JPS59221829A - Production of vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a titled recording medium which is free from curling and is particularly suitable for a vertical floppy disc by laminating a Ti film, Permalloy film and Co-Cr film respectively under specific conditions on the surface of a polyethylene terephthalate film while running said film along the circumferential surface of a can. CONSTITUTION:A Ti film 4 having about 300-800Angstrom film thickness is deposited by vacuum evaporation on the surface of a polyethylene terephalate film 10 (1 in the accompanying figure) having about 17-50mu film thickness while said film is run along the circumferential surface of a can 6, then a Permalloy film 3 having about 1,000-5,000Angstrom film thickness is formed thereon by maintaining the circumferential surface temp. of the can 6 at about 10-80 deg.C. Order of forming the films 3 and 4 may be reversed. A Co-Cr vertical magnetized film 2 having about 600-2,500Angstrom film thickness is deposited by vacuum evaporation on the film 3 or 4 by maintaining the circumferential surface temp. of the can 6 at about 120-250 deg.C. The vapor deposition of the film 2 is accomplished while about <=800g/mm.<2> tension is applied on the film 10. An excellent magnetic recording medium free from curling is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to perpendicular magnetic recording media with excellent high-density recording characteristics;
In particular, it relates to a method of manufacturing vertical floppy disks.

Conventional Structure and Problems There is a perpendicular recording method as a magnetic recording method with excellent short wavelength recording characteristics. This method requires a perpendicular magnetic recording medium in which residual magnetization remains in a direction substantially perpendicular to the film surface of the recording medium. Perpendicular magnetic recording media consist of a magnetic layer (mainly composed of CO and (r) with residual magnetization remaining in a direction approximately perpendicular to the film surface) on a substrate made of a non-magnetic material such as a polymeric material or a non-magnetic metal.
This magnetic layer (hereinafter referred to as a co-Cr perpendicular magnetization film) is formed by a sputtering method or a vacuum evaporation method (including a method in which a film is deposited by ionizing some of the evaporated atoms, such as the ion derating method). This is what I did.

When forming a C0-Cr perpendicularly magnetized film on a substrate made of a polymer material (by vacuum evaporation method), first T
It is known that the characteristics of perpendicularly magnetized films such as l), co(:r) are improved by depositing an i film and a co-Cr film thereon. When a permalloy film is provided between the -Cr perpendicular magnetization film, recording efficiency and reproduction output are improved compared to the case where there is no permalloy film.

The medium shown in FIG. 1 (al) has a permalloy film 3 formed on a base or plate 1 made of a polymeric material, and a Ti film 4
The medium shown in FIG. It has a structure in which a perpendicular magnetization film 2 is formed through (o-(r).

Generally, when a metal thin film is formed on a substrate made of a polymeric material, curling occurs such that the metal thin film 5 is on the inside or outside, as shown in FIG. (a) is called a positive curl, and (b) is called a reverse curl.When such a curl occurs, ferromagnetic metal is deposited as a thin film, and when used as a floppy disk, it is necessary to improve rotational stability and magnetic rad touch. etc. is not bad, also,
A problem arises in that the magnetic surface is easily scratched by contact with the cartridge. In order to use it as a floppy disk, the width of the tape must be (Lo-L) /
It is necessary that Lo be 10 inches or less. However, L
is the length in the curled state as shown in FIG. 2(a), (bl), and Lo is the length in the uncurled state.

Currently, polyethylene terephthalate film is mainly used as the substrate for floppy disks. Polyethylene terephthalate film has excellent cost and stability, and it is desirable to use this film as a substrate for vertical floppy disks. Note that a perpendicular recording type floppy disk is referred to herein as a vertical floppy disk. When a perpendicular magnetic recording medium is fabricated by a vacuum evaporation method using a polyethylene terephthalate film as a substrate, it is generally found that (Lo-L
, ) /Lo exceeds 10 inches, making it difficult to use as a floppy disk.Purpose of the InventionThe present invention is to produce a perpendicular magnetic recording medium by a vacuum evaporation method using a polyethylene terephthalate film as a substrate. Ti film, permalloy film and Co-(:r
By appropriately setting the film thickness and the temperature of the circumferential surface of the cylindrical can during vapor deposition, (L)/Lo is 1.
The object of the present invention is to obtain a perpendicular magnetic recording medium having an excellent perpendicular magnetic recording medium with a coefficient of 0 or less and almost no curling.

