TW201341498A - Thermoconductive adhesive sheet - Google Patents

Abstract

A thermoconductive adhesive sheet, wherein the quantity of organic compound gas generated by heating for 30 minutes at a temperature of 150 DEG C does not exceed 50mug/cm2, and the thermal resistance after being stored for 30 minutes at 25 DEG C does not exceed 10cm2sK/W.

Description

Thermally conductive adhesive sheet

The present invention relates to a thermally conductive adhesive sheet, and more particularly to a thermally conductive adhesive sheet which is preferably disposed in a sealed space of an electronic device.

Adhesive sheets are known to be attached, for example, to a confined space within a housing that houses an electronic device for subsequent attachment of the member.

However, in such a sealed space, if a volatile organic compound is generated from the adhesive sheet, contact failure of the switch or deterioration of the electronic device may occur.

Therefore, in order to reduce the volatile organic compound, for example, an adhesive tape comprising an acrylic adhesive having a volatile component concentration of 500 ppm or less at 90 ° C for 30 minutes is provided (for example, see Patent Document 1 below). ).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 4-315767

However, in the case where the heat generating member is housed in the casing of the electronic device, in this case, in addition to the requirement that the amount of the volatile organic compound to be produced be reduced, the adhesive sheet is required to have excellent thermal conductivity. However, the tape of the above Patent Document 1 has a problem that the above requirements cannot be satisfied.

Moreover, when the adhesive sheet is used in the field where thermal conductivity is required, due to stickiness The sheet is easily heated to a high temperature, so that when it is heated to a high temperature, it is required to further reduce the amount of volatile organic compound produced.

Further, in the case where the adhesive sheet is bonded to the adherend, it is necessary to suppress the incorporation of the bubbles.

An object of the present invention is to provide a thermally conductive adhesive sheet which is excellent in thermal conductivity and which can reduce the amount of generation of an organic compound gas when heated to a high temperature.

The thermally conductive adhesive sheet of the present invention is characterized in that the amount of generation of the organic compound gas generated by heating at 150 ° C for 30 minutes is 50 μg / cm ² or less, and the thermal resistance after storage at 25 ° C for 30 minutes is 10 cm ² . Below K/W.

Further, the thermally conductive adhesive sheet of the present invention preferably has a thickness of 10 μm or more and less than 500 μm.

Further, the thermally conductive adhesive sheet of the present invention is preferably bonded to a stainless steel sheet and heated at 150 ° C for 30 minutes, and then peeled off at 180 degrees with respect to the stainless steel sheet at a peeling speed of 300 mm/min. The peel strength is 2 N/20 mm or more.

Further, the thermally conductive adhesive sheet of the present invention preferably has a thermal resistance of 10 cm ² ‧ K/W or less after heating at 150 ° C for 30 minutes.

Further, the thermally conductive adhesive sheet of the present invention preferably has a substrate provided on the surface.

Further, the thermally conductive adhesive sheet of the present invention preferably comprises two layers and is provided to sandwich the substrate in the thickness direction.

The heat conductive adhesive sheet of the present invention has an organic compound gas generated by heating at 150 ° C for 30 minutes of 50 μg / cm ² or less, and has a thermal resistance of 10 cm ² after being stored at 25 ° C for 30 minutes. ‧K/W or less.

Therefore, the amount of generation of the organic compound gas when heated to a high temperature can be reduced, and further, pores caused by the generation of the organic compound gas can be reduced, and excellent thermal conductivity can be maintained.

Further, when the thermally conductive adhesive sheet of the present invention is bonded to the adherend, it is possible to suppress the incorporation of air bubbles. Therefore, the thermally conductive adhesive sheet can exhibit the above-described excellent thermal conductivity.

As a result, when the thermally conductive adhesive sheet of the present invention is disposed in the vicinity of the heat source in the sealed space of the electronic device, the heat from the heat source can be efficiently conducted, and the damage of the member in the sealed space can be effectively prevented. .

1‧‧‧ Thermally conductive adhesive sheet

1A‧‧‧ Thermal conductive adhesive sheet on the upper side

1B‧‧‧ underside thermal conductive adhesive sheet

2‧‧‧Substrate

3‧‧‧Protected sheet

4‧‧‧Release sheets

C‧‧‧heat radiator

D‧‧‧Temperature Sensor

H‧‧‧heating body

L‧‧‧ box

P‧‧‧ probe

R‧‧‧ load meter

T‧‧‧Pressure adjustment screw

Fig. 1 is a cross-sectional view showing an embodiment of a thermally conductive adhesive sheet of the present invention.

Fig. 2 is a cross-sectional view showing another embodiment of the thermally conductive adhesive sheet of the present invention.

Fig. 3 is a cross-sectional view showing another embodiment of the thermally conductive adhesive sheet of the present invention.

4 is an explanatory view of a thermal characteristic evaluation device for measuring thermal resistance in the embodiment,

Figure 4 (a) shows a front view,

Figure 4 (b) shows a side view.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing an embodiment of the present invention.

In Fig. 1, the thermally conductive adhesive sheet 1 is formed, for example, of a thermally conductive adhesive composition.

