JPS62219314A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent overall performances including still durability, corrosion resistance and reliability by forming a protective film consisting of an amorphous diamond film and org. material film on a recording film. CONSTITUTION:The recording film 2 consisting of a ferromagnetic metal such as Co, Cr, Ni or Fe is formed by a vacuum deposition method or sputtering method on the surface of a substrate 1. The thickness thereof is about 1,000-3,000Angstrom and the extreme surface layer of the recording film 2 is Cr-rich. The amorphous diamond film 3 by a PI-CVD method is formed on the surface of the recording film 2. The org. material film 4 which effectively removes the dust in air sticking to the surface and transfer stains from near the gap during sliding of the magnetic head and decreases the friction resistance in special environment is formed on the amorphous film 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium that uses a thin film of ferromagnetic metal as a recording film and records signals such as video, audio, and data.

Conventional technology Go is used as a recording medium to realize high-density magnetic recording.
-Thin films of ferromagnetic metals such as Ni, Cr, and Fe are attracting attention, and their practical application is being considered.

In magnetic recording, spacing loss occurs when a gap occurs between the recording film and the magnetic head. This loss is particularly noticeable in areas where the recording frequency is high, and this gap must be made as small as possible. When recording and reproducing video and audio signals, the magnetic head and recording film are often in contact, and even in the case of data signals, when the requirements for reliability are relatively loose, such as with floppy disks, the recording film and the magnetic head are is in contact with When high reliability is required, the magnetic head is floated above the surface of the recording film so that it does not make contact. However, even in this case, the magnetic head is configured so that the two come into contact, for example, when starting and stopping the rotation of the recording medium. There are many devices. Furthermore, in this case, the flying height of the magnetic head results in a spacing loss, making it unsuitable for high-density recording. Considering the above, when considering high-density recording by magnetic recording, it is ideal that the magnetic head and the recording film are in contact with each other and that high reliability is ensured. That is, magnetic recording has a fundamentally different problem from optical recording in that the recording film and the magnetic head come into contact with each other.

Now, the recording media whose recording film is a ferromagnetic thin film such as Co, Or, Ni, or Fe mentioned above have a large coercive force and are suitable for high-density recording, and media for perpendicular recording are also being considered. has been done. However, the recording film suffers damage such as peeling off in a short time due to sliding with the magnetic head, so forming an effective protective film to protect the recording film is an important issue.

Magnetic recording media, which have been commonly used in the past and are made by mixing magnetic powder with a binder and coating it on a base film, improve the sliding contact with the magnetic head by adding a substance with excellent wear resistance and lubricity to the binder. However, in the case of magnetic recording media whose recording film is a ferromagnetic metal thin film, wear resistance, lubricity, and environmental resistance can be improved by oxidizing the film surface of the recording film itself. If we try to improve things like magnetic properties, deterioration of magnetic properties is inevitable.

Therefore, in this case, it is necessary to form a protective film on the surface of the recording film to ensure properties such as wear resistance. However, such a protective film creates a gap between the magnetic head and the recording film, and its thickness must be as small as possible.

Conventionally, as a protective film for a ferromagnetic metal thin film, a lubricating material made of an organic substance is coated or vacuum-deposited7'+;
The sweetness was l-1h-, the coating was low, the durability was poor, and it could not withstand long-term use. Alternatively, vacuum evaporation,
Amorphous carbon by sputtering etc.

It is thought that it forms a graphite film, but
Although lubricity was improved, wear resistance was insufficient.

Problems to be Solved by the Invention When using the above-mentioned materials as a protective film for a magnetic recording medium whose recording film is a ferromagnetic metal thin film,
Due to insufficient wear resistance, the protective film must be made thicker, and the gap between the magnetic head and the recording film is large, resulting in cisbasing loss.

In addition, these protective films wear out due to sliding with the magnetic head, and the resulting fine powder adheres to the magnetic head, sometimes causing a significant drop in playback output (e.g. head clogging, dropouts). .

The above-mentioned problems significantly limit the practical application of high-density magnetic recording media using ferromagnetic metal thin films as recording films, and unless these problems are solved, it is thought that original high-density recording will not be achieved.

