JPS63291214A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent perpendicular magnetic anisotropy and to improve electromagnetic conversion characteristics by specifying the squareness ratio of a perpendicularly magnetized film to >=0.83. CONSTITUTION:Rs* is specified to >=0.83 when the magnetization at the intersected point N of a straight line S having an inclination theta2 equal to an inclination theta1 in the part where the hysteresis curve of the perpendicularly magnetized film in the direction perpendicular to the film plane intersects with the abscissa X and passing an origin O and the hysteresis curve H is designated as Mr and the value Mr/Ms obtd. by dividing this Mr by the saturation magnetization Ms is designated as squareness ratio Rs*. The perpendicularly magnetized Co-O film having the excellent perpendicular magnetic anisotropy is, therefore, produced. The recording medium having the excellent electromagnetic conversion characteristics of a perpendicular magnetic recording medium is thereby easily obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perpendicular magnetic recording medium that is compatible with high-density recording.

[Summary of the invention]

The present invention aims to improve electromagnetic conversion characteristics by setting the squareness ratio Rs' within a predetermined range in a perpendicular magnetic recording medium formed by forming a Co-0 perpendicularly magnetized film on a non-magnetic support. The objective is to provide a perpendicular magnetic recording medium with excellent physical durability and high productivity.

[Conventional technology]

In recent years, there has been a remarkable improvement in recording density due to shorter wavelengths and narrower trunks in magnetic recording, and perpendicular magnetism using so-called perpendicular magnetization films, which can be magnetized in the perpendicular direction of the film surface, has put into practical use an areal recording density close to that of optical recording. It is expected that this will be achieved by using recording media. Under these circumstances, perpendicular magnetic recording media using a Co-Cr-based perpendicular magnetization film and a perpendicular magnetic recording medium using a Co-0-based perpendicular magnetization film as the perpendicular magnetization film have been proposed. Although the perpendicular magnetic recording medium using the Co-0 perpendicular magnetization film is advantageous in manufacturing compared to the perpendicular magnetic recording medium using the Co-Cr perpendicular magnetization film, its magnetic properties are However, there is a problem that the electromagnetic conversion characteristics are not sufficient, especially the recording/reproducing characteristics in the short wavelength range are not sufficient.

[Problem that the invention seeks to solve]

As mentioned above, the Go-0-based perpendicular magnetic recording medium is a G type perpendicular magnetic recording medium that has been conventionally proposed as a perpendicular magnetic recording medium.

There is a problem in that the magnetic properties are inferior to -Cr-based perpendicular magnetic recording media.

The present invention was proposed in view of the above-mentioned circumstances, and aims to improve the magnetic properties of a Co-0 perpendicular magnetic recording medium, thereby improving electromagnetic conversion properties and mechanical durability. The object of the present invention is to provide an excellent perpendicular magnetic recording medium with high productivity.

[Means for solving problems]

In order to achieve the above-mentioned object, the present inventors have conducted extensive research and have determined Rs'', which is a standard for the perpendicular magnetic anisotropy of a perpendicular magnetic recording medium when manufacturing a Go-0 perpendicular magnetic recording medium. It has been found that a Co-0-based perpendicular magnetic recording medium with excellent magnetic properties can be obtained by setting the value of .

The present invention was proposed based on the above-mentioned findings, and as shown in FIG. A straight line (S) that has a slope (θ2) equal to the slope (θI) at the point where the hysteresis curve (H) perpendicular to the film surface of the magnetized film intersects with the horizontal axis (X) and passes through the origin (0) and hysteresis The magnetization at the intersection (N) with the curve (H) is M
``Then, the value M r /
When M s is defined as R311, R3° is 0.83
It is characterized by the above.

Here, the above R3* is one of the methods for evaluating the perpendicular magnetic anisotropy of a perpendicular magnetic recording medium newly introduced by the inventors in the present invention.

Generally, it is widely known that the squareness ratio of a hysteresis loop is used as one of the methods for evaluating an in-plane magnetized film.

It is determined that the above-mentioned in-plane magnetized film exhibits better in-plane orientation as the squareness ratio increases. On the other hand, the above squareness ratio can also be applied when evaluating the perpendicular magnetic anisotropy of a perpendicularly magnetized film of a perpendicular magnetic recording medium. However, in this case, the hysteresis curve appears to be around 1 above due to the action of the demagnetizing field, so it is necessary to make corrections when determining the squareness ratio. As one of the above correction methods, a method of correction using a demagnetizing field Hd-4πM has been proposed. However, with the method of correcting using a demagnetizing field Hd-4πM, sufficient correction cannot be made, and the perpendicular magnetic anisotropy cannot be accurately evaluated.

