JPS60261027A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate curling and to decrease the range of output fluctuation by providing two layers consisting of a ''Permalloy(R)'' layer and CoCr layer on a high-polymer film and maintaining the coefft. of linear expansion of the high- polymer film provided with such magnetic layer at a prescribed value or below. CONSTITUTION:A vertical magnetic recording medium is formed by providing the two layers consisting of the ''Permalloy(R)'' layer and CoCr layer on the high- polymer film. Said medium is so constituted that the coefft. of linear expansion of the high-polymer film provided with the magnetic layer is made >=6X10<-6>/ deg.C and <=10X10<-6>/ deg.C. The expansion and shrinkage of the high-polymer film and the metal are made coincident with each other by such constitution. Curling is eliminated and the range of the output fluctuation is decreased with the one-side medium. The generation of a crack during traveling of a driver or under thermal impact is obviated with the double-side medium.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a perpendicular magnetic recording medium that can be used as a magnetic storage medium such as a magnetic tape or a flexible magnetic disk.

Conventional Structures and Their Problems In recent years, perpendicular magnetic recording media have attracted attention as high-density magnetic storage elements, and research and development have been actively conducted.

In horizontal magnetic recording, this decreases as the density increases.

This is because the magnetic field increases and the upper limit is 30 to 60 KBPI, whereas in perpendicular magnetic recording, the demagnetizing field decreases in principle as the density increases, so it is possible to obtain a recording density of 200 KBPI or more. Further, as a perpendicular magnetic recording medium, there are sputtering or vapor deposition of Go Or, vapor deposition of C0-0, sputtering or coating of Ba ferrite, and the Go Or sputtered film is the most excellent in terms of characteristics. In particular, a two-layer structure with permalloy as a high magnetic permeability layer is best.

Then, the polymer film is sputtered onto polyethylene terephthalate (hereinafter referred to as PET), polyimide, polyamide, or the like, but this is done under heating in order to obtain good magnetic properties.

However, during sputtering, the temperature of the film increases due to the incidence of secondary electrons on the film. As the film undergoes a slight temperature rise during the sputtering process, the coefficient of linear expansion and shrinkage are different from the original film. It causes curls. If you apply a screwdriver to check the electromagnetic conversion characteristics in this state, you will find that the head is lifted off the medium due to the curl. Therefore, the magnitude of the output varies greatly depending on the location, and the so-called output fluctuation range becomes large. Conventionally, as a means to improve this, the same material was sputtered on the other side of the polymer film to balance the metal surfaces on both sides and correct the shikaru3.However, with this method, the film and metal were always Due to the stress being applied between the wheels and the surface, clunks are more likely to occur when the driver is driving. Additionally, due to the different linear expansion coefficients of metal and polymer film, the degree of expansion or contraction is different in response to thermal shock, which causes a large change in internal stress, which causes cracks to easily occur. was.

Purpose of the Invention The purpose of the present invention is to make the linear expansion coefficient of the polymer film provided with the magnetic layer within the above range, so that the expansion and contraction match that of the metal, and there is no curling on one side, resulting in a small output fluctuation range. Moreover, the present invention provides a perpendicular magnetic recording medium that has small internal stress on both sides and does not produce cranking when running with a driver or during thermal shock.

Structure of the Invention The perpendicular magnetic recording medium of the present invention has two layers, a permalloy layer and a CoCr layer, provided on a polymer film, and the linear expansion coefficient of the polymer film provided with the magnetic layer is 6X.
10'/' (2 or more and 10x1O-67c or less).

With this configuration, the expansion and contraction of the polymer film and the metal match, and with single-sided media, there is no curling and output fluctuation range is small, and with double-sided media, no cracks occur when running with a driver or during thermal shock.

DESCRIPTION OF EXAMPLES Hereinafter, the present invention will be explained based on Examples and with reference to Comparative Examples.

<Example 1> PK before forming a sputtered film on the PICT film
T 7 ilm to 150°C heat roller 30CIn7
The permalloy was heat-treated at a speed of 100°C and Ar gas 8×10-' by continuous DC magnetron sputtering.
Torr, power 3KW1, film feed speed 10c
In/min, 0.6 μm thick, Co Or at 145°C, A
r gas 8 x 10-5 T:orr, power 2.5K
A single-sided medium was prepared by forming the film to a thickness of 0.2 μm at a film feed rate of 12 cIrL/min so that the coefficient of thermal expansion of the PET film after the two-layer structure was 6×10 −6 /c. Here, the COO linear expansion coefficient is 12.5 x 10'/CSCr is 6.5 x 1 in the data book.
0'/C.

