an oil component comes into contact with the adhesive layer of the adhesive sheet of the fixing member, the adhesive absorbs oil and softens, and may cause problems such as expansion, deformation, and reduction in cohesive force. In this regard, for example, in Patent Document 1, a double-sided adhesive sheet having the following properties has been studied: even if the oil is infiltrated, the adhesive is hard to swell, and when used for fixing a part, the adhesive does not bleed out. On the other hand, since it is an adhesive sheet for a fixing member, it is of course important to maintain the performance of the member, that is, to maintain the member in a fixed state. Moreover, the above-mentioned retention performance is a performance that continues to be required after the adhesive sheet fixing member is used in the manufacturing process of the portable device, and is required to be in contact with the oil component which may be generated after the portable device is manufactured. . However, in the prior art relating to the improvement of the oil resistance of the adhesive sheet for fixing a member, the holding property of the adhesive sheet is often insufficient. As the form of portable devices (especially mobile electronic devices) is diversified or the use scene becomes wider, adhesive sheets for fixing members are increasingly required to have higher retention performance. The present invention has been made in view of this fact, and an object thereof is to provide an adhesive sheet which has high holding performance and is difficult to penetrate oil. [Technical means for solving the problem] According to the present specification, an adhesive sheet for a fixing member in a portable device is provided. The adhesive sheet contains an adhesive layer formed using an adhesive composition containing an acrylic polymer as a base polymer, a tackifier resin, and a crosslinking agent. The monomer component constituting the acrylic polymer contains more than 50% by weight of an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at the ester terminal (hereinafter, sometimes referred to as "(methyl) ) C _1-6 alkyl acrylate "). The content of the tackifier resin is more than 10 parts by weight based on 100 parts by weight of the acrylic polymer. Further, the crosslinking agent includes an epoxy crosslinking agent and an isocyanate crosslinking agent. Adhesive agent constituting the adhesive layer contains the (meth) acrylic acid C _1-6 alkyl ester as a main monomer component constituting the acrylic polymer as the base polymer, it is difficult to absorb the oil. Moreover, by using an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in combination, the cohesive force of the above-mentioned adhesive layer can be improved and the retention property of the adhesive sheet can be improved. Further, since the pressure-sensitive adhesive layer contains a specific amount or more of a tackifier resin, the adhesion to the adherend is good. Therefore, the oil penetration of the interface between the self-adhesive layer and the adherend can be effectively suppressed. As the tackifying resin, a phenol-based tackifying resin (for example, a phenol resin) can be preferably used. By including the phenol-based tackifying resin in the adhesive layer, the adhesion to the adherend can be improved, and the penetration of the oil can be effectively prevented. The content of the phenol-based tackifying resin is preferably an amount exceeding 10 parts by weight based on 100 parts by weight of the acrylic polymer. In a preferred embodiment of the adhesive sheet, the tackifying resin contained in the adhesive layer contains a tackifying resin having a hydroxyl value of 30 mgKOH/g or more. By including the tackifier resin having a relatively high hydroxyl value in the adhesive layer as described above, the adhesion to the adherend can be improved, and the penetration of the oil can be effectively suppressed. As the tackifying resin having a hydroxyl value of 30 mgKOH/g or more, for example, a phenol-based tackifying resin (typically an indophenol resin) can be preferably used. It is preferred that the monomer component constituting the acrylic polymer contains a carboxyl group-containing monomer. Thereby, there is a tendency that the cohesive force of the adhesive layer is increased, and the retention property of the adhesive sheet is improved. The inclusion of the carboxyl group-containing monomer in the monomer component can also advantageously contribute to the improvement of the adhesion between the adhesive layer and the adherend. The content of the carboxyl group-containing monomer in the monomer component is usually suitably from about 0.5% by weight to about 10% by weight from the viewpoint of compatibility with other components. The content of the epoxy-based crosslinking agent is preferably substantially less than 0.05 parts by weight based on 100 parts by weight of the acrylic polymer. By using this amount of the epoxy-based crosslinking agent in combination with the isocyanate-based crosslinking agent, it tends to form an adhesive layer having a high cohesive force and good adhesion to the adherend. Thereby, it is possible to achieve an adhesive sheet which more satisfactorily inhibits the penetration of oil from the interface. In one aspect, the content of the epoxy-based crosslinking agent may be approximately 1/100 or less of the content of the isocyanate crosslinking agent. According to this aspect, a higher level of cohesive force and adhesion of the adhesive layer can achieve superior oil penetration resistance. The technique disclosed herein can be preferably applied to an adhesive sheet having a thickness of the above-mentioned adhesive layer of approximately 30 μm or less (for example, approximately 25 μm or less). If the thickness of the adhesive layer becomes small, even if the amount of oil adhered is the same, the amount of oil per unit volume supplied to the adhesive becomes more. In addition, when the thickness of the adhesive layer is small, there is a tendency that the adhesion between the adhesive layer and the adherend is easily lowered, and the oil component at the interface between the adhesive layer and the adherend is easily formed. Infiltration. Therefore, it is of particular interest to apply the techniques disclosed herein to inhibit the penetration of oil. The adhesive sheet disclosed herein preferably has a 180 degree peel strength of approximately 17 N/25 mm or more. According to the adhesive sheet which exhibits the adhesive force, there is a tendency to suitably prevent the penetration of oil from the interface between the adhesive layer and the adherend. A preferred aspect of the adhesive sheet comprises any of the adhesive layers disclosed herein, and a substrate film that supports the adhesive layer. In the above-mentioned adhesive layer, by using an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in combination, even if the cohesive force of the above-mentioned adhesive layer is increased, the adhesion to the base film is not easily lowered. Thereby, the penetration of oil from the interface between the adhesive layer and the substrate film can be suppressed. The technique disclosed herein can be preferably carried out by a double-sided adhesive sheet (which can be a double-sided adhesive sheet having an adhesive on one surface of the substrate film and the other surface). The fixing portion of the member of the double-sided adhesive sheet contains more interfaces than the fixed portion of the member of the single-sided adhesive sheet, so that oil is easily infiltrated from the interfaces. Therefore, it is of particular interest to apply the techniques disclosed herein to inhibit oil permeation from the above interfaces.

Hereinafter, preferred embodiments of the present invention will be described. Furthermore, in addition to the matters specifically mentioned in the present specification and necessary for the implementation of the present invention, the manufacturer may be based on the instructions on the implementation of the invention and the technical common sense at the time of filing the application described in the present specification. Understood. The present invention can be implemented in accordance with the teachings of the present invention and the technical knowledge in the field. In the following description, members and portions that perform the same functions are denoted by the same reference numerals, and the description thereof will be omitted or simplified. Further, the embodiments described in the drawings are schematically illustrated to clearly describe the present invention, and the size or reduction ratio of the adhesive sheet of the present invention actually provided as a product is not necessarily accurately indicated. In the specification, the term "adhesive" means a material having a property of exhibiting a soft solid (viscoelastic body) in a temperature region near room temperature, which is simply followed by pressure. On the body. The term "adhesive" as used herein, as defined in "CA Dahlquist, "Adhesion: Fundamental and Practice"', McLaren & Sons, (1966) P. 143", generally has a complex tensile modulus E. ^* (1Hz)<10 ⁷ Dyne/cm ² A material of a nature (typically a material having the above properties at 25 ° C). In the present specification, the term "(meth)acryloyl) refers to the meaning of an alkylene group and a methacryl group. Similarly, the term "(meth)acrylate" refers to the meaning of acrylate and methacrylate, and the term "(meth)acrylic group" refers to both acrylic acid and methacrylic acid. The meaning. In the present specification, the term "acrylic polymer" means a monomer unit derived from a monomer having at least one (meth)acryl fluorenyl group in one molecule, and is a monomer unit constituting the polymer. polymer. Hereinafter, a monomer having at least one (meth) acrylonitrile group in one molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in the present specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. The adhesive sheet disclosed herein is composed of an adhesive layer. A typical aspect of the above adhesive sheet is a substrate-attached adhesive sheet having an adhesive layer on at least one surface of a substrate film (support). The concept of an adhesive sheet herein may be referred to as an adhesive tape, an adhesive label, an adhesive film, or the like. Furthermore, the adhesive sheet disclosed herein may be in the form of a roll or a single piece. Alternatively, it may be an adhesive sheet which is further processed into various shapes. Further, the base film may not be present. The adhesive sheet disclosed herein may be, for example, a cross-sectional structure schematically shown in FIG. The adhesive sheet 1 includes a base film 10 and a first adhesive layer 21 and a second adhesive layer 22 which are respectively supported by the first surface 10A and the second surface 10B of the base film 10. The first surface 10A and the second surface 10B are non-peelable surfaces (non-peeling surfaces). The adhesive sheet 1 is used by attaching the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 to the adherend. That is, the adhesive sheet 1 is formed