JPS6032119A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which prevents effectively seizure of a magnetic layer to a magnetic head while maintaining the physical characteristic of the magnetic layer by compounding specific unsatd. sulfide with the magnetic layer consisting of ferromagnetic metallic powder dispersed in a binder. CONSTITUTION:The unsatd. sulfide expressed by the formula (x is 1 or 2, n is 1-10) is incorporated in a 0.5-10pts.wt. range into 100pts.wt. ferromagnetic metallic powder to form a magnetic layer. The magnetic coating contg. ferromagnetic metallic powder of, for example, Fe-Ni-Co alloy or the like having preferably 0.1-0.5mu average grain size and >=5 ratio between long diameter and short diameter, a binder contg. a vinyl chloride/vinyl acetate/vinyl alcohol copolymer and urethane elastomer, a necessary polishing agent, etc. and the above- mentioned unsatd. polysulfide is applied on a nonmagnetic base to form the magnetic layer. Sulfide is generated on the surface of the magnetic powder by which the seizure of the magnetic layer to a magnetic head is prevented and the magnetic recording medium having an excellent still characteristic, durability, etc. is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of a so-called coated metal tape that uses ferromagnetic metal powder as a magnetic material, and particularly relates to the improvement of a so-called coated metal tape that uses a ferromagnetic metal powder as a magnetic material, and particularly relates to a coated metal tape that improves the physical properties of the magnetic layer, especially the sliding properties. This invention relates to a type of magnetic recording medium.

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-Fe20g 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. 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. Not yet. That is, if a large amount of an inorganic material such as Cr2O5 or Al2O8 having 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 that has the following characteristics.

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. Ta. The magnetic recording medium of the present invention is based on such knowledge, and more specifically, on a non-magnetic support,
In a magnetic recording medium in which a magnetic layer is formed by dispersing ferromagnetic metal powder in a binder, the magnetic layer is expressed by the general formula, (where X is 1 or 2, and n is an integer from 1 to 10). It is characterized by containing an unsaturated sulfide.

The above-mentioned unsaturated sulfide itself has traditionally been added to machine oils such as gear oil, cutting oil, and engine oil as an extreme pressure agent to strengthen the oil film strength. It was discovered for the first time by the present inventors that it exerts an excellent effect when added to the liquid. The reason why the desired effect is obtained by blending the unsaturated sulfide is not necessarily clear, but the number of unsaturated sulfides in the unsaturated sulfide forms a sulfide layer on the surface of the magnetic metal powder, which acts as a kind of protective layer. It is estimated that this contributes to preventing the magnetic layer from sticking to the magnetic head and improving wear resistance.

The above-mentioned unsaturated 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 "1 part" indicating the composition are based on weight unless otherwise specified.

The structure of the magnetic recording medium of the present invention is no different from that of a conventional metal powder coated magnetic recording medium, except for the use of the above-mentioned unsaturated sulfide. i.e. 1
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 warps made of relatively heat-resistant plastic such as polyethylene terephthalate, polycarbonate, polyacetate, polyamide, polyimide, etc. is preferably used. , non-magnetic metal foil, etc. can be used as 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, the above-mentioned unsaturated sulfide, and a binder.

The ferromagnetic metal powder is generally a ferromagnetic alloy mainly composed of Fe, C'o, Ni, etc., with an average particle size of 0.1 to 0.
5 ends or less, preferably with a major axis/minor axis ratio of 5
Acicular particles having the above properties are preferably used. As the binder, preferably used are thermoplastic resins, thermosetting resins, or mixtures thereof, which have excellent film-forming properties in themselves and can uniformly disperse the ferromagnetic metal powder mentioned above, such as vinyl chloride-acetic acid. One or a mixture of two or more of vinyl copolymers or partially saponified products thereof, vinyl chloride-vinyl acetate-maleic acid copolymers, nitrocellulose, polyurethane elastomers, polyester resins, 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 unsaturated sulfide used in the present invention has the formula (1)
and in the same formula, X is 1 or 2, and n is 1-10
It is expressed as an integer.

These unsaturated sulfides are preferably contained in the magnetic layer in an amount of 0.5 to 10 parts per 100 parts of ferromagnetic metal powder. 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 unsaturated sulfide, a normal lubricant such as higher fatty acid or its ester can also be used, but in this case as well, the amount of lubricant added must be such that the total amount with the above-mentioned unsaturated sulfide is JIF prefers not to exceed 10 copies out of 100 copies. In addition to this, the magnetic layer also contains Al2O.

If necessary, auxiliary agents such as abrasives such as or Cr201, surfactants, or dispersants may be added in commonly used amounts.

The magnetic recording medium of the present invention is generally obtained by adding, if necessary, a known lubricant, dispersion IP1, abrasive, etc. to the unsaturated sulfide, binder, and magnetic powder described above, and dispersing and kneading them together with a solvent. A magnetic 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.
After the orientation treatment and drying, a curing reaction is further performed as necessary to form a magnetic layer having a thickness of about 1-1 ol L.

As described above, according to the present invention, in a so-called metal powder coated magnetic recording medium, by blending an unsaturated sulfide having a specific structure with ferromagnetic metal powder in the magnetic layer, sliding against the magnetic head is improved. The characteristics, especially the problem of seizure in alloy magnetic heads, are improved and durability is 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.

Point "11" Ferromagnetic metal powder (Fe-1-〇〇 alloy, 100 major diameter 9.25 gm, axial ratio 8, Hc 14500e) Vinyl chloride-vinyl acetate-, vinyl 15 parts Alcohol copolymer (polymerization molar ratio 91 /3/ill) Polyurethane elastomer 10 parts α-AIzOs (abrasive 1 particle size 0.4 l) 5 parts Lecithin (dispersant) 1 part Methyl ethyl ketone 120 parts Toluene, 120 parts Unsaturated sulfide 1 part (formula (1) ) corresponding to x = 2, n = 2) A mixture of the above composition was mixed and dispersed with a sand grinder, and 5 parts of a polyisocyanate crosslinking agent represented by the following formula was added,
After thorough stirring, a magnetic paint was obtained. The magnetic paint thus obtained was applied onto a polyester film with a thickness of IOpm, and after going through 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 about 3#Lm. Formed. After being left at 50°C for 24 hours, it was cut into a predetermined width to obtain a magnetic tape.

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

1 turtle 1'' In Example 1, as the unsaturated sulfide, X=2, n
A magnetic tape was obtained in the same manner except that one corresponding to 4 was used.

10 In Example 1, as the unsaturated sulfide, X==1,
A magnetic tape was obtained in the same manner except that one corresponding to n=8 was used.

1 part of butyl stearate was 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 unsaturated sulfide.

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

Regarding the various magnetic tapes obtained in this way, low-temperature still characteristics at 0°C and high-temperature running (40°C, 80% R
The seizing state of the Sendust head and the rate of increase in the coefficient of dynamic friction of the tape after the test was investigated. The results are summarized in the table below.

In the table above, the methyl characteristic indicates the time (minutes) until a still image deteriorates significantly, and is the most severe durability test for magnetic tape because a magnetic head repeatedly slides over the same location on the magnetic tape. becomes. On the other hand, burn-in of the head was observed using an optical microscope.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer formed by dispersing ferromagnetic metal powder in a non-magnetic medium is formed on a non-magnetic support, the magnetic layer has a general formula (where X is 1 or 2.n
is an integer from 1 to 10).