TW201716323A - Pressure-sensitive adhesive sheet for graphite sheet - Google Patents

Abstract

Provided is a pressure-sensitive adhesive sheet for graphite sheets which, even when thin, has excellent stability of adhesion to graphite sheets which are adherends. The present invention provides a single-sided pressure-sensitive adhesive sheet to be superposed on a graphite sheet. The pressure-sensitive adhesive sheet has a thickness of 12 [mu]m or less and comprises a substrate film containing a black colorant and a pressure-sensitive adhesive layer disposed on one surface of the substrate film.

Description

Adhesive sheet for graphite sheet

The present invention relates to an adhesive sheet for a graphite sheet. The present application claims priority to Japanese Patent Application No. 2015-176141, filed on Sep

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 way, the adhesive is widely used for the purpose of joining, fixing, and protecting members in a portable electronic device such as a mobile phone, for example, in the form of an adhesive sheet with a base material (Patent Documents 1 and 2). ). Further, for example, inside a portable electronic device, a heat sink such as a graphite sheet is attached for the purpose of allowing heat from a heat generating element such as a battery to escape. On the above-mentioned heat sink (typically, a graphite sheet), an adhesive sheet colored in black is attached for the purpose of protection or appearance of the sheet. The adhesive sheet for a heat sink is typically one in which an adhesive layer is disposed on one surface of a base film having a laminated structure of a resin film layer and a coloring layer. Patent Document 3 is cited as a document showing a prior art relating to an adhesive sheet attached to a graphite sheet. [Prior Art Document] [Patent Document 1] Japanese Patent Application Publication No. 2007-284551 [Patent Document 2] Japanese Patent Application Publication No. 2013-146903 (Patent Document 3) Japanese Patent Application Publication No. 2013-203965 Bulletin

[Problems to be Solved by the Invention] The adhesive sheet used in the heat sink as described above is preferably thin in thickness from the viewpoint of sufficiently exhibiting the heat dissipation effect of the heat sink. The thinning of the thickness of the adhesive sheet also requires the miniaturization or weight reduction of the article (such as a portable electronic device) in which it is used. However, it has been clarified that if the heat-shielding black-adhesive sheet is actually set to a thin thickness, peeling of the end portion of the graphite sheet or the like may occur, and the subsequent stability may be impaired. As a result of the investigation, it was found that the adhesive sheet for a heat sink of the prior type which is typical as described in Patent Document 3 has a different coefficient of thermal expansion between the resin film layer and the coloring layer constituting the base film, and therefore is derived from the heat sink. The heat of the surrounding area or the surrounding area causes the base film to be deformed (curled), and the load is applied to the adhesive surface due to the deformation, which causes one end peeling. Further, in consideration of this phenomenon, it is considered that in the thin base film, the ratio of the thickness of the colored layer to the entire base film is relatively large, and it is easy to express the thermal expansion coefficient of the resin film layer and the color layer. Different effects, so it is impossible to control the deformation by adhesion, and peeling occurs. As a background thereof, there is a fact that the adhesive layer must have a certain thickness due to the surface roughness of the graphite sheet used as the heat sink. However, in the adhesive sheet having a small thickness, the adhesion cannot be sufficiently ensured. The thickness of the agent layer. In other words, the above peeling can be said to be a problem unique to the case where the thickness of the adhesive sheet for a graphite sheet including the base film having the colored layer is reduced (particularly, the thickness of the base film is reduced). The present invention has been made in view of the above-described facts, and an object of the invention is to provide an adhesive sheet for a graphite sheet which is excellent in adhesion stability to a graphite sheet as a member to be bonded, even when it is set to a thin thickness. [Technical means for solving the problem] According to the present invention, there is provided a one-sided adhesive sheet laminated on a graphite sheet. The adhesive sheet includes a base film having a thickness of 12 μm or less and containing a black colorant, and an adhesive layer disposed on one surface of the base film. As described above, as the base film having a specific thickness or less, a base film containing a black colorant is used, whereby the black print layer previously provided is not required. Thereby, thermal deformation (curl) of the substrate film caused by the black printed layer can be prevented, and excellent adhesion stability can be achieved. Further, by removing the black printed layer, the thickness of the portion can be offset to the adhesive layer. Therefore, the adhesion to the graphite sheet is improved, and in this respect, the stability is also improved. In a preferred aspect of the technique disclosed herein, the total thickness of the adhesive sheet is 30 μm or less. By using an adhesive sheet having a small thickness, the heat dissipation property of the graphite sheet is sufficiently exhibited. Further, the subsequent stability obtained by the technique disclosed herein can be preferably achieved in an adhesive sheet having a relatively small thickness as described above. In a preferred aspect of the technique disclosed herein, the thickness of the adhesive layer is 40% or more of the total thickness of the adhesive sheet. By making the ratio of the thickness of the adhesive layer relatively large, even when the adhesive sheet is set to a thin thickness, it is possible to exhibit good adhesion to the graphite sheet. In a preferred aspect of the technique disclosed herein, the adhesive sheet exhibits a 180 degree peel strength of 2 N/20 mm or more. By having a specific peeling strength or more, the adhesive sheet can be adhered to the graphite sheet well and stably. In a preferred aspect of the adhesive sheet disclosed herein, the thickness of the adhesive layer is 1.2 μm or more. By setting the adhesive layer to a specific thickness or more, the adhesive sheet can exert good adhesion properties to the graphite sheet regardless of the surface roughness of the graphite sheet. In a preferred aspect of the adhesive sheet disclosed herein, the adhesive layer is an acrylic adhesive layer. By using an acrylic adhesive, an adhesive having a target adhesive property can be suitably designed. In a preferred aspect of the technique disclosed herein, the adhesive sheet has a vertical light transmittance of 15% or less. The adhesive sheet having the above characteristics exhibits good light blocking properties. In a preferred aspect of the technique disclosed herein, the brightness L ^* defined by the L ^* a ^* b ^* color system on the back side of the adhesive sheet is 40 or less. By applying the technique disclosed herein, the brightness of the back surface of the adhesive sheet can be set to the above range without providing a black printed layer. Further, the adhesive sheet having the above brightness can be preferably used in the use of a graphite sheet. In a preferred aspect of the adhesive sheet disclosed herein, the base film is a polyethylene terephthalate resin film containing the black colorant. The effect obtained by the technique disclosed herein can be preferably achieved by using a polyethylene terephthalate (PET) resin film as a substrate film. Further, since the PET-based resin film has moderate toughness, even when it is formed in a thin thickness, it has relatively good rationality or workability. The adhesive sheet disclosed herein exhibits excellent adhesion stability to the graphite sheet even when it is formed in a thin thickness. Therefore, when the thickness of the adhesive sheet is set to a specific value or less, excellent adhesive properties (typically, subsequent stability) can be maintained, and the heat dissipation property of the graphite sheet as the adherend can be sufficiently exhibited. Moreover, it can function in miniaturization or weight reduction of the product containing a graphite sheet. Specifically, it is suitable as an adhesive sheet for use in a portable electronic device such as a mobile phone or a smart phone. Therefore, the adhesive sheet provided by the present specification may be a laminate of graphite sheets disposed in a portable electronic machine.

