WO2006001943A2 - Multi-layered thermally conductive sheet - Google Patents
Multi-layered thermally conductive sheet Download PDFInfo
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- WO2006001943A2 WO2006001943A2 PCT/US2005/017283 US2005017283W WO2006001943A2 WO 2006001943 A2 WO2006001943 A2 WO 2006001943A2 US 2005017283 W US2005017283 W US 2005017283W WO 2006001943 A2 WO2006001943 A2 WO 2006001943A2
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- thermally conductive
- conductive sheet
- acrylic
- layer
- layered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
- H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
- H01L23/3737—Organic materials with or without a thermoconductive filler
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
- B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/022—Mechanical properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2250/00—Layers arrangement
- B32B2250/24—All layers being polymeric
- B32B2250/246—All polymers belonging to those covered by groups B32B27/32 and B32B27/30
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2250/00—Layers arrangement
- B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
- B32B2264/10—Inorganic particles
- B32B2264/105—Metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
- B32B2307/206—Insulating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/30—Properties of the layers or laminate having particular thermal properties
- B32B2307/302—Conductive
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/30—Properties of the layers or laminate having particular thermal properties
- B32B2307/306—Resistant to heat
- B32B2307/3065—Flame resistant or retardant, fire resistant or retardant
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2405/00—Adhesive articles, e.g. adhesive tapes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
- Y10T428/24917—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] including metal layer
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
- Y10T428/31855—Of addition polymer from unsaturated monomers
- Y10T428/31909—Next to second addition polymer from unsaturated monomers
Definitions
- the present invention relates to a multi-layered thermally conductive sheet. More specifically, the present invention relates to a multi-layered thermally conductive sheet having superior thermal conductivity and flame retardancy as well as superior handleability and adhesion with an object on which the sheet is disposed.
- thermally conductive sheet is used in such a condition that it is arranged to be in contact with a heat- generating body such as electronics. Therefore, a thermally conductive sheet is required to have superior thermal conductivity and high flame retardancy.
- the flame retardancy is desired to correspond to "V-O" level in UL Flameproof Test Standard UL-94 (Underwriters Laboratories, Inc. Standard No. 94) "flammability test of plastic materials for devices and electronic parts (hereinbelow referred to as "UL-94 flammability test”).”
- UL-94 flammability test flammability test of plastic materials for devices and electronic parts
- a silicone resin As a binder constituting a thermally conductive sheet, a silicone resin has recently been used. However, there is an indication that siloxane gas generated from the silicone resin causes a contact failure in electronics. Therefore, it is preferred to use a non-silicone resin. However, it has been difficult for a conventionally-known thermally conductive sheet containing a non- silicone resin as a binder to have a flame retardancy corresponding to V-O in UL-94 flammability test when the sheet has a thickness of less than 1 mm. In addition, when a thermally conductive sheet is made so thin, the thermally conductive sheet has relatively low strength. Therefore, it has been difficult to simultaneously achieve superior adhesion with electronics, or the like, and handleability of the thermally conductive sheet.
- a radiating sheet which comprises an elastic substrate and an adhesive layer, each containing a filler having high thermal conductivity is disclosed in, for example, JP-A- 11-74667.
- the adhesive layer constituting the radiation sheet is unvulcanized, it is prone to cause a flame drip in a perpendicular flaming test such as UL-94 flammability test. Therefore, it has been difficult to achieve flame retardancy corresponding to V-O in UL-94 flammability test when the radiating sheet is made to have a thickness of below 1 mm.
- the unvulcanized adhesive layer sometimes causes adhesive transfer when the sheet is peeled off from the object since the adhesive layer is unvulcanized.
- the radiation sheet disclosed, in JP-A- 11-74667 has insufficient thermal conductivity because of a low coefficient of thermal conductivity thereof.
- an adhesive tape which comprises an elastic substrate and an adhesive layer, each containing a filler having thermal conductivity and electrical insulation, is disclosed in, for example, JP-B-2003- 160775.
- the adhesive tape has a problem of not showing sufficient flame retardancy in UL-94 flammability test.
- the adhesive tape disclosed in the document has insufficient thermal conductivity because of a low coefficient of thermal conductivity thereof.
- the present invention has been made in consideration of the conventional problems, aiming to provide a multi-layered thermally conductive sheet which can have superior thermal conductivity and flame retardancy as well as superior handleability and adhesion even without using any of a halogen-containing flame retardant, red phosphorous, and silicone resin.
- the present inventors made an energetic study to address the above object and, as a result, found out that the above problems can be solved by laminating at least two acrylic thermally conductive sheet layers which contain a metal hydrate at a predetermined content and which have different crosslinking density.
- a multi-layered thermally conductive sheet comprising: a first acrylic thermally conductive sheet layer, and a second acrylic thermally conductive sheet layer disposed on one or both surfaces of the first acrylic thermally conductive sheet layer; the first acrylic thermally conductive sheet layer having an Asker C hardness of 60 or more, the first acrylic thermally conductive sheet layer being obtained by curing a first composition containing 10% by volume or more of a metal hydrate, the second acrylic thermally conductive sheet layer having an Asker C hardness of 50 or less, the second acrylic thermally conductive sheet layer being obtained by curing a second composition containing 5% by volume or more of a metal hydrate, and the first acrylic thermally conductive sheet layer having half or less thickness with respect to thickness of the whole sheet.