When the thermally conductive adhesive composition is obtained by solution polymerization (described below) to obtain an acrylic polymer, it is obtained by acrylic polymerization containing an acrylic polymer. The resin solution, the crosslinking agent, the thermal conductive material, and the dispersing agent are added to the solution to prepare a varnish.

The acrylic polymer can be obtained by reacting a monomer containing a (meth) acrylate and a functional group-containing (meth) acrylate.

The (meth) acrylate is an alkyl methacrylate and/or an alkyl acrylate, and specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, and ethyl (meth)acrylate. Ester, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, tert-butyl (meth)acrylate, ( Amyl methacrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate Ester, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, (meth)acrylic acid Undecyl ester, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, Cetyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, hexadecyl (meth) acrylate, (meth) acrylate Decyl ester and other carbon number 1~20 (C _1-20 ) an alkyl (meth)acrylate or the like.

The acrylate is preferably a C _2-14 alkyl (meth)acrylate, more preferably a C _4-9 alkyl (meth)acrylate.

The acrylates may be used singly or in combination of two or more. Preferably, a different type of C _4-9 alkyl (meth)acrylate is used in combination, and further preferably, a C _4-6 alkyl (meth)acrylate and a C ₇ (meth)acrylate are used in combination. _{The -9} alkyl ester is specifically exemplified by a combination of butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate.

The blending ratio of the acrylate is, for example, 70 to 99.9% by mass, preferably 80 to 98% by mass, and more preferably 85 to 97% by mass based on the monomer.

Further, when a different type of acrylate is used in combination, the compounding ratio of the (meth)acrylic acid C _4-6 alkyl ester is, for example, 10 to 40 parts by mass, based on 100 parts by mass of the (meth) acrylate. The blending ratio of the C _7-9 alkyl (meth)acrylate is preferably from 60 to 90 parts by mass, preferably from 65 to 85 parts by mass, per 15 to 35 parts by mass.

Further, the functional group-containing (meth) acrylate contains a functional group, and is contained in the thermally conductive adhesive composition in order to introduce a crosslinking point for thermally crosslinking the (meth) acrylate. By polymerizing the functional group-containing (meth) acrylate, the adhesion to the adherend can be improved.

Examples of the functional group-containing (meth) acrylate include a hydroxyl group-containing (meth) acrylate, a sulfonic acid group-containing (meth) acrylate, an amine group-containing (meth) acrylate, and the like. Glycidyl (meth) acrylate or the like.

Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. 6-hydroxyhexyl acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (meth)acrylic acid (4- Hydroxymethylcyclohexyl)methyl ester and the like.

Examples of the sulfonic acid group-containing (meth) acrylate include sulfopropyl (meth)acrylate and the like.

Examples of the amino group-containing (meth) acrylate include dimethylaminoethyl (meth)acrylate and t-butylaminoethyl (meth)acrylate.

Examples of the glycidyl group-containing (meth) acrylate include glycidyl (meth)acrylate and the like.

The functional group-containing (meth) acrylate is preferably a hydroxyl group-containing (meth) acrylate, and more preferably 2-hydroxyethyl (meth) acrylate.

The functional group-containing (meth) acrylate may be used singly or in combination of two on.

Further, the compounding ratio of the functional group-containing (meth) acrylate is, for example, 0.01 to 10% by mass, preferably 0.02 to 1% by mass based on the monomer.

When the compounding ratio of the functional group-containing (meth) acrylate is more than the above upper limit, the cohesive force is too high, and the adhesion of the thermally conductive adhesive sheet formed of the thermally conductive adhesive composition may be insufficient. On the other hand, if the lower limit is not reached, the cohesive force is lowered and the holding force is insufficient.

Further, in the monomer, for example, in order to achieve various characteristics such as cohesive force, a copolymerizable monomer copolymerizable with the (meth) acrylate may be contained as needed.

The copolymerizable monomer may, for example, be a carboxyl group-containing monomer such as (meth)acrylic acid, itaconic acid, maleic acid, crotonic acid or maleic anhydride or an anhydride thereof, for example, (methyl) Acrylamide, N,N-dimethyl(meth)acrylamide, N-methylol (meth) propylene ether amine, N-methoxymethyl (meth) acrylamide, N- A mercapto group-containing monomer such as butoxymethyl (meth) acrylamide, for example, a vinyl ester such as vinyl acetate, for example, an aromatic vinyl compound such as styrene or vinyl toluene, such as (meth) propylene. Nitrile, such as N-(methyl) propylene fluorenyl A porphyrin such as N-vinyl-2-pyrrolidone or the like.

The copolymerizable monomer is preferably a carboxyl group-containing monomer, and more preferably (meth)acrylic acid.

These copolymerizable monomers may be used singly or in combination of two or more.

The blending ratio of the copolymerizable monomer is from 0.1 to 15% by mass, preferably from 0.3 to 10% by mass based on the monomer.

In order to carry out the reaction of the monomer, for example, a monomer containing an acrylate, a functional group-containing (meth) acrylate, and, if necessary, a copolymerizable monomer is polymerized.

Further, examples of the method for polymerizing the monomer include known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerization, and solution polymerization is preferred.

In the solution polymerization, a monomer solution is prepared by dissolving a monomer in a solvent, and thereafter, a polymerization initiator is prepared while heating the monomer solution.

