KR20230133269A - Thermal conductive adhesive composition, adhesive sheet, and method of manufacturing the same - Google Patents

Abstract

A thermally conductive adhesive composition containing an adhesive resin and graphene having a two-dimensional structure. The content of graphene having a two-dimensional structure is preferably 15 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the adhesive resin. Additionally, the glass transition temperature (Tg) of the adhesive resin is preferably -70°C or higher and 50°C or lower. The thermally conductive adhesive composition has excellent thermal conductivity.

Description

Thermal conductive adhesive composition, adhesive sheet, and method of manufacturing the same

The present invention relates to a thermally conductive adhesive composition, an adhesive sheet, and a method of manufacturing the same.

Conventionally, in electronic devices such as thermoelectric conversion devices, photoelectric conversion devices, and semiconductor devices such as large-scale integrated circuits, heat dissipation members having thermal conductivity have been used to dissipate generated heat. For example, as a method for efficiently dissipating heat generated from an electronic device to the outside, a heat dissipation sheet with excellent thermal conductivity is provided between the electronic device and a heat sink, or a heat dissipation grease is interposed between the electronic device and the heat sink. .

The heat dissipation sheet as described above is disclosed in Patent Document 1 as an example. The heat dissipation sheet of Patent Document 1 is manufactured by applying a coating liquid of a heat dissipation material containing an adhesive resin, an inorganic filler, a curing agent, and a solvent to a release sheet or a base material and drying it. As the inorganic filler, plate-shaped inorganic particles made of aluminum, silver, copper, boron nitride, graphite, etc., and spherical inorganic particles made of silica, alumina, graphite, etc. are disclosed.

In addition, the heat dissipation grease as described above is disclosed in Patent Document 2 as an example. In the heat dissipation grease of Patent Document 2, aluminum, boron nitride, graphite, magnesium oxide, alumina, and aluminum nitride are used as heat conductive fillers to be blended.

Japanese Patent Publication No. 2015-67713 Japanese Patent Publication No. 2016-162929

However, there are cases where conventional heat dissipation sheets cannot always obtain the desired thermal conductivity. In order to obtain high thermal conductivity, if a conventional heat dissipation sheet is highly filled with an inorganic filler, the surface roughness increases and tucks become difficult to appear, causing inconveniences such as the inability to obtain adhesiveness when sticking to an adherend. It happens. Additionally, if the inorganic filler is highly charged, the flexibility of the heat dissipation sheet may decrease, making it unable to sufficiently follow and adhere to an electronic device or heat sink, and the thermal conductivity between members may decrease.

On the other hand, conventional heat dissipation grease has a problem in that it repeats expansion and contraction due to temperature rise and cooling accompanying the operation and stop of the electronic device, resulting in a pump-out phenomenon in which the grease leaks. For this reason, the heat dissipation material provided between the electronic device and the heat sink is required to have adhesion performance that is difficult to leak in addition to flexibility and conformability.

The present invention was made in light of these realities, and its purpose is to provide a thermally conductive adhesive composition with excellent thermal conductivity and adhesiveness, an adhesive sheet, and a method for manufacturing the same.

In order to achieve the above object, the first invention provides a heat conductive adhesive composition containing an adhesive resin and graphene having a two-dimensional structure (invention 1).

Due to the structure of graphene having a two-dimensional structure, contact between graphenes easily occurs, and a heat conduction path for transferring heat is easily formed in the heat conductive adhesive composition. Additionally, graphene, which has a two-dimensional structure, has the characteristic of very high thermal conductivity in the plane direction. For this reason, the thermally conductive adhesive composition according to the above invention (invention 1) has excellent thermal conductivity even if the content of graphene having a two-dimensional structure is small. In addition, the heat conductive adhesive composition according to the above-mentioned invention (invention 1) contains an adhesive resin, and since the mixing ratio can be increased, it can exhibit good adhesive performance and flexibility and followability.

In the invention (invention 1), the content of graphene having the two-dimensional structure is preferably 15 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the adhesive resin (invention 2).

The content of graphene having the two-dimensional structure is preferably 15 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the adhesive resin (invention 2).

In the above inventions (inventions 1 and 2), the glass transition temperature (Tg) of the adhesive resin is preferably -70°C or higher and 50°C or lower (invention 3).

The second invention provides a pressure-sensitive adhesive sheet having at least an adhesive layer, wherein the adhesive layer is composed of the thermally conductive adhesive composition (Inventions 1 to 3) (Invention 4).

In the above invention (invention 4), it is preferable that the adhesive force to stainless steel polished 600 times is 0.1 N/25mm or more (invention 5).

In the above inventions (inventions 4 and 5), it is preferable that the thermal conductivity of the pressure-sensitive adhesive layer is 5 W/m·K or more (invention 6).

In the above inventions (inventions 4 to 6), the absorption intensity peak value (I _G ) of the G band around wave number 1570 cm ^-1 in the absorption spectrum of the pressure-sensitive adhesive layer obtained by Raman measurement is D around wave number 1250 cm ^-1 . It is preferable that the ratio (D/G) of the absorption intensity peak value (I _D ) of the band is 0.5 or less (invention 7).

The ratio of the absorption intensity peak value (ID) of the D band around a wave number of 1250 cm ^-1 to the absorption intensity peak value (IG) of the G band around a wave number of 1570 cm ^-1 in the absorption spectrum of the pressure-sensitive adhesive layer (ID) ( D/G) is preferably 0.5 or less (Invention 7).

The third present invention is a method for producing the above-described adhesive sheet (inventions 4 to 7), comprising the steps of preparing a coating liquid of the thermally conductive adhesive composition, coating the coating liquid of the thermally conductive adhesive composition, and drying the above-mentioned adhesive sheet. A step of forming an adhesive layer is provided, and the step of preparing the coating solution involves dispersing a mixture containing a portion of the total amount of the adhesive resin to be blended, the graphene having the two-dimensional structure, and a solvent. A first step of obtaining a preliminary mixture, and a second step of adding at least the remainder of the adhesive resin to the preliminary mixture and dispersing the adhesive resin in the first step. A method for manufacturing an adhesive sheet is provided, wherein the mixing amount is 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of graphene having the above-described two-dimensional structure (invention 8).

The thermally conductive adhesive composition and adhesive sheet according to the present invention are excellent in thermal conductivity and adhesiveness. In addition, according to the method for manufacturing an adhesive sheet according to the present invention, an adhesive sheet having excellent thermal conductivity and adhesiveness can be manufactured.

1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.
Figure 2 is a cross-sectional view of a heat dissipating device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described.