- a first acrylic thermally conductive sheet layer is obtained by curing a first composition containing: 100 parts by weight of a monofunctional (meth)acrylic monomer, 0.1 to 5 parts by weight of a polyfunctional (meth)acrylic monomer and/or 0.5 to 20 parts by weight of a triazine skeleton-containing compound copolymerizable with the monofunctional (meth)acrylic monomer and the polyfunctional (meth)acrylic monomer, and 150 parts by weight or more of a metal hydrate
- a second acrylic thermally conductive sheet layer is obtained by curing a second composition containing: 100 parts by weight of the monofunctional (meth)acrylic monomer, 0.05 to 1.5 parts by weight of the polyfunctional (meth)acrylic monomer and/or 0.1 to 5 parts by weight of the triazine skeleton-containing compound, and 50 parts by weight or more of the metal hydrate.
- the multi-layered thermally conductive sheets of the present invention it is preferable to have a thermal conductivity of 1 W/(m • K) or more. In the multi-layered thermally conductive sheets of the present invention, it is preferable to have a flame retardancy corresponding to V-O in the flammability test based on UL Flameproof Test Standard UL-94 (Underwriters Laboratories, Inc. Standard No. 94). In the multi-layered thermally conductive sheets of the present invention, it is preferable to have a whole thickness of 1 mm or less.
- the multi-layered thermally conductive sheet is provided with a first acrylic thermally conductive sheet layer and a second acrylic thermally conductive sheet layer disposed on one or both surfaces of the first acrylic thermally conductive sheet layer.
- the first acrylic thermally conductive sheet layer is obtained by curing a first composition containing 10% by volume or more of a metal hydrate and has an Asker C hardness of 60 or more.
- the second acrylic thermally conductive sheet layer is obtained by curing a second composition containing 5% by volume or more of a metal hydrate and has an Asker C hardness of 50 or less.
- the first acrylic thermally conductive sheet layer has half or less thickness with respect to thickness of the whole sheet. Therefore, the first multi-layered thermally conductive sheet can have superior thermal conductivity and flame retardancy as well as superior handleability and adhesion even without substantially using any of a halogerrcontaining flame retardant, red phosphorous, and silicone resin.
- (meth) acrylic means "acrylic or methacrylic”
- (meth)acrylic monomer means an acrylic monomer such as acrylic acid or acrylic ester, or a methacrylic monomer such as methacrylic acid or methacrylic ester.
- the multi-layered thermally conductive sheet which is the first embodiment of the present invention, is a so-called lamination-type thermally conductive sheet provided with the first acrylic thermally conductive sheet layer and the second acrylic thermally conductive sheet layer disposed on one or both surfaces of the first acrylic thermally conductive sheet layer.
- the first acrylic thermally conductive sheet layer constituting the first multi-layered thermally conductive sheet of the first embodiment is a layer obtained by curing the first composition containing 10% by volume or more of a metal hydrate and has an Asker C hardness of 60 or more.
- the second acrylic thermally conductive sheet layer is a layer obtained by curing the second composition containing 5% by volume or more of a metal hydrate and has an Asker C hardness of 50 or less. That is, the multi-layered thermally conductive sheet of the present embodiment has a laminated structure of two kinds of layers each containing a metal hydrate at a predetermined content and having different Asker C hardness. By employing such a lamination-type structure, the multi-layered thermally conductive sheet of the present embodiment hardly causes a flame drip even in a perpendicular flaming test such as UL- 94 flammability test described below and shows superior flame retardancy corresponding to V"0 and superior thermal conductivity.
- the first multi-layered sheet thermally conductive sheet of the present embodiment is not constituted only by the first acrylic thermally conductive sheet layer having high hardness, but has a laminated structure with the second multi-layered thermally conductive sheet, which is more flexible than the first acrylic thermally conductive sheet layer. Therefore, the first multi-layered thermally conductive sheet has high flexibility as a whole with sufficient flame retardancy and superior in handleability and adhesion with an object on which the sheet is disposed.
- each layer may have an Asker C hardness of 50 or less, and each of the second acrylic thermally conductive sheet layers may have the same or different Asker C hardness.
- the content of the metal hydrate contained in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered conductive sheet of the present embodiment is 10% by volume or more, preferably 15% by volume or more, more preferably 20% by volume or more. When the content is less than 10% by volume, the resultant multi-layered thermally conductive sheet sometimes has poor flame retardancy.
- the content of a metal hydrate contained in the first composition may be 80% by volume or less from the viewpoint of practical manufacturability.
- the content of a metal hydrate contained in the second composition constituting the first acrylic thermally conductive sheet layer of the multi-layered conductive sheet of the present embodiment is 5% by volume or more, preferably 8% by volume or more.
- the resultant multi-layered thermally conductive sheet sometimes has poor flame retardancy.
- the content may be 80% by volume or less from the viewpoint of practical manufacturability.
- the first acrylic thermally conductive sheet layer has an Asker C hardness of 65 or more, and that the second acrylic thermally conductive sheet layer has an Asker C hardness of 45 or less, and it is further preferred that the first acrylic thermally conductive sheet layer has an Asker C hardness of 70 or more, and that the second acrylic thermally conductive sheet layer has an Asker C hardness of 40 or less.
- the multi-layered thermally conductive sheet tends to have insufficient flame retardancy.
- the second acrylic thermally conductive sheet layer has an Asker C hardness of above 50, the multi-layered thermally conductive sheet tends to have deteriorated adhesion with an object on which the sheet is disposed.
- the Asker C hardness may be 100 or less from the viewpoint of practical manufacturability.
- the multi-layered thermally conductive sheet of the present embodiment is a so-called lamination-type thermally conductive sheet provided with the first acrylic thermally conductive sheet layer and the second acrylic thermally conductive sheet layer disposed on one or both surfaces of the first acrylic thermally conductive sheet layer.
- the first acrylic thermally conductive sheet layer constituting the multi-layered thermally conductive sheet of the present embodiment preferably has a crosslinking density higher than that of the second acrylic thermally conductive sheet layer.