The solvent may, for example, be an aromatic solvent such as toluene, benzene or xylene, or an organic solvent such as an ether solvent such as ethyl acetate.

The solvent may be used singly or in combination.

The blending ratio of the solvent is, for example, 10 to 1000 parts by mass, preferably 50 to 500 parts by mass, per 100 parts by mass of the monomer.

Examples of the polymerization initiator include a peroxide polymerization initiator, an azo polymerization initiator, and the like.

Examples of the peroxide-based polymerization initiator include peroxycarbonate, ketone peroxide, peroxyketal, hydrogen peroxide, dialkyl peroxide, dimercapto peroxide, peroxyester, and the like. Organic peroxides.

Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis. An azo compound such as (2,4-dimethylvaleronitrile) or dimethyl 2,2'-azobisisobutyrate.

The polymerization initiator is preferably an azo polymerization initiator.

The compounding ratio of the polymerization initiator is, for example, 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, per 100 parts by mass of the monomer.

The heating temperature is, for example, 50 to 80 ° C, and the heating time is, for example, 1 to 24 hours.

The monomer is polymerized by the above solution polymerization to obtain an acrylic polymer solution containing an acrylic polymer.

About the viscosity of the acrylic polymer solution at 30 ° C, for example, at 30 ° C It is 0.1 to 100 Pa‧s, preferably 0.5 to 50 Pa‧s. Further, the method of measuring the viscosity is described in detail in the examples below.

When the viscosity of the acrylic polymer solution is less than the above range, moldability or workability may be insufficient.

The blending ratio of the acrylic polymer to the thermally conductive adhesive composition is, for example, 20 to 70% by mass, preferably 20 to 60% by mass.

When the blending ratio of the acrylic polymer is less than the above range, cohesive force and adhesive strength may be insufficient.

In order to impart adhesion, the adhesion-imparting resin is formulated in the thermally conductive adhesive composition as needed.

Examples of the adhesion-imparting resin include a petroleum resin, a terpene resin, a coumarone/quinone resin, a styrene resin, a rosin resin, an alkylphenol resin, and a xylene resin.

The adhesiveness-providing resin is preferably a rosin-based resin because of its excellent heating stability.

The weight average molecular weight of the adhesion-imparting resin (according to the following method) is, for example, 5,000 or less, preferably 100 to 4,000, more preferably 500 to 3,000.

When the weight average molecular weight of the adhesion-imparting resin exceeds the above upper limit, the cohesive force may be insufficient. On the other hand, if the lower limit is not reached, the adhesive strength may be insufficient.

The softening point (ring and ball method) of the adhesive imparting resin is, for example, 80 to 200 ° C, preferably 90 to 200 ° C.

If the softening point of the adhesion-imparting resin does not reach the above range, the cohesive force may be insufficient.

The ratio of adhesion imparting resin to 100 parts by mass of the acrylic polymer The ratio is, for example, 5 to 50 parts by mass, preferably 10 to 40 parts by mass.

When the blending ratio of the adhesion-imparting resin exceeds the above upper limit, the cohesive force may be insufficient. On the other hand, if the lower limit is not reached, the adhesive strength may be insufficient.

In order to improve the cohesive force of the thermally conductive adhesive sheet 1, a crosslinking agent is blended in the thermally conductive adhesive composition as needed.

Examples of the crosslinking agent include an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, and a metal chelate crosslinking agent. Preferably, an isocyanate type crosslinking agent is mentioned.

Examples of the isocyanate crosslinking agent include aromatic diisocyanates such as toluene diisocyanate and xylene diisocyanate, and alicyclic diisocyanates such as isophorone diisocyanate, and aliphatic aliphatic groups such as hexamethylene diisocyanate. Isocyanates such as such modified ones and the like.

Further, examples of the isocyanate-based crosslinking agent include isocyanate adducts such as toluene diisocyanate adduct of trimethylolpropane (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L").

The isocyanate crosslinking agent is preferably an isocyanate adduct.

The crosslinking agent may be used singly or in combination.

The blending ratio of the crosslinking agent is, for example, 0.01 to 20 parts by mass, preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, per 100 parts by mass of the acrylic polymer.

When the blending ratio of the crosslinking agent exceeds the above upper limit, the flexibility may be insufficient. On the other hand, if the lower limit is not reached, the cohesive force may be insufficient.

Examples of the thermally conductive material include boron nitride, aluminum nitride, and tantalum nitride. a nitride such as gallium nitride, for example, a metal hydroxide such as aluminum hydroxide or magnesium hydroxide, such as a telluride such as tantalum carbide or ruthenium dioxide, such as alumina, titania, zinc oxide, tin oxide, copper oxide, or nickel oxide. a metal oxide such as antimony-doped tin oxide, for example, a carbonic acid compound such as calcium carbonate, such as a metal titanate such as barium titanate or potassium titanate, such as a metal such as copper, silver, gold, nickel, aluminum or platinum, such as carbon black or carbon. Carbonaceous materials such as tubes (nanocarbon tubes), carbon fibers, and diamonds.

Preferable examples thereof include a nitride, a metal hydroxide, and a metal oxide, and more preferably a metal hydroxide.