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). <Composition of Adhesive Sheet> The adhesive sheet disclosed herein is a substrate-attached single-sided adhesive sheet in the form of an adhesive layer on one surface of a base film (support). Here, the concept of the adhesive sheet 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. The adhesive sheet disclosed herein may be, for example, a cross-sectional structure schematically shown in FIG. The adhesive sheet 1 shown in Fig. 1 includes a base film 10 and an adhesive layer 20 provided on one surface (non-releasable) 10A of the base film 10. The surface of the adhesive layer 20 adheres to the back surface 1A of the sheet 1. The other surface 10B of the base film 10 constitutes the back surface 1B of the adhesive sheet 1. The adhesive sheet 1 has a structure in which the adhesive layer 20 is protected by a release liner 30 which is a release surface on the side of the adhesive layer 20. <Base Film> The base film disclosed herein is a base film containing a black colorant, and is typically a resin film in which a black colorant is kneaded. Here, the base film in which a black colorant is kneaded refers to a substrate in which a black colorant is mixed in a main constituent material of a base film (a material which is most contained in a base film, typically a resin material). membrane. The black colorant is substantially contained in the base film in a dispersed state. The black colorant in the base film is not required to be completely uniformly dispersed, but the black colorant is preferably dispersed in a plurality of portions (for example, 10 or more) of the base film in the base film to have a transmittance of 15 % below. Excellent back stability is achieved by using the above-described base film containing a black colorant. Further, the base film containing the black colorant has a toughness in which the resin film is relatively thicker than the laminated structure base film having the same thickness as the base film and the resin film. Excellent in terms of reason. This improvement in handleability is particularly remarkable when the adhesive sheet is set to a thin thickness, which contributes to the stable performance of adhesion or subsequent stability. Further, the previous adhesive sheet on the back side of the colored layer (typically a black printed layer) has the following problem: when the sebum attached to the back surface is wiped with alcohol, the colored layer is also applied to the top coat layer (fingerprint layer, etc.) It is also removed, and this problem can be eliminated by using a substrate film containing a black colorant. The base film is typically a resin film containing a resin material as a main component (for example, a component containing more than 50% by weight in a base 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 the so-called non-woven fabric or woven fabric (in other words, the concept of non-woven fabric or woven fabric is excluded). . The base film contains a black colorant as described above. In other words, the substrate film is colored black by itself. Thereby, a good appearance of black can be imparted to the surface of the graphite sheet to be subjected to the object. Further, by containing a black coloring agent (typically a black pigment), workability (pressing workability, etc.) is also improved. As the black colorant contained in the base film, an organic or inorganic coloring agent (pigment, dye, or the like) can be used. Specific examples of the black colorant include carbon black, graphite, copper oxide, manganese dioxide, nigrosine, ruthenium black, titanium black, cyanine black, activated carbon, ferrite iron, black iron, chromium oxide, and oxidation. Iron, molybdenum disulfide, chromium complex, lanthanide colorant, and the like. Among them, carbon black is preferred. The black coloring agent may be used alone or in combination of two or more. Although not particularly limited, for example, carbon black having an average particle diameter of 10 nm to 500 nm (more preferably 10 nm to 120 nm) is preferably used. In addition, the "average particle diameter" in the present specification means a particle diameter of 50% in the particle size distribution measured by a particle size distribution measuring apparatus based on a laser scattering or diffraction method unless otherwise specified. (50% volume average particle size; the following is sometimes also abbreviated as D ₅₀ ). The blending amount of the black colorant in the base film is not particularly limited, and is preferably, for example, about 0.1 to 30% by weight, preferably 0.1 to 25% by weight, based on the coloring effect and mechanical properties (typically It is 0.1 to 20% by weight). When the inspection property of the graphite sheet is required to be adhered to the adhesive sheet, the blending amount of the black colorant in the base film may be 15% by weight or less, or may be 10% by weight or less (for example, 5% by weight or less, Typically, it is 3% by weight or less and further 2% by weight or less. In the base film, a filler (inorganic filler, organic filler, etc.), a dispersant (surfactant, etc.), an anti-aging agent, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, and the like may be blended as needed. Various additives such as plasticizers. The proportion of the various additives is usually in the range of less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight). The substrate film disclosed herein may have a single layer structure or a multilayer structure having two layers, three layers or more. The base 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, typically a resin containing a black colorant). The method for producing the base film (typically a resin film) is not particularly limited as long as it is suitable for 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. The thickness of the substrate film disclosed herein is 12 μm or less. From the viewpoint of heat dissipation efficiency of the graphite sheet functioning as a heat sink, it is preferable to limit the thickness of the base film in this manner. Further, in the use of such an adhesive sheet of a substrate film having a relatively small thickness, the subsequent stability of the technique disclosed herein is achieved. The thickness of the base film is preferably approximately 9 μm or less (for example, 7 μm or less, typically 5 μm or less). When the heat dissipation, miniaturization, and weight reduction are particularly emphasized, the thickness of the base film is more preferably 3 μm or less (for example, 2 μm or less, and typically 1.5 μm or less). The lower limit of the thickness of the base film is preferably about 0.5 μm or more (for example, 1 μm or more) from the viewpoints of handleability and workability. Further, a surface treatment layer such as a fingerprint-resistant layer (also referred to as a top coat layer depending on the arrangement portion) may be provided on the back surface of the base film. The above top coat layer preferably has a thickness of less than 2 μm from the viewpoint of adhesion stability. Further, the top coat layer is preferably not a colored layer (printed layer). The coloring function is achieved by a substrate film, so the adhesive sheets disclosed herein typically do not have a coloring layer other than the substrate film. The adhesive sheet disclosed herein may also have no such surface treatment layer. Further, the back surface of the base film may be subjected to a peeling treatment as needed. The release treatment can be carried out, for example, by a film-like form of a general polyfluorene-based, long-chain alkyl-based or fluorine-based release treatment agent in an amount of typically 0.01 μm to 1 μm (for example, 0.01 μm to 0.1 μm). deal with. By performing the peeling treatment, it is possible to obtain an effect of facilitating the rewinding of the wound body in which the adhesive sheet is wound into a roll shape. The side surface of the adhesive layer of the base film (the surface indicated by symbol 10A in Fig. 1) may be subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or primer