JPH09282633A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium having excellent C/N characteristics by laminating two or more Co-O magnetic films in such a manner that in the interface between magnetic films, the o density is higher than the Co density. SOLUTION: This magnetic recording medium has Co-O magnetic films. In the Co-O magnetic film, the o density is higher than the Co density in the region from 25% depth of the film thickness (especially 30%) from the surface of the film to 60% depth (especially 55%) of the film thickness from the surface, or, the recording medium has Co-O magnetic films, and Auger electron spectroscopy analysis of the Co-O magnetic film shows the following property. In the middle part of the time period from the 25% (especially 30%) of the whole sputtering time from the start of sputtering to 60% (especially 55%) of the whole sputtering time in the graph indicating amts. of Co and O as the vertical axis and the sputtering time as the horizontal axis, the O density is higher than the Co density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a Co-O type magnetic film.

[0002]

In a magnetic recording medium such as a magnetic tape, due to the demand for high density recording, the magnetic film provided on the non-magnetic support is not a coating type using a binder resin. , A metal thin film type that does not use a binder resin has been proposed. That is, there has been proposed a magnetic recording medium having a magnetic film formed by a wet plating means such as electroless plating or a dry plating means such as vacuum deposition, sputtering or ion plating. This kind of magnetic recording medium is suitable for high-density recording because of its high packing density of magnetic material. As a magnetic material in this kind of metal thin film type magnetic recording medium, for example, a Co-based metal containing Co as a main component such as Co, Co—Cr alloy or Co—Ni alloy is used.

By the way, the demand for high-density recording has been increasing in recent years, and therefore, improvement of C / N characteristics is awaited. In order to improve the C / N characteristic, it has been proposed to supply a large amount of oxygen to the surface of the magnetic film when forming the Co-based magnetic film, but this is not sufficient. Therefore,
An object of the present invention is to provide a magnetic recording medium having excellent C / N characteristics.

[0004]

The object of the present invention is to stack two or more Co--O based magnetic films, and the O concentration at the interface between the magnetic films is higher than the Co concentration. It is solved by a magnetic recording medium characterized by high price. In addition, a Co—O based magnetic film is provided,
From the surface of the O-based magnetic film, the thickness of the Co-O-based magnetic film is 25
% From the surface of the Co—O-based magnetic film to the C
This is solved by a magnetic recording medium characterized in that there is a region where the O concentration is higher than the Co concentration in the middle layer portion up to a position of 60% of the thickness of the o-O magnetic film.

In addition, a Co—O type magnetic film is provided, and in the Auger electron spectroscopy analysis of the Co—O type magnetic film,
When the Co amount and the O amount are plotted on the vertical axis and the sputtering time is plotted on the horizontal axis, O in the middle layer portion from the position of 25% of the total sputtering time from the start of sputtering to the position of 60% of the total sputtering time from the start of sputtering. This is solved by a magnetic recording medium characterized in that there is a region where the concentration is higher than the Co concentration.

The 25% position in the above is preferably the 30% position, and the 60% position is preferably the 55% position. That is, in the middle layer portion of the Co—O-based magnetic film (the magnetic film formed by supplying oxygen or the like when depositing Co-based metal particles such as Co or Co alloy), a region where the O concentration is higher than the Co concentration ( In particular, the maximum value of the difference between the two in this area is 5 to 1
5 at. %), Magnetic separation is effectively performed, noise is reduced, and C / N is improved.

In the present invention, there may be one region where the O concentration is higher than the Co concentration, but there may be two regions or three or more regions. However, one or two cases are preferable. Further, at the highest O concentration in the region where the O concentration is higher than the Co concentration, the O concentration is 50 to 60 at. % (Particularly 52 to 56 at.%) Is preferable. This makes the magnetic separation more effective.

