TW201323553A - Thermally conductive adhesive resin composition and thermally conductive adhesive sheet - Google Patents

Abstract

This thermally conductive adhesive resin composition contains an acrylic polymer and a metal hydroxide. The weight average molecular weight in terms of standard polystyrene of the toluene-soluble fraction of an adhesive layer, which is formed from the thermally conductive adhesive resin composition, as determined by GPC using a differential refractometer detector is 250,000 or more but less than 400,000 in the high molecular weight region where the molecular weight in terms of polystyrene is 10,000 or more, while being 5,000 or less in the low molecular weight region where the molecular weight in terms of polystyrene is less than 10,000. The adhesive layer formed from the thermally conductive adhesive resin composition has a density of 1.2-1.7 g/cm3.

Description

Thermally conductive adhesive resin composition and thermally conductive adhesive sheet

The present invention relates to a thermally conductive adhesive resin composition and a thermally conductive adhesive sheet, and more particularly to a thermally conductive adhesive resin composition and a thermally conductive adhesive sheet for use in power electronics.

In recent years, in a high-brightness LED (Light Emitting Diode) device, an electromagnetic induction heating device, or the like, a power electronic technology that converts and controls electric power by a semiconductor element is employed. In power electronics technology, in order to convert a large current into heat or the like, a material disposed on a semiconductor element is required to have high heat dissipation (high thermal conductivity). Further, the material disposed on such a semiconductor element is required to have a bonding property and a holding force in order to continue the semiconductor element.

For example, there is proposed a heat dissipation for a heat-generating electronic product formed of a pressure-sensitive adhesive composition comprising a (meth)acrylate polymer having a weight average molecular weight of 30,000 to 250,000 and a metal hydroxide. A sheet (for example, refer to Patent Document 1 below).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-285121

However, in the heat dissipation sheet for heat-generating electronic products described in Patent Document 1, the adhesion force and the holding force are not sufficient.

An object of the present invention is to provide a thermally conductive adhesive sheet having excellent thermal conductivity, adhesion, and retention, and a thermally conductive adhesive resin composition formed therewith.

The thermally conductive adhesive resin composition of the present invention is characterized in that it contains an acrylic polymer and a metal hydroxide, and is equipped with a GPC (Gel Permeation Chromatograph) equipped with a differential refractometer detector. The standard polystyrene-equivalent weight average molecular weight obtained by measuring the toluene-soluble component of the adhesive layer formed of the above-mentioned thermally conductive adhesive resin composition is 250,000 or more in a polymer region having a polystyrene-equivalent molecular weight of 10,000 or more. The amount of the adhesive layer formed of the above thermally conductive adhesive resin composition is 1.2 to 1.7 g/cm ^{3 in} the low molecular region of which the molecular weight of polystyrene is less than 10,000 is 5,000 or less.

Further, in the thermally conductive adhesive resin composition of the present invention, it is preferred that the peak area ratio of the low molecular region to the polymer region is 0.85 to 1.30 in a chromatogram obtained by the GPC measurement.

Moreover, in the thermally conductive adhesive resin composition of the present invention, it is preferred to further contain an adhesion-imparting resin.

Further, in the thermally conductive adhesive resin composition of the present invention, it is preferred that the thermal conductivity of the adhesive layer formed of the thermally conductive adhesive resin composition is 0.3 W/m. K or more.

Further, in the thermally conductive adhesive resin composition of the present invention, it is preferred that the acrylic polymer is composed of an acrylate having a carbon number of 2 to 14 and containing The functional group-containing acrylate-containing monomer is obtained by reacting, and the ratio of the acrylate is 70 to 99.9% by mass based on the monomer, and the ratio of the functional group-containing acrylate is relative to the monomer. 0.01 to 10% by mass.

Further, the thermally conductive adhesive sheet of the present invention is characterized by comprising a substrate and an adhesive layer comprising the thermally conductive adhesive resin composition laminated on at least one side of the substrate.

Further, in the thermally conductive adhesive sheet of the present invention, it is preferable that the peeling adhesion force at the peeling angle of 180 degrees and the peeling speed of 300 mm/min with respect to the stainless steel sheet after the stainless steel sheet is 4 N/ 20 mm or more.