Therefore, as shown in FIG. 1, the vertical hysteresis curve (H) of the perpendicularly magnetized film has a slope (θ2) equal to the slope (θ1) at the intersection with the horizontal axis (X), and the origin (,0 ) The magnetization at the intersection (N) of the straight line (S) passing through
We decided to evaluate the perpendicular magnetic anisotropy of the perpendicularly magnetized film.

The above-mentioned squareness ratio R3* is influenced by the oxygen concentration introduced and changes with changes in the saturation magnetic flux density Bs when producing a Co-0 perpendicularly magnetized film. therefore,
It is important to obtain a predetermined saturation magnetic flux density of 13 s by the introduced oxygen concentration when producing the Co-0 perpendicular magnetization film.
The magnetic layer of Co-0 to be produced exhibits perpendicular magnetic anisotropy when the saturation east density Bs is 5000<Bs<12000. Therefore, even if the amount of oxygen introduced is too large, the value of Bs will become small, which is not preferable.According to experiments by the present inventors, when CO gold content is f185 at% and oxygen content is 1t15 at%, C.

The −〇-based perpendicular magnetization film had the best magnetic properties.

In the present invention, the squareness ratio Rs" is preferably 0.83 or more. If the squareness ratio Rs0 is smaller than 0.83, a predetermined perpendicular magnetic anisotropy cannot be obtained.

In the present invention, when producing a perpendicular magnetic recording medium,
It is preferable that the introduced oxygen be introduced at an incident angle close to that of the 00 steam flow so as not to disturb the perpendicular magnetic anisotropy of the Co-0 perpendicularly magnetized film, and within the range of 0" to ψ≦45"'. It is preferable to keep it within.

If the incident angle of oxygen gas is 0°, it will be the same as the incident angle of the Co 5 vapor flow onto the non-magnetic support, which is unsuitable for practical reasons. Also, the incident angle of oxygen gas is 4
If it is larger than 5°, the incident state of the CO evaporation vapor flow onto the non-magnetic support will be disturbed, the perpendicular magnetic anisotropy of the Co-0 perpendicularly magnetized film will be easily disturbed, and the electromagnetic conversion characteristics etc. This is because there is a risk of deterioration of magnetic properties.

In addition, oxygen gas can be introduced from the upstream side in the direction of movement of the non-magnetic support (direction of arrow A in Figure 2), or from the downstream side of the direction of movement of the non-magnetic support (direction of arrow mark B in Figure 2). Although it may be introduced from the upstream side in the direction of movement of the nonmagnetic support, it is preferable to introduce it from the upstream side in the direction of movement of the nonmagnetic support, although it has no effect on the magnetic properties such as perpendicular magnetic anisotropy and electromagnetic conversion characteristics of the perpendicular magnetic recording medium. If oxygen gas is introduced from the upstream side in the direction of movement of the non-magnetic support, a large amount of oxygen will exist in the lower layer of the Co-0 perpendicularly magnetized film where a concentration gradient of oxygen gas is created.
The peel strength between the -0 perpendicular magnetization film and the nonmagnetic support can be increased, and the strength of the surface of the Co-0 perpendicular magnetization film can also be increased.

On the other hand, if oxygen gas is introduced from the downstream side in the direction of movement of the nonmagnetic support, a large amount of oxygen will exist in the upper layer of the Co-0 perpendicularly magnetized film where a concentration gradient of oxygen gas is created. , the surface of the Go-0 perpendicular magnetization film may be easily damaged.

As the material for the nonmagnetic support used in the present invention, any material that is used as a nonmagnetic support for ordinary magnetic recording media can be used. Organic polymer materials are particularly suitable in terms of processability, moldability, flexibility, etc. Among them, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethylene,
Polyolefins such as polypropylene, polymethyl methacrylate, polycarbonate, polysulfone, polyamide, aromatic polyamide, polyphenylene sulfide, polyphenylene oxide, polyamideimide, polyimide, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polytetrafluoroethylene, acetic acid Cellulose, methylcellulose, ethylcellulose, epoxy resin, urethane resin, or mixtures and copolymers thereof are suitable. In addition, the shape of the non-magnetic support is as follows:
These nonmagnetic supports, which may be in the form of drums, disks, sheets, tapes, cards, etc., are treated to facilitate adhesion, improve flatness, be colored, be antistatic, and have resistance to abrasion before forming the magnetic recording layer. Surface treatment or pretreatment may be performed for the purpose of imparting properties or the like.

Vacuum deposition methods that are applied in manufacturing perpendicular magnetic recording media in the present invention include resistance heating deposition, induction heating deposition, electron beam deposition, ion beam deposition, ion brating, laser beam deposition, arc discharge deposition, etc. Although any of the vacuum deposition methods can be performed, electron beam deposition and ion blating are used to improve the magnetic properties of the perpendicular magnetic recording medium, such as coercive force and anisotropic magnetic field, and to obtain a high deposition rate. The following methods are suitable, and the electron beam evaporation method is most suitable from the industrial viewpoint of operability and mass production.

