JP4344192B2 - Resin composition for heat dissipation material and cured product thereof - Google Patents

Description

  The present invention relates to a resin composition for obtaining a heat dissipation material and a cured product thereof, and more particularly to a resin composition capable of obtaining a heat dissipation material excellent in flexibility and moldability and a cured product thereof. .

  A heat-dissipating sheet obtained by molding (curing) a resin composition obtained by blending a flexible resin with an inorganic filler that enhances thermal conductivity such as alumina into a sheet shape is, for example, a plasma display (PDP) or an integrated circuit. This is used to prevent the occurrence of functional failures due to the temperature rise of various parts accompanying heat generation.

  These heat radiating sheets are used by being inserted between a heat generating body and a heat radiating body such as a metal plate or a heat sink, but generally the surface of the heat generating body or the heat radiating body is often not smooth, and the contact area with these In order to increase the heat transfer efficiency and increase the heat conductivity, the sheet is required to have high flexibility.

  Conventionally, silicone rubbers and silicone gels have been used as flexible resins, but these resins are expensive in price, take a long time to cure and are inferior in productivity, and generate low molecular weight siloxanes. There were problems such as defective contact of electronic parts.

  In order to solve the above problems, for example, a composition containing a polymer gel such as an acrylic gel and a thermal softener and a thermally conductive filler that becomes liquid when heated in a solid or paste form at room temperature is shown (for example, Patent Document 1).

  However, as a result of examination by the present inventors in this Patent Document 1, since the silicone rubber and the silicone gel are not used, the problem of contact failure of electronic parts due to generation of low molecular weight siloxane can be improved, but the obtained thermal conductivity is obtained. The sheet was found to be inferior in flexibility.

Japanese Patent Laid-Open No. 2002-234952

  Accordingly, in the present invention, in consideration of the above-mentioned problems of the prior art, it is an object to provide a resin composition for a heat radiation material that is not only excellent in thermal conductivity but also excellent in moldability and flexibility of the heat radiation sheet and a cured product thereof. Are listed.

  The present invention that has solved the above problems is a resin composition for a heat dissipation material containing a liquid resin containing liquid oily substances and a crosslinkable polymer as essential components, the liquid resin forming a gel, and the hardness of the gel Is 5 to 80. So far, there has been no example of designing and using a liquid resin having a gel hardness of 5 to 80, which is a feature of the present invention, for a known heat dissipation material. By using a liquid resin capable of forming a gel hardness in this range, the resulting heat-radiating cured product is excellent in flexibility, so it is possible to increase the contact area with the heat-generating body and the heat-dissipating body, and the heat-dissipating characteristics are excellent. This inventor discovered this.

  The crosslinkable polymer is a polymer obtained by copolymerizing a polymerizable monomer (A) and a polymerizable monomer (B) having a functional group for crosslinking, and (A) And a polymer in which the ratio of (B) is 0.1 to 5 mol% with respect to the total amount of (B).

  The heat dissipation resin composition preferably has a weight loss of 5% by mass or less when the cured product of the heat dissipation resin composition is held at 100 ° C. for 168 hours.

  Furthermore, the present invention includes a heat-radiating cured product obtained by curing the resin composition for heat-dissipating material.

  The resin composition for a heat dissipation material of the present invention and the cured product thereof contain a liquid resin containing a liquid oily substance and a crosslinkable polymer as essential components, the liquid resin forms a gel, and the hardness of the gel is 5 to 5. Since it was 80, it not only was excellent in thermal conductivity, but also succeeded in efficiently obtaining a cured product having good moldability and flexibility of the heat dissipation sheet. Therefore, it is used for the purpose of dissipating the heat generated from PDP, electric / electronic parts, etc. by interposing between the heat generating elements, such as PDP, electric / electronic parts, etc. and heat radiators, such as heat sinks, heat radiating fins, metal plates, etc. Can do.

  The resin composition for a heat dissipation material of the present invention (hereinafter simply referred to as a resin composition) contains a liquid resin containing a liquid oily substance and a crosslinkable polymer as essential components.

  The liquid oily substance only needs to be liquid and oily (having a property not to be mixed with water) under the conditions of normal pressure and 25 ° C. For example, hydrocarbons such as higher alcohols (5 to 18 carbon atoms), esters, ethers, paraffin, liquid paraffin, chlorinated paraffin, process oil, fatty oil, phthalic acid plasticizer, trimellitic acid plastic Agent, adipic acid plasticizer, polyester plasticizer, epoxy plasticizer, phosphate ester plasticizer, rubber plasticizer, aliphatic monobasic acid plasticizer, aliphatic dibasic acid plasticizer, liquid rubber And synthetic rubbers, among which various plasticizers are preferable. Furthermore, when these liquid oily substances are used, two or more kinds may be used in combination.