The present invention solves this problem and provides a magnetic recording medium having a protective film with excellent wear resistance and environmental resistance on the surface of a ferromagnetic metal recording film.

Means for Solving the Problems The protective film that solves the above-mentioned problems has (1) good slip properties and excellent abrasion resistance even if it is thin.

(2) Excellent adhesion to ferromagnetic metals.

The following characteristics are required, and (1) the substrate (for example, in the case of tape, the base film of polyethylene, etc.) is not damaged due to temperature rise during film formation.

(2) A homogeneous film is formed even if it is thin.

(2) The film formation rate is high and mass productivity is excellent.

Formation conditions such as these are required.

Diamond can be considered as a material for the protective film that satisfies the above characteristics. Diamond is a crystalline substance that exhibits the highest hardness among substances and is extremely chemically stable, making it an ideal protective film material with excellent wear resistance and environmental resistance. Many reports have been made regarding techniques for forming diamond thin films.

(References) (1) Yoshihide Namba: Research on low-pressure synthesis of diamond thin films,
Applied Mechanical Engineering (2) Seiichi Matsumoto: Low-pressure synthesis of diamonds, Gendai Kagaku, September 1984 issue (2) Nobuo Setaka: Low-pressure synthesis of diamonds 2 Japan Industrial Technology Promotion Association, Technical Documents 138, 59/6/ 20 However, all of these are still in the research stage and have not yet been put into practical use. In addition, both methods (1) require high-temperature heating of the substrate (over 400°C); It was extremely difficult to use it as a forming means.

We have developed a method to form a high-hardness carbon film that exhibits properties similar to those of diamond (Kuroyo et al.: Formation and evaluation of high-hardness carbon film by plasma injection CVD method, Academic lecture at the 1985 Japan Society of Mechanical Engineers Spring Conference) collection of papers). This method uses hydrocarbon gas as a material gas at a pressure of 10 to 100 Pa.
This process converts this into plasma at low pressure, and injects this plasma onto the substrate while accelerating at least the ions to form a film.
We use plasma injection CVD method (PI-CVD method)
D method). According to the PI-CVD method, a high hardness carbon film with a Vickers hardness of 2000 Kg+/nuJ or more can be formed at a temperature as low as room temperature without heating the substrate.
This makes it possible to perform high-speed film formation at a rate of about 1,000 people/minute.

Crystallinity (electron beam diffraction,
Analysis of the composition (secondary ion mass spectrometry) and structure (Raman spectroscopy, energy loss spectroscopy) revealed that this film has diamond bonds (
It was found that the film was an amorphous carbon film in which graphite bonds (SP2 electron configuration) and hydrogen were present in the film, and could be called an amorphous diamond film.

High-hardness carbon films formed by conventional methods are films with diamond crystals aggregated or amorphous carbon films dotted with diamond crystals, which are not completely amorphous and are essentially different from amorphous diamond films. It is.

Amorphous diamond film is 2Q○o Kg/ma
It exhibits a Vickers hardness of at least 100% and has excellent wear resistance.

Furthermore, the thermal conductivity is 0,6 Ca (1/(yB・Wat・℃)
It is almost as good as metal and has excellent dissipation of frictional heat.

However, in order to form an amorphous diamond film using the Pl-CVD method, there are two limitations on the substrate material. First, it is desirable that the specific resistance of the base material be approximately 1013Ω or less. Materials with a resistivity of more than 1013 Ω are generally good electrical insulators, and P l- is formed by spraying ion-containing plasma onto a substrate.
In the CVD method, the surface is charged and ions are repelled, making it impossible to form a strong film. However, this is not the case if a neutralizing means such as electron beam irradiation is added, but this is not preferable since it causes drawbacks such as complicating the device configuration.

As a second limitation, it is desirable that the substrate material has a strong chemical affinity with carbon and a strong bonding force between the atoms of the carbide formed.

Materials that satisfy the above two conditions are Aβ and Be.

Co, Cr, Fe, Mn, Ni, Zn,
Hf, V, Nb, Ta.

These include metals such as Mo and W, or alloys containing these as main components, and semiconductors such as Si, Ge, B, and SiC.

