JP6045929B2 - Flame retardant thermal conductive adhesive sheet - Google Patents

Description

  The present invention relates to a flame-retardant heat conductive pressure-sensitive adhesive sheet having both flame retardancy and heat conductivity.

  Conventionally, in a heat conductive adhesive sheet, it is known that heat conductivity is improved compared with the adhesive used as a base by containing a heat conductive filler in an acrylic adhesive.

  For example, it has been proposed that high adhesive strength (adhesive strength) can be imparted to a thermally conductive adhesive sheet by using boron nitride particles having a specific particle diameter and an acrylic polymer component (see, for example, Patent Document 1). ).

  In addition, such a heat conductive adhesive sheet is widely used in electronic component applications such as sealing chip components and forming an insulating layer between a circuit on which a heat generating component is mounted and a heat sink. In order to reduce the risk of ignition due to thermal runaway, in addition to thermal conductivity and adhesive properties (adhesiveness, holding power, etc.), high flame retardancy is required.

  Specifically, for example, a feeling comprising 100 parts by mass of an acrylic copolymer prepared from a monomer mixture essentially containing 0.5 to 10 parts by mass of a polar vinyl monomer such as acrylic acid, and 10 to 100 parts by mass of a tackifier resin. Electrically insulating heat-conducting difficulty containing 50 to 250 parts by mass of a hydrated metal compound having both functions of heat-conductive particles and non-halogen flame retardant with respect to 100 parts by mass of the pressure-sensitive adhesive composition A flammable pressure sensitive adhesive and a pressure sensitive adhesive tape have been proposed (see, for example, Patent Document 2).

  In addition, for example, a heat conductive difficulty containing an acrylic polymer, a flame retardant having thermal conductivity and containing no halogen (for example, aluminum hydroxide), and a heat conductive filler (for example, aluminum oxide). A flammable pressure sensitive adhesive and a sheet have been proposed (see, for example, Patent Document 3).

  In addition, as a heat conductive adhesive sheet, by holding it with a base material of a plastic film such as a polyolefin film, the heat conductive adhesive sheet is applied while following an adherend having a special shape such as an uneven surface or a curved surface. It has also been proposed to suppress wrinkles, tears, elongation, etc. that occur when trying to attach (see, for example, Patent Document 4).

JP 2010-174173 A JP-A-11-269438 JP 2002-294192 A JP 2001-168246 A

  However, in the thermally conductive sheets described in Patent Documents 1 to 3, in order to satisfy thermal conductivity and flame retardancy, a large amount of thermally conductive particles and flame retardant are blended, and an adhesive composition (viscous The fluidity of the (liquid) may be lost. Such a heat conductive sheet is difficult to manufacture, and has a problem that the pressure-sensitive adhesive layer becomes hard and the adhesive performance is lowered.

  Moreover, in the thermally conductive sheet described in Patent Document 4, plastic films such as polyolefin films used as a base material are often flammable, and for example, satisfy the flame retardancy of UL94 VTM-0 standard. There is a problem that is difficult.

  Furthermore, as a heat conductive sheet, further improvement in heat conductivity and flame retardancy is required.

  The objective of this invention is providing the flame-retardant heat conductive adhesive sheet which is excellent in heat conductivity and a flame retardance, and excellent in the ease of sticking to a to-be-adhered body.

In order to achieve the above object, the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention comprises a base material and a flame-retardant heat conductive pressure-sensitive adhesive layer provided on at least one surface of the base material. A conductive adhesive sheet, wherein the base material includes a polyester film, and the ratio of the thickness of the base material to the total thickness of the flame retardant thermally conductive adhesive sheet is less than 0.2, and the thermal resistance is It is 10 cm ² · K / W or less.

  Such a flame-retardant thermally conductive pressure-sensitive adhesive sheet can ensure excellent thermal conductivity and flame retardancy, and can improve adhesion to an adherend.

  In the flame-retardant heat conductive adhesive sheet of this invention, it is suitable for the thickness of the said base material to be 5 micrometers or more and less than 50 micrometers.

  According to such a flame-retardant heat conductive pressure-sensitive adhesive sheet, an excellent tensile elastic modulus can be ensured, and adhesion to an adherend can be improved.

  Moreover, in the flame-retardant heat conductive adhesive sheet of this invention, it is suitable that the total thickness of the said flame-retardant heat conductive adhesive sheet is 120-1000 micrometers.

  According to such a flame-retardant heat conductive pressure-sensitive adhesive sheet, an excellent tensile elastic modulus can be ensured, and adhesion to an adherend can be improved.

  Furthermore, in the flame-retardant heat conductive adhesive sheet of this invention, it is suitable for a tensile elasticity modulus to be 10 Mpa or more.

  Since such a flame-retardant heat conductive adhesive sheet is excellent in tensile elastic modulus, the adhesiveness to an adherend can be improved.

  According to the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention, excellent heat conductivity and flame retardancy can be secured, and furthermore, excellent sticking property can be secured.

FIG. 1 is a schematic cross-sectional view partially showing an example of the flame-retardant heat-conductive pressure-sensitive adhesive sheet of the present invention. FIG. 1A shows a flame-retardant heat-conductive pressure-sensitive adhesive layer formed on one surface of a substrate. (B) is a structure in which a flame-retardant heat conductive adhesive layer is formed on both surfaces of the substrate, and (c) is a flame-retardant heat conductive adhesive layer on one surface of the substrate. Is formed, and a non-flame retardant thermally conductive pressure-sensitive adhesive layer is formed on the other surface of the substrate. FIG. 2 is an explanatory view of a thermal property evaluation apparatus for measuring thermal conductivity and thermal resistance in the examples, where (a) shows a front view and (b) shows a side view.

(Flame retardant thermal conductive adhesive sheet)
The flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention is a flame-retardant heat-conductive pressure-sensitive adhesive sheet having a base material and a flame-retardant heat-conductive pressure-sensitive adhesive layer provided on at least one side of the base material, The ratio of the thickness of the base material to the total thickness of the flame-retardant heat-conductive pressure-sensitive adhesive sheet is less than 0.2, and the thermal resistance is 10 cm ² · K / W or less.

  The flame-retardant heat conductive adhesive sheet of this invention is demonstrated with reference to drawings.

  The flame-retardant heat conductive adhesive sheet of this invention is equipped with the flame-retardant heat conductive adhesive layer in the at least single side | surface of the base material containing a polyester film.

  As such a flame-retardant heat conductive adhesive sheet, either a form in which both surfaces are adhesive surfaces (adhesive surface) or a form in which only one surface is an adhesive surface may be used.

  Specifically, as shown in FIG. 1 (a), a flame-retardant heat conductive pressure-sensitive adhesive sheet having an adhesive surface only on one side where a flame-retardant heat-conductive pressure-sensitive adhesive layer is formed on one side of the substrate, As shown in FIG. 1 (b) or (c), both surfaces are adhesive surfaces, and at least one of the adhesive surfaces is formed of a flame-retardant heat-conductive pressure-sensitive adhesive layer. Etc.

  In the present invention, “sheet” is used as a concept including shapes such as “tape”, “sheet”, and “film”. Further, a punching process or a cutting process may be performed in a shape according to the purpose of use.

  FIG. 1 is a schematic sectional view partially showing an example of the flame-retardant heat-conductive adhesive sheet of the present invention.

  In FIG. 1, 11, 12, and 13 are flame-retardant heat-conductive pressure-sensitive adhesive sheets each having a flame-retardant heat-conductive pressure-sensitive adhesive layer provided on at least one surface of a substrate including a polyester film, and 2 is flame-retardant. A heat conductive adhesive layer, 3 is a base material, 4 is an adhesive layer (non-flame-retardant heat conductive adhesive layer).

  The flame-retardant heat conductive adhesive sheet 11 shown in FIG. 1A has a configuration in which a flame-retardant heat conductive pressure-sensitive adhesive layer 2 is provided on one side of a base material 3.

  The flame-retardant heat conductive adhesive sheet 12 shown by FIG.1 (b) has the structure by which the flame-retardant heat conductive adhesive layer 2 was provided in both surfaces of the base material 3. FIG.

  The flame-retardant heat conductive adhesive sheet 13 shown in FIG. 1 (c) has the flame-retardant heat conductive adhesive layer 2 formed on one surface of the substrate 3, and the pressure-sensitive adhesive layer on the other surface. (Non-flame retardant thermally conductive pressure-sensitive adhesive layer) 4 is formed.

  In addition, in the case of the structure where the flame-retardant heat conductive adhesive layer 2 is formed on one surface of the substrate 3 shown in FIG. 1A, the flame-retardant heat conductive adhesive layer 2 is not formed. On the other surface of the substrate 3, a treatment layer for preventing dirt and scratches may be formed.

  As a treatment layer for preventing dirt, for example, a layer obtained by treating the surface of a substrate with silicone or fluorine having a low surface tension to make it difficult to get dirt can be used.

  The surface tension is not particularly limited, but is preferably 50 dyne / cm or less, more preferably 40 dyne / cm or less, and still more preferably 30 dyne / cm or less.

  Examples of the treatment layer for preventing scratches include a hard coat layer. The pencil hardness of the hard coat layer is, for example, H or higher, preferably 2H or higher, more preferably 3H or higher.

  Moreover, the flame-retardant heat conductive adhesive sheet of this invention may be formed with the form wound by roll shape, and may be formed with the form on which the sheet | seat was laminated | stacked.

  When the flame-retardant heat conductive pressure-sensitive adhesive sheet has a form wound in a roll shape or is laminated, the flame-retardant heat conductive pressure-sensitive adhesive layer is prevented from coming into direct contact with the release liner. be able to.

  The thickness (total thickness) of the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention is, for example, 100 to 1000 μm, preferably 120 to 1000 μm. If the thickness (total thickness) of the sheet is within the above range, an excellent tensile elastic modulus can be ensured, and adhesion to an adherend can be improved.

  In addition, in this invention, the thickness (total thickness) of a flame-retardant heat conductive adhesive sheet is the thickness of the base material which comprises a flame-retardant heat conductive adhesive sheet, and a flame-retardant heat conductive adhesive layer. For example, the thickness of the release liner (described later) is not included.

  Moreover, the flame-retardant heat conductive adhesive sheet (base material and flame-retardant heat conductive pressure-sensitive adhesive layer) of the present invention is preferably substantially free of halogen-based flame retardant components from the viewpoint of reducing environmental burden. It is desirable.

In the present invention, the phrase “substantially free of a halogen-based flame retardant component” means that no halogen-based flame retardant component is used at all or that it is below the detection limit in a generally used evaluation method.
(Base material)
In the present invention, the substrate includes a polyester film. Examples of the polyester film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and the like.

  These materials can be used alone or in combination of two or more.

  The base material of the polyester film has an advantage that the breaking strength, Young's modulus, and dielectric breakdown voltage are higher than those of the base material such as polyolefin film, polyamide film, and polyimide film.

  In the present invention, the thickness of the substrate is, for example, 1 μm or more and less than 100 μm, preferably 5 μm or more and less than 50 μm, and more preferably 10 μm or more and less than 40 μm.

