JPS60124027A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve runnability, wear resistance and durability by forming a protective layer by using a mixture in which the compsn. ratio of monoester, diester and triester in fatty acid glyceride is within a specific range. CONSTITUTION:A protective layer consisting of a fatty acid glyceride mixture having a residual fatty acid group of 11-21 carbon atoms and contg. monoester, diester and triester at a compsn. ratio of 20-90%:5-70%:5-70% by weight per cent. The lubricity of the fatty acid glyceride decreases the friction on the surface of the magnetic layer contributing consequently to an improvement in running stability. The adsorptive power thereof contributes to an improvement in the durability, i.e., wear resistance of the formed protective layer.

Description

[Detailed description of the invention] In the present invention, Co is deposited on a substrate made of a flexible non-magnetic material.

The present invention relates to a magnetic recording medium in which a ferromagnetic metal thin film such as Ni is provided as a magnetic layer.

In recent years, with the increasing density of magnetic recording, thin-film magnetic recording media have been developed, in other words, ferromagnetic metal thin films have been made magnetic by methods such as electroplating, electroless plating, vacuum deposition, ion blating, and sputtering on non-magnetic film substrates. Research and development of magnetic recording media formed as layers (hereinafter referred to as vapor-deposited tapes) are becoming more active. However, compared to conventional magnetic thin film coated tapes, this vapor-deposited tape has only one metal in the magnetic layer.
Because it is directly exposed to the surface of the tape, the magnetic layer surface is easily damaged or worn out when it runs in contact with magnetic heads, tape guides, etc. Also, the high friction makes running stability difficult (such as two There was a drawback.

Conventionally, in order to improve these various drawbacks, there have been methods of coating the magnetic layer with a thin film of polymeric material, methods of applying a thin layer of lubricant to the surface of the magnetic layer, methods of applying lubricants such as solid wax, Siol, etc. Many attempts have been made and implemented, including a method of forming a protective film by sputtering. However, coating with a film causes too much spacing loss, which is undesirable for high-density recording, and coating with a thin lubricant film does not provide long-lasting retention, resulting in rapid increase in friction or destruction of the magnetic layer during use. will occur. Similar drawbacks occur in the case of sputtered films of lubricants; on the other hand, sputtered films such as Sing have excellent wear resistance, but have drawbacks such as high friction and lack of running stability. In any case, according to the prior art, a satisfactory protective film for vapor-deposited tapes has not yet been obtained.

An object of the present invention is to eliminate the various drawbacks of the prior art described above and to provide a magnetic recording medium having a protective layer with excellent running stability and wear resistance.

That is, according to the present invention, Fe, Co and
A magnetic recording medium in which a ferromagnetic metal thin film made of , Ni, or an alloy containing these as a main component is provided as a magnetic layer by a method such as electroplating, electroless plating, vacuum evaporation, ion blating, sputtering, etc. The surface of the magnetic layer of the medium has fatty acid residues having 11 to 21 carbon atoms, and the composition ratio of monoesters, diesters, and triesters in weight percentages is 20 to 90 parts: 5 to 70 parts: 5 to 70 parts. It is characterized by providing a protective layer of a fatty acid glyceride mixture containing.

The fatty acid glyceride used in the present invention has the following general formula: Such fatty acid glycerides have a relatively active water 3-acid group or ester bond in their molecular structure, and this causes adsorption of water distributed on the metal surface of the magnetic layer as well as oxides and water of the magnetic metal. The oxide is chemically adsorbed by hydrogen bonding with the magnetic layer using the oxide as an adsorption active site.

In addition, fatty acid residues in fatty acid glyceride molecules rise from the surface of the magnetic layer (secondarily, they greatly contribute to the surface smoothness of the adsorption surface).

By the way, when comparing monoesters, diesters, and triesters, the greater the number of fatty acid residues contained in the molecule, the higher the lubricity in the order of triester>diester>monoester, while the higher the number of fatty acid residues contained in the molecule, the higher the lubricity The greater the number of residues (hydroxyl groups), the greater the adsorption capacity in the order of monoester>diester>triester. Here, the lubricity of fatty acid glyceride contributes to lowering the friction on the surface of the magnetic layer of a magnetic recording medium, thereby improving running stability, while the adsorption ability contributes to the durability of the protective layer formed, that is, improving wear resistance. Contribute to

The inventors of the present invention have focused on the above-mentioned points and have conducted various studies, and have found that a protective layer can be formed using a mixture of fatty acid glycerides in which the composition ratio of monoesters, diesters, and triesters is within a certain range. It was discovered that a magnetic recording medium having excellent running properties, abrasion resistance, and durability can be obtained. That is, as shown in FIG. 1, the monoester, diester, and triester in the fatty acid glyceride mixture are 20 to 90% by weight: 5
~70 inches: 5 to 70 inches, preferably 40 to 60 inches; 20
The intended purpose is achieved when the composition ratio is within the range of 20 to 30 m.

