Curable silicone composition and cured product thereof

A curable silicone composition comprising:

• (A) an epoxy-functional silicone resin represented by the following average unit formula:
• (R13SiO1/2)a (R12SiO2/2)b (R1SiO3/2)c(SiO4/2)d
• wherein each R1 is the same or different organic group selected from a C1-6 monovalent aliphatic hydrocarbon group, a C6-10 monovalent aromatic hydrocarbon group, and a monovalent epoxy-substituted organic group, provided that at least about 15 mol % of the total R1 are the C6-10 monovalent aromatic hydrocarbon groups;
• and “a”, “b”, “c” and “d” are numbers that satisfy the following conditions:
• 0≤a<0.4, 0<b<0.5, 0<c<1, 0≤d<0.4, 0.1≤b/c≤0.6, and a+b+c+d=1;
• and about 2 to about 30 mol % of the total siloxane units have the monovalent epoxy-substituted organic groups;
• (B) an epoxy-functional silicone represented by the following general formula:
• X1-R22SiO(SiR22O)mSiR22-X1
• wherein each R2 is the same or different organic group selected from a C1-6 monovalent aliphatic hydrocarbon group and a C6-10 monovalent aromatic hydrocarbon group;
• each X1 is the same or different group selected from a monovalent epoxy-substituted organic group and an epoxy-functional siloxy group represented by the following general formula:
• X2-R32SiO(SiR32O)xSiR32-R4-
• wherein each R3 is the same or different C1-6 monovalent aliphatic hydrocarbon group;
• R4 is a C2-6 alkylene group;
• X2 is a monovalent epoxy-substituted organic group;
• “x” is a number of from about 0 to about 5;
• and “m” is a number of from about 0 to about 100, in an amount of from about 5 mass % to about 40 mass % of the total mass of components (A), (B) and (C);
• and
• (C) a mixture of cationic photoinitiators comprising:
• (C-1) an iodonium salt type cationic photoinitiator;
• and
• (C-2) a sulfonium salt type cationic photoinitiator;
• in an amount of from about 0.2 mass % to about 2 mass % of the total mass of components (A), (B) and (C);
• wherein component (C-1) comprises (c1) 4-isopropyl-4′-methyldiphenyliodonium tetrakis(pentafluorophenyl) borate salt represented by the following formula:
• and
• wherein component (C-2) comprises at least one of (c2) and (c3):
• (c2) a triarylsulfonium borate salt represented by the following formula:
• where each R5 is the same or different alkyl group, aryl group, alkoxy group, or heteroatom-containing organic group, and X− is SbF6-, AsF6-, PF6-, BF4-, B(C6F5)4-, HSO4-, ClO4-, CF3SO3-, nonafluorobutanesulfonate, tris (pentafluoroethyl) trifluorophosphate, tris (hepta fluoropropyl) trifluorophosphate, tris (nonafluoroisobutyl) trifluoro phosphate, or bis (nonafluorobutyl isobutyl) tetrafluoro phosphate;
• (c3) a triarylsulfonium tetrakis(pentafluorophenyl) borate salt represented by the following formula