  When the thickness of the substrate is within the above range, flame retardancy satisfying the flame retardancy standard of UL94 VTM-0 can be obtained. Furthermore, it is possible to ensure an excellent tensile elastic modulus, and it is possible to improve the adherence to the adherend.

  On the other hand, if the thickness of the substrate containing the polyester film is less than the above lower limit or greater than or equal to the above upper limit, the flame retardant standard of UL94 VTM-0 may not be satisfied.

  Specifically, if the thickness of the substrate is less than the above lower limit, a tape drip phenomenon may occur during fire spreading, and the flame retardancy standard of UL94 VTM-0 may not be satisfied. Moreover, the base material containing a polyester film burns that the thickness of a base material is more than the said upper limit, and it may be unable to satisfy the flame-retardant specification of UL94 VTM-0.

  Moreover, in the flame-retardant heat conductive adhesive sheet of the present invention, the ratio between the thickness of the substrate containing the polyester film and the thickness of the flame-retardant heat conductive adhesive layer (the thickness of the adhesive layer (described later)) Is less than 0.2, preferably less than 0.15, more preferably less than 0.1, usually 0.0025 or more.

  If the ratio of the thickness of the flame-retardant heat-conductive pressure-sensitive adhesive layer to the thickness of the substrate is not less than the above upper limit, the heat conductivity may be impaired.

  The base material of the present invention may be a single polyester film, but may be laminated with other base materials as long as the effects of the present invention are not impaired.

  As such a substrate, for example, a paper-based substrate such as paper, for example, a fiber-based substrate such as cloth, unemployed cloth, a net, for example, a metal-based substrate such as a metal foil, a metal plate, for example, Plastic base materials such as plastic films and sheets, for example, rubber base materials such as rubber sheets, foams such as foam sheets, and laminates thereof (particularly between plastic base materials and other base materials) An appropriate thin leaf body such as a laminate, a laminate of plastic films or sheets, or the like can be used.

  As a material in such a plastic film or sheet, for example, α-olefin such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA) is used as a monomer component. An olefin resin such as polyvinyl chloride (PVC), for example, vinyl acetate resin, for example, polyphenylene sulfide (PPS), for example, polyamide (nylon), amide resin such as wholly aromatic polyamide (aramid), For example, polyimide resin, for example, polyetheretherketone (PEEK) and the like can be mentioned.

  These materials can be used alone or in combination of two or more, and the form of lamination is not particularly limited.

  The surface of the base material containing the polyester film is a conventional surface treatment, for example, corona treatment, chromic acid treatment, ozone exposure treatment, flame exposure treatment, in order to improve the adhesion with the flame retardant heat conductive adhesive layer, etc. An oxidation treatment by a chemical or physical method such as a high piezoelectric exposure treatment or an ionizing radiation treatment may be applied, or a coating treatment or the like may be performed by a primer or a release agent.

In this invention, the heat resistance of a flame-retardant heat conductive adhesive sheet is 10 cm < ² > * K / W or less, Preferably, it is 6 cm < ² > * K / W or less, More preferably, it is 4 cm < ² > * K / W or less. When the heat resistance of the flame-retardant heat conductive adhesive sheet exceeds 10 cm ² · K / W, the function as the heat conductive sheet cannot be sufficiently exhibited.

Moreover, the flame retardance of the flame-retardant heat conductive adhesive sheet of this invention needs to satisfy UL94 VTM-0 specification. If the UL94 VTM-0 standard is satisfied, there is an advantage that vertical fire spread can be suppressed even when ignited, and the flame-retardant heat conductive adhesive sheet can be used as a heat conductive member of an electronic device, for example.
(Flame retardant thermal conductive adhesive layer)
The flame-retardant heat conductive pressure-sensitive adhesive layer used in the flame-retardant heat conductive sheet of the present invention is not particularly limited, and a conventionally known flame-retardant heat conductive pressure-sensitive adhesive layer can be used.

  In the present invention, the flame-retardant thermally conductive pressure-sensitive adhesive layer refers to a pressure-sensitive adhesive layer that satisfies, for example, UL94 VTM-2, preferably VTM-1, more preferably VTM-0.

  An acrylic pressure-sensitive adhesive layer is preferred because it is easy to achieve both thermal conductivity and flame retardancy and is excellent in adhesive properties such as adhesive strength and holding power.

In particular, in order to satisfy the UL94 VTM-0 standard by setting the thermal resistance of the flame-retardant thermally conductive adhesive sheet to 10 cm ² · K / W or less, preferably (a) an acrylic polymer and (b) a hydrated metal Compound is included.
(Acrylic polymer)
In the present invention, the (a) acrylic polymer constituting the flame-retardant thermally conductive pressure-sensitive adhesive layer is obtained by copolymerizing a monomer component containing (meth) acrylic acid alkyl ester as a main component and a polar group-containing monomer. An acrylic polymer is given.

  Acrylic polymers can be used alone or in combination of two or more.

Examples of the (meth) acrylic acid alkyl ester constituting the acrylic polymer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic. Butyl acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, ( Heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, Isodecyl (meth) acrylate, undecyl (meth) acrylate, ( T) Dodecyl acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, (meth) octadecyl acrylate, (meta And (meth) acrylic acid C _1-20 alkyl esters such as nonadecyl acrylate and eicosyl (meth) acrylate.

In particular, (meth) acrylic acid C _2-12 alkyl ester, and more preferably (meth) acrylic acid C _4-9 alkyl ester can be used from the viewpoint of easily balancing the adhesive properties.

  The said (meth) acrylic-acid alkylester is used as a main component in the monomer component which comprises an acrylic polymer.

  The proportion of the (meth) acrylic acid alkyl ester is, for example, 60% by mass or more (for example, 60 to 99% by mass), preferably 80% by mass or more (for example, based on the total amount of monomer components for preparing the acrylic polymer). 80-98 mass%).

  The (a) acrylic polymer in the present invention preferably contains a polar group-containing monomer as a monomer component in an amount of 5% by mass or more in the monomer component.

  If the polar group-containing monomer is contained in the monomer component in an amount of 5% by mass or more, the adhesion of the flame-retardant heat-conductive pressure-sensitive adhesive layer to the adherend is improved, or the flame-retardant heat-conductive pressure-sensitive adhesive layer is aggregated. You can increase your power.

  Examples of the polar group-containing monomer include nitrogen-containing monomers, hydroxyl group-containing monomers, sulfonic acid group-containing monomers, and phosphate group-containing monomers.

  A polar group containing monomer can be used individually or in combination of 2 or more types. In the present invention, a nitrogen-containing monomer and a hydroxyl group-containing monomer are preferable because high adhesiveness and holding power are obtained. Moreover, although a polar group containing monomer is mentioned later in detail, Preferably, a carboxyl group containing monomer is not contained.

  In the present invention, examples of the nitrogen-containing monomer include N- (2-hydroxyethyl) (meth) acrylamide (HEAA), N- (2-hydroxypropyl) (meth) acrylamide, and N- (1-hydroxypropyl) (meta). ) Acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) N-hydroxyalkyl (meth) acrylamides such as (meth) acrylamide, for example, cyclic (meth) acrylamides such as N- (meth) acryloylmorpholine, N-acryloylpyrrolidine, such as (meth) acrylamide, N-substituted (meth) Acrylamide (eg, N-ethyl N-alkyl (meth) acrylamides such as (meth) acrylamide, Nn-butyl (meth) acrylamide, for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl N, N- such as (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide Acyclic (meth) acrylamides such as dialkyl (meth) acrylamide), for example, N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2- Caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholine di Monomers having an amino group such as N-vinyl cyclic amides such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, For example, monomers having a maleimide skeleton such as N-cyclohexylmaleimide, N-phenylmaleimide, such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-2-ethylhexylitaconimide, N- Itaconimide monomers such as lauryl itaconimide and N-cyclohexylitaconimide are listed.

  These nitrogen-containing monomers are preferably N- (2-hydroxyethyl) (meth) acrylamide, N-vinyl-2-pyrrolidone, N- (meta) from the viewpoint of good adhesion at the initial stage of application. ) Acryloylmorpholine, N, N-diethyl (meth) acrylamide.

  Examples of the hydroxyl group-containing monomer in the present invention include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. , (Meth) acrylic acid 8-hydroxyoctyl, (meth) acrylic acid 10-hydroxydecyl, (meth) acrylic acid 12-hydroxylauryl, (4-hydroxymethylcyclohexyl) methyl methacrylate, and the like.

  Of these hydroxyl group-containing monomers, hydroxyethyl (meth) acrylate and hydroxybutyl (meth) acrylate are preferable from the viewpoint of good wettability to the adherend.

  In the present invention, sulfonic acid group-containing monomers include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth And acryloyloxynaphthalene sulfonic acid.

  In the present invention, examples of the phosphoric acid group-containing monomer include 2-hydroxyethyl acryloyl phosphate.

  In the present invention, the proportion of the polar group-containing monomer is 5% by mass or more, for example, 5 to 30% by mass, preferably 6 to 25% by mass, based on the total amount of monomer components for preparing the acrylic polymer. .

  If the usage-amount of a polar group containing monomer is 5 mass% or more, favorable retention strength can be obtained.

  On the other hand, if the use amount of the polar group-containing monomer is less than 5% by mass, the cohesive force of the flame-retardant thermally conductive pressure-sensitive adhesive layer is lowered, and a high holding power may not be obtained, which exceeds 30% by mass. In some cases, the cohesive force of the flame-retardant heat-conductive pressure-sensitive adhesive layer becomes excessively high, and the adhesiveness of the flame-retardant heat-conductive pressure-sensitive adhesive layer is lowered.

  In this invention, a polyfunctional monomer can be used as a monomer component as needed. By using a polyfunctional monomer, a crosslinked structure can be introduced into the acrylic polymer, and the cohesive force required as a flame-retardant thermally conductive pressure-sensitive adhesive layer can be adjusted.

  Examples of the polyfunctional monomer include hexanediol (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and pentaerythritol diester. (Meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) Acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, dibutyl (meth) acrylate, hexidyl (meth) acrylate, etc. And the like.

  Polyfunctional monomers can be used alone or in combination of two or more.

  In this invention, the ratio of a polyfunctional monomer is 2 mass% or less with respect to the monomer component whole quantity for preparing an acryl-type polymer, for example, 0.01-2 mass%, Preferably, it is 0.02-1 mass%. It is.

  If the amount of the polyfunctional monomer used exceeds 2% by mass with respect to the total amount of monomer components for preparing the acrylic polymer, the cohesive force of the flame-retardant heat-conductive adhesive layer becomes too high and flame-retardant heat conduction In some cases, the adhesiveness of the adhesive layer is reduced.

  Moreover, the cohesion force of a flame-retardant heat conductive adhesive layer may fall that it is less than 0.01 mass% with respect to the monomer component whole quantity for preparing an acryl-type polymer.

  The (a) acrylic polymer in the present invention can use other monomers as the monomer component as necessary. By using other monomers, for example, various properties of the pressure-sensitive adhesive and the structure of the acrylic polymer can be more appropriately controlled.

