JP2014234493A - Adhesive sheet and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet which is resistant to cracking even when folded and is excellent in thermal conductivity and an electronic apparatus adhered with the adhesive sheet.SOLUTION: An adhesive sheet consists of an adhesive layer (A) laminated on one or both sides of a metal substrate (B) which is composed of a laminate of two or more metal substrates (b1). An electronic apparatus adhered with the adhesive sheet is also provided.

Description

  The present invention relates to a pressure-sensitive adhesive sheet that can be used for fixing various members such as an electronic device, particularly a heat generating member.

  In recent years, along with the downsizing, thinning, and high performance of electronic devices such as communication devices, higher integration of members constituting them has been progressing. Since various members are arranged in a limited space without gaps inside the highly integrated device, the electronic device itself may be relatively hot due to heat generated by the member. . In particular, mobile devices such as mobile phones and smartphones tend to store heat, and the heat may cause malfunctions such as causing the mobile device to malfunction.

As a method of dissipating heat from the inside of the electronic device, a method of connecting a heat generating member and a heat receiving member with a heat conductive sheet is known, and as the heat conductive sheet, for example, a graphite sheet and a specific heat A thermal diffusion sheet in which a conductive adhesive layer is laminated is known (see Patent Document 1).
However, since the graphite sheet constituting the heat diffusion sheet is relatively brittle and may cause cracking when bent, the heat diffusion sheet is folded in a limited space inside an electronic device or the like. It was sometimes difficult to place them. In addition, the heat diffusion sheet that causes cracks or the like may not be able to efficiently conduct heat from the heat generating portion to the heat radiating portion.

JP2013-102180A

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive sheet that is less likely to cause cracking or the like even when bent, and has excellent thermal conductivity, and an electronic device to which the pressure-sensitive adhesive sheet is attached. is there.

  The pressure-sensitive adhesive sheet is characterized in that the pressure-sensitive adhesive layer (A) is laminated on one side or both sides of a metal substrate (B) comprising a laminate of two or more metal substrates (b1). It is about.

  The pressure-sensitive adhesive sheet of the present invention is less susceptible to cracking even when bent into an arbitrary shape, has excellent thermal conductivity, and is a pressure-sensitive adhesive tape resulting from the repulsive force of the metal base material when bent Therefore, it can be used exclusively for connection between various heat generating members and heat radiating members constituting electronic devices such as mobile devices.

It is the conceptual diagram which looked at the apparatus and test tape which were used by the thermal conductivity evaluation test from the side. It is the conceptual diagram which looked at the apparatus and metal base material which were used in the evaluation test of bending strength from the side. It is a conceptual diagram of the measurement chart obtained by the bending strength evaluation test.

  The pressure-sensitive adhesive sheet of the present invention is characterized in that the pressure-sensitive adhesive layer (A) is laminated on one side or both sides of a metal substrate (B) composed of a laminate of two or more metal substrates (b1). To do. Since the pressure-sensitive adhesive sheet has excellent thermal conductivity, it efficiently guides heat from the heat generating portion to the metal base material constituting the pressure-sensitive adhesive tape, and further efficiently dissipates heat from the metal base material to the heat receiving member. Can be made.

  In addition, the pressure-sensitive adhesive sheet of the present invention can be bent into a predetermined shape even when a relatively thick metal base is used to improve thermal conductivity, and the pressure-sensitive adhesive caused by the repulsive force of the metal base. It is difficult to cause peeling of the sheet.

  As the pressure-sensitive adhesive sheet of the present invention, it is possible to use one having a bending strength in the range of 0.1 N / 30 mm to 2 N / 30 mm, which can be used by being bent into an arbitrary shape, and due to the repulsive force of the metal substrate. It is preferable because it does not easily cause peeling of the adhesive sheet.

  In addition, the pressure-sensitive adhesive sheet of the present invention preferably has an elastic modulus in the range of 10 GPa to 200 GPa when bent into an arbitrary shape and used.

[Adhesive layer (A)]
The pressure-sensitive adhesive layer (A) constituting the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive layer formed using a conventionally known pressure-sensitive adhesive (A-1).

As the pressure-sensitive adhesive layer (A), in order to further improve the thermal conductivity of the adhesive sheet of the present ^invention, it has a thermal resistivity in the range of ^{0.1K · cm 2 / W~10K · cm} 2 / W it is preferred to use ^ones, it is more preferable to use those having a thermal resistivity in the range of ^{0.1K · cm 2 / W~5K · cm} 2 / W.

  The thermal conductivity of the pressure-sensitive adhesive layer (A) can be adjusted to the predetermined range by examining the thickness of the pressure-sensitive adhesive layer (A), the use of a heat conductive filler (a2) described later, and the like. it can.

  In addition, the adhesive layer (A) having electrical insulation as well as the predetermined thermal resistivity can prevent short-circuiting of parts that are a concern when used inside an electronic device. Therefore, it is preferable.

Specifically, the electrical insulation property is preferably such that the volume resistance value when applied with 500 V is 10 ¹³ Ω · cm or more, for example, 10 ¹⁴ Ω · cm or more. It is preferable for preventing a short circuit between the two.

  The pressure-sensitive adhesive layer (A) is, for example, a pressure-sensitive adhesive (A-1) containing various polymers, a crosslinking agent as necessary, an additive such as a heat conductive filler as necessary, and a solvent. Can be used. Hereinafter, the pressure-sensitive adhesive (A-1) will be described.

(Polymer)
As the polymer contained in the pressure-sensitive adhesive (A-1), for example, an acrylic polymer (a1), a rubber polymer, a silicone polymer, a urethane polymer, and the like can be used. Among them, the use of the acrylic polymer (a1) and the rubber polymer is less likely to cause peeling due to the influence of heat even when it is attached to a heat generating member, for example, and to the repulsive force of the metal substrate. It is preferable for obtaining a pressure-sensitive adhesive sheet that hardly causes peeling over time, and it is more preferable to use the acrylic polymer (a1) because the thermal conductivity can be further improved.

