JPS5837614B2 - magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film layer as a magnetic recording layer, and specifically relates to a magnetic recording medium having a protective layer made of silicon-silicon oxide on its surface. It is related to.

Conventionally, as a magnetic recording medium, γ-
Fe203, co-doped r-Fe203, Fe3
04. Powder magnetic materials such as Co-doped Fe304, γ-Fe203 and Fe304 beltride compounds, magnetic powders such as Cr02, or ferromagnetic alloy powders are combined with vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy Coating-type materials have been widely used, in which a material dispersed in an organic binder such as a resin or polyurethane resin is applied and dried.

In recent years, as the demand for high-density recording has increased, magnetic recording layers are made of ferromagnetic metal thin films formed by paper deposition methods such as vacuum evaporation, sputtering, and ion plating, or plating methods such as electroplating and electroless plating. ,
So-called binder-free magnetic recording media that do not use a binder are attracting attention, and various efforts are being made to put them into practical use.

Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinning required for high-density recording leads to a reduction in signal output, which has reached its limit. Moreover, the manufacturing process is complicated, and it has the drawback of requiring large auxiliary equipment for solvent recovery and pollution prevention.

In non-binder type magnetic recording media, a ferromagnetic metal with a saturation magnetization higher than that of the above-mentioned oxides is formed as a thin film without containing a non-magnetic substance such as a binder, so it can be made ultra-thin for high-density recording. Moreover, the manufacturing process is simple.

As one of the requirements for magnetic recording media for high-density recording, high coercive force and thinness have been proposed both theoretically and experimentally. There are great expectations for non-binder type magnetic recording media that can be easily made small and thin and have a high saturation magnetic flux density.

Major problems concerning magnetic recording media made of ferromagnetic metal thin films include strength against corrosion and abrasion, and running stability.

A magnetic recording medium is subjected to high-speed relative motion with a magnetic head during the process of recording, reproducing, and erasing magnetic signals.
At this time, the running must be smooth and stable, and at the same time, wear or damage due to contact with the head must not occur.

It is also required that recorded signals should not be reduced or lost due to changes over time due to corrosion or the like during storage of the magnetic recording medium.

There are few ferromagnetic metal layers that can withstand the harsh conditions of magnetic recording and reproducing processes, and various protective layers are applied to the surface.

The material selected for the protective layer must be hard and must adhere thinly, uniformly, and firmly to the surface on which it is formed.

A protective film that easily peels off or falls off under harsh environments not only does not protect the magnetic recording layer, but also creates new problems such as the generation of fragments.

Additionally, it is desirable that these materials be electrically conductive to reduce static electricity problems in high speed magnetic recording systems.

Furthermore, it is desired that the means for forming the protective layer be easy.

Formation of a protective layer by rhodium electroplating has been partially put into practical use as a protective layer, and there is also a method of applying a lubricant, and in the case of a ferromagnetic metal thin film containing cobalt as a magnetic material, a method of applying a suitable temperature and temperature. A method of oxidizing the surface by placing it under humidity (Special Publication No. 42-20025,
(U.S. Pat. No. 3,353,166) A method in which a dialloy magnetic thin film is brought into contact with nitric acid, then heat treated to form an oxide layer on the surface, and then a lubricant is impregnated (British Patent No. 126,517)
No. 5): A method is known in which Cr is deposited on the surface of a ferromagnetic metal thin film in a moderate vacuum to form a layer of a mixture of Cr and Cr oxide (Japanese Patent Publication No. 4393/1983). .

Further, it is known from US Pat. No. 3,109,746, US Pat. No. 3,353,166, and Japanese Patent Application Laid-open No. 80102/1983 to use a silicon monoxide vapor deposited film as a protective layer.

However, although a protective layer of a silicon monoxide film or a silicon dioxide film shows some improvement in wear resistance and durability, it is still not sufficient and there are still problems in terms of runnability.

Furthermore, since the silicon oxide film is non-conductive, it has the disadvantage that static electricity cannot be sufficiently dissipated in high-speed magnetic recording systems.

An object of the present invention is to provide a magnetic recording medium with a protective layer having better wear resistance, durability, and runnability than conventional hard metal layers or oxide layers.

