JPS6032118A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent effectively seizure of a magnetic layer to a magnetic head while maintaining satisfactorily the physical characteristic of the magnetic layer by compounding specific cyclic sulfide with the magnetic layer consisting of ferromagnetic metallic powder dispersed in a binder. CONSTITUTION:A magnetic coating soln. contg. the cyclic sulfide expressed by the formula in a 0.5-10pts.wt. range in 100pts.wt. ferromagnetic metallic powder is prepd. A lubricant may be added together with the cyclic sulfide to the extent at which the total amt. of the lubricant and the cyclic sulfide does not exceed 10pts.wt. with respect to 100pts.wt. magnetic metallic powder. An additive such as a dispersion assistant for magnetic powder, polishing agent or the like may be added thereto according to need. Then the surface of the ferromagnetic powder is protected by the sulfide consisting of the cyclic sulfide by which seizure of the magnetic layer to a magnetic head is prevented. The magnetic recording medium having a long life is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of so-called coated metal tapes that use ferromagnetic metal powder as the magnetic material, and particularly relates to the improvement of so-called coated metal tapes that use ferromagnetic metal powder as the magnetic material. The present invention relates to powder-coated magnetic recording media.

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-Fe20s 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 large saturation magnetization (Bs) and coercive force (Hc), and has excellent magnetic properties. However, when using the conventional γ-Fe203 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. The mechanism of this seizure is not necessarily clear, but once it occurs, gap loss (spacing)
This causes large losses, especially in high-density recording with short recording wavelengths.

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 Cr2O5 or Al2O3, which has a high Mohs' hardness, is added to the magnetic layer as an abrasive, it is possible to eliminate the seizure. 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 Adding lubricants such as higher fatty acids or their esters, modified silicones, and paraffin wax is also impractical because it increases the amount of wear.While these lubricants have some effect in preventing seizure, these lubricants has a relatively low molecular weight and has a large plasticizing effect on the magnetic layer coating, and if it is added to the extent that it exhibits 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 that has the following characteristics.

According to the research conducted by the inventors, it was 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. Ta. The magnetic recording medium of the present invention is based on such knowledge, and more specifically, on a non-magnetic support,
A magnetic recording medium having a magnetic layer formed by dispersing ferromagnetic metal powder in a binder is characterized in that the magnetic layer includes a ring h1 melphide represented by the following formula (1).

The above-mentioned cyclic sulfide 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 is obtained by blending the cyclic sulfide is not necessarily clear, but the sulfur in the cyclic sulfide forms a sulfide layer on the surface of the magnetic metal powder, which acts as a kind of protective layer and forms a magnetic layer. It is presumed that this contributes to preventing seizure and improving wear resistance of the magnetic head. The above-mentioned cyclic sulfide also functions as a lubricant by itself, but when used in combination with a known lubricant, a magnetic layer with further improved wear resistance can be provided.

The present invention will be explained in more detail below. In the following description, "%" and "part" indicating 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 a conventional metal powder coated magnetic recording medium, except for the use of the above-mentioned cyclic sulfide. That is, the magnetic recording medium of the present invention is basically formed by forming a magnetic layer containing ferromagnetic metal powder on a nonmagnetic support.

As the non-magnetic support, a film with a thickness of about 3 to 20 IL made of relatively heat-resistant plastic such as polyethylene terephthalate, polycarbonate, polyacetate, polyamide, polyimide, etc. is preferably used, but paper, A non-magnetic metal foil or the like may be used if necessary, and basically any non-magnetic solid material that provides a 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, a cyclic sulfide, 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.
Needle-shaped particles having a length of 1.5 mm or less, preferably a length/breadth 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 cyclic sulfide used in the present invention is represented by the above formula (1). This cyclic sulfide is contained in the magnetic layer in an amount of 0.5 to 10 parts per 100 parts of ferromagnetic metal powder.
It is preferable to include within the range of If it is less than 0.5 parts, the effect of addition is poor, and if it is added in excess of 10 parts, the plasticizing effect becomes large and the durability of the magnetic layer decreases.

In addition to the above-mentioned cyclic sulfide, a normal lubricant such as a higher fatty acid or its ester can also be used, but in this case as well, the amount of the lubricant added is such that the total amount with the above-mentioned cyclic sulfide is 100 parts of the magnetic metal. Preferably, the amount does not exceed 10 parts. In addition to this, the magnetic layer also contains A
Auxiliary agents such as abrasives such as l2O and Cr2O3, surfactants, and dispersants may be added as necessary in amounts commonly used.

The magnetic recording medium of the present invention is generally obtained by adding known lubricants, dispersants, abrasives, etc. to the above-described cyclic sulfide, epithio compound, binder, and magnetic powder, and dispersing and kneading them together with a solvent. The magnetic ink that was
It is coated by a conventional method on a non-magnetic support such as a polyester film that has been subjected to adhesion strengthening treatment such as corona discharge treatment as necessary, and after orientation treatment and drying, a further curing reaction is performed as necessary to reduce the thickness. 1-10#1. This can be obtained by forming a magnetic layer of approximately

As described above, according to the present invention, in a so-called metal powder coated magnetic recording medium, by blending a cyclic sulfide having a specific structure with ferromagnetic metal powder in the magnetic layer, the sliding properties against the magnetic head are improved. In particular, the problem of seizure in alloy magnetic heads can be improved, and durability can also be maintained at a good level. 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.

Support m Ferromagnetic metal powder (Fe-old-GO alloy, 100 major diameter 0.251 parts m, axial ratio 8, Hc 14500e) Vinyl chloride-vinyl acetate-vinyl 15 parts Alcohol copolymer (polymerization molar ratio 91/3 /11).

Polyurethane elastomer lO part α-A l 20s (abrasive, particle size Q, 4 ILm
) 5 parts lecithin (dispersant) 1 part methyl ethyl ketone 120 parts toluene 120 parts cyclic sulfide of the above formula (1) 1 part A polyisocyanate crosslinking agent represented by the 0th order obtained by mixing and dispersing the mixture of the above composition with a sand grinder Add 5 parts of
After thorough stirring, a magnetic paint was obtained. The magnetic paint thus obtained was applied onto a polyester film with a thickness of 10 Bm, and after undergoing an orientation treatment and a drying process, a calender treatment was performed to smooth the surface to form a magnetic layer with a thickness of approximately 3 pm. . After being left at 50° C. for 24 hours, it was cut into a predetermined width to obtain a magnetic tape.

Support 1+ A magnetic tape was obtained in the same manner as in Example 1 except that the amount of cyclic sulfide added was changed to 5 parts.

1 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 cyclic sulfide.

A magnetic tape was obtained using the same amount of butyl stearate in place of the cyclic sulfide 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)
%RH, 100 p a s s), the seizing state of the Senges 1 hend and the rate of increase in the coefficient of dynamic friction of the tape were investigated. The results are summarized in the table above. Still characteristics indicate the time (minutes) until a still image deteriorates significantly. Since the magnetic head repeatedly slides over the same part of the magnetic tape, it is used as a durability test for magnetic tape. is the most severe. On the other hand, burn-in of the head was observed using an optical microscope.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a cyclic sulfide represented by a magnetic field, in which a magnetic layer formed by dispersing ferromagnetic metal powder in a binder is formed on a non-magnetic support.