KR20170065883A

KR20170065883A - Heat-Dissipation Sheet

Info

Publication number: KR20170065883A
Application number: KR1020150172208A
Authority: KR
Inventors: 권혁봉; 김영진; 이경환
Original assignee: 주식회사 케이씨씨
Priority date: 2015-12-04
Filing date: 2015-12-04
Publication date: 2017-06-14

Abstract

A heat-radiating sheet comprising a graphite heat-radiating layer and an adhesive layer formed on one side of the graphite heat-radiating layer, wherein the graphite heat-radiating layer comprises a polymer resin and graphite particles having an average particle diameter of 1 to 20 m, A heat-radiating sheet including the thermally conductive particles and having excellent thermal conductivity in the horizontal and vertical directions is provided.

Description

A heat-dissipating sheet {Heat-Dissipation Sheet}

The present invention relates to a heat-radiating sheet, and more particularly, to a heat-radiating sheet having flexibility and excellent heat radiation characteristics in horizontal and vertical directions.

Electronic products such as mobile phones, tablet PCs, notebook computers, PDPs, LEDs, and LCDs generate heat inside the system, including the backside circuit board, and the generated heat must be rapidly diffused to the outside to avoid shortening the life, malfunction, and malfunction. . A variety of thermally conductive sheets are used to effectively diffuse heat generated from electronic products, and a typical example thereof is a graphite heat-radiating sheet.

The heat-radiating sheet is configured such that a pressure-sensitive adhesive is applied to one surface of the heat-radiating sheet so as to adhere to a heat-generating body of the electronic product to emit heat.

In the graphite heat-radiating sheet, the graphite particles are horizontally oriented, and the thermal conductivity in the horizontal direction is high, but the thermal conductivity in the thickness direction, that is, the vertical direction is low. Generally, the graphite heat-radiating sheet is manufactured by a rolling method in which graphite powder expanded on a substrate is pressed and laminated at a constant pressure using a roll press. However, the graphite heat-radiating sheet produced by the rolling method is not uniform in thickness and a gap is formed between the expanded graphite particles to lower the thermal conductivity in the vertical direction, and the formed graphite layer is easily peeled off. When the graphite sheet is warped or bent, There is a problem in that it occurs or tears.

In order to overcome this problem, Korean Patent No. 10-0975885 discloses a method for producing a mixed carbon sheet by coating a mixed dispersion solution obtained by dispersing additives such as carbon nanotubes and binders in a dispersion solvent on one side or both sides of an expanded graphite sheet . In order to solve the problem that the thermal conductivity is lowered in the vertical direction, the patent discloses that by using carbon nanowires that are much smaller than the size of the expanded graphite particles, they can be placed in the voids to make the density higher, And it is described that the efficiency of the conductivity can be further maximized by placing such carbon nanowires on the surface portion. However, the binder present on the surface of the sheet can improve flexibility, but can impair heat diffusion performance.

Korean Patent No. 10-0975885

It is an object of the present invention to provide a heat-radiating sheet having flexibility and excellent heat radiation characteristics in horizontal and vertical directions.

On the other hand, the present invention is a heat-radiating sheet comprising a graphite heat-radiating layer and a pressure-sensitive adhesive layer formed on one side of the graphite heat-radiating layer, wherein the graphite heat-radiating layer comprises a polymer resin and graphite particles having an average particle size of 1 to 20 m, Wherein the adhesive layer comprises thermally conductive particles.

In one embodiment of the present invention, the adhesive layer may be formed from a sticky composition comprising an acrylic polymer, thermally conductive particles and a crosslinking agent.

In one embodiment of the present invention, the thermally conductive particles may comprise boron nitride.

In one embodiment of the present invention, the thermally conductive particles may further include at least one selected from the group consisting of metal hydroxides, metal oxides, metal carbides, conductive carbon materials, and mixtures thereof.

In one embodiment of the present invention, the adhesive layer composition may further comprise at least one of a dispersant and a pressure-sensitive adhesive resin.

