KR20140101739A - Thermally conductive adhesive resin composition and thermally conductive adhesive sheet - Google Patents

Abstract

The thermally conductive adhesive resin composition of the present invention is a thermally conductive pressure-sensitive adhesive resin composition containing an acrylic polymer and a metal hydroxide. The weight average molecular weight in terms of standard polystyrene obtained by measuring the toluene soluble component of the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition by GPC equipped with a differential refractometer detector is from 250000 to less than 400000 in a polymer region having a molecular weight of 10,000 or more in terms of polystyrene, Or less in a low molecular region having a converted molecular weight of less than 10,000. The density of the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition is 1.2 to 1.7 g / cm 3.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a thermally conductive adhesive resin composition and a thermally conductive pressure-

TECHNICAL FIELD The present invention relates to a thermally conductive pressure-sensitive adhesive resin composition and a thermally conductive pressure-sensitive adhesive sheet, and more particularly to a thermally conductive pressure-sensitive adhesive resin composition and a thermally conductive pressure-sensitive adhesive sheet used in power electronics technology.

BACKGROUND ART [0002] Recently, in high-brightness LED devices, electromagnetic induction heating devices and the like, power electronics technologies for converting and controlling electric power by semiconductor devices are employed. In the power electronics technology, in order to convert a large current into heat or the like, a material disposed in a semiconductor device is required to have high heat radiation property (high thermal conductivity). In addition, adhesiveness and retention force are also required for the material disposed in such a semiconductor element in order to continue the adhesion to the semiconductor element.

For example, there has been proposed a heat-radiating sheet for an exothermic electronic product formed from a pressure-sensitive adhesive composition containing a (meth) acrylate-based polymer having a weight average molecular weight of 30000 to 250000 and a metal hydroxide See Patent Document 1 below).

Japanese Patent Application Laid-Open No. 2002-285121

However, in the heat-radiating sheet for a heat-generating electronic product described in Patent Document 1, the adhesive force and the holding power thereof are insufficient.

An object of the present invention is to provide a thermally conductive pressure-sensitive adhesive sheet excellent in thermal conductivity, adhesive force and holding force, and a thermally conductive pressure-sensitive adhesive resin composition for forming the same.

The thermally conductive pressure-sensitive adhesive resin composition of the present invention is a thermally conductive pressure-sensitive adhesive resin composition containing an acrylic polymer and a metal hydroxide. The thermally conductive pressure-sensitive adhesive resin composition of the present invention is measured by GPC equipped with a differential refractometer In a low molecular weight region in which the weight average molecular weight in terms of polystyrene is less than or equal to 250000 and less than 400000 in a high molecular weight region having a molecular weight of 10,000 or more in terms of polystyrene and less than 10000 in terms of polystyrene is 5,000 or less, And a density of 1.2 to 1.7 g / cm < 3 >.

In the thermally conductive pressure-sensitive adhesive resin composition of the present invention, it is preferable that the peak area ratio of the low-molecular region to the high molecular region in the chromatogram obtained by the GPC measurement is from 0.85 to 1.30.

Further, in the thermally conductive pressure-sensitive adhesive resin composition of the present invention, it is preferable to further contain a tackifier resin.

In the thermally conductive adhesive resin composition of the present invention, it is preferable that the adhesive layer formed of the thermally conductive adhesive resin composition has a thermal conductivity of 0.3 W / m · K or more.

Further, in the thermally conductive pressure-sensitive adhesive resin composition of the present invention, the acrylic polymer is obtained by reacting a monomer containing an acrylate having 2 to 14 carbon atoms and a functional group-containing acrylate containing a functional group, It is preferable that the content of the functional group-containing acrylate is from 70 to 99.9 mass% based on the monomer, and the blend ratio of the functional group-containing acrylate is from 0.01 to 10 mass% with respect to the monomer.

Further, the thermally conductive pressure-sensitive adhesive sheet of the present invention is characterized by comprising a base material and an adhesive layer comprising the aforementioned thermally conductive pressure-sensitive adhesive resin composition laminated on at least one side of the base material.

In addition, in the thermally conductive pressure-sensitive adhesive sheet of the present invention, it is preferable that the adhesive strength to peel adhesion to the stainless steel sheet after peeling at a peel rate of 300 mm / min at a peel angle of 180 degrees after adhering to the stainless steel sheet is 4N / 20 mm or more.

