JPS63138519A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase reproduction output at the time of executing recording and reproducing with a ring head by using crystalline Co as the Co to be incorporated into a perpendicularly magnetized layer. CONSTITUTION:The perpendicularly magnetized layer essentially consisting of the Co and the oxide thereof is formed on a substrate (e.g.: PE terephthalate film) and the Co in said film is made crystalline. The crystalline Co in the magnetized layer is hexagonal and the dispersion angle ( theta50) of the C axis is preferably <=15 deg.. Fe, Ni or the oxide thereof is preferably incorporated into the magnetized layer in order to adjust magnetic characteristics or to improve corrosion resistance. Then, the medium having the large reproduction output by the ring head is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film type perpendicular magnetic recording medium.

[Prior Art] Examples of perpendicular magnetic recording media equipped with a perpendicularly magnetized film mainly composed of cobalt and its oxides include those disclosed in Japanese Patent Application Laid-open Nos. 140629-1982, 162622-1980, and those by the present inventors. There is Japanese Patent Application Laid-open No. 61-57028. The magnetostatic properties of these conventional perpendicularly magnetized films mainly made of cobalt and its oxides are comparable to those of perpendicularly magnetized films made of C--Cr.

[Problems to be Solved by the Invention] However, in the conventional perpendicular magnetic recording medium equipped with a perpendicularly magnetized film mainly composed of cobalt and cobalt oxides, when recording and reproducing are performed using a ring head, the reproducing output is small. There were drawbacks.

Although the ring head has a proven track record and is reliable for longitudinal recording media, its low reproduction output is a major problem in putting perpendicular magnetic recording media into practical use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a perpendicular magnetic recording medium which has improved the above-mentioned drawbacks, that is, has a large reproduction output when recording and reproduction is performed using a ring head and can be put to practical use.

[Means for Solving the Problems] That is, the present invention provides a perpendicular magnetic recording system having a perpendicularly magnetized film mainly made of cobalt and its oxides, which has magnetic anisotropy in the direction perpendicular to the film surface, on a substrate. The perpendicular magnetic recording medium is characterized in that cobalt in the perpendicular magnetization film is crystalline.

The substrate that can be used in the present invention is not particularly limited, but suitable organic polymer materials include polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polyethylene dicarboxylate, aromatic polyamides, and polyphenylene. Sulfide etc. are suitable. In particular, biaxially stretched films and sheets made of the above-mentioned organic polymer materials are most suitable because of their excellent flatness and dimensional stability.

The thickness of the substrate is also not particularly limited, but in the case of sheets, tapes, cards, etc., it is preferably in the range of 3 to 500 μm, particularly 4 to 200 μm, from the viewpoint of workability and dimensional stability.

Prior to forming the perpendicularly magnetized film, which will be described later, the substrate used in the present invention is prepared to facilitate adhesion, improve flatness, prevent coloring and antistatic properties, etc.
Various surface treatments and pre-treatments may be performed for the purpose of imparting wear resistance and the like.

In the present invention, a perpendicularly magnetized film having magnetic anisotropy in the direction perpendicular to the film surface is defined as having an anisotropic magnetic field (Hk) value of 2.0.
The perpendicularly magnetized film has a KO of 8 or more, and the perpendicularly magnetized film is composed of columnar structured grains and voids oriented approximately perpendicularly to the substrate surface.

In the perpendicular magnetic recording medium of the present invention, it is necessary that cobalt, which constitutes one of the main components of the perpendicular magnetization film, be crystalline. Here, crystalline cobalt refers to one whose diffraction image can be obtained by X-ray diffraction, and specifically refers to one in which a diffraction peak of the (002> plane of cobalt (hexagonal crystal) appears in the X-ray diffraction pattern.

In order to roughly improve reproduction output and recording density characteristics, it is desirable that the C-axis fractional angle (Δθ50) of crystalline cobalt in the perpendicularly magnetized film is 15° or less.

In the present invention, the cobalt oxide constituting another main component of the perpendicularly magnetized film is specifically Co0. CO2O
3. refers to CO3O4, etc., and also includes cobalt peroxides and suboxides having non-stoichiometric compositions.