Further, it is preferable that there is a valley in the O concentration distribution from the surface to the region where the O concentration is higher than the Co concentration. That is, the O concentration on the surface of the Co—O based magnetic film is higher than the lower concentration, that is, the surface oxidation of the magnetic film is performed to some extent, and the O concentration from the surface of the Co—O based magnetic film is the Co concentration. This is because the O concentration distribution up to the higher region is substantially J-shaped, which is preferable from the viewpoint of corrosion resistance and durability.

Further, the magnetic recording medium of the present invention may have a magnetic film other than the Co--O type magnetic film having the above-mentioned characteristics, but on the Co--O type magnetic film having the above-mentioned characteristics. There is no magnetic film used for recording / reproducing, that is, Co--O having the above characteristics.
It is preferable that the system magnetic film is the uppermost layer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention comprises a Co-
An O-based magnetic film is provided, and 25% (especially, 30%) of the thickness of the Co-O-based magnetic film from the surface of the Co-O-based magnetic film.
%) From the surface of the Co—O based magnetic film to the position of 60% (particularly 55%) of the thickness of the Co—O based magnetic film in the middle layer portion. Indicates that there is a region higher than the Co concentration. In addition, a Co—O-based magnetic film is provided, and in Auger electron spectroscopic analysis of the Co—O-based magnetic film, when the vertical axis represents Co content and O content and the horizontal axis represents sputtering time, sputtering starts. A region in which the O concentration is higher than the Co concentration in the middle layer portion from the position of 25% (especially 30%) of the total sputtering time to the position of 60% (especially 55%) of the total sputtering time from the start of sputtering Is. In addition, two or more Co—O based magnetic films are laminated, and the O concentration is higher than the Co concentration at the interface between the magnetic films. This magnetic recording medium is the same as the magnetic recording medium described above when it is considered that one magnetic film is divided into two or more by the high O concentration layer in the middle layer portion. That is, a Co-O-based magnetic film (C or C such as Co alloy) is used.
When the o-based metal particles are deposited, the O concentration is C in the middle layer of the magnetic film formed by supplying oxygen or the like.
There is a region higher than the o concentration (in particular, the maximum value of the difference between the two is 5 to 15 at.% in this region). O concentration is Co
There are one, two, three or more regions above the concentration. Also, O
At the highest point of the O concentration in the region where the concentration is higher than the Co concentration, the O concentration is 50 to 60 at. % (Especially 52 to
56 at. %). Further, there is a valley in the O concentration distribution from the surface to the region where the O concentration is higher than the Co concentration. That is, the O concentration distribution from the surface of the Co—O based magnetic film to the region where the O concentration is higher than the Co concentration is substantially J-shaped.

The magnetic recording medium of the present invention is a method for producing a magnetic recording medium by forming a magnetic film on a support by, for example, an oblique vapor deposition method, and the oblique vapor deposition step is performed in plural times. It is obtained by controlling the supply of oxygen in each oblique vapor deposition process. 1 and 2 show an oblique vapor deposition apparatus used in the present invention. 1 and 2, 1 is a support, 2a is a supply side roll of the support 1, 2b is a winding side roll of the support 1, 3a and 3b are can rolls, 4a and 4b are shielding plates,
Reference numerals 5a and 5b are crucibles, 6 is a Co-based metal, 7a and 7b are electron guns, 8a, 8b and 8c are oxygen gas supply nozzles, and 9 is a vacuum chamber. In addition, in this apparatus, the oblique vapor deposition is performed a plurality of times in succession, but it may be repeated in one apparatus. However, even in such a case, be careful about the supply of oxygen gas.

