JP7317577B2 - Adhesive heat dissipation sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive heat-dissipating sheet.

2. Description of the Related Art Conventionally, in electronic devices such as thermoelectric conversion devices, photoelectric conversion devices, and semiconductor devices such as large-scale integrated circuits, heat dissipation sheets having thermal conductivity have been used in order to dissipate generated heat. For example, as a method for efficiently dissipating heat generated from a semiconductor device to the outside, an adhesive heat dissipation sheet with excellent thermal conductivity is provided between the semiconductor device and a heat sink or heat dissipation plate. there is

As exemplified in Patent Document 1, the adhesive heat-dissipating sheet as described above is obtained by applying a heat-dissipating material coating liquid containing an adhesive resin, an inorganic filler, a curing agent, and a solvent to a release sheet or base material. , produced by drying.

JP 2015-67713 A

However, conventional adhesive heat-dissipating sheets do not necessarily have sufficient thermal conductivity.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an adhesive heat-dissipating sheet having excellent thermal conductivity.

To achieve the above objects, firstly, the present invention provides an adhesive heat-dissipating sheet containing an adhesive and an inorganic filler, wherein at least one surface of the adhesive heat-dissipating sheet has an arithmetic mean roughness Ra of 20 μm. is less than 30 μm, the average length RSm of the roughness curve elements is less than 30 μm, and the probe tack value is 13 mN/5 mmΦ or more (Invention 1).

The adhesive heat-dissipating sheet according to the above invention (invention 1) exhibits excellent thermal conductivity by having the above-described composition and physical properties. Specifically, when the adhesive heat-dissipating sheet having the above composition satisfies the above physical properties, the filling rate of the inorganic filler is high, and the inorganic fillers contact and adhere to each other, resulting in an efficient heat conduction path. is formed, and the thermal conductivity is considered to be improved. In addition, when the surface roughness is above, the surface smoothness is high, thereby increasing the contact area with the adherend, and the probe tack value is above, so that the adhesion with the adherend also higher. Therefore, it becomes a thing excellent in thermal conductivity also from these aspects.

In the above invention (invention 1), the adhesive is preferably an acrylic adhesive (invention 2).

In the above inventions (Inventions 1 and 2), the content of the inorganic filler in the adhesive heat-dissipating sheet is preferably 35 parts by volume or more and 500 parts by volume or less with respect to 100 parts by volume of the adhesive ( Invention 3).

In the above inventions (inventions 1 to 3), the inorganic filler is preferably granular (invention 4).

In the above inventions (inventions 1 to 4), the inorganic filler preferably has an average particle size of 10 μm or more and 100 μm or less (invention 5).

In the above inventions (inventions 1 to 5), the inorganic filler preferably comprises boron nitride (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that the adhesive heat-dissipating sheet is sandwiched between two release sheets so as to be in contact with the release surfaces of the release sheets (invention 7).

ADVANTAGE OF THE INVENTION The adhesive thermal radiation sheet which concerns on this invention is excellent in thermal conductivity.

1 is a cross-sectional view showing an adhesive heat-dissipating sheet according to an embodiment of the present invention; FIG. It is explanatory drawing which shows an example of the manufacturing method of the adhesive thermal radiation sheet which concerns on one Embodiment of this invention.

Embodiments of the present invention will be described below.
An adhesive heat-dissipating sheet according to one embodiment of the present invention contains an adhesive and an inorganic filler. At least one surface, preferably both surfaces, of the adhesive heat-dissipating sheet has an arithmetic mean roughness Ra of less than 20 μm, an average length RSm of the roughness curvilinear element of less than 30 μm, and a probe tack value of , 13 mN/5 mmΦ or more.

The adhesive heat-dissipating sheet according to the present embodiment has the composition and physical properties described above, thereby exhibiting excellent thermal conductivity, bonding properties, and adhesiveness. Specifically, when the adhesive heat-dissipating sheet having the composition described above satisfies the arithmetic mean roughness Ra and the average length RSm of the roughness curve element, the inorganic filler hardly protrudes on the surface of the adhesive heat-dissipating sheet. tend to exist in large amounts in the heat-dissipating sheet. As a result, the filling rate of the inorganic filler in the adhesive heat-dissipating sheet increases, and the inorganic fillers come into contact and adhere to each other, forming an efficient thermal conduction path and improving thermal conductivity. . In addition, since the arithmetic average roughness Ra and the average length RSm of the roughness curve element are above, the surface smoothness is high, thereby increasing the contact area with the adherend, and the probe tack value is above. As a result, when the adhesive heat-dissipating sheet is attached to an adherend such as a heat-generating member or a heat-transfer member, the bonding property (handling property and adhesion) is improved, and excellent adhesiveness is exhibited.

From the viewpoint of thermal conductivity, the arithmetic mean roughness Ra is preferably 18 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less, so that the probe tack value and adhesive strength can be increased. It is preferably 8 μm or less, more preferably 7 μm or less, from the viewpoint of being able to do so. On the other hand, the lower limit of the arithmetic mean roughness Ra is not particularly limited, but is preferably 0 μm or more, preferably 1 μm or more, particularly preferably 2 μm or more, and further preferably 4 μm or more. is preferred.

Similarly, from the viewpoint of thermal conductivity, the average length RSm of the roughness curve element is preferably 28 μm or less, particularly preferably 26 μm or less, and from the viewpoint of increasing the probe tack value and adhesive strength, Furthermore, it is preferably 25 μm or less. On the other hand, the lower limit of the average length RSm of the roughness curve element is not particularly limited, but is preferably 0 μm or more, preferably 1 μm or more, particularly preferably 2 μm or more, and further preferably 4 μm. It is preferable that it is above.

The arithmetic average roughness Ra and the average length RSm of the roughness curve element in this specification are values measured according to JIS B0601-1994.

In addition, from the viewpoint of lamination property (handling property and adhesion) and adhesion strength improvement, the probe tack value is 13 mN/5 mmΦ or more, preferably 15 mN/5 mmΦ or more, and 21 mN/5 mmΦ or more. is more preferably 30 mN/5 mmφ or more, more preferably 40 mN/5 mmφ or more, and most preferably 60 mN/5 mmφ or more. On the other hand, from the viewpoint of reworkability, the lower limit of the probe tack value is preferably 200 mN/5 mmφ or less, particularly preferably 150 mN/5 mmφ or less, further preferably 120 mN/5 mmφ or less. In addition, the probe tack value in this specification refers to a value measured according to JIS Z0237:1991, and the detailed measuring method will be shown in Examples described later.

As described above, the adhesive heat-dissipating sheet according to this embodiment contains an adhesive and an inorganic filler. The type of adhesive is not particularly limited as long as the above physical properties are satisfied. For example, any of acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, silicone adhesives, etc. good too. Among them, an acrylic pressure-sensitive adhesive that easily satisfies the physical properties described above is preferable.