[Thermal conductive adhesive composition]

The thermally conductive adhesive composition according to one embodiment of the present invention contains an adhesive resin and graphene having a two-dimensional structure. The thermally conductive adhesive composition according to the present embodiment has the above-described structure and thus has excellent thermal conductivity and adhesiveness.

Since the graphene having the two-dimensional structure of the present embodiment has a planar structure that expands in two dimensions, contact between graphenes easily occurs, and a heat conduction path for transferring heat is easily formed in the heat conductive adhesive composition. In addition, graphene, which has a two-dimensional structure, has a very high thermal conductivity in the plane direction of about 3000 W/m·K. In addition, graphene has a specific gravity as low as 2.25 compared to conventional inorganic fillers such as metals, metal oxides, and nitride compounds, and has the characteristic of being less prone to sedimentation. For this reason, even if the content of graphene having the above-described two-dimensional structure is small (for example, about 10% by volume), the thermally conductive adhesive composition according to the present embodiment has excellent thermal conductivity. Specifically, it can exhibit very excellent thermal conductivity of 5.0 W/m·K or more.

In addition, since the heat conductive adhesive composition according to the present embodiment contains an adhesive resin, there is no risk of leakage due to a pump-out phenomenon like grease, and good adhesive performance can be maintained. Moreover, as described above, since there is no need to mix a large amount of graphene, the mixing ratio of the adhesive resin can be relatively increased. For this reason, the heat conductive adhesive composition according to the present embodiment can sufficiently exhibit the properties of the adhesive resin, such as adhesiveness, flexibility, and conformability. That is, the heat conductive adhesive composition according to the present embodiment is excellent in adhesiveness and also excellent in flexibility and conformability. Regarding the adhesiveness, specifically, it can exhibit excellent adhesiveness of 0.1N/25mm or more. Therefore, it can sufficiently follow and adhere to a heat source such as an electronic device or a heat dissipation member such as a heat sink, and can exhibit excellent thermal conductivity even during use.

Here, in a conventional heat dissipation sheet using an inorganic filler such as alumina with a thermal conductivity of 20 to 36 W/m·K or boron nitride with a planar thermal conductivity of about 200 W/m·K, the thermal conductivity is 5.0 W/m·K or more. In order to develop it, based on Bruggeman's formula, it is necessary to add at least 50% by volume of inorganic filler. However, in that case, since the filling rate of the inorganic filler was close to close filling (about 70% by volume), there was a limit to the development of high thermal conductivity as described above. Additionally, in a heat dissipation sheet to which 50% by volume or more of an inorganic filler is added, flexibility and adhesion are significantly lowered, the sheet cannot follow or adhere closely to a heat source or heat dissipation member, and thermal conductivity is impaired. In addition, carbon fibers (carbon nanotubes, carbon nanofibers) are known as materials with high thermal conductivity, but since carbon fibers have a cylindrical structure with a high aspect ratio, the mixture thickens significantly due to the entanglement of the carbon fibers. Therefore, it is difficult to add a compounding amount that can sufficiently increase thermal conductivity.

1. Each ingredient

(1) Adhesive resin

The type of adhesive resin in the heat conductive adhesive composition according to the present embodiment is not particularly limited, and may be any of, for example, acrylic, polyester, polyurethane, rubber, or silicone. Additionally, the adhesive may be of an emulsion type, solvent type, or non-solvent type, and may be of a crosslinked type or non-crosslinked type. In addition, it may be non-curable by active energy rays, or it may be curable by active energy rays.

The glass transition temperature (Tg) of the adhesive resin in this embodiment is preferably -70°C or higher, more preferably -60°C or higher, especially preferably -50°C or higher, and even more preferably -40°C or higher. do. Additionally, the glass transition temperature (Tg) is preferably 50°C or lower, more preferably 40°C or lower, particularly preferably 25°C or lower, and even more preferably 15°C or lower. When the glass transition temperature (Tg) is within the above range, the dispersibility of graphene having a two-dimensional structure in the heat conductive adhesive composition becomes good, and at the same time, flexibility and adhesiveness become better. Meanwhile, the glass transition temperature (Tg) of the adhesive resin in this specification is a value calculated based on the FOX formula.

Preferred acrylic adhesive resins include (meth)acrylic acid ester polymers obtained by polymerizing (meth)acrylic acid ester monomers, etc. Meanwhile, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same goes for other similar terms. In addition, “polymer” shall also include the concept of “copolymer.”

The (meth)acrylic acid ester polymer as the adhesive resin preferably contains an alkyl (meth)acrylic acid ester as a monomer unit constituting the polymer. For this reason, the resulting heat conductive adhesive composition can exhibit good adhesiveness. The alkyl group may be linear, branched, or cyclic.

As the (meth)acrylic acid alkyl ester, from the viewpoint of adhesiveness, (meth)acrylic acid alkyl ester whose alkyl group has 1 to 20 carbon atoms is preferable. Examples of (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. n-pentyl acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, (meth)acrylic acid Myristyl, plimityl (meth)acrylate, stearyl (meth)acrylate, etc. can be mentioned.

Among the above, from the viewpoint of providing good adhesion and the dispersibility of graphene having a two-dimensional structure, (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 9 carbon atoms are more preferable, and (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 6 carbon atoms ( Meth)acrylic acid alkyl esters are particularly preferable, and (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 4 carbon atoms are even more preferable. Specifically, methyl (meth)acrylate is preferable, and methyl acrylate is particularly preferable. These may be used individually, or two or more types may be used in combination.

The (meth)acrylic acid ester polymer contains 20% by mass or more of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer from the viewpoint of providing good adhesiveness and the dispersibility of graphene having a two-dimensional structure. Preferred, it is more preferable to contain 30 mass% or more, especially preferably 35 mass% or more, and even more preferably 40 mass% or more. In addition, from the viewpoint of securing the content of other monomers (for example, monomers containing reactive functional groups described later), it is preferable to contain 99.9% by mass or less of alkyl (meth)acrylate, and more preferably 95% by mass or less. In particular, it is preferable to contain 90% by mass or less, and it is more preferable to contain 85% by mass or less.

The (meth)acrylic acid ester polymer as an adhesive resin preferably contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer constituting the polymer. By containing a reactive functional group-containing monomer, the dispersibility of graphene having a two-dimensional structure can be further improved due to its polarity, etc. Additionally, when the heat conductive adhesive composition according to the present embodiment contains a crosslinking agent, the reactive functional group derived from the reactive functional group-containing monomer becomes a crosslinking point and can form a crosslinked structure.