  Furthermore, the liquid oily substance has high heat resistance, that is, the weight loss at 100 ° C. is preferably 10% by mass or less, more preferably 8% by mass or less, and most preferably 5% by mass or less. The weight loss of the liquid oily substance used is determined by measuring the weight loss when 3 g of the plasticizer is placed in an aluminum watch glass having a diameter of 5 cm and kept in an oven heated to 100 ° C. for 168 hours. be able to. When a liquid oily substance having a weight loss at 100 ° C. of less than 10% by mass is used, the flexibility of the cured product of the obtained resin composition tends to be maintained over a long period, while the weight loss exceeds 10% by mass. Further, due to volatilization of the liquid oily substance, the weight loss of the cured product of the obtained resin composition is large, and the hardness of the cured product tends to be high.

  The liquid resin of the present invention may contain components other than the liquid oily substance and the crosslinkable polymer, which are essential components of the liquid resin. However, an inorganic filler, a reinforcing fiber, and a thermal conductivity of less than 20 W / m · K that have a thermal conductivity of 20 W / m · K or more, which can be used for the crosslinking agent described later and the resin composition of the present invention. Inorganic fillers, organic fillers, inorganic flame retardants, magnetic materials, and electromagnetic wave absorbers are excluded from the liquid resin component.

  The state in which the liquid resin forms a gel means that a container is filled with a mixture of a liquid resin containing a crosslinkable polymer and a liquid oily substance as mandatory components and a crosslinker described later, and further crosslinks with the crosslinker. When a cross-linked polymer is obtained by reacting with a water-soluble polymer, a liquid oily substance is retained in the cross-linked polymer, and the mixture is not fluid and is in a gel or solid state.

  The crosslinkable polymer may be any polymer that can form a polymer having a crosslinked structure (crosslinked polymer) by reacting with a crosslinking agent described later, and has one radical polymerizable unsaturation in the molecule. Polymerizable monomer (A) (hereinafter simply referred to as monofunctional monomer), monomer (B) having one functional group for crosslinking and one radically polymerizable unsaturated group in the molecule (hereinafter referred to as “monofunctional monomer”) A polymer obtained by copolymerization with a simple functional group-containing monomer) is preferred.

  The monofunctional monomer used in the crosslinkable polymer is not particularly limited as long as it is a monomer having one radical polymerizable unsaturated group in the molecule, and among them, a cured product of the obtained resin composition (Meth) acrylic acid alkyl ester having 2 to 18 carbon atoms in the alkyl group is preferable. Specifically, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , N-hexyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, octyl (meth) acrylate, i-octyl (meth) acrylate, i-myristyl (meth) acrylate, lauryl (meth) ) Acrylate, nonyl (meth) acrylate, i-nonyl (meth) acrylate, i-decyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, i-stearyl (meth) acrylate, and the like. . These (meth) acrylic acid alkyl esters having 2 to 18 carbon atoms in these alkyl groups may be used alone or in combination of two or more.

  The amount of the alkyl group (meth) acrylic acid alkyl ester having 2 to 18 carbon atoms in these alkyl groups is preferably 50% by mass or more in 100% by mass of the monomer component constituting the crosslinkable polymer. 70 mass% or more is more preferable, and 80 mass% or more is most preferable.

  The functional group-containing monomer used in the crosslinkable polymer may be a monomer having one functional group for crosslinking and one radical polymerizable unsaturated group in the molecule. Examples of the functional group include a carboxyl group, a hydroxyl group, a mercapto group, a nitrile group, an amino group, an amide group, a carboxylic anhydride group, an epoxy group, and an isocyanate group. Of these, a hydroxyl group is preferred. Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, and polypropylene glycol. Examples thereof include mono (meth) acrylate, glycerin (meth) acrylate, and hydroxystyrene.

  The cross-linking agent may be any compound that has two or more functional groups for cross-linking in the molecule and does not have a radical polymerizable unsaturated group. It selects suitably according to the functional group kind of a monomer. For example, in the case of a polymer using a functional group-containing monomer having a hydroxyl group, a crosslinking agent having an isocyanate group is preferably used. For example, hexamethylene diisocyanate, isophorone diisocyanate, p-pheny Examples thereof include range isocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate and the like.

  A preferred functional group combination of the functional group-containing monomer and the crosslinking agent is at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, a mercapto group, an amino group, and an amide group, a carboxylic anhydride group, and an epoxy. A combination of at least one functional group selected from the group consisting of a group and an isocyanate group. By selecting a functional group-containing monomer and a crosslinking agent from the above combinations, unreacted functional groups can be reduced.

  A particularly preferred combination is a combination of a functional group-containing monomer having a hydroxyl group and a crosslinking agent having an isocyanate group. By this combination, unreacted functional groups can be reduced at a lower temperature and in a shorter time, and the cost is excellent.

  Moreover, you may use the crosslinking accelerator for accelerating | stimulating a crosslinking reaction and a crosslinking promotion adjuvant as needed.

