JPS5939014A - Method for manufacturing magnetic recording body with flexibility - Google Patents

Abstract

PURPOSE:To prevent crack and curl cause of adverse traveling or dropout generation, by a method wherein a continuous thin film of magnetic iron oxide is oxidized at temperature region where thermal contraction ratio of a fiexible substrate is in prescribed region. CONSTITUTION:On a flexible substrate is formed a continuous thin film of magnetic iron comprising Fe3O4 or intermediate composition of Fe3O4 and gamma-Fe2O3 as main constituent or further including other additive and then the thin film is oxidized. The oxidation is performed at temperature region where thermal contraction ratio of the flexible substrate becomes 0.3%-0.7%. In this constitution, crack or curl can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible magnetic recording medium, and in particular to a method for manufacturing a flexible magnetic recording medium, in which a thin film of magnetic iron oxide is formed on a flexible substrate, which is used in magnetic tapes, 7-lexiple disks, etc. The present invention relates to a method of manufacturing an iron oxide continuous thin film magnetic recording medium.

So-called coating-type magnetic recording media, in which needle-shaped crystals such as γ-Fe2O3 are bonded to a flexible substrate with an organic binder such as vinyl chloride-vinyl acetate copolymer or polyurethane, have been commonly used as magnetic recording media. It is being said.

In recent years, there has been a demand for high-density recording, and metal thin film magnetic recording bodies, particularly cobalt-based vapor-deposited tapes that can be easily made thinner and have higher coercive force, have attracted attention. However, such a metal thin film medium has problems such as damage, wear and corrosion of the film surface due to contact with a hard head such as ferrite, and as the layer becomes thinner, it becomes more difficult to ensure reliability.

In order to solve this problem, we applied r-FegO, an iron oxide magnetic thin film with good wear resistance and corrosion resistance, on a flexible substrate.
A flexible magnetic recording material has been proposed in which a magnetic iron oxide continuous thin film containing a composition between s- or r-Fe20g' and Fe3O4 or Fe3O4 as a main component is directly formed. Such flexible magnetic recording bodies are used for magnetic tapes, flexible magnetic disks, and in the case of flexible magnetic disks, substrates having a substrate thickness of about 50 μm (microns) are used. In addition, magnetic tapes are usually about 20 .mu.m in diameter, but tapes designed for long-term recording/reproduction and miniaturization are increasingly using substrates of 10 .mu.m or less. When a continuous thin film (for example, a CO thin film) is formed on such an outer thin substrate, the compressive stress of the CO thin film
Curling occurs with the O thin film inside, resulting in poor running performance and frequent dropouts.

For this purpose, a method of forming a thin film of the same type or a different type on the concrete surface opposite to the magnetic thin film medium and removing the curl (Japanese Unexamined Patent Publication No. 56-1
6939), a method using a substrate that can overcome the thermal expansion of a thin metal film and undergo thermal contraction (Japanese Patent Laid-Open No. 56-1693)
8) etc. have been proposed.

On the other hand, when a magnetic iron oxide continuous thin film is formed on such a thin substrate, curling occurs with the same thin film on the inside, although there are differences in degree, and when it is oxidized at elevated temperatures, the metal thin film The shrinkage of the magnetic film due to a decrease in the crystal lattice constant due to a change in the composition of the magnetic film causes cracks and curls in the magnetic film. In particular, cracks are a problem specific to continuous thin films, including not only iron oxide thin films but also metal thin films, and along with curling, they cause dropouts during recording and playback and unstable tape running, making them problematic when used as magnetic tapes. Met.

The present invention aims to solve these problems, and is to produce a flexible magnetic recording medium using a magnetic iron oxide continuous thin film as a recording medium, which has excellent runnability and dropout, and is free from curls and cracks. The purpose is to provide a method.

That is, according to the present invention, after forming a magnetic iron oxide continuous thin film mainly composed of F630< or an intermediate composition of Fe3O4 and γ-Fe2es, or containing other additives to these, on a flexible substrate, by oxidizing r-Fe20
3 or r-Fe20g and Fe504 as main components or containing other additives therein, A method for producing a flexible magnetic recording material is obtained, which is characterized in that oxidation occurs in a temperature range where the shrinkage rate is 0.3 inches to 0.7 inches.

