JP6352159B2 - Thermally conductive adhesive tape and thermally conductive adhesive composition - Google Patents

Description

The present invention relates to a heat conductive pressure-sensitive adhesive tape and a heat conductive pressure-sensitive adhesive composition having high heat conductivity and high constant load peelability to a heating element and a heat radiator.

Conventionally, the heat generated by a semiconductor element is transmitted to the radiator, and the semiconductor element and the radiator are thermally conductive for the purpose of operating the semiconductor element normally and stably over a long period of time by always maintaining the semiconductor element at an appropriate temperature. A technique of joining using an adhesive tape is known.
As such a heat conductive pressure-sensitive adhesive tape, for example, Patent Document 1 discloses a heat conduction containing a specific organopolysiloxane, a specific hydrolyzable group-containing methyl polysiloxane, a heat conductive filler, and a curing agent. An adhesive tape using a conductive silicone rubber composition is disclosed.
Patent Document 2 is a bonding material containing an epoxy resin, a curing agent, a curing accelerator, and a specific amount of filler showing specific physical properties, and the thermal conductivity of the cured product is a specific value or more, There is disclosed a bonding material that is used to bond a power semiconductor element having a power consumption of 1.7 W or more to a support member via the bonding material.
Patent Document 3 discloses an insulating sheet containing a specific amount of thermally conductive filler in an organopolysiloxane substrate, and the amount of conductive impurities in the insulating sheet is not more than a specific value. An insulating sheet and a semiconductor device assembly used for a vehicle manufactured using the insulating sheet are disclosed.
Furthermore, Patent Document 4 contains an adhesive and thermally conductive particles, the main component of the adhesive is an acrylic adhesive having an acid value of 5 mgKOH / g or less, and a carboxylic acid dispersant is 0.05 to An adhesive tape using a heat conductive adhesive composition containing 2.0% by mass is described.

In order to more efficiently conduct the heat generated by the heating element to the heat radiating body, the heat conductive adhesive tape is required to have high thermal conductivity. On the other hand, if the heat conductive adhesive tape cannot sufficiently adhere to the heat generating body and the heat radiating body, heat conduction loss occurs at the non-contact portion. Therefore, in addition to heat conductivity, the heat conductive pressure-sensitive adhesive tape is required to have adhesiveness and tackiness that can be sufficiently adhered to a heating element and a heat dissipation body, and in particular, to be excellent in constant load peelability.

JP 2000-256558 A Japanese Patent No. 4507488 Japanese Patent Laying-Open No. 2005-064291 JP 2014-132049 A

The inventors of the present application have studied to further improve the thermal conductivity of the thermally conductive adhesive tape. As measures for improving the thermal conductivity, for example, it was considered to increase the content of the thermally conductive filler in the pressure-sensitive adhesive layer or to reduce the thickness of the thermally conductive pressure-sensitive adhesive tape. However, each of the measures has a problem that even if the thermal conductivity itself is improved, the adhesiveness to the heating element and the heat radiating body, in particular, the constant load peelability is lowered.

In view of the above-mentioned present situation, the present invention aims to provide a heat conductive pressure-sensitive adhesive tape and a heat conductive pressure-sensitive adhesive composition having high heat conductivity and high constant load peelability to a heating element and a heat radiator. To do.

This invention is a heat conductive adhesive tape which has an adhesive layer containing the acrylic polymer of molecular weight distribution (Mw / Mn) 1.05-2.5 obtained by living radical polymerization, and a heat conductive filler. is there.
The present invention is described in detail below.

The present inventors have an adhesive containing an acrylic polymer having a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 obtained by living radical polymerization (hereinafter also referred to as “living radical polymerization acrylic polymer”). It has been found that the pressure-sensitive adhesive tape having the agent layer is not easily peeled even if it is a thin pressure-sensitive adhesive tape, and can exhibit high constant load peelability to the adherend. And by blending such a pressure-sensitive adhesive layer with a heat conductive filler, even if the thickness of the tape is reduced to such an extent that a high heat conductivity can be exhibited, a high constant load peelability with respect to a heating element and a heat radiating element can be obtained. The present invention has been completed by finding that it can be maintained.
In the heat conductive pressure-sensitive adhesive tape of the present invention, since the thickness of the tape can be reduced by using a living radical polymerization acrylic polymer, sufficient heat conductivity can be exhibited even if the amount of the heat conductive filler is reduced, and therefore heat A synergistic effect that can further prevent the deterioration of the adhesive performance due to the conductive filler blend can be exhibited.

The heat conductive adhesive tape of this invention has an adhesive layer containing a living radical polymerization acrylic polymer. When the pressure-sensitive adhesive layer contains the living radical polymerization acrylic polymer, the heat-conductive pressure-sensitive adhesive tape of the present invention is not easily peeled even if it is a thin pressure-sensitive adhesive tape, and has a high constant load peelability to the adherend. High heat conductivity can be exhibited by blending such a pressure-sensitive adhesive layer with a heat conductive filler.

