JP6353273B2 - Pressure-sensitive adhesive layer, pressure-sensitive adhesive sheet, and method for producing pressure-sensitive adhesive layer - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet, and a method for producing a pressure-sensitive adhesive layer.

  Conventionally, heat generators such as machines and electronic parts that generate heat may deteriorate in performance or be damaged if heat is accumulated inside. By dissipating it, performance is maintained and damage is prevented.

  As a method for adhering the heat generating body and the heat radiating body, a method using heat radiating grease having thermal conductivity may be mentioned. The heat-dissipating grease is a paste-like material containing silicone or a heat conductive substance, and is applied between the heat generating body and the heat dissipating body so as to adhere the heat generating body and the heat dissipating body. It is configured. The heat dissipating grease as described above has an advantage that it has good adhesion to the surface of the adherend, but it requires work to be applied to the adherend and requires a considerable amount of time to cure.

  Furthermore, as another method of bonding the heat generating body and the heat radiating body, a double-sided pressure-sensitive adhesive sheet having thermal conductivity can be mentioned. As the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet having thermal conductivity, the polymer itself forming the pressure-sensitive adhesive layer may be one having thermal conductivity, or in the pressure-sensitive adhesive layer, separately from the polymer. In addition, a material that improves thermal conductivity by containing a thermally conductive substance is known. In particular, a heat conductive double-sided pressure-sensitive adhesive sheet containing a heat conductive substance in a pressure-sensitive adhesive layer is widely used in that it can be bonded to various adherends while maintaining high adhesion reliability.

  Moreover, the metal which integrally formed the heat radiator and the heat conductive adhesive sheet by using the metal foil of predetermined thickness as a heat radiator, and forming the adhesive layer which has heat conductivity in the single side | surface of the said metal foil. A heat conductive adhesive sheet with a foil has also been proposed (see Patent Document 1).

JP-A-11-186473

  The heat conductive (double-sided) pressure-sensitive adhesive sheet as described above (hereinafter sometimes simply referred to as “pressure-sensitive adhesive sheet”) is formed in a sheet shape, and thus is easier to handle than heat dissipation grease. However, thermal conductivity tends to depend on the amount of thermally conductive material added. Generally, if the amount of thermally conductive material added is small, it is easy to obtain adhesion reliability, but thermal conductivity is difficult to obtain. However, if the amount of the thermally conductive material added is large, the thermal conductivity increases, but a phenomenon such as a decrease in adhesion reliability is observed, and the thermal conductivity of the adhesive sheet and the adhesion reliability can be balanced. It has become difficult.

  In addition, when the amount of the heat conductive material added is large, the tackiness of the adhesive is lost, and it is attached to a heating element or a heat radiating body (hereinafter sometimes referred to as “adhered body”). In some cases, air is interposed between the adherend and the thermal resistance (contact thermal resistance) between the adhesive sheet and the adherend is increased. For this reason, heat transfer between the pressure-sensitive adhesive sheet and the adherend is not efficiently performed, and it becomes difficult to cool the heat generating body by effectively moving the heat of the heat generating body to the heat radiating body side. There is.

  Then, this invention makes it a subject to provide the heat conductive adhesion layer with high adhesive reliability with respect to a heat generating body and a heat radiator, and excellent in thermal conductivity.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made efficient heat generation by setting the morphology (phase separation structure) of the pressure-sensitive adhesive layer constituting the heat conductive pressure-sensitive adhesive sheet to a predetermined condition. The inventors have found a heat conductive pressure-sensitive adhesive layer that can achieve conductivity, and have completed the present invention.

  That is, the thermally conductive pressure-sensitive adhesive layer of the present invention contains a polymer (A), a polymer (B), and a thermally conductive substance (C), and a continuous phase containing the polymer (A), and A dispersed phase containing the polymer (B) is formed.

  In the heat conductive pressure-sensitive adhesive layer of the present invention, it is preferable that the heat conductive material (C) is contained in the continuous phase more than in the dispersed phase.

  In the heat conductive adhesive layer of the present invention, the difference in solubility parameter (SP) value calculated from the Fedors equation of the polymer (A) and the polymer (B) is preferably 0.2 or more. .

  In the heat conductive adhesive layer of the present invention, the solubility parameter (SP) value of the polymer (A) is preferably larger than the solubility parameter (SP) value of the polymer (B).

  The heat conductive adhesive layer of this invention is the monomer unit whole quantity which comprises the said polymer (A) with respect to the mass ratio (mass%) of a polar group containing monomer in the monomer unit whole quantity which comprises the said polymer (B). Among them, the mass ratio (% by mass) of the polar group-containing monomer is preferably 1% by mass or more.

  The heat conductive adhesive layer of the present invention preferably has a blending ratio (A / B) (mass ratio) of the polymer (A) to the polymer (B) of 3/100 to 150/100.

The heat conductive pressure-sensitive adhesive layer of the present invention preferably has the following general formula (1) and a heat conductivity parameter of 0.0023 or more.
[Thermal conductivity parameter (W / (cm · K))]
= [Thickness of heat conductive adhesive layer (cm)] / [Total thermal resistance (cm ² · K / W)] (1)

  In the heat conductive pressure-sensitive adhesive layer of the present invention, the polymer (B) contains a polymerizable monomer (b) constituting a monomer unit, and the polymer (B) emits the polymerizable monomer (b) with radiation. It is preferably obtained by polymerization with energy.

  In the thermally conductive pressure-sensitive adhesive layer of the present invention, the polymerizable monomer (b) is preferably an acrylic monomer, and the polymer (B) is preferably an acrylic polymer.

  It is preferable that the heat conductive adhesive sheet of this invention has the said heat conductive adhesive layer.

  The manufacturing method of the heat conductive adhesive layer of this invention mixes the polymer monomer (b) which comprises the said polymer (A), the monomer unit of the said polymer (B), and a heat conductive substance (C). Preparing a pressure-sensitive adhesive composition, and polymerizing the pressure-sensitive adhesive composition with radiation energy to obtain a continuous phase containing the polymer (A) and a dispersed phase containing the polymer (B). And preparing a pressure-sensitive adhesive layer to be formed.

  According to the present invention, a heat conductive pressure-sensitive adhesive layer excellent in adhesion reliability and heat conductivity (sometimes simply referred to as “pressure-sensitive adhesive layer”), a heat conductive pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer (simply , And may be referred to as “pressure-sensitive adhesive sheet”), and a method for producing the pressure-sensitive adhesive layer can be provided and is useful.

It is a transmission electron microscope (TEM) photograph (magnification 12000 times) of the adhesive layer formed from two components which are incompatible. It is a schematic diagram which shows the morphology of the adhesive layer which has the phase-separation structure which concerns on this embodiment, and a heat conductive substance is unevenly distributed in a continuous phase. It is a schematic diagram which shows the morphology of the adhesive layer which has a general phase-separation structure, and a heat conductive substance disperse | distributes uniformly. It is a schematic diagram which shows the morphology of the adhesive layer which has a general homogeneous phase structure, and a heat conductive substance disperse | distributes uniformly. It is a transmission electron microscope (TEM) photograph (magnification: 12000 times, Example 1) of the adhesive layer which has the phase-separation structure which concerns on this embodiment, and a heat conductive substance is unevenly distributed in a continuous phase. It is a transmission electron microscope (TEM) photograph (magnification: 12000 times, comparative example 5) of the adhesive layer which has a general phase-separation structure, and a heat conductive substance disperse | distributes uniformly. It is a three-dimensional electron microscope (SEM) photograph (magnification: 5000 times, Example 1) which shows the heat conduction path in the adhesive layer which concerns on this embodiment. It is a three-dimensional electron microscope (SEM) photograph (magnification: 5000 times, comparative example 5) showing a heat conduction path in a pressure-sensitive adhesive layer having a general phase separation structure. It is a conceptual diagram which shows the calculation method of the average path | route width of a heat conduction path. It is a conceptual diagram which shows the calculation method of the average path length of the heat conduction path with respect to the thickness direction. It is a conceptual diagram which shows the calculation method (thinning) of the average path length of the heat conduction path with respect to the thickness direction. It is a conceptual diagram which shows the calculation method (minimization) of the average path length of the heat conduction path with respect to the thickness direction. It is a schematic diagram which shows the thermal-characteristic evaluation apparatus used for the measurement of the total thermal resistance at the time of calculating a thermal conductivity parameter.

  Hereinafter, embodiments of the present invention will be described in detail.

  The heat conductive pressure-sensitive adhesive layer of the present invention contains a polymer (A), a polymer (B), and a heat conductive material (C), and a continuous phase containing the polymer (A), and A disperse phase containing a polymer (B) is formed (a sea-island structure is formed). The thermally conductive adhesive layer (thermally conductive adhesive sheet) is disposed between the heating element and the heat radiating body, and is configured to adhere (join) them and to transmit the heat of the heating element to the heat radiating body side. It is a thing. Specifically, the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) is mainly formed from a pressure-sensitive adhesive composition containing a polymer component and a heat conductive substance, and includes a pressure-sensitive adhesive layer having a continuous phase and a dispersed phase. More reliable adhesive than pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) that contains a general heat-conducting substance and does not form a continuous phase or dispersed phase (non-phase-separated, uniform phase) This improves the balance between heat conductivity and heat conductivity.

  The heat-conductive pressure-sensitive adhesive layer of the present invention includes a material in which the pressure-sensitive adhesive composition itself is retained in a sheet shape to form a pressure-sensitive adhesive layer (base material-less), and a base material such as a resin film (support) ) And a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition has one side laminated on both sides.

  Hereinafter, the raw material constituting the pressure-sensitive adhesive composition used when the pressure-sensitive adhesive layer of the present invention is manufactured, the pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer, and the method for producing the pressure-sensitive adhesive layer are described in detail. Explained. Hereinafter, the polymer (A), the polymer (B), and the heat conductive substance (C) that are essential components of the heat conductive pressure-sensitive adhesive layer of the present invention are hereinafter referred to as “component (A)”, Sometimes referred to as “component (B)” and “component (C)”.

<Polymer (A)>
The thermally conductive pressure-sensitive adhesive layer of the present invention is characterized by containing a polymer (A). As the polymer (A), the polymer (B) blended together with the polymer (A), and the thermal conductivity When the substance (C) is contained, it is a polymer that is contained in the continuous phase and can form the continuous phase, and can be used without particular limitation as long as it is normally used in the field of pressure-sensitive adhesives. For example, various polymers such as acrylic polymer, rubber polymer, silicone polymer, polystyrene polymer, olefin polymer, polyvinyl acetal polymer, polyurethane polymer, and polyester polymer are used as the polymer (A). Can do. In particular, from the viewpoint of ease of control of physical properties (storage elastic modulus, loss elastic modulus, etc.) and adhesive properties (wetability, peelability, adhesive force, holding force, etc.), cost and versatility, etc. Polymers and rubber polymers are preferably used.

<(A) component: acrylic polymer>
The heat conductive adhesive layer of this invention is a preferable aspect that it is an acrylic polymer as said polymer (A). Since the polymer (A) is an acrylic polymer, it is easy to control physical properties (storage modulus, loss modulus, etc.) and adhesive properties (wetability, peelability, adhesive force, holding force, etc.). It is useful because it is excellent in terms.

  The acrylic polymer is, for example, a monomer unit of (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms as a polymerizable monomer constituting the monomer unit of the acrylic polymer. It is preferable to contain as a main component. The monomers can be used alone or in a combination of two or more. In addition, a main component means the component of the largest content rate in a component, Preferably it exceeds 30 mass%, More preferably, it exceeds 40 mass%, More preferably, it exceeds 50 mass%.

  The ratio of the (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms exceeds 50% by mass with respect to the total amount of monomer units for preparing the acrylic polymer. It is a more preferable aspect to contain, 60-99.9 mass% is still more preferable, 70-99 mass% or less is especially preferable, and 80-98 mass% is the most preferable. Within the above range, the adhesive properties (particularly adhesive strength and wettability to the adherend) are excellent, which is a preferred embodiment.

Examples of the (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms (C _1-20 ) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, Propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, (meth) acryl Pentyl acid, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, (meth) Nonyl acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic Isodecyl acid, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic such as cetyl, isocetyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate Acid C _1-20 alkyl ester is preferable, (meth) acrylic acid C _2-14 alkyl ester is more preferable, and (meth) acrylic acid C _2-10 alkyl ester is more preferable. In addition, (meth) acrylic acid alkyl ester means acrylic acid alkyl ester and / or methacrylic acid alkyl ester, and “(meth)...” Has the same meaning.

  The acrylic polymer may contain other monomer components (others) that can be copolymerized with the (meth) acrylic acid alkyl ester, if necessary, for the purpose of modifying cohesion, heat resistance, crosslinkability, and the like. (Co) polymerizable monomer) may be included. Among them, as the other (co) polymerizable monomer, a monomer having a polar group (polar group-containing monomer) can be preferably used. Specifically, the following carboxyl group-containing monomer and hydroxyl group-containing monomer are used. , (N-substituted) amide monomers, nitrogen-containing heterocyclic monomers, and the like.