  As said acrylic polymer (a1), what is obtained by superposing | polymerizing vinyl monomers, such as a (meth) acryl monomer, can be used.

  As the (meth) acrylic monomer, for example, a (meth) acrylate having an alkyl group having 1 to 14 carbon atoms can be used as a main component.

  Examples of the (meth) acrylate having an alkyl group having 1 to 14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t -Butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. One kind or a combination of two or more kinds can be used. Among these, as the (meth) acrylate having 1 to 14 carbon atoms in the alkyl group, it is preferable to use (meth) acrylate having 4 to 12 carbon atoms in the alkyl group. It is more preferable to use a (meth) acrylate having a linear or branched structure having 4 to 9 carbon atoms, and using n-butyl acrylate or 2-ethylhexyl acrylate alone or in combination, For example, it is preferable for obtaining a pressure-sensitive adhesive sheet that is less likely to cause peeling due to the influence of heat and less likely to be peeled over time due to the repulsive force of the metal substrate even when attached to a heat generating member.

  The (meth) acrylate having 1 to 14 carbon atoms in the alkyl group is 80% by mass to 98.5% by mass with respect to the total mass of vinyl monomers used for the production of the acrylic polymer. It is preferable to use it in the range of 90 mass% to 98.5 mass%.

  As a vinyl monomer that can be used in the production of the acrylic polymer (a1), in addition to (meth) acrylates in which the alkyl group has 1 to 14 carbon atoms, peeling due to the influence of heat is possible. It is preferable to use a highly polar vinyl monomer in order to obtain a pressure-sensitive adhesive sheet that is difficult to cause and does not easily cause peeling over time due to the repulsive force of the metal substrate.

  As the highly polar vinyl monomer, a vinyl monomer having a carboxyl group, a vinyl monomer having a hydroxyl group, a vinyl monomer having an amide group, or the like can be used alone or in combination. Among these, the use of a vinyl monomer having a carboxyl group as the high-polarity vinyl monomer can prevent peeling due to heat and peeling over time due to the repulsive force of the metal substrate. It is preferable when obtaining an adhesive sheet.

  Examples of the vinyl monomer having a carboxyl group include acrylic acid, methacrylic acid, β-carboxyethyl (meth) acrylate, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, and ethylene oxide modified salt. Acid acrylate, etc. can be used, preferably acrylic acid or methacrylic acid is used, and acrylic acid is used, peeling due to the influence of heat and peeling over time due to the repulsive force of the metal substrate It is preferable for obtaining a pressure-sensitive adhesive sheet capable of preventing the above.

  The vinyl monomer having a carboxyl group is preferably used in the range of 1% by mass to 10% by mass with respect to the total mass of the vinyl monomers used for the production of the acrylic polymer. It is preferably used in the range of mass% to 6 mass%, more preferably in the range of 2 mass% to 4 mass%. Thereby, it is possible to obtain a pressure-sensitive adhesive sheet that has excellent initial adhesiveness and can prevent peeling due to the influence of heat and peeling over time due to the repulsive force of the metal substrate.

  In particular, when acrylic acid is used as the vinyl monomer having a carboxyl group, 1 mass of acrylic acid is used with respect to the total mass of vinyl monomers used in the production of the acrylic polymer (a1). % To 6% by mass is excellent in wettability and adhesive strength to metal substrates, and can prevent peeling due to heat and peeling over time due to the repulsive force of metal substrates It is preferable when obtaining a sheet.

  Examples of the vinyl monomer having a hydroxyl group that can be used for the highly polar vinyl monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. , 6-hydroxyhexyl (meth) acrylate and the like can be used.

  As the vinyl monomer having an amide group, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide and the like can be used.

  Examples of the highly polar vinyl monomer include vinyl acetate, ethylene oxide-modified succinic acid acrylate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid, 2-methoxyethyl (meth), in addition to those described above. Other highly polar vinyl monomers such as terminal alkoxy-modified (meth) acrylates such as acrylate and 2-phenoxyethyl (meth) acrylate can be used.

  The acrylic polymer (a1) can be produced by polymerizing the vinyl monomer by a known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these, the use of a solution polymerization method is preferable for improving the production efficiency of the acrylic polymer (a1).

  Examples of the solution polymerization method include a method in which the vinyl monomer, a polymerization initiator, and an organic solvent are mixed and stirred at a temperature of preferably 40 to 90 ° C. to cause radical polymerization.

If the acrylic polymer (a1) obtained by the above method is produced by, for example, a solution polymerization method, it may be in a state dissolved or dispersed in an organic solvent.
The weight average molecular weight of the acrylic polymer obtained by the above method is preferably in the range of 300,000 to 1,500,000, and more preferably in the range of 500,000 to 1,200,000.

  Moreover, as a rubber-type polymer which can be used for the said polymer, what is obtained by superposing | polymerizing vinyl monomers, such as styrene, isoprene, a butadiene, can be used, for example.

  The vinyl polymer may be a vinyl polymer obtained by random polymerization of the vinyl monomer, and may generally be a vinyl polymer having an AB block structure or an ABA block structure. Specifically, a polystyrene-polyisopyrene-polystyrene copolymer or the like can be used.

  The vinyl polymer can be produced by polymerizing the vinyl monomer by a known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method.

  Examples of the solution polymerization method include a method in which the vinyl monomer, a polymerization initiator, and an organic solvent are mixed and stirred at a temperature of preferably 40 to 90 ° C. to cause radical polymerization.

  The vinyl polymer obtained by the above method may be in a state dissolved or dispersed in an organic solvent, for example, when it is produced by a solution polymerization method.

  The weight average molecular weight of the vinyl polymer obtained by the above method is preferably in the range of 300,000 to 1,500,000, and more preferably in the range of 500,000 to 1,200,000.