The present invention makes it possible to prevent the occurrence of cracks and control curling by absorbing shrinkage due to changes in the composition of the magnetic film due to oxidation by thermal shrinkage of the substrate. Examples of the flexible substrate include polyamideimide, polyimide, polysulfide, polysulfone, and polyester. Also Fe3O4t
Co, Co,
Examples include Cu + Zn and Mn + Ti.

Hereinafter, one embodiment of the present invention will be described in detail.

Example Using a target mainly composed of magnetite containing cobalt and copper (CF@5Oa), sputtering power was 2.2 on polyimide and polyester substrates in an argon gas atmosphere.
Fe, O,
We created a sample with a continuous magnetic iron oxide thin film whose main component is . When these were oxidized for 1 hour at various temperatures, the heat shrinkage rate of the substrate, crack occurrence, curl state, and tape running properties are shown in the table.

The heat shrinkage rate of the substrate referred to here is the length of the substrate before heat treatment L
If the length after heat treatment is L', then (L-L')/L
It is indicated by X100chi.

(Table) In the table, curl indicates the state in the tape width direction, and when the curl was made with the magnetic film on the inside, it was shown as + (plus), and when the curl was made with the magnetic film on the outside, it was shown as - (minus). Moreover, the magnetic thin films of these samples have γ
-Fe, O, and Fe, 0. A continuous iron oxide thin film containing an intermediate composition as the main component was used.

As is clear from the table, sample A shown in this example is made of polyimide as the base type, has a base thickness of 12.5 μm, has an oxidation temperature of 250°C, and has a heat shrinkage rate of 03% at the oxidation temperature.
In this case, there were no cracks or curls, and the running performance was improved.

In addition, sample D of this example had a polyimide substrate type, a substrate thickness of 12.5 μm, and an oxidation temperature of 280° C.
When the heat shrinkage rate at the oxidation temperature was 0.4 cm, there were no cracks or curls, and the running properties were improved as described above.

Furthermore, sample E of this example had a polyimide substrate type, a substrate thickness of 12.5 μm, an oxidation temperature of 320°C,
When the heat shrinkage rate at the oxidation temperature was 0.7 inches, there was no cracking, cracking or curling, and the running properties were improved.

Sample A has a polyimide substrate type and a substrate thickness of 12
．． At 5 μm, cracks and curls (
It was located on the south side and had poor drivability.

Sample C has a polyimide substrate type and a substrate thickness of 12
．． When the thickness was 5 μm, the oxidation temperature was 350° C., and the thermal shrinkage rate at the oxidation temperature was 0.8 cm, there were some cracks and curls (on the @ side), so the runnability was poor.

Similarly, as shown in the table, sample F also had sagging and curling, and its running properties were poor.

As described above, in Samples B, D, and E of this example, the thermal contraction rate range of the flexible substrate at the oxidation temperature is 0.3.
% to 0.7g6, it can be seen that cracks and curls associated with deterioration of running performance and occurrence of dropouts are prevented.

As explained above, the present invention uses a method for manufacturing a flexible magnetic recording medium according to the present embodiment to record a magnetic iron oxide continuous thin film that is free from cracks and curls, exhibits good runnability, and has little drop-out or drop-out. It becomes possible to manufacture a flexible magnetic recording medium as a medium.

Claims (1)

[Claims] Fe3O4 or Feas4 and r-Fe on a flexible substrate
After forming a magnetic iron oxide continuous thin film based on an intermediate composition of zOs or containing other additives thereto, it is oxidized to form γ-Fez0.3 or γ-Fe2O3.
and F6a04 as main components or containing other additives, in which the heat shrinkage rate of the flexible substrate is 0.3%. 1. A method for producing a flexible magnetic recording material, comprising oxidizing a continuous magnetic iron oxide thin film in a temperature range of 0.7 to 0.7 cm.