In one embodiment of the present invention, the graphite heat-radiating layer may be formed from a coating composition in which expanded graphite powder and thermally conductive particles are dispersed in a polymer resin solution.

In one embodiment of the present invention, the heat radiation sheet has a thermal conductivity of 300 W / m · K or more, for example, 300 to 500 W / m · K in the horizontal direction and a thermal conductivity of 5 W / m · K or more in the vertical direction 5 to 8 W / m · K.

The heat-radiating sheet having the graphite heat-releasing layer and the pressure-sensitive adhesive layer according to the present invention is not only excellent in thermal conductivity in the horizontal direction because the graphite particles having flexibility and small particle size are dispersed by the introduction of the polymer resin into the graphite heat- The thermally conductive particles are present in the layer and the thermal conductivity in the vertical direction can be improved.

Hereinafter, the present invention will be described in more detail.

An embodiment of the present invention is a heat-radiating sheet comprising a graphite heat-radiating layer and an adhesive layer formed on one side of the graphite heat-radiating layer, wherein the graphite heat-radiating layer comprises a polymer resin and graphite particles having an average particle diameter of 1 to 20 m , And the adhesive layer comprises thermally conductive particles.

The acrylic polymer may be obtained by copolymerizing a (meth) acrylic acid alkyl ester monomer having an alkyl group having 2 to 14 carbon atoms as a main component which imparts tackiness and bufferability to the heat radiation sheet of the present invention.

The (meth) acrylic acid alkyl ester monomer may be represented by the following general formula (1)

[Chemical Formula 1]

CH ₂ = C (R ₁ ) COOR ₂

In this formula,

R < ₁ _> is hydrogen or a methyl group,

R ₂ is an alkyl group having 2 to 14 carbon atoms, specifically an alkyl group having 3 to 12 carbon atoms, more specifically an alkyl group having 4 to 9 carbon atoms.

Examples of the (meth) acrylic acid alkyl ester monomer having an alkyl group of 2 to 14 carbon atoms include ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (Meth) acrylate, isobutyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (Meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl acrylate, isononyl (Meth) acrylate, isodecyl (meth) acrylate, isodecyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl Decyl, (meth) Rilsan include iso-tridecyl. Among them, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and the like can be used in consideration of the adhesive force of the adhesive layer. These may be used alone or in combination of two or more.

The content of the (meth) acrylic acid alkyl ester monomer may be from 50 to 98 mass% with respect to the total monomer components. If the content is less than 50 mass%, the adhesive property may be deteriorated.

The polar group-containing monomer is used as a component of the acryl-based polymer to improve the adhesion to the surface of the mounting substrate and the graphite heat-releasing layer, or to increase the cohesive strength of the adhesive layer.

Examples of the polar group-containing monomer include a nitrogen-containing monomer, a hydroxyl group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and a carboxyl group-containing monomer. These monomers may be used singly or in combination.

Examples of the nitrogen-containing monomer include N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) Amide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (Meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide such as N-hydroxyalkyl (Meth) acrylamides such as N-butoxymethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Vinylpyrrolidone (NVP), N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl- Pyrrolidone, aminoethyl (meth) acrylate, N, N-methylaminoethyl ( (Meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N- (meth) acryloylmorpholine and the like, and acrylonitrile , Methacrylonitrile, and other cyano group-containing monomers. Of these, N-hydroxyalkyl (meth) acrylamide and N-vinyl cyclic amide can be used particularly in view of good initial adhesion.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylic acid, 3-hydroxypropyl (meth) acrylic acid, 4-hydroxybutyl (meth) acrylic acid, 2- Hydroxypropyl (meth) acrylate, hydroxyhexyl (meth) acrylic acid, 8-hydroxyoctyl (meth) acrylic acid, (Meth) acrylamide, N-hydroxy (meth) acrylamide, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like. Of these, 4-hydroxybutyl (meth) acrylic acid and 2-hydroxyethyl (meth) acrylic acid can be used.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalenesulfonic acid.

An example of the phosphate group-containing monomer is 2-hydroxyethyl acryloyl phosphate.