That is, the degree of vacuum is 2 × 10 ^-5 to 2 × 10
^In a vacuum atmosphere evacuated to about ^-6 Torr, Co-based metal particles from the crucible 5a are obliquely vapor-deposited on the support 1 fed from the supply-side roll 2a at the position of the can roll 3a. The output of the electron gun 7a is about 10 to 20 kW, and the evaporation rate of the Co-based metal particles from the crucible 5a is controlled by the output of the electron gun. This allows
A Co-based metal magnetic film is formed. During this oblique deposition, oxygen gas is supplied obliquely upward from the oxygen gas supply nozzle 8a (toward the direction in which Co-based metal particles are obliquely deposited at the maximum incident angle), and the can roll 3a is supplied from the oxygen gas supply nozzle 8b. Is supplied toward the center of the can roll 3a, particularly in the vicinity of the end of oblique vapor deposition of the Co-based metal particles. Oxygen gas supply nozzle 8b
The oxygen from is heated so that it is highly active. The oxygen gas supply amount from the oxygen gas supply nozzle 8a is 50 to 2
00SCCM, the oxygen gas supply amount from the oxygen gas supply nozzle 8b is 30 to 100 SCCM. That is, the magnetic film as defined by the present invention can be obtained by such a method. After this first oblique vapor deposition step, Co-based metal particles from the crucible 5b are obliquely vapor-deposited on the Co—O magnetic film on the support 1 formed in the first oblique vapor deposition step. As a result, a two-layered Co—O-based magnetic film is formed.
Even in this second oblique deposition, 50 to 150 SCCM
Oxygen gas is supplied obliquely upward from the oxygen gas supply nozzle 8c at the ratio. Then, after the second oblique vapor deposition, the support 1 is wound around the winding-side roll 2b.

The magnetic recording medium according to the present invention thus obtained is shown in FIG. In FIG. 3, 1 is a support. The support 1 may be magnetic or non-magnetic, but is generally non-magnetic. For example, polyester such as polyethylene terephthalate, polyamide, polyimide, polysulfone, polycarbonate,
Polymer materials such as olefin resins such as polypropylene, cellulose resins and vinyl chloride resins, inorganic materials such as glass and ceramics, and metal materials such as aluminum alloys are used. An undercoat layer for improving the adhesion of the magnetic film is provided on the surface of the support 1 as needed. That is, in order to improve the adhesion of the magnetic film formed by dry plating and to improve the running property by making the surface roughness of the surface of the magnetic recording medium moderate, for example, Si
The thickness containing particles such as O ₂ is 0.01 to 0.5 μm
The undercoat layer is formed by providing the coating film.

On the undercoat layer, a Co—O type metal thin film type magnetic film 11 (11a, 11b) of 500 to 5000 Å, especially 5 by the oblique vapor deposition apparatus shown in FIG.
It is formed with a thickness of 00 to 2500Å. The minimum angle of incidence during oblique deposition is 30 ° -80 °, preferably about 45 ° -70 °. In addition, 11a is a lower layer Co—O based magnetic film formed in the first oblique deposition process, and its thickness is 800 to 15
It is 00Å. The surface layer of the Co—O based magnetic film 11a has a high oxygen concentration. Reference numeral 11b is an upper layer Co—O based magnetic film formed by the second oblique vapor deposition process, and has a thickness of 8
The thickness is 00 to 1300Å, which is thinner than the Co—O based magnetic film 11a formed in the first oblique deposition process. The magnetic film 11 has the characteristics described above.

A thickness of 10 is formed on the Co—O type magnetic film 11.
A protective film 12 having a thickness of about 200 Å is provided. For example, a carbon film such as diamond-like carbon or graphite, or a silicon-containing film such as silicon oxide or silicon carbide is provided. A protective film made of diamond-like carbon is preferable. 13 is a lubricant layer. That is, about 2 to 50 Å, preferably about 10 to 10 Å, preferably about 10 by applying a coating agent containing a hydrocarbon-based lubricant or a fluorine-based lubricant such as perfluoropolyether, especially a fluorine-based lubricant by a predetermined means. A lubricant layer 13 having a thickness of about 30Å is provided.

Reference numeral 14 is a back coat layer having a thickness of about 0.1 to 1 μm, which is provided on the other surface of the support 1 and contains carbon black or the like. The back coat layer 14 is
For example, it may be formed by vapor-depositing a metal such as an Al-Cu alloy.