Acrylic pressure-sensitive adhesives may be emulsion-type, solvent-type or non-solvent-type. In addition, the acrylic pressure-sensitive adhesive may be crosslinkable, or may be curable such as active energy ray-curable or thermosetting. Among the above, from the viewpoint of easily satisfying the physical properties described above, non-curable acrylic pressure-sensitive adhesives are preferable, and crosslinkable acrylic pressure-sensitive adhesives are particularly preferable.

Specifically, the material constituting the adhesive heat-dissipating sheet according to the present embodiment is a heat-dissipating sheet containing a (meth)acrylic acid ester polymer (A), a cross-linking agent (B), and an inorganic filler (C). It is preferably obtained by cross-linking a forming composition (hereinafter sometimes referred to as “heat-dissipating sheet-forming composition C”). In addition, in this specification, (meth)acryloyl means both acryloyl and methacryloyl. The same applies to other similar terms. In addition, in this specification, the concept of "copolymer" is also included in "polymer".

1. Each component (1) (meth) acrylic acid ester polymer (A)
The (meth)acrylic acid ester polymer (A) in the present embodiment is a reactive group-containing monomer having, as a monomer unit constituting the polymer, a reactive group that reacts with the cross-linking agent (B) described later in the molecule. is preferably included. A reactive group derived from this reactive group-containing monomer reacts with the cross-linking agent (B) to form a cross-linked structure (three-dimensional network structure), and an adhesive heat-dissipating sheet having desired cohesion is obtained.

Examples of the reactive group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxy group in the molecule (carboxy group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer ) and the like are preferably mentioned. One of these reactive functional group-containing monomers may be used alone, or two or more thereof may be used in combination.

Among the above reactive functional group-containing monomers, hydroxyl group-containing monomers and carboxy group-containing monomers are preferable from the viewpoint of reactivity with the cross-linking agent (B) and improvement of filling properties of the inorganic filler (C). The (meth)acrylic acid ester polymer (A) in the present embodiment may contain both a hydroxyl group-containing monomer and a carboxy group-containing monomer as monomer units constituting the polymer, or may contain each alone. may In particular, it is preferable to contain both a hydroxyl group-containing monomer and a carboxy group-containing monomer from the viewpoint of ease of satisfying the probe tack value described above.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth) ) hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate; Among them, 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate is preferable from the viewpoint of ease of satisfying the probe tack value described above, and particularly 2-hydroxyethyl acrylate or 4-hydroxyethyl acrylate. -hydroxybutyl is preferred, and 2-hydroxyethyl acrylate is more preferred. These may be used alone or in combination of two or more.

Carboxy group-containing monomers include, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among the above, acrylic acid is preferable from the viewpoint of ease of satisfying the probe tack value described above. These may be used alone or in combination of two or more.

The content of the reactive functional group-containing monomer as a constituent monomer unit in the (meth)acrylic acid ester polymer (A) (when two or more reactive functional group-containing monomers are contained, the total amount) is It is preferably 0.4% by mass or more, particularly preferably 0.8% by mass or more, and further preferably 1.2% by mass or more. Also, the content is preferably 12% by mass or less, particularly preferably 6% by mass or less, and further preferably 3% by mass or less. When the content of the reactive functional group-containing monomer is within the above range, the probe tack value described above can be easily satisfied. In addition, the filling property of the inorganic filler (C) is improved, and the heat dissipation property is more likely to be exhibited.

When the (meth)acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a reactive functional group-containing monomer as a monomer unit constituting the polymer, the content is 0.1% by mass or more. is preferably 0.2% by mass or more, and more preferably 0.4% by mass or more. The content is preferably 5% by mass or less, particularly preferably 3% by mass or less, and further preferably 1% by mass or less.

Further, when the (meth)acrylic acid ester polymer (A) contains a carboxy group-containing monomer as a reactive functional group-containing monomer as a monomer unit constituting the polymer, the content is 0.1 It is preferably at least 0.4% by mass, and more preferably at least 0.8% by mass. The content is preferably 10% by mass or less, particularly preferably 6% by mass or less, and further preferably 2% by mass or less.

The (meth)acrylic acid ester polymer (A) preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. As a result, the probe tack value described above can be easily satisfied, and good bonding properties (handling properties and adhesion) and good adhesiveness can be exhibited. Alkyl groups may be linear, branched or cyclic.

As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferable from the viewpoint of lamination properties (handling properties and adhesion) and adhesiveness. Examples of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-(meth)acrylate, Butyl, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, (meth)acrylic acid Examples include n-dodecyl, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. Among them, from the viewpoint of further improving lamination properties (handling properties and adhesion) and adhesiveness, (meth)acrylic acid esters having an alkyl group having a carbon number of 1 to 8 are preferable, methyl (meth)acrylate, (meth) ) n-butyl acrylate or 2-ethylhexyl (meth)acrylate is more preferred, methyl acrylate, n-butyl acrylate or 2-ethylhexyl acrylate is particularly preferred, and n-butyl acrylate or 2-ethylhexyl acrylate is more preferred. More preferred. In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer (A) preferably contains 60% by mass or more, particularly 80% by mass or more, of (meth)acrylic acid alkyl ester as monomer units constituting the polymer. It is preferably contained in an amount of 90% by mass or more. When the lower limit of the content of the (meth)acrylic acid alkyl ester is the above, the probe tack value described above is easily satisfied, and the filling property of the inorganic filler (C) is good, so that the heat dissipation property is further exhibited. becomes easier. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 99% by mass or less, particularly 98% by mass or less, of (meth)acrylic acid alkyl ester as the monomer units constituting the polymer. It is preferable to contain 96% by mass or less. When the upper limit of the content of the (meth)acrylic acid alkyl ester is the above, a suitable amount of another monomer component such as a reactive functional group-containing monomer is introduced into the (meth)acrylic acid ester polymer (A). be able to.

The (meth)acrylic acid ester polymer (A) may optionally contain other monomers as monomer units constituting the polymer. The other monomer is preferably a monomer that does not contain a reactive functional group so as not to inhibit the action of the reactive functional group-containing monomer. Examples of such reactive functional group-free monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, and vinyl acetate. These may be used alone or in combination of two or more.

Among the above, the (meth)acrylic acid ester polymer (A) preferably contains vinyl acetate as a monomer unit constituting the polymer. This makes it easier to satisfy the probe tack value described above.

The (meth)acrylic acid ester polymer (A) preferably contains 0.5% by mass or more, particularly preferably 1% by mass or more, of vinyl acetate as a monomer unit constituting the polymer. is preferably contained in an amount of 2% by mass or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 10% by mass or less, particularly preferably 7% by mass or less, of vinyl acetate as a monomer unit constituting the polymer. is preferably contained in an amount of 4% by mass or less. When the content of vinyl acetate is within the above range, the probe tack value described above can be more easily satisfied.

The (meth)acrylate polymer (A) is preferably a linear polymer. By being a straight-chain polymer, entanglement of molecular chains is likely to occur, and an improvement in cohesive strength can be expected. As a result, it is easier to obtain an adhesive heat-dissipating sheet that satisfies the probe tack value described above and has excellent durability.