In particular, SL, B, and Cr can form strong bonds such as covalent bonds with carbon. Further, the specific resistance of the amorphous diamond film is approximately in the range of 10 to 10 Ω·saw, which naturally satisfies the first condition.

Ferromagnetic metals such as Co, Cr, Ni, and Fe satisfy the film formation conditions for the PI-CVD method described above, and it is possible to form a strong protective film of amorphous diamond film on this surface. becomes. At this time, it is more effective to clean the surface of the recording film by plasma treatment such as Ar, 02 or the like. Further, for example, a tape-shaped magnetic recording medium requires a certain level of precision, and when polyethylene or the like is used as a base film, there is a limit to the temperature rise during film formation.

It is only possible to form an amorphous diamond film on the surface of such a magnetic recording medium by using the Pl-CVD method.

As described above, the Pl-CVD method makes it possible to form a protective film of amorphous diamond on the surface of a ferromagnetic metal recording film, thereby obtaining a magnetic recording medium with excellent durability and wear resistance. be able to. However, even when amorphous diamond is used as a protective film, head clogging and dropouts caused by dust in the air, peeling from the edge of the tape, chips, and dirt transfer from the back of the tape can occur. Occur. Furthermore, the wear coefficient of the amorphous diamond protective film increases under special environments such as high temperature and high humidity. To prevent this, the most effective way to prevent this is to form an organic material film with excellent slip properties, such as a fluorine-containing organic material, on the surface of the amorphous diamond protective film, which has the effect of removing the aforementioned dust and dirt. It is. This organic film may be formed directly on the surface of the amorphous diamond film, or may be formed indirectly by a method such as transfer. In addition, the method for forming the organic film may be a dry process method such as sputtering or vapor deposition, in addition to the conventionally commonly used wet coating method.

Function As described above, it is possible to form an amorphous diamond film on the surface of a recording film made of a ferromagnetic metal such as Co, Or, Ni, or Fe, especially in the case of a Co1Cr-based ferromagnetic metal thin film. It is known that a large amount of Cr is unevenly distributed on the surface, and a particularly strong film is formed.

Since the amorphous diamond film has properties similar to diamond in an amorphous state, it can protect the recording film extremely effectively. Furthermore, since the amorphous diamond film is amorphous, it has some flexibility and is effective as a protective film for a recording film on a flexible base film such as polyethylene.

If the thickness of the amorphous diamond film exceeds about 500 mm, the bending rigidity increases and contact with the magnetic head becomes unstable, and in the case of a flexible medium, cracks may occur due to minute deformation, which is undesirable. Also, 20
If the number of people is less than about 30, the film will not be uniform but will have an island-like structure, resulting in extremely low still durability and corrosion resistance.

From the above, when an amorphous diamond film formed by the Pl-CVD method is used as a protective film for a magnetic recording medium, a film thickness of 300 to 500 mm is desirable. Further, in the case of a tape-shaped magnetic recording medium, a film thickness of 50 to 300 layers is desirable in consideration of contact stability and reliability with the magnetic head. Furthermore, in the case of media aimed at high-density recording, such as ME tape for perpendicular recording 8wn VTR, the spacing loss due to the amorphous diamond film (for an ex recording wavelength of 0.5 μm, a spacing of about 6 db at a thickness of 300 mm) 50~ to reduce loss) and take advantage of its characteristics.
A film thickness of about 150 people is desirable.

Dust in the air, transferred dirt, etc. are effectively removed by the organic film on the amorphous diamond film, and head clogging and dropouts are prevented. By selecting the material of the organic film, it is possible to have the effect of lowering the coefficient of friction under special environments (for example, temperature of 40° C. and humidity of 90% RH), further improving running stability.

An embodiment of the present invention is shown in the drawings. In the figure, reference numeral 1 denotes a base body in the form of a tape, card, or disk, and is made of a nonmagnetic material such as plastic, glass, or metal. Co, Cr, Ni, Fe, etc. are on the surface of the base 1.
A recording film 2 made of ferromagnetic metal is formed by vacuum evaporation, sputtering, or the like. This thickness is 1000~300
For example, in a perpendicular magnetic recording medium made of a Co, Cr-based alloy, CO is the main component and 10 to 30% Cr is added to form a columnar structure of CO, with Cr segregated at the boundaries. It has a similar structure. Therefore, in this case, the outermost portion of the recording film 2 is Cr-rlch.