  Other monomers include monomers having an epoxy group such as glycidyl (meth) acrylate and allyl glycidyl ether, such as 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, and (meth) acrylic. Monomers having an alkoxy group such as methoxyethylene glycol acid and methoxypolypropylene glycol (meth) acrylate, for example, monomers having a cyano group such as acrylonitrile and methacrylonitrile, for example, styrenes such as styrene and α-methylstyrene Monomers, for example α-olefins such as ethylene, propylene, isoprene, butadiene, isobutylene, for example isocyanates such as 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate Monomers having a carbonate group, for example, vinyl ester monomers such as vinyl acetate and vinyl propionate, for example, vinyl ether monomers such as vinyl ether, for example, tetrahydrofurfuryl (meth) acrylate and the like having a heterocyclic ring (meth) Monomers having a halogen atom, such as acrylic ester, for example, fluorine (meth) acrylate, for example, monomers having an alkoxysilyl group, such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, for example, silicone (meta ) Monomers having a siloxane bond, such as acrylate, for example, alkyl (meth) acrylates having an alkyl group having 21 or more carbon atoms, such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate (Meth) acrylates having an alicyclic hydrocarbon group, such as phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, (Meth) acrylate having an aromatic hydrocarbon group, such as (meth) acrylic acid phenoxydiethylene glycol, and the like.

  Other monomers can be used alone or in combination of two or more.

  Among these monomers, a monomer having an alkoxy group is preferably used in the present invention. More preferably, 2-methoxyethyl acrylate is used.

  By using together the monomer which has an alkoxy group, the wettability of a flame-retardant heat conductive adhesive layer can be improved, and the heat from a to-be-adhered body (heat generation source) can be conducted efficiently. .

  In the present invention, the proportion of other monomers is suitably 30% by mass or less, preferably 20% by mass or less, based on the total amount of monomer components for preparing the acrylic polymer. It may be a monomer component not contained.

  The content of the monomer having an alkoxy group is, for example, 5% by mass to 20% by mass, and preferably 8% by mass to 15% by mass with respect to the total amount of monomer components for preparing the acrylic polymer. be able to.

  In the present invention, preferably, the acrylic polymer does not substantially contain a carboxyl group-containing monomer as a monomer component.

  Here, the “carboxyl group-containing monomer” is a monomer having one or more carboxyl groups (may be in the form of anhydrides) in one molecule, such as (meth) acrylic acid, itaconic acid, maleic acid. Examples include acids, fumaric acid, crotonic acid, isocrotonic acid, maleic anhydride, itaconic anhydride and the like.

  Further, the monomer component of the acrylic polymer “substantially free of carboxyl group-containing monomer” means that the monomer component does not contain any carboxyl group-containing monomer or the content is 0.1% by mass of the monomer component. It means the following.

  On the other hand, when a carboxyl group-containing monomer is contained in the acrylic polymer in the present invention, the adhesiveness tends to be lowered.

  Moreover, when mix | blending with a hydrated metal compound (after-mentioned), the fluidity | liquidity of an adhesive composition falls and the preparation of an adhesive sheet may become difficult.

  The cause of these problems has not been fully clarified, but the functional group (for example, hydroxyl group) contained in the hydrated metal compound reacts with the carboxyl group, and the acrylic polymer and the hydrated metal compound are bonded. Thus, it is considered that the effect of improving the adhesion as a polar group of the carboxyl group-containing monomer cannot be exhibited.

  Further, since the acrylic polymer becomes pseudo-crosslinked (becomes hard), it is considered that the fluidity is lowered and the adhesive property is lowered by reducing the wettability.

  Therefore, although it is not a problem to contain a very small amount of a carboxyl group-containing monomer, in the case where it is substantially contained, a hydrated metal compound cannot be contained in a large amount, which is the object of the present invention. In some cases, it is impossible to provide a flame-retardant heat-conductive adhesive sheet that is excellent in flame retardancy and is easy to stick to an adherend.

  In the present invention, the acrylic polymer can be obtained by copolymerizing the monomer components. The method of copolymerization is not particularly limited, and it can be cured by heat or ultraviolet rays using a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator).

  As such a polymerization initiator, a photopolymerization initiator is preferably used because of the advantage that the polymerization time can be shortened, and a monomer component is copolymerized by using polymerization using ultraviolet rays, and acrylic resin is used. A base polymer is obtained.

  In addition, a polymerization initiator can be used individually or in combination of 2 or more types.

  The polymerization initiator is not particularly limited, and for example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactivity An oxime photopolymerization initiator, a benzoin photopolymerization initiator, a benzyl photopolymerization initiator, a benzophenone photopolymerization initiator, a ketal photopolymerization initiator, a thioxanthone photopolymerization initiator, or the like can be used.

  Specifically, examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane- Examples include 1-one and anisole methyl ether. Examples of the acetophenone photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). Examples include dichloroacetophenone. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. . Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime.

  The benzoin photopolymerization initiator includes, for example, benzoin. Examples of the benzyl photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Examples of the ketal photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, decylthioxanthone, and the like.

  Although it does not specifically limit as the usage-amount of a photoinitiator, For example, it is 0.01-5 mass parts with respect to 100 mass parts of monomer components, Preferably, it can select from the range of 0.05-3 mass parts.

  In activating the photopolymerization initiator, it is important to irradiate the mixture of the monomer component and the photopolymerization initiator with ultraviolet rays. The irradiation energy of the ultraviolet rays, the irradiation time, etc. are not particularly limited as long as the photopolymerization initiator can be activated to cause the monomer component to react.

  Examples of the thermal polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis (2-methylpropionic acid). ) Dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (5-methyl -2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (N, N'-dimethyleneisobutylamidine) hydrochloride Azo polymerization initiators such as 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, , Dibenzoyl peroxide, t-butyl permaleate, t-butyl hydroperoxide, peroxide-based polymerization initiators such as hydrogen peroxide, for example, persulfates such as potassium persulfate and ammonium persulfate, such as persulfate Examples thereof include redox polymerization initiators such as a combination of a salt and sodium bisulfite and a combination of a peroxide and sodium ascorbate.

  The usage-amount of a thermal polymerization initiator is not specifically limited, What is necessary is just the range conventionally available as a polymerization initiator.

  When the monomer component is polymerized by the thermal polymerization method, the monomer component and the thermal polymerization initiator are dissolved in an appropriate solvent (for example, toluene or ethyl acetate), for example, 20 to 100 ° C. (typically 40 to 80 ° C.). ) By heating at a polymerization temperature of about.

  In the present invention, (a) the acrylic polymer has a glass transition temperature (Tg) of about −10 ° C. or lower (typically about −10 ° C. to −70 ° C.), preferably −20 ° C. or lower ( The monomer component is preferably about −20 ° C. to −70 ° C., and the composition and blending of the monomer component are preferably such that the Tg of the acrylic polymer obtained by polymerizing the monomer component is in the above range. Adjust the amount.

Here, the Tg of the acrylic polymer refers to a value obtained from the Fox formula based on the Tg of the homopolymer of each monomer constituting the monomer component and the weight fraction (copolymerization composition) of the monomer. The value of Tg of the homopolymer can be obtained from various known materials (such as “Adhesion Technology Handbook” of Nikkan Kogyo Shimbun).
(Hydrated metal compounds)
Contained in the flame-retardant thermally conductive pressure-sensitive adhesive layer (b) a hydrated metal compound, in the range of decomposition temperature is 150 to 500 ° C., the general formula _{M m O n · XH 2 O} (M here A metal, m, n are an integer of 1 or more determined by the valence of the metal, and X is a compound represented by water containing crystal water) or a double salt containing the above compound.

Examples of the (b) hydrated metal compound in the present invention include aluminum hydroxide [Al ₂ O ₃ .3H ₂ O; or Al (OH) ₃ ], boehmite [Al ₂ O ₃ .H ₂ O; or AlOOH]. , Magnesium hydroxide [MgO.H ₂ O; or Mg (OH) ₂ ], calcium hydroxide [CaO.H ₂ O; or Ca (OH) ₂ ], zinc hydroxide [Zn (OH) ₂ ], silicic acid [ H ₄ SiO ₄ ; or H ₂ SiO ₃ ; or H ₂ Si ₂ O ₅ ], iron hydroxide [Fe ₂ O ₃ .H ₂ O or 2FeO (OH)], copper hydroxide [Cu (OH) ₂ ], barium hydroxide [BaO · _H 2 O; or BaO · _9H 2 O], zirconium oxide hydrate [ZrO · _nH 2 O], tin oxide hydrate [SnO · _H 2 O], basic magnesium carbonate [3MgC _{3 · Mg (OH) 2 ·} 3H 2 O], hydrotalcite _{[6MgO · Al 2 O 3 ·} H 2 O], dawsonite _{[Na 2 CO 3 · Al 2} O 3 · nH 2 O], borax [Na ₂ O.B ₂ O ₅ · 5H ₂ O], zinc borate [2ZnO · 3B ₂ O ₅ · 3.5H ₂ O] and the like. Examples of the hydrated metal compound include hydrotalcite and borax.

  These hydrated metal compounds may be used alone or in combination of two or more.

  Among these hydrated metal compounds, aluminum hydroxide is preferably used because of its high thermal conductivity and high flame retardancy.

  The shape of the (b) hydrated metal compound used in the present invention is not particularly limited, and may be a bulk shape, a needle shape, a plate shape, or a layer shape. The bulk shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a crushed shape, or a deformed shape thereof.

  In the present invention, the particle diameter of the hydrated metal compound (b) is 0.1 to 1000 μm, preferably 1 to 100 μm as the primary average particle diameter in the case of a bulk (spherical) hydrated metal compound. Preferably, it is 5-80 micrometers. When the primary average particle diameter exceeds 1000 μm, there is a problem that the hydrated metal compound exceeds the thickness of the flame-retardant heat conductive pressure-sensitive adhesive layer and causes thickness variation.

The primary average particle diameter is a volume-based value obtained by the particle size distribution measurement method in the laser scattering method. Specifically, it is calculated | required by measuring _D50 value with a laser scattering type particle size distribution system.

  (B) When the hydrated metal compound is a needle-shaped or plate-shaped thermally conductive particle, the maximum length is 0.1 to 1000 μm, preferably 1 to 100 μm, more preferably 5 to 45 μm.

  When the maximum length exceeds 1000 μm, the heat conducting particles tend to aggregate and there is a problem that handling becomes difficult.

  These aspect ratios are 1-10000, for example, Preferably, it is 1-1000. In the case of needle crystals, the aspect ratio is expressed by major axis length / minor axis length or major axis length / thickness. In the case of a plate-like crystal, it is expressed by diagonal length / thickness or long side length / thickness.

  In the present invention, preferably, (b) the hydrated metal compound is used in combination of two or more hydrated metal compounds having different particle diameters.

  When two or more kinds of hydrated metal compounds having different particle diameters are used in combination, it is preferable to combine a large particle having a particle diameter of 5 μm or more and a small particle having a particle diameter of less than 5 μm.

  Here, the particle diameter means the primary average particle diameter or the maximum length.

  By using hydrated metal compounds with different particle sizes in this way, the thermally conductive particles are more closely packed in the flame retardant thermally conductive pressure-sensitive adhesive layer. As a result, the heat conduction path is easily constructed, and the heat conductivity is improved.

