JP2014167094A - Thermally conductive adhesive sheet - Google Patents

Abstract

A pressure-sensitive adhesive sheet having excellent electrical insulation as well as thermal conductivity is provided.
The heat conductive pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer, has a thermal conductivity of 0.5 W / mK or more, and is allowed to stand for 1 day in an environment of 40 ° C. and 92% RH. The relative dielectric constant at a frequency of 120 Hz is 30 or less. The thermal conductive pressure-sensitive adhesive sheet preferably further has a relative dielectric constant of 30 or less at a frequency of 1 kHz after being left for 1 day in an environment of 40 ° C. and 92% RH.
[Selection figure] None

Description

  The present invention relates to a pressure-sensitive adhesive sheet having both thermal conductivity and electrical insulation, that is, a thermally conductive pressure-sensitive adhesive sheet having electrical insulation.

  With higher integration and higher performance of electronic devices, thermal conductivity and electrical insulation have been required for heat conductive members (such as adhesive sheets) used in electronic devices. In particular, in a device used at a high voltage such as a large capacitor, high electrical insulation reliability is required.

  As a pressure-sensitive adhesive sheet having thermal conductivity and electrical insulation, a pressure-sensitive adhesive sheet in which particles (for example, aluminum hydroxide, alumina, etc.) are added to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is known (see Patent Document 1).

JP 2004-27039 A

  However, in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer to which particles (for example, aluminum hydroxide, alumina, etc.) are added, impurity ions may elute into the pressure-sensitive adhesive layer due to moisture absorption, and the dielectric constant of the pressure-sensitive adhesive sheet may increase. As a result, there is a problem that a leakage current may occur, and when the leakage current occurs, there is a problem that the electrical insulation of the adhesive sheet is impaired.

  Therefore, the objective of this invention is providing the adhesive sheet which is excellent in electrical insulation with heat conductivity.

  As a result of intensive studies, the present inventors have determined that the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer has a specific dielectric constant at a frequency of 120 Hz after leaving the thermal conductivity at a specific value or more for 1 day in an environment of 40 ° C. and 92% RH. It was found that a pressure-sensitive adhesive sheet excellent in electrical insulation as well as thermal conductivity was obtained when the rate was not more than a specific value, and the present invention was completed.

  That is, the present invention has an adhesive layer, a thermal conductivity of 0.5 W / mK or more, and a relative dielectric constant at a frequency of 120 Hz after being left for 1 day in an environment of 40 ° C. and 92% RH. Provided is a heat conductive pressure-sensitive adhesive sheet characterized by the following.

  The thermal conductive pressure-sensitive adhesive sheet preferably further has a relative dielectric constant of 20 or less at a frequency of 1 kHz after being left for 1 day in an environment of 40 ° C. and 92% RH.

  It is preferable that each of the heat conductive adhesive sheets has a relative dielectric constant of 30 or less at a frequency of 120 Hz to 1 MHz after being left for 1 day in an environment of 40 ° C. and 92% RH.

  The thermally conductive pressure-sensitive adhesive sheet is preferably composed only of the pressure-sensitive adhesive layer.

  The heat conductive adhesive sheet of this invention is excellent in electrical insulation with heat conductivity.

FIG. 1 is a schematic diagram showing a thermal characteristic evaluation apparatus. FIG. 2 is a chart showing the relative dielectric constant at each frequency in the pressure-sensitive adhesive sheets of Examples and Comparative Examples after being left for 1 day in an environment of 40 ° C. and 92% RH. FIG. 3 is a chart showing the relative dielectric constant at each frequency in the pressure-sensitive adhesive sheets of Examples and Comparative Examples before being left for 1 day in an environment of 40 ° C. and 92% RH.

  The heat conductive pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, has a thermal conductivity of 0.5 W / mK or more, and a frequency after being left for 1 day in an environment of 40 ° C. and 92% RH. The pressure-sensitive adhesive sheet has a relative dielectric constant of 30 or less at 120 Hz.

  The heat conductivity in the heat conductive adhesive sheet of this invention is 0.5 W / mK or more, Preferably it is 0.8 W / mK or more, More preferably, it is 1.0 W / mK or more. When the thermal resistivity is less than 0.5 W / mK, it is difficult to obtain good thermal conductivity, and heat from the adherend is efficiently obtained when an adhesive sheet is attached to the adherend (a source of heat generation). It cannot be conducted well and may cause damage or failure of the adherend.

  In the heat conductive adhesive sheet of the present invention, the relative dielectric constant at a frequency of 120 Hz after being left for 1 day in an environment of 40 ° C. and 92% RH is 30 or less, preferably 25 or less, more preferably 20 or less. is there. The lower limit of the relative dielectric constant is not particularly limited, but is preferably 1 or more, more preferably 1.5 or more. If the relative dielectric constant exceeds 30, problems may occur in terms of electrical insulation. For example, when the adherend to which the adhesive sheet is affixed is an electronic or electronic component, if the adhesive sheet has a large dielectric constant, a leakage current may occur when a voltage is applied. Then, the electrical insulation of the adhesive sheet is impaired, and the adherend may be damaged or broken. The above “relative permittivity at a frequency of 120 Hz after being left in a 40 ° C., 92% RH environment for 1 day” refers to a pressure sensitive adhesive sheet that is a target for measuring the relative permittivity for 1 day in a 40 ° C., 92% RH environment. It is a relative dielectric constant at a frequency of 120 Hz measured after being left. In this specification, “relative permittivity at a frequency of 120 Hz after being left for one day in an environment of 40 ° C. and 92% RH” is referred to as “relative permittivity at a frequency of 120 Hz (after 40 ° C./92% RH 1 day)”. Sometimes called.

  In the heat conductive pressure-sensitive adhesive sheet of the present invention, the relative dielectric constant at a frequency of 120 Hz before being left for 1 day in an environment of 40 ° C. and 92% RH is not particularly limited, but from the point of obtaining good electrical insulation, The following is preferable, More preferably, it is 20 or less, More preferably, it is 10 or less. The lower limit of the relative dielectric constant is not particularly limited, but is preferably 1 or more, more preferably 1.5 or more. When the relative dielectric constant exceeds 30, it is the same as in the case of the above-mentioned “relative dielectric constant at a frequency of 120 Hz (40 ° C./92% RH after 1 day)”, which may cause a problem in terms of electrical insulation. The above “relative permittivity at a frequency of 120 Hz before leaving for 1 day in an environment of 40 ° C. and 92% RH” is the pressure-sensitive adhesive sheet to be measured for relative permittivity in an environment of 40 ° C. and 92% RH. It is a relative dielectric constant at a frequency of 120 Hz measured at a time point before being left for one day. In this specification, the “relative permittivity at a frequency of 120 Hz before being left for one day in an environment of 40 ° C. and 92% RH” may be referred to as “relative permittivity at a frequency of 120 Hz (initial)”.

  In particular, the heat conductive pressure-sensitive adhesive sheet of the present invention has a relative dielectric constant at a frequency of 120 Hz (40 ° C./92% RH after 1 day) and a relative dielectric constant at a frequency of 120 Hz from the viewpoint of effectively suppressing a decrease in electrical insulation over time. Both (initial) are preferably 30 or less (more preferably 20 or less).

  In the heat conductive pressure-sensitive adhesive sheet of the present invention, the relative dielectric constant at a frequency of 1 kHz after being left for 1 day in an environment of 40 ° C. and 92% RH is not particularly limited, but from the point of obtaining good electrical insulation, Or less, more preferably 20 or less, and still more preferably 15 or less. In addition, although the minimum of the said dielectric constant is not specifically limited, It is preferable that it is 1.0 or more, More preferably, it is 1.5 or more. When the relative dielectric constant exceeds 30, it is the same as in the case of the above-mentioned “relative dielectric constant at a frequency of 120 Hz (40 ° C./92% RH after 1 day)”, which may cause a problem in terms of electrical insulation. The above “relative permittivity at a frequency of 1 kHz after being left in a 40 ° C., 92% RH environment for 1 day” means that the pressure-sensitive adhesive sheet to be measured for the relative permittivity is 1 day in a 40 ° C., 92% RH environment. It is a relative dielectric constant at a frequency of 1 kHz measured after being left standing. In the present specification, the “relative permittivity at 1 kHz after being left for one day in an environment of 40 ° C. and 92% RH” is referred to as “relative permittivity at a frequency of 1 kHz (after 40 ° C./92% RH 1 day)”. There is a case.

  In the heat conductive pressure-sensitive adhesive sheet of the present invention, the relative dielectric constant at a frequency of 1 kHz before being left for 1 day in an environment of 40 ° C. and 92% RH is not particularly limited, but from the point of obtaining good electrical insulation, The following is preferable, More preferably, it is 20 or less, More preferably, it is 15 or less. In addition, although the minimum of the said dielectric constant is not specifically limited, It is preferable that it is 1.0 or more, More preferably, it is 1.5 or more. When the relative dielectric constant exceeds 30, it is the same as in the case of the above-mentioned “relative dielectric constant at a frequency of 120 Hz (40 ° C./92% RH after 1 day)”, which may cause a problem in terms of electrical insulation. The above “relative permittivity at a frequency of 1 kHz before being left for 1 day in an environment of 40 ° C. and 92% RH” is the pressure-sensitive adhesive sheet to be measured for relative permittivity in an environment of 40 ° C. and 92% RH. It is a relative dielectric constant at a frequency of 1 kHz measured at a time point before being left for 1 day. In the present specification, the “relative permittivity at a frequency of 1 kHz before being left for one day in a 40 ° C., 92% RH environment” may be referred to as “relative permittivity at a frequency of 1 kHz (initial)”.

