CN115989293A - Thermally conductive adhesive composition, adhesive sheet, and method for producing same - Google Patents

Thermally conductive adhesive composition, adhesive sheet, and method for producing same Download PDF

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Publication number
CN115989293A
CN115989293A CN202180052846.8A CN202180052846A CN115989293A CN 115989293 A CN115989293 A CN 115989293A CN 202180052846 A CN202180052846 A CN 202180052846A CN 115989293 A CN115989293 A CN 115989293A
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mass
graphene
thermally conductive
adhesive
parts
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吉延毅朗
市川功
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Lintec Corp
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Lintec Corp
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C08K3/042—Graphene or derivatives, e.g. graphene oxides
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/04—Non-macromolecular additives inorganic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J201/00—Adhesives based on unspecified macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/10—Adhesives in the form of films or foils without carriers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon

Abstract

The invention provides a heat-conductive adhesive composition, which contains adhesive resin and graphene with a two-dimensional structure. The content of the 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. The glass transition temperature (Tg) of the adhesive resin is preferably from-70 ℃ to 50 ℃. The thermally conductive adhesive composition has excellent thermal conductivity.

Description

Thermally conductive adhesive composition, adhesive sheet, and method for producing same
Technical Field
The present invention relates to a thermally conductive adhesive composition having thermal conductivity, an adhesive sheet, and a method for producing the same.
Background
Conventionally, in electronic devices such as semiconductor devices including thermoelectric conversion devices, photoelectric conversion devices, and large-scale integrated circuits, heat dissipation materials having thermal conductivity have been used to dissipate heat generated by heat generation. For example, as a method for efficiently radiating heat generated in an electronic device to the outside, a heat sink having excellent thermal conductivity is provided between the electronic device and a heat sink (heat sink), or a thermal grease (thermal grease) is inserted.
As an example of the heat sink, patent document 1 discloses a heat sink. The heat sink of patent document 1 is produced by applying a coating liquid of a heat sink material containing an adhesive resin, an inorganic filler, a curing agent and a solvent onto a release sheet or a base material and drying the coating liquid. As the inorganic filler, plate-like inorganic particles formed of aluminum, silver, copper, boron nitride, graphite, or the like, and spherical inorganic particles formed of silica, alumina, graphite, or the like are disclosed.
As an example of the above-described heat dissipating paste, patent document 2 discloses a heat dissipating paste. In the heat dissipating paste of patent document 2, aluminum, boron nitride, graphite, magnesium oxide, aluminum oxide, and aluminum nitride are used as the heat conductive filler to be blended.
Documents of the prior art
Patent literature
Patent document 1: japanese patent laid-open No. 2015-67713
Patent document 2: japanese patent laid-open publication No. 2016-162929
Disclosure of Invention
Technical problem to be solved by the invention
However, the conventional heat sink is not always capable of obtaining the desired thermal conductivity. When an inorganic filler is highly filled in a conventional heat sink to obtain high thermal conductivity, surface roughness increases, and thus tackiness (tack) is less likely to occur, and problems such as tackiness when adhering to an adherend cannot be obtained occur. Further, if the inorganic filler is highly filled, the flexibility of the heat sink sheet decreases, and the heat sink sheet may not sufficiently follow and closely adhere to the electronic device or the heat sink, thereby decreasing the thermal conductivity between the components.
On the other hand, the conventional heat dissipating paste has the following problems: the expansion and contraction are repeated with the temperature rise and cooling caused by the driving and stopping of the electronic device, and a phenomenon of paste leakage (pump out) occurs. Therefore, a heat dissipating material provided between an electronic device and a heat sink is desired to have flexibility, followability, and adhesion performance that does not easily leak out.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a thermally conductive adhesive composition having excellent thermal conductivity and adhesiveness, an adhesive sheet, and a method for producing the same.
Means for solving the problems
In order to achieve the above object, the first aspect of the present invention provides a thermally conductive adhesive composition containing an adhesive resin and graphene having a two-dimensional structure (invention 1).
In the case of graphene having a two-dimensional structure, the graphene is likely to come into contact with each other in the structure, and a heat conduction path for transferring heat in the thermally conductive adhesive composition is likely to be formed. In addition, graphene having a two-dimensional structure is characterized by very high thermal conductivity in the plane direction. Therefore, the thermally conductive adhesive composition of the invention (invention 1) has excellent thermal conductivity even when the content of the graphene having a two-dimensional structure is small. Further, the thermally conductive adhesive composition of the invention (invention 1) contains an adhesive resin and can increase the blending ratio thereof, and thus can exhibit good adhesive performance, flexibility and conformability.
In the above invention (invention 1), it is preferable that: the content of the graphene having a 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 (invention 2).
In the above inventions (inventions 1 and 2), it is preferable that: the glass transition temperature (Tg) of the adhesive resin is-70 ℃ or higher and 50 ℃ or lower (invention 3).
The second aspect of the present invention provides an adhesive sheet comprising at least an adhesive layer, wherein the adhesive layer is composed of the thermally conductive adhesive composition (aspects 1 to 3) (aspect 4).
In the above invention (invention 4), it is preferable that: the adhesive force of the adhesive sheet to stainless steel polished with a mesh size of 600 is 0.1N/25mm or more (invention 5).
In the above inventions (inventions 4 and 5), it is preferable that: the adhesive layer has a thermal conductivity of 5W/mK or more (invention 6).
In the above inventions (inventions 4 to 6), it is preferable that: a wave number of 1250cm in an absorption spectrum of the adhesive layer obtained by Raman measurement -1 Absorption intensity peak (I) of nearby D band D ) Relative to wave number of 1570cm -1 Absorption intensity peak (I) of near G band G ) The ratio (D/G) is 0.5 or less (invention 7).
Third, the present invention provides a method for producing an adhesive sheet (inventions 4 to 7), comprising: a step of preparing a coating liquid of the thermally conductive adhesive composition; and a step of forming the adhesive layer by applying a coating solution of the thermally conductive adhesive composition and drying the coating solution, wherein the step of preparing the coating solution includes: a first step of performing a dispersion treatment on a mixture containing a part of the total amount of the adhesive resin to be blended, the graphene having a two-dimensional structure, and a solvent to obtain a preliminary mixture; and a second step of adding at least the remaining adhesive resin to the preliminary mixture and performing a dispersion treatment, wherein the amount of the adhesive resin mixed 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 a two-dimensional structure (invention 8).