  In the case of obtaining the above effect, the blending ratio (weight ratio) is, for example, 1:10 to 10: 1, preferably 1: 5 to 5: 1, and more preferably 1: 2 to 2: 1.

  In the present invention, as the (b) hydrated metal compound, a general commercially available product can be used. As the aluminum hydroxide, for example, trade name “Hijilite H-100-ME” (primary average particle) Diameter 75 μm) (manufactured by Showa Denko KK), trade name “Hijilite H-10” (primary average particle diameter 55 μm) (manufactured by Showa Denko KK), trade name “Heidilite H-32” (primary average particle diameter 8 μm) ) (Manufactured by Showa Denko KK), trade name “Hijilite H-42” (primary average particle diameter 1 μm) (manufactured by Showa Denko KK), etc., trade name “B103ST” (primary average particle diameter 8 μm) (Nippon Light Metal Co., Ltd.) As the magnesium hydroxide, for example, trade name “KISUMA 5A” (primary average particle diameter 1 μm) (manufactured by Kyowa Chemical Industry Co., Ltd.) can be used.

  The content of the (b) hydrated metal compound constituting the flame-retardant heat conductive pressure-sensitive adhesive layer of the present invention is not particularly limited, but is 100 parts by mass of the acrylic polymer in the flame-retardant heat conductive pressure-sensitive adhesive layer. On the other hand, it is 100-500 mass parts, Preferably, it is 200-450 mass parts, More preferably, it is 300-400 mass parts.

  When the content of the hydrated metal compound is 100 to 500 parts by mass with respect to 100 parts by mass of the acrylic polymer, high thermal conductivity and flame retardancy can be obtained.

  On the other hand, if the content of the hydrated metal compound is less than 100 parts by mass, sufficient thermal conductivity and flame retardancy may not be imparted, and if it exceeds 500 parts by mass, the flexibility is low. Thus, the adhesive strength and holding power may be reduced.

  In the present invention, other heat conductive particles may be included in order to improve the heat conductivity.

  Examples of the thermally conductive particles that can be used in the present invention include boron nitride, aluminum nitride, silicon nitride, gallium nitride, silicon carbide, silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, tin oxide, and oxide. Copper, nickel oxide, antimonic acid doped tin oxide, calcium carbonate, barium titanate, potassium titanate, copper, silver, gold, nickel, aluminum, platinum, carbon black, carbon tube (carbon nanotube), carbon fiber, diamond, etc. Can be mentioned.

  In addition, about the magnitude | size (particle diameter) of a heat conductive particle, it can handle similarly to the said hydrated metal compound.

  In the present invention, as such heat conductive particles, general commercial products can be used. For example, as boron nitride, trade name “HP-40” (manufactured by Mizushima Alloy Iron Company), trade name “PT620” ( As the aluminum oxide, for example, trade name “AS-50” (manufactured by Showa Denko KK), etc., and as the antimonate doped tin, for example, trade name “SN-100S” (manufactured by Ishihara Sangyo Co., Ltd.) ), Trade name “SN-100P” (made by Ishihara Sangyo Co., Ltd.), trade name “SN-100D (water-dispersed product)” (made by Ishihara Sangyo Co., Ltd.), etc. Examples of zinc oxide (Ishihara Sangyo Co., Ltd.) include, for example, trade name “SnO-310” (manufactured by Sumitomo Osaka Cement Co., Ltd.), trade name “SnO-350” (manufactured by Sumitomo Osaka Cement Co., Ltd.), and trade name “SnO”. 410 "(manufactured by Sumitomo Osaka Cement Co., Ltd.), and the like.

  In the present invention, when the heat conductive particles are used in combination, the content is not particularly limited, but for example 100 parts by weight or less with respect to 100 parts by weight of the acrylic polymer in the flame retardant heat conductive pressure-sensitive adhesive layer, Preferably, it is 1-270 mass parts, More preferably, it is 5-280 mass parts.

  When content of a heat conductive particle exceeds 280 mass parts, the flexibility of a flame-retardant heat conductive adhesive layer may fall, or a flame retardance may fall.

  Moreover, in the flame-retardant heat conductive adhesive layer of the present invention, a dispersant is preferably used in order to stably disperse the hydrated metal compound and the heat conductive particles without agglomerating. Although it does not specifically limit as a dispersing agent, Preferably, phosphate ester is mentioned. Examples of the phosphoric acid ester include phosphoric acid monoesters including polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether or polyoxyethylene alkyl aryl ether, phosphoric acid including polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether Examples thereof include diesters and phosphoric acid triesters, and derivatives thereof.

  These phosphate ester dispersants may be used alone or in combination of two or more.

  Among them, in view of the temporal stability of the heat conductive particles, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphate monoester or phosphate diester is preferably used.

  Such dispersants are, for example, trade name “Plisurf A212E” (Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Plisurf A210G” (Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Plisurf A212C” (No. 1). Made by Ichi Kogyo Seiyaku Co., Ltd., trade name “Plisurf A215C” (made by Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Phosphanol RE610” (made by Toho Chemical Co., Ltd.), trade name “Phosphanol RS710” (Toho Chemical Co., Ltd.) Product name) “Phosphanol RS610” (manufactured by Toho Chemical Co., Ltd.).

Moreover, the blending amount of the dispersant is not particularly limited, but is, for example, 0.01 to 10 parts by weight, preferably 0.05 parts by weight to 5 parts by weight, more preferably, with respect to 100 parts by weight of the acrylic polymer. 0.1 parts by mass to 3 parts by mass.
In the present invention, in order to improve flame retardancy, other flame retardants may be contained within a range that does not adversely affect adhesiveness and thermal conductivity.

  Examples of the flame retardant that can be used in the present invention include metal carbonates such as basic magnesium carbonate, magnesium carbonate-calcium, calcium carbonate, barium carbonate, and dolomite, such as barium metaborate, magnesium oxide, ammonium polyphosphate, Examples include zinc borate, tin compounds, organic phosphorus, red phosphorus, carbon black, and silicone flame retardants.

  When the flame retardant is used in the present invention, the content is not particularly limited, but is 250 parts by mass or less with respect to 100 parts by mass of the acrylic polymer in the flame retardant thermally conductive pressure-sensitive adhesive layer.

  When the content of the flame retardant exceeds 250 parts by mass, the adhesion of the flame retardant thermally conductive pressure-sensitive adhesive layer may be significantly lowered or the thermal conductivity may be lowered due to the bleeding out of the monomer.

  In addition, the content of the flame retardant is preferably 1 to 270 parts by mass, more preferably 5 to 280 parts by mass with respect to 100 parts by mass of the acrylic polymer.

  In the present invention, in addition to (b) the hydrated metal compound, when the heat conductive particles and / or the flame retardant are used in combination, the total amount thereof is the acrylic polymer 100 in the flame retardant heat conductive pressure-sensitive adhesive layer. It is 100-500 mass parts with respect to a mass part, Preferably, it is 200-450 mass parts, More preferably, it is 300-400 mass parts.

  When the content of the hydrated metal compound, the thermally conductive particles and / or the flame retardant is 100 to 500 parts by mass with respect to 100 parts by mass of the acrylic polymer, the flame retardant thermally conductive adhesive sheet has a high heat. Conductivity and flame retardancy can be obtained.

  On the other hand, if the content of the hydrated metal compound, the thermally conductive particles and / or the flame retardant is less than 100 parts by mass, sufficient thermal conductivity and flame retardancy may not be imparted. If it exceeds the mass part, the flexibility becomes low, and the adhesive force and holding force of the flame-retardant heat conductive adhesive layer may be reduced.

  In the present invention, when the heat conductive particles and / or the flame retardant are used in addition to (b) the hydrated metal compound, the content of the hydrated metal compound is such that the hydrated metal compound, the heat conductive particles and / or It is 50 mass% or more with respect to the total amount of a flame retardant, Preferably, it is 60 mass% or more, More preferably, it is 70 mass% or more.

  If the content rate of a hydrated metal compound is 50 mass% or more, the flame-retardant heat conductive adhesive sheet can obtain high heat conductivity and flame retardance.

On the other hand, if the content ratio of the hydrated metal compound is less than 50% by mass, the flame-retardant heat conductive pressure-sensitive adhesive sheet may not be able to impart sufficient heat conductivity and flame resistance.
(Bubbles)
In the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention, the flame-retardant heat conductive pressure-sensitive adhesive layer can also contain bubbles.

  By including air bubbles in the flame-retardant heat conductive pressure-sensitive adhesive layer, the flame-retardant heat conductive pressure-sensitive adhesive sheet can be provided with thickness and cushioning properties, and the followability to the uneven surface of the adherend is improved.

  The bubble content can be appropriately selected within a range that does not impair the heat conduction characteristics of the flame-retardant heat conductive pressure-sensitive adhesive sheet, but is generally 5 to the total volume of the flame-retardant heat conductive pressure-sensitive adhesive layer. It is 50 volume%, Preferably, it is 10-40 volume%, More preferably, it is 12-35 volume%.

  When the amount of bubbles is less than 5% by volume, the adhesion to the adherend and the unevenness followability are often poor.

  On the other hand, if the volume exceeds 50% by volume, the heat insulation effect due to the bubbles becomes too large, and the heat conductivity of the flame-retardant heat-conductive adhesive sheet may be lowered. Problems such as the possibility of deterioration of the adhesiveness of the sheet and the possibility of reducing the shearing force due to the flame-retardant thermally conductive pressure-sensitive adhesive layer becoming too soft occur.

  Basically, it is desirable that the air bubbles mixed in the flame-retardant heat conductive adhesive layer are closed-cell type bubbles, but the closed-cell type bubbles and open-cell type bubbles are mixed. Also good.

  In addition, such bubbles usually have a spherical shape, but may have an irregular spherical shape.

  In the said bubble, it does not specifically limit as the average bubble diameter (diameter), For example, 1-1000 micrometers, Preferably, it can select from the range of 10-500 micrometers, More preferably, it is 30-300 micrometers.

  The gas component contained in the bubbles (a gas component that forms bubbles, sometimes referred to as “bubble-forming gas”) is not particularly limited, and is an air other than an inert gas such as nitrogen, carbon dioxide, or argon. Various gas components such as can be used.

  However, as a bubble forming gas, when a reaction such as a polymerization reaction is performed after mixing the bubble forming gas, it is necessary to use a gas that does not inhibit the reaction.

  The bubble-forming gas is preferably nitrogen from the viewpoint of not inhibiting the reaction or from the viewpoint of cost.

  The method of mixing the bubbles is not particularly limited, but is preferably a mixture of monomer components containing (meth) acrylic acid alkyl ester as a main component and containing a polar group-containing monomer in an amount of 5% by mass or more, or partial polymerization thereof. (C) mixing bubbles with a precursor composition of a flame retardant thermally conductive pressure-sensitive adhesive layer containing a product and a hydrated metal compound (hereinafter sometimes referred to as “precursor composition”) Then, a precursor composition containing bubbles is prepared, and this is irradiated with ultraviolet rays to form a flame-retardant heat conductive adhesive layer.

  As a method of mixing bubbles, a known bubble mixing method can be used.

  For example, as a device, a stator with many fine teeth on a disk with a through hole in the center is opposed to a stator with teeth, and the same fine teeth as the stator are on the disk. And a device equipped with a rotor.

