Glass material

Abstract

A glass including SiO 2 , Na 2 O, MgO, Al 2 O 3 , and cobalt oxide, wherein the cobalt oxide is 4.5-85 wt % as an oxide of CoO or 4.9-91 wt % as an oxide of Co 3 O 4 .

What is claimed is:  
     
         1 . A glass substrate for optical information recording medium, comprising transition metal oxides or rare earth element oxides, and silicon oxide, wherein said glass substrate contains said transition metal oxides or rare earth element oxides in an amount of 0.1% to 29% by weight, and said glass substrate is made of a glass which varies in light density distribution.  
     
     
         2 . A glass substrate for optical information recording medium according to  claim 1 , wherein transition metals or rare earth elements, for forming said transition metal oxides or said rare earth element oxides, are selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nd, Ce, Pr, Sm, Eu, Tb, Ho, Er and Tm.  
     
     
         3 . A glass substrate for optical information recording medium according to  claim 2 , wherein said transition metals or rare earth elements is Co.  
     
     
         4 . A glass substrate for optical information recording medium comprising cobalt oxide and silicon oxide, wherein said glass substrate contains said cobalt oxide in an amount of 0.1% to 29% by weight as converted to CoO, and said glass substrate is made of a glass which varies in light intensity distribution.  
     
     
         5 . A glass substrate for optical information recording medium according to  claim 4 , wherein said glass substrate is made of a glass comprising SiO 2 : 6-80% by weight; alkali metal oxide: 0-20% by weight; and B 2 O 3 : 0-30% by weight, in addition to said cobalt oxide.  
     
     
         6 . A glass substrate for optical information recording medium according to  claim 1 , wherein said glass substrate is made of a glass comprising SiO 2 : 6-80% by weight; alkali metal oxide: 0-20% by weight; and B 2 O 3 : 0-30% by weight, in addition to said transition metal oxides or rare earth element oxides.