MANUFACTURE OF GLASS SUBSTRATE FOR HIGH RECORDING DENSITY MAGNETIC DISK

• Main Authors: OSUGA TAKUO, MANNAMI KAZUO, MATSUSHITA KEIZO, NISHIMURA YOSHIAKI
• Format: Patent
• Language: English
• Published: 21.08.1998
• Edition: 6
• Subjects: CHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUSENAMELS; CHEMISTRY; GLASS; INFORMATION STORAGE; INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER; JOINING GLASS TO GLASS OR OTHER MATERIALS; METALLURGY; MINERAL OR SLAG WOOL; PHYSICS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS,MINERALS OR SLAGS; SURFACE TREATMENT OF GLASS

PROBLEM TO BE SOLVED: To obtain a glass substrate extremely reduced in surface defects by ion-exchanging a glass substrate surface having a specific surface roughness or below at a glass transition temperature or below, and then grinding the surface of the substrate again. SOLUTION: The surface of a glass substrate is ground to a surface roughness Rmax of less than 20nm. Then, an ion-exchange is applied to the surface of the substrate at the glass transition temperature or below. Then, the surface is ground again. By conducting the grinding after the ion-exchange, the surface defects caused by the ion-exchange are removed. It is desired that the amount of the grinding after the ion-exchange is limited to <=1/5 of the thickness of the compressive stress layer formed by the ion-exchange. If the grinding is kept to <=1/5, the adverse effect on the ion-exchanged layer caused by the grinding is maintained to a minimum, no reduction in the strength of the glass substrate occurs and the surface defects are efficiently eliminated. Also, it is highly desirably to define the Rmax as <=10nm.