coating. Previously known surface treatments such as cloth. Such a surface treatment can be a treatment for improving the adhesion between the base film and the adhesive layer, in other words, the adhesion of the adhesive layer to the base film. <Adhesive Layer> In the technique disclosed herein, the type of the adhesive constituting the adhesive layer is not particularly limited. The above-mentioned adhesive may be an acrylic polymer, a rubber-based polymer, a polyester-based polymer, a urethane-based polymer, a polyether-based polymer, or a polyoxymethylene-based polymer which is known in the field of an adhesive. One or two or more kinds of various rubbery polymers such as a polyamide polymer or a fluorine polymer are used as the base polymer. From the viewpoints of adhesion performance or cost, etc., an adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably used. Among them, an adhesive (acrylic adhesive) using an acrylic polymer as a base polymer is preferred. Hereinafter, an adhesive sheet having an adhesive layer containing an acrylic adhesive, that is, an acrylic adhesive layer will be mainly described, but it is not intended to limit the adhesive layer of the adhesive sheet disclosed herein to include an acrylic system. Adhesive. In addition, the "base polymer" of the adhesive means the main component of the rubbery polymer contained in the adhesive. The rubbery polymer refers to a polymer which exhibits rubber elasticity in a temperature region near room temperature. In the specification, the term "main component" means a component containing more than 50% by weight, unless otherwise specified. In addition, the "acrylic polymer" means a monomer unit containing a monomer derived from at least one (meth)acryl fluorenyl group in one molecule as a monomer unit constituting the 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. Typical examples of the acrylic polymer include an acrylic polymer in which the proportion of the acrylic monomer in all the monomer components of the acrylic polymer is more than 50% by weight. Moreover, the term "(meth)acryloyl) refers to the meaning of a propylene group and a methacryl group. Similarly, the term "(meth)acrylate" refers to the meaning of acrylate and methacrylate, and "(meth)acrylic" refers to the meaning of acryl and methacryl. As the acrylic polymer, for example, a polymer containing a (meth)acrylic acid alkyl ester as a main monomer and further containing a monomer raw material having a copolymerizable sub-monomer with the main monomer is preferable. Here, the main single system means a component which accounts for more than 50% by weight of the monomer composition in the above monomer raw material. As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used. CH ₂ =C(R ¹ )COOR ² (1) Here, R in the above formula (1) ¹ It is a hydrogen atom or a methyl group. Also, R ² It is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, the range of such a carbon number is sometimes expressed as "C" _1-20 "." From the viewpoint of the storage elastic modulus of the adhesive, etc., it is appropriate to use R ² For C _1-14 (eg C _2-10 Typically C _4-8 The alkyl (meth) acrylate of a chain alkyl group is used as a main monomer. From the viewpoint of self-adhesive properties, it is preferred to use R ¹ Is a hydrogen atom, R ² For C _4-8 Alkyl acrylate of a chain alkyl group (hereinafter also referred to as acrylic acid C) _4-8 The alkyl ester) is used as the main monomer. As R ² For C _1-20 Examples of the alkyl (meth)acrylate of the chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and isopropyl (meth)acrylate. Ester, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, (methyl) Hexyl acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, Isodecyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, (meth)acrylic acid Tridecyl ester, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, Octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and the like. These alkyl (meth)acrylates may be used alone or in combination of two or more. Preferred examples of the alkyl (meth)acrylate include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). The proportion of the alkyl (meth)acrylate in all the monomer components used for the synthesis of the acrylic polymer is preferably 70% by weight or more, more preferably 85% by weight or more, and still more preferably 90% by weight or more. . The upper limit of the ratio of the alkyl (meth)acrylate is not particularly limited, but is usually preferably 99.5% by weight or less (for example, 99% by weight or less). Alternatively, the acrylic polymer may be one obtained by substantially polymerizing only an alkyl (meth)acrylate. Also, in the use of acrylic acid C _4-8 When the alkyl ester is used as a monomer component, the acrylic acid C in the alkyl (meth)acrylate contained in the monomer component _4-8 The proportion of the alkyl ester is preferably 70% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more (typically 99 to 100% by weight). The technique disclosed herein can be preferably carried out by using 50% by weight or more (e.g., 60% by weight or more, typically 70% by weight or more) of all monomer components in the form of BA. In a preferred embodiment, all of the above monomer components may contain 2EHA in a smaller ratio than BA. In the acrylic polymer in the technique disclosed herein, a monomer other than the above (other monomer) may be copolymerized within a range that does not significantly impair the effects of the present invention. The other monomer may be used for the purpose of adjusting the glass transition temperature (Tg) of the acrylic polymer, adjusting the adhesion property (for example, peelability), and the like. 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 phosphate group-containing monomer, a cyano group-containing monomer, a vinyl ester, and an aromatic vinyl group. A compound or the like. 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. Of these, VAc is preferred. In addition, as a monomer which can introduce a functional group which can be a crosslinking point in an acrylic polymer, or can contribute to the improvement of an adhesive force, the monomer which has a hydroxyl group (OH group), and a carboxyl group is mentioned. Monomer, acid anhydride group-containing monomer, guanamine group-containing monomer, amine group-containing monomer, ruthenium group-containing monomer, epoxy group-containing monomer, (meth) propylene oxime 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 monomer having a carboxyl group as the other monomer. 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 the like. Fumaric acid, crotonic acid, methacrylic acid, and the like. Among them, AA and MAA are preferred. Other suitable examples include an acrylic polymer in which a monomer having a hydroxyl group is copolymerized as the other 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. Hydroxyalkyl (meth)acrylate such as 2-hydroxybutyl ester or 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; N-hydroxyethyl(meth)acrylamide . In particular, examples of the hydroxyl group-containing monomer include a linear hydroxyalkyl (meth)acrylate having an alkyl group of 2 to 4 carbon atoms. The above-mentioned "other monomers" may be used alone or in combination of two or more. The total content of the other monomers is preferably about 40% by weight or less (typically 0.001 to 40% by weight) of all the monomer components, more preferably about 30% by weight or less (typically 0.01 to 30% by weight). %, for example, 0.1 to 10% by weight). When a monomer having a carboxyl group is used as the above other monomer, the content thereof is suitably about 0.1 to 10% by weight (for example, 0.2 to 8% by weight, typically 0.5 to 5% by weight, based on all the monomer components). ). In the case where a monomer having a hydroxyl group is used as the above other monomer, it is suitably used in an amount of about 0.001 to 10% by weight (for example, 0.01 to 5% by weight, typically 0.02 to 2% by weight) based on the total of all monomer components. %). The copolymerization composition of the acrylic polymer is suitably designed such that the glass transition temperature (Tg) of the polymer is -15 ° C or lower (typically -70 ° C or higher and -15 ° C or lower). The Tg of the acrylic polymer is preferably -25 ° C or lower (for example, -60 ° C or higher and -25 ° C or lower), more preferably -40 ° C or lower (for example, -60 ° C or higher and -40 ° C or lower). The Tg of the acrylic polymer is preferably equal to or less than the above upper limit value from the viewpoint of adhesion workability of the adhesive sheet. 