TRANSPARENT MATERIAL HAVING ANTIREFLECTION FILM

PURPOSE:To improve adhesive strength and transmittance by providing two layers of antireflection films on the surface of a transparent base material, making the refractive index of the 1st layer larger than that of the 2nd layer, and making the optical film thicknesses of the 1st and 2nd layers 1/4 times the light wavelength or odd times thereof. CONSTITUTION:An alcohol soln. of hydrolyzate or gamma-glycidoxypropyl trimethoxysilane, tetra-n-butyl titanate, etc. is coated on the surface of a transparent lens (refractive index n=1.50) of polycarbonate or the like, and is cured, whereby the antireflection film of the 1st layer is obtd. The refractive index n1 thereof is regulated to 1.73 and the film thickness d1 to 70nm. The antireflection film of the 2nd layer smaller than the refractive index of the 1st layer is provided. The refractive index n1 of the 2nd layer is regulated to 1.48 and the film thickness d2 to 117nm. The optical film thicknesses of the 1st and 2nd layers are defined as n1d1, n2d2 and the conditions of the inequalitiesI, II are satisfied. Thus the adhesive strength of the antireflection films is improved, and the generation of ghosts, flares, etc. is eliminated.