JPH02260219A - Metallic thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling durability and still durability by incorporating a lubricant into the narrow pores of a metallic thin-film magnetic layer which has the pore volume as large as 0.07 to 0.20ml per 1 gram metallic thin-film magnetic layer. CONSTITUTION:A lower layer film consisting of metals, such as Sn, Bi, Al, and Be, having the m. p. lower than the m. p. of the metal elements forming the metallic thin-film magnetic layer or the oxide, nitride, etc., thereof is formed by a vacuum film forming method on a nonmagnetic base before the formation of the metallic thin-film magnetic layer thereon and the metallic thin-film magnetic layer is formed on this layer. Since the pore volume in the metallic thin- film magnetic layer is as large as 0.07 to 0.2ml, the adequate lubricant is supplied to the metallic thin-film magnetic layer by holding the lubricant in the pores; in addition, the lubricant is supplied to the surface of the metallic thin- film magnetic layer over a long period of time. The traveling durability and the still characteristics are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium having a metal thin film magnetic layer, and particularly to a magnetic recording medium suitable for use as a videotape with excellent still durability.

[Prior art and its problems] Conventionally, magnetic recording media have been produced by coating a magnetic coating liquid consisting of magnetic powder, binder resin, additives, etc. on a non-magnetic support.
So-called coated magnetic recording media in which a magnetic layer is formed by drying have been used.

On the other hand, the demand for high-density magnetic recording is increasing year by year, and high output can be obtained even in the short recording wavelength region. High-energy magnetic recording media are attracting attention, and the focus of technology is shifting to this type of magnetic recording media.

Development trends in high-energy magnetic recording media include: (1) In the coating-type magnetic recording media, metal magnetic powder with high magnetic energy is used as the magnetic powder;
and the use of so-called metal tapes with improved surface smoothness of the magnetic layer; ■ Use of so-called metal thin-film magnetic recording media such as vapor-deposited tapes whose magnetic layer is a metal thin film that does not use binder resin in the magnetic layer; heading in the direction.

The metal tape of the present invention has the advantage of being able to utilize much of the manufacturing equipment and know-how of conventional coated media. In the density area, there is no limit.

On the other hand, the metal thin film type magnetic recording medium of item ① is 6 mm higher than the metal tape in the high band 8 mm standard.
It is possible to obtain a high output of dB or more, and it can be said to be extremely advantageous in promoting even higher recording densities in the future.

The metal thin film type magnetic recording medium is generally a so-called evaporation tape in which a magnetic layer is formed by vacuum evaporation, in which a CoN io-based metal thin film magnetic layer is provided on a nonmagnetic support. , extremely good magnetic properties can be obtained.

A problem with the metal thin film magnetic layer media is that the still durability is not good.

In order to improve this problem, for example, SiOx, T
Many methods have been proposed for providing a protective layer of an inorganic compound such as iOx or TiNx on a metal thin film magnetic layer. However, in order to have a sufficient effect on still durability, the protective layer must be made considerably thicker, and a decrease in output due to spacing loss is unavoidable.

A method of providing a lubricant layer on the metal thin film magnetic layer has also been proposed. This method is effective in reducing the frictional force between the metal thin film magnetic layer and the magnetic head, and fluorine-based lubricants are particularly effective.

However, as reproduction is continued repeatedly in the still mode, the lubricant comes off from the thin metal film magnetic layer, resulting in a problem that the effect does not last, especially under low humidity.

Furthermore, as disclosed in Japanese Unexamined Patent Publication No. 56-3428, there is a technique in which a lubricant is contained in the gaps between columnar particles constituting a metal thin film magnetic layer.

However, even with this technique, the effect was still insufficient.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems of the prior art, and provides a metal thin film magnetic recording medium that has excellent running durability and still durability. The purpose is to

[Means for Solving the Problems] An object of the present invention is to provide a metal thin film magnetic recording medium having a metal thin film magnetic layer on a non-magnetic support, in which the pore volume in the metal thin film magnetic layer is smaller than the metal thin film magnetic layer. Magnetic F'! This is achieved by a metal thin film type magnetic recording medium characterized by having a lubricant content of 0.07 to 0.20 ml per gram and containing a lubricant in its pores.