  In this device, a precursor composition is introduced between the teeth on the stator and the teeth on the rotor, and a gas component (bubble forming gas) for forming bubbles through the through-holes while rotating the rotor at a high speed is the precursor. By introducing into the composition, a bubble-containing precursor composition in which a bubble-forming gas is finely dispersed and mixed in the precursor composition can be obtained.

  In order to suppress or prevent the coalescence of bubbles, it is preferably performed continuously as a series of steps from mixing of bubbles to formation of a flame-retardant thermally conductive pressure-sensitive adhesive layer.

That is, after preparing a precursor composition containing bubbles by mixing bubbles as described above, it is difficult to use the precursor composition containing the bubbles and then using an appropriate forming method. A flammable heat conductive adhesive layer is formed.
(Fluorosurfactant)
In the present invention, a fluorine-based surfactant can be added to the precursor composition containing bubbles.

  Using a fluorosurfactant reduces the adhesion and frictional resistance between the hydrated metal compound and the acrylic polymer in the flame retardant thermally conductive adhesive layer, and reduces the stress between the hydrated metal compound and the acrylic polymer. Are dispersed, and the flame-retardant heat-conductive pressure-sensitive adhesive layer obtains a high adhesive force.

  When it has a fluorinated hydrocarbon group, the effect which improves the bubble mixing property and bubble stability in a flame-retardant heat conductive adhesive layer is also acquired.

As the fluorine-based surfactant, a fluorine-based surfactant having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group in the molecule is used.

The oxy C _2-3 alkylene group is represented by the formula: —R—O— (where R is a linear or branched alkylene group having 2 or 3 carbon atoms).

The fluorosurfactant is not particularly limited as long as it has an oxy _C2-3 alkylene group and a fluorinated hydrocarbon group, but is preferably a nonionic surfactant from the viewpoint of dispersibility with respect to an acrylic polymer. Is good.

Further, oxy- _{(C 2-3)} alkylene group in the molecule of the fluorine-based surfactant, an oxyethylene group _{(-CH 2} CH 2 O-), oxypropylene group _{[-CH 2 CH (CH 3)} O-] , etc. Any one of these may be used, or two or more may be used.

  In addition, a fluorine-type surfactant can be used individually or in combination of 2 or more types.

  Although it does not restrict | limit especially as a fluorinated hydrocarbon group, Preferably, a perfluoro group is mentioned.

  The perfluoro group may be monovalent or divalent or higher. Further, the fluorinated hydrocarbon group may have a double bond or a triple bond, and may be linear or have a branched structure or a cyclic structure.

  It does not specifically limit as carbon number of a fluorinated hydrocarbon group, For example, 1 or 2 or more, Preferably it is 3-30, More preferably, it is 4-20. One or two or more of these fluorinated hydrocarbon groups are introduced into the surfactant molecule.

Examples of the oxy _C2-3 alkylene group include alcohols in which a hydrogen atom is bonded to a terminal oxygen atom, ethers bonded to other hydrocarbon groups, and esters bonded to other hydrocarbon groups via a carbonyl group. Form may be sufficient.

Moreover, the form which has the said oxy _C2-3 alkylene group structure in some cyclic structures, such as cyclic ethers and lactones, may be sufficient.

The structure of the fluorosurfactant is not particularly limited. For example, a copolymer containing a monomer having an oxy _C2-3 alkylene group and a monomer having a fluorinated hydrocarbon group as monomer components. Is mentioned.

  As such a copolymer, various structures such as a block copolymer and a graft copolymer are conceivable, but any of them may be used.

Examples of the block copolymer (copolymer having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group in the main chain) include, for example, polyoxyethylene perfluoroalkyl ether, polyoxyethylene perfluoroalkylate, polyoxyethylene Examples include propylene perfluoroalkyl ether, polyoxyisopropylene perfluoroalkyl ether, polyoxyethylene sorbitan perfluoroalkylate, polyoxyethylene polyoxypropylene block copolymer perfluoroalkylate, and polyoxyethylene glycol perfluoroalkylate.

Examples of the graft copolymer (a copolymer having an oxy _C2-3 alkylene group and a fluorinated hydrocarbon group in the side chain) include a vinyl compound having a polyoxyalkylene group and a fluorinated hydrocarbon group. A copolymer with a vinyl compound, an acrylic copolymer, etc. are mentioned, Preferably an acrylic copolymer is mentioned.

  Examples of the vinyl compound having a polyoxyalkylene group include polyoxyalkylene (meth) acrylates such as polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, and polyoxyethylene polyoxypropylene (meth) acrylate. Can be mentioned.

  Examples of vinyl compounds having a fluorinated hydrocarbon group include perfluoroalkyl (meth) acrylates such as perfluorobutyl (meth) acrylate, perfluoroisobutyl (meth) acrylate, perfluoropentyl (meth) acrylate, and fluorine. (Meth) acrylic acid ester containing a fluorinated hydrocarbon.

  In addition to the above structure, the fluorosurfactant may have a structure such as an alicyclic hydrocarbon group or an aromatic hydrocarbon group in the molecule, and does not impair dispersibility in the acrylic polymer. And may have various functional groups such as a carboxyl group, a sulfonic acid group, a cyano group, an amide group, and an amino group.

  For example, when the fluorosurfactant is a vinyl copolymer, a monomer component copolymerizable with a vinyl compound having a polyoxyalkylene group and a vinyl compound having a fluorinated hydrocarbon group is used as the monomer component. It may be used.

  Such monomers can be used alone or in combination of two or more.

Examples of the copolymerizable monomer component include (meth) acrylic acid C _1-20 alkyl esters such as undecyl (meth) acrylate and dodecyl (meth) acrylate, for example, alicyclic rings such as cyclopentyl (meth) acrylate. (Meth) acrylic acid ester which has a formula hydrocarbon group, for example, (meth) acrylic acid ester which has aromatic hydrocarbon groups, such as phenyl (meth) acrylate, etc. are mentioned. In addition, carboxyl group-containing monomers such as maleic acid and crotonic acid, for example, sulfonic acid group-containing monomers such as sodium vinyl sulfonate, for example, aromatic vinyl compounds such as styrene and vinyl toluene, such as ethylene and butadiene Olefins or dienes such as vinyl ethers such as vinyl alkyl ethers, amide group-containing monomers such as acrylamide, for example amino group-containing monomers such as (meth) acryloylmorpholine, such as (meth) Examples include glycidyl group-containing monomers such as methyl glycidyl acrylate, for example, isocyanate group-containing monomers such as 2-methacryloyloxyethyl isocyanate. Moreover, you may use polyfunctional copolymerizable monomers (polyfunctional monomer), such as dipentaerythritol hexa (meth) acrylate and divinylbenzene.

  The weight average molecular weight of the fluorosurfactant is not particularly limited, but when the weight average molecular weight is less than 20000 (for example, 500 or more and less than 20000), an acrylic polymer in the flame-retardant thermally conductive pressure-sensitive adhesive layer, The effect of reducing adhesion between the heat conductive particles and frictional resistance is high.

  Furthermore, when a fluorosurfactant having a weight average molecular weight of 20000 or more (for example, 20,000 to 100,000, preferably 22,000 to 80,000, more preferably 24,000 to 60,000) is used in combination, the mixing property of the bubbles, Increased stability.

As a specific example, a fluorine-based surfactant having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group and having a weight average molecular weight of less than 20000 is trade name “Factent 251” (manufactured by Neos), trade name "FTX-218" (manufactured by Neos), trade name "Megafac F-477" (manufactured by Dainippon Ink and Chemicals), trade name "megafuck F-470" (manufactured by Dainippon Ink and Chemicals), product Name “Surflon S-381” (manufactured by Sey Chemical Co., Ltd.), Trade name “Surflon S-383” (manufactured by Sey Chemical Co., Ltd.), Product name “Surflon S-393” (manufactured by Sey Chemical Co., Ltd.), Product name “Surflon KH- 20 "(manufactured by Sey Chemical Co., Ltd.), trade name" Surflon KH-40 "(manufactured by Sey Chemical Co., Ltd.), and the like.

As a specific example, a fluorosurfactant having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group and having a weight average molecular weight of 20000 or more is a trade name “F-top EF-352” (manufactured by Gemco). , Trade name “F-top EF-801” (manufactured by Gemco), trade name “Unidyne TG-656” (manufactured by Daikin Industries), and the like.

  Any fluorosurfactant can be suitably used in the present invention.

  The amount of use (solid content) of the fluorosurfactant is not particularly limited. For example, it is 0 with respect to 100 parts by mass of the total monomer components for forming the acrylic polymer of the flame retardant thermally conductive pressure-sensitive adhesive layer. .01 to 5 parts by mass, preferably 0.02 to 3 parts by mass, and more preferably 0.03 to 2 parts by mass.

  When the amount is less than 0.01 parts by mass, it is difficult to obtain the stability of the bubbles, and when it exceeds 5 parts by mass, the adhesion performance may be deteriorated.

  In the present invention, the degree of adhesion and frictional resistance between the dispersant for stably dispersing the hydrated metal compound and the acrylic polymer in the hydrated metal compound and the flame-retardant thermally conductive adhesive layer are reduced. A fluorine-based surfactant that exhibits stress dispersibility can be used in combination.

  When these dispersants and fluorosurfactants are used in combination, the hydrated metal compound aggregates in the flame retardant thermally conductive adhesive layer in a smaller amount of fluorosurfactant than when used alone. The heat conductivity is improved without stabilization.

  Furthermore, the stress dispersibility of the flame retardant thermally conductive pressure-sensitive adhesive layer is also improved, and higher adhesive strength can be expected.

  When these two types of additives are used in combination, the blending amount is not particularly limited, but the ratio (weight ratio) of the dispersant to the fluorosurfactant is 1:20 to 20: 0.01, preferably 1:10 to 10: 0.01, more preferably 1: 5 to 5: 0.01.

  In order to stabilize the state in which bubbles are mixed in the flame retardant thermally conductive adhesive layer, the step of mixing the precursor composition of the flame retardant thermally conductive adhesive layer and the bubbles is preferably a series of steps. It is set as the last process of a flame-retardant heat conductive adhesive layer formation process. In the above step, more preferably, the viscosity of the precursor composition before mixing the bubbles is increased.

  The viscosity of the precursor composition is not particularly limited as long as it is a viscosity capable of stably holding the mixed bubbles, but is, for example, 5 to 50 Pa · s, preferably 10 to 40 Pa · s. (The measurement conditions are a BH viscometer, the rotor is a No. 5 rotor, the rotation speed is 10 rpm, and the temperature is 30 ° C.).

  When the viscosity of the precursor composition is less than 5 Pa · s, the viscosity is too low, and the mixed bubbles may immediately coalesce and come out of the system, while exceeding 50 Pa · s. If it is, when the flame-retardant heat-conductive pressure-sensitive adhesive layer is formed, the viscosity is too high and coating becomes difficult.

  In addition, the viscosity of the precursor composition is, for example, a method of blending various polymer components such as acrylic rubber and a thickening additive, a monomer component for forming an acrylic polymer (for example, for forming an acrylic polymer) It can be adjusted by a method of partially polymerizing a monomer component such as (meth) acrylic acid ester, etc. to obtain a partial polymer.