[0017]

Example 1 In the oblique vapor deposition apparatus shown in FIG. 1 and FIG.
A PET film 1 having a thickness of m is attached, and the PET film 1 is run at a running speed of 3 m / min. The vacuum chamber 9 is evacuated to 3 × 10 ^-6 Torr. Co is contained in the crucibles 5a and 5b made of magnesium oxide, and Co is evaporated by the electron gun 7a having an output of 18 kw and the electron gun 7b having an output of 15 kw, and Co is vapor-deposited on the PET film 1.

The can roll 3a is kept at 50 ° C. and the can roll 3b is kept at 20 ° C. Oxygen gas supply nozzle 8a
100 SCCM of oxygen from the oxygen gas supply nozzle 8
50 SCCM oxygen heated to 100 ° C. is supplied from b, and 80 SCCM oxygen is supplied from the oxygen gas supply nozzle 8c. The minimum incident angle in the first oblique vapor deposition process is 60.
The angle of incidence in the second oblique deposition step is 60 °.

C of the lower layer formed in the first oblique vapor deposition process
The OO-based magnetic film 11a is 900Å, and the upper Co-O-based magnetic film 11b formed in the second oblique vapor deposition process is 850Å.
It is. ECR-CV is formed on the Co-O magnetic film 11b.
By D, a 100Å thick diamond-like carbon film was provided.

A back coat layer containing carbon black or the like and having a thickness of 0.5 μm was provided on the opposite surface of the PET film 1. A lubricant was applied to the surface of the diamond-like carbon film. Auger profile of the above magnetic tape (measurement conditions: electron gun; acceleration voltage 10 kV, emission current 10 nA, magnification 2000)
4 times the etching conditions; etching gas: argon, accelerating voltage: 3 kV, ion current: 300 nA, etching every 30 seconds). In the Auger profile of this Co—O-based magnetic film, the vertical axis represents the C content, Co content, and O content.
Amount (C amount + Co amount + O amount = 100%. Note that C from the lubricant component is found in the outermost surface layer, and C from the support component is found at the interface with the support. (There is basically no C in the region of the —O-based magnetic film.), The horizontal axis represents the sputtering time, and when the sputtering time of the Co—O-based magnetic film is about 48% of the total sputtering time. At a position (that is, a position near 48% from the surface of the Co—O based magnetic film), the O concentration is about 54 at. %, Co concentration is about 45a
t. %, And there is a region where the O concentration is higher than the Co concentration.

The interface between the Co-O magnetic film and the support (or the diamond-like carbon film) is considered to be the interface at the point where the Co concentration and the C concentration are equal in the Auger profile.

[0022]

[Embodiment 2] 90 SCC from the oxygen gas supply nozzle 8a
The oxygen of M is supplied from the oxygen gas supply nozzle 8b at 55 SCCM of oxygen heated to 90 ° C., and the C of 900Å is supplied.
A magnetic tape of the type shown in FIG. 3 was obtained in the same manner as in Example 1 except that the OO magnetic film 11a and the 900 Å thick Co-O magnetic film 11b were formed.

Auger profile of the above magnetic tape (measurement condition: electron gun; acceleration voltage 10 kV, emission current 10 nA, magnification 2000 times, etching condition; etching gas is argon, acceleration voltage 3 kV, ion current 3)
(00 nA, etching every 30 seconds) is shown in FIG. In the Auger profile of this Co—O based magnetic film,
The amount of C, the amount of Co, and the amount of O on the vertical axis (C amount + Co amount + O amount =
100%. The outermost surface layer contains C from the lubricant component,
Although C from the support component is recognized on the interface side with the support, it is considered that there is basically no C in the region of the Co—O type magnetic film. ), When the sputtering time is plotted on the abscissa, at a position near 50% of the total sputtering time from the start of sputtering of the Co—O magnetic film (that is, at a position near 50% from the surface of the Co—O magnetic film). , O concentration is 52a
t. %, Co concentration is 48 at. %, And the O concentration is Co
There is a region higher than the concentration.