Preferred examples of the reactive functional group-containing monomer include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxylic group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers). . Among these, from the viewpoint of the dispersibility of graphene having a two-dimensional structure, hydroxyl group-containing monomers are preferable. These reactive functional group-containing monomers may be used individually or in combination of two or more types.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylic acid, 2-hydroxypropyl (meth)acrylic acid, 3-hydroxypropyl (meth)acrylic acid, 2-hydroxybutyl (meth)acrylic acid, and (meth)acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth)acrylic acid and 4-hydroxybutyl (meth)acrylic acid. Among them, from the viewpoint of dispersibility of graphene having a two-dimensional structure, 2-hydroxyethyl (meth)acrylate is preferable, and 2-hydroxyethyl acrylate is especially preferable. These may be used individually, or two or more types may be used in combination.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually, or two or more types may be used in combination.

Examples of amino group-containing monomers include amino ethyl (meth)acrylate, n-butyl amino ethyl (meth)acrylate, and the like. These may be used individually, or two or more types may be used in combination.

The (meth)acrylic acid ester polymer preferably contains, as a lower limit, 0.1% by mass or more of a reactive functional group-containing monomer as a monomer constituting the polymer, more preferably 0.5% by mass or more, and especially 1% by mass or more. It is preferable to contain it, and it is more preferable to contain 5 mass% or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 30% by mass or less of a reactive functional group-containing monomer as the monomer unit constituting the polymer, as an upper limit, and more preferably contains 25% by mass or less. , it is particularly preferable to contain 20% by mass or less, and it is more preferable to contain 15% by mass or less. If the (meth)acrylic acid ester polymer contains a reactive functional group-containing monomer in the above range as the monomer unit constituting the polymer, the dispersibility of graphene having a two-dimensional structure will be better.

The (meth)acrylic acid ester polymer as an adhesive resin may further contain other monomers as monomers constituting the polymer. Examples of the other monomers include (meth)acrylic acid alkoxy alkyl esters such as methoxy ethyl (meth)acrylate and ethoxy ethyl (meth)acrylate; non-crosslinkable acrylamides such as acryl amide and methacryl amide; ( (meth)acrylic acid esters having a non-crosslinkable tertiary amino group such as N, N-dimethyl amino ethyl (meth)acrylate, N, N-dimethyl amino propyl (meth)acrylate; vinyl acetate; styrene, etc. These may be used individually, or two or more types may be used in combination.

The polymerization mode of the (meth)acrylic acid ester polymer may be a random polymer or a block polymer.

The weight average molecular weight of the (meth)acrylic acid ester polymer is preferably 10,000 or more, more preferably 20,000 or more, particularly preferably 50,000 or more, and even more preferably 100,000 or more. In addition, the weight average molecular weight is preferably 2 million or less, more preferably 1.5 million or less, particularly preferably 1.2 million or less, and even more preferably 1 million or less. When the weight average molecular weight is within the above range, the dispersibility of graphene having a two-dimensional structure in the heat conductive adhesive composition becomes better, and at the same time, flexibility and adhesiveness become better. Meanwhile, the weight average molecular weight in this specification is a standard polystyrene conversion value measured by gel permeation chromatography (GPC) method.

On the other hand, the heat conductive adhesive composition according to the present embodiment may contain one type of the above-mentioned (meth)acrylic acid ester polymer, or may contain two or more types. In addition, the heat conductive adhesive composition according to the present embodiment may contain other (meth)acrylic acid ester polymers in addition to the (meth)acrylic acid ester polymer described above.

As the adhesive resin in the heat conductive adhesive composition according to the present embodiment, a rubber-based adhesive resin can also be used. Rubber-based adhesive resins include, for example, polyisobutylene-based resin, polybutene-based resin, isoprene-isobutylene copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, and styrene- Preferred examples include butadiene rubber copolymer, natural rubber, and modified natural rubber.

The content of the adhesive resin in the heat conductive adhesive composition is preferably 30% by mass or more, and more preferably 35% by mass or more, based on the total solid content (i.e., when the total solid content excluding the solvent is 100% by mass). , It is especially preferable that it is 40 mass% or more, and it is more preferable that it is 50 mass% or more. Moreover, the content is preferably 90 mass% or less, more preferably 85 mass% or less, and especially preferably 80 mass% or less. When the content of the adhesive resin is within the above range, the dispersibility of graphene having a two-dimensional structure in the heat conductive adhesive composition becomes better, and at the same time, the flexibility and adhesiveness become better.

(2) Graphene with a two-dimensional structure

The thermally conductive adhesive composition according to this embodiment contains graphene having a two-dimensional structure. Graphene is a two-dimensional compound originally made up of a single layer of atoms, with a two-dimensional structure in which carbon atoms are arranged in regular rows in a hexagon. “Graphene with a two-dimensional structure” in this specification may be a multi-layer one, and its thickness is preferably 1/10 or less of the shortest length in plan view. Meanwhile, graphene in this specification includes those produced by thinly exfoliating (cleaving) graphite. In this specification, graphite itself does not correspond to the above-mentioned “graphene with a two-dimensional structure.”

As described above, graphene having a two-dimensional structure may be a single layer or a multiple layer. In the case of a duplex, it is usually about 2 to 1,000 floors. The planar shape of graphene having a two-dimensional structure is not particularly limited.

The graphene having a two-dimensional structure of this embodiment is preferably graphene having a two-dimensional crystal structure because it has better thermal conductivity. Here, “graphene having a two-dimensional crystal structure” means that it has a structural periodicity in the two-dimensional direction and has a layer with a thickness of a single atom, and is composed of only that layer, or the layer is formed from the second layer by van der Waals forces. This refers to stacking up to about 100 layers. In the case of such “graphene having a two-dimensional crystal structure,” a clear crystal peak can be obtained experimentally from its periodic structure through wide-angle X-ray diffraction measurement (WAXD). Additionally, in the case of multiple stacks, a crystal peak attributable to the periodic structure in the stack thickness direction can also be obtained.

When the thermally conductive adhesive composition (adhesive layer consisting of) containing graphene having a two-dimensional crystal structure was measured using a CuKα ray source (wavelength 0.15418 nm) according to the X-ray diffraction method, 2θ was 26.6° and 42.4°. It is desirable for a peak to be detected at that location. The diffraction peaks at positions where 2θ is 26.6° and 42.4° are crystal peaks between layers and in-plane of graphene, and the peaks detected at these positions may indicate that the graphene has a crystal structure.

The method of producing graphene with a two-dimensional structure is not particularly limited, but examples include a method of physically cleaving graphite or a method of producing single-layered graphene by cleaving once oxidized graphite (graphene oxide) and reducing this. (Reduced graphene oxide (RGO)), etc. can be mentioned. Among them, graphene obtained by a method of physically cleaving graphite is preferable because it has a good two-dimensional crystal structure and has better thermal conductivity.

