JPH0192924A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a magnetic recording medium by incorporating fluorine and carbon into a magnetic recording layer essentially consisting of a ferromagnetic material and the oxide thereof on a substrate. CONSTITUTION:The fluorine and carbon are incorporated into the magnetic recording layer of the magnetic recording medium provided with the magnetic recording layer essentially consisting of the ferromagnetic material and the oxide thereof on a substrate. The content of the fluorine contained in the magnetic recording layer is confined to a 0.1-10% range in carbon atoms of the ferromagnetic material atoms. The corrosion resistance of the magnetic recording layer itself is thereby improved and the degradation in the magnetic characteristics and recording density of the magnetic recording layer itself is obviated; in addition, the magnetic recording layer is efficiently formed under high productivity.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a thin film magnetic recording medium.

(Prior Art) In contrast to conventional magnetic recording media that have a magnetic recording layer mainly composed of a magnetic material and a binder, metals, oxides or
Thin-film magnetic recording media, which are mainly made of a combination of metals and oxides and have a thin-film magnetic recording layer that does not use a binder, are being actively studied as being capable of high-density recording. The present inventors also developed a thin magnetic recording film mainly composed of cobalt, cobalt oxide, iron and/or nickel, and their oxides in JP-A-61-177.
It was proposed in issue 566.

One of the most important issues in putting thin-film magnetic recording media into practical use is improving corrosion resistance.

Conventionally, as methods for improving corrosion resistance, a method of providing a protective layer (for example, JP-A-61-17224) and a method of providing a rust-preventing layer (for example, JP-A-61-8232) have been proposed. In addition, methods for improving the corrosion resistance of the magnetic recording layer itself include methods that define the distribution of oxygen atom temperature in the film thickness direction, and methods that add metal elements such as Yakrom (for example, Japanese Patent Application Laid-open Nos. 59-58, 58804 and 61-66217). Proposed.

[Problems to be Solved by the Invention] However, the method of providing a protective layer or anti-corrosion layer on a magnetic recording layer has the disadvantage that if there are pinholes on these layers, these can become a starting point for corrosion and reduce the overall corrosion resistance. There is a problem of significantly lowering the performance.

Furthermore, in the case of the conventional method of forming a layer with a high oxygen concentration on the surface layer of a magnetic recording layer (Japanese Unexamined Patent Publication No. 59-58804), according to the study of the present inventors, in order to improve corrosion resistance, it is necessary to reduce the oxygen concentration. There is a problem in that a layer with a high oxygen concentration must be formed to a thickness of several hundred Å or more, and since the layer with a high oxygen concentration is non-magnetic, making this layer thick will increase the distance between the magnetic recording layer and the magnetic head. There was a problem in that the reproduction output and recording density were significantly reduced due to spacing loss.

Adding a metal element to the magnetic recording layer, which is effective in improving corrosion resistance, is useful in the vacuum deposition method, which allows thin films to be deposited quickly and with high productivity, due to the difference in vapor pressure between materials.
Not only is it difficult to adapt to production because it is difficult to control the composition, but if added in an amount sufficient to produce the effect of improving corrosion resistance,
The inventors' studies have revealed that there is a problem in that the magnetic properties of the magnetic recording layer, particularly the saturation magnetization, is reduced with a reduction in the reproduction output.

There is also a proposal to add carbon to the magnetic recording layer for the purpose of improving wear resistance (Japanese Patent Laid-Open No. 61-99923), but according to the studies of the present inventors, this is not effective in improving corrosion resistance. It became clear that there was no.

The present inventors have arrived at the present invention as a result of intensive study on measures for improving corrosion resistance that do not have the above-mentioned problems.

[Means for solving problems]

The present invention has the following configuration.

That is, the present invention provides a magnetic recording medium comprising a magnetic recording layer mainly made of a ferromagnetic material and its oxide on a substrate, the magnetic recording layer containing fluorine and carbon. It is a magnetic recording medium.

Examples of the substrate used in the present invention include metals such as aluminum, copper, iron, and stainless steel, inorganic materials such as glass and ceramics, and various organic polymer materials such as plastic films. In particular, organic polymer materials are suitable for cases where workability, formability, and flexibility are important, such as in the case of chives and flexible disks. In particular, biaxially stretched films such as sheet 1 are most suitable due to their excellent flatness and dimensional stability, and among them, polyester, polyphenylene sulfide, aromatic polyamide, polyimide, etc. are most suitable.

Prior to the formation of the magnetic recording layer, etc., the substrate used in the present invention is subjected to various surface treatments and pretreatments for the purpose of facilitating adhesion, improving flatness, coloring, preventing static electricity, imparting wear resistance, etc. Good too.

