WO2023100818A1

WO2023100818A1 - Thermally conductive sheet

Info

Publication number: WO2023100818A1
Application number: PCT/JP2022/043817
Authority: WO
Inventors: 真由尾▲崎▼; 大輔水野; 秀平福富
Original assignee: 日東電工株式会社
Priority date: 2021-11-30
Filing date: 2022-11-28
Publication date: 2023-06-08
Also published as: TW202330867A

Abstract

Provided is a thermally conductive sheet that has favorable thermal conductivity and that also has high transparency.　The thermally conductive sheet comprises a resin layer containing a resin and a thermally conductive filler, wherein: the total light transmittance of the resin layer is at least 85%; the refractive index np of the resin is no more than 1.469; and a value (np-nf) obtained by subtracting the refractive index nf of the thermally conductive filler from the refractive index np of the resin is －0.01 to 0.01.

Description

thermally conductive sheet

The present invention relates to thermally conductive sheets.

In recent years, as electronic devices (for example, semiconductor elements) have become smaller and more functional, the amount of heat generated from electronic devices has increased. From the viewpoint of ensuring performance and functions, appropriate thermal design of electronic device products (that is, appropriate temperature control of products) is required. Against this background, in electronic device products, a thermally conductive sheet is placed between a heating element such as a diode and a radiator such as a heat spreader or a housing, so that the heat from the heating element is efficiently transferred to the radiator. It is used for purposes such as communication.

As such a thermally conductive sheet, a thermally conductive sheet having a thermally conductive layer in which a thermally conductive filler is dispersed in a resin is known (Patent Document 1).

JP 2013-176980 A

Transparency (light transmittance) is not particularly considered in the thermally conductive sheet above. However, if the thermally conductive sheet has transparency, it becomes easier to check the arrangement position of parts such as semiconductor elements and the thermally conductive sheet in the manufacturing process of electronic device products, so it is advantageous in that manufacturing accuracy and work efficiency are improved. effect can be exhibited.

The present invention was conceived under such circumstances, and an object of the present invention is to provide a thermally conductive sheet having good thermal conductivity and high transparency. be.

As a result of intensive studies to achieve the above object, the present inventors have found a thermally conductive sheet comprising a resin layer containing a specific resin and a thermally conductive filler, wherein the resin and the thermally conductive filler have a specific refractive index. It has been found that the thermally conductive sheet has good thermal conductivity and high transparency in the case of showing the coefficient. The present invention has been completed based on these findings.

That is, the present invention provides a thermally conductive sheet comprising a resin layer containing a resin and a thermally conductive filler,
The total light transmittance of the resin layer is 85% or more,
The refractive index np of the resin is 1.469 or less,
Provided is a thermally conductive sheet, wherein a value (np-nf) obtained by subtracting the refractive index nf of the thermally conductive filler from the refractive index np of the resin is -0.01 or more and 0.01 or less.

The thermally conductive filler preferably has a haze value of 15% or less in the resin layer.

The content of the thermally conductive filler is preferably 50 parts by weight or more with respect to 100 parts by weight of the resin.

The adhesion of the resin layer to glass is preferably 1 N/25 mm or more.

The thermally conductive sheet of the present invention has good thermal conductivity and high transparency.

It is a cross-sectional schematic diagram of the heat conductive sheet which concerns on one Embodiment. It is a cross-sectional schematic diagram of the heat conductive sheet which concerns on other one Embodiment. It is a cross-sectional schematic diagram of the heat conductive sheet which concerns on still another one embodiment. It is a cross-sectional schematic diagram of the heat conductive sheet which concerns on still another one embodiment.

The thermally conductive sheet of the present invention is characterized by having a resin layer. The resin layer may be an adhesive layer (a layer having adhesiveness) or a non-adhesive layer (a layer having no adhesiveness). When the resin layer is an adhesive layer, the thermally conductive sheet can be called a thermally conductive adhesive sheet.

The thermally conductive sheet may have a form composed only of the resin layer (for example, a form without a supporting substrate, that is, a form of a substrate-less resin sheet), or may further include a supporting substrate. form (that is, the form of a thermally conductive sheet with a substrate). The thermally conductive sheet may also include a release liner laminated on the resin layer. That is, it may be a thermally conductive adhesive sheet with a release liner.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the thermally conductive sheet of the present invention. The thermally conductive sheet X1 in FIG. 1 is configured as a substrateless thermally conductive sheet comprising a resin layer 10 that is a non-adhesive layer. The thermally conductive sheet has a first surface 10a, which is a non-adhesive surface formed by one surface of the resin layer 10, and a second surface 10b, which is a non-adhesive surface formed by the other surface of the resin layer 10. Prepare. The thermally conductive sheet is used, for example, by arranging the first surface 10a and the second surface 10b so as to be in close contact with the corresponding members. The parts where the first surface 10a and the second surface 10b are arranged may be present in different members or may be present in the same member.

FIG. 2 is a schematic cross-sectional view showing another embodiment of the thermally conductive sheet of the present invention. The thermally conductive sheet X2-1 in FIG. 2(A) is configured as a substrate-less thermally conductive adhesive sheet comprising a resin layer 20, which is an adhesive layer. The thermally conductive adhesive sheet has a first adhesive surface 20 a formed by one surface of the resin layer 20 and a second adhesive surface 20 b formed by the other surface of the resin layer 20 . The thermally conductive adhesive sheet is usually used by attaching the first adhesive surface 20a and the second adhesive surface 20b to different adherends. The locations where the first adhesive surface 20a and the second adhesive surface 20b are attached may be located on different members or may be located on the same member.

The thermally conductive sheet X2-2 in FIG. 2B has a resin layer 20 as an adhesive layer, and a release liner 21 and a release liner 22 laminated on the first adhesive surface 20a and the second adhesive surface 20b, respectively. It is configured as a substrate-less thermally conductive adhesive sheet consisting of. As the

release liners

21 and 22, those having a release surface subjected to a release treatment on the adhesive layer side surface of the sheet-like liner base material are preferably used. The release liner may be configured to have release surfaces on both sides, and when the release liner 22 is not laminated, by spirally winding such a release liner, for example, , the second adhesive surface 20b is protected by coming into contact with the back surface 21a of the release liner 21 (the back surface of the release liner 21 as seen from the resin layer 20). may

The above thermally conductive sheet may be a thermally conductive sheet with a substrate in which a resin layer is laminated on one or both sides of a supporting substrate. In the thermally conductive sheet, the resin layer may be an adhesive layer or a non-adhesive layer, but is preferably an adhesive layer from the viewpoint of adhesion to the supporting substrate. Hereinafter, the supporting substrate may be simply referred to as "substrate".

FIG. 3 is a cross-sectional schematic diagram showing another embodiment of the thermally conductive sheet of the present invention. The thermally conductive sheet X3 of FIG. 3 includes a supporting substrate 30 having a first surface 30a and a second surface 30b, a first adhesive layer 31 provided on the first surface 30a side, and a and a second adhesive layer 32 provided. The thermally conductive adhesive sheet is a thermally conductive adhesive sheet with a release liner in which the adhesive surface 31a of the first adhesive layer 31 and the adhesive surface 32b of the second adhesive layer 32 are protected by

release liners

33 and 34, respectively. There may be. When the release liner 33 is a release liner having release surfaces on both sides and does not have the release liner 34, the thermally conductive adhesive sheet is spirally wound so that the adhesive surface 32b is exposed to the release liner 33. (the back surface of the release liner 33 as viewed from the first adhesive layer 31) to protect the back surface 33a of the release liner 33 (roll form).

The thermally conductive sheet may be a thermally conductive adhesive sheet in which an adhesive layer is laminated on one side or both sides of a resin layer. In the thermally conductive sheet, the resin layer may be an adhesive layer or a non-adhesive layer.

