JP6579949B2 - Adhesive sheet for graphite sheet - Google Patents

Description

  The present invention relates to an adhesive sheet for graphite sheets.

  In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same shall apply hereinafter) is in the form of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive is widely used in the form of a pressure-sensitive adhesive sheet with a base material for the purpose of bonding, fixing, protecting and the like of various members. For example, in a portable electronic device such as a mobile phone, the pressure-sensitive adhesive sheet having the above-described configuration is used for the purpose of protecting a graphite sheet installed for heat dissipation or imparting design properties (Patent Document 1). Specifically, the pressure-sensitive adhesive sheet for this use has a configuration in which a pressure-sensitive adhesive layer is disposed on one side of a base material on which a colored layer is formed.

JP 2013-203965 A

  The pressure-sensitive adhesive sheet provided with the colored layer is usually required to have a predetermined appearance according to the affixed portion or the like. For example, in a pressure-sensitive adhesive sheet used in a portable electronic device, a black colored layer is preferably employed from the viewpoints of harmony with peripheral members and texture. Moreover, it is desirable that the pressure-sensitive adhesive sheet attached to the graphite sheet has a light transmittance such that the presence or absence of defects or foreign matters in the graphite sheet as the adherend can be confirmed through the pressure-sensitive adhesive sheet. Specifically, for example, in Patent Document 1, the light transmittance of the colored base material constituting the pressure-sensitive adhesive sheet is set within a range of 0.4 to 8%, and visual inspection through the pressure-sensitive adhesive sheet using a light box is performed. Is going. However, in the configuration of Patent Document 1, since the light transmittance is set low, a whited defect (white light leakage from a pinhole, etc.), a foreign object, a blackish defect, etc. (attached to the surface or internal There is a limit to the visual detection of foreign matter buried in the surface or unevenness due to scratches on the surface), and the detection accuracy may not be sufficient in applications where the required level for the quality of the adherend is high. In addition, when the back surface of the pressure-sensitive adhesive sheet is glossy, the detection accuracy can be lowered by glossiness (reflected light). It would be beneficial if the detection accuracy of defects and the like could be improved without sacrificing the appearance.

  The present invention has been created in view of the above circumstances, and an object thereof is to provide a pressure-sensitive adhesive sheet for graphite sheets having an excellent appearance and improved accuracy in detecting defects and the like.

According to the present invention, a single-sided adhesive sheet that is used by being attached to a graphite sheet is provided. This pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer provided on one surface of the base material. The substrate includes a black layer. Moreover, the 60 degree gloss value of the said adhesive sheet back surface is 10 or less. Furthermore, the light transmittance of the pressure-sensitive adhesive sheet is 12 to 30%.
According to the said structure, since the light transmittance of an adhesive sheet is set in the range of 12 to 30%, the detection precision of the defect etc. of the graphite sheet performed through an adhesive sheet improves. In particular, it tends to be excellent in detectability of white or black defects and foreign matters (hereinafter also simply referred to as defects). Moreover, since the glossiness on the back surface of the pressure-sensitive adhesive sheet is suppressed, adverse effects on the inspection due to the reflected light on the back surface of the pressure-sensitive adhesive sheet are also suppressed. Furthermore, when the light transmittance of the pressure-sensitive adhesive sheet is set in the above range, the color tone of the graphite sheet as the adherend is moderately reflected, and an appearance having a desired color and texture can be obtained. Furthermore, because the 60 ° gloss value is limited to 10 or less, combined with the black layer, a glossy, suppressed black color is imparted to the back surface of the adhesive sheet, and the color of the graphite sheet and its peripheral members An appearance that harmonizes with taste is created. Therefore, according to the present invention, a pressure-sensitive adhesive sheet for graphite sheets is realized that has an excellent appearance when attached to a graphite sheet and has improved accuracy in detecting defects and the like.

  In a preferable aspect of the pressure-sensitive adhesive sheet disclosed herein, the base material includes a resin film layer and a black layer. Moreover, as for the said adhesive sheet, the said adhesive layer, the said resin film layer, and the said black layer are laminated | stacked in this order. By comprising in this way, the adhesive sheet which has the outstanding external appearance and is excellent in the detectability of a defect etc. is implement | achieved preferably.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the black layer has a thickness of 2 μm or less. The effect by the technique disclosed here is preferably realized by the configuration including the thin black layer as described above. Moreover, the thickness increase of an adhesive sheet can be suppressed by restrict | limiting the thickness of a black layer. This can be a favorable feature in applications that require a reduction in thickness and weight.

In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the back surface of the pressure-sensitive adhesive sheet has a lightness L ^* defined by the L ^* a ^* b ^* color system of 40 or less. By configuring in this way, an excellent appearance is preferably realized.

  In a preferable aspect of the pressure-sensitive adhesive sheet disclosed herein, the base material further includes a mat layer. The base material has a laminated structure in which the resin film layer, the black layer, and the mat layer are laminated in this order. With this configuration, a configuration having a predetermined gloss value and light transmittance is preferably realized.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the mat layer includes a particulate mat material. By comprising in this way, the low gloss of the back surface of an adhesive sheet is implement | achieved preferably.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the thickness of the mat layer is 2 μm or less. By comprising in this way, the improvement of a desired external appearance can be implement | achieved, suppressing the thickness increase of an adhesive sheet. This can be a favorable feature in applications that require a reduction in thickness and weight.

  In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the total thickness of the pressure-sensitive adhesive sheet is 30 μm or less. In such a thin pressure-sensitive adhesive sheet, the effects of the technology disclosed herein are preferably realized.

  Moreover, according to this invention, an adhesive sheet with a release liner provided with one of the adhesive sheets disclosed here and the release liner which protects the adhesive surface of this adhesive sheet is provided. This pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer provided on one surface of the base material. The substrate includes a black layer. Moreover, the 60 degree gloss value of the said adhesive sheet back surface is 10 or less. Furthermore, the light transmittance of the pressure-sensitive adhesive sheet is 12 to 30%.

  The pressure-sensitive adhesive sheet for graphite sheet disclosed herein is excellent in appearance and has improved accuracy in detecting defects and the like. Taking advantage of this feature, it is suitable as an adhesive sheet used for a graphite sheet disposed in a portable electronic device such as a mobile phone or a smartphone. Therefore, the pressure-sensitive adhesive sheet provided by this specification can be laminated on a graphite sheet disposed in a portable electronic device.

It is sectional drawing which shows one structural example of an adhesive sheet typically.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings on the implementation of the invention described in the present specification and the common general technical knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, in the following drawings, members / parts having the same action may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. In addition, the embodiment described in the drawings is schematically illustrated for clearly explaining the present invention, and does not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product. .

In this specification, the “pressure-sensitive adhesive” refers to a material that exhibits a soft solid (viscoelastic body) state in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure as described above. . The adhesive here is generally defined as “CA Dahlquist,“ Adhesion: Fundamental and Practice ”, McLaren & Sons, (1966) P. 143”, and generally has a complex tensile modulus E ^* (1 Hz). <10 < ⁷ > dyne / cm < ² > material (typically a material having the above properties at 25 [deg.] C.).

<Configuration of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein is a single-sided adhesive pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on one surface of a base material (support). The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a single sheet. Or the adhesive sheet of the form processed into various shapes may be sufficient.

  The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 includes a sheet-like base material 10 and a pressure-sensitive adhesive layer 20 provided on one surface 10 </ b> A of the base material 10. The substrate 10 includes a resin film layer 12 and a black layer 14. In this embodiment, the pressure-sensitive adhesive layer 20 is provided on the first surface 12 </ b> A of the resin film layer 12, and the black layer 14 is provided on the second surface 12 </ b> B of the resin film layer 12. The substrate 10 further includes a mat layer 16. The base material 10 has a laminated structure in which a resin film layer 12, a black layer 14, and a mat layer 16 are laminated in this order. In this embodiment, the mat layer 16 is the outermost layer of the substrate 10, and the outer surface 16 </ b> A of the mat layer 16 is the back surface 1 </ b> B of the pressure-sensitive adhesive sheet 1. Further, in this pressure-sensitive adhesive sheet 1, the surface of the pressure-sensitive adhesive layer 20 is an adhesive surface 1 </ b> A of the pressure-sensitive adhesive sheet 1.