  In particular, the heat conductive pressure-sensitive adhesive sheet of the present invention has a relative dielectric constant at a frequency of 1 kHz (40 ° C./92% RH after 1 day) and a relative dielectric constant at a frequency of 1 kHz from the viewpoint of effectively suppressing a decrease in electrical insulation over time. Both (initial) are preferably 30 or less (more preferably 20 or less).

  Furthermore, in the heat conductive adhesive sheet of the present invention, from the point of obtaining good electrical insulation, the relative dielectric constant at a frequency of 120 Hz to 1 MHz after being left for 1 day in an environment of 40 ° C. and 92% RH is any Is preferably 30 or less (more preferably 20 or less).

  Furthermore, in the heat conductive adhesive sheet of the present invention, the relative dielectric constant at a frequency of 120 Hz to 1 MHz before being left for 1 day in an environment of 40 ° C. and 92% RH is obtained from the point of obtaining good electrical insulation. In any case, it is preferably 30 or less (more preferably 20 or less).

  In particular, the heat conductive pressure-sensitive adhesive sheet of the present invention is allowed to stand in an environment of 40 ° C. and 92% RH for 1 day from the viewpoint of obtaining good electrical insulation and effectively suppressing deterioration of electrical insulation over time. The relative dielectric constant at a frequency of 120 Hz to a frequency of 1 MHz and the relative dielectric constant at a frequency of 120 Hz to a frequency of 1 MHz before being left for 1 day in an environment of 40 ° C. and 92% RH is 30 or less (more preferably Is preferably 20 or less).

  Although the thickness of the heat conductive adhesive sheet of this invention is not specifically limited, 50 micrometers or more and 5000 micrometers or less are preferable. The upper limit is more preferably 100 μm or more, and further preferably 500 μm or more. The lower limit is more preferably 3000 μm or less, still more preferably 2000 μm or less, and particularly preferably 1000 μm or less.

  The “sheet” in the heat conductive adhesive sheet of the present invention is a concept including the shapes of “tape”, “sheet”, and “film”. Moreover, the heat conductive adhesive sheet of this invention may be processed into the shape according to the intended purpose (for example, a punching process, a cutting process, etc.).

  The heat conductive adhesive sheet of the present invention may be a single-sided adhesive sheet having one adhesive surface, or may be a double-sided adhesive sheet having two adhesive surfaces among the two adhesive surfaces. Moreover, in the heat conductive adhesive sheet of this invention, such an adhesive surface may be protected by the release liner.

  Moreover, the heat conductive adhesive sheet of this invention may be an adhesive sheet which has a base material (adhesive sheet with a base material), and may be an adhesive sheet which does not have a base material (base material-less adhesive sheet). .

  More specifically, as the form of the heat conductive pressure-sensitive adhesive sheet of the present invention, for example, a double-sided pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on both sides of the base material, a pressure-sensitive adhesive layer on one side of the base material And a single-sided pressure-sensitive adhesive sheet with a base material and a base-less double-sided pressure-sensitive adhesive sheet composed only of a pressure-sensitive adhesive layer.

  In particular, the thermally conductive pressure-sensitive adhesive sheet of the present invention is preferably a substrate-less double-sided pressure-sensitive adhesive sheet composed only of a pressure-sensitive adhesive layer from the viewpoint of flexibility. In addition, in the heat conductive adhesive sheet of this invention, when flexibility is favorable, it follows the level | step difference and uneven | corrugated | grooved part of a to-be-adhered body, can fill a clearance gap (air layer), and can improve thermal conductivity more.

  Moreover, the heat conductive adhesive sheet of this invention may have "other layers", such as an intermediate | middle layer provided between a base material and an adhesive layer.

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

(Adhesive layer)
The heat conductive adhesive sheet of this invention has an adhesive layer. The pressure-sensitive adhesive layer exhibits adhesiveness and has electrical insulation. Such an adhesive layer is formed of an adhesive composition. For example, an acrylic pressure-sensitive adhesive layer described later is formed from an acrylic pressure-sensitive adhesive composition. In addition, an adhesive composition includes the meaning of the composition which forms an adhesive.

  Although it does not specifically limit as an adhesive which comprises the said adhesive layer, For example, a urethane adhesive, an acrylic adhesive, a rubber adhesive, a silicone adhesive, a polyester adhesive, a polyamide adhesive, epoxy Based pressure-sensitive adhesives, vinyl alkyl ether pressure-sensitive adhesives, fluorine-based pressure-sensitive adhesives, and the like. Among these, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of weather resistance, heat resistance, function, cost, and ease of designing a pressure-sensitive adhesive according to the purpose of use. In addition, these adhesives can be used individually or in combination of 2 or more types.

  That is, it is preferable that the heat conductive adhesive sheet of this invention has an acrylic adhesive layer.

  The acrylic pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The content of the acrylic polymer in the acrylic pressure-sensitive adhesive layer is not particularly limited, but is preferably 15% by volume or more with respect to the total amount of the acrylic pressure-sensitive adhesive layer (total volume, 100% by volume). More preferably, it is 20 volume%. In addition, although the upper limit of the content rate of the said acrylic polymer is not specifically limited, It is preferable that it is 59.9 volume% or less, More preferably, it is 55 volume% or less.

  The acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth) acryloyl group in the molecule) as a constituent monomer component. The acrylic polymer is preferably a polymer containing (meth) acrylic acid alkyl ester as a constituent monomer component. In addition, an acrylic polymer can be used individually or in combination of 2 or more types.

Examples of the (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, (meth ) Isobutyl acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate , Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic acid Isodecyl, undecyl (meth) acrylate, dodecyl (meth) acrylate (Meth) acrylic acid tridecyl, (meth) acrylic acid tetradecyl, (meth) acrylic acid pentadecyl, (meth) acrylic acid hexadecyl, (meth) acrylic acid heptadecyl, (meth) acrylic acid octadecyl, (meth) acrylic acid nonadecyl, ( Examples include (meth) acrylic acid C _1-20 alkyl esters in which the alkyl group has 1-20 carbon atoms, such as eicosyl acrylate. In addition, the said (meth) acrylic-acid alkylester can be used individually or in combination of 2 or more types.

Among them, the (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid C _2-12 alkyl ester in which the number of carbon atoms of the alkyl group is 2-12 from the viewpoint of easily balancing the adhesive properties. Preferably, it is a (meth) acrylic acid C _4-9 alkyl ester having 4-9 carbon atoms in the alkyl group.

  The ratio of the (meth) acrylic acid alkyl ester to the total monomer components (100% by weight) constituting the acrylic polymer is not particularly limited, but is preferably 60% by weight or more, more preferably 70% by weight or more. More preferably, it is 80 weight or more.

  The acrylic polymer may be a polymer containing only the (meth) acrylic acid alkyl ester as a constituent monomer component, but it is possible to impart functions according to necessity, various properties of the adhesive, From the point of controlling the structure of the acrylic polymer and the like more appropriately, the monomer component may be a polymer containing a copolymerizable monomer together with the (meth) acrylic acid alkyl ester. In addition, a copolymerizable monomer can be used individually or in combination of 2 or more types.

  Examples of the copolymerizable monomer include polar group-containing monomers. Although it does not specifically limit as said polar group containing monomer, For example, a carboxyl group containing monomer, a nitrogen containing monomer, a hydroxyl group containing monomer, a sulfonic acid group containing monomer, a phosphoric acid group containing monomer etc. are mentioned. In addition, a polar group containing monomer can be used individually or in combination of 2 or more types.

  The carboxyl group-containing monomer is a monomer having one or more carboxyl groups in one molecule, but may be in the form of an anhydride. The carboxyl group-containing monomer is not particularly limited, and examples thereof include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, maleic anhydride, and itaconic anhydride. In addition, a carboxyl group-containing monomer can be used individually or in combination of 2 or more types.

  In particular, the acrylic polymer preferably contains substantially no carboxyl group-containing monomer as a constituent monomer component. Further, “substantially free of” a carboxyl group-containing monomer means that the monomer component constituting the acrylic polymer contains no carboxyl group-containing monomer or all the monomer components (100 wt. %) Of the carboxyl group-containing monomer is 0.1% by weight or less.

