High transparency silica-titania glass beads, method for making, and light transmission epoxy resin compositions

A method for preparing high transparency silica-titania glass beads, comprising the steps of:

• hydrolyzing and polycondensing a silicon alkoxide and a titanium alkoxide to form a silica-titania sol,
• forming a gel from the silica-titania sol,
• drying the gel,
• grinding the dry gel to a predetermined particle size, and
• thereafter heating the ground gel at a temperature of 1,050.degree. to 1,250.degree. C. into a sintered glass.

A method for preparing high transparency silica-titania glass beads, comprising the steps of:

• hydrolyzing and polycondensing a silicon alkoxide and a titanium alkoxide to form a silica-titania sol,
• forming a gel from the silica-titania sol,
• drying the gel,
• heating the dry gel at a temperature of 1,050.degree. to 1,150.degree. C. into a sintered glass, and
• thereafter grinding the sintered glass.

A light transmission epoxy resin composition comprising

• (A) a curable epoxy resin,
• (B) a curing agent, and
• (C) silica-titania glass beads having a linear transmittance of at least 70% as measured at a wavelength in the range of from 900 nm to 600 nm by a linear transmittance measurement method, said method comprising
• mixing a bisphenol type epoxy resin of the general formula (1) shown below or a novolak type epoxy resin of the general formula (2) shown below with phenylglycidyl ether to form a solution having a difference in refractive index from the silica-titania glass beads within .+-.0.002,
• mixing the solution with the silica-titania glass beads which have been ground to a mean particle diameter of 5 to 30 .mu.m in a weight ratio of 1:1, and
• measuring the linear transmittance of the mixture across a light path length of 1 mm,
• wherein formula (1) is ##STR4## where n is an integer of from 0 to 10, and formula (2) is ##STR5## where n is an integer of from 0 to 10.