(Crosslinking agent)
The pressure-sensitive adhesive layer (A) has a cross-linked structure formed by using a cross-linking agent, which further improves the cohesive force, and prevents the peeling due to the influence of heat and the repulsive force of the metal substrate. It is preferable when obtaining the adhesive sheet which can prevent the peeling with time. When forming the pressure-sensitive adhesive layer in which the crosslinked structure is formed, a pressure-sensitive adhesive (A-1) containing a combination of a crosslinking agent and a polymer such as the acrylic polymer (a1) is used. It is preferable.

  As the crosslinking agent, for example, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a chelate-based crosslinking agent, an aziridine-based crosslinking agent, and the like can be appropriately selected and used depending on the functional group of the polymer.

  The cross-linking agent may be mixed with a polymer such as the acrylic polymer (a1) or an organic solvent solution thereof and used as an adhesive (A-1) before being applied to the surface of the metal substrate. preferable.

  If the said acrylic polymer (a1) is used as said polymer, for example, the said crosslinking agent is used in the range from which the gel fraction of an adhesive layer (A) will be 25 mass%-65 mass%. It is more preferable that it is used in the range of 35% by mass to 60% by mass, and it is more preferable to use it in the range of 40% by mass to 55% by mass. In addition, a gel fraction points out the value computed by the method described in the Example of this-application specification.

(Additive)
As the pressure-sensitive adhesive (A-1) that can be used for forming the pressure-sensitive adhesive layer (A), in addition to the polymer and the crosslinking agent, those containing various additives can be used as necessary. .

  As the additive, for example, a tackifier resin can be used for the purpose of further improving the adhesive strength of the pressure-sensitive adhesive sheet of the present invention.

  Examples of the tackifying resin include rosin resins, terpene resins, aliphatic (C5) and aromatic (C9) petroleum resins, styrene resins, phenol resins, xylene resins, methacrylic resins, and the like. Can be used. Among these, as the tackifier, it is preferable to use a rosin resin, and it is more preferable to use a polymerized rosin resin.

  The tackifier resin is preferably used in the range of 10 to 50 parts by mass (solid content) with respect to 100 parts by mass (solid content) of a polymer such as a (meth) acrylic polymer.

  As the additive, in addition to the tackifier resin, it is preferable to use a thermally conductive filler (a2) for the purpose of further improving the thermal conductivity of the adhesive sheet. The heat conductive filler (a2) is not essential for forming the pressure-sensitive adhesive layer (A) having the predetermined thermal resistivity, but further improves the heat conductivity of the pressure-sensitive adhesive layer (A). It is preferable to use it when the thickness of the pressure-sensitive adhesive layer (A) is set to be relatively thick.

  Examples of the heat conductive filler (a2) include electrically insulating heat conductive fillers such as aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, and boron nitride; gold, silver, Conductive and thermally conductive fillers such as copper, nickel, aluminum, carbon, and graphite can be used.

  Especially, as the heat conductive filler (a2), use of an electrically insulating heat conductive filler promotes heat dissipation when used inside an electronic device, and shorts between components. It is more preferable to achieve both prevention and more preferable to use aluminum hydroxide and aluminum oxide.

  As the heat conductive filler (a2), a regular shape or an irregular shape can be used. Examples of the shape include a polygonal shape, a cubic shape, an elliptical shape, a spherical shape, a needle shape, a flat plate shape, a scale shape, and a mixture or aggregate thereof. Among them, the use of a relatively spherical one is preferable for forming the pressure-sensitive adhesive layer (A) having further excellent thermal conductivity because the pressure-sensitive adhesive layer (A) can be filled with high density.

  As a heat conductive filler (a2), what has the average particle diameter which is the average value of the width | variety used as the maximum according to the thickness of an adhesive layer (A) can be used. For example, in the case of a particulate heat conductive filler, those having an average particle diameter of 0.5 μm to 50 μm are preferably used, and those having 1 μm to 30 μm are more preferably used.

  The heat conductive filler (a2) is not an essential component, but, for example, when the pressure-sensitive adhesive layer (A) having a thickness exceeding about 30 μm is formed, the acrylic polymer contained in the pressure-sensitive adhesive layer (A). It is preferable to use in the range of 10% by mass to 300% by mass with respect to the total amount of (a1), more preferable to use in the range of 100% by mass to 300% by mass, and in the range of 200% by mass to 300% by mass. It is more preferable to use in. Therefore, also as an adhesive (A-1) used for formation of an adhesive layer (A), a heat conductive filler (a2) is used for the acrylic polymer (a1) contained in the said adhesive (A-1). It is preferable to use those contained in the same range as described above.

  In addition to those described above, the pressure-sensitive adhesive (A-1) used for forming the pressure-sensitive adhesive layer (A) is, as necessary, an adhesive deterioration preventing agent, a plasticizer, a softening agent, a metal deactivator, an oxidation agent. Those containing additives such as inhibitors, pigments and dyes can be used.

  As said adhesiveness fall prevention agent, a triazole type compound can be used, for example. As the triazole compound, benzotriazole, tolyltriazole and its potassium salt, 3- (N-salicyloyl) amino-1,2,4 triazole, 2- (2′-hydroxy-5methylphenyl) benzotriazole, and the like are used. Can do. Among them, it is preferable to use benzotriazole in order to prevent a decrease in adhesive strength.

The pressure-sensitive adhesive (A-1) that can be used for forming the pressure-sensitive adhesive layer (A) is a polymer such as the acrylic polymer (a1) or a mixture of the polymer and a solvent. It can manufacture by mixing additives, such as resin and a heat conductive filler (a2). In that case, a dissolver, a butterfly mixer, a BDM biaxial mixer, a planetary mixer, etc. can be used as needed, and it is preferable to use a dissolver and a butterfly mixer. In addition, it is preferable to mix and use a crosslinking agent with the said mixture, before apply | coating an adhesive to a base material etc.
Examples of the solvent that can be used for producing the pressure-sensitive adhesive (A-1) include various organic solvents such as toluene, ethyl acetate, methyl ethyl ketone, butyl acetate, hexane, acetone, cyclohexanone, 3-pentanone, and acetonitrile, and water. Can be used.