in the form of a double-sided adhesive sheet (double-sided adhesive sheet). The adhesive sheet 1 before use has a configuration in which the first adhesive surface 21A and the second adhesive surface 22A are respectively protected by release liners 31 and 32 having a peelable surface (release surface) on at least the adhesive surface side. Alternatively, the release liner 32 may be omitted, and the release liner 31 may be a release surface, and the adhesive sheet 1 may be wound to bring the second adhesive surface 22A into contact with the back surface of the release liner 31. Thus, the second adhesive surface 22A is also protected by the release liner 31. The technique disclosed herein can also be practiced in the form of a single-sided adhesive sheet having an adhesive layer on only one side of the substrate film. One of the single-sided adhesive sheets is exemplified in FIG. The adhesive sheet 2 includes a base film 10 and a first adhesive layer 21 supported by the first surface 10A, and the surface (first adhesive surface) 21A of the first adhesive layer 21 is attached to the adherend. And use. The adhesive sheet 2 before use has a configuration in which the first adhesive surface 21A is protected by a release liner 31 in which at least the adhesive surface side is a release surface. Alternatively, the release liner 31 may be omitted, and the base film 10 may be a release surface by using the second surface 10B, and the adhesive sheet 2 may be wound to bring the first adhesive surface 21A into contact with the base film. The first surface 10B of 10 is used to protect the first adhesive surface 21A. Alternatively, although the adhesive sheet disclosed herein is not particularly illustrated, it may be a double-sided adhesive sheet having no base material (that is, having no base material) containing only the adhesive layer. <Adhesive Layer> The adhesive sheet disclosed herein has an adhesive layer formed using an adhesive composition containing an acrylic polymer as a base polymer, a tackifying resin, and a crosslinking agent. The adhesive sheet may be, for example, a substrate-attached adhesive sheet having the above-described adhesive layer on at least one surface of the base film. Here, the term "base polymer" means a main component of a rubber-like polymer (a polymer exhibiting rubber elasticity in a temperature region near room temperature) contained in an adhesive layer. In the specification, the term "main component" means a component containing more than 50% by weight, unless otherwise specified. (Acrylic polymer) The above acrylic polymer contains (meth)acrylic acid C _1-6 The alkyl ester is a main monomer, and may further contain a polymer of a monomer component of a secondary monomer having copolymerizability with the main monomer. Here, the main single system means a main component of a monomer component, that is, a component of more than 50% by weight. As (meth)acrylic acid C _1-6 Specific examples of the alkyl ester are not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and isopropyl (meth)acrylate. Base) n-butyl acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate Wait. The (meth)acrylic acid C _1-6 The alkyl esters may be used alone or in combination of two or more. For (meth)acrylic acid C _1-6 The acrylic polymer having an alkyl ester as a main monomer is compared with an acrylic polymer having an alkyl (meth)acrylate having an alkyl group having a larger number of carbon atoms as a main monomer. Generally speaking, the affinity for oil is low. Therefore, the above-mentioned adhesive layer containing the acrylic polymer as a base polymer tends to be difficult to absorb oil in the adhesive layer. The acrylic polymer is preferably a main monomer of (meth)acrylic acid C from the viewpoint of lowering the lipophilicity of the adhesive layer. _1-5 Alkyl ester, more preferably (meth)acrylic acid C _1-4 Alkyl ester. The acrylic monomer which is one of the preferred aspects is considered to have excellent adhesion to the adherend or adhesion to the base film in the constitution of the base film. Acrylic acid C _2-6 Alkyl ester, more preferably (meth)acrylic acid C _4-6 Alkyl ester. As a preferred aspect of the acrylic polymer, the main monomer is acrylic acid C from the viewpoint of improving the adhesion. _1-6 Alkyl ester, more preferably acrylic acid C _1-4 Alkyl esters (eg acrylic acid C _2-4 Alkyl ester). As the above (meth)acrylic acid C _1-6 The alkyl ester may preferably have a glass transition temperature (Tg) of a homopolymer of about 20 ° C or less from the viewpoint of lowering the lipophilicity of the adhesive layer and improving the adhesion to the adherend or the substrate film. Typically, the (meth)acrylic acid C is preferably 10 ° C or less, preferably about 0 ° C or less, more preferably about -10 ° C or less, and still more preferably about -15 ° C or less. _1-6 Alkyl ester. The technique disclosed herein can be preferably carried out, for example, by the aspect in which the main monomer of the acrylic polymer is n-butyl acrylate (BA). Moreover, from the viewpoint of lowering the lipophilicity of the adhesive layer, (meth)acrylic acid C among the monomer components constituting the acrylic polymer described above _1-6 Alkyl ester (typically acrylic C _1-6 The proportion of the alkyl ester, for example, BA), is preferably about 60% by weight or more, more preferably about 75% by weight or more, still more preferably about 85% by weight or more. The technique disclosed herein may be, for example, substantially 70% by weight or more (more preferably approximately 80% by weight or more, still more preferably approximately 85% by weight or more, and may be approximately 90% by weight or more or substantially 95). % or more) is preferably implemented in the form of BA. In the acrylic polymer in the technique disclosed herein, a monomer other than the above (other monomer) may be copolymerized as needed within a range that does not significantly impair the effects of the present invention. The above other monomer can be used, for example, for the purpose of adjusting the Tg of the acrylic polymer, improving the cohesive force, and adjusting the initial adhesion. For example, examples of the monomer which can improve the cohesive force or heat resistance of the adhesive include a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a cyano group-containing monomer, a vinyl ester, and an aromatic vinyl compound. As a suitable example of these, a vinyl ester is mentioned. Specific examples of the vinyl esters include vinyl acetate (VAc), vinyl propionate, and vinyl laurate. Among them, VAc is preferred. Further, examples of the other functional group which can introduce a functional group which can be a crosslinking point in the acrylic polymer or which can contribute to the improvement of the peeling strength include a hydroxyl group-containing (OH group) monomer, a carboxyl group-containing monomer, and an acid anhydride. Base monomer, mercapto group-containing monomer, amine group-containing monomer, ruthenium-containing monomer, epoxy group-containing monomer, (meth) propylene group Porphyrins, vinyl ethers, and the like. A suitable example of one of the acrylic polymers in the technique disclosed herein is an acrylic polymer obtained by copolymerizing a carboxyl group-containing monomer as the other monomer. There is a tendency to easily obtain an adhesive layer having a high cohesive force. The monomer component containing a carboxyl group-containing monomer can also advantageously contribute to an improvement in adhesion between the adhesive layer and the adherend or substrate film. Examples of the carboxyl group-containing monomer include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, and fumaric acid. Butenoic acid, methacrylic acid, and the like. Among them, preferred examples of the carboxyl group-containing monomer include AA and MAA. Very good for AA. Other suitable examples of the acrylic polymer in the technique disclosed herein include an acrylic polymer in which a hydroxyl group-containing monomer is copolymerized as the other monomer. The hydroxyl group-containing monomer may also be copolymerized together with the carboxyl group-containing monomer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylic acid 2 a hydroxyalkyl (meth)acrylate such as hydroxybutyl ester or 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; N-hydroxyethyl(meth)acrylamide. In particular, a preferred hydroxyl group-containing monomer is a hydroxyl group at the terminal of a linear alkyl group having about 2 to 4 carbon atoms, such as 2-hydroxyethyl acrylate or 4-hydroxybutyl (meth)acrylate. A hydroxyalkyl (meth) acrylate. In the acrylic polymer of the technology disclosed herein, copolymerization of (meth)acrylic acid C can be carried out within a range that does not significantly impair the effects of the present invention. _1-6 A hydrocarbyl (meth) acrylate other than the alkyl ester is used as the other monomer described above. Examples of such a (meth) acrylate include an alicyclic (meth) acrylate having an alicyclic group at the ester terminal or a carbon number of 7 or more at the ester terminal (typically 7 to 20). An alkyl (meth) acrylate of an alkyl group. Examples of the alicyclic (meth) acrylate include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, and cyclomethacrylate (meth) acrylate. Ester, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, (meth) acrylate Ester, dicyclopentanyl (meth)acrylate, and the like. As (meth)acrylic acid C _7-20 Examples of the alkyl esters include heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and (methyl). Ethyl acrylate, isodecyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (meth) acrylate, ( Stearyl methacrylate, isostearyl (meth) acrylate, and the like. The above-mentioned "other monomers" may be used alone or in combination of two or more. The total content of the other monomers may be, for example, approximately 50% by weight (typically about 0.001 to 40% by weight) of all the monomer components, and usually it is suitably about 25% by weight or less (typically It is about 0.01 to 25% by weight, for example, about 0.1 to 20% by weight. When a carboxyl group-containing monomer is used as the other monomer, the amount thereof is usually suitably from 0.1 to 20% by weight (preferably from 0.1 to 15% by weight, typically 0.2) of all the monomer components. It is about 12% by weight, for example, about 0.5 to 10% by weight. When the amount of the carboxyl group-containing monomer used is increased, the cohesive force of the adhesive layer tends to generally increase. By using the amount of the carboxyl group-containing monomer in the above range, the adhesion-promoting effect of the tackifying resin described later is suitably exhibited, and an adhesive layer which exhibits good adhesion to the adherend and the substrate film can be suitably obtained. In one aspect, the content of the carboxyl group-containing monomer may be approximately 1 to 8% by weight (e.g., approximately 2 to 7% by weight) of all the monomer components. Further, when a hydroxyl group-containing monomer is used as the other monomer, the content thereof is usually suitably 0.001 to 10% by weight based on all the monomer components (for example, approximately 0.01 to 5% by weight, typically approximately 0.02%) ～2% by weight). The copolymerization composition of the acrylic polymer is suitably designed such that the Tg of the polymer is approximately -15 ° C or lower (typically approximately -70 ° C or higher and -15 ° C or lower). Here, the Tg of the acrylic polymer means the Tg obtained by the Fox formula according to the composition of the monomer component for synthesizing the polymer. The Fox equation is a relationship between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing the monomers constituting the copolymer as follows. 