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). Here, the Tg of the acrylic polymer means the Tg obtained by the Fox formula based on the composition of the monomer component for synthesizing the polymer. The Fox formula 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 of the homopolymer used for the calculation 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 other than the above, use the “Polymer Handbook” (3rd edition, John) The values stated by John Wiley & Sons, Inc., 1989. Regarding the monomers in which a plurality of values are described in the literature, the highest value is employed. When the glass transition temperature of the homopolymer is not described in the above document, 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. 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 is measured by the shear mode at a temperature rise rate of 5 ° C / min in a temperature range of -70 to 150 ° C, and the temperature corresponding to the peak top temperature of the shear loss elastic modulus G'' is (G ''The curve becomes the maximum temperature) as the Tg of the homopolymer. 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 used. 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 40 to 140 ° C). In a preferred embodiment, a polymerization temperature of substantially 75 ° C or less (more preferably about 65 ° C or less, for example, about 45 ° C to 65 ° C) may be employed. The solvent (polymerization solvent) used in the solution polymerization can be appropriately selected from previously known organic solvents. For example, any one of the following solvents may be used, or a mixed solvent of two or more kinds thereof: an aromatic compound such as toluene (typically an aromatic hydrocarbon); an acetate such as ethyl acetate; a hexane or a 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); a third butylmethyl group; 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. Further examples of the polymerization initiator include a redox initiator which is a combination of a peroxide and a reducing agent. 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 usual amount, and may be, for example, selected from the range of 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) based on 100 parts by weight of all the monomer components. . 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 synthesizing 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, 10×10. ⁴ ~500×10 ⁴ The scope. From the viewpoint of adhesion performance, the Mw of the base polymer is preferably 10 × 10 ⁴ ~150×10 ⁴ (eg 20×10) ⁴ ~75×10 ⁴ Typically 35×10 ⁴ ~65×10 ⁴ 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. The adhesive in the techniques disclosed herein can be a composition comprising a tackifying resin. The tackifying resin is not particularly limited. For example, a rosin-based tackifying resin, a terpene-based tackifying resin, a hydrocarbon-based tackifying resin, an epoxy-based tackifying resin, a polyamide-based tackifying resin, and an elastic system can be used. Various tackifying resins such as tackifying resins, phenol-based tackifying resins, and ketone tackifying resins. These tackifier resins may be used alone or in combination of two or more. In the case where an acrylic polymer is used as the base polymer, it is preferred to use a rosin-based tackifying resin. Examples of the rosin-based tackifying resin include unmodified rosin (raw rosin) such as rosin gum, wood rosin, and tall oil rosin; and the unmodified rosin is modified by hydrogenation, disproportionation, polymerization, or the like. Modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc., the same below); various other rosin derivatives. Examples of the rosin derivative include those obtained by esterifying an unmodified rosin with an alcohol (that is, an esterified product of rosin), and esterifying the modified rosin with an alcohol. (ie, modified rosin esterified) rosin esters; unsaturated fatty acid modified rosins modified by unsaturated fatty acids on unmodified rosin or modified rosin; by unsaturated fatty acid pairs Unsaturated fatty acid modified rosin ester modified by rosin ester; reduction of carboxyl group in unmodified rosin, modified rosin, unsaturated fatty acid modified rosin or unsaturated fatty acid modified rosin ester Made of rosin alcohol; unmodified rosin, modified rosin, various rosin derivatives and other rosin (especially rosin esters) metal salts; by using acid catalyst in rosin (unmodified rosin, change A rosin phenol resin obtained by adding a phenol and thermally polymerizing it, such as a rosin or a rosin derivative. The softening point (softening temperature) of the tackifying resin to be used is not particularly limited. For example, it is preferred to use a softening point of approximately 100 ° C or higher (preferably approximately 120 ° C or higher). A rosin-based tackifying resin having such a softening point (for example, an esterified product of a polymerized rosin) can be preferably used. The upper limit of the softening point of the tackifier resin is not particularly limited, and may be approximately 200 ° C or less (typically approximately 180 ° C or lower, for example, approximately 150 ° C or lower). In addition, the softening point of the tackifying resin is defined as a value measured by a softening point test method (ring and ball method) prescribed by any one of JIS K 5902 and JIS K 2207. The amount of the tackifying resin to be used is not particularly limited and may be appropriately set depending on the target adhesive property (peel strength, etc.). For example, it is preferred to use a tackifying resin in a ratio of approximately 10 to 100 parts by weight (more preferably 15 to 80 parts by weight, still more preferably 20 to 60 parts by weight) based on 100 parts by weight of the base polymer. In the techniques disclosed herein, the adhesive composition used to form the adhesive layer may also contain a crosslinking agent as needed. The type of the crosslinking agent is not particularly limited, and can be appropriately selected from previously known crosslinking agents. Examples of such a crosslinking agent include an isocyanate crosslinking agent and an epoxy crosslinking agent. An oxazoline crosslinking agent, an aziridine crosslinking agent, a melamine crosslinking agent, a peroxide crosslinking agent, a urea crosslinking agent, a metal alkoxide crosslinking agent, and a metal chelate compound A crosslinking agent, a metal salt crosslinking agent, a carbodiimide crosslinking agent, an amine crosslinking agent, and the like. The crosslinking agent may be used alone or in combination of two or more. Among them, from the viewpoint of improving the cohesive force, it is preferred to use an isocyanate crosslinking agent and/or an epoxy crosslinking agent, and it is particularly preferable to use an isocyanate crosslinking agent. The amount of the crosslinking agent used is not particularly limited. For example, it may be substantially 10 parts by weight or less based on 100 parts by weight of the base polymer (preferably an acrylic polymer), and may be preferably from about 0.005 to 10 parts by weight, more preferably from about 0.01 to 5 parts by weight. Choose within the scope. The adhesive layer in the techniques disclosed herein can also be colored to exhibit desired design or optical properties (e.g., light blocking properties, etc.). For the coloring, one type of a known organic or inorganic coloring agent (pigment, dye, etc.) may be used, or two or more types may be used in combination as appropriate. For example, the adhesive layer can be colored black by including a black coloring agent such as carbon black in the adhesive layer. The content of the colorant is not particularly limited, and may be, for example, less than 15 parts by weight based on 100 parts by weight of the base polymer. The content of the colorant is preferably set to less than 10 parts by weight (for example, less than 5 parts by weight, typically less than 3 parts by weight) based on 100 parts by weight of the base polymer, from the viewpoint of suppressing reduction in adhesion characteristics. degree. The techniques disclosed herein are preferably practiced from the standpoint of adhesion properties by the fact that the adhesive layer is substantially free of inorganic and organic colorants. For example, it can be preferably carried out by setting the content of the colorant to 0 to 1 part by weight based on 100 parts by weight of the base polymer. The above adhesive composition may contain an adhesive composition such as a leveling agent, a crosslinking assistant, a plasticizer, a softener, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, etc., as needed. A variety of additives in general. 