JPS63191317A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce a medium having high long-term reliability on a lubricating surface by coating an Si(OH)4 soln. on a thin magnetic film and subjecting the coating to a primary heat treatment, then coating a lubricating agent of perfluoropolyethers having at least one polar group and subjecting the coating to a heat treatment. CONSTITUTION:An alumite film is formed by an anodic oxidation treatment on an aluminum substrate and the surface is finished smooth by surface polishing. A thin magnetic oxide film essentially consisting of Fe is formed to 0.13mum thereon by a reactive sputtering method and is further converted to a magnetic gamma-Fe2O3 film by an oxidation treatment in the atm. The Si(OH)4 soln. is then coated on said film by a spin coating method and thereafter, the coating is baked for 3hr at 150 deg.C in an electric furnace to form an SiO2 film in which many silanol groups (Si-OH) remain to about 200Angstrom film thickness. The perfluoropolyether having carboxylic -COOH at the terminal polar group and having about 4,000mol.wt. is diluted by a fluorine solvent to 0.005wt.% and the soln. is coated on the film by a spin coating method. The coating is dried for 10min at 80 deg.C and is baked for 10min at 260 deg.C.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to magnetic recording media, and more specifically to magnetic disks for large capacity, high density recording, which have a surface with excellent lubricity and protection. The present invention relates to a method of manufacturing a magnetic recording medium provided with a layer.

[Conventional technology and its drawbacks]

Generally, a magnetic recording device is composed of a magnetic head for recording/reproducing and a magnetic recording medium (disk). In the magnetic recording device, contact φ start/stop (CSS)
Recording and reproduction are performed using this method. For this reason, the recording/reproducing magnetic head and the magnetic recording medium (disk) operate in static or dynamic contact with each other or under pressure, resulting in a contact friction state. In other words, in order to protect the magnetic thin film layer of a magnetic recording medium, it is desirable to coat the surface with a protective film and form a protective layer.The purpose of this protective layer is to improve so-called head crash resistance and wear resistance. The protective layer must have properties such as lubricity, environmental resistance, and not affecting the magnetic properties of the underlying magnetic material.Furthermore, the protective layer must have properties such as lubricity, environmental resistance, and no influence on the magnetic properties of the underlying magnetic material. It is required to reduce the contact friction force generated as much as possible, that is, to reduce the friction coefficient. In order to meet these requirements, 5i021i, which is relatively hard and has excellent wear resistance, is formed by a sputtering method or a spin-neat method, and a liquid type lubricant (for example, perfluoropolyethers) is applied thereon. A method has been proposed (Japanese Unexamined Patent Publication No. 58-185029).

However, if a liquid lubricant is simply applied on the 5i02 protective film, the liquid lubricant molecules may evaporate due to the temperature rise inside the magnetic recording device (HDA), or the molecules may spin off due to the high speed rotation of the magnetic recording medium (disk). The lubricated surface lacks long-term reliability, resulting in head crashes.

In order to eliminate such drawbacks, 5102
A method of chemically bonding and fixing a protective film and a liquid type lubricant has also been proposed (Proceedings of the 1981 IEICE General Meeting P, 1-18?), in this case, 5i02
A spin-neat method, a dipping method, or the like is used to form an amimedilan layer on the protective film to a thickness of several to 50 layers. However, when carrying out these methods, it is extremely difficult to control the reaction activity of the aminosilane dissolved in the solvent, which poses a problem in terms of productivity in the mass production process.

[Means for solving problems]

By solving the above-mentioned problems, it is possible to realize a magnetic recording medium having a protective layer and a lubricating layer that have good properties as a protective layer, especially the long-term reliability of the lubricity on the surface of the protective layer, even in a mass production process. As a result of repeated research on manufacturing by this method, after applying a 5i(OH)n solution on an oxide magnetic thin film by a spin code method and performing a primary heat treatment at a low temperature of about 100 to 180°C to form 5i02, It has been found that it is practically effective to apply a method of coating a perfluoropolyether having at least one polar group.

