JPH0312817A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having excellent corrosion resistance and traveling stability by forming a protective layer consisting of a specific compd. onto a magnetic recording layer consisting of the thin film of a ferromagnetic metal. CONSTITUTION:The protective layer consisting of at least one kind of the compds. selected from the group expressed by formulas I to IV is formed on the magnetic recording layer consisting of the thin film of the ferromagnetic metal. In the formula I to IV, R denotes >=10C alkyl group. The alkyl group which creates a lubricating effect is introduced as a substituent in the molecules of the compd. having an extremely high rust inhibitive effect in such a manner and, therefore, the protective layer itself has the function as the lubricating rust inhibitive agent. The thin metallic film type magnetic recording medium having the excellent corrosion resistance and traveling stability is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media. More specifically, the present invention relates to a magnetic recording medium with excellent corrosion resistance and running stability.

[Prior Art] Magnetic recording media that have been widely used in the past are coating-type media in which a magnetic layer is formed by coating a magnetic coating mainly consisting of acicular magnetic powder and a polymeric binder on a non-magnetic substrate. This is a magnetic recording medium.

Currently, there is a trend toward higher density magnetic recording and reproducing devices, and there is a demand for magnetic recording media with excellent short wavelength recording characteristics.

However, there are limits to the improvement of short wavelength recording characteristics in coated magnetic recording media. On the other hand, CO+ CoN
Metal thin film type magnetic recording media are made by forming a ferromagnetic material mainly composed of CO, such as i, CoN1P, or CoCr, on a nonmagnetic substrate by a so-called physical vapor deposition method such as vacuum evaporation, sputtering, or ion blating. Since no non-magnetic binder is mixed in the magnetic layer, a significantly high residual magnetic flux density can be obtained, and the magnetic layer can be formed extremely thin, resulting in high output and excellent short wavelength response. It has the advantage of being This feature allows
Recently, thin film magnetic recording media have become the mainstream of magnetic media.

[Problems to be solved by the invention] Although thin-film magnetic recording media have a high magnetic recording density and excellent short wavelength recording characteristics, Co is relatively easily corroded, and the magnetic layer is exposed. has poor corrosion resistance,
It has the disadvantage of being susceptible to magnetic deterioration, which is a serious problem in practical use.

To solve this problem, for example, thiazole compounds (Japanese Patent Publication No. 58-188
(see Publication No. 333), cuperones (Special Publication No. 1984-194)
138), diamines, polyamines (see Japanese Patent Publication No. 59-3724), etc. have been proposed. All of these are intended to suppress surface corrosion under high humidity, which is the main cause of popular corrosion.

That is, the attempt is made to react these with cobalt ions or cobalt oxides to form an insoluble salt on the surface of the thin film medium.

However, since the reactivity of these materials is not high, insoluble salts are not formed to the extent that the antirust effect is sufficiently exhibited, and therefore, the corrosion resistance does not satisfy a practical level.

In addition to these problems, media provided with a rust preventive layer also have the drawback of poor running stability. If the lubricating layer were to come off due to a heavy load, this layer would be exposed and work to impair running durability, resulting in contamination of the head and a risk of deterioration of output due to poor running.

In fact, in all conventional rust inhibitors, the lubrication effect has been largely ignored in exchange for the anticorrosion effect. Exceptionally, straight-chain fatty acids have both effects only in monomolecular films, but the technology to mass-produce monomolecular films in medium-L has not been established, and conversely, the presence of a small amount of free fatty acids causes ferromagnetism. Accelerates corrosion of thin metal films.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional products, which are easy to corrode in the atmosphere and difficult to obtain running stability, and to provide a metal thin film magnetic recording medium with excellent corrosion resistance and running stability. The goal is to provide the following.

[Means for Solving the Problem] As a means for achieving the above object, the present invention provides a magnetic recording medium in which a ferromagnetic metal thin film magnetic recording layer is formed on a non-magnetic substrate, which has the following general formula ( I), (n), (
III) and (IV), (wherein R has 1 carbon atom
0 or more alkyl groups) is formed on the ferromagnetic metal thin film magnetic recording layer. provide.

A lubricating layer can also be provided on top of the protective layer.

[Function] According to the present invention, a linear alkyl group that produces a lubricating effect is introduced as a substituent into the molecule of a compound having a remarkable rust-preventing effect, so that it itself becomes a lubricating rust-preventing agent (or a rust-preventing lubricant). ).

If this layer-L is further provided with a lubricating layer having a high lubricating effect, even more desirable results can be obtained. Even if the outermost lubricant layer were to peel off, the lubricant and rust preventive agent of the present invention takes over the lubricating function, so there will be no problem with running durability.