In addition to cobalt and its oxides, which are the main components, the perpendicularly magnetized film of the present invention contains iron, nickel, or oxides thereof for the purpose of adjusting magnetic properties or improving corrosion resistance. This is desirable, and it is effective to add iron to make the perpendicular magnetization film have a coercive force suitable for a ring head, and it is useful to add nickel to improve corrosion resistance.

When iron and/or nickel are added, the ratio of iron and nickel metal atoms to the amount of cobalt, iron and nickel metal atoms in the perpendicularly magnetized film is 20% by weight in terms of dosage ratio.
The following is desirable in order not to reduce the anisotropic magnetic field (T1k).

The perpendicular magnetic recording medium of the present invention can be formed by a so-called reactive vacuum deposition method in which vapor deposition is performed by introducing both a gas with low chemical activity and oxygen gas into a vacuum atmosphere. Any method such as resistance heating evaporation, induction heating evaporation, electron beam evaporation, or ion brating can be used as a vacuum evaporation method, but electron beam evaporation is the most suitable method because it is capable of high-speed evaporation and is easy to control. There is.

In the present invention, the method of forming crystalline cobalt in the perpendicularly magnetized film is to increase the pressure near the base portion where the film is formed to some extent and to reduce the absolute amount of oxygen gas in the supplied gas to some extent. is desirable,
Specifically, the pressure near the base is 1, Qx 10-
The range is 3 Torr to 2.0x10''''2 Torr, and it is desirable that the ratio of oxygen gas supply amount/evaporation rate is 10 cc/μm or more and less than 70 CC/μm during the supply of oxygen gas.

The above manufacturing method is an example and is not necessarily limited to this. .

Next is “JJ” based on the drawing? An example of method j will be explained. FIG. 2 is a schematic diagram without showing an example of an electron beam evaporation apparatus for manufacturing the perpendicular magnetic recording medium of the present invention.

A running system for a long organic polymer film serving as a base is arranged inside the vapor deposition apparatus.

In FIG. 2, reference numeral 1 denotes a substrate supply device, and an organic polymer film 6 wound into a roll is attached to a core. The film 6 passes through the nip roll 2, the main drum 3, and the nip roll 4, and is then wound onto a winding core provided in a substrate winding device 5.

Reference numeral 14 denotes a partition wall that divides the vacuum chamber 10 into an upper tank 15 and a lower tank 16. As shown in the figure, the central part of the partition wall 14 is bent toward the lower tank near the drum to form a side wall portion 20 of a predetermined length. At the same time, both ends of the blocking plate 7 are connected to the tip of the side wall portion 20.

The upper tank 15 and the lower tank 16 are each exhausted from exhaust ports 11.12. The blocking plate 7 is for restricting the incident angle of the evaporated vapor flow, and has an opening 17 in the center for the evaporated vapor inflow and injection.
is formed to prevent components of the evaporated vapor flow from obliquely entering the base film.

That is, the evaporated vapor flow not restricted by the shield plate 7, that is, the component incident approximately perpendicularly to the substrate film is 17
A8 is an electron beam evaporator, and 9 is an evaporation material, for example cobalt.

A space 19 surrounded by the side wall portion 20, the blocking plate 7, and the lower end side peripheral surface of the main drum 3 is a gas supply chamber.

Among the gases supplied to the deposition atmosphere, one type (e.g., oxygen gas) enters the gas mixer 21 from the gas control valve 13A, and the other type (e.g., nitrogen gas) enters the gas mixer 21 from the gas control valve 13B. After being mixed and stirred in the gas supply pipe 18, the gas is supplied to the gas supply chamber 19.

A long film, such as a polyethylene terephthalate film, is disposed in the long film running system of the vapor deposition apparatus shown in FIG. From 11.12 onwards, the air will be evacuated. The pressure of the upper tank 15 is 5×10''4 Torr.
The pressure in the gas supply chamber 19 is maintained at 5X until the pressure is below r.
Each exhaust port 11.12 until the pressure is below 10-” Torr.
Exhaust more.