As a specific example of the (co) polymerizable monomer,
Carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid;
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, (meta ) Hydroxyl-containing monomers such as hydroxyalkyl (meth) acrylates such as hydroxylauryl acrylate and (4-hydroxymethylcyclohexyl) methyl methacrylate;
Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride;
Sulphonic acid groups such as styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid Containing monomers;
Phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate;
(Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di N, N-dialkyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) such as (n-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide Acrylamide, N-butyl (meth) acrylamide, Nn-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-ethylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl ( (Meth) acrylamide, N-methoxyethyl (meta) Acrylamide, N- butoxymethyl (meth) acrylamide, N- acryloyl morpholine, etc. (N- substituted) amide monomers;
Succinimide monomers such as N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) acryloyl-8-oxyhexamethylenesuccinimide;
Maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide;
Itaconimides such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide System monomers;
N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N- Vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-2-piperidone, N-vinyl-3-morpholinone N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, Contains nitrogen such as N-vinylisothiazole and N-vinylpyridazine Ring-based monomer;
N-vinylcarboxylic acid amides;
Lactam monomers such as N-vinylcaprolactam;
Cyanoacrylate monomers such as acrylonitrile and methacrylonitrile;
(Meth) acrylic such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate Acid aminoalkyl monomers;
(Meth) acrylic acid alkoxyalkyl monomers such as (meth) acrylic acid methoxyethyl, (meth) acrylic acid ethoxyethyl, (meth) acrylic acid propoxyethyl, (meth) acrylic acid butoxyethyl, (meth) acrylic acid ethoxypropyl ;
Styrene monomers such as styrene and α-methylstyrene;
Epoxy group-containing acrylic monomers such as (meth) glycidyl acrylate;
Glycol-based acrylic ester monomers such as (meth) acrylic acid polyethylene glycol, (meth) acrylic acid polypropylene glycol, (meth) acrylic acid methoxyethylene glycol, (meth) acrylic acid methoxypolypropylene glycol;
(Meth) acrylic acid tetrahydrofurfuryl, fluorine atom-containing (meth) acrylate, silicone (meth) acrylate and other heterocyclic rings, halogen atoms, silicon atoms and the like, acrylic ester monomers;
Olefin monomers such as isoprene, butadiene, isobutylene;
Vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether;
Vinyl esters such as vinyl acetate and vinyl propionate;
Aromatic vinyl compounds such as vinyltoluene and styrene;
Olefins or dienes such as ethylene, butadiene, isoprene, isobutylene;
Vinyl ethers such as vinyl alkyl ethers;
Vinyl chloride;
Sulfonic acid group-containing monomers such as sodium vinyl sulfonate;
Imide group-containing monomers such as cyclohexylmaleimide and isopropylmaleimide;
Isocyanate group-containing monomers such as 2-isocyanatoethyl (meth) acrylate;
(Meth) acrylic acid ester having an alicyclic hydrocarbon group such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate;
(Meth) acrylic acid ester having an aromatic hydrocarbon group such as phenyl (meth) acrylate;
(Meth) acrylic acid ester obtained from terpene compound derivative alcohol;
Etc. In addition, these polymerizable monomers can be used individually or in combination of 2 or more types.

  The content of the (co) polymerizable monomer is not particularly limited. Usually, the polymerizable monomer is added in an amount of 0.1 to 0.1% with respect to the total amount of monomer units (100% by mass) for preparing the acrylic polymer. The content is preferably 40% by mass, more preferably 0.5 to 35% by mass, and still more preferably 1 to 30% by mass. By containing 0.1% by mass or more of the polymerizable monomer, it is possible to maintain the pressure-sensitive adhesive (layer) retention and repulsion resistance. In addition, by setting the content of the polymerizable monomer to 40% by mass or less, the cohesive force of the pressure-sensitive adhesive layer is prevented from becoming too high, and the tackiness at room temperature (25 ° C.) is improved, or the pressure-sensitive adhesive force is increased. Can be high.

Moreover, it is preferable to contain a nitrogen atom containing vinyl monomer and / or a carboxyl group containing vinyl monomer among the monomer units (components) described above as the polymerizable monomer constituting the monomer unit of the acrylic polymer. By containing the monomer, the pressure-sensitive adhesive (layer) can have an appropriate cohesive force, and excellent adhesive properties can be obtained, which is a preferred embodiment. Examples of the nitrogen atom-containing vinyl monomer include (meth) acrylamides and N-vinyl cyclic amides represented by the following general formula (2). Examples of the carboxyl group-containing vinyl monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, and carboxypentyl acrylate. Among them, N-vinyl-2-pyrrolidone (R ¹ has a propylene group which is a divalent organic group) and acrylic acid can be suitably used.

[In Formula (2), R ¹ is a divalent organic group. ]

  Although it does not restrict | limit especially as content of the said (co) polymerizable monomer represented by the said General formula (2), Usually, 0.1-0.1 with respect to the monomer unit whole quantity for preparing the said acrylic polymer. It is preferable to contain 40 mass%, More preferably, it is 0.5-35 mass%, More preferably, it is 1-30 mass%. If it is within the above range, the pressure-sensitive adhesive layer has excellent adhesive properties, which is a preferred embodiment.

  Further, the acrylic polymer may contain a polyfunctional monomer as a monomer unit (polymerizable monomer) as necessary in order to adjust the cohesive force of the pressure-sensitive adhesive layer.

  Examples of the polyfunctional monomer include (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, penta Erythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,12-dodecanediol di (meth) Acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate Polyester acrylate, urethane acrylate, butyl di (meth) acrylate, hexyl di (meth) acrylate. Among these, trimethylolpropane tri (meth) acrylate, hexanediol di (meth) acrylate, and dipentaerythritol hexa (meth) acrylate can be preferably used. The said polyfunctional monomer can be used individually or in combination of 2 or more types.

  The content of the polyfunctional monomer varies depending on the molecular weight, the number of functional groups, etc., but is 0.01% with respect to the total amount of monomer units (components) for preparing the polymer (A) (for example, acrylic polymer). -10% by mass, preferably 0.02-7% by mass, more preferably 0.03-5% by mass. When content of the said polyfunctional monomer exceeds 10 mass%, the cohesive force of an adhesive layer will become high too much, and adhesive force may fall. On the other hand, if it is less than 0.01% by mass, the cohesive force of the pressure-sensitive adhesive layer may be reduced.

  A method for synthesizing the polymer (A) (for example, an acrylic polymer) is not particularly limited, and as a method for synthesizing an acrylic polymer such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and radiation curing polymerization, Various polymerization methods commonly used can be applied.

<Polymerization initiator>
In the preparation of the polymer (A), it is preferable that the polymerizable monomer is obtained by polymerization with radiation energy (for example, irradiation with heat, ultraviolet rays, etc.) when polymerizing the polymerizable monomer. During the polymerization, acrylic polymers can be easily prepared using a polymerization reaction by radiation energy (for example, heat or ultraviolet light) using a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator). This is a preferred embodiment. In particular, a photopolymerization initiator can be preferably used because of the advantage that the polymerization time can be shortened. A polymerization initiator can be used individually or in combination of 2 or more types.

  Examples of the thermal polymerization initiator include azo polymerization initiators (for example, 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′-di) Methyleneisobutylamidine) dihydrochloride, etc.); peroxide polymerization initiators (for example, dibenzoyl peroxide, t-butylpermaleate, lauro peroxide) Le etc.); redox polymerization initiators, and the like.

  The content of the thermal polymerization initiator is not particularly limited, but is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the total amount of monomer units (polymerizable monomers) for preparing the polymer (A). More preferably, it is 0.05-3 mass parts.

  The photopolymerization initiator is not particularly limited. For example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photo Active oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, acylphosphine oxide photopolymerization initiator An 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- 1-one [trade name: Irgacure 651, manufactured by BASF Corporation], anisole methyl ether and the like can be mentioned. Examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone [trade name: Irgacure 184, manufactured by BASF Corp.], 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- ( 2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one [trade name: Irgacure 2959, manufactured by BASF Corp.], 2-hydroxy-2-methyl-1-phenyl-propane- 1-one [trade name: Darocur 1173, manufactured by BASF Corporation], methoxyacetophenone, and the like can be given. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropane-1- ON etc. are mentioned. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl 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 and the like. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like are included.

  Examples of the acylphosphine photopolymerization initiator include bis (2,6-dimethoxybenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide, bis ( 2,6-dimethoxybenzoyl) -n-butylphosphine oxide, bis (2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl)-(1- Methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl) -t-butylphosphine oxide, bis (2,6-dimethoxybenzoyl) cyclohexylphosphine oxide, bis (2,6-dimethoxybenzoyl) octylphosphine Oxide, bis (2- Toxibenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2-methoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (2-methyl Propan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-dibutoxybenzoyl) (2-methylpropane-1- Yl) phosphine oxide, bis (2,4-dimethoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2,4,6-trimethylbenzoyl) (2,4-dipentoxyphenyl) phosphine oxide Bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis 2,6-dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis (2,6 -Dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide Bis (2,4,6-trimethylbenzoyl) -2,5-diisopropylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2-methylphenylphosphine oxide, bis (2 4,6-trimethylbenzoyl) -4-methylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,5-diethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2, 3,5,6-tetramethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethyl Benzoyl-n-butylphosphine oxide, bis (2,4,4 -Trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dibutoxyphenylphosphine oxide, 1,10-bis [bis (2,4,6-trimethylbenzoyl) phosphine oxide] Examples include decane and tri (2-methylbenzoyl) phosphine oxide.

  The content of the photopolymerization initiator is not particularly limited. For example, 0.01% with respect to 100 parts by mass of the total amount of monomer units (polymerizable monomer) for preparing the polymer (A) (for example, acrylic polymer). -5 mass parts is preferable, More preferably, it is 0.05-3 mass parts. When the content is less than 0.01 parts by mass, the polymerization reaction may become insufficient. Moreover, when the said content exceeds 5 mass parts, the molecular weight of a polymer may become small too much. And thereby, the cohesive force of the adhesive layer formed becomes low, and adhesive characteristics, such as holding | maintenance property and repulsion resistance, may fall.

  Examples of the radiation include ultraviolet (UV), laser beam, α-ray, β-ray, γ-ray, X-ray, and electron beam. Ultraviolet rays are preferable from the viewpoints of controllability, ease of handling, and cost. Used for. More preferably, ultraviolet rays having a wavelength of 200 to 400 nm are used. Ultraviolet rays can be irradiated using an appropriate light source such as a high-pressure mercury lamp, a microwave excitation lamp, or a chemical lamp.

  Furthermore, it is also possible to use a photopolymerization initiation assistant such as amines together with the photopolymerization initiator. Examples of the photopolymerization initiation assistant include 2-dimethylaminoethylbenzoate, dimethylaminoacetophenone, p-dimethylaminobenzoic acid ethyl ester, p-dimethylaminobenzoic acid isoamyl ester, and the like. These compounds may be used alone or in combination of two or more. It is preferable to mix 0.05-10 mass parts with respect to 100 mass parts of said polymers (A), and, as for photopolymerization start adjuvant, it is more preferable to mix | blend in the range of 0.1-7 mass parts. Within the above range, it is preferable from the viewpoint of easily controlling the polymerization reaction and obtaining an appropriate molecular weight.

In addition, when the photopolymerization initiator is blended, the pressure-sensitive adhesive composition is directly applied on an adherend (protected body) or after being applied to a predetermined coated body such as a separator. Alternatively, the pressure-sensitive adhesive layer can be obtained by light irradiation after coating on one side of the support (base material). Usually, the pressure-sensitive adhesive layer is obtained by irradiating ultraviolet rays having an illuminance of 1 to 200 mW / cm ² at a wavelength of 300 to 400 nm and photopolymerizing them with a light amount of about 200 to 4000 mJ / cm ² .

  The weight average molecular weight (Mw) of the polymer (A) is preferably, for example, 30,000 to 5,000,000, more preferably 100,000 to 2,000,000, still more preferably 200,000 to 1,000,000. If the weight average molecular weight (Mw) is too smaller than the above range, the cohesive force of the pressure sensitive adhesive (layer) will be insufficient, and if the weight average molecular weight (Mw) is too large than the above range, the flowability of the pressure sensitive adhesive will be low. There is a case where the wetness with respect to the body is insufficient and the adhesive strength is lowered.

  The weight average molecular weight can be measured in terms of polystyrene by GPC (gel permeation chromatography) method. Specifically, it can be measured on a HPLC 8020 manufactured by Tosoh Corporation using TSKgelGMH-H (20) × 2 columns as a column with a tetrahydrofuran solvent at a flow rate of about 0.5 ml / min.

  As said polymer (A), it is preferable that the glass transition temperature (Tg) is less than 120 degreeC, More preferably, it is less than 90 degreeC, More preferably, it is less than 70 degreeC, Usually -80 degreeC or more It is. When the glass transition temperature (Tg) of the polymer (A) is 120 ° C. or higher, the polymer is difficult to flow, wetness to the adherend becomes insufficient, and adhesive strength may be reduced.

  In the present invention, when the polymer (A) is a copolymer, its glass transition temperature (Tg) can be calculated based on the following formula (3) (Fox formula).