  The pressure-sensitive adhesive sheet 1 before use has a configuration in which the pressure-sensitive adhesive layer 20 is protected by a release liner 50 having a pressure-sensitive adhesive layer 20 side as a release surface 50B. When the pressure-sensitive adhesive sheet 1 with the release liner 50 is in the form of a roll (pressure-sensitive adhesive sheet roll) for the purpose of transportation or storage, the outer surface 50A of the release liner 50 (the surface located on the side opposite to the release surface 50B) ) And the back surface 1B of the adhesive sheet (in this embodiment, the outer surface 16A of the mat layer 16) may be in contact with each other.

  In the above embodiment, the base material 10 has a laminated structure of the resin film layer 12, the black layer 14, and the mat layer 16, but is not limited thereto. For example, the mat layer may be omitted. In that case, the 60 ° gloss value on the back surface of the pressure-sensitive adhesive sheet can be reduced to 10 or less by making the base material a laminated structure composed of a resin film layer and a black layer and performing a mat treatment on the back surface. When a base material is provided with a resin film layer and a black layer, unlike the said embodiment, a black layer may be arrange | positioned rather than the resin film layer at the adhesive layer side. In that case, the pressure-sensitive adhesive sheet has a laminated structure in which a pressure-sensitive adhesive layer, a black layer, a resin film layer, and a mat layer (optional) are laminated in this order. Alternatively, the base material can be composed only of the black layer. In that case, the base material can have both the strength of the resin film layer and the color of the black layer.

<Characteristics of adhesive sheet>
The 60 ° gloss value of the back surface of the pressure-sensitive adhesive sheet disclosed herein is 10 or less. Thereby, the adverse effect of the reflected light on the back surface of the pressure-sensitive adhesive sheet is suppressed, and the inspection property of the graphite sheet is improved. Further, due to such low gloss, together with the black layer, the back surface of the pressure-sensitive adhesive sheet can exhibit a solid black color with suppressed gloss. The 60 ° gloss value on the back surface of the pressure-sensitive adhesive sheet is more preferably 7 or less, still more preferably 6 or less (typically 5.5 or less). The lower limit of the 60 ° gloss value is not particularly limited, but is suitably 1 or more in consideration of the design properties and color, and preferably 2 or more (for example, 3 or more, typically 3.5 or more). ). The gloss value can be obtained by forming a mat layer on the back side of the pressure-sensitive adhesive sheet, or performing a mat treatment (surface treatment) such as embossing or sand blasting.

  The 60 ° gloss value on the back surface of the pressure-sensitive adhesive sheet is measured using a commercially available gloss meter (for example, trade name “High Gloss Gloss Checker IG-410” manufactured by HORIBA, Ltd.) at a measurement angle of 60 °. The same applies to the embodiments described later.

  The light transmittance of the pressure-sensitive adhesive sheet disclosed herein is 12 to 30%. Thereby, the detection accuracy of graphite sheet defects (particularly whiteness and blackness defects and foreign matter) performed through the adhesive sheet is improved. In addition, by setting the light transmittance of the pressure-sensitive adhesive sheet within the above range, the color tone of the graphite sheet as the adherend is moderately reflected, and an excellent color and texture can be obtained. The light transmittance is preferably 25% or less, more preferably 20% or less, and still more preferably 18% or less. The light transmittance is preferably 14% or more, more preferably 15% or more (for example, 16% or more). In the technology disclosed herein, from the viewpoint of obtaining an excellent appearance (color, texture, etc.), the light transmittance can be adjusted by the colorant content and thickness in the black layer and the number of sub-layers stacked. it can.

  The light transmittance of the pressure-sensitive adhesive sheet is measured by irradiating light with a wavelength of 380 to 780 nm perpendicularly to one surface of the pressure-sensitive adhesive sheet using a commercially available spectrophotometer and measuring the intensity of the light transmitted through the other surface. Is required. As the spectrophotometer, for example, a spectrophotometer manufactured by Hitachi, Ltd. (device name “U4100 type spectrophotometer”) can be used. The same applies to the embodiments described later.

In a preferred embodiment, the back surface of the pressure-sensitive adhesive sheet may have a lightness L ^* defined by the L ^* a ^* b ^* color system of 50 or less (eg, 40 or less, typically 35 or less). The lightness L ^* is preferably 30 or less. The pressure-sensitive adhesive sheet having the lightness is preferably used for application to a graphite sheet where black is desired. The pressure-sensitive adhesive sheet having the back surface exhibits a solid black color with suppressed gloss and is laminated on the graphite sheet to have a color well harmonized with its peripheral members (for example, a battery). Although there is no restriction | limiting in particular about the lower limit of the said lightness L ^* , From viewpoints, such as an external appearance, it can set to about 15 or more (for example, 20 or more).

The chromaticity a ^* defined by the L ^* a ^* b ^* color system on the back surface of the pressure-sensitive adhesive sheet is not particularly limited, but the color tone around the portion to which the pressure-sensitive adhesive sheet is applied (which may be a member) In consideration of harmony, it is preferable that the range be ± 15 (eg, ± 5, typically ± 2). The chromaticity b ^* is not particularly limited, but is preferably in the range of ± 15 (for example, ± 10, typically ± 5). In the present specification, “range of ± X” is used to mean a range of −X to + X.

Note that the L ^* a ^* b ^* color system in this specification shall conform to the rules recommended by the International Lighting Commission in 1976 or the rules of JIS Z 8729. Specifically, L ^* a ^* b ^* is measured at a plurality of locations (for example, 5 points or more) on the back side of the adhesive sheet using a color difference meter (trade name “CR-400” manufactured by Minolta Co .; color difference meter). The average value may be adopted. The same applies to the embodiments described later.

  The pressure-sensitive adhesive sheet disclosed herein preferably has a 180 degree peel strength of 0.5 N / 20 mm or more. The pressure-sensitive adhesive sheet exhibiting the above characteristics can be adhered well to the graphite sheet as the adherend. The peel strength is more preferably 1.0 N / 20 mm or more, and further preferably 2.0 N / 20 mm or more. The peeling strength here refers to 180 degree peeling strength (180 degree peeling adhesive strength) with respect to a stainless steel plate.

  The 180 degree peel strength can be measured as follows. Specifically, after attaching a single-sided adhesive tape (trade name “No. 31B”, manufactured by Nitto Denko Corporation, total thickness 50 μm) to the back of the adhesive sheet, the adhesive sheet is made into a size of 20 mm in width and 100 mm in length. With respect to the cut measurement sample, in an environment of 23 ° C. and 50% RH, the adhesion surface of the measurement sample is pressed against the surface of a stainless steel plate (SUS304BA plate) by reciprocating a 2 kg roller once. After leaving this in the same environment for 30 minutes, using a universal tensile compression tester, in accordance with JIS Z 0237: 2000, under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees, the peel strength (N / 20 mm). As a universal tensile and compression tester, for example, “Tensile and compression tester, TG-1kN” manufactured by Minebea can be used. In the examples described later, the same method is used.

  The total thickness of the pressure-sensitive adhesive sheet disclosed here (including a pressure-sensitive adhesive layer and a base material but not including a release liner) is not particularly limited, and is suitably about 2 μm or more (for example, 3 μm or more). Also, it is appropriate that the thickness is about 150 μm or less (for example, 100 μm or less, typically 50 μm or less). The total thickness of the pressure-sensitive adhesive sheet according to a preferred embodiment is about 30 μm or less (for example, 20 μm or less, typically 10 μm or less), and the total thickness may be 7 μm or less. A thin pressure-sensitive adhesive sheet can be advantageous in terms of reducing the thickness, size, weight, and resource saving of products to which the pressure-sensitive adhesive sheet is applied. Moreover, the heat dissipation effect of a graphite sheet is fully exhibited by comprising the adhesive sheet disclosed here thinly.