The living radical polymerization acrylic polymer is obtained by living radical polymerization using an acrylic monomer such as (meth) acrylic acid ester or (meth) acrylic acid as a raw material, preferably living radical polymerization using an organic tellurium polymerization initiator. Acrylic polymer.
Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. According to living radical polymerization, for example, a polymer having a more uniform molecular weight and composition than that of free radical polymerization or the like can be obtained, and the production of low molecular weight components and the like can be suppressed. The constant load peelability to the body is improved. In particular, when the living radical polymerization acrylic polymer has a crosslinkable functional group and a crosslinker is used in combination, a particularly high constant load peelability can be exhibited.

FIG. 1 shows a schematic diagram for explaining living radical polymerization. Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. In living radical polymerization, the reaction proceeds without the growth terminal radicals being deactivated and without generating new radical species during the reaction. In the middle of the reaction, all polymer chains are polymerized while uniformly reacting with the monomer, and the composition of all polymers approaches uniform. Therefore, it is possible to suppress the generation of low molecular weight components that cause peeling.
Furthermore, when the living radical polymerization acrylic polymer has a crosslinkable functional group and a crosslinker is used in combination, a particularly high constant load peelability can be exhibited. This is because the living radical polymerization includes the crosslinkable functional group-containing monomer 12 in all the polymers of the living radical polymerization crosslinkable acrylic polymer 1. When the living radical polymerization acrylic polymer 1 having such a crosslinkable functional group is cross-linked using a cross-linking agent, almost all polymers can participate in cross-linking between polymer chains. In particular, since there are few low molecular weight components that do not contain a crosslinkable functional group-containing monomer, the probability that all polymer chains are involved in crosslinking is improved even with fine crosslinking with a gel fraction of 15% by weight or less. FIG. 2 is a schematic diagram illustrating a case where a living radical polymerization acrylic polymer having a crosslinkable functional group is crosslinked. In the living radical polymerization acrylic polymer, the composition of all polymers is uniform, and since the crosslinkable functional group-containing monomer is included, all polymer chains are involved in crosslinking. In FIG. 2, a hydroxyl group is shown as an example of the crosslinkable functional group. Thus, since almost all polymers can participate in crosslinking between polymer chains, it is difficult to remove even a thin adhesive tape, and an adhesive tape capable of exhibiting a high constant load peelability is obtained. be able to.

The effect of the present invention cannot be obtained even when an acrylic polymer obtained by conventional free radical polymerization is used.
FIG. 3 is a schematic diagram for explaining free radical polymerization. In free radical polymerization, radical species are continuously generated during the reaction and added to the monomer, and the polymerization proceeds. Therefore, in the free radical polymerization, a polymer 23 in which the growing terminal radical is deactivated during the reaction and a polymer 24 grown by the radical species newly generated during the reaction are generated. These low molecular weight components and the like cause peeling. Further, when an acrylic polymer containing a crosslinkable functional group is produced by free radical polymerization, a polymer containing no relatively low molecular weight crosslinkable functional group-containing monomer is produced. Even if such a free radical polymerization crosslinkable acrylic polymer 2 is cross-linked using a cross-linking agent, a polymer that does not contain a crosslinkable functional group-containing monomer cannot participate in cross-linking between polymer chains. FIG. 4 shows a schematic diagram for explaining a case where a free radical polymerization crosslinkable acrylic polymer is crosslinked. In the free radical polymerization crosslinkable acrylic polymer, there is a polymer chain that cannot participate in crosslinking because the composition of the polymer is non-uniform and the polymer does not contain a relatively low molecular weight crosslinkable functional group-containing monomer. . In FIG. 4, a hydroxyl group is shown as an example of the crosslinkable functional group. When a load is applied by attaching to an adherend as a thin adhesive tape, peeling occurs from a site that does not contain a crosslinkable functional group-containing monomer that cannot participate in crosslinking. The peelability cannot be exhibited.

Among living radical polymerizations, living radical polymerization using an organic tellurium polymerization initiator has a crosslinkable functional group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, and a nitrile group, unlike other living radical polymerizations. Without protecting any radically polymerizable monomer, it is possible to obtain a polymer having a uniform molecular weight and composition by polymerizing with the same initiator. For this reason, the radically polymerizable monomer which has a crosslinkable functional group can be copolymerized easily.

