JPH10134348A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of abnormal projections during the use of a magnetic recording medium by successively forming a magnetic layer and a protective layer on a substrate, then subjecting the surface of this protective layer to an etching treatment. SOLUTION: A ground surface layer 2 consisting of a Cr film is formed on the main surface of the glass substrate 1 and the magnetic layer 3 consisting of a CoNiCrTa film is formed thereon. A liquid mixture contg. silica particles and tetraethoxysilane is applied on the magnetic layer 3 and is heat treated, by which the protective layer 4 dispersed with the silica particles is formed. Next, the surface of the protective layer 4 is subjected to an etching treatment by wet etching by hydrofluoric acid. The amt. of the metal oxide covering the upper parts of the silica particles may be decreased by executing the etching. A good result with respect to head burnishing is obtd. when the surface of the protective layer 4 is etched at 2 to 30% of the film thickness. A lubricant is applied on the layer 4 to form a lubricative layer 5, by which the magnetic disk is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic recording medium, and more particularly to a method for manufacturing a magnetic disk.

[0002]

2. Description of the Related Art With an increase in the amount of data handled by various data processing devices such as personal computers, larger recording capacities are also required for magnetic disk devices for storing data. In addition, as the size of computers has been reduced, the size of magnetic disk devices built into computers must also be reduced. In order to increase the capacity of a small magnetic disk device, the recording density of a magnetic disk (magnetic recording medium) must be increased. In addition, high reliability is required at the same time.

As described above, the CSS method is often used to obtain high density and high reliability. In the CSS system, when a magnetic disk is stopped in a magnetic disk device, a magnetic head is brought into contact with the magnetic disk, and when the magnetic disk rotates, utilizing the air flow accompanying the rotation of the magnetic disk, This is a control method for floating the magnetic head.

In such a CSS system, when the magnetic disk drive is started and stopped, the magnetic head slides on the magnetic disk, causing friction. If the amount of friction is large, adsorption is caused. Attraction of the magnetic head causes damage to the magnetic head and the magnetic disk. Therefore, in order to suppress the amount of friction, a texture (irregularities) is provided on the surface of the magnetic disk to reduce the contact area between the magnetic disk and the magnetic head.

Conventionally, various methods have been proposed for forming a texture. A method of forming irregularities on a substrate surface, a method of forming a thin film having an irregular surface on a substrate, and using a material in which particulate matter is dispersed in a binder as a material of a protective layer on the substrate surface, and forming a magnetic layer thereon. A method is provided in which unevenness is formed on the surface of the protective layer by applying the composition to a substrate and drying the applied composition. Among these methods, in the method of forming the protective layer, a projection is formed on the surface of the protective layer, which protrudes upward beyond the flying height (the distance between the magnetic head and the surface of the rotating magnetic disk). Specifically, after the formation of the protective layer, a burnishing step is provided for removing projections that collide with the magnetic head. At present, there are mainly two types of varnishes, one is a tape varnish in which a magnetic disk surface is polished using a tape-like polishing tape, and the other is a waffle head (a varnish) instead of a magnetic head. Head varnish to which the head is attached and the surface of the magnetic disk is polished.

[0006]

Conventionally, however, the protective layer material removed as a result of the above-described burnishing process is left as a shaving residue and remains on the surface of the magnetic disk or adheres to the burnishing head. There was a problem. In particular, recently, the recording density has been increased by making the distance between the magnetic head and the rotating magnetic disk surface smaller, and it is necessary to make the magnetic head fly lower and more stably. The removal amount of abnormal projections due to burnishing also gradually increased, and as a result, shaving residues often remained on the surface of the magnetic disk and adhered to the burnishing head. If the shavings remain on the surface of the magnetic disk, stable flying height cannot be guaranteed, and if the shavings adhere to the burnishing head, the burnishing head must be replaced frequently, resulting in mass production. It is a big hindrance.

[0007]

In order to solve the above-mentioned problems, the present invention provides a method in which a magnetic layer and a protective layer are sequentially formed on a substrate, and then the surface of the protective layer is etched. I do. Further, according to the present invention, after a magnetic layer and a protective layer are sequentially formed on a substrate, a scrub treatment is performed on the surface of the protective layer by adding an etchant.