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, it is preferable that the thickness of the pressure-sensitive adhesive layer is 30 to 200 占 퐉.

Further, in the thermally conductive pressure-sensitive adhesive sheet of the present invention, it is preferable that the substrate is formed of a plastic film, and the thickness of the substrate is 12 to 50 mu m.

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

The thermally conductive pressure-sensitive adhesive resin composition of the present invention has a weight average molecular weight in terms of standard polystyrene obtained by measuring a toluene-soluble fraction of the pressure-sensitive adhesive layer formed from the thermally conductive pressure-sensitive adhesive resin composition of the present invention by GPC equipped with a differential refractometer In a low molecular weight region having a polystyrene reduced molecular weight of less than 10000, and a density of the pressure-sensitive adhesive layer of 1.2 to 1.7 g / cm < 3 >. As a result, the thermally conductive pressure-sensitive adhesive sheet formed therefrom is excellent in adhesive force and holding force.

Therefore, when the thermally conductive pressure-sensitive adhesive sheet formed of the thermally conductive pressure-sensitive adhesive resin composition of the present invention is disposed so as to cover the heat-radiating object, it is possible to more reliably conduct the heat generated by the heat- have.

1 is a cross-sectional view of one embodiment of a thermally conductive pressure-sensitive adhesive sheet of the present invention. Fig. 1 (a) is an embodiment in which an adhesive layer is laminated on one side of a substrate, Fig. 1 (b) An adhesive layer is laminated.
Fig. 2 shows the chromatogram of GPC measured for the toluene-soluble fraction of the adhesive layer of Example 1. Fig.
Fig. 3 is an explanatory view of a thermal characteristic evaluation apparatus for measuring the thermal conductivity in the embodiment, Fig. 3 (a) is a front view, and Fig. 3 (b) is a side view.
4 shows a cross-sectional view for explaining a method of measuring the holding force.

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 a functional group.

As the alkyl acrylate, alkyl methacrylate and / or alkyl acrylate, specifically, there may be mentioned methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (Meth) acrylate, isobutyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) (Meth) acrylate, octyl (meth) acrylate, octyl (meth) acrylate, isooctyl (Meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, )acryl Sites, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) having 1 to 20 carbon atoms, such as acrylate, eicosyl (meth) acrylate (C _{1 -20} ) alkyl (meth) acrylate.

The acrylate is preferably C _{2 -14} alkyl (meth) acrylate, more preferably C _{4 -9} alkyl (meth) acrylate.

The acrylate may be used alone or in combination of two or more. Preferably a combination of different types of C _{4 -9} alkyl (meth) acrylate may be mentioned a combination of, more preferably C _4-6 alkyl (meth) acrylates and C _{7 -9} alkyl (meth) acrylate Specific examples thereof include the combination of butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.

Acrylate is, for example, 70 to 99.9 mass%, preferably 80 to 98 mass%, and more preferably 85 to 97 mass% with respect to the monomer.

When different types of acrylates are used in combination, the blending ratio of, for example, C _{4 -6} alkyl (meth) acrylate relative to 100 parts by mass of the alkyl (meth) acrylate is, for example, 10 to 40 mass parts, preferably from 15 and to 35 parts by mass, C _{7 -9} alkyl (meth) acrylate, a mixing ratio of, for example, to 60 to 90 parts by weight, preferably from 65 to 85 parts by mass.

The functional group-containing acrylate containing a functional group is contained in the thermally conductive pressure-sensitive adhesive resin composition in order to introduce a crosslinking point for thermally crosslinking the monomer. By polymerizing the functional group-containing acrylate, it is possible to improve the adhesion to an adherend.

Examples of the acrylate containing a functional group include a hydroxyl group-containing acrylate, a sulfonic acid group-containing acrylate, an amino group-containing acrylate, and a glycidyl group-containing acrylate.

Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, (Meth) acrylate, and the like.

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

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

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

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

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

The blending ratio 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.