  When the acrylic pressure-sensitive adhesive layer contains thermally conductive particles, if the carboxyl group-containing monomer is included as the monomer component of the acrylic polymer, depending on the thermally conductive particles, a polar group-containing monomer may be contained. It may be difficult to obtain the effect of improving the adhesiveness due to the adhesive, and the fluidity of the acrylic pressure-sensitive adhesive composition, which is a composition for forming the acrylic pressure-sensitive adhesive layer, is reduced, and the pressure-sensitive adhesive layer May be difficult to form. The cause of these problems has not been sufficiently clarified, but the carboxyl group of the carboxyl group-containing monomer reacts with the functional group (for example, hydroxyl group) of the thermally conductive particles, so that the acrylic pressure-sensitive adhesive composition is more than necessary. This is presumably because it becomes harder or the pressure-sensitive adhesive layer becomes harder than necessary, and the wettability of the pressure-sensitive adhesive layer decreases.

  When a hydroxyl group-containing monomer is contained as a copolymerizable monomer, the dispersibility of the heat conductive particles is improved, and good wettability to the adherend is easily obtained with the acrylic pressure-sensitive adhesive layer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, ( Examples include 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl methacrylate. Of these, hydroxyethyl (meth) acrylate and hydroxybutyl (meth) acrylate are preferred. In addition, a hydroxyl-containing monomer can be used individually or in combination of 2 or more types.

When a nitrogen-containing monomer is included as a copolymerizable monomer, appropriate polarity is imparted, and good adhesive properties such as adhesiveness at the initial stage of application and adhesive reliability can be easily obtained with an acrylic pressure-sensitive adhesive layer. Examples of the nitrogen-containing monomer include N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) acrylamide, etc. N-hydroxyalkyl (meth) acrylamides; cyclic (meth) acrylamides such as N- (meth) acryloylmorpholine and N-acryloylpyrrolidine; acyclic (meth) acrylamides such as (meth) acrylamide and N-substituted (meth) acrylamides Is mentioned. Examples of the N-substituted (meth) acrylamide include N-alkyl (meth) acrylamides such as N-ethyl (meth) acrylamide and Nn-butyl (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-butyl) (meth) acrylamide, N, N-di (t And N, N-dialkyl (meth) acrylamide such as (butyl) (meth) acrylamide.
Further, examples of the nitrogen-containing monomer include N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl- N-vinyl cyclic amides such as 1,3-oxazin-2-one and N-vinyl-3,5-morpholinedione; aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N Monomers having amino groups such as dimethylaminopropyl (meth) acrylate; monomers having a maleimide skeleton such as N-cyclohexylmaleimide and N-phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide N-2-ethylhexylitaconimide, N-lauryl Kon'imido and itaconimide monomers such as N- cyclohexyl itaconic imide.
In addition, a nitrogen-containing monomer can be used individually or in combination of 2 or more types.

  Among these, as the nitrogen-containing monomer, N-hydroxyalkyl (meth) acrylamide, N-vinyl cyclic amide, cyclic (meth) acrylamide, and N-substituted (meth) acrylamide are preferable, and N- (2-hydroxyethyl) is more preferable. ) (Meth) acrylamide, N-vinyl-2-pyrrolidone, N- (meth) acryloylmorpholine, N, N-diethyl (meth) acrylamide.

  The ratio of the nitrogen-containing monomer to the total monomer component (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit is preferably 1% by weight or more, more preferably 2% by weight or more. It is. Further, the upper limit is preferably 10% by weight or less, more preferably 7% by weight or less.

  Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth And acryloyloxynaphthalene sulfonic acid. In addition, a sulfonic acid group containing monomer can be used individually or in combination of 2 or more types.

  As said phosphate group containing monomer, 2-hydroxyethyl acryloyl phosphate etc. are mentioned, for example. In addition, a phosphate group containing monomer can be used individually or in combination of 2 or more types.

  The ratio of the polar group-containing monomer to the total monomer components (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit is preferably 1% by weight or more, more preferably 2% by weight or more. . Further, the upper limit is preferably 30% by weight or less, more preferably 25% by weight or less. When the ratio of the polar group-containing monomer is 1% by weight or more, it is preferable because high cohesive force can be obtained and high holding power can be easily obtained. On the other hand, when the proportion of the polar group-containing monomer is 30% by weight or less, the cohesive force becomes too high, and the occurrence of a problem that the adhesiveness is lowered can be suppressed.

  Moreover, as said copolymerizable monomer, the monomer which has an alkoxy group is mentioned. When a monomer having an alkoxy group is included as a copolymerizable monomer, the wettability of the acrylic pressure-sensitive adhesive layer can be improved, and heat from the adherend (heat generation source) can be efficiently conducted. it can. Examples of the monomer having an alkoxy group include 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate. Can be mentioned. In addition, the monomer which has an alkoxy group can be used individually or in combination of 2 or more types.

  The ratio of the monomer having the alkoxy group to the total monomer component (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit is preferably 3% by weight or more, more preferably 5% by weight. The upper limit is preferably 20% by weight or less, and more preferably 15% by weight or less.

  Furthermore, a polyfunctional monomer is mentioned as said copolymerizable monomer. According to such a polyfunctional monomer, a crosslinked structure can be introduced into the acrylic polymer, and the cohesive force of the pressure-sensitive adhesive layer can be adjusted. Examples of the polyfunctional monomer include hexanediol (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and pentaerythritol diester. (Meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) Acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, dibutyl (meth) acrylate, hexidyl (meth) acrylate, etc. And the like. In addition, the said polyfunctional monomer can be used individually or in combination of 2 or more types.

  The ratio of the polyfunctional monomer to the total monomer component (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit is preferably 0.01% by weight or more, more preferably 0.8%. The upper limit thereof is preferably 2% by weight or less, more preferably 1% by weight or less. When the ratio of the polyfunctional monomer is 0.01% by weight or more, it is preferable because a high cohesive force can be obtained and a high holding power can be easily obtained. On the other hand, when the ratio of the polyfunctional monomer is 2% by weight or less, the cohesive force becomes too high, and the occurrence of a problem that the adhesiveness is lowered can be suppressed.

  In addition, examples of the copolymerizable monomer include monomers having an epoxy group such as glycidyl (meth) acrylate and allyl glycidyl ether; monomers having a cyano group such as acrylonitrile and methacrylonitrile; styrene, α-methylstyrene, and the like. Styrene monomers; α-olefins such as ethylene, propylene, isoprene, butadiene, and isobutylene; monomers having isocyanate groups such as 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate; vinyl esters such as vinyl acetate and vinyl propionate Monomers; vinyl ether monomers such as vinyl ether; (meth) acrylic acid esters having a heterocycle such as tetrahydrofurfuryl (meth) acrylate; fluorine (meth) acrylate A monomer having a halogen atom such as 3-methacryloxypropyltrimethoxysilane, a monomer having an alkoxysilyl group such as vinyltrimethoxysilane; a monomer having a siloxane bond such as silicone (meth) acrylate; a cyclopentyl (meth) acrylate, (Meth) acrylates having alicyclic hydrocarbon groups such as cyclohexyl (meth) acrylate, bornyl (meth) acrylate and isobornyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate And (meth) acrylate having an aromatic hydrocarbon group such as phenoxydiethylene glycol (meth) acrylate.

  The glass transition temperature (Tg) of the acrylic polymer is not particularly limited, but it is easy to obtain a low-elasticity acrylic pressure-sensitive adhesive layer, and it is easy to obtain an acrylic pressure-sensitive adhesive layer having good step absorbability. The upper limit is preferably −10 ° C., more preferably −20 ° C., and the lower limit is preferably −70 ° C., more preferably −65 ° C. The Tg of the acrylic polymer can be prepared by selecting the composition and blending amount of the constituent monomer components. Here, the Tg of the acrylic polymer refers to a value obtained from the Fox equation based on the Tg of the homopolymer of each monomer constituting the monomer component and the weight fraction (copolymerization composition) of the monomer. The value of Tg of the homopolymer can be obtained from various known materials (such as “Adhesion Technology Handbook” of Nikkan Kogyo Shimbun).

  The acrylic polymer can be obtained by polymerizing the monomer component. Although it does not specifically limit as a polymerization method, For example, solution polymerization, emulsion polymerization, block polymerization, photopolymerization (active energy ray polymerization) etc. are mentioned. Among them, a polymerization method using heat or active energy rays (for example, ionizing radiation such as α rays, β rays, γ rays, neutral beam, electron beams, ultraviolet rays, etc.) is preferable, more preferably a thermal polymerization initiator. A polymerization method using a heat or active energy ray using a polymerization initiator such as a photopolymerization initiator is preferred. In particular, the polymerization method is preferably a polymerization method using active energy rays (particularly ultraviolet rays) using a photopolymerization initiator because of the advantage that the polymerization time can be shortened. In addition, a polymerization initiator can be used individually or in combination of 2 or more types.

  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 Examples thereof include active oxime photopolymerization initiators, benzoin photopolymerization initiators, benzyl photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, and thioxanthone photopolymerization initiators. In addition, a photoinitiator can be used individually or in combination of 2 or more types.

  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, Anisole methyl ether etc. are mentioned. Examples of the acetophenone photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). ) Dichloroacetophenone and the like. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. It is done. Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime. Examples of the benzoin photopolymerization initiator include benzoin. Examples of the benzyl photopolymerization initiator include benzyl. Examples of the benzophenone 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 methyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and decylthioxanthone.