_{1 / Tg = W 1 / Tg} 1 + W 2 / Tg 2 + ··· + Wn / Tg n (3)
[In the formula (3), Tg is the glass transition temperature (unit: K) of the copolymer, and Tg _i (i = 1, 2,... N) is the glass transition when the monomer i forms a homopolymer. Temperature (unit: K), W _i (i = 1, 2,... N) represents a mass fraction of all monomer components of monomer i. ]
The glass transition temperature Tgi of the monomer i is a nominal value described in the literature (for example, polymer handbook, adhesive hand log, etc.).

<(A) component: Rubber polymer>
In a preferred embodiment of the thermally conductive pressure-sensitive adhesive layer of the present invention, the polymer (A) is a rubber-based polymer. When the rubber polymer is a polymer (B) described later, such as an acrylic polymer, even if the blending ratio of the rubber polymer is lower than that of the acrylic polymer, a normal rubber system is used. Like a pressure-sensitive adhesive (layer) obtained by blending a polymer and an acrylic polymer, when forming a so-called phase-separated (sea-island) structure, the rubber-based polymer is in the continuous phase (sea phase) that occupies the majority. Rather than forming a dispersed phase (island phase) (see Fig. 1, reverse phase separation structure), a continuous phase (sea phase) can be formed, that is, a dense phase separation structure (see Fig. 5) It can be formed and can exhibit excellent adhesive properties even on a low surface energy adherend (for example, polyolefin), which is useful.

  Examples of the rubber-based polymer include copolymers such as polybutadiene, polyisoprene, polyisobutylene, polystyrene-butadiene-styrene, polystyrene-isoprene-styrene, polystyrene-isobutylene-styrene, polystyrene-vinyl polyisoprene-styrene, polystyrene-vinyl polyisoprene. Styrene-based triblock copolymers such as ethylenepropylene-styrene, polystyrene-butadiene, polystyrene-isoprene, polystyrene-isobutylene, polystyrene-vinylpolyisoprene, styrene-based diblock copolymers such as polystyrene-vinylpolyisoprene-ethylenepropylene, polyethylenepropylene, Olefin copolymers such as polyethylene butene and polypropylene butene, Styrene-ethylene butylene-styrene, polystyrene-ethylene-ethylene propylene-styrene, polystyrene-ethylene propylene-styrene, polystyrene-butadiene-butylene-styrene, polystyrene-hydrogenated vinyl polyisoprene-styrene, polystyrene-hydrogenated vinyl polyisoprene-ethylene Partially hydrogenated or fully hydrogenated styrene triblock copolymers such as propylene-styrene, polystyrene-ethylenebutylene, polystyrene-ethylene-ethylenepropylene, polystyrene-ethylenepropylene, polystyrene-butadiene-butylene, polystyrene-hydrogenated vinylpolyisoprene , Polystyrene-hydrogenated vinyl polyisoprene-ethylenepropylene and other partially hydrogenated or fully hydrogenated styrene diblocks It can be used various rubber polymers such as copolymers. Among them, partially hydrogenated or fully hydrogenated, so-called saturated styrene triblock copolymer or diblock copolymer (saturated styrene block copolymer), polyisobutylene, polystyrene-isobutylene-styrene, in terms of weather resistance, etc. In addition, it is preferable to use a copolymer such as polystyrene-isobutylene, and in order to obtain cohesive strength of the copolymer, a partially hydrogenated type or a fully hydrogenated type, so-called saturated styrene triblock copolymer, polystyrene-isobutylene-styrene, etc. The styrenic triblock copolymer can be suitably used.

  When the rubber-based polymer is a copolymer having polystyrene blocks, the proportion of polystyrene blocks in the copolymer (styrene (St) content) is preferably 2 to 80% by mass, more preferably 3 to 75% by mass. More preferably, it is 5-65 mass%. When the styrene (St) content exceeds 80% by mass, the polymer is difficult to flow, wetness to the adherend becomes insufficient, and adhesive properties may be deteriorated. On the other hand, if the styrene (St) content is less than 2% by mass, the intended cohesive force may not be sufficiently obtained.

<Polymer (B)>
The thermally conductive pressure-sensitive adhesive layer of the present invention is characterized by containing a polymer (B). As the polymer (B), the polymer (A) blended together with the polymer (B), and the thermal conductivity When the substance (C) is contained, it is a polymer that can be contained in the dispersed phase and can form the dispersed phase, and can be used without particular limitation as long as it is normally used in the field of pressure-sensitive adhesives. For example, various polymers such as acrylic polymer, rubber polymer, silicone polymer, polystyrene polymer, olefin polymer, polyvinyl acetal polymer, polyurethane polymer, and polyester polymer are used as the polymer (B). Can do. In particular, from the viewpoint of ease of control of physical properties (storage elastic modulus, loss elastic modulus, etc.) and adhesive properties (wetability, peelability, adhesive force, holding force, etc.), cost and versatility, etc. A polymer is preferably used.

  In the heat conductive pressure-sensitive adhesive layer of the present invention, the polymer (B) contains a polymerizable monomer (b) constituting a monomer unit, and the polymer (B) emits the polymerizable monomer (b) with radiation. It is preferably obtained by polymerization with energy. As the polymerizable monomer (b), a polymerizable monomer constituting a monomer unit similar to the component (A) described above can be used. By irradiating the pressure-sensitive adhesive composition containing the polymer (A) and the polymerizable monomer (b) with radiation energy, in the vicinity (periphery) of the polymer (A), the polymerizable monomer (b) Has undergone a polymerization reaction, and an island phase having a phase separation (sea island) structure can form the polymer (B), and the polymer (A) can form a sea phase, and phase separation (sea island) with excellent adhesion reliability. A morphological pressure-sensitive adhesive layer having a structure can be formed and is useful.

<(B) component: acrylic polymer>
The heat conductive adhesive layer of this invention is a preferable aspect that the said polymerizable monomer (b) is an acryl-type monomer, and the said polymer (B) is an acryl-type polymer. Since the polymer (B) is an acrylic polymer, it is easy to control physical properties (storage elastic modulus, loss elastic modulus, etc.) and adhesive properties (wetability, peelability, adhesive force, holding force, etc.). It is useful because it is excellent in terms.

As the polymerizable monomer (b), a polymerizable monomer that can be used as the monomer unit of the component (A) described above can be used in the same manner. For example, the above-described linear or branched group having 1 to 20 carbon atoms (C _1-20 ) It is preferable to contain (meth) acrylic acid alkyl ester having a chain alkyl group as the main component of the monomer unit, more preferably (meth) acrylic acid C _3-14 alkyl ester, and still more preferably (meth). Acrylic acid C _4-12 alkyl ester. In addition, the proportion of the (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms is based on the total amount of monomer units for preparing the acrylic polymer (B). It is preferable to contain 80-100 mass% or more, 85-100 mass% is more preferable, 90-100 mass% is still more preferable, 95-100 mass% is especially preferable. Within the above range, the adhesive properties (particularly adhesive strength and wettability to the adherend) are excellent, which is a preferred embodiment.

  In addition, as the polymerizable monomer (b) other than the (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms, it can be used as a monomer unit of the component (A) described above. Other (co) polymerizable monomers can be used in the same manner as the polymerizable monomer (b). Usually, the polymerization is performed with respect to the total amount of monomer units (100% by mass) for preparing the acrylic polymer. It is preferable to contain 0.1-40 mass% of a property monomer (b), More preferably, 0.5-30 mass%, More preferably, it can contain 1-20 mass%. By containing 1% by mass or more of the polymerizable monomer (b), it is possible to maintain the pressure-sensitive adhesive (layer) retention and repulsion resistance. Further, by setting the content of the polymerizable monomer (b) to 40% by mass or less, it is possible to prevent the cohesive force from becoming too high, improve the tack feeling at room temperature (25 ° C.), and increase the adhesive strength. can do.

  As a method for synthesizing the polymer (B) (for example, an acrylic polymer), the same method as the polymer (A) described above can be used.

  The weight average molecular weight (Mw) of the polymer (B) is preferably, for example, 30,000 to 5,000,000, more preferably 100,000 to 2,000,000, still more preferably 200,000 to 1,000,000. If the weight average molecular weight (Mw) is too smaller than the above range, the cohesive force of the pressure sensitive adhesive (layer) will be insufficient, and if the weight average molecular weight (Mw) is too large than the above range, the flowability of the pressure sensitive adhesive will be low. There is a case where the wetness with respect to the body is insufficient and the adhesive strength is lowered. In addition, the measuring method of a weight average molecular weight is the same as that of the polymer (A) mentioned above.

  In addition, the glass transition temperature (Tg) of the polymer (B) is preferably less than 0 ° C, more preferably less than -10 ° C, still more preferably less than -40 ° C, and usually -80 ° C or more. . When the glass transition temperature (Tg) of the polymer (B) is 0 ° C. or higher, the polymer is difficult to flow, wetness to the adherend becomes insufficient, and adhesive strength may be reduced. In addition, the measuring method of glass transition temperature (Tg) is the same as that of the polymer (A) mentioned above.

The heat conductive adhesive layer of the present invention preferably has a blending ratio (A / B) (mass ratio) of the polymer (A) to the polymer (B) of 3/100 to 150/100. / 100 to 100/100 is more preferable, 7/100 to 70/100 is still more preferable, and 10/100 to 50/100 is particularly preferable. Within the above range, the pressure-sensitive adhesive (layer) as shown in FIG. 2 (schematic diagram) and FIG. 5 (TEM photograph) can form a dense phase separation structure (sea-island structure). It has excellent adhesive properties such as adhesive strength, retention (cohesive strength), and repulsion resistance, and is useful.

<Component (C): Thermally conductive substance (C)>
The heat conductive adhesive layer of this invention contains a heat conductive substance (C), It is characterized by the above-mentioned. The heat conductive substance in the present invention can improve the thermal conductivity of the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) by being contained in the pressure-sensitive adhesive layer, and is not particularly limited. Boron nitride, aluminum nitride, silicon nitride, gallium nitride, aluminum hydroxide, magnesium hydroxide, silicon carbide, silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, tin oxide, copper oxide, 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 and the like. Among these thermally conductive substances, it is more preferable to use boron nitride, aluminum hydroxide, and aluminum oxide because they have high thermal conductivity and electrical insulation. These heat conductive substances may be used alone or in combination of two or more.

  Although the shape of the said heat conductive substance (C) is not specifically limited, For example, a bulk shape, needle shape, plate shape, and layer shape may be sufficient. The bulk shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a crushed shape, or a deformed shape thereof.

  When the heat conductive material (C) has a bulk shape (for example, a spherical shape), the primary average particle diameter is preferably 0.02 to 1000 μm, more preferably 0.03 to 100 μm, and still more preferably. 0.05 to 20 μm. By setting the primary average particle size to 1000 μm or less, even when the pressure-sensitive adhesive layer is formed with a thickness of less than 1000 μm, the bulk-shaped thermally conductive material exceeds the thickness of the pressure-sensitive adhesive layer, and the thickness of the pressure-sensitive adhesive layer It is possible to prevent the variation from occurring. In addition, by setting the thickness to 0.02 μm or more, the heat conductive materials are likely to be present in the vicinity, and a connection path of the heat conductive materials (the heat conduction path, see FIGS. 2, 5, 7, etc.) is generated. For example, it is useful because the heat of the heating element can be effectively moved to the side of the heat dissipation body via the connection path (heat conduction path) to cool the heating element efficiently. 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 meter.

  When the heat conductive material (C) has a needle shape or a plate shape, the maximum length is preferably 0.02 to 1000 μm, more preferably 0.03 to 100 μm, still more preferably. Is 0.05 to 20 μm. By setting the maximum length to 1000 μm or less, agglomeration between needle-shaped or plate-shaped thermally conductive substances is suppressed, and handling becomes easy. Moreover, by setting it as 0.02 micrometer or more, it becomes easy for heat conductive substances to exist in the vicinity, and it becomes easy to produce the connection path | pass (heat conduction path) of a heat conductive substance, for example, heat of a heating element is effective. In particular, it is possible to efficiently perform the cooling by moving the heat generating body to the heat radiating body side via a connection path (heat conduction path). Furthermore, these aspect ratios (in the case of acicular crystals, they are expressed as major axis length / minor axis length, or major axis length / thickness. In the case of plate crystals, the diagonal length is also expressed. / Thickness or long side length / thickness) is preferably 1 to 10,000, and more preferably 10 to 1,000.

  The amount of the heat conductive substance used is preferably 10 to 1000 parts by mass, more preferably 20 to 500 parts by mass with respect to 100 parts by mass of the total amount of the polymer components constituting the pressure-sensitive adhesive layer. More preferably, it is 30-400 mass parts. By making the usage-amount of a heat conductive substance 1000 mass parts or less, while being able to obtain the adhesive layer (adhesive sheet) which has favorable flexibility, favorable adhesive force can be exhibited. Moreover, sufficient thermal conductivity can be provided by setting it as 10 mass parts or more.

  In the thermally conductive pressure-sensitive adhesive layer of the present invention, it is preferable that the thermally conductive material (C) is contained in the continuous phase more than the dispersed phase, and the thermally conductive material (C) The total amount is preferably 100% by mass, more preferably 60% by mass or more, and still more preferably 70% by mass or more in the continuous phase. That is, it is preferable that the heat conductive material (C) is unevenly distributed in the continuous phase containing the polymer (A) in the entire pressure-sensitive adhesive layer. Since the thermal conductive material (C) has a structure unevenly distributed in the continuous phase, the thermal conductive materials are likely to be present in the vicinity, and the connection path (thermal conduction path) of the thermal conductive materials is efficient. For example, it is possible to efficiently carry out cooling of the heating element by effectively transferring the heat of the heating element to the radiator side through the heat conduction path, and not only the bonding reliability but also the heat The conductivity is also high and useful.