1/Tg=Σ(Wi/Tgi) Further, in the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, and Wi represents the weight fraction of the monomer i in the copolymer (weight basis The copolymerization ratio), Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i. As the glass transition temperature for calculating the homopolymer of Tg, the values described in the publicly known materials are used. For example, regarding the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer. 2-ethylhexyl acrylate-70°C n-butyl acrylate-55°C ethyl acrylate-22°C methyl acrylate 8°C methyl methacrylate 105°C 2-hydroxyethyl acrylate-15°C 4-hydroxybutyl acrylate -40°C Vinyl acetate 32°C Styrene 100°C Acrylic acid 106°C Methacrylic acid 228°C For the glass transition temperature of the homopolymer of the monomer other than the above, use the “Polymer Handbook” (No. 3) Edition, John Wiley & Sons, Inc., 1989. Regarding the monomers in which a plurality of values are described in the literature, the highest value is employed. Regarding the monomer in which the glass transition temperature of the homopolymer is not described in the above literature, the value obtained by the following measurement method is used. Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen gas introduction tube, and a reflux condenser. 200 parts by weight, and the mixture was stirred for 1 hour while circulating nitrogen gas. After the oxygen in the polymerization system was removed in this manner, the temperature was raised to 63 ° C and the reaction was carried out for 10 hours. Next, it was cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Next, the homopolymer solution was cast-coated on a release liner, and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. The test sample was punched into a disk shape of 7.9 mm in diameter, and was sandwiched by a parallel plate, and a shear strain of 1 Hz was applied to one side using a viscoelasticity tester (manufactured by TA Instruments Japan, machine name "ARES"). The viscoelasticity was measured by a shear mode at a temperature elevation rate of 5 ° C / min in a temperature range of -70 to 150 ° C, and the peak top temperature of tan δ (loss tangent) was taken as the Tg of the homopolymer. Although it is not particularly limited, from the viewpoint of adhesion to the adherend or the substrate film, it is advantageous that the Tg of the acrylic polymer is approximately -25 ° C or lower, preferably approximately -35 ° C or lower, more preferably It is approximately -40 ° C or less. Further, from the viewpoint of the cohesive force of the adhesive layer, it is advantageous that the Tg of the acrylic polymer is approximately -65 ° C or higher, preferably approximately -60 ° C or higher, more preferably approximately -55 ° C or higher. The technique disclosed herein can be preferably carried out by using a Tg of the acrylic polymer of approximately -65 ° C or more and -35 ° C or less (for example, approximately -55 ° C or more and -40 ° C or less). The Tg of the acrylic polymer can be adjusted by suitably changing the monomer composition (i.e., the kind or amount ratio of the monomers used to synthesize the polymer). The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as a method for synthesizing an acrylic polymer, such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method, can be suitably used. For example, a solution polymerization method can be preferably employed. As a monomer supply method at the time of solution polymerization, a one-time loading method, a continuous supply (drop) method, a split supply (drop) method, and the like of all the monomer raw materials can be suitably used. The polymerization temperature can be appropriately selected depending on the type of the monomer and solvent to be used, the type of the polymerization initiator, and the like, and can be, for example, about 20 to 170 ° C (typically about 40 to 140 ° C). In a preferred embodiment, the polymerization temperature can be set to approximately 75 ° C or lower (more preferably approximately 65 ° C or lower, for example, approximately 45 ° C to 65 ° C). The solvent (polymerization solvent) used in the solution polymerization can be appropriately selected from previously known organic solvents. For example, any one selected from the following solvents or a mixed solvent of two or more kinds may be used: aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; hexane or ring An aliphatic or alicyclic hydrocarbon such as hexane; a halogenated alkane such as 1,2-dichloroethane; a lower alcohol such as isopropyl alcohol (for example, a monohydric alcohol having 1 to 4 carbon atoms); Ethers such as ethers; ketones such as methyl ethyl ketone. The initiator to be used in the polymerization can be appropriately selected from previously known polymerization initiators depending on the kind of the polymerization method. For example, one type or two or more types of azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Examples of other examples of the polymerization initiator include persulfate such as potassium persulfate; peroxide initiators such as benzamidine peroxide and hydrogen peroxide; and substituted ethane substituted by phenyl. An alkane initiator; an aromatic carbonyl compound or the like. As another example of the polymerization initiator, a redox initiator which is a combination of a peroxide and a reducing agent can be mentioned. These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator to be used may be a normal amount, and may be, for example, about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of all the monomer components. Choose within the scope. According to the solution polymerization described above, a polymerization reaction solution in which the acrylic polymer is dissolved in an organic solvent can be obtained. The adhesive layer in the technique disclosed herein may be formed of an adhesive composition comprising the above polymerization reaction solution or an acrylic polymer solution obtained by subjecting the reaction liquid to a suitable post treatment. As the acrylic polymer solution, those having a suitable viscosity (concentration) can be used as needed. Alternatively, an acrylic polymer obtained by dissolving an acrylic polymer by a polymerization method other than solution polymerization (for example, emulsion polymerization, photopolymerization, bulk polymerization, or the like) and dissolving the acrylic polymer in an organic solvent may be used. Solution. The weight average molecular weight (Mw) of the base polymer (suitably an acrylic polymer) in the technique disclosed herein is not particularly limited, and may be, for example, approximately 10×10. ⁴ ~500×10 ⁴ The scope. From the viewpoint of adhesion performance, it is preferred that the Mw of the base polymer is approximately 30×10. ⁴ ~200×10 ⁴ (better than roughly 45×10) ⁴ ~150×10 ⁴ Typically, roughly 65×10 ⁴ ~130×10 ⁴ Within the scope of). Here, Mw means a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC device, for example, the device type name "HLC-8320GPC" (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used. (Crosslinking Agent) The crosslinking agent contains an epoxy crosslinking agent and an isocyanate crosslinking agent. By using these two kinds of crosslinking agents in combination, the cohesive force of the adhesive layer can be sufficiently improved. Further, in the configuration including the base film (supporting substrate), good adhesion to the base film can be ensured. The adhesive layer in the technique disclosed herein may contain the above-mentioned crosslinking agent in the form after the crosslinking reaction, the form before the crosslinking reaction, the form of the partial crosslinking reaction, the intermediate or composite form, and the like. The above-mentioned crosslinking agent is typically mainly contained in the adhesive layer in the form of a crosslinking reaction. The epoxy-based crosslinking agent can be used without any particular limitation in a compound having two or more epoxy groups in one molecule. An epoxy-based crosslinking agent having 3 to 5 epoxy groups in one molecule is preferred. The epoxy-based crosslinking agent may be used alone or in combination of two or more. Although not particularly limited, specific examples of the epoxy-based crosslinking agent include N, N, N', N'-tetraglycidyl-m-xylylenediamine, and 1,3-double (N). , N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. As a commercial item of the epoxy-based crosslinking agent, the trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Co., Ltd. and the trade name "TETRAD-X", and the trade name "Epiclon CR-5L" manufactured by DIC Corporation, The product name "DENACOL EX-512" manufactured by Nagase Chemical Co., Ltd., and the trade name "TEPIC-G" manufactured by Nissan Chemical Industries Co., Ltd. The amount of the epoxy-based crosslinking agent used is not particularly limited. The amount of the epoxy-based crosslinking agent to be used is, for example, more than 0 parts by weight and substantially 1 part by weight or less (typically about 0.001 to 0.5 parts by weight) based on 100 parts by weight of the acrylic polymer. The amount of the epoxy-based crosslinking agent to be used is usually substantially 0.002 parts by weight or more based on 100 parts by weight of the acrylic polymer, and is preferably substantially the same as the effect of improving the effect of the aggregation. 