The thermally conductive substance may be used singly or in combination of two or more.

The shape of the thermally conductive material is not particularly limited, and may be, for example, a block shape, a needle shape, a plate shape, or a layer shape. The block shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a pulverized shape, or the like shapes.

In the case where the thermally conductive substance has a bulk shape (spherical shape), the primary average particle diameter is, for example, 0.1 to 1000 μm, preferably 1 to 100 μm, and more preferably 2 to 20 μm. Further, the primary average particle diameter is a value based on a volume basis determined by a particle size distribution measurement method in a laser scattering method.

In the case where the thermally conductive substance is in the shape of a needle or a plate, the maximum length thereof is 0.1 to 1000 μm, preferably 1 to 100 μm, and more preferably 2 to 20 μm. The aspect ratio (in the case of needle crystals, expressed as long axis length/short axis length, or long axis length/thickness. Also, in the case of plate crystal, diagonal length/thickness, Or the length of the long side/thickness is, for example, 1 to 10,000, preferably 10 to 1,000.

A commercially available product can be used as the thermal conductive material. For example, as the boron nitride, "HP-40" manufactured by Mizushima Alloy Iron Co., Ltd., "PT620" manufactured by Moto Corporation, etc. can be used; for example, as aluminum hydroxide. "Higilite H-32" "Higilite H-42" manufactured by Showa Denko Co., Ltd., etc.; for example, as alumina, "AS-50" manufactured by Showa Denko Co., Ltd., etc.; for example, "KISUMA 5A" manufactured by Kyowa Chemical Industry Co., Ltd. can be used as the magnesium hydroxide; for example, as antimony-doped tin oxide, "Ishihara Sangyo Co., Ltd." can be used. SN-100S", "SN-100P", "SN-100D (water dispersion)", etc., for example, as the titanium oxide, for example, "TTO series" manufactured by Ishihara Sangyo Co., Ltd. can be used; for example, zinc oxide can be used. "SnO-310", "SnO-350" and "SnO-410" manufactured by Sumitomo Osaka Cement Co., Ltd. are used.

Further, the blending ratio of the thermally conductive material is adjusted so as to be 10 to 80% by volume, preferably 20 to 50% by volume, based on the volume ratio of the thermally conductive adhesive composition.

In the case where the thermally conductive material is a metal hydroxide, the blending ratio is, for example, 30 to 600 parts by mass, preferably 50 to 500 parts by mass, per 100 parts by mass of the acrylic polymer.

When the blending ratio of the thermally conductive material exceeds the above upper limit, moldability or workability may be insufficient. On the other hand, if the lower limit is not reached, the thermal conductivity may be insufficient.

In the thermally conductive adhesive composition, a dispersing agent is prepared in order to prevent the thermally conductive substance from aggregating and to stably disperse.

As such a dispersing agent, a phosphate ester is mentioned, for example.

As the phosphate ester, for example, a polyoxyethylene alkyl (or alkyl allyl) ether or a polyoxyethylene alkyl aryl ether phosphate monoester, such as a polyoxyethylene alkyl ether or a polyoxyethylene alkyl aryl group, may be mentioned. A phosphate such as a phosphodiester, a phosphate triester or a derivative thereof.

The dispersing agent may be used singly or in combination of two or more.

Preferred examples thereof include a phosphoric acid monoester or a phosphodiester of a polyoxyethylene alkyl ether or a polyoxyethylene alkyl aryl ether.

As a dispersing agent, a commercial item can be used, for example, the product name "Plysurf A212E" (manufactured by Daiichi Kogyo Co., Ltd.), the trade name "Plysurf A210G" (manufactured by Daiichi Kogyo Co., Ltd.), and the trade name "Plysurf A212C" can be used. The product name "Plysurf A215C" (manufactured by Daiichi Pharmaceutical Co., Ltd.), the trade name "Phosphanol RE610" (manufactured by Toho Chemical Co., Ltd.), the trade name "Phosphanol RS710" (manufactured by Toho Chemical Co., Ltd.), and the product Named "Phosphanol RS610" (manufactured by Toho Chemical Co., Ltd.).

The blending ratio of the dispersing agent is, for example, 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the acrylic polymer.

Further, additives such as an anti-aging agent, an antioxidant, a processing aid, a stabilizer, an antifoaming agent, a flame retardant, a tackifier, and a pigment may be blended in the thermally conductive adhesive composition at an appropriate ratio.

Further, in order to obtain the thermally conductive adhesive sheet 1, the varnish is applied onto the surface of the release sheet 4 indicated by a chain double-dashed line.

Examples of the coating method of the varnish include roll coating, gravure coating, bar coating, blade coating, curtain coating, lip coating, and slit extrusion coating.

The release sheet 4 is made of a plastic sheet such as a polyester sheet such as a polyethylene terephthalate sheet, for example, a porous sheet such as paper or nonwoven fabric, or a metal foil such as aluminum foil. form. It is preferably formed of a plastic sheet.

Further, the surface of the release sheet 4 may be subjected to a release treatment.

The thickness of the release sheet 4 is, for example, 1 to 200 μm, preferably 5 to 150 μm.