Effects of the invention
The thermally conductive adhesive composition and the adhesive sheet of the present invention have excellent thermal conductivity and adhesiveness. Further, according to the method for producing an adhesive sheet of the present invention, an adhesive sheet having excellent thermal conductivity and adhesiveness can be produced.
Drawings
FIG. 1 is a sectional view of an adhesive sheet according to an embodiment of the present invention.
Fig. 2 is a sectional view of a heat dissipating device according to an embodiment of the present invention.
Detailed Description
Hereinafter, embodiments of the present invention will be described.
[ thermally 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 of the present embodiment has the above-described configuration, and thus has excellent thermal conductivity and adhesiveness.
Since the graphene having a two-dimensional structure of the present embodiment has a planar structure extending two-dimensionally, the graphene is likely to come into contact with each other, and a heat conduction path for transferring heat in the thermally conductive adhesive composition is likely to be formed. Further, graphene having a two-dimensional structure has a very high thermal conductivity of about 3000W/m · K in the planar direction. Further, graphene has a specific gravity as low as about 2.25 and is characterized by being less likely to settle, compared with conventional inorganic fillers such as metals, metal oxides, and nitrides. Therefore, even if the content of the graphene having the above-described two-dimensional structure is small (for example, even 10 vol%), the thermal conductivity of the thermally conductive adhesive composition of the present embodiment is excellent. Specifically, the composition can exhibit a very excellent thermal conductivity of 5.0W/mK or more.
Further, since the thermally conductive adhesive composition of the present embodiment contains an adhesive resin, there is no fear that the adhesive composition leaks out due to a spill phenomenon as in the case of a paste, and it is possible to maintain a good adhesive performance. Further, since it is not necessary to blend a large amount of graphene as described above, the blending ratio of the adhesive resin can be relatively increased. Thus, the thermally conductive adhesive composition of the present embodiment can sufficiently exhibit the properties of the adhesive resin, such as adhesiveness, flexibility, and conformability. That is, the thermally conductive adhesive composition of the present embodiment is excellent not only in adhesiveness but also in flexibility and followability. Specifically, the tackiness can exhibit an excellent adhesive force of 0.1N/25mm or more. Therefore, the heat conductive material can sufficiently follow and adhere to a heat source of an electronic device or the like, a heat radiating member such as a heat sink, and can exhibit excellent heat conductivity even in use.
Here, in the conventional heat sink using an inorganic filler such as alumina having a thermal conductivity of 20 to 36W/m · K or boron nitride having a thermal conductivity in the plane direction of about 200W/m · K, it is necessary to add at least 50 vol% or more of the inorganic filler based on the Bruggeman relation in order to exhibit a thermal conductivity of 5.0W/m · K or more. However, in this case, since the filling rate of the inorganic filler is close to the closest filling (about 70 vol%), there is a limit to exhibiting the above-mentioned high thermal conductivity. In addition, in the heat sink to which 50% by volume or more of an inorganic filler is added, flexibility and adhesiveness are significantly reduced, and the heat sink cannot follow and closely adhere to a heat source or a heat dissipating member, and thermal conductivity is impaired. Further, carbon fibers (carbon nanotubes or carbon nanofibers) are known as a high thermal conductivity material, but since carbon fibers have a cylindrical structure with a high aspect ratio (aspect ratio), entanglement of carbon fibers causes significant thickening of a blend, and it is difficult to add a blend amount in which thermal conductivity is sufficiently improved.
1. Each component
(1) Adhesive resin
The type of the adhesive resin in the thermally conductive adhesive composition of the present embodiment is not particularly limited, and may be any of acrylic, polyester, polyurethane, rubber, silicone, and the like, for example. The adhesive may be any of an emulsion type, a solvent type, or a non-solvent type, and may be any of a crosslinking type or a non-crosslinking type. The curable composition may be either non-active energy ray-curable or active energy ray-curable.
The glass transition temperature (Tg) of the adhesive resin in the present embodiment is preferably-70 ℃ or higher, more preferably-60 ℃ or higher, particularly preferably-50 ℃ or higher, and still more preferably-40 ℃ or higher. The glass transition temperature (Tg) is preferably 50 ℃ or lower, more preferably 40 ℃ or lower, particularly preferably 25 ℃ or lower, and further preferably 15 ℃ or lower. When the glass transition temperature (Tg) is within the above range, the dispersibility of the graphene having a two-dimensional structure in the thermally conductive adhesive composition becomes good, and the flexibility and adhesiveness also become further good. In addition, the glass transition temperature (Tg) of the adhesive resin in the present specification is a value calculated based on the FOX formula.
As the acrylic pressure-sensitive adhesive resin, a (meth) acrylate polymer obtained by polymerizing a (meth) acrylate monomer or the like is preferably used. In the present specification, the term (meth) acrylate refers to both acrylate and methacrylate. Other similar terms are also the same. Further, "polymer" also encompasses the concept of "copolymer".
The (meth) acrylate polymer as the adhesive resin preferably contains an alkyl (meth) acrylate as a monomer unit constituting the polymer. Thus, the resulting thermally conductive adhesive composition can exhibit good adhesion. The alkyl group may be linear, branched or cyclic.
The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms from the viewpoint of tackiness. Examples of the alkyl (meth) acrylate 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, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate.
Among them, from the viewpoint of imparting good adhesiveness and the viewpoint of dispersibility of graphene having a two-dimensional structure, an alkyl (meth) acrylate in which the alkyl group has 1 to 9 carbon atoms is more preferable, an alkyl (meth) acrylate in which the alkyl group has 1 to 6 carbon atoms is particularly preferable, and an alkyl (meth) acrylate in which the alkyl group has 1 to 4 carbon atoms is further preferable. Specifically, methyl (meth) acrylate is preferably used, and methyl acrylate is particularly preferably used. These alkyl (meth) acrylates may be used alone or in combination of two or more.
From the viewpoint of imparting good adhesiveness and the viewpoint of dispersibility of graphene having a two-dimensional structure, the (meth) acrylate polymer preferably contains 20% by mass or more, more preferably 30% by mass or more, particularly preferably 35% by mass or more, and further preferably 40% by mass or more of an alkyl (meth) acrylate as a monomer unit constituting the polymer. From the viewpoint of ensuring the content of other monomers (for example, reactive functional group-containing monomers described later), the content of the alkyl (meth) acrylate is preferably 99.9% by mass or less, more preferably 95% by mass or less, particularly preferably 90% by mass or less, and still more preferably 85% by mass or less.