Next, a predetermined amount of cobalt is melted and evaporated by electron beam evaporation while running the polyethylene terephthalate film that is the base. By adjusting the pressure near the substrate, that is, the pressure in the gas supply chamber 19, is set to a predetermined pressure, and by appropriately setting the beam current value of the electron beam evaporator, the ratio of oxygen amount/evaporation rate can be adjusted. It is set to a predetermined level. As described above, a perpendicularly magnetized film containing crystalline cobalt can be continuously formed on the base film.

The thickness of the perpendicular magnetization film of the present invention is not particularly limited, but is practically in the range of 0.02 μm to 5 μm, and is suitable for flexibility, contact with the magnetic head, and the thickness of the magnetic recording layer. When considering the film formation rate, a range of 0.05 μm to 2.0 μm is desirable.

[Operation of the invention] The reason why the reproduction output of conventional perpendicularly magnetized films made of cobalt and cobalt oxides in ring heads is low is unknown, but these films have poor crystallinity and orientation, and
The peak of the cobalt (002> plane) does not appear in the line diffraction pattern, or even if it does appear, it is very small.

As a result of intensive studies by the present inventors, it was possible to obtain a perpendicularly magnetized film with improved crystallinity and orientation.

It is considered that by using a perpendicular magnetic recording medium containing the improved crystalline cobalt of the present invention in a film, it was possible to increase the reproduction output.

[Method for evaluating properties ① Method for evaluating crystallinity The crystallinity of cobalt was determined by whether or not a peak of the diffraction line appeared at the plane index (002>) of hexagonal cobalt in the X-ray diffraction pattern. Surface index of hexagonal cobalt (
002>, the diffraction angle (2θ) is approximately 44.4°.

The xm diffraction pattern was obtained by wide-angle X-ray diffraction (diffractometer) method. The measuring device and measurement conditions are shown below.

X-ray generator: Rigaku Denki RU-2008 (rotating anode cathode type), X-ray source: CLIKα ray, output 40KV, 1
00mA Goniometer: 2155D model manufactured by Rigaku Denki ■ Detector Niscintillation counter counting recording device: RAD-B type manufactured by Rigaku Denki Also, the dispersion angle (Δθ5°) of the cobalt C axis is set at the (002>peak of the sample). The measurement was carried out using the rocking curve method, in which the sample was fixed at a position and the θ axis was moved at a speed of 2°/min to obtain a diffraction intensity curve (rocking curve).The half width (Δθ50) of the obtained diffraction intensity curve was This is the dispersion angle of the C axis.

The equipment used was the same equipment used for wide-angle X-ray diffraction.

(2) Quantitative analysis method for metal atoms in the film Hydrochloric acid was added to the sample to dissolve the film, and quantitative analysis was performed using the ICP emission spectrometer described below.

Analyzer @2 ■ 5PS1100 plasma emission spectrometer manufactured by Daini Seikosha.

■Measurement method of playback output Apply lubricant to the obtained porcelain recording medium, and
The test material is punched out in the shape of a 5-inch floppy disk.

A commercially available floppy disk drive (“MDD516A” manufactured by Canon Electronics) was used as a recording/playback device.
Recording/reproducing characteristic curves were obtained.

Recording was performed at the optimum recording current, and the recording frequency range was 10
0KHz to 3.5MHz. The reproduction output used in Examples and Comparative Examples is expressed as a relative value using the value when the recording frequency was 2.5 MH2.

The head used has a gap length of 0.25 μm and a number of windings of 30.
A turn ferrite ring head was used. The relative speed between the head and the medium is 1.28 m/sec.

[Example] The present invention will be explained based on examples.

Example 1.2 Comparative Example 1.2 The perpendicular magnetic recording media of Example 1.2 and Comparative Example 1.2 were obtained using the electron beam evaporation apparatus shown in FIG. 2 and under the manufacturing conditions shown in Table 1. Ta.