  When the functional group-containing monomer and the monofunctional monomer are copolymerized, the ratio of the functional group-containing monomer is 0 with respect to the total of the functional group-containing monomer and the monofunctional monomer. 0.1-5 mol% is preferable, 0.3-4 mol% is more preferable, and 0.5-3 mol% is most preferable. When the functional group-containing monomer exceeds 5 mol%, the flexibility of the cured product of the obtained resin composition tends to decrease. When the functional group-containing monomer is less than 0.1 mol%, the liquid oily substance has a crosslinking weight. There is a tendency not to be retained in the coalescence and to form a gel.

  The glass transition point of the crosslinkable polymer is preferably 0 ° C. or lower, more preferably −20 ° C. or lower, still more preferably −30 ° C. or lower. When it exceeds 0 degreeC, the cured | curing material of the obtained resin composition tends to be insufficient in terms of flexibility. The glass transition point can be measured by a conventional method using, for example, a differential scanning calorimeter.

  The molecular weight of the crosslinkable polymer is preferably in the range of 50,000 to 2,000,000, more preferably in the range of 100,000 to 1,800,000 in terms of polystyrene by gel permeation chromatography (GPC), more preferably 200,000. Most preferably within the range of ~ 1.5 million. When the weight average molecular weight is less than 50,000, there is a tendency that it takes a long time to obtain a gel-like resin, or a liquid oily substance is not retained in the crosslinked polymer and a gel cannot be obtained. On the other hand, when the weight average molecular weight exceeds 2 million, the viscosity of the liquid resin is increased, which tends to hinder workability.

The crosslinkable polymer can be obtained by polymerizing by a known polymerization method such as bulk polymerization, solution polymerization, emulsion polymerization using a known polymerization initiator. Among these, if a polymerization method in which polymerization is performed in a liquid oily substance is employed, a mixture of a crosslinkable polymer and a liquid oily substance can be obtained in one step, which is convenient and preferable. Of course, the mixture may be adjusted by adding a monomer or an additive separately.
The liquid resin of the present invention has a gel hardness in the range of 5 to 80 when the liquid resin forms a gel. If the hardness is in the range of 5 to 80, the flexibility of the cured product of the obtained resin composition can be suitable as a heat dissipation material.

  The hardness is a value measured at 25 ° C. using an Asuka-F type rubber hardness meter manufactured by Kobunshi Keiki Co., Ltd. The hardened | cured material used for a measurement uses the disk-shaped thing which has a thickness of 15 mm in thickness, and a diameter of 5 cm or more-8 cm or less. For the measurement value, a hardness meter is placed on the center of the measurement sample, and the maximum indicated value immediately after that is adopted.

  Moreover, as for liquid resin, when this liquid resin forms a gel, the hardness of this gel is more preferably in the range of 5 to 70, and most preferably in the range of 10 to 60.

  The liquid resin of the present invention preferably comprises 10 to 50% by mass of the crosslinkable polymer and 50 to 90% by mass of the liquid oily substance, when the total of the crosslinkable polymer and the liquid oily substance is 100% by mass. More preferably, it consists of 20 to 45% by mass of a crosslinkable polymer and 55 to 80% by mass of a liquid oily substance, most preferably 20 to 40% by mass of a crosslinkable polymer and 60 to 80% by mass of a liquid oily substance.

  When the crosslinkable polymer is less than 10% by mass, that is, when the liquid oily substance component exceeds 90% by mass, the liquid oily substance is not sufficiently retained in the crosslinked polymer and a gel cannot be obtained. The cured product of the composition may be sticky, the surface smoothness may be deteriorated, or the resin and the inorganic filler may be separated. On the other hand, when the crosslinkable polymer exceeds 50% by mass, that is, when the liquid oily substance is less than 50% by mass, the flexibility of the cured product of the obtained resin composition is reduced, or the viscosity of the resin composition is high. There is a tendency to hinder workability.

  The resin composition of the present invention preferably contains an inorganic filler having a thermal conductivity of 20 W / m · K or more in order to increase thermal conductivity. Specific examples include aluminum oxide, magnesium oxide, zinc oxide, silicon carbide, aluminum nitride, boron nitride, and silicon nitride. When using these, you may use 2 or more types together. The thermal conductivity of the inorganic filler to be used can be measured using the sintered product, using a thermal conductivity measuring device, part number TPA-501, by the hot disk method manufactured by Kyoto Electronics Industry Co., Ltd.

  The inorganic filler having a thermal conductivity of 20 W / m · K or more is preferably contained in an amount of 50 to 1500 parts by mass, more preferably 100 to 1300 parts by mass with respect to 100 parts by mass of the liquid resin. . These inorganic fillers increase the thermal conductivity of the resulting resin composition and improve the heat dissipation performance as the filling amount with respect to the liquid resin increases, but on the other hand, the flexibility of the cured product of the obtained resin composition Therefore, for example, it is preferable to adjust the filling amount according to the required thermal conductivity and the hardness of the gelled liquid resin to be used.

  The inorganic filler may be subjected to surface treatment by silane treatment or the like in order to increase the dispersibility in the composition or increase the filling amount, if necessary.

