Magnetic recording medium

Claim 2

An improved back-coated magnetic recording medium which attains a desirably high video color S/N ratio and has a substantially even and uniform back coat, which comprises: a non-magnetic base, a magnetic recording coat formed on one side of the base, and a back coat formed on the other side of the base; said back coat being a substantially even and uniform coat formed of a substantially thorough or uniform dispersion of inorganic pigment particles in the form of a powder in a resinous binder, and providing improved running or operational properties to the magnetic recording medium and allowing the attainment of a desirably high video color S/N ratio and substantial freedom from cinching, back coat scraping, loading-unloading damage, and blocking of the back coat to the magnetic coat; said inorganic pigment powder having an average particle diameter in the range of about 0.2 μm to about 0.5 μm and a particle hardness of not greater than about 6 on the Mohs scale; said resinous binder being formed of a copolymer component, a rubbery binder component, and a polyisocyanate crosslinking component; said copolymer component being formed of vinyl chloride, vinyl alkyl carboxylate, another monomer copolymerizable with vinyl chloride, and saponified vinyl alkyl carboxylate having an OH/CH absorption ratio in the range of about 0.2 to about 0.7 as determined from its infrared absorption spectrum.

Claim 3

A magnetic recording medium according to claim 1 wherein said inorganic pigment powder includes a member selected from the group consisting of finely-divided calcium carbonate and titanium oxide.

Claim 4

A magnetic recording medium according to claim 1 wherein said rubbery binder component is at least one member selected from the group consisting of polyester resins, polyurethane resins, and admixtures thereof.

Claim 5

A magnetic recording medium according to claim 1 wherein said inorganic pigment powder includes a member selected from the group consisting of finely-divided calcium carbonate and titanium oxide, and said rubbery binder component is at least one member selected from the group consisting of polyester resins, polyurethane resins, and admixtures thereof.

Claim 6

A magnetic recording medium according to claim 1 wherein said copolymer component is formed, on a weight basis, of about 50 to 90% of vinyl chloride, about 5 to 40% of vinyl alkyl carboxylate, about 1.5 to 5% of another monomer compolymerizable with vinyl chloride, and the remainder of said copolymer component is saponified vinyl alkyl carboxylate having an OH/CH absorption ratio in the range of about 0.2 to about 0.7 as determined from its infrared absorption spectrum.

Claim 7

A magnetic recording medium according to claim 1 wherein said inorganic pigment powder includes a member selected from the group consisting of finely-divided calcium carbonate and titanium oxide, and said copolymer component is formed, on a weight basis, of about 50 to 90% of vinyl chloride, about 5 to 40% of vinyl alkyl carboxylate, about 1.5 to 5% of another monomer copolymerizable with vinyl chloride, and the remainder of said copolymer component is saponified vinyl alkyl carboxylate with an OH/CH absorption ratio in the range of about 0.2 to about 0.7 as determined from its infrared absorption spectrum.

Claim 8

An improved back-coated magnetic recording medium which attains a desirably high video color S/N ratio and has a substantially even and uniform back coat, which comprises: a non-magnetic base, a magnetic recording coat formed on one side of the base, and a back coat formed on the other side of the base; said back coat being a substantially even and uniform coat formed of a substantially thorough or uniform dispersion of inorganic pigment particles in the form of a powder in a resinous binder, and providing improved running or operational properties to the magnetic recording medium and allowing the attainment of a desirably high video color S/N ratio and substantial freedom from cinching, back coat scraping, loading-unloading damage, and blocking of the back coat to the magnetic coat; said inorganic pigment powder includes a member from the group consisting of finely-divided calcium carbonate and titanium oxide, and has an average particle diameter in the range of about 0.2 μm to about 0.5 μm and a particle hardness of not greater than about 6 on the Mohs scale; said resinous binder being formed of a copolymer component, a rubbery binder component, and a polyisocyanate crosslinking component; said copolymer component being formed, on a weight basis, of about 50 to 90% of vinyl chloride, about 5 to 40% of vinyl alkyl carboxylate, about 1.5 to 5% of another monomer copolymerizable with vinyl chloride, and the remainder of said copolymer component is saponified vinyl alkyl carboxylate having an OH/CH absorption ratio in the range of about 0.2 to about 0.7 as determined from its infrared absorption spectrum; said rubbery binder component being formed of at least one member selected from the group consisting of polyester resins, polyurethane resins, and admixtures thereof.

Claim 9

An improved back-coated magnetic recording medium which attains a desirably high video color S/N ratio and has a substantially even and uniform back coat, which comprises: a non-magnetic base, a magnetic recording coat formed on one side of the base, and a back coat formed on the other side of the base; said back coat being a substantially even and uniform coat formed of a substantially thorough or uniform dispersion of inorganic pigment particles in the form of a powder in a resinous binder, and providing improved running or operational properties to the magnetic recording medium and allowing the attainment of a desirably high video color S/N ratio and substantial freedom from cinching, back coat scraping, loading-unloading damage, and blocking of the back coat to the magnetic coat; said inorganic pigment powder includes a member from the group consisting of finely-divided calcium carbonate and titanium oxide, and has an average particle diameter in the range of about 0.2 μm to about 0.5 μm and a particle hardness of not greater than about 6 on the Mohs scale; said resinous binder being formed of a copolymer component, a rubbery binder component, and a polyisocyanate crosslinking component; said copolymer component being formed, on a weight basis, of about 50 to 90% of vinyl chloride, about 5 to 40% of vinyl alkyl carboxylate, about 1.5 to 5% of another monomer copolymerizable with vinyl chloride, and the remainder of said copolymer component is saponified vinyl alkyl carboxylate having an OH/CH absorption ratio in the range of about 0.2 to about 0.7 as determined from its infrared absorption spectrum; said rubbery binder component being formed of at least one member selected from the group consisting of polyester resins, polyurethane resins, and admixtures thereof.

Claim 10

A magnetic recording medium according to claim 7 wherein the back coat, as applied to the base, has a film thickness of about 0.3 to about 1.5 μm and a surface roughness, Rz, of about 0.1 to about 0.5 μm.

Claim 11

A magnetic recording medium according to claim 7 wherein the substantially thorough or uniform dispersion of inorganic pigment and resinous binder is present in the back coat in a weight ratio of about 4:1 to about 1:1.

Claim 12

A magnetic recording medium according to claim 9 wherein the back coat, as applied to the base, has a film thickness of about 0.3 to about 1.5 μm and a surface roughness, Rz, of about 0.1 to about 0.5 μm.

Claim 13

A magnetic recording medium according to claim 7 wherein the back coat has a friction-reducing lubricant.