JPS5897131A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent a magnetic recording medium from curling due to temp. change, by forming a thin film of a ferromagnetic metal on the surface of a molded base of a polymer, and a metallic thin film mainly made of Al on the reverse side in a thickness larger than a specified thickness. CONSTITUTION:A Co-Ni alloy or the like is vapor deposited on the surface of a base of a polyester or the like to form a thin film of a ferromagnetic metal. A >=20nm thin film made of Al or an Al-Cu alloy is formed on the other side, thus permitting the magnetic side 1 of this magnetic tape to be prevented from curling in the inside or outside direction due to temp. change. A film of polymer, such as vinyl chloride or urethane resin, may be formed on the Al (Al alloy) surface in order to enhance smoothness of this surface, permitting wrong travelling, irregular winding, or the like to be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium in which a ferromagnetic metal thin film is formed on a polymer molded substrate, and is designed to prevent curl humidity changes caused by a laminated structure of different materials. be.

Magnetic recording media such as magnetic tapes and magnetic disks, which have a magnetic thin film of metal such as cobalt alloy formed on a polymer molded substrate by vacuum evaporation, ion blasting, sputtering, etc., have excellent high-density recording properties. However, because such magnetic recording media have a laminated structure of different materials such as polymeric materials and metals, even if they are processed into a flat shape by heat treatment, curling may occur due to changes in humidity. This not only causes problems such as running fluctuations and irregular winding, but also significantly reduces the product value in terms of appearance. In particular, among the polyester films widely used as substrates for magnetic recording media, the humidity expansion coefficient in the width direction is larger than that in the longitudinal direction for thin reinforced stretched polyester films used as substrates for magnetic tapes, which is 2 x 10- 5
It is said that the radius of curvature is about [%RH-1)2.If the metal thin film does not change due to humidity changes and only the substrate changes by the above value, a flat shape will have a radius of curvature of 7 due to a humidity change of 20%RH. .3 It becomes a state of drunken curls.

The present inventor previously proposed to prevent curling by forming a metal thin film reinforcing layer with a high melting point and high Young's modulus comparable to the magnetic metal thin film on the front surface on the back side of the polymer molded substrate.
This led to increases in material and manufacturing costs, and it was not put into practical use.

The inventors of the present invention conducted extensive research to solve these problems, and found that by forming an aluminum thin film of 200 Å or more on the opposite side of the polymer molded substrate from the side on which the magnetic metal thin film was formed. The inventors have discovered that the occurrence of curls due to changes in humidity can be eliminated and have arrived at the present invention.

Note that the surface of aluminum has poor lubricity when used as a magnetic tape, so a polymer film made of vinyl chloride resin, urethane resin, epoxy resin, phenoxy resin, etc. may be formed on the surface, and a coating of a polymeric material such as vinyl chloride resin, urethane resin, epoxy resin, phenoxy resin, etc. may be formed on the surface. A lubricant such as ester or silicone oil may be added.

The present invention will be explained below using experimental examples.

・A reinforced stretched polyethylene terephthalate film with a thickness of 6μ is used as a substrate, and a Co-Ni alloy (weight ratio 8:2) is deposited on one side at 6X10-5 torr to form a 0.3μ thin magnetic metal film. A sample board (D other side Vc1X 10
-5torr to evaporate aluminum to 200″ and 4
Sample B is a metal thin film of ooL.
, C. Next, these were taken out into the atmosphere and heated to 25°C.
, the curl change of a sample heat-treated to become flat in an environment of 60% RH at 26°C from 10% RH to 90%
The results shown in FIG. 1 were obtained when the measurements were carried out in a thermostatic chamber with humidity controlled up to RH.

Curl measurement: As shown in Figure 2, the apparent width C of a sample cut into a strip of approximately 251 EI is the true width Q.

The value divided by is expressed as a percentage, and + indicates the state where the magnetic surface 1 is on the inside, and - indicates the state where the aluminum surface 2 is on the inside. Note that an alloy of aluminum and copper may be deposited.

As is clear from the above experimental examples, according to the present invention, it is possible to provide a metal thin film type magnetic recording medium that does not cause curling due to changes in humidity, and its effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between humidity and curl change according to an experimental example of the present invention, and FIG. 2 is a diagram for explaining male curl measurement. 1... Magnetic surface, 2... Aluminum surface. Name of agent: Patent attorney Toshi Nakao (1 person)
11! l Wen Ling Figure 2

Claims (1)

[Claims] A magnetic recording medium characterized in that a ferromagnetic metal thin film is formed on the front surface of a polymer molded substrate, and a metal thin film with a thickness of 2oo1 or more and mainly composed of aluminum is formed on the back surface.