Electromagnetic wave-shielding silicone composition

Abstract

To provide a silicone composition exhibiting superior workability, high thermal conductivity, and electromagnetic wave-shielding property.SOLUTION: An electromagnetic wave-shielding silicone composition characterized by containing: (A) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms per molecule; (B) aluminum powder; (C) an organohydrogenpolysiloxane with hydrogen atoms bonded to silicon atoms; (D) a hydrosilylation reaction catalyst; and a hydrolyzable methylpolysiloxane having three functional groups at one terminal end.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silicone composition having electromagnetic wave shielding properties. [Background technology]

[0002] With the development of information technology, electronic devices that use electromagnetic waves, such as wireless LAN, smartphones, portable information terminals, road information systems, and driving assistance systems, are becoming widespread in society. As the amount of information increases, the electromagnetic waves used are shifting to the high-frequency range.

[0003] On the other hand, as these electronic devices and technologies become more widespread, problems have arisen in that the electromagnetic waves they emit affect other electronic devices, causing them to malfunction. Therefore, electronic devices are required to minimize the unwanted emission of electromagnetic waves as much as possible, or to prevent malfunctions even when exposed to electromagnetic waves. Technologies are being developed to give devices shielding capabilities that absorb or reflect electromagnetic waves.

[0004] Many materials that shield electromagnetic waves use conductive metals. Conventional technologies generally use laminates in which a metal mesh (such as wire netting) is sandwiched between thermoplastic resins and processed into a plate or sheet shape. Recently, technologies have been developed that apply metal plating to a substrate, sandwich metal foil between thermoplastic resins, incorporate metal powder into thermoplastic resins, or apply ink containing metal powder in a pattern onto a substrate (Patent Document 1).

[0005] However, such laminates require complicated processes to be produced and are difficult to use in today's small, complex devices. On the other hand, a technology has been developed that blends metal powder into silicone, which has excellent fluidity.

[0006] These technologies use powders of highly conductive metals such as gold, silver, copper, and nickel, or powders coated or vapor-deposited with these metals to create compositions. However, these powders are expensive and difficult to fill highly into silicone, which means that electromagnetic waves easily penetrate the material, making it difficult to provide sufficient electromagnetic wave shielding.

[0007] On the other hand, aluminum metal powder is relatively inexpensive, lightweight, has high thermal conductivity, and has excellent filling properties, and is therefore widely used in thermally conductive silicone compositions (Patent Documents 2, 3, and 4).

[0008] These compositions are used for the purpose of flexibly conforming to heat-generating elements to promote heat dissipation and prevent deterioration or malfunction of the elements due to heat generation. However, although these techniques mention the thermal conductivity of aluminum powder and compositions containing it, they make no mention of the electromagnetic wave shielding performance. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-045946 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-059237 [Patent Document 3] International Publication No. 2014-115456 [Patent Document 4] Japanese Patent Application Publication No. 2018-012809 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the above problems, and has as its object to provide a silicone composition that is easy to work with, has high thermal conductivity, and exhibits electromagnetic wave shielding properties. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides: (A) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in each molecule; (B) aluminum powder, (C) an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom; (D) Hydrosilylation reaction catalyst and, (E) the following general formula (1) [ka] (In the formula, R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a positive number of 5 to 100. A hydrolyzable methylpolysiloxane having one terminal trifunctional group represented by the formula The present invention provides an electromagnetic wave shielding silicone composition comprising:

[0012] The electromagnetic wave shielding silicone composition of the present invention has fluidity and excellent workability, and can flexibly conform to complex structures containing elements, promoting heat dissipation while also shielding against undesired electromagnetic waves that can cause elements to malfunction.

[0013] The present invention further provides an electromagnetic wave shielding silicone composition comprising 100 parts by mass of component (A); component (B) in an amount that is 50 to 90% by volume, assuming the total of components (A) to (E) and other components to be 100% by volume; component (C) in an amount such that silicon-bonded hydrogen atoms of component (C) are 0.2 to 2.0 moles per mole of silicon-bonded alkenyl groups in component (A); component (D) in an amount that is 0.1 to 1,000 ppm, based on the mass of platinum atoms, relative to component (A); and component (E) in an amount of 10 to 1,000 parts by mass, relative to 100 parts by mass of components (A) and (C) combined.

