Patent ID: 6475613
Filing Date: 2002-11-05
Classification: G11B,Y10S,Y10T

Abstract:
A magnetic recording medium comprising a magnetic layer on one surface of a non-magnetic support and a back-coat layer, containing mainly a non-magnetic powder and a binder, on the other surface, wherein the back-coat layer includes, as the non-magnetic powder:(a) a first carbon black having an average particle size of approximately 15 to approximately 25 nm, an oil absorption ranging from approximately 50 to approximately 110 cc/100 g and a specific surface area ranging from approximately 100 to approximately 300 m2/g measured by the BET method; (b) a second carbon black having an average particle size of approximately 60 to approximately 80 nm, an oil absorption ranging from approximately 20 to approximately 80 cc/100 g and a specific surface area ranging from approximately 10 to approximately 50 m2/g measured by the BET method; and (c) at least one of CaCO3 and BaSO4, said at least one of CaCO3 and BaSO4 having an average particle size of 30 to 75 nm; and wherein the back-coat layer includes said first carbon black, said second carbon black and said at least one of CaCO3 and BaSO4 in a ratio of said first carbon black/said second carbon black/said at least one of CaCO3 and BaSO4=60-80/3-15/15-30 by weight.