The organic tellurium polymerization initiator is not particularly limited as long as it is generally used for living radical polymerization, and examples thereof include organic tellurium compounds and organic telluride compounds.
Examples of the organic tellurium compound include (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl-propyl) benzene, 1-chloro-4- (methylterranyl-methyl) benzene, 1-hydroxy- 4- (methylterranyl-methyl) benzene, 1-methoxy-4- (methylterranyl-methyl) benzene, 1-amino-4- (methylterranyl-methyl) benzene, 1-nitro-4- (methylterranyl-methyl) benzene, 1- Cyano-4- (methylterranyl-methyl) benzene, 1-methylcarbonyl-4- (methylterranyl-methyl) benzene, 1-phenylcarbonyl-4- (methylterranyl-methyl) benzene, 1-methoxycarbonyl-4- (methylterranyl-methyl) ) Benzene, 1- Enoxycarbonyl-4- (methylterranyl-methyl) benzene, 1-sulfonyl-4- (methylterranyl-methyl) benzene, 1-trifluoromethyl-4- (methylterranyl-methyl) benzene, 1-chloro-4- (1 -Methyl terranyl-ethyl) benzene, 1-hydroxy-4- (1-methyl terranyl-ethyl) benzene, 1-methoxy-4- (1-methyl teranyl-ethyl) benzene, 1-amino-4- (1-methyl terranyl-ethyl) Benzene, 1-nitro-4- (1-methylterranyl-ethyl) benzene, 1-cyano-4- (1-methylterranyl-ethyl) benzene, 1-methylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1- Phenylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-meth Sicarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-phenoxycarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-sulfonyl-4- (1-methylterranyl-ethyl) benzene, 1-trifluoromethyl -4- (1-methylteranyl-ethyl) benzene, 1-chloro-4- (2-methylterranyl-propyl) benzene, 1-hydroxy-4- (2-methylterranyl-propyl) benzene, 1-methoxy-4- (2 -Methyl teranyl-propyl) benzene, 1-amino-4- (2-methyl teranyl-propyl) benzene, 1-nitro-4- (2-methyl teranyl-propyl) benzene, 1-cyano-4- (2-methyl teranyl-propyl) Benzene, 1-methylcarbonyl-4- (2-methylterranyl-propyl ) Benzene, 1-phenylcarbonyl-4- (2-methylterranyl-propyl) benzene, 1-methoxycarbonyl-4- (2-methylterranyl-propyl) benzene, 1-phenoxycarbonyl-4- (2-methylterranyl-propyl) benzene 1-sulfonyl-4- (2-methylterranyl-propyl) benzene, 1-trifluoromethyl-4- (2-methylterranyl-propyl) benzene, 2- (methylterranyl-methyl) pyridine, 2- (1-methylterranyl-ethyl) ) Pyridine, 2- (2-methylterranyl-propyl) pyridine, 2-methylterranyl-methyl ethanoate, methyl 2-methylterranyl-propionate, methyl 2-methylterranyl-2-methylpropionate, 2-methylterranyl-ethyl ethanoate, 2 -Methylterranil Ethyl propionate, 2-Mechiruteraniru -2-methylpropionic acid ethyl, 2-methyl-Terra alkylsulfonyl acetonitrile, 2-methyl-Terra sulfonyl propionitrile, 2-methyl-2-methyl-Terra sulfonyl propionitrile, and the like. The methyl terranyl group in these organic tellurium compounds may be an ethyl terranyl group, n-propyl terranyl group, isopropyl terranyl group, n-butyl terranyl group, isobutyl terranyl group, t-butyl terranyl group, phenyl terranyl group, etc. These organic tellurium compounds may be used alone or in combination of two or more.

Examples of the organic telluride compound include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di-n-butyl ditelluride, di-sec-butyl ditelluride. , Di-tert-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis- (p-methoxyphenyl) ditelluride, bis- (p-aminophenyl) ditelluride, bis- (p-nitrophenyl) ditelluride, bis -(P-cyanophenyl) ditelluride, bis- (p-sulfonylphenyl) ditelluride, dinaphthyl ditelluride, dipyridyl ditelluride and the like can be mentioned. These organic telluride compounds may be used alone or in combination of two or more. Of these, dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, di-n-butyl ditelluride and diphenyl ditelluride are preferable.

In addition, within the range which does not impair the effect of this invention, in addition to the said organic tellurium polymerization initiator, you may use an azo compound as a polymerization initiator for the purpose of acceleration | stimulation of a polymerization rate.
The azo compound is not particularly limited as long as it is generally used for radical polymerization. For example, 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2-methylbutyronitrile) ), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis (cyclohexane-1-carbonitrile) ), 1-[(1-cyano-1-methylethyl) azo] formamide, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobis (2-methylpropionate), Dimethyl-1,1′-azobis (1-cyclohexanecarboxylate), 2,2′-azobis {2-methyl-N- [1,1′-bis (hydroxymethyl) -2-hydroxyethyl Propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2 , 2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [2- (2-imidazoline-2 -Yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis [2 -(2-imidazolin-2-yl) propane], 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionami Tetrahydrate, 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis (2,4,4-trimethylpentane) and the like. It is done. These azo compounds may be used alone or in combination of two or more.

The living radical polymerization acrylic polymer preferably has a crosslinkable functional group.
Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, and a nitrile group. Especially, since adjustment of the gel fraction of the said adhesive layer is easy, a hydroxyl group or a carboxyl group is preferable and a hydroxyl group is more preferable.

A monomer having a crosslinkable functional group is preferably blended as a monomer that is polymerized in the living radical polymerization.
Examples of the monomer having a hydroxyl group include (meth) acrylic acid esters having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate.
Examples of the monomer having a carboxyl group include (meth) acrylic acid. Of these, acrylic acid is preferred.
Examples of the monomer having a glycidyl group include glycidyl (meth) acrylate.
Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, dimethylaminopropyl acrylamide, and the like.
Examples of the monomer having a nitrile group include acrylonitrile.

