Patent ID: 8785011

Claim:
A glass substrate for information recording medium, which is comprised of glass comprising, denoted as molar percentages, a total of 70 to 85 percent of SiO 2 and Al 2 O 3 , where SiO 2 content is equal to or greater than 50 percent and Al 2 O 3 content is equal to or greater than 3 percent; a total of equal to or greater than 10 percent of Li 2 O, Na 2 O and K 2 O; equal to or greater than 5 percent of Li 2 O, a total of 1 to 6 percent of CaO and MgO, where CaO content is greater than MgO content; a total of greater than 0 percent but equal to or lower than 3 percent of ZrO 2 , HfO 2 , Nb 2 O 5 , Ta 2 O 5 , La 2 O 3 , Y 2 O 3 and TiO 2 ; with a molar ratio of MgO content to CaO content (MgO/CaO) being equal to or greater than 0.14; with the molar ratio of a total content of Li 2 O, Na 2 O and K 2 O to a total content of SiO 2 , Al 2 O 3 , ZrO 2 , HfO 2 , Nb 2 O 5 , Ta 2 O 5 , La 2 O 3 , Y 2 O 3 and TiO 2 ((Li 2 O+Na 2 O+K 2 O)/(SiO 2 +Al 2 O 3 +ZrO 2 +HfO 2 +Nb 2 O 5 +Ta 2 O 5 +La 2 O 3 +Y 2 O 3 +TiO 2 )) being equal to or less than 0.28 and a molar ratio of Li 2 O content to Na 2 O content (Li 2 O/Na 2 O) being equal to or less than 0.7904, and, which has been subjected to chemical strengthening treatment, and has a hole in the center.