<Base material>
(Structure of base material)
The substrate disclosed herein includes a black layer. Moreover, the base material which concerns on a preferable one aspect | mode may be equipped with a resin film layer and a black layer, and may be further provided with a mat layer. Especially, the base material which has the laminated structure on which the resin film layer, the black layer, and the mat | matte layer were laminated | stacked in this order like the said embodiment is especially preferable. This laminated structure may have an optimal configuration that achieves the effects of the technology disclosed herein. In another preferred embodiment, the base material can be composed only of a black layer. Accordingly, the substrates disclosed herein have a single layer structure or a multilayer structure.

(Black layer)
The black layer disclosed herein includes all layers exhibiting black color, and usually refers to a layer containing a black colorant. For example, a layer having a surface showing a lightness L ^* defined by the above-mentioned L ^* a ^* b ^* color system of 40 or less (for example, 35 or less, typically 30 or less) is a typical example of a black layer. When the base material includes a black layer, an excellent appearance can be obtained when laminated on the graphite sheet in combination with the light transmittance and the low gloss value. The black layer which concerns on one preferable aspect is a black printed layer printed on the surface (1st surface or 2nd surface) of the resin film layer mentioned later. From the viewpoint of appearance and the like, the black layer is preferably provided on the second surface of the resin film layer (surface opposite to the pressure-sensitive adhesive layer side surface). In another preferred embodiment, the black layer may be one obtained by coloring a resin film layer described later in black. In that case, the substrate may consist of only the black layer.

  In a preferred embodiment, the black layer can be formed by applying a black layer forming composition containing a black colorant and a binder to a resin film layer described below. As the binder, a material known in the field of paint or printing can be used without particular limitation. For example, polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate and the like are exemplified. The composition for forming a black layer can be, for example, a solvent type, an ultraviolet curable type, a thermosetting type, or the like. Formation of the black layer can be carried out by employing any means conventionally used for forming the black layer without any limitation. For example, a method of forming a black layer (black print layer) by printing such as gravure printing, flexographic printing, and offset printing can be preferably employed. Of these, gravure printing is particularly preferred. The color of the black layer can be adjusted relatively easily by controlling the gravure printing plate.

  The black layer may have a single layer structure composed entirely of one layer, or may have a multilayer structure including two layers, three layers, or more sublayers. When the black layer has a multilayer structure, at least one sublayer (preferably all sublayers) is preferably a black layer (subblack layer). A black layer having a multilayer structure including two or more sub-layers can be formed, for example, by repeatedly applying (for example, printing) the black layer forming composition. The type and blending amount of the colorant contained in each sub layer may be the same or different.

As the black colorant used for coloring the black layer, organic or inorganic colorants (pigments, dyes, etc.) can be used. Specific examples of black colorants include carbon black, acetylene black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, and disulfide. Molybdenum, chromium complexes, anthraquinone colorants and the like can be mentioned. Of these, carbon black is preferable. The black colorant can be used alone or in combination of two or more. Although not particularly limited, for example, it is preferable to use carbon black having an average particle diameter of 10 nm to 500 nm (more preferably 10 nm to 120 nm). In this specification, “average particle size” means, unless otherwise specified, a particle size (50% volume) at an integrated value of 50% in a particle size distribution measured based on a particle size distribution measuring device based on a laser scattering / diffraction method. average particle diameter; _hereinafter refers to also) be abbreviated as _{D 50..}

  The content of the black colorant is not limited to a specific range because it is set according to the required color, texture, etc., but it is appropriate to set it to about 1% by weight or more in the black layer. And preferably 2% by weight or more (for example, 5% by weight or more, typically 15% by weight or more). Further, the content of the black colorant is suitably about 65% by weight or less in the black layer, and is preferably 30% by weight or less (eg, 15% by weight or less, typically from the viewpoint of inspection). Is 8% by weight or less). The black layer may contain white pigments such as titanium dioxide, zinc white, lead white, and other colorants, and may contain substantially no colorant other than the black colorant. Also good.

  The thickness of the entire black layer is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more (for example, 0.8 μm or more, typically 1 μm or more), In general, the thickness is suitably 10 μm or less, preferably 7 μm or less, more preferably 5 μm or less (for example, 3 μm or less, typically 2 μm or less). In a black layer including two or more sub-layers, the thickness of each sub-layer is usually preferably about 0.5 μm to 2 μm.

(Resin film layer)
In the pressure-sensitive adhesive sheet disclosed herein, the base material (supporting base material) that supports (backs) the pressure-sensitive adhesive layer typically includes a resin material as a main component (for example, a component contained in an amount exceeding 50% by weight). It is preferable to include a resin film layer. In this specification, “resin film” typically refers to a substantially non-foamed resin film. In other words, the resin film in this specification may be one (voidless) substantially free of bubbles in the resin film. Therefore, the said resin film is the concept distinguished from what is called a foam film. The resin film is typically a substantially non-porous film and is a concept that is distinguished from a so-called nonwoven fabric or woven fabric. A substrate that does not include a porous layer, such as a foam, a nonwoven fabric, or a woven fabric, that is, a substrate composed of a non-porous layer can be preferably used. Resin films generally tend to be superior in mechanical strength such as tensile strength as compared with foams, nonwoven fabrics, and woven fabrics. Moreover, it is excellent in workability (for example, punching workability). Therefore, the pressure-sensitive adhesive sheet using a base material including a resin film is advantageous in terms of workability, dimensional accuracy, and handleability. In addition, the base material including such a resin film can be preferably used as a base material in the technology disclosed herein from the viewpoints of dimensional stability, thickness accuracy, economy (cost), and the like.

  Preferable examples of the resin material constituting the resin film layer disclosed herein include polyolefin resins and polyester resins. Here, the polyolefin-based resin refers to a resin containing a polyolefin in a proportion exceeding 50% by weight. Similarly, the polyester resin refers to a resin containing polyester in a proportion exceeding 50% by weight. Examples of the polyolefin resin film include polyethylene (PE) resin, polypropylene (PP) resin, ethylene-propylene copolymer, and ethylene-butene copolymer. Examples of the polyester resin include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate resin, polybutylene naphthalate resin, and the like. Of these, polyester resins are preferable from the viewpoint of anchoring properties (particularly, anchoring properties of the acrylic pressure-sensitive adhesive layer), and PET resins are particularly preferable from the viewpoint of strength and workability.

  Various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, etc., may be added to the resin film layer as necessary. May be blended. The blending ratio of various additives is usually less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

  As the resin film layer, a transparent film (typically a transparent resin film) can be preferably employed. Such a resin film layer may be substantially free of colorant. Here, that the resin film layer substantially does not contain a colorant means that the content of the colorant is less than 1% by weight, preferably less than 0.1% by weight. Alternatively, the resin film layer in the technology disclosed herein is colored in black, white (for example, milky white) or other colors in order to express desired design properties and optical characteristics (for example, light shielding properties) in the pressure-sensitive adhesive sheet. May be. For the coloring, for example, a known organic or inorganic coloring agent (pigment, dye, etc.) may be blended with the material constituting the resin film layer. The resin film layer colored black can be a black layer.

  The resin film layer disclosed herein may have a single layer structure, or may have a multilayer structure of two layers, three layers or more. From the viewpoint of shape stability, the resin film layer preferably has a single layer structure. The method for producing the resin film layer is not particularly limited as long as a conventionally known method is appropriately adopted. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately employed.

  The surface of the resin film layer may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer (formation of a primer layer). Good. Such a surface treatment may be a treatment for improving the adhesion between the resin film layer and the pressure-sensitive adhesive layer and the adhesion between the resin film layer and the black layer. Note that the technology disclosed herein is such that an undercoat layer is not formed between the resin film layer and the pressure-sensitive adhesive layer and / or between the resin film layer and the black layer, and the resin film layer and the pressure-sensitive adhesive layer, and It can be preferably carried out in an embodiment in which the resin film layer and the black layer are in direct contact. The pressure-sensitive adhesive sheet having such a configuration can be thinner.