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 providing 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 of directly forming (typically coating) an adhesive composition on a substrate film as described above and drying it to form an adhesive layer (direct method) can be employed. 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. Further, after the adhesive composition is dried, the composition may be aged for the purpose of adjusting the movement 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. In a preferred aspect, the thickness of the adhesive layer accounts for more than 40% of the total thickness of the adhesive sheet. By using the substrate film disclosed herein, the thickness of the adhesive layer can be relatively increased in the adhesive sheet whose total thickness is limited. The thickness of the adhesive layer is greater than that of the graphite sheet. From this viewpoint, the ratio of the thickness of the adhesive layer to the total thickness of the adhesive sheet is preferably 50% or more (for example, 70% or more, typically 80% or more). From the viewpoints of productivity and workability of the adhesive sheet, it is appropriate to set the ratio of the thickness of the adhesive layer to the total thickness of the adhesive sheet to be approximately 95% or less (for example, 90% or less). The thickness of the adhesive layer disclosed herein is not particularly limited and may be appropriately selected depending on the purpose. In general, from the viewpoints of productivity such as drying efficiency and adhesion performance, it is suitably about 1 to 200 μm (for example, 2 to 140 μm, typically 4 to 80 μm). The thickness is preferably about 1 μm or more and 40 μm or less, more preferably 1.2 μm or more and 30 μm or less (for example, 20 μm or less, and typically 10 μm or less) from the viewpoint of the total thickness of the adhesive sheet. The technique disclosed herein can be carried out even in the case where the thickness of the adhesive layer is 5 μm or less (and further 3 μm or less). From the viewpoint of heat dissipation efficiency of the graphite sheet, it is preferred that the thickness of the adhesive layer be thin. Further, the adhesive layer having a small thickness is also advantageous in terms of thinning, miniaturization, weight reduction, and resource saving of the adhesive sheet. <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. <Characteristics of Adhesive Sheet, etc.> The adhesive sheet disclosed herein preferably has a 180-degree peel strength of 2.0 N/20 mm or more. The adhesive sheet exhibiting the above characteristics can be satisfactorily adhered to the graphite sheet as the adherend. The above peeling strength is more preferably 3.0 N/20 mm or more, and further preferably 5.0 N/20 mm or more (for example, 8.0 N/20 mm or more). Here, the peel strength means a 180-degree peel strength (180-degree peel strength adhesion force) to a stainless steel plate. The 180 degree peel strength can be measured as follows. Specifically, after attaching a single-sided tape (trade name "No. 31B", manufactured by Nitto Denko Corporation, with a total thickness of 50 μm) to the back surface of the adhesive sheet, the adhesive sheet was cut into a width of 20 mm and a length of 100 mm. The measurement sample was prepared by measuring the size of the measurement sample, and the 2 kg roller was reciprocated once in an environment of 23 ° C and 50% RH, and the back surface of the measurement sample was pressure-bonded to a stainless steel plate (SUS304BA plate). surface. After leaving it in the same environment for 30 minutes, the peel strength (N/) 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 Z 0237:2000. 20 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. The adhesive sheet disclosed herein preferably has a vertical light transmittance of 15% or less. Thereby, the adhesive sheet exhibits good light blocking properties. The above vertical light transmittance is preferably less than 15%, more preferably 10% or less, and further preferably less than 10% (for example, 7% or less, typically 5% or less). In addition, the light transmittance may be more than 1% or more than 3% (for example, 4% or more) from the viewpoint of the inspection property of the graphite sheet to be adhered. The perpendicular light transmittance of the adhesive sheet can be obtained by directly irradiating one surface of the adhesive sheet with light having a wavelength of 380 to 780 nm using a commercially available spectrophotometer, and measuring the light transmitted to the other side. Strength. As the spectrophotometer, for example, a spectrophotometer (device name "U4100 spectrophotometer") manufactured by Hitachi, Ltd. can be used. The same applies to the embodiment described later. In a preferred aspect, the back side of the adhesive sheet is L. ^* a ^* b ^* Brightness L specified by the color system ^* It may be 50 or less (for example, 40 or less, typically 35 or less). The above brightness L ^* It is preferably 30 or less. By applying the techniques disclosed herein, the above brightness can be achieved without the provision of a black printed layer. About the above brightness L ^* The lower limit is not particularly limited, and may be set to be approximately 15 or more (for example, 20 or more) from the viewpoint of appearance and the like. The adhesive sheet having the above brightness can be preferably used in graphite sheet applications. Furthermore, the term "brightness L" in this specification ^* ", refers to by L ^* a ^* b ^* Brightness L specified by the color system ^* It is based on the recommendations of the International Commission on Illumination in 1976 or JIS Z 8729. Specifically, the brightness L ^* A color difference meter (trade name "CR-400", manufactured by Minolta Co., Ltd.; color color difference meter) was used to measure the back surface of the adhesive sheet in a plurality of portions (for example, five or more points), and the average value thereof was used. The same applies to the embodiment described later. The total thickness of the adhesive sheet (including the adhesive layer and the base film but not including the release liner) disclosed herein is not particularly limited, and is suitably set to be approximately 2 to 150 μm (for example, 3 to 100 μm, typically For the range of 3 to 50 μm). Preferably, the total thickness of the adhesive sheet is 30 μm or less (for example, 20 μm or less, typically 10 μm or less), and the total thickness may be 5 μm or less (for example, less than 5 μm, typically not reached) 4 μm). By forming the adhesive sheet to a thin thickness, the heat dissipation effect of the graphite sheet can be sufficiently exerted. Further, the adhesive sheet having a small thickness can be advantageously used for thinning, miniaturization, weight reduction, resource saving, and the like of the product to which the adhesive sheet is applied. <Use> The adhesive sheet disclosed herein can be attached to a graphite sheet and used. The graphite sheet