JPS589217A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To easily obtain a magnetic recording medium which has improved corrosion resistance and can be stored for a long period, by treating the surface of a magnetic layer made of a Co metal or Co alloy with a solution of specific materials. CONSTITUTION:In a solution which consists of 0.05-2% ethylenediaminetetraacetic acid, 0.1-5% H2O2, and 0.0005-0.01N (normal) NaOH, a magnetic recording medium which has a magnetic layer made of a Co metal or Co alloy is immersed at 20-60 deg.C for 5-30min, and then washed sufficiently with ion exchange water or distilled water to wash off said remaining stuck chemicals completely. After sticking drops of the water are sucked up with filter paper, etc., a drying treatment is carried out at 60-80 deg.C for 10-20min. Thus, Co is oxidized to fix a stable complex, produced by reaction with ethylene diamine tetraacetic acid, on the magnetic layer. Therefore, the corrosion resistance is improved.

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a magnetic recording medium.

Vacuum magnetization and sputtering of thin films of iron, cobalt, nickel, or alloys containing these as main components.

Metal thin film type magnetic recording tape formed on a substrate film by methods such as ion grating or plating, or metal powder type magnetic recording tape #'i in which these metal powders are bonded with a resin binder. Unlike ordinary coated tape, which is made of ferromagnetic powder mainly composed of iron oxide bound with a resin binder, it is susceptible to corrosion in high humidity or corrosive gases.

Therefore, the surface of metal thin film type or metal powder type magnetic recording tape is stabilized by oxidation using glow discharge or anti-rust treatment such as extremely thin resin coating, but the condition is sufficiently satisfactory for practical use. Currently, it is difficult to obtain such things.

In particular, many regions of our country have a rainy season.

This period is particularly hot and humid, leading to corrosion of metals. 3.2 In fact, there is a tendency for complaints about corrosion of various metal parts to occur frequently during this period.

Furthermore, our country is surrounded by the sea, and residents near the coast are constantly exposed to a highly corrosive atmosphere containing salt. Furthermore, our country is a volcanic country, and many areas have hot springs and volcanic gases.

In such areas, sulfide water foils (H2S) are often present.

Sulfur dioxide (802) *Generates corrosive gases such as ammonia (NH3). Additionally, many regions have industrial zones, some of which generate various corrosive gases and dust.

As is well known, iron corrodes even under normal environments, while nickel and cobalt, although superior in corrosion resistance compared to iron, corrode under the above-mentioned environments. Especially the metal plate and butterfly are different from vacuum deposition, sputtering, and ion blating.

Metal thin films made by methods such as rusting are generally more active than metal plates and tend to be more susceptible to corrosion.

Magnetically recorded cassette tapes, whether audio or video recording, must be able to be stored for a long period of time without corrosion or deterioration. For example, in the case of long-term records of human childhood, corrosion resistance of 10 to 20 years would be required. □ Vacuum-deposited tapes that are simply coated with iron, nickel, cobalt, or their alloys using the vacuum deposition method.

If left in various atmospheres, it may corrode in a relatively short period of time. For example, corrosion may occur in a few weeks in an atmosphere with a relative humidity of 60 to 60C9 eo%, and corrosion products in the form of white specks may be observed in a few months even if the product is left indoors during the rainy season. be. In order to prevent such deterioration due to corrosion, one surface layer is oxidized by glow discharge or coated, but it is still difficult to completely guarantee corrosion resistance for an extremely long period of time.

In the present invention, the surface of the magnetic layer of a magnetic device medium made of a ferromagnetic metal thin film of cobalt metal or cobalt alloy is coated with EDTA.
The present invention will be described below as an attempt to improve the corrosion resistance of the surface of a magnetic layer by treating it with an aqueous solution containing hydrogen peroxide and sodium hydroxide at a predetermined temperature and time.

ICDTA concentration is 0106-2%, hydrogen peroxide concentration is 0
．． 1 to 6- and sodium hydroxide concentration is 0.0006 to
The magnetic layer is treated by immersing a mixed aqueous solution of the three components at 0.01 N (regular) in a treatment tank set at a temperature of 20 to 60 r for 6 to 30 minutes.

After treatment, the magnetic layer is thoroughly washed with ion-exchanged water or distilled water to completely wash away any remaining chemicals.