The average particle diameter of graphene having a two-dimensional structure is preferably 0.5 μm or more, more preferably 1.0 μm or more, particularly preferably 3.0 μm or more, and even more preferably 5.0 μm or more. Because of this, each graphene becomes easy to contact each other and a heat conduction path is easily formed, so the characteristics of the two-dimensional structure function, and the heat conductive adhesive composition becomes excellent in terms of heat conductivity. In addition, the average particle diameter of graphene having a two-dimensional structure is preferably 30 μm or less, particularly preferably 20 μm or less, and more preferably 15 μm or less. As a result, the dispersion state is maintained in other materials such as solvents and adhesive resins, the formation of heat conduction paths due to segregation is suppressed, and heat conductivity is improved.

Additionally, the thickness of graphene having a two-dimensional structure is preferably 500 nm or less, more preferably 300 nm or less, particularly preferably 200 nm or less, and even more preferably 100 nm or less. For this reason, the flexibility of the heat conductive adhesive composition (the adhesive layer consisting of) is maintained well. On the other hand, the lower limit of the thickness of graphene having a two-dimensional structure is not particularly limited, but is usually 0.7 nm or more, and from the viewpoint of thermal conductivity, it is preferably 5.0 nm or more, especially 10 nm or more, and even more preferably 15 nm or more. do.

The content of graphene having a two-dimensional structure is preferably 15 parts by mass or more, more preferably 17 parts by mass or more, especially preferably 18.5 parts by mass or more, and even more preferably 20 parts by mass or more, based on 100 parts by mass of the adhesive resin. desirable. Since the lower limit of the graphene content is the above, it becomes easy for each graphene to come into contact with each other and a heat conduction path is easily formed, resulting in better thermal conductivity.

In addition, the content of graphene having a two-dimensional structure is preferably 200 parts by mass or less, more preferably 170 parts by mass or less, especially preferably 150 parts by mass or less, and 130 parts by mass or less, based on 100 parts by mass of the adhesive resin. It is more desirable. In this embodiment, by using graphene having a two-dimensional structure, desired thermal conductivity can be obtained even at a relatively small content as described above. Moreover, as the content of adhesive resin relatively increases, flexibility and adhesiveness become more excellent.

The content of graphene having a two-dimensional structure in the heat conductive adhesive composition is preferably 5 volume% or more, more preferably 7 volume% or more, especially preferably 8 volume% or more, and even more preferably 9 volume% or more. . Additionally, the graphene content is preferably 50 volume% or less, more preferably 40 volume% or less, especially preferably 35 volume% or less, and even more preferably 15 volume% or less. When the graphene content is within the above range, thermal conductivity becomes more excellent. Additionally, as the content of adhesive resin relatively increases, flexibility and adhesiveness become more excellent.

(3) Various additives

A crosslinking agent, an ultraviolet absorber, an antistatic agent, a tackifier, an antioxidant, a light stabilizer, a softener, a filler, a refractive index regulator, a waterproofing agent, a flame retardant, etc. can be added to the heat conductive adhesive composition according to the present embodiment as desired. The heat conductive adhesive composition according to the present embodiment may contain conventional heat conductive fillers such as aluminum, boron nitride, graphite, magnesium oxide, alumina, and aluminum nitride, in addition to graphene having a two-dimensional structure. It is preferable that the heat conductive adhesive composition according to the present embodiment does not contain a conventional heat conductive filler other than graphene having a two-dimensional structure. Meanwhile, the solvent described later is not included in the additives constituting the heat conductive adhesive composition.

The heat conductive adhesive composition according to the present embodiment may contain a thermosetting component such as an epoxy resin if desired, but the content of the thermosetting component in the heat conductive adhesive composition in that case is preferably less than 5% by mass, 3 It is more preferable that it is % by mass or less, and it is especially preferable that it is 1 % by mass or less. On the other hand, it is preferable that the heat conductive adhesive composition according to this embodiment does not contain a thermosetting component.

2. Preparation of coating solution for heat conductive adhesive composition

Inorganic fillers such as metals, metal oxides, and nitride compounds that have been used conventionally have a higher specific gravity than the adhesive resin or solvent component, and are prone to settling in the composition, which has been a problem. Here, for the purpose of controlling the distribution and sedimentation of the inorganic filler, it is necessary to adjust the viscosity of the coating solution components, modify the inorganic filler, add a dispersant, etc. from the material perspective, and from the process perspective, dispersion methods and coating equipment must be used. There was a need to reconsider. In contrast, graphene, which has a two-dimensional structure used in the present embodiment, has a relatively low specific gravity of 2.25 and has the characteristic of being difficult to settle by uniformly dispersing, so there is no need for modification treatment or the use of dispersants, and it has a wide viscosity. Handling within the range is possible.

The coating liquid of the heat conductive adhesive composition of the present embodiment can be prepared according to a conventional method. However, the method of preparing the coating liquid of the heat conductive adhesive composition of the present embodiment includes a portion of the total amount of the adhesive resin to be blended, A first step of obtaining a preliminary mixture by performing dispersion treatment on a mixture containing graphene having a two-dimensional structure and a solvent, and performing dispersion treatment by adding the remainder of the adhesive resin and the solvent to the preliminary mixture. It is desirable to provide a second process. As a result, it is possible to obtain a coating liquid of a thermally conductive adhesive composition in which graphene having a two-dimensional structure is uniformly dispersed.

2-1. 1st process

In the first step in this embodiment, a mixture containing a portion of the total amount of the adhesive resin to be blended, graphene having a two-dimensional structure, a solvent, and, if desired, a crosslinking agent or additive is prepared, and the mixture is , perform distributed processing. Because of this, the dispersion treatment is performed with a relatively high viscosity, and aggregation of the graphene can be suppressed. As a result, the graphene can be uniformly dispersed in the mixture.

The upper limit of the mixing amount of the adhesive resin in the first step is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and especially preferably 25 parts by mass or less, based on 100 parts by mass of graphene having a two-dimensional structure. . Because of this, dispersion treatment can be performed with a relatively high viscosity, making it easier to more uniformly disperse graphene with a two-dimensional structure. In addition, the lower limit of the mixing amount of the adhesive resin in the first step is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and especially 2 parts by mass or more, based on 100 parts by mass of graphene having a two-dimensional structure. It is preferable, and it is more preferable that it is 3 parts by mass or more.

The dispersion treatment of the mixture may be performed using a conventionally known method, for example, a known kneader or disperser such as a homogenizer, bead mill, ball mill, jet mill, disper, mixer, kneader, or ultrasonic disperser. can be used. Dispersion processing can be used as a single device or in combination of two or more types of devices.