can be preferably used in various small electronic devices as a heat sink for allowing heat from a heat generating element (battery, IC chip, etc.) to escape. For example, the graphite sheet is disposed at a position adjacent to a power generating element such as a battery or an IC chip in the electronic device or around the power generating element. Such a graphite sheet has an uneven appearance and is easily broken by a thinner one. Therefore, the adhesive sheet is preferably attached to the surface thereof for the purpose of improving the appearance and protection. The surface of the graphite sheet is not necessarily smooth, but for such a graphite sheet, the adhesive sheet disclosed herein exhibits excellent adhesion stability and functions such as imparting or protecting the appearance. Although not particularly limited, the adhesive sheet disclosed herein can be preferably applied to a graphite sheet having a thickness of 5 to 100 μm and/or an arithmetic mean surface roughness Ra of 0.005 to 5 μm. In a preferred aspect, the adhesive sheet disclosed herein can be used for attachment to a graphite sheet disposed in a portable electronic device. For example, it can be preferably applied 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, by a jig Or a type of module that is worn on one part of the body, including a goggle type of a glasses type (single-eye 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. Clothes type, such as earphones mounted on the ear, etc.), digital camera, digital video camera, audio equipment (portable digital music device, IC recorder, etc.), computer (calculator, etc.), Portable gaming machines, electronic dictionaries, electronic organizers, e-books, information devices for vehicles, portable radios, portable televisions, portable printers, portable scanners, portable data modems, etc. On the graphite sheet configured in the portable electronic machine. 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 matters disclosed by the present specification include the following. (1) An adhesive sheet comprising a single-sided adhesive sheet laminated on a graphite sheet, and comprising: a base film having a thickness of 12 μm or less and containing a black colorant; an adhesive layer; It is disposed on one surface of the above substrate film. (2) The adhesive sheet according to (1) above, wherein the total thickness of the adhesive sheet is 30 μm or less. (3) The adhesive sheet according to (1) or (2) above, wherein the thickness of the adhesive layer is 40% or more of the total thickness of the adhesive sheet. (4) The adhesive sheet according to any one of the above (1) to (3), which exhibits a 180-degree peel strength of 2 N/20 mm or more. (5) The adhesive sheet according to any one of the above (1) to (4) wherein the thickness of the adhesive layer is 1.2 μm or more. (6) The adhesive sheet according to any one of (1) to (5) above wherein the adhesive layer is an acrylic adhesive layer. (7) The adhesive sheet according to any one of (1) to (6) wherein the adhesive sheet has a vertical light transmittance of 15% or less. (8) The adhesive sheet according to any one of (1) to (7) above, wherein the back surface of the adhesive sheet is L ^* a ^* b ^* Brightness L specified by the color system ^* It is 40 or less. (9) The adhesive sheet according to any one of the above aspects, wherein the base film is a polyethylene terephthalate resin film containing the black colorant. (10) The adhesive sheet according to any one of the above (1) to (9), which is for use in a portable electronic device. (11) The adhesive sheet according to any one of the above (1), wherein the adhesive layer contains acrylic polymerization in a ratio exceeding 50% by weight of the polymer component contained in the adhesive layer. The acrylic polymer contains the alkyl (meth)acrylate represented by the formula (1) as a monomer component in a ratio of 70% by weight or more: CH ₂ =C(R ¹ )COOR ² (1) (R in the above formula (1) ¹ Is a hydrogen atom or a methyl group; again, R ² It is a chain alkyl group having 1 to 20 carbon atoms. (12) The adhesive sheet according to the above (11), wherein the alkyl (meth)acrylate is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. Isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, amyl (meth)acrylate, (meth)acrylic acid Isoamyl ester, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, ( Ethyl methacrylate, isodecyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauric (meth) acrylate Ester, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, (methyl) At least one selected from the group consisting of heptadecyl acrylate, octadecyl (meth) acrylate, pentadecyl (meth) acrylate, and eicosyl (meth) acrylate. (13) The adhesive sheet according to (11) or (12) above, wherein the alkyl (meth)acrylate is n-butyl acrylate and 2-ethylhexyl acrylate. (14) The adhesive sheet according to any one of (11) to (13) above, wherein the alkyl (meth)acrylate is n-butyl acrylate and 2-ethylhexyl acrylate, 2-ethyl acrylate The hexyl ester is contained in the above monomer component in a ratio less than n-butyl acrylate. (15) The adhesive sheet according to any one of the above (11), wherein the acrylic polymer further contains a monomer having a functional group as the monomer component, and the single system containing the functional group is selected. Free acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate And at least one of the group consisting of 4-hydroxybutyl (meth)acrylate. (16) The adhesive sheet according to any one of (1) to (15) wherein the base film contains carbon black as the black colorant. The adhesive sheet according to any one of the above (1), wherein the base film contains carbon black having an average particle diameter of 10 nm to 500 nm as the black colorant. The adhesive sheet according to any one of the above aspects (1), wherein the black colorant in the base film is formulated in an amount of 0.1 to 30% by weight. (19) The adhesive sheet according to any one of (1) to (18), wherein the base film has a single layer structure. (20) An adhesive sheet comprising a single-sided adhesive sheet laminated on a graphite sheet in a portable electronic device, and comprising: a single-layered substrate film comprising a black colorant-containing polymer a polyethylene terephthalate resin film; and an acrylic pressure-sensitive adhesive layer disposed on one surface of the base film, wherein the total thickness of the adhesive sheet is 30 μm or less, and the thickness of the base film The thickness of the adhesive layer is 1.2 μm or more, and the thickness of the adhesive layer is 40% or more of the total thickness of the adhesive sheet, and is 180% of 2 N/20 mm or more. Degree of peeling strength, the perpendicular light transmittance of the adhesive sheet is 15% or less, and the back surface of the adhesive sheet is L ^* a ^* b ^* Brightness L specified by the color system ^* 40 or less, the acrylic pressure-sensitive adhesive layer contains an acrylic polymer in an amount of more than 50% by weight based on the polymer component contained in the pressure-sensitive adhesive layer, and the acrylic polymer is contained in an amount of 70% by weight or more. As the monomer component, the alkyl (meth)acrylate is n-butyl acrylate and 2-ethylhexyl acrylate, and 2-ethylhexyl acrylate is less than n-butyl acrylate. The ratio is contained in the monomer component, and the acrylic polymer further includes a monomer having a functional group as the monomer component, and the single system containing the functional group is selected from the group consisting of acrylic acid, methacrylic acid, and (meth)acrylic acid 2 -hydroxyethyl ester, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate In at least one of the group, the black colorant is carbon black having an average particle diameter of 10 nm to 500 nm, and the black colorant in the base film is formulated in an amount of 0.1 to 30% by weight. In the following, several embodiments of the invention are described, but are not intended to limit the invention to the embodiments shown. In the following description, "parts" and "%" are based on weight unless otherwise specified. <Example 1> In a reaction vessel having a stirrer, a thermometer, a nitrogen introduction tube, a reflux condenser, and a dropping funnel, 70 parts of BA as a monomer component, 27 parts of 2EHA, 3 parts of AA, and 4-hydroxybutyl acrylate were charged. 