  The amount of the photopolymerization initiator used is not particularly limited, but the lower limit is preferably 0.01 parts by weight or more, more preferably 100 parts by weight of the monomer component constituting the acrylic polymer. It is 0.05 weight part or more, and it is preferable that the upper limit is 5 weight part or less, More preferably, it is 3 weight part or less.

  In the photopolymerization, the irradiation energy, irradiation time, etc. of active energy rays (particularly ultraviolet rays) are not particularly limited. It is only necessary that the photopolymerization initiator is activated to cause the monomer component to react.

  Examples of the thermal polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis (2-methylpropionic acid) dimethyl, , 4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (5-methyl-2-imidazoline) -2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (N, N'-dimethyleneisobutylamidine) hydrochloride, 2,2 Azo polymerization initiators such as' -azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate; Peroxide-based polymerization initiators such as sid, t-butylpermaleate, t-butyl hydroperoxide, hydrogen peroxide; persulfates such as potassium persulfate and ammonium persulfate; persulfates and sodium bisulfite Examples thereof include redox polymerization initiators such as a combination and a combination of peroxide and sodium ascorbate. In addition, a thermal polymerization initiator can be used individually or in combination of 2 or more types.

  Although the usage-amount of a thermal-polymerization initiator is not specifically limited, For example, conventionally, it can select in the range which can be utilized as a polymerization initiator. In the case of polymerization using heat, for example, the monomer component and the thermal polymerization initiator are dissolved in an appropriate solvent (for example, an organic solvent such as toluene or ethyl acetate), and the temperature is high (for example, 20 to 100 ° C. (preferably 40 to Acrylic polymer can be obtained by reacting at 80 ° C.).

  Furthermore, in the pressure-sensitive adhesive layer (particularly the acrylic pressure-sensitive adhesive layer) of the heat-conductive pressure-sensitive adhesive sheet of the present invention, from the viewpoint of the ease of obtaining a heat-conductive pressure-sensitive adhesive sheet having a thermal conductivity of a predetermined value or more, It is preferable that thermally conductive particles are contained. In addition, when the heat conductive adhesive sheet of the present invention contains heat conductive particles in the pressure-sensitive adhesive layer, it becomes easy to obtain good heat conductivity, and the pressure-sensitive adhesive sheet can be made difficult to burn. Can be difficult to spread. That is, flame retardancy can also be obtained. Thermally conductive particles can be used alone or in combination of two or more.

Examples of the heat conductive particles include hydrated metal compounds. The hydrated metal compound has a decomposition start temperature in the range of 150 to 500 ° C., and has a general formula M _m O _n · XH ₂ O (where M is a metal and m and n are 1 or more determined by the valence of the metal) Or a double salt containing the compound. In addition, a hydrated metal compound can be used individually or in combination of 2 or more types.

Examples of the hydrated metal compound include aluminum hydroxide [Al ₂ O ₃ .3H ₂ O; or Al (OH) ₃ ], boehmite [Al ₂ O ₃ .H ₂ O; or AlOOH], magnesium hydroxide [ MgO.H ₂ O; or Mg (OH) ₂ ], calcium hydroxide [CaO.H ₂ O; or Ca (OH) ₂ ], zinc hydroxide [Zn (OH) ₂ ], silicic acid [H ₄ SiO ₄ ; Or H ₂ SiO ₃ ; or H ₂ Si ₂ O ₅ ], iron hydroxide [Fe ₂ O ₃ .H ₂ O or 2FeO (OH)], copper hydroxide [Cu (OH) ₂ ], barium hydroxide [BaO H ₂ O; or BaO · 9H ₂ O], zirconium oxide hydrate [ZrO · nH ₂ O], tin oxide hydrate [SnO · H ₂ O], basic magnesium carbonate [3MgCO ₃ · Mg (OH ) ₂ · 3H ₂ O], hydrotalcite [ _{6MgO · Al 2 O 3 · H} 2 O], dawsonite _{[Na 2 CO 3 · Al 2} O 3 · nH 2 O], borax _{[Na 2 O · B 2 O} 5 · 5H 2 O], zinc borate [2ZnO _{· 3B 2 O 5 · 3.5H 2} O] , and the like. Furthermore, hydrotalcite, borax, etc. are also mentioned.

  Furthermore, a general commercial item can be used for the said hydrated metal compound. As a commercial item of aluminum hydroxide, for example, trade name “Hijilite H-100-ME” (average particle size 75 μm) (manufactured by Showa Denko KK), trade name “Hijilite H-10” (average particle size 55 μm) (Made by Showa Denko KK), trade name “Hijilite H-32” (average particle size 8 μm) (made by Showa Denko KK), trade name “Heidilite H-42” (average particle size 1 μm) (made by Showa Denko) And trade name “B103ST” (average particle size 8 μm) (manufactured by Nippon Light Metal Co., Ltd.). Moreover, as a commercial item of magnesium hydroxide, a brand name "KISUMA 5A" (average particle diameter 1 micrometer) (made by Kyowa Chemical Industry Co., Ltd.) etc. are mentioned, for example.

  Furthermore, examples of the heat conductive particles include metal nitrides such as boron nitride, aluminum nitride, silicon nitride, and gallium nitride; aluminum oxide (alumina), magnesium oxide, titanium oxide, zinc oxide, tin oxide, copper oxide, Examples thereof include metal oxides such as nickel oxide and antimonic acid doped tin oxide. In addition, silicon carbide, silicon dioxide, calcium carbonate, barium titanate, potassium titanate, copper, silver, gold, nickel, aluminum, platinum, carbon black, carbon tube (carbon nanotube), carbon fiber, diamond, etc. .

  A general commercial item can be used for such a heat conductive particle. As a commercial item of boron nitride, a brand name "HP-40" (made by Mizushima alloy iron company), a brand name "PT620" (made by Momentive company), etc. are mentioned, for example. As a commercial item of aluminum oxide, a brand name "AS-50" (made by Showa Denko KK), a brand name "AL-13KT" (average particle diameter 96 micrometers) (made by Showa Denko KK), etc. are mentioned, for example. As a commercial item of antimonic acid dope tin, for example, a brand name "SN-100S" (made by Ishihara Sangyo Co., Ltd.), a brand name "SN-100P" (made by Ishihara Sangyo Co., Ltd.), and a brand name "SN-100D (water dispersion product). (Ishihara Sangyo Co., Ltd.). As a commercial item of titanium oxide, a brand name "TTO series" (made by Ishihara Sangyo Co., Ltd.) etc. are mentioned, for example. As commercial products of zinc oxide, trade name “SnO-310” (manufactured by Sumitomo Osaka Cement Co., Ltd.), trade name “SnO-350” (manufactured by Sumitomo Osaka Cement Co., Ltd.), trade name “SnO-410” (Sumitomo Osaka Cement Co., Ltd.) Manufactured).

  Among these, as the heat conductive particles, hydrated metal compounds and metal oxides are preferable from the viewpoint of heat conductivity, flame retardancy, and cost, and aluminum hydroxide and alumina are more preferable. That is, the thermally conductive particles are preferably at least one particle selected from the group consisting of hydrated metal compounds and metal oxides, and more preferably at least one selected from the group consisting of aluminum hydroxide and alumina. Particles.

  The shape of the heat conductive particles is not particularly limited, and may be a bulk shape, a needle shape, a plate shape, or a layer shape. The bulk shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a crushed shape, or a deformed shape thereof.

  Although the average particle diameter of the said heat conductive particle is not specifically limited, 0.1-1000 micrometers is preferable. The lower limit is more preferably 0.2 μm or more, and further preferably 0.5 μm or more. Moreover, the upper limit is 200 micrometers or less, More preferably, it is 150 micrometers or less. When the average particle size is 1000 μm or less, the size of the heat conductive particles is preferably smaller than the thickness of the pressure-sensitive adhesive layer, which can suppress the problem that the thickness of the pressure-sensitive adhesive layer varies. Moreover, since heat conductive particles do not protrude from the surface, it is easy to obtain good adhesive properties, which is preferable.

  In the heat conductive adhesive sheet of this invention, it is preferable that the said adhesive layer contains simultaneously 2 or more types of heat conductive particles from which an average particle diameter differs from the point which obtains more favorable heat conductivity. That is, the heat conductive particles are preferably used in combination of heat conductive particles having a small average particle diameter and heat conductive particles having a large average particle diameter. For example, it is preferable to use a combination of large heat conductive particles having an average particle diameter of 5 μm or more and small heat conductive particles having an average particle diameter of less than 5 μm. Thus, by using together the heat conductive particles having different average particle sizes, the dispersibility of the heat conductive particles can be increased, and the adhesive layer can be filled with many heat conductive particles. . In addition, when the heat conductive particles are packed more densely in the pressure-sensitive adhesive layer, a heat conduction path by the heat conductive particles is easily constructed, and there is an effect that the heat conductivity is further improved.