  Since there are several methods for containing the thermally conductive substance (C) in the continuous phase more than in the dispersed phase, it will be described in detail below.

In order that the thermally conductive pressure-sensitive adhesive layer of the present invention contains the thermally conductive substance (C) in the continuous phase more than the dispersed phase, the polymer (A) and the polymer ( The difference in solubility parameter (SP) value ((cal / cm ³ ) ^1/2 ) calculated from the B) Fedors equation is preferably 0.2 or more, more preferably 0.4 or more, and still more preferably Is 0.6 or more. By combining the polymer (A) and polymer (B) having such a difference in SP value, the pressure-sensitive adhesive (layer) can form a dense phase separation structure (sea-island structure), and the adhesive strength to the adherend It has excellent adhesive properties such as retention (cohesive strength) and resilience resistance, and is useful. For example, when the SP value of the polymer (A) is larger than the SP value of the polymer (B) and the thermally conductive material is a highly polar material, the thermal conductivity is added to the continuous phase mainly containing the polymer (A). When the substance (C) is contained more, conversely, the SP value of the polymer (A) is smaller than the SP value of the polymer (B), and the thermally conductive substance is a substance having a low polarity (no polarity), The continuous phase mainly containing the polymer (A) contains more of the heat conductive substance (C). Further, due to the difference in SP value, in the process of phase separation into the continuous phase mainly containing the polymer (A) and the dispersed phase mainly containing the polymer (B), the heat conductive substance (C) The polymer (B) (dispersed phase) undergoes a behavior that is excluded from polymerization and curing, and as a result, the continuous phase mainly containing the polymer (A) contains a larger amount of the thermally conductive substance (C). Therefore, an adhesive layer having excellent thermal conductivity is obtained and useful.

  Moreover, in order that the heat conductive adhesive layer of this invention may contain the said heat conductive substance (C) in the said continuous phase more than the said dispersed phase, the solubility parameter (( The SP) value is preferably larger than the solubility parameter (SP) value of the polymer (B). When the SP value of the polymer (A) is larger than the SP value of the polymer (B), the pressure-sensitive adhesive (layer) can form a dense phase separation structure (sea-island structure). As a result, it has excellent adhesive properties such as adhesion to the adherend, retention (cohesive force), and resilience, and is useful. Further, as the heat conductive substance (C), for example, by blending with a material such as boron nitride or aluminum hydroxide having high polarity, the polar functional group of the polymer (A) and the heat conductive substance (C) And the continuous phase containing the polymer (A) as a main component contains a larger amount of the heat conductive substance (C), so that a pressure-sensitive adhesive layer having excellent heat conductivity is obtained. Useful.

  Based on a specific solubility parameter (SP) value, it has a phase separation structure composed of a continuous phase containing the polymer (A) (as the main component) and a dispersed phase containing the polymer (B) (as the main component). As a method of forming the pressure-sensitive adhesive layer, radiation energy (for example, ultraviolet (UV)) is irradiated to a mixture in which an arbitrary monomer component for constituting the polymer (A) and a polymerization initiator are blended. , Preparing a partially polymerized product (polymer syrup) in which the monomer component is partially polymerized, and then mixing the polymerizable monomer (b) with the polymer syrup to obtain a pressure-sensitive adhesive composition. The difference between the SP value of the polymer (A) and the SP value of the polymerizable monomer (b) (the component that will later become the polymer (B)) is adjusted to provide a difference of 0.2 or more. Further, the adhesive composition is irradiated with radiation energy (for example, ultraviolet (UV)) to polymerize and cure the polymerizable monomer (b), and contains a polymer (A) (as a main component). It is possible to form a pressure-sensitive adhesive layer having a phase separation (sea island) structure composed of a dispersed phase containing the polymer (B) (as a main component).

In addition, as a method of knowing the solubility parameter (SP) value of the polymer, a method using a conventionally known estimation equation such as a Fedors equation, a Small equation, or a Vam Krebelen equation, a method of actually measuring by experiments, and the like can be mentioned. Among these, it is preferable to use the Fedors equation used in the present invention in order to easily obtain a reasonable estimated value. The Fedors formula is as shown in the following general formula (4).
SP value ((cal / cm ³ ) ^1/2 ) = (Σei / Σvi) ^0.5 (4)
Here, ei represents the evaporation energy of each atomic group of the compound (monomer) constituting the polymer, and vi represents the molar volume of each atomic group of the compound (monomer) constituting the polymer.

  In order to obtain a polymer having a desired SP value, attention should be paid to the functional group of the monomer constituting the polymer, and a monomer having a suitable functional group may be appropriately used. For example, a polymer having a high SP value can be obtained by using a large number of monomers having a relatively polar functional group such as a carboxyl group, an amide group, or a hydroxyl group. In addition, a polymer having a low SP value can be obtained by using only a small amount of a monomer having a relatively polar functional group as described above.

More specific examples (1) include, for example, an acrylic polymer having a mass ratio of 2-ethylhexyl acrylate units and acrylic acid units of 98: 2 as the polymer (A), and poly (B) The adhesive layer formed from the adhesive composition containing butyl acrylate is mentioned. At this time, the SP value ((cal / cm ³ ) ^1/2 ) calculated from the Fedors equation of the polymer (A) is 9.29, and the SP value calculated from the Fedors equation of the polymer (B) is 9. In the process of phase separation into a continuous phase mainly containing the polymer (A) and a dispersed phase mainly containing the polymer (B) due to the difference in SP value, the heat conductive substance (C) becomes dense As a result, the structure of the pressure-sensitive adhesive layer has a continuous phase containing the polymer (A) (as a main component) and the polymer (B It is possible to form a heat conductive pressure-sensitive adhesive layer having a phase separation (sea island) structure in which a dispersed phase containing (as a main component) is formed.

  Subsequently, based on a specific solubility parameter (SP) value, as a method of containing (unevenly) the thermal conductive material (C) in the continuous phase more than the dispersed phase, the polymer (A) And a method of using a material having a specific SP value for each of the polymers (B). For example, a highly polar material is generally used for the thermally conductive substance (C), and the highly polar thermally conductive substance (C) tends to be more polar than a general synthetic rubber or acrylic polymer. It is in. On the other hand, when the SP values of the polymer (A) and the polymer (B) are compared, if the SP value of the polymer (A) is higher, the thermally conductive substance (C) It is possible to form a phase separation (sea island) structure in which a larger amount exists in the continuous phase containing the polymer (A) (as the main component) than in the dispersed phase containing (as the main component).

As a more specific example (2), the polymer (A) is an acrylic polymer in which the butyl acrylate unit and the 2-hydroxyethyl acrylate unit are in a mass ratio of 97: 3, and the polymer (B) is a polyacrylic polymer. Examples thereof include a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing boron nitride as acid 2-ethylhexyl (poly-2-ethylhexyl acrylate) and the heat conductive substance (C). At this time, the SP value ((cal / cm ³ ) ^1/2 ) calculated from the Fedors equation of the polymer (A) is 9.90, and the SP value calculated from the Fedors equation of the polymer (B) is Thus, the structure of the pressure-sensitive adhesive layer is such that the phase containing the polymer (A) (as a main component) is a continuous phase and the phase containing the polymer (B) (as a main component) is a dispersed phase. And boron nitride which is a heat conductive substance (C) can form the heat conductive adhesive layer which has a structure which exists abundantly in a continuous phase.

As other specific example (3), as polymer (A), 2-ethylhexyl acrylate unit, N-vinyl-2-pyrrolidone unit, and 2-hydroxyethyl acrylate unit are 67:15:18. Acrylic polymer having a mass ratio, polybutyl acrylate (polybutyl acrylate) as polymer (B), and pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition containing aluminum hydroxide as thermal conductive substance (C) Layer. At this time, the SP value ((cal / cm ³ ) ^1/2 ) calculated from the Fedors equation of the polymer (A) is 10.26, and the SP value calculated from the Fedors equation of the polymer (B) is 9. 77, the phase of the pressure-sensitive adhesive layer is such that the phase containing the polymer (A) (as the main component) is a continuous phase and the phase containing the polymer (B) (as the main component) is a dispersed phase. And aluminum hydroxide which is a heat conductive substance (C) can form the heat conductive adhesive layer which has a structure which exists abundantly in a continuous phase.

  Furthermore, the thermally conductive pressure-sensitive adhesive layer of the present invention contains the polymer (B) so that the thermally conductive substance (C) is contained in the continuous phase more than the dispersed phase (is unevenly distributed). Difference in the mass ratio (mass%) of the polar group-containing monomer in the total amount of monomer units constituting the polymer (A) with respect to the mass ratio (mass%) of the polar group-containing monomer in the entire monomer unit constituting Is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more. When the polymer (A) contained in the continuous phase contains more monomers having a polar group (polar group-containing monomer) than the polymer (B) contained in the dispersed phase, the pressure-sensitive adhesive (layer) becomes A dense phase separation structure (sea-island structure) can be formed, and it has excellent adhesive properties such as adhesion to the adherend, retention (cohesion), and resilience, and is useful. Further, as the heat conductive substance (C), for example, by blending with a material such as boron nitride or aluminum hydroxide having high polarity, the polar functional group of the polymer (A) and the heat conductive substance (C) Interact with each other, and the continuous phase contains a larger amount of the heat conductive substance (C), so that a pressure-sensitive adhesive layer having excellent heat conductivity is obtained and useful.

  Moreover, as another method (not based on the SP value) in which the thermal conductive material (C) is contained in the continuous phase more than the dispersed phase, for example, a monomer constituting the polymer (A) As a unit, the carboxyl group-containing monomer, which is a copolymerizable polar group-containing monomer, can be copolymerized as a monomer unit that constitutes the polymer (B) with a mass ratio in the total amount of monomer units constituting the polymer (A). The carboxyl group-containing monomer is preferably added in an amount of 1 (mass%) or more, more preferably 2 (mass%) or more than the mass ratio of the total monomer units constituting the polymer (B). The method of doing is mentioned. As a result, when, for example, aluminum hydroxide or the like is used as the thermally conductive substance (C) that strongly interacts with the carboxyl group, the thermally conductive substance (C) (mainly) the polymer (B). It is possible to form a phase-separated (sea island) structure in which a continuous phase containing the polymer (A) (as a main component) is present more than the dispersed phase contained. In this case, even if the SP value of the polymer (A) is not larger than the SP value of the polymer (B) or the difference in SP value is not 0.2 or more, the above-described phase separation (sea island) structure is used. Can be formed.

  As a more specific example (4), the polymer (A) is an acrylic having a mass ratio of 2-ethylhexyl acrylate units and acrylic acid units that are carboxyl group-containing monomers that are polar group-containing monomers in a mass ratio of 98: 2. Pressure sensitive adhesive composition containing, as a polymer, polymer (B), polybutyl acrylate that does not contain a carboxyl group-containing monomer that is a polar group-containing monomer as a monomer unit, and aluminum hydroxide as a thermally conductive substance (C) An adhesive layer formed from At this time, the structure of the pressure-sensitive adhesive layer is a continuous phase containing the polymer (A) (as a main component) and a dispersed phase containing the polymer (B) (as a main component). And aluminum hydroxide as a heat conductive substance (C) can form the heat conductive adhesive layer which has a structure which exists abundantly in a continuous phase.

<Crosslinking agent>
In order to adjust the cohesive strength of the pressure-sensitive adhesive layer of the present invention, the pressure-sensitive adhesive composition may contain a crosslinking agent. As the cross-linking agent, a cross-linking agent generally used in the pressure-sensitive adhesive field can be used. For example, an isocyanate cross-linking agent, an epoxy cross-linking agent, a silicone cross-linking agent, an oxazoline cross-linking agent, an aziridine cross-linking agent, or a silane type. Crosslinking agents, melamine crosslinking agents (alkyl etherified melamine crosslinking agents, etc.), metal chelate crosslinking agents and the like can be mentioned. Moreover, it is also possible to use the said polyfunctional monomer which can be used as a polymerizable monomer (b) which comprises the said polymer (B) mentioned above as a crosslinking agent. In particular, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, and a metal chelate-based crosslinking agent can be preferably used. These compounds may be used alone or in combination of two or more.

  Examples of the isocyanate-based crosslinking agent (isocyanate compound) include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, cycloaliphatic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate. , Aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L, Nippon Polyurethane Manufactured by Kogyo Co., Ltd.), trimethylolpropane / hexamethylene diisocyanate trimer adduct (trade name Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), hexamethylene dii Isocyanate adducts such as isocyanurate of socyanate (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.). Alternatively, a compound having at least one isocyanate group and one or more unsaturated bonds in one molecule, specifically, 2-isocyanatoethyl (meth) acrylate or the like may be used as an isocyanate-based crosslinking agent. Can do.

  Examples of the epoxy crosslinking agent (epoxy compound) include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol. Glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylenediamine (trade name: TETRAD-X, manufactured by Mitsubishi Gas Chemical Co., Inc.) and 1 , 3-bis (N, N-diglycidylaminomethyl) cyclohexane (trade name: TETRAD-C, manufactured by Mitsubishi Gas Chemical Company, Inc.).