If the water droplets on the magnetic layer are left to dry, they will remain as "0 stains", so wipe them with something like dry F paper.
After removing excess moisture, dry at 60-80C for 10-20 minutes.

The corrosion resistance of the magnetic layer treated in this way was evaluated using a high temperature test (so
c, RHeo%) from a certain itt! After testing with corrosion test,
Evaluate corrosion resistance by observing with an optical microscope.

The reason why the corrosion resistance of the magnetic layer treated by the method according to the present invention is improved can be inferred as follows.

Ethylenediaminenatodiacetic acid (EDTA) has the following structure and forms chelate compounds with many metal ions.

However, since the tetraacetic acid form is not soluble in water, disodium salt or tetrasodium salt is usually commercially available. ED'r of cobalt (1) and cobalt (1) under strong acidity
The stability constants of A salt are jI 0qKco(
1) Y'=16, 31 and II 09KCo(1)Y
=40-7, which is large and extremely stable.

, On the other hand, in alkaline conditions, the stability constant is unknown, but in the coexistence of hydrogen peroxide, it forms extremely stable 0EDTA*tz-)(CdN)(OH)Y,12-. This chelate changes reversibly as described below by adding acid or alkali.

The reason why the corrosion resistance of the cobalt-based magnetic layer treated by the method of the present invention is improved is considered to be due to the following reasons. - In other words, a part of the cobalt constituting the magnetic layer is ionized, and this is oxidized by hydrogen peroxide (Co → C
o), which reacts with EDTA under alkaline conditions to form a stable complex, a part of which is fixed on the magnetic layer.

As a result, areas with poor corrosion resistance, especially on the magnetic layer.

In other words, it is preferentially fixed to the defective parts of the oxide film due to glow discharge oxidation, that is, the raised parts of cobalt metal, forming a thin film (100A or less) and exhibiting a protective effect.

The formation of a cobalt EDTA complex on a magnetic recording medium has been confirmed by photoelectron spectroscopy (Ei9CA) or electron beam diffraction.

When the magnetic i-layer is treated by the method according to the present invention, the conditions are preferably within the following range.

(1) EDT A concentration: 0.05-2ch (2
) Hydrogen peroxide concentration: 0.1 to 6% (3) Sulfuric acid concentration
:0.0005-0.01 N (4) Processing temperature
: 20-60C (6) Processing time = 6-30 minutes When processing under conditions that significantly deviate from the above conditions.

Care must be taken as it may dissolve the magnetic layer.

In addition, the combination of each treatment condition is also important. For example, if the amount of treatment agent is large, it is necessary to treat at a low temperature, and if the treatment temperature is high, a short treatment time is required.

This is to minimize the unavoidable dissolution of the magnetic layer due to the treatment according to the present invention.

Next, examples will be specifically described.

Example 1 Magnetic layer material: CO: N1 = 80:20 x DTA: 1 inch H2O2: 29b NaOH: 0.001 N Treatment temperature = 26C Treatment time: 10 minutes Those treated under the above conditions are replaced with those without this treatment. In comparison, it showed approximately three times the corrosion resistance in the dew corrosion test.

Example 2 Magnetic layer material: co: N; = ao: 2° EDTA: o, oes% H2O2: 0.6% Na OH: 0,0005 N Processing temperature = 40C Processing time: 20 minutes Processed under the above conditions The material showed approximately four times the corrosion resistance in high humidity tests (SOC, RHEO) as compared to the material not subjected to this treatment. shows excellent corrosion resistance and is easy to process.
Since continuous processing of long objects is also possible, the effect is extremely large.

Claims (2)

[Claims] (1) A method for manufacturing a magnetic recording medium, which comprises treating the surface of a magnetic layer made of cobalt metal or cobalt alloy with an aqueous solution containing EDTA (ethylenediamine-acetic acid), hydrogen peroxide, and sodium hydroxide. (2) I! : Concentrations of DTA, urea peroxide and sodium hydroxide are 0.66-2qA and 0.1-6qA, respectively.
and 1N (normative).A patent characterized in that the temperature of treatment with an aqueous solution is in the range of 20 to eoc. A method for manufacturing a magnetic recording medium according to claim 1g1*. - The method for manufacturing a magnetic recording medium according to claim 1, characterized in that the treatment time with the aqueous solution is in the range of 6 to 3 minutes.