GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM AND METHOD FOR PRODUCING THE SAME

THERE IS PROVIDED A GLASS SUBSTRATE WHICH HAS THE PROPERTIES REQUIRED IN THE USE AS A SUBSTRATE FOR INFORMATION RECORDING MEDIUM OF NEXT GENERATION SUCH AS A PERPENDICULAR MAGNETIC RECORDING SYSTEM, AND CAN BE APPLIED AS A SUBSTRATE FOR AN INFORMATION RECORDING MEDIUM OF THE NEXT GENERATION PARTICULARLY ON THE PREMISE OF USING THE GLASS SUBSTRATE IN A DYNAMIC ENVIRONMENT. MORE PARTICULARLY, THERE IS PROVIDED A GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM WHICH HAS SUFFICIENTLY HIGH SURFACE HARDNESS, HAS A GOOD BALANCE BETWEEN SPECIFIC GRAVITY AND MECHANICAL STRENGTH, AND HAS HIGH STRENGTH TO WITHSTAND HIGH SPEED ROTATION OR DROP IMPACT, AND WHICH CAN BE PRODUCED WITH A HIGH PRODUCTIVITY ADEQUATE FOR A DIRECT PRESS METHOD, WITHOUT THE OCCURRENCE OF BUBBLES IN THE GLASS BLANK OR REBOIL UPON PRESSING EVEN IF ARSENIC COMPONENTS OR ANTIMONY COMPONENTS ARE NOT SUBSTANTIALLY USED. A GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM, INCLUDES, AS EXPRESSED IN TERMS OF PERCENT BY MASS ON THE OXIDE BASIS: 52 TO 67% OF SIO2, 3 TO 15% OF AL2O3, AND 0.2 TO 8% OF P2O5, THE GLASS SUBSTRATE HAVING A YOUNG'S MODULUS OF 85 GPA OR GREATER, A SPECIFIC GRAVITY OF 2.60 OR LESS, A RATIO OF YOUNG'S MODULUS TO SPECIFIC GRAVITY (YOUNG'S MODULUS/SPECIFIC GRAVITY) OF 33.0 OR GREATER.