TRANSPARENT POLYCRYSTALLINE SPINEL SUBSTRATE, PROCESS FOR PRODUCING THE SUBSTRATE, AND OPTICAL ARTICLE USING THE SUBSTRATE

摘要

Disclosed is a transparent polycrystalline spinel substrate characterized in that the transmittance in a crossed Nichol system as measured under conditions of thickness 1 mm and wavelength 450 nm is less than or equal to 0.005%. The transparent polycrystalline spinel substrate, even when used as an optical article, is free from blurring or contrast of images. There is also provided a process for producing a transparent polycrystalline spinel substrate, comprising the steps of providing a spinel powder, molding the spinel powder to produce a spinel molded product, sintering the spinel molded product to produce a spinel sintered compact, and subjecting the spinel sintered compact to HIP to produce a spinel polycrystal. A receiver for a rear-projection television with the transparent polycrystalline spinel substrate and a liquid crystal projector with the transparent polycrystalline spinel substrate are also provided.