Among the above, dispers, mixers, and jet mills are used in that they can uniformly disperse the graphene in the mixture while suppressing excessive pulverization of the graphene and significantly lowering the thermal conductivity and suppressing the agglomeration of the graphene. Alternatively, it is preferable to perform dispersion treatment using an ultrasonic disperser. When carrying out dispersion treatment of the above mixture using a disper, it is preferably carried out by stirring for more than 10 minutes at a disper rotation speed of 500 to 5000 rpm, and stirring for more than 20 minutes at the same rotation speed of 1000 to 4000 rpm. It is more desirable to carry out.

The solvent used in preparing the coating solution for the heat conductive adhesive composition is not particularly limited, and examples include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methylene chloride, and ethylene chloride. Halogenated hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, ethyl acetate, and butyl acetate. Ester such as ethyl cellosolve, cellosolve-based solvent such as ethyl cellosolve, N,N-dimethyl form amide, trimethyl-2-pyrrolidone, butyl capitol, etc. are used, but methyl ethyl ketone is preferable.

The upper limit of the mixing amount of solvent in the first step is preferably 10,000 parts by mass or less, especially 5,000 parts by mass or less, and more preferably 2,000 parts by mass or less, per 100 parts by mass of graphene having a two-dimensional structure. Because of this, dispersion treatment can be performed with a relatively high viscosity, making it easier to more uniformly disperse graphene with a two-dimensional structure. In addition, the lower limit of the mixing amount of the adhesive resin in the first step is preferably 200 parts by mass or more, more preferably 500 parts by mass or more, and especially 800 parts by mass or more, based on 100 parts by mass of graphene having a two-dimensional structure. It is preferable, and it is more preferable that it is 1000 parts by mass or more. For this reason, dispersion processing can be performed satisfactorily.

2-2. 2nd process

In the second step in this embodiment, at least the remainder of the adhesive resin is added to the premix obtained in the first step, and dispersion treatment is performed. In this second step, it is also preferable to add a solvent. The type of solvent and the conditions for dispersion treatment are the same as in the first step.

The amount of solvent added in the second step is not particularly limited as long as the viscosity of the coating liquid of the resulting heat conductive adhesive composition is within a range that can be coated, and can be appropriately selected depending on the situation. Usually, the solid content concentration of the heat conductive adhesive composition is preferably 2 to 50% by mass, particularly preferably 5 to 40% by mass, and more preferably 10 to 35% by mass.

Through the above steps, a coating liquid of a heat conductive adhesive composition in which graphene having a two-dimensional structure is uniformly dispersed can be obtained. By applying a coating solution of the heat conductive adhesive composition, an adhesive layer in which graphene having a two-dimensional structure is uniformly dispersed can be formed.

[Adhesive sheet]

The adhesive sheet of this embodiment has at least an adhesive layer, and the adhesive layer is composed of the heat conductive adhesive composition according to the above-described embodiment.

Fig. 1 shows a specific configuration as an example of the adhesive sheet according to this embodiment.

As shown in FIG. 1, the adhesive sheet 1 according to one embodiment includes two release sheets 12a and 12b, and the two release sheets 12a and 12b so as to contact the release surfaces of the two release sheets 12a and 12b. It consists of an adhesive layer (11) sandwiched between release sheets (12a, 12b). Meanwhile, the release surface of the release sheet in this specification refers to the surface of the release sheet that has peelability, and includes either a surface that has undergone a peeling treatment or a surface that exhibits peelability even without performing a peeling process.

1. Each member

1-1. adhesive layer

The adhesive layer 11 in this embodiment is comprised from the heat conductive adhesive composition according to the above-described embodiment.

1-2. release sheet

The release sheets 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

The release sheets 12a and 12b include, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, and polyethylene. Naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, Polycarbonate film, polyimide film, fluororesin film, etc. are used. Additionally, these crosslinked films are also used. Additionally, these laminated films may be used.

It is preferable that a peeling treatment is performed on the peeling surfaces of the release sheets 12a and 12b (particularly the surface in contact with the adhesive layer 11). Examples of the release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. On the other hand, among the release sheets 12a and 12b, one release sheet may be a medium release type release sheet with a large release force, and the other release sheet may be a light release type release sheet with a small release force.

There is no particular limitation on the thickness of the release sheets 12a and 12b, but it is usually about 20 to 150 μm.

2. Manufacturing of adhesive sheet

In one example of manufacturing the adhesive sheet 1, a coating solution of a heat conductive adhesive composition is applied to the peeling surface of one release sheet 12a (or 12b). Next, the coating film is dried (heated), and the peeling surface of the other release sheet 12b (or 12a) is placed on the coating film. If a curing period is necessary, a curing period is provided, and if a curing period is not necessary, the coating film becomes the adhesive layer 11 as is. As a result, the adhesive sheet 1 is obtained.

As a method for applying the coating liquid of the heat conductive adhesive composition, for example, a bar coat method, a knife coat method, a roll coat method, a blade coat method, a die coat method, a gravure coat method, etc. can be used.

By drying (heating) the coating liquid of the heat conductive adhesive composition, the solvent volatilizes and an adhesive layer is formed. Drying conditions are preferably 0.5 to 30 minutes at 90 to 150°C, and especially 1 to 10 minutes at 100 to 120°C.

On the other hand, when the heat conductive adhesive composition contains a crosslinking agent, crosslinking can usually be performed by heat treatment (dry treatment as described above may also be used). After heat treatment, if necessary, a curing period of 1 to 2 weeks may be provided at room temperature (e.g., 23°C, 50%RH).

Here, since carbon fibers such as carbon nanotubes and carbon nanofibers, which are representative conventional heat dissipation materials, have anisotropy in the long axis direction (one dimension) of the fiber, in order to develop thermal conductivity, they are used in combination with other particulate fillers to control the orientation. Alternatively, it was necessary to align the orientation of the carbon fiber using a powerful magnetic field generator. In contrast, the graphene used in this embodiment is an anisotropic material, but since it has a two-dimensionally expanded planar structure, contact between graphene easily occurs, and the adhesive layer 11 is obtained even without special orientation treatment. can exhibit excellent thermal conductivity.

3. Physical properties, etc.

(1) Thickness of adhesive layer

From the viewpoint of adhesiveness, the thickness of the adhesive layer 11 (value measured according to JIS K7130) is preferably 2 μm or more, more preferably 5 μm or more, and especially preferably 10 μm or more, and 20 μm. It is more desirable to have more than this.

