Epoxy-functional radiation-curable composition containing an epoxy-functional siloxane oligomer for enhanced film retention and adhesion during solvent development

A method of preparing a flexible planar optical waveguide assembly, comprising the steps of:

• (i) applying a first silicone composition to a surface of a substrate to form a first silicone film, the first silicone composition comprising
• (A) an epoxy-functional organopolysiloxane resin having the average unit formula
• (R1R2R3SiO1/2)a(R4R5SiO2/2)b(R6SiO3/2)c(SiO4/2)d (I)
• wherein R1, R2, R3, R4, R5, and R6 are organic groups independently selected from C1-6 monovalent aliphatic hydrocarbon groups, C6-10 monovalent aromatic hydrocarbon groups, and monovalent epoxy-substituted organic groups, 0≦a<0.4, 0<b<0.5, 0<c<1, 0≦d<0.4, 0.1≦b/c≦0.3, a+b+c+d=1, the resin has a number-average molecular weight of at least about 2000, at least about 15 mol % of the organic groups are C6 to C10 monovalent aromatic hydrocarbon groups, and about 2 to about 50 mol % of siloxane units have epoxy-substituted organic groups,
• (B) an epoxy-functional organosiloxane oligomer having an average of at least two epoxy-substituted organic groups per molecule and a molecular weight not greater than about 1500,
• (C) a cationic photoinitiator, and
• (D) optionally, an organic solvent;
• and
• (ii) exposing at least one selected region of the first silicone film to radiation having a wavelength of from about 150 to about 800 nm to produce a partially exposed film having at least one exposed region and at least one non-exposed region;
• (iii) removing the non-exposed region of the partially exposed film with a developing solvent to form a patterned film;
• (iv) heating the patterned film for an amount of time sufficient to form at least one silicone core having a refractive index of from about 1.45 to about 1.60 at about 23° C. for light having a wavelength of about 589 nm;
• wherein the substrate has a refractive index less than the refractive index of the silicone core;
• (v) optionally covering the substrate and the silicone core with a second silicone composition to form a second silicone film;
• and
• (vi) optionally curing the second silicone film to form a clad layer, wherein the clad layer has a refractive index less than the refractive index of the silicone core.

A method of preparing a flexible planar optical waveguide assembly, comprising the steps of:

• (i) applying a first silicone composition to a surface of a substrate to form a first silicone film;
• (ii) curing the first silicone film to form a lower clad layer;
• (iii) applying a second silicone composition to the lower clad layer to form a second silicone film;
• (iv) exposing at least one selected region of the second silicone film to radiation having a wavelength of from about 150 to about 800 nm to produce a partially exposed film having at least one exposed region and at least one non-exposed region;
• (v) removing the non-exposed region of the partially exposed film with a developing solvent to form a patterned film;
• (vi) heating the patterned film for an amount of time sufficient to form at least one silicone core having a refractive index of from about 1.45 to about 1.60 at about 23° C. for light having a wavelength of 589 nm;
• wherein the lower clad layer has a refractive index less than the refractive index of the silicone core;
• (vii) optionally covering the lower clad layer and the silicone core with a third silicone composition to form a third silicone film;
• and
• (viii) optionally curing the third silicone film to form an upper clad layer, wherein the upper clad layer has a refractive index less than the refractive index of the silicone core,
• wherein at least one of the first silicone composition and the second silicone composition comprises, and the third silicon composition optionally comprises:
• (A) an epoxy-functional organopolysiloxane resin having the average unit formula
• (R1R2R3SiO1/2)a(R4R5SiO2/2)b(R6SiO3/2)c(SiO4/2)d (I)
• wherein R1, R2, R3, R4, R5, and R6 are organic groups independently selected from C1-6 monovalent aliphatic hydrocarbon groups, C6-10 monovalent aromatic hydrocarbon groups, and monovalent epoxy-substituted organic groups, 0≦a<0.4, 0<b<0.5, 0<c<1, 0≦d<0.4, 0.1≦b/c≦0.3, a+b+c+d=1, the resin has a number-average molecular weight of at least about 2000, at least about 15 mol % of the organic groups are C6 to C10 monovalent aromatic hydrocarbon groups, and about 2 to about 50 mol % of siloxane units have epoxy-substituted organic groups,
• (B) an epoxy-functional organosiloxane oligomer having an average of at least two epoxy-substituted organic groups per molecule and a molecular weight not greater than about 1500,
• (C) a cationic photoinitiator, and
• (D) optionally, an organic solvent.