JPS5837615B2 - 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 chromium and silicon-silicon oxide on the surface. It is related to recording media.

Conventionally, as a magnetic recording medium, 1-
1-Fe203, Fe3 doped with Fe203, Co
04, Co-doped F30,, r-F203 and Fe
Powder magnetic materials such as 304 Bertolide compound, magnetic powder such as Cr02, or ferromagnetic alloy powder are dispersed in an organic binder such as hinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, polyurethane resin, etc. Coating type products have been widely used, in which a predetermined amount is applied and dried.

In recent years, with the increasing demand for high-density recording, 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.

The major problems associated with magnetic recording media made from ferromagnetic metal thin films include corrosion and abrasion, strength, 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.
In this case, 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 by themselves, and they are formed on the surfaces of various protective layers.

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

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. Method of oxidizing the surface by placing it under humidity (Japanese Patent Publication No. 42-20025, U.S. Pat. No. 3,353,166): After bringing the alloy magnetic thin film into contact with nitric acid, it is heat-treated to form an oxidized layer on the surface. , and then soaking the lubricant (British Patent No. 1265)
175): A method is known in which Cr is vapor-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 on which a protective layer is formed that has superior wear resistance, durability, and runnability than conventional hard metal layers or oxide layers.

That is, the present invention forms a protective layer made of chromium and silicon-silicon oxide on the surface of a ferromagnetic metal thin film 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 that has excellent wear resistance, corrosion resistance, and good running properties.

The present inventors have arrived at the present invention as a result of preliminary research regarding the protective layer of a magnetic recording medium having a ferromagnetic metal thin film.
When only a chromium layer is provided as a protective layer, wear resistance,
Although the corrosion resistance is improved, the wear resistance is somewhat insufficient, and when a silicon-silicon oxide layer is provided as a protective layer, the runnability, abrasion resistance, and durability of the magnetic recording medium are improved. Although both corrosion resistance was improved, it was discovered that the corrosion resistance was somewhat insufficient, and it was discovered that an extremely good magnetic recording medium could be obtained by providing a chromium layer as a protective layer followed by a silicon-silicon oxide layer. It is something that

Furthermore, when a ferromagnetic metal thin film is formed on a flexible support by vapor deposition, sputtering, ion plating, etc., or when a ferromagnetic metal thin film is formed using certain plating baths and plating conditions, Due to the internal stress of the metal 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.

Providing a protective layer of chromium does not solve the above-mentioned problems, and often makes them worse; however, forming a protective layer of silicon-silicon oxide damages the flexibility of the flexible support. In the case of a solid support, the curl is removed* and the contact condition with the magnetic head is improved, and in the case of a solid support, the internal stress of the silicon-silicon oxide protective film and the internal stress of the ferromagnetic metal thin film are reduced. Due to the balance, adhesion is extremely good.

In the present invention, the chromium layer is preferably formed by vapor deposition, ion plating, sputtering, etc., and the conditions in the present invention for forming the chromium layer by each method are preferably within the ranges shown in Table 1 below.

In the above method, the chromium layer is provided on the ferromagnetic metal thin film, but in order to increase the hardness, Ti, V, Zr, Mo, Rh,
Other metals such as W may be included in the chromium layer up to 220 wt.%.

In the present invention, the protective layer made of silicon-silicon oxide provided on the chromium layer has a thickness of 10-3 to 5X 10
Preferably, silicon is obtained by heating silicon to its melting point in an oxidizing gas atmosphere in air at a pressure of 1000 Torr, vaporizing it, and precipitating it.

The precipitation rate was 500 kyu/sec. The following is good. 1 0-3
At a vacuum pressure of ~5X 10" 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.

The silicon-silicon oxide layer of the present invention is considered to have a composition of Si--SiOx (1≦X<2).

The thickness of the chromium layer and silicon-silicon oxide layer provided as a protective layer must be determined based on conditions such as ensuring sufficient protection and ensuring that the output does not decrease due to spacing loss due to the gap between the magnetic recording layer surface and the magnetic head. about 0.005 to 0.3 μm, preferably 0.01 to 0
．． The thickness is preferably in the range of 2 μm, and the ratio of the thickness of the chromium layer and the silicon-silicon oxide layer is preferably in the range of 1/5 to 5/1.

The ferromagnetic metal layer according to the present invention includes iron, cobalt, nickel and other ferromagnetic metals, or FeCo, Fe-
Ni, Co-Ni, Fe-Si1Fe-R
h, Fe-V, Co-P, Co-B, Co-Si, Co
-V, Co-Y, Co-La, Co-Ce, CoPr,
Co-Sm, Co-Mn, Fe-Co-Ni1Co -
Ni-P, Co-Ni-B, Co-Ni
Ag, Co-Ni-Nd, Co-Ni-
C e 1CoNi-Zn, Co-Ni-Cu, Co-
Ni-Hg, Co-Ni-W, Co-Ni-
Re, Co-Mn-P, Co-Zn-P, Co
-Pb-P, Co-SmCu, Co-Ni-Zn-P,
A ferromagnetic alloy such as Co-Ni-Mn-P is formed into a thin film by a paper deposition method or a plating method.