The (meth) acrylate polymer as the 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 the reactive functional group-containing monomer, the dispersibility of the graphene having a two-dimensional structure can be further improved depending on the polarity and the like. In addition, when the thermally conductive adhesive composition of 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.
Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and a monomer having an amino group in the molecule (amino group-containing monomer). Among them, a hydroxyl group-containing monomer is preferable from the viewpoint of dispersibility of graphene having a two-dimensional structure. These reactive functional group-containing monomers may be used alone or in combination of two or more.
Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate is preferable, and 2-hydroxyethyl acrylate is particularly preferable, from the viewpoint of dispersibility of graphene having a two-dimensional structure. These hydroxyl group-containing monomers may be used alone or in combination of two or more.
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 carboxyl group-containing monomers may be used alone or in combination of two or more.
Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These amino group-containing monomers may be used alone or in combination of two or more.
The lower limit of the content of the reactive functional group-containing monomer in the (meth) acrylate polymer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and further preferably 5% by mass or more. The (meth) acrylate polymer (a) preferably contains 30% by mass or less, more preferably 25% by mass or less, particularly preferably 20% by mass or less, and further preferably 15% by mass or less of the reactive functional group-containing monomer as a monomer unit constituting the polymer, in terms of the above limit value. When the (meth) acrylate polymer contains the reactive functional group-containing monomer as a monomer unit constituting the polymer in the above range, the dispersibility of graphene having a two-dimensional structure becomes further favorable.
The (meth) acrylate ester polymer as the adhesive resin may further contain other monomers as monomers constituting the polymer. Examples of the other monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; non-crosslinkable acrylamides such as acrylamide and methacrylamide; non-crosslinkable (meth) acrylic acid esters having a tertiary amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate; vinyl acetate; styrene, and the like. These other monomers may be used alone or in combination of two or more.
The polymerization form of the (meth) acrylate polymer may be a random polymer or a block polymer.
The weight average molecular weight of the (meth) acrylate polymer is preferably 1 ten thousand or more, more preferably 2 ten thousand or more, particularly preferably 5 ten thousand or more, and further preferably 10 ten thousand or more. The weight average molecular weight is preferably 200 ten thousand or less, more preferably 150 ten thousand or less, particularly preferably 120 ten thousand or less, and further preferably 100 ten thousand or less. When the weight average molecular weight is within the above range, the dispersibility of the graphene having a two-dimensional structure in the thermally conductive adhesive composition becomes better, and the flexibility and adhesiveness also become better. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC).
The thermally conductive adhesive composition of the present embodiment may contain 1 kind of the above (meth) acrylate polymer, or may contain 2 or more kinds of the above (meth) acrylate polymers. The thermally conductive adhesive composition of the present embodiment may contain another (meth) acrylate polymer in addition to the (meth) acrylate polymer.
As the adhesive resin in the thermally conductive adhesive composition of the present embodiment, a rubber-based adhesive resin can be used. Examples of the rubber-based adhesive resin include polyisobutylene-based resins, polybutene-based resins, isoprene-isobutylene copolymers, styrene-isoprene-styrene block copolymers, styrene-butadiene rubber copolymers, natural rubbers, modified natural rubbers, and the like.
The content of the adhesive resin in the thermally conductive adhesive composition is preferably 30% by mass or more, more preferably 35% by mass or more, particularly preferably 40% by mass or more, and further preferably 50% by mass or more, based on the total amount of solid components (that is, when all solid components except the solvent are taken as 100% by mass). The content is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. When the content of the adhesive resin is within the above range, the dispersibility of the graphene having a two-dimensional structure in the thermally conductive adhesive composition becomes better, and the flexibility and the adhesiveness also become better.
(2) Graphene having two-dimensional structure
The thermally conductive adhesive composition of the present embodiment contains graphene having a two-dimensional structure. Graphene is a two-dimensional compound originally composed of one layer of atoms, and has a two-dimensional structure in which carbon atoms are regularly arranged in a hexagonal shape. In the present specification, the "graphene having a two-dimensional structure" may be a multilayer, and the thickness is preferably 1/10 or less of the shortest length in a planar view. The graphene in the present specification includes a substance produced by thinly peeling off (cleaving) graphite. In the present specification, graphite itself does not correspond to the "graphene having a two-dimensional structure".
As described above, the graphene having a two-dimensional structure may be a single layer or a multilayer. When the number of layers is plural, the number is usually about 2 to 1,000. The shape of the graphene having a two-dimensional structure in a plan view is not particularly limited.
The graphene having a two-dimensional structure according to the present embodiment is preferably graphene having a two-dimensional crystal structure, since it is more excellent in thermal conductivity. Here, the "graphene having a two-dimensional crystal structure" refers to graphene having a structural periodicity in two-dimensional directions and having a layer having a thickness of a single atom, which is composed of only the layer, or graphene in which the layer is formed by stacking about 2 to several hundred layers by van der Waals force (van der Waals force). For such "graphene having a two-dimensional crystal structure", experimentally, a clear crystallization peak can be obtained from its periodic structure in wide-angle X-ray diffraction measurement (WAXD). In addition, when a plurality of layers are stacked, a crystal peak attributed to a periodic structure in the thickness direction of the stack can be obtained.
Preferably, the following components: when a thermally conductive adhesive composition containing graphene having a two-dimensional crystal structure (an adhesive layer composed of the thermally conductive adhesive composition) was measured by an X-ray diffraction method using a CuK α ray source (wavelength of 0.15418 nm), peaks were detected at positions where 2 θ was 26.6 ° and 42.4 °. The diffraction peaks at the positions where the 2 θ is 26.6 ° and 42.4 ° are crystal peaks between layers and in the plane of graphene, and since the peaks are detected at the positions, the graphene can be said to have a crystal structure.
The method for producing graphene having a two-dimensional structure is not particularly limited, and examples thereof include a method in which graphite is physically cleaved, and a method in which oxidized graphite is cleaved to form a single layer (graphene oxide) and reduced to produce Reduced Graphene Oxide (RGO). Among them, graphene obtained by a method of physically cleaving graphite is preferable in that it has a good two-dimensional crystal structure and thus has more excellent thermal conductivity.
