JPH0528462A - Magnetic recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a magnetic recording medium exhibiting excellent running property, abrasion resistance and durability under various use conditions. A thin-film magnetic recording medium having a magnetic layer on a non-magnetic support is characterized in that a lubricant containing phosphoric acid is applied to the surface of the magnetic layer for use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic disk, and in particular, it is characterized in that phosphoric acid is added to a lubricant on the surface of a magnetic layer and applied. It is about.

[0002]

2. Description of the Related Art For example, in a so-called metal thin film type magnetic recording medium in which a ferromagnetic metal material is deposited on a non-magnetic support by a technique such as vapor deposition and the magnetic layer is used as a magnetic layer, the surface of the magnetic layer is not smooth. Since it is extremely good, the substantial contact area with sliding members such as magnetic heads and guide rollers is large, and therefore the coefficient of friction is large, and the adhesion phenomenon (so-called sticking) is likely to occur and running and durability are improved. There are many problems such as chipping.

Therefore, use of various kinds of lubricants has been studied in order to improve these problems, and a higher fatty acid or its ester has been conventionally top-coated on the magnetic layer of the magnetic recording medium. Attempts have been made to reduce the coefficient of friction. By the way, the lubricant used for the magnetic recording medium is required to have extremely strict characteristics, and it is difficult to cope with the conventional lubricant.

That is, the lubricant used in the magnetic recording medium is (1) excellent in low temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions. (2) Since the spacing with the magnetic head becomes a problem,
Being able to apply a very thin coating and exhibiting sufficient lubrication characteristics even in that case. (3) It must withstand a long time or use for a long time, and the lubricating effect should continue. Etc. are required.

However, conventionally used higher fatty acids and esters thereof are frozen and solidified under low temperature conditions such as 0 ° C. or lower to impair the function as a lubricant, and have long-term durability. Tend to lack.

[0006]

As described above, in the field of magnetic recording media, practical properties such as running property and durability are unsatisfactory due to lack of ability of the lubricant used. .. Therefore, the problem to be solved by the present invention is
An object of the present invention is to provide a magnetic recording medium that has excellent lubricity under various conditions of use, has a long-lasting lubrication effect, and has excellent running properties, abrasion resistance, durability, and the like.

[0007]

As a result of earnestly researching this invention, it is suitable to solve this problem by adding phosphoric acid to the lubricant on the surface of the magnetic layer. They found out that, and completed the present invention. That is, the metal thin film type magnetic recording medium of the present invention is a magnetic recording medium having at least a magnetic layer formed on a non-magnetic support, and phosphoric acid in the lubricant on the surface of the magnetic layer is preferably 10 wt%. It is characterized by applying in addition to the above.

That is, the present invention has good durability even when used under severe conditions such as high temperature and high humidity or low temperature and low humidity by applying to the surface of a metal thin film type magnetic recording medium such as a vapor deposition tape. And the characteristics thereof are not deteriorated. The magnetic recording medium of the present invention is one in which phosphoric acid is added as a lubricant to the surface of the magnetic layer and applied.

The magnetic recording medium to which the present invention is applied is, for example, a so-called metal thin film type magnetic recording medium in which a metal film is formed as a magnetic layer on the surface of a non-magnetic support by a method such as vapor deposition. Applicable. Further, this metal thin film type magnetic recording medium can be applied to a magnetic recording medium having a structure in which an underlayer is interposed between a non-magnetic support and a magnetic layer.

In this case, the applicable nonmagnetic support of the metal thin film type magnetic recording medium and the metal magnetic thin film are not limited, and any conventionally known one can be used. For example, as the non-magnetic support, the same one as the above-mentioned coating type magnetic recording medium can be used. In this case, when a rigid substrate such as an Al alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as an alumite treatment or a Ni-P film is formed on the surface of the substrate to harden the surface. You may do so.

The metal magnetic thin film is formed as a continuous film by a PVD method such as plating, sputtering or vacuum deposition, and is made of a metal such as Fe, Co or Ni or Co-Ni.
Alloys, Co-Pt alloys, Fe-Co-Ni alloys,
Fe-Co based alloy, Fe-Ni based alloy, Fe-Ni-B
Alloys, Fe-Co-B alloys, Fe-Co-Ni-B
Examples include an in-plane magnetization recording metal magnetic film and a Co—Cr alloy thin film made of a system alloy.

Particularly, in the case of in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga, on the non-magnetic support in advance
An underlayer of a low melting point non-magnetic material such as In, Ge, or Ti is formed in advance, and a metal magnetic material is vapor-deposited or sputtered from the vertical direction to diffuse these low melting point non-magnetic material in the metal magnetic thin film, and the orientation May be eliminated to ensure in-plane isotropy and to improve anti-magnetism.

In the case of a hard disk, a hard protective film such as a carbon film, a diamond-like or amorphous carbon film, a chromium oxide film, a zirconium oxide film, and a SiO ₂ film is formed on the surface of the metal magnetic thin film. You may do it. Examples of the method of allowing the lubricant of the present invention to be retained in the magnetic recording medium include a method of top-coating a lubricant layer on the surface of the magnetic film or the surface of the protective film. In this case, the coating amount of the lubricant including phosphoric acid is
Again, it is preferably 0.5-100 mg / m ² , 1-20 mg
/ M ² is more preferable.