[0008]

FIG. 1 is a schematic diagram showing a configuration of a magnetic disk manufactured by a method for manufacturing a magnetic recording medium according to an embodiment of the present invention. Hereinafter, the configuration of a magnetic disk manufactured by the manufacturing method of the embodiment of the present invention will be briefly described with reference to FIG. 1, and then the method of manufacturing the magnetic recording medium of the embodiment of the present invention will be described. .

As shown in FIG. 1, a magnetic disk manufactured by the manufacturing method according to the embodiment of the present invention comprises a base layer 2, a magnetic layer 3, and a protective layer 4 sequentially on a glass substrate 1.
And a lubrication layer 5.

The glass substrate 1 is made of aluminosilicate glass having an outer diameter of 95 mmφ, a central hole diameter of 25 mmφ, and a thickness of 0.1 mm.
It is formed in the shape of a disk of 8 mm, and its main surface is precisely polished so as to have a maximum surface roughness Rmax of 30 angstroms and then chemically strengthened. Here, as the chemically strengthened glass constituting the glass substrate 1, SiO ₂ is 62 to 75% and Al ₂ O ₃ is 5% by weight as main components.
１５15%, Li ₂ O 4-10%, Na ₂ O 4-12
%, Each containing ZrO ₂ 5.5 to 15%. Na ₂ O / ZrO ₂ is 0.5 to 2.0 in weight ratio, A
l ₂ O ₃ / ZrO ₂ is from 0.4 to 2.5 by weight ratio.
Then, such a glass for chemical strengthening is subjected to ion exchange treatment in a treatment bath containing Na ions and K ions, or Na ions or K ions to chemically strengthen the glass substrate 1.
And

The underlayer 2 is a 2,000 Å Cr film. The magnetic layer 3 is a CoNiCrTa film having a thickness of 500 Å. Here, CoNiCr
The composition ratio of the Ta film is represented by the atomic composition ratio of Co: Ni: Cr:
It has a composition of Ta = 66: 25: 8: 1. The protective layer 4 is formed by forming a metal oxide film containing colloidal silica ultrafine particles by a sol-gel method, and has a thickness of about 100 angstroms. The lubricating layer 5 is made of a lubricant made of perfluoropolyether (for example, ZD manufactured by Montezison).
DL # 2000) is applied on the protective layer 4 by an immersion method to form a film having a thickness of about 20 angstroms.

Next, a method for manufacturing a magnetic recording medium according to an embodiment of the present invention will be described. First, a sheet material of chemically strengthened glass was cut out and had an outer diameter of 95 mmφ and a central hole diameter of 25 m.
It is formed into a disk having a diameter of 0.8 mm and a diameter of 0.8 mm, and its main surface is precisely polished to a maximum surface roughness Rmax of about 3 mm.
The glass substrate 1 is obtained so as to have a thickness of 0 Å. Next, after cleaning the glass substrate 1, the main surface of the glass substrate 1 is coated with a C film having a film thickness of about 2000 angstroms by a sputtering method using a Cr target and Ar gas.
An underlayer 2 made of an r film is formed. Next, this underlayer 2
Then, a magnetic layer 3 made of a CoNiCrTa film having a thickness of about 500 angstroms is formed by a sputtering method using a CoNiCrTa target and Ar gas.

Next, tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ), which is a metal alkoxide, water, methanol, acetic acid, and namamide are mixed in a molar ratio of 1/2/10 / 0.1.
/0.01 to prepare a first solution.
In addition, silica particles having an average particle size of 100 angstroms (the average particle size was measured with a particle size distribution analyzer, Cole Counter N4 manufactured by Cole Counter Co., Ltd .; the same applies hereinafter), silica particles having a minimum maximum particle size of ± 30 angstroms, and an average particle size of Silica particles having a thickness of 350 angstroms and a maximum and a minimum particle size of ± 50 angstroms were respectively dissolved in methanol.
A second solution is prepared by dispersing 5 wt% and 5 wt% each. Then, the first solution, IPA (isopropyl alcohol) and the second solution are mixed at a ratio of 10: 100: 0.1, and the obtained mixed solution is applied on the magnetic layer 3 by spin coating. Then, heat treatment at 300 ° C. for 90 minutes,
By converting a metal alkoxide, tetraethoxysilane, to a silicon oxide, which is a metal oxide as a binder, to form a metal oxide film, silica particles having an average particle size of 100 Å in the metal oxide film are formed. A protective layer 4 in which silica particles having an average particle diameter of 350 angstroms are dispersed is formed on the magnetic layer 3 to a thickness of 110 angstroms. Here, when the existence density of the silica particles in the metal oxide film was measured by a scanning electron microscope,
For silica particles having an average particle diameter of 100 angstroms, it is about 100 particles / 1 μm square, and the average particle diameter is 35 μm.
For silica particles of 0 Å, about 10 particles /
It was 1 μm □.