  The solid content of the pressure-sensitive adhesive (A-1) obtained by the above method is preferably in the range of 10% by mass to 70% by mass, more preferably in the range of 30% by mass to 65% by mass, and 40% by mass. More preferably, it is in the range of% to 55% by mass.

[Metal base material (B)]
As a metal base material (B) used for manufacture of the adhesive sheet of this invention, the laminated body obtained by laminating | stacking two or more metal base materials (b1) can be used. Specifically, two or more metal substrates (b1) that are the same or different may be bonded and laminated through, for example, an adhesive layer (b2).

  The thickness of the metal substrate (B) prevents excellent heat conductivity and peeling of the adhesive tape due to the repulsive force of the metal substrate (B), and easily bends into a predetermined shape. In obtaining a possible pressure-sensitive adhesive sheet, it is preferably in the range of 1 μm to 300 μm, more preferably in the range of 30 μm to 170 μm, and still more preferably in the range of 80 μm to 130 μm. Note that the thickness of the metal base material (B) obtained by laminating the metal base material (b1) via, for example, the pressure-sensitive adhesive layer (b2) includes the thickness of the pressure-sensitive adhesive layer (b2) constituting the metal base material (b2). Shall be.

  On the other hand, as the metal substrate (b1) constituting the metal substrate (B), one having a thickness in the range of 1 μm to 150 μm is preferably used, and one having a thickness in the range of 5 μm to 110 μm is used. It is more preferable to use a material having a range of 15 μm to 80 μm, and it is more preferable to use a material having a range of 30 μm to 50 μm. It is preferable in producing an adhesive tape that hardly causes peeling due to the repulsive force.

  As said metal base material (b1), gold, silver, copper, aluminum, nickel, iron, tin, these alloys etc. can be used, for example. Especially, it is preferable to use the base material which consists of copper, when manufacturing the adhesive tape excellent in thermal conductivity efficiently.

  Examples of the base material made of copper include a base material made of rolled copper and a base material made of electrolytic copper. However, the adhesive tape has excellent thermal conductivity and the repulsive force of the metal base material (B). It is preferable to use a base material made of rolled copper in order to produce a pressure-sensitive adhesive sheet that prevents peeling and the like and can be easily folded into a predetermined shape.

  As the metal substrate (b1), a metal substrate (B) obtained by using a combination of two or more different metal substrates (b1) among those described above may be used. It is preferable to use a metal substrate (B) obtained by using a combination of two or more metal substrates (b1), more preferably a substrate made of copper, more preferably a substrate made of rolled copper foil. It is possible to use a metal substrate (B) made of a laminate obtained by laminating two or more of the above, excellent thermal conductivity, peeling of the adhesive tape due to the repulsive force of the metal substrate (B), etc. It is preferable for producing a pressure-sensitive adhesive sheet that can be easily bent into a predetermined shape.

  As the metal substrate (B), using two or more of the metal substrates (b1) laminated via the pressure-sensitive adhesive layer (b2) can relieve stress when the pressure-sensitive adhesive sheet is folded. As a result, it is preferable because peeling of the adhesive tape due to the repulsive force of the metal substrate (B) can be further prevented.

As said adhesive layer (b2), the thing similar to what was illustrated as said adhesive layer (A) can also be used. Especially, it is preferable to use the adhesive layer (b2) whose storage elastic modulus (G ') in 25 degreeC is 10 < ⁵ > -10 < ⁷ > dyn / cm < ² >.

  As said adhesive layer (b2), the adhesive layer which consists of a single layer or a multilayer formed using an adhesive (b2-1) is mentioned. Moreover, as said adhesive layer (b2), the layer formed using the double-sided adhesive tape in which the adhesive layer formed using the adhesive (b2-1) was provided in both surfaces of the center core is mentioned. In particular, due to the repulsive force of the metal substrate (B), it is a layer formed using a double-sided adhesive tape in which an adhesive layer is provided on both sides of a resin film such as a polyethylene terephthalate film as the core. It is preferable because peeling of the adhesive tape can be further prevented.

  The said adhesive layer (b2) can use the thing similar to what was illustrated as said adhesive (A-1).

For example, the metal substrate (B) is coated on the surface of one metal substrate (b1) with a part of or all of the pressure-sensitive adhesive (b2-1) and, if necessary, dried. The other metal substrate (b1) can be placed on and pressure-bonded. When manufacturing what laminated | stacked three or more metal base materials (b1) as said metal base material (B), an adhesive (b2-1) is apply | coated to the metal base material surface by the same method as the above, The method of mounting and crimping | bonding another metal base material (b1) is mentioned. Alternatively, a transfer coating method may be used in which a pressure-sensitive adhesive is applied to a release liner, dried, and then bonded to a metal substrate.
Moreover, the said metal base material (B) affixes one adhesive surface of the double-sided adhesive tape provided with the said adhesive layer (b2) on a part or all of the surface of one metal base material (b1), for example. The other metal substrate (b1) can be placed on the other adhesive surface and crimped or the like. When manufacturing what laminated | stacked three or more metal base materials (b1) as said metal base material (B), a double-sided adhesive tape is used for the adhesive (b2-1) on the metal base material surface by the same method as the above. The method of sticking and mounting another metal base material (b1), and crimping | bonding is mentioned. Similarly, an adhesive tape consisting only of an adhesive layer without a core may be attached.

  The thickness of the pressure-sensitive adhesive layer (b2) is 1 μm to suppress excellent adhesiveness between the metal substrates (b1) and thermal conductivity due to the provision of the pressure-sensitive adhesive layer (b2). The thickness is preferably 60 μm, more preferably 3 μm to 35 μm, and still more preferably 5 μm to 20 μm. Moreover, the said adhesive layer (b2) may contain a heat conductive filler, when improving the heat conductivity further.

  The metal base material (B) obtained by the above method preferably has a bending strength in the range of 0.1 N / 30 mm to 2 N / 30 mm, for example.