0.05 part of the ester and 135 parts of toluene as a polymerization solvent were stirred for 2 hours while introducing nitrogen gas. After the oxygen in the polymerization system was removed as described above, 0.1 part of AIBN as a polymerization initiator was added, and solution polymerization was carried out at 60 ° C for 6 hours to obtain a toluene solution of an acrylic polymer. The Mw of the acrylic polymer is about 40×10 ⁴ . A polymerized rosin ester (trade name "PENSEL D-125", softening point: 120 to 130 ° C, manufactured by Arakawa Chemical Industries Co., Ltd.) 30 as a tackifier resin was added to 100 parts of the acrylic polymer contained in the toluene solution. An acrylic pressure-sensitive adhesive composition was prepared by dissolving two parts of an isocyanate-based crosslinking agent (trade name "CORONATE L", manufactured by Nippon Polyurethane Co., Ltd., and a solid content of 75%). As a release liner, a polyester release film (trade name "DIAFOIL MRF" having a thickness of 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) having a release surface of a release treatment was prepared. The adhesive composition was applied to the release surface of the release liner so that the thickness after drying became 25 μm, and dried at 100 ° C for 2 minutes. An adhesive layer is formed on the release surface of the release liner as described above. Next, on the surface of a PET film having a thickness of 4.5 μm thickened with carbon black as a black pigment, an adhesive sheet formed on the release liner was bonded to each other to prepare an adhesive sheet (transfer method) of this example. The release liner is directly left on the adhesive layer for the protection of the surface (adhesive surface) of the adhesive layer. The adhesive sheet is formed on one surface of a PET film (base film) containing a black colorant (mixed with a black pigment) having a thickness of 4.5 μm, and has a thickness of 25 μm formed by the above adhesive composition. A single-sided adhesive sheet having a total thickness of the adhesive layer of about 29.5 μm. <Examples 2 to 9> A PET film containing a black colorant (mixed with a black pigment) having the thickness shown in Table 1 was used as a base film, and the thickness of the adhesive layer was changed to the thickness shown in Table 1, except Otherwise, the adhesive sheet of each example was produced in the same manner as in Example 1. <Example 10> In this example, a transparent PET film (trade name "Lumirror", manufactured by Toray Industries, Inc.) having a thickness of 4.5 μm and a single film set on the PET film (base film) were used as the base film. A base film having a total thickness of 9.5 μm of a black printed layer (colored layer) having a thickness of 5 μm on the surface. The black printed layer is formed by printing by a gravure printing method using an ink composition containing a black colorant. An adhesive sheet of this example was produced in the same manner as in Example 1 except that the thickness of the adhesive layer was changed to 20 μm using the base film having the black printed layer. The total thickness of the adhesive sheet was about 29.5 μm, and the adhesive layer was formed on the surface of the substrate film on the side opposite to the black printed layer. <Examples 11 to 14> The adhesion of each example was carried out in the same manner as in Example 10 except that the thickness of the base film, the thickness of the adhesive layer, and the thickness of the black printed layer were changed to those shown in Table 1. Sheet. [Evaluation] For each of the adhesive sheets, the 180-degree peel strength (N/20 mm), the vertical light transmittance (%), and the brightness of the back surface were measured. ^* . The results are shown in Table 1. The schematic configuration of the adhesive sheets of the respective examples is also shown in Table 1. [Following the stability evaluation test] A commercially available graphite sheet (trade name "Graphinity 25 μm", manufactured by Kaneka Co., Ltd., thickness: 25 μm) was prepared, and a double-sided tape (product name " having the same size as the stainless steel plate was prepared. No. 5000NS, manufactured by Nitto Denko Co., Ltd.) is fixed on a stainless steel plate 150 mm long by 30 mm wide by 2 mm thick. The adhesive sheets of the respective examples were cut into a size of 100 mm × 20 mm in width and placed on the other surface of the above graphite sheet, and a 2 kg roller was rotated at a speed of 5 mm/sec from above the adhesive sheet. One time, the adhesive sheet is attached to the graphite sheet. Then, the temperature was kept at a high temperature of 80 ° C for a specific number of days (maximum of 10 days), and the number of days of bulging or peeling was recorded. The results are shown in Table 1. [Evaluation of Handling Property] Regarding the rationality of Examples 3 and 11 having the same total thickness, comparative evaluation was carried out. Specifically, an adhesive sheet having a size of approximately A4 was prepared as an adhesive sheet of the above-described example, and bonded to a stainless steel plate (SUS304BA plate) under the conditions of a pressure of 0.3 MPa and a speed of 1.0 m/min. The presence or absence of the wrinkles at the time of the bonding was visually confirmed, and the case where the wrinkles were not attached was evaluated as "○", and the case where the wrinkles were pasted was evaluated as "x". The results are shown in Table 1. [Table 1] As shown in Table 1, when the adhesion stability of Examples 7 to 9 and Example 14 using an adhesive sheet having a total thickness of 4.0 μm or less was compared, Example 7 using a substrate film containing a black colorant was used. Between ~9 and the example 14 in which the black printed layer was formed, a significant difference was found on the basis of one day of storage. In addition, when the examples 3, 6, 11, 12, and 13 of the adhesive sheet having a total thickness of more than 4.0 μm and 10 μm or less are used, the base containing the black colorant is used for 3 days of storage. The examples 3 and 6 of the film were found to be significantly different from the examples 11 to 13 in which the black printed layer was formed. The same tendency was also found in Examples 1, 4 and 10 using an adhesive sheet having a total thickness of more than 20 μm. Adhesive sheets having a total thickness of more than 10 μm and 20 μm or less (Examples 2 and 5) are also expected to exhibit the same tendency. In general, the adhesive sheets of Examples 1 to 9 using a base film containing a black colorant having a thickness of 12 μm or less and the adhesive sheets of Examples 10 to 14 having the same total thickness formed with a black printed layer were used. Compared to the material, it shows excellent adhesion stability. In Examples 10 to 14 in which the black printed layer was formed, the stability was poor, and the reason was considered to be that the thermal expansion coefficient of the base film and the black printed layer could not be pressed by the adhesive force of the adhesive. Thermal deformation of the substrate film. Further, according to the comparison between Example 3 and Example 11, it was found that when the black printed layer was not provided, there was a tendency that the handleability was improved. According to the above results, it was found that the adhesive sheet having the base film containing the black colorant having a thickness of 12 μm or less can exhibit excellent adhesion stability to the graphite sheet even when it is set to a thin thickness. 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‧‧‧Adhesive sheet
1A‧‧‧Next
1B‧‧‧Back
10‧‧‧Base film
10A‧‧‧One surface of the substrate film (adhesive layer side surface)
10B‧‧‧The other surface of the substrate film (back side surface)
20‧‧‧Adhesive layer
30‧‧‧Release liner