Moreover, the (meth)acrylate polymer (A) is preferably a solution polymer obtained by a solution polymerization method. Since it is a solution polymer, it becomes easy to obtain a polymer with a high molecular weight, and an improvement in cohesion can be expected. As a result, it is easier to obtain an adhesive heat-dissipating sheet that satisfies the probe tack value described above and has excellent durability.

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

The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 300,000 or more, particularly preferably 500,000 or more, further preferably 800,000 or more as a lower limit. When the lower limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is above, the resulting adhesive heat-dissipating sheet has excellent durability.

Further, the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 1,600,000 or less as an upper limit, particularly preferably 1,400,000 or less, and further preferably 1,200,000 or less. preferable. When the upper limit of the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is above, the physical properties related to surface roughness described above and the probe tack value described above are easily satisfied.

In the heat-dissipating sheet-forming composition C, the (meth)acrylate polymer (A) may be used singly or in combination of two or more.

(2) Crosslinking agent (B)
The cross-linking agent (B) cross-links the (meth)acrylic acid ester polymer (A) by heating the heat-dissipating sheet-forming composition C, so that a three-dimensional network structure can be satisfactorily formed. As a result, the cohesive force of the obtained adhesive heat-dissipating sheet is improved, the probe tack value described above is more easily satisfied, and the durability is excellent.

The cross-linking agent (B) may be one that reacts with the reactive groups of the (meth)acrylic acid ester polymer (A). Examples include isocyanate cross-linking agents, epoxy cross-linking agents, and amine cross-linking agents. , melamine cross-linking agent, aziridine cross-linking agent, hydrazine cross-linking agent, aldehyde cross-linking agent, oxazoline cross-linking agent, metal alkoxide cross-linking agent, metal chelate cross-linking agent, metal salt cross-linking agent, ammonium salt cross-linking agent, etc. is mentioned. Among the above, it is preferable to use an isocyanate-based cross-linking agent that has excellent reactivity with the reactive groups of the (meth)acrylic acid ester polymer (A). In addition, a crosslinking agent (B) can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based cross-linking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. , and their biuret, isocyanurate, and adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferable from the viewpoint of reactivity with hydroxyl groups.

The content of the cross-linking agent (B) in the heat-dissipating sheet-forming composition C is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A), particularly It is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more. Also, the content is preferably 5 parts by mass or less, particularly preferably 4 parts by mass or less, and further preferably 2 parts by mass or less. When the content of the cross-linking agent (B) is within the above range, the resulting adhesive heat-dissipating sheet exhibits good cohesive force, more easily satisfies the probe tack value described above, and has excellent durability.

(3) inorganic filler (C)
The composition C for forming a heat-dissipating sheet contains an inorganic filler (C). The inorganic filler (C) preferably has excellent thermal conductivity. Specifically, the thermal conductivity at 25° C. is preferably 10 W/m·K or more, particularly preferably 20 W/m·K or more, and further preferably 30 W/m·K or more. . Although the upper limit of the thermal conductivity is not limited, it is usually 300 W/m·K or less.

Materials for the inorganic filler (C) include metal oxides such as aluminum oxide, magnesium oxide, zinc oxide, titanium oxide and iron oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; Examples include nitrides, carbides such as silicon carbide and calcium carbide, and talc.

Among these, metal oxides, metal hydroxides or nitrides are preferred, and nitrides are particularly preferred, from the viewpoint of ease of satisfying physical properties related to heat dissipation and surface roughness. Among nitrides, boron nitride is particularly preferable because it has excellent heat dissipation properties and easily satisfies the physical properties related to the surface roughness described above. In addition, boron nitride does not have electrical conductivity, and is therefore preferable for applications requiring insulation. In addition, the said inorganic filler (C) may be used individually by 1 type, and may be used in combination of 2 or more type.

The shape of the inorganic filler (C) may be any of granular, needle-like, plate-like, scale-like, irregular shape, and the like. Granules include granules formed by agglomeration of particles of other shapes (for example, needle-like, plate-like, scale-like, irregular shape, etc.). For example, the shape of primary particles of boron nitride is often scaly, but the scaly primary particles may aggregate to form granules. In this embodiment, it is particularly preferable to use boron nitride in which scaly primary particles are aggregated into granules. Such granular boron nitride is excellent in heat dissipation, and more easily satisfies the physical properties regarding the surface roughness described above.

The average particle size of the inorganic filler (C) is preferably less than the intended thickness of the heat-dissipating sheet. This makes it difficult for the inorganic filler (C) to protrude from the surface of the heat-dissipating sheet, making it easier to satisfy the physical properties related to the surface roughness described above.

The average particle size of the inorganic filler (C) is preferably 10 µm or more, particularly preferably 20 µm or more, and further preferably 30 µm or more. The average particle size is preferably 100 μm or less, more preferably 80 μm or less, particularly preferably 60 μm or less, and further preferably 50 μm or less. When the average particle size of the inorganic filler (C) is within the above range, the filling rate of the inorganic filler (C) in the resulting adhesive heat-dissipating sheet can be increased, resulting in more excellent heat dissipation. The physical properties related to the surface roughness described above are more likely to be satisfied.

The average particle size of the inorganic filler (C) in this specification refers to the major axis diameter of 20 randomly selected fillers (in the case of granules, the major axis diameter of the granules) measured with an electron microscope. and the particle size calculated as the arithmetic mean value.

The content of the inorganic filler (C) in the heat-dissipating sheet-forming composition C is a total of 100 volumes of the adhesive (acrylic adhesive), that is, the (meth)acrylic acid ester polymer (A) and the cross-linking agent (B). It is preferably 35 parts by volume or more, more preferably 50 parts by volume or more, particularly preferably 70 parts by volume or more, further preferably 90 parts by volume or more. In addition, the content of the inorganic filler (C) is preferably 500 parts by volume or less, more preferably 300 parts by volume or less, particularly preferably 200 parts by volume or less, and further 120 parts by volume. The following are preferable. When the content of the inorganic filler (C) is within the above range, the physical properties and probe tack value relating to the surface roughness described above are easily satisfied. If the content of the inorganic filler (C) is less than 35 parts by volume, especially 30 parts by volume or less, it is difficult to obtain the desired thermal conductivity.

(4) Various Additives Various additives such as tackifiers, flame retardants, antioxidants, light stabilizers, softeners, and rust preventives may be added to the composition C for forming a heat-dissipating sheet, if desired. can be done. It should be noted that a polymerization solvent and a dilution solvent, which will be described later, are not included in the additives constituting the composition C for forming a heat-dissipating sheet.

2. Preparation of heat-dissipating sheet-forming composition The heat-dissipating sheet-forming composition C is prepared by producing a (meth)acrylic acid ester polymer (A), and combining the obtained (meth)acrylic acid ester polymer (A) with a cross-linking agent. It can be produced by mixing (B) with an inorganic filler (C) and optionally adding an additive.