The fatty acid glyceride used in the present invention is a reaction product of glycerin and a fatty acid, and the greater the number of carbon atoms in the alkyl group or alkenyl group as a fatty acid residue in the molecule, the greater the lubricity and adsorption ability. Alkenyl group has 11 to 21 carbon atoms, preferably 17 to 21 carbon atoms
fatty acids are used.

Examples of such fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linoleic acid, arachidic acid, behenic acid, and tocosanoic acid.

By controlling the reaction between glycerin and fatty acids stoichiometrically (monoesters, diesters, or triesters of fatty acid glycerides can be easily produced by di-stoichiometry).

Examples of fatty acid glycerides obtained in this way are:
As monoesters, laflic acid monoglyceride, myristic acid monoglyceride, stearic acid monoglyceride, valmitic acid monoglyceride, oleic acid monoglyceride, elaidic acid monoglyceride.

As diesters, lauric acid diglyceride, myristic acid diglyceride, stearic acid diglyceride,
Valmitic acid diglyceride, oleic acid diglyceride, elaidic acid diglyceride. Examples of triesters include lauric acid triglyceride, myristic acid triglyceride, stearic acid triglyceride, valmitic acid triglyceride, oleic acid triglyceride, and elaidic acid triglyceride.

In the present invention, a fatty acid glyceride mixture consisting of monoester, diester, and triester having the composition ratio shown in FIG. A protective layer having excellent physical properties such as abrasion resistance and a thickness of about 1 to 20 nm is formed on the surface by applying it to the surface by an appropriate means and drying it. Here, as an organic solvent, toluene, xylene, methyl ethyl ketone, methyl isobutyl cotton, and butyl acetate are used.

Ethyl acetate, ethyl cellosolve, etc. or a mixed solution thereof can be used.

The present invention forms a protective layer with excellent physical properties as described above from a fatty acid glyceride mixture. However, in order to further improve the abrasion resistance, durability, etc. of the protective layer,
In a preferred embodiment of the present invention, a synthetic resin is further added to the above mixture, applied to the surface of the magnetic layer, and cured by an appropriate method to form an organic film containing the fatty acid glyceride mixture as a protective layer. be able to.

Examples of synthetic resins used in preferred embodiments of the present invention include vinyl chloride copolymers such as vinyl chloride-vinyl acetate copolymer, vinyl chloride 7-copolymer, and vinyl chloride-acrylonitrile copolymer; Thermoplastic resins such as acrylic acid or methacrylic acid ester copolymers, butadiene-acrylonitrile copolymers, polyamides, polyvinyl butyral, urethane elastomers, polyvinyl fluoride, polyester resins, amino resins; unsaturated polyester resins, epoxy resins, Moisture curing resins with terminal incyanate or terminal isocyanate polyether; polyisocyanate prepolymers, diisocyanate oligomers, polyisocyanate prepolymers and polyester polyols, polyether polyols, acrylic acid copolymers, maleic acid copolymers, methacrylic acid copolymers Thermosetting or reactive resins such as copolymers; unsaturated polyester resins,
Examples include acrylic or methacrylic esters such as epoxy, urethane, polyester, alkyd, and silicone, radiation-reactive resins such as polyene/polythiol resins, spiran resins, and epoxy resins. Among these, polyvinyl butyral, polyester mol resin, polyvinyl fluoride, unsaturated polyester resin, which have high adhesion to the surface of the magnetic layer and whose resin itself has 8-wear resistance,
Preferably, epoxy resins, terminal isocyanate polyesters, thermosetting resins of acrylic acid copolymers, and radiation-reactive resins are used.

According to the invention, such synthetic resin is added to the fatty acid glyceride mixture in a ratio of 2:8 to 9:1. This mixture may be dissolved in the above-mentioned suitable organic solvent and applied to the surface of the magnetic layer to a desired thickness.