Paper deposition method is a method in which the substance or compound to be deposited is deposited on a substrate as vapor or ionized vapor in a gas or vacuum space, and includes vacuum evaporation, sputtering, ion plating, and chemical vapor plating. (Chemical Vap
This method corresponds to the method such as ``or Deposition'' 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.

Regarding the formation method using the paper deposition method, for example, see "VacuumDep" by L. Holland.
position of Thin Films (Ch
aman & Hall Ltd, 1956)
:L. I. Maissel &R. Co-edited by Glang” Handbook of Thin Film T
technology” (McGraw-Hill C.
o. , 1970): US Patent 2671034
No. 3329601; No. 3342632゛33
No. 42633; No. 3516860: No. 3615911
No. 3625849゜No. 3700500; 37
No. 72174; No. 3775179; No. 3787237
No. 3856579 and other specifications.

Furthermore, regarding the shape by plating method, for example, W. G
“Metal licCoating” written by oldie
of plastics” (Electro-
Chem i cal publications
Ltd. , 1968); US Pat. No. 3,116,159; US Pat. No. 3,138,479; US Pat. No. 3,219,471; US Pat.
No. 7635; No. 3238061; No. 3267017; No. 3353986; No. 3360397; No. 336
No. 2893゛No. 3416932; No. 3446657; No. 3549417; No. 3578571: No. 363
It is described in specifications such as No. 7471; No. 3672968.

The thickness of the non-magnetic support is approximately 4 to 50 mm in the case of a flexible support.
The thickness of the ferromagnetic metal layer is approximately 0.02 to 5 μm, preferably 0.05 to 2 μm.

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. It will be done.

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

Ferromagnetic metal thin films formed by methods such as plating or vapor deposition may become unstable due to friction with the magnetic head, may become scratched, or debris may adhere to or 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.

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

Example 1 A 1/2 inch wide, 25 μm thick tape-shaped polyethylene terephthalate film (L/L/
Mylar film, E. I, du Pont de
Nemours & Co. Co-P (Co: 9) using the following plating solution and plating conditions:
8%, P: 2%) A magnetic film was electrolessly plated to a thickness of 0.20 μm.

US Shipl is used as an activation pretreatment solution for electroless plating.
ey company (2300 Washington S
t. , Newton, Massachusetts
ts) Catalyst 6 F solution and Acce
lerator 19 solution was used.

Kobal chloride I-9.51'/
l (CoC12・6H20) Sodium hypophosphite 5.3P/l (Na
H2PO2・H20) Ammonium chloride 1o. 7'i? /1 citric acid 2 6. 5? /1 boric acid 3 0.9? /lpH
7.3, Liquid temperature: 80℃ Next, the tape is placed in a vacuum chamber at 10-5 Torr.
After forming a 0.02 μm chromium layer in a vacuum of 8×1
The silicon was evaporated in air at a pressure of 0'Torr to form a 0.05 μm silicon-silicon oxide layer.

The magnetic tape thus obtained (referred to as sample A) was unified.■
Model VTR (manufactured by SONY Corp., AV-8700)
When I turned it on (type), the running was smooth and stable output was obtained.

Furthermore, the same point on the magnetic tape was brought into sliding contact with a magnetic head, and the time until scratches appeared on the magnetic layer was measured.
It looked like a table.

For comparison, we used a magnetic tape (sample B) on which no protective layer was formed, and as a protective layer, chromium was evaporated in a vacuum of 10-5 Torr to form only a 0.07μ chromium film on the magnetic plating layer. A magnetic tape (sample C) was also measured at the same time.

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

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

The sample thus produced (Sample D) was curled so that the magnetic thin film side was concave, and had poor running properties when exposed to a unified ■-type VTR (see Example 1), and the portions corresponding to the edges of the video track The magnetic thin film has peeled off.

Furthermore, when a chromium layer with a thickness of 0.03 μm was formed as a protective layer in a vacuum of 5.0×10−6 Torr, the curling became even larger.

After forming the ferromagnetic metal thin film with the chromium layer as described above, air was introduced into the vacuum chamber through a needle bump at 2×10
The sample (Sample E), which was placed until the temperature reached 1000 Torr and a protective layer of silicon-silicon oxide was formed to a thickness of 0.07 μm in the same manner as in Example 1, showed no curl at all and ran on the VTR described above. The properties were also good.