  In addition, examples of the shape of the inorganic filler include, but are not particularly limited to, a spherical shape, a fibrous shape, a scale shape, a planar shape, a crushed shape, and an indefinite shape.

  The resin composition of the present invention can be obtained using a conventionally known kneader. For example, a continuous kneader such as a mixer, a roll mill, a Banbury mixer, a kneader, a pressure type kneader, or a twin-screw kneader may be used, but it is not particularly limited. If necessary, the kneading may be performed while reducing the pressure in the apparatus to remove air contained in the composition, or while heating or pressurizing. Further, the kneaded resin composition of the present invention can be used as it is, or after kneading, for example, can be used as a molded product obtained by a molding method described later. The hardened | cured material of the resin composition of this invention means the state which does not have the fluidity | liquidity of this resin composition, when the liquid resin in this resin composition formed the gel.

The resin composition of the present invention is obtained when the cured product of the resin composition is kept in an oven heated to 100 ° C. for 168 hours in order to stably express the flexibility of the obtained cured product over a long period of time. The weight loss is preferably 5% by mass or less, more preferably 3% by mass or less, and most preferably 2% by mass or less. By holding the cured product of the resin composition in an oven heated to 100 ° C. for 168 hours and measuring the weight loss, it is possible to determine whether or not the flexibility necessary for the heat dissipation material is maintained for a long period of time.
A heat-radiating cured product can be obtained by curing the resin composition of the present invention. Further, the resin composition can be cured into a desired shape such as a sheet shape, a tape shape, a tube shape, or a roll shape, and the shape, the curing method, and the curing apparatus are not particularly limited. For example, the heat-dissipating cured product may be obtained by charging the above resin composition into an injection mold or batch mold and curing it into a desired shape. It may be obtained by curing. During molding, heating may be performed while promoting formation of a desired shape and formation of a gel, and molding and obtaining a cured product of the resin composition of the present invention may be performed simultaneously. And then cured or aged (stored at room temperature for a long time) to form a gel to obtain a cured product of the resin composition of the present invention.

  In addition, the resin composition of the present invention may be impregnated or adhered to the surface of the resin composition with a resin, an inorganic fiber, an organic fiber, or the like in order to increase the strength, the handleability, and the like of the obtained resin composition.

  The resin composition of the present invention includes conventionally known reinforcing fibers, inorganic fillers having a thermal conductivity of less than 20 W / m · K, organic fillers, polymerization initiators, polymerization inhibitors. , Low shrinkage agent, mold release agent, thickener, defoaming agent, wetting and dispersing agent, thixotropic agent, UV absorber, UV stabilizer, antioxidant, phosphorus flame retardant, halogen flame retardant Agent, inorganic flame retardant such as aluminum hydroxide and magnesium hydroxide, coupling agent, pigment, dye, magnetic substance, antistatic agent, electromagnetic wave absorber, pasty oil, paraffin wax, microcrystalline wax, higher fat Any additives such as oil and heat softener can be used as long as they do not impair the object of the present invention.

  As an indication of the amount added, an amount that does not violate the object of the present invention is preferable. Specifically, it is desirable that the total amount of additives is 1000 parts by mass or less per 100 parts by mass of the liquid resin. A more preferable upper limit of the addition amount is 900 parts by mass, and a more preferable upper limit is 800 parts by mass.

  The present invention will be described in further detail with reference to the following examples. However, the following examples are not intended to limit the present invention, and all modifications that are made without departing from the spirit of the preceding and following description are all included in the technical scope of the present invention. The In Examples and Comparative Examples, “parts” means “parts by mass” and “%” means “mass%” unless otherwise specified.

Synthesis example 1
In a container equipped with a thermometer, a stirrer, a gas introduction tube, a reflux condenser and a dropping funnel, 39.48 parts of 2-ethylhexyl acrylate, 0.52 parts of 2-hydroxyethyl acrylate (hydroxyl group in all polymerizable monomers) The content monomer was set to 2 mol%), and 50 parts of trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C880”) as a liquid oily substance was charged, and the inside of the container was replaced with nitrogen gas . The temperature was raised to 75 ° C., 0.05 parts of dimethyl 2,2-azobis (2-methylpropionate) as a polymerization initiator and 10 parts of trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “ADEKA” A mixture of sizer C880 ") was charged into a dropping funnel and dropped over 3 hours. Furthermore, 0.02 part of dimethyl 2,2-azobis (2-methylpropionate) as a polymerization initiator was added, the temperature was raised to 90 ° C., and polymerization was performed for 3 hours. Before completion of the polymerization, 0.4 part of dibutyltin dilaurate as a crosslinking accelerator is added, air is blown, the system is cooled to terminate the polymerization, and an acrylic copolymer containing 2 mol% hydroxyl group as a crosslinkable polymer is terminated. A mixture of polymer and trimellitic acid plasticizer as a liquid oily substance (hereinafter referred to as acrylic resin A) was obtained. The residual 2-ethylhexyl acrylate by gas chromatography (GC) was 0.1%, and the 2 mol% hydroxyl group-containing acrylic copolymer as a crosslinkable polymer in the acrylic resin A was 39.9%.

