To obtain a compound useful not only as an optical sensitizer for a silicon coating, but also as a fluorescent dye marker by binding a fluorescent substituting group to a high molecular weight silicone with a C-O-C bond.

This compound having a fluorecent property, an optical sensitizing property or both of them simultaneously, has the structural formula: MDnDEm-pD*pM [M is R3SiO1/2 and R2ESiO1/2 (R is independently a monovalent hydrocarbon; E is an epoxide functioned substituting group selected from among an epoxyether substituting group of the formula: C6H11O2 or an alkylcyclohexeneoxide substituting group; D is the formula: R2Si1/2; DE is the formula: RESiO2/2; D* is a reaction product of a compound selected from among R'COOH, (R'CO)2O (R' is a fluorescent substituting group), etc., with DE; (n), (m), (p) are integers, and (n+m+P) is approximately 10-2000]. As the fluorescent substituting group, dansyl, anthracenyl cumarinyl, xanthanyl, etc., groups are cited.