Structure of the Invention The method for manufacturing a perpendicular magnetic recording medium of the present invention is carried out as follows. Namely, polyethylene terephthalate film,! : A Ti film with a thickness of about 300 to 800 μm and a Ti film with a thickness of about 1000 to 5000 μm are applied on the film while running the film along the surface of the can. The permalloy film is formed at a temperature of about 10 to 80°C at the surface of the can. Then, (o-(
The surface temperature of the can of the perpendicularly magnetized film is about 120 to 25
It is formed by vacuum deposition at 0°C. Note that either the Ti film or the permalloy film may be formed first.

EXAMPLE In the vacuum deposition method, a long perpendicular magnetic recording medium can be produced by performing the deposition while running the polyethylene terephthalate film along the curved surface of a cylindrical can. FIG. 3 is a schematic diagram of the internal structure of the continuous winding type vacuum evaporation apparatus.

A polyethylene telefter (V-) 10 serving as a substrate runs along the circumferential surface of the cylindrical can 6. 7.8 is a roll for winding the substrate, and 9 is a vapor deposition source. It will be explained below that when a two-layer film medium is produced using such a vacuum evaporation apparatus, a medium with less curl can be obtained by using the method of the present invention.

In a floppy disk, when polyethylene terephthalate 10 is used as a substrate and a magnetic layer made of a thin metal film is formed on the surface thereof, the thickness of this film 10 is preferably within the range of about 17 to 50 μm.
If it is thinner than 7 μm, the stiffness is too low, and if it exceeds 50 μm, the stiffness is too strong. As a result, about 17~
If a film 10 outside the range of 50 μm is used, it will be difficult to use as a floppy disk due to poor mechanical customization such as rotational stability and poor magnetic rad touch.

As a floppy disk (:o-Cr perpendicular magnetization film 2
, the thickness of the permalloy film 3 and the TI film 4 is 60 mm.
0-2500 people, 1000-5000 people and 300 people
It is necessary to increase the number to ~800 people. If the thickness of either film is less than the above range, sufficient recording and reproducing characteristics for a floppy disk will not be obtained due to deterioration of crystal orientation, decrease in total magnetic flux, etc. Furthermore, if the film thickness exceeds the above range, cracks will occur when a polyethylene terephthalate film with a film thickness of 17 to 50 μm is used as a substrate, making it impossible to use it as a floppy disk.

Under the above film thickness conditions, a two-layer film medium as shown in Fig. 1(a) and (bl) was prepared using a continuous winding type vacuum evaporation apparatus having the structure shown in Fig. 4, and the curl was examined. The results will be explained using a table.The device shown in Figure 4 is
Although it is almost the same as the apparatus shown in the figure, a shielding plate 11 is installed to prevent high-incident-angle components of evaporated atoms from adhering to the substrate. A floppy disk is completed by punching out a long medium on which a magnetic layer is formed into a circular shape using the apparatus shown in FIG.

The table shows the temperature and curl state (L
o−L)/Lo is shown.

Surface Ti had almost no effect on curling as long as the film thickness was within the range of about 300 to 800 layers. Also, Figure 1 fat
, (bl) In either structure, there was no difference in curl and the results shown in the table were obtained.The surface of the cylindrical can 6 when C0-Cr or permalloy 1-3 was vapor-deposited was heated at 250°C.
If the temperature exceeds 100%, the melting point of polyethylene terephthalate becomes extremely close to that of polyethylene terephthalate, and the film becomes punctured or cut, making vapor deposition impossible.