  The viscosity of the obtained acrylic resin A at 25 ° C. was 12980 mPa · s. As for the molecular weight of the polymer using GPC (gel permeation chromatography), the weight average molecular weight Mw was 1106,000 and the number average molecular weight Mn was 101,000. The glass transition temperature of the 2 mol% hydroxyl group-containing acrylic copolymer as a crosslinkable polymer measured by a conventional method using a differential scanning calorimeter was −64 ° C.

Synthesis example 2
Charge into the reaction vessel was 39.70 parts of 2-ethylhexyl acrylate, 0.30 parts of 2-hydroxyethyl acrylate (hydroxyl-containing monomer in all polymerizable monomers set to 1 mol%), liquid oily substance 1 mol% hydroxyl group-containing acrylic as a crosslinkable polymer in the same manner as in Synthesis Example 1 except that it was changed to 50 parts trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C880”). A mixture (hereinafter referred to as acrylic resin B) of a copolymer and a trimellitic acid plasticizer as a liquid oily substance was obtained. The residual 2-ethylhexyl acrylate by GC was 0.1%, and the 1 mol% hydroxyl group-containing acrylic copolymer as the crosslinkable polymer in the acrylic resin B was 39.9%. The viscosity of the obtained acrylic resin B at 25 ° C. was 11500 mPa · s. Regarding the molecular weight of the polymer using GPC, the weight average molecular weight Mw was 1006,000 and the number average molecular weight Mn was 105,000. Further, the glass transition temperature of the 1 mol% hydroxyl group-containing acrylic copolymer measured by a conventional method using a differential scanning calorimeter was −62 ° C.

Synthesis example 3
Trimellitic acid-based plasticizer as a liquid oily substance, manufactured by Asahi Denka Kogyo Co., Ltd .; containing 2 mol% hydroxyl group as a crosslinkable polymer in the same manner as in Synthesis Example 1 except that the product name is “Adeka Sizer C79” A mixture (hereinafter referred to as acrylic resin C) of an acrylic copolymer and trimellitic acid plasticizer as a liquid oily substance was obtained. The residual 2-ethylhexyl acrylate by GC was 0.1%, and the 2 mol% hydroxyl group-containing acrylic copolymer as a crosslinkable polymer in the acrylic resin C was 39.9%. The viscosity of the obtained acrylic resin C at 25 ° C. was 11500 mPa · s. As for the molecular weight of the polymer using GPC, the weight average molecular weight Mw was 1106,000 and the number average molecular weight Mn was 135,000. Further, the glass transition temperature of the 2 mol% hydroxyl group-containing acrylic copolymer measured by a conventional method using a differential scanning calorimeter was −65 ° C.

Example 1
Acrylic resin A 62 parts, trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adekasizer C880”) 100 parts liquid resin 100 parts (2 mol% hydroxyl group-containing acrylic copolymer as crosslinkable polymer) A liquid resin containing about 25% coalescence and about 75% liquid oily substance), 0.1 part of a defoaming agent (manufactured by Big Chemie; trade name “A-515”), isophorone diisocyanate as a crosslinking agent PET obtained by adding 0.86 parts (the amount of hydroxyl group of the acrylic copolymer in the liquid resin and the amount of isocyanate equivalent to this mole) and defoaming was subjected to a mold release treatment with a thickness set to 15 mm. It poured into the glass cell which has a film, and it heated in 80 degreeC oven for 2 hours, and liquid resin was gelatinized. The obtained gel was measured for hardness according to the following criteria, and the results are shown in Table 1. The weight loss when the trimellitic acid plasticizer used (Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C880”) was kept in an oven at 100 ° C. for 168 hours was 0.2%.

  Next, 100 parts of the above-mentioned liquid resin, 0.1 part of a defoaming agent (manufactured by Big Chemie; trade name “A-515”), 0.86 part of isophorone diisocyanate as a crosslinking agent, and a thermal conductivity of 30 W / m · 200 parts of aluminum oxide (made by Showa Denko KK; product number AS-10), which is k, was uniformly kneaded to obtain a resin composition for a heat dissipation material. Then, the resin composition for heat radiating material is defoamed, poured into a glass cell having a PET film subjected to a release treatment having a thickness of 1 mm, heated at 80 ° C. for 2 hours, The reaction between the hydroxyl group and the isocyanate group was completed to obtain a sheet-like cured product of the resin composition for a heat dissipation material. The sheet obtained at this time, that is, the cured product of the resin composition for a heat dissipation material was evaluated according to the following criteria, and the results are shown in Table 1.

[Hardness of gel]
A container in which isophorone diisocyanate as a crosslinking agent is added in an equimolar amount with the amount of hydroxyl group of the acrylic copolymer in the liquid resin to 100 parts of the liquid resin, and then defoamed is set to a thickness of 15 mm. And heated in an oven at 80 ° C. for 2 hours to gel the liquid resin. The sample shape used is a disc shape having a diameter of 5 cm to 8 cm. As a measurement value, an Asuka-F type rubber hardness meter manufactured by Kobunshi Keiki Co., Ltd. is placed on the center of the measurement sample, and the maximum indicated value immediately after that is adopted. The measurement is performed at 25 ° C.