  For the combination of the heat conductive particles having a small average particle diameter and the heat conductive particles having a large average particle diameter, the average particle diameter and average of the heat conductive particles having a large average particle diameter are obtained from the point of obtaining a larger heat conductivity. A combination in which the difference from the average particle size of the heat conductive particles having a small particle size is 20 μm or more (preferably 40 μm or more) is preferable. In addition, said difference is a difference of what has the largest average particle diameter and what has the smallest average particle diameter, when 3 or more types are included.

  Further, when combining the heat conductive particles having a small average particle diameter and the heat conductive particles having a large average particle diameter, the ratio of the heat conductive particles having a small average particle diameter and the heat conductive particles having a large average particle diameter is: Although not particularly limited, from the viewpoint of obtaining a larger thermal conductivity, the former: the latter (weight ratio) is preferably 1:10 to 10: 1, more preferably 1: 5 to 5: 1, and still more preferably 1: 2 to 2: 1.

  Although the content rate of the said heat conductive particle in the said adhesive layer is not specifically limited, It is preferable that they are 40 volume% or more and 75 volume% or less with respect to the whole volume (100 volume%) of an adhesive layer. The lower limit is more preferably 50% by volume or more, and still more preferably 55% by volume or more. Moreover, the upper limit is 70 volume% or less more preferably, More preferably, it is 65 volume% or less. It is preferable that the content ratio of the heat conductive particles is 40% by volume or more because good heat conductivity and good flame retardancy are easily obtained. Moreover, it is preferable for the content ratio of the heat conductive particles to be 75% by volume or less, since a decrease in flexibility can be suppressed and a decrease in adhesive force and holding force can be suppressed. The unit “volume%” used in the above content ratio can be converted to the unit “weight%” using the density of the heat conductive particles.

  Furthermore, in the said adhesive layer (especially said acrylic adhesive layer) of the heat conductive adhesive sheet of this invention, from the point which obtains favorable heat conductivity and favorable flame retardance, with the said heat conductive particle, It is preferable that a dispersant is contained. When the pressure-sensitive adhesive layer contains a dispersant, the heat conductive particles can be contained in a stably dispersed state without causing aggregation of the heat conductive particles. For this reason, when the said adhesive layer contains the dispersing agent, it can contain heat conductive particle in large quantities, maintaining an adhesive characteristic. Therefore, the heat conductive pressure-sensitive adhesive sheet of the present invention is more likely to exhibit good heat conductivity and good flame retardancy when the pressure-sensitive adhesive layer contains both heat conductive particles and a dispersant. Become. In addition, a dispersing agent can be used individually or in combination of 2 or more types.

  Among these, as the dispersant, a phosphate ester dispersant is preferable.

  In particular, the phosphate ester dispersant is preferably a phosphate ester dispersant containing a phosphate triester. When the pressure-sensitive adhesive layer contains a phosphate ester-based dispersant containing a phosphoric acid triester, it is possible to suppress the occurrence of a problem that the electrical insulation of the pressure-sensitive adhesive sheet deteriorates over time, and excellent electrical insulation It is because it becomes easy to obtain. In general, when heat-conductive particles are contained in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for the purpose of imparting thermal conductivity or electrical insulation to the pressure-sensitive adhesive sheet, impurity ions are absorbed from the heat-conductive particles due to moisture absorption over time. May elute in the pressure-sensitive adhesive layer, and the dielectric constant of the pressure-sensitive adhesive sheet may increase. However, if a phosphate ester-based dispersant containing a phosphate triester is contained, an increase in the dielectric constant can be suppressed. . This is presumed to be because the phosphate ester-based dispersant containing the phosphate triester body traps impurity ions and reduces the migration speed of impurity ions.

The phosphate ester-based dispersant containing the phosphate triester body preferably contains at least a phosphate triester body represented by the following formula (3). Further, the phosphate ester dispersant containing the phosphate triester may contain a phosphate monoester represented by the following formula (1) or a phosphate diester represented by the following formula (2). Good. In other words, the phosphate ester dispersant containing the phosphate triester may be a phosphate ester dispersant containing a phosphate monoester, phosphate diester and phosphate triester. A phosphoric acid ester-based dispersant containing a phosphoric acid monoester body and a phosphoric acid triester body, or a phosphoric acid ester-based dispersant containing a phosphoric acid diester body and a phosphoric acid triester body, Alternatively, it may be a phosphate ester dispersant containing only a phosphate triester.
In the above formulas (1) to (3), n is a positive integer of 1 or more, and R is an organic group. In formulas (2) and (3), n and R may all be the same or different.

  R is not particularly limited, and may be, for example, a linear or branched structure, a cyclic structure, a structure having an aromatic ring, or a combination of these. More specifically, examples thereof include an alkyl group having 1 to 20 carbon atoms, a phenyl group having an alkyl group having 1 to 20 carbon atoms as a substituent, and a phenyl group having an aralkyl group having 7 to 20 carbon atoms as a substituent. .

  In the above formulas (1) to (3), n is not particularly limited, but is preferably 2 to 20 (more preferably 2 to 10).

  In addition, the phosphate ester type | system | group dispersing agent containing a phosphoric acid triester body is the compound which substituted some or all of the ethyleneoxy groups in the parenthesis of the compound of said formula (1)-(3) by the propyleneoxy group. You may contain.

  Examples of the phosphoric acid ester dispersant containing the phosphoric acid triester body include, for example, a phosphoric acid ester dispersant containing a triester body of polyoxyalkylene alkylphenyl ether phosphoric acid ester, and polyoxyalkylene alkyl ether phosphoric acid. Phosphate ester dispersants containing ester triesters, phosphate ester dispersants containing triesters of polyoxyethylene tridecyl ether phosphate esters, polyoxyethylene styrenated phenyl ether phosphate triesters Examples thereof include phosphate ester-based dispersants containing ester bodies.

  As the phosphate ester dispersant containing the phosphate triester, a general commercial product can be used. For example, trade name “Plisurf A208F” (Daiichi Kogyo Seiyaku Co., Ltd.) and the like can be mentioned. The trade name “Plisurf A208F” is a phosphate ester-based dispersant containing a phosphate monoester, a phosphate diester, and a phosphate triester.

  The content rate of the dispersing agent in the said adhesive layer is not specifically limited. For example, when the phosphoric acid ester-based dispersant containing the phosphoric acid triester is contained in the pressure-sensitive adhesive layer, the content ratio (volume basis) is not particularly limited, but the thermally conductive particles can be stabilized. It is 0.1 volume% or more and 10 volume% or less with respect to the whole volume (100 volume%) of an adhesive layer from the point contained in the disperse | distributed state and the point which suppresses the electrical insulation fall over time. Is preferred. The lower limit is more preferably 0.3% by volume or more, and further preferably 0.5% by volume or more. Further, the upper limit is more preferably 8.0% by volume or less, and still more preferably 5.0% by volume or less. The unit “volume%” used in the above content ratio can be converted to the unit “weight%” by using the density of the phosphate ester dispersant containing the phosphate triester.

  Further, the content (weight basis) of the phosphate ester-based dispersant containing the phosphate triester in the pressure-sensitive adhesive layer is not particularly limited, but for the same reason as above, the base in the pressure-sensitive adhesive layer It is preferable that it is 0.1-10 weight part with respect to 100 weight part of polymers (For example, the said acrylic polymer in the case of an acrylic adhesive layer). The lower limit is more preferably 0.5 parts by weight or more, and still more preferably 1.0 parts by weight or more. Moreover, the upper limit becomes like this. More preferably, it is 8.0 weight part or less, More preferably, it is 5.0 weight part or less.

  The said adhesive layer may contain the crosslinking agent from the point of cohesion force improvement. The crosslinking agent is not particularly limited, and examples thereof include an epoxy crosslinking agent, an isocyanate crosslinking agent, a silicone crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a silane crosslinking agent, and an alkyl etherified melamine crosslinking agent. And metal chelate crosslinking agents. Of these, isocyanate crosslinking agents and epoxy crosslinking agents are preferred. In addition, a crosslinking agent is used individually or in combination of 2 or more types.

  Examples of the isocyanate crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenyl. Examples include methane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these with polyols such as trimethylolpropane. Furthermore, “a compound having at least one or more isocyanate groups and one or more unsaturated bonds in one molecule” such as 2-isocyanatoethyl (meth) acrylate is also included.

  Examples of the epoxy crosslinking agent 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-xylylenediamine and 1,3-bis (N, N′-diamine glycidylaminomethyl) ) Cyclohexane and the like.

  The content of the crosslinking agent in the pressure-sensitive adhesive layer is not particularly limited, but relative to 100 parts by weight of the base polymer in the pressure-sensitive adhesive layer (for example, the acrylic polymer in the case of an acrylic pressure-sensitive adhesive layer), 0.01-5 weight part is preferable. The lower limit is more preferably 0.02 parts by weight or more. Further, the upper limit is more preferably 3 parts by weight or less, and still more preferably 2 parts by weight or less. When the content of the crosslinking agent is 0.01 parts by weight or more, it is easy to obtain cohesiveness, which is preferable. Further, it is preferable that the content of the crosslinking agent is 5 parts by weight or less because flexibility is easily obtained.