[0024]

Example 3 55S in which the can roll 3a was kept at 70 ° C., 100 SCCM of oxygen was heated from the oxygen gas supply nozzle 8a, and 130 ° C. was heated from the oxygen gas supply nozzle 8b.
Example 1 was repeated except that CCM oxygen was supplied to form a 1300Å-thick Co-O magnetic film 11a and a 1000Å-thick Co-O based magnetic film 11b using an electron gun 7b having an output of 18 kw. Then, the magnetic tape of the type shown in FIG. 3 was obtained.

Auger profile of the above magnetic tape (measurement condition: electron gun; acceleration voltage 10 kV, emission current 10 nA, magnification 2000 times, etching condition; etching gas is argon, acceleration voltage 3 kV, ion current 3)
(00 nA, etching every 30 seconds) is shown in FIG. In the Auger profile of this Co—O based magnetic film,
The amount of C, the amount of Co, and the amount of O on the vertical axis (C amount + Co amount + O amount =
100%. The outermost surface layer contains C from the lubricant component,
Although C from the support component is recognized on the interface side with the support, it is considered that there is basically no C in the region of the Co—O type magnetic film. ), When the sputtering time is plotted on the horizontal axis, at a position of about 44% of the total sputtering time from the start of sputtering of the Co—O based magnetic film (that is, a position of about 44% from the surface of the Co—O based magnetic film). , O concentration is 56a
t. %, Co concentration is 44 at. %, And the O concentration is Co
There is a region higher than the concentration.

[0026]

[Comparative Example 1] With the can roll 3a kept at 20 ° C, 50 SCCM of oxygen was supplied from the oxygen gas supply nozzle 8a and 50 SCCM of oxygen was supplied from the oxygen gas supply nozzle 8b at 20 ° C, and 900 Å thick Co-O was supplied. System magnetic film 11a
A magnetic tape of the type shown in FIG. 3 was obtained in the same manner as in Example 1 except that the Co—O type magnetic film 11b having a thickness of 900 Å was formed.

Auger profile of the above magnetic tape (measurement condition: electron gun; acceleration voltage 10 kV, emission current 10 nA, magnification 2000 times, etching condition; etching gas is argon, acceleration voltage 3 kV, ion current 3)
(00 nA, etching every 30 seconds) is shown in FIG. In the Auger profile of this Co—O based magnetic film,
The amount of C, the amount of Co, and the amount of O on the vertical axis (C amount + Co amount + O amount =
100%. The outermost surface layer contains C from the lubricant component,
Although C from the support component is recognized on the interface side with the support, it is considered that there is basically no C in the region of the Co—O type magnetic film. ) Is the sputtering time on the horizontal axis, the O concentration is 40 at.% At a position of 54% of the total sputtering time from the start of the sputtering of the Co—O magnetic film.
%, Co concentration is 60 at. %, And there is no region where the O concentration is higher than the Co concentration.

[0028]

Comparative Example 2 The oxygen gas supply nozzle 8b was not supplied with oxygen, and the 1200Å-thick Co—O magnetic film 11b was
A magnetic tape of the type shown in FIG. 3 was obtained in the same manner as in Example 1 except that the 000Å-thick Co-O magnetic film 11a was formed. Auger profile of the above magnetic tape (measurement condition: electron gun; acceleration voltage 10 kV, emission current 10 nA, magnification 2000 times, etching condition; etching gas is argon, acceleration voltage 3 kV, ion current 3)
(00 nA, etching every 30 seconds) is shown in FIG. In the Auger profile of this Co—O based magnetic film,
The amount of C, the amount of Co, and the amount of O on the vertical axis (C amount + Co amount + O amount =
100%. The outermost surface layer contains C from the lubricant component,
Although C from the support component is recognized on the interface side with the support, it is considered that there is basically no C in the region of the Co—O type magnetic film. ), The horizontal axis indicates the sputtering time, and the O concentration is 41 at.
%, Co concentration is 57 at. %, And there is no region where the O concentration is higher than the Co concentration.