The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a conventional radical polymerization method. Polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method, optionally using a polymerization initiator. However, the present invention is not limited to this, and may be polymerized without a solvent. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used in combination.

Examples of polymerization initiators include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of azo compounds include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane 1-carbonitrile), 2 ,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate) , 4,4′-azobis(4-cyanovaleric acid), 2,2′-azobis(2-hydroxymethylpropionitrile), 2,2′-azobis[2-(2-imidazolin-2-yl) propane] and the like.

Examples of organic peroxides include benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxy dicarbonate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionylperoxide, diacetylperoxide and the like.

The weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol in the polymerization step.

After the (meth)acrylic acid ester polymer (A) is obtained, the solution of the (meth)acrylic acid ester polymer (A) is added with a crosslinking agent (B), an inorganic filler (C), and optionally a diluent solvent and additives. and thoroughly mixed to obtain a heat-dissipating sheet-forming composition C diluted with a solvent. In any of the above components, if a solid one is used, or if precipitation occurs when mixed with other components in an undiluted state, the component is added alone in advance to a dilution solvent. It may be dissolved or diluted prior to mixing with other ingredients.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

The viscosity of the heat-dissipating sheet-forming composition C thus prepared is not particularly limited as long as it is within a range that allows coating, and can be appropriately selected depending on the situation. The addition of a diluent solvent or the like is not a necessary condition, and the diluent solvent may not be added as long as the composition C for forming a heat-dissipating sheet has a viscosity that allows coating. In this case, the heat-dissipating sheet-forming composition C becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) is used as it is as a dilution solvent.

3. Formation of Adhesive Heat-Dissipating Sheet The adhesive heat-dissipating sheet according to the present embodiment is formed by applying a heat-dissipating sheet-forming composition containing an adhesive and an inorganic filler, preferably a coating solution of the heat-dissipating sheet-forming composition C described above. It is preferable to form a coating layer by heating and pressing the coating layer (details will be described later). By heat-pressing the coating layer in this manner, the physical properties and probe tack value relating to the surface roughness described above are easily satisfied. By such a method, an adhesive heat-dissipating sheet having excellent thermal conductivity can be easily produced.

4. Specific Configuration of Adhesive Heat-Dissipating Sheet FIG. 1 shows a specific configuration as an example of the adhesive heat-dissipating sheet according to the present embodiment.
As shown in FIG. 1, the adhesive heat-dissipating sheet 1 according to the present embodiment is in contact with the release surfaces of two release sheets, specifically a first release sheet 21 and a second release sheet 22. It is sandwiched between the first release sheet 21 and the second release sheet 22 . In this specification, the release surface of the release sheet refers to the surface of the release sheet that has releasability, and includes both the surface that has been subjected to a release treatment and the surface that exhibits releasability without being subjected to a release treatment. .

Examples of the first release sheet 21 and the second release sheet 22 include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, and polyethylene terephthalate film. , polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylate copolymer film, polystyrene film , a polycarbonate film, a polyimide film, a fluororesin film, and the like are used. Crosslinked films of these are also used. Furthermore, a laminated film of these may be used.

The release surfaces of the first release sheet 21 and the second release sheet 22 (especially the surfaces in contact with the adhesive heat-dissipating sheet) are preferably subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

Although the thickness of the first release sheet 21 and the second release sheet 22 is not particularly limited, it is usually about 20 to 150 μm.

The adhesive heat-dissipating sheet 1 according to this embodiment is sandwiched between the two release sheets 21 and 22 as described above, so that it is protected until a desired time (for example, when it is used). In addition, it is preferable to use two release sheets when performing the above-described heat pressing, and by laminating these on the adhesive heat-dissipating sheet 1 as they are, the adhesive heat-dissipating sheet 1 can be protected. However, the first release sheet 21 and the second release sheet 22 are not limited to the release sheets used at this time.

5. Physical properties of material (1) Gel fraction A composition obtained by removing the inorganic filler (C) from the heat-dissipating sheet-forming composition C, and the composition in a state immediately before heat pressing (hereinafter sometimes referred to as “composition RC” ) is preferably 1% or more, more preferably 2% or more, from the viewpoint of durability of the adhesive heat-dissipating sheet. From the viewpoint that it is easy to be removed, the content is preferably 5% or more, and particularly preferably 10% or more. In addition, the gel fraction is preferably 70% or less, more preferably 50% or less, particularly preferably 30% or less, further preferably 20% or less. As a result, air bubbles generated in the coating layer of the heat-dissipating sheet-forming composition C due to the heat pressing are easily crushed and eliminated, and as a result, the physical properties and probe tack value relating to the surface roughness described above are easily satisfied.

In addition, the above-mentioned "state immediately before hot pressing" refers to the same state as the state when subjected to hot pressing. Crosslinking may be complete or in progress (same below). Moreover, the method for measuring the gel fraction is as shown in the test examples described later.

(2) Relaxation modulus The maximum relaxation modulus G (t) max (MPa) is the maximum relaxation modulus value measured when the composition RC is strained by 10% in accordance with JIS K7244-1. and the composition RC is continuously strained by 10% until 1800 seconds after the maximum relaxation modulus G(t)max is measured, and the minimum relaxation modulus value measured during that time is defined as the minimum relaxation modulus G (t) _min (MPa), the relaxation modulus fluctuation value ΔlogG(t) calculated from the following formula (I) is preferably 1.01 or more, particularly preferably 1.1 or more , and more preferably 1.2 or more.
ΔlogG(t)=logG(t) _max −logG(t) _min (I)
The details of the method for measuring the relaxation modulus G(t) are as shown in the test examples described later.

When the relaxation elastic modulus fluctuation value ΔlogG(t) is above, the applied layer (immediately before heat pressing) of the heat-dissipating sheet-forming composition C is easily stress-relaxed. As a result, air bubbles generated in the coating layer of the heat-dissipating sheet-forming composition C due to the heat pressing are easily crushed and eliminated, and as a result, the physical properties and probe tack value relating to the surface roughness described above are easily satisfied.

The upper limit of the relaxation modulus fluctuation value ΔlogG(t) is not particularly limited, but is usually preferably 1.8 or less, particularly preferably 1.5 or less, and further preferably 1.3 or less. is preferred.

The maximum relaxation modulus G(t) _max of the composition RC is preferably 0.1 MPa or more, particularly preferably 0.5 MPa or more, further preferably 1 MPa or more as an upper limit. . By setting the lower limit of the maximum relaxation modulus G(t) _max to the above value, the relaxation modulus fluctuation value ΔlogG(t) easily satisfies the aforementioned value. The upper limit of the maximum relaxation modulus G(t) _max is not particularly limited. It is preferably 8 MPa or less, most preferably 1.7 MPa or less.