In benzotriazole and benzimidazole represented by general formulas (I) and (n), the substituent R is preferably present at any of the 4th to 7th positions of the benzene ring.

5- 6- Furthermore, in the triazole represented by the general formula (I[[),
The substituent R is preferably present at either the 4th or 5th position of the heterocycle. On the other hand, in the imidazole represented by the general formula (IV), the substituent R is preferably present at the 2nd, 4th or 5th position of the heterocycle.

If the chain length of the alkyl substituent in the anticorrosion lubricant used in the present invention is too short, a high lubricating effect cannot be obtained.
0 or more, preferably 12 or more are required. Since this alkyl group having 10 or more carbon atoms does not contain an unsaturated bond in its molecule, it is highly effective in increasing orientation and improving lubricity.

Further, any alkyl group having 10 or more carbon atoms can be suitably used regardless of whether or not it has a branch, but it is more preferably a straight chain without branching in order to improve the lubricity.

As a method for forming the above-mentioned lubricating anticorrosion layer on the magnetic recording layer, all conventional thin film layer forming methods such as gravure coating, spin coating, and vacuum evaporation are preferably used.

Although the thickness of the lubricating and rust-preventing layer itself is not an essential requirement of the present invention,
- For boat fishing, it is preferable that the number of people is within the range of 20 to 300 people. If there are less than 20 people, it will not only be difficult to form a lubricating and rust-preventing layer with a uniform thickness, but also the desired effect will not be obtained sufficiently. On the other hand, when there are more than 300 people, the lubrication and rust prevention effect is saturated.
This is not only uneconomical, but also increases spacing loss, which is unfavorable from the viewpoint of magnetic properties.

The magnetic recording layer formed on the substrate is Co1Fe1Nis
Co-Ni alloy, Co-Cr alloy, Co-P alloy, C
Vacuum deposition of ferromagnetic metals and alloys such as o-N1-P alloy,
It is formed by attaching it to a substrate by means such as ion blasting, sputtering, plating, or the like.

Magnetic recording media include magnetic tapes based on synthetic resin films such as polyester films and polyimide films, and magnetic disks and magnetic drums based on glass plates, aluminum plates, synthetic resin plates, etc., which have a structure that makes sliding contact with the magnetic head. It includes various forms.

[Example] The present invention will be explained in more detail with reference to Examples.

A 10 μm thick polyethylene terephthalate (PET) was used as the non-magnetic substrate, and Co-
A 20 wt% Ni alloy was used. 10”-5 Torr in advance
Oxygen gas is added to a vacuum chamber with a reduced pressure of 0°5J! The Co--Ni alloy was evaporated at a rate of 3000 g/sec while introducing the Co-Ni alloy at a rate of 3000 g/sec to form a CoNi vapor deposited layer with a thickness of 1500 g/sec on the PET.

A lubricating and rust-preventing layer was formed on the thus formed tape-shaped ferromagnetic metal thin film medium 7. Benzotriazole having a dodecyl group at the 5th position of the benzene ring as a substituent was used to form the lubricating and rust-preventing layer. A solution of 5-dodecylbenzotriazole diluted to a concentration of 0.1 wt% in a solvent (isopropyl alcohol) was applied and dried.

After applying a lubricating and rust-preventing layer in the same manner as in Example 1 and drying it, a fluorine-based perfluoroalkyl polyether lubricant (Fomblin Z manufactured by Nippon Montageson Co., Ltd.) was applied.
25) diluted to a concentration of 0.1 wt % (the solvent was Freon) and dried to provide a lubricating layer.

A magnetic recording medium was produced in the same manner as in Example 1, except that 5-dodecyltriazole was used instead of 5-dodecylbenzotriazole used in Example 1.

A fluorine-based lubricant layer was provided on the medium prepared in Example 3 in the same manner as in Example 2.

Comparison 10-A magnetic recording medium was prepared in the same manner as in Example 2 except that 9-0 benzotriazole not substituted with a dodecyl group was applied.

A magnetic recording medium was prepared in the same manner as in Example 4 except that a triazole not substituted with a dodecyl group was applied in Example 3.

In Example 1, a magnetic recording medium was produced by forming only a fluorine-based lubricating layer without providing a lubricating anticorrosion layer on the magnetic film.

The media produced in each of the above pieces were cut into tapes of 8 mm r11, the short tapes were wound into a cassette half, sine waves were recorded on a commercially available 8 mm VTR deck, and played back in still mode to test its durability. The performance (still life) was investigated. Durability was defined as the time until the initial output voltage decreased by 50%.