[Formability of sheet]
The obtained cured product of the obtained sheet-shaped resin composition for heat dissipation material was visually observed and evaluated according to the following criteria.
◯: There is no unevenness or bubbles on the sheet surface. There is no stickiness on the sheet. As long as the inorganic filler is uniform without separation and sedimentation, it was evaluated as ◯.
X: There are irregularities and bubbles on the sheet surface. Liquid oily substance is separated on the sheet surface. Separation of the liquid resin component and the inorganic filler occurred, and any phenomenon was confirmed as a non-uniform sheet was obtained. The case was evaluated as x.

[Initial thermal conductivity of sheet]
It was measured with a rapid thermal conductivity meter, product number QTM-500, manufactured by Kyoto Electronics Industry. As the measurement sample, a sheet-like cured product of the resin composition for a heat dissipation material laminated so as to have a thickness of 10 mm is used. The measurement is performed at 25 ° C.

[Initial hardness of sheet]
According to JIS K7312, it measured using the Asker rubber hardness meter C type | mold by Kobunshi Keiki Co., Ltd. The smaller the obtained numerical value, the more flexible. For the measurement value, a hardness meter is placed on the center of the measurement sample, and the maximum indicated value immediately after that is adopted. The measurement is performed at 25 ° C.
As the measurement sample, a sheet-like cured product of the resin composition for a heat dissipation material laminated so as to have a thickness of 10 mm is used.

[Heat-resistant]
The sheet-shaped cured resin composition for heat dissipation material is held in an oven set at 100 ° C. for 168 hours, and then the weight loss, hardness, and thermal conductivity of the sheet are measured.
The weight loss is obtained from (weight before measurement−weight after measurement) / weight before measurement × 100 = weight loss (%). The hardness is measured according to JIS K7312 using an Asker rubber hardness meter C type manufactured by Kobunshi Keiki Co., Ltd. The smaller the obtained numerical value, the more flexible, and the smaller the difference in hardness before and after the heat resistance test (initial hardness of the sheet), the longer the flexibility. In addition, the sample of hardness measurement uses what laminated | stacked the cured | curing material of the sheet-like resin composition for heat radiating materials so that it might become thickness of 10 mm. The thermal conductivity was measured by a rapid thermal conductivity meter product number QTM-500 manufactured by Kyoto Electronics Industry. As the sample, a sheet-like cured product of the resin composition for a heat dissipation material laminated so as to have a thickness of 10 mm is used. The measurement is performed at 25 ° C.

[durability]
A hardness difference (Δ hardness) between the initial hardness of the sheet and the sheet hardness after the heat resistance test is obtained.
If this value is small, the flexibility of the sheet can be maintained over a long period of time. Therefore, when the sheet is interposed between the heating element and the heat dissipation element, the contact area between them can be maintained over a long period of time, and as a result, the heat dissipation from the heating element The heat conduction efficiency to the body does not decrease, and stable heat dissipation characteristics can be obtained for a long period of time.

Example 2
Acrylic resin A 75 parts, trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C880”) 100 parts of liquid resin (2 mol% hydroxyl group-containing acrylic copolymer as crosslinkable polymer) A liquid resin containing about 30% coalescence and about 70% liquid oily substance), and 1.03 parts isophorone diisocyanate as a cross-linking agent (the amount of hydroxyl groups of the acrylic copolymer in the liquid resin and this mole of isocyanate) In the same manner as in Example 1 except that the amount of natto was used, a gel product of a liquid resin and a cured product of a resin composition for a heat dissipation material were obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1.

Example 3
Acrylic resin B62 parts, trimellitic acid plasticizer (Asahi Denka Kogyo Co., Ltd .; trade name "Adekasizer C880") 100 parts liquid resin 100 parts (1 mol% hydroxyl group-containing acrylic copolymer as crosslinkable polymer) Liquid resin containing about 25% coalescence and about 75% liquid oily substance), and liquid resin gel in the same manner as in Example 1 except that 0.43 part of isophorone diisocyanate was used as a crosslinking agent. And the hardened | cured material of the resin composition for heat dissipation materials was obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1.

Example 4
Acrylic resin B 75 parts, trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C880”) 100 parts of liquid resin (1 mol% hydroxyl group-containing acrylic copolymer as crosslinkable polymer) Liquid resin containing about 30% coalescence and about 70% liquid oily substance), and a gel of liquid resin in the same manner as in Example 1 except that 0.52 part of isophorone diisocyanate was used as a crosslinking agent. And the hardened | cured material of the resin composition for heat dissipation materials was obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1.