In the metal thin film magnetic recording medium of the present invention, the pore volume in the metal thin film magnetic layer is 0.07 to 0.2 ml, which is larger than that of the conventional metal thin film magnetic layer. By holding the metal thin film magnetic layer, an appropriate amount of lubricant is supplied to the metal thin film magnetic layer, and the lubricant is also supplied to the surface of the metal thin film magnetic layer for a long period of time, resulting in excellent running durability and good still characteristics. It has the following characteristics.

The pore volume of the metal thin film magnetic layer of the present invention is the metal thin film magnetic N
The amount is 0.07 to 0.20 ml per gram, preferably 0.09 to 0.20 ml.

If the pore volume becomes too large, the mechanical strength of the metal thin film magnetic layer decreases and the adhesion to the nonmagnetic support becomes poor.

Moreover, if it becomes too small, the supply of lubricant will not last for a long time, and the still durability will not be maintained for a long time.

Various methods can be considered for adjusting the pore volume of the metal thin film magnetic layer of the metal thin film magnetic recording medium of the present invention to 0.07 to 0.20 ml per gram of metal thin film magnetic N.

Among them, the most effective method is to deposit metal N! on a non-magnetic support. Before forming the I magnetic layer, a metal element having a lower melting point than the metal element forming the metal thin film magnetic layer, for example, S n I B
The present inventor has developed a method of forming a lower layer film of a metal such as spAlpBe or its oxide or nitride by a vacuum film forming method such as a vacuum evaporation method, and then forming a metal thin film magnetic layer thereon. etc. were found.

According to this method, the pore volume of the metal thin film magnetic layer of the present invention formed thereon can be controlled by the size of the forming unit of the lower layer film.

For the underlayer film, oxides, nitrides, etc. of metals obtained by reactive vapor deposition are more preferable than metals in terms of adhesion to the nonmagnetic support and corrosion resistance.

It has been found that by changing the film forming conditions such as the thickness of the underlayer and the temperature of the cooling can, the pore volume of the thin metal magnetic layer formed thereon can be controlled.

Another method for adjusting the pore volume of the metal thin film magnetic layer to 0.07 to 0.20 ml per gram of the metal thin film magnetic layer is to expose the metal thin film magnetic layer to a glow discharge of a certain intensity or higher, for example, For a metal thin film magnetic recording medium with a width of 100 mm, there are methods such as exposing it to Ar and 02 glow of 1000 V and 80 mA or more for 10 seconds or more.

The pore volume of the metal thin film magnetic layer of the metal thin film magnetic recording medium of the present invention can be determined by various methods. The most common method is to obtain it from the adsorption/desorption equidistant crosstalk obtained by the nitrogen gas adsorption method.

As the lubricant contained in the metal thin film magnetic layer of the metal thin film magnetic recording medium of the present invention, many conventionally known compounds can be used and there are no particular limitations.

Examples include fatty acids having 12 to 18 carbon atoms such as oleic acid, myristic acid, and stearic acid, metal salts thereof, or esters thereof, and fluorine-substituted compounds of these fatty acids.

The content of the lubricant in the metal thin film magnetic layer is 3 to 30 mg/m, preferably 5 to 15 mg/m.
It is. If the content is too high, a droplet of lubricant will form during running in a VTR, which will cause a decrease in output and unstable running, which is not preferable.

On the other hand, if it is too small, burn-in occurs between the magnetic head and the metal thin film magnetic layer, reducing still durability.

Methods for incorporating a lubricant into a metal thin film magnetic layer include a method in which a lubricant solution is applied and dried on the metal thin film magnetic layer, and a method in which the lubricant is deposited on the metal thin film magnetic layer by a vacuum evaporation method, followed by a puff treatment. There are various methods such as, and there are no particular limitations in the present invention.

The metal thin film magnetic layer of the present invention contains cobal (CO) as a main component, and the Co content is 50 to 10
It is 0% by weight.

For example, pure Co, CoNi, CoCr, CoFe, Co
FeNi, CoNiCr, CoPr, CoNiPr, C
oPt, CoSm, CoTi, CoNlTi, CoCu
, CoNiCu, etc.