  As said metal base material (B), it is preferable to use what has the antirust process on the surface.

  Examples of the rust prevention treatment include organic rust prevention treatment and inorganic rust prevention treatment. Among them, inorganic rust prevention treatment by chromate treatment is preferable.

(Method for producing adhesive sheet)
In the pressure-sensitive adhesive sheet of the present invention, for example, the pressure-sensitive adhesive (A-1) is applied to the surface of a release liner using a roll coater or a die coater, and the coating layer is dried in an environment of about 50 ° C to 120 ° C. Then, the adhesive layer (A) is formed by removing the solvent, and then the adhesive layer (A) is bonded to one or both surfaces of the previously produced metal substrate (B), and then necessary. Accordingly, the adhesive layer (A) can be produced by curing at a temperature of about 15 ° C. to 50 ° C. for about 48 hours to 168 hours so that the predetermined gel fraction is achieved.

  The pressure-sensitive adhesive layer (A) preferably has a thickness of 1 μm to 60 μm, more preferably 1 μm to 50 μm, and still more preferably 1 μm to 30 μm. By providing the pressure-sensitive adhesive layer (A) having the thickness in the above range, it is excellent in thermal conductivity, hardly causes peeling due to the influence of heat, and is caused by the repulsive force of the metal substrate (B). A pressure-sensitive adhesive sheet that hardly causes peeling over time can be produced.

  Examples of the release liner include paper such as kraft paper, glassine paper, and high-quality paper; resin films such as polyethylene, polypropylene (OPP, CPP), and polyethylene terephthalate; laminated paper in which the paper and the resin film are laminated, and the paper A material obtained by applying a release treatment such as a silicone-based resin to one or both surfaces of a material subjected to a sealing treatment with clay or polyvinyl alcohol can be used.

  The pressure-sensitive adhesive sheet obtained by the above method preferably has a total thickness of 360 m or less, preferably 205 μm or less, and more preferably 150 μm or less. The lower limit value of the total thickness of the pressure-sensitive adhesive sheet is preferably 30 μm or more.

  By using the adhesive sheet having the total thickness, it is difficult to cause peeling over time due to the repulsive force of the metal substrate (B), and the thermal conductivity can be improved. In addition, the total thickness of the said adhesive sheet refers to the thickness which does not contain the said release liner. Moreover, when the said adhesive sheet is what laminated | stacked the resin film (C) mentioned later, the said total thickness represents the thickness containing the thickness of the said resin film (C).

[Resin film (C)]
The pressure-sensitive adhesive tape of the present invention has the pressure-sensitive adhesive layer (A) on one side of the metal substrate (B) and a resin film (C on the other side for the purpose of preventing short-circuit between components. ) Can be used.

  The resin film (C) is preferably capable of forming an electrical insulating layer in order to prevent the short circuit.

Specifically, the electrical insulation of the resin film (C) is preferably such that the volume resistance value when applied with 500 V is 10 ¹³ Ω · cm or more, for example, 10 ¹⁴ Ω · cm or more. This is preferable for preventing a short circuit between components inside the electronic device.

Moreover, it is preferable that the said resin film (C) can form a heat insulation layer in order to conduct the heat | fever of a heat generating member to a heat receiving member efficiently. Specifically, the resin film (C) is preferably one having a 100K · ^cm 2 / W or more thermal ^resistance, in the range of ^{100K · cm 2 / W~500K · cm} 2 / W thermal More preferably, it has a resistivity.

  As the resin film (C), it is preferable to use a polyethylene terephthalate film (PET film) or the like.

  The resin film (C) preferably has a thickness in the range of 3 μm to 50 μm, more preferably in the range of 10 μm to 50 μm, and more preferably in the range of 10 μm to 30 μm. It is preferable to prevent the pressure-sensitive adhesive sheet from peeling off with time due to the repulsive force of the resin film (C).

  It is preferable that the said resin film (C) and the said metal base material (B) are laminated | stacked through the adhesive layer (c1). Specifically, an adhesive layer (c1) is formed in advance on one surface of the resin film (C), and then the adhesive layer (c1) and one surface of the metal substrate (B) are formed. They can be laminated by sticking.

  The pressure-sensitive adhesive sheet of the present invention obtained by the above method can be used for fixing various members. Especially, since the adhesive sheet of this invention is excellent in heat conductivity, it can be used for bonding with the heat-emitting member provided in various electronic devices, and another member, for example.

  Examples of the heat generating member include a semiconductor element such as a CPU, an LED backlight, a battery, and the like.

  On the other hand, as the other member, it is preferable to use a heat receiving member in order to efficiently dissipate heat. Examples of the heat receiving member include a stainless casing, an aluminum substrate, glass epoxy, and the like.

  Since the pressure-sensitive adhesive tape of the present invention can be bent into an arbitrary shape as described above, the pressure-sensitive adhesive sheet may be attached to the heat generating member and the heat receiving member, for example, in a state where the pressure-sensitive adhesive sheet is curved or bent. With the attached electronic device, it is possible to sufficiently dissipate the heat generated inside it while maintaining its thinned and highly integrated state.

  Examples and comparative examples will be specifically described below.

[Preparation of adhesive (I)]
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 96.4 parts by mass of n-butyl acrylate, 0.1 part by mass of 2-hydroxyethyl acrylate, 3.5 parts by mass of acrylic acid, and polymerization As an initiator, 0.1 part by mass of 2,2′-azobisisobutylnitrile was dissolved in 100 parts by mass of ethyl acetate, the inside of the reaction vessel was purged with nitrogen, and then polymerized at 80 ° C. for 12 hours to obtain a weight average. A solvent solution of acrylic polymer (I) having a molecular weight of 600,000 was obtained.