Further, a protective sheet 3 indicated by a chain double-dashed line may be additionally provided on the surface of the varnish coated on the surface of the release sheet 4 to protect the surface thereof. Protective sheet 3 The same as the above-mentioned release sheet 4 is mentioned.

Thereafter, the solution was dried by heating, and the acrylic polymer was crosslinked.

The heating temperature is, for example, 50 to 160 ° C, preferably 100 to 140 ° C, and the heating time is, for example, 1 to 60 minutes, preferably 2 to 30 minutes.

Thereby, the thermally conductive adhesive sheet 1 is obtained.

The thickness T of the thermally conductive adhesive sheet 1 is, for example, 10 μm or more and less than 500 μm, preferably 30 μm or more and 200 μm or less, and more preferably 30 μm or more and 50 μm or less.

When the thickness T exceeds the above upper limit, the following thermal resistances R1 and 2R cannot be set to a desired range, and there is a case where it is not possible to suppress the incorporation of bubbles when attached to the adherend. Further, when heating to a high temperature, there is a case where the occurrence of voids cannot be suppressed.

On the other hand, in terms of molding stability, it is difficult to manufacture the thermally conductive adhesive sheet 1 having a thickness T that does not reach the above lower limit.

Further, the amount V of the organic compound gas generated by heating the thermally conductive adhesive sheet 1 at 150 ° C for 30 minutes is 50 μg / cm ² or less, preferably 30 μg / cm ² or less, and more preferably 20 μg/cm ² or less, particularly preferably 10 μg/cm ² or less, and also 0 μg/cm ² or more.

When the amount V of the organic compound gas generated exceeds 50 μg/cm ² , the amount V of the organic compound gas cannot be reduced, and the electronic device (described below) provided with the thermally conductive adhesive sheet 1 is damaged.

The amount V of the organic compound gas produced was measured by the following method.

First, the thermally conductive adhesive sheet 1 is cut into a specific size, and then the release sheet 4 is peeled off, and then the aluminum is bonded to the release surface (one surface) of the thermally conductive adhesive sheet 1 After the foil was peeled off, the protective sheet 3 was peeled off, and the peeling surface (the other surface) was exposed, and it was placed in a small glass bottle and plugged. Then, the vial was heated at 150 ° C for 30 minutes, and then, at 150 ° C, the gas in the small glass bottle in the heated state was injected into the following conditions (Gas Chromatograph, gas chromatograph). The measurement was carried out in the middle.

The measurement conditions are shown below.

Carrier gas: helium

Column: non-polar capillary column

Column temperature: heating rate 10 ° C / min: temperature maintained after heating (low temperature) 40 ~ 300 ° C

Column pressure: 113 kPa

Detector: FID (Flame Ionization Detector)

The measurement of the organic compound gas was carried out by using a toluene gas of a known gas amount, and was carried out based on a calibration curve. Specifically, based on a calibration curve of toluene, the total area of each peak appearing from the start of the temperature up to 20 minutes was converted into mass, and the amount of generation of the organic compound gas was measured.

Further, in the thermally conductive adhesive sheet 1, the thermal resistance R1 after storage at 25 ° C for 30 minutes is 10 cm ² ‧ K / W or less, preferably 5 cm ² ‧ K / W or less, and further preferably 4 cm ² ‧K / W or less, particularly preferably 3 cm ² ‧K / W or less, most preferably ² cm 2 ‧K / W or less, and, also exceeds 0 cm ² ‧K / W of the range.

When the thermal resistance R1 exceeds the above limit, there is a case where the thermal conductive adhesive sheet 1 cannot be provided with sufficient thermal conductivity in a normal temperature (25 ° C) environment.

Further, the thermal resistance R1 is measured by a thermal characteristic evaluation device (see Fig. 4) of the following embodiment.

Further, the thermal resistance R2 after heating at 150 ° C for 30 minutes is, for example, 10 cm ² ‧ K/W or less, preferably 5 cm ² ‧ K/W or less, and further preferably 4 cm ² ‧ K/W or less It is preferably 3 cm ² ‧ K/W or less, preferably 2 cm ² ‧ K/W or less, and is also in the range of more than 0 cm ² ‧ K/W

When the thermal resistance R2 exceeds the above limit, the thermally conductive adhesive sheet 1 may not be provided with sufficient thermal conductivity in a high temperature environment.

Further, the thermal resistance R2 was measured by a thermal characteristic evaluation device (see Fig. 4) of the following example.

Moreover, after cutting the protective sheet 3 from the heat conductive adhesive sheet 1, the heat-conductive adhesive sheet 1 was peeled, and the peeling surface of the heat conductive adhesive sheet 1 was bonded to the stainless steel plate, and it heated at 150 degreeC. After a minute, the peeling strength S at a peeling speed of 300 mm/min is 180 N degrees with respect to the stainless steel sheet, for example, 2 N/20 mm or more, preferably 3 N/20 mm or more, and further It is preferably 5 N/20 mm or more, especially preferably 10 N/20 mm or more, and is also 50 N/20 mm or less.

Further, the peeling strength S was measured by peeling off the thermally conductive adhesive sheet 1 together with the release sheet 4.