As is clear from the table, when permalloy film 3 is deposited and c
The temperature of the curved surface of the cylindrical can 6 during the deposition of the o-0, r perpendicularly magnetized film 2 was set to about 10 to 80°C and about 120 to 2°C, respectively.
When the temperature is 50°C, a two-layer film medium with (Lo-L)/L0 of 10% or less can be obtained. If the film is formed outside this temperature range, it will curl so much that it will be difficult to use it as a floppy disk.

In a continuous winding type vacuum evaporation apparatus as shown in FIG. 4, the film 10 is run under tension. If this tension is too strong, the film 10 is likely to wrinkle. especially,
co-(r) When the perpendicularly magnetized film 2 is deposited, the temperature of the diethylene terephthalate film 10 is not above 100°C, and the glass transition point (approximately 70 to 80°C) has been exceeded. As a result of experiments, it became clear that the tension should be less than 800P/single to prevent this from happening.

Although the above description has been made of a single-sided floppy disk in which the magnetic layer is formed only on one side of the substrate, the method of the present invention can also be applied to a double-sided floppy disk in which the magnetic layer is formed on both sides of the substrate. By doing so, a disk with almost no curls can be obtained.

Next, a concrete example will be described. A Ti film 4 with a thickness of 40 OA is formed on a polyethylene terephthalate film 10 with a thickness of 30 μm using a vacuum evaporation apparatus as shown in FIG.
A C0-Cr perpendicular magnetization film 2 having a thickness of 1,500 yen was formed through the following steps. However, when permalloy film 3 is deposited and co-
(The temperature of the surface of the cylindrical can 6 during the deposition of the perpendicularly magnetized film 2 was 40°C and 220°C, respectively, and the traveling speed of the film 10 during the deposition was 10 m 7 minutes.The tension was 600 t/rran. ”.

The obtained bilayer film medium was reversely curled and its (Lo
-L)/Lo was 5%. Furthermore, there were no cracks or wrinkles, and the rotational stability and recording/reproducing characteristics as a floppy disk were excellent compared to the egg weight.

Effects of the Invention According to the present invention, while using a polyethylene terephthalate film which is excellent in cost and stability as a substrate, it is possible to easily produce a perpendicular magnetic recording medium having a two-layer film structure with almost no curl, which is particularly useful as a perpendicular floppy disk. It has the advantage that it can be manufactured in

[Brief explanation of the drawing]

(81 and (bl) in FIG. 1 are partial cross-sectional views showing the structure of a double-layer film medium, (al and fbl in FIG. 2 are partial cross-sectional views showing the curled state of a general recording medium, and FIG. Figure 4 is a schematic configuration diagram showing the internal structure of the continuous winding vacuum evaporation apparatus. 2... co-Cr perpendicular magnetization film, 3... permalloy film, 4... ru@, 6-...・Can, 10...Polyethylene terephthalate film (a) (b) Figure 1 (a) (b) Figure 2

Claims (1)

Scope of Claims (11! While running a polyethylene terephthalate film with a thickness of about 17 to 50 μm along the curve of the can, a Ti film with a thickness of about 300 to 800 and a Ti film with a thickness of about 1000 to 5,000 people permalloy membrane, the surface temperature of the can is about 10 ~
Each film was formed by vacuum evaporation at a temperature of 80°C, and then an o-Cr perpendicular magnetization film with a film thickness of about 600 to 2,500 was deposited in a vacuum at a surface temperature of about (3) to 250°C. A method for manufacturing a perpendicular magnetic recording medium, characterized in that the perpendicular magnetic recording medium is formed by vapor deposition. (2) The tension applied to the polyethylene terephthalate film during the formation of the co-1:r perpendicular magnetization film is about 8.
00 f/1tan Claim No. (
1) A method for manufacturing a perpendicular magnetic recording medium according to item 1). (3) A method of manufacturing a perpendicular magnetic recording medium according to claim (1) or (2), characterized in that the Ti film is the Ti film among the Ti film and the permalloy film. (4) The above 7i The method for manufacturing a perpendicular magnetic recording medium according to claim 1 or 2, wherein the permalloy film is the one of the film and the permalloy film.