Further, in the thermally conductive adhesive sheet of the present invention, it is preferable that the thickness of the adhesive layer is 30 to 200 μm.

Further, in the thermally conductive adhesive sheet of the present invention, preferably, the substrate is formed of a plastic film, and the substrate has a thickness of 12 to 50 μm.

Since the thermally conductive adhesive resin composition of the present invention contains a metal hydroxide, the thermally conductive adhesive sheet formed of the thermally conductive adhesive resin composition of the present invention is excellent in thermal conductivity. Therefore, the thermally conductive adhesive sheet formed of the thermally conductive adhesive resin composition of the present invention can be used for various heat dissipation applications.

Further, in the thermally conductive adhesive resin composition of the present invention, the standard polystyrene obtained by the toluene-soluble fraction of the adhesive layer formed of the thermally conductive adhesive resin composition of the present invention is measured by GPC equipped with a differential refractometer detector. The converted weight average molecular weight is 250,000 or more and less than 400,000 in a polymer region having a molecular weight of 10,000 or more in terms of polystyrene, and is 5,000 or less in a low molecular region having a molecular weight of less than 10,000 in terms of polystyrene, and the adhesive layer is The density is 1.2~1.7 g/cm ³ . Therefore, the heat conductive adhesive sheet formed therefrom has excellent adhesion and retention.

Therefore, when the thermally conductive adhesive sheet formed of the thermally conductive adhesive resin composition of the present invention is disposed so as to cover the heat-dissipating object, it is possible to more reliably conduct the heat-dissipating object while exhibiting an excellent adhesive force and a holding force. heat.

The thermally conductive adhesive resin composition of the present invention contains an acrylic polymer and a metal hydroxide.

The acrylic polymer is obtained by reacting a monomer containing an acrylate and a functional group-containing acrylate-containing monomer.

The acrylate is an alkyl methacrylate and/or an alkyl acrylate, and specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. Isopropyl acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate Ester, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (methyl) ) isooctyl acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate , dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, (meth)acrylic acid Cetyl ester, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, hexadecyl (meth) acrylate, eicosyl (meth) acrylate, etc. (meth)acrylic acid Number 1 ~ 20 (C _1-20) alkyl esters.

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

The acrylate may be used alone or in combination of two or more. Preferable examples thereof include a combination of different kinds of C _4-9 alkyl (meth)acrylates, and more preferably C _4-6 alkyl (meth)acrylate and C _7-9 alkyl (meth)acrylate. The base ester is used in combination, and specific examples thereof include a combination of butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate.

The proportion 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 proportion 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 alkyl (meth) acrylate. It is preferably 15 to 35 parts by mass, and the compounding ratio of the C _7-9 alkyl (meth)acrylate is, for example, 60 to 90 parts by mass, preferably 65 to 85 parts by mass.

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

As the functional group-containing acrylate, for example, a hydroxy group-containing propylene can be cited. An acid ester, an acrylate containing a sulfonic acid group, an acrylate containing an amine group, an acrylate containing a glycidyl group, and the like.

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

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

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

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

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

These functional group-containing acrylates may be used alone or in combination of two or more.

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

When the blending ratio of the functional acrylate-containing acrylate exceeds the above upper limit, the cohesive force becomes too high, and the adhesion of the thermally conductive adhesive sheet formed of the thermally conductive adhesive resin 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 case of the monomer, various characteristics such as cohesive force are sought. High, it may also be desirable to contain a copolymerizable monomer copolymerizable with the acrylate.

Examples of the copolymerizable monomer include a carboxyl group-containing monomer such as (meth)acrylic acid, itaconic acid, maleic acid, crotonic acid, and maleic anhydride, or an acid anhydride thereof; for example, (methyl) ) acrylamide, N,N-dimethyl(meth)acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N- A monomer containing a guanamine group such as butoxymethyl (meth) acrylamide; a vinyl ester such as vinyl acetate; an aromatic vinyl compound such as styrene or vinyl toluene; for example, (meth) propylene Nitrile; for example, N-(methyl) propylene A porphyrin; for example, N-vinyl-2-pyrrolidone or the like.

