JP2558632B2 - Magnetic recording media - Google Patents

Description

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

Conventional technology In order to develop magnetic recording media for magnetic disks, magnetic tapes, etc., conventional γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ or ferromagnetic powder such as CrO ₂ in an organic binder. In place of the coating type magnetic recording medium prepared by dispersing in, the ferromagnetic metal thin film is directly plated on the non-magnetic substrate by the plating method, the sputtering method, the vacuum deposition method, the ion plating method, etc. for the purpose of further increasing the density. Metal thin film magnetic recording media to be formed have been actively researched.

However, the above-mentioned metal thin film type magnetic recording medium causes unstable running property due to friction or wear due to contact with a magnetic head or the like under high-speed relative motion at the time of signal recording / reproduction, or abrasion powder or damage. It easily occurs and cannot withstand long-term use. Therefore, it is strongly desired for practical use that the magnetic recording medium keeps smooth running property and wear resistance under the use environment condition.

Therefore, it has been conventionally improved by providing a protective film on a ferromagnetic metal thin film to improve friction and wear resistance. Among various proposals, for example, after surface treatment with a silane coupling agent, a higher fatty acid is used. There is a case that a protective film is further laminated with a fluoropolymer or a fluoropolymer (Japanese Patent Laid-Open No. 59-17215).
No. 9, JP-A-59-167848).

Problems to be Solved by the Invention However, although there are certainly some improvements in running performance, there are many insufficient points in which phenomena such as peeling or deterioration of the properties are observed.

Therefore, in consideration of the points according to the present invention, good lubricity with a magnetic head and the like, a protective film excellent in wear resistance,
It is an object of the present invention to provide a magnetic recording medium which is further excellent in running stability and durability by interposing an intermediate film which enhances the adhesiveness between this and a metal thin film.

Means for Solving the Problems An intermediate film containing a silane-based or titanium-based coupling agent is provided on the surface of a ferromagnetic metal thin film provided on a non-magnetic substrate, and a polymer film of p-xylylene or its derivative is further provided. Laminate as a protective film.

Action Due to the interposition of the intermediate film that firmly adheres the protective film and the metal thin film, and the low-friction and abrasion-resistant properties of the protective film itself, a magnetic recording medium excellent in running property and durability can be obtained. .

This is probably because the coupling agent of the interlayer film is chemically bonded to the surface of the metal film, while p-xylylene or a derivative thereof is strongly bonded by a radical reaction or the like when polymerized on the surface of the interlayer film. It is considered that the improvement of the physical strength and the adhesive force contributes.

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, 3 is an intermediate film containing a silane-based or titanium-based coupling agent, and 4 is a protective film made of a polymerized film of p-xylylene or its derivative.

Examples of the non-magnetic substrate 1 that can be used in the magnetic recording medium of the present invention include polymer materials such as polyamide, polyimide, polysulfone, polycarbonate, polypropylene, polyethylene, polyethylene terephthalate, poly (cellulose acetate), and polyvinyl chloride, non-magnetic metal. There are films, plates and the like made of known materials such as materials, glass, ceramic materials such as porcelain.

As the ferromagnetic material forming the ferromagnetic metal thin film 2, at least one metal selected from Fe, Co, Ni, or Mn, Cr, Ti, P, V, Sm, Bi, etc., or an oxide of these metals is selected. There are alloys that combine materials, and among them, metal thin films composed of at least two elements selected from Co, Cr, and Ni are preferable because they have high magnetic anisotropy energy and corrosion resistance. It can be formed by a vapor deposition method, a sputtering method, an ion plating method, a plating method, or the like. Needless to say, the ferromagnetic metal thin film 2 used in the present invention is not limited to the above composition.

