Patent ID: 6336945
Filing Date: 2002-01-08
Classification: B24B,C09G,C09K,G11B

Abstract:
A process for producing substrates of magnetic recording media, the process comprising abrading a raw substrate with an abrasive composition containing at least an abrasive, an abrasive auxiliary and water, whereinthe abrasive comprises &agr;-Al2O3 or &ggr;-Al2O3 particles having a Knoop hardness number of 1500 to 3000 and a purity of 99.9% by weight or higher; the abrading comprises a lapping process followed by a polishing process, and a polishing pad having a Shore hardness (JIS A (JIS K-6301)) of 88 to 98 is used in the polishing process; the abrasive auxiliary comprises an aliphatic organic sulfate represented by the formula (1): Râ€”Oâ€”SO3Mâ€ƒâ€ƒ(1) â€ƒwhere R represent a straight-chain or branched-chain alkyl group, an aryl group or an alkylaryl group each having 8 to 14 carbon atoms; and M represents an alkali metal, an alkaline earth metal or an organic cation, or an oxyalkylene alkyl ether sulfate represented by the formula (2): Râ€”Oâ€”(AO)nâ€”SO3Mâ€ƒâ€ƒ(2) â€ƒwhere R represents a straight-chain or branched-chain alkyl group, an aryl group or an alkyaryl group each having 8 to 14 carbon atoms; AO represents an oxyalkylene group having 2 or 3 carbon atoms; n represents a natural number of 2 to 4; and M represents an alkali metal, an alkaline earth metal or an organic cation; the weight ratio of the abrasive to the abrasive auxiliary is from 0.01 to 25; the raw substrate is selected from the group consisting of a carbon substrate and a Niâ€”P plated aluminum alloy substrate; and the abrasive composition has a pH of 1 to 6.