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

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

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

When the monomer is reacted, for example, a monomer containing an acrylate, a functional acrylate-containing, and optionally a copolymerizable monomer is polymerized.

Further, examples of the method of polymerizing the monomer component 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 mixing a monomer component in a solvent, and then 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 proportion 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 component.

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 organic peroxides such as peroxycarbonate, ketone peroxide, peroxyketal, hydrogen peroxide, dialkyl peroxide, dinonyl peroxide, and peroxyester. Oxide.

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.

As a polymerization initiator, an azo polymerization initiator is preferable.

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

The viscosity of the acrylic polymer solution is, for example, 0.1 to 100 Pa at 30 ° C. s, preferably 0.5 to 50 Pa. s.

When the viscosity of the monomer mixture does not satisfy the above range, moldability or workability may be insufficient.

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

If the blending ratio of the acrylic polymer does not satisfy the above range, there is condensation. Convergence and subsequent forces become insufficient.

The metal hydroxide is formulated in the thermally conductive adhesive resin composition in order to impart thermal conductivity.

Examples of the metal hydroxide include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, nickel hydroxide, cobalt hydroxide, tin hydroxide, zinc hydroxide, copper hydroxide, barium hydroxide, and titanium hydroxide. .

As the metal hydroxide, aluminum hydroxide is preferred.

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

The primary average particle diameter of the metal hydroxide is, for example, 0.1 to 20 μm, preferably 1 to 10 μm. The primary average particle diameter can be measured, for example, by a laser particle size analyzer.

The compounding ratio of the metal hydroxide 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 metal hydroxide 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.

Further, in the thermally conductive adhesive resin composition, for example, an adhesion-imparting agent can be formulated.

The adhesive-imparting resin is blended in the thermally conductive adhesive resin composition as needed in order to impart an adhesive force.

Examples of the adhesion-imparting resin include a petroleum resin, a terpene resin, a kumquat-anthraquinone resin, a styrene resin, a rosin resin, an alkylphenol resin, and a xylene resin.

The adhesive-imparting resin is preferably based on the reason that the heating stability is excellent. A rosin-type resin is mentioned.

The weight average molecular weight of the adhesion-imparting resin (method according to the method described later) is, for example, 5,000 or less, preferably 100 to 4,000, and 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, there is a case where the adhesion force is insufficient.

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

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

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

When the blending ratio of the tackifying resin exceeds the above upper limit, the cohesive force may be insufficient. On the other hand, if the lower limit is not reached, there is a case where the adhesion force is insufficient.

Further, in the thermally conductive adhesive resin composition, a crosslinking agent, an anti-aging agent, an antioxidant, a processing aid, a stabilizer, an antifoaming agent, a flame retardant, a tackifier, and a pigment may be added in an appropriate ratio as needed. And other additives.

The crosslinking agent is blended in the thermally conductive adhesive resin composition as needed in order to increase the cohesive force of the thermally conductive adhesive sheet.

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, for example, toluene diisocyanate. An aromatic diisocyanate such as an ester or xylene diisocyanate; an alicyclic diisocyanate such as isophorone diisocyanate; an aliphatic diisocyanate such as hexamethylene diisocyanate; or a modified product such as the isocyanate.

In addition, examples of the isocyanate-based crosslinking agent include isocyanate adducts such as toluene diisocyanate adduct of trimethylolpropane (manufactured by Nippon Polyurethane Industry, 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.

The thermally conductive adhesive resin composition can be obtained by blending and mixing an additive such as the acrylic polymer, the metal hydroxide, the adhesion-imparting agent, and the optional crosslinking agent prepared in the above ratio in the above ratio.

The thermally conductive adhesive sheet can be obtained by laminating an adhesive layer containing a thermally conductive adhesive resin composition on the surface of a substrate.

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

In FIG. 1(a), the thermally conductive adhesive sheet 11 includes a substrate 2 and an adhesive layer 3 laminated on one surface of the substrate 2.

The thickness of the adhesive layer 3 is, for example, 30 to 200 μm, preferably 30 to 100 μm.