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

1‧‧‧Adhesive sheet

1A‧‧‧Next

1B‧‧‧Back

10‧‧‧Base film

10A‧‧‧One surface of the substrate film (adhesive layer side surface)

10B‧‧‧The other surface of the substrate film (back side surface)

20‧‧‧Adhesive layer

30‧‧‧Release liner

Claims (10)

An adhesive sheet comprising a single-sided adhesive sheet laminated on a graphite sheet, and comprising: a substrate film having a thickness of 12 μm or less and containing a black colorant; and an adhesive layer, the system configuration On one surface of the above substrate film. The adhesive sheet of claim 1, wherein the total thickness of the adhesive sheet is 30 μm or less. The adhesive sheet according to claim 1 or 2, wherein a ratio of the thickness of the adhesive layer to the total thickness of the adhesive sheet is 40% or more. The adhesive sheet according to any one of claims 1 to 3, which exhibits a 180 degree peel strength of 2 N/20 mm or more. The adhesive sheet according to any one of claims 1 to 4, wherein the thickness of the above adhesive layer is 1.2 μm or more. The adhesive sheet according to any one of claims 1 to 5, wherein the adhesive layer is an acrylic adhesive layer. The adhesive sheet according to any one of claims 1 to 6, wherein the adhesive sheet has a vertical light transmittance of 15% or less. The adhesive sheet according to any one of claims 1 to 7, wherein a brightness L ^* defined by the L ^* a ^* b ^* color system of the back surface of the adhesive sheet is 40 or less. The adhesive sheet according to any one of claims 1 to 8, wherein the base film is a polyethylene terephthalate resin film containing the black colorant. The adhesive sheet of any one of claims 1 to 9 which is intended for use in a portable electronic device.