FIG. 4 is a cross-sectional schematic diagram showing another embodiment of the thermally conductive sheet of the present invention. The thermally conductive sheet X4 of FIG. 4 includes a resin layer 40 having a first surface 40a and a second surface 40b, a first adhesive layer 41 provided on the first surface 40a side, and a resin layer 41 provided on the second surface 40b side. It is a thermally conductive adhesive sheet provided with a second adhesive layer 42 attached. The thermally conductive adhesive sheet is a thermally conductive adhesive sheet with a release liner in which the adhesive surface 41a of the first adhesive layer 41 and the adhesive surface 42b of the second adhesive layer 42 are protected by release liners 43 and 44, respectively. There may be. When the release liner 43 is a release liner having release surfaces on both sides and does not have the release liner 44, the heat conductive adhesive sheet is spirally wound so that the adhesive surface 42b is exposed to the release liner 43. 43a (the back surface of the release liner 43 as seen from the first adhesive layer 41) to protect the heat conductive adhesive sheet with a release liner in a roll form.

The resin layer in the thermally conductive sheet contains a resin and a thermally conductive filler. Although the resin is not particularly limited, for example, one type of various polymers such as acrylic polymer, rubber polymer, polyester polymer, urethane polymer, polyether polymer, silicone polymer, polyamide polymer, fluorine polymer, etc. Or it may contain two or more kinds. The resin may also contain a polyfunctional monomer as described below. Among these, the above resin preferably contains a fluorine-based polymer as a base polymer in terms of imparting high transparency to the thermally conductive sheet. The base polymer is a polymer that accounts for 50% by weight or more (preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more, and particularly preferably 99% by weight or more) of the resin. means.

The resin layer may be formed from a resin composition containing the resin and a thermally conductive filler. The form of the resin composition is not particularly limited, and examples thereof include water dispersion type, solvent type, hot melt type, and active energy ray-curable (for example, photocurable) resin compositions. As used herein, the active energy ray refers to an energy ray having energy capable of causing a chemical reaction such as a polymerization reaction, a cross-linking reaction, or decomposition of an initiator. The active energy rays include light such as ultraviolet rays (UV), visible rays, and infrared rays, and radiation such as α rays, β rays, γ rays, electron beams, neutron rays, and X rays.

Examples of the fluorine-based polymer include tetrafluoroethylene-based polymer, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, and acrylic polymer containing fluorine-containing acrylic monomer (hereinafter referred to as "fluorine-containing acrylic polymer"). ) and the like. Among these, fluorine-containing acrylic polymers are preferable from the viewpoint of improving the transparency of the thermally conductive sheet. That is, the resin preferably contains a fluorine-containing acrylic polymer as the fluorine-based polymer. The fluorine-containing acrylic polymer can also be rephrased as a polymer of acrylic monomers containing fluorine-containing acrylic monomers as monomer units. Also, the fluorine-based polymer can be used alone or in combination of two or more.

　Fluorine-based polymers have a lower refractive index than general resins. Therefore, the refractive index np of the resin can be adjusted to a relatively low range by blending the fluorine-based polymer with the resin used for the thermally conductive sheet of the present invention. Thermally conductive fillers also tend to have a lower refractive index nf than general resins. From this, it is possible to realize a resin layer containing a resin having a small refractive index difference |np−nf| by appropriately blending the fluorine-based polymer in the resin. As a result, the transparency of the thermally conductive sheet tends to be high.

The reason why fluorine-based polymers have a lower refractive index than general resins will be explained below using the case of fluorine-containing acrylic polymers. However, this description does not limit the fluorine-based polymer to the fluorine-containing acrylic polymer.

The fluorine-containing acrylic polymer contains a fluorine-containing acrylic monomer as a monomer unit, and the fluorine-containing acrylic monomer may be used in combination with other monomers (for example, (meth)acrylates having an alkyl group having 1 to 20 carbon atoms, copolymerizable monomers, etc. described later). ) tend to contribute more strongly to the reduction of the refractive index of the polymer. Although the reason for this is not clear, it is believed that the fluorine atoms contained in the fluorine-containing acrylic monomer greatly affect the decrease in the refractive index of the polymer.

As described above, in order to reduce the refractive index difference |np-nf| A fluorine-containing acrylic polymer exhibiting a low refractive index is useful where it is necessary to adjust the refractive index np of the resin to a relatively low range. However, if the value of the refractive index np becomes too lower than the value of the refractive index nf due to the influence of the fluorine-containing acrylic polymer, the refractive index difference |np-nf| In order to avoid such a situation and make the refractive index difference |np-nf| and (2) a fluorine-containing acrylic monomer or a monomer other than a fluorine-containing acrylic monomer (for example, a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms described later. and copolymerizable monomers, etc.) to appropriately adjust the refractive index of the fluorine-containing acrylic polymer and use it by blending it with the above resin, (3) above (1) and (2), it is possible to adjust the refractive index difference |np-nf| to an appropriate range.

As monomers other than the above fluorine-containing acrylic monomers, (meth)acrylates and copolymerizable monomers having alkyl groups of 1 to 20 carbon atoms were exemplified, but the refractive index of the above resin is adjusted through the fluorine-containing acrylic polymer. From the viewpoint of doing, preferably (meth) acrylate having an alkyl group having 6 or less carbon atoms, (meth) acrylate having an alkyl group having 6 or more carbon atoms, polar groups described later (e.g., carboxy group, hydroxyl group, amide group etc.), (meth)acrylates having an alicyclic hydrocarbon group, (meth)acrylates having an aromatic hydrocarbon group, hydroxyl group-containing monomers, and monomers having a nitrogen atom-containing ring.

As used herein, the term "acrylic polymer" refers to a polymer containing monomer units derived from acrylic monomers, for example, a polymer containing more than 50% by weight of monomer units derived from acrylic monomers. Moreover, an acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule. Here, "(meth)acryloyl group" is meant to comprehensively refer to acryloyl groups and methacryloyl groups. Similarly, in this specification, "(meth)acrylate" is meant to comprehensively refer to acrylate and methacrylate, respectively.

Although the fluorine-containing acrylic monomer is not particularly limited, examples include 2,2,2-trifluoroethyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 2,2,3,3,3 - pentafluoropropyl (meth) acrylate, 2-(perfluorobutyl) ethyl (meth) acrylate, 3-perfluorobutyl-2-hydroxypropyl (meth) acrylate, 3-perfluorohexyl-2-hydroxypropyl (meth) acrylates, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl (meth)acrylate, 1H,1H,3H-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,7H-dodecafluoroheptyl (meth)acrylate, 1H-1-(trifluoromethyl)trifluoroethyl (meth)acrylate, 1H,1H,3H-hexafluorobutyl (meth)acrylate, 1,2,2 , 2-tetrafluoro-1-(trifluoromethyl)ethyl (meth)acrylate and the like. Among these, 2,2,2-trifluoroethyl (meth)acrylate is preferable because it can impart high transparency to the heat conductive sheet.

Although the ratio of the fluorine-containing acrylic monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is not particularly limited, it is, for example, preferably 1% by weight or more, more preferably 2% by weight or more, and still more preferably. is at least 3% by weight, particularly preferably at least 5% by weight, most preferably at least 8% by weight. Further, the proportion of the fluorine-containing acrylic monomer is, for example, preferably 60% by weight or less, more preferably 40% by weight or less, still more preferably 30% by weight or less, particularly preferably 25% by weight or less, most preferably 20% by weight or less. % by weight or less. When the proportion of the fluorine-containing acrylic monomer in the fluorine-containing acrylic polymer is within the above range, there is a tendency to obtain a thermally conductive sheet having both high transparency and thermal conductivity. When the monomer component contains two or more fluorine-containing acrylic monomers, the content of the fluorine-containing acrylic monomer in the monomer component refers to the total amount of the two or more fluorine-containing acrylic monomers.

The fluorine-containing acrylic polymer preferably contains a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms (C _1-20 alkyl (meth)acrylate) as an acrylic monomer other than the fluorine-containing acrylic monomer.

C _1-20 alkyl (meth)acrylates are not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate , 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate , tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like. Among them, (meth)acrylates having an alkyl group having 2 to 10 carbon atoms (C _2-10 alkyl (meth)acrylates) are preferred, and (meth)acrylates having an alkyl group having 4 to 9 carbon atoms (C _4-9 alkyl (Meth)acrylates) are more preferred, and (meth)acrylates having an alkyl group of 6 to 8 carbon atoms (C _6-8 alkyl (meth)acrylates) are even more preferred.