  The thickness of a resin film layer is not specifically limited, For example, it can be 30 micrometers or less. By reducing the thickness of the resin film layer, the pressure-sensitive adhesive sheet is also thinned, and as a result, the product to which the pressure-sensitive adhesive sheet is applied can be advantageous in terms of thinning, downsizing, lightening, and resource saving. Further, by reducing the thickness of the resin film layer, the heat dissipation efficiency of the heat dissipation sheet (typically a graphite sheet) can be improved. The thickness of the resin film layer is preferably 12 μm or less, more preferably 9 μm or less (for example, 7 μm or less, typically 5 μm or less). In the case where reduction in size, weight reduction, etc. are particularly important, the thickness of the resin film layer is particularly preferably 3 μm or less (for example, 2 μm or less). From the viewpoint of handling properties, processability, etc., the thickness of the resin film layer is preferably about 0.5 μm or more (for example, 1 μm or more).

(Matte layer)
The substrate disclosed herein preferably includes a matte layer. Thereby, the gloss value can be preferably adjusted to a desired range. Here, the matte layer refers to a layer that reduces gloss on the back surface of the pressure-sensitive adhesive sheet when the layer is formed. In addition, the presence or absence and the level of the gloss reduction can be grasped by the measurement of the 60 ° gloss value described above. Since the mat layer surface can be the back surface of the adhesive sheet, the 60 ° gloss value of the mat layer surface can take a value within the range indicated as the 60 ° gloss value of the back surface of the adhesive sheet.

  The mat layer disclosed herein can typically be a layer constituting the back surface of the pressure-sensitive adhesive sheet. In that case, a mat | matte layer may be arrange | positioned so that the surface of a black layer may be covered in an adhesive sheet. The mat layer is preferably provided on the outer surface of the black layer from the viewpoint of having a black layer protective function. Moreover, since the color tone and designability in the back surface side of an adhesive sheet depend on a black layer, it is preferable that a mat | matte layer is typically transparent (a semi-transparent is included). The mat layer may be a layer whose surface is subjected to a surface treatment such as embossing or sandblasting (a layer having a mat treatment surface), and is matte when formed on the surface of the black layer by coating or the like. It may be a mat layer having properties. The mat layer typically has a single layer structure, but may have a multilayer structure.

  The mat layer disclosed herein preferably has a matte property depending on its composition. For example, the mat layer can include a mat material. As a result, matte properties can be imparted without additional surface treatment. The mat material is typically in the form of particles and is preferably transparent (typically colorless and transparent). The particle shape of the mat material is not particularly limited, and may be a sphere or the like.

  The mat material may be either organic particles or inorganic particles, or a combination of both. Examples of the organic particles include acrylic resin particles such as polymethyl methacrylate particles, polystyrene particles, styrene-acrylic resin particles, polycarbonate particles, urethane resin beads, epoxy resin beads, polyester resin beads, and polyester. Examples include urethane resin beads. Examples of the inorganic particles include silicon dioxide (silica) particles, titanium dioxide particles, barium sulfate particles, calcium carbonate particles, mica, and talc. These may be used alone or in combination of two or more. Of these, acrylic resin particles, urethane resin beads, and silica particles are preferable.

  The average particle size of the mat material is not limited to a specific range because it is determined according to the required degree of matting, the thickness of the mat layer, etc., but it should be about 0.1 μm or more. It is suitable, and preferably 0.5 μm or more (for example, 1 μm or more, typically more than 1 μm). The average particle size is suitably 20 μm or less, and preferably about 8 μm or less (eg, 3 μm or less, typically 2 μm or less). The average particle diameter of the mat material is preferably half or more of the thickness of the mat layer, and is preferably equal to or greater than the thickness of the mat layer, from the viewpoint of sufficiently expressing the matte properties. From the viewpoint of appearance and coating properties, the average particle diameter of the mat material is preferably about 10 times or less (for example, 5 times or less, typically 3 times or less) of the thickness of the mat layer.

  The content of the mat material is not limited to a specific range because it is set according to the required level of matting or the particle size of the mat material, but is approximately 0.5% by weight or more in the mat layer. And preferably 1% by weight or more (for example, 2% by weight or more, typically 3% by weight or more). The content of the mat material is suitably about 40% by weight or less in the mat layer, and preferably 20% by weight or less (for example, 10% by weight or less, typically 8% by weight or less). .

  The mat layer may contain other additive components such as a resin component and a dispersant. When the mat layer is transparent, the mat layer is substantially free of colorant. Here, the fact that the mat layer does not substantially contain a colorant means that the content of the colorant is less than 1% by weight, preferably less than 0.1% by weight.

  Examples of the resin component contained in the mat layer include polyurethane resin, phenol resin, epoxy resin, urea melamine resin, silicone resin, phenoxy resin, methacrylic resin, acrylic resin, polyarylate resin, and polyester resin. Resin, polyolefin resin, polystyrene resin, styrene-acrylic resin, styrene-maleic acid resin, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, polyvinyl acetate, polychlorinated Examples include vinylidene, polycarbonate, celluloses, polyacetal, and alkyd resin. A resin component can be used individually by 1 type or in combination of 2 or more types. The resin composition for forming the mat layer (resin composition for forming the mat layer) can be a solvent-type composition, a thermosetting composition, or an ultraviolet curable composition. From the viewpoint, a thermosetting type or an ultraviolet curable type is preferable.

  A method for forming the mat layer using the mat layer forming composition is not particularly limited, and various printing methods can be employed. The printing method is not particularly limited, and various known or commonly used methods such as offset printing, silk screen printing, letterpress printing, flexographic printing, and gravure printing can be appropriately employed. Specifically, it is obtained by dissolving or dispersing a solid content (typically a resin component or a dispersant) constituting the above composition in an appropriate solvent, and employing an appropriate method among the above printing methods. The mat layer can be formed by printing the obtained composition on a black layer or a resin film layer.

  The thickness of the mat layer is suitably about 0.1 μm or more in consideration of imparting matte properties and coating properties, preferably about 0.2 μm or more (for example, 0.3 μm or more, typically Is 0.5 μm or more). From the viewpoint of thinning, the thickness is suitably about 5 μm or less, preferably about 3 μm or less (for example, 2 μm or less, typically 1.5 μm or less).

(Additional layer)
The base material disclosed here may have an additional layer in addition to the black layer, the resin film layer, and the mat layer. For example, the base material may have an additional top coat layer such as a chemical-resistant protective layer or a release treatment layer on the surface of the mat layer or in place of the mat layer. Such a topcoat layer can constitute the outermost surface (back surface of the pressure-sensitive adhesive sheet) of the substrate. In addition, from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet, it is preferable that there is no undercoat layer between the resin film layer and the black layer, or between the black layer and the matte layer. A layer or the like may be provided.

  The thickness (total thickness) of the substrate is not particularly limited, and can be about 100 μm or less. By reducing the thickness of the base material, the pressure-sensitive adhesive sheet is also thinned, and as a result, the product to which the pressure-sensitive adhesive sheet is applied can be advantageous in terms of thinning, downsizing, lightening, and resource saving. Further, by reducing the thickness of the base material, the heat dissipation efficiency of the heat dissipation sheet (typically a graphite sheet) can be improved. From the viewpoint of limiting the total thickness of the pressure-sensitive adhesive sheet to a predetermined value or less and obtaining high pressure-sensitive adhesive performance and the like, the thickness of the substrate is preferably 40 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less, and particularly preferably 12 μm. Hereinafter, it is more preferably 9 μm or less (for example, 7 μm or less, typically 5 μm or less). From the viewpoint of handling properties, workability, etc., the thickness of the substrate is usually about 2 μm or more, preferably 3 μm or more (for example, 3.5 μm or more).

<Adhesive layer>
In the technology disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The above-mentioned pressure-sensitive adhesives are various rubbery polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers and the like known in the field of pressure-sensitive adhesives. 1 type, or 2 types or more may be included as a base polymer. From the viewpoint of adhesive performance and cost, an adhesive containing an acrylic polymer or a rubber polymer as a base polymer can be preferably used. Of these, an adhesive (acrylic adhesive) having an acrylic polymer as a base polymer is preferable. Hereinafter, the pressure-sensitive adhesive layer constituted by the acrylic pressure-sensitive adhesive, that is, the pressure-sensitive adhesive sheet having the acrylic pressure-sensitive adhesive layer will be mainly described. The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein is constituted by the acrylic pressure-sensitive adhesive. It is not intended to be limited.