  Specifically, for example, a monomer component for forming an acrylic polymer (for example, a monomer component such as (meth) acrylic acid ester for forming an acrylic polymer) and a polymerization initiator (for example, photopolymerization) Initiator, thermal polymerization initiator, etc.) are mixed to prepare a monomer mixture, and the monomer mixture is subjected to a polymerization reaction according to the type of polymerization initiator, and only a part of the monomer components are polymerized. A composition (syrup) containing a partial polymer is prepared. A precursor of viscosity suitable for stably containing bubbles by blending the syrup with a hydrated metal compound and, if necessary, a monomer, a dispersant, a fluorosurfactant and various additives (described later). A body composition can be prepared.

  Furthermore, a precursor composition containing stable bubbles can be obtained by introducing and mixing bubbles into the precursor composition.

In preparing the syrup, a fluorosurfactant or a hydrated metal compound may be appropriately blended in advance during monomer mixing.
In the present invention, in order to adjust the cohesive strength of the flame retardant thermally conductive pressure-sensitive adhesive layer, a crosslinking agent can be used in addition to the above-described method of blending the polyfunctional monomer and introducing a crosslinked structure into the acrylic polymer. It is.
As the crosslinking agent, a commonly used crosslinking agent can be used. For example, an epoxy crosslinking agent, an isocyanate crosslinking agent, a silicone crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a silane crosslinking agent, an alkyl etherification agent. A melamine type crosslinking agent, a metal chelate type crosslinking agent, etc. are mentioned, Especially preferably, an isocyanate type crosslinking agent and an epoxy type crosslinking agent are mentioned.

  Specifically, as the isocyanate-based crosslinking agent, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, Examples include triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these with polyols such as trimethylolpropane.

  Also, a compound having at least one isocyanate group and one or more unsaturated bonds in one molecule, specifically, 2-isocyanatoethyl (meth) acrylate, etc. should be used as an isocyanate crosslinking agent. Can do.

  Epoxy crosslinking agents include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane tri Examples include glycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N′-diamine glycidylaminomethyl) cyclohexane. It is done.

  When the crosslinking agent is used in the present invention, the content is not particularly limited, but 0.01 to 5 parts by mass, preferably 100 parts by mass with respect to 100 parts by mass of the acrylic polymer in the flame-retardant heat-conductive pressure-sensitive adhesive layer. 0.01-3 parts by mass, and more preferably 0.01-2 parts by mass.

  When the content of the crosslinking agent exceeds 5 parts by mass, flexibility may not be obtained, and when it is less than 0.01 parts by mass, agglomeration may not be obtained.

  In order to improve adhesiveness, the flame-retardant heat conductive adhesive layer of this invention can be made to contain tackifying resin.

  Although it does not specifically limit as tackifying resin, Preferably, hydrogenation type tackifying resin is mentioned. Such a resin hardly inhibits the ultraviolet copolymerization of the acrylic polymer even when used in combination with the acrylic polymer.

  Examples of such hydrogenated tackifying resins include hydrogenation to tackifying resins such as petroleum resins, terpene resins, coumarone / indene resins, styrene resins, rosin resins, alkylphenol resins, and xylene resins. The derivatives can be selected. The hydrogenated petroleum resin can be selected from, for example, aromatic, dicyclopentadiene, aliphatic, and aromatic-dicyclopentadiene copolymer. The hydrogenated terpene resin can be selected from, for example, a terpene phenol resin and an aromatic terpene resin. Among these, Preferably, petroleum-type resin or terpene-type resin is mentioned.

  The softening point of the tackifier resin is preferably 80 to 200 ° C, more preferably 100 to 200 ° C.

  When the softening point of the tackifying resin is in the above range, a high cohesive force can be obtained.

  In this invention, when using tackifying resin, the content is not specifically limited, Preferably, it is 1-50 mass parts with respect to 100 mass parts of acrylic polymers in a flame-retardant heat conductive adhesive layer. Yes, more preferably 2 to 40 parts by mass, and particularly preferably 3 to 30 parts by mass.

  When the addition amount of the tackifying resin exceeds 50 parts by mass, the cohesive force may be reduced. When the addition amount is less than 1 part by mass, the effect of improving the adhesive force of the flame-retardant thermally conductive pressure-sensitive adhesive layer cannot be obtained. There is a case.

  In the present invention, an acrylic oligomer can be contained in order to improve adhesiveness.

  The acrylic oligomer (a) is a polymer having a glass transition temperature (Tg) higher than that of the acrylic polymer and a small weight average molecular weight, functions as a tackifier resin, and is polymerized at the time of polymerization using ultraviolet rays. It has the advantage that it is difficult to cause inhibition.

  In the present invention, the acrylic oligomer has a glass transition temperature (Tg) of, for example, about 0 ° C. or higher and 300 ° C. or lower, preferably about 20 ° C. or higher and 300 ° C. or lower, more preferably about 40 ° C. or higher and 300 ° C. or lower. is there.

  When the glass transition temperature (Tg) is less than about 0 ° C., the cohesive strength of the flame retardant thermally conductive pressure-sensitive adhesive layer at room temperature or higher is lowered, and the retention characteristics and high temperature of the flame retardant thermally conductive pressure sensitive adhesive layer are reduced. The adhesive strength in the area may be reduced.

  Note that the Tg of the acrylic oligomer can be calculated based on the Fox equation, similar to the Tg of the acrylic polymer (a).

  The weight average molecular weight of the acrylic oligomer is, for example, 1000 or more and less than 30000, preferably 1500 or more and less than 20000, and more preferably 2000 or more and less than 10,000.

  When the weight average molecular weight is 30000 or more, the effect of improving the adhesive strength of the flame-retardant heat conductive pressure-sensitive adhesive sheet may not be sufficiently obtained.

  Moreover, when it is less than 1000, the adhesive force of a flame-retardant heat conductive adhesive sheet and the fall of a retention characteristic may be caused.

  In the present invention, the measurement of the weight average molecular weight of the acrylic oligomer can be obtained by polystyrene conversion by the GPC method.

  Specifically, TSKgelGMH-H (20) × 2 columns are used in HPLC 8020 manufactured by Tosoh Corporation, and measurement is performed with a tetrahydrofuran solvent at a flow rate of about 0.5 ml / min.

  In the present invention, examples of the monomer constituting the acrylic oligomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and butyl (meth) acrylate. , Isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, (meth) 2-ethylhexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, ( (Meth) isodecyl acrylate, undecyl (meth) acrylate, (meth) (Meth) acrylic acid alkyl esters such as dodecyl crylate, for example, (meth) acrylic acid cyclohexyl, (meth) acrylic acid such as isobornyl ester with an alicyclic alcohol, such as (meth ) (Meth) acrylic acid aryl esters such as phenyl acrylate and benzyl (meth) acrylate, for example, (meth) acrylic esters obtained from terpene compound derivative alcohols.

  Such (meth) acrylic acid esters can be used alone or in combination of two or more.

  The (meth) acrylic oligomer is preferably a (meth) acrylic acid alkyl ester in which an alkyl group such as isobutyl (meth) acrylate or t-butyl (meth) acrylate has a branched structure, (meth) Esters of (meth) acrylic acid with cycloaliphatic alcohols such as cyclohexyl acrylate and isobornyl (meth) acrylate, aryl (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate As represented by (meth) acrylate having a cyclic structure such as, an acrylic monomer having a relatively bulky structure is included as a monomer unit.

  By giving such a bulky structure to the acrylic oligomer, the adhesiveness of the flame-retardant thermally conductive pressure-sensitive adhesive layer can be further improved.

  In particular, those having a ring structure in terms of bulkiness are highly effective, and those having a plurality of rings are more effective.

  In addition, when ultraviolet rays (ultraviolet rays) are used when synthesizing acrylic oligomers or when preparing flame retardant thermally conductive pressure-sensitive adhesive layers, monomers having saturated bonds are less likely to cause polymerization inhibition. Such a monomer is preferably (meth) acrylate or alicyclic alcohol in which the alkyl group has a branched structure.

  From this point, in the present invention, as the acrylic oligomer, for example, a copolymer of cyclohexyl methacrylate (CHMA) and isobutyl methacrylate (IBMA), cyclohexyl methacrylate (CHMA) and isobornyl methacrylate (IBXMA) Copolymer of cyclohexyl methacrylate (CHMA) and acryloylmorpholine (ACMO), copolymer of cyclohexyl methacrylate (CHMA) and diethylacrylamide (DEAA), 1-adamantyl acrylate (ADA) and methacrylic acid Copolymer of methyl (MMA) or copolymer of dicyclopentanyl methacrylate (DCPMA) and isobornyl methacrylate (IBXMA), dicyclopentanyl methacrylate (DCP) A), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), 1-adamantyl acrylate ( ADA) homopolymers and the like.

  In the present invention, when an acrylic oligomer is used, the content thereof is not particularly limited, but is, for example, 1 to 70 parts by weight, preferably 100 parts by weight with respect to 100 parts by weight of the acrylic polymer in the flame-retardant thermally conductive pressure-sensitive adhesive layer. Is 2 to 50 parts by mass, more preferably 3 to 40 parts by mass. When the addition amount of the acrylic oligomer exceeds 70 parts by mass, the cohesive force of the flame retardant thermally conductive pressure-sensitive adhesive layer may be reduced.

  Moreover, the elasticity modulus of the said flame-retardant heat conductive adhesive layer becomes high too much, and the malfunction of the adhesive force fall of a low temperature range and the adhesive force loss | disappearance of a room temperature region may generate | occur | produce.

  On the other hand, when the addition amount of the acrylic oligomer is less than 1 part by mass, the effect of improving the adhesive force may not be obtained.

  A silane coupling agent can be used in the flame-retardant heat-conductive pressure-sensitive adhesive layer of the present invention for the purpose of improving adhesive strength, durability, and affinity between the hydrated metal compound and the acrylic polymer.

  As the silane coupling agent, known ones can be appropriately used without particular limitation.

  Specifically, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltri Epoxy group-containing silane coupling agents such as methoxysilane, such as 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1, Amino group-containing silane coupling agents such as 3-dimethylbutylidene) propylamine, for example, (meth) acryl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, For example, 3-isocyanatopropyl Such Inshianeto group-containing silane coupling agents such as triethoxysilane and the like.

  These silane coupling agents may be used alone or in combination of two or more.

  The content of the silane coupling agent is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, more preferably 100 parts by mass of the acrylic polymer. 0.05 to 2 parts by mass.

By using the silane coupling agent in the above range, the cohesive force and durability can be improved more reliably. If it is less than 0.01 parts by mass, the surface of the thermally conductive particles contained in the flame retardant thermally conductive pressure-sensitive adhesive layer cannot be coated, and the affinity may not be improved. On the other hand, if it exceeds 10 parts by mass, Thermal conductivity may be reduced.
(Other ingredients)
In the present invention, the flame retardant thermally conductive adhesive layer includes (a) an acrylic polymer, (b) a hydrated metal compound, and the above-described bubbles and various components, as well as a flame retardant thermally conductive adhesive layer. Depending on the application, an appropriate additive may be contained. For example, appropriate additives such as a plasticizer, a filler, an anti-aging agent, and a colorant (such as pigments and dyes) may be included.
(Preparation of flame retardant thermally conductive adhesive layer)
In the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention, a flame-retardant heat conductive pressure-sensitive adhesive composition containing at least (a) an acrylic polymer and (b) a hydrated metal compound is used. When forming the adhesive layer, it can be formed using a known forming method. For example, a monomer component for forming an acrylic polymer, a polymerization initiator (for example, a photopolymerization initiator, a thermal polymerization initiator, etc.), and an appropriate solvent (toluene, ethyl acetate, etc.) are mixed to form a monomer. Prepare the solution.

