JPH0675285B2 - Magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high recording density magnetic recording medium used in the information industry field and the like.

Conventional technology γ as an organic binder due to the demand for high-density recording of information
In place of the coating type magnetic recording medium in which ferromagnetic powder such as —Fe ₂ O ₃ is dispersed, vacuum deposition method on a non-magnetic substrate such as plastic,
A magnetic recording medium directly provided with a ferromagnetic metal thin film by a sputtering method, an ion plating method or the like has been researched and developed, and is partially put to practical use.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a ferromagnetic metal medium, the thin film layer easily peels, wears, or damages upon contact scanning with the head during recording and reproduction. In order to improve the above defects, it has been proposed to provide a protective film on the surface of the medium. For example, a proposal is made by forming a metal oxide layer of SiO ₂ , Al ₂ O ₃ , etc., and forming a film of a fatty acid-based lubricant on the surface thereof to form a composite protective film (JP-A-59-154642). Has been done. However, in this case
Since the fatty acid type lubricant has weak bond with the underlying oxide layer and low heat resistance, peeling and decomposition due to frictional heat occur during running while contacting with the magnetic recording head for long-term durability. And less effective.

Means for Solving Problems A metal oxide-containing layer is formed on the surface of a ferromagnetic metal thin film provided on a non-magnetic substrate, and a polyphosphazene-containing layer is formed and protected on the surface of the metal oxide-containing layer. The film.

Action Improves wear resistance by the metal oxide-containing layer on the surface of the ferromagnetic metal thin film and enhances the binding force with the lubricant phosphophazene. At the same time, the heat resistance and oxidation resistance of the lubricant itself suppresses dissociation and decomposition. It is possible to obtain a high recording density magnetic recording medium having excellent properties.

Example FIG. 1 is a sectional view of a magnetic recording medium of the present invention. In the figure, 1 is a non-magnetic substrate, 2 is a ferromagnetic metal thin film, 3 is a metal oxide containing layer, and 4 is a polyphosphazene containing layer. As the non-magnetic substrate 1 that can be used in the magnetic recording medium according to the present invention, polymer materials such as polyvinyl chloride, polyethylene terephthalate, polyimide and polyamide, non-magnetic metal materials such as aluminum, ceramic materials such as glass and porcelain are well known. Examples include films and plates made of the above materials. A ferromagnetic metal thin film 2 that can be used in the magnetic recording medium of the present invention
Examples of such alloys include one or more alloys of iron, cobalt, and nickel, and alloys of these in combination with manganese, chromium, titanium, phosphorus, yttrium, samarium, bismuth, and the like. In order to form the ferromagnetic metal thin film 2 on the non-magnetic substrate 1, known methods such as a vacuum vapor deposition method, a sputtering method, an ion plating method and a plating method are used. In the present invention, the metal oxide containing layer 3 is formed on the surface of the ferromagnetic metal thin film 2 as described above, and the polyphosphazene containing layer 4 is further provided on the surface thereof. Examples of the metal oxide layer 3 usable in the present invention include Al ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ and Zr.
_{O 2, TiO 2, WO 2} , CrO 2, ferrite, and a laminated glass. Ferrite has the general formula MO ・ Fe ₂ O ₃ (where M is M
n ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ ). As the method of forming the above-mentioned metal oxide-containing layer, sputtering method, reactive vapor deposition, reactive ion plating, and A
There is a coating method in which l, Si, Zr, Ti, W alcoholate is hydrolyzed and polymerized, in particular, Si alcoholate and Zr alcoholate, Ti
The composite glass film prepared by mixing either alcoholate or W alcoholate was effective in controlling physical properties such as thermal expansion coefficient and mass productivity. In the case of CrO ₂ , in addition to the above method, a Co—Cr based ferromagnetic metal film was selectively treated with dilute nitric acid under a certain condition to selectively form a CrO ₂ film on the magnetic thin film.

The polyphosphazene has the general formula; (In the formula, m and m'are integers of 0 to 7 and n is an integer of 4 to 30). Polyfluoroalkoxyphosphazene is particularly preferable. When m and m'of the side chain molecule were 7 or more, heat resistance and lubricity were deteriorated. When n of the main chain is less than 4, heat resistance and bond strength with the substrate are deteriorated and durability cannot be sufficiently exhibited. When n is 31 or more, polyphosphazene is hardly soluble in a solvent and thus the surface of the substrate. It became difficult to form a uniform film, and the function of the protective film could not be exhibited. The polyphosphazene-containing layer was formed by dissolving in a solvent of ethanol, methylisobutylketone, tetrahydrofuran, methylethylketone, dimethylketone, dimethylformamide, dimethylsulfoxide and forming a thin film in the coating step.
The sum of the thickness of the metal oxide-containing layer and the thickness of the polyphosphazene-containing layer was preferably 50 to 500Å. If it exceeds 501 Å, the output will drop due to spacing loss during signal playback,
When it is less than Å, it is difficult to form a uniform protective film, and wear resistance,
There was a problem with lubricity.

An example will be described below.