The substrate used in the Examples and Comparative Examples was 50 μm thick 2
It is an axially stretched polyethylene terephthalate film. The evaporation rate was adjusted by the beam current, and the film speed was adjusted so that the thickness of the perpendicularly magnetized film was approximately 3,000 mm.

In Example 1.2, oxygen gas and nitrogen gas were supplied via a gas mixer, the amount of oxygen gas supplied was reduced relative to the evaporation rate, and the pressure in the gas supply chamber was increased to obtain a perpendicularly magnetized film on the substrate. This is an example. In addition, Comparative Example 1 is an example in which only oxygen gas is supplied and formed under low pressure, and Comparative Example 2 is an example in which oxygen gas and nitrogen gas are supplied through a gas mixer. This is an example in which a perpendicularly magnetized film is obtained on a substrate by relatively increasing the amount of gas and making the pressure in the gas supply chamber low.

FIG. 1 shows the X-ray diffraction patterns of the perpendicular magnetic recording media obtained in Example 1.2 and Comparative Example 1.2 together with the polyethylene terephthalate film as the substrate.

In Figure 1, the vertical axis is the relative diffraction intensity, and the horizontal axis is the diffraction angle (2
θ). In addition, in Fig. 1, 20 corresponds to the (002> plane of hexagonal cobalt at approximately 44.4°.
In each of the figures, the small peaks seen at about 47° and 54° of 20 are peaks originating from the base polyethylene terephthalate film.

As is clear from Figure 1, Example 1.2 has a diffraction peak of the hexagonal cobalt (002> plane, and the cobalt is crystalline), but Comparative Example 1 has no diffraction peak of the cobalt (002) plane. Although Comparative Example 2 had a diffraction peak, it was very small, and it was clear that crystalline cobalt was not contained in the perpendicularly magnetized film of Comparative Example 1.2.

Hexagonal cobalt (0
02> Presence or absence of peak of plane, cobalt C-axis dispersion angle (△θ5
Table 1 also shows the reproduction output (relative value) when the reproduction output of Comparative Example 1 is taken as the reference value.

As shown in Table 1, Example 1.2 has a large reproduction output;
Although the effects of improved crystallinity and orientation were seen, Comparative Examples 1 and 2 had poor crystallinity and small reproduction output, making it difficult to put them to practical use as perpendicular magnetic recording media.

[Effects of the Invention] As described above, the perpendicular magnetic recording medium of the present invention in which the crystallinity and orientation of cobalt are improved can obtain the effect of increasing the reproduction output, and a perpendicular magnetic recording medium that can be put to practical use can be obtained. I was able to provide it.

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction diagram for explaining the crystallinity of perpendicular magnetic recording media of the present invention and a comparative example, in which the vertical axis represents relative diffraction intensity and the horizontal axis represents diffraction angle (2θ). FIG. 2 is a schematic diagram showing an example of a vacuum evaporation apparatus for manufacturing the perpendicular magnetic recording medium of the present invention. 1: Substrate supply device @ 3: Main drum 5: Substrate winding device @ 6: Organic polymer film 7: Blocking plate 8: Electron beam evaporator 9: Evaporation material
10: Vacuum chamber 11: Exhaust port 12: Exhaust port 13A, 13B: Gas flow rate control valve 18
: Gas supply pipe 19: Gas supply to 21 Nigas mixer

Claims (3)

[Claims] (1) In a perpendicular magnetic recording medium provided with a perpendicular oxide film mainly composed of cobalt and its oxide having magnetic anisotropy perpendicular to the film surface on a substrate, the cobalt in the perpendicular magnetization film is crystallized. A perpendicular magnetic recording medium characterized by high quality. (2) The crystalline cobalt in the perpendicularly magnetized film is hexagonal,
The perpendicular magnetic recording medium according to claim 1, wherein the cobalt has a C-axis dispersion angle (Δθ_5_0) of 15° or less. (3) Claim 1, characterized in that the perpendicularly magnetized film contains iron, nickel, and oxides thereof, and the proportion of iron and nickel metal atoms to all metal atoms is 20% by weight or less. The perpendicular magnetic recording medium described in (1).