The average particle diameter of the 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 further preferably 5.0 μm or more. Thus, the graphene is easily brought into contact with each other, and a heat conduction path is easily formed, so that the feature of a two-dimensional structure is exerted, and the heat conductivity of the heat conductive adhesive composition is further excellent. The average particle size of the 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. This makes it possible to maintain the dispersion state in other materials such as a solvent and an adhesive resin, to suppress the occurrence of thermal conduction paths due to segregation, and to achieve further excellent thermal conductivity.
The thickness of the graphene having a two-dimensional structure is preferably 500nm or less, more preferably 300nm or less, particularly preferably 200nm or less, and further preferably 100nm or less. This makes it possible to maintain the flexibility of the thermally conductive adhesive composition (adhesive layer made of the thermally conductive adhesive composition) satisfactorily. On the other hand, the lower limit of the thickness of the graphene having a two-dimensional structure is not particularly limited, but is usually preferably 0.7nm or more, and from the viewpoint of thermal conductivity, more preferably 5.0nm or more, particularly preferably 10nm or more, and further preferably 15nm or more.
The content of the graphene having a two-dimensional structure is preferably 15 parts by mass or more, more preferably 17 parts by mass or more, particularly preferably 18.5 parts by mass or more, and further preferably 20 parts by mass or more, relative to 100 parts by mass of the adhesive resin. When the lower limit of the content of the graphene is set to the above value, the graphene is easily brought into contact with each other, and a heat conduction path is easily formed, so that the thermal conductivity is further excellent.
The content of the graphene having a two-dimensional structure is preferably 200 parts by mass or less, more preferably 170 parts by mass or less, particularly preferably 150 parts by mass or less, and further preferably 130 parts by mass or less, relative to 100 parts by mass of the adhesive resin. In the present embodiment, by using graphene having a two-dimensional structure, as described above, a desired thermal conductivity can be obtained even with a small content. Further, by relatively increasing the content of the adhesive resin, flexibility and adhesiveness are more excellent.
The content of the graphene having a two-dimensional structure in the thermally conductive adhesive composition is preferably 5% by volume or more, more preferably 7% by volume or more, particularly preferably 8% by volume or more, and further preferably 9% by volume or more. The content of the graphene is preferably 50% by volume or less, more preferably 40% by volume or less, particularly preferably 35% by volume or less, and further preferably 15% by volume or more. When the content of the graphene is within the above range, the thermal conductivity is further excellent. Further, by relatively increasing the content of the adhesive resin, flexibility and adhesiveness become more excellent.
(2) Various additives
The thermally conductive adhesive composition of the present embodiment may contain a crosslinking agent, an ultraviolet absorber, an antistatic agent, a thickener, an antioxidant, a light stabilizer, a softener, a filler, a refractive index adjuster, a rust inhibitor, a flame retardant, and the like, as needed. The thermally conductive adhesive composition of the present embodiment may contain a conventional thermally conductive filler such as aluminum, boron nitride, graphite, magnesium oxide, aluminum oxide, and aluminum nitride, in addition to graphene having a two-dimensional structure. The thermally conductive adhesive composition of the present embodiment preferably does not contain a conventional thermally conductive filler other than graphene having a two-dimensional structure. The additive constituting the thermally conductive adhesive composition does not include a solvent described later.
The thermally conductive adhesive composition of the present embodiment may contain a thermosetting component such as an epoxy resin if necessary, but the content of the thermosetting component in the thermally conductive adhesive composition in this case is preferably less than 5% by mass, more preferably 3% by mass or less, and particularly preferably 1% by mass or less. In addition, the thermally conductive adhesive composition of the present embodiment preferably does not contain a thermosetting component.
2. Preparation of coating liquid of thermally conductive adhesive composition
Inorganic fillers such as metals, metal oxides, and nitrogen compounds, which have been used in the past, have a higher specific gravity than adhesive resins and solvent components, and therefore, have a problem of being easily precipitated in the composition. Therefore, for the purpose of controlling the distribution and sedimentation of the inorganic filler, it is necessary to adjust the viscosity of the coating liquid component, modify the inorganic filler, add a dispersant, and the like to the material surface, and it is necessary to reconsider the dispersing method and the coating equipment in terms of the process. However, since graphene having a two-dimensional structure used in the present embodiment has a low specific gravity of 2.25 and is characterized by being hardly sedimented by being uniformly dispersed, it can be handled in a wide viscosity range without modification treatment, use of a dispersant, or the like.
The coating liquid of the thermally conductive adhesive composition of the present embodiment can be prepared by a conventional method, but the preparation method of the coating liquid of the thermally conductive adhesive composition of the present embodiment preferably includes the steps of: a first step of performing a dispersion treatment on a mixture containing a part of the total amount of an adhesive resin to be blended, graphene having a two-dimensional structure, and a solvent to obtain a preliminary mixture; and a second step of adding the remaining adhesive resin to the preliminary mixture, and adding a solvent to the preliminary mixture to perform a dispersion treatment. Thus, a coating liquid of the thermally conductive adhesive composition in which graphene having a two-dimensional structure is uniformly dispersed can be obtained.
2-1. First step
In the first step in this embodiment, a mixture containing a part of the total amount of the adhesive resin to be blended, graphene having a two-dimensional structure, a solvent, a crosslinking agent as needed, and an additive is prepared, and the mixture is subjected to a dispersion treatment. Thus, the dispersion treatment is performed in a state of high viscosity, and the aggregation of the graphene can be suppressed. As a result, the graphene can be uniformly dispersed in the mixture.
The upper limit of the amount of the adhesive resin to be mixed in the first step is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less, per 100 parts by mass of the graphene having a two-dimensional structure. Thus, the dispersion treatment can be performed in a state of high viscosity, and graphene having a two-dimensional structure can be more easily dispersed uniformly. The lower limit of the amount of the adhesive resin to be mixed in the first step is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, particularly preferably 2 parts by mass or more, and further preferably 3 parts by mass or more, per 100 parts by mass of the graphene having a two-dimensional structure.
The dispersion treatment of the mixture may be carried out by a conventionally known method, and for example, a known kneader or disperser such as a homogenizer, a bead mill, a ball mill, a jet mill, a disperser, a mixer, a kneader, or an ultrasonic disperser can be used. The dispersion treatment may be performed by a single apparatus or by a combination of two or more apparatuses.
