PRODUCTION OF THIN PLANAR GLASS AND PRODUCTION OF GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM AS WELL AS MAGNETIC RECORDING MEDIUM

PROBLEM TO BE SOLVED: To obtain thin planar glass having excellent flatness with good mass productivity by supplying fused glass between a lower die and an upper die held at a prescribed temp., press forming the fused glass, ending the press forming at the internal temp. higher than the glass transition temperature and ending the correction of warpage when the inside is above the glass transition point. SOLUTION: The fused glass is supplied onto the forming surface of the lower die stuck with heat resistant solid lubricant powder on the forming surface and thereafter, the upper die is lowered onto the lower die and the fused glass is press formed to the thin planar glass. The press forming is ended by raising the upper die when the temp. in the thin planar glass is at the temp. above the glass transition temperature. Next, this thin planar glass is subjected to warpage correction pressing and the warpage press correction is ended when the temp. in the thin planar glass is at the temp. above the glass transition temperature and thereafter, the planar glass is annealed. As a result, the thin planar glass having a warpage rate of 0.001 to 1% is obtd. and the flat polishing with high accuracy in lap polishing is made possible.