In the present invention, the coupling agent used for the intermediate film 3 is a silane-based coupling agent such as vinyltrichlorosilane, trimethoxyvinylsilane, dimethoxy-3-mercaptopropylmethylsilane, triethoxyvinylsilane, 3-chloropropyldimethoxymethylsilane, tris (2-methoxy). (Ethoxy) vinylsilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, diethoxy-3-glycidoxypropylmethylsilane, 3- (2-aminoethylamino) Propyl) dimethoxymethylsilane, 3-chloropropyltrimethoxysilane, triacetoxyvinylsilane, etc., and titanium-based compounds such as isopropyltriisostearoyl titanate and isoprotonyl. Lutridecylbenzenesulfonyl titanate, di (methacryl) oxyacetate titanate, di (octylbairophosphate) ethylene titanate, isopropyl di (4-aminobenzoyl) stearoyl titanate, isopropyl trimethacry titanate, isopropyl triacrylic titanate or di (acryl) ethylene titanate. However, the effects described in the present invention are not limited to the above substances.

On the other hand, the protective film 4 is a polymerized film of p-xylylene or its derivative, and has the following general formula: And R is an alkyl group such as -CH ₃ , -C ₂ H ₅ , or -C ₃ H ₇ , or -C
Hydroxyalkyl group such as H ₂ OH, -C ₂ H ₅ OH, -CH ₂ OCH ₃ ,,-
CH ₂ OC ₂ H ₅ ,, -C ₂ H ₅ OCH ₃ and other alkoxyalkyl groups, -OCH
Alkoxy group such as ₃ , -OC ₂ H ₅ , carboalkoxy group such as -COOCH ₃ , -COOC ₂ H ₅ , carboxyl group, hydroxyl group, -CH ₂ NH
₂ , -NH ₂ , -C ₂ H ₅ NH ₂ and other amino groups, cyano groups, nitro groups, F, Cl, Br, I halogen groups, aryl groups or alkenyl groups, each of which may be used alone or in combination. It is a polymerized film. n is 10 to 10000, and preferably 4000 or more. Since these are easily formed at room temperature by the vapor phase pyrolysis method, they are formed to have a desired film thickness without damaging the recording medium.

It is considered that these polymerized films have good physical properties because they have high tensile strength and molecular cohesive energy, and also have good properties because they have good chemical stability and environmental resistance.

The total thickness of the intermediate film and the protective film is preferably 500 A or less.

 Hereinafter, detailed description will be made in Examples.

Example 1 On a polyamide film substrate having a film thickness of 12 μm, Co—Cr (atomic ratio Co: Cr = 8: 2) was used to form a film having a film thickness of 1300 A (AE
A ferromagnetic metal thin film of S analysis was prepared (Sample No.
1). 3-methacryloxypropyltrimethoxysilane (aqueous solution 1: 5 v / v ratio) was spin-coated on the metal thin film of Sample No. 1 with methanol approximately 1000 times (v / v ratio) and dried by heating at 100 ° C. After that, a coupling treatment was performed at a thickness of about 50A. Further, a poly (p-xylylene) film was formed on this by about 350 A (p-xylylene dimer was pyrolyzed by vapor phase pyrolysis under conditions of 0.5 Torr and 680 ° C. and laminated at 25 ° C. and 0.1 Torr) (sample). No.2). As a comparative example, poly (p
-Xylylene) Instead of a film, stearic acid [diluted 10 times (wt%) with chloroform] solution or polyfluoropolyether (klytox157FS, Dupont) [diluted 100 times (wt%) with trichlorotrifluoroethane] solution was spin coated ( Film thickness 3
20A or 370A) to produce sample Nos. 3 and 4, respectively.

The above samples were compared and evaluated by measuring the dynamic friction coefficient,
The results are shown in Table 1.

The evaluation device was a reciprocating dynamic friction coefficient meter, using a steel ball (SUJ2) of φ6.3 mm for the head, load (P) = 5 gf,
The test was performed at a running speed (v) = 10 mm / sec.

According to Table 1, the untreated sample No. 1 had a large μ value from the beginning, and scratches became clear after about 30 passes during running, and the μ value began to fluctuate, eventually increasing to μ = 0.65 and increasing to metal. Abrasion powder of was strongly seen. The samples Nos. 3 and 4 were improved in wear resistance to 0.2 or less, but scratches occurred as the running continued, and the μ value increased with 300 Pass, which was not good.

However, in sample No. 2, the μ value was small from the beginning.
Even after 300 passes, there was almost no change at 0.19, and there were almost no scratches on the surface observation, which was a good result.