Among them, the dispersion treatment is preferably performed using a dispersing machine, a mixer, a jet mill, or an ultrasonic dispersing machine in order to suppress a significant decrease in thermal conductivity due to excessive pulverization of graphene, suppress aggregation of graphene, and uniformly disperse the graphene in a mixture. When the dispersion treatment of the mixture is carried out using a dispersing machine, the dispersing machine is preferably stirred at 500 to 5000rpm for 10 minutes or longer, more preferably at 1000 to 4000rpm for 20 minutes or longer.
The solvent used for preparing the coating liquid of the thermally conductive adhesive composition is not particularly limited, and examples thereof include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and dichloroethane, alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, cellosolve solvents such as ethyl cellosolve, N-dimethylformamide, trimethyl-2-pyrrolidone and butyl carbitol, but methyl ethyl ketone is preferable.
Mixing of the solvent in the first step with respect to 100 parts by mass of graphene having a two-dimensional structure
The upper limit of the total amount is preferably 10000 parts by mass or less, particularly 5000 parts by mass or less, and further preferably 2000 parts by mass or less. Thus, the dispersion treatment can be performed in a state of high viscosity, and graphene having a two-dimensional structure can be more easily dispersed uniformly. The lower limit of the amount of the solvent to be mixed in the first step is preferably 200 parts by mass or more, more preferably 500 parts by mass or more, particularly preferably 800 parts by mass or more, and further preferably 1000 parts by mass or more, per 100 parts by mass of the graphene having a two-dimensional structure.
2-2. Second step
In the second step of the present embodiment, at least the remaining adhesive resin is added to the preliminary mixture obtained in the first step, and dispersion treatment is performed. In the second step, a solvent is preferably added. The kind of solvent and the conditions of the dispersion treatment are the same as those in the first step.
The amount of the solvent to be added in the second step is not particularly limited as long as the viscosity of the coating liquid of the obtained thermally conductive adhesive composition can be made within a range in which the coating liquid can be applied, and can be appropriately selected according to the situation. In general, the solid content concentration of the thermally conductive adhesive composition is preferably 2 to 50 mass%, particularly preferably 5 to 40 mass%, and more preferably 10 to 35 mass%.
Through the above steps, a coating liquid of the thermally conductive adhesive composition in which graphene having a two-dimensional structure is uniformly dispersed can be obtained. By applying the coating liquid of the thermally 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 the present embodiment includes at least an adhesive layer composed of the thermally conductive adhesive composition of the above embodiment.
Fig. 1 shows a specific configuration of an example of the pressure-sensitive adhesive sheet according to the present embodiment.
As shown in fig. 1, the adhesive sheet 1 of one embodiment is composed of 2 release sheets 12a and 12b and an adhesive layer 11, and the adhesive layer 11 is sandwiched between the 2 release sheets 12a and 12b so as to be in contact with the release surfaces of the 2 release sheets 12a and 12b. The release surface of the release sheet in the present specification means a surface having releasability in the release sheet, and includes a surface subjected to a release treatment and a surface showing releasability even without being subjected to the release treatment.
1. Parts of
1-1. Adhesive layer
The adhesive layer 11 in the present embodiment is composed of the thermally conductive adhesive composition of the above embodiment.
1-2. Release sheet
The release sheets 12a, 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are released when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 of the present embodiment, one or both of the release sheets 12a and 12b are not essential.
Examples of the release sheets 12a and 12b include a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene- (meth) acrylic acid copolymer film, an ethylene- (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, and a fluororesin film. In addition, crosslinked films of these films may also be used. Further, a laminated film of these films may be used.
The release surfaces (particularly, the surfaces contacting the adhesive layer 11) of the release sheets 12a and 12b are preferably subjected to a release treatment. Examples of the release agent used in the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax. One of the release sheets 12a and 12b may be a heavy release sheet having a large release force, and the other may be a light release sheet having a small release force.
The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.
2. Production of adhesive sheet
As one example of the production of the adhesive sheet 1, a coating solution of a thermally conductive adhesive composition is applied to the release surface of one release sheet 12a (or 12 b). Next, the coating film is dried (heated), and the coating film is superimposed on the release surface of the other release sheet 12b (or 12 a). When the curing period is required, the adhesive layer 11 is obtained by providing the curing period, and when the curing period is not required, the coating film directly becomes the adhesive layer 11. This gives the adhesive sheet 1.
Examples of a method for applying a coating liquid of the thermally conductive adhesive composition include a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, and a gravure coating method.
By drying (heating) the coating liquid of the thermally conductive adhesive composition, the solvent is volatilized, and an adhesive layer is formed. The drying is preferably carried out at 90 to 150 ℃ for 0.5 to 30 minutes, particularly preferably at 100 to 120 ℃ for 1 to 10 minutes.
When the thermally conductive adhesive composition contains a crosslinking agent, crosslinking can be performed by a heat treatment (which may be the above-mentioned drying treatment) in general. After the heat treatment, a maturation period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH) as necessary.
Here, carbon fibers such as carbon nanotubes and carbon nanofibers, which are typical heat dissipation materials in the prior art, have anisotropy in the long axis direction (one-dimensional) of the fibers, and therefore, in order to exhibit thermal conductivity, it is necessary to simultaneously use other particulate fillers to control the orientation, or to align the orientation of the carbon fibers using a strong magnetic field generator. However, although the graphene used in the present embodiment is an anisotropic material, since the graphene has a two-dimensionally extended planar structure, the graphene is likely to come into contact with each other, and the obtained adhesive layer 11 can exhibit excellent thermal conductivity without performing a special orientation treatment.
3. Physical properties and the like
(1) Thickness of adhesive layer
From the viewpoint of adhesiveness, the thickness of the adhesive layer 11 (value measured in accordance with JIS K7130) is preferably 2 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, and further preferably 20 μm or more, in the lower limit.
From the viewpoint of thermal conductivity, 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 further preferably 50 μm or less, as the upper limit.
Here, in the conventional carbon fibers such as carbon nanotubes and carbon nanofibers, a space in which the carbon fibers can move freely is required for the alignment treatment. Therefore, when the carbon fibers are oriented in the film thickness direction of the heat sink, 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 2.0mm. In the method of manufacturing the heat sink after the orientation treatment, since the heat sink is cut by a slicer (slicer) such as a cutter or a laser, the heat sink must be stably manufactured by setting the thickness of the sheet film to 1mm or more for the sake of a slicer mechanism.
