Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1992-06-08
1994-04-26
Resan, Stevan A.
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428212, 428323, 428332, 428341, 428480, 428481, 428483, 428510, 428522, 428694TS, 428694TB, 428694BS, 428694BB, 428694SL, 428694SG, G11B 500
Patent
active
053065387
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a polyester film for a magnetic recording medium. More particularly, the invention relates to a polyester film useful in manufacture of a magnetic recording medium excelling in running properties, electromagnetic performance, storage durability, etc.
BACKGROUND ART
Ferromagnetic thin metallic film magnetic recording media in which a ferromagnetic thin metallic film is formed on a non-magnetic support, by a physical deposition method such as vacuum deposition and sputtering or by a plating method, are known. Examples thereof include magnetic tape on which Co is deposited (Japanese Laid-Open Patent Publication No. 147010/1979) and a perpendicular magnetic recording medium in which Co-Cr alloy is used (Japanese Laid-Open Patent Publication No. 134706/1977). The thin metallic film formed by such film-forming means as vacuum evaporation, sputtering or ion-plating is as extremely thin as no more than 1.5 .mu.m. Nevertheless, it has the advantage of providing a recording medium which exhibits the performance equal to, or greater than, that of a coating type magnetic recording medium (a magnetic recording medium formed by applying a mixture of a magnetic powder and an organic polymer binder onto a non-magnetic support) whose magnetic recording layer has a thickness of no less than 3 .mu.m.
There is a concept that magnetic properties such as coercive force Hc, which is a static property, or squareness ratio of hysteresis loop, of the magnetic recording medium do not appreciably depend on surface conditions of the non-magnetic support used. As a product embodying such a concept, U.S. Pat. No. 3,787,327 discloses a Co-Cr multi-layered structure formed by means of vacuum evaporation.
With regard to magnetic recording media with thin metallic film, however, the metallic film formed on a non-magnetic support surface is extremely thin, and the surface condition (surface unevenness) of the non-magnetic support is faithfully reflected as the surface unevenness of the magnetic recording layer. This is considered as a defect of this type of media, because the surface unevenness gives a cause of undesirable noise.
In order to eliminate noise, it is preferred that the non-magnetic support has a surface as smooth as possible. Whereas, for handling, such as winding and unwinding, of the base film, a film with smooth surface has a poor film-to-film slip property and in consequence, a blocking phenomenon occurs and such film cannot be used as a commercially acceptable product. For this reason, the base film is required to have a rough surface. Thus, from the standpoint of electromagnetic performance, the non-magnetic support is required to have a smooth surface, while from the standpoint of handling property, the surface is required to be rough. It is therefore necessary that both of those contradictory requirements are satisfied simultaneously.
Another important problem in actual use of magnetic recording media of thin metallic film type is the running property of the thin metallic film surface. With conventional coating type magnetic recording media prepared by mixing magnetic powder with an organic polymer binder and then applying the mixture onto the base film, the running property of the magnetic surface can be improved by dispersing a lubricant in the binder. However, such a means cannot be adopted with the metallic film type magnetic recording media, and it is extremely difficult to stably maintain satisfactory running property. The media have a defect that their running property is inferior, particularly under high temperature and high humidity.
For the purpose of improving this defect, Japanese Patent Publication No. 30105/1987 proposes to form fine projections on the film surface, using fine particles, a water-soluble resin and a silane coupling agent. Japanese Patent Publication No. 30106/1987 and Japanese Laid-Open Patent Publication No. 229316/1984 also propose to form fine projections on the film surface, using fine particles and a water-soluble resin. In all of those pro
REFERENCES:
patent: 4153781 (1979-05-01), Thillier et al.
patent: 4367261 (1983-01-01), Miyoshi et al.
patent: 4552807 (1985-11-01), Yamada et al.
patent: 4670319 (1987-06-01), Katoh et al.
Kurihara Hideshi
Miura Sadayoshi
Nagai Tsuyoshi
Resan Stevan A.
Teijin Limited
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