[0014] Such an electromagnetic wave shielding silicone composition has excellent thermal conductivity and electromagnetic wave shielding performance. [Effects of the Invention]

[0015] As described above, the electromagnetic wave shielding silicone composition of the present invention has fluidity and excellent workability, and can flexibly conform to complex structures containing elements, promoting heat dissipation while also shielding against undesired electromagnetic waves that can cause elements to malfunction. DETAILED DESCRIPTION OF THE INVENTION

[0016] As described above, there has been a need for the development of a silicone composition that is easy to work with, has high thermal conductivity, and exhibits electromagnetic wave shielding properties.

[0017] As a result of extensive research into the above-mentioned problems, the present inventors discovered that the electromagnetic wave shielding silicone composition of the present invention has fluidity and excellent workability, and can flexibly conform to complex structures including elements, promoting heat dissipation while also shielding against undesired electromagnetic waves that can cause elements to malfunction, thereby completing the present invention.

[0018] That is, the present invention provides: (A) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in each molecule; (B) aluminum powder, (C) an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom; (D) Hydrosilylation reaction catalyst and, (E) the following general formula (1) [ka] (In the formula, R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a positive number of 5 to 100. A hydrolyzable methylpolysiloxane having one terminal trifunctional group represented by the formula The electromagnetic wave shielding silicone composition is characterized by comprising:

[0019] The present invention will be described in detail below, but the present invention is not limited thereto.

[0020] [(A) Organopolysiloxane] Component (A) is an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule. Component (A) is an organopolysiloxane that does not have alkoxy groups bonded to silicon atoms at the molecular chain terminals, but contains an average of more than one silicon-bonded alkenyl group per molecule, preferably 0.01 to 5 mol% of all organic groups. These silicon-bonded alkenyl groups may be present at either the molecular chain terminals or non-terminal positions, or both, within the organopolysiloxane molecule. However, because this improves flexibility, it is preferable for them to be present only at both molecular chain terminals.

[0021] There are no particular limitations on the molecular structure of the organopolysiloxane of component (A), and examples include linear and branched chain structures.

[0022] The kinematic viscosity of the organopolysiloxane of component (A) at 25°C is not particularly limited, but is typically 100 to 1,000,000 mm 2 This improves the stability of the electromagnetic wave shielding silicone composition of the present invention and facilitates mixing with components (B), (C), and (D), which will be described later. Therefore, a viscosity of 500 to 100,000 mm is preferred. 2 The kinematic viscosity is a value measured using an Ostwald meter at 25°C.

[0023] The alkenyl group bonded to the silicon atom typically has 2 to 10 carbon atoms, and preferably 2 to 6. Specific examples include a vinyl group, an allyl group, a 1-butenyl group, and a 1-hexenyl group, with a vinyl group being preferred from the viewpoints of ease of synthesis and economy.

[0024] The organic group bonded to the silicon atom other than the alkenyl group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group having usually 1 to 20, preferably 1 to 6 carbon atoms. Specific examples thereof include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, dodecyl group; aryl groups such as phenyl group; aralkyl groups such as 2-phenyl ethyl group, 2-phenyl propyl group; and chloromethyl group, 3,3,3-trifluoropropyl group, etc. in which a part or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine atom, fluorine atom. Among these, from the viewpoints of ease of synthesis and economy, preferably, they are methyl group and phenyl group, and particularly, 80 mol% or more, especially 90 mol% or more of all the organic groups other than the alkenyl group bonded to the silicon atom are methyl groups.

[0025] (A) The organopolysiloxane of the component is represented by, for example, the following formula (2). R a R 2 b SiO (4-a-b) / 2 (2) (In the formula, R is independently an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, R 2 is independently an alkenyl group, a is a number of 0 ≦ a < 2.2, b is a number of 0 < b ≦ 2.2, provided that a + b is a number of 1.8 to 2.2)

[0026] In the above formula (2), the unsubstituted or substituted monovalent hydrocarbon group represented by R has usually 1 to 20, preferably 1 to 6 carbon atoms. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the organic group bonded to the silicon atom above.