If the compounding ratio of the functional group-containing acrylate exceeds the upper limit, the cohesive force becomes too high, and the adhesive force of the thermally conductive pressure-sensitive adhesive sheet formed of the thermally conductive pressure-sensitive adhesive resin composition may be insufficient. On the other hand, if it is less than the lower limit, the cohesive force is lowered and the holding force may become insufficient.

The monomers may also contain a copolymerizable monomer capable of copolymerizing with an acrylate, if necessary, in order to improve various properties such as cohesion.

Examples of the copolymerizable monomer include carboxyl group-containing monomers such as (meth) acrylic acid, itaconic acid, maleic acid, crotonic acid and maleic anhydride, or acid anhydrides thereof such as (meth) acrylamide, N, (Meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide and N-butoxymethyl (meth) acrylamide, Vinyl esters, for example aromatic vinyl compounds such as styrene and vinyl toluene, such as (meth) acrylonitrile, for example N- (meth) acryloylmorpholine, for example N-vinyl- - pyrrolidone, and the like.

As the copolymerizable monomer, a carboxyl group-containing monomer is preferable, and (meth) acrylic acid is more preferable.

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

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

In order to react the monomer, for example, a monomer containing an acrylate, a functional group-containing acrylate and, if necessary, a copolymerizable monomer is polymerized.

As a method of polymerizing the monomer component, known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, various kinds of radical polymerization and the like can be given, and solution polymerization can be exemplified.

In solution polymerization, a monomer component is added to a solvent to prepare a monomer solution, and then the polymerization initiator is added while heating the monomer solution.

Examples of the solvent include aromatic solvents such as toluene, benzene and xylene, and organic solvents such as ether solvents such as ethyl acetate.

The solvent may be used alone or in combination.

The mixing ratio of the solvent is, for example, 10 to 1000 parts by mass, preferably 50 to 500 parts by mass with respect to 100 parts by mass of the monomer component.

Examples of the polymerization initiator include a peroxide-based polymerization initiator and an azo-based polymerization initiator.

Examples of the peroxide-based polymerization initiator include organic peroxides such as peroxycarbonate, ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide and peroxy ester .

Examples of the azo-based polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis Dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate, and the like.

As the polymerization initiator, an azo-based polymerization initiator is preferably exemplified.

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

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

By the solution polymerization described above, the monomer component is polymerized 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 · s, preferably 0.5 to 50 Pa · s at 30 ° C.

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

The blend ratio of the acrylic polymer is, for example, 20 to 70 mass%, preferably 20 to 60 mass parts, relative to the thermally conductive pressure-sensitive adhesive resin composition.

If the blending ratio of the acrylic polymer does not satisfy the above range, the cohesive force and the adhesive force may be insufficient.

The metal hydroxide is added to the thermally conductive pressure-sensitive adhesive resin composition 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, iron hydroxide and titanium hydroxide.

As the metal hydroxide, aluminum hydroxide is preferably used.

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 占 퐉, preferably 1 to 10 占 퐉. The primary average particle diameter can be measured by, for example, a laser particle size analyzer.

The mixing ratio of the metal hydroxide is, for example, 30 to 600 parts by mass, and preferably 50 to 500 parts by mass, relative to 100 parts by mass of the acrylic polymer.

If the compounding ratio of the metal hydroxide exceeds the upper limit, moldability or workability may be insufficient. On the other hand, if the lower limit is not reached, the thermal conductivity may become insufficient.

The thermally conductive pressure-sensitive adhesive resin composition may, for example, be blended with a tackifier.

The tackifying resin is compounded in the thermally conductive pressure-sensitive adhesive resin composition as necessary in order to give an adhesive force.

Examples of the tackifier resin include a petroleum resin, a terpene resin, a coumarone-indene resin, a styrene resin, a rosin resin, an alkylphenol resin, and a xylene resin.

As the tackifier resin, a rosin-based resin is preferably used for the reason of excellent heat stability.

The weight-average molecular weight (in accordance with the method described later) of the tackifier resin is, for example, 5000 or less, preferably 100 to 4000, and more preferably 500 to 3000.

If the weight average molecular weight of the tackifier resin exceeds the upper limit, the cohesive force may become insufficient. On the other hand, if it does not reach the lower limit, the adhesive strength may be insufficient.

The softening point (recurring type) of the tackifier is, for example, 80 to 200 占 폚, preferably 90 to 200 占 폚.

