Curable silicone composition, curable hot-melt silicone, and optical device

A curable hot-melt silicone that is non-flowable at 25° C. and that has a melt viscosity at 100° C. of 5000 Pa·s or less, wherein the curable hot melt silicon is formed by subjecting a curable silicone composition to a hydrosilylation reaction to a degree that does not form a cured product, and wherein the curable silicone composition comprises:

• (A) 100 parts by mass of an organopolysiloxane represented by the average unit formula:
• (R13SiO1/2)a(R22SiO2/2)b(R3SiO3/2)c(SiO4/2)d(R4O1/2)e
• wherein,
• R1, R2, and R3 are the same or different and are each a phenyl group, an alkyl group having from 1 to 6 carbons, or an alkenyl group having from 2 to 6 carbons;
• provided that, 40 mol % or less of R1, 30 mol % or greater of R2, and 10 mol % or less of R3 are alkenyl groups, and 30 to 60 mol % of the total of R1, R2, and R3 are phenyl groups;
• R4 is a hydrogen atom or an alkyl group having from 1 to 6 carbons;
• and
• “a” is a number of 0 to 0.2, “b” is a number of 0.2 to 0.5, “c” is a number of 0 to 0.8, “d” is a number of 0 to 0.5, “e” is a number of 0 to 0.1, “c +d” is a number of 0.3 to 0.8, and “a+b+c+d” is 1;
• (B) from 0 to 40 parts by mass of an organopolysiloxane represented by the average unit formula:
• (R53SiO1/2)f(R52SiO2/2)g(R5SiO3/2)h(SiO4/2)i(R6O1/2)j
• wherein,
• R5 are the same or different and are each a phenyl group, an alkyl group having from 1 to 6 carbons, or an alkenyl group having from 2 to 6 carbons;
• provided that, 10 to 70 mol % of all R5 are phenyl groups, and at least one of all R5 is an alkenyl group;
• R6 is a hydrogen atom or an alkyl group having from 1 to 6 carbons;
• and
• “f” is a number of 0.01 to 0.3, “g” is a number of 0.4 to 0.99, “h” is a number of 0 to 0.2, “i” is a number of 0 to 0.2, “j” is a number of 0 to 0.1, “h+i” is a number of 0 to 0.2, and “f+g+h+i” is 1;
• (C) an organohydrogenpolysiloxane represented by the average composition formula:
• R7k Hl SiO(4-k-l)/2
• wherein,
• R7 is a phenyl group or an alkyl group having from 1 to 6 carbons;
• provided that, 10 to 70 mol % of all R7 are phenyl groups;
• “k” is a number of 1.0 to 2.5, “l” is a number of 0.01 to 0.9, and “k+l” is a number of 1.5 to 3.0;
• and
• wherein component (C) is present in an amount such that silicon atom-bonded hydrogen atoms in component (C) is from 0.5 to 2.0 mol per 1 mol of the total alkenyl groups in components (A) and (B);
• and
• (D) a hydrosilylation catalyst in an amount sufficient to accelerate hydrosilylation reaction of the composition.