  Furthermore, the said adhesive layer may contain tackifying resin from the point of an adhesive improvement. The tackifying resin is not particularly limited, and examples thereof include petroleum resins, terpene resins, coumarone / indene resins, styrene resins, rosin resins, alkylphenol resins, and xylene resins. Of these, petroleum resins and terpene resins are preferable. In addition, tackifying resin can be used individually or in combination of 2 or more types.

  In particular, when the pressure-sensitive adhesive layer is formed of an active energy ray-curable pressure-sensitive adhesive composition, for example, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive layer is a monomer mixture described later or a mixture thereof. When formed with an active energy ray-curable acrylic pressure-sensitive adhesive composition containing at least a partial polymer, it is preferable to use a hydrogenated type tackifying resin from the viewpoint of difficulty in causing an inhibition reaction. Such a hydrogenated type tackifying resin is not particularly limited, and examples thereof include derivatives obtained by hydrogenating the above tackifying resin. More specifically, the hydrogenated petroleum resin can be selected from aromatic, dicyclopentadiene, aliphatic, and aromatic-dicyclopentadiene copolymer. Further, the hydrogenated terpene resin can be selected from terpene phenol resin, aromatic terpene resin, and the like.

  Further, the tackifying resin is preferably a tackifying resin having a softening point of 80 to 200 ° C. (preferably 100 to 200 ° C.) from the viewpoint of easily obtaining a high cohesive force.

  The content of the tackifying resin in the pressure-sensitive adhesive layer is not particularly limited, but relative to 100 parts by weight of the base polymer in the pressure-sensitive adhesive layer (for example, the acrylic polymer in the case of an acrylic pressure-sensitive adhesive layer). 1 to 50 parts by weight is preferable. The lower limit is more preferably 2 parts by weight or more, and still more preferably 3 parts by weight or more. Further, the upper limit is more preferably 40 parts by weight or less, and still more preferably 30 parts by weight or less. When the content of the tackifying resin is 1 part by weight or more, the effect of improving adhesiveness is easily obtained, which is preferable. Moreover, when the content of the tackifying resin is 50 parts by weight or less, a decrease in cohesive force can be suppressed, which is preferable.

  Furthermore, the pressure-sensitive adhesive layer may contain an acrylic oligomer as long as the effects of the present invention are not impaired. Since the acrylic oligomer functions as a tackifier component, adhesion can be improved.

  Further, the adhesive layer may contain a silane coupling agent from the viewpoint of improving the adhesive strength and durability, and improving the affinity between the thermally conductive particles and the base polymer (particularly acrylic polymer). Good. The silane coupling agent is not particularly limited. For example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3 , 4-epoxycyclohexyl) ethyltrimethoxysilane and other epoxy group-containing silane coupling agents; 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl Amino group-containing silane coupling agents such as -N- (1,3-dimethylbutylidene) propylamine; (meth) acryl group-containing silanes such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane Coupling agent; 3-iso Inshianeto group-containing silane coupling agent such as A sulfonate triethoxysilane and the like. The said silane coupling agent can be used individually or in combination of 2 or more types.

  The content of the silane coupling agent in the pressure-sensitive adhesive layer is not particularly limited, but is 100 parts by weight of the base polymer in the pressure-sensitive adhesive layer (for example, the acrylic polymer in the case of the acrylic pressure-sensitive adhesive layer). It is preferably 0.01 to 10 parts by weight. The lower limit is more preferably 0.02 parts by weight or more, and still more preferably 0.05 parts by weight or more. Further, the upper limit is more preferably 5 parts by weight or less, and still more preferably 2 parts by weight or less. When the content of the silane coupling agent is 0.01 parts by weight or more, an effect of improving affinity is easily obtained, which is preferable. Further, it is preferable that the content of the silane coupling agent is 10 parts by weight or less because the problem of a decrease in thermal conductivity due to the silane coupling agent hardly occurs.

  Furthermore, the pressure-sensitive adhesive layer contains additives such as plasticizers, anti-aging agents, colorants (pigments, dyes, etc.) and antistatic agents, as necessary, as long as the effects of the present invention are not impaired. You may go out. Furthermore, air bubbles may be included from the viewpoint of improving the cushioning property and improving the unevenness following property.

  The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition as described above. For example, the acrylic pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition may have any form, and examples thereof include an emulsion type, a solvent type (solution type), an active energy ray curable type, and a hot melt type (hot melt type). Among these, a solvent-type pressure-sensitive adhesive composition and an active energy ray-curable pressure-sensitive adhesive composition are preferable. In particular, the pressure-sensitive adhesive composition is preferably an active energy ray-curable pressure-sensitive adhesive composition in terms of productivity, environmental aspects, and ease of obtaining a thick pressure-sensitive adhesive layer.

  The solvent-type pressure-sensitive adhesive composition is preferably a composition containing at least a base polymer. Moreover, it is preferable that the said active energy ray hardening-type adhesive composition is a composition which contains at least the monomer mixture which is a composition which forms a base polymer, or its partial polymer. The active energy ray-curable pressure-sensitive adhesive composition may contain a monomer component together with the partially polymerized monomer mixture. In this specification, the “monomer mixture” means a mixture of only monomer components, and includes a case of being composed of only one monomer component.

  In particular, when the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer, the acrylic pressure-sensitive adhesive layer is preferable because it has good thermal conductivity, good flame retardancy, good electrical insulation, and suppresses a decrease in electrical insulation over time. When the acrylic pressure-sensitive adhesive composition forming the adhesive layer is a solvent type, the acrylic pressure-sensitive adhesive contains at least a phosphoric acid ester-based dispersant containing an acrylic polymer, heat conductive particles, and a phosphoric acid triester. The composition is preferably a composition, and in the case of the active energy ray curable type, it contains at least a phosphate ester-based dispersant containing a monomer mixture or a partial polymer thereof, thermally conductive particles, and a phosphate triester. It is preferable. Among these, the acrylic pressure-sensitive adhesive composition is preferably an active energy ray-curable acrylic pressure-sensitive adhesive composition from the viewpoint of productivity, environmental aspects, and ease of obtaining a thick pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition using a known or conventional method. For example, the pressure-sensitive adhesive layer is formed by coating the pressure-sensitive adhesive composition on a suitable support such as a release liner or a substrate to form a pressure-sensitive adhesive composition layer, and then curing the pressure-sensitive adhesive composition layer. (For example, it may be formed by curing with heat or active energy rays). Furthermore, if necessary, in addition to curing, it may be further dried by heating. In addition, since the photopolymerization reaction is easily inhibited by oxygen in the air, curing by active energy rays (photocuring) is performed in an environment where oxygen is blocked by covering with a release liner or by reacting in a nitrogen atmosphere. Preferably it is done.

  In particular, the pressure-sensitive adhesive layer is a pressure-sensitive adhesive containing a polymerization initiator (the photopolymerization initiator or the thermal polymerization initiator, particularly the photopolymerization initiator) from the viewpoint of stably containing thermally conductive particles. The composition is preferably formed by utilizing a curing reaction by heat or active energy rays.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably larger than the step absorbability point, the adhesive property point, the thermal conductivity and the electrical insulation point. Although the minimum of the said thickness is not specifically limited, 50 micrometers or more are preferable, More preferably, it is 100 micrometers or more, More preferably, it is 500 micrometers or more. The upper limit of the thickness is not particularly limited, but is preferably 5000 μm or less, more preferably 3000 μm or less, even more preferably 2000 μm or less, and particularly preferably 2000 μm or less, in view of ease of obtaining a pressure-sensitive adhesive layer having uniform thickness and workability. Preferably it is 1000 micrometers or less. The pressure-sensitive adhesive layer may have a single layer structure or a laminated structure.

(Base material)
The heat conductive adhesive sheet of this invention may be an adhesive sheet with a base material as mentioned above. Although it does not specifically limit as said base material, For example, Fiber-type base materials, such as cloth, a nonwoven fabric, felt, a net; Paper-type base materials, such as various papers; Metal-type base materials, such as metal foil and a metal plate; Examples thereof include plastic substrates such as films and sheets made of resin; foams such as foam sheets; and laminates thereof. Among these, a plastic substrate is preferable from the viewpoint of strength, toughness, and electrical insulation. In addition, the said base material may be a base material which consists of one layer, and may have a laminated structure of two or more layers.

  The material constituting the plastic substrate is not particularly limited. For example, polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymer Polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, celluloses, fluororesin, polyether, polyether amide, polyether ether ketone, polyphenylene sulfide Polystyrene resins such as polystyrene; polycarbonate; polyethersulfone; and the like. In addition, the said material can be used individually or in combination of 2 or more types.

  Among them, the material constituting the plastic substrate is preferably polyester, more preferably polyethylene terephthalate (PET), because of the good balance of strength, handleability (handling properties), cost, dimensional stability, and anchoring force. . That is, the substrate is preferably a polyester film, more preferably a polyethylene terephthalate film.

  The deformability of the substrate may be controlled by a stretching process (uniaxial stretching or biaxial stretching) or the like.