Although the ratio of C _1-20 alkyl (meth)acrylate to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is not particularly limited, for example, it is preferably 10% by weight or more, more preferably 20% by weight. % or more, more preferably 40 wt % or more, particularly preferably 60 wt % or more, and most preferably 80 wt % or more. The proportion of C _1-20 alkyl (meth)acrylate is, for example, preferably 99% by weight or less, more preferably 98% by weight or less, still more preferably 95% by weight or less, and particularly preferably 90% by weight or less. is. When the proportion of C _1-20 alkyl (meth)acrylate in the fluorine-containing acrylic polymer is within the above range, there is a tendency to obtain a thermally conductive sheet having both high transparency and thermal conductivity. In the case where the monomer component contains two or more C _1-20 alkyl (meth)acrylates, the content of the C _1-20 alkyl (meth)acrylate in the monomer component is the two or more C _{1- 20} Refers to the total amount of alkyl (meth)acrylates.

The fluorine-containing acrylic polymer is a monomer other than the fluorine-containing acrylic monomer and the C _1-20 alkyl (meth)acrylate, and is copolymerizable with the fluorine-containing acrylic monomer or the C _1-20 alkyl (meth)acrylate. (hereinafter referred to as a copolymerizable monomer) may be included as a monomer unit. As the copolymerizable monomer, a monomer having a polar group (eg, carboxy group, hydroxyl group, amide group, etc.) can be preferably used. A monomer having a polar group can have the effect of introducing cross-linking points into the fluorine-containing acrylic polymer and increasing its cohesive strength. As such a monomer having a polar group, a carboxy group-containing monomer, a hydroxyl group-containing monomer, and a monomer having a nitrogen atom-containing ring are particularly preferable. The copolymerizable monomers may be used singly or in combination of two or more.

Although the copolymerizable monomer is not particularly limited, examples thereof include the following.
Carboxy group-containing monomers: for example acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and the like. Among these, acrylic acid is particularly preferred.
Acid anhydride group-containing monomers: for example maleic anhydride, itaconic anhydride.
Hydroxyl group-containing monomers: for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate , 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth) hydroxy(meth)acrylates such as acrylates; Among these, 2-hydroxybutyl (meth)acrylate is particularly preferred.
Monomers containing sulfonic or phosphoric acid groups: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfo propyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethyl acryloyl phosphate and the like.
Epoxy group-containing monomers: For example, epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate and 2-ethylglycidyl ether (meth)acrylate, allyl glycidyl ether, glycidyl ether (meth)acrylate, and the like.
Cyano group-containing monomers: for example acrylonitrile, methacrylonitrile and the like.
Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate and the like.
Amido group-containing monomers: for example, (meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth) N,N-dialkyl(meth)acrylamides such as acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-di(t-butyl)(meth)acrylamide; N-ethyl(meth) N-alkyl (meth)acrylamides such as acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, Nn-butyl (meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide genus; monomers having a hydroxyl group and an amide group, such as N-(2-hydroxyethyl)(meth)acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth) acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, N-(4-hydroxybutyl) ( N-hydroxyalkyl (meth)acrylamides such as meth)acrylamide; monomers having an alkoxy group and an amide group, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-butoxymethyl ( N-alkoxyalkyl(meth)acrylamides such as meth)acrylamide; N,N-dimethylaminopropyl(meth)acrylamide, N-(meth)acryloylmorpholine and the like.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N- Vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3 -morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinyl thiazole, N-vinylisothiazole, N-vinylpyridazine and the like (for example, lactams such as N-vinyl-2-caprolactam); Among these, N-vinyl-2-pyrrolidone is particularly preferred.
Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyhexamethylenesuccinimide and the like.
Maleimides: For example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide and the like.
Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-lauryl itaconimide and the like.
Aminoalkyl (meth)acrylates: for example aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
Alkoxy group-containing monomers: for example, 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxypropyl Alkoxyalkyl (meth)acrylates such as (meth)acrylate; Alkoxyalkylene glycol (meth)acrylates such as methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (meth)acrylate.
Vinyl esters: For example, vinyl acetate, vinyl propionate and the like.
Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene and the like.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene and the like.
(Meth)acrylates having an alicyclic hydrocarbon group: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate and the like.
(Meth)acrylates having an aromatic hydrocarbon group: for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate and the like.
In addition, heterocyclic ring-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylates meth)acrylates, (meth)acrylates obtained from terpene compound derivative alcohols, and the like.

The ratio of the copolymerizable monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is not particularly limited, but for example, it is preferably 0.01 to 20% by weight, more preferably 0.1%. ~10% by weight, more preferably 0.5 to 5% by weight. When the monomer component contains two or more copolymerizable monomers, the content of the copolymerizable monomer in the monomer component refers to the total amount of the two or more copolymerizable monomers.

The ratio of the copolymerizable monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is not particularly limited, but for example, it is preferably 0.01% by weight or more, more preferably 0.1% by weight. Above, more preferably 0.5% by weight or more. Also, the proportion of the copolymerizable monomer is, for example, preferably 40% by weight or less, more preferably 20% by weight or less, and even more preferably 15% by weight or less. When the monomer component contains two or more copolymerizable monomers, the content of the copolymerizable monomer in the monomer component refers to the total amount of the two or more copolymerizable monomers.

When the fluorine-containing acrylic polymer contains a carboxy group-containing monomer as a copolymerizable monomer, the ratio of the carboxy group-containing monomer to the total monomer component (100% by weight) of the fluorine-containing acrylic polymer is not particularly limited. It is preferably 0.1% by weight or more, more preferably 1% by weight or more, and still more preferably 1.5% by weight or more. Also, the proportion of the carboxy group-containing monomer is, for example, preferably 40% by weight or less, more preferably 20% by weight or less, still more preferably 15% by weight or less, and particularly preferably 10% by weight or less. When the monomer component contains two or more carboxy group-containing monomers, the content of the carboxy group-containing monomer in the monomer component refers to the total amount of the two or more carboxy group-containing monomers.

When the fluorine-containing acrylic polymer contains a hydroxyl group-containing monomer as a copolymerizable monomer, the ratio of the hydroxyl group-containing monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is not particularly limited. 01% by weight or more, more preferably 0.1% by weight or more, and still more preferably 0.5% by weight or more. Also, the proportion of the hydroxyl group-containing monomer is, for example, preferably 40% by weight or less, more preferably 10% by weight or less, even more preferably 5% by weight or less, and particularly preferably 3% by weight or less. When the monomer component contains two or more types of hydroxyl group-containing monomers, the content of hydroxyl group-containing monomers in the monomer component refers to the total amount of the two or more types of hydroxyl group-containing monomers.

When the fluorine-containing acrylic polymer contains a monomer having a nitrogen atom-containing ring as a copolymerizable monomer, the ratio of the monomer having a nitrogen atom-containing ring to the total monomer component (100% by weight) of the fluorine-containing acrylic polymer is particularly Although not limited, for example, it is preferably 0.1% by weight or more, more preferably 1% by weight or more, still more preferably 3% by weight or more, and particularly preferably 5% by weight or more. Also, the proportion of the monomer having a nitrogen atom-containing ring is, for example, preferably 40% by weight or less, more preferably 30% by weight or less, and even more preferably 20% by weight or less. In the case where the monomer component contains a monomer having two or more types of nitrogen atom-containing rings, the content of the monomer having a nitrogen atom-containing ring in the monomer component is the monomer having two or more types of nitrogen atom-containing rings. refers to the total amount of

The method for synthesizing the fluorine-containing acrylic polymer is not particularly limited, and various known methods for synthesizing acrylic polymers such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, and photopolymerization method can be used. Any suitable polymerization method can be employed.

Polymerization initiators such as thermal polymerization initiators and photopolymerization initiators can be used as appropriate for the synthesis of fluorine-containing acrylic polymers. The above polymerization initiators may be used alone or in combination of two or more.

The thermal polymerization initiator is not particularly limited. , benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane-based initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox-based polymerization initiators, and the like. Examples of the azo polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis(2-methylpropionate)dimethyl, 4,4'-azobis-4-cyanovaleric acid and the like. The amount of the thermal polymerization initiator to be used is not particularly limited, but is preferably 0.005 to 2 parts by weight, more preferably 0.01 to 1 part by weight, based on 100 parts by weight of the monomer component.