[0027] In the above formula (2), the alkenyl group represented by R 2 has usually 2 to 10, preferably 2 to 6 carbon atoms. Specific examples thereof include those exemplified as the alkenyl group bonded to the silicon atom above.

[0028] The organopolysiloxane of component (A) is preferably represented by the following general formula (3), for example. [ka] (In the formula, R 3 are independently unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, and R 4 are independently unsubstituted or substituted monovalent hydrocarbon groups, provided that R 4 at least one of the groups is an alkenyl group, and m is a positive number of 50 to 3,000.

[0029] In the above formula (3), R 3 The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically has 1 to 20 carbon atoms, and preferably 1 to 6. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the above-mentioned silicon-bonded organic group other than the silicon-bonded alkenyl group.

[0030] In the above formula (3), R 4 The number of carbon atoms in the unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically ranges from 1 to 20, and preferably from 1 to 6. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the silicon-bonded organic group other than the silicon-bonded alkenyl group described above, and those exemplified as the silicon-bonded alkenyl group described above.

[0031] In the above formula (3), m is preferably an integer of 100 to 2,000.

[0032] Specific examples of the organopolysiloxane of component (A) include organopolysiloxanes represented by the following formulas (4) to (6), and preferably organopolysiloxanes represented by formulas (4) and (5).

[0033] [ka] (wherein m is the same as in formula (3) above.)

[0034] [ka] (In the formula, m1 and m2 are positive numbers that satisfy the relationship m=m1+m2.)

[0035] [ka] (In the formula, m1 and m3 are positive numbers that satisfy the relationship m=m1+m3.)

[0036] The organopolysiloxane of component (A) may use either a single compound, or a combination of two or more different compounds.

[0037] [(B) Aluminum powder] Component (B) is aluminum powder, which is a component that imparts thermal conductivity and electromagnetic shielding properties to the electromagnetic wave shielding silicone composition of the present invention. The aluminum powder may be spherical particles, scaly particles, or a mixture of particles of various shapes with no particular defined shape. The average particle size of the aluminum powder is not particularly limited, but is preferably 0.1 to 200 μm, more preferably 1 to 100 μm, from the viewpoints of packing ability and the uniformity, viscosity, and stretchability of the electromagnetic wave shielding silicone composition of the present invention. Here, the average particle size of the powder in the present invention is the cumulative average diameter D 50 (median diameter) and can be measured using a Microtrac MT3300EX or similar device manufactured by Microtrac Bell Corporation.

[0038] The total amount of component (B) blended is preferably 50 to 90% by volume, and more preferably 60 to 80% by volume, assuming the total of components (A) to (E) and the other components described below as 100% by volume. If the blending amount is within this range of 50 to 90% by volume, the electromagnetic shielding silicone composition of the present invention will have excellent thermal conductivity and electromagnetic shielding performance.

[0039] The surface of the aluminum powder (B) may be coated with an organic substance or ceramic, or metal vapor deposition may be applied. For example, it is well known that coatings such as silicon dioxide are applied to prevent scattering or fusion of the aluminum powder and improve compounding workability. It is also common to suppress unnecessary oxidation of aluminum by organic treatment or metal vapor deposition.

[0040] [(C) Organohydrogenpolysiloxane] Component (C) is an organohydrogenpolysiloxane having silicon-bonded hydrogen atoms, and preferably has at least two silicon-bonded hydrogen atoms per molecule, and more preferably 2 to 30. These silicon-bonded hydrogen atoms may be present at either the molecular chain terminals or non-terminal positions within the organohydrogenpolysiloxane molecule, or may be present in both locations.

[0041] There are no particular limitations on the molecular structure of the organohydrogenpolysiloxane of component (C), and examples include linear and branched chain structures.

[0042] The kinematic viscosity of the organohydrogenpolysiloxane of component (C) at 25°C is not particularly limited, but is typically 10 to 300 mm 2 / s, preferably 20 to 200 mm 2 The kinematic viscosity is a value measured using an Ostwald meter at 25°C.