That is, the present invention relates to ferromagnetic metals formed by methods such as electroplating, electroless plating, vapor phase plating, sputtering, vapor deposition, and ion plating. The present invention relates to a magnetic recording medium made of a ferromagnetic metal thin film having excellent wear resistance, corrosion resistance, and good running properties, which is formed by forming a protective layer made of silicon-silicon oxide on the film surface.

In the present invention, a protective layer made of silicon-silicon oxide is formed by heating silicon to its melting point in an oxidizing gas atmosphere in the air at a pressure of 10-3 to 5 x 10-5 Torr and evaporating it to form a ferromagnetic layer. Obtained by depositing on a metal thin film.

The deposition rate is preferably 500 persons/See or less.

At a vacuum pressure of 10-3X5X10-5 Torr, there is enough oxygen to react with some of the silicon atoms during evaporation, forming silicon-silicon oxide on the ferromagnetic metal thin film, which has good wear resistance. , corrosion resistance, and running properties.

If pure oxygen is used instead of air, the pressure can be reduced by about 1/5 to obtain the desired protective layer.

It is believed that the silicon-silicon oxide layer of the present invention will have a composition of Si-SiOX (1≦X×2).

The thickness of the silicon-silicon oxide layer to be provided as a protective layer is determined by the following conditions: to obtain a sufficient protective effect, and to avoid a decrease in output due to spacing loss due to the gap between the magnetic recording layer and the magnetic head. 0.005-0.3
μm1 is preferably in the range of 0.01 to 0.2 μm.

The ferromagnetic metal layer according to the present invention may be iron, cobalt, nickel or other ferromagnetic metals, or Fe-Co, F
e-Ni, Co-Ni, Fe-Si, F
e-Rh, Fe-V, Co-P, Co-B
, Co-Si. eoichi ■, Co-Y, Co-La
, Co-Ce, Co-Pr, Co-Sm, Co-Mn,
Fe-co-Ni, Co-Ni-P, Co-Ni-B,
Co-Ni-Ag, Co-Ni-Nd, Co-N
i -Ce, Co -Ni -Zn, Co-Ni-
Cu, Co-Ni-Hg, Co-Ni-W, Co-
Ni-Re, Co-Mn-P, Co-Z
n-P, Co-Pb-P, Co-Sm-Cu, Co
A ferromagnetic alloy such as -Ni-Zn-P or Co-Ni-Mn-P is formed into a thin film by a vapor deposition method or a plating method.

Paper deposition method is a method in which a substance or its compound is deposited on a substrate as vapor or ionized vapor in a gas or vacuum space. Plating (Chemical Vapo
This method corresponds to the method such as the rDeposition method.

The plating method refers to a method of depositing a substance onto a substrate from a liquid phase, such as electroplating or electroless plating.

For example, L. "Vacum Deposit" by Holland
tion of Thin Film” (Chapm
an & Hall Ltd. 1 9 5 6)
:L. I, Maissel & R, Gla
co-edited by ng “Handbook of Thin”
Film Technology” (Me Graw
-Hill Co. , 1970); US Pat. No. 2,671,034; US Pat. No. 3,329,601: 33426
No. 32; No. 3342633: No. 3516860: No. 3615911; No. 36.25849; No. 3700
No. 500; No. 3772174; No. 3775179;
It is described in specifications such as No. 3787237; No. 3856579.

Furthermore, regarding the form of precepts using the plating method, for example, W, G
Written by 01di6 “MetallicCoating o”
f Plastics” (Electro-Che
mical Publications Ltd
．． , 1968); U.S. Patent No. 3,116,159;
No. 8479: No. 3219471; No. 3227635; No. 3238061, No. 3267017; No. 335
No. 3986; No. 3360397; No. 3362893; No. 3416932; No. 3446657; No. 354
It is described in specifications such as No. 9417; No. 3578571; No. 3637471; No. 3672968.

The thickness of the non-magnetic, flexible support is about 4 to 50 μm, and the thickness of the ferromagnetic metal layer is about 0.02 to 5 μm, preferably 0.02 to 5 μm.
05~2μ group is good.

Supports according to the present invention include cellulose acetate; nitrocellulose; polyamide: polymethyl methacrylate; polytetrafluoroethylene: polytrifluoroethylene; polymers or copolymers of α-olefins such as ethylene and flopylene; vinyl chloride. Polymers or copolymers; polyvinylidene chloride; polycarbonate; polyimide; plastic bases such as polyesters such as polyethylene terephthalate and polyethylene naphthalate, as well as metals such as aluminum, brass, and stainless steel, or glass and ceramics. etc. are used.