Next, the surface of the protective layer 4 is etched by wet etching using hydrofluoric acid. This wet etching removes the metal oxide film by about 10 angstroms to form a protective layer 4 having a thickness of about 100 angstroms. By performing the etching as described above, the amount of the metal oxide film covering the upper part of the silica particles can be reduced. In this case, the silica particles may be exposed from the metal oxide film.

Next, a burnishing process is performed on the surface of the protective layer 4 using a burnishing head made of AlTiO ₂ (Altic) to remove the abnormal projections of the metal oxide film. Thereafter, the surface of the protective layer 4 was observed with a microscope, but no shaving residue and no silica particles were dropped off. Burnish was performed on 1,000 magnetic disks. However, metal oxide shavings hardly adhered to the burnish head, and the burnish head was not replaced during this time.

The relationship between the conditions of the wet etching and the results of the head burnish was examined by changing various conditions of the wet etching performed before the head burnish. Table 1 shows the results.

[Table 1] From this table, it can be seen that when the surface of the protective layer 4 is wet-etched by 2% to 30% with respect to the thickness of the protective layer 4, good results can be obtained with respect to head burnishing.

Finally, a lubricant made of perfluoropolyether is applied on the protective layer 4 by a dipping method to form a lubricating layer 5 having a thickness of about 20 angstroms, thereby completing a magnetic disk. About this magnetic disk, AlTi
Using a magnetic head having an O ₂ (altic) slider, a CSS test was performed in an atmosphere having an average relative humidity of 80% and an average temperature of 60 ° C. to obtain CSS durability (magnetism when the head repeatedly slides and flies). Disk durability). As a result, the magnetic disk manufactured in the present embodiment not only withstands the number of CSS times of 10,000 or more, but also has an average static friction coefficient with the magnetic head of about 0.5 after the number of CSS times of 10,000. It was an extremely small value. In addition, the magnetic head did not stick to the surface of the magnetic disk, and no head crash occurred. Burnish may be performed after forming a lubricating layer on the protective layer.

As described above, according to the manufacturing method of the embodiment of the present invention, the etching treatment is performed on the protective layer 4 before the burnishing step, whereby the generation of shaving residue at the time of burnishing is generated. Can be suppressed, stable flying height can be guaranteed, and smooth burnishing can be performed. In some cases, the burnishing step can be omitted. Further, since the shaving residue is small and the shaving residue does not remain on the surface of the magnetic disk, when reading / writing with the MR head (magnetic resistance type head), the TA head peculiar to the MR head generated when the MR head comes into contact with the shaving residue or the like. (Th
ermal Asperity: a phenomenon in which a resistance value changes due to thermal energy generated by a mechanical shock and a magnetic-resistance conversion is not normally performed. If the magnetic disk is used in a magnetic disk drive, it is possible to remove in advance fine particles that may become abnormal projections in the future when the magnetic disk is used in a magnetic disk drive. The occurrence of the above-mentioned TA due to the contact of the head can also be suppressed.

In the above embodiment, two types of silica particles (particulates) having an average particle diameter of 100 Å and 350 Å are dispersed in the metal oxide film of the protective layer 4. The average particle size of the product is 3
Preferably, it is 0 to 500 angstroms. Further, the particle diameter may be one kind,
Types or three or more types having different particle sizes may coexist. When two or more particle groups having different average particle diameters are used as the particles, for example, a particle having an average particle diameter in the range of 30 to 150 angstroms and a particle having an average particle diameter in the range of 150 to 500 angstroms are used. Particulates can be used. In the case where a particulate material including two or more types of particle groups having different average particle sizes is used, CSS durability under a high humidity environment is further improved. Further, as the particulate matter, for example, inorganic fine particles such as alumina, zirconia, titania, silicon carbide, and tungsten carbide, in addition to the silica fine particles used in the embodiment, can be used. In particular, from the viewpoints of hardness, wettability, and industrial ease of production, the particulate matter is preferably colloidal silica.