When the thickness of the adhesive layer 3 exceeds the above upper limit, thermal conductivity may be insufficient. On the other hand, if the lower limit is not reached, there is a case where the adhesion force and the holding force are insufficient.

The base material 2 is formed of, for example, a polyester film (for example, a polyethylene terephthalate film), an olefin resin film (for example, a polyethylene film, a polypropylene film, or the like), a polyvinyl chloride film, and a poly A plastic film (synthetic resin film) such as a ruthenium film, a polyamide film (nylon film) or a spiral film; a porous sheet such as paper or nonwoven fabric; and a metal foil such as aluminum foil. It is preferably formed from a plastic film.

Further, the surface of the substrate 2 may be subjected to a release treatment.

The thickness of the substrate 2 is, for example, 12 to 50 μm, preferably 12 to 40 μm.

When the adhesive layer 3 is laminated on the substrate 2, for example, the thermally conductive adhesive resin composition is applied to one surface of the substrate 2, and then thermally cured.

Examples of the coating method of the thermally conductive adhesive resin composition include a roll coating method, a contact roll coating method, a dip roll coating method, a gravure coating method, a bar coating method, and a reverse roll coating method. Cloth method, roll brushing method, spray coating method, knife coating method, air knife coating method, curtain coating method, lip coating method, die coating method, wet laminating roll coating method Wait.

When the thermally conductive adhesive resin composition is thermally cured, for example, the thermally conductive adhesive resin composition is heated.

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.

Further, on the surface of the thermally conductive adhesive resin composition coated on the surface of the substrate 2, a protective sheet 4 indicated by an imaginary line may be additionally provided to Protect its surface. The protective sheet 4 is the same as the base material 2 described above.

In addition, the standard polystyrene-equivalent weight average molecular weight obtained by measuring the toluene-soluble fraction of the adhesive layer 3 by GPC equipped with a differential refractometer detector is a polymer region having a polystyrene-converted molecular weight of 10,000 or more. 250,000 or more and less than 400,000, and in the low molecular region where the molecular weight of polystyrene is less than 10,000, it is 5,000 or less.

When the weight average molecular weight does not satisfy the above range in the polymer region, the cohesive force is lowered, and the holding force of the thermally conductive adhesive sheet 11 is insufficient. On the other hand, when the weight average molecular weight does not satisfy the above range in the low molecular region, the adhesion of the thermally conductive adhesive sheet 11 is insufficient.

The toluene soluble fraction of the adhesive layer 3 was obtained in the following manner.

For example, first, a specific amount (for example, 300 mg) of the adhesive layer 3 is accurately weighed, and immersed in 100 parts by mass of the adhesive layer 3, for example, 50 ml of toluene at 25 ° C for 168 hours to dissolve the adhesive layer 3 in toluene. in. Thereafter, the impregnation liquid is filtered, for example, using a filter of 80 mesh, thereby removing toluene-insoluble matter, thereby preparing a toluene-soluble fraction.

Then, when the weight average molecular weight of the toluene soluble fraction of the adhesive layer 3 is obtained, it can be calculated by measuring the adhesive layer by a gel permeation chromatography (GPC) equipped with a differential refractometer detector (RI). The molecular weight distribution of the soluble fraction of toluene, from the obtained chromatogram (chart), based on the calibration curve of standard polystyrene, respectively, the polymer region with a molecular weight of 10,000 or more in standard polystyrene conversion and less than 10,000 The weight average molecular weight of the peak area in the low molecular region.

In the above polymer region, the weight average molecular weight is preferably 270,000 or more, more preferably 320,000, and, for example, less than 400,000; in the above low molecular region, the weight average molecular weight is preferably from 100 to 5,000, and further preferably. It is 500~4000.

Further, in the chromatogram obtained by the GPC measurement, the peak area ratio of the low molecular region to the polymer region (hereinafter sometimes referred to as low molecular weight/polymer ratio) is, for example, 0.85 to 1.30, preferably. It is 0.89~1.26.