Example 5
Acrylic resin C62 parts, trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name "Adekasizer C79") 100 parts of liquid resin (2 mol% hydroxyl group-containing acrylic copolymer as a crosslinkable polymer) A liquid resin gel product and a cured product of a heat-dissipating resin composition were prepared in the same manner as in Example 1 except that a liquid resin containing about 25% coalescence and about 75% liquid oily substance was used. Obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1. The weight loss when the trimellitic acid plasticizer used (Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C79”) was kept in an oven at 100 ° C. for 168 hours was 0.5%.

Example 6
Acrylic resin C75 part, trimellitic acid plasticizer (manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C79”) 100 parts liquid resin (2 mol% hydroxyl group-containing acrylic copolymer as crosslinkable polymer) A liquid resin gel product and a cured product of a heat-dissipating resin composition were prepared in the same manner as in Example 1 except that a liquid resin containing about 30% coalescence and about 70% liquid oily substance was used. Obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1.

Example 7
Except for changing aluminum oxide to 100 parts of boron nitride having a thermal conductivity of 50 W / m · k (manufactured by Kyoritsu Materials Co., Ltd .; product number BN-100), in the same manner as in Example 1, a liquid resin gel and heat dissipation A cured product of the resin composition for a material was obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1.

Example 8
Except for changing aluminum oxide to 200 parts of aluminum nitride (product number R-15, manufactured by Toyo Aluminum Co., Ltd.) having a thermal conductivity of 120 W / m · k, a liquid resin gel and a heat dissipation material in the same manner as in Example 1. A cured product of the resin composition was obtained. Moreover, it evaluated similarly to Example 1, and showed the result in Table 1.

Comparative Example 1
In a container equipped with a thermometer, stirrer, gas inlet tube, reflux condenser and dropping funnel, 39.70 parts of 2-ethylhexyl acrylate, 0.30 parts of 2-hydroxyethyl acrylate (the hydroxyl group-containing single monomer in all monomers) The monomer was set to 1 mol%), 50 parts of toluene and 0.2 part of α-methylstyrene as a chain transfer agent were charged, and the inside of the container was replaced with nitrogen gas. The temperature was raised to 80 ° C., and a mixture of 0.05 part of azoisobutyronitrile as a polymerization initiator and 10 parts of toluene was charged in a dropping funnel and dropped over 2 hours. Furthermore, 0.01 part of azoisobutyronitrile was added, the temperature was raised to 90 ° C., and polymerization was carried out for 3 hours. Before completion of the polymerization, 0.4 part of dibutyltin dilaurate as a crosslinking accelerator was added, air was blown, the system was cooled to complete the polymerization, and a 1 mol% hydroxyl group-containing copolymer as a crosslinking polymer was obtained. % Toluene resin solution was obtained. Regarding the molecular weight of the copolymer using GPC, the weight average molecular weight Mw was 306,000, and the number average molecular weight Mn was 101,000. Moreover, the glass transition temperature of the polymer measured by a conventional method using a differential scanning calorimeter was −60 ° C.

  Next, 100 parts of the toluene resin solution that does not contain the liquid oily substance that is an essential component as the liquid resin component is added to 0.69 parts of isophorone diisocyanate as a crosslinking agent (the hydroxyl amount of the crosslinkable polymer in the toluene resin solution). Is added to the PET film which has been subjected to a release treatment so that the thickness is set to 15 mm, and the system is decompressed to completely stop the toluene. I left it. Next, it heated in 80 degreeC oven for 2 hours, the hydroxyl group and isocyanate in a polymer were made to react, and the gel thing was obtained. The obtained gel product was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

  Next, to 100 parts of the toluene resin solution, 0.69 parts of isophorone diisocyanate as a crosslinking agent, 80 parts of aluminum oxide (manufactured by Showa Denko; product number AS-10) (the crosslinkable polymer 100 in the toluene resin solution). Part was added to 200 parts) uniformly to obtain a resin composition for heat dissipation material. Then, the resin composition for heat radiating material was developed on a PET film that had been subjected to a release treatment so as to have a thickness of 1 mm, and the inside of the system was decompressed to completely distill off toluene. Next, it heated in 80 degreeC oven for 2 hours, the hydroxyl group and isocyanate in a polymer were made to react, and the cured | curing material of the resin composition for heat radiation materials of a sheet form was obtained. The sheet obtained at this time was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The resulting gel had a hardness value of 95. This is presumably because the gel was high in hardness and poor in flexibility because the liquid oily substance was not a gel obtained by being held in the cross-linked polymer. Moreover, the sheet | seat initial stage hardness was 70 and was larger than the hardened | cured material obtained in any Example. For this reason, when interposing between a heat generating element such as a PDP or an electric / electronic component and a heat dissipating element such as a heat sink, a heat radiating fin, or a metal plate to dissipate heat generated from the PDP, electric / electronic component, etc. There is a risk that the contact area with the heat sink becomes smaller and the heat dissipation characteristics deteriorate. As a result of the heat resistance test, the weight loss was 0.6%, but the sheet hardness was 89, and the amount of change in hardness before and after the test was greater than the cured product obtained in any of the examples. . For this reason, it has become clear that it does not have long-term flexibility and is inferior in stable heat dissipation characteristics.