The shape of the base body may be any shape such as a drum shape, a disk shape, a sheet shape, a tape shape, a card shape, etc., and the thickness is not particularly limited. In the case of sheets, tapes, cards, etc., the thickness should be 2 to 500μ in terms of processability and dimensional stability.
m, preferably in the range of 4 to 20 μm.

The ferromagnetic material used in the present invention is not particularly limited, but it is preferable to use metals such as Kobal 1 to iron and nickel alone or in combination of two or more. Among these, cobalt or cobalt and iron and/or nickel is preferable because a perpendicularly magnetized film can be formed.

The composition ratio of cobalt, iron, and nickel is not particularly limited, but when cobalt and iron are used, a weight ratio of 97 to 85:3 to 15 is recommended for increasing reproduction output and magnetic Preferable in terms of preventing a decrease in anisotropy, from 95 to
9o: The range of 5 to 1o is more preferable.

Also, when using cobalt and nickel, the weight ratio is 9
A range of 7 to 60:3 to 4o is preferable from the viewpoint of increasing reproduction output and corrosion resistance, and a range of 95 to 70:5 to 30 is more preferable.

When cobalt, iron, and nickel are used in the coating, 65≦P≦ when the weight is expressed as P, Q, and R, respectively, as a percentage.
98.1≦Q≦15.1≦R≦30, P100R=10
It is preferable to set the value within the range of 0 from the viewpoint of increasing reproduction output and S/N and preventing a decrease in magnetic anisotropy, and 75≦P≦94.
The range of 1≦Q≦10.1≦R≦15 is generally preferred.

The oxides contained in the magnetic recording layer include Coo and CO2O.
3. CO3O4, Fed, Fe2O3, Fe3O4, N
io etc. are the main ones, but in addition to these, Coa
x, FeO'y, N ioz (x, y, Z are from O to 2
Non-stoichiometric suboxides and peroxides represented by numbers between 1 and 2) may also be included.

Nitride and hydroxide may be contained within a range that does not impair the magnetic properties of the perpendicularly magnetized film.

It is important that the magnetic recording layer contains carbon and fluorine at the same time.

The amount of fluorine contained in the magnetic recording layer is not particularly limited, but if the amount of fluorine is small, the effect of improving corrosion resistance will be difficult to appear, while if it is too large, it will affect the lubricating layer, protective layer, etc. laminated on the magnetic recording layer. This is undesirable because it tends to reduce the adhesion with the medium and lowers the abrasion resistance of the medium.

In the present invention, the preferred amount of fluorine contained in the magnetic recording layer is 0.1 to 10% by number of atoms based on the ferromagnetic material atoms.
It is preferably in the range of , more preferably 0.2 to
6%, more preferably in the range of 0.3 to 3%.

Further, the amount of carbon contained in the magnetic recording layer is not particularly limited, but if the amount of carbon is small, the effect of improving corrosion resistance will be difficult to appear, while if it is too large, cracks will easily occur in the magnetic recording layer, which is undesirable. .

The number of carbon atoms contained in the magnetic recording layer is preferably in the range of 0.5 to 30%, more preferably in the range of 1 to 20%, based on the number of atoms of the ferromagnetic material.

In the present invention, fluorine and carbon in the magnetic recording layer exist throughout the thickness direction of the magnetic recording layer, but the concentration is high at the surface of the magnetic recording layer or at the interface between the magnetic recording layer and the magnetic layer. From the viewpoint of improving corrosion resistance, it is preferable to contain Ni such that

When there is a concentration distribution of fluorine and carbon in the film thickness direction, the concentrations of fluorine and carbon are respectively expressed as the average in the film thickness direction. In other words, since the surface layer of the magnetic recording layer is affected by contamination and oxidation, atoms of fluorine, carbon, and ferromagnetic substances are The ratio of the numbers is measured at predetermined intervals (or continuously) in the film thickness direction, and the average concentration ratio is calculated by adding these data in the film thickness direction.

The magnetic recording layer also contains elements and compounds other than the above-mentioned cobalt, iron, and nickel, such as copper, chromium, aluminum, silicon, vanadium, titanium, zinc, manganese, tantalum, and their oxides, nitrides, and hydroxides. may be included within a range that does not impair the magnetic properties of the magnetic recording layer.

In addition, it is preferable from the viewpoint of magnetic properties that the magnetic recording layer contains 10 to 50% by volume of voids.

The thickness of the magnetic recording layer is not particularly limited, but from the viewpoint of reproduction output, flatness, flexibility, etc., it is preferably in the range of 0.05 μm to 2 μm, and most preferably in the range of 0.1 μm to 0.5 μm.

The magnetic recording layer may be provided on one side or both sides of the substrate.

In the present invention, the perpendicular magnetization film in the following description is defined as follows.