The photopolymerization initiator is not particularly limited. Active oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and the like are included. Other examples include acylphosphine oxide photopolymerization initiators and titanocene photopolymerization initiators. Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, anisole methyl ether and the like. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, 4-(t-butyl ) and dichloroacetophenone. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. be done. Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone (1-hydroxy-cyclohexyl-phenyl-ketone). etc. Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. . Examples of the titanocene photopolymerization initiator include bis(η ⁵ -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl ) titanium and the like. The amount of the photopolymerization initiator to be used is not particularly limited, but for example, it is preferably 0.01 to 3 parts by weight, more preferably 0.02 to 1.5 parts by weight with respect to 100 parts by weight of the monomer component. .

The fluorine-containing acrylic polymer is in the form of a partially polymerized product (fluorine-containing acrylic polymer syrup) obtained by irradiating a mixture of the above-described monomer components with a polymerization initiator and irradiating ultraviolet rays to partially polymerize the monomer components. and can be included in the resin composition for forming the resin layer. A resin composition containing such an acrylic polymer syrup can be applied to a predetermined object to be coated and irradiated with ultraviolet rays to complete the polymerization. That is, the fluorine-containing acrylic polymer syrup can be said to be a precursor of the fluorine-containing acrylic polymer. The resin layer can be formed, for example, using a resin composition containing a fluorine-containing acrylic polymer as a base polymer in the form of the above-mentioned fluorine-containing acrylic polymer syrup and, if necessary, an appropriate amount of a polyfunctional monomer described later. .

The resin composition may contain a cross-linking agent for the purpose of adjusting the cohesive force. As the cross-linking agent, known or commonly used cross-linking agents in the field of resins including pressure-sensitive adhesives can be used. Cross-linking agents, silane-based cross-linking agents, alkyl-etherified melamine-based cross-linking agents, metal chelate-based cross-linking agents, and the like can be mentioned. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

The resin composition may contain a cross-linking catalyst in order to promote the cross-linking reaction more effectively. Cross-linking catalysts include, for example, tin-based catalysts (particularly dioctyltin dilaurate).

The resin composition may contain a polyfunctional monomer as a resin for the purpose of adjusting the cohesive force. That is, the resin layer may contain a polyfunctional monomer. Multifunctional monomers can be used in place of or in combination with the cross-linking agents described above. A polyfunctional monomer is preferably used, for example, in a resin layer formed from a photocurable resin composition.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, Pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecane Diol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl diol (meth)acrylate, hexyldiol di(meth)acrylate and the like. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The content of the polyfunctional monomer with respect to 100 parts by weight of the resin in the resin layer is not particularly limited, but is preferably 0.0001 to 5 parts by weight, more preferably 0.001 to 2 parts by weight, and still more preferably is 0.005 to 1 part by weight.

The resin composition may contain a tackifying resin. The tackifier resin is not particularly limited, but for example, rosin-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, hydrocarbon-based tackifier resins, ketone-based tackifier resins, polyamide-based tackifier resins, Epoxy-based tackifying resins, elastomer-based tackifying resins, and the like are included. Tackifying resin can be used individually by 1 type or in combination of 2 or more types.

The refractive index np of the resin contained in the resin layer is not particularly limited as long as it is 1.469 or less, but the lower limit is preferably 1.3, more preferably 1.35, further preferably 1.4. Especially preferred is 1.43, most preferred is 1.45. When the refractive index np is in the above range, that is, the resin contained in the resin layer has a relatively low refractive index, the refractive index difference with air tends to be small, resulting in a tendency to reduce interfacial reflection. , the haze value of the resin layer tends to be low. In this specification, the refractive index np can be measured using a commercially available Abbe refractometer (for example, model "DR-M2", manufactured by ATAGO). More specifically, the refractive index np can be measured by the method described in Examples below. The same applies to the refractive index nf of the thermally conductive filler, which will be described later.

The resin layer contains a thermally conductive filler. Moreover, the resin layer may contain other fillers than the thermally conductive filler as long as the effects of the present invention are not impaired. Hereinafter, the thermally conductive filler and fillers other than the thermally conductive filler may be collectively referred to as "filler". A filler can be used individually by 1 type or in combination of 2 or more types.

The shape of the filler is not particularly limited, and for example, a particulate or fibrous filler can be used, but a particulate filler is preferably used from the viewpoint of less impairing the smoothness of the surface of the resin layer. The shape of the particles is not particularly limited, and may be bulk shape, needle shape, plate shape, or layer shape. Bulk shapes include, for example, spherical shapes, rectangular parallelepiped shapes, crushed shapes, or modified shapes thereof. The structure of the particles is not particularly limited, and examples thereof include dense structures, porous structures, hollow structures, and the like. Among these, a filler having a dense structure of particles, for example, a filler containing fused silica (that is, a fused silica-containing filler) is preferable because of its high thermal conductivity and low refractive index.

The constituent material of the filler is not particularly limited, but examples include inorganic materials and organic materials. That is, the resin layer may contain a thermally conductive filler made of an inorganic material and/or a thermally conductive filler made of an organic material as the thermally conductive filler.

The inorganic material is not particularly limited, but examples include metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, and stainless steel; aluminum oxide, silicon oxide (e.g., silicon dioxide), titanium oxide, and zirconium oxide. , zinc oxide, tin oxide, antimonic acid _- doped tin oxide _, copper oxide, _nickel oxide; aluminum hydroxide [ _Al2O3.3H2O or Al(OH) ₃ ], boehmite [ _Al2O3 H ₂ O or AlOOH], magnesium hydroxide [MgO.H ₂ O or Mg(OH) ₂ ], calcium hydroxide [CaO.H ₂ O or Ca(OH) ₂ ], zinc hydroxide [Zn(OH) ₂ ], silicic acid [ _H4SiO4 , _H2SiO3 _, or _H2Si2O5 _] , iron hydroxide [ _Fe2O3.H2O or _2FeO (OH) _] , copper hydroxide _[ _Cu (OH ) ₂ ], barium hydroxide [BaO.H ₂ O or BaO.9H ₂ O], zirconium oxide hydrate [ZrO.nH ₂ O], tin oxide hydrate [SnO.H ₂ O], basic _magnesium carbonate [ _3MgCO3.Mg (OH ₎ _2.3H2O ], _hydrotalcite _[ _{6MgO.Al2O3.H2O} ] _, dawsonite _[ _{Na2CO3.Al2O3.nH2O} _] , Hydrated _metal compounds such as borax [ _{Na2O.B2O5.5H2O} _] and zinc borate _[ 2ZnO.3B2O5.3.5H2O] _; silicon carbide _, boron carbide, nitrogen _carbide , carbonization Carbide such as calcium; Nitride such as aluminum nitride, silicon nitride, boron nitride, gallium nitride; Carbonate such as calcium carbonate; Titanate such as barium titanate, potassium titanate; Carbon black, carbon tube (for example, carbon nanotubes), carbon fibers, diamond, and other carbon-based materials; crystalline silica, fused silica (amorphous silica), and other silica;

The organic material is not particularly limited, but examples include polystyrene, acrylic resin (e.g., polymethyl methacrylate), phenol resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyethylene, polypropylene, polyamide (e.g., nylon, etc.). ), polyimide, polyvinylidene chloride and other polymers.

When using a photocurable (for example, ultraviolet curable) resin composition, it is preferable to use a filler made of an inorganic material from the viewpoint of the photocurability (polymerization reactivity) of the resin composition.

The thermally conductive filler can impart good thermal conductivity to the thermally conductive sheet, and can adjust the refractive index nf of the filler to a suitable range to impart high transparency. From the viewpoint of the thermal conductivity, it is preferably a thermally conductive filler made of an inorganic material, more preferably a silicon atom-containing filler, still more preferably a silica-containing filler, and particularly preferably a fused silica-containing filler. That is, it preferably contains an inorganic material as a constituent material, more preferably contains silica, and particularly preferably contains fused silica.