However, since the graphene having a two-dimensional structure does not require the above-described special orientation treatment, the adhesive layer 11 in the present embodiment can be formed into a film even when it has a small thickness as described above, and can be easily formed into a thick film by lamination. That is, in the present embodiment, the thickness of the adhesive agent layer 11 can be easily controlled.
(2) Thermal conductivity
The thermal conductivity of the adhesive layer 11 is preferably 5W/mK or more, more preferably 5.5W/mK or more, and particularly preferably 6.0W/mK or more. Thus, the adhesive sheet 1 can have excellent thermal conductivity. In particular, it is difficult to achieve high thermal conductivity of 5W/m · K or more even with a large amount of addition to conventional inorganic fillers such as carbon black, alumina, and boron nitride. However, the adhesive sheet 1 of the present embodiment can achieve the above-described high thermal conductivity by using graphene having a two-dimensional structure. The method of measuring thermal conductivity in the present specification is as shown in test examples described below.
(3) Adhesive force
The adhesive sheet 1 of the present embodiment has an adhesive force to stainless steel polished to 600 mesh preferably 0.1N/25mm or more, more preferably 0.15N/25mm or more, and particularly preferably 0.2N/25mm or more. Since the adhesive sheet 1 of the present embodiment can exhibit excellent thermal conductivity even when 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 large, and excellent adhesive force can be exhibited.
On the other hand, the upper limit of the above-mentioned adhesive force is not particularly limited, but is usually preferably 50N/25mm or less, more preferably 15N/25mm or less, and particularly preferably 5N/25mm or less. The method of measuring the adhesive force in the present specification is shown in test examples described below.
(4) Raman peak intensity ratio D/G
With respect to the adhesive layer 11 in the present embodiment, the wave number in the absorption spectrum obtained by raman measurement is 1250cm -1 Absorption intensity peak (I) of nearby D band D ) Relative to wave number of 1570cm -1 Absorption intensity peak (I) of near G band G ) The ratio (D/G) (hereinafter also referred to as "raman peak intensity ratio D/G") is preferably 0.5 or less, more preferably 0.4 or less, particularly preferably 0.3 or less, and further preferably 0.2 or less. As described above, it is found that graphene having a two-dimensional structure contains a good crystal structure. Thus, the adhesive sheet 1 exhibits more excellent thermal conductivity due to the graphene having a two-dimensional structure. The lower limit of the raman peak intensity ratio D/G is not particularly limited, but is preferably 0.001 or more in general.
The specific method of raman measurement in the present specification is shown in test examples described later. Further, the wave number here is 1570cm -1 The peak of the near G band is represented by a wavenumber of 1570cm -1 . + -. 100cm centered -1 Has a peak having a peak in the region of (A), and has a peak absorption intensity (I) G ) The absorption intensity relative value at the peak top obtained by measurement is shown. Similarly, the wave number is 1250cm -1 The peak of the nearby D band is expressed in wavenumber of 1250cm -1 Centered + -100 cm -1 Has a peak having a peak in the region of (A), and an absorption intensity peak value (I) D ) The absorption intensity relative value of the peak top obtained by measurement is shown.
[ Heat dissipating device ]
As shown in fig. 2, a heat sink device 3 according to an embodiment of the present invention includes: a heat generating member 31, a heat transfer member 32, and an adhesive layer 11 provided between the heat generating member 31 and the heat transfer member 32.
The adhesive layer 11 in the present embodiment is preferably composed of the thermally conductive adhesive composition of the above embodiment, or is the adhesive layer 11 of the adhesive sheet 1 of the above embodiment. The heat generating member 31 and the heat transfer member 32 are bonded to each other via the adhesive layer 11. The adhesive layer 11 contains graphene having a two-dimensional structure, has excellent thermal conductivity, and can flexibly follow and closely adhere to the heat generating member 31 and the heat transfer member 32. Therefore, the heat emitted from the heat generating member 31 is thermally conducted to the heat transfer member 32 well through the adhesive layer 11, and is efficiently dissipated to the outside by the heat transfer member 32.
The heat generating member 31 in the present embodiment generates heat as it performs a predetermined function, but is a member that needs to suppress a temperature rise, or a member that needs to control the flow direction of heat emitted from the member in a specific direction, or the like. Examples of the heat generating component 31 include a semiconductor device such as a thermoelectric conversion device, a photoelectric conversion device, or a large-scale integrated circuit, an electronic device such as an LED light emitting element, an optical pickup, or a power transistor, various electronic devices such as a portable terminal and a wearable terminal, a battery, a motor, and an engine.
The heat transfer member 32 in the present embodiment is a member that dissipates the received heat, or a member that transfers the received heat to another member, or the like. The heat transfer member 32 is made of a material having high thermal conductivity, and is preferably made of metal such as aluminum, stainless steel, or copper, graphite, or carbon nanofibers. The form of the heat transfer member 32 may be any one of a substrate, a frame, a heat spreader, a heat sink (heat spreader), and the like, and is not particularly limited.
In manufacturing the heat dissipating device 3, for example, one release sheet 12a (or 12 b) is peeled off from the adhesive sheet 1, and one surface of the exposed adhesive layer 11 is attached to the heat generating component 31. Next, the other release sheet 12b (or 12 a) is peeled from the adhesive layer 11 provided on the heat-generating component 31, and the other surface of the exposed adhesive layer 11 is bonded to the heat-transfer component 32. After the heat transfer member 32 is attached to one surface of the adhesive layer 11, the heat generating member 31 may be attached to the other surface of the adhesive layer 11.
The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments also includes all design changes, equivalents, and the like, which fall within the technical scope of the present invention.
For example, the release sheet 12a or the release sheet 12b laminated on the adhesive sheet 1 may be omitted in fig. 1.
