JPS6032114A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which maintains satisfactorily the physical characteristic of a magnetic layer and prevents effectively seizure to a magnetic head by compounding a specific epithio fatty acid ester together with ferromagnetic metallic powder with the magnetic layer. CONSTITUTION:A magnetic coating contg. a binder resin and if necessary an additive such as a dispersant or the like for magnetic powder is prepd. by compounding 0.5-10pts.wt. the compd. expressed by the formula (x, y are 1-20) having preferably x+y in a 2-30 range with 100pts.wt. ferromagnetic metallic powder is prepd. The above-described epithio compd. itself has lubricity and improves additionally wear resistance when used in combination with a known lubricant. The total amt. of the lubricant and said compd. is made <=10pts.wt. with respect to 100pts.wt. magnetic powder. Such coating is applied on a nonmagnetic base and a protective layer consisting of a sulfide layer is formed on the surface of the magnetic powder by S in the epithio compd., by which the seizure of the magnetic layer to a magnetic head, particularly a magnetic head using a magnetic alloy is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses ferromagnetic metal powder as the magnetic material. The present invention is devoted to improving so-called coating-type metal tapes, and in particular relates to a metal tape type magnetic recording medium in which the physical properties of the magnetic layer, especially the sliding properties, are improved.

BACKGROUND ART Conventionally, coated magnetic recording media or tapes, which are formed by coating magnetic powder dispersed in a binder on a non-magnetic support such as a polyester film, have been widely used. Generally, oxide magnetic powder such as γ-Fe2O3 is used as magnetic powder, but in recent years, ferromagnetic metal powder has been used instead of oxide magnetic powder, mainly for the purpose of improving recording density. It became so. but,
This ferromagnetic metal powder has high saturation magnetization (Bs) and coercive force (He), and has excellent magnetic properties. However, when using the conventional γ-Fe208 magnetic powder, is causing another problem that was not seen.

In other words, since ferromagnetic metal powder has a large coercive force, in order to record on a metal powder-coated magnetic recording medium coated with ferromagnetic metal powder, a magnetic head made of a soft magnetic material with a high saturation magnetic flux density is used. There is a need. Examples of such magnetic head materials include alloy-based magnetic materials such as sendust, but when recording and reproducing a metal powder-coated recording medium using such an alloy magnetic head, the head core slides. Burn-in development may occur on the surface. Although the mechanism of this burn-in is not necessarily clear, once it occurs, it causes a one-gap loss (spacing self-loss), which causes a particularly large loss in high-density recording with a short recording wavelength.

In order to prevent the magnetic layer from sticking to the sliding surface of the head core as described above, it has been proposed to add abrasives or lubricants to the magnetic layer, but this has not always yielded satisfactory results. In other words, if a large amount of an inorganic material such as Cr2O or Al2O3, which has a high Mohs hardness, is added to the magnetic layer as an abrasive, seizure can be eliminated by its effect. However, in this case, even if seizure can be prevented, the reduction in surface smoothness of the magnetic layer due to the addition of these abrasive powders cannot be ignored as a cause of gap loss in high-density recording, and the head However, adding lubricants such as higher fatty acids or their esters, modified silicones, and paraffin wax is somewhat effective in preventing seizure, but these lubrication agents The agent has a relatively low molecular weight and has a large effect of plasticizing the magnetic layer coating, and if it is added in an amount sufficient to exhibit a sufficient anti-seizure effect, problems will arise in terms of the durability of the magnetic layer.

In view of the above-mentioned circumstances, the main object of the present invention is to effectively prevent the magnetic layer from sticking to the magnetic head in a metal powder-coated magnetic recording medium while maintaining good physical properties of the magnetic layer. The object of the present invention is to provide a magnetic recording medium with +L.

According to the research conducted by the present inventors, it has been found that adding an organic sulfur compound having a specific structure to a magnetic layer containing ferromagnetic metal powder is extremely effective in achieving the above objective. The magnetic recording medium of the present invention is based on such findings, and more specifically, the magnetic recording medium of the present invention is based on the above findings.
In a magnetic recording medium in which a magnetic layer is formed by dispersing ferromagnetic metal powder in a binder, the magnetic recording layer is
It is characterized by containing an epithio compound represented by the general formula: (where X-ly represents an integer of 1 or more and less than 20).

The above-mentioned epithio compound itself has traditionally been added as an extreme pressure agent to machine oils such as gear oil, cutting oil, and engine oil to strengthen the oil film strength. It was discovered for the first time by the present inventors that it exhibits excellent effects when added to. The reason why the desired effect can be obtained by blending the epithio compound described above is not necessarily clear, but the sulfur in the epithio compound forms a sulfide layer on the surface of the magnetic metal powder, and this acts as a kind of protective layer. It is presumed that this contributes to preventing the magnetic layer from sticking to the magnetic head and improving wear resistance. This process is similar to that described above, and has the function of a lubricant by itself, but when used in combination with a known lubricant, it is possible to provide a magnetic layer with further improved wear resistance.

The present invention will be explained in more detail below. In the following description, "r%" and "part J" representing the composition are based on weight unless otherwise specified.

The structure of the magnetic recording medium of the present invention is not particularly different from that of conventional metal powder coated magnetic recording media, except for the use of the above-mentioned epithio compound.
The magnetic recording medium of the present invention is basically formed by forming a magnetic layer containing ferromagnetic metal powder on a non-magnetic support.

As the non-magnetic support, a film with a thickness of about 3 to 20 g made of a relatively heat-resistant plastic such as polyethylene terephthalate, polycarbonate, polyacetate-1, polyamide, polyimide, etc. is usually preferably used. Paper, non-magnetic metal foil, etc. can also be used as needed.1. Essentially any non-magnetic solid material that provides the desired magnetic layer formation surface can be used.