As the binder, one obtained by converting a metal alkoxide into a metal oxide as in the embodiment is preferable. The metal alkoxide can be appropriately selected depending on the type of the metal oxide serving as a protective layer to be formed. Examples of the metal of the metal alkoxide include silicon, aluminum, tantalum, tungsten, tin, zirconium, and titanium. Further, two or more kinds of metals can be used as the metal of the metal alkoxide. The metal alkoxide can be generally formed by a sol-gel method, but a metal alkoxide formed by a method other than the sol-gel method can also be used.

When a silicon oxide is formed as the metal oxide, a metal alkoxide may be used as a raw material for forming a metal oxide film made of silicon oxide.
Silicon alkoxide, a part thereof, or a hydrolyzate can be used. Examples of silicon alkoxides or partial or complete hydrolysates thereof include tetraethoxysilane, tetramethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, Tetra-te
tetraalkoxysilane such as rt-butoxysilane,
These include silicon alkoxides such as tetraalkoxysilane, dialkoxysilane, and trialkylmonoalkoxysilane, and parts or hydrolysates thereof. In addition, as long as a silicon oxide is formed by a sol-gel method, a silicon alkoxide other than the above, or a partial or complete hydrolyzate thereof can be used.

When the metal oxide is formed of aluminum oxide, an aluminum alkoxide formed by a sol-gel method or a partial or complete hydrolyzate thereof is used. Examples thereof include trialkoxyaluminums such as triethoxyaluminum, trimethoxyaluminum, tri-n-poloxyaluminum, tri-i-propoxyaluminum, tri-n-butoxyaluminum, and trialkyldialkoxyaluminums thereof. Alkoxides of aluminum, such as dialkyl monoalkoxy aluminum, and partial or complete hydrolysates thereof.

Further, by using alkoxides such as tantalum, tungsten, tin, zirconium, and titanium, and partial or complete hydrolysates thereof as metal alkoxides, oxide films of these metals can be formed. The metal oxide in the protective layer 4 is
It also includes oxides of metalloids such as oxides of silicon as described above. For the formation (hydrolysis) of the metal alkoxide, for example, a mixture of water, methanol, acetic acid, and formamide can be used. However, one or both of acetic acid and formamide may be omitted. Furthermore, without actively using water,
It is also possible to obtain a solution containing a hydrolyzate of a metal alkoxide by taking in water (steam) in the atmosphere. Also,
Ethyl alcohol or butyl alcohol may be used instead of methanol. The thickness of the protective layer 4 is 50
~ 500 Å is preferred.

In the case of wet etching, the protective layer 4 is etched using an aqueous ammonia solution, an aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous hydrofluoric acid solution, an aqueous ammonium fluoride solution, Silicic hydrofluoric acid, or a mixed solution of hydrofluoric acid and nitric acid, sulfuric acid, hydrochloric acid, or the like can be used. Further, depending on the material of the protective layer 4, an organic solvent can be used.
Hexane, acetone, benzene and the like can be mentioned. Also,
Dry etching can be used instead of wet etching. In the case of dry etching, CF ₄ , S
It is possible to use F ₆ , CHF ₃ , a mixed gas thereof, or a single or mixed gas of these gases with O ₂ added. Furthermore, in both cases of wet etching and dry etching, it is desired that the binder has a higher etching rate than the particulate matter.
Such etching selectivity depends on the material of the particulate matter and the binder, or on the type of etchant or etching gas.

The etching of the protective layer 4 is performed so as to remove the binder, for example, by 2% to 30% of the film thickness. By this etching, an excessive binder layer coated on the particulate matter can be removed. If the amount of the binder removed is too small, the effect of the etching is small, and if it is too large, the particulate matter cannot be fixed to the surface of the magnetic disk.

In the above embodiment, the glass substrate 1 is used as the nonmagnetic substrate, and the magnetic layer 3 is made of CoN.
Although the iCrTa film was used, the non-magnetic substrate and the magnetic layer are not particularly limited in the present invention. The non-magnetic substrate is preferably a glass substrate in consideration of flatness, but other than that, an aluminum substrate, a carbon substrate, or the like can be used. On the other hand, as the magnetic layer, CoPt, CoCr, CoNi,
CoNiCr, CoCrTa, CoPtCr, CoP
tCrTa, CoNiCrPt, CoNiCrTa, C
Co-based magnetic thin films such as oCrPtSiO, ferrite-based, iron rare earth-based, and the like. The magnetic layer may be of either horizontal magnetic recording or vertical magnetic recording. In addition, the magnetic layer is separated by a non-magnetic intermediate layer to reduce noise.
A multilayer structure such as oPtCr / CrMo / CoPtCr may be used.