  Examples of the melamine-based crosslinking agent include hexamethylol melamine. Examples of the aziridine-based cross-linking agent (aziridine derivative) include, for example, a commercial product name HDU (manufactured by Mutual Pharmaceutical Co., Ltd.), a product name TAZM (manufactured by Mutual Pharmaceutical Co., Ltd.), and a trade name TAZO (mutual pharmaceutical Co., Ltd.). Manufactured).

  Examples of the metal chelate-based crosslinking agent (metal chelate compound) include aluminum, iron, tin, titanium and nickel as metal components, and acetylene, methyl acetoacetate and ethyl lactate as chelate components.

  Although the content of the crosslinking agent used in the present invention is not particularly limited, for example, it is contained in an amount of 0.001 to 3 parts by mass with respect to 100 parts by mass of the polymerizable monomer (b) constituting the polymer (B). The content is preferably 0.01 to 2 parts by mass. When the content of the cross-linking agent is less than 0.001 part by mass, the cohesive force of the pressure-sensitive adhesive (layer) becomes small, and when the content of the cross-linking agent exceeds 3 parts by mass, the cohesive force of the pressure-sensitive adhesive (layer) Is large, the fluidity is lowered, the wetness to the adherend is insufficient, and the adhesive force may be lowered.

  Further, the content of the polyfunctional monomer is appropriately selected depending on the balance with the polymer to be crosslinked, and further depending on the intended use of the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet). In addition, in order to obtain sufficient heat resistance by the cohesive force of the pressure-sensitive adhesive (layer), 0.001 to 5 parts by mass with respect to 100 parts by mass of the total amount of the polymerizable monomer (b) constituting the polymer (B). It is preferable to mix with. Moreover, it is more preferable to mix | blend at 2 mass parts or less from the point of a softness | flexibility and adhesive force.

  In addition, when using the said polyfunctional monomer as a crosslinking agent, in order to advance a crosslinking reaction, radiation irradiation can be performed. Examples of the radiation include ultraviolet rays, laser beams, α rays, β rays, γ rays, X rays, and electron beams, but ultraviolet rays are preferably used from the viewpoint of good controllability and handleability and cost. . More preferably, ultraviolet rays having a wavelength of 200 to 400 nm are used. Ultraviolet rays can be irradiated using an appropriate light source such as a high-pressure mercury lamp, a microwave excitation lamp, or a chemical lamp. When ultraviolet rays are used as radiation, the pressure-sensitive adhesive composition includes a photopolymerization initiator (photoinitiator) that can be used in the preparation (polymerization) of the polymer (B) described above, and a photopolymerization initiation assistant. Can be similarly blended and added. In addition, when the polyfunctional monomer is used as a crosslinking agent, it can be irradiated with radiation, but as the photopolymerization initiator used in this case, depending on the type of the radiation reactive component, the polymerization reaction may be performed. Any substance that generates radicals or cations by irradiating ultraviolet rays having an appropriate wavelength that can be triggered can be used.

  When the polyfunctional monomer is used as the crosslinking agent, the photopolymerization initiator is usually 0.1, for example, with respect to 100 parts by mass of the total amount of the polymerizable monomer (b) constituting the polymer (B). It is preferable to mix | blend -10 mass parts, and to mix | blend in the range of 0.2-7 mass parts. Within the above range, it is preferable from the viewpoint of easily controlling the polymerization reaction and obtaining an appropriate molecular weight.

In the case where the photopolymerization initiator is added, the pressure-sensitive adhesive composition is directly applied on an adherend (protected body) or after being applied to a predetermined coated body such as a separator, or Then, after coating on one side of the support (base material), the cross-linking reaction is advanced by light irradiation to obtain a pressure-sensitive adhesive layer. Usually, the pressure-sensitive adhesive layer is obtained by irradiating ultraviolet rays having an illuminance of 1 to 200 mW / cm ² at a wavelength of 300 to 400 nm and photopolymerizing them with a light amount of about 200 to 4000 mJ / cm ² .

  The pressure-sensitive adhesive composition used in the present invention may further contain a crosslinking accelerator. The kind of crosslinking accelerator can be suitably selected according to the kind of crosslinking agent to be used. In the present specification, the crosslinking accelerator refers to a catalyst that increases the speed of the crosslinking reaction by the crosslinking agent. Examples of the crosslinking accelerator include tin (Sn) -containing compounds such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, and trimethyltin hydroxide; N, N , N ′, N′-tetramethylhexanediamine, amines such as triethylamine, and nitrogen (N) -containing compounds such as imidazoles. Of these, Sn-containing compounds are preferred. The amount of the crosslinking accelerator contained in the pressure-sensitive adhesive composition is, for example, about 0.0001 to 1.0 part by mass (preferably with respect to 100 parts by mass of the polymerizable monomer (b) constituting the polymer (B)). Can be about 0.001 to 0.5 parts by mass).

<Dispersant (dispersion stabilizer)>
In the pressure-sensitive adhesive composition used in the present invention, various dispersants can be used for the purpose of stably dispersing the heat conductive material. The dispersant can be appropriately selected from an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, and the like. Of these, anionic surfactants are preferred. Examples of the anionic surfactant include sulfonates and phosphate esters, and examples thereof include alkyl ether sulfonates, alkyl phosphate esters, and alkyl ether phosphate esters.

  The content of the dispersant is preferably 0.01 to 10 parts by mass of the dispersant with respect to 100 parts by mass of the heat conductive material (C) constituting the pressure-sensitive adhesive layer, more preferably It is 0.1-8 mass parts, More preferably, it is 0.2-5 mass parts. By using the said dispersing agent in the said range, a heat conductive substance (C) can be uniformly disperse | distributed in an adhesive composition (solution) reliably. Moreover, by setting it as 0.01 mass part or more, for example, the surface of a particulate-form heat conductive substance (C) can fully be coat | covered, and affinity with the said polymer (A) can be improved. it can. Moreover, it becomes favorable heat conductivity by setting it as 10 mass parts or less, and becomes a preferable aspect.

<Silane coupling agent>
Moreover, when preparing the said adhesive composition, the objective which improves the affinity of the said polymer (A) (formation of a continuous phase) and the said heat conductive substance (C), and a heat conductive adhesive layer are used. For the purpose of increasing the affinity between the adherend to be bonded and the pressure-sensitive adhesive layer and improving the adhesive strength and durability of the pressure-sensitive adhesive layer, a silane coupling agent can be used. The silane coupling agent is not particularly limited, and a known silane coupling agent can be appropriately selected and used. For example, epoxy such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Group-containing silane coupling agent; 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propyl Amino group-containing silane coupling agents such as amines; (Meth) acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; 3-isocyanatopropyltriethoxysilane and the like Insane Such as group-containing silane coupling agent. Use of such a silane coupling agent is preferable for improving durability. The said silane coupling agent may be used independently, and may mix and use 2 or more types.

  As content of the said silane coupling agent, it is preferable to contain 0.01-10 mass parts of said silane coupling agents with respect to 100 mass parts of polymer components whole quantity which comprises the said adhesive layer, More preferably, It is 0.02-5 mass parts, More preferably, it is 0.05-2 mass parts. By using the silane coupling agent in the above range, the cohesive force and durability can be improved more reliably. Moreover, by setting it as 0.01 mass part or more, for example, the surface of a particulate-form heat conductive substance (C) can fully be coat | covered, and affinity with the said polymer (A) can be improved. it can. Moreover, it becomes favorable heat conductivity by setting it as 10 mass parts or less, and becomes a preferable aspect.

<Tackifying resin>
Moreover, when preparing the said adhesive composition, tackifying resin can be used in order to improve the adhesive force and durability of the adhesive layer formed with the said adhesive composition more. The tackifying resin is not particularly limited and can be appropriately selected from known ones. For example, rosin resins, terpene resins, aliphatic petroleum resins, aromatic petroleum resins , Copolymer petroleum resins, alicyclic petroleum resins, xylene resins, acrylic resins, and elastomers. The acrylic resin described here refers to a (meth) acrylic polymer having a weight average molecular weight of 1000 to 30000 obtained by polymerizing an acrylic monomer. In addition, as the various tackifying resins other than the acrylic resin, the various tackifying resins hydrogenated (hydrogenated) can be preferably used.

  The softening point (ring and ball method) of the tackifying resin is preferably 80 to 200 ° C, more preferably 90 to 180 ° C. When the softening point of the tackifying resin is within the above range, it is possible to achieve both a high adhesive force and a good balance of properties such as excellent retention and repulsion resistance.

  The content of the tackifying resin is preferably 1 to 100 parts by mass, more preferably 2 to 80 parts by mass with respect to 100 parts by mass of the total amount of the polymer components constituting the adhesive layer. More preferably, it is 3-50 mass parts.

  Furthermore, the pressure-sensitive adhesive composition may contain a compound that causes keto-enol tautomerism. For example, in a pressure-sensitive adhesive composition containing a cross-linking agent or a pressure-sensitive adhesive composition that can be used by blending a cross-linking agent, an embodiment including a compound that produces the keto-enol tautomerism can be preferably employed. Thereby, the excessive viscosity raise and gelation of an adhesive composition after a crosslinking agent mixing | blending can be suppressed, and the effect of extending the pot life of an adhesive composition may be implement | achieved. When at least an isocyanate compound is used as the crosslinking agent, it is particularly meaningful to contain a compound that causes keto-enol tautomerism. This technique can be preferably applied when, for example, the pressure-sensitive adhesive composition is in an organic solvent solution or a solvent-free form.

  Various β-dicarbonyl compounds can be used as the compound that causes keto-enol tautomerism. Specific examples include acetylacetone, 2,4-hexanedione, 3,5-heptanedione, 2-methylhexane-3,5-dione, 6-methylheptane-2,4-dione, 2,6-dimethylheptane- Β-diketones such as 3,5-dione; acetoacetates such as methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, tert-butyl acetoacetate; ethyl propionyl acetate, ethyl propionyl acetate, isopropyl propionyl acetate, propionyl acetate propionyl acetates such as tert-butyl; isobutyryl acetates such as ethyl isobutyryl acetate, ethyl isobutyryl acetate, isopropyl isobutyryl acetate, tert-butyl isobutylyl acetate; malonates such as methyl malonate and ethyl malonate; etc. And the like. Among these, acetylacetone and acetoacetic acid esters are preferable compounds. Such compounds that produce keto-enol tautomerism may be used alone or in combinations of two or more.

  Content of the compound which produces the keto-enol tautomerism can be 0.1-20 mass parts with respect to 100 mass parts of said polymers (B), and usually is 0.5-15 mass parts. (For example, 1 to 10 parts by mass) is appropriate. If the amount of the compound is too small, it may be difficult to achieve a sufficient use effect. On the other hand, if the compound is used more than necessary, it may remain in the pressure-sensitive adhesive layer and reduce the cohesive force.

  In addition, the pressure-sensitive adhesive composition includes various general components in the field of pressure-sensitive adhesives in addition to the polymer components (polymer (A) and polymer (B), etc.) and the heat conductive material (C). These additives can be contained as optional components. Such optional components include anti-aging agents, antioxidants, processing aids, stabilizers, antifoaming agents, flame retardants, thickeners, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), A leveling agent, an antiseptic, an antistatic agent, and the like can be appropriately added as long as the effects of the present invention are not impaired.

<Morphological observation>
Examples of the method of morphological observation (observation of phase separation structure) of the pressure-sensitive adhesive layer of the present invention include an analysis method using an electron microscope such as SEM (scanning electron microscope) and TEM (transmission electron microscope). For example, what corresponds to FIG.5 and FIG.6 corresponds.

In determining a more detailed morphology (phase separation structure) of the pressure-sensitive adhesive layer, it is preferable to use a three-dimensional structural analysis (see FIGS. 7 and 8). For example, the SEM image analysis using a focused ion beam (FIB) (product name: Helios NanoLab 600, manufacturing company name: FEI Company) analyzes the morphology of the heat conductive adhesive layer three-dimensionally (three-dimensional analysis) )can do.
In addition, the rectangular parallelepiped in FIG.7 and FIG.8 shows the heat conductive adhesive layer of this invention, The white (gray) part inside the said rectangular parallelepiped shows a heat conductive substance, The black part inside the said rectangular parallelepiped, A thin line portion indicates a polymer, and a thin linear portion indicates a connection path (heat conduction path) of the heat conductive material. The connection path (heat conduction path) indicates, for example, a path for transferring heat from the front surface side S to the bottom surface (back surface) side B of the adhesive layer as shown in FIG. is there.