If the softening point of the tackifier does not satisfy the above range, the cohesive force may become insufficient.

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

If the blending ratio of the tackifier resin exceeds the upper limit, the cohesive force may become insufficient. On the other hand, if it does not reach the lower limit, the adhesive strength may be insufficient.

If necessary, additives such as a crosslinking agent, an anti-aging agent, an antioxidant, a processing aid, a stabilizer, a defoaming agent, a flame retardant, a thickener and a pigment may be added to the thermally conductive pressure-sensitive adhesive resin composition in an appropriate ratio.

The cross-linking agent is incorporated in the thermally conductive pressure-sensitive adhesive resin composition as needed in order to improve the cohesive strength of the thermally conductive pressure-sensitive adhesive sheet.

Examples of the crosslinking agent include an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, and a metal chelating crosslinking agent. And isocyanate-based crosslinking agents.

Examples of the isocyanate crosslinking agent include aromatic diisocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate, For example, denatured isocyanates thereof.

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

As the isocyanate-based crosslinking agent, an isocyanate adduct is preferable.

The crosslinking agent may be used alone 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, based on 100 parts by mass of the acrylic polymer.

If the blending ratio of the cross-linking agent exceeds the upper limit, the flexibility may be insufficient. On the other hand, if it does not reach the lower limit, the cohesive force may become insufficient.

The thermally conductive pressure-sensitive adhesive resin composition can be obtained by mixing and mixing the above-prepared acrylic polymer, metal hydroxide, tackifier and, if necessary, additives such as a cross-linking agent at the above ratios.

The thermally conductive pressure-sensitive adhesive sheet can be obtained by laminating a pressure-sensitive adhesive layer comprising a thermally conductive pressure-sensitive adhesive resin composition on the surface of a substrate.

Fig. 1 shows a cross-sectional view of one embodiment of a thermally conductive pressure-sensitive adhesive sheet of the present invention.

1 (a), a thermally conductive pressure-sensitive adhesive sheet 11 includes a base material 2 and an adhesive layer 3 laminated on one surface of the base material 2.

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

If the thickness of the adhesive layer 3 exceeds the upper limit, the thermal conductivity may become insufficient. On the other hand, if it is less than the lower limit, the adhesive force and the holding force thereof may become insufficient.

The base material 2 may be, for example, a polyester film (e.g., a polyethylene terephthalate film), an olefin based resin film (e.g., a polyethylene film or a polypropylene film), a polyvinyl chloride film, (Synthetic resin film) such as polyimide film (nylon film) and rayon film, a porous sheet such as paper, nonwoven fabric, metal foil such as aluminum foil, or the like. And is preferably formed of a plastic film.

The surface of the substrate 2 may also be peeled off.

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

In order to laminate the adhesive layer 3 on the substrate 2, for example, a thermally conductive pressure-sensitive adhesive resin composition is coated on one surface of the substrate 2, and then thermally cured.

Examples of the application method of the thermally conductive pressure-sensitive adhesive resin composition include roll coater, kiss roll coater, dip roll coater, gravure coater, bar coater, reverse roll coater, roll brush, spray coater, knife coater, air knife coater, A lip coater, a die coater, a wet roll roll coater and the like.

In order to thermally cure the thermally conductive pressure-sensitive adhesive resin composition, for example, the thermally conductive pressure-sensitive adhesive resin composition is heated.

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

The surface of the thermally conductive pressure-sensitive adhesive resin composition coated on the surface of the base material 2 may be provided with a protective sheet 4 indicated by a virtual line. The protective sheet 4 may be the same as the base sheet 2 described above.

The weight average molecular weight in terms of standard polystyrene obtained by measuring the toluene soluble fraction of the adhesive layer 3 by GPC equipped with a differential refractometer detector is in the range of from 250,000 to less than 400,000 in a polymer region having a molecular weight of 10000 or more in terms of polystyrene, And less than 5000 in the low molecular region of less than 10,000.

If the weight average molecular weight does not satisfy the above range in the polymer region, the cohesive force decreases and the holding force of the thermally conductive pressure-sensitive adhesive sheet 11 becomes insufficient. On the other hand, if the weight average molecular weight does not satisfy the above range in the low-molecular region, the adhesive force of the thermally conductive pressure-sensitive adhesive sheet 11 becomes insufficient.

