JPS5873018A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a titled recording medium having good water repellency, running characteristic, heat resistance, lubricity, etc. by providing a chemical adsorbing layer of metallic salts of perfluoroalkyl carboxylic acids and a coating layer of satd. hydrocarbon on the surface of a thin film of cobalt type ferromagnetic materials. CONSTITUTION:Metallic salts of perfluoroalkyl carboxylic acids are chemically adsorbed on the surface of a thin film of ferromagnetic materials consisting of cobalt or its alloys formed on a nonconductive substrate by a vapor deposition method, a sputtering method, a coating method, etc. Further, a coating layer consisting of hydrocarbons of >=18C hydrocarbons such as, for example, n-octadecane, n-nonadecane, n-dodecane, n-docosane, n-dotriacontane is provided thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to modifying the surface of a ferromagnetic thin film formed on a non-magnetic substrate (for example, made of cobalt), changing the wettability of the surface, and further improving water repellency. , improved running performance,
It is an object of the present invention to obtain a metal thin film type magnetic recording medium having good corrosion resistance and lubricity.

It is said that metal thin film magnetic recording media made by vacuum deposition or plating are superior in high-density recording. In recent years, thin films of cobalt-based alloys formed by vacuum deposition on polyester substrates for audio and video recording have entered the realm of practical use and are now commercially available. However, in general, ferromagnetic metals are easily corroded, and in order to avoid this corrosion, it is necessary to alloy the magnetic material itself, form a polymer film on the magnetic layer, or use a metal film or 8i02 film. However, in the case of alloying a magnetic layer, an alloy with good corrosion resistance is not necessarily good from the viewpoint of magnetic properties. On the other hand, it is effective to form a corrosion-resistant film on the magnetic layer, but from the viewpoint of electromagnetic conversion characteristics, too thick a film is not desirable as it may lead to a decrease in output. The permissible range of the thickness of the corrosion-resistant film is at most 500, preferably about 2008. It is extremely difficult to form a corrosion-resistant film with a film IWv of about 9 in a stable manner and with good mass production.
Accompany. ''!: Even if a film is formed at this level of thickness, it is difficult to completely prevent moisture from entering.Furthermore, regarding runnability, in coated magnetic recording media, epoxy resin, Binders such as urethane resins, vinyl chloride-vinyl acetate copolymers, phenoxy resins, and polyvinyl butyral are mixed with lubricants such as metal salts of stearic acid, various esters of stearic acid, and pentaerythritol tetrastearate. In addition, the desired running properties can be obtained by appropriately dispersing the particles.However, the above method cannot be used in metal thin film type magnetic recording media.

The present invention was developed in view of the above points, and is based on a metal salt of a strongly hydrophobic perfluoroalkylcarboxylic acid. Chemical adsorption to the surface of the magnetic layer, and even better running properties? A saturated hydrocarbon coating was applied to improve the corrosion resistance, and this two-layer coating provided sufficient corrosion resistance and lubricity.

The present invention will be explained below.

A metal salt of perfluoroalkylcarboxylic acid is chemically adsorbed onto a magnetic layer made of a ferromagnetic metal such as cobalt, which is prepared by the vacuum evaporation N method, sputtering, electroplating, or the like. Perfluoroalkylcarphonic acids are common fatty acids (OnH2
It is expressed as OnF 2n+ 1COOII, and has better chemical resistance, solubility, and heat resistance than ordinary fatty acids. Alkali metal to gold which becomes metal salt,
Select one or more of alkaline earth metals and transition metals.

Specific examples include alkali metal salts and alkaline earth metal salts of nonadecafluorodecanoic acid, metal salts of cobalt, nickel, and copper, and alkali metal salts and alkaline earth metal salts of pentadecafluorooctanoic acid. ,cobalt,
Metallic salts of nickel and copper.

Alkali metal salt of heptadecafluorobutanoic acid.

Alkaline earth metal salts, cobalt, nickel, copper gold salts are used in this case. The above metal salt of perfluoroalkylcarboxylic acid is synthesized by the following method. For the salts of cobalt, nickel, and copper, add an aqueous sodium hydroxide solution to an aqueous nitrate solution to obtain the hydroxide. After decantation, centrifugation is performed to remove impurities. except. This hydroxide aqueous solution? It was dropped into a perfluoroalkyl carboxylic acid aqueous solution, and after confirming that P)I was 7, the precipitate was filtered, water was removed from the filtrate, and the transition metal salt was removed. obtain. alkali.

The alkaline earth metal salts are synthesized by a neutralization reaction between the respective hydroxides and doperfluoroalkylcarboxylic acids. Chemical adsorption of metal salts of perfluoroalkylcarboxylic acids onto the surface of the metal magnetic thin film can be achieved by vapor deposition, sputtering, coating, etc. In this case, the coating method is used. Method 2: Perfluoroalkylcarboxylic acid is dissolved in water or a special organic solvent and applied to the surface of a magnetic thin film, causing chemical adsorption to occur on the surface of the magnetic thin film. After the reaction, the solvent is removed by hot air drying.