- the first acrylic thermally conductive sheet layer may have a crosslinking density higher than those of the second acrylic thermally conductive sheet layers, and each of the second acrylic thermally conductive sheet layers may have the same or different composition.
- the multi-layered thermally conductive sheet of the present embodiment has a laminated structure comprising two kinds of layers having different crosslinking densities, that is, hardness. By employing such a lamination-type structure, the multi-layered thermally conductive sheet of the present embodiment hardly cause a flame drip even in a perpendicular flaming test such as UL-94 flammability test described below and shows superior flame retardancy corresponding to V-O and superior thermal conductivity.
- the second multi-layered thermally conductive sheet of the present embodiment is not constituted only by the first acrylic thermally conductive sheet layer having high crosslinking density and high hardness, but has a laminated structure with the second multi-layered thermally conductive sheet, which has a lower crosslinking density and a higher flexibility in comparison with the first acrylic thermally conductive sheet layer. Therefore, the second multi-layered thermally conductive sheet has high flexibility as a whole with sufficient flame retardancy and superior handleability and adhesion with an object on which the sheet is disposed.
- the first acrylic thermally conductive sheet layer has half or less thickness with respect to thickness of the whole sheet (the first acrylic thermally conductive sheet layer plus the second acrylic thermally conductive sheet layer).
- thickness of the first acrylic thermally conductive sheet layer is preferably 1/20 to 1/2, further preferably 1/10 to 1/3, with respect to the thickness of the whole sheet in consideration of a balance of the properties such as thermal conductivity, flame retardancy, handleability, and adhesion with the object.
- thickness of the first acrylic thermally conductive sheet layer is preferably 1/20 to 1/2, further preferably 1/10 to 1/3, with respect to the thickness of the whole sheet in consideration of a balance of the properties such as thermal conductivity, flame retardancy, handleability, and adhesion with the object.
- Monofunctional (meth)acrylic monomer used for the multi-layered thermally conductive sheet of the present embodiment is not particularly limited and may be a monomer used in order to form a general (meth) acrylic polymer. Incidentally, only one kind or a mixture of two or more kinds of monofunctional (meth)acrylic monomers may be used.
- Preferable examples are monofunctional (meth)acrylic monomers having alkyl groups having 20 or less carbons, including ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, acrylic acid, methacrylic acid.
- monofunctional (meth)acrylic monomers having alkyl groups having 20 or less carbons including ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl
- Polyfunctional (meth)acrylic monomer used for the multi-layered thermally conductive sheet of the present embodiment is a compound having two or more functional groups selected from the group consisting of acryloxy group and methacryloxy group. Incidentally, only one kind or a mixture of two or more kinds of monofunctional (meth)acrylic monomers may be used. Preferable examples includes : di(meth)acrylates such as 1,6'hexanediol diacrylate, 1,4-butanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate,
- tri(meth)acrylates such as trimethylol propane triacrylate,
- the content of the polyfunctional (meth)acrylic monomer in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is 0.1 to 5 parts by mass, preferably 1 to 4 parts by mass, more preferably 1 to 3 parts by mass, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer in the first composition.
- the content is less than 0.1 part by mass, the resultant multi-layered thermally conductive sheet sometimes has insufficient flame retardancy.
- the content is more than 5 parts by mass, the first acrylic thermally conductive sheet layer becomes brittle, which sometimes cause cracks, or the like.
- the content of the polyfunctional (meth) acrylic monomer in the second composition constituting the second acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is 0.05 to 1.5 parts by mass, preferably 0.1 to 0.45 part by mass, more preferably 0.15 to 0.4 part by mass, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer in the second composition.
- the content is less than 0.05 part by mass, the second acrylic thermally conductive sheet layer has deteriorated hardness, and the resultant multi-layered thermally conductive sheet is prone to have insufficient flame retardancy with deteriorated handleability.
- the content is more than 1.5 parts by mass, the second acrylic thermally conductive sheet layer has excessive hardness, and the resultant multi-layered thermally conductive sheet sometimes has deteriorated adhesion with an object.
- Triazine skeleton-containing compound used for the multi-layered thermally conductive sheet of the present embodiment is a compound copolymerizable with (meth)acrylic monomer, for example, triallyl isocyanurate and trimethallyl isocyanurate.
- the content of the triazine skeleton-containing compound in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is 0.5 to 20 parts by mass, preferably 3 to 15 parts by mass, more preferably 4 to 12 parts by mass, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the first composition.
- the resultant multi-layered thermally conductive sheet sometimes has insufficient flame retardancy.
- the content is more than 20 parts by mass, the first acrylic thermally conductive sheet layer becomes brittle, which sometimes cause cracks, or the like.
- the content of the triazine skeleton-containing compound in the second composition constituting the second acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is 0.1 to 5 parts by mass, preferably 1.8 parts by weight or less, more preferably 1.6 parts by weight or less, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the second composition.
- the second acrylic thermally conductive sheet layer has excessive hardness, and the resultant multi-layered thermally conductive sheet sometimes has deteriorated adhesion with an object.
- the content is less than 0.1 part by mass, the second acrylic thermally conductive sheet layer has deteriorated hardness, and the resultant multi-layered thermally conductive sheet is prone to have insufficient flame retardancy with deteriorated handleability.
- Metal hydrate Examples of a metal hydrate used for the multi-layered thermally conductive sheet of the present embodiment includes aluminum hydroxide, magnesium hydroxide, barium hydroxide, calcium hydroxide, dawsonite, hydrotalcite, zinc borate, calcium aluminate, and zirconium oxide hydrate. Only one kind or a mixture of two or more kinds of these metal hydrates may be used. Among these, aluminum hydroxide and magnesium hydroxide are preferable from the viewpoint of the effect on flame retardancy. Generally, these metal hydrates are added to the material in the form of particles.