Further, based on the results of the three-dimensional analysis and the theory of electrical resistance, the larger the cross-sectional area of the connection path (thermal conduction path) of the heat conductive material (filler) in the thickness direction, the shorter the path length, It can be said that the conductivity is good. For example, in the case of an adhesive layer (adhesive sheet) that contains 125 parts by mass of a heat conductive substance (filler) with respect to 100 parts by mass of the polymers (A) and (B), the width direction is 20 μm × the depth direction. When the space of 15 μm × 10 μm in the thickness direction was analyzed, the average path width (μm) (see FIG. 9) of the connection path (thermal conduction path) of the heat conductive material in the thickness direction was divided by 2 and squared. The value obtained by multiplying the object by the circumference ratio (that is, the average cross-sectional area of the path when the heat conduction path is assumed to be a cylinder) is divided by the average path length (μm) (see FIG. 10). Thermal conductivity can be evaluated.
The average path width can be calculated, for example, by averaging the lengths of the portions where the fillers are in contact with each other.
In addition, as the average path length, for example, the number of pixels that are connected at the time of image analysis until the minimum pixel (pixel) is reached from the front surface side of the image analysis space to the back surface side (that is, in the thickness direction). It can be obtained by calculating and converting to the actual distance (μm) based on this and calculating the average value of the lengths of all paths.
Specifically, a method of determining the minimum pixel corresponding to the center position with respect to the width of the heat conduction path formed by connecting the heat conductive materials (fillers) (see “thinning”, see FIG. 11). By combining the methods of determining the shortest distance route ("Minimization", see Fig. 12) when there are multiple types of route advancement, and performing the same calculation for all routes and averaging The average path length with respect to the thickness direction in the analysis space can be obtained.

The heat conductive pressure-sensitive adhesive layer of the present invention preferably has the following general formula (1) and a heat conductivity parameter of 0.0023 or more.
[Thermal conductivity parameter (W / (cm · K))]
= [Thickness of heat conductive adhesive layer (cm)] / [Total thermal resistance (cm ² · K / W)] (1)
The thermal conductivity parameter value (standard) of the pressure-sensitive adhesive layer is preferably 0.0023 or more, more preferably 0.0024 or more, and further preferably 0.0025 or more. If the thermal conductivity parameter value is within the above range, it can be said that the thermal conductivity of the pressure-sensitive adhesive layer is good, for example, even when it is used by being adhered to a heat sink or the like of a semiconductor module. It becomes possible to exhibit thermal conductivity.

  In addition, about the composition distribution of each phase (continuous phase and dispersed phase) of the pressure-sensitive adhesive layer that is phase-separated, or by determining the ease of dyeing of the dyeing agent, or by combining conventionally known composition analysis methods, Judgment is possible.

<Method for producing pressure-sensitive adhesive layer>
The manufacturing method of the heat conductive adhesive layer of this invention mixes the polymer monomer (b) which comprises the said polymer (A), the monomer unit of the said polymer (B), and a heat conductive substance (C). Preparing a pressure-sensitive adhesive composition, and polymerizing the pressure-sensitive adhesive composition with radiation energy to obtain a continuous phase containing the polymer (A) and a dispersed phase containing the polymer (B). And preparing a pressure-sensitive adhesive layer to be formed. By mixing the polymer (A) synthesized in advance using the polymerizable monomer (b), the polymer (A) is dissolved or dispersed in the polymerizable monomer (b). Therefore, when the polymerization reaction proceeds based on the radiation energy, a continuous phase containing the polymer (A) (as a main component) can be formed and the dispersion containing the polymer (B) (as a main component). A dense phase separation structure having phases can be formed. Although the detailed reason why the polymer (A) is contained in the continuous phase (forms a continuous phase) is not clear, the polymer (A) is aggregated (interaction) in the polymerizable monomer (b). ) To form a continuous phase (sea phase), and the dispersed phase (island phase) is filled with the polymer (B) obtained by the polymerization reaction of the polymerizable monomer (b) around the continuous phase (sea phase). ) Is presumed to form a phase separation (sea island) structure (see FIG. 2). By having the phase separation (sea-island) structure, not only the function of the polymer (B) but also the function of the polymer (A) can be exhibited, not only excellent adhesion properties to the adherend, By including the thermally conductive substance (C) in the continuous phase (sea phase), a pressure-sensitive adhesive layer having excellent thermal conductivity can be obtained, which is useful.

The method for forming the pressure-sensitive adhesive layer having a phase separation (sea island) structure composed of a continuous phase and a dispersed phase according to the present invention is specifically described below.
(1) First, the polymer (A) is mixed with the polymerizable monomer (b), which is a monomer component for forming the polymer (B), and stirred, so that the polymer (A) is contained in the polymerizable monomer (b). In step (1), a solution (or dispersion) that is uniformly mixed (dissolved or dispersed) is prepared.
(2) Subsequently, the thermally conductive substance (C) and, if necessary, other polymerizable monomer (b), a polymerization initiator, a polyfunctional monomer, etc. are added here and stirred again. A uniform pressure-sensitive adhesive composition (solution) is prepared.
(3) The pressure-sensitive adhesive composition (solution) is coated on the release-treated surface of a release-treated substrate (for example, polyethylene terephthalate film) to form a pressure-sensitive adhesive layer having a predetermined thickness, thereby blocking oxygen. For the purpose, the other release-treated substrate (for example, polyethylene terephthalate film) is bonded to the coated surface and irradiated with radiation energy (for example, ultraviolet (UV)).
(4) Upon irradiation with radiation energy (for example, ultraviolet rays (UV)), the polymerizable monomer (b) is polymerized, and the raw materials constituting the pressure-sensitive adhesive composition are cross-linked, so that the polymer (A) is used as a main component. A pressure-sensitive adhesive layer having a phase separation structure formed from a dispersed phase containing a continuous phase and a polymer (B) (as a main component).
In this case, the heat conductive substance (C) having a high affinity with the polymer (A) is mainly present in the continuous phase.

  The thickness of the pressure-sensitive adhesive layer of the present invention is preferably 10 μm to 5 mm, more preferably 20 μm to 2 mm, and further preferably 30 μm to 1 mm. By having such a thickness, good adhesive properties can be realized.

<Method for preparing pressure-sensitive adhesive composition containing thermal conductive substance (C)>
Hereinafter, a method for preparing a pressure-sensitive adhesive composition using boron nitride particles as the thermally conductive substance (C) will be specifically described. Here, the polymer (A) is an acrylic polymer, the polymerizable monomer (b) is an acrylic monomer, and the thermally conductive substance (C) is an aggregated boron nitride having an average particle size of 60 to 200 μm. A method for preparing a liquid pressure-sensitive adhesive composition (coating liquid) containing particles will be described.

  First, in order to prepare the coating liquid, the boron nitride particles are blended together with the acrylic polymer in a mixer that can be stirred under reduced pressure. Further, if necessary, a dispersant can be contained in the coating liquid for the purpose of improving the dispersibility of the boron nitride particles in the acrylic polymer. As the dispersant, it is preferable to use a dispersant containing a compound having an amine value of more than 0 mgKOH / g and not more than 35 mgKOH / g from the viewpoint of excellent dispersibility improvement effect of boron nitride particles with respect to an acrylic polymer or the like. preferable.

  Boron nitride particles as a heat conductive substance (C) are charged into the mixer, and then an acrylic polymer and other components are dissolved and dispersed in an acrylic monomer as a polymerizable monomer (b). A part of the composition (solution) is put into the mixer. And the particle size adjustment process which refines | miniaturizes the boron nitride particle of an aggregation state by, for example, stirring at normal temperature under reduced pressure of 1-20 kPa is implemented.

  As a more specific particle size adjustment step, for example, the rotation speed of the mixer is preferably 30 rpm or less, more preferably 10 to 20 rpm, and all boron nitride particles are dispersed in the pressure-sensitive adhesive composition (solution). Then, a method of continuing the stirring operation until the viscosity becomes such that adhesion to the stirring blade of the mixer is not observed can be employed.

  Next, the remaining amount of the pressure-sensitive adhesive composition (solution) is added to the mixer, and stirred at room temperature under a reduced pressure of 1 to 20 kPa, for example, so that the viscosity becomes lower than that in the particle size adjustment step, and nitriding A particle size readjustment step for refining the boron particles is performed. In addition, if necessary, the remaining amount of the pressure-sensitive adhesive composition (solution) can be divided into several degrees, and this particle size readjustment step can be divided into a plurality of steps.

  More specifically, for example, the rotation speed of the mixer is preferably 20 to 50 rpm which is equal to or higher than the rotation speed in the particle size adjustment step, and more preferably the rotation speed is 20 to 30 rpm. In addition, a method of continuing the stirring operation to such an extent that large aggregates are not visually observed can be employed. Thereby, the adhesive composition (coating liquid, for coating) which adjusted the particle size can be prepared.

<Adhesive sheet>
It is preferable that the heat conductive adhesive sheet of this invention has the said heat conductive adhesive layer. The pressure-sensitive adhesive sheet is a so-called pressure-sensitive adhesive sheet with a base material provided with the pressure-sensitive adhesive layer fixed on one or both sides of a sheet-like base material (support), that is, without intention to separate the pressure-sensitive adhesive layer from the base material ( Single-sided or double-sided pressure-sensitive adhesive sheet), or the pressure-sensitive adhesive layer on a substrate having releasability such as a release film (release liner) (release paper, resin sheet having a surface subjected to release treatment). It may be a so-called base material-less (double-sided) pressure-sensitive adhesive sheet in which the base material supporting the pressure-sensitive adhesive layer at the time of sticking is removed. The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. The pressure-sensitive adhesive layer is not limited to those formed continuously, and may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as a spot or stripe. In addition, when using a base material, it is a preferable aspect to use (contain) the substance which has heat conductivity similarly to the said adhesive layer.

  Examples of the substrate (support) include plastic substrates such as polyethylene terephthalate (PET) and polyester film, porous materials such as paper and nonwoven fabric, and metal foil.

  The plastic substrate is not particularly limited as long as it can be formed into a sheet shape or a film shape. For example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene -Polyolefin films such as propylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer; polyethylene terephthalate, polyethylene naphthalate, Polyester film such as polybutylene terephthalate; Polyacrylate film, Polystyrene film, Polyamide film such as nylon 6, Nylon 6,6, Partially aromatic polyamide; Polyvinyl chloride film, Polyvinylidene chloride film, Poly Such as turbo titanate film, and the like.

  The base material has a thickness of usually 4 to 100 μm, preferably about 4 to 25 μm.

  If necessary, the plastic substrate may be released from a silicone, fluorine, long chain alkyl or fatty acid amide release agent, silica powder, etc., and antifouling treatment, acid treatment, alkali treatment, primer treatment. Further, anti-adhesion treatment such as corona treatment, plasma treatment and ultraviolet treatment, coating type, kneading type, vapor deposition type and the like can be carried out.

  Examples of the release film (release liner) include plastic films such as polyethylene, polypropylene, and polyethylene terephthalate, porous materials such as paper, cloth, and nonwoven fabric, nets, foamed sheets, metal foils, and laminates thereof. From the point of excellent surface smoothness, a plastic film is preferably used.

  The plastic film used for the release film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film. Polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, and the like can be used.

  For the release film, if necessary, mold release and antifouling treatment with silicone, fluorine, long chain alkyl or fatty acid amide release agent, silica powder, etc., coating type, kneading type, vapor deposition An antistatic treatment such as a mold may be performed. In particular, the release property from the pressure-sensitive adhesive layer can be further improved by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the release film.

  The thickness of the release film is usually about 5 to 200 μm, preferably about 5 to 100 μm.

  The pressure-sensitive adhesive layer of the present invention is a cured layer of the pressure-sensitive adhesive composition. After the pressure-sensitive adhesive composition (solution) is applied (for example, applied) to an appropriate substrate (support), a curing treatment is performed. Can be formed by appropriately applying. When performing 2 or more types of hardening processes (drying, bridge | crosslinking, superposition | polymerization, etc.), these can be performed simultaneously or in multiple steps. In a pressure-sensitive adhesive composition using a partial polymer (acrylic polymer syrup), typically, as the curing treatment, a final copolymerization reaction is performed (the partial polymer is subjected to a further copolymerization reaction). A complete polymer is formed). For example, if a photocurable pressure-sensitive adhesive composition is used, light irradiation is performed. If necessary, curing treatment such as cross-linking and drying may be performed. For example, when it is necessary to dry with a photocurable pressure-sensitive adhesive composition, photocuring may be performed after drying. In the pressure-sensitive adhesive composition using a completely polymerized product, typically, as the curing treatment, treatments such as drying (heat drying) and crosslinking are performed as necessary.

  The method for applying the pressure-sensitive adhesive composition (solution) is not particularly limited, but for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air A method such as an extrusion coating method using a knife coat, curtain coat, lip coat, die coater or the like can be used.

<Application>
The heat conductive pressure-sensitive adhesive sheet having the heat conductive pressure-sensitive adhesive layer of the present invention has high adhesion reliability in bonding of adherends, and therefore can be suitably used for electronic / electric devices. For example, an electronic device including a circuit board such as a semiconductor device, a hard disk, an LED device (television, illumination, display, etc.), an EL device (organic EL display, organic EL illumination, etc.), for example, a capacitor, a battery (lithium ion battery, etc.) ) Etc., for example, a power module etc. are mentioned. Specifically, this heat conductive adhesive sheet is bonded and affixed to heat generating components (an example of an object to be adhered, such as a circuit board, a secondary battery, and a power module) of these electronic / electrical devices. Thereby, since these electronic / electrical devices can be suitably joined and fixed, the heat of the heat-generating component can be stably dissipated, which is useful.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

  Table 1 shows the physical property values of the polymers, the component contents of the pressure-sensitive adhesive compositions according to Examples 1 to 4 and Comparative Examples 1 to 6, and the pressure-sensitive adhesive layer. The evaluation results of the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) are shown in Tables 2 and 3.