0.005 parts by weight or more, more preferably about 0.008 parts by weight or more. In addition, the amount of the epoxy-based crosslinking agent to be used is usually substantially 0.2 with respect to 100 parts by weight of the acrylic polymer, from the viewpoint of avoiding excessive adhesion of the adherend or the substrate film. The amount by weight or less is preferably about 0.1 part by weight or less, more preferably about 0.05 part by weight or less, still more preferably about 0.03 part by weight or less (for example, substantially 0.025 part by weight or less). As the isocyanate crosslinking agent, a polyfunctional isocyanate (a compound having an average of two or more isocyanate groups per molecule, and a structure having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent may be used alone or in combination of two or more. Examples of the polyfunctional isocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Specific examples of the aliphatic polyisocyanate include 1,2-ethylidene diisocyanate, 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-four. Tetramethylene diisocyanate such as methylene diisocyanate; 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5- Hexamethylene diisocyanate, hexamethylene diisocyanate such as hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate or 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, quaternary acid diisocyanate, and the like. Specific examples of the alicyclic polyisocyanate include isophorone diisocyanate; cyclohexyl group such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; Diisocyanate; cyclopentyl diisocyanate such as 1,2-cyclopentyl diisocyanate or 1,3-cyclopentyl diisocyanate; hydrogenated dimethyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, Hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate or the like. Specific examples of the aromatic polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 2,4'-diphenylmethane. Diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenyl Propane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, isophthalic diisocyanate, para-benzene Diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, benzodimethyl-1,4 - Diisocyanate, benzodimethyl-1,3-diisocyanate, and the like. Preferable polyfunctional isocyanates are polyfunctional isocyanates having an average of three or more isocyanate groups per molecule. The trifunctional or higher isocyanate may be a polyfunctional (typically dimer or terpolymer) or a derivative of a bifunctional or trifunctional or higher isocyanate (for example, an addition of a polyhydric alcohol and a polyfunctional isocyanate of 2 or more molecules). Reaction product), polymer, and the like. For example, a dimer or a trimer of diphenylmethane diisocyanate, an isocyanurate body of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), and a trishydroxyl group can be mentioned. A reaction product of a propane and toluene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, a polyfunctional isocyanate such as polymethylene polyphenyl isocyanate, polyether polyisocyanate or polyester polyisocyanate. As a commercial product of the polyfunctional isocyanate, the product name "Duranate TPA-100" manufactured by Asahi Kasei Chemical Co., Ltd., the trade name "Coronate L" manufactured by Japan Polyurethane Industry Co., Ltd., and the trade name "Coronate" manufactured by Japan Polyurethane Industry Co., Ltd. HL", the trade name "Coronate HK" manufactured by Japan Polyurethane Industry Co., Ltd., the trade name "Coronate HX" manufactured by Japan Polyurethane Industry Co., Ltd., and the trade name "Coronate 2096" manufactured by Japan Polyurethane Industry Co., Ltd., etc. The amount of the isocyanate crosslinking agent used is not particularly limited. The amount of the isocyanate-based crosslinking agent to be used is, for example, more than 0 parts by weight and substantially 10 parts by weight or less (typically approximately 0.01 parts by weight or more and 10 parts by weight or less) based on 100 parts by weight of the acrylic polymer. In general, the amount of the isocyanate-based crosslinking agent to be used is suitably 0.1 parts by weight or more and 8 parts by weight or less, preferably about 0.3 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the acrylic polymer. More preferably, it is about 0.5 part by weight or more and less than 4 parts by weight (for example, about 0.7 part by weight or more and 3.5 parts by weight or less). By using this amount of the isocyanate-based crosslinking agent in combination with the epoxy-based crosslinking agent, the adhesion to the adherend and the substrate film and the cohesive force can be achieved at a high level. Thereby, an adhesive sheet which exhibits excellent oil-repellent permeability (oil resistance) and excellent retention property (cohesive force of the adhesive layer) can be realized. In the technique disclosed herein, the relationship between the content of the epoxy-based crosslinking agent and the content of the isocyanate-based crosslinking agent is not particularly limited. The content of the epoxy-based crosslinking agent can be, for example, approximately 1/50 or less of the content of the isocyanate crosslinking agent. The content of the epoxy-based crosslinking agent is appropriately set to be approximately 1/75 or less of the content of the isocyanate-based crosslinking agent, from the viewpoint of the adhesion to the adherend and the base film and the cohesive force. Preferably, it is set to approximately 1/100 or less (for example, 1/150 or less). In addition, from the viewpoint of the effect of using an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in combination, the content of the epoxy-based crosslinking agent is usually set to be an isocyanate-based crosslinking. The content of the crosslinking agent is approximately 1/1000 or more, for example, approximately 1/500 or more. The adhesive composition in the technique disclosed herein may contain other crosslinking agents as needed, in addition to the epoxy-based crosslinking agent and the isocyanate-based crosslinking agent, to the extent that the effects of the present invention are not significantly impaired. As an example of such other crosslinking agent, An oxazoline crosslinking agent, a carbodiimide crosslinking agent, an anthraquinone crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, and the like. Alternatively, it may be an adhesive composition which does not contain the above other crosslinking agents. (Tackifying Resin) As the tackifying resin, a phenol-based tackifying resin, an oxime-based tackifying resin, a modified lanthanum-based tackifying resin, a rosin-based tackifying resin, a hydrocarbon-based tackifying resin, and an epoxy-based resin can be used. One or more of various known tackifying resins such as a tackifying resin, a polyamide-based tackifying resin, an elastic system tackifying resin, and a ketone tackifying resin. Examples of the phenolic tackifying resin include indophenol resin, hydrogenated indophenol resin, alkylphenol resin, and rosin phenol resin. The term "phenolic resin" refers to a polymer comprising a hydrazine residue and a phenol residue, which comprises a copolymer of a hydrazine and a phenol compound (a hydrazine-phenol copolymer resin), and a phenol of a hydrazine homopolymer or a copolymer. The concept of both modified (phenol-modified resin). Examples of suitable examples of the oxime constituting the phenol resin include a monoterpenoid such as α-pinene, β-pinene, and limonene (including a d-form, a l-form, and a d/l (dipentene)). The hydrogenated indophenol resin refers to a hydrogenated indophenol resin having a structure in which the indophenol resin is hydrogenated. Sometimes referred to as hydrogenated indophenol resin. The alkylphenol resin is a resin (oily phenol resin) obtained from an alkylphenol and formaldehyde. Examples of the alkylphenol resin include a novolac type and a novolac type. The rosin phenol resin is typically a phenolic modification of rosin or various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of the rosin phenol resin include rosin phenol resins obtained by the following methods: rosin or various rosin derivatives described above, a method of adding a phenol by an acid catalyst, and performing thermal polymerization. Examples of the lanthanum-based tackifying resin include polymers of anthraquinones (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one type of anthracene or a copolymer of two or more types of anthracene. Examples of the homopolymer of one type of anthracene include an α-pinene polymer, a β-pinene polymer, and a dipentene polymer. Examples of the modified oxime resin include those obtained by modifying the above ruthenium resin. Specifically, a styrene-modified oxime resin, a hydrogenated hydrazine resin, or the like can be exemplified. The concept of the rosin-based tackifying resin herein includes both rosin-based and rosin-derived resins. Examples of rosin include: unmodified rosin (raw rosin) such as rosin gum, wood rosin, high oil rosin; modified rosin modified by hydrogenation, disproportionation, polymerization, etc. (Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc.). The rosin derivative resin is typically a rosin derivative as described above. The concept of the rosin-based resin herein includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). For example, an unmodified rosin ester which is an ester of an unmodified rosin and an alcohol, or a rosin ester such as a modified rosin ester which is an ester of a modified rosin and an alcohol; for example, an rosin is used for an unsaturated fatty acid. Modified unsaturated fatty acid-modified rosin; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; for example, rosin or various rosin derivatives (including rosin) A rosin alcohol obtained by reducing a carboxyl group of an ester, an unsaturated fatty acid-modified rosin, and an unsaturated fatty acid-modified rosin ester; for example, a rosin or a metal salt of the above various rosin derivatives. Specific examples of the rosin esters include methyl esters, triethylene glycol esters, glycerin esters, and pentaerythritol esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, and polymerized rosin). Examples of the hydrocarbon-based tackifier resin include an aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, an aliphatic cyclic hydrocarbon resin, and an aliphatic-aromatic petroleum resin (styrene-olefin copolymer). Various hydrocarbon-based resins such as an aliphatic-alicyclic petroleum resin, a hydrogenated hydrocarbon resin, a chlorpyrifos resin, and a kasuga-ruthenium resin. The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving the cohesive force, in one aspect, a tackifying resin having a softening point (softening temperature) of substantially 80 ° C or higher (preferably substantially 100 ° C or higher) can be preferably used. The technique disclosed herein may exceed 50% by weight (more preferably, more than 70% by weight, for example, more than 90% by weight) of the tackifying resin contained in the adhesive layer by the tackifying resin having the above softening point. It is preferably implemented as such. For example, a phenol-based tackifying resin (indophenol resin or the like) having such a softening point can be preferably used. In a preferred embodiment, an indophenol resin having a softening point of substantially 135 ° C or higher (further, approximately 140 ° C or higher) can be used. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of the adhesion of the adherend or the substrate film, in one aspect, a tackifier resin having a softening point of approximately 200 ° C or less (more preferably approximately 180 ° C or less) can be preferably used. Further, the softening point of the tackifying resin can be measured in accordance with the softening point test method (ring and ball method) prescribed in JIS K2207. The content of the tackifier resin is preferably an amount of more than 10 parts by weight based on 100 parts by weight of the acrylic polymer. Thereby, it is possible to achieve an adhesive sheet which exhibits an effect of improving the adhesion to the adherend and exhibits good oil repellency. The content of the tackifier resin to 100 parts by weight of the acrylic polymer is preferably about 15 parts by weight or more, more preferably about 18 parts by weight or more (for example, about 20 parts by weight or more) from the viewpoint of obtaining higher adhesion. . The technique disclosed herein can also be preferably carried out by using the tackifying resin in an amount of about 25 parts by weight or more based on 100 parts by weight of the acrylic polymer. The upper limit of the content of the tackifying resin is not particularly limited. From the viewpoint of compatibility with the base polymer (acrylic polymer) or initial adhesion, in one aspect, it is usually appropriate to set the content of the tackifying resin relative to 100 parts by weight of the acrylic polymer. It is preferably about 55 parts by weight or less, more preferably about 55 parts by weight or less, still more preferably about 45 parts by weight or less (for example, substantially 40 parts by weight or less). As a preferable aspect, the tackifier resin may be one or more kinds of phenol-based tackifying resins (typically indophenol resins). By using a phenol-based tackifying resin, the adhesion of the adhesive layer to the adherend can be improved, and the penetration of oil from the interface with the adherend can be effectively suppressed. Further, the phenol tackifying resin tends to have a low affinity for oil as compared with a rosin-based tackifying resin. Therefore, the phenol-containing tackifying resin can also function to suppress the penetration of the oil into the adhesive layer (oil absorption). The technique disclosed herein can be preferably carried out, for example, by using about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of the tackifying resin as the indophenol resin. About 50% by weight or more of the total amount of the tackifying resin may be an indophenol resin, or approximately 80% by weight or more (for example, approximately 90% by weight or more) may be an indophenol resin. It is also possible to use substantially all of the tackifying resin (for example, approximately 95 to 100% by weight, and further preferably approximately 99 to 100% by weight) of the indophenol resin. The content of the phenol-based tackifying resin (for example, a phenol resin) is suitably in the range of approximately 5 to 55 parts by weight (for example, approximately more than 10 parts by weight and not more than 55 parts by weight) based on 100 parts by weight of the acrylic polymer. It is preferably in the range of approximately 15 to 45 parts by weight (e.g., approximately 20 to 40 parts by weight). Although it is not particularly limited, as the tackifier resin in the technique disclosed herein, a hydroxyl value of more than 20 mgKOH/g can be used, and a tackifier resin having a hydroxyl value of 30 mgKOH/g or more can be preferably used. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH/g or more may be referred to as a "high hydroxyl value resin". According to the tackifier resin containing such a high hydroxyl value resin, an adhesive layer which is excellent in adhesion to the adherend and has a high cohesive force can be obtained. The use of a high hydroxyl value resin can also play a role in reducing the lipophilicity of the adhesive layer. In a preferred embodiment, the tackifying resin may also contain a high hydroxyl value resin having a hydroxyl value of 50 mgKOH/g or more (more preferably 70 mgKOH/g or more). Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method defined in JIS K0070:1992 can be employed. The specific measurement method is as follows. [Method for measuring hydroxyl value] 1. Reagent (1) As the acetamidine reagent, the following reagent was used: about 12.5 g (about 11.8 mL) of acetic anhydride was added, and pyridine was added thereto to make a total amount of 50 mL. Stir well. Alternatively, the following reagents may be used: about 25 g (about 23.5 mL) of acetic anhydride is added, and pyridine is added thereto to make the total amount 100 mL, which is sufficiently stirred. (2) As a measuring reagent, a 0.5 mol/L potassium hydroxide ethanol solution was used. (3) Further, toluene, pyridine, ethanol, and distilled water are prepared. 2. Operation (1) Accurately weigh approximately 2 g of sample in a flat-bottomed flask, add 5 mL of acetamidine reagent and 10 mL of pyridine, and install an air condenser. (2) The flask was heated in a bath at 100 ° C for 70 minutes, left to cool, and 35 mL of toluene was added as a solvent from the upper portion of the condenser, and stirred, and then 1 mL of distilled water was added and stirred to decompose acetic anhydride. In order to complete the decomposition and heat again in the bath for 10 minutes, it was left to cool. (3) The condenser was washed with 5 mL of ethanol and taken out. Next, 50 mL of pyridine was added as a solvent and stirred. (4) Add 25 mL of 0.5 mol/L potassium hydroxide ethanol solution using a full pipette. (5) Potentiometric titration was carried out by a 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve was taken as the end point. (6) In the blank test, the above (1) to (5) were carried out without placing a sample. 3. Calculation The hydroxyl value was calculated by the following formula. Hydroxyl value (mgKOH/g) = [(B-C) × f × 28.05] / S + D Here, B: amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (mL), C: sample The amount of 0.5 mol/L potassium hydroxide ethanol solution used (mL), f: 0.5 mol/L potassium hydroxide ethanol solution factor, S: sample weight (g), D: acid value, 28.05: hydrogen The molecular weight of potassium oxide is 1/2 of 56.11. As the high hydroxyl value resin, those having a specific value or more among the various tackifying resins described above can be used. The high-hydroxyl resin may be used alone or in combination of two or more. For example, as the high hydroxyl value resin, a phenol-based tackifying resin having a hydroxyl value of 30 mgKOH/g or more can be preferably used. In a preferred embodiment, as the tackifying resin, at least a nonylphenol resin having a hydroxyl value of 30 mgKOH/g or more is used. The indophenol resin is preferably controlled by arbitrarily controlling the hydroxyl value by the copolymerization ratio of the phenol. The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. The hydroxyl value of the high hydroxyl value resin is usually suitably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, more preferably about 160 mgKOH/g or less, from the viewpoint of compatibility with the base polymer. More preferably, it is about 140 mgKOH/g or less. The technique disclosed herein can be preferably carried out by a state in which the tackifying resin contains a high hydroxyl value resin having a hydroxyl value of 30 to 160 mgKOH/g, such as a phenol-based tackifying resin, preferably an indophenol resin. Although not particularly limited, in the case of using a high hydroxyl value resin, the proportion of the high hydroxyl value resin (for example, indophenol resin) in the bulk of the tackifier resin contained in the adhesive layer can be set, for example, to approximately 25 The weight% or more is preferably approximately 30% by weight or more, more preferably approximately 50% by weight or more (for example, approximately 80% by weight or more, and typically approximately 90% by weight or more). Further, substantially all of the tackifier resin (for example, approximately 95 to 100% by weight, and further preferably approximately 99 to 100% by weight) may be a high hydroxyl value resin. As the high hydroxyl value resin, a resin R1 having a hydroxyl value of less than 70 mgKOH/g and a resin R2 having a hydroxyl value of 70 mgKOH/g or more may be used in combination. Although it is not specifically limited, the content of the resin R2 can be about 0.2 to 5 times the content of the resin R1, and it is usually about 0.3 to 3 times as appropriate. The content of the resin R2 may be about 1 to 3 times the content of the resin R1. (Other Additives) The adhesive composition may contain, in addition to the above components, a leveling agent, a crosslinking assistant, a plasticizer, a softener, an antistatic agent, an anti-aging agent, an ultraviolet absorber, and an antioxidant. Various additives generally in the field of adhesive compositions such as light stabilizers. Regarding such various additives, those previously known can be used according to the conventional practice, and since the features of the present invention are not particularly specified, detailed descriptions are omitted. The adhesive layer (layer comprising an adhesive) disclosed herein may be formed from an aqueous adhesive composition, a solvent-based adhesive composition, a hot-melt adhesive composition, and an active energy ray-curable adhesive composition. Adhesive layer. The water-based adhesive composition is an adhesive composition in the form of an adhesive (adhesive layer-forming component) in a solvent (aqueous solvent) containing water as a main component, and is typically referred to as a water-dispersed type. An adhesive composition (a composition in which at least a part of an adhesive is dispersed in water) or the like. Moreover, the solvent-type adhesive composition means an adhesive composition in the form of an adhesive in an organic solvent. The technique disclosed herein can be preferably carried out by including an adhesive layer formed of a solvent-based adhesive composition from the viewpoint of adhesion characteristics and the like. The adhesive layer disclosed herein can be formed by previously known methods. For example, a method may be employed in which an adhesive composition is applied to a surface having a peelable surface (peeling surface) or a non-releasable surface and dried to form an adhesive layer. In the adhesive sheet having the structure of the base film, for example, a method of directly applying (typically coating) the adhesive composition onto the base film and drying it, thereby forming an adhesive layer (direct method) law). Further, the adhesive composition may be applied to a surface having a peeling property (release surface) and dried to form an adhesive layer on the surface, and the adhesive layer may be transferred onto the substrate film. Method (transfer method). From the viewpoint of productivity, a transfer method is preferred. As the peeling surface, the surface of the release liner or the back surface of the base film which has been subjected to the release treatment can be used. Further, the adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may be, for example, an adhesive layer formed in a regular or random pattern such as a dot shape or a striped shape. The application of the adhesive composition can be carried out, for example, by a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the adhesive composition may be applied by an impregnation or a curtain coating method or the like. The drying of the adhesive composition is preferably carried out under heating from the viewpoint of promoting the crosslinking reaction and improving the production efficiency. The drying temperature can be, for example, about 40 to 150 ° C, and usually about 60 to 130 ° C. After the adhesive composition is dried, the composition may be aged for the purpose of adjusting the