[0043] The organic groups bonded to the silicon atom other than the hydrogen atom bonded to the silicon atom are usually unsubstituted or substituted monovalent hydrocarbon groups having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms. Specific examples thereof include alkyl groups such as methyl group, ethyl group, propyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group; cycloalkyl groups such as cyclopentyl group, cyclohexyl group; alkenyl groups such as vinyl group, allyl group; aryl groups such as phenyl group, tolyl group; aralkyl groups such as 2-phenylethyl group, 2-methyl-2-phenylethyl group; halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl group, 3-(perfluorobutyl)ethyl group, 2-(perfluorooctyl)ethyl group, p-chlorophenyl group, in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine atom and fluorine atom. Among these, from the viewpoints of ease of synthesis and economy, preferably, 90 mol% or more of all the organic groups other than the hydrogen atom bonded to the silicon atom are methyl groups. <000023 >

[0044] (C) The organohydrogenpolysiloxane is represented by, for example, the following formula (7). R 5 c H d SiO (4-c-d) / 2 (7) (In the formula, R< >is independently an unsubstituted or substituted monovalent hydrocarbon group, c is a number satisfying 0 ≦ c < 3, d is a number satisfying 0 < d ≦ 3, provided that c + d is a number satisfying 0 < c + d ≦ 3)

[0045] In the above formula (7), the unsubstituted or substituted monovalent hydrocarbon group represented by R 5 usually has 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon groups in the organic groups bonded to the silicon atom other than the hydrogen atom bonded to the silicon atom, and preferably include methyl group, ethyl group, propyl group, and phenyl group.

[0046] The organopolysiloxane of component (C) is preferably represented by the following general formula (8), for example. [ka] (wherein n is a positive number from 5 to 200, and R 6 are independently a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, provided that at least two are hydrogen atoms.

[0047] In the above general formula (8), R 6 The number of carbon atoms in the unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) is usually 1 to 20, and preferably 1 to 6. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the above-mentioned organic group bonded to a silicon atom other than a hydrogen atom bonded to a silicon atom.

[0048] In the above general formula (8), n is preferably a number from 10 to 100.

[0049] The amount of component (C) blended is preferably such that the number of silicon-bonded hydrogen atoms is 0.2 to 2.0 moles per mole of silicon-bonded alkenyl groups in component (A), more preferably 0.5 to 1.5 moles, and even more preferably 0.7 to 1.3 moles.

[0050] The organohydrogenpolysiloxane of component (C) may use either a single compound, or a combination of two or more different compounds.

[0051] [(D) Hydrosilylation reaction catalyst] Component (D) is a hydrosilylation catalyst that promotes the formation of a crosslinked structure by the addition reaction between components (A) and (C). Conventional hydrosilylation catalysts can be used as component (D), including, for example, platinum alone and platinum compounds such as chloroplatinic acid, platinum-olefin complexes, and platinum-alcohol complexes.

[0052] The amount of component (D) blended is preferably an amount that corresponds to 0.1 to 1,000 ppm, and more preferably 1 to 500 ppm, based on the mass of platinum atoms relative to component (A).

[0053] The hydrosilylation reaction catalyst of component (D) may use either a single compound, or a combination of two or more different compounds.

[0054] [(E) Hydrolyzable methylpolysiloxane] Component (E) is a hydrolyzable methylpolysiloxane having trifunctional groups at one end and represented by the following general formula (1). [ka] (In the formula, R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a positive number of 5 to 100.

[0055] Component (E) is a component that improves the wettability of component (B) with components (A) and (C), increasing the loading of component (B) and improving the thermal conductivity and electromagnetic shielding properties of the electromagnetic wave shielding silicone composition of the present invention.

[0056] In the above formula (1), R 1 is an alkyl group having 1 to 6 carbon atoms, examples of which include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group.

[0057] In the above formula (1), a is an integer between 5 and 100, and preferably between 10 and 60. If a is less than 5, oil bleeding from the electromagnetic shielding silicone composition of the present invention will be severe, reducing workability and reliability. If a is greater than 100, wettability will be insufficient.

[0058] The amount of the hydrolyzable methylpolysiloxane having trifunctional groups at one end (component (E)) added is preferably 10 to 1,000 parts by mass, more preferably 50 to 600 parts by mass, per 100 parts by mass of the total of components (A) and (C). When the amount is within the range of 10 to 1,000 parts by mass, the wettability of component (B) is improved.