The saturated hydrocarbon in the second layer is n-octadeca/.

n-nonadecane, n-dodecane + n)” cosane.

One or several saturated hydrocarbons having 18 or more carbon atoms are selected, such as n-todoriacontane. Hydrocarbons having 18 or less carbon atoms are liquid at room temperature and are therefore not used in the invention. The thickness of the surface treatment layer coated on the magnetic thin film on which the metal salt of perfluoroalkyl carboxylic acid is chemically adsorbed by dissolving this saturated hydrocarbon in a specific organic solvent is at least 500 mm.
Must be 8 or less.

Next, the present invention will be explained in more detail.

An example of a magnetic recording medium will be described in which a ferromagnetic metal thin film is formed by a vacuum evaporation method, has a columnar crystal structure 2, and the columnar crystals are covered with an oxide layer of the ferromagnetic metal.

Generally, vacuum vaporization in the formation of ferromagnetic metal thin films, 1
The evaporated material is heated in a gas at a pressure of 0' to 10 torr, and the generated vapor is recrystallized on the substrate material. At this time, the gas remaining in the vacuum deposition tank contains water, gas equivalent to air components, and gases generated from the substrate and other sources. It is not always possible to vaporize fC in the underworld surrounding gas.One way to solve this problem is to introduce a limited number of gases to determine the material of the gas in the vacuum,
Reproducibility of quantity? There are ways to improve it. This has a significant effect on the crystal growth of metal thin films that are deposited at the same time, and films made in a vacuum evaporation tank with oxygen gas introduced have a much higher regularity and reproducibility. The same is true for γ1. Ru.

- As an example, the data are shown: Deposition substance: CO1 Deposition rate: 30000 people/min Oxygen partial pressure: lX10
torr, Substrate: Polyethylene terephthalate Coercive force: 30o~eoo The oxide layer covering the ferromagnetic crystal with an Oersted columnar structure is estimated to have a thickness of 20 Å or more. Although it is not a hindrance, in the case of materials that become non-magnetic through oxidation, it leads to a decrease in the residual magnetic flux density and is not necessarily advantageous. No. 53-42010, No. 53-42004.

1. Described in the publications No. 54-21309 and No. 54-31708. ing.

(1) A ferromagnetic thin film of a cobalt alloy made of 80% cobalt and 20% nickel and having an oxide layer on its surface is treated with the solution shown below.

Cobalt 0.001 mol/l Aqueous treatment liquid (fb): Sodium nonadecafluorodecanoate 0001 mol/l Aqueous treatment liquid (Ic): Magnesium pentadecafluorooctanoate 00o1 mol/l Aqueous treatment liquid (la): n- Octadecane 2 x 10 mol Acetone 11 Treatment liquid (Ilb): n-dodecane 2 x 10 mol Toluene 11 Treatment liquid (Ilc): n-Tocosan 2 x 10 mol n-hexane 11 Treatment liquid (Ila): n-Todoriacontane 2 x 1o malt)vx
7.10 Experimental results are shown in the following table.

It became clear.

(1) Corrosion resistance is significantly improved by forming a chemically adsorbed layer of a metal salt of perfluoroalkyl carboxylic acid on a thin magnetic layer of a metal alloy with an oxide layer on its surface.

(2) When a coated layer of saturated hydrocarbon is further formed on the surface of the thin film magnetic layer of the rut alloy having a chemically adsorbed layer of a metal salt of perfluoroalkyl carboxylic acid, the coefficient of friction is significantly lowered.

The inventors will not be able to confirm the effectiveness of the present invention with respect to other magnetic layers. That is, 00100%, GO90%Ni2O%, 0
085%Ni151%, 0070%Ni30%, 001
0%F690%, GO50%F650%.

GO95%V5%, 0096%Pt5%, 0097%R
Similar results to those shown in the above-mentioned coating were obtained even when the coating was applied to 3% H, 90% Go, 5% Ni, 5% W, etc.

There are differences in corrosion resistance, coefficient of friction, and contact angle between the magnetic layers not according to the present invention, but there are almost no differences between the magnetic layers according to the present invention. It is confirmed that it will disappear.

Similar results were obtained for ferromagnetic thin films made of cobalt metal and cobalt alloy 9, which were formed without introducing oxygen gas.

As is clear from the above description, the present invention allows
The problems of corrosion resistance and runnability of magnetic recording media having ferromagnetic thin films made of cobalt or cobalt alloys can be solved.

Name of agent: Patent attorney Toshio Nakao and one other person JP-A-58-73018 (4)

Claims (1)

[Claims] A ferromagnetic thin film made of cobalt or its alloy formed on a non-magnetic substrate has a chemical adsorption layer made of a metal salt of perfluoroalkyl carboxylic acid on the surface thereof, and a chemical adsorption layer made of a metal salt of perfluoroalkyl carboxylic acid is further formed on the chemical adsorption layer. A magnetic recording medium characterized by having a coating layer r.