Examples of the carboxyl group-containing monomers include (meth) acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid and derivatives thereof, among which (meth) acrylic acid can be used.

The polar group-containing monomer may be contained in an amount of 0.05 to 10 parts by mass based on 100 parts by mass of the alkyl (meth) acrylate monomer. When the content is less than 0.05 part by mass, the cohesive force of the adhesive composition may be small, and when it is more than 10 parts by mass, the adhesive force may be deteriorated due to a high gel fraction.

The monomer components may be polymerized in the presence of a thermal polymerization initiator. Examples of the thermal polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyro Nitrile, dimethyl 2,2'-azobis (2-methylpropionic acid), 4,4'-azobis-4-cyanovaleric acid, azobisisobalonitrile, 2,2'-azobis Azobis [N, N ', N'-bis (diphenylphosphino) propane] dihydrochloride, 2,2'- Azo polymerization initiator such as 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, di (2-ethylhexyl) Peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxineodecanoate, t-hexylperoxypivalate , t-Bu Peroxides such as peroxypivalate, dilauryl peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di (t-hexylperoxy) cyclohexane and t- A polymerization initiator. Of these, azo-based polymerization initiators, in particular AIBN, can be used. These may be used alone or in combination of two or more.

The polymerization initiator may be used in an amount of 0.005 to 1 part by mass, particularly 0.01 to 0.2 part by mass based on 100 parts by mass of the total monomer component.

The production method of the acryl-based polymer is not particularly limited, and can be produced by methods such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization which are generally used in the art, and solution polymerization is preferable. For example, in order to prepare an acrylic polymer by solution polymerization, a solution obtained by dissolving a monomer component and a thermal polymerization initiator in an appropriate solvent such as toluene or ethyl acetate is heated at a temperature of 20 to 100 캜, for example, at 40 to 80 캜, And the mixture is heated and stirred at a temperature of 50 to 80 DEG C for 1 to 16 hours, particularly 3 to 8 hours. Further, the reaction is carried out in an inert gas atmosphere such as nitrogen.

The weight average molecular weight of the acrylic polymer obtained by this method is 450,000 or more, for example, 600,000 to 2,500,000, particularly 80,000 to 150,000. If the weight average molecular weight is less than 450,000, durability may be insufficient. On the other hand, the weight average molecular weight is a value measured by GPC and calculated by polystyrene conversion.

The glass transition temperature (Tg) of the acrylic polymer may be -5 deg. C or lower, for example, -10 deg. C or lower, particularly -30 deg. When the glass transition temperature of the acrylic polymer is higher than -5 DEG C, the acrylic polymer is difficult to flow and the leakage to the mounting substrate and the cooling member becomes insufficient and the adhesive force may be lowered. The glass transition temperature of the acryl-based polymer can be adjusted within the above-mentioned range by suitably changing the monomer component or the composition ratio to be used.

As a component for imparting tackiness, a thermoplastic elastomer, an isobutylene-based elastomer, a silicone rubber or the like may be used singly or in combination of two or more in place of the acryl-based polymer as described above.

In one embodiment of the present invention, the thermally conductive particles are included in the adhesive layer to improve the thermal conductivity, particularly, the thermal conductivity in the vertical direction. As a result, the adhesive layer of the present invention has adhesiveness due to use of the acrylic polymer, .

As the thermally conductive particles, boron nitride (BN) may be used. Boron nitride has a structure similar to that of graphite, has a high thermal conductivity, has a high thermal shock resistance when applied to a heat-radiating sheet, and has thermal superiority such that cracking or breakage does not occur even when rapid heating and quenching are repeated. In addition, boron nitride is excellent in chemical stability because it is highly resistant to most organic solvents and does not react with other components in solution.

For example, boron nitride has a thermal conductivity of approximately 600 W / m · K, and this boron nitride acts as a thermal diffusion material in the adhesive layer laminated on one side of the graphite heat-radiating layer, thereby greatly improving the thermal conductivity in the vertical direction.