The “base polymer” of the pressure-sensitive adhesive refers to the main component of the rubbery polymer contained in the pressure-sensitive adhesive. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range near room temperature. Further, in this specification, “main component” refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.
The “acrylic polymer” refers to a polymer containing monomer units derived from a monomer having at least one (meth) acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth) acryloyl group in one molecule is also referred to as an “acrylic monomer”. Accordingly, the acrylic polymer in this specification is defined as a polymer including monomer units derived from an acrylic monomer. A typical example of the acrylic polymer is an acrylic polymer in which the proportion of the acrylic monomer in all monomer components used for the synthesis of the acrylic polymer is more than 50% by weight.
The term “(meth) acryloyl” means acryloyl and methacryloyl comprehensively. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acryl” generically means acrylic and methacryl.

  As the acrylic polymer, for example, a polymer of a monomer raw material that includes alkyl (meth) acrylate as a main monomer and can further include a submonomer copolymerizable with the main monomer is preferable. Here, the main monomer means a component occupying more than 50% by weight of the monomer composition in the monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, such a range of the number of carbon atoms may be expressed as “C _1-20 ”. From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive and the like, an alkyl (meth) acrylate that is a chain alkyl group in which R ² is C _1-14 (for example, C _2-10 , typically C _4-8 ) is used as a main monomer. It is appropriate to do. From the viewpoint of adhesive properties, the main monomer is alkyl acrylate (hereinafter, also simply referred to as C _4-8 alkyl acrylate) in which R ¹ is a hydrogen atom and R ² is a C _4-8 chain alkyl group. Is preferred.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. (Meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) Acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, And eicosyl (meth) acrylate. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

The proportion of alkyl (meth) acrylate in the total 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 further preferably 90% by weight or more. Although the upper limit of the ratio of alkyl (meth) acrylate is not particularly limited, it is usually preferably 99.5% by weight or less (for example, 99% by weight or less). Alternatively, the acrylic polymer may be obtained by polymerizing substantially only alkyl (meth) acrylate. Moreover, when using _C4-8 alkylacrylate as a monomer component, it is preferable that the ratio of _C4-8 alkylacrylate among the alkyl (meth) acrylate contained in this monomer component is 70 weight% or more, It is more preferably 90% by weight or more, and further preferably 95% by weight or more (typically 99 to 100% by weight). The technique disclosed herein can be preferably implemented in an embodiment in which 50% by weight or more (for example, 60% by weight or more, typically 70% by weight or more) of the total monomer components is BA. In a preferred embodiment, the total monomer component may further comprise 2EHA in a proportion less than BA.

  Monomers (other monomers) other than those described above may be copolymerized in the acrylic polymer in the technology disclosed herein within a range that does not significantly impair the effects of the present invention. The other monomers can be used for the purpose of adjusting the glass transition temperature (Tg) of the acrylic polymer, adjusting the adhesive performance (for example, peelability), and the like. Examples of monomers that can improve the cohesive strength and heat resistance of the pressure-sensitive adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, and aromatic vinyl compounds. Preferred examples of these include vinyl esters. Specific examples of vinyl esters include vinyl acetate (VAc), vinyl propionate, vinyl laurate, and the like. Of these, VAc is preferable.

Other monomers that can introduce a functional group that can serve as a cross-linking point to an acrylic polymer or contribute to an improvement in adhesive strength include a hydroxyl group (OH group) -containing monomer, a carboxy group-containing monomer, an acid anhydride group-containing monomer, and an amide. Examples thereof include a group-containing monomer, an amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, (meth) acryloylmorpholine, and vinyl ethers.
As a preferable example of the acrylic polymer in the technology disclosed herein, an acrylic polymer obtained by copolymerizing a carboxy group-containing monomer as the other monomer may be mentioned. Examples of carboxy group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Is done. Of these, AA and MAA are preferable.
As another preferred example, an acrylic polymer obtained by copolymerizing a hydroxyl group-containing monomer as the other monomer may be mentioned. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meta ) Hydroxyalkyl (meth) acrylates such as acrylate; polypropylene glycol mono (meth) acrylate; N-hydroxyethyl (meth) acrylamide and the like. Among these, a preferred hydroxyl group-containing monomer includes hydroxyalkyl (meth) acrylates in which the alkyl group is a straight chain having 2 to 4 carbon atoms.

The “other monomers” may be used alone or in combination of two or more. The total content of other monomers is preferably about 40% by weight or less (typically 0.001 to 40% by weight) of all monomer components, and is preferably about 30% by weight or less (typically 0.01%). -30% by weight, for example, 0.1-10% by weight) is more preferable.
When a carboxy group-containing monomer is used as the other monomer, the content is about 0.1% by weight or more (for example, 0.2% by weight or more, typically 0.5% by weight or more) of all monomer components. In addition, it is appropriate that the amount is about 10% by weight or less (for example, 8% by weight or less, typically 5% by weight or less). When a hydroxyl group-containing monomer is used as the other monomer, the content should be about 0.001% by weight or more (for example, 0.01% by weight or more, typically 0.02% by weight or more) of all monomer components. It is appropriate that the amount is 10% by weight or less (for example, 5% by weight or less, typically 2% by weight or less).

  The copolymer 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 (eg, −60 ° C. or higher and −25 ° C. or lower), more preferably −40 ° C. or lower (eg, −60 ° C. or higher and −40 ° C. or lower). Setting the Tg of the acrylic polymer to be equal to or lower than the above-described upper limit value is preferable from the viewpoint of workability for attaching the adhesive sheet.

The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of monomers used for the synthesis of the polymer). Here, the Tg of the acrylic polymer refers to a Tg determined by the Fox formula based on the composition of the monomer component used for the synthesis of the polymer. The formula of Fox is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1 / Tg = Σ (Wi / Tgi)
In the above Fox equation, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for the calculation of Tg, the values described in known materials are used. For example, for 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 ℃
Methyl methacrylate 105 ° C
2-hydroxyethyl acrylate -15 ° C
4-hydroxybutyl acrylate -40 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

  For the glass transition temperatures of homopolymers other than those exemplified above, the values described in the “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) are used. The highest value is adopted for the monomer whose values are described in this document.

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, a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser is charged with 100 parts by weight of monomer, 0.2 part by weight of 2,2′-azobisisobutyronitrile and acetic acid as a polymerization solvent. 200 parts by weight of ethyl is added and stirred for 1 hour while flowing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and shear strain at a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name “ARES”). Temperature range -70 ° C. to 150 ° C., the viscoelasticity is measured by a shear mode at a heating rate of 5 ° C./min, and the temperature corresponding to the peak top temperature of the shear loss elastic modulus G ″ (G ″ curve is The maximum temperature) is defined as the Tg of the homopolymer.

  The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthetic methods for acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. Can be adopted as appropriate. For example, a solution polymerization method can be preferably used. As a monomer supply method when performing solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided supply (dropping) method, or the like that supplies all monomer raw materials at once can be appropriately employed. The polymerization temperature can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, and the like, and can be, for example, about 20 ° C. or higher (typically 40 ° C. or higher). It can be set to about ℃ or less (typically 140 ℃ or less). In a preferred embodiment, a polymerization temperature of about 75 ° C. or less (more preferably about 65 ° C. or less, for example, about 45 ° C. to 65 ° C.) can be employed.

  The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane, etc. Halogenated alkanes; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one kind of solvent or two or more kinds of mixed solvents can be used.

  The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of the polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of the polymerization initiator include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds And the like. Still another example of the polymerization initiator includes a redox initiator based on a combination of a peroxide and a reducing agent. Such a polymerization initiator can be used individually by 1 type or in combination of 2 or more types. The amount of the polymerization initiator used may be a normal amount, for example, about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) with respect to 100 parts by weight of all monomer components. You can choose from a range.