- a metal hydrate containing a group of relatively large particles having the average particle diameter of 5 to 50 micrometers and a group of relatively small particles having the average particle diameter of below 5 micrometers in combination be used so as to increase the amount of the metal hydrate to be added to the material. It is further preferred to use a metal hydrate subjected to a surface treatment with silane, titanate, fatty acid, or the like, so as to enhance strength (for example, tensile/breaking strength) of the resultant multi-layered thermally conductive sheet. Further, it is preferred to add a thermally conductive filler in addition to a metal hydrate so as to enhance thermal conductivity of the resultant multi-layered thermally conductive sheet.
- suitable fillers include one or more kinds selected from the group consisting of metallic oxides, metallic nitrides, and metallic carbides.
- metallic oxide include aluminum oxide, magnesium oxide, beryllium oxide, titanium oxide, zirconium oxide, and zinc oxide.
- metallic nitrides include boron nitride, aluminum nitride, and silicon nitride.
- metallic carbides include boron carbide, aluminum carbide, and silicon carbide. Among these, further preferable are aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, and silicon carbide from the viewpoint of thermal conductivity and mechanical properties.
- the content of the metal hydrate in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 150 parts by weight or more, more preferably 250 parts by weight or more, particularly preferably 350 parts by weight or more, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the first composition.
- the content is less than 150 parts by mass, sometimes flame retardancy of the resultant multi-layered thermally conductive sheet is hardly enhanced.
- the content of the metal hydrate may be 700 parts by weight or less from the viewpoint of practical manufacturability.
- the content of the metal hydrate in the second composition constituting the second acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 50 parts by weight or more, more preferably 100 parts by weight or more, particularly preferably 150 parts by weight or more, with respect to 100 parts by weight of monofunctional (meth) acrylic monomer.
- the content is less than 50 parts by mass, sometimes flame retardancy of the resultant multi-layered thermally conductive sheet is hardly enhanced.
- the content of the metal hydrate may be 700 parts by weight or less from the viewpoint of practical manufacturability.
- Other additives 5.1) Crosslinking agent It is also possible to use a suitable crosslinking agent with or in place of the aforementioned triazine skeleton-containing compound used for the multi-layered thermally conductive sheet of the present embodiment. By adjusting the kind, amount, etc., of the crosslinking agent to be used, crosslinking density of the first acrylic thermally conductive sheet layer and the second acrylic thermally conductive sheet layer as well as strength (i.e., tensile/breaking strength) of the resultant multi-layered thermally conductive sheet can be suitably adjusted.
- crosslinking agent capable of being activated by heat.
- the crosslinking agent includes: hexamethoxymethyl melamine (e.g., commercial name : Cymel 303, produced by American Cyanamide Company), tetramethoxymethyl urea (e.g., commercial name : Beetle 65, produced by American Cyanamide Company), and tetrabutoxymethyl urea (e.g., commercial name ⁇ Beetle 85, produced by American Cyanamide Company).
- hexamethoxymethyl melamine e.g., commercial name : Cymel 303, produced by American Cyanamide Company
- tetramethoxymethyl urea e.g., commercial name : Beetle 65, produced by American Cyanamide Company
- tetrabutoxymethyl urea e.g., commercial name ⁇ Beetle 85, produced by American Cyanamide Company
- the content of the crosslinking agent in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 0.5 to 2.5 parts by weight with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the first composition.
- the content is less than 0.5 part by mass, the resultant multi-layered thermally conductive sheet sometimes has insufficient flame retardancy.
- the resultant multi-layered thermally conductive sheet has lowered flexibility, and the first acrylic thermally conductive sheet layer becomes brittle, which sometimes cause cracks, or the like, therein.
- the content of the crosslinking agent in the second composition constituting the second acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 0.01 to 0.5 part by weight with respect to 100 parts by weight of nionofunctional (meth) acrylic monomer of the second composition.
- the content is lower than 0.01 part by mass, the second acrylic thermally conductive sheet layer has lowered hardness, and the resultant multi-layered thermally conductive sheet is prone to have insufficient flame retardancy with deteriorated handleability.
- the content is more than 0.5 part by mass, the second acrylic thermally conductive sheet layer has excessive hardness, and the resultant multi-layered thermally conductive sheet sometimes has deteriorated adhesion with the object.
- additives may be added to the materials constituting the first and the second acrylic thermally conductive sheet layers of the multi-layered thermally conductive sheet of the present embodiment as long as the characteristics of the multi-layered thermally conductive sheet of the present invention are not spoiled.
- the additive include ⁇ tackifiers, antioxidants, chain-transfer agents, plasticizers, flame retardants, flame retarding auxiliaries, precipitation inhibitors, thickeners, thixotropy agents such as silica ultra fine powder, surfactants, antifoamers, colorants, electrically conductive particles, antistatic agents, and surface treatments agents.
- thixotropy agents such as silica ultra fine powder, surfactants, antifoamers, colorants, electrically conductive particles, antistatic agents, and surface treatments agents.
- only one kind or a combination of two or more kinds of these additives may be used.
- halogen-free flame retardant When a flame retardant is added to the composition, it is preferred to use a flame retardant which is substantially free from halogen (hereinbelow referred to as "halogen-free flame retardant").
- halogen-free flame retardant include- organic phosphorus compounds, expansible graphite, poly(phenylene ether), and triazine skeleton-containing compounds (including the aforementioned triazine skeleton-containing compounds).