As the silica, silica powder is preferable, and fused silica powder is more preferable. Further, the fused silica powder includes spherical fused silica powder and crushed fused silica powder, and from the viewpoint of fluidity, spherical fused silica powder is preferable.
The purity of silica is preferably 95% or higher, more preferably 99% or higher, and particularly preferably 99.5% or higher. If the purity of silica is low, the optical transparency may decrease due to scattering by impurities.

The content of the thermally conductive filler in the resin layer is not particularly limited. parts by weight or more, particularly preferably 50 parts by weight or more. In addition, the content of the thermally conductive filler is, for example, preferably 300 parts by weight or less, more preferably 250 parts by weight or less, still more preferably 200 parts by weight or less, and particularly preferably 100 parts by weight of the resin. 160 parts by weight or less. When the content of the thermally conductive filler is within the above range, the thermal conductivity of the resin layer tends to be improved. In addition, there is a tendency that the deterioration of the light transmittance of the resin layer is suppressed. Furthermore, deterioration of the surface smoothness of the resin layer is suppressed, and there is a tendency to easily obtain a good adhesion state with the adherend.

The refractive index nf of the thermally conductive filler is not particularly limited as long as it satisfies the relationship described later with the refractive index np of the resin. .6, more preferably 1.4 to 1.55, particularly preferably 1.41 to 1.5, and most preferably 1.43 to 1.46. Since the refractive index nf is within the above range, that is, the resin contained in the resin layer has a relatively low refractive index, the difference in refractive index from air tends to be small, resulting in a tendency to reduce interfacial reflection. , the haze value of the resin layer tends to be low.

In the above thermally conductive sheet, the difference between the refractive index np of the resin contained in the resin layer and the refractive index nf of the thermally conductive filler is 0.01 or less. By providing a resin layer containing a combination of a resin having a small refractive index difference and a thermally conductive filler, good light transmittance is exhibited and the haze value tends to be small.

The refractive index np of the resin and the refractive index nf of the thermally conductive filler do not matter as long as the refractive index difference satisfies the above relationship. That is, the value (np−nf) obtained by subtracting the refractive index nf of the thermally conductive filler from the refractive index np of the resin is −0.01 or more and 0.01 or less. The above (np-nf) is preferably -0.005 or more and 0.008 or less, more preferably -0.002 or more and 0.006 or less, and still more preferably 0 or more and 0.004 or less. When the above (np-nf) is within the above range, the light transmittance of the thermally conductive sheet tends to improve and the haze value tends to decrease. The refractive index difference |np−nf| is a concept that means the absolute value of (np−nf).

The resin composition for forming the resin layer may contain a dispersant as necessary in order to disperse the filler well in the resin composition. A resin composition in which the filler is well dispersed can form a resin layer with improved uniformity of thermal conductivity. As a dispersant, a known or commonly used surfactant can be used. The above surfactants include nonionic, anionic, cationic and amphoteric ones. A dispersing agent can be used individually by 1 type or in combination of 2 or more types.

Although the dispersant is not particularly limited, examples thereof include monoesters of phosphoric acid, diesters of phosphoric acid, triesters of phosphoric acid, and mixtures thereof. Specific examples include phosphate monoesters, phosphate diesters, and phosphate triesters of polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers or polyoxyethylene aryl ethers, and derivatives thereof.

In addition to the dispersant, the resin layer contains a leveling agent, a plasticizer, a softening agent, a coloring agent (dye, pigment, etc.), an antistatic agent, an antiaging agent, and an ultraviolet absorbing agent, as long as the effects of the present invention are not impaired. Known or commonly used additives that can be used in resins such as pressure-sensitive adhesives, such as agents, antioxidants, light stabilizers, preservatives, etc., may optionally be contained.

The resin layer may be formed by curing (for example, drying, cross-linking, polymerization, etc.) of the resin composition. That is, the resin layer is formed, for example, by applying a resin composition to the surface of an appropriate base material (eg, a release liner or a supporting base material) and then performing a curing treatment. When two or more curing treatments are carried out, they can be carried out simultaneously or in multiple stages. In a resin composition using a partially polymerized monomer component (for example, an acrylic polymer syrup), for example, a final copolymerization reaction is performed as the curing treatment. That is, the partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, in the case of a photocurable resin composition, light irradiation is performed. Curing treatments such as cross-linking and drying may be performed as necessary. For example, when the photocurable resin composition needs to be dried, photocuring may be performed after drying. In a resin composition using a complete polymer, for example, as the curing treatment, drying (drying by heating), cross-linking, or the like is performed as necessary. In the formation of the resin layer using the photocurable resin composition, for example, the resin composition may be sandwiched between two sheets and cured by irradiating light in a state in which the air is shut off.

The resin composition may be a solventless resin composition. A solvent-free resin composition is a resin composition having a solvent content of 0.1% by weight or less. The solvent refers to a component (volatile solvent) that is not contained in the finally formed resin layer. Therefore, unreacted monomers and the like that may be contained in acrylic polymer syrup, for example, are excluded from the above concept of solvent.

Application of the resin composition can be carried out using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater and a spray coater.

Although the thickness of the resin layer of the thermally conductive sheet is not particularly limited, it is preferably 10 to 600 μm, more preferably 30 to 300 μm, still more preferably 30 to 300 μm, from the viewpoint of improving thermal conductivity and light transmittance. is 50-200 μm, particularly preferably 80-150 μm.

In the above thermally conductive sheet, the substrate (supporting substrate) functions as a support. The material constituting the substrate is not particularly limited as long as it does not impair the effects of the present invention, but from the viewpoint of obtaining a thermally conductive sheet with good light transmittance, a transparent resin film can be preferably used. The substrate layer may be a single layer, or may be a laminate of the same or different substrates.

Examples of the substrate include polyolefin films mainly composed of polyolefin such as polypropylene and ethylene-propylene copolymer, polyester films mainly composed of polyester such as polyethylene terephthalate (PET) and polybutylene terephthalate, and polyvinyl chloride. A polyvinyl chloride film containing as a main component, and the like.

Although the thickness of the base material is not particularly limited, it is preferably 5 to 100 μm, more preferably 5 to 75 μm.

The release liner is configured to cover and protect the surface of the adhesive layer (adhesive surface), and is removed from the adhesive layer when the thermally conductive sheet is attached to an adherend for use. When the thermally conductive sheet has release liners on both sides, the thermally conductive sheet is, for example, first peeled off one of the release liners, and the exposed adhesive layer surface is adhered to one adherend, and then The adhesive layer surface (adhesive surface) exposed by peeling off the other release liner is attached to the other adherend for use.

The release liner is not particularly limited, and can be appropriately selected and used from known or commonly used release liners. Examples of the release liner include those having a release treatment layer on at least one surface of a substrate (substrate for release liner). The base material may be a single layer or a laminate of the same or different base materials.

Examples of the base material of the release liner (liner base material) include plastic base materials, paper, foams, various thin sheets such as metal foil, etc., preferably plastic base materials.

Examples of the resin constituting the plastic substrate include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymerized polypropylene, block copolymerized polypropylene, and homopolypropylene. , polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylate copolymer, ethylene-(meth)acrylate ester (random, alternating) copolymer, ethylene-butene copolymer Polyolefin resins such as polymers and ethylene-hexene copolymers; polyurethanes; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonates; polyimides; , wholly aromatic polyamide; polyphenyl sulfide; fluorine resin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; The above resins may be used singly or in combination of two or more.

Although the thickness of the release liner is not particularly limited, it is preferably 5-100 μm, more preferably 5-75 μm, even more preferably 8-60 μm, and particularly preferably 12-40 μm. When the thickness is 5 μm or more, workability in peeling off the release liner is excellent. When the thickness is 100 µm or less, it is possible to suppress an increase in rigidity, to provide excellent conformability to the surface of the adhesive layer, and to prevent the release liner from floating in the thermally conductive sheet. In addition, the diameter of the roll when used as a roll does not become too large. When the thermally conductive sheet includes two or more release liners, the thickness of the substrate in the release liners may be the same or different.

The thermal conductivity of the resin layer is not particularly limited. K or more, more preferably 0.26 W/m·K or more, particularly preferably 0.28 W/m·K or more, most preferably 0.30 W/m·K or more. The upper limit of the thermal conductivity of the resin layer is not particularly limited. K or less, 0.8 W/m·K or less, 0.5 W/m·K or less, or less than 0.5 W/m·K. In this specification, the thermal conductivity of the resin layer refers to a value measured by a steady heat flow method. More specifically, it can be measured by the method described in Examples below.