When the (meth) acrylic acid ester having a hydroxyl group is used, the content is not particularly limited, but a preferable upper limit in the radical polymerizable monomer to be polymerized in the living radical polymerization is 30% by weight. When the content exceeds 30% by weight, the gel fraction of the pressure-sensitive adhesive layer becomes too high and the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered.

When the acrylic monomer having a carboxyl group is used, the content thereof is not particularly limited, but the preferable lower limit in the radical polymerizable monomer polymerized in the living radical polymerization is 0.1% by weight, and the preferable upper limit is 10% by weight. is there. When the content is less than 0.1% by weight, the pressure-sensitive adhesive layer becomes too soft and heat resistance may be lowered. When the content exceeds 10% by weight, the pressure-sensitive adhesive layer may become too hard and the pressure-sensitive adhesive tape may be easily peeled off.

As the acrylic monomer that is polymerized in the living radical polymerization, other radical polymerizable monomers other than the acrylic monomer having a crosslinkable functional group may be used. As said other radically polymerizable monomer, other (meth) acrylic acid ester is mentioned, for example. In addition to the acrylic monomer, a vinyl compound may be used as a monomer.

The other (meth) acrylic acid esters are not particularly limited, and are methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2 -(Meth) acrylic acid alkyl esters such as ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isomyristyl (meth) acrylate, stearyl (meth) acrylate, Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate , Tetrahydrofurfuryl (meth) acrylate, polypropylene glycol mono (meth) acrylate. These (meth) acrylic acid esters may be used alone or in combination of two or more.

The said vinyl compound is not specifically limited, For example, N-vinyl pyrrolidone, N-vinyl caprolactam, N-acryloyl morpholine, styrene, vinyl acetate etc. are mentioned. These vinyl compounds may be used alone or in combination of two or more.

In the living radical polymerization, a dispersion stabilizer may be used. Examples of the dispersion stabilizer include polyvinyl pyrrolidone, polyvinyl alcohol, methyl cellulose, ethyl cellulose, poly (meth) acrylic acid, poly (meth) acrylic acid ester, and polyethylene glycol.
As the living radical polymerization method, conventionally known methods are used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
When a polymerization solvent is used in the living radical polymerization, the polymerization solvent is not particularly limited. For example, a nonpolar solvent such as hexane, cyclohexane, octane, toluene, xylene, water, methanol, ethanol, propanol, butanol, acetone, Highly polar solvents such as methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, N, N-dimethylformamide can be used. These polymerization solvents may be used alone or in combination of two or more.
The polymerization temperature is preferably 0 to 110 ° C. from the viewpoint of the polymerization rate.

The living radical polymerization acrylic polymer has a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. When the molecular weight distribution exceeds 2.5, the low molecular weight components and the like generated in the living radical polymerization increase, so that the pressure-sensitive adhesive tape is easily peeled off and the constant load peelability to the adherend is lowered. A preferable upper limit of the molecular weight distribution is 2.0, a more preferable upper limit is 1.8, and a further preferable upper limit is 1.7.

The living radical polymerization acrylic polymer has a preferable lower limit of 300,000 and a preferable upper limit of 2 million for the weight average molecular weight (Mw). If the weight average molecular weight is less than 300,000, the pressure-sensitive adhesive layer may be too soft and heat resistance may be lowered. If the weight average molecular weight exceeds 2,000,000, the viscosity at the time of coating becomes too high to be applied, which may cause uneven thickness of the pressure-sensitive adhesive layer. The minimum with a more preferable weight average molecular weight (Mw) of the said living radical polymerization acrylic polymer is 400,000, and a more preferable upper limit is 1.5 million.

The molecular weight distribution (Mw / Mn) is a ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn).
A weight average molecular weight (Mw) and a number average molecular weight (Mn) are measured as a polystyrene conversion molecular weight by the gel permeation chromatography (GPC) method. Specifically, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are obtained by filtering a diluted solution obtained by diluting a living radical polymerization acrylic polymer with tetrahydrofuran (THF) 50 times through a filter. It is measured as a polystyrene equivalent molecular weight by the GPC method using the filtrate obtained. In the GPC method, for example, 2690 Separations Model (manufactured by Waters) or the like can be used.

The pressure-sensitive adhesive layer may contain a polymer component other than the living radical polymerization acrylic polymer, for example, a polymer obtained by free radical polymerization.
However, the lower limit of the content of the living radical polymerization acrylic polymer in the polymer component is preferably 60% by weight, and the total amount of the polymer component (100% by weight) is more preferably the living radical polymerization acrylic polymer. . By making the content of the living radical polymerization acrylic polymer in the polymer component 60% by weight or more, it is difficult to peel off even if it is thin, and it is also high for adherends such as polycarbonate (PC) plates and polypropylene (PP) plates. A heat conductive pressure-sensitive adhesive tape that can exhibit constant load peelability can be obtained.
In addition, the tackifier resin mentioned later is not included in the polymer component.

The pressure-sensitive adhesive layer contains a heat conductive filler.
The material of the heat conductive filler is not particularly limited, and examples thereof include aluminum nitride, boron nitride, aluminum oxide, diamond, aluminum, silicon nitride, zirconia, and magnesium oxide. Among these, aluminum oxide is particularly preferable because a heat conductive adhesive having high insulation and heat insulation can be obtained even at high temperatures.