In addition, samples cut out from each medium (A) = 60 ° C.
1 week in 90% RH atmosphere; (B): 40°C, 75
An exposure test was carried out for 10 hours in an atmosphere of %RH and SO2 lppm to determine the rate of decrease in saturation magnetization. The results are shown in Table 1 below.
The following is a summary.

As is clear from the above results, by coating a substituted benzotriazole or a substituted triazole on a magnetic layer according to the present invention to form a lubricating and rust-preventing layer, a magnetic material with excellent corrosion resistance and at the same time excellent running durability can be obtained. A recording medium is obtained.

10 μm thick polyethylene terephthalate (PET) is used as the non-magnetic substrate, and Co-
A 20 wt% Ni alloy was used. 0°5J of oxygen gas is added to a vacuum chamber whose pressure has been reduced to 1O-5Torr in advance! /min, the Co--Ni alloy was evaporated at a rate of 3,000 SeC to form a CoNi vapor deposited layer with a thickness of 1,500 SeC on the PET.

A lubricating and rust-preventing layer was formed on the thus formed tape-shaped ferromagnetic metal thin film medium. Benzimidazole having a dodecyl group at the 5th position of the benzene ring as a substituent was used to form the lubricating and rust-preventing layer. It was formed by applying a solution of 5-dodecylbenzimidazole diluted to a concentration of 0.1 wt% in a solvent (isopropyl alcohol) and then drying it.

After applying a lubricating and rust-preventing layer in the same manner as in Example 5 and drying it, a fluorine-based perfluoroalkyl polyether lubricant (Fomblin Z manufactured by Nippon Montageson Co., Ltd.) was applied.
A lubricating layer was provided by coating and drying a solution prepared by diluting Q25) to a concentration of 1 wt% (the solvent was Freon).

A magnetic recording medium was produced in the same manner as in Example 5, except that 5-dodecylbenzimidazole used in Example 5 was replaced with 5-dodecyl imidazole.

Ken Ken 1 Example 6: Applying a fluorine-based lubricant layer on the medium prepared in Example 7
It was set up in a similar way.

Hi Ai (eyes)

A magnetic recording medium was produced in the same manner as in Example 6 except that benzimidazole not substituted with a dodecyl group was applied.

A magnetic recording medium was produced in the same manner as in Example 8 except that imidazole not substituted with a dodecyl group was applied.

Lu Keken 1 In Example 5, a magnetic recording medium was produced by forming only a fluorine-based lubricating layer without providing a lubricating anticorrosion layer on the magnetic film.

The media produced in each of the above pieces were cut into 8 mm r11 pieces and made into tape, and the short tape was wound into a skein and a thread h-).
Record the sine wave with a commercially available 8mm VTR device,
It was played back in still mode and its durability (still life) was investigated. Durability is 50% of initial output voltage
This is the time until it goes down.

In addition, samples cut out from each medium (A) were placed at 0°C.
1 week in 90% RH atmosphere; (B): 40°C, 75
A 10-hour exposure test was conducted in an atmosphere of %RH and 802 lppm, and the rate of decrease in saturation magnetization was investigated. The results are shown in Table 2 below.
The following is a summary.

[Effects of the Invention] As explained above, according to the present invention, a linear alkyl group that produces a lubricating effect is introduced as a substituent into the molecule of a compound that has a remarkable rust-preventing effect. Functions as a rust agent (or anti-rust lubricant).

Even more desirable results can be obtained by providing a lubricating layer with a higher lubricating effect on this layer. Even if the outermost lubricant layer were to peel off, the lubricant and rust preventive agent of the present invention takes over the lubricating function, so there will be no problem with running durability.

As is clear from the above results, by coating a substituted benzimidazole or substituted imidazole on a magnetic layer to form a lubricating and rust-preventing layer according to the present invention, a magnetic material with excellent corrosion resistance and excellent running durability can be obtained. A recording medium is obtained.

Claims (3)

[Claims] (1) In a magnetic recording medium formed by forming a ferromagnetic metal thin film magnetic recording layer on a nonmagnetic substrate, the following general formula (I),
(II), (III) and (IV), ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I), ▲Mathematical formulas,
There are chemical formulas, tables, etc. ▼ (II), ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III), ▲ Mathematical formulas,
There are chemical formulas, tables, etc. ▼(IV) (In the formula, R is an alkyl group having 10 or more carbon atoms.) A magnetic recording medium characterized in that it is formed on a metal thin film magnetic recording layer. (2) The magnetic recording medium according to claim 1, wherein R is a linear alkyl group. (3) The magnetic recording medium according to claim 1, further comprising another lubricating layer provided on the protective layer.