Comparative Example 2
Toluene was completely distilled off from the toluene resin solution obtained in Comparative Example 1 to obtain a 1 mol% hydroxyl group-containing copolymer as a crosslinkable polymer.
75 parts of a 1 mol% hydroxyl group-containing copolymer as the crosslinkable polymer, and 25 parts of paraffin that is solid at room temperature and has a melting point of 47 ° C. (manufactured by Nippon Seiwa Co., Ltd .; product number paraffin wax 115) as a thermosoftening agent. 100 parts of heat softening resin (that is, not including the liquid oily substance essential as a liquid resin), 1.30 parts of isophorone diisocyanate as a crosslinking agent (the amount of hydroxyl groups and equimolar amount of the crosslinkable polymer in the heat softening resin) ) Is developed on a PET film that has been subjected to a release treatment so that the thickness is set to 15 mm, and heated in an oven at 80 ° C. for 2 hours to remove hydroxyl groups and isocyanate in the polymer. A gel was obtained by reaction. The obtained gel product was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

  Next, 100 parts of the heat softening resin, 1.30 parts of isophorone diisocyanate as a crosslinking agent, 200 parts of aluminum oxide having a thermal conductivity of 30 W / m · k (manufactured by Showa Denko; product number AS-10), It knead | mixed for 30 minutes at 50 degreeC using the pressure type kneader. Then, it extruded by the 1 mm thickness setting between the two PET films using the extruder, and obtained the resin composition for heat sinks of a sheet form. Next, the obtained sheet-shaped resin composition for a heat dissipation material was heated at 80 ° C. for 2 hours to complete the reaction between the hydroxyl group and the isocyanate group in the composition. The sheet obtained at this time was evaluated in the same manner as in Example 1. The results are shown in Table 1.

The hardness value of the obtained gel was 90. This is presumably because the gel was high in hardness and poor in flexibility because the liquid oily substance was not a gel obtained by being held in the cross-linked polymer. Moreover, the sheet | seat initial stage hardness was 60 and was larger than the hardened | cured material obtained in any Example. For this reason, when interposing between a heat generating element such as a PDP or an electric / electronic component and a heat dissipating element such as a heat sink, a heat radiating fin, or a metal plate to dissipate heat generated from the PDP, electric / electronic component, etc. There is a risk that the contact area with the heat sink becomes smaller and the heat dissipation characteristics deteriorate.
Further, the obtained sheet was uniform without separation of the resin and the inorganic filler used, but there were irregularities and bubbles on the surface, and the surface smoothness was inferior. That is, the formability of the sheet was not good.

  As a result of the heat resistance test, the weight loss was 6.1%, and the sheet hardness exceeded the maximum value of 100. This is thought to be due to an increase in weight loss due to volatilization of the heat softener used, and an increase in hardness. Therefore, it was revealed that the obtained sheet does not have long-term flexibility and is inferior in stable heat dissipation characteristics. Furthermore, many blisters occurred in the sheet after the heat test.

The abbreviations used in Table 1 have the following meanings.
C880: Plasticizer manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C880”
C79: Plasticizer manufactured by Asahi Denka Kogyo Co., Ltd .; trade name “Adeka Sizer C79”
Cross-linking agent: isophorone diisocyanate A-515: manufactured by Big Chemie Co., Ltd. Defoaming agent; trade name “A-515”
Δ Hardness: Difference in hardness between the initial sheet hardness value and the sheet hardness value after the heat resistance test

As is clear from Table 1, the present invention example can efficiently obtain a cured product that not only has excellent thermal conductivity but also has, for example, good moldability of the heat dissipation sheet and long-term flexibility. On the other hand, it was clarified that all of the comparative examples were inferior in moldability and initial and long-term flexibility of the heat dissipation sheet as compared with the examples.

Claims (4)

A resin composition for a heat dissipation material containing a liquid resin containing trimellitic acid plasticizer and acrylic copolymer as essential components, and further comprising a crosslinking agent having an isocyanate group, aluminum oxide, boron nitride and nitriding A resin composition for a heat dissipation material , comprising an inorganic filler selected from aluminum . The acrylic copolymer is polymerizable with the 2 to 18 carbon atoms in the alkyl group as the polymerizable monomer (A) and (meth) acrylic acid alkyl ester, a functional group for crosslinking the hydroxyl group-containing monomer as a monomer (B), by copolymerizing such ratio is 0.1 to 5 mol% of (a) and the total amount of (B) (B) The resin composition for a heat radiating material according to claim 1, wherein The resin composition for a heat radiation material according to claim 1 or 2 , wherein the cured product of the resin composition for a heat radiation material has a weight loss of not more than 5 mass% when held at 100 ° C for 168 hours. A gel obtained by curing the heat dissipation material for the resin composition according to any one of claims 1 to 3, the heat radiation cured material, wherein the hardness of the gel is 5 to 80.