Lubricants added to the above phosphoric acid include
It may be used in combination with a conventionally known lubricant such as ester or carboxylic acid of long chain hydrocarbon, amine salt compound of long chain carboxylic acid, long chain alkyl ester of perfluorocarboxylic acid and perfluoropolyether. Also,
In addition to the above-mentioned lubricant, a rust preventive agent may be used in combination, if necessary.

As the rust preventive agent, any rust preventive agent commonly used as a rust preventive agent for this type of magnetic recording medium can be used. For example, phenols, naphthols, quinones,
A heterocyclic compound containing a nitrogen atom, a heterocyclic compound containing an oxygen atom, a heterocyclic compound containing a sulfur atom, and the like. The rust preventive agent may be used in combination with the lubricant containing phosphoric acid of the present invention, but after forming a magnetic layer on a non-magnetic support and applying a rust preventive agent layer thereon, a lubricant layer is formed. Like applying 2
The effect is high when it is applied in layers or more.

By the way, in any of the above-mentioned magnetic recording media, a back coat layer, an underlayer, etc. may be formed, if necessary, in addition to the magnetic coating film and the metallic coating film which are the magnetic layers. For example, the back coat layer is formed by coating a resin binder similar to that of the magnetic coating film with carbon fine powder for imparting conductivity and an inorganic pigment for controlling the surface roughness. In the present invention, the above-mentioned lubricant containing phosphoric acid may be internally added to the back coat layer or may be contained by a top coat. Alternatively, various combinations are possible such as internally adding a lubricant containing phosphoric acid to each of the magnetic coating film, the metal magnetic coating film and the back coat layer, and top coating.

[0017]

[Function] A lubricant containing phosphoric acid exhibits a good lubricating effect to reduce the friction coefficient. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, the magnetic recording medium using the lubricant containing phosphoric acid as the lubricant has improved running properties and improved durability.

[0018]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples. Using the lubricant composition shown in Table 1, magnetic recording media shown below were prepared. An example applied to a metal thin film type magnetic recording medium (vapor deposition tape) will be described.

Example 1 Co was deposited on a polyethylene terephthalate film having a thickness of 14 μm by the oblique evaporation method to form a ferromagnetic metal thin film having a thickness of 200 nm. Then, the lubricant composition 1 shown in Table 1 was applied to the surface of the magnetic thin film by a vacuum vapor deposition method so that the coating amount was 5 mg / m ^2, and cut into a width of 8 mm to prepare a sample tape.

-Examples 2 to 6-In Example 1, the lubricating composition 1 in Table 1 used as the lubricant was changed to a lubricating composition 2-lubricating composition 6, and the others were as in Example 1. Similarly, a sample tape was prepared. For each sample tape prepared as described above, measure the friction coefficient, still durability, and shuttle durability at a temperature of 25 ° C and a humidity of 60%, a temperature of -5 ° C, and a temperature of 40 ° C and a humidity of 80%. went. For still durability, the decay time until the output in the paused state decreased by 3 dB was evaluated. The shuttle durability was evaluated by the number of shuttles until the output decreased by 3 dB after the shuttle traveled for 2 minutes each time.

As a comparative example, a blank tape containing no lubricant and a case using a lubricant alone were also evaluated. The results are shown in Table 2. As is clear from Table 2, the friction coefficient, the still durability, the shuttle durability, etc. are significantly improved by the addition of phosphoric acid as compared with the case where the lubricant is used alone without deterioration under various conditions. Good results have been obtained.

Next, a lubricant was fixed to methyl stearate and the amount of phosphoric acid added was changed to prepare a sample tape in the same manner. The coefficient of friction of each sample tape manufactured as described above was measured at a temperature of 40 ° C. and a humidity of 80%. The result is shown in FIG. As is clear from this result, phosphoric acid has an effect of reducing friction, and it is understood that the friction coefficient becomes the minimum value especially when the addition amount is 10 wt% or more. ..

[0023]

As is clear from the above description, the magnetic recording medium of the present invention possesses a lubricant having phosphoric acid added, which has a very excellent lubricity, and therefore, the lubricity is improved under any use condition. It can be maintained and its lubricity can be maintained for a long time. The effect is particularly remarkable when the added amount is 10 wt% or more. Therefore, the magnetic recording medium of the present invention is excellent in running property, wear resistance and durability.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in friction coefficient with respect to phosphoric acid concentration.

[0024]

[Table 1] Lubricant composition

[0025]

[Table 2] Durability measurement results

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[Procedure amendment]

[Submission date] September 13, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction content]

[0024]

[Table 1] Lubricant composition

Claims (1)

1. A magnetic recording medium comprising at least a magnetic layer on a non-magnetic support, wherein the surface of the magnetic layer is coated with phosphoric acid in a lubricant. And a magnetic recording medium.