- organic phosphorous compounds are most preferable from the viewpoint of exhibition of flame retardant effect. Incidentally, only one kind or a combination of two or more kinds of these flame retardants may be used.
- the organic phosphorous compound may be a copolymerizable or uncopolymerizable with the monofunctional (meth)acrylic monomer and the polyfunctional (meth)acrylic monomer.
- Examples of organic phosphorous compound copolymerizable with these monomers include phosphate ester-containing (meth)acrylic monomers shown by the following general formula (l).
- O O HX : C?-C-O-R 0 -O-P-O-R, ( D R 1 O O R.
- Examples of the phosphate-containing (meth)acrylic monomer include : dimethyl-(meth)acryloyloxymethyl phosphate, diethyl-(meth)acryloyloxymethyl phosphate, diphenyl-(meth)acryloyloxymethyl phosphate, dimethyl-2-(meth)acryloyloxyethyl phosphate, diethyl- 2 - (meth)acry loyloxy ethyl phosphate , diphenyl-2-(meth)acryloyloxyethyl phosphate, dimethyl-3-(meth)acryloyloxypropyl phosphate, diethyl- 3- (meth)acryloyloxypropyl phosphate, and diphenyl-3-(meth)acryloyloxypropyl phosphate, and diphenyl-3-(meth)acryloyloxypropyl phosphate, and diphenyl-3-(meth)acryloyloxypropyl
- the content of the phosphate-containing (meth)acrylic monomer in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 10 to 50 parts by mass, more preferably 10 to 30 parts by mass, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the first composition.
- the content is less than 10 parts by mass, flame retardant effect is sometimes deteriorated.
- the content is more than 50 parts by mass, the resultant multi-layered thermally conductive sheet has lowered flexibility.
- the content of the phosphate-containing (meth)acrylic monomer in the second composition constituting the second acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 2 to 30 parts by mass, more preferably 5 to 15 parts by mass, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the second composition.
- the content is less than 2 parts by mass, flame retardant effect is sometimes deteriorated.
- the content is more than 30 parts by mass, the resultant multi-layered thermally conductive sheet has lowered flexibility.
- Examples of organic phosphorous compound uncopolymerizable with monofunctional (meth)acrylic monomers and polyfunctional (meth)acrylic monomers include: phosphate esters, aromatic condensed phosphates, and ammonium polyphosphates.
- Examples of the phosphate esters include: triphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, 2-ethylhexyldiphenyl phosphate, tri-n-butyl phosphate, trixylenyl phosphate, resorcinol bis(diphenyl phosphate), and bisphenol A bis(diphenyl phosphate).
- ammonium polyphosphates examples include: ammonium polyphosphate, melamine modified ammonium polyphosphate, and coated ammonium polyphosphate.
- coated ammonium polyphosphate means ammonium polyphosphate which is resin-coated or micro-encapsulated to enhance water resisting property.
- the content of the organic phosphate compound substantially uncopolymerizable with monofunctional (meth)acrylic monomer, or the like, in the first composition constituting the first acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, with respect to 100 parts by weight of monofunctional (meth) acrylic monomer of the first composition.
- the content of the organic phosphate compound substantially uncopolymerizable with monofunctional (meth)acrylic monomer, or the like, in the second composition constituting the second acrylic thermally conductive sheet layer of the multi-layered thermally conductive sheet of the present embodiment is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, with respect to 100 parts by weight of monofunctional (meth)acrylic monomer of the second composition.
- the content is less than 5 parts by mass, flame retardant effect is sometimes deteriorated.
- a multi-layered thermally conductive sheet of the present invention can be manufactured by: applying the first and the second compositions constituting the first and the second acrylic thermally conductive sheet layers, respectively, on a surface of each suitable support such as a release liner; subjecting the compositions to calendering or press molding to obtain sheets of the compositions; hardening (polymerizing) the sheets of the compositions; peeling the sheets from the supports to give layers; and laminating the layers.
- a multi-layered thermally conductive sheet of the present embodiment by: preparing the first acrylic thermally conductive sheet layer by forming the layer of the first composition according to the above manner; directly applying the second composition on one or both surfaces of the first acrylic thermally conductive sheet layer obtained; and hardening (polymerizing) the second composition.
- a multi-layered thermally conductive sheet of the present embodiment may be manufactured by forming each of the first composition and the second composition in lamination, laminating the first and the second compositions by a so-called multi-layer coating method as disclosed in JP-A-63- 118392, and simultaneously hardening (polymerizing) the first and the second compositions.
- micro grooves or a three-dimensional micro pattern may be formed on at least one surface of a multi-layered thermally conductive sheet of the present embodiment to have the surface from which gas can be easily removed.
- Monofunctional (meth)acrylic monomers generally have low viscosity and in some cases have insufficient handleability. In such a case, a component of the metal hydrate, or the like, sometimes precipitates. It is preferred to increase viscosity by previous partial polymerization of monofunctional (meth) acrylic monomers contained in the first and the second composition for constituting the first and the second acrylic thermally conductive sheet layers, respectively, of the multi-layered thermally conductive sheet of the present embodiment.
- Partial polymerization can be performed in various manners, for example, thermal polymerization, ultraviolet polymerization, electron beam polymerization, gamma-ray polymerization, and ion-beam polymerization.
- polymerization initiators such as photopolymerization initiators and thermal polymerization initiators may be added to the first and the second compositions to perform the above partial polymerization.
- thermal polymerization initiators include organic peroxide such as diacyl peroxides, peroxy ketals, ketone peroxides, hydro peroxides, dialkyl peroxides, peroxy esters, and peroxydicarbonates.
- organic peroxide examples include : lauroyl peroxide, benzoyl peroxide, cyclohexanone peroxide, l,l-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 5-butylhydro peroxide.
