Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Patent
1996-03-28
1999-08-03
Resan, Stevan A.
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
428323, 428336, 4284259, 428694BU, 428694BG, 428694BS, 428694BM, 428900, G11B 5702
Patent
active
059323302
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a coated magnetic recording medium which has a magnetic layer with excellent surface smoothness, electromagnetic conversion characteristics, still durability and slitting properties. The present invention further relates to a paint for the coated magnetic recording medium and a method for its production.
DESCRIPTION OF RELATED ART
Recent advances in the recording art require magnetic recording media, such as video tapes, audio tapes, data cartridge tapes or floppy discs, to have increased recording density or increased recording capacity per unit volume.
To increase recording density, the following avenues have been explored:(1) improving the surface smoothness of the magnetic layer, (2) decreasing the thickness of the magnetic layer, (3) miniaturizing the particle sizes of the magnetic material, (4) increasing the coercive force (Hc) of the magnetic material, and (5) concentrated packing of the magnetic material.
With video tape, audio tape or data cartridge tape, recording capacity per unit volume has been increased by increasing recording capacity (or extending recording time) as a whole while maintaining size. This has been achieved by decreasing the total thickness of the magnetic tape and increasing its length, or, by decreasing the width of the magnetic tape so that a smaller cassette or cartridge can be used.
When the total thickness of the magnetic tape is decreased and its length is increased, the following problems arise: affects the electromagnetic conversion characteristics, and deterioration of the reproducing output may occur. effect", which absorbs impact applied on the magnetic layer when it contacts the magnetic head, is decreased. The magnetic layer is then easily damaged, which deteriorates still durability.
To solve the above problems, Japanese Patent Publication No. 2-63257 discloses a floppy disc comprising a polyester support, a nonmagnetic primer layer and a magnetic layer applied on the primer layer. The primer layer has a thickness of 2 mm or less and comprises a three dimensional crosslinked resin having a Young's modulus of 100 to 8000 kg/cm.sup.2. The '257 Publication teaches that a polyurethane resin and vinyl chloride base resin (vinyl chloride-vinyl acetate-vinyl alcohol copolymer) are preferred as the resins for the primer layer and the magnetic layer. However, since the primer layer contains no nonmagnetic powder, and has few voids, the following problem arises.
It is well known in the art that the magnetic layer may be calendered to improve its surface smoothness. However, in the invention described in the 'b 257 publication the calendering is not effective, and the magnetic layer surface cannot be smoothed to a satisfactory level. Accordingly, the electromagnetic conversion characteristics, such as, for example, reproducing output in the high frequency range, RF output or S/N ratio in the low frequency range, and chroma S/N are insufficient to achieve high recording density.
Japanese Patent Kokai Publication No. 1-94523 discloses a magnetic recording medium comprising a nonmagnetic layer containing nonmagnetic powder. The disclosed coated magnetic recording medium comprises a polyethylene terephthalate support, a primer layer formed on the support which comprises a nonmagnetic powder (e.g. titanium oxide, carbon black, etc.), vinyl chloride base resin (vinyl chloride-vinyl alcohol copolymer), and a polyurethane resin having a solubility parameter of 9.0 to 9.5. A magnetic layer formed on said primer layer comprises a ferromagnetic powder and a binder containing a vinyl chloride resin (vinyl chloride-vinyl alcohol copolymer) and a lower molecular weight isocyanate compound. The '523 Kokai Publication teaches that the inclusion of a polyurethane resin as a binder in the magnetic layer improves overall performance.
To solve the above problems, Japanese Patent Kokai Publication No. 63-103429 proposes the formation of a coated magnetic layer with two sub-layers, a first (lower) layer with a Young's modulus of 500 to
REFERENCES:
patent: 4265931 (1981-05-01), Tamai et al.
patent: 4857388 (1989-08-01), Ogawa et al.
patent: 5085941 (1992-02-01), Ohkubo
Ohkubo Takatoshi
Yoshida Yuko
Imation Corp.
Levinson Eric D.
Resan Stevan A.
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