The toluene-soluble fraction of the adhesive layer (3) is obtained as follows.

For example, first, a predetermined amount (for example, 300 mg) of the pressure-sensitive adhesive layer 3 is precisely weighed, and 100 parts by mass of the pressure-sensitive adhesive layer 3, for example, Deg.] C for 168 hours to dissolve the adhesive layer 3 in toluene. Thereafter, the immersion liquid is filtered with, for example, an 80-mesh filter to remove the toluene-insoluble matter, thereby preparing a toluene-soluble substance.

In order to obtain the weight average molecular weight of the toluene-soluble fraction of the adhesive layer 3, the molecular weight distribution of the toluene-soluble fraction of the adhesive layer was measured by a gel permeation chromatograph (GPC) equipped with a differential refractometer (RI) , And from the obtained chromatogram (chart), the weight average molecular weights of the peak areas in the polymer region having a molecular weight of 10,000 or more in terms of standard polystyrene and the low molecular region of less than 10000 can be calculated based on the calibration curve of standard polystyrene .

In the polymer region, the weight average molecular weight is preferably not less than 270000, more preferably not more than 320000, and is, for example, less than 400000. The weight average molecular weight in the above low molecular weight region is preferably 100 to 5000, More preferably 500 to 4,000.

In the chromatogram obtained by the GPC measurement described above, the peak area ratio of the low molecular region to the high molecular region (hereinafter sometimes referred to as the low molecular weight / high molecular ratio) is, for example, from 0.85 to 1.30, preferably from 0.89 to 1.26 to be.

In the chromatogram obtained by the above GPC measurement, if the peak area ratio of the above-mentioned low-molecular region to the polymer region exceeds the upper limit, the cohesive force decreases and the holding force of the thermally conductive pressure-sensitive adhesive sheet 11 becomes insufficient . On the other hand, if the lower limit is not reached, the adhesive strength of the thermally conductive pressure-sensitive adhesive sheet 11 may be insufficient.

The ratio of the low molecular weight / high molecular weight to the peak area included in the high molecular weight region having a molecular weight of 10,000 or more in terms of polystyrene of the peak area included in the low molecular weight region of less than 10000 in terms of polystyrene reduced from the chromatogram obtained by the above GPC measurement, Can be calculated.

The density of the adhesive layer 3 is, for example, 1.2 to 1.7 g / cm3, preferably 1.3 to 1.7 g / cm3, more preferably 1.5 to 1.7 g / cm3.

If the density of the adhesive layer 3 exceeds the upper limit, the adhesiveness of the thermally conductive pressure-sensitive adhesive sheet 11 becomes insufficient. On the other hand, if the lower limit is not reached, the formability of the thermally conductive pressure-sensitive adhesive sheet 11 is lowered.

The heat conductivity of the adhesive layer 3 is, for example, 0.3 W / m · K or more, preferably 0.4 W / m · K or more, for example, 1.0 W / m · K or less.

When the thermally conductive pressure-sensitive adhesive sheet 11 is adhered to the stainless steel sheet, the peel adhesion strength when the stainless steel sheet is peeled off at a peel rate of 300 mm / min at a peel angle of 180 degrees is, for example, 4N / Is preferably 6 N / 20 mm or more, more preferably 9 N / 20 mm or more, particularly preferably 10 N / 20 mm or more, and most preferably 11 N / 20 mm or more, for example, 20 N / 20 mm or less.

If the peel adhesion of the thermally conductive pressure-sensitive adhesive sheet 11 does not satisfy the above range, the adhesive force to the adherend may be insufficient.

The thermally conductive adhesive sheet 11 is excellent in thermal conductivity as described above. Therefore, the thermally conductive pressure-sensitive adhesive sheet 11 formed from the thermally conductive pressure-sensitive adhesive resin composition of the present invention can be used in various heat-radiating applications.

Further, the thermally conductive pressure-sensitive adhesive sheet 11 is excellent in adhesion and holding force as described above. Therefore, when the thermally conductive pressure-sensitive adhesive sheet 11 is disposed so as to cover a heat-radiating object such as a semiconductor, the heat generated by the heat-radiating object can be more reliably conducted while exhibiting excellent adhesive force and holding force.