The shape of the support may be tape, sheet, card, desk, or drum.

If the ferromagnetic metal thin film formed by methods such as plating or vapor deposition is left as it is, it may become unstable due to abrasion with the magnetic head, become scratched and scratched, and debris may adhere to and accumulate on the head. The output of magnetic recording often drops significantly.

Furthermore, if exposed to a high temperature and high humidity environment for a long time, the metal film will decompose, hydroxides will form, and corrosion will occur, resulting in a significant deterioration of the surface quality and a decrease in the saturation magnetic flux density, making it unusable as a magnetic recording medium. becomes.

The magnetic recording medium having the protective layer according to the present invention is a good magnetic recording medium in which the above phenomenon is significantly improved.

Furthermore, when a ferromagnetic metal thin film is formed on a flexible support by vapor deposition, sputter linking, ion plating, etc., or when a ferromagnetic metal thin film is formed in a certain plating bath or plating condition, the metal Due to the internal stress of the thin film, curling occurs so that the ferromagnetic metal thin film side becomes a concave surface, which is undesirable for use as a magnetic recording medium.

Alternatively, when a ferromagnetic thin film is formed on a rigid support, there is a problem that the adhesion of the magnetic thin film becomes poor due to the internal stress of the metal thin film.

Forming a silicon-silicon oxide protective film according to the present invention eliminates curl in the case of a flexible support and improves the contact condition with the magnetic head, and in the case of a rigid support, silicon-silicon Since the internal stress of the oxide protective film and the internal stress of the ferromagnetic metal thin film are balanced, the adhesion is extremely good.

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 A tape-shaped polyethylene terephthalate film (Myla
r film, E. I, du pont de Nem
ours & co. Co., Ltd.) on top of the following plating solution (
aqueous solution), Co-P under plating conditions (Co:9
8%, P: 2%) The magnetic film was electrolessly mended to a thickness of 0.20 μm.

US Shipl is used as an activation pretreatment solution for electroless plating.
ey Co., Ltd. (2300 Washington St., N.
Cat in Ewton, Massachusetts)
alyst 6 F solution and Accelerator
19 liquids were used.

Cobalt chloride (COCI.

-6H20) 9.5f/7 Hypophosphorous acid (NaH2PO2・H20) 5°31/l Ammonium chloride 10.7? /1 citric acid
26.5′? /l boric acid
30.9g/. epH: 7.3, liquid temperature: 8
0°C Next, this tape was placed in a vacuum chamber and 8 × 10 −
Silicon was evaporated in air at a pressure of 'Torr to form a 0.07 μm protective layer of silicon-silicon oxide on the plated magnetic film.

The magnetic tape thus obtained (referred to as sample A) was unified.■
VTR (AV8700 manufactured by SONY Corp.)
On the surface, the running was smooth and stable output was obtained.

Furthermore, the same part of the magnetic tape is brought into sliding contact with the magnetic head,
The time required for scratches to appear on the magnetic layer was measured, and the results were as shown in Table 1 below.

For comparison, a magnetic tape with no protective layer formed (Sample B) and a 0.07 μm silicon monoxide layer formed on the magnetic plating layer by evaporating silicon monoxide (Sin) in a vacuum of 10-5 Torr as a protective layer. A magnetic tape with a film (Sample C) was also measured at the same time.

It was found that the sample provided with the silicon-silicon oxide protective layer has excellent wear resistance.

Example 2 A 22 μm thick polyethylene terephthalate film was placed in a vacuum evaporation apparatus, and a Co (95% by weight)-V (5% by weight) alloy was deposited on the film in a vacuum of 5.0 x 10-6 Torr from an evaporation source. A ferromagnetic metal thin film of 0.3 μm was formed by vapor deposition.

The sample thus produced (Sample D) was curled so that the magnetic thin film side was concave, and when it was applied to a unified ■-type VTR (see Example 1), it had poor running properties, and the surface corresponded to the edge of a video track. The magnetic thin film in some areas has peeled off.

After forming the ferromagnetic metal thin film as described above, air was pumped through a 21 dollar valve in a vacuum chamber to 2×10−″ Torr.
The sample (sample E) in which a protective layer of silicon-silicon oxide was formed to a thickness of 0.1 μm in the same manner as in Example 1 had no curling at all and had good runnability in the VTR described above. It was good.

