JPS59167831A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent curling by providing a magnetic layer on the surface of a base film made into the two-layered structure in which the base film consisting of a high polymer molding contg. solid powder particles is laminated on the rear of the base film consisting of a high polymer molding. CONSTITUTION:A base film 1 consisting of a polymer molding of an underlayer for constituting base films 1, 2 by laminating these films into the two-layered structure is formed by incorporating solid particles into the film 1 in a range of 2-50wt% range in order to improve the mechanical strength of the resulting magnetic recording medium and to suppress curling. Various powders of carbon black, molybdenum disulfide, etc. are adequate as the solid powder particles to be incorporated therein and particularly it is possible to obtain a lubricating effect with these powders by incorporating a solid lubricant therein.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium that has good mechanical strength, almost no curling, and excellent running stability.

In general, magnetic recording media, which are made by coating a magnetic paint on a base film made of a molded polymer such as a polyester film and drying it, tend to curl with the magnetic layer side inward because the magnetic layer shrinks during drying. In addition, ferromagnetic metal thin film magnetic recording media, which are made by vacuum-depositing a ferromagnetic material onto a base film made of a molded polymer, are produced by directing extremely high-temperature ferromagnetic material vapor to the base film. The substrate film is exposed to high temperatures during vapor deposition.The elastic modulus of the upper substrate film and the ferromagnetic metal thin film layer is too different, so curling is likely to occur, and the curling may impede runnability.

Therefore, as a method to effectively prevent such curling, methods such as using a plastic film that has been stretched and strengthened in the longitudinal direction as the base film, or performing heat treatment after forming the magnetic layer are used to correct the curling. However, it is still not possible to sufficiently prevent curling.

The inventors conducted various studies in view of the current situation, and as a result, they created a two-layer structure by laminating a base film made of a polymer molded product mixed with solid powder particles on the back side of a base film made of a polymer molded product. When a magnetic layer is provided on the surface of this two-layered base film, the base film containing solid C powder particles laminated on the back side of the two-layered base film provides sufficient mechanical strength. The present inventors have discovered that a magnetic recording medium with almost no curl can be obtained by strengthening the magnetic field, sufficiently suppressing curl, and completing the present invention.

In this invention, when two-layered base films are laminated, the lower base film made of a polymer molded material provides the resulting magnetic recording medium with good mechanical strength and sufficiently suppresses curling. In order to do this, solid powder particles are mixed into the base film in a range of 2 to 50% by weight,
It is preferable to include it, and if the content is too small, the desired effect will not be obtained.

Suitable solid powder particles to be contained include, for example, powders of carbon blank, graphite, molybdenum disulfide, tungsten disulfide, boron nitride, alumina, chromium oxide, zinc oxide, calcium carbonate, barium sulfate, talc, titanium oxide, etc. When used as powder, especially when solid lubricants such as carbon blank, graphite, molybdenum disulfide, tungsten disulfide, and boron nitride are contained, these powders also exert a lubricating effect, suppressing curling. At the same time, driving stability is further improved. Specific examples of base films containing such solid powder particles include polyester films, polyimide films, polyamide films, polypropylene films, polycarbonate films, and polyethylene films.

In addition, in the present invention, when the two-layer structure base film is laminated, the upper layer base film made of a polymer molded product is preferably made of the same material as that used for the lower layer base film. When the base film containing the solid powder particles is laminated on the back side of this base film, a base film with a two-layer structure with sufficiently strengthened mechanical strength is constructed. Curling of a magnetic recording medium obtained by forming a magnetic layer on a base film is sufficiently suppressed, and running stability is also improved.

The magnetic layer is formed using r Fe203, Fe304, C
o-containing 7-Fe203, Co-containing Fe3O4, Cr
Magnetic powder such as O2, F' e -, Co, Fe-Ni, etc. is applied to the surface of the two-layer structure base film together with a binder and an organic solvent, and then dried;
01Ni, Fe, Go-Ni, C.

Vacuum deposition of ferromagnetic material such as P%CoNip,
This is carried out by applying it to the surface of the two-layered base film by means such as ion blasting, sputtering, or plating.

Next, embodiments of the invention will be described.

Example 1 A 5μ thick polyester film 1 containing 10% by weight of zinc oxide powder was laminated on the back side of a 5μ thick polyester film 2 to form a 2N Tj& structure.
A polyester base film 3 of μ is loaded into a vacuum evaporation device, and a cobalt-nickel alloy (weight ratio 8:2) is heated and evaporated under a residual gas pressure of 5×10 −4 Torr to coat the polyester base film 3. Ferromagnetic metal thin film N4 made of cobalt-nickel alloy with a thickness of 2000 mm
was formed. Next, this was cut into a predetermined width to form a magnetic tape A as shown in FIG.

Example 2 Fe magnetic powder 80 parts by weight VAG
H (manufactured by U, C, C, USA, 16 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer) Takene 1-L-10074 (manufactured by Narita Pharmaceutical Co., Ltd., urethane prepolymer) Methyl isobutyl ketone 61 Toluene
61 A magnetic paint was prepared by mixing and dispersing the mixture having this composition in a ball mill for 72 hours. This magnetic paint was applied onto the same two-layered polyester base film as used in Example 1 so that the dry FF thickness was 5μ, and was dried to form a magnetic layer, which was then cut into a predetermined width. Then, a magnetic tape similar to that shown in FIG. 1 was made.

Comparative Example 1 Same as Example 1 except that instead of the two-layer polyester base film in Example 1, a 10μ thick polyester base film without laminated with a polyester film containing zinc oxide powder on the back side was used. and made magnetic tape.

Comparative Example 2 Example 2 except that the same 10 μm thick polyester base film used in Comparative Example 1 was used instead of the two-layer polyester base film in Example 2.
I made magnetic tape in the same way.

The degree of curl was measured for the magnetic tapes obtained in each Example and each Comparative Example, and running stability was tested. To measure the degree of curl, place the magnetic tape A on the flat plate 5 as shown in FIG. 2, and measure the width of the magnetic tape A! The maximum height h of the magnetic tape A from the surface of the flat plate was measured, and the degree of curl was expressed as the ratio h/β. In addition, the running stability test was carried out by installing each magnetic tape in a cartridge, loading it into a tape recorder, running the tape at a running speed of approximately 4.75 cm/sec, recording a 3000 Hz signal, and measuring wow and flutter. went.

The table below shows the results.

As is clear from the above table, the magnetic tapes obtained according to the present invention (Examples 1 and 2) have a lower degree of curl and less wow and flutter than the conventional magnetic tapes (Comparative Examples 1 and 2). This shows that the magnetic recording medium obtained by the present invention has almost no curl and has excellent running stability.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of the magnetic tape obtained in Example 1, and FIG. 2 is a perspective view of a flat plate for measuring the degree of curl of the magnetic tape obtained in Example 1. 1... Polyester film (lower layer base film)
, 2... Polyester film (upper layer base film), 3... Two-layer structure polyester base film (
base film), 4...ferromagnetic metal thin film layer (magnetic ii
), 'A...Magnetic tape (magnetic recording medium) Figure 1. Figure 2

Claims (1)

[Claims] 1. A base film made of a polymer molded product mixed with solid powder particles is laminated on the back side of a base film made of a polymer molded product to form a two-layer structure base film,
A magnetic recording medium characterized in that a magnetic layer is provided on the surface of this two-layer structure base film.