Fe is 12. IX 10-6/c, Ni is 13.3
X10', I'(, which is a large value, but since the sputtered film is polycrystalline, GoOr,
Be in an alloy state of FeNi, and CoCr0.2μ
Due to the interaction between the m film and the permalloy 0.6 μm film, 2
It is thought that the linear expansion coefficient of the layered film is close to the above value.

The media prepared in this way can be heated at temperatures between 10°C and 50°C.
There was no curl between. -! The electromagnetic conversion characteristics were measured using a 5-inch floppy disk and a main pole excitation type head. As a result, a voltage fluctuation range of 10% or less was obtained when the driver was driving.

<Example 2> Before forming a sputtered film on the PET film, the PET film was heat-treated by passing it through a heated roller at 150°C at 4ocrn4, and permalloy and CoOr were each coated with a thickness of 0.6 μm.
A single-sided medium was prepared by forming the PΣT film to a thickness of 0.2 μm under the same conditions as in Example 1 so that the linear expansion coefficient of the PΣT film after the two-layer structure was 10×10 −6 /=c. As a result, there was no curling between 10° C. and 50° C., and the voltage fluctuation width during driver driving was 10% or less under the same conditions as in Example 1.

<Example 3> Before forming a sputtered film on PF and T film, PET
The PET film was heat treated under the same conditions as in Example 2, and permalloy and CoCr were formed to a thickness of 0.6 μm and 0.2 μm under the same conditions as in Example 1, respectively.
The linear expansion coefficient of the PET film after layer construction is 8 x 10
A double-sided medium was prepared so that the ratio was -6/C. and,
When the media was examined after running it with a screwdriver for 1,000 passes, 10,000 passes, and 100,000 passes, no cracks were found. Furthermore, it was stable without cracking even when subjected to thermal shock from 50'C to O'C.

<Comparative Example 1> PET film was coated with 0.6-10.2μ of Permalloy and CoCr under the same conditions as Example 1 without pre-heat treatment.
The coefficient of linear expansion is 13 x 10-6//=c when the single-sided medium is formed to a thickness of The width was 25%, and there were two large voltage areas and two small voltage areas per round.

<Comparative Example 2> Polyimide film was heated at 100°C, Ar gas 8X103 Torr, and power 3KW without preheating.
, 0.6 pm thickness at a film feeding speed of 10 cIrL/min,
Go Or to 300°C1Ar gas IX 10-2T
orr.

Power 3KW, film feed rate 12crn/min 0.2
It was formed to a thickness of μm to produce a single-sided medium. The coefficient of linear expansion at this time is 6 x 10-6/°C, and at room temperature, the metal is on the inside and the polyimide surface is on the outside, and the voltage fluctuation width when the driver is running is 30%. Each had two large and small voltage sections.

<Comparative Example 3> A double-sided medium was produced under the same conditions as Comparative Example 1. The coefficient of linear expansion at this time is 1'I x 10-6/'c, which is 10°
There was no apparent curl between C and 50'C. When the medium was inspected after 1,000 passes and 10,000 passes with a driver, no cracks had occurred at the 1,000 passes, but cracks had occurred at the 10,000 passes.

Also, cracks were generated due to thermal shock from 50°C to '@o'c.

Effects of the Invention As is clear from the above explanation, the present invention has two layers, a permalloy layer and a CoCr layer, on a polymer film.
In addition, by setting the linear expansion coefficient of the polymer film provided with the magnetic layer to e x 10-6100 or more and 10 The effect is that cracks are less likely to occur during running or thermal shock. Furthermore, since there is no curling, the rotational torque is small when placed in a jacket, and the durability at high and low temperatures is also excellent.

Claims (1)

[Claims] Two permalloy layers and a CjoOr layer on the polymer film.
The linear expansion coefficient of the polymer film provided with the magnetic layer is exl, o-64 or more 10X10'4
A perpendicular magnetic recording medium characterized by the following.