migration of the components in the adhesive layer, the progress of the crosslinking reaction, and the relaxation of the strain which may be present in the substrate film or the adhesive layer. The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer is usually suitably about 100 μm or less, preferably about 70 μm or less, more preferably about 50 μm or less, and still more preferably about 30 μm or less, from the viewpoint of avoiding excessive thickening of the adhesive sheet. . In one preferred embodiment, the thickness of the adhesive layer may be approximately 28 μm or less, or may be approximately 25 μm or less (for example, less than 25 μm), or may be approximately 20 μm or less. In general, when the thickness of the adhesive layer is small, the adhesion to the adherend is lowered, and the oil from the interface with the adherend tends to be easily infiltrated. Therefore, it is of particular interest to apply the techniques disclosed herein to prevent oil penetration from the above interface. It may also be an adhesive sheet having an adhesive layer of this thickness on one or both sides of the substrate film. The lower limit of the thickness of the adhesive layer is not particularly limited, and is preferably about 4 μm or more, preferably about 6 μm or more, and more preferably about 10 μm or more from the viewpoint of adhesion to the adherend. For example, approximately 15 μm or more). It may also be an adhesive sheet having an adhesive layer of this thickness on one or both sides of the substrate film. <Base film> In the adhesive sheet containing the substrate film, as the base film, a resin film as a base film can be preferably used. The above-mentioned base film is typically a member that can independently maintain a shape (non-dependent). The substrate film in the techniques disclosed herein can be substantially constructed from such a base film. Alternatively, the base film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an undercoat layer, an antistatic layer, a colored layer, and the like provided on the surface of the base film. The resin film is a film containing a resin material as a main component (containing more than 50% by weight of the component in the resin film). Examples of the resin film include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyethylene terephthalate (PET) and polyterephthalic acid. Polyester resin film such as butadiene diester (PBT) or polyethylene naphthalate (PEN); vinyl chloride resin film; vinyl acetate resin film; polyimine resin film; polyamine resin Membrane; fluororesin film; serfen or the like. The resin film may be a rubber film such as a natural rubber film or a butyl rubber film. Among them, from the viewpoint of handling property and workability, a polyester film is preferable, and a PET film is particularly preferable. Further, in the present specification, the "resin film" is typically a non-porous sheet which is distinguished from a so-called non-woven fabric or woven fabric (in other words, a concept other than non-woven fabric or woven fabric). ). In the above resin film (for example, PET film), a filler (inorganic filler, organic filler, etc.), a coloring agent, a dispersing agent (surfactant, etc.), an anti-aging agent, an antioxidant, and an ultraviolet absorber may be blended as needed. , antistatic agents, lubricants, plasticizers and other additives. The blending ratio of the various additives is generally about 30% by weight (e.g., substantially less than 20% by weight, typically less than about 10% by weight). The above resin film may have a single layer structure or a multilayer structure having two layers, three layers or more. The resin film is preferably a single layer structure from the viewpoint of shape stability. In the case of a multilayer structure, it is preferred that at least one layer (preferably all layers) be a layer having a continuous structure of the above-mentioned resin (for example, a polyester resin). The method for producing the resin film is not particularly limited as long as it is suitably used in a conventionally known method. For example, a conventionally known general film forming method such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be suitably employed. In the adhesive sheet containing the substrate film, the thickness of the base film is not particularly limited. The thickness of the base film can be, for example, approximately 200 μm or less, preferably approximately 150 μm or less, and more preferably approximately 100 μm or less from the viewpoint of avoiding excessive thickness of the adhesive sheet. The thickness of the base film may be approximately 70 μm or less, or approximately 50 μm or less, or approximately 30 μm or less (for example, approximately 25 μm or less), depending on the purpose of use or the use of the adhesive sheet. In one aspect, the thickness of the base film may be approximately 20 μm or less, may be approximately 15 μm or less, or may be approximately 10 μm or less (for example, approximately 5 μm or less). By making the thickness of the base film small, the thickness of the adhesive layer can be made larger even if the total thickness of the adhesive sheets is the same. This situation can be advantageous from the viewpoint of improving the adhesion to the substrate. The lower limit of the thickness of the base film is not particularly limited. The thickness of the base film is usually approximately 0.5 μm or more (for example, 1 μm or more) from the viewpoint of handleability (handleability) or workability of the adhesive sheet, and is preferably approximately 2 μm or more, for example, approximately 4 μm or more. In one aspect, the thickness of the base film may be approximately 6 μm or more, or may be approximately 8 μm or more, or may be approximately 10 μm or more (for example, more than 10 μm). The surface of the base film may be subjected to a previously known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer. Such a surface treatment may be a treatment for improving the adhesion between the substrate film and the adhesive layer, in other words, the adhesion of the adhesive layer to the substrate film. <Release liner> In the technique disclosed herein, a release liner can be used in the formation of an adhesive layer, the production of an adhesive sheet, the storage, distribution, shape processing, and the like of the adhesive sheet before use. The release liner is not particularly limited, and for example, it can be used as a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or a fluorine-containing polymer (such as polytetrafluoroethylene) or a poly A release liner of a low-adhesive material of an olefin resin (such as polyethylene or polypropylene). The release treatment layer may be formed by, for example, surface-treating the backing substrate by a release treatment agent such as polyfluorene-based, long-chain alkyl, fluorine or molybdenum sulfide. <Adhesive Sheet> The total thickness of the adhesive sheet (including the adhesive layer including the base film and including the release liner in the configuration of the base film) is not particularly limited. The total thickness of the adhesive sheet can be, for example, approximately 500 μm or less, and is generally preferably 350 μm or less, preferably approximately 250 μm or less (for example, approximately 200 μm or less) from the viewpoint of thinning of the portable device. . The technique disclosed herein may be by an adhesive sheet having a total thickness of approximately 150 μm or less (more preferably approximately 100 μm or less, and even more preferably approximately less than 60 μm, for example, approximately 50 μm or less) (typically double-sided The form of the adhesive sheet is preferably carried out. The lower limit of the thickness of the adhesive sheet is not particularly limited, but is usually preferably about 10 μm or more, preferably about 20 μm or more, and more preferably about 30 μm or more. The adhesive force of the adhesive sheet disclosed herein is not particularly limited. Preferably, the 180 degree peel strength of the adhesive sheet is approximately 17 N/25 mm or more. Since the adhesive sheet exhibiting such adhesiveness has high adhesion to the adherend, it can be excellent in preventing oil penetration. More preferably, the 180-degree peel strength is an adhesive sheet having a peel strength of approximately 17.5 N/25 mm or more (more preferably approximately 18 N/25 mm or more, for example, approximately 18.5 N/25 mm or more). The upper limit of the 180-degree peel strength is not particularly limited from the viewpoint of the higher the adhesion of the adherend, and is generally suitably 80 N/25 mm or less (typically approximately 70 N/25 mm). Hereinafter, for example, approximately 50 N/25 mm or less). Here, the 180-degree peel strength refers to a 180-degree peel strength (180-degree peeling adhesion force) to a stainless steel sheet. The 180 degree peel strength can be measured as described below. Specifically, for the measurement sample in which the adhesive sheet is cut into a size of 25 mm in width and 100 mm in length, the measurement sample is taken by rotating the roller of 2 kg once in a 23 ° C, 50% RH environment. The adhesive surface was crimped onto the surface of a stainless steel plate (SUS304BA plate). After leaving it in the same environment for 30 minutes, the peel strength (N/25) was measured under the conditions of a tensile speed of 300 mm/min and a peeling angle of 180 degrees using a universal tensile compression tester in accordance with JIS Z0237:2000. Mm). As the universal tensile compression tester, for example, a "tensile compression tester, TG-1kN" manufactured by Minebea Co., Ltd. can be used. The same measurement method is also employed in the examples described later. <Use> The adhesive sheet disclosed herein has high retention properties and exhibits good oil resistance (oil penetration resistance), that is, self-adhesive layer and adherend in addition to oil absorption of the adhesive layer itself. The oil penetration at the interface is also suppressed. With such a feature being utilized, the above-mentioned adhesive sheet can be preferably utilized for a fixing member in various portable devices (portable machines). For example, it is suitable for the fixed use of components in mobile electronic devices. Non-limiting examples of the above-mentioned mobile electronic devices include: attached to a mobile phone, a smart phone, a tablet computer, a notebook computer, and various wearable devices (for example, a wrist worn type worn on a wrist like a watch, borrowed A module type that is worn on one part of the body by a jig or a strip, and includes a goggle type of a glasses type (monocular or double-eye type, also including a helmet type), and is attached to a shirt, a sock, a hat, etc., for example, in the form of an attachment. On the clothes type, such as earphones mounted on the ear, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), computers (calculators, etc.) , portable game consoles, electronic dictionaries, electronic organizers, e-books, vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable data Machine and so on. Non-limiting examples of