In the chromatogram obtained by the GPC measurement, when the peak area ratio of the low molecular region to the polymer region exceeds the upper limit, the cohesive force decreases, and the holding force of the thermally conductive adhesive sheet 11 does not become Sufficient situation. On the other hand, if the lower limit is not reached, the adhesion of the thermally conductive adhesive sheet 11 may be insufficient.

The low molecular/polymer ratio can be obtained from the chromatogram obtained by the above GPC measurement, and the peak area included in the low molecular region having a molecular weight of less than 10,000 in terms of polystyrene is 10,000 or more with respect to the molecular weight in terms of polystyrene. The ratio (area ratio) of the peak areas included in the polymer region was calculated.

Further, the density of the adhesive layer 3 is, for example, 1.2 to 1.7 g/cm ³ , preferably 1.3 to 1.7 g/cm ³ , and more preferably 1.5 to 1.7 g/cm ³ .

When the density of the adhesive layer 3 exceeds the above upper limit, the adhesion of the thermally conductive adhesive sheet 11 becomes insufficient. On the other hand, if the lower limit is not reached, the formability of the thermally conductive adhesive sheet 11 is lowered.

Moreover, the thermal conductivity of the adhesive layer 3 is, for example, 0.3 W/m. Above K, preferably 0.4 W/m. Above K, for example, also 1.0 W/m. Below K.

And, after the thermally conductive adhesive sheet 11 is attached to the stainless steel plate, the relative The peeling adhesion force when the stainless steel sheet is peeled at a peeling angle of 180 degrees and a peeling speed of 300 mm/min is, for example, 4 N/20 mm or more, preferably 6 N/20 mm or more, and further preferably 9 N/20 mm. More preferably, it is 10 N/20 mm or more, and most preferably 11 N/20 mm or more, for example, 20 N/20 mm or less.

When the peeling adhesion force of the heat conductive adhesive sheet 11 does not satisfy the above range, there is a case where the adhesion force to the adherend is insufficient.

Further, as described above, the thermally conductive adhesive sheet 11 is excellent in thermal conductivity. Therefore, the thermally conductive adhesive sheet 11 formed of the thermally conductive adhesive resin composition of the present invention can be used for various heat dissipation applications.

Moreover, as described above, the thermally conductive adhesive sheet 11 is excellent in the adhesive force and the holding power. Therefore, when the thermally conductive adhesive sheet 11 is placed so as to coat a heat dissipating object such as a semiconductor, it is possible to more reliably conduct heat generated by the heat radiating object while exhibiting an excellent adhesion force and a holding force.

Examples of the heat radiation target to which the thermally conductive adhesive sheet 11 is attached may be an electronic component or an electronic component mounted on a substrate.

Examples of the electronic component include an IC (integrated circuit) wafer, a capacitor, a coil, a resistor, and an electronic component of a light-emitting diode. Further, electronic components such as a thyristor (rectifier), a motor component, an inverter, and a power transmission component may be used.

Further, examples of the heat radiation target include an LED heat sink substrate and a battery heat sink.

Furthermore, in the embodiment of FIG. 1(a), the adhesive layer 3 is laminated on one surface of the substrate 2, but as shown in FIG. 1(b), the adhesive layer 3 may be laminated on the substrate 2. The thermally conductive adhesive sheet 12 is formed on both sides.

[Examples]

The present invention will be more specifically illustrated by the following examples and comparative examples, but the present invention is not limited by the examples and comparative examples.

Examples 1 to 5 and Comparative Examples 1 to 5 (Preparation of thermally conductive adhesive resin composition)

AIBN (trade name, 2,2'-azo) was 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. After dissolving uniformly, 0.08 g of bis-isobutyronitrile and Wako Pure Chemical Industries, Ltd. and 150 g of toluene were 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 , measured temperature 30 ° C) was about 25 Pa. s.

Then, according to the formulation of Table 1, an adhesive resin, a metal hydroxide, and a crosslinking agent were added to the acrylic polymer solution to prepare a thermally conductive adhesive resin composition.

In the table, the details of each component are described below.

Rosin resin: trade name "SUPER ESTER", average weight molecular weight 1520, softening point (global method) 95~105 °C, manufactured by Arakawa Chemical Industry Co., Ltd.