Commercially available products of boron nitride that can be used include SGP-grade (manufactured by Denka) and PT620 (manufactured by Momentive).

Further, as the thermally conductive particles, at least one selected from the group consisting of metal hydroxides, metal oxides, metal carbides, conductive carbon materials, and mixtures thereof may be further used.

Examples of the metal hydroxides include aluminum hydroxide [Al (OH) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], zinc hydroxide [Zn (OH) ₂ ] Examples of the metal oxide is iron oxide (Fe ₂ O _3), silicon oxide (silica), aluminum (alumina), magnesium oxide, titanium oxide, zinc oxide, titanium barium, hydrotalcite [6MgO · Al ₂ O ₃ · H ₂ O]. Examples of the metal carbide include silicon carbide, boron carbide, aluminum carbide, titanium carbide, and tungsten carbide. Examples of the conductive carbon material include carbon black, graphite, fullerene, carbon nanotubes, and carbon nanofibers. Of these, aluminum oxide may be particularly used, and commercially available products of aluminum oxide include AS-20 (manufactured by Showa Denko K.K.) and DAW-03 (manufactured by Denka Co., Ltd.).

The shape of the thermally conductive particles is not particularly limited, and may have a shape such as a sphere, a plate, or a layer.

The size of the thermally conductive particles may be in the range of 0.1 to 200 μm, for example, 1 to 100 μm, particularly 2 to 50 μm, in the case of spherical particles. If the particle diameter exceeds the above range, the thermally conductive particles may exceed the thickness of the pressure-sensitive adhesive layer, which may cause a thickness variation of the pressure-sensitive adhesive layer. On the other hand, when the thermally conductive particles are in a plate-like shape, the average value of the maximum length may be 0.1 to 1000 占 퐉, for example, 1 to 100 占 퐉, especially 5 to 45 占 퐉. If the average value of the maximum length exceeds the above range, coagulation between the thermally conductive particles may occur and handling may become difficult.

The thermally conductive particles may be used alone or in combination of two or more. When two or more thermally conductive particles having different average particle diameters or average maximum lengths are mixed, for example, a combination of large particles having an average particle diameter or average maximum length of 10 占 퐉 or larger and particles smaller than 10 占 퐉 in combination may be used , The thermally conductive particles can be filled more densely in the adhesive layer. As a result, a heat conduction path due to the thermally conductive particles is apt to be established, and the thermal conductivity of the adhesive layer can be improved.

In order to improve the above-mentioned effect, a blending ratio of a large particle having an average particle size of 10 탆 or more and a small particle having a particle size of less than 10 탆 is in the range of 1:10 to 10: 1, specifically 1: 5 to 5: 1, 2: 1. For example, boron nitride having an average particle size of 10 mu m or more and aluminum oxide having an average particle size of less than 10 mu m can be used in a blending ratio of 1:10 to 10: 1.

The thermally conductive particles may be contained in an amount of 15 to 300 parts by mass based on 100 parts by mass of the acrylic polymer to impart high thermal conductivity. When the content of the thermally conductive particles is less than 15 parts by mass, sufficient thermal conductivity can not be imparted. If the content is more than 300 parts by mass, the flexibility may decrease and the adhesive force and the holding power may be lowered.

The cross-linking agent is a component for further improving the adhesive force and durability of the adhesive layer, and a cross-linking agent conventionally used in the art can be used. Examples of usable crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents and metal chelating crosslinking agents. Of these, isocyanate crosslinking agents may be particularly used.

The isocyanate crosslinking agent is a polyfunctional isocyanate having a plurality of isocyanate groups in the molecule, and examples thereof include tolylene diisocyanate, xylene diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, butylenediisocyanate, hexamethylene Diisocyanate, 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, polymethylene polyphenyl isocyanate trimethylolpropane / tolylene diisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., , Hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HL), isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HX), etc. , Polyether polyisocyanates, polyester polyisocyanates, and polyisocyanates that are multifunctionalized with adducts of these with various polyols, and the like. These crosslinking agents may be used alone or in combination of two or more.