The steresis loop in the film surface direction is measured by the method shown in JIS C-2561.

A tangent line is drawn from the origin to this hysteresis loop, and the value of the externally applied magnetic field at which the value of magnetization on this tangent line is the same as the saturation magnetization is called an anisotropic magnetic field. The larger the anisotropic magnetic field, the easier it is to magnetize in the perpendicular direction. In the present invention, a perpendicularly magnetized film has an anisotropic magnetic field of 2 km/hr or more.

Next, one example of the method for manufacturing a magnetic recording layer of the present invention will be explained with reference to the accompanying drawings.

The figure shows an example of manufacturing equipment using the reactive vapor deposition method.
A substrate unwinding shaft 2 capable of supporting and moving a long film-like substrate 1, a cylindrical substrate support drum 3, and a substrate winding shaft 4.
A vacuum chamber 5 equipped with a substrate traveling system such as
Bleed air to below 10-5 torr. Next, a mixed gas of oxygen gas, nitrogen gas, and fluorocarbon gas in a volume ratio of 10:80:10 is passed through the barrier pull leak valve 7 by applying a current of 0°6 d/min.
Introduce more.

Next, cobalt is evaporated from the evaporation source 8, and a perpendicularly magnetized film mainly composed of cobalt and cobalt oxide is deposited on the substrate moving along the drum 2 at a speed of about 5 μm/min.
,000 people thick.

9 and 10 are shielding plates for regulating the angle of incidence of the metal evaporated from the evaporation source onto the substrate, and the angle between the incident vapor at the starting point of incidence on the substrate and the normal to the substrate is 45°.
It will be set up as follows.

Reference numerals 11 and 12 denote partition walls provided between predetermined middle positions on the upper surfaces of the shielding plates 9 and 10 and the substrate support drum 3;
．． By introducing a predetermined mixed gas into the space surrounded by 10, a thin film that is partially oxidized and contains fluorine and oxygen can be obtained.

The magnetic recording layer of the present invention ionizes hydrogen fluoride,
It can also be obtained by Δ-in assisted vapor deposition in which the thin film is irradiated during thin film formation.

Between the substrate and the magnetic recording layer, there is a layer that improves the magnetic properties of the magnetic recording layer.
For the purpose of improving corrosion resistance, adhesion, etc., one or more base layers can be laminated. In particular, it is preferable to provide a soft magnetic layer as an underlayer because it has a great effect on increasing the recording/reproducing sensitivity.

It is permissible to further layer a lubricating layer, a protective layer, a rust prevention layer, etc. on the magnetic recording layer for the purpose of improving wear resistance, corrosion resistance, etc. In particular, it is preferable to provide a carbon film on the magnetic recording layer because it has a large effect of improving wear resistance and corrosion resistance.

〔Effect of the invention〕

In the present invention, the corrosion resistance of the magnetic recording layer itself can be significantly improved because the magnetic recording layer itself, which is mainly composed of a ferromagnetic material and its oxide, simultaneously contains fluorine and carbon. Further, according to the present invention, there is no deterioration in performance such as the magnetic properties and recording density of the magnetic recording layer itself, and there is an advantage that the magnetic recording layer can be formed efficiently and with high productivity.

Although the details of this effect are unknown, it is thought that the water-repellent light coating that contains fluorine is effective in improving corrosion resistance. It is also assumed that carbon has the function of stably existing fluorine in the form of carbon fluoride.

The magnetic recording medium obtained by the present invention can be used in the form of a tape, a sheet, a card, a disk, a drum, etc. for audio,
It can be widely used for magnetic recording applications such as video and digital signals.

(Characteristics Measuring Method/Evaluation Criteria) (1) Measurement of magnetic anisotropy of perpendicularly magnetized film The hysteresis loop in the film surface direction is measured by the method shown in JIS C-2561. The value of magnetization at the saturation point of the hysteresis loop is called saturation magnetization. A tangent line is drawn from the origin to this hysteresis loop, and the value of the external magnetic field at the point on this tangent line where the value of magnetization becomes the same as the saturation magnetization is called an anisotropic magnetic field (Hk).

In the present invention, a perpendicularly magnetized film having an Hk of 2 kilometrested or more is used.

For measurement, a sample vibrating magnetometer (manufactured by Riken Denshi Co., Ltd., B
HV-30> was used.

(2) Corrosion Resistance Test Samples were placed in an atmosphere of 60°C and 90% RH, and changes in the state of the sample surface over time were observed using a differential interference microscope, and the degree of corrosion resistance was compared relative to each other.