The adhesive sheet of the present invention may be a sheet obtained by laminating a desired substrate, the adhesive layer 11, and the release sheet 12a (or 12 b) in this order. The material constituting the substrate is not particularly limited, and examples thereof include a resin film, a nonwoven fabric, paper, a graphite sheet, a graphene sheet, and a metal substrate, and a resin film is generally used. Examples of the resin material constituting the resin film include polyamides such as polyester, polyolefin, nylon 6, nylon 66, and partially aromatic polyamide, polyimide, polyamideimide, polyether ether ketone, polyether sulfone, polyphenylene sulfide, polycarbonate, polyurethane, an ethylene-vinyl acetate copolymer, fluorine resins such as polytetrafluoroethylene, acrylic resins, polyacrylates, polystyrene, polyvinyl chloride, and polyvinylidene chloride. The resin film may be formed using a single resin material containing one of the resins, or may be formed using a mixture of two or more resin materials. The resin film may be a non-stretched film or a stretched (e.g., uniaxially or biaxially stretched) film.
Further, the shapes of the heat generating member 31 and the heat transfer member 32 in the heat dissipating device 3 are not limited to those shown in fig. 2, and may be various shapes.
Examples
The present invention will be described in more detail with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.
[ example 1]
An acrylic ester polymer as an adhesive resin was mixed by 5 parts by mass (5 parts by mass in total 100 parts by mass; solid content concentration), 25 parts by mass (solid content concentration) of graphene having a two-dimensional structure (product name "CNS-1A1" manufactured by ADEKA corporation) and 325 parts by mass of methyl ethyl ketone as a solvent, and the mixture was stirred at 3000rpm for 30 minutes by using a dispersing machine (product name "ROBOMIX" manufactured by PRIMIX corporation) to prepare a preliminary mixture (first step). The details of the acrylate polymer and the graphene having a two-dimensional structure are as follows.
Acrylate polymers: a copolymer obtained by copolymerizing 85 parts by mass of methyl acrylate and 15 parts by mass of 2-hydroxyethyl acrylate, wherein the weight average molecular weight: 30 ten thousand, glass transition temperature (Tg): 6 ℃ is adopted.
Graphene with a two-dimensional structure: manufactured by ADEKA corporation, product name "CNS-1A1", two-dimensional crystal structure, average particle diameter of 12 μm, thickness of 50nm or less, raman peak intensity ratio D/G =0.1, and peaks were detected at positions of 26.6 ° and 42.4 ° 2 θ by X-ray diffraction method using CuK α ray source (wavelength 0.15418 nm).
To the preliminary mixture, 95 parts by mass of the same acrylate polymer (95 parts by mass in 100 parts by mass in total; solid content concentration) and 175 parts by mass of methyl ethyl ketone as a solvent were added, and the mixture was stirred at 3000rpm for 30 minutes by using a disperser (product name "ROBOMIX" manufactured by PRIMIX corporation) to carry out dispersion treatment (second step) to obtain a coating liquid of the thermally conductive adhesive composition. The coating liquid of the thermally conductive adhesive composition had a solid content concentration of 20 mass%.
The coating liquid of the obtained thermoconductive adhesive composition was applied to a release-treated surface of a release film (product name "SP-PET3811 (S)" manufactured by LINTEC corporation) in which one surface of a polyethylene terephthalate film was subjected to a release treatment with a silicone-based release agent by an applicator (applicator), and was heat-treated at 100 ℃ for 2 minutes to be dried, thereby forming an adhesive layer. Then, a release-treated surface of a release film (product name "SP-PET381031" manufactured by LINTEC corporation) obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment with a silicone-based release agent was bonded to the adhesive layer, and an adhesive sheet (release film/adhesive layer/release film) having an adhesive layer thickness of 30 μm was prepared.
[ examples 2 to 3]
An adhesive sheet was produced in the same manner as in example 1, except that the mixing amount of the acrylate polymer, the mixing amount of the graphene having a two-dimensional structure, and the mixing amount of the solvent in the first step, and the mixing amount of the acrylate polymer and the mixing amount of the solvent in the second step were changed as shown in table 1.
[ example 4]
A dispersion treatment was carried out by mixing 5 parts by mass (5 parts by mass in total 100 parts by mass; solid content concentration) of a polyisobutylene-based resin as an adhesive resin, 2.5 parts by mass of a hydrogenated petroleum resin (Arakawa Chemical Industries, ltd., product name "ARKON P-125") as a thickener, 25 parts by mass (solid content concentration) of graphene having a two-dimensional structure (product name "CNS-1A1" manufactured by ADEKA Co., ltd.), and 245 parts by mass of toluene as a solvent, and stirring the mixture at 3000rpm for 30 minutes using a disperser (product name "ROBOMIX" manufactured by PRIMIX Co., ltd.), thereby preparing a preliminary mixture (first step).
To the preliminary mixture, 95 parts by mass of the same polyisobutylene-based resin (95 parts by mass in 100 parts by mass in total; solid content concentration), 47.5 parts by mass of a hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, ltd., product name "ARKON P-125") as a thickener, and 132 parts by mass of toluene as a solvent were added, and stirred at 3000rpm for 30 minutes using a disperser (manufactured by PRIMIX, product name "ROBOMIX") to obtain a coating liquid of a thermally conductive adhesive composition (second step). Using the coating liquid of the obtained thermally conductive adhesive composition, an adhesive sheet was produced in the same manner as in example 1.
Comparative example 1
100 parts by mass (solid content concentration) of the same acrylate polymer as in example 1 as an adhesive resin, 43 parts by mass (solid content concentration) of carbon black (product name "#3030B" manufactured by mitsubishi chemical corporation) and 330 parts by mass of methyl ethyl ketone as a solvent were mixed, and stirred at 3000rpm for 30 minutes using a disperser (product name "ROBOMIX" manufactured by PRIMIX corporation) to perform dispersion treatment, thereby preparing a coating liquid of a thermally conductive adhesive composition. Using the coating liquid of the obtained thermally conductive adhesive composition, an adhesive sheet was produced in the same manner as in example 1.
Comparative example 2
100 parts by mass (solid content concentration) of the same acrylate polymer as in example 1 as an adhesive resin, 195 parts by mass (solid content concentration) of alumina (product name "CB-P10" manufactured by shodadenkosya. Co. Ltd., having an average particle diameter of 8 μm) as a solvent, and 690 parts by mass of methyl ethyl ketone as a solvent were mixed, and stirred at 3000rpm for 30 minutes using a disperser (product name "ROBOMIX" manufactured by PRIMIX corporation) to prepare a coating liquid of a thermally conductive adhesive composition. Using the coating liquid of the obtained thermally conductive adhesive composition, an adhesive sheet was produced in the same manner as in example 1.