The minimum relaxation modulus G(t) _min of the composition RC is preferably 2 MPa or less, more preferably 1 MPa or less, and particularly preferably 0.5 MPa or less, as an upper limit. Furthermore, it is preferably 0.2 MPa or less, most preferably 0.15 MPa or less. By setting the upper limit of the minimum relaxation modulus G(t) _min to the above value, the relaxation modulus fluctuation value ΔlogG(t) easily satisfies the aforementioned value. The lower limit of the minimum relaxation modulus G(t) _min is not particularly limited, but it is usually preferably 0.01 MPa or more, particularly preferably 0.04 MPa or more, and further preferably 0.08 MPa or more. is preferred.

(3) Storage modulus The storage modulus (G') of the composition RC at 100°C is preferably 50 MPa or less, more preferably 30 MPa or less, particularly preferably 15 MPa or less, and further preferably 15 MPa or less. is preferably 11 MPa or less. When the storage elastic modulus (G′) at 100° C. is above, the coating layer of the heat-dissipating sheet-forming composition C (immediately before heat-pressing) is easily deformed by heat-pressing. As a result, air bubbles generated in the coating layer of the heat-dissipating sheet-forming composition C due to the heat pressing are easily crushed and eliminated, and as a result, the physical properties and probe tack value relating to the surface roughness described above are easily satisfied.

The lower limit of the storage elastic modulus (G′) is preferably 1 MPa or more, particularly preferably 4 MPa or more, and further preferably 9 MPa or more, from the viewpoint of durability of the adhesive heat-dissipating sheet to be obtained. is preferred.

(4) Loss tangent The loss tangent (tan δ) of the composition RC at 100°C is preferably 0.1 or more, particularly preferably 0.2 or more, and further preferably 0.3 or more. is preferred. Also, the loss tangent (tan δ) is preferably 1 or less, particularly preferably 0.8 or less, further preferably 0.6 or less. When the loss tangent (tan δ) at 100° C. is within the above range, the air bubbles generated in the coating layer of the heat-dissipating sheet-forming composition C by hot pressing are easily crushed and eliminated, and as a result, the above-mentioned surface roughness Physical properties and probe tack values are more likely to be met.

6. Specific Example of Method for Producing Adhesive Heat-Dissipating Sheet Hereinafter, a method for producing an adhesive heat-dissipating sheet according to a preferred embodiment of the present invention will be described with reference to the drawings. In the present embodiment, it is assumed that the adhesive (the (meth)acrylic acid ester polymer (A) in the heat-dissipating sheet-forming composition C) is crosslinkable, but is not limited to this. do not have. In addition, in the present embodiment, the composition C for forming a heat-dissipating sheet is used as an example of the composition for forming a heat-dissipating sheet, but the composition is not limited to this.

First, as shown in FIG. 2(a), the release surface of the first release sheet 21 is coated with the heat-dissipating sheet-forming composition C to form the coating layer 1A. At this time, heat treatment is preferably performed to crosslink (thermally crosslink) the composition C for forming a heat-dissipating sheet.

As a method for applying the heat-dissipating sheet-forming composition C, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

The heat treatment can also serve as a drying treatment for volatilizing the diluent solvent and the like from the coating layer 1A of the composition C for forming a heat-dissipating sheet. The heating temperature of the heat treatment is preferably 50 to 150°C, particularly preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes.

Next, as shown in FIG. 2B, a second release sheet 22 is laminated on the formed coating layer 1A so that the release surface thereof contacts the coating layer 1A.

In this embodiment, a curing step may be provided at this stage in order to complete the cross-linking reaction in the composition C for forming a heat-dissipating sheet. On the other hand, when the adhesive strength of the resulting adhesive heat-dissipating sheet is to be increased, or when the cross-linking reaction in the heat-dissipating sheet-forming composition C is almost completed by the above heat treatment, the curing step is not necessary. good too.

Curing conditions in the curing step are not particularly limited, but normal temperature (eg, 10 to 30° C.) and normal humidity (eg, 30 to 70% RH) are preferred. The curing period in the curing step is preferably 0.5 to 30 days, particularly preferably 1 to 14 days, further preferably 1 to 7 days.

The thickness (value measured according to JIS K7130) of the coating layer 1A at the stage immediately before the heat pressing process (the stage after the curing process if a curing process is provided) is preferably 100 μm or more, particularly It is preferably 140 μm or more, more preferably 180 μm or more. Also, the thickness is preferably 300 μm or less, particularly preferably 250 μm or less, further preferably 220 μm or less. This makes it easy to control the thickness of the adhesive heat-dissipating sheet obtained by the heat pressing process to a desired thickness.

Next, as shown in FIG. 2(c), the laminate composed of the first release sheet 21, the coating layer 1A and the second release sheet 22 is hot-pressed by a hot press machine 3 to adhere the coating layer 1A. A heat-dissipating sheet 1 is used. When the coating layer 1A is heated and pressed in this way, the filling rate of the inorganic filler (C) in the resulting adhesive heat-dissipating sheet 1 is improved, and the physical properties related to the surface roughness described above are easily satisfied. The tack value is easily met.

In order to obtain such an effect, it is preferable to compress the coating layer 1A until the thickness of the coating layer 1A becomes 40 to 90%, particularly preferably 50 to 80%, by the above-described hot pressing. , and more preferably compressed to 60 to 70%.

Moreover, in order to obtain the above effects, it is preferable to perform the above hot pressing at 25 to 160° C. and 50 to 200 kg/cm ² for 0.5 to 60 minutes. The temperature of the hot press is more preferably 28 to 160°C, particularly preferably 50 to 140°C, further preferably 80 to 120°C, from the viewpoint of improving thermal conductivity. However, when avoiding high-temperature heating from the viewpoint of worker safety, the temperature is preferably 25 to 40°C. The pressure of the hot press is preferably 70-150 kg/cm ² , more preferably 90-120 kg/cm ² . The heat pressing time is preferably 5 to 45 minutes, more preferably 15 to 30 minutes, from the viewpoint of improving thermal conductivity. However, from the viewpoint of improving productivity, the time is preferably 0.5 to 5 minutes.

Finally, as shown in FIG. 2(d), the laminate composed of the first release sheet 21, the adhesive heat-dissipating sheet 1 and the second release sheet 22 is removed from the hot press machine 3. According to the above method, the adhesive heat-dissipating sheet 1 having excellent thermal conductivity can be easily produced.

7. Physical properties of the adhesive heat-dissipating sheet (1) Thickness The thickness of the adhesive heat-dissipating sheet obtained according to the present embodiment (also referred to as the "adhesive heat-dissipating sheet according to the present embodiment") (value measured according to JIS K7130) ) has a lower limit of preferably 40 μm or more, more preferably 80 μm or more, particularly preferably 100 μm or more, further preferably 120 μm or more. When the lower limit value of the thickness of the adhesive heat-dissipating sheet is above, it is easy to exhibit good adhesive strength. In addition, since the thermally conductive filler having a particle size that is excellent in heat dissipation is less likely to protrude from the surface of the heat dissipation sheet, the physical properties relating to the surface roughness described above are easily satisfied.