The cross-linking agent may be included in an amount of 0.01 to 10 parts by mass, for example, 0.01 to 5 parts by mass, based on 100 parts by mass of the acrylic polymer.

The dispersant is a component for stably dispersing the thermally conductive particles in the acrylic polymer without aggregation, for example, phosphate esters can be used.

Examples of such phosphate esters include phosphoric acid monoesters of polyoxyethylene alkyl (or alkylallyl) ethers or polyoxyethylene alkylaryl ethers, phosphoric acid diesters, triesters of polyoxyethylene alkyl ethers or polyoxyethylene alkylaryl ethers, Derivatives, etc. Among them, phosphoric acid monoester, phosphoric acid diester and the like of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether can be used particularly. These dispersants may be used alone or in combination of two or more. These types of dispersants are commercially available as BYK-220 S, BYK-9076, BYK-9077, BYK-P 104 (BKY-Chemie).

The dispersant may be included in an amount of 0.01 to 10 parts by mass, for example, 0.05 to 5 parts by mass, particularly 0.1 to 3 parts by mass, based on 100 parts by mass of the acrylic polymer.

Examples of the adhesion-imparting resin include a rosin-based resin and the like, and when it is contained in an amount of 5 to 50 parts by mass, for example, 10 to 40 parts by mass, based on 100 parts by mass of the acrylic polymer, a desired level of tackiness can be imparted.

The adhesive layer formed from the adhesive composition as described above may have a thickness of 10 to 250 占 퐉, for example, 10 to 100 占 퐉, particularly 10 to 50 占 퐉. When the thickness is less than 10 탆, sufficient adhesive force and holding force can not be obtained, and when the thickness exceeds 250 탆, sufficient thermal conductivity is hardly obtained and the adhesive layer may be easily peeled off.

The polymer resin solution is obtained by dissolving the polymer resin in an organic solvent (e.g., methyl ethyl ketone, toluene, etc.), and the polymer resin is introduced into the graphite heat-releasing layer to give flexibility to improve the cracking phenomenon. May be used in an amount of 15 to 35 mass% as solid content.

As the polymer resin, there can be used an elastic rubber having a substituent or a nitrobutadiene rubber in which an elastic material is modified, a butadiene liquid rubber in which carboxyl groups are substituted at both ends, a butadiene liquid rubber in which amine groups are substituted at both ends, These commercial products include N631, N34, N34J, 1072S, 1072J and DN601 (Nippon Zeon).

The expanded graphite powder may have an average particle diameter of 1 to 20 占 퐉, particularly 3 to 7 占 퐉. Such small-sized graphite powder is densely dispersed in the graphite heat-dissipating layer to minimize the inter-particle porosity, thereby improving the thermal conductivity in the horizontal direction. On the other hand, graphite powder having a large particle diameter causes problems of coating failure and cracking .

The expanded graphite powder may be contained in an amount of 5 to 30 parts by weight, for example, 10 to 20 parts by weight, based on 100 parts by weight of the polymer resin solution. When the content is less than 5 parts by mass, the thermal conductivity of the graphite heat-dissipating layer is lowered, and when it exceeds 30 parts by mass, coating defects and cracks may occur.

The thermally conductive particles fill the voids between the graphite particles in the graphite heat-radiating layer, thereby further improving not only the thermal conductivity in the horizontal direction but also the thermal conductivity in the vertical direction.

The type, size, and shape of the thermally conductive particles are the same as those described in the adhesive layer, so that the substrate is omitted in order to avoid duplication.

The content of the thermally conductive particles may be 3 to 30 parts by mass, for example, 5 to 20 parts by mass with respect to 100 parts by mass of the polymer resin solution. When the content is less than 3 parts by mass, the increase of the thermal conductivity in the vertical direction is small. When the content exceeds 30 parts by mass, coating defects and cracks may occur.

The coating composition for forming the graphite heat-releasing layer may further comprise a dispersing agent, which is the same as that described in the above-mentioned adhesive layer, so that the substrate is omitted in order to avoid duplication.