[0059] [Other ingredients] <Reaction control agent> The electromagnetic wave shielding silicone composition of the present invention can be blended with a reaction inhibitor to suppress the catalytic activity of component (D). The reaction inhibitor inhibits the progress of the hydrosilylation reaction at room temperature, thereby extending shelf life and pot life. Known reaction inhibitors can be used, including acetylene compounds, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

[0060] The amount of the reaction inhibitor is preferably 0.1 to 5 mass % of component (A), more preferably 0.15 to 4 mass %. When the amount is 0.1 to 5 mass %, sufficient shelf life and pot life are obtained, and a sufficient curing rate is obtained.

[0061] To improve dispersibility of the reaction inhibitor in the electromagnetic wave shielding silicone composition, the reaction inhibitor may be diluted in an organic solvent such as toluene, xylene, or isopropyl alcohol.

[0062] <Non-reactive organopolysiloxane> Non-reactive organopolysiloxanes are organopolysiloxanes that do not contain reactive groups in the molecule and that allow for favorable adjustment of the viscosity and workability of the resulting electromagnetic wave shielding silicone composition. There are no particular restrictions on the molecular structure of these non-reactive organopolysiloxanes, and they may be linear or branched.

[0063] Examples of the reactive group include a hydrogen atom bonded to a silicon atom, a hydroxy group bonded to a silicon atom (i.e., a silanol group), an alkoxy group bonded to a silicon atom, an amino group, a carboxyl group, an epoxy group, a vinyl group, a mercapto group, and a methacryloxy group.

[0064] The non-reactive organopolysiloxane is not particularly limited, but dimethylpolysiloxane, phenylmethylpolysiloxane, etc. are preferred from an economical viewpoint.

[0065] The non-reactive organopolysiloxane preferably has a kinematic viscosity at 25°C of 10 to 1,000,000 mm 2 / s, more preferably 100 to 100,000 mm 2 The kinematic viscosity is a value measured using an Ostwald meter at 25°C.

[0066] The amount of non-reactive organopolysiloxane added is preferably 0 to 50 parts by mass, and more preferably 0 to 30 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0067] <Filler> The electromagnetic wave shielding silicone composition of the present invention may contain powders of metal oxides, metal nitrides, and metal hydroxides to improve adhesion to substrates and workability, specific examples of which include zinc oxide powder, aluminum oxide powder, magnesium oxide powder, silicon oxide powder, aluminum nitride powder, silicon nitride powder, and aluminum hydroxide powder.

[0068] These fillers are not particularly limited and may be, for example, spherical particles, scaly particles, or a mixture of particles of various shapes with no particular defined shape. The average particle size of these fillers is not particularly limited, but is preferably 0.1 to 100 μm, more preferably 0.2 to 30 μm, since a uniform composition can be obtained by co-blending with aluminum powder, which is component (B).

[0069] The amount of these fillers added is preferably 3 to 30% by volume, and more preferably 5 to 20% by volume, when the total of components (A) to (E) and other components is taken as 100% by volume. If the amount is within the range of 3 to 30% by volume, adhesion to the substrate and workability can be improved.

[0070] These fillers may be used alone or in combination of two or more.

[0071] In addition to the components described above, the electromagnetic wave shielding silicone composition of the present invention may also contain, as necessary, an adhesion aid to improve adhesion to substrates, an antioxidant to prevent deterioration, a heat resistance improver, and the like.

[0072] The electromagnetic wave shielding silicone composition of the present invention can be produced by mixing the specified amounts of the aforementioned components (A) to (E) in a mixer such as Trimix, Twinmix, or Planetary Mixer (all registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultra Mixer (registered trademark of mixers manufactured by Mizuho Kogyo Co., Ltd.), or Hivis Dispermix (registered trademark of mixers manufactured by Tokushu Kika Kogyo Co., Ltd.).

[0073] The electromagnetic wave shielding silicone composition of the present invention may be finished in the form of a one-component or two-component type depending on the application and process. In the case of a one-component type, the material may be cured after mounting, or the composition may be cured during the manufacturing process and then finished into a paste by applying an appropriate shear force. In the case of a two-component type, the composition may be divided into two parts so that they will form the electromagnetic wave shielding silicone composition of the present invention after mixing, and the mixing ratio may also be adjusted so that they will form the composition after mixing.

