JPS60131627A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a protective layer on the rear surface having sufficient abrasion resistance and improved running stability by forming the protective layer contg. an oranic sulfur compd. on the surface of a magnetic supporting body opposed to the magnetic metallic thin film forming surface. CONSTITUTION:A protective layer is obtained on the rear surface by coating an organic sulfur compd. having specified structure along with a biner. An unsaturated sulfide, a cyclic sulfide, an epithio compd., and a diepithio compd. among others are preferably used as the organic sulfur compd. A thermoplastic or a thermosetting resin which is commonly used for forming a magnetic layer of a coating-type magnetic recording medium such as a vinyl chloride-vinyl acetate or its partially saponified substance, a vinyl chloride-vinyl acetate-maleic acid copolymer, nitrocellulose, a polyurethane elastomer, a polyester resin, an epoxy resin, and an acrylic resin is used for the rear surface protective layer. Nemely, 5-30pts. organic sulfur compd. is added to 10pts. binder consisting of a mixture of one or >=2 kinds among said resins, and coated along with a suitable solvent on the rear surface of a supporting body to obtain the rear surface protective layer. The rear surface protective layer can be formed before or after the surface magnetic layer is forfmed. The thickness of the rear surface protective layer is preferably regulated to 0.5-3mum, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of a so-called vapor-deposited metal tape that uses a ferromagnetic metal thin film as a magnetic material, and particularly to the improvement of a so-called vapor-deposited metal tape that uses a ferromagnetic metal thin film as a magnetic material. The present invention relates to a metal thin film type magnetic recording medium in which running properties are improved by forming a protective layer.

Conventionally, so-called vapor-deposited metal tapes, which are made by forming a thin ferromagnetic metal film by sputtering or the like on a non-magnetic support such as a polyester film or sheet, are made by dispersing ferromagnetic powder in a binder and coating it. Since it does not contain a filler in the magnetic layer, it has superior magnetic properties such as residual magnetic flux density (Br), and has attracted particular attention in recent years.

However, since the magnetic film of this type of vapor-deposited tape is mainly made of a ferromagnetic alloy, it has the problem of being extremely hard mechanically. However, there were drawbacks such as rapid wear of the magnetic head and poor running stability.

Secondly, when forming a magnetic thin film by vapor deposition, the metal particles are deposited along the roughness of the surface of the non-magnetic support, resulting in a smooth surface with little gap loss. Therefore, in order to obtain a magnetic thin film with stable magnetic properties, it is necessary to reduce the surface roughness of the asymmetric support, that is, the base film.

In this way, even if good results are obtained in terms of magnetic properties on the front side of the magnetic layer, the back side of the support has a smooth surface, so when the tape runs, a so-called tape sticking phenomenon occurs. The drawback was a lack of running stability.

In order to eliminate these drawbacks and improve running properties, conventional vapor-deposited tapes coat the back side of the support with a so-called back coat of, for example, Cr2O3, A12O,!
? , - is carried out by applying inorganic abrasive grains such as 5i02 together with a binder, or by applying an organic lubricant such as a higher fatty acid or its ester, a silicone resin, or paraffin wax together with a binder.

However, the method of applying inorganic □ abrasive grains together with a binder not only causes a lot of wear on guide bottles, etc., but also may damage the magnetic thin film when wound in layers. On the other hand, methods using organic lubricants have the advantage of being easier to apply and forming a thin layer than those using inorganic abrasive grains, but they are not sufficiently effective in improving running performance. The problem is that it cannot be obtained. In other words, conventionally used organic lubricants have a relatively low molecular weight and have a large plasticizing effect, so a back layer containing enough lubricants to exhibit sufficient anti-sticking effects has poor wear durability. It becomes insufficient.

For this reason, a sufficient amount of additive could not be added, and therefore only an insufficient effect of improving running performance could be obtained.

An object of the present invention is to provide a metal thin film type magnetic recording medium having a back protective layer that exhibits sufficient wear resistance and running stability improvement effects by adding a specific organic lubricant.

According to research by Nagisa et al., it was found that applying an organic sulfur compound with a specific structure together with a binder to form a backside protective layer is effective for achieving the above-mentioned purpose. .

The magnetic recording medium of the present invention is based on such knowledge, and more specifically, in a magnetic recording medium in which a metal magnetic thin film is formed on a non-magnetic support sheet, the magnetic recording medium is based on the above-mentioned non-magnetic support sheet. A protective layer containing a sulfur compound is formed on the surface opposite to the surface on which the metal magnetic thin film is formed.

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 thin film type magnetic recording medium, except that a protective layer containing the above-mentioned organic sulfur compound is provided on the back surface. That is, the magnetic recording medium of the present invention basically has the following features:
It consists of a ferromagnetic fully refracting thin film formed 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 other non-magnetic metals are also used. Foil or the like may be used if necessary, and basically any sheet-like or film-like solid material having a desired smooth magnetic layer forming surface and back surface can be used.