Comparative example 3
100 parts by mass (solid content concentration) of the same acrylate polymer as in example 1 as an adhesive resin, 43 parts by mass (solid content concentration) of boron nitride (manufactured by showdenkosya. Co. Ltd., product name "UHP2", average particle diameter 11 μm) and 330 parts by mass of methyl ethyl ketone as a solvent were mixed, and stirred at 3000rpm for 30 minutes using a disperser (manufactured by PRIMIX corporation, product name "ROBOMIX") to prepare a coating liquid of a thermally conductive adhesive composition. Using the coating liquid of the obtained thermally conductive adhesive composition, an adhesive sheet was produced in the same manner as in example 1.
Test example 1 < measurement of thermal conductivity >
From the adhesive layers of the adhesive sheets prepared in examples and comparative examples, square samples each having a side of 5mm were obtained. The thermal conductivity (W/m.K) of the above sample (adhesive layer) was measured using a thermal diffusivity/thermal conductivity measuring apparatus (ai-Phase co., ltd. Company, product name "ai-Phase mobile") at 23 ℃ and 50% RH in an environment of ISO 22007-3. The results are shown in Table 1.
Test example 2 < measurement of adhesive force >
Coating liquids of the thermally conductive adhesive compositions prepared in examples and comparative examples were applied to a polyethylene terephthalate (PET) film (tosobo co., ltd., product name "CosmoShine PET50a4100", film thickness 50 μm), and then heat-treated at 100 ℃ for 2 minutes to dry, thereby producing an adhesive sheet (PET film/adhesive layer) having an adhesive layer thickness of 30 μm.
The obtained adhesive sheet was cut into a short strip shape having a width of 25mm and a length of 250mm, and the adhesive layer of the adhesive sheet was attached to the polished surface of a stainless (SUS) plate polished to 600 mesh, and pressed by rolling a 2kg rubber roller back and forth once. After the sheet was left to stand at 23 ℃ and 50% RH for 24 hours, the adhesive sheet was peeled off from the SUS plate at a peeling speed of 300mm/min and a peeling angle of 180 degrees using a tensile tester (オリエンテック, TENSILON). The conditions other than those described herein were measured in accordance with JIS Z0237: 2009. The results are shown in Table 1.
Test example 3 < evaluation of dispersibility of Filler >
The coating liquids of the thermally conductive adhesive compositions prepared in examples and comparative examples were put into sample bottles (capacity 70 mL) and left to stand, and the dispersion state of the fillers (graphene, carbon black, alumina, and boron nitride) was visually confirmed after 24 hours. Then, the dispersibility of the filler was evaluated according to the following criteria. The results are shown in Table 1.
O: the filler is not settled and is uniformly dispersed.
And (delta): part of the filler settles.
X: most of the filler settled.
[ test example 4] < Raman measurement >
The adhesive layer of the adhesive sheet prepared in example was subjected to raman measurement using a laser micro raman spectrometer (manufactured by Thermo Fisher, product name "DXR 2"). Then, the wave number was 1570cm, which was obtained from a graph of the absorption spectrum measured at a laser wavelength of 532nm -1 Absorption intensity peak (I) of near G band G ) Wave number 1250cm -1 Absorption intensity peak (I) of nearby D band D ) Calculating the absorption intensity peak value (I) G ) Relative to the peak of absorption intensity (I) D ) The ratio (Raman peak intensity ratio D/G). The results are shown in Table 1. In addition, in this raman measurement, information of graphene itself contained in the adhesive agent layer can be obtained regardless of a difference in the amount of graphene added.
Figure BDA0004095174360000231
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As can be seen from table 1, the adhesive sheets produced in the examples have excellent thermal conductivity and adhesive force. In addition, in (a coating solution of) the thermally conductive adhesive composition prepared in the examples, the dispersibility of graphene having a two-dimensional structure is excellent.
Industrial applicability
The thermally conductive adhesive composition and the adhesive sheet of the present invention are suitably used, for example, between an electronic device that generates heat and a substrate or a heat sink that dissipates heat to cool the electronic device.
Description of the reference numerals
1: an adhesive sheet; 11: an adhesive layer; 12a, 12b: a release sheet; 3: a heat dissipating device; 11: an adhesive layer; 31: a heat generating component; 32: a heat transfer member.

Claims (8)

1. A thermally conductive adhesive composition contains an adhesive resin and graphene having a two-dimensional structure.
2. The thermally conductive adhesive composition according to claim 1, wherein the content of the graphene having a 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.
3. The thermally conductive adhesive composition according to claim 1 or 2, wherein the adhesive resin has a glass transition temperature (Tg) of-70 ℃ or higher and 50 ℃ or lower.
4. An adhesive sheet comprising at least an adhesive layer, wherein the adhesive layer is composed of the thermally conductive adhesive composition according to any one of claims 1 to 3.
5. The adhesive sheet according to claim 4, wherein the adhesive force of the adhesive sheet to stainless steel polished with a mesh size of 600 mesh is 0.1N/25mm or more.
6. The adhesive sheet according to claim 4 or 5, wherein the adhesive layer has a thermal conductivity of 5W/m-K or more.
7. The adhesive sheet according to any one of claims 4 to 6, wherein the wave number of the adhesive layer in an absorption spectrum obtained by Raman measurement is 1250cm -1 Absorption intensity peak (I) of nearby D band D ) Relative to wave number of 1570cm -1 Absorption intensity peak (I) of near G band G ) The ratio (D/G) is 0.5 or less.
8. A method for producing an adhesive sheet according to any one of claims 4 to 7, comprising:
a step of preparing a coating liquid of the thermally conductive adhesive composition; and
a step of forming the adhesive layer by applying a coating solution of the thermally conductive adhesive composition and drying the coating solution,
the step of preparing the coating liquid includes:
a first step of performing a dispersion treatment on a mixture containing a part of the total amount of the adhesive resin to be blended, the graphene having a two-dimensional structure, and a solvent to obtain a preliminary mixture; and
a second step of adding at least the remaining adhesive resin to the preliminary mixture and performing a dispersion treatment,
the amount of the adhesive resin to be mixed 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 a two-dimensional structure.
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CN117070166B (en) * 2023-08-08 2024-04-02 德州科顺建筑材料有限公司 Adhesive layer composition, polyolefin waterproof coiled material, and preparation method and application thereof

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