Further, the thermally conductive adhesive sheet 1 is provided in the vicinity of a heat source in a sealed space of an electronic device, and specifically, is provided on a surface of a semiconductor element (adhered body) housed in a casing of an electronic device.

Specifically, after the release sheet 4 is peeled off, the peeling surface of the thermally conductive adhesive sheet 1 is bonded (pressure-sensitive) to cover the semiconductor element.

Thereby, since the semiconductor element and the thermally conductive adhesive sheet 1 are attached, the generated heat can be efficiently conducted to the heat sink or the like housed in the casing.

Further, in the thermally conductive adhesive sheet 1, the amount of generation of the organic compound gas generated by heating at 150 ° C for 30 minutes is 50 μg / cm ² or less, and the thermal resistance after storage at 25 ° C for 30 minutes R1 is 10 cm ² ‧K/W or less.

Therefore, the amount of generation of the organic compound gas when heated to a high temperature can be reduced, and further, pores caused by the generation of the organic compound gas can be reduced, and excellent thermal conductivity can be maintained.

Specifically, when the amount V of the organic compound gas is more than the above upper limit, pores are formed at the interface between the semiconductor element and the thermally conductive adhesive sheet 1 and the vicinity thereof, so that the contact area between the semiconductor element and the thermally conductive adhesive sheet 1 is reduced. As a result, the thermal conductivity of the thermally conductive adhesive sheet 1 is lowered.

On the other hand, in the thermally conductive adhesive sheet 1, the amount V of the organic compound gas generated is equal to or less than the above upper limit. Therefore, the occurrence of the pores can be effectively prevented, and the thermal conductivity of the thermally conductive adhesive sheet 1 can be prevented from being lowered.

Therefore, it is possible to effectively prevent the damage of the member such as the switch in the sealed space of the electronic device while efficiently transferring the heat from the semiconductor element.

Moreover, the thermally conductive adhesive sheet 1 can suppress the incorporation of air bubbles when it is bonded to the adherend. Therefore, the above excellent thermal conductivity can be exhibited.

2 and 3 are cross-sectional views showing other embodiments of the present invention.

In the following drawings, the same components as those described above are denoted by the same reference numerals, and their description will be omitted.

In the embodiment of Fig. 1, a release sheet 4 is provided on the surface of the thermally conductive adhesive sheet 1, and for example, as shown in Fig. 2, a substrate 2 may be provided instead of the release sheet 4.

That is, the substrate 2 is provided on one surface (the lower surface in FIG. 2) of the thermally conductive adhesive sheet 1.

The base material 2 is formed of a plastic sheet such as a polyester sheet such as a polyethylene terephthalate (PET) sheet, for example, a porous sheet such as paper or nonwoven fabric, or a metal foil such as aluminum foil. It is preferably formed of an aluminum foil.

The thickness of the substrate 2 is, for example, 1 to 200 μm, preferably 2 to 50 μm.

In the embodiment of FIG. 2, the substrate to which the varnish is applied is changed from the release sheet 4 to the substrate 2, and processed in the same manner as in the embodiment of FIG. Thermally conductive adhesive sheet 1.

The embodiment of Fig. 2 can exhibit the same operational effects as those of the embodiment of Fig. 1.

In FIG. 3, the thermally conductive adhesive sheet 1 is composed of two layers, whereby the substrate 2 is sandwiched in the thickness direction.

That is, the upper thermally conductive adhesive sheet 1A is formed on the upper surface of the substrate 2, and the lower thermally conductive adhesive sheet 1B is formed on the lower surface of the substrate 2. That is, it is formed as an intermediate layer in which the base material 2 is sandwiched between the two sheets of the thermally conductive adhesive sheet 1.

Furthermore, in the above description, the sheet includes the concept of a tape and a film.

[Examples]

Hereinafter, the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited thereto.

(Production of thermal conductive adhesive sheet)

Example 1

AIBN (Azobisisobutyronitrile) (trade name, 2'2') is formulated in a monomer containing 70 g of 2-ethylhexyl acrylate, 30 g of n-butyl acrylate, 0.05 g of 2-hydroxyethyl acrylate, and 3 g of acrylic acid. - azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd., 0.08 g, and 150 g of toluene, which were uniformly dissolved, and then polymerized at 65 ° C for 8 hours to obtain an acrylic polymer solution. The viscosity of the obtained acrylic polymer solution (BH viscosity meter, No. 5 rotor, 10 s ^-1 , measurement temperature 30 ° C) was about 25 Pa‧s.

To 100 g of the obtained acrylic polymer solution, 1.5 g of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate L, active ingredient 55%), modified rosin ester resin (adhesive-imparting resin, trade name "Pensel" was added. D125", Arakawa Manufactured by the company, 25 g, aluminum hydroxide (thermally conductive substance, trade name "Higilite H-32", primary average particle size 8 μm, manufactured by Showa Denko) 100 g, and polyoxyethylene alkylphenyl ether phosphate (trade name "Plysurf A212E", dispersant, manufactured by Dai-ichi Kogyo Co., Ltd.) 0.5 g, which was stirred and mixed to prepare a varnish.