- a combination of persulfate and bisulfite can also be used.
- photopolymerization initiators include ⁇ benzoin ethers such as benzoin ethyl ether and benzoin isopropyl ether; anisoin ethyl ether, anisoin isopropyl ether, Michler's ketone (4,4Hetramethyldiaminobenzophenone); and substituted acetophenones such as 2,2-dimethoxy2-phenylacetophenone (e.g., commercial name: KB-I produced by Sartomer Co., Inc. and commercial name : Irgacure 651 produced by Ciba Specialty Chemicals K.K.), 2,2-diethoxyacetophenone.
- benzoin ethers such as benzoin ethyl ether and benzoin isopropyl ether
- anisoin ethyl ether anisoin isopropyl ether
- Michler's ketone (4,4Hetramethyldiaminobenzophenone
- thermal polymerization initiators and photo polymerization initiators may be used in any combination.
- the content of the polymerization initiator used upon partial polymerization of monofunctional (meth)acrylic monomers is generally 0.001 to 5 parts by weight with respect to 100 parts by weight of monofunctional (meth)acrylic monomers.
- chain-transfer agent selected from mercaptanes, disulfides, or a -methylstyrene dimer, or a combination thereof to the first and the second compositions upon partial polymerization so as to control molecular weight and content of polymers contained in partially polymerized polymers obtained by the partial polymerization.
- the content of the chain-transfer agent is preferably 0.01 to 1 parts by mass, more preferably 0.02 to 0.5 parts by mass, with respect to 100 parts by weight of monofunctional (meth) acrylic monomer.
- the first and second composition containing a monofunctional (meth)acrylic monomer, a metal hydrate, and any or both of a polyfunctional (meth)acrylic monomer and a triazine skeleton-containing compound copolymerizable with the monofunctional (meth) acrylic monomer and if present, the polyfunctional (meth)acrylic monomer; a partially polymerized polymer obtained by partially polymerizing the above monofunctional (meth)acrylic monomer and/or polymerization initiator are added to the first and the second composition as necessary.
- Polymerization can be performed in various manners, for example, thermal polymerization, ultraviolet polymerization, electron beam polymerization, gamma-ray polymerization, and ion-beam polymerization.
- first and the second compositions are thermally polymerized, a suitable amount of the above thermal polymerization initiator is contained in the first and second compositions.
- first and the second compositions are photopolymerized, a suitable amount of the above photopolymerization initiator is contained in the first and second composition.
- polymerization is conducted by the use of particle beam like electron beam polymerization, no polymerization initiator is required generally.
- thermal polymerization is performed by heating the first and the second compositions to 50 to 200 °C.
- the first and the second acrylic thermally conductive sheet layers can be obtained by deaerating and mixing the material with a planetary mixer to obtain a mixture, forming the mixture in the shape of a sheet, and irradiating ultraviolet radiation.
- thermal polymerization is preferably employed in place of ultraviolet polymerization.
- the multi-layered thermally conductive sheet of the present embodiment shows superior flame retardancy corresponding to V-O in UL- 94 flammability test even without using a halogen-containing flame retardant.
- the multi-layered thermally conductive sheet has enhanced flexibility because the amount of the flame retardant, which has been used for improving flame retardancy, can be reduced.
- the multi-layered thermally conductive sheet has sufficiently excellent handleability and adhesion to an object on which the sheet is disposed without employing any silicone resin.
- the multi-layered thermally conductive sheet has a coefficient of thermal conductivity of preferably 1 W/(m • K) or more, more preferably 2 W/(m • K) or more, to sufficiently exhibit an effect of heat radiation.
- the value of a coefficient of thermal conductivity of the multi-layered thermally conductive sheet can suitably be set by adjusting, for example, the amount of filler to be contained in the composition. Incidentally, a method for measuring "coefficient of thermal conductivity" referred to in this specification is described later.
- the multi-layered thermally conductive sheet of the present embodiment is disposed between a heat sink, a radiator, or the like, and electronic parts, particularly, semiconductor electronic parts such as a power transistor, a graphic integrated circuit, a chip set, a memory set, and central processing unit, and used to suitably bond them.
- the multi-layered thermally conductive sheet of the present embodiment has a thickness of preferably 1 mm or less, more preferably 0.8 mm or less, furthermore preferably 0.6 mm or less, so as to cope with the development in miniaturization and high integration of electronics.
- the thickness may be 0.2 mm or more from the viewpoint of practical manufacturability and handleability.
- "UL-94 flammability test" is hereinbelow described. First, specimens having the size of 13 mm X 125 mm are prepared for thermally conductive sheets to be tested. Each specimen is suspended vertically by holding with a holding clamp at one longitudinal end thereof. Cotton is disposed at the place 30 cm below the specimen.
- a burner flame is applied to the other longitudinal end (free end portion) of the specimen for 10 seconds (first application). After the flame spread to the specimen ceases, the burner flame is further applied for 10 seconds (second application). Taking the first application and the second application for 5 specimens as one set, two sets of the test are carried out for the thermally conductive sheets. Each of the specimens is measured for the following (l) to (5), and the evaluations for the measurements are given.
- the thermal conductive sheet can be evaluated as the one having flame retardancy corresponding "V-O".
- the total flaming combustion time per each specimen is 10 seconds or less.
- the total flaming combustion time of all the specimens in each set is 50 seconds or less.
- the total of the flaming combustion time and the glowing combustion time of each specimen after the second application is 30 seconds or less.
- the cotton is not ignited by the flaming drip.
- the glowing or the flaming combustion does not reach the holding clamp.
- Example 1 The present invention is hereinbelow described specifically on the basis of Examples. However, the present invention is by no means limited to the Examples.