In addition, the upper limit of the thickness of the adhesive heat-dissipating sheet according to the present embodiment is preferably 270 μm or less, more preferably 225 μm or less, particularly preferably 180 μm or less, and further preferably 160 μm or less. It is preferably 140 μm or less, and most preferably 140 μm or less. When the upper limit value of the thickness of the adhesive heat-dissipating sheet is above, it can be made more excellent in heat dissipation.

(2) Thermal conductivity The thermal conductivity (value measured according to ISO 22007-3) of the adhesive heat-dissipating sheet according to the present embodiment at 23 ° C. and 50% RH is 4 W / m K or more. It is preferably 6 W/m·K or more, particularly preferably 7 W/m·K or more, further preferably 8 W/m·K or more, and 9 W/m·K or more. is most preferred. Accordingly, it can be said that the adhesive heat-dissipating sheet is excellent in heat dissipation. The adhesive heat-dissipating sheet obtained from the heat-dissipating sheet-forming composition C described above can satisfy the above thermal conductivity. Although the upper limit of the thermal conductivity at 23° C. and 50% RH of the adhesive heat-dissipating sheet according to the present embodiment is not particularly limited, it is usually preferably 20 W/m·K or less, particularly 18 W/m·K. It is preferably K or less, more preferably 16 W/m·K or less.

(3) Adhesive strength Adhesive strength of the adhesive heat dissipation sheet according to the present embodiment to stainless steel (SUS304, #360 polished) is preferably 0.1 N/25 mm or more, and is 0.3 N/25 mm or more. is more preferable, particularly preferably 0.6 N/25 mm or more, and further preferably 0.8 N/25 mm or more. As a result, it can adhere well to adherends such as heat-generating members and heat-transfer members, and exhibit excellent heat dissipation properties. The adhesive heat-dissipating sheet obtained from the heat-dissipating sheet-forming composition C described above can satisfy the adhesive strength described above.

The adhesive strength is preferably 10 N/25 mm or less, more preferably 5 N/25 mm or less, particularly preferably 2 N/25 mm or less, and further preferably 1.5 N/25 mm or less. is preferred. As a result, good reworkability can be obtained, and re-bonding becomes possible even when a bonding error occurs.

The adhesive strength in this specification basically refers to the adhesive strength measured by the 180 degree peeling method according to JIS Z0237:2009, and the specific measuring method is as shown in the test examples described later. .

8. Use of Adhesive Heat Dissipating Sheet The adhesive heat dissipating sheet according to the present embodiment is suitable for obtaining a heat dissipating device by laminating a heat generating member and a heat transfer member, for example. The heat-generating member is a member that generates heat as it performs a predetermined function, but requires suppression of temperature rise, or a member that requires control of the flow of heat generated by the member in a specific direction. . Such heat-generating members include, for example, thermoelectric conversion devices, photoelectric conversion devices, semiconductor devices such as large-scale integrated circuits, electronic devices such as LED light-emitting elements, optical pickups, and power transistors, and various electronic devices such as mobile terminals and wearable terminals. , batteries, batteries, motors, engines, etc.

Further, the heat transfer member is a member that dissipates received heat, a member that transfers received heat to another member, or the like. Such a heat transfer member is preferably made of a material having high thermal conductivity, such as a metal such as aluminum, stainless steel, or copper, graphite, or carbon nanofiber. The form of the heat transfer member is not particularly limited and may be any of a substrate, a housing, a heat sink, a heat spreader, and the like.

In order to manufacture the heat dissipating device as described above, for example, the second release sheet 22 (or the first release sheet 21) is peeled off from the adhesive heat dissipating sheet 1 shown in FIG. One surface of the sheet 1 is attached to the heat generating member. Next, the first release sheet 21 (or the second release sheet 22) is peeled off from the adhesive heat-dissipating sheet 1 provided on the heat-generating member, and the other surface of the exposed adhesive heat-dissipating sheet 1 is attached to the heat-transfer member. affix. Alternatively, after one surface of the adhesive heat-dissipating sheet 1 is attached to the heat transfer member, the heat-generating member may be attached to the other surface of the adhesive heat-dissipating sheet 1 .

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

For example, one or both of the first release sheet 21 and the second release sheet 22 laminated on the adhesive heat dissipation sheet 1 may be peeled off at any stage.

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]
1. Preparation of (meth)acrylic acid ester polymer 95.5 parts by mass of n-butyl acrylate, 3 parts by mass of vinyl acetate, 0.5 parts by mass of 2-hydroxyethyl acrylate, and 1 part by mass of acrylic acid were subjected to solution polymerization. It was copolymerized to prepare a (meth)acrylic acid ester polymer (A). When the molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the following method, the weight average molecular weight (Mw) was 1,000,000.

The weight average molecular weight (Mw) of the (meth)acrylic acid ester polymer (A) is a standard polystyrene conversion value measured by gel permeation chromatography (GPC) under the following conditions.
<Measurement conditions>
・ Measuring device: HLC-8320 manufactured by Tosoh Corporation
・ GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel super HM-H
TSK gel super H2000
・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

2. Preparation of a composition for forming a heat-dissipating sheet 100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in the above step 1 (solid content conversion value; the same shall apply hereinafter), and trimethylolpropane as a cross-linking agent (B) 1 part by mass of modified tolylene diisocyanate (manufactured by Toyochem, product name "BHS8515") and 82 parts by mass of granular boron nitride (average particle size of granules: 40 µm) as an inorganic filler (C) ((meth)acrylic acid ester 100 parts by volume with respect to a total of 100 parts by volume of the polymer (A) and the cross-linking agent (B); got

3. Formation and curing of coating layer The composition for forming a heat-dissipating sheet obtained in the above step 2 is used as a release sheet (first release sheet; manufactured by Lintec Corporation, product name "SP-PET751031") was coated with an applicator, followed by heat treatment at 90°C for 1 minute and 120°C for 1 minute to form a coating layer. A release sheet (second release sheet; manufactured by Lintec Corporation, product name "SP-PET751130 ”), and cured for 7 days under conditions of 23° C. and 50% RH.

The thickness of the coating layer after the curing (thickness before hot pressing) was 200 μm. The thickness of the coating layer and the thickness of the adhesive heat-dissipating sheet to be described later are based on JIS K7130, and are measured using a constant pressure thickness gauge (manufactured by Teclock, product name "PG-02"). value.

4. Heat press The laminate consisting of the first release sheet, the coating layer (after curing) and the second release sheet obtained in the above step 3 was subjected to a heat press machine (manufactured by Imoto Seisakusho Co., Ltd., product name “Test Press 15t IMC”). -18E7 type") at 100° C. and 100 kg/cm ² for 1 minute to form the coating layer into an adhesive heat-dissipating sheet. The thickness of the adhesive heat-dissipating sheet thus obtained (thickness after hot pressing) was 130 μm.

[Example 2]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 100° C., 100 kg/cm ² and 10 minutes.

[Example 3]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 100° C., 100 kg/cm ² and 30 minutes.

[Example 4]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 60° C., 100 kg/cm ² and 1 minute.