Then, by varnishing, the varnish was applied to a PET sheet having a thickness of 60 μm which was subjected to peeling treatment on one side by roll coating (polyoxygenated product, trade name " Lumirror S-10 #75", release sheet, manufactured by Toray Industries, Inc.) on the surface of the treated surface. Thereafter, the acrylic polymer is cured (crosslinked) at 130 ° C for 5 minutes to adhere the surface of the varnish to the surface of the varnish by peeling the surface of the varnish in contact with the varnish. A 38 μm protective sheet containing PET (see Fig. 1) was used to produce a thermally conductive adhesive sheet.

Further, the volume ratio of aluminum hydroxide to the thermally conductive adhesive sheet was 29% by volume.

Example 2

The thermally conductive adhesive sheet was produced in the same manner as in Example 1 except that the thickness after hardening was changed to 20 μm.

Example 3

The thermally conductive adhesive sheet was produced in the same manner as in Example 1 except that the thickness after hardening was changed to 30 μm.

Example 4

The thermally conductive adhesive sheet was produced in the same manner as in Example 1 except that the thickness after curing was changed to 50 μm in the application of the varnish.

Example 5

In addition to the coating of the varnish, the thickness after hardening is changed to 100 μm. A thermally conductive adhesive sheet was produced in the same manner as in Example 1.

Example 6

The thermally conductive adhesive sheet was produced in the same manner as in Example 1 except that the thickness after curing was changed to 200 μm in the application of the varnish.

Example 7

In the application of the varnish, the varnish was applied to a PET sheet having a thickness of 12 μm (base material, trade name "Lumirror S10 #12", manufactured by Toray Industries, Inc.) so as to have a thickness of 45 μm after hardening. On one side, a protective sheet containing PET having a thickness of 38 μm which was subjected to a release treatment was attached to the surface of the varnish, and the varnish was applied to the PET sheet so that the thickness after hardening became 45 μm. On the other hand, a protective sheet containing PET having a thickness of 38 μm which was subjected to a release treatment on the surface of the varnish was bonded to the surface of the varnish, and a thermally conductive adhesive sheet was produced in the same manner as in Example 1. Material (refer to Figure 3).

Comparative example 1

In the same manner as in Example 1, except that the thickness after hardening was changed to 5 μm, the production of the thermally conductive adhesive sheet was attempted.

However, since such a coating cannot be performed, a thermally conductive adhesive sheet cannot be produced, and therefore performance evaluation has not been performed.

Comparative example 2

The thermally conductive adhesive sheet was produced in the same manner as in Example 1 except that the thickness after hardening was changed to 500 μm.

Comparative example 3

The thermally conductive adhesive sheet was produced in the same manner as in Example 1 except that the thickness after hardening was changed to 1000 μm in the application of the varnish.

(test evaluation)

The following tests were conducted on the thermally conductive adhesive sheet. The test results are shown in Table 1.

1. The amount of organic compound gas produced (V)

First, the thermally conductive adhesive sheet is cut into a size of 1 cm × 1 cm, and then the release sheet is peeled off, and then the aluminum foil is bonded to the release surface (one surface) of the thermally conductive adhesive sheet, and thereafter, The protective sheet was peeled off and exposed to the peeling surface (the other surface), and placed in a 20 ml vial and stoppered. Then, the vial was heated at 150 ° C for 30 minutes, and then, at 150 ° C, a headspace sampler (HSS, Headspace Sampler) was used to inject 1 ml of the gas in the heated glass vial into the gas. The measurement was carried out in a phase chromatograph under the following measurement conditions.

Carrier gas: helium

Column: non-polar capillary column

Column temperature: heating rate 10 ° C / min: temperature maintained after heating (low temperature) 40 ~ 300 ° C

Column pressure: 113 kPa

Detector: FID

Further, the measurement was carried out by using a toluene gas having a known gas amount to prepare a calibration curve, and based on the calibration curve. Specifically, based on a calibration curve of toluene, the total area of each peak appearing from the start of the temperature up to 20 minutes was converted into mass, and the amount of generation of the organic compound gas was measured.

2. Thermal resistance (R1 and R2)

First, the thermally conductive adhesive sheet 1 was allowed to stand at 25 ° C for 30 minutes. Further, the thermally conductive adhesive sheet 1 was placed in a dryer at 150 ° C for 30 minutes.

Thereafter, the thermal resistance of the thermally conductive adhesive sheet 1 was measured using the thermal characteristic evaluation apparatus shown in FIG. 4.

Specifically, a pair of squares (also referred to as rods) of aluminum (A5052, thermal conductivity: 140 W/m‧K) formed as a cube having a side of 20 mm is formed between L and clips. The thermally conductive adhesive sheet 1 (20 mm × 20 mm) from which the protective sheet 3 and the release sheet 4 were peeled off was adhered, and the pair of squares L was bonded by the thermally conductive adhesive sheet 1.

In addition, a pair of squares L are arranged in the vertical direction, and are disposed between the heat generating body (heating block) H and the heat radiating body (the cooling floor formed so that the cooling water circulates inside) C. Specifically, the heating element H is placed above the upper block L, and the radiator C is placed below the lower square L.