Although the total light transmittance of the resin layer is not particularly limited as long as it is 85% or more, for example, it is preferably 90% or more, more preferably 91.5% or more, and still more preferably 91.8% or more. . Although the upper limit of the total light transmittance of the resin layer is not particularly limited, it is, for example, 99%. In this specification, the total light transmittance of the resin layer is measured using a commercially available transmittance meter (for example, a high-speed integrating sphere type spectral transmittance meter, model "DOT-3", manufactured by Murakami Color Research Laboratory). can be used for measurement at a temperature of 23° C. and a measurement wavelength of 400 nm. More specifically, it can be measured by the method described in Examples below.

The haze value of the resin layer is not particularly limited, but from the viewpoint of visibility of the adherend, for example, it is preferably 15% or less, more preferably 10% or less, still more preferably 9% or less, and still more preferably 9% or less. 6% or less, particularly preferably 3% or less. Although the lower limit of the haze value is not particularly limited, it is theoretically 0%, and may be 0.1%, for example. In this specification, the haze value can be represented by, for example, the following formula.
Th[%]=Td/Tt×100
In the above formula, Th is the haze value [%], Td is the scattered light transmittance, and Tt is the total light transmittance.

Also, the haze value can be measured according to JIS K 7361-1, for example, using a haze meter. As the haze meter, the device name "HSP-150Vis" manufactured by Murakami Color Research Laboratory Co., Ltd. or its equivalent can be used. More specifically, it can be measured by the method described in Examples below.

Although the adhesive strength of the resin layer to glass (adhesive strength to glass) is not particularly limited, for example, it is preferably 1.0 N/25 mm or more, more preferably 3.0 N/25 mm or more. Since the adhesive strength to glass is within the above range, the thermally conductive sheet can be preferably used for purposes such as joining and fixing members, for example.

The adhesion to glass is measured by pressing the adhesive surface of the object to be measured against a glass plate by reciprocating a 2 kg rubber roller once, and using a tensile tester in an environment of 23°C and 50% RH, according to JIS Z 0237. According to the above, it is obtained by measuring the peel strength when the thermally conductive sheet is peeled off from the glass plate under the conditions of a peeling angle of 180 degrees and a tensile speed of 300 mm/min.

Because the above thermally conductive sheet has excellent transparency, it becomes easier to confirm the arrangement position of parts such as semiconductor elements and the thermally conductive sheet in the manufacturing process of electronic device products, improving manufacturing accuracy and work efficiency. Therefore, the thermally conductive sheet is suitably used as a means of thermal design in electronic device products such as precision instruments and small precision instruments that require high precision. In addition, when the thermally conductive sheet is configured as a thermally conductive adhesive sheet, the thermally conductive adhesive sheet has high transparency and adhesiveness, so that it can be used for fixing, joining and supporting parts in precision equipment and the like. Also suitable for

Although the present invention will be described in more detail with reference to examples below, the present invention is not limited by these examples.

<Preparation Example 1>
2-ethylhexyl acrylate (86 parts by weight), 2,2,2-trifluoroethyl acrylate (13 parts by weight), 4-hydroxybutyl acrylate (1 part by weight), 2,2-dimethoxy-1,2-diphenyl-1 -one (trade name “Irgacure 651”, manufactured by IGM Resins B.V.) (0.05 parts by weight), and 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, IGM Resins B.V.) Co., Ltd.) (0.05 parts by weight) was put into a four-necked flask and partially photopolymerized by exposing it to ultraviolet rays in a nitrogen atmosphere to obtain a partial polymer (monomer syrup). After adding 1,6-hexanediol diacrylate (0.25 parts by weight) to this partially polymerized product (100 parts by weight), the mixture was uniformly mixed to prepare Resin 1.

<Preparation Example 2>
2-ethylhexyl acrylate (99 parts by weight), 4-hydroxybutyl acrylate (1 part by weight), 2,2-dimethoxy-1,2-diphenyl-1-one (trade name “Irgacure 651”, IGM Resins B.V. ) (0.05 parts by weight), and 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by IGM Resins B.V.) (0.05 parts by weight) in a four-necked flask. and partially photopolymerized by exposure to ultraviolet rays in a nitrogen atmosphere to obtain a partially polymerized product (monomer syrup). After adding 1,6-hexanediol diacrylate (0.25 parts by weight) to this partially polymerized product (100 parts by weight), the mixture was uniformly mixed to prepare Resin 2.

<Preparation Example 3>
2-ethylhexyl acrylate (77 parts by weight), 2,2,2-trifluoroethyl acrylate (22 parts by weight), 4-hydroxybutyl acrylate (1 part by weight), 2,2-dimethoxy-1,2-diphenyl-1 -one (trade name “Irgacure 651”, manufactured by IGM Resins B.V.) (0.05 parts by weight), and 1-hydroxy-cyclohexylphenyl-ketone (trade name “Irgacure 184”, IGM Resins B.V.) Co., Ltd.) (0.05 parts by weight) was put into a four-necked flask and partially photopolymerized by exposing it to ultraviolet rays in a nitrogen atmosphere to obtain a partial polymer (monomer syrup). After adding 1,6-hexanediol diacrylate (0.25 parts by weight) to this partially polymerized product (100 parts by weight), the mixture was uniformly mixed to prepare Resin 3.

<Preparation Example 4>
2-ethylhexyl acrylate (82 parts by weight), 2,2,2-trifluoroethyl acrylate (12 parts by weight), 4-hydroxybutyl acrylate (1 part by weight), butyl acrylate (5 parts by weight), 2,2-dimethoxy -1,2-diphenyl-1-one (trade name “Irgacure 651”, manufactured by IGM Resins B.V.) (0.05 parts by weight), and 1-hydroxy-cyclohexylphenyl-ketone (trade name “Irgacure A partial polymer ( monomer syrup) was obtained. After adding 1,6-hexanediol diacrylate (0.25 parts by weight) to this partially polymerized product (100 parts by weight), the mixture was uniformly mixed to prepare Resin 4.

<Preparation Example 5>
2-ethylhexyl acrylate (82 parts by weight), 2,2,2-trifluoroethyl acrylate (12 parts by weight), 4-hydroxybutyl acrylate (1 part by weight), acrylic acid (5 parts by weight), 2,2-dimethoxy -1,2-diphenyl-1-one (trade name “Irgacure 651”, manufactured by IGM Resins B.V.) (0.05 parts by weight), and 1-hydroxy-cyclohexylphenyl-ketone (trade name “Irgacure A partial polymer ( monomer syrup) was obtained. After adding 1,6-hexanediol diacrylate (0.25 parts by weight) to this partially polymerized product (100 parts by weight), the mixture was uniformly mixed to prepare Resin 5.

<Preparation Example 6>
2-ethylhexyl acrylate (57 parts by weight), 2,2,2-trifluoroethyl acrylate (30 parts by weight), 4-hydroxybutyl acrylate (1 part by weight), N-vinyl-2-pyrrolidone (12 parts by weight), 2,2-dimethoxy-1,2-diphenyl-1-one (trade name “Irgacure 651”, manufactured by IGM Resins B.V.) (0.05 parts by weight), and 1-hydroxy-cyclohexylphenyl-ketone (trade name “Irgacure 184”, manufactured by IGM Resins B.V.) (0.05 parts by weight) is put into a four-necked flask and partially photopolymerized by exposing it to ultraviolet rays in a nitrogen atmosphere. , a partial polymer (monomer syrup) was obtained. After adding 1,6-hexanediol diacrylate (0.25 parts by weight) to this partially polymerized product (100 parts by weight), the mixture was uniformly mixed to prepare Resin 6.