Aluminium hydroxide: trade name "Higilite H-32", 1 time average particle size 8 μm, manufactured by Showa Denko

Isocyanate crosslinking agent: trade name "Coronate L", toluene diisocyanate adduct of trimethylolpropane, solid content of 75 mass%, manufactured by Nippon Polyurethane Industry Co., Ltd.

(Production of thermally conductive adhesive sheet)

The thermally conductive adhesive resin composition was introduced into a wet laminating roll coater by a test tube (having an inner diameter of 19 mm and a length of about 1.5 m), and was applied to Diafoil MRF38 so as to have a thickness of 50 μm after hardening. Trade name, polyethylene terephthalate substrate, thickness 38 μm, manufactured by Mitsubishi Plastics Co., Ltd.).

Thereafter, the thermally conductive adhesive resin composition was heated at 110 ° C for 3 minutes to be thermally cured, whereby an adhesive layer was formed.

Then, Diafoil MRN38 (trade name, protective sheet, thickness: 38 μm, manufactured by Mitsubishi Plastics Co., Ltd.) was placed on the surface of the thermally conductive adhesive resin composition to prepare a thermally conductive adhesive sheet.

(Evaluation)

With respect to the thermally conductive adhesive sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 5, (1) the weight average molecular weight and the low molecular region in the polymer region and the low molecular region of the toluene-soluble fraction obtained by GPC were evaluated. Relative to high scores Peak area ratio (low molecular/polymer ratio), (2) density, (3) thermal conductivity, (4) peeling adhesion force, and (5) holding power of the subregion.

The details of each evaluation are described below.

(1) The weight average molecular weight in the polymer region and the low molecular region of the toluene-soluble fraction obtained by GPC and the peak area ratio (low molecular/polymer ratio) of the low molecular region to the polymer region

300 mg of the adhesive layer was poured into 50 ml of toluene, and immersed at 25 ° C for 168 hours to dissolve the adhesive layer in toluene. Thereafter, the impregnation liquid was filtered through a nylon mesh of 80 mesh to thereby remove toluene-insoluble matter, thereby preparing a toluene-soluble fraction.

A sample was obtained by removing toluene from the obtained toluene-soluble fraction, and the sample was measured by GPC under the following measurement conditions, and the polymer region having a molecular weight of 10,000 or more in terms of polystyrene and the molecular weight in terms of polystyrene were not as low as 10,000. The weight average molecular weight in terms of polystyrene was calculated in the molecular region.

GPC measurement conditions

GPC measuring device: HCL-8120GPC (manufactured by TOSO)

Pipe column: TSKgel SuperHZM-H/HZ4000/HZ3000/HZ2000, 6.0 (ID) mm × 150 (L) mm × 4 (manufactured by Tosoh Corporation)

Column temperature: 40 ° C

Eluent: tetrahydrofuran

Flow rate: 0.6 ml/min

Detector: differential refractometer detector

Sample concentration: 1 mg/ml

Injection volume: 20 μl

Calibration curve: polyethylene

Further, in the chromatogram obtained by the above GPC measurement, the peak area ratio of the low molecular region to the polymer region was determined.

The results are shown in Table 1.

Further, a GPC chromatogram (GPC differential molecular weight distribution curve, horizontal axis: weight average molecular weight in terms of standard polystyrene) obtained by measuring the toluene soluble fraction of the adhesive layer of Example 1 is shown in Fig. 2 .

(2) Density

The density of the adhesive layer 3 was evaluated.

The thermally conductive adhesive sheet was cut into 50 × 50 mm, and after peeling off the protective sheet, the thickness and weight of the adhesive layer were measured, and the density was calculated by the following calculation formula.

Density (g/cm ³ ) = weight of the adhesive layer (g) / (area of the adhesive layer (cm ² ) × thickness of the adhesive layer (cm))

The results are shown in Table 1.

(3) Thermal conductivity

In the measurement of the thermal conductivity, the thermal property evaluation device shown in Fig. 3 was used.

Specifically, a pair of blocks (also sometimes referred to as rods) L made of aluminum (A5052, thermal conductivity: 140 W/m.K) formed as a cube having a side of 20 mm, The adhesive layer 3 (20 mm × 20 mm) is sandwiched, and a pair of blocks L are bonded by the adhesive layer 3.