Examples of the heat radiation object onto which the thermally conductive pressure-sensitive adhesive sheet 11 is adhered include electronic devices and electronic parts mounted on the substrate.

Examples of the electronic device include an IC (integrated circuit) chip, a capacitor, a coil, a resistor, and an electronic device of a light emitting diode. Electronic parts used in power electronics, such as thyristors (rectifiers), motor parts, inverters, and transmission parts, and the like can also be used.

As the heat dissipation object, for example, an LED heat dissipation substrate and a heat dissipation material for a battery may be used.

1 (a), the pressure-sensitive adhesive layer 3 is laminated on one surface of the base material 2, but the pressure-sensitive adhesive layer 3 is formed on the surface of the base material 2 as shown in Fig. 1 (b) The thermally conductive pressure-sensitive adhesive sheet 12 may be formed by laminating it on both sides of the thermally conductive pressure-sensitive adhesive sheet 2.

<Examples>

EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the examples and the comparative examples at all.

Examples 1 to 5 and Comparative Examples 1 to 5

(Production of thermally conductive pressure-sensitive adhesive resin composition)

To 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 was added AIBN (trade name: 2'2'-azobisisobutyronitrile, 0.08 g) and toluene (150 g) were mixed and homogeneously dissolved, followed by polymerization at 65 ° C for 8 hours to obtain an acrylic polymer solution. The viscosity of the obtained acrylic polymer solution (BH viscometer, No.5 rotor, 10s &lt; ^-1 &gt;, measurement temperature 30 DEG C) was about 25Pa s.

Subsequently, a thermosetting adhesive resin composition was prepared by adding a tackifier resin, a metal hydroxide and a crosslinking agent to the acrylic polymer solution according to the formulation of Table 1.

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

Rosin resin: trade name &quot; super ester &quot;, average weight molecular weight 1520, softening point (ring method) 95 to 105 占 폚, manufactured by Arakawa Chemical Industries,

Aluminum hydroxide: trade name &quot; HIGi Light H-32 &quot;, primary average particle diameter 8 mu m, manufactured by Showa Denko K.K.

Isocyanate-based crosslinking agent: "Coronate L", a tolylene diisocyanate adduct of trimethylolpropane, solid content 75% by mass, manufactured by Nippon Polyurethane Industry Co., Ltd.

(Production of thermally conductive pressure-sensitive adhesive sheet)

A thermo-conductive pressure-sensitive adhesive resin composition was introduced into a wet laminate roll coater by a tube (inner diameter 19 mm, length about 1.5 m) while a diaphragm MRF 38 (trade name, based on polyethylene terephthalate, , Manufactured by Mitsubishi Jusisha).

Thereafter, the thermally conductive pressure-sensitive adhesive resin composition was heated at 110 DEG C for 3 minutes to thermally cure to form an adhesive layer.

Subsequently, a thermally conductive pressure-sensitive adhesive sheet was prepared by providing Diafoyle MRN38 (trade name, protective sheet, thickness 38 mu m, manufactured by Mitsubishi Jusi Co., Ltd.) on the surface of the thermally conductive pressure-sensitive adhesive resin composition.

(evaluation)

The thermally conductive pressure-sensitive adhesive sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated for (1) a weight average molecular weight in a polymer region and a low molecular region of a toluene-soluble fraction by GPC and a peak area ratio (Low molecular weight / high molecular weight ratio), (2) density, (3) thermal conductivity, (4) peel adhesion and (5) retention force.

Details of each evaluation are described below.

(1) weight average molecular weight in the high molecular weight region and low molecular weight region of the toluene soluble fraction by GPC and peak area ratio (low molecular weight / high molecular weight ratio) of the low molecular weight region to the high molecular weight region,

300 mg of the adhesive layer was placed in 50 ml of toluene and immersed at 25 캜 for 168 hours to dissolve the adhesive layer in toluene. Thereafter, the immersion liquid was filtered through a 80 mesh nylon mesh to remove the toluene-insoluble matter, thereby preparing a toluene-soluble substance.