Although the average particle diameter of the said heat conductive filler is not specifically limited, A preferable minimum is 0.1 micrometer and a preferable upper limit is 10 micrometers. When the average particle size of the heat conductive filler is less than 0.1 μm, the viscosity of the heat conductive pressure sensitive adhesive coating liquid increases, and the applicability, workability, and the like during tape production may decrease. When the average particle diameter of the heat conductive filler exceeds 10 μm, the surface of the thin pressure-sensitive adhesive layer is roughened, the adhesion to the adherend may be lowered, and the constant load peelability may be lowered. The minimum with a more preferable average particle diameter of the said heat conductive filler is 0.2 micrometer, and a more preferable upper limit is 3 micrometers.

The shape of the said heat conductive filler is not specifically limited.
The aspect ratio of the heat conductive filler is not particularly limited, but a preferable lower limit is 2, a preferable upper limit is 80, a more preferable lower limit is 10, and a more preferable upper limit is 50.
In the present specification, the aspect ratio means the ratio of the length of the major axis of the particle to the length of the minor axis of the particle (length of major axis / length of minor axis). The closer the aspect ratio value is to 1, the closer the shape of the thermally conductive filler is to a true sphere.

The minimum with preferable content of the said heat conductive filler in the said adhesive layer is 20 volume%, and a preferable upper limit is 80 volume%. When the content of the heat conductive filler is less than 20% by volume, sufficient heat conductivity may not be obtained. When the content exceeds 80% by volume, the adhesion to the adherend is reduced, and a constant load is applied. Peelability may be reduced. The minimum with more preferable content of the said heat conductive filler is 30 volume%, and a more preferable upper limit is 60 volume%.
The volume% can be calculated using specific gravity.

When the living radical polymerization acrylic polymer has a crosslinkable functional group, the pressure-sensitive adhesive layer preferably contains a crosslinker. It becomes easy to adjust the gel fraction of the pressure-sensitive adhesive layer by appropriately adjusting the type or amount of the crosslinking agent. The crosslinking agent is not particularly limited, and may be, for example, an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, etc., depending on the type of crosslinking functional group of the living radical polymerization acrylic polymer. Select and use.
For example, when the living radical polymerization acrylic polymer has a hydroxyl group as a crosslinkable functional group, the living radical polymerization acrylic polymer can be crosslinked by using, for example, an isocyanate crosslinking agent as a crosslinking agent. Moreover, when the living radical polymerization acrylic polymer has a carboxyl group as a crosslinkable functional group, the living radical polymerization acrylic polymer can be crosslinked by using, for example, an epoxy crosslinking agent or an aziridine crosslinking agent as a crosslinking agent. it can.
Since the living radical polymerization acrylic polymer has a uniform composition of all the polymers contained and has a crosslinkable functional group, all the polymers can participate in crosslinking between polymer chains. For this reason, even if it is a thin adhesive tape, it is hard to peel and the adhesive tape which can exhibit high constant load peelability with respect to a to-be-adhered body can be obtained.
Especially, since it is excellent in the adhesive stability with respect to a base material, an isocyanate type crosslinking agent is preferable. Examples of the isocyanate-based crosslinking agent include Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation).

The blending amount of the crosslinking agent is preferably 0.01 to 5 parts by weight and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the living radical polymerization acrylic polymer. Within this range, the gel fraction of the pressure-sensitive adhesive layer can be adjusted to 15% by weight or less.

The pressure-sensitive adhesive layer preferably further contains a tackifier resin. When the said adhesive layer contains tackifying resin, the constant load peelability with respect to the adherend of an adhesive tape improves. Especially, when using the tackifier which has a crosslinkable functional group, it can bridge | crosslink with the living radical polymerization acrylic polymer which has the said crosslinkable functional group through a crosslinking agent.

The tackifying resin has a preferred lower limit of hydroxyl value of 25 and a preferred upper limit of 55. When the hydroxyl value is out of the above range, the constant load peelability of the adhesive tape to the adherend may be lowered. A more preferred lower limit of the hydroxyl value is 30, and a more preferred upper limit is 50.
The hydroxyl value can be measured by JIS K1557 (phthalic anhydride method).

The tackifying resin has a preferable lower limit of the softening temperature of 70 ° C and a preferable upper limit of 170 ° C. When the softening temperature is less than 70 ° C., the tackifying resin may be too soft and the constant load peelability may be lowered. When the softening temperature exceeds 170 ° C., the pressure-sensitive adhesive layer becomes too hard, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. A more preferable lower limit of the softening temperature is 120 ° C.
The softening temperature is a softening temperature measured by the JIS K2207 ring and ball method.