■ Measuring the concentration of fluorine and carbon in the magnetic recording layer X-ray photoelectron spectrometer (ESCAL manufactured by VG Scientific)
AB5) was used. In order to eliminate the effects of contamination and oxidation, X-ray photoelectrons from all ferromagnetic materials and X-ray photoelectrons from carbon and fluorine were measured at a depth of 400 Å or more from the surface of the magnetic recording layer. The relative number of atoms of each was calculated from their intensities. The concentrations of fluorine and carbon are expressed as the ratio of the number of atoms to the number of atoms of all ferromagnetic materials.

If the concentration of fluorine and carbon is distributed in the film thickness direction,
The concentrations of fluorine and carbon are expressed as averages in the film thickness direction. In other words, the ratio of the number of atoms of fluorine, carbon, and ferromagnetic material is determined at predetermined intervals in the film thickness direction in a range from a depth of 400 mm below the surface of the magnetic recording layer to the substrate-side interface of the magnetic recording layer. The average concentration is calculated by dividing these data by the number of data added in each film thickness direction.

(Example) Example 1 Using the apparatus shown in the figure, the evaporation source 8 was filled with Kobal 1~, nickel, and iron in an IB ratio of 85:10:5. An electron beam heater was used as the evaporation source, and the substrate was made of biaxially stretched polyethylene terephthalate with a thickness of 50 μm.
It was made into a film. After evacuating the inside of the vacuum chamber to below 5X10' Torr, a mixed gas of oxygen, nitrogen, and 02F6 in a volume ratio of 10:80:10 is introduced from valve 7 at a volume ratio of 0.60. /min.

Next, nickel and iron are evaporated from evaporation source 8 to Pal 1, and a perpendicularly magnetized film mainly consisting of cobalt, nickel, iron, and their oxides is deposited on the substrate moving along drum 3 at a rate of about 5 μm/min. It was deposited to a thickness of about 3,000 people at a speed. □The anisotropic magnetic field To1 of the obtained perpendicularly magnetized film was 3.2 kilooersteds. Further, after 400 etchings, fluorine atoms accounted for 1.5% of the ferromagnetic atoms (cobalt, nickel, and iron), and carbon atoms accounted for 8% of the ferromagnetic atoms.

Next, cut out the 1q sample to 20 x 20 mm, and
A corrosion resistance test was conducted in a C90%RH atmosphere. When the specimen was observed after being exposed for one week, seven corroded points with a diameter of 2 to 30 μm were observed on the whole specimen.
(The corrosion resistance was significantly better than the multiple comparative examples.

Example 2 A perpendicularly magnetized film was formed in the same manner as in Example 1 except that the evaporation source was filled with cobalt ingots.

) The perpendicularly magnetized film No. 11 was 3.9 kOersted. Furthermore, after etching for 400 people, the number of fluorine atoms opened was 1.8% of the ferromagnetic atoms, and the number of carbon atoms was 13% of the ferromagnetic atoms.

Next, cut out the obtained sample to 20 x 20 mm, and
A corrosion resistance test was conducted in a C90%RH atmosphere. After being left for one week, observation revealed that the sample had a total of 11 corrosion points with a diameter of 2 to 30 μm, and the corrosion resistance was significantly better than that of each comparative example.

Comparative Example 1 A perpendicularly magnetized film was formed in the same manner as in Example 1, except that the mixed gas introduced was oxygen and nitrogen at a volume ratio of]O:90.

The Hk of the obtained perpendicularly magnetized film was 3.2 kOersted. No fluorine atoms were measured in 400 person etching changes, and carbon atoms were present at 5% of the ferromagnetic atoms.

Next, a corrosion resistance test was conducted on the obtained sample in the same manner as in Example 1, and the overall diameter was 4 μm to 1.5 m.
Corrosion points with a size of 20 m occurred, and the corrosion resistance was significantly poorer than that of the present invention.

Comparative Example 2 A perpendicularly magnetized film was formed in the same manner as in Example 2, except that the mixed gas introduced was oxygen:nitrogen at a volume ratio of 10:90.

The perpendicularly magnetized film thus obtained had a T1 of 4.2 kOersted. No fluorine atoms were measured in the 400-person etching experiment, and carbon atoms were present at 4% of the ferromagnetic atoms.

A corrosion resistance test was conducted in the same manner as in Example 2, and the sample had two large serrated corrosion points with a diameter of 4 μm to 1 mm.
40 pieces were generated, and the corrosion resistance was significantly poorer than that of the present invention.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing one example of an apparatus for manufacturing the magnetic recording medium of the present invention. 1: Substrate, 5: Vacuum chamber, 8: Evaporation source.

Claims (1)

[Claims] (1) A magnetic recording medium comprising a magnetic recording layer mainly made of a ferromagnetic material and its oxide on a substrate, characterized in that the magnetic recording layer contains fluorine and carbon. Medium.