In the present invention, as mentioned above, fatty acid glyceride is adsorbed onto the magnetic layer surface using metal oxides and hydroxides or adsorbed water on the surface as adsorption active sites. Increasing the density can increase the adsorption amount and further improve the wear resistance of the protective layer.

Effective surface treatments for increasing the density of adsorption active sites include ozone treatment, corona discharge treatment, electron beam irradiation treatment, plasma treatment, and ion bombardment. Further, by performing such surface treatment, the wettability of the surface of the magnetic layer is also improved, and even when an organic film is formed, the adhesion of the coating film can be improved and the durability can be increased.

Next, the present invention will be explained with reference to examples, but it is not intended to be limited thereto.

Example 1 C on 2 μm thick polyethylene terephthalate film
2 A vapor deposition tape was formed by diagonally vapor depositing a cobalt-nickel alloy magnetic thin film (thickness: 0.2 μrn) using a conventional method, and this was used as sample portion 1.

A toluene solution containing 0.1 parts by weight of stearic acid was applied and dried to form a protective layer on the surface of a vapor-deposited tape obtained in the same manner as Sample Nu 1, and this was used as Sample Magnet 2 (comparative example).

Similarly, a toluene solution containing 1% by weight of fatty acid monoglyceride was applied to the surface of the vapor-deposited tape and dried to form a protective layer, which was used as sample portion 3 (comparative example).

Thereafter, in the same manner, a 1% by weight solution of a fatty acid glyceride mixture having a monoester:diester:triester composition ratio as shown in FIG. 2 was applied to the surface of the vapor deposition tape and dried to form a protective layer. These were respectively designated as samples Na4 to 16 (example), and samples Nl17 and 1.
Adding an acrylic resin or a polyester urethane resin to a mixture having a composition ratio shown as 0 and 17 at a mixing ratio of 1:1,
This was applied as a 1% by weight) toluene/methyl ethyl ketone solution and dried to form a protective layer.
9 uses polyester urethane resin as the synthetic resin)
And so.

In Figure 2, ○ mark is stearic acid glyceride, Δ
The mark represents oleic acid glyceride, the mark represents palmitic acid glyceride, and the number on the shoulder represents sample N[L.

For each of the samples ml to 19 thus obtained, the coefficient of kinetic friction (μk) regarding wear resistance and running performance was measured by the following method, and the results shown in Table 1 were obtained.

Abrasion resistance: The sample with the slit was attached to a video tape recorder and rotated for 5 minutes in static + h image output state (still playback). The degree of peeling was determined by microscopic observation.

Coefficient of dynamic friction: The sample was mounted on a video tape recorder, and the sample was run back and forth to measure the coefficient of dynamic friction at the initial stage, after 200 reciprocations, and after 500 reciprocations.

(The following is a blank space) 12-Table 1 As is clear from the results in Table 1, according to the present invention, a mixture of fatty acid glycerides consisting of mono-, di-, and triesters of a predetermined composition ratio or an organic film containing the same is coated on the surface of the magnetic layer. It can be seen that by providing the anti-abrasive layer, it is possible to obtain a magnetic recording medium which has excellent running properties and abrasion resistance, and which maintains such physical properties for a long period of time.

[Brief explanation of drawings]

FIG. 1 shows triangular coordinates showing the range of composition ratios of monoesters, diesters, and triesters in the fatty acid glyceride mixture used in the present invention, and FIG. 2 shows examples of the present invention (
These are triangular coordinates showing the composition ratios of monoesters, diesters, and triesters used in each sample. 15- Figure 1 Figure 2 Monoester

Claims (2)

[Claims] (1) In a magnetic recording medium in which a magnetic layer made of a ferromagnetic metal thin film is provided on a substrate, the surface of the magnetic layer has a carbon number of 1.
Protection of fatty acid glyceride mixtures having 1 to 21 fatty acid residues and containing monoesters, diesters, and triesters in a weight percentage of 20 to 90 parts = 5 to 70 parts: 5 to 70 parts. A magnetic recording medium characterized by having a layer. (2) A patent claim characterized in that a protective layer of an organic film made by adding a synthetic resin to a fatty acid glyceride mixture containing a monoester, a diester, and a triester in a predetermined composition ratio is provided on the surface of the magnetic layer. The magnetic recording medium according to scope 1.