Magnetic recording medium comprising a specified binder resin, specified ferromagnetic metal powder and .alpha.-alumina
First Claim
1. A magnetic recording medium comprising a support having provided thereon a magnetic layer, said magnetic layer containing;
- (1) a ferromagnetic powder having an adsorbed moisture content of 1.0% to 2.5% by weight based on said ferromagnetic powder,a specific surface area of at least 45 m2 /g as measured by the BET method, anda pH value of 9.0 to 11.5,(2) α
-alumina having a BET specific surface area of 11 m2 /g to 35 m2 /g; and
(3) a binder resin having at least one polar group selected form the group consisting of ##STR10## wherein M represents hydrogen, lithium, sodium, or potassium; and
M1 and M2 each represents hydrogen, lithium, sodium, potassium, or an alkyl group,said resin having a molecular weight of 2,000 to 70,000, the molecular weight of said resin is 200 to 70,000 per polar group.
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Abstract
A magnetic recording medium having a support and provided thereon, a magnetic layer containing a ferromagnetic metal powder and a binder is disclosed. The ferromagnetic powder comprises an adsorbed moisture of not less than 1.0 weight % and not more than 2.5 weight % of said ferromagnetic metal powder, a pH value of not less than 9.0 and not morer than 11.5, and a specific surface area of not less than 45 m2 /g measured by a BET method; and the binder comprises at least one polar group selected from the group consisting of: ##STR1## wherein M represents an atom selected from the group consisting of hydrogen, lithium, sodium, and potassium; and M1 and M2 represent atoms of hydrogen, lithium, sodium and potassium, and an alkyl group, provided that M1 and M2 may be same with or different from each other.
118 Citations
18 Claims
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1. A magnetic recording medium comprising a support having provided thereon a magnetic layer, said magnetic layer containing;
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(1) a ferromagnetic powder having an adsorbed moisture content of 1.0% to 2.5% by weight based on said ferromagnetic powder, a specific surface area of at least 45 m2 /g as measured by the BET method, and a pH value of 9.0 to 11.5, (2) α
-alumina having a BET specific surface area of 11 m2 /g to 35 m2 /g; and(3) a binder resin having at least one polar group selected form the group consisting of ##STR10## wherein M represents hydrogen, lithium, sodium, or potassium; and
M1 and M2 each represents hydrogen, lithium, sodium, potassium, or an alkyl group,said resin having a molecular weight of 2,000 to 70,000, the molecular weight of said resin is 200 to 70,000 per polar group. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A magnetic recording medium comprising a support having a magnetic layer provided thereon, said magnetic layer containing;
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(1) a ferromagnetic powder having an adsorbed moisture content of 1.0% to 2.5% by weight based on said ferromagnetic powder, and a specific surface area of at least 45 m2 /g as measured by the BET method and a pH value of 9.0-11.5; (2) alpha alumina having a BET specific surface area of 11 m2 /g to 35 m2 /g, (3) a fatty acid in an amount of not more than 4 mg/m2, and a fatty acid ester in an amount of 5 mg/m2 to 100 mg/m2 based on said recording medium, as determined by extraction dipping said medium in cyclohexane for three minutes; and (4) a binder resin having at least one polar group selected from the group consisting of;
##STR11## wherein M represents hydrogen, lithium, sodium, or potassium; and
M1 and M2 each represent hydrogen, lithium, sodium, potassium, or an alkyl group,said resin having a molecular weight of 2,000 to 70,000, and each polar group having a molecular weight of 200 to 70,000. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification