| CPC C08L 79/08 (2013.01) [C08G 8/10 (2013.01); C08G 73/127 (2013.01); C08J 5/18 (2013.01); C08K 3/22 (2013.01); C08K 3/38 (2013.01); C08K 5/3492 (2013.01); C09D 179/08 (2013.01); H01L 23/295 (2013.01); H01L 23/31 (2013.01); H05K 1/03 (2013.01); C08J 2379/08 (2013.01); C08K 2003/2227 (2013.01); C08K 2003/385 (2013.01)] | 11 Claims | 

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               1. A resin sheet made using a resin composition comprising a thermosetting component (A) and a thermally conductive filler (C), wherein 
              the thermosetting component (A) comprises a first maleimide resin (A1), a second maleimide resin (A2), and a third maleimide resin (A3), 
                the first maleimide resin (A1) is a maleimide resin that is solid at a temperature of 25 degrees C. and has two or more maleimide groups in one molecule, at least a pair of the maleimide groups being bonded by a bonding group whose main chain comprises four or more methylene groups, 
                the second maleimide resin (A2) is represented by a formula (1) below or a formula (4) below, 
                the third maleimide resin (A3) is a maleimide resin that is liquid at a temperature of 25 degrees C. and has two or more maleimide groups in one molecule, at least a pair of the maleimide groups being bonded by a bonding group whose main chain comprises four or more methylene groups, 
                the first maleimide resin (A1) is represented by a formula (A1) below, 
                the third maleimide resin (A3) is represented by a formula (7) below, 
                a thermal diffusion rate of the resin sheet after being thermally cured is 1.0×10−6 m2/s or more, and 
                when a cross section (P) of the resin sheet taken by cutting the resin sheet in a vertical direction to a surface of the resin sheet is observed in an area (P1), a condition represented by a numerical formula (F1) below is satisfied, the area (P1) being defined by a square whose sides are four times as large as a thickness of the resin sheet, the area (P1) including two surfaces of the resin sheet, 
                0.25≤Ld/Lt≤1  (F1) 
                where Ld is a vertical length of a filler particle having a largest cross-sectional diameter in the vertical direction of the thermally conductive filler (C), and Lt is a length of the resin sheet in the vertical direction, 
              ![]() where, in the formula (A1): 
                n11 is an integer of 0 or more, and an average of n11 is in a range from 0.5 to 5, 
                L11 and L12 are each independently a substituted or unsubstituted alkylene group having 4 or more carbon atoms, in the alkylene group, at least one of —CH2— is optionally replaced with —CH2—O—, when a hydrogen atom of the alkylene group is replaced with a substituent, the substituent is an alkyl group having 1 to 14 carbon atoms or an alkoxy group having 1 to 14 carbon atoms, and the substituents are optionally bonded with each other to form an alicyclic or heterocyclic structure, and 
                X11 is each independently a group not having a substituted or unsubstituted alkylene group having 4 or more carbon atoms, 
              ![]() where, in the formula (1): 
                k is an integer of 1 or more, and an average of k is in a range from 1 to 10, 
                m1 and m2 are each independently an integer of 1 or more and 2 or less, and a sum of m1 and m2 is 3 or less, 
                n1 and n2 are each independently an integer of 0 or more and 4 or less, 
                R1 and R2 are each independently an alkyl group having 1 to 6 carbon atoms, 
              ![]() where, in the formula (4): 
                R3 to R6 are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, L1 is an alkylene group having 1 to 3 carbon atoms, L2 and L3 are each independently an alkylene group having 1 to 2 carbon atoms, or an arylene group having 6 to 10 carbon atoms, p and q are each independently 0 or 1, and a sum of the carbon atoms of L1, L2 and L3 in a form of an alkylene group or alkylene groups is 3 or less, 
              ![]() where, in the formula (7): 
                n is an integer of 0 or more, and an average of n is in a range from 0.5 to 5, 
                L4 and L5 are each independently a substituted or unsubstituted alkylene group having 4 or more carbon atoms, in the alkylene group, at least one of —CH2— is optionally replaced with —CH2—O—, when a hydrogen atom of the alkylene group is replaced with a substituent, the substituent is an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, and the substituents are optionally bonded to form an alicyclic structure, and 
                X is each independently a group not having a substituted or unsubstituted alkylene group having 4 or more carbon atoms. 
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