[Example 5]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 60° C., 100 kg/cm ² and 10 minutes.

[Example 6]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 60° C., 100 kg/cm ² and 30 minutes.

[Example 7]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 30° C., 100 kg/cm ² and 1 minute.

[Example 8]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 30° C., 100 kg/cm ² and 10 minutes.

[Example 9]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the hot press conditions were changed to 30° C., 100 kg/cm ² and 30 minutes.

[Example 10]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the coating layer was not cured and the hot pressing was performed immediately after forming the coating layer. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was cured for 7 days under the conditions of 23 ° C. and 50% RH, and then subjected to the test. attached.

[Example 11]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the curing period of the coating layer was changed to 1 day. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was cured for 6 days under the conditions of 23 ° C. and 50% RH, and then subjected to the test. attached.

[Example 12]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the curing period of the coating layer was changed to 3 days. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was cured for 4 days under conditions of 23 ° C. and 50% RH, and then subjected to the test. attached.

[Example 13]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the curing period of the coating layer was changed to 14 days.

[Example 14]
An adhesive heat-dissipating sheet was produced in the same manner as in Example 1, except that the curing period of the coating layer was changed to 21 days.

[Example 15]
100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in Step 1 of Example 1, and trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") as a cross-linking agent (B) ) 1 part by mass and 310 parts by mass of granular boron nitride (average particle size of granules 40 μm) as inorganic filler (C) ((meth) acrylic acid ester polymer (A) and crosslinking agent (B) total 100 400 parts by volume; 80% by volume), diluted with methyl ethyl ketone, and sufficiently stirred to obtain a composition for forming a heat-dissipating sheet.

The obtained composition for forming a heat-dissipating sheet was applied to the release-treated surface of a release sheet (first release sheet; manufactured by Lintec, product name: "SP-PET751031") obtained by releasing one side of a polyethylene terephthalate film with a silicone-based release agent. After coating with an applicator, heat treatment was performed at 90° C. for 1 minute and at 120° C. for 1 minute to form a coating layer. A release sheet (second release sheet; manufactured by Lintec Corporation, product name "SP-PET751130 ”) was laminated with the release-treated surface. The thickness of the coating layer at this time (thickness before hot pressing) was 220 μm.

Then, without curing the coating layer, immediately after forming the coating layer, heat pressing was performed in the same manner as in Example 1 to produce an adhesive heat-dissipating sheet. The thickness of the adhesive heat-dissipating sheet thus obtained (thickness after hot pressing) was 175 μm. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was cured for 7 days under the conditions of 23 ° C. and 50% RH, and then subjected to the test. attached.

[Comparative Example 1]
The coating layer (after curing) immediately before heat pressing in Example 1 was used as an adhesive heat-dissipating sheet.

[Comparative Example 2]
The coating layer immediately before heat pressing in Example 15 was used as an adhesive heat-dissipating sheet. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was cured for 7 days under the conditions of 23 ° C. and 50% RH, and then subjected to the test. bottom.

[Comparative Example 3]
100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in Step 1 of Example 1, and trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") as a cross-linking agent (B) ) 1 part by mass, and 35 parts by mass of granular boron nitride (average particle size of granules 40 μm) as inorganic filler (C) ((meth)acrylic acid ester polymer (A) and crosslinking agent (B) total 100 42.86 parts by volume; 30% by volume), diluted with methyl ethyl ketone, and sufficiently stirred to obtain a composition for forming a heat-dissipating sheet.

The obtained composition for forming a heat-dissipating sheet was applied to the release-treated surface of a release sheet (first release sheet; manufactured by Lintec, product name: "SP-PET751031") obtained by releasing one side of a polyethylene terephthalate film with a silicone-based release agent. After coating with an applicator, heat treatment was performed at 90° C. for 1 minute and at 120° C. for 1 minute to form a coating layer. A release sheet (second release sheet; manufactured by Lintec Corporation, product name "SP-PET751130 ”) was laminated with the release-treated surface. The thickness of the coating layer at this time (thickness before hot pressing) was 150 μm.

Then, without curing the coating layer, immediately after forming the coating layer, heat pressing was performed in the same manner as in Example 1 to produce an adhesive heat-dissipating sheet. The thickness of the adhesive heat-dissipating sheet thus obtained (thickness after hot pressing) was 55 μm. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was aged for 5.35 days under conditions of 23 ° C. and 50% RH, and then the test Attached to

[Comparative Example 4]
The coating layer immediately before heat pressing in Comparative Example 3 was used as an adhesive heat-dissipating sheet. In addition, in tests according to Test Examples 4, 5, 6 and 7 described later, the adhesive heat-dissipating sheet produced in this example was cured for 7 days under the conditions of 23 ° C. and 50% RH, and then subjected to the test. bottom.

Here, Table 1 shows the conditions of hot pressing, the thickness of the coating layer (thickness before hot pressing), the thickness of the adhesive heat-dissipating sheet (thickness after hot pressing) and the curing period in each example.

[Test Example 1] (Measurement of gel fraction)
100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in Step 1 of Example 1, and trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") as a cross-linking agent (B) ) was mixed with 1 part by mass, diluted with methyl ethyl ketone, and sufficiently stirred to obtain a composition (a composition obtained by removing the inorganic filler (C) from the composition for forming a heat-dissipating sheet).

Using the obtained composition, a coating layer was formed and cured in the same manner as in each example and comparative example. The composition constituting the coating layer after curing corresponds to the "composition RC" in the state immediately before hot pressing. Cut the coating layer obtained as described above into a size of 80 mm × 80 mm, wrap the coating layer in a polyester mesh (mesh size 200), weigh the mass with a precision balance, and measure the mesh alone. By subtracting the mass, the mass of only the coating layer (composition RC) was calculated. Let the mass at this time be M1.

Next, the coated layer (composition RC) wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23° C.) for 72 hours. After that, the composition RC was taken out, air-dried for 24 hours in an environment of a temperature of 23° C. and a relative humidity of 50%, and further dried in an oven of 80° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the composition RC alone was calculated by subtracting the mass of the mesh alone. Let the mass at this time be M2. A gel fraction (%) is represented by (M2/M1)×100. From this, the gel fraction of composition RC was derived. Table 2 shows the results.

[Test Example 2] (Measurement of relaxation modulus)
In the same manner as in Test Example 1, a cured coating layer (composition RC) corresponding to each example and comparative example was obtained. A plurality of the coating layers were laminated to form a laminate having a thickness of 0.5 mm. A cylindrical body (height: 0.5 mm) with a diameter of 8 mm was punched out from the laminate of the coating layer (composition RC) thus obtained, and this was used as a sample.