<Example 1>
To 100 parts by weight of Resin 1, 80 parts by weight of fused silica (“SC6103-SQ”, manufactured by Admatechs) was added and mixed and stirred to obtain Resin Composition 1. The above resin composition was applied to the release-treated surface of a 38 μm-thick release liner A (polyester film, trade name “Diawheel MRF”, manufactured by Mitsubishi Chemical Corporation) whose one side was release-treated with silicone so as to have a thickness of 100 μm. to form a coating layer, and on the coating layer, a 38 μm thick release liner B (trade name “Diawheel MRE”, manufactured by Mitsubishi Chemical Co., Ltd.) with a silicone release treatment on one side is pasted. Ultraviolet rays were irradiated from the surface on the release liner A side with a black light lamp whose lamp height was adjusted so that the intensity of the irradiated surface directly below the lamp was 2.6 mW/cm ² . Polymerization was carried out until the integrated light amount was 2400 mJ/cm ² to produce a thermally conductive sheet 1 having a resin layer thickness of 100 μm.

<Example 2>
To 100 parts by weight of Resin 1, 120 parts by weight of fused silica (“SC6103-SQ”, manufactured by Admatechs) was added and mixed and stirred to obtain Resin Composition 2.
A thermally conductive sheet 2 was produced in the same manner as in Example 1, except that the resin composition 2 was used instead of the resin composition 1.

<Example 3>
To 100 parts by weight of Resin 3, 120 parts by weight of fused silica (“SC6103-SQ”, manufactured by Admatechs) was added and mixed and stirred to obtain Resin Composition 3. A thermally conductive sheet 3 was produced in the same manner as in Example 1, except that the resin composition 3 was used instead of the resin composition 1.

<Example 4>
To 100 parts by weight of Resin 4, 120 parts by weight of fused silica (“SC6103-SQ”, manufactured by Admatechs) was added and mixed and stirred to obtain Resin Composition 4. A thermally conductive sheet 4 was produced in the same manner as in Example 1, except that the resin composition 4 was used instead of the resin composition 1.

<Example 5>
To 100 parts by weight of resin 5, 120 parts by weight of fused silica ("SC6103-SQ", manufactured by Admatechs) was added and mixed and stirred to obtain resin composition 5. A thermally conductive sheet 5 was produced in the same manner as in Example 1, except that the resin composition 5 was used instead of the resin composition 1.

<Example 6>
To 100 parts by weight of Resin 6, 120 parts by weight of fused silica (“SC6103-SQ”, manufactured by Admatechs) was added and mixed and stirred to obtain Resin Composition 6. A thermally conductive sheet 6 was produced in the same manner as in Example 1, except that the resin composition 6 was used instead of the resin composition 1.

<Comparative Example 1>
80 parts by weight of fused silica (“SC6103-SQ”, manufactured by Admatechs) was added to 100 parts by weight of Resin 2, and the mixture was mixed and stirred to obtain Resin Composition 7. A thermally conductive sheet 7 was produced in the same manner as in Example 1, except that the resin composition 7 was used instead of the resin composition 1.

<Comparative Example 2>
120 parts by weight of fused silica ("SC6103-SQ", manufactured by Admatechs) was added to 100 parts by weight of Resin 2, and the mixture was mixed and stirred to obtain Resin Composition 8. A thermally conductive sheet 8 was produced in the same manner as in Example 1, except that the resin composition 8 was used instead of the resin composition 1.

Measurement of refractive index For resins 1 to 6, the refractive index of the cured product obtained by curing in the same manner as the method for producing the thermally conductive sheet of Example 1 was measured by a multi-wavelength Abbe refractometer (ATAGO Co., Ltd. using a model "DR-M2"), measured under the measurement conditions of a wavelength of 589 nm and 23 ° C. (the same applies to the refractive index measurement of the thermally conductive filler below), and the obtained values are shown in Table 1 "Resin "Refractive index (np)" column. In addition, as a thermally conductive filler, the refractive index of fused silica ("SC6103-SQ", manufactured by Admatechs) was measured with a multi-wavelength Abbe refractometer, and the obtained value is shown in Table 1 as "filler refractive index ( nf)” column. Furthermore, for the thermally conductive sheet according to each example, the value obtained by subtracting the filler refractive index (nf) from the measured resin refractive index (np) was calculated, and the column of "refractive index difference (np-nf)" in Table 1 was calculated. It was shown to.

Measurement of Total Light Transmittance and Haze Value The release liner B of the thermally conductive sheets 1 to 8 of Examples and Comparative Examples was peeled off, and the sheets were bonded to Eagle Glass (manufactured by Matsunami Glass Industry Co., Ltd.) with a hand roller. Further, the release liner A was peeled off, the above Eagle Glass was laminated, and autoclaved (50° C., 0.5 MPa, 15 min). The total light transmittance (%) and haze value (%) of the obtained glass sample in visible light of 380 nm to 780 nm were measured using a spectroscopic haze meter ("HSP-150Vis", manufactured by Murakami Color Research Laboratory). , the results are shown in Table 1.

・Measurement of thermal conductivity The release liners A and B of the thermally conductive sheets 1 to 8 of Examples and Comparative Examples were peeled off, and the thermal diffusivity was measured using a thermal diffusivity measuring device ("Thermo Wave Analyzer TA", Bethel Co., Ltd.). was measured. In addition, the release liners A and B of the thermally conductive sheets of Examples and Comparative Examples were peeled off, and the specific heat was measured with a specific heat measuring device (“DSC 7020”, manufactured by SII). The conductivity (W/m·K) was calculated and the results are shown in Table 1.

The thermally conductive sheets of Examples 1 and 2 were excellent in thermal conductivity. The thermally conductive sheets of Examples 1 and 2, in which the value obtained by subtracting the refractive index nf of the thermally conductive filler from the refractive index np of the resin (np−nf) is −0.01 or more and 0.01 or less, It was confirmed that the haze value was smaller and the total light transmittance was higher than the thermally conductive sheets of Comparative Examples 1 and 2, which did not satisfy the above formula.

Variations of the present invention are described below.
[Appendix 1]
A thermally conductive sheet comprising a resin layer containing a resin and a thermally conductive filler,
The total light transmittance of the resin layer is 85% or more,
The refractive index np of the resin is 1.469 or less,
A thermally conductive sheet, wherein a value obtained by subtracting the refractive index nf of the thermally conductive filler from the refractive index np of the resin (np-nf) is -0.01 or more and 0.01 or less.
[Appendix 2]
The resin contains at least one selected from the group consisting of an acrylic polymer, a rubber polymer, a polyester polymer, a urethane polymer, a polyether polymer, a silicone polymer, a polyamide polymer, and a fluorine polymer. The thermally conductive sheet according to Appendix 1.
[Appendix 3]
3. The thermally conductive sheet according to