  According to the solution polymerization, a polymerization reaction liquid in a form in which an acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the technology disclosed herein may be formed from a pressure-sensitive adhesive composition containing the above-mentioned polymerization reaction liquid or an acrylic polymer solution obtained by subjecting the reaction liquid to an appropriate post-treatment. As said acrylic polymer solution, what prepared the said polymerization reaction liquid to the appropriate viscosity (concentration) as needed can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (for example, emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used. Good.

The weight average molecular weight (Mw) of the base polymer (preferably acrylic polymer) in the technique disclosed herein is not particularly limited, and may be, for example, in the range of 10 × 10 ^{4 to} 500 × 10 ⁴ . From the viewpoint of adhesive performance, the Mw of the base polymer is preferably in the range of 10 × 10 ⁴ or more (for example, 20 × 10 ⁴ or more, typically 35 × 10 ⁴ or more), and 150 × 10 ⁴ or less ( For example, it is preferably in the range of 75 × 10 ⁴ or less, typically 65 × 10 ⁴ or less. Here, Mw refers to a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used.

  The pressure-sensitive adhesive in the technology disclosed herein can be a composition containing a tackifying resin. The tackifying resin is not particularly limited. For example, rosin tackifying resin, terpene tackifying resin, hydrocarbon tackifying resin, epoxy tackifying resin, polyamide tackifying resin, elastomer tackifying resin, Various tackifying resins such as a phenolic tackifying resin and a ketone tackifying resin can be used. Such tackifier resin can be used individually by 1 type or in combination of 2 or more types. When an acrylic polymer is employed as the base polymer, it is preferable to use a rosin tackifier resin.

  Examples of rosin-based tackifier resins include gum rosin, wood rosin, tall rosin and other unmodified rosins (raw rosin); these unmodified rosins modified by hydrogenation, disproportionation, polymerization, etc. Rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc. The same shall apply hereinafter); other various rosin derivatives. Examples of the rosin derivative include rosins such as those obtained by esterifying an unmodified rosin with an alcohol (that is, an esterified product of rosin) and those obtained by esterifying a modified rosin with an alcohol (that is, an esterified product of a modified rosin). Esters: Unmodified rosins and modified rosins modified with unsaturated fatty acids Unsaturated fatty acid modified rosins; Unmodified rosins, modified rosins, unsaturated rosin esters modified with unsaturated fatty acids Rosin alcohols obtained by reducing carboxyl groups in fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin and various rosin derivatives; rosins (Unmodified rosin, modified rosin, various rosin derivatives, etc.) Rosin phenol resins obtained by thermal polymerization by adding Lumpur acid catalyst; and the like.

  The softening point (softening temperature) of the tackifying resin used is not particularly limited. For example, those having a softening point of about 100 ° C. or higher (preferably about 120 ° C. or higher) can be preferably used. A rosin tackifying resin having such a softening point (for example, an esterified product of polymerized rosin) can be preferably used. The upper limit of the softening point of the tackifying resin is not particularly limited, and can be about 200 ° C. or lower (typically about 180 ° C. or lower, for example, about 150 ° C. or lower). In addition, the softening point of the tackifier resin here is defined as a value measured by a softening point test method (ring and ball method) defined in either JIS K 5902 or JIS K 2207.

  The amount of the tackifying resin used is not particularly limited, and can be appropriately set according to the target adhesive performance (peel strength, etc.). For example, it is preferable to use the tackifier resin at a ratio of about 10 parts by weight or more (more preferably 15 parts by weight or more, more preferably 20 parts by weight or more) with respect to 100 parts by weight of the base polymer. It is preferable to use it at a ratio of not more than parts (more preferably not more than 80 parts by weight, still more preferably not more than 60 parts by weight).

  In the technology disclosed herein, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may contain a crosslinking agent as necessary. The kind in particular of a crosslinking agent is not restrict | limited, It can select from a conventionally well-known crosslinking agent suitably and can be used. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxides. Examples of the crosslinking agent include a metal chelate crosslinking agent, a metal salt crosslinking agent, a carbodiimide crosslinking agent, and an amine crosslinking agent. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Among these, from the viewpoint of improving cohesive strength, the use of an isocyanate-based crosslinking agent and / or an epoxy-based crosslinking agent is preferable, and the use of an isocyanate-based crosslinking agent is particularly preferable. The amount of the crosslinking agent used is not particularly limited. For example, the amount can be about 10 parts by weight or less, preferably about 0.005 to 10 parts by weight, more preferably about 0.01 to 5 parts by weight with respect to 100 parts by weight of the base polymer (preferably an acrylic polymer). You can select from a range of parts.

  The pressure-sensitive adhesive layer in the technology disclosed herein may be colored in order to express desired design properties and optical properties (for example, light shielding properties). For this coloring, one or more known organic or inorganic coloring agents (pigments, dyes, etc.) can be used in appropriate combination. For example, by including a black colorant such as carbon black in the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer can be colored black. Content of a coloring agent is not specifically limited, For example, it can be made into less than 15 weight part with respect to 100 weight part of base polymers. From the viewpoint of suppressing the deterioration of the adhesive properties, the content of the colorant may be less than 10 parts by weight (for example, less than 5 parts by weight, typically less than 3 parts by weight) with respect to 100 parts by weight of the base polymer. preferable. The technique disclosed here can be preferably implemented in a mode in which the pressure-sensitive adhesive layer substantially does not contain inorganic and organic colorants from the viewpoint of pressure-sensitive adhesive performance. For example, it can be preferably implemented in an embodiment in which the content of the colorant is 0 to 1 part by weight with respect to 100 parts by weight of the base polymer.

  The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition such as a leveling agent, a crosslinking aid, a plasticizer, a softening agent, an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, or a light stabilizer, if necessary. Various additives generally used in the field of products may be contained. About such various additives, conventionally well-known things can be used by a conventional method, and since it does not characterize this invention in particular, detailed description is abbreviate | omitted.

  The pressure-sensitive adhesive layer (layer made of pressure-sensitive adhesive) disclosed herein is formed from a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, and an active energy ray-curable pressure-sensitive adhesive composition. It can be an adhesive layer. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer forming component) in a water-based solvent (water-based solvent), and is typically dispersed in water. What is called a type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like are included. Moreover, a solvent-type adhesive composition means the adhesive composition of the form which contains an adhesive in an organic solvent. The technique disclosed here can be preferably implemented in an aspect including a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition from the viewpoint of pressure-sensitive adhesive properties and the like.

  The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method (direct method) of forming the pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to the substrate as described above and drying it can be employed. Also, a method for forming a pressure-sensitive adhesive layer on the surface by applying a pressure-sensitive adhesive composition to a surface having a peelable property (peeling surface) and drying it, and transferring the pressure-sensitive adhesive layer to a substrate (transfer method) May be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of the release liner, the back surface of the substrate after the release treatment, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, for example, a regular or random pattern such as a dot or stripe. The formed adhesive layer may be sufficient.

The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating.
From the viewpoint of promoting the crosslinking reaction and improving the production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. A drying temperature can be about 40-150 degreeC, for example, and it is preferable to usually be about 60-130 degreeC. After drying the pressure-sensitive adhesive composition, it may be further aged for the purpose of adjusting component migration in the pressure-sensitive adhesive layer, progress of the crosslinking reaction, relaxation of strain that may exist in the base material or pressure-sensitive adhesive layer, etc. Good.

  The thickness of the pressure-sensitive adhesive layer disclosed herein is not particularly limited and can be appropriately selected depending on the purpose. Usually, from the viewpoint of productivity such as drying efficiency and adhesive performance, about 1 μm or more (for example, 2 μm or more, typically 4 μm or more) is appropriate, and 200 μm or less (for example, 140 μm or less, typically 80 μm or less) is appropriate. From the viewpoint of limiting the total thickness of the pressure-sensitive adhesive sheet, the thickness is preferably about 1 to 40 μm, more preferably 1.2 to 30 μm (for example, 20 μm or less, typically 10 μm or less). The technique disclosed herein can also be carried out in an embodiment in which the thickness of the pressure-sensitive adhesive layer is 5 μm or less (further 3 μm or less). The thin pressure-sensitive adhesive layer is advantageous in terms of reducing the thickness, reducing the size, reducing the weight, and saving resources of the pressure-sensitive adhesive sheet. Moreover, it is preferable that an adhesive layer is thin from a viewpoint of the thermal radiation efficiency by a graphite sheet.