At this time, the pair of squares L bonded by the thermally conductive adhesive sheet 1 are located between the pair of pressure adjusting screws T that penetrate the heating element H and the radiator C. In addition, a load meter R is disposed between the pressure adjusting screw T and the heating element H, and is configured to measure the pressure at the time of tightening the pressure adjusting screw T, and the pressure is set to a thermally conductive adhesive sheet. 1 used to apply pressure.

In addition, three probes P (diameter: 1 mm) of the contact type displacement meter are provided so as to penetrate the lower side block L and the thermally conductive adhesive sheet 1 from the side of the heat sink C. At this time, the upper end portion of the probe P is in contact with the lower surface of the upper block L, and is configured to be capable of measuring the interval between the upper and lower blocks L (the thickness of the thermally conductive adhesive sheet 1).

A temperature sensor D is attached to the heating element H and the upper and lower blocks L. Specifically, the temperature sensor D is attached to one of the heating elements H, and the temperature sensor D is attached to the upper portion of the block L at intervals of 5 mm at intervals of 5 mm.

In the measurement, first, the pressure adjusting screw T is tightened, pressure is applied to the thermally conductive adhesive sheet 1, the temperature of the heating element H is set to 80 ° C, and the cooling water of 20 ° C is circulated in the radiator C.

Further, after the temperature of the heating element H and the upper and lower blocks L are stabilized, the temperature of the upper and lower squares L is measured by each temperature sensor D, and the thermal conductivity (W/m‧K) and temperature gradient of the upper and lower squares L are measured. The heat flow rate through the thermally conductive adhesive sheet 1 was calculated, and the temperature at the interface between the upper and lower blocks L and the thermally conductive adhesive sheet 1 was calculated. Further, using these, the thermal resistance (cm ² ‧ K/W) at the pressure was calculated using the following thermal conductivity equation (Fourier's law).

Q=-λgradT

R=L/λ

Q: thermal flow rate per unit area

gradT: temperature gradient

L: thickness of the sheet

λ: thermal conductivity

R: thermal resistance

In this evaluation, the thermal resistance at a pressure of 25 N/cm ² (250 kPa) applied to the thermally conductive adhesive sheet 1 was measured.

3. Peel strength (S)

The thermally conductive adhesive sheets of Examples 1 to 6 and Comparative Examples 2 and 3 were placed in a dryer at 150 ° C for 30 minutes. Thereafter, after the thermally conductive adhesive sheet is cut to a size of 20 mm × 100 mm, the protective sheet is peeled off, and thereafter, the peeled surface of the thermally conductive adhesive sheet is bonded to the stainless steel sheet, and then peeled off. The peeling strength was measured by peeling off the thermally conductive adhesive sheet and the release sheet at 180 degrees with respect to the stainless steel sheet at a speed of 300 mm/min.

On the other hand, the thermally conductive adhesive sheet of Example 7 was cut to a size of 20 mm × 100 mm, and the protective sheet was peeled off, and thereafter, the peeled surface of the thermally conductive adhesive sheet was attached to a stainless steel plate. After that, it was placed in a dryer at 150 ° C for 30 minutes, and the protective sheet on one side was peeled off. Thereafter, the thermally conductive adhesive sheet was placed at 180 degrees with respect to the stainless steel sheet at a peeling speed of 300 mm/min. Material, another The protective sheet on one side and the substrate were peeled off together to measure the peel strength.

4. Appearance evaluation

First, the protective sheet is peeled off from the thermally conductive adhesive sheet, and then the peeled surface of the thermally conductive adhesive sheet is placed on the surface of the glass plate, and then the 2 kg load roller is reciprocated once to visually The entry (mixing in) of the bubbles when the thermally conductive adhesive sheet was bonded to the glass plate was observed.

"○" indicates that the entry of the bubble is not confirmed, and "X" indicates that the entry of the bubble is confirmed.

Furthermore, the invention is provided by the exemplified embodiments of the invention, but is merely illustrative and not limiting. Variations of the invention as clarified by those skilled in the art are included in the scope of the following claims.

[Industrial availability]

Thermally conductive adhesive sheets are used in electronic devices.

1‧‧‧ Thermally conductive adhesive sheet

3‧‧‧Protected sheet

4‧‧‧Release sheets

Claims (6)

A thermally conductive adhesive sheet characterized in that the amount of organic compound gas generated by heating at 150 ° C for 30 minutes is 50 μg / cm ² or less, and the thermal resistance after storage at 25 ° C for 30 minutes is 10 Cm ² ‧K/W or less. The thermally conductive adhesive sheet of claim 1, which has a thickness of 10 μm or more and less than 500 μm . The thermally conductive adhesive sheet according to claim 1, wherein the film is bonded to a stainless steel plate and heated at 150 ° C for 30 minutes, and then peeled at 180 degrees with respect to the stainless steel plate at a peeling speed of 300 mm/min. The peel strength is 2 N/20 mm or more. The thermally conductive adhesive sheet of claim 1, which has a thermal resistance of 10 cm ² ‧ K/W or less after heating at 150 ° C for 30 minutes. A thermally conductive adhesive sheet according to claim 1, which is provided with a substrate on the surface. The thermally conductive adhesive sheet of claim 5, which comprises two layers and is provided in such a manner as to sandwich the substrate in the thickness direction.