The tackifying resin is not particularly limited, and examples thereof include rosin resins such as rosin ester resins, terpene resins such as terpene phenol resins, and petroleum resins. Of these, rosin ester resins and terpene phenol resins are preferable.
The above-mentioned rosin ester resins are rosin resins mainly composed of abietic acid, disproportionated rosin resins and hydrogenated rosin resins, dimers of polymer acids such as abietic acid (polymerized rosin resins), etc. It is the resin obtained by making it. A part of the hydroxyl group of the alcohol used for esterification is contained in the resin without being used for esterification, so that the hydroxyl value is adjusted to the above range. Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.
Resin esterified rosin resin is rosin ester resin, disproportionated rosin resin esterified disproportionated rosin ester resin, hydrogenated rosin resin esterified resin is hydrogenated rosin ester resin, polymerized rosin A resin obtained by esterifying the resin is a polymerized rosin ester resin.
The terpene phenol resin is a resin obtained by polymerizing terpene in the presence of phenol.

Examples of the disproportionated rosin ester resin include Superester A75 (hydroxyl value 23, softening temperature 75 ° C.) manufactured by Arakawa Chemical Industries, Superester A100 (hydroxyl value 16, softening temperature 100 ° C.) manufactured by Arakawa Chemical Co., Ltd. Examples thereof include ester A115 (hydroxyl value 19, softening temperature 115 ° C.), super ester A125 (hydroxyl value 15, softening temperature 125 ° C.) manufactured by the same company. Examples of the hydrogenated rosin ester resin include Pine Crystal KE-359 (hydroxyl value 42, softening temperature 100 ° C.) manufactured by Arakawa Chemical Industries, and ester gum H (hydroxyl value 29, softening temperature 70 ° C.) manufactured by the same company. It is done. Examples of the polymerized rosin ester resin include Pencel D135 (Hydroxyl value 45, softening temperature 135 ° C.) manufactured by Arakawa Chemical Industries, Pencel D125 (Hydroxyl value 34, softening temperature 125 ° C.) manufactured by Arakawa Chemical Co., Ltd. 42, softening temperature 160 ° C.) and the like.
Examples of the terpene resin include YS Polystar G150 (softening point 150 ° C.) manufactured by Yasuhara Chemical, YS Polyster T100 (softening point 100 ° C.), YS Polyster G125 (softening point 125 ° C.), YS Polyster Examples thereof include T115 (softening point 115 ° C.), YS Polystar T130 (softening point 130 ° C.) manufactured by the same company.
These tackifier resins may be used alone or in combination of two or more.

The content of the tackifier resin is preferably 5 parts by weight with respect to 100 parts by weight of the living radical polymerization acrylic polymer, and 40 parts by weight with a preferable upper limit. If the content is less than 5 parts by weight, a sufficient constant load peelability improvement effect may not be obtained. Even if the content exceeds 40 parts by weight, the pressure-sensitive adhesive layer may become too hard due to an increase in the glass transition temperature (Tg), and the pressure-sensitive adhesive tape may be easily peeled off.

The pressure-sensitive adhesive layer may contain other resins such as additives such as a plasticizer, an emulsifier, a softener, a filler, a pigment, a dye, a silane coupling agent, and an antioxidant, if necessary. Good.

The pressure-sensitive adhesive layer preferably has a gel fraction of 15% by weight or less excluding the thermally conductive filler.
In the pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a free radical polymerization acrylic polymer as a polymer component, if the gel fraction is lowered, the constant load peelability is improved. . On the other hand, when the gel fraction is increased, the adhesive cohesion is improved, but the constant load peelability is lowered. For this reason, in a pressure-sensitive adhesive layer containing a free radical polymerization crosslinkable acrylic polymer as a polymer component, it is common to adjust the gel fraction to 15 to 35% by weight to achieve both constant load peelability and pressure-sensitive adhesive cohesive strength. Is.
On the other hand, in the pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a living radical polymerization acrylic polymer as a polymer component, the adhesive strength is reduced when the gel fraction is 80% by weight or more, and the performance that no adhesive remains at the time of peeling is exhibited. It is known that This means that the adhesive strength increases when the gel fraction is less than 80% by weight. However, in adhesive tapes having an adhesive layer containing living radical polymerization acrylic polymer as a polymer component, it is difficult to peel off even if it is thin, and it is known about the range of gel fraction that can exhibit high constant load peelability to the adherend. It was not done.

As a result of intensive studies, the inventors have made the gel fraction of the pressure-sensitive adhesive layer excluding the thermally conductive filler 15% by weight or less, so that even if it is thin, it is difficult to peel off and is high with respect to the adherend. It was found that the constant load peelability can be exhibited. This is because living radical polymerized acrylic polymers have a uniform composition of all polymers and have crosslinkable functional groups, so all polymers can participate in crosslinking between polymer chains. It is considered that the adhesive cohesive force can be exhibited and the constant load peeling force is improved.
When the gel fraction exceeds 15% by weight, the pressure-sensitive adhesive layer becomes hard and the constant load peelability to the adherend is lowered. The gel fraction is preferably 10% by weight or less, and more preferably 5% by weight or less.