Example 1 A ferromagnetic metal thin film having a film thickness of 1500 Å made of cobalt (90 wt%)-chromium (10 wt%) was formed on a polyimide film substrate having a heat of 20 μm by a vacuum deposition method. An Al ₂ O ₃ oxide layer of 112 Å was formed on the surface of this medium by reactive vapor deposition, and 0.1 wt% ethanol of polyditrifluoroethoxyphosphazene (m, m '= 0, n = 4) was further formed on the surface. The solution was applied and dried to form a thin film having a thickness of 154Å. The film thickness was measured with an ellipsometer (hereinafter, this method was used). The sample shape was a 3.5 inch disk.

Example-2 A Zn ferrite thin film having a film thickness of 105Å was provided on the surface of a ferromagnetic metal thin film having the same structure as in Example 1 by a sputtering method. Further, a 0.05 wt% tetrahydrofuran solution of polydipentafluoropropoxy phosphazene (m, m ′ = 1, n = 6) was applied on the surface and dried to form a 210 Å thin film. The sample shape is
It was prepared in the same manner as in Example 1.

Example 3 A composite solution of Si isopropylate and Zr isopropylate was formed on a surface of a ferromagnetic metal thin film having a film thickness of 2000 Å consisting of cobalt (85%)-chromium (15%) by sputtering on a polyethylene terephthalate substrate having a heat of 50 μm. (Product name Glasca 40
1, manufactured by Tsukiita Kenkyusho Co., Ltd., is hydrolyzed and polymerized at 100 ° C in the presence of a catalyst to form a glass film composed of ZrO ₂ -SiO ₂ (thickness: 20
0Å) formed. Furthermore, a 0.05 wt% solution of polyfluoroalkoxyphosphazene (m, m ′ = 4, n = 10) in dimethylformamide and acetone (volume ratio 1: 4) was applied to the surface and dried to form a thin film with a thickness of 120Å. Formed. The sample was formed in the same shape as in Examples 1 and 2.

Example 4 A ferromagnetic metal thin film having the same structure as in Example 3 was added to a 0.1N HNO ₃ solution.
After soaking for 1 minute, dry with hot air at 95 ° C for 1 minute, and
A film of CrO ₂ was formed. Furthermore, 0.01 wt% of polyfluoroalkoxyphosphazene (m, m '= 6, n = 25) dimethyl sulfoxide and tetrahydrofuran (volume ratio
A mixed solvent solution of 1: 3) was applied and dried to form a thin film having a thickness of 255 Å, and a sample similar to the above-mentioned example was prepared.

Comparative Example-1 Only a stearic acid-containing layer having a thickness of 200 Å was provided on a ferromagnetic metal thin film having the same structure as in Examples 1 and 2, and a sample having the same shape as that of Example was prepared.

Comparative Example-2 A SiO ₂ thin film having a film thickness of 200 Å was provided on a ferromagnetic metal thin film having the same configuration as in Examples 3 and 4, and a perfluorolauric acid-containing layer was further formed on the surface to a thickness of 100 Å. did. A sample having the same shape as that of the example was prepared.

Table 1 shows the results of examining the friction coefficient and durability of the medium surface for each magnetic disk obtained in the above Examples and Comparative Examples.
It was shown to. The test conditions are shown below.

a Friction test condition Measuring machine: reciprocating static, dynamic friction coefficient automatic measuring machine Head material, shape, steel ball (SUJ) diameter 3m / m 〃 load; 20gr 〃 running speed; 10mm / S measurement atmosphere; 25 ℃ 60% RH b durability Test conditions Measuring machine: Disk type magnetic recording measuring machine Head load; 10 gr 〃 Running speed; 3 m / S Measurement atmosphere; 25 ° C 60% RH The number of running times until the output decreased by 3 dB from the initial value was measured.

As is clear from the results shown in Table-1, the product of the present invention is excellent in both lubricity and durability. In addition to the examples, SiO ₂
The same effect was also obtained in the combination of TiO ₂ , SiO ₂ -WO ₂ composite glass and polyfluoroalkoxyphosphazene.

Effect of the Invention The magnetic recording medium of the present invention has been confirmed to have excellent lubricity and durability, and is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium in an example of the present invention. 1 ... Non-magnetic substrate, 2 ... Ferromagnetic metal thin film, 3 ... Metal oxide containing layer, 4 ... Polyphosphazene containing layer.

Claims (5)

[Claims] 1. A magnetic recording medium in which a metal oxide-containing layer is formed on a surface of a ferromagnetic metal thin film provided on a non-magnetic substrate, and a polyphosphazene-containing layer is formed on the surface of the metal oxide-containing layer. 2. The metal oxide containing layer comprises Al, Fe, Si, Zr, Ti, W, C.
The magnetic recording medium according to claim 1, which is an oxide of any of r. 3. The metal oxide-containing layer has the following general formula: MO.Fe ₂ O ₃ (where M is Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn). The magnetic recording medium according to claim 1, which is a ferrite represented by the formula: at least one selected from ²⁺ . 4. The magnetic recording medium according to claim 1, wherein the metal oxide-containing layer comprises a composite glass comprising at least one selected from the group consisting of silicon oxide, zirconia oxide, titanium oxide and tungsten oxide. . 5. A polyphosphazene having the following general formula; The magnetic recording medium according to claim 1, which is a polyfluoroalkoxyphosphazene represented by the formula (m and m'are integers of 0 to 7 and n is an integer of 4 to 30).