- Example 1 Then, the composition No. 1 was held by two ultraviolet transmitting polyethylene terephthalate liners (PET liners) treated with silicone, and the composition was subjected to calendering to give a sheet having a thickness of 0.14 mm (excluding the thickness of the PET liners).
- PET liners polyethylene terephthalate liners
- ultraviolet radiation was irradiated at an intensity of 0.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain an acrylic thermally conductive sheet layer having a thickness of 0.15 mm (first acrylic thermally conductive sheet layer (first layer)) which was held between two the PET liners.
- One of the PET liners was peeled to expose the first acrylic thermally conductive sheet layer (first layer)).
- the first acrylic thermally conductive sheet layer (first layer) had an Asker C hardness of 80, which was measured by the method described later. Then, the composition No. 2 was held between a PET liner treated with silicone and the above first acrylic thermally conductive sheet layer (first layer), and the composition was subjected to calendering to give a multi-layer sheet having a total thickness of 0.46 mm (excluding the thickness of the PET liners).
- ultraviolet radiation was irradiated at an intensity of 2.0 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to form an acrylic thermally conductive sheet layer (second acrylic thermally conductive sheet layer (second layer)) to obtain a multi-layered thermally conductive sheet having a thickness of 0.5 mm (Example l) which was held between two PET liners.
- the second acrylic thermally conductive sheet layer (second layer) had an Asker C hardness of 25.
- Example 2 An acrylic thermally conductive sheet layer (first layer) having a thickness of 0.15 mm and held between two PET liners was obtained in the same manner as in Example 1 except that the composition No. 3 was used. Then, the composition No. 2 was held between a PET liner treated with silicone and the above first layer, and the composite was subjected to calendering to give a multi-layer sheet having a thickness of 0.46 mm (excluding the thickness of the PET liners). In this state, ultraviolet radiation was irradiated at an intensity of 4.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain a multi-layered thermally conductive sheet having a thickness of 0.5 mm (Example 2) which was held between two PET liners.
- the first layer comprising the composition No. 3 and the second layer comprising the composition No. 2 had an Asker C hardness of 20 and 66, respectively.
- Example 3 The composition No. 4 was held between a PET liner treated with silicone and the above first layer comprising the composition No. 1 and obtained in Example 1, and the composition was subjected to calendering to give a multi-layer sheet having a thickness of 0.74 mm (excluding the thickness of the PET liners).
- ultraviolet radiation was irradiated at a strength of 4.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain a multi-layered thermally conductive sheet having a thickness of 0.8 mm (Example 3) which is and held between two PET liners.
- the second layer comprising the composition No. 4 had an Asker C hardness of 15.
- Example 4 The composition No. 5 was held between a PET liner treated with silicone and the above first layer comprising the composition No. 1 and obtained in Example 1, and the composition was subjected to calendering to give a multi-layer sheet having a thickness of 0.74 mm (excluding the thickness of the PET liner).
- the obtained molded sheet was heated at 140 0 C for 15 minutes in an oven to obtain a multi-layered thermally conductive sheet having a thickness of 0.8 mm (Example 4) which was held between two PET liners.
- the second layer comprising the composition No. 5 had an Asker C hardness of 37.
- Example 5 An acrylic thermally conductive sheet layer (first layer) having a thickness of 0.15 mm and held between two PET liners was obtained in the same manner as in Example 1 except that the composition No. 6 was used. Then, the composition No. 7 was held between a PET liner treated with silicone and the above first layer, and the composition was subjected to calendering to give a sheet having a thickness of 0.92 mm (excluding the thickness of the PET liners). The obtained molded sheet was heated at 140 °C for 15 minutes with an oven to obtain a multi-layered thermally conductive sheet having a thickness of 1.0 mm (Example 5) which was held between two PET liners.
- the first layer comprising the composition No. 6 and the second layer comprising the composition No. 7 had an Asker C hardness of 78 and 29, respectively.
- Example 6 The composition No. 4 was held by two PET liners treated with silicone, and the composition was subjected to calendering to give a sheet having a thickness of 0.46 mm (excluding the thickness of the PET liners). In this state, ultraviolet radiation was irradiated at a strength of 4.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain the second layer having a thickness of 0.5 mm which was held between two PET liners.
- the second layer comprising the composition No. 4 had an Asker C hardness of 12. Further, the second layer comprising the composition No.
- Example 4 was superposed on the multi-layered thermally conductive sheet obtained in Example 1 in such a manner that the second layer is brought into contact with the surface on the side of the first layer (i.e., layer of high hardness) comprising the composition No. 1, followed by a lamination treatment to obtain a multi-layered thermally conductive sheet having a thickness of 1.0 mm (excluding the thickness of the PET liners) (Example 6).
- Comparative Example 1 The composition No. 1 was held by two PET liners treated with silicone, and the composition was subjected to calendering to give a sheet having a thickness of 0.46 mm (excluding the thickness of the PET liners).
- ultraviolet radiation was irradiated at an intensity of 0.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain a thermally conductive sheet having a thickness of 0.5 mm and an Asker hardness of 88, which was held between two PET liners.
- Comparative Example 2 There was obtained a thermally conductive sheet having a thickness of 0.5 mm and an Asker hardness of 39 (Comparative Example 2), which was held between two PET liners in the same manner as in the above Comparative Example 1 except that the composition No. 2 was used in place of the composition No. 1.
- Comparative Example 3 The first layer having a thickness of 0.15 mm and held between two PET liners was obtained in the same manner as in Example 1 except that the composition No. 8 was used. Then, the composition No. 2 was held between a PET liner treated with silicone and the above first layer, and the composition was subjected to calendering to give a sheet having a thickness of 0.46 mm (excluding the thickness of the PET liners). In this state, ultraviolet radiation was irradiated at an intensity of 0.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain a multi-layered thermally conductive sheet having a thickness of 0.5 mm (Comparative Example 3) which was held between two PET liners.