The magnetic layer is formed by coating on the non-magnetic support as described above, after performing adhesion strengthening treatment such as corona treatment and primer treatment, if necessary. It can also be formed by transferring a magnetic layer formed on a support to a non-magnetic support as described above.

The magnetic layer of the magnetic recording medium of the present invention basically consists of ferromagnetic metal powder, the above-mentioned epithio compound, and a binder.

The ferromagnetic metal powder is generally a ferromagnetic alloy mainly composed of Fe, Co, Ni, etc., with an average particle size of 0.1 to 0.5.
Acicular particles having a long diameter/breadth diameter ratio of 5 or more are preferably used. As the binder, a thermoplastic resin which itself has excellent film-forming properties and can uniformly disperse the above-mentioned ferromagnetic metal powder,
Thermosetting resins or mixtures thereof are preferably used, such as vinyl chloride-vinyl acetate copolymers or partially saponified products thereof, vinyl chloride-vinyl acetate-maleic acid copolymers, nitrocellulose, polyurethane elastomers, polyester resins, One type or a mixture of two or more of epoxy resins, acrylic resins, etc. can be used. These binders are used in an amount of 10 to 40 parts per 100 parts of the above-mentioned ferromagnetic metal powder as solid content.

The epithio compound used in the present invention is represented by the above formula (1), in which x and y are each represented by an integer of 1 or more and less than 20, especially when x+y is 2
Those in the range of 30 to 30 are particularly preferably used. These epithio compounds are contained in a magnetic layer containing 10 ferromagnetic metal powders.
It is preferable to include it in the range of 0.5 to 10 parts per 0 parts.If it is less than 0.5 parts, the addition effect will be poor, and if it is added in excess of 10 parts, the plasticizing effect will increase, and the durability of the magnetic layer will deteriorate. Sexuality decreases.

In addition to the above-mentioned epithio compound, a normal lubricant such as a higher fatty acid or its ester can also be used, but in this case as well, the lubricant should be added so that the total amount with the above-mentioned epithio compound is 100 parts of the magnetic metal. In addition to this, the magnetic layer preferably does not exceed 10 parts of A.
l2O, or Cr20. Auxiliary agents such as abrasives such as surfactants, surfactants, and dispersants may be added as necessary in commonly used amounts.

The magnetic recording medium of the present invention is generally prepared by adding a known lubricant, a dispersant, an abrasive, etc. to the epithio compound, binder, and magnetic powder as described above, and dispersing and kneading them together with a solvent. The ink is applied by a conventional method onto a non-magnetic support such as a polyester film which has been subjected to adhesion strengthening treatment such as corona discharge treatment as necessary, and after orientation treatment and drying, a curing reaction is further performed as necessary, This can be obtained by forming a magnetic layer with a thickness of about 1-10 #L.

As described above, according to the present invention, in a so-called metal powder coated magnetic recording medium, a magnetic layer contains an epithio compound (epithio fatty acid ester) having a specific structure together with ferromagnetic metal powder, especially for alloy magnetic heads. This improves the problem of seizure and maintains good durability. Therefore, by using the magnetic recording medium of the present invention, gap loss can be kept low even in high-density recording with a short recording wavelength.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Ferromagnetic metal powder 100 parts Vinyl chloride-vinyl acetate-vinyl 15 parts Alcohol copolymer polyurethane elastomer 10 parts α-At20. (Abrasive material) 5 parts Lecithin (Dispersant) 1 part Methyl ethyl ketone 120 parts Toluene 120 parts Epithio compound 1 part (corresponding to x=14°Y=2 in the above formula (1)) A mixture of the above composition was put into a sand grinder. Mixing and dispersion was performed. 5 parts by weight of the next polyisocyanate crosslinking agent was added and sufficiently stirred to obtain a magnetic paint. The magnetic paint thus obtained was applied onto a polyester film with a thickness of 10 μm, and after undergoing an orientation treatment and a drying process, a calendar treatment was performed.
The surface was smoothed to form a magnetic layer with a thickness of about 3 JLm. After being left at 50° C. for 24 hours, it was cut into a predetermined width to obtain a magnetic tape.

Support 11'' A magnetic tape was obtained in the same manner as in Example 1 except that the amount of the epithio compound added was changed to 5 parts.

1 In Example 1, as an epithio compound, X=12,
A magnetic tape was obtained in the same manner except that one corresponding to y=5 was used.

One part of butyl stearate was further added as a lubricant to the composition of Example 1, and a magnetic tape was obtained in the same manner.

A magnetic tape was obtained in the same manner as in Example 1 without adding the epithio compound.

A magnetic tape was obtained using the same amount of butyl stearate in place of the epithio compound in Example 1.

Regarding various magnetic tapes obtained in this way, low-temperature still characteristics at 0°C and high-temperature running (4o'c, 80'c)
The seizing state of the Sendust head and the increase rate of the coefficient of dynamic friction of the tape after %RH1100paSS) were investigated. The results are summarized in the table above. Still characteristics indicate the time (minutes) at which a still image deteriorates significantly;
This is the most severe durability test for magnetic tape because the magnetic head repeatedly slides over the same location on the magnetic tape. - Burning of the labor head was observed using an optical microscope.

Looking at the results in the table above, it can be seen that by adding a specified epithio compound to the magnetic coating film according to the wood-based method, it is possible to prevent head seizure and obtain a magnetic recording medium with excellent durability. I can understand.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer formed by dispersing 1 ferromagnetic metal powder in a binder is formed on a non-magnetic support, the magnetic layer has a general formula (where x and y are integers of 1 or more and less than 20). 1. A magnetic recording medium comprising an epithio compound represented by .