Magnetic recording medium having a smooth biaxially tensilized film substrate
View Patent ↗A magnetic recording medium which includes a non-magnetic substrate having a front side and a backside, a longitudinal direction and a crossweb direction, with a particulate/binder magnetic layer formed over the front side of the substrate, wherein the magnetic medium has a cross web dimensional difference from the magnetic recording head used therewith of less than 900 microns/meter over a 35 degree temperature range, and over a 70% relative humidity range. In one embodiment, the substrate is a polymeric film which has been subjected to a biaxial tensilization process, thus having a lower coefficient of hygroscopic expansion and coefficient of thermal expansion than an otherwise identical film substrate which has not been biaxially tensilized. The magnetic recording medium formed using such a tensilized substrate has a Wyko Ra smoothness of less than about 10 nm, and a coefficient of thermal expansion from about 5 ppm/C to about 10 ppm/C.
1. A magnetic recording medium comprising a biaxially tensilized substrate having a front side and a backside, a longitudinal direction and a crossweb direction, said substrate having a magnetic layer formed over said front side of said substrate comprising magnetic pigment particles, and a binder system therefor; said magnetic recording medium having a cross web dimensional difference from a substrate wafer of an Al 2 O 3 —TiC bi-phase ceramic formed from aluminum oxide and titanium carbide of less than 900 microns/meter over a temperature range of about 35 degrees, and over a relative humidity range of about 70%, and a coefficient of thermal expansion having a value said magnetic recording medium having a coefficient of thermal expansion of from about 5 ppm/C to about 10 ppm/C, said coefficient of thermal expansion being from about 50% to about 150% of the coefficient of thermal expansion for the substrate wafer.
2. A magnetic recording medium according to claim 1 having a Wyko surface roughness of less than 10 nm.
3. A magnetic recording medium according to claim 1 wherein said magnetic recording medium is used with a magnetic recording head formed on a substrate wafer of an Al 2 O 3 —TiC bi-phase ceramic formed from aluminum oxide and titanium carbide.
4. A magnetic recording medium according to claim 1 wherein said biaxially tensilized substrate is selected from the group consisting of polyesters, polyolefins, cellulose derivatives, polyamides, and polyimides.
5. A magnetic recording medium according to claim 1 wherein said biaxially tensilized substrate comprises a substrate subjected to film tensilization, said substrate being selected from the group consisting of polyethylene naphthalate and polyethylene terephthalate.
6. A magnetic recording medium according to claim 1 wherein said substrate has a thickness of from about 1 to about 10 microns.
7. A magnetic recording medium according to claim 1 wherein the magnetic recording medium has a crossweb modulus of at least about 7 GPa.
8. A magnetic recording medium according to claim 1 wherein the magnetic recording medium has a hygroscopic expansion coefficient of less than about 7 ppm/% RH.
9. A magnetic recording medium according to claim 1 wherein the magnetic layer comprises a ferromagnetic pigment aluminum oxide, a spherical large particle carbon material having a particle size of from about 50 to about 500 nm, a polyurethane binder, a non-halogenated vinyl binder, a hardener, a fatty acid ester lubricant, and a fatty acid lubricant.
10. A magnetic recording medium according to claim 1 wherein the magnetic layer comprises a ferromagnetic pigment, aluminum oxide, a spherical large particle carbon material having a particle size of from about 50 to about 500 nm, a polyurethane binder, a polyvinylchloride binder, a hardener, a fatty acid ester lubricant, and a fatty acid lubricant.