  10 parts by mass of polymerized rosin pentaerythritol ester (Arakawa Chemical Industries, Ltd., Pencel D-135, softening point 135 ° C.) with respect to 100 parts by mass of the solid content of the solvent solution of the acrylic polymer (I) Rosin glycerin ester (Arakawa Chemical Industries, Ltd., Superester A-100, softening point 100 ° C.) 10 parts by mass, then ethyl acetate is supplied to adjust the solid content concentration of the acrylic polymer (I) to 45 The pressure-sensitive adhesive composition (I) was prepared by adjusting the mass%.

  100 parts by mass of the pressure-sensitive adhesive composition (I) and 2.1 parts by mass of an isocyanate-based crosslinking agent (manufactured by DIC Corporation, Vernock NC40, solid content 40% by mass) were mixed, and the solid content concentration was 47% by mass. The pressure-sensitive adhesive (I) was obtained by mixing what was supplied with ethyl acetate for 10 minutes using a dispersion stirrer.

[Production of Metal Substrate (B-1)]
A metal substrate (B-1) was produced by laminating two rolled copper foils having a thickness of 35 μm using a double-sided adhesive tape # 8602TNW-05 (manufactured by DIC Corporation) having a total thickness of 5 μm.

[Production of Metal Substrate (B-2)]
A metal substrate (B-2) was produced by laminating three rolled copper foils having a thickness of 35 μm using two double-sided adhesive tapes # 8602TNW-05 (manufactured by DIC Corporation) having a total thickness of 5 μm.

  The bending strength of the metal substrates (B-1) and (B-2) was measured by the following method.

  By sandwiching the metal base material having a width of 30 mm and a length of 50 mm in an environment of 25 ° C. and 50% RH with a chuck portion provided in Tensilon RTG-1210 (manufactured by A & D) as a measuring device, the metal base The material was fixed in a vertical state. At that time, the portion of the metal substrate sandwiched between the chuck portions was adjusted to be a portion of 10 mm on both upper and lower ends of the metal substrate (FIG. 2).

  Next, the metal substrate was compressed in the vertical direction. The compression strength at that time was 300 mm / min, and the compression length was 20 mm. Based on the measurement result (FIG. 3) obtained by the compression test, the bending strength was determined.

Example 1
The pressure-sensitive adhesive (I) was applied to the surface of the release liner using a roll coater, and dried for 3 minutes using a dryer adjusted to 80 ° C., whereby a pressure-sensitive adhesive layer (I The laminated body in which -1) was formed was obtained.

  Next, the pressure-sensitive adhesive layer (I-1) of the laminate was bonded to one surface of the metal substrate (B-1). Next, on the other surface of the metal substrate (B-1), an adhesive having a thickness of 14 μm that adheres the polyethylene terephthalate film and the metal substrate to the surface of a polyethylene terephthalate film (resin film) having a thickness of 16 μm in advance. The laminated body provided with the agent layer was pasted.

Next, the adhesive sheet (X-1) was produced by curing the patch in a 40 ° C. environment for 72 hours. The heat resistance of the pressure-sensitive adhesive layer (I-1) having a thickness of 30 μm included in the pressure-sensitive adhesive sheet (X-1) was 2.54 K · cm ² / W.

The volume resistance value of the polyethylene terephthalate film (resin film) having a thickness of 16 μm was measured at an applied voltage of 500 V using “R8430A ULTRA HIGH RESISTANCE METER” manufactured by ADVANTEST in an environment of 23 ° C. and 50% RH. In some cases, it was 10 ¹⁴ Ω · cm or more.

(Example 2)
A pressure-sensitive adhesive sheet (X-2) is produced in the same manner as in Example 1 except that the metal substrate (B-2) is used instead of the metal substrate (B-1) used in Example 1. did. The heat resistance of the pressure-sensitive adhesive layer (I-1) having a thickness of 30 μm included in the pressure-sensitive adhesive sheet (X-2) was 2.54 K · cm ² / W.

(Comparative Example 1)
A pressure-sensitive adhesive sheet (X-3) was produced in the same manner as in Example 1 except that a rolled copper foil having a thickness of 70 μm was used instead of the metal substrate (B-1) used in Example 1. . The heat resistance of the pressure-sensitive adhesive layer (I-1) having a thickness of 30 μm included in the pressure-sensitive adhesive sheet (X-3) was 2.54 K · cm ² / W.

(Comparative Example 2)
An adhesive sheet (X-4) was produced in the same manner as in Example 1 except that a rolled copper foil having a thickness of 105 μm was used instead of the metal substrate (B-1) used in Example 1. . The heat resistance of the pressure-sensitive adhesive layer (I-1) having a thickness of 30 μm included in the pressure-sensitive adhesive sheet (X-4) was 2.54 K · cm ² / W.

  Example, Comparative Example The pressure-sensitive adhesive sheets prepared in Comparative Examples have gel fraction, pressure-sensitive adhesive layer thickness, pressure-sensitive adhesive sheet thickness, pressure-sensitive adhesive layer thickness, pressure-sensitive adhesive sheet heat mobility, pressure-sensitive adhesive sheet adhesion Resilience) and electrical insulation were evaluated by the following methods.

[Measurement method of gel fraction]
The pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples were cut into 40 mm × 50 mm, and the sample peeled off from the release film was measured with a balance. Next, the sample was immersed in toluene and allowed to stand at room temperature for 24 hours. After immersion, the sample was taken out, dried at 105 ° C. for 1 hour by a dryer, cooled at room temperature, and then the mass of the sample was measured. The mass after the sample was immersed in toluene was divided by the mass before the sample was immersed in toluene, and the proportion of insoluble matter (gel fraction) was determined as a percentage. In addition, when the heat conductive filler was included in the sample, the gel fraction was calculated using the mass obtained by subtracting the content of the heat conductive filler.