In addition to the above metal elements in the metal thin film magnetic layer, 0,
It is also possible to improve the properties of the metal thin film magnetic layer by incorporating light elements such as N and C. In particular, by including oxygen,
The metal thin film magnetic layer can be made tougher and the magnetostatic properties, especially the coercive magnetic force, can be improved.

The thickness of the metal thin film magnetic layer of the present invention is o.

2 to 2 μm, preferably 0.05 to 0.5 μm
It is m. If the film thickness is thinner than this range, sufficient reproduction output cannot be obtained. Further, if the thickness exceeds this range, curling of the magnetic recording medium becomes large and cracks occur in the metal thin film magnetic layer, which is a problem.

Examples of the nonmagnetic support used in the metal thin film magnetic recording medium of the present invention include polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate,
Examples include plastic materials such as polycarbonate and polyethylene naphthalate.

In the present invention, the metal thin film magnetic layer may be formed directly on the nonmagnetic support, or may be formed via an underlayer provided on the nonmagnetic support.

The underlayer further improves the running durability of the metal thin film magnetic recording medium, reduces problems such as head clogging,
It is also effective in controlling the surface shape of the magnetic layer.

The underlayer is an inorganic/organic composite layer formed on the nonmagnetic support.

For example, Al103, S i02 , MgO, T i
02, metal oxides such as ZnO, Fe203, CdO, NiO, carbonates such as CacO3, BacO3, CocO3, metals such as Au, Ag, Fe, Ni, Co, etc.
Applying fine particles of 0.005 to 0.1 μm onto the non-magnetic support with a mixture of a polyester such as polyethylene terephthalate or polybutylene terephthalate and an organic solvent such as dichloroacetic acid, orthochlorophenol, or tetrachlorethane mixture. formed by.

By forming the metal thin film magnetic layer on the underlayer, there are minute protrusions on the surface of the magnetic layer, and their presence can further improve the running durability of the metal thin film magnetic recording medium.

Furthermore, in the metal thin film magnetic recording medium of the present invention,
A back layer may be provided on the surface opposite to the surface on which the metal thin film magnetic layer is provided for the purpose of improving running properties. As this back layer, a coating film obtained by coating and drying a coating liquid in which CaCO3° carbon fine particles and the like are mixed and dispersed together with a binder resin is used.

[Effects of the Invention] By making the pore volume in the metal thin film magnetic layer relatively large at 0.07 to 0.20 ml per gram of the metal thin film magnetic layer and containing a lubricant, excellent running durability is achieved. Moreover, a metal thin film type magnetic recording medium having good still durability can be obtained.

The novel effects of the metal thin film magnetic recording medium of the present invention described above will be explained in more detail with reference to the following Examples and Comparative Examples.

[Example 1] A sample of a metal thin film type magnetic recording medium was prepared using a vacuum evaporation apparatus whose main parts are schematically shown in FIG.

Thickness 10μm5 from the delivery roll 2 in the first vapor deposition chamber 1
A non-magnetic support 3 made of polyethylene terephthalate with a width of 100 mm is pulled out, and the transport roll 4 is pulled out at a transport speed of 20 m/min.
The film was then conveyed along the first cooling can 5 to the second vapor deposition chamber 8 by conveyor rolls 6.7.

The temperature of the surface of the cooling can was set to 50° C. by passing a cold/hot medium into the first cooling can.

The degree of vacuum in the first vapor deposition chamber 1 and the second vapor deposition chamber 8 is 1Xl0 from the exhaust ports 9 and 10 connected to the vacuum pump.
Evacuation was performed until Torr was reached.

Thereafter, 5N12 with a purity of 3N was placed in the raw material crucible 11 provided in the first vapor deposition chamber 1 and heated by a resistance heating method. Oxygen gas is introduced from the gas inlet 14 at a rate of 50 ml/min, and the Sn vapor flow 15 is caused to enter the non-magnetic support on the first cooling can 5 at an incident angle from the opening of the shielding plate 140. Vapor deposition is carried out at an angle of 90 to 50 degrees (angle to the normal line on the cooling drum), and the thickness of the lower layer is 30 degrees.
One film of 5nOx of A was formed.