When the same location was brought into sliding contact with a magnetic head, no scratches were observed even after 450 seconds or more had elapsed.

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

Furthermore, we investigated the corrosion resistance of Samples D and E, and Sample F as a comparative example, in which only a silicon-silicon oxide layer with a thickness of 0.1μ was provided as a protective layer, and the results were shown in Figure 1. .

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

As is clear from this, a protective layer of chromium and silicon-silicon oxide was provided according to the present invention (sample E).
) was found to have improved corrosion resistance.

Moreover, it was also confirmed 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 30? /73(N
iSO4・7H20) Nickel chloride 5 g/l (Ni
Cl2・6H20) Cobalt sulfate 30'ff/l
(CoSO4・7H20) Cobalt chloride (CoCl2・6H20) Copper sulfate (CuSO4 5 H20) Formalin borate 1,5-naphthalene di-sulfo/sodium acid pH: 5.0, A/di Liquid temperature: 40℃, 5 ′? /l 0.25g/l 7.5g/l O. I CC/l! 0.25! ii'/. e Current density; 0.6 Co-Ni-Cu (Co6 7%, Ni32
%, Cu 1%) was formed to a thickness of 0.3 μm.

Next, in the same manner as in Example 1, a chromium layer of 0.04
A silicon oxide layer having a thickness of 0.06 μm was formed so that the entire protective layer had a thickness of 0.1 μm.

When we examined the adhesion using a peel test using cellophane tape, we found that the product with a protective layer of chromium and silicon-silicon oxide (sample G) had extremely good adhesion, but the product with no protective layer (sample H) ) had poor adhesion.

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

For comparison, measurements were also taken on a sample (sample I) in which a 0.1 μm chromium film was formed on the magnetic plating by evaporating chromium in a vacuum of 10 −5 Torr as a protective layer.

When the tungsten carbide ball was brought into contact with the sample and the number of passes until the sample was scratched was investigated, the results were as shown in Table 3 below.

As is clear from this, it was found that the wear resistance of the sample provided with the protective layer of chromium and silicon-silicon oxide of the present invention (Sample G) was improved.

Example 4 25 μm thick polyimide base (Kapton film, E, I. du Pont de Nemour)
Co-Si (Co 9
0%, Silo%) magnetic film was formed to a film thickness of about 0.15μ by ion plating method.

Ion plating is performed at argon gas pressure of 0. OITor
The experiment was carried out at an accelerating voltage of 2 KV and a substrate temperature of 80°C.

Next, after evacuating the vacuum chamber to 10-7 Torr, a chromium layer of 0.02 μm was deposited, and air was further introduced through a 21 dollar valve to achieve a pressure of 8×10” Torr, and silicon-silicon oxide was formed in the same manner as in Example 1. protective layer of 0
．． The sample was shaped to have a thickness of 0.3 μm (Sample J).

In the case where a protective layer was not formed (sample K), curling occurred so that the metal thin film side had a concave surface, but when the protective layer was formed, the curling disappeared.

Samples J and K were brought into sliding contact with a magnetic head and the time taken until scratches appeared on the magnetic layer was measured, and the results were as shown in Table 4 below.

As described above, it has been found that the magnetic recording medium provided with the protective layer of chromium and silicon-silicon oxide of the present invention has excellent wear resistance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the corrosion resistance effect 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, a chromium layer is provided as a protective layer on the ferromagnetic metal thin film, and a silicon-silicon oxide layer is provided on the chromium layer. Features of magnetic recording media. 2% In claim 1, the silicon-silicon oxide layer is evaporated in an oxidizing gas atmosphere corresponding to the acid partial pressure that the silicon-silicon oxide layer occupies in air at a pressure of 10-3 to 5 x 10-5 Torr. A magnetic recording medium characterized by having a protective layer formed by. 3. The magnetic recording medium according to claim 1, wherein the chromium layer is a protective layer formed by vapor deposition, ion plating, or sputtering. 4. A magnetic recording medium according to claims 1, 2, and 3, characterized in that the total thickness of the protective layer consisting of the chromium layer and the silicon-silicon oxide layer is in the range of about 0.005 to 0.3 μm. . 5. A magnetic recording medium according to claim 4, characterized in that the thickness ratio of the chromium layer and the silicon-silicon oxide layer is in the range of 1/5 to 5/1. 6 In claim 1, the ferromagnetic metal thin film layer is about 0
．． 1. A magnetic recording medium comprising a ferromagnetic metal layer having a thickness of 0.02 to 5 μm and formed by a paper deposition method or a plating method. 7. A magnetic recording medium according to claims 1 and 6, characterized in that a ferromagnetic metal thin film layer is provided on a nonmagnetic support.