The gel fraction is measured as follows. First, the adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece. After the test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate and subjected to a condition of 110 ° C. For 1 hour. The weight of the test piece after drying is measured, and the gel fraction is calculated using the following formula (1). In addition, the release film for protecting an adhesive layer shall not be laminated | stacked on the test piece.
Gel fraction (% by weight) = 100 × (W2−W0− (W1−W0) × P) / ((W1−W0) − (W1−W0) × P) (1)
(W0: weight of base material, W1: weight of test piece before dipping, W2: weight of test piece after dipping and drying, P: weight fraction of heat transfer filler in pressure-sensitive adhesive layer)

Since the heat conductive adhesive tape of this invention is thin even if it is thin, the said adhesive layer and the base material mentioned later can be made thin according to a use.
The thickness of the pressure-sensitive adhesive layer is not particularly limited because it is set depending on the use, but a preferable lower limit is 1 μm and a preferable upper limit is 20 μm. When the thickness is less than 1 μm, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. When the thickness exceeds 20 μm, sufficiently high thermal conductivity may not be exhibited. The more preferable lower limit of the thickness of the pressure-sensitive adhesive layer is 2 μm, the more preferable upper limit is 15 μm, the still more preferable lower limit is 3 μm, and the still more preferable upper limit is 10 μm.

The heat conductive pressure-sensitive adhesive tape of the present invention may be a support type having a base material or a non-support type having no base material. In the case of the support type, the pressure-sensitive adhesive layer may be formed on one side of the substrate, or the pressure-sensitive adhesive layer may be formed on both sides.
Although the said base material is not specifically limited, A resin film, a resin foam, paper, a nonwoven fabric, a yarn cloth cloth etc. are mentioned. A base material having high thermal conductivity such as aluminum foil can also be used.

The manufacturing method of the heat conductive adhesive tape of this invention is not specifically limited, For example, the said living radical polymerization acrylic polymer, the said heat conductive filler, as needed, the other compounding components, such as said tackifier resin, a crosslinking agent Are mixed together and stirred to prepare a pressure-sensitive adhesive solution. Subsequently, this pressure-sensitive adhesive solution is coated and dried on a release-treated PET film to form a pressure-sensitive adhesive layer, and the resulting pressure-sensitive adhesive layer is used as a base material. The method of transferring to one side or both sides, the method of directly coating and drying the substrate, and the like. The pressure-sensitive adhesive layer formed by coating and drying the PET film obtained by releasing the pressure-sensitive adhesive solution may be used as a non-support type pressure-sensitive adhesive tape without a substrate.

Although the use of the heat conductive adhesive tape of this invention is not specifically limited, It uses suitably for the joining etc. of heat-emitting electronic components, such as a semiconductor element and an organic EL element, and the heat radiator which consists of a heat sink, a graphite sheet, etc. it can.
A heat conductive adhesive composition containing an acrylic polymer having a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 obtained by living radical polymerization and a heat conductive filler is also one aspect of the present invention. It is.

ADVANTAGE OF THE INVENTION According to this invention, the heat conductive adhesive tape and heat conductive adhesive composition provided with high heat conductivity and the high constant load peelability with respect to a heat generating body and a heat radiator can be provided.

It is a schematic diagram explaining living radical polymerization. It is a schematic diagram explaining the case where a living radical polymerization crosslinkable acrylic polymer is bridge | crosslinked. It is a schematic diagram explaining free radical polymerization. It is a schematic diagram explaining the case where a free radical polymerization crosslinkable acrylic polymer is bridge | crosslinked.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Preparation of living radical polymerization acrylic polymer)
Tellurium (40 mesh, metal tellurium, manufactured by Aldrich) 6.38 g (50 mmol) was suspended in tetrahydrofuran (THF) 50 mL, and 1.6 mol / L n-butyllithium / hexane solution (Aldrich) 34 was added thereto. 4 mL (55 mmol) was slowly added dropwise at room temperature. The reaction solution was stirred until the metal tellurium disappeared completely. To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain a yellow oily ethyl 2-methyl-2-n-butylteranyl-propionate.

In a glove box substituted with argon, 35 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis Example 1-1, V-60 (2,2′-azobisisobutyro) was prepared in a reaction vessel. Nitrile (manufactured by Wako Pure Chemical Industries, Ltd.) 2.6 mg and ethyl acetate 1 mL were added. Subsequently, while flowing argon gas into the reaction vessel, 60.0 g of butyl acrylate, 36.7 g of 2-ethylhexyl acrylate, 3 g of acrylic acid and 0.3 g of 2-hydroxyethyl acrylate as a polymerization solvent are introduced into the reaction vessel. 66.5 g of ethyl acetate was added, and a polymerization reaction was performed at 60 ° C. for 20 hours to obtain a living radical polymerization acrylic polymer-containing solution.
The obtained living radical polymerization acrylic polymer was diluted 50-fold with tetrahydrofuran (THF) and the resulting diluted solution was filtered with a filter (material: polytetrafluoroethylene, pore size: 0.2 μm), and the resulting filtrate was obtained. Was supplied to a gel permeation chromatograph (manufactured by Waters, 2690 Separations Model), GPC measurement was performed under the conditions of a sample flow rate of 1 ml / min and a column temperature of 40 ° C., and the molecular weight in terms of polystyrene of the polymer was measured. The average molecular weight (Mw) was 680,000, and the molecular weight distribution (Mw / Mn) was 1.5. In addition, GPC KF-806L (made by Showa Denko KK) was used as the column, and a differential refractometer was used as the detector.