[Effect]

According to the present invention, the squareness ratio R3'' of the perpendicularly magnetized film is 0.83
By doing the above, Co-
Since a 0-system perpendicular magnetization film can be produced, it is possible to improve the electromagnetic conversion characteristics of a perpendicular magnetic recording medium.

Further, since the saturation magnetic flux density and squareness ratio can be adjusted by adjusting the oxygen concentration introduced, a perpendicular magnetic recording medium having predetermined magnetic properties can be easily produced.

〔Example〕

Embodiments to which the present invention is applied will be described below with reference to the drawings.

Figure 2 shows an example of an electron beam evaporation apparatus for carrying out the method of manufacturing a perpendicular magnetic recording medium according to the present invention. The above electron beam evaporation apparatus includes a chamber (6) equipped with an exhaust system (5) and an electron gun (8), a supply roller (2) for a non-magnetic support (9), a cooling can (1), a perpendicular magnetic recording Medium (9)
A running system of a long non-magnetic support (9) consisting of a winding roller (3), and a vapor deposition system consisting of a crucible (4) equipped with Co and an oxygen gas introduction pipe (7). It is.

A non-magnetic support (on which a Co-0 perpendicular magnetization film is deposited)
9) is supplied from the supply roller (2) of the non-magnetic support (9), and after a Co-0 perpendicularly magnetized film is formed on the cooling can (1), it is wound up by the take-up roller (3). It will be done. Note that the cooling can (1) in which the Co-0 perpendicular magnetization film is deposited has a surface temperature of 1118°C near 0°C.
1, it has a cooling function (not shown).

The cooling can (
A shielding plate (
10) and (10) are provided to control the deposition state of the Co vapor flow from the crucible (4) and the introduction state of oxygen gas from the oxygen gas introduction pipe (7).

A crucible (4) equipped with Go is heated by an electron beam from an electron gun (8) provided in a chamber (6), and a non-magnetic support ( 9) Deposit on the surface.

At this time, oxygen gas is also introduced from the oxygen gas introduction pipe (7) provided on the upstream side in the direction of movement of the non-magnetic support, and the Co
A -0 perpendicular magnetization film is deposited on the non-magnetic support (9). Note that Co, which is heated and evaporated by the electron beam from the electron gun (8), can be deposited by controlling the deposition rate as desired.

Furthermore, by controlling the amount of oxygen gas introduced from the oxygen introduction tube (7) when depositing Co, it is possible to form a Go-0 perpendicular magnetization film having a predetermined oxygen concentration gradient. .

Note that the apparatus used in the manufacturing method of the present invention is not limited to the above-mentioned apparatus.

A perpendicular magnetic recording medium was manufactured using the apparatus described above. At this time, the crucible (4) contains Go with a purity of 99.9%.
was prepared, the deposition rate was 3600 people/sec, the running speed of the nonmagnetic support (9) was 16 m/sin, and the film thickness was 200 m/sin.
I tried to get 0 people. In addition, the oxygen introduction pipe (7) was installed on the upstream side in the direction of movement of the nonmagnetic support, and the incident angle of the introduced oxygen gas was set to 30'', and the oxygen gas flow rate was set to 300 cc/sin.
It was set to The atmospheric gas pressure during vapor deposition was 2 X L O-
A sample tape was prepared as described above.

A perpendicular magnetic recording medium was fabricated using the apparatus described above. At this time, Co with a purity of 99.9% is placed in the crucible (4).
was prepared, the deposition rate was 3600 persons/see, the running speed of the nonmagnetic support (9) was 15 m/+gin, and the film thickness was 2.
000 people. In addition, the oxygen introduction pipe (7) is installed on the upstream side in the direction of movement of the non-magnetic support, and the incident angle of the introduced oxygen gas is 50'' and the oxygen gas flow rate is 500cc/win.
It was set to The atmospheric gas pressure during vapor deposition was 2 x 10-'
A sample tape was prepared as described above with a Torr of 0 or more.

FIG. 3 shows an example of an electron beam evaporation apparatus used in Comparative Example 2. The electron beam evaporation apparatus described above includes a chamber (11) equipped with an exhaust system (20) and electron guns (18) and (19), a supply roller (12) for a non-magnetic support (22), and a first cooling can. (11), a running system for a long non-magnetic support (22) consisting of an intermediate roller (14), a second cooling can (12), and a take-up roller (15) for a perpendicular magnetic recording medium (22); A first crucible (16) with Ti and a second crucible (16) with Co-Cr.
7).