The graphite heat-radiating layer formed from the coating composition as described above may have a thickness of 10 to 250 탆, for example, 20 to 100 탆. When the thickness is less than 10 탆, sufficient adhesive force and holding force can not be obtained, and when the thickness exceeds 250 탆, sufficient thermal conductivity is hardly obtained and the adhesive layer may be easily peeled off.

Meanwhile, a heat-radiating sheet according to an embodiment of the present invention includes a release layer, a release layer, and a release layer, wherein the release layer is formed on the release layer by applying a pressure-sensitive adhesive composition comprising an acrylic polymer and thermally- A coating composition in which expanded graphite powder and thermally conductive particles are dispersed in a polymer resin solution is applied on another release film to a predetermined thickness and then dried to form a graphite heat radiation layer; Lamination the graphite heat-radiating layer on the pressure-sensitive adhesive layer, and then removing each of the release films used.

The release film used in the production of the heat-radiating sheet may be a polyester film such as a polyethylene terephthalate film, an olefin-based resin film such as a polyethylene film or a polypropylene film, a polyvinyl chloride film, a polyimide film, An amide film, or a rayon film. The releasing film may be treated with a silicone releasing agent, a fluorine releasing agent and a long chain alkyl releasing agent. The thickness of the releasing film is not particularly limited,

In the production of the heat-radiating sheet, the drying process after application of each composition may be performed by hot air at a temperature of 30 to 150 ° C, for example, at 50 to 100 ° C for 5 to 30 minutes.

The heat-radiating sheet thus produced according to the embodiment of the present invention contains a polymer resin in the graphite heat-radiating layer and is flexible and has a small particle size of graphite particles dispersed therein, so that not only the thermal conductivity in the horizontal direction is excellent, The thermally conductive particles can be present and the thermal conductivity in the vertical direction can be improved.

That is, the heat-radiating sheet according to one embodiment of the present invention is high in the range of that of the horizontal thermal conductivity of 300W / m · K or more, such as 300 to 500 W / m · K, is the vertical thermal conductivity of 5W / m · K or more, for example, 5 to 8 W / m · K, which is superior to the existing heat-radiating sheet.

Accordingly, it is possible to rapidly diffuse the heat generated by attaching to the heat generating portion of electronic products such as mobile phones, tablet PCs, notebook computers, PDPs, LEDs, and LCDs.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Manufacturing example One: The adhesive layer Produce

&Lt; Preparation of acrylic polymer solution >

A reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer was charged with 70 parts by mass of butyl acrylate as the alkyl (meth) acrylate and 30 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid as the polar group- 0.05 part by mass of 4-hydroxybutyl acrylate, 0.1 part by mass of 2,2'-azobisisobutyronitrile as a thermal polymerization initiator, and 155 parts by mass of a mixed solution of toluene / ethyl acetate (3/1 by mass ratio) , The inside of the reactor was sufficiently purged with nitrogen gas, and the mixture was heated and stirred at 80 占 폚 for 3 hours to obtain an acrylic polymer solution having a solid content of 40 mass%.

&Lt; Preparation of sticky composition >

(Foral 85E, EASTMAN), boron nitride (plate-like shape, average maximum length of 18 탆, SGP (weight average particle size of 18 μm) as the thermoconductive particles) was prepared in accordance with the composition (BYK-9076, manufactured by BYK-Chemie), an isocyanate-based crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) ), MEK as a solvent was blended, and the blend was stirred in a planetary mixer for 45 minutes to prepare a tacky composition.

&Lt; Preparation of pressure-sensitive adhesive layer &

The adhesive composition was applied on the surface of the polyethylene terephthalate film treated with the silicone release agent so that the thickness became 50 탆 and dried at 80 캜 for 10 minutes to prepare an adhesive layer-forming film.

