A composition for an optical waveguide is cured into a sheet to give a cured product. A difference in light transmittance with respect to light having a wavelength of 450 nm is 15% or less between this cured product and this cured product after retention in atmosphere at 175 C. for 40 hours, the light transmittance being calculated in terms of the cured product at a thickness of 50 m.

A composition for an optical waveguide is cured into a sheet to give a cured product. A difference in light transmittance with respect to light having a wavelength of 450 nm is 15% or less between this cured product and this cured product after retention in atmosphere at 175 C. for 40 hours, the light transmittance being calculated in terms of the cured product at a thickness of 50 m.

A composition for an optical waveguide is cured into a sheet to give a cured product. A difference in light transmittance with respect to light having a wavelength of 450 nm is 15% or less between this cured product and this cured product after retention in atmosphere at 175 C. for 40 hours, the light transmittance being calculated in terms of the cured product at a thickness of 50 m.

A composition for an optical waveguide is cured into a sheet to give a cured product. A difference in light transmittance with respect to light having a wavelength of 450 nm is 15% or less between this cured product and this cured product after retention in atmosphere at 175 C. for 40 hours, the light transmittance being calculated in terms of the cured product at a thickness of 50 m.

The present invention relates to a thermosetting resin composition, and a prepreg and a printed circuit board using the same and, more particularly, to a thermosetting resin composition, and a prepreg and a printed circuit board using the same, wherein the thermosetting resin composition can be used for a printed circuit board which simultaneously has excellent low dielectric loss characteristics, good moisture absorption and heat resistance, low thermal expansion characteristics, and thermal stability.

A composition for an optical waveguide is cured into a sheet to give a cured product. A difference in light transmittance with respect to light having a wavelength of 450 nm is 15% or less between this cured product and this cured product after retention in atmosphere at 175 C. for 40 hours, the light transmittance being calculated in terms of the cured product at a thickness of 50 m.

A composition for an optical waveguide is cured into a sheet to give a cured product. A difference in light transmittance with respect to light having a wavelength of 450 nm is 15% or less between this cured product and this cured product after retention in atmosphere at 175 C. for 40 hours, the light transmittance being calculated in terms of the cured product at a thickness of 50 m.

A Formula of a phosphorous fire-retardant hardener having fire-retardant and heat-resistant properties as well as a low-dielectric constant. With a preparation of glass-fiber laminated board, the hardener meets UL-94V fire-retardant requirements and has a dielectric constant 5 of 4.0 (1 GHz).

A Formula of a phosphorous fire-retardant hardener having fire-retardant and heat-resistant properties as well as a low-dielectric constant. With a preparation of glass-fiber laminated board, the hardener meets UL-94V fire-retardant requirements and has a dielectric constant 5 of 4.0 (1 GHz).

There is provided a photocurable and thermosetting resin composition which suppresses decrease of adhesive strength in a moisture resistance test of the cured resin composition, and has a sufficiently long pot life. The resin composition includes (A) an acrylic resin, (B) a multifunctional nitrogen-containing heterocyclic compound represented by a specific chemical formula, (C) a latent curing agent, (D) a radical polymerization inhibitor, and (E) an anionic polymerization retarder. The resin composition preferably further includes (F) a compound having a glycidyl group, other than the acrylic resin.