[Measurement method of thermal resistivity of adhesive layer]
A part of each laminated body in which the pressure-sensitive adhesive layer (I-1) was formed on the surface of the release liner used when producing the pressure-sensitive adhesive sheet in Examples and Comparative Examples was cut, and they were subjected to a 40 ° C. environment. After curing for 72 hours below, the release liner was removed to prepare a film composed of the pressure-sensitive adhesive layer (I-1).
The thermal resistance value of the film composed of the pressure-sensitive adhesive layer (I-1) was measured by a temperature gradient method. As a measuring device, Agne thermal conductivity measuring device "ARC-TC-1 type" was used.
A film made of the pressure-sensitive adhesive layer (I-1) cut into a circular shape with a diameter of 50 mm is stuck between a stainless steel layer and a copper layer so as not to contain air, and is brought into close contact with a pressure of 10 kPa. It was.
From the temperature gradient of the thermocouple embedded in the stainless steel layer (thermal conductivity 16 W / m · k) with a known thermal conductivity, the heating unit of the measuring device is set to 80 ° C. The heat flow rate q [W / cm ² ] was calculated.
Formula 1
Heat flow rate q [W / cm ² ] = temperature gradient of stainless steel layer [K / m] × thermal conductivity of stainless steel layer [W / m · k] / area of stainless steel layer [cm ² ]
Next, the thermal resistivity [cm ² K / W] was calculated from the temperature difference between the upper and lower sides of the film made of the pressure-sensitive adhesive layer using the following formula 2.
Formula 2
Thermal resistivity [cm ² K / W] = {Surface temperature [K] of the upper surface of the pressure-sensitive adhesive sheet−Surface temperature [K] of the lower surface of the pressure-sensitive adhesive sheet] / Heat flow rate q [W / cm ² ]

[Measurement method of adhesive sheet thickness]
The thickness of the pressure-sensitive adhesive sheet was measured using a thickness meter “TH-102” manufactured by Tester Sangyo Co., Ltd.

[Method for measuring thickness of pressure-sensitive adhesive layer (I-1)]
Using a part of each laminate in which the pressure-sensitive adhesive layer (I-1) was formed on the surface of the release liner used when producing the pressure-sensitive adhesive sheet in Examples and Comparative Examples, the surface of the pressure-sensitive adhesive layer was used. Samples lined with a polyethylene terephthalate film (S25 manufactured by Unitika Ltd., thickness 25 μm) were prepared.
The thickness of the sample was measured with a thickness meter “TH-102” manufactured by Tester Sangyo Co., Ltd., and the thickness of the polyethylene terephthalate film used for the release film and the backing was reduced to reduce the thickness of the pressure-sensitive adhesive layer. A thickness of (I-1) was obtained.

[Method for evaluating thermal conductivity]
A test tape was prepared by cutting an adhesive sheet into a size of 30 mm width × 30 mm length.

  Next, an aluminum plate (X) having a thickness of 0.5 mm, a width of 70 mm, and a length of 75 mm (JIS)

  H4000 regulation A1050) is prepared, and one end portion in the length direction of the test tape is placed at an intermediate position of a side of 70 mm width of the aluminum plate (X), and its application area is 30 mm width × 10 mm length. Then, a reciprocating load was applied from above the test tape using a 200 g roller.

  Next, the other end of the test tape is attached to an intermediate position of the side of 70 mm width of an aluminum plate (Y) (A1050 defined in JIS H4000) having a thickness of 0.5 mm, a width of 70 mm and a length of 75 mm. The area was 30 mm wide and 10 mm long, and a reciprocating load was applied from above the test tape using a 200 g roller.

  Next, to the center of the aluminum plate (X), a heat conductive double-sided adhesive tape having a width of 50 mm and a length of 50 mm (manufactured by Shin-Etsu Chemical Co., Ltd., TC-10SAS, thickness 0.1 mm, thermal conductivity 1 W / m · k). ) Was affixed. The heat conductive double-sided adhesive tape was affixed to the same surface as the aluminum plate (X) to which the test tape was affixed.

  Moreover, the thermocouple temperature sensor (T) was affixed on the surface of the aluminum plate (Y) which comprises the member of a heat receiving side. The thermocouple temperature sensor (T) was attached next to the test tape attached to the aluminum plate (Y).

  Next, a polyethylene foam (Furukawa Electric Co., Ltd., SN-500) having a width of 80 mm, a length of 80 mm, and a thickness of 5 mm is placed on a horizontal plane, and the aluminum plate (Y) is placed thereon, On top of that, a polyethylene foam (SN-500, manufactured by Furukawa Electric Co., Ltd.) having a width of 80 mm, a length of 80 mm, and a thickness of 5 mm is placed, and the aluminum plate (Y) and the test tape are placed thereon. The bonded aluminum plate (X) was placed. At that time, the test tape connecting the aluminum plates (X) and (Y) was adjusted to be curved.

  Next, a silicone rubber heater in which a thermocouple temperature sensor (S) (a set of ST-50 and W-ST50A-1000-Y3, manufactured by Rika Kogyo Co., Ltd.) is attached to the upper surface of the thermally conductive double-sided adhesive tape ( Aswan, 1-130-01) was placed, and a foamed polyethylene sheet (Furukawa Electric Co., Ltd., SN-500) having a width of 50 mm, a length of 50 mm, and a thickness of 5 mm was placed thereon. A 100 g weight was placed on top.

  A DC power supply device (manufactured by Kikusui Kogyo Co., Ltd., PAS160) connected to the silicone rubber heater so that the surface temperature (L) of the upper surface of the silicone rubber heater is about 50 ° C. in a windless environment at 23 ° C. and 50% RH. The output of -2) was adjusted to 2W. The surface temperature (P) of the aluminum plate (Y) (heat receiving part) 30 minutes after the adjustment was measured. On the other hand, the same configuration as described above was formed except that the aluminum plate (X) and the aluminum plate (Y) were not bonded with the test tape. A DC power supply device (manufactured by Kikusui Kogyo Co., Ltd., PAS160) connected to the silicone rubber heater so that the surface temperature (L) of the upper surface of the silicone rubber heater is about 50 ° C. in a windless environment at 23 ° C. and 50% RH. The output of -2) was adjusted to 2W. The surface temperature (Q) of the aluminum plate (Y) (heat receiving part) 30 minutes after the adjustment was measured.