An amorphous diamond film 3 is formed on the surface of the recording film 2 by the PI-CVD method.

As mentioned above, for example, in a perpendicular recording medium whose recording film is a Co--Cr alloy thin film, an amorphous diamond film with strong adhesion is formed because the surface is Cr-rich. This film thickness is 1000 Å or less, preferably 30 Å or less.
Although it is 0 Å or less, it will be determined as appropriate depending on the required reliability and magnetic recording device.

An organic film 4 is formed on the amorphous diamond film 3, which effectively removes dust in the air, transfer dirt, etc. adhering to the surface from near the gap when the magnetic head slides, and further reduces frictional resistance under special environments. has been done. There are four groups of organic films that can effectively remove dust, transfer stains, etc. and reduce the coefficient of friction under special environments.

◎Group A: An organic compound film in which the carboxyl group at the end of the molecule has one or more mercapto groups and one or more fatty alkyl groups having 8 or more carbon atoms (Example) ■ C1□H36COOH.

■ CH3(CH2)7CH=CH(CH2)7C○O
H.

CH2C0oH ■ Cl8H3□sH ■ CHoCoC3H1□ CHoCoC3H1□ H2SH ◎Organic compound having at least one fluoroalkyl group with 3 or more carbon atoms and one or more aliphatic alkyl group with 8 or more carbon atoms at the bimolecular terminal of group B (Example) ■ CHoCoC3H1□ CHOCOCI2H2゜CH2oCocI2H2゜■ CHC00C8F1a■ Cl8H3□CH2-8-CH2CH2C8F1□
■ Cl8H37CH2 o-08F17 ■ 018H37CH2 0-CH2-CH2-No5oC8F1□CF3 ■ Cl2H2, UCOCH2CH2C8F18CF3 ■ C3F17S02UC18H3 CF3 ■ CH3 (cE(2)7CH=CH(CH2) 7CO
O(CF2)9H■ C3H1□-0-P-QC8F1
□C3F17 ◎Organized metal film having at least one fluoroalkyl group having 3 or more carbon atoms, an aliphatic alkyl group having 8 or more carbon atoms, and a carboxyl group at the bimolecular terminal of C group (Example) ■ CH20COC6F, 1 CHOCOC1゜H26 CH2CoOH ■ H Cl8H37-C-COOH O-08F17゜■ H Cl8H37-C-COOH ! S-CH20H208F1□ ■ H 0-08F17 ■ H 0-CH2CH2No5OC8F1□ H3 H ■ S-CH2CH2C8F1□ ■ Cl2H26NCOCH2CH2C8F1□CH2
CooH ■ C3F17S02NC18H37 CH2COoH COOH ◎D group: Organic compound film having one or more each of a fluoroalkyl group with 3 or more carbon atoms, an aliphatic alkyl group with 8 or more carbon atoms, and a mercapto group at the molecular end (Example) ■ CH20COC8F1 Chococh23h CH20COC1 ゜ H25 CH20COC1 □ H35 ■ SH CHCO ○ CL8H3 □ CH2C00ch2CH2CH2C8H3 □ It is formed by dissolving and applying drying, or by vacuum vapor (organic vapor) be done.

Regarding the ME tape formed with these organic compound films,
Steel durability, corrosion resistance, friction coefficient under special environments,
The table below shows the results of examining practical characteristics such as head wear.

As will be seen from now on, a protective film made only of organic matter lowers the coefficient of friction, but does not improve still durability or corrosion resistance. Furthermore, although the amorphous diamond protective film improves the still durability and effectively protects the recording film 2, it increases the coefficient of friction under special environments and does not improve head wear. In addition, because of its amorphous structure, it has little moisture-proofing effect.
The corrosion resistance is equal to or lower than that of an organic protective film. On the other hand, by forming the organic film 4 as described above on the amorphous diamond film 3, the still durability and corrosion resistance are dramatically improved due to a synergistic effect compared to when each is used alone. Furthermore, as the coefficient of friction decreases under special environments, the amount of wear on the head also decreases, making it possible to obtain a magnetic recording medium with excellent overall performance.