<Release liner>
In the technology disclosed herein, a release liner can be used in forming the pressure-sensitive adhesive layer, preparing the pressure-sensitive adhesive sheet, storing the pressure-sensitive adhesive sheet before use, distributing it, and processing the shape. The release liner is not particularly limited. For example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluoropolymer (polytetrafluoroethylene, etc.), a polyolefin resin (polyethylene, A release liner made of a low adhesion material such as polypropylene can be used. The release treatment layer may be formed, for example, by surface-treating the liner base material with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. The release liner used for a single-sided adhesive sheet is typically configured such that the surface that contacts the adhesive surface of the adhesive sheet is a peelable surface (peeled surface), and the other surface is a non-peeled surface. It can be. The thickness (total thickness) of the release liner is not particularly limited, but is preferably about 10 μm or more (for example, 15 μm or more), and preferably 500 μm or less (for example, 100 μm or less) from the viewpoints of release workability, handleability, strength, and the like. It is preferable to set the degree.

<Application>
The pressure-sensitive adhesive sheet disclosed herein is used by being attached to a graphite sheet. The graphite sheet is preferably used in various small electronic devices as a heat radiating sheet for releasing heat from a heat generating element (battery, IC chip, etc.). For example, the graphite sheet is disposed at a position adjacent to a power generation element such as a battery or an IC chip in the electronic device or around the power generation element. Such a graphite sheet has uneven appearance, and thin ones are easily damaged. Therefore, an adhesive sheet is attached to the surface for the purpose of improving the appearance and protecting the graphite sheet. By applying the pressure-sensitive adhesive sheet disclosed herein to a graphite sheet, improvement in appearance quality is preferably realized. Also, those with a predetermined color (low brightness, chromaticity) and gloss value on the back of the adhesive sheet can exhibit a profound black color with reduced gloss, so it is good with the color of the graphite sheet and its peripheral members. It can be harmonious. Furthermore, according to the pressure-sensitive adhesive sheet having a light transmittance within a predetermined range, the color tone of the graphite sheet can be moderately reflected on the outer surface, and desired color tone, texture, and design can be imparted. Although not particularly limited, the pressure-sensitive adhesive sheet disclosed herein is a graphite sheet having a thickness of 4 to 100 μm and / or an arithmetic average surface roughness Ra of 0.005 to 5 μm. Preferably applied.

  The pressure-sensitive adhesive sheet disclosed herein can be preferably applied to portable electronic device applications. For example, mobile phones, smartphones, tablet computers, laptop computers, various wearable devices (for example, wristwear devices that are worn on the wrist like wristwatches, modular devices that are worn on a part of the body with clips, straps, etc.) (Eyewear type including monocular type and binocular type, including head mounted type), clothing type attached to shirts, socks, hats, etc. in the form of accessories, earwear type attached to ears like earphones, etc.), Digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game machines, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information equipment, portable radios, portable TVs, mobile phones Protection and design of components in portable electronic devices such as printers, portable scanners, and portable modems It may be preferably used for the purpose of imparting the like. In this specification, “carrying” means that it is not sufficient to be able to carry it alone, but that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. Shall mean.

The matters disclosed by this specification include the following.
(1) A single-sided adhesive sheet used by being attached to a graphite sheet,
A base material, and a pressure-sensitive adhesive layer provided on one surface of the base material,
The substrate includes a black layer;
The 60 ° gloss value on the back of the adhesive sheet is 10 or less,
The pressure-sensitive adhesive sheet has a light transmittance of 12 to 30%.
(2) The base material includes a resin film layer and a black layer,
The said adhesive sheet is an adhesive sheet as described in said (1) with which the said adhesive layer, the said resin film layer, and the said black layer are laminated | stacked in this order.
(3) The adhesive sheet according to (2), wherein the black layer has a thickness of 2 μm or less.
(4) The pressure-sensitive adhesive sheet according to (2) or (3) above, wherein the back surface of the pressure-sensitive adhesive sheet has a lightness L ^* defined by the L ^* a ^* b ^* color system of 40 or less.
(5) The base material further includes a mat layer,
The said base material is an adhesive sheet in any one of said (2)-(4) which has the laminated structure by which the said resin film layer, the said black layer, and the said mat | matte layer were laminated | stacked in this order.
(6) The adhesive sheet according to (5), wherein the mat layer includes a particulate mat material.
(7) The pressure-sensitive adhesive sheet according to (5) or (6), wherein the mat layer has a thickness of 2 μm or less.
(8) The adhesive sheet in any one of said (1)-(7) whose total thickness of the said adhesive sheet is 30 micrometers or less.
(9) A pressure-sensitive adhesive sheet with a release liner, comprising the pressure-sensitive adhesive sheet according to any one of (1) to (8) above and a release liner that protects the adhesive surface of the pressure-sensitive adhesive sheet.
(10) The pressure-sensitive adhesive sheet according to any one of (1) to (8), which is disposed in a portable electronic device.

(11) The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion exceeding 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer has a formula (1):
CH ₂ = C (R ¹ ) COOR ² (1)
(R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms.) An alkyl (meth) acrylate represented by: The pressure-sensitive adhesive sheet according to any one of (1) to (10), which is contained at a ratio of 70% by weight or more.
(12) The alkyl (meth) acrylate includes methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s -Butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate , Nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate , Tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate and eicosyl (meth) acrylate The pressure-sensitive adhesive sheet according to (11), which is at least one selected from the group consisting of:
(13) The pressure-sensitive adhesive sheet according to (11) or (12), wherein the alkyl (meth) acrylate is n-butyl acrylate and 2-ethylhexyl acrylate.
(14) The alkyl (meth) acrylate is n-butyl acrylate and 2-ethylhexyl acrylate, and the 2-ethylhexyl acrylate is contained in the monomer component in a smaller proportion than the n-butyl acrylate (11) -The adhesive sheet in any one of (13).
(15) The acrylic polymer further includes a functional group-containing monomer as the monomer component,
The functional group-containing monomers include acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4 -The adhesive sheet in any one of said (11)-(14) which is at least 1 sort (s) selected from the group which consists of hydroxybutyl (meth) acrylate.
(16) The pressure-sensitive adhesive layer contains, as a tackifier resin, a rosin-based tackifier resin having a softening point of 100 ° C or higher and 180 ° C or lower,
Content of the said tackifying resin is an adhesive sheet in any one of said (1)-(15) which is 20-60 weight part with respect to 100 weight part of base polymers of the said adhesive layer.
(17) The adhesive sheet according to any one of (1) to (16), wherein the base material includes a polyethylene terephthalate resin film layer.
(18) The pressure-sensitive adhesive sheet according to any one of (1) to (17), wherein the black layer contains carbon black as a black pigment.
(19) The pressure-sensitive adhesive sheet according to any one of (1) to (18), wherein the base material has a thickness of 9 μm or less.