◎ The test tape does not crack when bent, and the surface temperature (P) and the surface temperature (Q) [surface temperature (P) −the surface temperature (Q)] are 3 ° C. or more Met.
○ The test tape does not crack when bent, and the surface temperature (P) and the surface temperature (Q) [surface temperature (P) −the surface temperature (Q)] are 2 ° C. or more. It was less than 3 ° C.
Δ: The test tape does not crack when bent, and the surface temperature (P) and the surface temperature (Q) [surface temperature (P) −the surface temperature (Q)] are 2 ° C. Was less than.
X: A crack or a crack occurred in a part of the test film when it was bent.

[Method for evaluating adhesive sheet adhesive strength (resilience resistance)]
A test piece was prepared by cutting the pressure-sensitive adhesive sheet peeled from the release film into a size of 10 mm width × 25 mm length. One end of the test piece was pasted on one surface of a 6 mm thick glass epoxy base material (manufactured by Shin-Kobe Electric Machinery Co., Ltd., KEL-GEF) for an area of 10 mm width × 3 mm length. The test piece was bent so that the bending radius of the test piece was 2 mm, and the other end of the test piece was attached to the other surface of the glass epoxy base material in an area of 10 mm width × 3 mm length. Thereafter, the upper surface of the affixing portion of the test piece was subjected to a reciprocating load using a 200 g roller, and left still at 70 ° C. for 72 hours. The float of the test piece after the standing was observed. When floating of 0.3 mm or more occurred in the affixed part, the adhesiveness of the pressure-sensitive adhesive sheet to the surface of the glass epoxy base material was poor and the thermal conductivity was lowered, so that it was evaluated that it was not suitable for this application.
○: The float of one or both of the pasting parts of the test piece was less than 0.3 mm.
(Triangle | delta): The float of one or both of the sticking part of a test piece was 0.3 mm or more.
X: One of the pasting parts of the test piece was peeled off.

[Evaluation method of electrical insulation of adhesive sheet]
The pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples were cut into a size of 100 mm width × 100 mm length in a state where they were peeled from the release film, and used as test pieces.
Using an RV430A ULTRA HIGH RESISTANCE METER manufactured by ADVANTEST in an environment of 23 ° C. and 50% RH, the volume resistance of the test piece at an applied voltage of 500 V was measured, and the electrical insulation was evaluated according to the following criteria. did.
○: The volume resistivity of the test piece is ^{10 14 Ω} · cm or more △: the volume resistivity of the test piece is ^{10 13 Ω} · cm or more, ^{10 14 Ω} · cm below ×: volume resistivity of the test piece ^{10 13} Omega · less than cm

1 Polyethylene foam 2 Thermocouple temperature sensor (S)
3 Silicone rubber heater 4 Thermal conductive double-sided adhesive tape 5 Aluminum plate (X)
6 Test tape 7 Aluminum plate (Y)
8 Thermocouple temperature sensor (T)
9 Weight 10 DC power supply device 11 Metal substrate 12 Chuck part provided in a bending strength measuring device

Claims (19)

A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer (A) is laminated on one or both sides of a metal substrate (B) comprising a laminate of two or more metal substrates (b1). The pressure-sensitive adhesive sheet according to claim 1, wherein the metal substrate (B) has a thickness in the range of 1 µm to 300 µm. The pressure-sensitive adhesive sheet according to claim 1, wherein the metal substrate (b1) has a thickness in the range of 1 µm to 150 µm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the metal substrate (b1) is a substrate made of rolled copper or a substrate made of electrolytic copper. The pressure-sensitive adhesive sheet according to any one of claims 1 to 16, wherein the metal substrate (B) has a bending strength in a range of 0.1 N / 30 mm to 2 N / 30 mm. The said metal base material (B) consists of a laminated body by which the 2 or more metal base material (b1) was laminated | stacked through the adhesive layer (b2), The any one of Claims 1-5. Adhesive sheet. The pressure-sensitive adhesive sheet according to claim 6, wherein the pressure-sensitive adhesive layer (b2) has a thickness in the range of 1 μm to 60 μm. The pressure-sensitive adhesive sheet according to claim 6 or 7, wherein the pressure-sensitive adhesive layer (b2) has a storage elastic modulus in a range of 10 ⁵ to 10 ⁷ dyn / cm ² at 25 ° C. The pressure-sensitive adhesive sheet according to the pressure-sensitive adhesive layer ^(A), any one of the preceding claims and has a thermal resistivity in the range of ^{0.1K · cm 2 / W~10K · cm} 2 / W . The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer (A) has a thickness in the range of 1 μm to 60 μm. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer (A) is an electrically insulating pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer (A) contains an acrylic polymer (a1) and a heat conductive filler (a2), and the heat conductive filler (a2) is the acrylic polymer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 11, which is contained in a range of 10% by mass to 300% by mass with respect to (a1). The pressure-sensitive adhesive layer (A) is laminated on one surface of the metal substrate (B), and the resin film (C) is laminated on the other surface of the metal substrate (B). The adhesive sheet of any one of -12. The pressure-sensitive adhesive sheet according to claim 13, wherein the resin film (C) forms an electrical insulating layer or a heat insulating layer. The pressure-sensitive adhesive sheet according to claim 13 or 14, wherein the resin film (C) has a volume resistance value of 10 ¹³ Ω · cm or more when a voltage of 500 V is applied. The pressure-sensitive adhesive sheet according to any one of claims 13 to 15, wherein a thickness of the resin film (C) is in a range of 10 µm to 50 µm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 16, wherein the resin film (C) and the metal substrate (B) are laminated via a pressure-sensitive adhesive layer (c1). An electronic apparatus having a structure in which the pressure-sensitive adhesive sheet according to any one of claims 1 to 17 is attached to a heat generating member. The electronic device according to claim 18, wherein the pressure-sensitive adhesive sheet according to any one of claims 1 to 17 is affixed to the heat generating member and the heat receiving member in a curved or bent state.

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