Then, the pair of blocks L are placed between the heat generating body (heater unit) H and the heat radiating body (the cooling base plate configured to circulate the inside of the cooling water) C between the upper and lower blocks. Specifically, heat is placed on the block L on the upper side. In the body H, the heat sink C is disposed below the lower block L.

At this time, one of the pair of blocks L bonded by the adhesive layer 3 is located between the one of the through heat generating body H and the heat radiating body C and the pressure adjusting screw T. Further, a load cell R is disposed between the pressure adjustment screw T and the heating element H, and is configured to measure the pressure when the pressure adjustment screw T is tightened, and the pressure is used as the pressure applied to the adhesive layer 3.

Further, three probes P (diameter: 1 mm) of the contact type displacement meter are provided so as to penetrate the lower block L and the adhesive layer 3 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 block L on the upper side, and the interval between the upper and lower blocks L (the thickness of the adhesive layer 3) can be measured.

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 portion of the heating element H, and the temperature sensor D is attached to each of the five portions of each block L at intervals of 5 mm in the vertical direction.

In the measurement system, the pressure adjusting screw T was first tightened, pressure was applied to the adhesive layer 3, and the temperature of the heating element H was set to 80 ° C, and the cooling water of 20 ° C was circulated in the radiator C.

Then, after the temperature of the heating element H and the upper and lower blocks L are stabilized, the temperature of the upper and lower blocks L is measured by each temperature sensor D, and the thermal conductivity (W/m.K) of the upper and lower blocks L and The temperature gradient calculates the amount of heat passing through the adhesive layer 3, and calculates the temperature at the interface between the upper and lower blocks L and the adhesive layer 3. Then, the thermal conductivity (W/m.K) at this pressure was calculated using the equivalent value and using the thermal conductivity equation (Fourier's law) described below.

Q=-λgradT

R=L/λ

Q: Heat flux per unit area

gradT: temperature gradient

L: thickness of the adhesive layer

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 adhesive layer 3 was measured.

The results are shown in Table 1.

(4) peeling force

After the thermally conductive adhesive sheet was cut to a size of 20 mm × 100 mm, the protective sheet was peeled off. Then, the peeling surface of the thermally conductive adhesive sheet was placed on a stainless steel (SUS304BA) plate at 23 ° C and 50% RH, and the roller was rubbed once with a 2 kg roller to bond the thermally conductive adhesive sheet. On stainless steel.

Thereafter, it was allowed to stand in an environment of 23° C. and 50% RH for 30 minutes to stabilize (adhered) the adhering (subsequent) state, and then peeled off at a peeling speed of 300 mm/min with respect to the stainless steel sheet at a peeling angle of 180 degrees. The adhesion layer and the substrate were used to measure the peel strength.

The results are shown in Table 1.

Further, in Comparative Example 3, since it could not be attached to a stainless steel plate, measurement was impossible.

(5) Retention

After the thermally conductive adhesive sheet 11 is cut to a size of 20 mm × 10 mm, A sample was obtained by attaching to a 25 μm thick PET (Polyethylene Terephthalate, polyethylene terephthalate) film. Then, in a 23 ° C, 50% RH environment, the peeling surface of the upper end portion of the sample of 10 mm × 20 mm was placed at the lower end of the stainless steel (SUS304BA) plate 20, and the roller was reciprocated once using a 2 kg roller. This places the thermally conductive adhesive sheet 11 against the stainless steel plate 20.

Thereafter, it was allowed to stand in an environment of 40 ° C for 30 minutes to stabilize (adhered) the adhering state, and then the upper end portion of the stainless steel plate 20 was fixed, and 300 g of lead was suspended at the lower end of the sample at 40 ° C. hammer. Then, it was investigated whether the sample fell off when placed at 40 ° C for 1 hour.

Furthermore, the invention described above is provided as an exemplified embodiment of the invention, which is merely illustrative and not to be construed as limiting. Modifications of the present invention which are obvious to those skilled in the art are included in the scope of the following patent application.