Therefore, it is understood that the recording medium constituted by the intermediate film of the silane coupling agent and the poly (p-xylylene) as the protective film on the ferromagnetic metal thin film is a magnetic recording medium having good running property and excellent durability. .

Example 2 A ferromagnetic metal thin film having a film thickness of 1250A was formed on a polyimide film substrate having a film thickness of 30 μm with the same metal composition as in Example 1. During the deposition of the ferromagnetic metal thin film, oxygen was introduced to reach 250 A
An oxide film layer of No. 5 was formed (Sample No. 5).

Triacetoxyvinylsilane or 3- (2-aminoethylaminopropyl) on the surface of the metal thin film of sample No.5
A solution of dimethoxydimethylsilane aqueous solution (10 vol%) diluted 500 times with isopropyl alcohol was spin-coated to a thickness of about 80A, and further 300A of poly (dichloro-p-xylylene) was laminated (Sample No. 6,7). . Similarly, a solution of di (methacryl) oxyacetate titanate or isopropyltriacryl titanate diluted 100 times with toluene was spin-coated at a thickness of about 80 A on the surface of the metal thin film of Sample No. 5, and poly (dichlorodichloromethane) was further coated thereon. -P-xylylene) was laminated at 300 A (Sample Nos. 8 and 9). For comparison, stearic acid was added to the sample coated with triacetoxyvinylsilane by 10 ^-4.
Approximately 300 A was deposited at room temperature under Torr (Sample No. 1
0).

Then, together with the measurement of the contact angle, the dynamic friction coefficient was measured under the test conditions shown in Table 2. Among them, Sample No. 5 had a high μ value and a large amount of abrasion powder as in Example 1, whereas Sample No. 5 was not good.
No. 10 has insufficient contact resistance, but lacks abrasion resistance, so good running performance is not sustained and the μ value increases, resulting in insufficient characteristics. On the other hand, sample Nos. 6 to 9 had a high contact angle of 88 ° to 90 °, and no abrasion powder was generated even after running, and the abrasion resistance was excellent.

Therefore, a magnetic recording medium having a polymer film formed from a derivative of p-xylylene such as poly (dichloro-p-xylylene) as a protective film and a silane- or titanium-based coupling agent as an intermediate film is resistant to abrasion. It was clarified that it can be realized as a recording medium having excellent wear resistance, and that the same effect can be obtained even when the surface portion of the ferromagnetic metal thin film is oxidized.

Example 3 The samples having the configurations shown in Table 3 were evaluated by a pin-disk type tester. At this time, in Samples Nos. 12 and 15, the metal thin film was surface-oxidized, and the intermediate film was spin-coated or vapor-deposited with the materials shown in the same manner as in Examples 1 and 2, and the poly (p -Xylylene) is formed by a polymer film in which only the substituent R in the general formula is changed, and the film thickness at that time is represented by () under the composition. The test conditions were φ3 mm SUJ2, P = 5 gf, v = 1.0 m / s, and the μ value after 120 min and surface observation were performed.

According to Table 3, all samples No. 11 to 16 are μ
It has excellent properties such as a small value of around 0.2 and almost no running scratches observed on the surface.
Since this can be achieved with a protective film within a film thickness of 500 A, it is effective in a range that does not affect spacing loss.
It can be said that this is a magnetic recording medium that can be put to practical use.

EFFECTS OF THE INVENTION According to the present invention, a magnetic recording medium having improved friction resistance and wear resistance that can be put to practical use can be obtained.

[Brief description of drawings]

The figure is a cross-sectional view of a magnetic recording medium in an example of the present invention. 1 ... Non-magnetic substrate, 2 ... Ferromagnetic metal thin film, 3 ... Intermediate film, 4 ... Protective film.

Claims (2)

(57) [Claims] 1. An intermediate film containing a silane-based or titanium-based coupling agent is provided on the surface of a ferromagnetic metal thin film provided on a non-magnetic substrate, and a polymer film of p-xylylene or its derivative is further protected thereon. A magnetic recording medium characterized by being laminated as a film. 2. The magnetic recording medium according to claim 1, wherein the total thickness of the intermediate film and the protective film is 500 A or less.