[0029]

Comparative Example 3 Auger profile of a commercially available magnetic tape (measurement condition: electron gun; acceleration voltage 10 kV, emission current 10 nA, magnification 2000 times, etching condition; etching gas is argon, acceleration voltage 3 kV, ion current 3)
FIG. 9 shows the result of etching (00 nA, etching every 30 seconds). In the Auger profile of this Co—O based magnetic film,
The amount of C, the amount of Co, and the amount of O on the vertical axis (C amount + Co amount + O amount =
100%. The outermost surface layer contains C from the lubricant component,
Although C from the support component is recognized on the interface side with the support, it is considered that there is basically no C in the region of the Co—O type magnetic film. ), The horizontal axis represents the sputtering time, and the O concentration was 42 at.% At a position near 64% of the total sputtering time from the start of the sputtering of the Co—O magnetic film.
%, Co concentration is 58 at. %, And there is no region where the O concentration is higher than the Co concentration.

[0030]

[Characteristics] The C / N values of the magnetic tapes of the above examples were examined, and the results are shown in Table-1. Table-1 C / N (dB) 1MHz 10MHz 20MHz Example 1 +1.8 +2.3 +3.4 Example 2 +1.3 +1.6 +2.4 Example 3 +2.1 +2.9 +4.1 Comparative example 1-0.3 -0.4 -0.6 Comparative example 2 +0.2 +0.3 +0.6 Comparative example 3 0 0 0 * The comparative example 3 of a commercial item is a reference (0 dB).

[0031]

The C / N characteristic is excellent, and high density recording can be supported.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetic recording medium manufacturing apparatus.

FIG. 2 is an enlarged schematic view of a main part of a magnetic recording medium manufacturing apparatus.

FIG. 3 is a schematic sectional view of a magnetic recording medium.

FIG. 4 is an Auger profile of the magnetic tape of Example 1.

FIG. 5: Auger profile of magnetic tape of Example 2

FIG. 6 Auger profile of magnetic tape of Example 3

FIG. 7 is an Auger profile of the magnetic tape of Comparative Example 1.

FIG. 8 is an Auger profile of the magnetic tape of Comparative Example 2.

FIG. 9 is an Auger profile of the magnetic tape of Comparative Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support 11a Lower Co-O type magnetic film 11b Upper layer Co-O type magnetic film 12 Protective film 13 Lubricant layer 14 Back coat layer

Claims (7)

[Claims] 1. A magnetic recording medium comprising a stack of two or more Co—O based magnetic films, wherein the O concentration is higher than the Co concentration at the interface between the magnetic films. 2. A Co—O-based magnetic film is provided, and the Co—O-based magnetic film is located at a depth of 25% of the thickness of the Co—O-based magnetic film from the surface of the Co—O-based magnetic film. A magnetic recording medium characterized in that there is a region where the O concentration is higher than the Co concentration in the middle layer portion from the surface of the system magnetic film to a position at a depth of 60% of the thickness of the Co-O magnetic film. 3. A Co—O based magnetic film is provided, wherein in the Auger electron spectroscopy analysis of the Co—O based magnetic film, the vertical axis represents Co content and O content, and the horizontal axis represents sputtering time. The magnetic recording medium is characterized in that there is a region where the O concentration is higher than the Co concentration in the middle layer portion from the position of 25% of the total sputtering time from the start of sputtering to the position of 60% of the total sputtering time from the start of sputtering. 4. The maximum difference between the two in the region where the O concentration is higher than the Co concentration is 5 to 15 at. %, The magnetic recording medium according to any one of claims 1 to 3. 5. The magnetic recording medium according to claim 1, wherein there is at least one region where the O concentration is higher than the Co concentration. 6. At the highest point of O concentration in a region where O concentration is higher than Co concentration, O concentration is 50-60 at.
% Is the magnetic recording medium according to any one of claims 1 to 5. 7. The magnetic recording medium according to claim 1, wherein there is a valley in the O concentration distribution from the surface to the region where the O concentration is higher than the Co concentration.