(Preparation of free radical polymerization acrylic polymer)
After adding 40 g of ethyl acetate as a polymerization solvent in the reaction vessel and bubbling with nitrogen, the reaction vessel was heated while flowing nitrogen and refluxing was started. Subsequently, a polymerization initiator solution in which 0.15 g of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10-fold with ethyl acetate was placed in the reaction vessel. A total of 100 g of a mixed monomer composed of 60.0 g of butyl acrylate, 36.7 g of 2-ethylhexyl acrylate, 3 g of acrylic acid and 0.3 g of 2-hydroxyethyl acrylate was added dropwise over 3 hours. After completion of dropping, a polymerization initiator solution in which 0.15 g of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10 times with ethyl acetate was added to the reaction vessel. Was added again, and a polymerization reaction was conducted for 4 hours to obtain a free radical polymerization acrylic polymer-containing solution.
When measured in the same manner as the living radical polymerization acrylic polymer, the weight average molecular weight (Mw) was 680,000, and the molecular weight distribution (Mw / Mn) was 6.2.

(Examples 1-8, Comparative Examples 1-5)
Ethyl acetate is added to the radical polymerization acrylic polymer-containing solution obtained above with respect to 100 parts by weight of the non-volatile content and stirred, and A-50-K (alumina particles, average particle size 1.. Coronate L (isocyanate-based crosslinking agent, manufactured by Nippon Polyurethane Co., Ltd.) as a crosslinking agent, Pencel D135 (polymerized rosin ester, manufactured by Arakawa Chemical Co.) or YS Polystar G150 (terpene phenol resin) as a crosslinking agent , Manufactured by Yasuhara Chemical Co., Ltd.) was added in a predetermined amount shown in Table 1 and stirred to obtain an adhesive solution having a nonvolatile content of 30% by weight. The obtained pressure-sensitive adhesive solution was applied to a 50 μm-thick release PET film so as to have the tape thickness shown in Table 1 after drying, and then dried at 70 ° C. for 10 minutes to obtain a pressure-sensitive adhesive tape. In addition, the release film for protecting an adhesive layer was laminated | stacked on the surface of the both sides of an adhesive layer.

The obtained adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece, and the release film was peeled off. The test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, then taken out from the ethyl acetate and dried at 110 ° C. for 1 hour. The weight of the test piece after drying was measured, and the gel fraction was calculated using the above formula (1).

(Evaluation)
The following evaluation was performed about the heat conductive adhesive tape obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Evaluation of heat conductivity About the sample which cut the obtained heat conductive adhesive tape into 10 mm x 10 mm, heat conductivity is measured using a heat conductivity measuring device (LFA447 nanoflash, NETZSCH). It was.

(2) Evaluation of constant load peelability to adherend A thermally conductive adhesive tape lined with a width of 20 mm x 50 mm was applied to an aluminum (SUS) plate or a polycarbonate (PC) plate and cured overnight at 23 ° C and 50% humidity. Then, a load of 50 g was applied in the direction of 90 ° at 85 ° C., and the peeling time was measured. Based on the obtained peeling time, the constant load peelability was evaluated according to the following criteria.
◎: Peeling time is 1 hour or more ○: Peeling time is 30 minutes or more, less than 1 hour Δ: Peeling time is 15 minutes or more, less than 30 minutes ×: Peeling time is less than 15 minutes

ADVANTAGE OF THE INVENTION According to this invention, the heat conductive adhesive tape and heat conductive adhesive composition provided with high heat conductivity and the high constant load peelability with respect to a heat generating body and a heat radiator can be provided.

DESCRIPTION OF SYMBOLS 1 Living radical polymerization acrylic polymer 11 Monomer which does not contain crosslinkable functional group 12 Crosslinkable functional group containing monomer 2 Free radical polymerization acrylic polymer 21 Monomer which does not contain crosslinkable functional group 22 Crosslinkable functional group containing monomer 23 In the middle of reaction Polymer with growth terminal radicals deactivated in 24 Polymer grown with radical species newly generated during reaction

Claims (5)

It has a pressure-sensitive adhesive layer containing an acrylic polymer having a crosslinkable functional group having a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 obtained by living radical polymerization, a thermally conductive filler, and a crosslinker. And
The heat conductive pressure-sensitive adhesive tape, wherein the crosslinkable functional group is a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group or a nitrile group . The heat conductive adhesive tape according to claim 1 , wherein the adhesive layer further contains a tackifier resin. The heat conductive pressure-sensitive adhesive tape according to claim 1 or 2, wherein the heat-sensitive filler has 20 to 60% by volume in the pressure-sensitive adhesive layer. The heat conductive adhesive tape according to claim 1, wherein the adhesive layer has a thickness of 1 to 20 μm. Containing an acrylic polymer having obtained the molecular weight distribution (Mw / Mn) 1.05~2.5 crosslinkable functional group by living radical polymerization, a thermally conductive filler, and a crosslinking agent, the crosslinking functional The group is a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, or a nitrile group .

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