Manufacturing example 2: Graphite The heat- Produce

&Lt; Preparation of graphite heat-releasing layer-forming coating composition >

NBR type polymer (1072J, manufactured by Nippon Zeon) was dissolved in a mixed solvent of MEK: Toluene = 8: 2 at room temperature according to the composition (unit: parts by mass) shown in the following Table 1 to obtain a polymer solution having a solid content of 20 mass% Were prepared. Boron nitride (plate-like shape, average maximum length of 18 占 퐉, SGP grade, manufactured by Denka Co.), aluminum oxide (spherical shape, average particle size of 3 占 퐉) as thermal conductive particles were added to the polymer solution, (BYK-9076, manufactured by BYK-Chemie), and the mixture was stirred in a plasticizer mixer or a ball mill mixer for 50 minutes to obtain a graphite heat releasing layer-forming coating composition .

&Lt; Production of Graphite Heat-Releasing Layer &

The coating composition was applied to the surface of the polyethylene terephthalate film treated with the silicone release agent to a thickness of 100 m and then dried at 60 DEG C for 10 minutes and at 100 DEG C for 10 minutes to obtain a graphite heat- Respectively.

Example 1: Manufacture of heat-radiating sheet

The adhesive layer of the film obtained in Production Example 1 and the graphite heat-releasing layer of the film obtained in Production Example 2 were faced to each other and heat-laminated. Then, the release film adhered to each layer was removed to prepare a heat-radiating sheet.

Example 2 to 9 and Comparative Example 1 to 7

Except that the composition (unit: mass part) and thickness shown in the following Table 1 were applied, the same processes as those of Production Examples 1 and 2 and Example 1 were carried out to prepare a heat radiation sheet. In particular, in Comparative Example 7, the heat-radiating sheet was produced by forming the graphite pressing layer by pressing the expanded graphite powder with a press without containing the thermally conductive particles in the adhesive layer.

Experimental Example One:

The physical properties of the heat-radiating sheet prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

&Lt; Measurement of vertical thermal conductivity &

The vertical thermal conductivity of the heat-radiating sheet was measured according to ASTM D-5470 standard. First, after the lamination of the pressure-sensitive adhesive layer and the graphite heat-releasing layer, the specimen was cut to a size of about 50 mm in width and 110 mm in length in a thickness of about 1 mm. The release film (PET) of the specimen was peeled off, and a wrap film was attached so that no air would enter the peeled surface of the release film. The size of the wrap film may be larger than that of the specimen. Then, the thermal conductivity (unit: W / m 占 의) of the specimen was measured while the wrap film was attached. At this time, the thermal conductivity was measured by an unsteady heat line comparison method using a rapid thermal conductivity meter (trade name " QTM-500 ", manufactured by Kyoto Electronics Industrial Co., Ltd.). Silicone rubber (0.2 W / m · K), quartz (1.4 W / m · K) and zirconia (3.4 W / m · K) were used in this order. The thermal conductivity was measured three times for the same specimen, and the average value thereof was determined.

The thermal conductivity of the heat-radiating sheet in the horizontal direction was measured in accordance with the ISO Standard 22007-2 standard. First, after the lamination of the adhesive layer and the graphite heat-releasing layer, the specimen was cut to a size of 50 mm in width and 50 mm in length in a state of about 1 mm in thickness. The release film (PET) of the specimen was peeled off, and a wrap film was attached so that no air would enter the peeled surface of the release film. The size of the wrap film may be larger than that of the specimen. Then, the thermal conductivity (unit: W / m · K) was measured using the specimen having the wrap film attached thereto. At this time, the thermal conductivity was measured using a device of "TPS2500S" (Hot disk). The thermal conductivity was measured three times for the same specimen, and the average value thereof was determined.

The crack resistance of the heat-radiating sheet was evaluated according to the ASTM E290 standard. First, support the sample on the support cylinder support and bend until the bending angle is 170 degrees as L (load receiving length) = 2r (support radius) + 3t (specimen thickness), then check the sample surface for breakage or other defects .