In addition, from the viewpoint of thermal conductivity, the upper limit of the thickness of the adhesive layer 11 is preferably 500 μm or less, more preferably 300 μm or less, particularly preferably 100 μm or less, and even more preferably 50 μm or less.

Here, when performing the above-described orientation treatment on carbon fibers such as conventional carbon nanotubes and carbon nanofibers, a space where the carbon fibers can move freely is required. To achieve this, when carbon fibers are oriented in the direction of the film thickness of the heat dissipation sheet, it is necessary to secure a film thickness equal to or greater than the filler length, and the film thickness is generally designed to be 0.5 to 2.0 mm. In addition, the method of manufacturing the heat dissipation sheet after performing the orientation treatment involves cutting with a slicer such as a cutter or laser, so due to the mechanism of the slicer, the sheet thickness had to be 1 mm or more for stable production.

On the other hand, in the case of graphene having a two-dimensional structure, as described above, no special orientation treatment is required, so the adhesive layer 11 in this embodiment can be formed even at a thin thickness as described above. , it is easy to thicken the film by laminating it. That is, in this embodiment, the thickness of the adhesive layer 11 can be easily controlled.

(2) Thermal conductivity

The thermal conductivity of the adhesive layer 11 is preferably 5 W/m·K or more, more preferably 5.5 W/m·K or more, and especially preferably 6.0 W/m·K or more. For this reason, the adhesive sheet 1 can be said to have excellent thermal conductivity. In particular, with conventional inorganic fillers such as carbon black, alumina, and boron nitride, it was difficult to achieve a high thermal conductivity of 5 W/m·K or more even if the amount added was large. However, the adhesive sheet 1 according to the present embodiment can achieve such high thermal conductivity by using graphene having a two-dimensional structure. Meanwhile, the method of measuring thermal conductivity in this specification is as shown in the test examples described later.

(3) Adhesion

The adhesive strength of the adhesive sheet 1 of this embodiment to stainless steel polished 600 times is preferably 0.1 N/25 mm or more, more preferably 0.15 N/25 mm or more, and especially preferably 0.2 N/25 mm or more. Since the adhesive sheet 1 according to the present embodiment exhibits excellent thermal conductivity even if the content of graphene having a two-dimensional structure is small, the content of the adhesive resin in the adhesive layer 11 can be relatively increased, resulting in excellent thermal conductivity. Adhesion can be achieved.

On the other hand, the upper limit of the adhesive force is not particularly limited, but is usually preferably 50 N/25 mm or less, more preferably 15 N/25 mm or less, and especially preferably 5 N/25 mm or less. Meanwhile, the method for measuring adhesive force in this specification is as shown in the test examples described later.

(4) Raman peak intensity ratio D/G

For the adhesive layer 11 in this embodiment, the absorption intensity peak value (I _G ) of the G band around wavenumber 1570cm ^-1 in the absorption spectrum obtained by Raman measurement is around wavenumber 1250cm ^-1 . The ratio (D/G) of the absorption intensity peak value (I _D ) of the D band (hereinafter sometimes referred to as “Raman peak intensity ratio D/G”) is preferably 0.5 or less, and more preferably 0.4 or less. , especially preferably 0.3 or less, and more preferably 0.2 or less. If the Raman peak intensity ratio D/G is above, it can be seen that graphene having a two-dimensional structure contains a good crystal structure. For this reason, the adhesive sheet 1 exhibits superior thermal conductivity due to graphene having a two-dimensional crystal structure. The lower limit of the Raman peak intensity ratio D/G is not particularly limited, but is usually preferably 0.001 or more.

Meanwhile, the specific Raman measurement method in this specification is as shown in the test examples described later. In addition, the peak of the G band around the wave number of 1570 cm ^-1 referred to here refers to a peak that has a peak in the region of ±100 cm ^-1 centered on the wave number of 1570 cm ^-1 , and the absorption intensity peak value (I _G ) is the peak obtained by measurement. Indicates the relative value of the absorption strength of the saw. Likewise, the peak of the D band around wave number 1250 cm ^-1 represents a peak that has a peak in the region of ±100 cm ^-1 centered on wave number 1250 cm ^-1 , and the absorption intensity peak value (I _D ) is the peak top obtained by measurement. Indicates the relative value of absorption intensity.

[Heat dissipation device]

As shown in FIG. 2, the heat dissipating device 3 according to one embodiment of the present invention includes a heat-generating member 31 and a heat-conducting member 32, and an adhesive provided between the heat-generating member 31 and the heat-conducting member 32. It has a layer (11).

The adhesive layer 11 in the present embodiment is preferably comprised of the heat conductive adhesive composition according to the above-described embodiment, or is the adhesive layer 11 of the adhesive sheet 1 according to the above-described embodiment. The heat generating member 31 and the heat conductive member 32 are bonded together through the adhesive layer 11. Since this adhesive layer 11 contains graphene with a two-dimensional structure, it has excellent thermal conductivity and flexibly follows and adheres to the heat generating member 31 and the heat conductive member 32. Accordingly, the heat generated by the heat generating member 31 is well conducted to the heat transfer member 32 through the adhesive layer 11, and is efficiently dissipated to the outside from the heat transfer member 32.

The heat generating member 31 in the present embodiment generates heat in conjunction with the exercise of a predetermined function, but is a member that requires suppression of temperature rise, or a member that requires controlling the flow of heat generated by the member in a specific direction. Absence, etc. Such heating members 31 include, for example, semiconductor devices such as thermoelectric conversion devices, photoelectric conversion devices, and large-scale integrated circuits, electronic devices such as LED light-emitting elements, optical pickups, and power transistors, and mobile terminals and wearable terminals. These include various electronic devices, batteries, cells, motors, engines, etc.

The heat transfer member 32 in this embodiment is a member that dissipates the received heat, or a member that transfers the received heat to another member. This heat conductive member 32 is preferably made of a material with high thermal conductivity, for example, metal such as aluminum, stainless steel, or copper, or graphite or carbon nanofiber. The form of the heat conductive member 32 may be any, such as a substrate, case, heat sink, or heat spreader, and is not particularly limited.

To manufacture the heat dissipating device 3, for example, one release sheet 12a (or 12b) is peeled off from the adhesive sheet 1, and one side of the exposed adhesive layer 11 is applied to the heat generating member 31. ) and attach it to the Next, the other release sheet 12b (or 12a) is peeled from the adhesive layer 11 provided on the heat generating member 31, and the other side of the exposed adhesive layer 11 is attached to the heat conductive member 32. do. Additionally, after attaching one side of the adhesive layer 11 to the heat conductive member 32, the heat generating member 31 may be bonded to the other side of the adhesive layer 11.