portable devices other than mobile electronic devices include: mechanical watches or pocket watches, flashlights, hand mirrors, wallets, and the like. In addition, in the present specification, the term "carrying" is not sufficient if it can be simply carried, but refers to the portability of a person (standard adult) that can be transported relatively easily. The adhesive sheets (typically double-sided adhesive sheets) disclosed herein can be utilized for the fixation of the members constituting the portable device by the form of the joined materials processed into various shapes. As a preferred use, the use of a member constituting a mobile electronic device can be cited. Among them, it can be preferably used for a mobile electronic device having a liquid crystal display device. For example, it is suitable for use in such a mobile electronic device in which a display portion (which may be a display portion of a liquid crystal display device) or a display portion protection member is bonded to a casing. A preferred embodiment of such a bonding material is a form having a narrow width of 4.0 mm or less (for example, 2.0 mm or less, typically less than 2.0 mm). Since the adhesive sheet disclosed herein is excellent in cohesive strength other than oil resistance, even if it is used in the form of a joint material including a shape of such a narrow portion (for example, a frame shape), the member can be satisfactorily fixed. In one aspect, the width of the narrow portion may be 1.5 mm or less, may be 1.0 mm or less, or may be about 0.5 mm or less. The lower limit of the width of the narrow portion is not particularly limited, and is usually suitably 0.1 mm or more (typically 0.2 mm or more) from the viewpoint of workability of the adhesive sheet. The narrow portion is typically linear. Here, the linear shape includes a circular shape, a curved line shape, a polygonal line shape (for example, an L shape), and the like, and includes a ring shape such as a frame shape or a circular shape, or a concept of a composite or intermediate shape. The above-mentioned ring shape is not limited to the one formed by a curved line, and includes, for example, a shape which is formed along a circumference of a quadrilateral (frame shape) or a shape which is partially or entirely formed along a circumference of a fan shape. concept. The length of the narrow portion is not particularly limited. For example, in the form in which the length of the narrow portion is 10 mm or more (typically 20 mm or more, for example, 30 mm or more), the effect of applying the technique disclosed herein can be suitably exerted. The following items are included in the matters disclosed in the present specification. (1) an adhesive sheet which is used for a fixing member in a portable device, and which comprises a substrate film and an adhesive layer disposed on at least one surface of the substrate film, the adhesive layer The adhesive composition is formed using an adhesive composition containing an acrylic polymer as a base polymer, a tackifier resin, and a crosslinking agent, and the monomer component constituting the acrylic polymer contains more than about 50% by weight. % (meth)acrylic acid C _1-6 The alkyl ester, the content of the tackifier resin is more than 10 parts by weight (for example, more than about 10 parts by weight and not more than 55 parts by weight) based on 100 parts by weight of the acrylic polymer, and the crosslinking agent contains epoxy. A crosslinking agent and an isocyanate crosslinking agent. (2) The adhesive sheet according to (1) above, wherein the tackifying resin comprises a phenol-based tackifying resin. (3) The adhesive sheet according to the above (2), wherein the content of the phenol-based tackifying resin is substantially more than 10 parts by weight based on 100 parts by weight of the acrylic polymer. (4) The adhesive sheet according to any one of (1) to (3) above wherein the tackifying resin comprises a tackifying resin having a hydroxyl value of approximately 30 mgKOH/g or more. (5) The adhesive sheet according to any one of the above (1) to (4) wherein the monomer component contains substantially 0.5% by weight to about 10% by weight of the carboxyl group-containing monomer. (6) The adhesive sheet according to any one of the above (1), wherein the content of the epoxy-based crosslinking agent is substantially less than 0.05 part by weight based on 100 parts by weight of the acrylic polymer. (7) The adhesive sheet according to any one of the above (1), wherein the content of the epoxy-based crosslinking agent is substantially 1/100 or less of the content of the isocyanate-based crosslinking agent. (8) The adhesive sheet according to any one of the above (1), wherein the thickness of the adhesive layer is substantially 25 μm or less. (9) The adhesive sheet according to any one of the above (1) to (8) wherein the 180-degree peel strength is approximately 17 N/25 mm or more. (10) The adhesive sheet according to any one of the above (1) to (9), which is in the form of a double-sided adhesive sheet having the above-mentioned adhesive layer on one surface and the other surface of the base film Composition. (11) The adhesive sheet according to any one of (1) to (10) above, wherein the above (meth)acrylic acid C _1-6 About 80% by weight or more (for example, approximately 95% by weight or more) of the alkyl ester is an alkyl acrylate having a linear alkyl group having 3 to 6 carbon atoms at the ester terminal. (12) The adhesive sheet according to any one of the above (1), wherein the monomer component contains more than about 50% by weight (preferably 80% by weight or more) of butyl acrylate. (13) The adhesive sheet according to any one of (1) to (12) above, wherein (meth)acrylic acid C among the above monomer components _7-18 The content of the alkyl ester is about 0 to 10% by weight (for example, about 0 to 5% by weight). The adhesive sheet of any one of the above-mentioned (1) to (13), wherein the adhesive layer contains an indophenol resin of approximately 15 parts by weight or more based on 100 parts by weight of the acrylic polymer. The adhesive sheet according to any one of the above-mentioned (1), wherein the adhesive layer contains substantially 15 parts by weight or more of a hydroxyl value of about 30 mgKOH with respect to 100 parts by weight of the acrylic polymer. a tackifying resin of /g or more (for example, approximately 50 mgKOH/g or more). (16) The adhesive sheet according to any one of (1) to (15) wherein the base film is a PET film having a single layer structure. (17) The adhesive sheet according to any one of the above (1), wherein the adhesive sheet has a narrow width, and the width of the narrow portion is substantially 0.2 mm or more and substantially less than 2.0 mm. (18) An adhesive sheet which is used for a fixing member in a portable device, and which is constructed in the form of a double-sided adhesive sheet, the double-sided adhesive sheet comprising a substrate film, and disposed thereon The adhesive layer on one surface and the other surface of the base film, the thickness of the adhesive layer is approximately 10 μm or more and approximately 25 μm or less, and the total thickness of the double-sided adhesive sheet is approximately 30 μm or more and substantially no Up to 60 μm, the base film is a PET film, and the adhesive layer is formed using an adhesive composition comprising an acrylic polymer as a base polymer, a phenol resin as a tackifying resin, And a crosslinking agent, the monomer component constituting the above acrylic polymer contains more than 80% by weight of butyl acrylate, and (meth)acrylic acid C _7-18 The content of the alkyl ester is about 0 to 5% by weight, the monomer component contains about 3 to 8% by weight of the carboxyl group-containing monomer, and the content of the phenol resin is 15 parts by weight based on 100 parts by weight of the acrylic polymer. ～45 parts by weight, the crosslinking agent contains an epoxy crosslinking agent and an isocyanate crosslinking agent, and the content of the epoxy crosslinking agent is substantially less than 0.05 by weight based on 100 parts by weight of the acrylic polymer. The content of the isocyanate crosslinking agent is substantially less than 4 parts by weight based on 100 parts by weight of the acrylic polymer, and the content of the epoxy crosslinking agent is approximately the content of the isocyanate crosslinking agent. 1/100 or less. (19) A portable device comprising the member to be fixed by using the adhesive sheet according to any one of the above (1) to (18). (20) The portable device of (19) above, wherein the portable device is a wearable device (for example, a wrist-worn wearable device). [Examples] Hereinafter, some examples of the present invention are described, but the present invention is not limited to the examples shown in the examples. In the following description, "parts" and "%" are based on weight unless otherwise specified. <Preparation of Adhesive Composition> [Example 1] In a reaction vessel having a stirrer, a thermometer, a nitrogen introduction tube, a reflux condenser, and a dropping funnel, BA 95 parts and AA 5 parts as a monomer component were charged as a polymerization. 233 parts of ethyl acetate of the solvent was stirred for 2 hours while introducing nitrogen gas. After the oxygen in the polymerization system was removed as described above, 0.2 part of 2,2'-azobisisobutyronitrile was added as a polymerization initiator, and solution polymerization was carried out at 60 ° C for 8 hours to obtain an acrylic polymer. Solution. The Mw of the acrylic polymer is about 70×10 ⁴ . In the above acrylic polymer solution, a phenolic resin (trade name "YS POLYSTAR T-115", which has a softening point of about 115, is added as a tackifying resin to 100 parts of the acrylic polymer contained in the solution. °C, a hydroxyl value of 30 to 60 mgKOH/g, manufactured by Anhara Chemical Co., Ltd.; hereinafter referred to as "tackifying resin A") 20 parts, an isocyanate crosslinking agent as a crosslinking agent (trade name "Coronate L", trishydroxyl a 75% ethyl acetate solution of a methyl propane/toluene diisocyanate trimer adduct, manufactured by Japan Polyurethane Industry Co., Ltd.; hereinafter referred to as "isocyanate crosslinking agent A"), 2 parts, and an epoxy crosslinking agent (product) "TETRAD-C", 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, manufactured by Mitsubishi Gas Chemical Co., Ltd.; hereinafter referred to as "epoxy crosslinker B") 0.01 The mixture was stirred and mixed to prepare an adhesive composition. [Examples 2 to 10] In the preparation of the adhesive composition of Example 1, as shown in Tables 1 and 2, the types and amounts of the tackifying resins used, and the types of the crosslinking agents used and Usage amount. On the other hand, in the same manner as in Example 1, the adhesive compositions of Examples 2 to 10 were prepared. Here, the tackifying resin B in Tables 1 and 2 is a trade name "YS POLYSTAR S-145" manufactured by Anwara Chemical Co., Ltd. (indophenol resin, softening point is about 145 ° C, and hydroxyl value is 70 to 110 mg KOH / g) The tackifier resin C is a trade name "TAMANOL 