[0074] The viscosity of the resulting electromagnetic shielding silicone composition at 25°C, measured using a spiral viscometer, is preferably 10 to 1000 Pa·s, and more preferably 50 to 800 Pa·s. A viscosity in the range of 10 to 1000 Pa·s ensures good workability in the mounting process.

[0075] The resulting electromagnetic wave shielding silicone composition can be cured preferably at 20 to 180° C., and more preferably at 25 to 170° C. The curing time is not particularly limited, as it depends on the product form, packaging process, and composition, but is preferably 0.5 to 48 hours, and more preferably 1 to 24 hours. [Example]

[0076] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0077] [Examples 1 to 4, Comparative Example 1] The components shown below were used in the amounts shown in Table 1 to prepare the compositions of Examples 1 to 4 and Comparative Example 1.

[0078] [Component (A)] (A-1) Linear chain with vinyl groups at both ends, kinematic viscosity 600mm 2 / s dimethylpolysiloxane (Vi value: 0.015 mol / 100 g, specific gravity: 1.0. The kinematic viscosity is a value measured using an Ostwald meter at 25°C.). (A-2) Linear chain with vinyl groups at both ends, kinematic viscosity 30,000mm 2 / s dimethylpolysiloxane (Vi value: 0.00375 mol / 100 g, specific gravity: 1.0. The kinematic viscosity is a value measured using an Ostwald meter at 25°C.).

[0079] [(B) Component] (B-1) Spherical aluminum powder (average particle size: 1.5 μm, specific gravity: 2.70) (B-2) Spherical aluminum powder (average particle size: 20 μm, specific gravity: 2.70) (B-3) Flake aluminum powder (average particle size: 20 μm, specific gravity: 2.70)

[0080] [(C) component] (C-1): Organohydrogenpolysiloxane (H value: 0.0014 mol / g, specific gravity: 1.0) represented by the following average composition formula: [ka] (C-2) Organohydrogenpolysiloxane (H value: 0.001 mol / g, specific gravity: 1.0) represented by the following average composition formula: [ka]

[0081] [(D) component] (D-1) A solution in which a platinum-divinyltetramethyldisiloxane complex was dissolved in the same dimethylpolysiloxane as in (A-1) above (platinum atom content: 1 mass %, specific gravity: 1.0).

[0082] [(E) component] (E-1): Methylpolysiloxane (specific gravity: 1.0) terminated at one end with a trimethoxysilyl group, represented by the following formula: [ka]

[0083] [Other ingredients] [Component (F)]: Reaction inhibitor (F-1) 1-ethynyl-1-cyclohexanol (specific gravity: 1.0)

[0084] [Component (G)]: Metal oxide (G-1) Zinc oxide powder (average particle size: 0.25 μm, specific gravity: 5.67)

[0085] [(H) Ingredient]: Silver powder (H-1) Spherical silver powder (average particle size: 3μm, specific gravity: 10.50)

[0086] The prepared compositions of Examples 1 to 4 and Comparative Example 1 were measured for viscosity, thermal conductivity, and electromagnetic wave shielding performance as follows.

[0087] [viscosity] The viscosity of each composition was measured at 25° C. using a spiral viscometer. Measurements were carried out at 25° C. using a Malcom viscometer (Type PC-10AA) manufactured by Malcom Corporation.

[0088] [Thermal Conductivity] The thermal conductivity of each composition was measured at 25°C by the hot disc method in accordance with ISO 22007-2 using a TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0089] [Electromagnetic wave shielding performance] The electromagnetic wave shielding performance of each composition was evaluated in the frequency band from 3 GHz to 18 GHz using the coaxial tube method in accordance with ASTM D4935. The shielding effectiveness is expressed in dB, with a larger negative value indicating higher electromagnetic wave shielding performance. -3 dB indicates a 50% shielding effect, -5 dB indicates a 70% shielding effect, -10 dB indicates a 90% shielding effect, and -20 dB indicates a 99% shielding effect, with -5 dB or higher being considered excellent.

[0090] The compositions of Examples 1 to 4 and Comparative Example 1 were prepared by the following method. Components (A) to (H) were added in the amounts shown in Table 1.