The embodiments described above are described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, in FIG. 1, the release sheet 12a or release sheet 12b laminated on the adhesive sheet 1 may be omitted.

Additionally, the adhesive sheet according to the present invention may be one in which a desired base material, the adhesive layer 11, and the release sheet 12a (or 12b) are laminated in that order. The material constituting the base material is not particularly limited and includes, for example, resin film, non-woven fabric, paper, graphite sheet, graphene sheet, metal base material, etc., and the resin film is generally used. Resin materials constituting the resin film include, for example, polyester, polyolefin, nylon 6, nylon 66, polyamide such as partially aromatic polyamide, polyimide, polyamideimide, polyetheretherketone, polyethersulfone, Fluororesins such as polyphenylene sulfide, polycarbonate, polyurethane, ethylene-vinyl acetate copolymer, polytetrafluoroethylene, and resins such as acrylic resin, polyacrylate, polystyrene, polyvinyl chloride, and polyvinylidene chloride can be used. there is. The resin film may be formed using a resin material that contains one type of resin alone, or may be formed using a resin material that is a blend of two or more types of resin. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched).

In addition, the shapes of the heat generating member 31 and the heat conductive member 32 in the thermal device 3 are not limited to those shown in FIG. 2 and may have various shapes.

[Example]

Hereinafter, the present invention will be described in more detail through examples, etc., but the scope of the present invention is not limited to these examples.

[Example 1]

5 parts by mass of acrylic acid ester polymer as an adhesive resin (5 parts by mass in 100 parts by mass; solids concentration), 25 parts by mass (solids concentration) of graphene with a two-dimensional structure (manufactured by ADEKA Corporation, product name "CNS-1A1"), , 325 parts by mass of ethyl methyl ketone as a solvent were mixed, and a dispersion treatment was performed by mixing 325 parts by mass of ethyl methyl ketone as a solvent and stirring at 3000 rpm for 30 minutes using a disper (product name “Robomix” manufactured by Primix Corporation) to prepare a preliminary mixture (step 1). . Meanwhile, details of the acrylic acid ester polymer and graphene having a two-dimensional structure are as follows.

Acrylic acid ester polymer: copolymer obtained by copolymerizing 85 parts by mass of methyl acrylate and 15 parts by mass of 2-hydroxyethyl acrylate, weight average molecular weight: 300,000, glass transition temperature (Tg): 6°C

・Graphene with two-dimensional structure: manufactured by ADEKA Corporation, product name "CNS-1A1", two-dimensional crystal structure, average particle size 12㎛, thickness 50nm or less, Raman peak intensity ratio D/G=0.1, CuKα ray source according to X-ray diffraction method When measured using (wavelength 0.15418nm), peaks were detected at positions where 2θ is 26.6° and 42.4°

To the above preliminary mixture, 95 parts by mass of the above-mentioned acrylic acid ester polymer (95 parts by mass in 100 parts by mass; solid content concentration) and 175 parts by mass of ethyl methyl ketone as a solvent were added, and Disper (manufactured by Primix Corporation, product name) was added. Using "Robomix"), dispersion treatment was performed by stirring at 3000 rpm for 30 minutes (second step) to obtain a coating liquid of the heat conductive adhesive composition. The solid content concentration of the coating liquid of this heat conductive adhesive composition was 20% by mass.

The coating liquid of the obtained heat conductive adhesive composition was applied using an applicator to the peeled surface of a release film (manufactured by LINTEC Corporation, product name "SP-PET3811(S)"), where one side of a polyethylene terephthalate film was peeled with a silicone-based release agent. Afterwards, it was dried by heat treatment at 100°C for 2 minutes to form an adhesive layer. Thereafter, the peeled side of a release film (manufactured by LINTEC Corporation, product name "SP-PET381031") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent is attached to the adhesive layer, and the thickness of the adhesive layer is 30%. A ㎛ adhesive sheet (release film/adhesive layer/release film) was produced.

[Examples 2 to 3]

Other than changing the mixing amount of the acrylic acid ester polymer, the mixing amount of graphene having a two-dimensional structure, and the mixing amount of the solvent in the first step, and the mixing amount of the acrylic acid ester polymer and the mixing amount of the solvent in the second step as shown in Table 1. An adhesive sheet was produced in the same manner as in Example 1.

[Example 4]

5 parts by mass of polyisobutylene-based resin as an adhesive resin (5 parts by mass in 100 parts by mass; solid content concentration), and hydrogenated petroleum resin as a tackifier (manufactured by Arakawa Chemical Industries, Ltd., product name “Alcon P-125”) 2.5 parts by mass of graphene with a two-dimensional structure (made by ADEKA Corporation, product name "CNS-1A1"), 25 parts by mass (solid content concentration), and 245 parts by mass of toluene as a solvent were mixed, and Disper (made by Primix Corporation, product name "CNS-1A1") was mixed. Using "Robomix"), dispersion treatment was performed by stirring at 3000 rpm for 30 minutes to prepare a preliminary mixture (first step).

To the above premix, 95 parts by mass of the above polyisobutylene resin (95 parts by mass in 100 parts by mass; solid content concentration), and hydrogenated fossil oil resin as a tackifier (manufactured by Arakawa Chemical Industries, Ltd., product name) 47.5 parts by mass of "Alcon P-125") and 132 parts by mass of toluene as a solvent were added, and dispersion treatment was performed by stirring at 3000 rpm for 30 minutes using Disper (manufactured by Primix Corporation, product name "Robomix") ( 2nd process), the coating liquid of the heat conductive adhesive composition was obtained. An adhesive sheet was produced in the same manner as in Example 1 using the coating liquid of the obtained heat conductive adhesive composition.

[Comparative Example 1]

As an adhesive resin, 100 parts by mass (solids concentration) of the same acrylic acid ester polymer as in Example 1, 43 parts by mass (solids concentration) of carbon black (manufactured by Mitsubishi Chemical Corporation, product name "#3030B"), and 330 parts by mass of ethyl methyl ketone as a solvent. The parts were mixed and dispersion treatment was performed by stirring at 3000 rpm for 30 minutes using a disper (product name “Robomix” manufactured by Primix Corporation) to prepare a coating liquid for the heat conductive adhesive composition. An adhesive sheet was produced in the same manner as in Example 1 using the coating liquid of the obtained heat conductive adhesive composition.