[Industrial availability]

The thermally conductive adhesive resin composition and the thermally conductive adhesive sheet of the present invention can be used for heat dissipation of various industrial parts.

2‧‧‧Substrate

3‧‧‧Adhesive layer

4‧‧‧Protected sheet

11‧‧‧ Thermally Conductive Adhesive Sheet

12‧‧‧ Thermally Conductive Adhesive Sheet

20‧‧‧Stainless steel plate

C‧‧‧heat radiator

D‧‧‧Temperature Sensor

H‧‧‧heating body

L‧‧‧ Block

P‧‧‧ probe

R‧‧‧ load weight

T‧‧‧Pressure adjustment screw

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing an embodiment of a thermally conductive adhesive sheet of the present invention, wherein (a) shows an embodiment in which an adhesive layer is formed on one of the substrate layers, and (b) shows an adhesive layer on two areas of the substrate. Implementation form.

Fig. 2 is a chromatogram showing the GPC obtained by measuring the toluene soluble fraction of the adhesive layer of Example 1.

Figure 3 is an illustration of a thermal characteristic evaluation device for measuring thermal conductivity in the examples. Figure (a) shows a front view and (b) shows a side view.

Fig. 4 is a cross-sectional view showing a method of measuring the holding force.

Claims (9)

A thermally conductive adhesive resin composition characterized in that it contains an acrylic polymer and a metal hydroxide, and an adhesive layer formed of the above thermally conductive adhesive resin composition is measured by GPC equipped with a differential refractometer detector. The weight average molecular weight of the standard polystyrene equivalent of the polystyrene-converted molecular weight of 10,000 or more in the polystyrene-converted molecular weight of 10,000 or more is less than 400,000, and the molecular weight in polystyrene is less than 10,000. In the molecular region, it is 5,000 or less, and the density of the adhesive layer formed of the above thermally conductive adhesive resin composition is 1.2 to 1.7 g/cm ³ . The thermally conductive adhesive resin composition of claim 1, wherein in the chromatogram obtained by the GPC measurement, a peak area ratio of the low molecular region to the polymer region is 0.85 to 1.30. The thermally conductive adhesive resin composition of claim 1, which further comprises an adhesion-imparting resin. The thermally conductive adhesive resin composition of claim 1, wherein the adhesive layer formed of the above thermally conductive adhesive resin composition has a thermal conductivity of 0.3 W/m. K or more. The thermally conductive adhesive resin composition of claim 1, wherein the acrylic polymer is obtained by reacting a acrylate having a carbon number of 2 to 14 and a functional acrylate-containing monomer having a functional group, the acrylic acid The proportion of the ester is 70 to 99.9% by mass relative to the above monomer. The compounding ratio of the functional group-containing acrylate is 0.01 to 10% by mass based on the above monomer. A thermally conductive adhesive sheet comprising: a substrate and an adhesive layer comprising a thermally conductive adhesive resin composition laminated on at least one side of the substrate; the thermally conductive adhesive resin composition comprising an acrylic polymer and A metal hydroxide, a standard polystyrene-equivalent weight average molecular weight obtained by measuring a toluene soluble fraction of an adhesive layer formed of the above thermally conductive adhesive resin composition by GPC equipped with a differential refractometer detector to polyphenylene In the polymer region having a molecular weight of 10,000 or more in terms of ethylene, it is 250,000 or more and less than 400,000, and in a low molecular region having a molecular weight of less than 10,000 in terms of polystyrene, it is 5,000 or less, and the adhesion is formed by the above thermally conductive adhesive resin composition. The density of the layers is 1.2 to 1.7 g/cm ³ . The thermally conductive adhesive sheet according to claim 6, wherein after the stainless steel sheet, the peeling adhesion force at the peeling angle of 180 degrees and the peeling speed of 300 mm/min with respect to the stainless steel sheet is 4 N/20 mm or more. The thermally conductive adhesive sheet of claim 6, wherein the adhesive layer has a thickness of 30 to 200 μm. The thermally conductive adhesive sheet according to claim 6, wherein the substrate is formed of a plastic film, and the substrate has a thickness of 12 to 50 μm.