(Component (A): Preparation of acrylic polymer 1 (2EHA / AA = 98/2))
100 parts by mass of 2-ethylhexyl acrylate (2EHA), 2 parts by mass of acrylic acid (AA), 150 parts by mass of ethyl acetate, and 0.2 parts by mass of azobisisobutyronitrile (AIBN) were charged into a four-necked flask. Then, the mixture was heated to 60 ° C. in a nitrogen atmosphere and polymerized for 8 hours while maintaining the inner bath temperature of 60 ° C., thereby obtaining a polymer solution having a solid content of about 40% by mass. Thereafter, volatile components (residual monomer and ethyl acetate) were removed by drying, and acrylic polymer 1 was obtained. The SP value calculated from the Fedors formula of acrylic polymer 1 was 9.29.

(Component (A): Preparation of acrylic polymer 2 (2EHA / MMA / NVP / HEA = 63/9/15/13))
63 parts by mass of 2-ethylhexyl acrylate (2EHA), 9 parts by mass of methyl methacrylate (MMA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 13 parts by mass of 2-hydroxyethyl acrylate (HEA), 200 parts by mass of ethyl acetate Part, 0.2 part by mass of azobisisobutyronitrile (AIBN) was charged into a four-necked flask. Then, the mixture was heated to 65 ° C. in a nitrogen atmosphere and polymerized for 8 hours while maintaining the inner bath temperature of 65 ° C. to obtain a polymer solution having a solid content of about 33% by mass. Thereafter, volatile components (residual monomer and ethyl acetate) were removed by drying, and an acrylic polymer 2 was obtained. The SP value calculated from the Fedors equation of the acrylic polymer 2 was 10.30.

(Component (A): Preparation of acrylic polymer 3 (BA / Vac / AA = 92/5/3))
4 parts 92 parts by mass of butyl acrylate (BA), 5 parts by mass of vinyl acetate (Vac), 3 parts by mass of acrylic acid (AA), 200 parts by mass of ethyl acetate, 0.2 parts by mass of azobisisobutyronitrile (AIBN) Charged to a neck flask. Then, the mixture was heated to 63 ° C. in a nitrogen atmosphere and polymerized for 10 hours while maintaining the inner bath temperature at 63 ° C. to obtain a polymer liquid having a solid content of about 33% by mass. Thereafter, volatile components (residual monomer and ethyl acetate) were removed by drying, and an acrylic polymer 3 was obtained. The SP value calculated from the Fedors formula of the acrylic polymer 3 was 9.91.

(Component (B): Preparation of acrylic polymer solution (BA / AA = 99/1))
99 parts by mass of butyl acrylate (BA), 1 part by mass of acrylic acid (AA), 230 parts by mass of ethyl acetate, and 0.2 parts by mass of azobisisobutyronitrile (AIBN) were charged into a four-necked flask. Then, the mixture was heated to 61 ° C. under a nitrogen atmosphere and allowed to undergo a polymerization reaction for 4 hours while maintaining the inner bath temperature of 61 ° C., and then further heated to 70 ° C. while maintaining the inner bath temperature of 70 ° C. By carrying out a polymerization reaction for 3 hours, an acrylic polymer solution having a solid content of about 30% by mass was obtained. The SP value calculated from the Fedors equation of the acrylic polymer (BA / AA = 99/1) was 9.81.

(Comparative Production Example 1: Preparation of acrylic polymer syrup 1 (BA / 2EHA / AA = 80/20 / 0.04))
80 parts by mass of butyl acrylate (BA), 20 parts by mass of 2-ethylhexyl acrylate (2EHA), 0.04 parts by mass of acrylic acid (AA), photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) 0.05 mass Parts and a photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) 0.05 parts by mass were charged into a four-necked flask. Then, the mixture was exposed to ultraviolet rays under a nitrogen atmosphere (irradiated with a black light lamp (manufactured by Toshiba Corporation) and irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a maximum sensitivity of about 350 nm) for 180 seconds. And partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 1) having a polymerization rate of about 8% by mass.

(Comparative Production Example 2: Preparation of acrylic polymer syrup 2 (BA / 2EHA / NVP / HEA = 82/13/3/2))
82 parts by mass of butyl acrylate (BA), 13 parts by mass of 2-ethylhexyl acrylate (2EHA), 3 parts by mass of N-vinyl-2-pyrrolidone (NVP), 2 parts by mass of 2-hydroxyethyl acrylate (HEA), photopolymerization initiator 0.05 parts by mass (trade name: Irgacure 184, manufactured by BASF) and 0.05 parts by mass of a photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) were charged into a four-necked flask. Then, the mixture was exposed to ultraviolet rays under a nitrogen atmosphere (irradiated with a black light lamp (manufactured by Toshiba Corporation) and irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a maximum sensitivity of about 350 nm) for 180 seconds. And partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 2) having a polymerization rate of about 8% by mass.

(Comparative Production Example 3: Preparation of acrylic polymer syrup 3 (2EHA / NVP / 2MEA / HEAA = 80/7 / 11.5 / 1.5))
2-ethylhexyl acrylate (2EHA) 80 parts by mass, N-vinyl-2-pyrrolidone (NVP) 7 parts by mass, 2-methoxyethyl acrylate (2MEA) 11.5 parts by mass, N-hydroxyethylacrylamide (HEAA) 1.5 4-neck flask containing 0.06 parts by mass, photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF) and 0.06 mass part of photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) It was thrown into. Then, the mixture was exposed to ultraviolet rays under a nitrogen atmosphere (irradiated with a black light lamp (manufactured by Toshiba Corporation) and irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a maximum sensitivity of about 350 nm) for 180 seconds. ) And partially photopolymerized to obtain a partially polymerized product (acrylic polymer syrup 3) having a polymerization rate of about 6% by mass.

Example 1
(Preparation of acrylic pressure-sensitive adhesive composition)
20 parts by mass of the acrylic polymer 1 (component (A)), 80 parts by mass of butyl acrylate as the polymerizable monomer (b), 0.05 part by mass of Irgacure 184 and 0.005 of Irgacure 651 as the photopolymerization initiator. 05 parts by mass, as a polyfunctional monomer, 0.3 parts by mass of trimethylolpropane triacrylate and 1.25 parts by mass of a phosphate ester dispersant (Price Surf A212, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are added. Then, after mixing these uniformly, 125 parts by mass of aluminum hydroxide (manufactured by Showa Denko Co., Ltd., Hygielite (H42)) is further added as a heat conductive material, and mixed uniformly again, and acrylic A pressure-sensitive adhesive composition was prepared. The SP value calculated from the Fedors formula of polybutyl acrylate corresponding to the polymer (B) was 9.77.

(Preparation of adhesive layer)
The final thickness of the acrylic pressure-sensitive adhesive composition described above is about 100 μm on the release-treated surface of a 38 μm-thick polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics Co., Ltd.) whose one side is peel-treated with silicone. It applied so that an application layer might be formed.
Next, a 38 μm-thick polyester film (trade name: Diafoil MRE, manufactured by Mitsubishi Plastics Co., Ltd.) having one surface peeled with silicone is applied to the surface of the coating layer so that the peeling treatment surface of the film is on the coating layer side. And coated. Thereby, the application layer (adhesive layer) of the acrylic adhesive composition was shielded from oxygen. The coating layer sheet thus obtained was irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² (measured with Topcon UVR-T1 having a maximum sensitivity at about 350 nm) for 360 seconds using a black light lamp (manufactured by Toshiba Corporation). Then, an adhesive layer (adhesive layer sheet) was obtained. In addition, the polyester film coat | covered on both surfaces of the said adhesive layer functions as a release liner.

As a result of TEM observation of the cross section of the obtained pressure-sensitive adhesive layer (see FIG. 5), a continuous phase mainly composed of acrylic polymer 1 and a dispersed phase mainly composed of polybutyl acrylate were formed, and the heat conductivity It was confirmed that Heidilite (H42) which is a substance is unevenly distributed in the continuous phase mainly composed of the acrylic polymer 1.
The TEM apparatus used for TEM observation was H-7650 manufactured by Hitachi, Ltd., and the acceleration voltage condition was 100 kV.
In addition, the white linear part in FIG. 5 which is a result of TEM observation of the cross section of the obtained pressure-sensitive adhesive layer corresponds to a continuous phase, and the black part is a part formed by a thermally conductive substance (filler). It was confirmed that the thermally conductive substance was unevenly distributed (contacted / included) in the continuous phase.

In addition, as a result of three-dimensional analysis by SEM observation using FIB (space of width 20 μm × depth 15 μm × thickness 10 μm), the heat conduction path in the thickness direction (Z direction) of Heidilite (H42), which is a heat conductive material, is shown. The average path length is 29.6 μm, the average path width of the heat conduction path is 0.31 μm, and the parameter value (hereinafter referred to as “heat conduction path parameter”) of (average cross-sectional area / average path length) is 0. It was 00255.
The FIB-SEM apparatus used for the three-dimensional analysis by SEM observation using FIB uses the product name: Helios NanoLab 600 (manufacturer name: FEI Company), and the acceleration voltage condition is 30 kV for FIB, SEM is It was set to 2 kV.

(Example 2)
Phosphate ester dispersant (Daiichi Kogyo Seiyaku Co., Ltd., Prisurf A212) is 2.0 parts by mass, and aluminum hydroxide (Showa Denko Co., Ltd., Heidilite (H42)) is 190 as a heat conductive substance. An acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive layer were obtained in the same manner as in Example 1 except that the content was changed to parts by mass. In the obtained pressure-sensitive adhesive layer, the phase mainly composed of the acrylic polymer 1 is a continuous phase, and the phase mainly composed of polybutyl acrylate is a dispersed phase, and the heat conductive material Heidilite (H42) is acrylic. It was confirmed that it was unevenly distributed in a continuous phase mainly composed of polymer 1.

(Example 3)
20 parts by mass of the acrylic polymer 2 (component (A)) described above, 80 parts by mass of butyl acrylate as a polymerizable monomer (b), 0.05 part by mass of Irgacure 184 as a photopolymerization initiator, and Irgacure 651 0.05 part by mass, as a polyfunctional monomer, 0.05 part by mass of trimethylolpropane triacrylate, and 2.0 parts by mass of a phosphoric ester dispersant (Plysurf A212 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Were added and 190 parts by mass of Heidilite (H42), which is a heat conductive material, was added and mixed uniformly again to prepare an acrylic pressure-sensitive adhesive composition. Using this acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1.
In the obtained pressure-sensitive adhesive layer, a continuous phase mainly composed of the acrylic polymer 2 and a dispersed phase mainly composed of polybutyl acrylate are formed, and the heat conductive material Heidilite (H42) is acrylic. It was confirmed that it was unevenly distributed in the continuous phase mainly composed of polymer 2.

Example 4
20 parts by mass of the acrylic polymer 3 (component (A)) described above, 80 parts by mass of 2-ethylhexyl acrylate as a polymerizable monomer (b), 0.05 parts by mass of Irgacure 184 as a photopolymerization initiator, 0.05 parts by mass of Irgacure 651, 0.05 parts by mass of dipentaerythritol hexaacrylate as a polyfunctional monomer, and 1.25 of a phosphate ester dispersant (Plysurf A212 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) After adding parts by mass and mixing these uniformly, 125 parts by mass of Heidilite (H42), which is a heat conductive material, was further added and mixed uniformly again to prepare an acrylic pressure-sensitive adhesive composition. . Using this acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1. The SP value calculated from the Fedors equation of poly-2-ethylhexyl acrylate corresponding to polymer (B) was 9.22.
In the obtained pressure-sensitive adhesive layer, a continuous phase mainly composed of the acrylic polymer 3 and a disperse phase mainly composed of poly-2-ethylhexyl acrylate are formed, and the high conductivity (H42) which is a heat conductive substance is formed. It was confirmed that it was unevenly distributed in the continuous phase mainly composed of the acrylic polymer 3.

(Comparative Example 1)
To 100 parts by mass of the acrylic polymer syrup 1 described above, as a polyfunctional monomer, 0.3 parts by mass of trimethylolpropane triacrylate and a phosphate ester dispersant (Daiichi Kogyo Seiyaku Co., Ltd., Prisurf A212) After adding 2.0 parts by mass and mixing them uniformly, further adding 190 parts by mass of Heidilite (H42), which is a heat conductive material, and mixing uniformly again, the acrylic pressure-sensitive adhesive composition A product was prepared. Using this acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1.
In the obtained pressure-sensitive adhesive layer, hygielite (H42), which is a heat conductive material, was uniformly dispersed.

(Comparative Example 2)
An acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive layer were obtained in the same manner as in Comparative Example 1 except that the heat conductive material Heidilite (H42) was changed to 250 parts by mass.
In the obtained pressure-sensitive adhesive layer, hygielite (H42), which is a heat conductive material, was uniformly dispersed.

(Comparative Example 3)
To 100 parts by mass of the acrylic polymer syrup 2 described above, 0.05 parts by mass of trimethylolpropane triacrylate as a polyfunctional monomer, and a phosphate ester dispersant (Plysurf A212, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) After adding 2.0 parts by mass and mixing them uniformly, further adding 190 parts by mass of Heidilite (H42), which is a heat conductive material, and mixing uniformly again, the acrylic pressure-sensitive adhesive composition A product was prepared. Using this acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer was obtained in the same manner as in Comparative Example 1.
In the obtained pressure-sensitive adhesive layer, hygielite (H42), which is a heat conductive material, was uniformly dispersed.