[0091] [Example 1] Components (A), (B), (G), and (E) were placed in a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the amounts shown in Table 1 and mixed at 170°C for 1 hour. After cooling to room temperature (25°C), component (F) was added and mixed. Component (D) was then added and mixed, and finally component (C) was added and mixed until uniform, yielding the composition of Example 1. [Examples 2 and 3] Components (A), (B), and (E) were placed in a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the amounts shown in Table 1 and mixed at 170°C for 1 hour. After cooling to room temperature (25°C), component (F) was added and mixed. Component (D) was then added and mixed, and finally component (C) was added and mixed until uniform, yielding the compositions of Examples 2 and 3. [Example 4] <Composition a> Components (A), (B), and (E) were placed in a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the amounts shown in Table 1 and mixed at 150°C for 1 hour. After cooling to room temperature (25°C), component (D) was added and mixed until uniform, yielding composition a. <Composition b> Components (A), (B), and (E) were placed in a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the amounts shown in Table 1 and mixed at 150°C for 1 hour. After cooling to room temperature (25°C), component (F) was added and mixed until uniform, and finally component (C) was added and mixed until uniform, thereby obtaining composition b.

[0092] The obtained compositions of Examples 1 to 4 were measured for viscosity, thermal conductivity, and electromagnetic wave shielding performance as described above. The results are shown in Table 1. Regarding the compositions of Examples 1 to 3, the electromagnetic wave shielding performance was evaluated using sheets molded in a 1 mm thick mold and cured at 150°C for 1 hour. Regarding Example 4, composition a and composition b were mixed until homogeneous, then molded in a 1 mm thick mold and cured at 25°C for 24 hours, and the evaluation was performed using a sheet.

[0093] [Comparative Example 1] Components (A) and (H) were placed in a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the amounts shown in Table 1 and mixed at 70°C for 1 hour. After cooling to room temperature (25°C), component (F) was added and mixed. Component (D) was then added and mixed, and finally component (C) was added and mixed until uniform, yielding the composition of Comparative Example 1. The viscosity, thermal conductivity, and electromagnetic wave shielding performance of the obtained composition of Comparative Example 1 were measured as described above. The results are shown in Table 1. The electromagnetic wave shielding performance was evaluated using a sheet that was molded in a 1 mm thick mold and cured at 150°C for 1 hour.

[0094] [Table 1] *For convenience, the number of hydrogen atoms bonded to silicon atoms in component (C) per alkenyl group bonded to a silicon atom in component (A) is represented as H / Vi. **Although there is fluidity, the measured values ​​are unstable due to the occurrence of dilatancy.

[0095] The compositions of Examples 1 to 3 and the mixture of Example 4 all exhibited high fluidity and thermal conductivity. Furthermore, cured sheets made from the compositions of Examples 1 to 4 exhibited higher electromagnetic wave shielding properties than cured sheets made from the composition of Comparative Example 1, which used silver powder.

[0096] From the above, it was found that the electromagnetic wave-shielding silicone composition of the present invention has fluidity and excellent workability, and can flexibly conform to complex structures including elements, promoting heat dissipation while also blocking undesired electromagnetic waves that can cause elements to malfunction.

[0097] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. (A) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in each molecule; (B) aluminum powder, (C) an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom; (D) Hydrosilylation reaction catalyst and, (E) a compound represented by the following general formula (1): 【Chemical 1】 (In the formula, R 1 is an alkyl group having 1 to 6 carbon atoms, and a is a positive number from 5 to 100. A hydrolyzable methylpolysiloxane having one terminal trifunctional group represented by the formula:

1. An electromagnetic wave shielding silicone composition comprising:

2. 100 parts by mass of the component (A), the component (B) is present in an amount of 50 to 90% by volume when the total of the components (A) to (E) and other components is taken as 100% by volume; the component (C) in an amount such that the number of silicon-bonded hydrogen atoms in the component (C) is 0.2 to 2.0 moles per mole of silicon-bonded alkenyl groups in the component (A); The component (D) is added in an amount of 0.1 to 1,000 ppm by mass of platinum atoms relative to the component (A); and The component (E) is used in an amount of 10 to 1,000 parts by mass per 100 parts by mass of the total of the components (A) and (C).

2. The electromagnetic wave shielding silicone composition according to claim 1, which comprises:

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