The magnetic layer is generally formed by depositing Fe, Co, Ni, etc. on the non-magnetic support described above, after performing adhesion strengthening treatment such as corona treatment and primer treatment as necessary. It is obtained by forming a thin film with a thickness of 0.05 to 0.5 mm of a ferromagnetic alloy as the main component.

On the other hand, the protective layer that characterizes the present invention is formed as a coating layer containing an organic sulfur compound on the back surface of the support. The organic sulfur compound is particularly preferably an unsaturated sulfide, a cyclic sulfide, an epithio compound or a jepithio compound, and among them, those represented by the following formula or general formula are preferably used.

e...e fist (1) (X is 1 or 2.' n is 1 to 1O) CH.

1 The back protective layer is generally made of vinyl chloride-vinyl acetate copolymer or a partially saponified product thereof, perforated vinyl-vinyl acetate-maleic acid copolymer, nitrocellulose, polyurethane elastomer, polyester resin, epoxy resin, acrylic resin, etc. Pine Goo 10, which is made of one or a mixture of two or more of thermal nf tffj or thermosetting resins used for forming the magnetic layer of coated magnetic recording media.
0 parts, 5 to 3 parts of organic sulfur compounds as described above
It can be obtained by adding about 0 parts of the mixture and coating it on the back side of a support together with a suitable solvent. This back surface image Wk layer may be formed before or after the formation of the surface magnetic layer. The thickness of the back surface protective layer may be about 1, for example, 0.5 to 3 gm.

As described above, according to the present invention, it is possible to obtain a metal thin film type magnetic recording medium having a back surface protective AfC layer containing an organic sulfur compound having a specific structure and exhibiting sufficient wear resistance and running stability improvement effects.

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

A ferromagnetic metal thin film with a thickness of about 0.1 JLm having a composition of 80% Co and 20% Ni is formed on one side of a polyester film with a thickness of about 12JLm using a known vapor deposition apparatus, and , treated with anti-oxidation treatment.

Next, on the opposite side of the polyester film from the side on which the magnetic thin film was formed (i.e., the back side), an organic sulfur compound represented by the formula (1) was added to 100 parts of the binder (polyester resin (average molecular weight 20,000)). A magnetic tape according to the present invention was obtained by coating and forming a protective layer containing 5 parts of unsaturated disulfide in a thickness of about 1 μm.

Eho 1'' As the organic sulfur compound, the above formula (2) (however, X = 2
A magnetic tape was obtained in the same manner as in Example 1, except that 5 parts of unsaturated sulfide represented by , n = 2) was used.

Support 11'' As the organic sulfur compound, the above formula (3) (where X = 2
A magnetic tape was obtained in the same manner as in Example 1, except that 5 parts of unsaturated sulfide represented by , y=2) was used.

An 81x tape was obtained in the same manner as in Example 1, except that 5 parts of the cyclic sulfide represented by the formula (4) above was used as the organic compound.

As the organic sulfur compound, the formula (5) (where x=1
A magnetic tape was obtained in the same manner as in Example 1, except that 5 parts of the epithio compound represented by 4,y:=2) was used.

A magnetic tape was obtained in the same manner as in Example 1, except that 5 parts of unsaturated sulfide represented by the above formula (6) was used as the organic sulfur compound.

In Example 1, except that the back surface protection layer was not formed,
A magnetic tape was obtained in the same manner.

Butyl stearate instead of organic sulfur compounds
A magnetic tape was obtained in the same manner as in Example 1, except that

In order to investigate the running stability of the magnetic tapes obtained in Examples 1 to 6 and Comparative Example 1.2, a) measurement of jitter (using Matsushita VTRNV-800) and After the tape ran, the state of the scratches on the stainless steel guide post that came into contact with the back surface of the tape was observed.

The results are summarized in the table below.

However, in the table below, the damage on the guide post is checked visually, and the criteria are as follows.

O... There are almost no scratches.

Δ...Thin scratches are confirmed.

×...A large scratch is confirmed.

As is clear from the results in the table above, the evaporated Zi type magnetic tape with the back protective layer containing the organic sulfur compound of the present invention is different from the magnetic tape without the back protective layer (Comparative Example 1) and the conventional organic lubricant. Compared to a magnetic tape having a backside protective layer containing an agent, running properties are improved in terms of both jitter and damage to guide posts.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a metal magnetic thin film is formed on a non-magnetic support sheet, an organic sulfur layer is provided on the surface of the non-magnetic support sheet opposite to the surface on which the metal magnetic thin film is formed. A magnetic recording medium comprising a retention layer containing a compound. 2. The magnetic recording medium according to claim 1, wherein the organic sulfur compound is selected from unsaturated sulfides, cyclic sulfides, epithio compounds, and diethio compounds.