The features, technical means, methods, etc. of the present invention will be described in detail below. Non-magnetic substrates in the present invention include aluminum and aluminum alloy substrates having an alumite film formed by anodic oxidation on the surface, glass, ceramics, etc. It may be a resin substrate. In either case, it has various mechanical and material characteristics suitable for a magnetic disk substrate, and the surface of the substrate has a mirror finish or a similar finishing treatment so that Rmax is 0. It is necessary to have smoothness equal to or lower than that of the 02 p layer and to have excellent washability. The magnetic medium is an oxide magnetic thin film mainly composed of iron by sputtering, heat treatment, etc., and the film forming method is to form an iron (Fe) film by reactive sputtering in an oxygen atmosphere.
A method of obtaining a ferromagnetic oxide through steps such as forming a non-magnetic hemagite (α-Fe20s) film containing as the main component, converting it into Fe304 by selecting one element, and then oxidizing it to γ-Fe203, Alternatively, any method may be used, such as directly forming ferromagnetic oxide magnetite (Fe304) by reactive sputtering by controlling the sputtering atmosphere, and then obtaining maghematite (γ-Fe203) through a process such as oxidation treatment. , 5i(0)1)4 solution was applied on this oxide magnetic thin film by spin code method, and 10
A 5i02 film is obtained by heat treatment at a low temperature of 0 to 180°C. The thickness of the 5i02 film is preferably thinner in order to reduce the gap between the head and the medium when recording and reading information, etc. It is necessary to have a certain thickness in terms of its function as a film, and more specifically, it is desirable to have a thickness of about 10 to 800.A Si(OH)4 solution is applied using a spin code method and treated at a low temperature. The 5i02 film with only silanol groups (Si
-OH) remains in large amounts.

On top of this, a liquid lubricant of perfluoropolyether oligomer having at least one polar group is coated for several times to 50 times, and when it is dried at a temperature of about 80°C, the solvent evaporates, and the silanol group in the 5i02 film and the lubricant are dried. The polar groups of the lubricant are bonded chemically or through hydrogen bonds, fixing the liquid lubricant on the 5i02 protective film.

After this, the 5i02 film is fired again at a high temperature of 250 to 300°C for 5 to 15 minutes, and the film-forming silanol groups are bonded to siloxane (Si-0-9i) through a dehydration condensation reaction, reinforcing the strength of the 5i02 protective film. do. The perfluoropolyether-fixed 5i02 protective film (lubricant-fixed protective film) formed by the above method is protected against evaporation of the lubricant due to temperature rise inside the magnetic recording device (HDA) and lubrication due to high-speed rotation of the magnetic disk. It does not cause agent spin-off and is fully effective in maintaining the long-term reliability of lubricated surfaces.

The perfluoropolyethers used in the present invention are F+CFCF20)-nC2F5 (however, n
= 10-90) CF3 F-GCF, 0+r+C2F5 (however, n=10-15
0) CF3 (where m = 10 to 50) n = 10 to 150) (where m = 10 to 70) n = 10 to 150) A polyether oligomer having the following molecular formula, where the oligomer has at least one polar group at its terminal are combined. Among the polyether oligomers, it is desirable to have a large molecular weight in view of low temperature dependence of viscosity or low vapor pressure, but if the molecular weight becomes too large, it is necessary to apply a lubricant on the 5i02 protective film. Since it is difficult to apply and fix uniformly, a molecular weight of about 1,000 to 8,000 is appropriate.An effective terminal polar group for use in the present invention is 1,000H2-GOORl-ROR. , -RO)l , -Nl2,
-NHROHL-NCO, -CONH2, -NHR, -
C) to etc.

The perfluoropolyethers on the 5i02 film are required to maintain good lubricity between the head and the magnetic recording medium and to prevent adsorption between the head and the magnetic recording medium. Therefore, the perfluoropolyether film should be as thin as possible (several to 50 mm) and free from defects such as uneven coating (after being coated with a uniform thickness on the 5i02 film, it should be fixed on the 5i02 film). In order to achieve such a state, the perfluoropolyether must be soaked in a fluorinated solvent with excellent thermal and chemical stability and a suitably high boiling point (100°C or higher) for 1 o, ooot to 100°C.
．． This is achieved by diluting it to about 0%zt% and coating it on the 5i02 film using a spin code or dipping method.

In such a coating method, the conditions are determined by the temperature and viscosity of the solution, the rotation speed or pulling speed during coating, and post-processing such as removing excess and solvent after coating, and are selected and used as appropriate. do.

[Effect]

After forming a 5i02 protective film on an oxide magnetic film, the method involves fixing the 5i02 protective film and a liquid type lubricant via aminosilane to prevent the lubricant from volatilizing, which involves controlling the activity of the aminosilane to form the aminosilane layer. Forming a thin and uniform film with good reproducibility has been problematic from the standpoint of mass production.

However, according to the method of the present invention, there is no need to use aminosilane.

A liquid type lubricant is fixed on the 5i02 protective film, and a magnetic recording medium with excellent long-term reliability of the lubricated surface can be manufactured by a method that is practical even during mass production.

Hereinafter, the features of the present invention will be explained in detail with reference to Examples.