Toluene was removed from the obtained toluene-soluble fraction to obtain a sample. The sample was measured by GPC under the following measurement conditions, and the weight average molecular weight in terms of polystyrene was changed to a polymer region having a molecular weight of 10,000 or less in terms of polystyrene and a polystyrene- Low molecular weight region.

GPC measurement conditions

GPC measurement apparatus: HCL-8120GPC (manufactured by TOSO)

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

Column temperature: 40 DEG C

Eluent: tetrahydrofuran

Flow rate: 0.6 ml / min

Detector: Differential refractometer detector

Sample concentration: 1 mg / ml

Injection amount: 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 high molecular region was obtained.

The results are shown in Table 1.

2 shows a chromatogram of GPC (GPC differential molecular weight distribution curve, horizontal axis: weight average molecular weight in terms of standard polystyrene) measured for the toluene-soluble fraction of the adhesive layer in Example 1.

(2) Density

The density of the adhesive layer 3 was evaluated.

The thermally conductive pressure-sensitive adhesive sheet was cut into 50 x 50 mm and the protective sheet was peeled off. The thickness and weight of the pressure-sensitive adhesive layer were measured, and the density was calculated by the following calculation formula.

Density (g / cm3) = weight of adhesive layer (g) / (area of adhesive layer (cm2) x thickness of adhesive layer (cm))

The results are shown in Table 1.

(3) Thermal conductivity

The thermal characteristic evaluation apparatus shown in Fig. 3 was used for measurement of the thermal conductivity.

Specifically, the pressure-sensitive adhesive layer 3 is sandwiched between a pair of blocks (sometimes called a rod) L made of aluminum (A5052, thermal conductivity: 140 W / m 占)) (20 mm x 20 mm) were sandwiched, and a pair of blocks L were bonded to each other with an adhesive layer 3.

Then, the heating element (heater block) H and the heat dissipator (cooling base plate configured to circulate the cooling water) C were arranged so that the pair of blocks L were up and down. Specifically, the heat generating body H is disposed on the upper block L and the heat radiating body C is disposed below the block L on the lower side.

At this time, a pair of blocks L joined with the adhesive layer 3 are positioned between the pair of pressure adjusting screws T passing through the heat generating element H and the heat discharging body C. A load cell R is disposed between the pressure adjusting screw T and the heating element H so that the pressure when the pressure adjusting screw T is tightly tightened is measured. (3). &Lt; / RTI &gt;

Three probes P (diameter 1 mm) of a contact type displacement meter were provided so as to penetrate the lower block L and the adhesive layer 3 from the side of the heat discharging body C. At this time, the upper end of the probe P is in contact with the lower surface of the upper block L, and the gap between the upper and lower blocks L (the thickness of the adhesive layer 3) can be measured.

A temperature sensor D is provided in the heating element H and the upper and lower blocks L. [ Specifically, a temperature sensor D was provided at one point of the heating element H and a temperature sensor D was provided at five points of each block L in the vertical direction at intervals of 5 mm.

First, the pressure adjusting screw T is tightly tightened to apply pressure to the adhesive layer 3 to set the temperature of the heating element H at 80 占 폚 and cooling water at 20 占 폚 to the heat discharging body Lt; / RTI &gt;

After the temperatures 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 the respective temperature sensors D and the thermal conductivity W / mK of the upper and lower blocks L is measured. The temperature of the interface between the upper and lower blocks L and the pressure-sensitive adhesive layer 3 was calculated by calculating the heat flow rate passing through the pressure-sensitive adhesive layer 3 from the temperature gradient. Then, the thermal conductivity (W / m · K) at the pressure was calculated by using the following thermal conductivity equation (Fourier's law).

Q = -λgradT

R = L / lambda

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) Peel adhesion

After cutting the thermally conductive pressure-sensitive adhesive sheet to a size of 20 mm x 100 mm, the protective sheet was peeled off. Subsequently, the thermally conductive pressure-sensitive adhesive sheet was placed on a stainless steel (SUS304BA) plate under a 23 deg. C, 50% RH environment, and the thermally conductive pressure-sensitive adhesive sheet was bonded to stainless steel by one reciprocation with a roller of 2 kg.

Thereafter, the adhesive layer was allowed to stand at 23 DEG C under a 50% RH environment for 30 minutes, and the adhesive layer was cured (cured) at a peeling rate of 300 mm / The peel strength was measured by peeling.