For the above sample, in accordance with JIS K7244-1, using a viscoelasticity measuring device (manufactured by Anton paar, product name "MCR302"), the composition RC was continuously strained by 10% under the following conditions, and the relaxation modulus was measured. G(t) (MPa) was measured. From the measurement results, the maximum relaxation modulus G (t) _max (MPa) is derived, and the minimum relaxation modulus G measured up to 1800 seconds after the maximum relaxation modulus G (t) _max is measured (t) _min (MPa) was derived.
Measurement temperature: 25°C
Measurement points: 1000 points (logarithmic plot)

From the obtained maximum relaxation modulus G(t) _max (MPa) and minimum relaxation modulus G(t) _min (MPa), the relaxation modulus fluctuation value ΔlogG(t) is calculated based on the following formula (I): Calculated. Table 2 shows the results.
ΔlogG(t)=logG(t) _max −logG(t) _min (I)

[Test Example 3] (Measurement of elastic modulus)
In the same manner as in Test Example 1, a cured coating layer (composition RC) corresponding to each example and comparative example was obtained. A plurality of the coating layers were laminated to form a laminate having a thickness of about 0.5 mm. A cylindrical body (height: 0.5 mm) with a diameter of 8 mm was punched out from the laminate of the coating layer (composition RC) thus obtained, and this was used as a sample.

For the above sample, in accordance with JIS K7244-1, using a viscoelasticity measuring device (manufactured by Anton paar, product name "MCR302"), the dynamic viscoelasticity was measured under the following conditions, and the storage elastic modulus at 25 ° C. (G′) (MPa) and loss modulus (G″) (MPa) were observed. From the two values obtained, the loss tangent (tan δ) was calculated (loss modulus (G″)/storage elastic modulus (G')). Table 2 shows the results.
Measurement frequency: 0.1Hz
Measurement temperature range: -20 to 140°C

[Test Example 4] (Measurement of surface roughness)
The arithmetic mean roughness Ra (μm) and the average length RSm (μm) of the roughness curve elements on one side (second release sheet side) of the adhesive heat-dissipating sheets obtained in Examples and Comparative Examples were Measurement was performed in accordance with JIS B 0601:2001 using a laser microscope (color 3D laser microscope, manufactured by Keyence Corporation, product name "VK-9700"). However, the adhesive heat-dissipating sheets of Comparative Examples 3 and 4 could not be measured accurately. Table 2 shows the results.

The results of the arithmetic mean roughness Ra and the mean length RSm of the roughness curve elements of the other surface (the surface on the side of the first release sheet) of the adhesive heat-dissipating sheet were almost the same as the above results.

[Test Example 5] (Measurement of probe tack value)
One side (the side facing the second release sheet) of the adhesive heat-dissipating sheets obtained in Examples and Comparative Examples was subjected to a probe tack test using a probe with a diameter of 5 mm (5 mmφ) in accordance with JIS Z0237:2009. A probe tack value (mN/5 mmφ) was measured under the following measurement conditions using a machine (manufactured by Tester Sangyo Co., Ltd., product name “TE-6001 probe tack tester”). Table 2 shows the results.
Load: 200gf/ ^cm2
Contact time: 1 sec Test speed: 1 cm/sec

The probe tack value of the other surface of the adhesive heat-dissipating sheet (the surface on the side of the first release sheet) was almost the same as the above results.

[Test Example 6] (Measurement of adhesive strength)
The first release sheet was peeled off from the adhesive heat-dissipating sheets obtained in Examples and Comparative Examples, and the exposed surface was coated with a polyethylene terephthalate film having an easy-adhesion layer (manufactured by Toyobo Co., Ltd., product name "PET A4300"). , thickness: 25 μm). The laminate was cut to a width of 25 mm and a length of 100 mm, and this was used as a sample. Then, the second release sheet was peeled off from the sample, and the exposed surface was attached to a stainless steel plate (SUS304, #360 polished).

Within 1 minute after application, the adhesive strength (N/25 mm) was measured using a tensile tester (manufactured by Orientec, product name "Tensilon") under the conditions of a peel speed of 300 mm/min and a peel angle of 180°. Conditions other than those described here were measured according to JIS Z0237:2009. Table 2 shows the results. However, for the adhesive heat-dissipating sheets of Comparative Examples 1, 2, and 4, cohesive failure of the adhesive occurred, making accurate measurement impossible.

The adhesive strength of the other surface of the adhesive heat-dissipating sheet (the surface on the side of the first release sheet) was also approximately the same as the above results.

[Test Example 7] (Measurement of thermal conductivity)
For the adhesive heat-dissipating sheets obtained in Examples and Comparative Examples, a thermal diffusivity/thermal conductivity measuring device (manufactured by i-Phase, product name “ai-phase mobile”) was used, and ISO 22007-3 was compliant. Then, the thermal conductivity (W/m·K) was measured. As a result, the value obtained by averaging five measured values within ±30% was taken as the value of thermal conductivity. Table 2 shows the results.

As can be seen from Table 2, the adhesive heat-dissipating sheets of Examples exhibited high thermal conductivity and were excellent in thermal conductivity. In addition, the adhesive heat-dissipating sheets of Examples had good adhesion.

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

REFERENCE SIGNS LIST 1 Adhesive heat dissipation sheet 21 First release sheet 22 Second release sheet 1A Coating layer 3 Heat press

Claims (7)

An adhesive heat dissipation sheet containing an adhesive and an inorganic filler,
On at least one surface of the adhesive heat-dissipating sheet,
Arithmetic mean roughness Ra is less than 20 μm,
the average length RSm of the roughness curvilinear element is less than 30 μm,
The probe tack value is 15 mN / 5 mmΦ or more,
The adhesive is an acrylic adhesive
An adhesive heat dissipation sheet characterized by: An adhesive heat dissipation sheet containing an adhesive and an inorganic filler,
On at least one surface of the adhesive heat-dissipating sheet,
Arithmetic mean roughness Ra is less than 20 μm,
the average length RSm of the roughness curvilinear element is less than 30 μm,
The probe tack value is 15 mN / 5 mmΦ or more,
The adhesive heat dissipation sheet has a thickness of 80 µm or more and 270 µm or less.
An adhesive heat dissipation sheet characterized by: An adhesive heat dissipation sheet containing an adhesive and an inorganic filler,
On at least one surface of the adhesive heat-dissipating sheet,
Arithmetic mean roughness Ra is less than 20 μm,
the average length RSm of the roughness curvilinear element is less than 30 μm,
The probe tack value is 15 mN / 5 mmΦ or more,
The average particle size of the inorganic filler is 20 μm or more and 100 μm or less
An adhesive heat dissipation sheet characterized by: 4. The content of the inorganic filler in the adhesive heat-dissipating sheet is 35 parts by volume or more and 500 parts by volume or less with respect to 100 parts by volume of the adhesive. The adhesive heat dissipation sheet described in . The adhesive heat-dissipating sheet according to any one of claims 1 to 4 , wherein the inorganic filler is granular. The adhesive heat-dissipating sheet according to any one of claims 1 to 5, wherein the inorganic filler comprises boron nitride. The adhesive heat-dissipating sheet according to any one of claims 1 to 6, wherein the heat-dissipating adhesive sheet is sandwiched between two release sheets so that the release surfaces of the two release sheets are in contact with each other.

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