A perpendicular magnetic recording medium was manufactured using the apparatus described above. At this time, the first crucible (16) has a purity of 99.9.
% Ti was prepared, the deposition rate was 900 people/31 IC, the running speed of the nonmagnetic support was 15 m/win, and the film thickness was 5 m/win.
The film was formed so that there were 00 people. Next, the second crucible (
17) Prepare Go-20 wt% Cr and set the deposition rate to 27
00 people/see, running speed of non-magnetic support 16 m/s
The film was formed to have a thickness of 1,500 layers. The atmospheric gas pressure during vapor deposition at this time was 3 x 10-'Tor.
A sample tape was prepared in the same manner as above.

For each sample tape produced as described above,
The saturation magnetic flux density Bs, perpendicular coercive force Hc, anisotropic magnetic field Hk, squareness ratio R3'', and mechanical durability were measured.For mechanical durability, phosphate ester lubricant was applied to the surface of the magnetic layer. The 0 surface condition was evaluated by visual observation after measuring the still durability and the still durability. Those with scratches on the surface of the magnetic layer after durability measurement are indicated with an x mark.The results are shown in
Also shown in the table is Example 1. The relationship between recording wavelength and reproduction output for Example 2 and Comparative Example 1 is shown in FIG. 4.
Symbol in Figure 4! The symbol ■ corresponds to Example 1, the symbol ■ corresponds to Comparative Example 1, and the symbol ■ corresponds to Comparative Example 2.

As is clear from Table 1 and FIG. 4, the perpendicular magnetic recording media of Example 1 comprising a Co-0 perpendicular magnetization film and Comparative Example 2 comprising a Co-Cr perpendicular magnetization film had R3″ The value of C is included within the scope of the present invention, and the electromagnetic conversion characteristics do not change much, but C .

It can be seen that Comparative Example 2, which is made of a Co-Cr-based perpendicular magnetization film, is inferior to Example 1, which is made of a -〇-based perpendicular magnetization film.

Therefore, these results show that the perpendicular magnetic recording medium according to the present invention has excellent magnetic properties, electromagnetic conversion properties, and mechanical durability.

〔Effect of the invention〕

As is clear from the above description, the perpendicular magnetic recording medium to which the present invention is applied has a perpendicular magnetization film with a squareness ratio Rs'' of 0.83.
By doing the above, it is possible to obtain a Co-0 perpendicularly magnetized film having excellent perpendicular magnetism and anisotropy, thereby providing a perpendicular magnetic recording medium having excellent electromagnetic conversion characteristics.

Furthermore, since the saturation magnetic flux density and squareness ratio can be adjusted by adjusting the oxygen concentration introduced, a perpendicular magnetic recording medium having predetermined magnetic properties can be easily produced.

Furthermore, by setting the introduction point of oxygen gas on the upstream side in the moving direction of the non-magnetic support, the oxygen concentration becomes higher in the lower layer of the Co-0 perpendicularly magnetized film, so that It is possible to form a Co-0 perpendicularly magnetized film with increased peel strength from the magnetic support and excellent mechanical strength.

Therefore, by applying the present invention, Co-0, which has excellent perpendicular magnetic anisotropy and electromagnetic conversion characteristics and has high mechanical strength, can be used.
A perpendicular magnetic recording medium having a perpendicular magnetization film can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the squareness ratio R3°. FIG. 2 is a schematic diagram showing an example of a vacuum evaporation apparatus used when manufacturing a perpendicular magnetic recording medium to which the present invention is applied. FIG. 3 is a schematic diagram showing an example of a vacuum evaporation apparatus used in manufacturing a perpendicular magnetic recording medium as a comparative example. FIG. 4 is a characteristic diagram showing the relationship between recording wavelength and reproduction output of a perpendicular magnetic recording medium to which the present invention is applied. H...Hysteresis curve θ1. θ8...Inclination 0...Origin S...Line N...Intersection Ms...Saturation magnetization Mr...Magnetization Rs"...Square ratio patent applicant Sony Corporation representative Patent attorney Akira Koike Sakae Enso - Masaru Sato tυ Figure 3 Figure 4

Claims (1)

[Claims] In a perpendicular magnetic recording medium comprising a Co--O perpendicularly magnetized film formed on a non-magnetic support, a hysteresis curve perpendicular to the film surface of the perpendicularly magnetized film intersects with the horizontal axis. The magnetization at the intersection of the hysteresis curve and a straight line that has the same slope and passes through the origin is M_r, and when the value M_r/M_s obtained by dividing this M_r by the saturation magnetization M_s is defined as R_s^*, R_s^
A perpendicular magnetic recording medium characterized in that * is 0.83 or more.