The results are shown in Table 1.

On the other hand, in Comparative Example 3, measurement could not be carried out because it could not be adhered to a stainless steel plate.

(5) Holding force

The thermally conductive pressure-sensitive adhesive sheet 11 was cut into a size of 20 mm x 10 mm, and then attached to a PET film having a thickness of 25 m to obtain a sample. Subsequently, a 10 mm x 20 mm portion of the upper end of the sample was placed on the lower end of a stainless steel (SUS304BA) plate 20 at a temperature of 23 DEG C and 50% RH, The pressure-sensitive adhesive sheet 11 was adhered to the stainless steel plate 20.

Thereafter, the upper end of the stainless steel plate 20 was fixed, and a weight of 300 g was placed at the lower end of the sample at a temperature of 40 캜 under a condition of 40 캜 Respectively. Then, the sample was allowed to stand for 1 hour under the environment of 40 캜, and the presence or absence of the sample was examined.

The above-mentioned invention is provided as an example of the present invention, but this is merely an example and should not be construed restrictively. Modifications of the invention that are obvious to those skilled in the art are within the scope of the following claims.

The thermally conductive pressure-sensitive adhesive resin composition and the thermally conductive pressure-sensitive adhesive sheet of the present invention can be used for heat radiation applications of various industrial parts.

Claims (9)

As a thermally conductive pressure-sensitive adhesive resin composition containing an acrylic polymer and a metal hydroxide,
The weight average molecular weight of the toluene soluble component of the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition measured by GPC equipped with a differential refractometer detector in terms of standard polystyrene is in the range of 250000 to less than 400000 in a polymer region having a molecular weight of 10,000 or more in terms of polystyrene Or less in a low molecular weight region having a polystyrene reduced molecular weight of less than 10000,
Wherein the density of the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition is 1.2 to 1.7 g / cm 3. The thermally conductive pressure-sensitive adhesive resin composition according to claim 1, wherein a peak area ratio of the low-molecular region to the polymer region in the chromatogram obtained by the GPC measurement is 0.85 to 1.30. The thermally conductive pressure-sensitive adhesive resin composition according to claim 1, further comprising a tackifier resin. The thermally conductive pressure-sensitive adhesive resin composition according to claim 1, wherein the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition has a thermal conductivity of 0.3 W / m · K or more. The acrylic polymer according to claim 1, wherein the acrylic polymer is obtained by reacting a monomer containing an acrylate having 2 to 14 carbon atoms and a functional group-containing acrylate containing a functional group,
The blending ratio of the acrylate is 70 to 99.9 mass% with respect to the monomer,
Wherein the blend ratio of the functional group-containing acrylate is 0.01 to 10% by mass relative to the monomer. And a pressure-sensitive adhesive layer comprising a substrate and a thermally conductive pressure-sensitive adhesive resin composition laminated on at least one side of the substrate,
The thermally conductive pressure-sensitive adhesive resin composition,
As a thermally conductive pressure-sensitive adhesive resin composition containing an acrylic polymer and a metal hydroxide,
The weight average molecular weight of the toluene soluble component of the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition measured by GPC equipped with a differential refractometer detector in terms of standard polystyrene is in the range of 250000 to less than 400000 in a polymer region having a molecular weight of 10,000 or more in terms of polystyrene Or less in a low molecular weight region having a polystyrene reduced molecular weight of less than 10000,
Wherein the density of the pressure-sensitive adhesive layer formed of the thermally conductive pressure-sensitive adhesive resin composition is 1.2 to 1.7 g / cm 3. The thermally conductive pressure-sensitive adhesive sheet according to claim 6, wherein the stainless steel sheet is bonded to the stainless steel sheet and the peel adhesion strength is 4 N / 20 mm or more when the strip is peeled off at a stripping rate of 180 and a stripping rate of 300 mm / min. The thermally conductive pressure-sensitive adhesive sheet according to claim 6, wherein the thickness of the pressure-sensitive adhesive layer is 30 to 200 占 퐉. 7. The method of claim 6, wherein the substrate is formed of a plastic film,
Wherein the thickness of the substrate is 12 to 50 占 퐉.

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