Abstract: A magnetic recording medium comprises a combination of two or more kinds of fine abrasive powders having different true specific gravities in a magnetic layer containing a magnetic powder.

Abstract: A magnetic tape cassette holding a wound magnetic tape comprising a transparent base film and a magnetic layer having a thickness of 5.mu. or less coated on the base film comprises a hole facing a light source for detecting the tape position, a hole facing a photosenser provided so as to form a light path passing to the hole for light source through which the magnetic tape is passed and a light-shielding filter having a light transmittance in the range between 0.5 and 10 percent placed in the light path.

Abstract: A magnetic recording tape comprises a polyethyleneterephthalate base film coated with a magnetic layer which has an index H given by the equation:1.5>19.00-0.406 d.sub.B -0.016 H-0.553 d.sub.Td.sub.T .ltoreq.18(.mu.m)wherein the reference d.sub.T (.mu.m) designates a total thickness of the magnetic recording tape; d.sub.B (.mu.m) designates a thickness of the base film and H designates a sum of numbers of interference rings (H.sub.1, H.sub.2, H.sub.3 . . . )per 1 mm.sup.2.

Abstract: A magnetic recording medium is prepared by preparing a nitrocellulose-based magnetic composition by kneading a magnetic powder with a mixture of nitrocellulose in a solvent system containing isopropyl alcohol and blending the kneaded mixture with a polyurethane containing unreacted isocyanate groups; coating a substrate with the resulting magnetic composition and allowing the coated substrate to dry. The improvement comprises replacing substantial portions of the isopropyl alcohol from the group consisting of polyurethane resins, polybutadiene resins, butadiene-acrylonitrile copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl acetate resins, epoxy resins, phenoxy resins, polyvinyl butyral resins, polyvinyl formal resins and polyester resins.