803L" manufactured by Arakawa Chemical Industries Co., Ltd. (indophenol resin, softening point is about 145 to 160 ° C, and hydroxyl value is 1 to 20 mgKOH/g). In addition, "(part)" in Tables 1 and 2 shows the amount used with respect to 100 parts of an acrylic polymer. [Examples 11, 12] In a reaction vessel having a stirrer, a thermometer, a nitrogen introduction tube, a reflux condenser, and a dropping funnel, 90 parts of 2-ethylhexyl acrylate (2EHA) as a monomer component and AA 10 were charged. In 199 parts of ethyl acetate as a polymerization solvent, the mixture was stirred for 2 hours while introducing nitrogen gas. After the oxygen in the system was removed as described above, 0.2 part of benzoyl peroxide as a polymerization initiator was added, and solution polymerization was carried out at 60 ° C for 6 hours to obtain a solution of an acrylic polymer. The Mw of the acrylic polymer is about 120×10 ⁴ . In the above acrylic polymer solution, the type and amount of the tackifying resin and the crosslinking agent shown in Table 2 were used for 100 parts of the acrylic polymer contained in the solution, and the examples 11 and 12 were prepared, respectively. Adhesive composition. [Examples 13 to 15] In the preparation of the adhesive composition of Example 1, only one of the isocyanate crosslinking agent and the epoxy crosslinking agent was used in the amounts shown in Table 2. On the other hand, in the same manner as in Example 1, the adhesive compositions of Examples 13 to 15 were prepared. <Production of Adhesive Sheets> [Examples 1 to 15] As a release liner, two release films (one of DIAFOIL MRF) having a thickness of 38 μm and a thickness of 38 μm were prepared as a release surface of a release-treated release surface. Made by polyester company). Each of the adhesive compositions of the examples was applied to the release faces of the release liners, and dried at 100 ° C for 2 minutes to form an adhesive layer having a thickness of 19 μm. The adhesive layers formed on the two release liners were bonded to the first surface and the second surface of a transparent base film having a thickness of 12 μm, respectively, to prepare a double-sided adhesive sheet having a total thickness of 50 μm. The release liner is directly left on the adhesive layer for protection of the surface (adhesive surface) of the adhesive layer. As the base film, a PET film (resin film) manufactured by Toray Industries, Inc., and a trade name "Lumirror" were used. [Example 16] The adhesive composition of Example 4 was applied to the release surface of the polyester release film (trade name "DIAFOIL MRF", manufactured by Mitsubishi Polyester Co., Ltd.) having a thickness of 38 μm, and was carried out at 100 ° C. It was dried in minutes to form an adhesive layer having a thickness of 25 μm. A release surface of a polyester release film (trade name "DIAFOIL MRF", thickness 25 μm, manufactured by Mitsubishi Polyester Co., Ltd.) having a thickness of 25 μm was bonded to the pressure-sensitive adhesive layer. As described above, a substrate-free double-sided adhesive sheet having a thickness of 25 μm protected by the above two polyester release films was obtained. After the obtained double-sided adhesive sheet was aged in an environment of 23 ° C and 50% RH for one day, the double-sided adhesive sheet was subjected to the following evaluation test. <Evaluation Test> [180-degree peel strength] Polyethylene terephthalate (PET) having a thickness of 50 μm was attached to one of the adhesive faces of the double-sided adhesive sheet in a measurement environment of 23 ° C and 50% RH. The film was subjected to a substrate and cut into a size of 25 mm in width and 100 mm in length to prepare a measurement sample. For the other adhesive side of the measurement sample, the 180-degree peel strength (N/25 mm) was measured by the above method. [Retention] The holding force test was carried out in accordance with JIS Z0237 (2004). That is, a PET film having a thickness of 50 μm was attached to one of the adhesive faces of the double-sided adhesive sheet in an environment of 23 ° C and 50% RH, and the substrate was cut into a width of 10 mm to prepare a measurement sample. The other adhesive face of the measurement sample was attached to the electric board as the adherend with a backing area of 10 mm in width and 20 mm in length. The measurement sample attached to the adherend as described above was allowed to stand under an environment of 80 ° C for 30 minutes, and then a load of 1 kg was applied to the free end of the measurement sample. The measurement sample was placed in an environment of 80 ° C for 1 hour in a state where the above load was applied, and the distance (mm) from the initial attachment position was measured. [Oil penetration distance] A film of 50 μm thick PET film was attached to one of the adhesive faces of the double-sided adhesive sheet at 23 ° C and 50% RH, and cut into a square of 30 mm square. sample. The other adhesive surface of the measurement sample was attached to a stainless steel plate (SUS304BA plate) and left for 30 minutes, and then uniformly coated from the entire back surface of the measurement sample (the surface of the PET film) to the stainless steel plate around the measurement sample. The oleic acid was kept at 65 ° C and 95% RH for 72 hours. Thereafter, oleic acid was wiped, and the distance (oil penetration distance) at which the oleic acid infiltrates from the outer edge of the measurement sample to the inside of the measurement sample is measured. Specifically, the four sides of the outer edge of the measurement sample were measured for the distance in which the oleic acid penetrated to the innermost portion, and the average value of the particles was calculated. [Crushing property] The double-sided adhesive sheets of Examples 1 to 15 were cut into a size of 100 mm in length and 20 mm in width, and an adhesive surface was attached to a stainless steel plate to be fixed. The other adhesive surface was exposed, and the tester gently wiped the adhesive surface with one finger in one direction. After the operation was repeated 30 times in a row, the adhesive layer was peeled off from the base film, and the adhesive layer was not found to be E (Excellent), and the first 70% by area or more of the adhesive layer was used. The case of remaining is evaluated as G (Good), and the case where the adhesive layer of the first 50% by area or more and less than 70% by area remains is evaluated as A (Acceptable), and the remaining on the substrate film The case where the adhesive layer did not reach the initial 50 area% was evaluated as P (Poor). The results obtained are shown in Tables 1 and 2 together with the schematic configurations of the adhesive sheets of the respective examples. [Table 1] [Table 2] As shown in Tables 1 and 2, it contains more than 50% by weight of (meth)acrylic acid C. _1-6 The acrylic polymer of the alkyl ester is used as the base polymer, and the adhesive sheets of Examples 1 to 8 and Example 16 in which the epoxy-based crosslinking agent and the isocyanate-based crosslinking agent are used in combination have an oil-infiltration distance of 5 mm or less, and Shows good oil penetration resistance. In addition, it was confirmed that the offset of each of the adhesive sheets was 2.5 mm or less in the evaluation of the holding power, and excellent cohesive force (holding property) was exhibited. The adhesive sheets of Examples 1 to 7 obtained particularly good results. On the other hand, in Examples 9 and 10 in which the amount of the tackifying resin used is 10 parts or less based on 100 parts of the acrylic polymer, and the main monomer of the acrylic polymer is acrylic acid C. ₈ Examples 11 and 12 of the alkyl esters have a long oil penetration distance and a low oil penetration resistance. Further, Examples 13 and 14 in which the isocyanate crosslinking agent was used alone had a low holding power. Example 15 in which an epoxy-based crosslinking agent is used alone has a long oil penetration distance and a low grip. The specific examples of the present invention have been described in detail above, but these are merely examples, and the scope of the patent application is not limited. The technology described in the scope of the patent application also includes various changes and modifications to the specific examples exemplified above.

1, 2‧‧‧Adhesive sheets
10‧‧‧Base film
10A‧‧‧1st
10B‧‧‧2nd
21‧‧‧1st adhesive layer
21A‧‧‧1st adhesive surface
22‧‧‧2nd adhesive layer
22A‧‧‧2nd adhesive surface
31, 32‧‧‧ peeling liner

Fig. 1 is a cross-sectional view schematically showing an example of the configuration of an adhesive sheet. Fig. 2 is a cross-sectional view schematically showing another configuration example of the adhesive sheet.

1‧‧‧Adhesive sheet

10‧‧‧Base film

10A‧‧‧1st

10B‧‧‧2nd

21‧‧‧1st adhesive layer

21A‧‧‧1st adhesive surface

22‧‧‧2nd adhesive layer

22A‧‧‧2nd adhesive surface

31, 32‧‧‧ peeling liner

Claims (11)

An adhesive sheet comprising a pressure-sensitive adhesive layer formed by using an adhesive composition containing an acrylic polymer as a base polymer, which is used for a fixing member in a portable device, a tackifying resin and a crosslinking agent, wherein the monomer component constituting the acrylic polymer contains more than 50% by weight of an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at the ester terminal, The content of the tackifier resin is more than 10 parts by weight based on 100 parts by weight of the acrylic polymer, and the crosslinking agent contains an epoxy crosslinking agent and an isocyanate crosslinking agent. The adhesive sheet of claim 1, wherein the tackifying resin comprises a phenol-based tackifying resin. The adhesive sheet according to claim 2, wherein the content of the phenol-based tackifying resin is more than 10 parts by weight based on 100 parts by weight of the acrylic polymer. The adhesive sheet according to any one of claims 1 to 3, wherein the tackifying resin comprises a tackifying resin having a hydroxyl value of 30 mgKOH/g or more. The adhesive sheet according to any one of claims 1 to 4, wherein the monomer component comprises from 0.5% by weight to 10% by weight of the carboxyl group-containing monomer. The adhesive sheet according to any one of claims 1 to 5, wherein the content of the epoxy-based crosslinking agent is less than 0.05 part by weight based on 100 parts by weight of the acrylic polymer. The adhesive sheet according to any one of claims 1 to 6, wherein the content of the epoxy crosslinking agent is 1/100 or less of the content of the isocyanate crosslinking agent. The adhesive sheet according to any one of claims 1 to 7, wherein the thickness of the adhesive layer is 30 μm or less. The adhesive sheet according to any one of claims 1 to 8, wherein the 180-degree peel strength is 17 N/25 mm or more. The adhesive sheet according to any one of claims 1 to 9, which further comprises a substrate film supporting the above adhesive layer. The adhesive sheet according to any one of claims 1 to 10, which is in the form of a double-sided adhesive sheet having the above-mentioned adhesive layer on one surface and the other surface of the base film.