A composite composition comprising a) a hydrolysate and/or condensate of a1) at least one hydrolysable alkylsilane having at least one alkyl group, a2) at least one hydrolysable arylsilane having at least one aryl group or at least one hydrolysable alkylarylsilane having at least one alkylaryl group, wherein said hydrolysable arylsilane or alkylarylsilane is selected from compounds represented by the general formula R' a SiX (4-a) wherein R', which may be the same or different, is a non-hydrolysable substituent selected from alkyl, aryl, and alkylaryl, at least one of which is an aryl or alkylaryl group, X is a hydrolysable substituent, and a is an integer from 1 to 3; and a3) at least one hydrolysable silane containing an epoxy group, wherein said hydrolysable silane containing an epoxy group is selected from compounds represented by the general formula RcSi b X (3-b) wherein Rc is a non-hydrolysable substituent having an epoxy group, R is a non-hydrolysable substituent, X is a hydrolysable substituent, and b is an integer of from 0 to 2; and b) at least one organic compound having at least 2 epoxy groups, which is in solid state at room temperature, and c) a cationic photoinitiator, and wherein at least one of three silanes (a1,a2,a3) contains two hydrolysable substituent groups; and wherein at least one hydrolysable silane for said hydrolysate and/or condensate has 3 hydrolysable substituents and wherein in said hydrolysate and/or condensate the abundance ratio of the total sum of T0 and T1 is less than 50 %, and the abundance ratio of T3 is more than 15 %, wherein T0: a Si atom that is not bonded to another silane molecule; T1: a Si atom that is bonded to one silane molecule through siloxane bond; T2: a Si atom which is bonded to two silane molecules through siloxane bond; and T3: a Si atom that is bonded to three silane molecules through siloxane bond; and the abundance ratio of TX (%) = TX / (T0 + T1 +T2 +T3) x 100 %, wherein X = 0, 1, 2 or 3; and wherein from 15 to 60 mol-% of at least one hydrolysable alkylsilane a1), from 30 to 80 mol-% of at least one hydrolysable arylsilane or alkylarylsilane a2), and from 1 to 60 mol-% of at least one hydrolysable silane containing an epoxy group a3), based on the total amount of hydrolysable compounds, are used for the hydrolysate and/or condensate. a) a hydrolysate and/or condensate of a1) at least one hydrolysable alkylsilane having at least one alkyl group, a2) at least one hydrolysable arylsilane having at least one aryl group or at least one hydrolysable alkylarylsilane having at least one alkylaryl group, wherein said hydrolysable arylsilane or alkylarylsilane is selected from compounds represented by the general formula R' a SiX (4-a) wherein R', which may be the same or different, is a non-hydrolysable substituent selected from alkyl, aryl, and alkylaryl, at least one of which is an aryl or alkylaryl group, X is a hydrolysable substituent, and a is an integer from 1 to 3; and a3) at least one hydrolysable silane containing an epoxy group, wherein said hydrolysable silane containing an epoxy group is selected from compounds represented by the general formula RcSi b X (3-b) wherein Rc is a non-hydrolysable substituent having an epoxy group, R is a non-hydrolysable substituent, X is a hydrolysable substituent, and b is an integer of from 0 to 2; and a1) at least one hydrolysable alkylsilane having at least one alkyl group, a2) at least one hydrolysable arylsilane having at least one aryl group or at least one hydrolysable alkylarylsilane having at least one alkylaryl group, wherein said hydrolysable arylsilane or alkylarylsilane is selected from compounds represented by the general formula R' a SiX (4-a) wherein R', which may be the same or different, is a non-hydrolysable substituent selected from alkyl, aryl, and alkylaryl, at least one of which is an aryl or alkylaryl group, X is a hydrolysable substituent, and a is an integer from 1 to 3; and a3) at least one hydrolysable silane containing an epoxy group, wherein said hydrolysable silane containing an epoxy group is selected from compounds represented by the general formula RcSi b X (3-b) wherein Rc is a non-hydrolysable substituent having an epoxy group, R is a non-hydrolysable substituent, X is a hydrolysable substituent, and b is an integer of from 0 to 2; and b) at least one organic compound having at least 2 epoxy groups, which is in solid state at room temperature, and c) a cationic photoinitiator, and T0: a Si atom that is not bonded to another silane molecule; T1: a Si atom that is bonded to one silane molecule through siloxane bond; T2: a Si atom which is bonded to two silane molecules through siloxane bond; and T3: a Si atom that is bonded to three silane molecules through siloxane bond;