The non-magnetic support 3 is passed through the transport roll 16 in the second vapor deposition chamber 8 and onto the second cooling can 17 whose surface temperature is 5°C.
Co80Ni20 alloy 1 in raw material crucible 18
9 is heated and evaporated by an electron beam heating method to generate a magnetic vapor flow 22, and at the same time, oxygen gas is introduced at a rate of 800 mlZ from a gas inlet 21 installed between the second cooling can 17 and the adhesion prevention plate 20. Then, the vapor flow 22 was deposited on the non-magnetic support 3 on the second cooling can 17 at an incident angle of 90 to 35 degrees to form a metal thin film magnetic layer having a thickness of 200 OA.

As described above, the non-magnetic support 3 provided with the lower layer film and the metal thin film magnetic layer was wound up on the take-up roll 23.Next, the metal thin film magnetic layer of the non-magnetic support 3 was formed. On the opposite side, a back coat layer, which was a composition in which carbon black and alumina were dispersed in a binder resin made of polyurethane and nitrocellulose, was applied to a thickness of 0.5 μm and dried.

Next, a mixture of oleic acid and perfluorocarboxylic acid in a weight ratio of 1:1 was applied to the surface of the metal thin film magnetic layer.
A solution was applied at a concentration of 0 mg/m2 to obtain a roll of metal thin film type magnetic recording medium.

The original fabric roll was cut into a width of 8 mm to obtain a sample of a metal thin film type magnetic recording medium for an 8 mm video.

The pore volume of the sample of the obtained metal thin film magnetic recording medium was determined by a nitrogen gas adsorption method.

That is, Autosorb-1 manufactured by Quanterchrome Co., Ltd. in the United States was used as a measuring device.

A sample of the 8 mm wide metal thin film magnetic recording medium was placed about 4 m long.
The measurement sample is wound around a glass rod. Helium gas is used as the carrier gas, and the partial pressure (relative pressure) of the nitrogen gas is gradually increased from 0 to 1 as a mixture of nitrogen and helium. was first determined, and then the nitrogen gas partial pressure (relative pressure) was gradually lowered from 1 to 0 to determine the desorption curve.

The total pore volume was determined from the amount of nitrogen adsorbed at a relative pressure of 1, assuming that the pores were filled with liquid nitrogen.

On the other hand, the weight of the metal thin film magnetic layer was determined by dissolving and removing the metal thin film magnetic layer by soaking it in 0.5N hydrochloric acid for 2 hours, and from the difference in weight before and after dissolution and removal.

On the other hand, an 8mm video tape recorder FUJIX-8M6-AF manufactured by Fuji Photo Film Co., Ltd. was modified to
Still characteristics under 5% RH were measured. The time at which the output decreased by 3 dB from the output value at the start of measurement was defined as the still life.

[Example 2] The surface temperature of the cooling can 5 in the first vapor deposition chamber 1 is set to 0.
A sample of a metal thin film type magnetic recording medium was prepared under the same conditions as in Example 1 except that the temperature was changed to .degree.

[Example 3] A sample of a metal thin film magnetic recording medium was prepared under the same conditions as in Example 1 except that the surface temperature of the cooling can 5 in the first vapor deposition chamber 1 was set to -50°C.

[Comparative Example-11 The surface temperature of the cooling can 5 in the first vapor deposition chamber 1 was set to 1
A sample of a metal thin film magnetic recording medium was prepared under the same conditions as in Example 1 except that the temperature was 00°C.

[Comparative Example-2] A sample of a metal thin film magnetic recording medium was prepared under the same conditions as in Example-1 except that no lower layer film was formed.

Table 1 shows the measurement results of the pore volume and still life of the sample of the metal thin film magnetic recording medium obtained as described above.

Table 1 15, 22 ・・・ Anti-adhesion plate ...Steam flow

Claims (1)

[Claims] In a metal thin film magnetic recording medium having a metal thin film magnetic layer on a nonmagnetic support, the pore volume in the metal thin film magnetic layer is 0.07 to 0.2 per gram of the metal thin film magnetic layer.
1. A metal thin film type magnetic recording medium characterized in that the pores are 0 ml and contain a lubricant in its pores.