  Moreover, the said base material may be surface-treated as needed. As such surface treatment, for example, a conventional surface treatment such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric impact exposure, ionizing radiation treatment or the like is used in order to enhance adhesion with the adhesive layer. Oxidation treatment by physical method; primer treatment for improving adhesion to the pressure-sensitive adhesive layer; hard coat treatment for improving surface scratch resistance (abrasion resistance): the pressure-sensitive adhesive sheet is wound into a roll For example, a peeling treatment on the back surface of the base material in the case of protecting the adhesive surface can be mentioned.

  The thickness of the substrate is not particularly limited, but the lower limit is preferably 1 μm or more, more preferably 10 μm or more, and the upper limit is preferably 100 μm or less, from the viewpoint of handleability and thermal conductivity. Preferably it is 50 micrometers or less.

(Release liner)
The pressure-sensitive adhesive surface of the heat conductive pressure-sensitive adhesive sheet of the present invention may be protected by a release liner. The release liner is not particularly limited, and examples thereof include a release liner having a release treatment layer formed on at least one surface of a conventional release paper, a low adhesion substrate, and a release liner substrate.

  The low-adhesive substrate is not particularly limited. For example, fluorine-based polymers (for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer) And low adhesive substrates made of nonpolar polymers (for example, olefinic resins such as polyethylene and polypropylene). .

  The release liner substrate in the release liner in which the release treatment layer is formed on at least one surface of the release liner substrate is not particularly limited. For example, a polyester film such as a polyethylene terephthalate film; a polyethylene film, a polypropylene film Examples include olefin resin films; polyvinyl chloride films; polyimide films; polyamide films such as nylon films; and plastic substrate films (synthetic resin films) such as rayon films. In addition, paper-based substrates such as high-quality paper, Japanese paper, kraft paper, glassine paper, synthetic paper, and top coat paper are also included. Furthermore, what laminated these by lamination, co-extrusion, etc. (2-3 layer composite body) etc. are mentioned.

  Further, in the release liner in which the release treatment layer is formed on at least one surface of the release liner substrate, the release treatment agent for forming the release treatment layer is not particularly limited. For example, a silicone release treatment agent , Fluorine-based release treatment agents, long-chain alkyl release treatment agents, and the like. In addition, an exfoliation processing agent can be used individually or in combination of 2 or more types.

  The thickness and formation method of the release liner are not particularly limited. In addition, the thickness of the said release liner is not included in the thickness of the heat conductive adhesive sheet of this invention.

[Heat conductive adhesive sheet]
The thermal conductive pressure-sensitive adhesive sheet of the present invention has a thermal conductivity of a predetermined value or more and a relative dielectric constant at a frequency of 120 Hz after being left for 1 day in an environment of 40 ° C. and 92% RH (ratio at a frequency of 120 Hz). Since the dielectric constant (40 ° C./92% RH after 1 day) is not more than a predetermined value, it has good thermal conductivity. In addition, leakage current is prevented and electrical insulation is excellent.

  Although the production method of the heat conductive adhesive sheet of this invention is not specifically limited, You may produce by a well-known thru | or usual method. For example, when the heat conductive adhesive sheet of this invention is a base material-less adhesive sheet which consists only of an adhesive layer, it produces by forming an adhesive layer with the said adhesive composition on a peeling liner. Moreover, when the heat conductive adhesive sheet of this invention is an adhesive sheet with a base material which has an adhesive layer and a base material at least, an adhesive layer is formed with the said adhesive composition on the at least one surface side of a base material. Or by transferring a pre-made adhesive layer to at least one side of the substrate.

  The heat conductive adhesive sheet of this invention is preferably used for an electrical or electronic device. As a more specific example, there is a case where it is used for heat dissipation or insulation of an electronic component. More specifically, fixing electronic parts such as ICs and capacitors to a housing or a heat sink by the heat conductive adhesive sheet of the present invention can be mentioned.

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

(Thermal conductivity)
About the adhesive sheet, the heat conductivity in the thickness direction was implemented using the thermal characteristic evaluation apparatus shown in FIG. 1A is a schematic front view of the thermal characteristic evaluation apparatus, and FIG. 1B is a schematic side view of the thermal characteristic evaluation apparatus. Note that the release liner A is removed during the measurement.
Specifically, between a pair of aluminum blocks (A5052, thermal conductivity: 140 W / m · K) (sometimes referred to as “rods”) L formed so as to form a cube having one side of 20 mm. The pressure-sensitive adhesive sheet 1 (width: 20 mm, length: 20 mm) was sandwiched between them, and a pair of blocks L were bonded together with the pressure-sensitive adhesive sheet 1.
And it arrange | positioned between the heat generating body (heater block) H and the heat radiating body (cooling base board comprised so that a cooling water circulates inside) C so that a pair of block L might become up-down. Specifically, the heating element H is disposed on the upper block L, and the radiator C is disposed below the block L on the lower side.
At this time, the pair of blocks L bonded together with the pressure-sensitive adhesive sheet 1 is positioned between a pair of pressure adjusting screws T that penetrates the heating element H and the radiator C. A load cell R is disposed between the pressure adjusting screw T and the heating element H, and is configured to measure the pressure when the pressure adjusting screw T is tightened. The pressure applied to the pressure-sensitive adhesive sheet 1 was used.
Specifically, in this test, the pressure adjusting screw T was tightened so that the pressure applied to the pressure-sensitive adhesive sheet 1 was 25 N / cm ² (250 kPa).
In addition, three probes P (diameter 1 mm) of a contact-type displacement meter were installed so as to penetrate the lower block L and the adhesive sheet 1 from the radiator C side. At this time, the upper end portion of the probe P is in contact with the lower surface of the upper block L, and the distance between the upper and lower blocks L (the thickness of the adhesive sheet 1) can be measured.
A temperature sensor D was attached to the heating element H and the upper and lower blocks L. Specifically, the temperature sensor D was attached to one place of the heating element H, and the temperature sensors D were attached to the five places of each block L at intervals of 5 mm in the vertical direction.
In the measurement, first, the pressure adjusting screw T was tightened, pressure was applied to the adhesive sheet 1, the temperature of the heating element H was set to 80 ° C., and cooling water of 20 ° C. was circulated through the radiator C. .
After the temperature of the heating element H and the upper and lower blocks L is stabilized, the temperature of the upper and lower blocks L is measured by each temperature sensor D, and the thermal conductivity (W / m · K) and temperature gradient of the upper and lower blocks L are measured. The heat flux passing through the pressure-sensitive adhesive sheet 1 was calculated, and the temperature at the interface between the upper and lower blocks L and the pressure-sensitive adhesive sheet 1 was calculated. And the thermal conductivity (W / m * K) and thermal resistance (cm < ² > * K / W) in pressure were calculated using the following thermal conductivity equations (Fourier's law) using these.
Q = −λgradT
R = L / λ
Q: Heat flow rate per unit area gradT: Temperature gradient L: Sheet thickness λ: Thermal conductivity R: Thermal resistance

(Relative permittivity)
The adhesive sheet was sandwiched between the copper plate and the electrode, and the relative dielectric constant at a specific frequency was measured by the following apparatus. The measurement was performed according to JIS K 6911 under the following conditions. The measurement was performed three times, and the average value of the measured values was taken as the relative dielectric constant at a specific frequency of the pressure-sensitive adhesive sheet.
As the measurement sample, “adhesive sheet before being left for 1 day in an environment of 40 ° C. and 92% RH” and “adhesive sheet left for 1 day in an environment of 40 ° C. and 92% RH” were used. Also, the release liner is removed during the measurement.
Measuring device: Agilent Technologies 4294A Precision Impedance Analyzer
Measurement method: Capacitance method Electrode configuration: 12.1 mmφ, 0.5 mm thick aluminum plate Counter electrode: 3 oz copper plate Measurement environment: 23 ± 1 ° C., 52 ± 1% RH

(Example of preparation of partially polymerized monomer mixture)
As monomer components, 2-ethylhexyl acrylate (2EHA): 82 parts by weight, 2-methoxyethyl acrylate (MEA): 12 parts by weight, N-vinyl-2-pyrrolidone (NVP): 5 parts by weight, and hydroxyethyl Acrylamide (HEAA): As a photopolymerization initiator in a monomer mixture containing 1 part by weight, trade name “Irgacure 184” (1-hydroxycyclohexyl phenyl ketone, manufactured by BASF): 0.05 part by weight and trade name “ “Irgacure 651” (2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by BASF): 0.05 parts by weight and then viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature) A composition (monomer) in which a part of the monomer components are polymerized by irradiating ultraviolet rays until the temperature reaches 30 Pa. Partially polymerized product of a mixture, a syrup) were produced.
In addition, the said composition may be called "syrup."

(Example of use of release liner)
As the release liner, a polyethylene terephthalate release liner (trade name “Diafoil MRF38”, manufactured by Mitsubishi Plastics, Inc.) having a release treatment on one surface was used.
The release liner may be referred to as “release liner A”.