  The monomer solution is subjected to a polymerization reaction according to the type of polymerization initiator to prepare a polymer solution containing an acrylic polymer copolymerized with monomer components, and then a hydrated metal compound and various additives as necessary. Is added to prepare a flame retardant thermally conductive pressure-sensitive adhesive composition having a viscosity suitable for coating.

  A flame-retardant heat conductive adhesive layer can be formed by apply | coating a flame-retardant heat conductive adhesive composition on a predetermined surface, and performing drying, hardening, etc. as needed.

  In the present invention, when curing using ultraviolet rays is used, a monomer mixture for preparing an acrylic polymer and a photopolymerization initiator are mixed to prepare a monomer mixture, and the monomer mixture is irradiated with ultraviolet rays. To prepare a composition (syrup) containing a partial polymer obtained by polymerizing only a part of the monomer components.

  The syrup is mixed with a hydrated metal compound and, if necessary, a monomer, a dispersant, a fluorosurfactant and various additives to prepare a precursor composition having a viscosity suitable for coating.

  After apply | coating the said precursor composition on a predetermined | prescribed surface, a flame-retardant heat conductive adhesive layer can be formed by irradiating with an ultraviolet-ray and making it harden | cure.

  Moreover, in this invention, when obtaining the flame-retardant heat conductive adhesive layer which has a bubble, the precursor composition which mixed the bubble with the said precursor composition is obtained. After applying the precursor composition containing bubbles to a predetermined surface, the flame retardant thermally conductive pressure-sensitive adhesive layer having bubbles can be formed by curing by irradiation with ultraviolet rays. .

  In addition, the coating method currently widely used can be employ | adopted as a coating method at the time of apply | coating the said flame-retardant heat conductive adhesive composition and precursor composition on a predetermined surface. For example, a flame retardant thermally conductive pressure-sensitive adhesive layer can be prepared by coating a coating liquid on a substrate or a release liner containing a polyester film, and drying and then bonding another release liner.

  Examples of the method for forming the flame retardant thermally conductive pressure-sensitive adhesive layer in the present invention include a roll coat, a kiss roll coat, a gravure coat, a reverse coat, a roll brush, a spray coat, a dip roll coat, a bar coat, a knife coat, and an air. Examples thereof include an extrusion coating method such as knife coating, curtain coating, lip coating, and die coater.

  In this invention, it does not restrict | limit especially as thickness of a flame-retardant heat conductive adhesive layer, For example, 1-950 micrometers, Preferably it is 20-200 micrometers, More preferably, it can select from the range of 30-100 micrometers.

  If the thickness of the flame-retardant heat-conductive pressure-sensitive adhesive layer is less than 10 μm, sufficient adhesion and holding power may not be obtained. On the other hand, if the thickness is greater than 950 μm, sufficient heat conductivity is obtained. You may not be able to.

  In the present invention, the flame-retardant thermally conductive pressure-sensitive adhesive sheet has a tensile modulus of, for example, 0.1 MPa or more, preferably 10 MPa or more, more preferably 20 MPa or more, and usually less than 1000 MPa.

If the tensile elastic modulus of the flame-retardant heat-conductive adhesive sheet is less than the above lower limit, the flame-retardant heat-conductive pressure-sensitive adhesive sheet may be stretched when pasted, resulting in poor pasting. The tensile modulus is measured according to the description in the evaluation of Examples (described later).
(Adhesive layer (non-flame retardant thermally conductive adhesive layer))
In the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention, a pressure-sensitive adhesive layer other than the above-mentioned flame-retardant heat-conductive pressure-sensitive adhesive layer (non-flame-retardant heat-conductive pressure-sensitive adhesive) unless the effects of the present invention are impaired. Agent layer).

  When the flame-retardant heat conductive adhesive layer is provided on one surface of the substrate and the non-flame-retardant heat conductive adhesive layer is provided on the other surface (FIG. 1 (c)), the non-flame retardant heat conductivity The pressure-sensitive adhesive layer is a known pressure-sensitive adhesive (for example, acrylic pressure-sensitive adhesive, rubber pressure-sensitive adhesive, vinyl alkyl ether pressure-sensitive adhesive, silicone pressure-sensitive adhesive, polyester pressure-sensitive adhesive, polyamide pressure-sensitive adhesive, urethane pressure-sensitive adhesive, fluorine And a pressure-sensitive adhesive layer, an epoxy pressure-sensitive adhesive, etc.).

Moreover, the thickness of a non-flame retardant heat conductive adhesive layer is not specifically limited, According to the objective, the usage method, etc., it can select suitably.
(Release liner)
In the present invention, a release liner may be used to protect the adhesive surface (adhesive surface) of the pressure-sensitive adhesive layer such as the flame-retardant heat-conductive pressure-sensitive adhesive layer or the non-flame-retardant heat-conductive pressure-sensitive adhesive layer.

  Note that the release liner is not necessarily provided. In the present invention, the release liner is used by being peeled off when the pressure-sensitive adhesive layer is attached to the adherend.

  A conventional release paper or the like can be used as such a release liner.

  Specifically, as a release liner, in addition to a substrate having a release treatment layer with a release treatment agent on at least one surface, a fluorine-based polymer (for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinyl fluoride). Low-adhesive substrates composed of vinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc., and nonpolar polymers (for example, olefin resins such as polyethylene and polypropylene) For example, a release liner having a release treatment layer formed on at least one surface of a release liner substrate. Such release liner substrates include polyester films (polyethylene terephthalate film, etc.), olefin resin films (polyethylene film, polypropylene film, etc.), polyvinyl chloride films, polyimide films, polyamide films (nylon films), rayon films. In addition to plastic base film (synthetic resin film) and papers (quality paper, Japanese paper, kraft paper, glassine paper, synthetic paper, topcoat paper, etc.), etc., these are laminated by laminating or coextrusion. (2-3 layer composite) etc. are mentioned.

On the other hand, the release treatment agent constituting the release treatment layer is not particularly limited, and for example, a silicone release treatment agent, a fluorine release treatment agent, a long-chain alkyl release treatment agent, or the like can be used. The release treatment agents can be used alone or in combination of two or more.
The thickness of the release liner, the formation method, etc. are not particularly limited.
According to the flame-retardant heat conductive pressure-sensitive adhesive sheet of the present invention, since it is excellent in heat conductivity and flame retardancy, it is suitable for applications such as hard disks, LED lighting, lithium ion batteries, etc., taking advantage of the characteristics.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples.
Example 1
As a monomer component, 82 parts by mass of 2-ethylhexyl acrylate and 12 parts by mass of 2-methoxyethyl acrylate are used. As a polar group-containing monomer, 5 parts by mass of N-vinyl-2-pyrrolidone (NVP) and hydroxyethylacrylamide (HEAA) are used. The product name “Irgacure 651” (2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by Ciba Japan Co., Ltd.) as a photopolymerization initiator was added to the monomer mixture mixed with 1 part by mass. 05 parts by mass and a trade name “Irgacure 184” (1-hydroxycyclohexyl phenyl ketone, manufactured by Ciba Japan) were mixed.

  The mixture of the monomer mixture and the photopolymerization initiator is irradiated with ultraviolet rays, and a part thereof is polymerized until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reaches about 20 Pa · s. A composition (syrup) was prepared.

  To 100 parts by mass of this syrup, 0.05 parts by mass of dipentaerythritol hexaacrylate (trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.) as a polyfunctional monomer, and the product name “Plisurf A212E” (as a dispersant) 1 part by mass of Daiichi Kogyo Seiyaku Co., Ltd.) was added.

  Furthermore, as a hydrated metal compound, 175 parts by mass of aluminum hydroxide powder, trade name “Hijilite H-32” (shape: crushed, particle size: 8 μm, Showa Denko) and aluminum hydroxide powder The name “Hijilite H-10” (shape: crushed, particle size: 55 μm) (Showa Denko) 175 parts by mass was added to prepare a precursor composition.

  The precursor composition was dried and separated between the release treated surfaces of two release liners made of polyethylene terephthalate (trade name “Diafoil MRF38” (Mitsubishi Chemical Polyester Film Co., Ltd.)). It applied so that the thickness after hardening might be set to 54 micrometers.

  That is, the precursor composition is sandwiched between release liners made of polyethylene terephthalate.

Subsequently, ultraviolet rays with an illuminance of about 5 mW / cm ² were irradiated from both sides for 3 minutes to polymerize the monomer component to obtain an acrylic polymer, and a flame-retardant heat conductive adhesive layer was produced. The glass transition temperature of the acrylic polymer was −62.8 ° C.

  The release liner on one side of the flame-retardant heat-conductive adhesive layer was peeled off, and the flame-retardant heat-conductive adhesive layer was replaced with a polyethylene terephthalate film having a thickness of 12 μm, trade name “Lumirror S-10” (manufactured by Toray Industries, Inc. ).