Example Comparative Example One 2 3 4 5 6 7 8 9 One 2 3 4 5 6 7 point

Cling

layer Acrylic polymer solution Acrylic polymer solution (TSC: 40% by mass) 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 Tackifying resin Foral 85E 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Cross-linking agent Coronate L 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Boron nitride BN SGP 12 23 23 30 30 30 30 30 30 15 15 15 Aluminum oxide Alumina DAW-03 7.5 9 11 15 15 15 15 15 15 15 15 15 Dispersant BYK-9076 One One One One One One One One One One One One One One One One solvent MEK 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Thickness of adhesive layer (占 퐉) 50 50 50 25 50 100 50 50 50 50 50 50 50 50 50 40 Gra
wave
this
The

room
Heat layer NBR type polymer NBR 1072J
(TSC: 20% by mass) 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 Graphite pressing layer Graphite powder Graphite particles
DN50
(Average particle size: 64 탆) 20 25 30 Graphite powder Graphite particles
GFG75
(Average particle size 75 mu m) 20 25 30 Graphite powder Graphite particles
GFG05
(Average particle size: 5 탆) 12 12 12 12 12 12 12 12 12 Boron nitride BN SGP 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 Aluminum oxide Alumina DAW-03 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Dispersant BYK-9076 One One One One One One One One One One One One One One One Heat dissipation layer thickness (탆) 100 100 100 100 100 100 25 50 100 100 100 100 100 100 100 50 complex
synthesis
city
The Vertical thermal conductivity value (W / mK) 5.2 5.9 6.5 4.5 5.9 7.5 4.4 5.1 5.7 2.5 2.1 2.3 2.8 3.2 3.3 1.7 Horizontal thermal conductivity value (W / mK) 320 335 350 333 360 370 305 388 390 210 250 270 280 260 290 220 Crack occurrence X X X X X X X X X ○ ○ ○ ○ ○ ○ ○

※ TSC: Total solid content

As can be seen from the above Table 1, the graphite heat dissipation layers of Examples 1 to 9 having graphite heat dissipation layers in which graphite particles of a small particle size are dispersed and an adhesive layer containing thermally conductive particles, in particular, boron nitride (BN) The sheet had excellent thermal conductivity both in the horizontal direction and in the vertical direction as compared with Comparative Examples 1 to 7. In addition, the heat-radiating sheets of Examples 1 to 9 had flexibility because they contained a polymer resin in the graphite heat-radiating layer, but in the comparative example, they were not flexible and cracks were generated.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims

And a pressure-sensitive adhesive layer formed on one side of the graphite heat-radiating layer,
Wherein the graphite heat-radiating layer comprises a polymer resin and graphite particles having an average particle diameter of 1 to 20 占 퐉, and the pressure-sensitive adhesive layer comprises thermally conductive particles.

The heat-radiating sheet according to claim 1, wherein the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition comprising an acrylic polymer, thermally conductive particles and a crosslinking agent.

The heat-radiating sheet according to claim 1, wherein the thermally conductive particles comprise boron nitride.

4. The heat-radiating sheet according to claim 3, wherein the thermally conductive particles further comprise at least one selected from the group consisting of metal hydroxides, metal oxides, metal carbides, conductive carbon materials, and mixtures thereof.

The heat-radiating sheet according to claim 2, wherein the acrylic polymer is produced by polymerizing an alkyl (meth) acrylate monomer and a polar group-containing monomer.

The heat-radiating sheet according to claim 2, wherein the thermally conductive particles are blended with two or more kinds of particles having different average particle diameters or average maximum lengths.

7. The heat-radiating sheet according to claim 6, wherein the thermally conductive particles are a mixture of boron nitride having an average particle size of 10 mu m or more and aluminum oxide having an average particle size of less than 10 mu m in a ratio of 1:10 to 10: 1.

The heat-radiating sheet according to claim 1, wherein the graphite heat-radiating layer is formed from a coating composition in which expanded graphite powder and thermally conductive particles are dispersed in a polymer resin solution.

The method of claim 1, wherein the thermal conductivity in the horizontal direction from 300 to 500 W / m · K, a heat radiation sheet is the vertical thermal conductivity of 5 to 8W / m · K.