Example 1
70 parts by weight of the syrup: 30 parts by weight of 2-ethylhexyl acrylate (2EHA), polyfunctional monomer (dipentaerythritol hexaacrylate, trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.): 0.05 Weight, dispersant (phosphate ester-based dispersant containing phosphate triester, trade name “Plisurf A208F”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 2.7 parts by weight, particles (aluminum hydroxide, average particle) Diameter 1 μm, trade name “Hijilite H-42” manufactured by Showa Denko KK: 170 parts by weight and particles (aluminum hydroxide, average particle size 55 μm, trade name “Hijilite H-10” manufactured by Showa Denko KK) ): 170 parts by weight were added to obtain an adhesive composition.
Using the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition layer is provided between the release treatment surfaces of two release liners A, and the release liner A, the pressure-sensitive adhesive composition layer, and the release liner A are laminated in this order. A sheet having a structure was obtained.
Next, the pressure-sensitive adhesive composition layer was cured by irradiating ultraviolet rays having an illuminance of 5 mW / cm ² from both sides of the sheet for 3 minutes to form a pressure-sensitive adhesive layer having a thickness of 1000 μm. And the adhesive sheet which has the structure laminated | stacked in order of the release liner A, the adhesive layer, and the release liner A was obtained.

(Example 2)
Syrup: 50 parts by weight, 2-ethylhexyl acrylate (2EHA): 50 parts by weight, polyfunctional monomer (dipentaerythritol hexaacrylate, trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.): 0.05 Weight, dispersant (phosphate ester-based dispersant containing phosphate triester, trade name “Plisurf A208F”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 3.4 parts by weight, particles (aluminum hydroxide, average particles) Diameter 1 μm, trade name “Hijilite H-42” (manufactured by Showa Denko KK): 170 parts by weight, particles (aluminum hydroxide, average particle diameter 55 μm, trade name “Heidilite H-10”, Showa Denko KK): 170 parts by weight and particles (alumina, average particle size: 96 μm, trade name “AL-13KT”, manufactured by Showa Denko KK): 76 parts by weight were added to form an adhesive group A composition was obtained.
Using the pressure-sensitive adhesive composition, a sheet having a structure in which the release liner A, the pressure-sensitive adhesive composition layer, and the release liner A are laminated in this order was obtained in the same manner as in Example 1.
Next, a pressure-sensitive adhesive sheet having a structure in which a release liner A, a pressure-sensitive adhesive layer, and a release liner A are laminated in this order was obtained from the above sheet in the same manner as in Example 1.

(Comparative Example 1)
70 parts by weight of the syrup: 30 parts by weight of 2-ethylhexyl acrylate (2EHA), polyfunctional monomer (dipentaerythritol hexaacrylate, trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.): 0.05 Weight, dispersant (phosphate ester-based dispersant not containing phosphate triester, trade name “Plisurf A212E”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 2.7 parts by weight, particles (aluminum hydroxide, average particles) Diameter 1 μm, trade name “Hijilite H-42” manufactured by Showa Denko KK: 170 parts by weight and particles (aluminum hydroxide, average particle size 55 μm, trade name “Hijilite H-10” manufactured by Showa Denko KK) ): 170 parts by weight were added to obtain an adhesive composition.
Using the pressure-sensitive adhesive composition, a sheet having a structure in which the release liner A, the pressure-sensitive adhesive composition layer, and the release liner A are laminated in this order was obtained in the same manner as in Example 1.
Next, a pressure-sensitive adhesive sheet having a structure in which a release liner A, a pressure-sensitive adhesive layer, and a release liner A are laminated in this order was obtained from the above sheet in the same manner as in Example 1.

(Comparative Example 2)
70 parts by weight of the syrup: 30 parts by weight of 2-ethylhexyl acrylate (2EHA), polyfunctional monomer (dipentaerythritol hexaacrylate, trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.): 0.05 Weight, dispersant (phosphate ester-based dispersant not containing phosphate triester, trade name “Plisurf AL”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 2.7 parts by weight, particles (aluminum hydroxide, average particle) Diameter 1 μm, trade name “Hijilite H-42” manufactured by Showa Denko KK: 170 parts by weight and particles (aluminum hydroxide, average particle size 55 μm, trade name “Hijilite H-10” manufactured by Showa Denko KK) ): 170 parts by weight were added to obtain an adhesive composition.
Using the pressure-sensitive adhesive composition, a sheet having a structure in which the release liner A, the pressure-sensitive adhesive composition layer, and the release liner A are laminated in this order was obtained in the same manner as in Example 1.
Next, a pressure-sensitive adhesive sheet having a structure in which a release liner A, a pressure-sensitive adhesive layer, and a release liner A are laminated in this order was obtained from the above sheet in the same manner as in Example 1.

(Evaluation)
About the adhesive sheet obtained by said Example and comparative example, thermal conductivity and electrical insulation were evaluated.

(Thermal conductivity)
The case where the heat conductivity of the said adhesive sheet was 0.5 W / mK or more was evaluated as "good", and the case where the heat conductivity of the said adhesive sheet was less than 0.5 W / mK was evaluated as "bad".
In addition, when the thermal conductivity of the pressure-sensitive adhesive sheet is less than 0.5 W / mK, heat from the adherend (heat generation source) cannot be efficiently conducted, and the adherend is damaged or broken. May occur.

(Electrical insulation)
Regarding the relative dielectric constant of the pressure-sensitive adhesive sheet, the case where the relative dielectric constant at a frequency of 120 Hz to 1 MHz is 30 or less is evaluated as “particularly good”, and the case where the relative dielectric constant at a frequency of 120 Hz is 30 or less. It was evaluated as “good”. Moreover, in the relative dielectric constant in the frequency of 120 Hz to 1 MHz, when the relative dielectric constant in any frequency exceeded 30, it was evaluated as “defective”.
If the relative dielectric constant at any frequency exceeds 30 in the pressure-sensitive adhesive sheet, the dielectric constant of the pressure-sensitive adhesive sheet increases with time, and a leakage current may be generated. Insulation properties are impaired, and the adherend may be damaged or broken.

The abbreviations used in Table 1 are as follows.
2EHA: 2-ethylhexyl acrylate Prisurf A208F: Dispersant (trade name “Pricesurf A208F”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Price Surf A212E: Dispersant (trade name “Price Surf A212E”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Price Surf AL: Dispersant (trade name “Price Surf AL”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
H-42: Particles (aluminum hydroxide, trade name “Hijilite H-42”, Showa Denko)
H-10: Particles (aluminum hydroxide, trade name “Hijilite H-10”, Showa Denko)
AL-13KT: Particles (Alumina, trade name “AL-13KT”, manufactured by Showa Denko KK)

The “added amount [volume%]” in Table 1 was calculated using the following density.
Aluminum hydroxide: 2.4 g / cm ³
Alumina: 4.0 g / cm ³
Dispersant: 1.0 g / cm ³

In Table 1, the column of “initial” in the relative permittivity at a frequency of 120 Hz is the relative permittivity at a frequency of 120 Hz of the pressure-sensitive adhesive sheet before being left for 1 day in an environment of 40 ° C. and 92% RH. The column of “40 ° C./92% RH after 1 day” in the relative dielectric constant in FIG. 4 is the relative dielectric constant at a frequency of 120 Hz of the pressure-sensitive adhesive sheet left for 1 day in an environment of 40 ° C. and 92% RH.
Furthermore, the column of “initial” in the relative dielectric constant at a frequency of 1 kHz is a relative dielectric constant at a frequency of 1 kHz of the pressure-sensitive adhesive sheet before being left for 1 day in an environment of 40 ° C. and 92% RH. The column of “40 ° C./92% RH after 1 day” in the dielectric constant is a relative dielectric constant at a frequency of 1 kHz of the pressure-sensitive adhesive sheet left for 1 day in an environment of 40 ° C. and 92% RH.
Furthermore, the column of “initial” in the relative permittivity at a frequency of 1 MHz is the relative permittivity at a frequency of 1 MHz of the pressure-sensitive adhesive sheet before being left for 1 day in an environment of 40 ° C. and 92% RH. The column of “40 ° C./92% RH after 1 day” in the relative dielectric constant is a relative dielectric constant at a frequency of 1 MHz of the pressure-sensitive adhesive sheet left for 1 day in an environment of 40 ° C. and 92% RH.

DESCRIPTION OF SYMBOLS 1 Adhesive sheet 2 Thermometer 3 Contact-type displacement meter C Radiator D Temperature sensor H Heat generating body (heat block)
L block (rod)
P probe R load cell T pressure adjusting screw

Claims (4)

Having an adhesive layer,
The thermal conductivity is 0.5 W / mK or more,
A heat conductive pressure-sensitive adhesive sheet characterized by having a relative dielectric constant of 30 or less at a frequency of 120 Hz after being left for 1 day in an environment of 40 ° C. and 92% RH.   Furthermore, the heat conductivity adhesive sheet of Claim 1 whose relative dielectric constant in the frequency of 1 kHz after leaving for 1 day in the environment of 40 degreeC and 92% RH is 30 or less.   3. The heat conductive adhesive sheet according to claim 1, wherein the dielectric constant at a frequency of 120 Hz to 1 MHz after being left for 1 day in an environment of 40 ° C. and 92% RH is 30 or less.   The heat conductive adhesive sheet of any one of Claims 1-3 comprised only from the said adhesive layer.