Among organic compounds, those in groups C and D are excellent. Those with a fluoroalkyl group having 3 or more carbon atoms have extremely excellent still durability, corrosion resistance, and head wear resistance.This improves non-adhesion and wettability, and has a remarkable synergistic effect with the amorphous diamond film. It is thought that this has increased. Furthermore, those having a carboxyl group or a mercapto group have the characteristic of further improving slip properties and still durability, especially under special environments.

Furthermore, those without an aliphatic alkyl group having 8 or more carbon atoms cannot obtain the above-mentioned synergistic effect, and the film formation tends to be non-uniform. This is considered to be due to insufficient affinity of the amorphous diamond film.

Note that the fatty acid alkyl group and the fluoroalkyl group may be of a linear type or a branched type.

The organic film 4 is normally formed directly on the amorphous diamond film 3, but in the case of a tape-shaped recording medium, the back coat film 5 coated on the surface of the substrate 1 on the opposite side from the recording film 2 is formed of the same material as the organic film. Alternatively, it may be formed by an indirect method such as forming an organic film on the surface of the back coat film 5 and transferring a part of the film to the surface of the amorphous diamond film 3 when the film is wound on a reel or the like.

Moreover, the coating amount of the organic compound may be 0.1 to 600~/-, particularly 0.5 to 2001 Mf/lr? is the most desirable.

Effects of the Invention By forming a protective film composed of an amorphous diamond film and the organic film on a recording film of a ferromagnetic metal thin film, the still durability and corrosion resistance are improved.

A magnetic recording medium with excellent overall performance such as reliability can be obtained.

As described above, the present invention is extremely effective in realizing high-density recording using a magnetic recording medium whose recording film is made of ferromagnetic metal.

[Brief explanation of drawings]

Figure 2 is an enlarged sectional view of a magnetic recording medium in an embodiment of the present invention. 2...Recording film, 3...Amorphous diamond film, 4...Organic substance film.

Claims (1)

[Claims] (1) A recording film of a ferromagnetic metal is provided on a base of a non-magnetic material, a high-hardness carbon film is formed on the recording film, and an organic film is formed on the surface of the high-hardness carbon film. magnetic recording medium. (2) Claim 1, wherein the organic film is composed of an organic compound having at least one fluoroalkyl group having 3 or more carbon atoms, an aliphatic alkyl group having 8 or more carbon atoms, and a carboxyl group at the molecular terminal. Magnetic recording medium described in Section 1. (2) Claim 1, wherein the organic film is composed of an organic compound having at least one fluoroalkyl group having 3 or more carbon atoms, an aliphatic alkyl group having 8 or more carbon atoms, and mercapto group at the molecular terminal. Magnetic recording medium described in Section 1. (4) The magnetism according to claim 1, wherein the organic film is composed of an organic compound having at least one fluoroalkyl group having 3 or more carbon atoms and one or more aliphatic alkyl group having 8 or more carbon atoms at the molecular terminal. recoding media. (5) The magnetic material according to claim 1, wherein the organic film is composed of an organic compound having at least one carboxy group or mercapto group and one or more aliphatic alkyl groups having 8 or more carbon atoms at the molecular terminals. recoding media. (6) The magnetic recording medium according to claim 1, wherein the high-hardness carbon film is synthesized at low temperature and pressure by spraying plasma containing hydrocarbon gas while accelerating at least ions in the plasma. (7) The magnetic recording medium according to claim 1, wherein the high-hardness carbon film is an amorphous carbon film composed of diamond bonds, diamond bonds and graphite bonds, or diamond bonds, graphite bonds, and hydrogen. . (8) High hardness carbon film has a Vickers hardness of 2000 kg/
The magnetic recording medium according to claim 1, which has a diameter of mm^2 or more. (9) The magnetic recording medium according to claim 1, wherein the high hardness carbon film has a specific resistance of 10^1^3 Ωcm or less. (10) The magnetic recording medium according to claim 1, wherein the high hardness carbon film has a thickness of 30 to 500 Å. (11) The magnetic recording medium according to claim 1, wherein the organic film is formed in a coating amount of 0.1 to 500 mg/m^2.