appendix

1 or 2, wherein the resin contains a fluoropolymer.
[Appendix 4]
4. The thermally conductive sheet according to any one of Appendices 1 to 3, wherein the resin contains a fluoropolymer as a base polymer.
[Appendix 5]
5. The thermally conductive sheet according to appendix 4, wherein the fluoropolymer accounts for 50% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more of the resin.
[Appendix 6]
The fluorine-based polymer is selected from the group consisting of a tetrafluoroethylene-based polymer, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, and an acrylic polymer containing a fluorine-containing acrylic monomer (fluorinated acrylic polymer). The thermally conductive sheet according to any one of Appendices 2 to 5, which is at least one.
[Appendix 7]
7. The thermally conductive sheet according to any one of Appendices 2 to 6, wherein the fluorine-based polymer is an acrylic polymer containing a fluorine-containing acrylic monomer (fluorine-containing acrylic polymer).
[Appendix 8]
The ratio of the fluorine-containing acrylic monomer to the total monomer component (100% by weight) of the fluorine-containing acrylic polymer is 1% by weight or more, 2% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. The thermally conductive sheet according to appendix 6 or 7, which is
[Appendix 9]
The ratio of the fluorine-containing acrylic monomer to the total monomer component (100% by weight) of the fluorine-containing acrylic polymer is 60% by weight or less, 40% by weight or less, 30% by weight or less, 25% by weight or less, or 20% by weight or less. The thermally conductive sheet according to any one of Appendices 6 to 8.
[Appendix 10]
The fluorine-containing acrylic polymer includes (meth)acrylate having an alkyl group having 1 to 20 carbon atoms, (meth)acrylate having an alkyl group having 2 to 10 carbon atoms, and (meth)acrylate having an alkyl group having 4 to 9 carbon atoms. ) The thermally conductive sheet according to any one of Appendices 6 to 9, which contains an acrylate or a (meth)acrylate having an alkyl group having 6 to 8 carbon atoms.
[Appendix 11]
The ratio of the (meth)acrylate having an alkyl group having 1 to 20 carbon atoms to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 10% by weight or more, 20% by weight or more, 40% by weight or more, 11. The thermally conductive sheet according to Appendix 10, which is 60% by weight or more, or 80% by weight or more.
[Appendix 12]
The ratio of the (meth)acrylate having an alkyl group having 1 to 20 carbon atoms to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 99% by weight or less, 98% by weight or less, or 95% by weight or less, Or the thermally conductive sheet according to appendix 10 or 11, which is 90% by weight or less.
[Appendix 13]
13. The thermally conductive sheet according to any one of Appendices 6 to 12, wherein the fluorine-containing acrylic polymer contains a copolymerizable monomer.
[Appendix 14]
13. The thermally conductive sheet according to any one of Appendices 6 to 12, wherein the fluorine-containing acrylic polymer contains a monomer having a polar group as a copolymerizable monomer.
[Appendix 15]
The fluorine-containing acrylic polymer contains, as a copolymerizable monomer (monomer having a polar group), at least one monomer selected from the group consisting of a carboxy group-containing monomer, a hydroxyl group-containing monomer, and a nitrogen atom-containing ring-containing monomer. The thermally conductive sheet according to any one of appendices 6 to 12, comprising:
[Appendix 16]
Note that the ratio of the copolymerizable monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. 16. The thermally conductive sheet according to any one of 13 to 15.
[Appendix 17]
Any one of Appendices 13 to 16, wherein the ratio of the copolymerizable monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 40% by weight or less, 20% by weight or less, or 15% by weight or less. 1. The thermally conductive sheet according to 1.
[Appendix 18]
Appendices 15 to 15, wherein the ratio of the carboxy group-containing monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 0.1% by weight or more, 1% by weight or more, or 1.5% by weight or more. 18. The thermally conductive sheet according to any one of 17.
[Appendix 19]
Appendix 15, wherein the ratio of the carboxy group-containing monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 40% by weight or less, 20% by weight or less, 15% by weight or less, or 10% by weight or less. 19. The thermally conductive sheet according to any one of 18.
[Appendix 20]
Supplementary Note 15, wherein the ratio of the hydroxyl group-containing monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. 20. The thermally conductive sheet according to any one of 19.
[Appendix 21]
Appendices 15 to 3, wherein the ratio of the hydroxyl group-containing monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 40% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less. 21. The thermally conductive sheet according to any one of 20.
[Appendix 22]
The ratio of the monomer having a nitrogen atom-containing ring to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 0.1% by weight or more, 1% by weight or more, 3% by weight or more, or 5% by weight or more. The thermally conductive sheet according to any one of Appendices 15 to 21.
[Appendix 23]
Appendices 15 to 22, wherein the ratio of the nitrogen atom-containing ring-containing monomer to the total amount (100% by weight) of the monomer components of the fluorine-containing acrylic polymer is 40% by weight or less, 30% by weight or less, or 20% by weight or less. The thermally conductive sheet according to any one of.
[Appendix 24]
24. The thermally conductive sheet according to any one of Appendices 1 to 23, comprising a silicon atom-containing filler as the thermally conductive filler.
[Appendix 25]
25. The thermally conductive sheet according to any one of Appendices 1 to 24, comprising silica as the thermally conductive filler.
[Appendix 26]
26. The thermally conductive sheet according to any one of appendices 1 to 25, comprising fused silica as the thermally conductive filler.
[Appendix 27]
Any one of Appendices 1 to 26, wherein the content of the thermally conductive filler is 5 parts by weight or more, 10 parts by weight or more, 30 parts by weight or more, or 50 parts by weight or more with respect to 100 parts by weight of the resin. The thermally conductive sheet described in .
[Appendix 28]
Any one of Appendices 1 to 27, wherein the content of the thermally conductive filler is 300 parts by weight or less, 250 parts by weight or less, 200 parts by weight or less, or 160 parts by weight or less with respect to 100 parts by weight of the resin. The thermally conductive sheet described in .
[Appendix 29]
The thermally conductive filler has a refractive index nf of 1.3 to 1.7, 1.35 to 1.6, 1.4 to 1.55, 1.41 to 1.5, or 1.43 to 1.5. 46, the thermally conductive sheet according to any one of Appendixes 1 to 28.
[Appendix 30]
The (np-nf) is -0.005 or more and 0.008 or less, -0.002 or more and 0.006 or less, or 0 or more and 0.004 or less. Thermally conductive sheet.
[Appendix 31]
The thermal conductivity of the resin layer is 0.2 W/m·K or more, 0.22 W/m·K or more, 0.24 W/m·K or more, 0.26 W/m·K or more, 0.28 W/m · The thermally conductive sheet according to any one of Appendices 1 to 30, which has K or more, or 0.30 W/m·K or more.
[Appendix 32]
The thermal conductivity of the resin layer is 2.0 W/m·K or less, 1.5 W/m·K or less, 1.0 W/m·K or less, 0.8 W/m·K or less, 0.5 W/m · The thermally conductive sheet according to any one of Appendices 1 to 31, which has K or less or less than 0.5 W/m·K.
[Appendix 33]
33. The thermally conductive sheet according to any one of Appendices 1 to 32, wherein the resin layer has a haze value of 15% or less, 10% or less, 9% or less, 6% or less, or 3% or less.
[Appendix 34]
34. The thermally conductive sheet according to any one of Appendices 1 to 33, wherein the resin layer has a total light transmittance of 90% or more, 91.5% or more, or 91.8% or more.
[Appendix 35]
35. The thermally conductive sheet according to any one of Appendices 1 to 34, wherein the resin layer has a thickness of 10 to 600 μm, 0 to 300 μm, 50 to 200 μm, or 80 to 150 μm.
[Appendix 36]
36. The thermally conductive sheet according to any one of Appendices 1 to 35, wherein the adhesive strength of the resin layer to glass is 1.0 N/25 mm or more or 3.0 N/25 mm or more.
[Appendix 37]
37. The thermally conductive sheet according to any one of Appendices 1 to 36, wherein the resin layer contains a multifunctional monomer.
[Appendix 38]
The content of the polyfunctional monomer with respect to 100 parts by weight of the resin in the resin layer is 0.0001 to 5 parts by weight, 0.001 to 2 parts by weight, or 0.005 to 1 part by weight. The thermally conductive sheet according to any one.

X1 Thermally conductive sheet X2-1 Thermally conductive sheet X2-2 Thermally conductive sheet X3 Thermally conductive sheet X4 Thermally conductive sheet 10 Resin layer (non-adhesive layer)
10a first surface 10b second surface 20 resin layer (adhesive layer)
20a first adhesive surface 20b second adhesive surface 20 resin layer (adhesive layer)
20a first adhesive surface 20b second adhesive surface 21 release liner 21a back surface of release liner 22 release liner 30 supporting substrate 30a first surface 30b second surface 31 first adhesive layer 31a adhesive surface 32 second adhesive layer 32b adhesive surface 33 Release liner 33a Back surface of release liner 34 Release liner 40 Resin layer 40a First surface 40b Second surface 41 First adhesive layer 41a Adhesive surface 42 Second adhesive layer 42b Adhesive surface 43 Release liner 44 Release liner

Claims

A thermally conductive sheet comprising a resin layer containing a resin and a thermally conductive filler,
The total light transmittance of the resin layer is 85% or more,
The refractive index np of the resin is 1.469 or less,
A thermally conductive sheet, wherein a value obtained by subtracting the refractive index nf of the thermally conductive filler from the refractive index np of the resin (np-nf) is -0.01 or more and 0.01 or less.
The thermally conductive sheet according to claim 1, wherein the resin layer has a haze value of 15% or less.
The thermally conductive sheet according to claim 1 or 2, wherein the content of said thermally conductive filler is 50 parts by weight or more with respect to 100 parts by weight of said resin.
The thermally conductive sheet according to claim 1 or 2, wherein the adhesive strength of the resin layer to glass is 1 N/25 mm or more.