(Comparative Example 4)
To 100 parts by mass of the acrylic polymer syrup 2 described above, 0.05 parts by mass of trimethylolpropane triacrylate as a polyfunctional monomer, and a phosphate ester dispersant (Plysurf A212, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) After adding 2.5 parts by mass and mixing them uniformly, 250 parts by mass of Heidilite (H42), which is a heat conductive material, is further added and mixed uniformly again to obtain an acrylic pressure-sensitive adhesive composition. A product was prepared. Using this acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer was obtained in the same manner as in Comparative Example 1.
In the obtained pressure-sensitive adhesive layer, hygielite (H42), which is a heat conductive material, was uniformly dispersed.

(Comparative Example 5)
To 100 parts by mass of the acrylic polymer syrup 3 described above, as a polyfunctional monomer, 0.3 parts by mass of trimethylolpropane triacrylate and a phosphate ester dispersant (Daiichi Kogyo Seiyaku Co., Ltd., Prisurf A212) After adding 1.25 parts by weight and mixing them uniformly, further adding 125 parts by weight of Heidilite (H42), which is a heat conductive material, and mixing uniformly again, the acrylic pressure-sensitive adhesive composition A product was prepared.
Using this acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer was obtained in the same manner as in Comparative Example 1.
As a result of TEM observation of the cross section of the obtained pressure-sensitive adhesive layer (see FIG. 6), it was confirmed that hygielite (H42) as a heat conductive material was uniformly dispersed in the obtained pressure-sensitive adhesive layer. It was done.
In addition, the white linear part in FIG. 6 which is a result of TEM observation of the cross section of the obtained pressure-sensitive adhesive layer corresponds to a continuous phase, and the black part is a part formed by a thermally conductive substance (filler). Compared with FIG. 5 (Example 1), the continuous phase was not clearly formed, and it was not confirmed that the thermally conductive material was unevenly distributed in the continuous phase.
In addition, as a result of three-dimensional analysis by SEM observation using FIB (space of width 20 μm × depth 15 μm × thickness 10 μm), the average path of the heat conduction path with respect to the thickness direction (Z direction) of Heidilite H42 which is a heat conductive material The length was 28.3 μm, the average path width of the heat conduction path was 0.28 μm, and the parameter (heat conduction path parameter) of (average cross-sectional area / average path length) was 0.00217. The measuring apparatus and conditions were in accordance with Example 1.

(Comparative Example 6)
(Adhesive composition solution preparation)
The acrylic polymer (BA / AA = 99/1) solution and the acrylic polymer 1 were mixed to obtain a polymer solution blended at a ratio as shown in Table 1. As a crosslinking agent, 0.1 part by mass of an epoxy compound (manufactured by Mitsubishi Gas Chemical Co., Ltd., Tetrad C) and a phosphate ester dispersant (Daiichi Kogyo Co., Ltd.) with respect to 100 parts by mass of the solid content of the polymer solution. After adding 1.25 parts by mass of Plysurf A212) manufactured by Pharmaceutical Co., Ltd. and mixing them uniformly, 125 parts by mass of aluminum hydroxide (manufactured by Showa Denko KK, Heidilite (H42)) was further added. Then, the mixture was uniformly mixed again to prepare an acrylic pressure-sensitive adhesive composition solution.

(Preparation of adhesive layer)
The acrylic adhesive composition solution described above is applied to the release surface of a 38 μm-thick polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics Co., Ltd.) whose one side is release-treated with silicone. A coating layer was formed by coating so as to have a thickness of about 100 μm, and this was dried at 110 ° C. for 2 minutes to obtain a pressure-sensitive adhesive layer. To this, a 38 μm thick polyester film (trade name: Diafoil MRE, manufactured by Mitsubishi Plastics Co., Ltd.), one side of which was peeled with silicone, was bonded so that the peeled surface was in contact with the adhesive layer.

  Among the monomer components constituting the polymers (A) and (B) in the table, those corresponding to the polar group-containing monomer are NVP, HEA, AA, and HEAA, and are nonpolar groups (or low polarity) Examples of such are 2EHA, BA, MMA, and Vac.

(Test method)
<Thermal conductivity parameters>
(1) Total thermal resistance The total thermal resistance was measured using the thermal characteristic evaluation apparatus shown in FIG.
First, each example in which the release films on both sides were peeled between a pair of rods L made of aluminum (A5052, thermal conductivity: 140 W / m · K) formed so as to be a cube having one side of 20 mm, and each example The pressure-sensitive adhesive sheet S (20 mm × 20 mm × 50 μm) of the comparative example was sandwiched, and a pair of rods L were bonded together with the pressure-sensitive 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 rod L might become up-down. Specifically, the heating element H is disposed on the upper rod L, and the radiator C is disposed below the lower rod L. At this time, the pair of rods L bonded together with the adhesive sheet S is positioned between a pair of pressure adjusting screws T penetrating the heating element and the heat radiating body. A load cell R is installed between the pressure adjusting screw T and the heating element H so that the pressure when the pressure adjusting screw T is tightened is measured. Was used as a pressure applied to the pressure-sensitive adhesive sheet S. The pressure applied to the adhesive sheet S was in the range of 90 to 110 kPa.
In addition, three probes P (diameter 1 mm) of the contact-type displacement meter A were installed so as to penetrate the lower rod L and the 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 rod L, and the distance between the upper and lower rods L (the thickness of the adhesive sheet S) can be measured.
A thermometer B having a temperature sensor D was attached to the heating element H and the upper and lower rods L. Specifically, the temperature sensor D was attached at one place on the heating element H and five places at intervals of 5 mm in the vertical direction of each rod L.
Thereafter, the pressure adjusting screw T was tightened to apply pressure to the adhesive sheet S, the temperature of the heating element H was set to 100 ° C., and 20 ° C. cooling water was circulated through the radiator C.
Then, after the temperatures of the heating element H and the upper and lower rods L are stabilized, the temperature of the upper and lower rods L is measured by each temperature sensor D, and passes through the adhesive sheet S from the thermal conductivity and temperature gradient of the upper and lower rods L. The total heat resistance (cm ² · K / W) at the pressure was calculated by calculating the heat flux and calculating the temperature at the interface between the upper and lower rods L and the adhesive sheet S.

In the present invention, the thermal conductivity parameter (parameter of the standard of thermal conductivity) (W / (cm · K)) is the total thermal resistance (cm ² · K / K) calculated as described above for the thickness (cm) of the adhesive sheet. The value was divided by W). The case where the calculated thermal conductivity parameter was 0.0025 or more was rated as ◯, and the case where it was less than 0.0025 was rated as x. The measurement results are shown in Table 2.

<Heat conduction path parameters>
As a result of three-dimensional analysis by SEM observation using FIB (space of width 20 μm × depth 15 μm × thickness 10 μm), the average path length of the heat conduction path in the thickness direction of Heidilite (H42) which is a heat conductive material is 29. The average path width of 6 μm and the heat conduction path was 0.31 μm, and the parameter value of (average cross-sectional area / average path length) was calculated as “heat conduction path parameter” (μm).

  The case where the heat conduction path parameter was 0.0023 or more was evaluated as ◯, and the case where it was less than 0.0023 was evaluated as ×. Table 3 shows the measurement results.

<Constant load peel test>
One release liner (polyester film) of the pressure-sensitive adhesive layer according to each example and each comparative example was peeled off, a polyethylene terephthalate film having a thickness of 50 μm was bonded, and the test piece was cut into a width of 15 mm. Then, the other release liner (polyester film) is peeled off, the adhesive surface of the adhesive layer is attached to a clean SUS plate (SUS304) by one-way crimping with a 2 kg roller, and then left at room temperature (25 ° C) for 30 minutes. did.
Thereafter, the SUS plate on which the polyethylene terephthalate film (hereinafter referred to as a heat conductive adhesive tape) is attached via the heat conductive adhesive layer is placed so that the heat conductive adhesive tape is positioned vertically downward. And an 8 g weight was suspended from one end of the test piece. As a result, the peel stress in the 90 ° direction with respect to the extending direction of the SUS plate was applied to the thermally conductive adhesive tape by gravity, and left in this state at room temperature (25 ° C.).
And from the edge part position (namely, test piece edge part) of the adhesion surface of SUS board and a test piece before applying a load to the edge part position of the adhesion surface of a SUS board and a test piece after applying a load. The time (unit: second) until the peeling distance, which is the distance, reaches 50 mm was measured.
When it was 1000 seconds or more: Very good (◎), when it was 500 seconds or more and less than 1000 seconds, it was judged as good (◯), and when it was less than 500 seconds, it was judged as bad (x). The measurement results are shown in Table 2.

  As shown in Table 2, in Examples 1 to 4, both the thermal conductivity and the constant load peeling characteristics are good results, and satisfy both the thermal conductivity and the adhesive characteristics in a well-balanced manner. Was confirmed. On the other hand, in Comparative Examples 1 to 6, it was confirmed that the desired effect could not be obtained in either one of thermal conductivity and constant load peeling characteristics, and both characteristics were not satisfied in a balanced manner. It was.

  Moreover, as shown in Table 3, in Example 1, it can be confirmed that the heat conduction path is efficiently formed, while in Comparative Example 5, the heat conduction path is not efficiently formed. I was able to confirm.

  From the above evaluation results, the heat conductive pressure-sensitive adhesive layer of the present invention is formed of a pressure-sensitive adhesive composition containing the polymer (A), the polymer (B), and the heat conductive substance (C), and the polymer ( A continuous phase containing A) (as a main component) can be formed, a dispersed phase containing polymer (B) (as a main component) can be formed, and a large amount of thermally conductive substance (C) exists in the continuous phase. As a result, it was confirmed that the heat conduction path was efficiently formed in the pressure-sensitive adhesive layer, and as a result, both the heat conductivity and the adhesive property were compatible at a high level, and an excellent effect that was not available in the past was obtained.

1: Dispersed phase (island phase) mainly composed of rubber-based polymer
2: Continuous phase mainly composed of acrylic polymer (sea phase)
10: Adhesive layer 11: Continuous phase (sea phase) mainly composed of polymer (A)
12: Dispersed phase mainly composed of polymer (B) (island phase)
13: Thermally conductive material (filler)
14: Uniform phase formed from polymer components 15: Path 15 ′: Position where the path width is thick 15 ″: Position where the path width is narrow 16: Start point 16 ′: End point 17: Distance between start point and end point (path length: 1 )
18: (thermal conductivity) pressure-sensitive adhesive layer thickness d
X: No thinning Y: Thinning Z: Thinning path S: Surface side of the adhesive layer B: Bottom side of the adhesive layer

Claims (8)

A continuous phase containing the polymer (A), the polymer (B), and the thermally conductive substance (C) and containing the polymer (A) and a dispersed phase containing the polymer (B) are formed. It is,
The polymer (A) is an acrylic polymer,
The polymer (B) contains a polymerizable monomer (b) constituting a monomer unit,
The polymerizable monomer (b) is an acrylic monomer,
The polymer (B) is an acrylic polymer,
The polymer (B) is obtained by polymerizing the polymerizable monomer (b) with radiation energy,
The mass ratio (mass of the polar group-containing monomer in the total amount of monomer units constituting the polymer (A) to the mass ratio (mass%) of the polar group-containing monomer in the total amount of monomer units constituting the polymer (B). %) Is greater by 1% by mass or more . The thermally conductive pressure-sensitive adhesive layer according to claim 1, wherein the thermally conductive substance (C) is contained in the continuous phase more than in the dispersed phase. 3. The heat according to claim 1, wherein a difference in solubility parameter (SP) value calculated from the Fedors equation of the polymer (A) and the polymer (B) is 0.2 or more. Conductive adhesive layer. The heat conductive adhesive according to any one of claims 1 to 3, wherein the solubility parameter (SP) value of the polymer (A) is larger than the solubility parameter (SP) value of the polymer (B). layer. The blending ratio (A / B) (mass ratio) of the polymer (A) with respect to the polymer (B) is 3/100 to 150/100, according to any one of claims 1 to 4 . Thermally conductive adhesive layer. Thermal conductivity parameters by the following general formula (1) is thermally conductive adhesive layer according to any one of claims 1 to 5, wherein the at 0.0023 or higher.
[Thermal conductivity parameter (W / (cm · K))]
= [Thickness of heat conductive adhesive layer (cm)] / [Total thermal resistance (cm ² · K / W)] (1) Heat conductive adhesive sheet characterized by having a thermally conductive adhesive layer according to any one of claims 1-6. It is a manufacturing method of the heat conductive adhesive layer in any one of Claims 1-6 ,
A step of preparing a pressure-sensitive adhesive composition by mixing the polymer (A), a polymerizable monomer (b) constituting the monomer unit of the polymer (B), and a thermally conductive substance (C);
Preparing a pressure-sensitive adhesive layer that forms a continuous phase containing the polymer (A) and a dispersed phase containing the polymer (B) by polymerizing the pressure-sensitive adhesive composition with radiation energy; The manufacturing method of the heat conductive adhesive layer characterized by including.