〔Example〕

An alumite film is formed on the aluminum substrate for the disk by anodizing treatment, and the surface is polished to (Rm
ax≧0.02xm), a 0.13 μm thick oxide magnetic thin film (Fe304H mulberry) containing Fe as a main component was formed thereon by a reactive sputtering method, and further oxidized in the air (300°C, γ-F
Converted to e203 magnetic film.

The γ-Fe203 thin film disk produced by the above treatment method was subjected to a protective film and surface lubrication treatment as follows.

S is deposited on the γ-Fe203 magnetic thin film using the spin code method.
After applying the i(OH)4 solution, baking was performed in an electric furnace at 150°C for 3 hours to form milanols (Si-O) into the film.
A 5i02 film having a thickness of about 200λ and containing a large amount of H) was formed. Next, perfluoropolyether having a terminal polar group of carboxylic acid -〇〇〇〇 and having a molecular weight of about 4,000 was diluted to 0.005 wt % in a two-strand solvent and applied by a spin cord method. After drying at 80°C for 10 minutes, it was fired at 280°C for 10 minutes.

The following measurements were performed on each disk on which the protective film and surface lubricant layer were formed as described above.

Recording and reproducing operations using the Contact Start Stop (CSS) method, in which the magnetic recording medium and the magnetic helad for recording and reproducing are in contact with each other at startup and stop, are performed repeatedly, and the presence or absence of scratches on the surface of each disk and the film are checked. Observation of surface conditions such as peeling and wear, and changes in electromagnetic conversion characteristics such as dynamic friction coefficient and output current value between the head and disk, and C
Changes in the coefficient of friction between the head and disk before and after 8S were also measured.

In addition, as an environmental resistance test, the coefficient of friction and the change in the thickness of the perfluoropolyether layer were measured when the film was left in an environment with a relative humidity of 80% and a temperature of 80° C. for 50 days, and the rate of increase in the number of errors at that time was measured.

These results are shown in Table 1.

For comparison, a magnetic recording medium was prepared using a conventional technique of processing Si(OH)4 at high temperature using aminosilane, and its characteristics were compared.

Comparative Example 1 S was deposited on a γ-Fe2 03 magnetic thin film by spin coding
i(OH)4 solution was applied and baked in an electric furnace at 300°C for 3 hours to form a 5i02 film with a thickness of about 200λ by dehydration condensation reaction. , molecular weight around 4000 (7)
A liquid lubricant of perfluoropolyether oligomer was diluted to 0.005 t% in a fluorinated solvent and applied onto the 5i02 protective film by a spin code method. It was dried at 80°C to remove the solvent and form a lubricating film.

This magnetic recording medium was subjected to the same tests as in the example, and the results are shown in Table 1.

Comparative Example 2 After forming a 5i02 protective film in the same manner as Comparative Example 1,
7 Mi/ Shira7NH2CH2CH2NH (CH2)
An N-butanol solution containing 35i(OCH3)3 dissolved at a concentration of 0.05 wt% was spin-coded and heated at 100°C to maintain SiO2! III and 7 The minosilane layers were bonded with siloxane, and then a perfluoropolyether having carboxylic acid -COOH as a terminal polar group was applied in the same manner as in Comparative Example 1. It was dried at 80°C to remove the solvent and form a lubricating film.

This magnetic recording medium was subjected to the same test as in the example,
The results are also listed in Table 1.

(The following is a blank space) Table 1 [Effects of the Invention] As is clear from the detailed description above, according to the method of the present invention, the lubricant can be applied to the protective film without intervening an intermediate layer between the 5i02 protective film and the 5i02 protective film. It is possible to manufacture a magnetic recording medium that has a lubricated surface that is fixed and has excellent long-term reliability.

In addition, a lubricating film having the same reliability can be produced at low cost without using difficult techniques such as controlling reaction activity as in the known 7-minosilane bonding method, so the practical effect is extremely large.

Claims (2)

[Claims] (1) Tetrahydroxysilane (Si(
OH)_4) After applying the solution and heat-treating at a temperature of 100 to 180°C, coat a lubricant made of perfluoropolyethers having at least one polar group thereon, and then heat-treating at 250 to 300°C. A method of manufacturing a magnetic recording medium, characterized in that: (2) Perfluoropolyethers have a molecular weight of 1000 or more
8000 oligomers, and at least one terminal polar group of the polyethers is -CO_2R, -ROR, -
2. The method for manufacturing a magnetic recording medium according to claim 1, wherein ROH, -NH-R-OH, -NH_2, and -NCO are used.