[Comparative Example 2]

As an adhesive resin, 100 parts by mass (solids concentration) of the same acrylic acid ester polymer as in Example 1, 195 parts by mass (solids concentration) of alumina (manufactured by Showa Denko K.K., product name "CB-P10", average particle size 8 μm), and as a solvent 690 parts by mass of ethyl methyl ketone were mixed, and dispersion treatment was performed by stirring at 3000 rpm for 30 minutes using a disper (product name "Robomix", manufactured by Primix Corporation) to prepare a coating liquid for a heat conductive adhesive composition. An adhesive sheet was produced in the same manner as in Example 1 using the coating liquid of the obtained heat conductive adhesive composition.

[Comparative Example 3]

As an adhesive resin, 100 parts by mass (solids concentration) of the same acrylic acid ester polymer as in Example 1, 43 parts by mass (solids concentration) of boron nitride (manufactured by Showa Denko K.K., product name "UHP2", average particle size 11 μm), and ethyl as a solvent. 330 parts by mass of methyl ketone were mixed, and dispersion treatment was performed by mixing at 3000 rpm for 30 minutes using a disper (product name "Robomix" manufactured by Primix Corporation) to prepare a coating liquid for a heat conductive adhesive composition. An adhesive sheet was produced in the same manner as in Example 1 using the coating liquid of the obtained heat conductive adhesive composition.

[Test Example 1] <Measurement of thermal conductivity>

A square sample with each side of 5 mm was obtained from the adhesive layer of the adhesive sheet produced in Examples and Comparative Examples. Using a thermal diffusivity/thermal conductivity measuring device (manufactured by aiphase Co., Ltd., product name “ai-phase mobile”), in an environment of 23°C and 50%RH, in accordance with ISO22007-3, the sample (adhesive layer) was measured. Thermal conductivity (W/m·K) was measured. The results are shown in Table 1.

[Test Example 2] <Measurement of adhesive force>

The coating solution of the heat conductive adhesive composition prepared in the examples and comparative examples was applied to a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO., LTD., product name “Cosmoshine PET50A4100”, film thickness 50 μm), and then applied at 100°C. It was heated and dried for 2 minutes to produce an adhesive sheet (PET film/adhesive layer) with an adhesive layer thickness of 30 μm.

The obtained adhesive sheet was cut into strips with a width of 25 mm and a length of 250 mm, and the adhesive layer of the adhesive sheet was attached to the polished surface of a stainless steel (SUS) plate polished 600 times and applied with a 2 kg rubber roller. It was compressed in a reciprocating manner. After standing for 24 hours in an environment of 23°C and 50%RH, the adhesive sheet was separated from the SUS plate using a tensile tester (Tensiron, manufactured by ORIENTEC CO., LTD.) under the conditions of a peeling speed of 300 mm/min and a peeling angle of 180 degrees. It was peeled off and the adhesion was measured. Conditions other than those described here were measured in accordance with JIS Z0237:2009. The results are shown in Table 1.

[Test Example 3] <Evaluation of filler dispersibility>

The coating liquid of the heat conductive adhesive composition prepared in the examples and comparative examples was placed in a sample bottle (capacity 70 mL) and left to stand, and the dispersion state of the filler (graphene, carbon black, alumina, and boron nitride) was visually confirmed after 24 hours. . Then, the filler dispersibility was evaluated according to the following criteria. The results are shown in Table 1.

O: There was no sedimentation of the filler and it was uniformly dispersed.

△: Some filler precipitated.

×: Most of the filler settled.

[Test Example 4] <Raman measurement>

Raman measurement was performed on the adhesive layer of the adhesive sheet produced in the examples using a microlaser Raman spectroscopy device (manufactured by Thermo Fisher Scientific Inc., product name "DXR2"). And, from the absorption intensity peak value (I _G ) of the G band around a wave number of 1570 cm ^-1 and the absorption intensity peak value of the D band (I _D ) around a wave number of 1250 cm ^-1 obtained from a graph of the absorption spectrum measured at a laser wavelength of 532 nm, , the ratio of the absorption intensity peak value (I _D ) to the absorption intensity peak value (I _G ) (Raman peak intensity ratio D/G) was calculated. The results are shown in Table 1. On the other hand, in this Raman measurement, information on the graphene itself contained in the adhesive layer is obtained and is not related to differences in the amount of graphene added.

As can be seen from Table 1, the adhesive sheets produced in Examples had excellent thermal conductivity and adhesive strength. In addition, the thermally conductive adhesive composition (coating liquid) prepared in the examples was excellent in dispersibility of graphene having a two-dimensional structure.

The thermally conductive adhesive composition and adhesive sheet according to the present invention can be suitably used to cool the electronic device, for example, by interposing it between a heat-generating electronic device and a heat-dissipating substrate or heat sink.

One … adhesive sheet
11 … adhesive layer
12a, 12b... release sheet
3 … heat dissipation device
11 … adhesive layer
31 … Absence of fever
32 … Heat transfer member

Claims (8)

adhesive resin, and
A thermally conductive adhesive composition containing graphene having a two-dimensional structure. According to paragraph 1,
A heat conductive adhesive composition, characterized in that the content of graphene having the two-dimensional structure is 15 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the adhesive resin. According to claim 1 or 2,
A heat conductive adhesive composition, characterized in that the glass transition temperature (Tg) of the adhesive resin is -70°C or more and 50°C or less. An adhesive sheet having at least an adhesive layer,
The adhesive layer is an adhesive sheet characterized in that it is composed of the thermally conductive adhesive composition according to any one of claims 1 to 3. According to paragraph 4,
An adhesive sheet characterized in that the adhesive strength to stainless steel polished 600 times is 0.1N/25mm or more. According to clause 4 or 5,
An adhesive sheet, characterized in that the thermal conductivity of the adhesive layer is 5W/m·K or more. According to any one of claims 4 to 6,
The ratio of the absorption intensity peak value (I _D ) of the D band around a wave number of 1250 cm ^-1 to the absorption intensity peak value (I _G ) of the G band around a wave number of 1570 cm ^-1 in the absorption spectrum of the pressure-sensitive adhesive layer obtained by Raman measurement. (D/G) is an adhesive sheet characterized in that it is 0.5 or less. A method for producing an adhesive sheet according to any one of claims 4 to 7,
A process of preparing a coating liquid of the thermally conductive adhesive composition,
A step of forming the adhesive layer by applying a coating solution of the thermally conductive adhesive composition and drying it,
The process of preparing the coating liquid is,
A first step of obtaining a preliminary mixture by performing dispersion treatment on a mixture containing a portion of the total amount of the adhesive resin to be blended, graphene having the two-dimensional structure, and a solvent, and
A second step of adding at least the remainder of the adhesive resin to the premix and performing dispersion treatment,
A method of manufacturing an adhesive sheet, characterized in that the mixing amount of the adhesive resin in the first step is 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the graphene having the two-dimensional structure.