When the same location was brought into sliding contact with a magnetic head, no scratches were observed even after 280 seconds or more.

On the other hand, in sample D, the magnetic thin film detached in less than 12 seconds.

Furthermore, when the corrosion resistance of Samples D and E was investigated, the results were as shown in FIG.

Figure 1 shows the change in saturation magnetic flux density (Bm) over time when a sample is kept in an environment of 60°C and 90% relative humidity. The vertical axis is the initial saturation magnetic flux density (Bm).
Bmo) as a percentage; the horizontal axis is 60°C, 90%
Number of days kept in relative humidity.

As is clear from this, it was confirmed that the corrosion resistance of the sample provided with the protective layer of silicon silicon oxide (Sample E) was improved.

Moreover, it was also found that sample E had less discoloration on the sample surface and less increase in pinholes.

Example 3 A disk-shaped copper substrate was thoroughly degreased and washed with water beforehand, and then magnetically plated in the following electroplating bath.

Nickel sulfate (NiSO4.7H20) 30k/'e Nickel chloride (NiCl2.6H20) 5"'Cobalt sulfate (COSO4-'7-H,,0) 3"/'Cobalt chloride (coCl2.6H20) 5? /l Copper sulfate (CuS04-5H20) Formalin borate■・5-naphthalene di・sodium sulfonate 0.25y'/l 7.5 ? /l O,l cc/l 0.25g/l H25.0, liquid temperature: 40℃, flow density 0.6A/dm Co-Ni-Cu (Co6 7%, Ni32
%, Cu1%) was formed with a thickness of 0.3μ.

Next, a protective layer of silicon oxide was formed thereon to a thickness of 0.1 μm in the same manner as in Example 1.

The adhesion was examined by a peel test using cellophane tape, and it was found that the product with a protective layer of silicon-silicon oxide (sample F)
) had extremely good adhesion, but the adhesion of the sample without a protective layer (sample G) was poor.

The abrasion resistance of the sample was measured using a Tabor type abrasion tester using a tungsten carbide ball having a diameter of 1/4 inch.

For comparison, silicon monoxide (Sin) was evaporated in a vacuum of 10'Torr as a protective layer and 0.00% was deposited on the magnetic plating.
A sample with a silicon monoxide film of 1 μm size (sample H)
were also measured.

When a tungsten carbide ball was brought into contact with a sample and the number of passes required until the sample was scratched was investigated, the results are shown in Table 2 below.

As is clear from this, the wear resistance of the specimen provided with the silicon-silicon oxide protective layer of the present invention (sample F) is improved.

Example 4 25 μm thick polyimide base (Kapton fi/
L/A, E. I. du Pont de N
emours & co. Co-Si (C
A magnetic film of 0.90%, SilO%) was formed to a thickness of 0.15 μm by ion plating.

The ion plating is done at argon gas pressure of 0. 0 1 T
The test was carried out at an acceleration voltage of 2 KV and a substrate temperature of 80°C.

Next, after evacuating the vacuum chamber to 10' Torr, air was introduced through a needle valve to make the pressure 8 x 10-5 Torr, and a protective layer of silicon-silicon oxide was formed to a thickness of 0.05 μm in the same manner as in Example 1. It was formed like this (
Sample ■).

The sample on which the protective layer was not formed (sample J) had curls so that the metal thin film side had a concave surface, but when the protective layer was formed, the curls disappeared.

Samples ■, J, and sample K, which had a silicon monoxide (Sin) film with a thickness of 0.05 μm formed as a protective layer, were brought into sliding contact with a magnetic head and the time until scratches appeared on the magnetic layer was measured, and the following results were obtained. It was as shown in Table 3.

From the above examples, it was confirmed that the magnetic recording medium provided with the silicon-silicon oxide protective layer of the present invention has excellent wear resistance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the effect of the wear resistance of the magnetic recording medium according to the present invention.

Claims (1)

[Claims] 1. In a magnetic recording medium having a ferromagnetic metal thin film layer as a magnetic recording layer, silicon is evaporated in an oxidizing gas atmosphere corresponding to the partial pressure of oxygen in air at a pressure of 10'' to 5X10' Torr to form a ferromagnetic layer. A magnetic recording medium characterized in that a protective layer made of silicon-silicon oxide is formed on the surface of a metal thin film.