- the first layer comprising the composition No. 8 and the second layer comprising the composition No. 2 had an Asker C hardness of 39 and 53, respectively.
- Comparative Example 4 The first layer having a thickness of 0.15 mm and held between two PET liners was obtained in the same manner as in Example 1 except that the composition No. 9 was used. Then, the composition No. 2 was held between a PET liner treated with silicone and the above first layer, and the composition was subjected to calendering to give a sheet having a thickness of 0.74 mm (excluding the thickness of the PET liners). In this state, ultraviolet radiation was irradiated at a strength of 0.5 mW/cm 2 for 10 minutes with a low pressure mercury lamp from both sides through the liners to obtain a multi-layered thermally conductive sheet having a thickness of 0.8 mm (Comparative Example 4) which was held between two PET liners.
- the first layer comprising the composition No. 9 and the second layer comprising the composition No. 2 had an Asker C hardness of 84 and 46, respectively.
- Comparative Example 5 The composition No. 7 was held by two PET liners treated with silicone, and the composition was subjected to calendering to give a sheet having a thickness of 0.92 mm (excluding the thickness of the PET liners). The obtained molded sheet was heated at 140 0 C for 15 minutes with an oven to obtain a thermally conductive sheet having a thickness of 1.0 mm and an Asker C hardness of 29 (Comparative Example 5) which was held between two PET liners. Table 1
- Flammabilitv (UL-94 flammability test) Flame retardancy was evaluated in accordance with UL Flameproof Test Standard UL-94 "flammability test of plastic materials for devices and electronic parts".
- Hardness A sample for the hardness test was prepared by laminating thermally conductive sheets to be tested so that the sample may have a thickness of 10 mm or a minimum thickness above 10 mm. The sample was measured for hardness under a load of 1 kg with an Asker C hardness meter. Incidentally, regarding the second acrylic thermally conductive sheet layer (low hardness layer) of the multi-layered conductive sheet in each Example, a sample for measuring hardness was obtained by slicing off the first acrylic thermally conductive sheet layer (high hardness layer).
- Compressive stress N/cm 2
- a thermally conductive sheet having the size of 25 mm X 25 mm was measured, as compressive stress, a peak pressure when the initial thickness is reduced by 20% by compression at a speed of 5 mm/min. with a precision universal tester (commercial name: Autograph produced by Shimadzu Corporation).
- ⁇ (W/(m • K)) Um) I (R 2 L(K- m 2 /W) - RL(K- m 2 /W))
- Handleabilitv A thermally conductive sheet held between two PET liners was cut to have a size of 20 mm X 100 mm together with the PET liners to obtain a sample for evaluation. Before and after the PET liners on both surfaces of the sheet were peeled off, the thermally conductive sheet was measured for the size to check whether or not deformation occurred (change in size). The standard of the evaluation is shown below. Incidentally, the smaller the deformation (change in size) is, the higher the handleability is.
- the multi-layered thermally conductive sheets of the Examples have flame retardancy corresponding to V-O without having impaired flexibility, and it is expected that the multi-layered thermally conductive sheets of the Examples exhibit superior adhesion between objects on which the sheet is disposed. Further, the multi-layered thermally conductive sheets of the Examples are excellent in handleability and have sufficient thermal conductivity.
- a multi-layered thermally conductive sheet of the present invention has superior thermal conductivity and flame retardancy as well as superior handleability and adhesion even without using any of a halogen-containing flame retardant, red phosphorous, and silicone resin.
- a multi-layered thermally conductive sheet of the present invention is suitable as a thermally conductive sheet to be used in such a state that the sheet is disposed between a heat release body such a heat sink and heat generating parts such as electronics and electronic parts including an integrated circuit (IC).
- IC integrated circuit
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- 2005-05-17 US US11/568,237 patent/US7709098B2/en active Active
- 2005-05-17 WO PCT/US2005/017283 patent/WO2006001943A2/en active Application Filing
- 2005-05-17 CN CNB2005800192763A patent/CN100540295C/en active Active
- 2005-05-17 KR KR1020067026222A patent/KR101202525B1/en active IP Right Grant
- 2005-06-01 TW TW094118059A patent/TWI369769B/en not_active IP Right Cessation
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
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EP3093832A1 (en) * | 2010-09-06 | 2016-11-16 | Mitsubishi Plastics, Inc. | Image display device |
EP2674464A4 (en) * | 2011-02-11 | 2017-01-25 | Nitto Denko Corporation | Flame-retardant thermally-conductive adhesive sheet |
EP2733181A4 (en) * | 2011-07-13 | 2015-08-05 | Posco | Resin composition for a surface treatment, and steel sheet coated with same |
US9376576B2 (en) | 2011-07-13 | 2016-06-28 | Posco | Resin composition for a surface treatment, and steel sheet coated with same |
Also Published As
Publication number | Publication date |
---|---|
TWI369769B (en) | 2012-08-01 |
CN100540295C (en) | 2009-09-16 |
US7709098B2 (en) | 2010-05-04 |
KR101202525B1 (en) | 2012-11-16 |
JP5175022B2 (en) | 2013-04-03 |
KR20070033995A (en) | 2007-03-27 |
CN1968810A (en) | 2007-05-23 |
TW200610115A (en) | 2006-03-16 |
JP2005354002A (en) | 2005-12-22 |
WO2006001943A3 (en) | 2006-02-02 |
US20070231552A1 (en) | 2007-10-04 |
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