(20) A single-sided adhesive sheet used by being attached to a graphite sheet disposed in a portable electronic device,
A base material, and a pressure-sensitive adhesive layer provided on one surface of the base material,
The base material has a laminated structure in which a resin film layer, a black layer, and a mat layer are laminated in this order,
The 60 ° gloss value on the back of the adhesive sheet is 10 or less,
The light transmittance of the adhesive sheet is 12-30%,
The back surface of the pressure-sensitive adhesive sheet has a lightness L ^* defined by L ^* a ^* b ^* color system of 40 or less,
The black layer has a thickness of 2 μm or less,
The mat layer includes a particulate mat material,
The mat layer has a thickness of 2 μm or less,
The total thickness of the adhesive sheet is 30 μm or less,
The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion exceeding 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer contains, as a monomer component, alkyl (meth) acrylate in a proportion of 70% by weight or more,
The alkyl (meth) acrylate is n-butyl acrylate and 2-ethylhexyl acrylate, and 2-ethylhexyl acrylate is contained in the monomer component in a smaller proportion than n-butyl acrylate,
The acrylic polymer further includes a functional group-containing monomer as the monomer component,
The functional group-containing monomers include acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4 -At least one selected from the group consisting of hydroxybutyl (meth) acrylate,
The pressure-sensitive adhesive layer includes, as a tackifying resin, a rosin-based tackifying resin having a softening point of 100 ° C. or higher and 180 ° C. or lower,
The content of the tackifying resin is 20 to 60 parts by weight with respect to 100 parts by weight of the base polymer of the pressure-sensitive adhesive layer,
The resin film layer is a polyethylene terephthalate resin film layer,
The black layer includes carbon black as a black pigment,
The adhesive sheet has a thickness of 9 μm or less.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

<Example 1>
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 70 parts of BA as monomer components, 27 parts of EHA, 3 parts of AA and 0.05 parts of 4-hydroxybutyl acrylate, and a polymerization solvent The toluene was charged with 135 parts of toluene and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.1 part of AIBN as a polymerization initiator was added, and solution polymerization was performed at 60 ° C. for 6 hours to obtain a toluene solution of an acrylic polymer. Mw of this acrylic polymer was about 40 × 10 ⁴ .
For 100 parts of the acrylic polymer contained in the toluene solution, 30 parts of a polymerized rosin ester (trade name “Pencel D-125”, softening point 120 to 130 ° C., manufactured by Arakawa Chemical Industries, Ltd.) as the tackifier resin and isocyanate-based crosslinking 2 parts of an agent (trade name “Coronate L”, manufactured by Tosoh Corporation, solid content 75%) was added to prepare an acrylic pressure-sensitive adhesive composition.

As a release liner, a polyester release film (trade name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) having a release surface on one side was prepared. The pressure-sensitive adhesive composition was applied to the release surface of the release liner so that the thickness after drying was 2 μm, and dried at 100 ° C. for 2 minutes. Thus, an adhesive layer was formed on the release surface of the release liner.
Next, a black printed layer having a thickness of about 1 μm is formed on one side (second surface) of a transparent PET film having a thickness of 2 μm (trade name “Mylar”, manufactured by Teijin DuPont Films Ltd.). A black printed layer-formed PET film (matte layer-forming substrate) on which a mat layer having a thickness of about 1 μm was formed was prepared. The mat layer is formed by adding a mat material to a resin material and mixing the mixture to form a mat layer forming composition on the surface of the black print layer. This is a company-made material.
The pressure-sensitive adhesive layer formed on the release liner was bonded to the surface of the mat layer-forming substrate on the PET film side (first surface of the PET film layer) to produce a pressure-sensitive adhesive sheet according to this example (transfer method) . The release liner was left on the pressure-sensitive adhesive layer as it was and used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer.

<Example 2>
Change the composition of the black print layer (change of resin type, amount of black pigment used, etc.) and the composition of the mat layer (specifically, amount of mat material used, etc.) so that the gloss and color tone on the back of the adhesive sheet change. Otherwise, the pressure-sensitive adhesive sheet according to this example was produced in the same manner as Example 1.

<Example 3>
A pressure-sensitive adhesive sheet according to this example was produced basically in the same manner as in Example 2 except that the mat layer was not formed.

<Example 4>
The same composition as the mat layer forming composition used in Example 2 was prepared except that it did not contain a mat material, and this mat material-free composition was used to form a non-mat on the black printed layer surface of the black printed layer-formed PET film. A layer (topcoat layer) was formed. Otherwise, the pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 2.

[Evaluation]
With respect to the pressure-sensitive adhesive sheet of each example, the back surface 60 ° gloss value, the back surface lightness L ^* , the chromaticity a ^* and the chromaticity b ^* , the light transmittance (%), and the 180 ° peel strength (N / 20 mm) were measured. The results are shown in Table 1.

[Defect detectability]
The pressure-sensitive adhesive sheet according to each example prepared above was attached to a commercially available graphite sheet (trade name “Graphinity 25 μm”, manufactured by Kaneka Corporation, thickness 25 μm), and the light box (trade name “Product name“ HF-SL-A48LCG ”(manufactured by Dentsu Sangyo Co., Ltd.). Then, the graphite sheet was visually inspected through the adhesive sheet, and the ease of detection of defects (specifically, pinholes and the like) was evaluated based on the following two criteria.
○: Defect detection work could be performed efficiently.
X: It was difficult to detect a defect.
The results are shown in Table 1.

[appearance]
The pressure-sensitive adhesive sheet according to each example prepared above was attached to a commercially available graphite sheet (trade name “Graphinity 25 μm”, manufactured by Kaneka Corporation, thickness 25 μm), and the appearance from the back side of the pressure-sensitive adhesive sheet was evaluated by 10 panelists. . In all cases, no poor appearance was observed, and the appearance was generally good. Therefore, in order to give superiority or inferiority, evaluation was performed in three stages of 1 to 3. Those having the best appearance were scored 3 points, then those having good appearance were scored 2 points, and those having the least appearance were scored 1 point. The results are shown in Table 1.

As shown in Table 1, in the pressure-sensitive adhesive sheet including the base material including the black layer, the 60 ° gloss value on the back surface of the pressure-sensitive adhesive sheet is 10 or less, and the light transmittance is 12 to 30%. ° Defect detection was superior to other examples that do not satisfy the gloss value or light transmittance. This result is considered to be due to the fact that the influence of reflection of room light could be suppressed in addition to the improvement of the detectability through the adhesive sheet due to the high light transmittance. Further, the pressure-sensitive adhesive sheet according to Example 1 obtained the most excellent evaluation in appearance evaluation. This is thought to be largely due to the color of the black layer, the transparency of the graphite sheet through the adhesive sheet, and the addition of a heavy feeling due to the lower back gloss.
From the above results, the back surface 60 ° gloss value is 10 or less, the light transmittance is 12 to 30%, and the base material has an excellent appearance according to the pressure-sensitive adhesive sheet containing a black layer, and has defects, etc. It can be seen that an adhesive sheet for graphite sheets with improved detection accuracy is realized.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 1 Adhesive sheet 1A Adhesive surface 1B Back surface 10 Base material 10A One surface of a base material (adhesive layer side surface)
10B The other surface of the substrate (the back side surface)
12 Resin Film Layer 12A First Surface 12B of Resin Film Layer Second Surface 14 of Resin Film Layer Black Layer 16 Mat Layer 20 Adhesive Layer 50 Release Liner

Claims (10)

A single-sided adhesive sheet used by being attached to a graphite sheet,
A base material, and a pressure-sensitive adhesive layer provided on one surface of the base material,
The substrate includes a black layer;
The 60 ° gloss value on the back of the adhesive sheet is 10 or less,
The pressure-sensitive adhesive sheet has a light transmittance of 12 to 30%. The base material includes a resin film layer and a black layer,
The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet, the resin film layer, and the black layer are laminated in this order.   The pressure-sensitive adhesive sheet according to claim 2, wherein the black layer has a thickness of 2 μm or less. The pressure-sensitive adhesive sheet according to claim 2 or 3, wherein the back surface of the pressure-sensitive adhesive sheet has a lightness L ^* defined by an L ^* a ^* b ^* color system of 40 or less. The base material further includes a mat layer,
The pressure-sensitive adhesive sheet according to any one of claims 2 to 4, wherein the base material has a laminated structure in which the resin film layer, the black layer, and the mat layer are laminated in this order.   The pressure-sensitive adhesive sheet according to claim 5, wherein the mat layer includes a particulate mat material.   The pressure sensitive adhesive sheet according to claim 5 or 6 whose thickness of said mat layer is 2 micrometers or less.   The total thickness of the said adhesive sheet is an adhesive sheet as described in any one of Claims 1-7 which is 30 micrometers or less.   A pressure-sensitive adhesive sheet with a release liner, comprising the pressure-sensitive adhesive sheet according to any one of claims 1 to 8 and a release liner that protects the adhesive surface of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, which is disposed in a portable electronic device.

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