Thus, the total thickness (excluding the thickness of the release liner, including the polyethylene terephthalate film and the flame-retardant heat conductive adhesive layer provided on both sides thereof. That is, the polyethylene terephthalate film has a thickness of 12 μm and each flame-retardant property. A flame-retardant heat-conductive pressure-sensitive adhesive sheet having a thickness of 54 μm (the same applies hereinafter) of a heat-conductive pressure-sensitive adhesive layer was prepared.
(Example 2)
In Example 1, a flame-retardant heat conductive adhesive sheet having a total thickness of 250 μm was prepared in the same manner as in Example 1 except that the thickness of the flame-retardant heat conductive adhesive layer was 119 μm. .
Example 3
In Example 1, a flame-retardant heat conductive adhesive sheet having a total thickness of 500 μm was prepared in the same manner as in Example 1 except that the thickness of the flame-retardant heat conductive adhesive layer was 244 μm. .
Example 4
In Example 1, the thickness of the flame retardant thermally conductive pressure-sensitive adhesive layer was 112.5 μm, and a polyethylene terephthalate film having a thickness of 25 μm as a base material, trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. Others were the same formulation as in Example 1, and a flame-retardant thermally conductive adhesive sheet with a total thickness of 250 μm was prepared.
(Example 5)
In Example 1, the flame retardant thermally conductive pressure-sensitive adhesive layer had a thickness of 237.5 μm, and a polyethylene terephthalate film having a thickness of 25 μm as a substrate, trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. Others were the same formulation as in Example 1, and a flame-retardant thermally conductive adhesive sheet having a total thickness of 500 μm was prepared.
( Comparative Example 6)
In Example 1, the thickness of the flame-retardant heat conductive adhesive layer was set to 106 μm, and a polyethylene terephthalate film having a thickness of 38 μm as a base material, a trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. A flame-retardant thermally conductive pressure-sensitive adhesive sheet having a total thickness of 250 μm was prepared in the same manner as in Example 1.
(Example 7)
In Example 1, the thickness of the flame retardant thermally conductive pressure-sensitive adhesive layer was 59 μm, and a polyethylene terephthalate film having a thickness of 2 μm as a base material, a trade name “Lumirror 2DC-61” (manufactured by Toray Industries, Inc.) was used. A flame-retardant thermally conductive pressure-sensitive adhesive sheet having the same formulation as in Example 1 and a total thickness of 120 μm was prepared.
(Example 8)
In Example 1, except that the thickness of the flame-retardant heat conductive adhesive layer was 122.5 μm and a polyethylene terephthalate film having a thickness of 5 μm was used as the base material, the total thickness was the same as in Example 1. Produced a flame-retardant thermally conductive pressure-sensitive adhesive sheet having a thickness of 250 μm.
( Comparative Example 9)
In Example 1, except that the thickness of the flame-retardant heat conductive adhesive layer was 102.5 μm and a polyethylene terephthalate film having a thickness of 45 μm was used as the base material, the total thickness was the same as in Example 1. Produced a flame-retardant thermally conductive pressure-sensitive adhesive sheet having a thickness of 250 μm.
(Comparative Example 1)
In Example 1, the thickness of the flame retardant thermally conductive pressure-sensitive adhesive layer was 231 μm, and a polyethylene terephthalate film having a thickness of 38 μm as a base material, a trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. A flame retardant thermally conductive pressure-sensitive adhesive sheet having a total thickness of 500 μm was prepared in the same manner as in Example 1.
(Comparative Example 2)
In Example 1, the thickness of the flame retardant thermally conductive pressure-sensitive adhesive layer was set to 100 μm, and a polyethylene terephthalate film having a thickness of 50 μm as a base material, a trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. A flame-retardant thermally conductive pressure-sensitive adhesive sheet having a total thickness of 250 μm was prepared in the same manner as in Example 1.
(Comparative Example 3)
In Example 1, the thickness of the flame retardant thermally conductive pressure-sensitive adhesive layer was set to 41 μm, and a polyethylene terephthalate film having a thickness of 38 μm as a base material, trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. A flame-retardant thermally conductive pressure-sensitive adhesive sheet having the same formulation as in Example 1 and a total thickness of 120 μm was prepared.
(Comparative Example 4)
In Example 1, the thickness of the flame-retardant thermally conductive pressure-sensitive adhesive layer was 47.5 μm, and a polyethylene terephthalate film having a thickness of 25 μm as a substrate, trade name “Lumirror S-10” (manufactured by Toray Industries, Inc.) was used. Others were the same formulation as in Example 1, and a flame-retardant thermally conductive adhesive sheet with a total thickness of 120 μm was prepared.
(Test evaluation)
The following test was done about the flame-retardant heat conductive adhesive sheet obtained by each Example and each comparative example. The test results are shown in Table 1.
(Thermal resistance)
The measurement of thermal resistance was performed using the thermal characteristic evaluation apparatus shown in FIG.

  Specifically, between a pair of aluminum blocks (A5052, thermal conductivity: 140 W / m · K) L (sometimes referred to as rods) L formed so as to be a cube having a side of 20 mm. The flame-retardant heat conductive adhesive sheet S (20 mm × 20 mm) of each example and each comparative example was sandwiched, and a pair of blocks L were bonded together with an adhesive sheet.

  And it arrange | positioned between the heat generating body (heater block) H and the heat radiating body (cooling base board comprised so that a cooling water circulates inside) C so that a pair of block L might become up-down. Specifically, the heating element H is disposed on the upper block L, and the radiator C is disposed below the block L on the lower side.

  At this time, the pair of blocks L bonded together with the flame-retardant heat-conductive adhesive sheet S is positioned between a pair of pressure adjusting screws T penetrating the heating element H and the radiator C. A load cell R is disposed between the pressure adjusting screw T and the heating element H, and is configured to measure the pressure when the pressure adjusting screw T is tightened. Was used as a pressure applied to the flame-retardant heat-conductive adhesive sheet S.

  In addition, three probes P (diameter 1 mm) of a contact displacement meter were installed so as to penetrate the lower block L and the flame-retardant heat conductive adhesive sheet S from the radiator C side. At this time, the upper end portion of the probe P is in contact with the lower surface of the upper block L, and the distance between the upper and lower blocks L (the thickness of the adhesive sheet S) can be measured.

  A temperature sensor D was attached to the heating element H and the upper and lower blocks L. Specifically, the temperature sensor D was attached to one place of the heating element H, and the temperature sensors D were attached to the five places of each block L at intervals of 5 mm in the vertical direction.

  First of all, the pressure adjusting screw T is tightened to apply pressure to the flame-retardant heat conductive adhesive sheet S, the temperature of the heating element H is set to 80 ° C., and the temperature of the radiator C is set to 20 ° C. Cooling water was circulated.

After the temperature of the heating element H and the upper and lower blocks L is stabilized, the temperature of the upper and lower blocks L is measured by each temperature sensor D, and the thermal conductivity (W / m · K) and temperature gradient of the upper and lower blocks L are measured. As well as calculating the heat flux passing through the flame-retardant heat conductive adhesive sheet S, the temperature at the interface between the upper and lower blocks L and the flame-retardant heat conductive adhesive sheet S was calculated. Then, using these, the thermal conductivity (W / m · K) and thermal resistance (cm ² · K / W) at the above pressure were calculated using the following thermal conductivity equation (Fourier's law).

Q = −λgradT
R = L / λ
Q: Heat flow rate per unit area gradT: Temperature gradient L: Sheet thickness λ: Thermal conductivity
R: Thermal resistance This time, thermal conductivity (described later) and thermal resistance at a pressure of 25 N / cm ² (250 kPa) applied to the flame-retardant thermal conductive adhesive sheet S were employed.
(Thermal conductivity)
The thermal conductivity was measured using the thermal property evaluation apparatus shown in FIG. 2 described above.

  The flame-retardant heat conductive adhesive sheet S (20 mm × 20 mm) of each example and each comparative example was loaded into the evaluation apparatus in the same manner as in the case of measuring the thermal resistance.

First of all, the pressure adjusting screw T is tightened and sandwiched between the upper and lower blocks, and a pressure of 25 N / cm ² (250 kPa) is applied to the flame-retardant heat-conductive adhesive sheet S. While setting the amount to be constant 30 W, cooling water at 20 ° C. was circulated through the radiator C. At that time, the case where the temperature change of the thermocouple was 0.02 ° C. or less in 30 seconds was regarded as a stable state, and the temperature of the thermocouple on the heater side closest to the sheet was read as the module temperature.
(Tensile modulus)
Using the flame-retardant heat conductive adhesive sheet of each example and each comparative example as an evaluation sample, the initial longitudinal length is 20 mm, the initial width is 10 mm, and the cross-sectional area (thickness direction and cross-sectional area along the longitudinal direction) is 1. ² to 5.0 mm ² (that is, in Examples 1 and 7 and Comparative Examples 3 and 4, 0.12 mm × 10 mm = 1.2 mm ² , Examples ² , 4, 6, 8, 9 and Comparative Example) 2 and 0.25 mm × 10 mm = 2.5 mm ² , and in Examples 3 and 5 and Comparative Example 1, 0.0.50 mm × 10 mm = 5.0 mm ² ) was cut. Subsequently, a tensile test was performed at a measurement temperature of 23 ° C., a distance between chucks of 20 mm, and a tensile speed of 300 mm / min, and the amount of change (mm) in elongation of the evaluation sample was measured. As a result, a tangent line was drawn at the initial rising portion of the obtained SS curve, and the tensile strength when the tangent line corresponds to 100% elongation was divided by the cross-sectional area of the evaluation sample to obtain the tensile elastic modulus.
(Flame retardance)
The flame-retardant heat conductive pressure-sensitive adhesive sheets prepared in each Example and each Comparative Example were cut into a size of 200 mm × 50 mm, the release films on both sides were peeled off and wound into a cylindrical shape, and five test pieces were obtained. One end of the test piece was held vertically and suspended. The burner flame was first applied to the free end for 3 seconds, separated from the flame, and then applied for an additional 3 seconds. Each of the obtained sheets was evaluated for pass / fail of UL94VTM-0 according to the following evaluation criteria.

In Example 5 and Comparative Example 2, the thickness of the test piece was 500 μm. In this case, the evaluation was performed in the same procedure as in the other examples.
(1) The total flammable combustion time (the total of the combustion time after applying the first flame and the combustion time after applying the second flame) of each test piece is within 10 seconds.
(2) The total of the total flammable combustion time of each test piece is within 50 seconds.
(3) The flaming combustion time and the flameless combustion time of each test piece after applying the flame for the second time are within 30 seconds.
(4) Combustion dripping material falls from one of the test pieces and does not ignite the cotton placed below.
(5) Any test piece does not burn up to its suspended part.

    A: The number of evaluation items satisfying the above (1) to (5) is 5 or more.

    X: The number of evaluation items satisfying the above (1) to (5) is less than 5.

As is clear from Table 1, the flame-retardant thermally conductive adhesive sheets of Examples 1 to 9 are polyesters having a ratio of the thickness of the base material to the total thickness of the flame-retardant thermally conductive adhesive sheet of less than 0.2. It can be seen that the film is used and has high flame retardancy (UL94VTM-0). It can also be seen that the thermal resistance is 10 cm ² · K / W or more, and the thermal conductivity is high.

On the other hand, Comparative Examples 2-4 use the polyester film whose ratio of the thickness of the above-mentioned base material to the total thickness of a flame-retardant heat conductive adhesive sheet is 0.2 or more, and flame retardant standard of UL94 VTM-0. Not satisfied. Moreover, since the thermal resistance is more than 10 cm < ² > * K / W, the comparative example 1 is inferior in heat conductivity, and does not fully function as a heat conductive sheet.

11 Flame Retardant Thermal Conductive Adhesive Sheet 12 Flame Retardant Thermal Conductive Adhesive Sheet 13 Flame Retardant Thermal Conductive Adhesive Sheet 2 Flame Retardant Thermal Conductive Adhesive Layer 3 Base Material

Claims (4)

A flame-retardant heat conductive pressure-sensitive adhesive sheet having a base material and a flame-retardant heat conductive pressure-sensitive adhesive layer provided on at least one side of the base material,
The substrate comprises a polyester film, and
The ratio of the thickness of the base material to the total thickness of the flame-retardant thermally conductive adhesive sheet state, and are less than 0.2,
The substrate has a thickness of 1 μm or more and 25 μm or less,
A flame-retardant heat conductive pressure-sensitive adhesive sheet having a thermal resistance of 10 cm ² · K / W or less. The thickness of said substrate, characterized in that it is a on 5μm or more, the flame-retardant thermally conductive pressure-sensitive adhesive sheet according to claim 1.   The flame retardant thermally conductive adhesive sheet according to claim 1 or 2, wherein the flame retardant thermally conductive adhesive sheet has a total thickness of 120 to 1000 µm.   The flame-retardant heat conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein a tensile elastic modulus is 10 MPa or more.

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