Magnetic recording medium
AssigneeTDK Corporation
InventorsTsutomu Ide, Akira Saitoh
Life of this patent
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Abstract
The invention provides a magnetic recording medium which is reduced in the occurrence of a dropout and has excellent durability. The magnetic recording medium comprises 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. The back-coat layer includes (a) a carbon black having an average particle size of 15 to 25 nm, (b) a carbon black having an average particle size of 60 to 80 nm and (c) CaCO3 and/or BaSO4 having an average particle size of 30 to 75 nm as the non-magnetic powder. The back-coat layer preferably includes said carbon black (a), said carbon black (b) and said CaCO3 and/or BaSO4 (c) in a ratio of (a)/(b)/(c)=60-80/3-15/15-30 by weight.
Claims1
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.
Dependencies are inferred from the claim text.