An underlayer 2 may be provided between the nonmagnetic substrate and the magnetic layer as in the embodiment. Examples of the material of the underlayer 2 include nonmagnetic materials such as Cr, Mo, Ti, and Ta. Further, the protective layer 4
Can have a lubricating layer 5 as in the embodiment. The lubricating layer 5 is generally prepared by diluting perfluoropolyether (PEPE), which is a liquid lubricant, with a solvent such as Freon, and applying it to the medium surface by a dipping method, a spin coating method, or a spraying method. Is formed.

In the embodiment, the protective layer whose surface is made uneven by the particulate matter is formed. However, even when a uniform protective layer containing no particulate matter is formed, the burnishing step of the burnishing step is also performed. By performing the etching process before,
Exactly the same effects as in the embodiment can be obtained. When a uniform protective layer containing no particulate matter is formed, the unevenness of the underlayer is reflected on the uniform protective layer by forming the unevenness on the surface of the underlayer. Irregularities can be formed on the surface of the protective layer. Examples of the uniform film material include SiO ₂ , SiN, and C formed by a wet process or a dry process. Also in this case, the etchant and the etching gas described above can be suitably used as the etchant and the etching gas in the etching step. As a dry process for forming a film, a sputtering method is specifically mentioned.

Further, in the embodiment, the head varnish is used as the varnish process, but it may be a tape varnish. Further, although the etching step is performed before the burnishing step, a scrub step in which the surface of the protective layer is rubbed with a brush in an etching solution and the etching solution is added may be used instead of the etching process. According to the scrub process in which the etching solution is added, physical removal by a brush is added in addition to chemical removal by the etching solution, so that unnecessary protrusions can be more effectively removed. Further, since unnecessary projections can be removed without etching the surface of the protective layer so deeply, the removal of unnecessary projections can be effectively performed by preventing the particulate matter from falling off. In addition, of course, by performing this scrubbing process, generation of shaving residues at the time of burnishing can be suppressed.

[0030]

As described above, according to the method of manufacturing a magnetic recording medium of the present invention, the surface of the protective layer is subjected to etching or scrubbing with an etching solution before the burnishing step. In addition, the generation of shaving residues at the time of burnishing can be suppressed, a stable flying height can be guaranteed, and smooth burnishing can be performed. In some cases, the burnishing step can be omitted. Furthermore, since the shaving residue is small and the shaving residue does not remain on the surface of the magnetic recording medium, the TA of the MR head when reading and writing with the MR head can be reduced. further,
Fine particles that become abnormal projections when the magnetic recording medium is actually used can be removed by etching or scrubbing with an etchant in advance, so that abnormal projections occur during use of the magnetic recording medium, and The occurrence of the above TA due to the MR head contacting the abnormal projection can also be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a magnetic disk manufactured by a method for manufacturing a magnetic recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 1 glass substrate 3 magnetic layer 4 protective layer

Claims (11)

[Claims] 1. A method for manufacturing a magnetic recording medium, comprising: forming a magnetic layer and a protective layer on a substrate in that order; and etching the surface of the protective layer. 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the etching process is performed by wet etching or dry etching. 3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the surface of the protective layer is removed by 2% to 30% of the thickness of the protective layer by etching. The method of manufacturing the medium. 4. A method for manufacturing a magnetic recording medium, comprising: after sequentially forming a magnetic layer and a protective layer on a substrate, performing a scrub treatment by adding an etchant to the surface of the protective layer. 5. The method for manufacturing a magnetic recording medium according to claim 1, wherein a burnishing step is performed on the surface of the protective layer after the etching process or the scrubbing process. A method for manufacturing a magnetic recording medium. 6. The method for manufacturing a magnetic recording medium according to claim 1, wherein the protective layer includes a particulate matter and a binder. 7. The method for manufacturing a magnetic recording medium according to claim 6, wherein the binder has a higher etching rate than the particulate matter. 8. The method for manufacturing a magnetic recording medium according to claim 6, wherein the particulate matter comprises two or more kinds of particles having different average particle diameters. 9. The method for manufacturing a magnetic recording medium according to claim 6, wherein the particulate matter is colloidal silica. 10. The method of manufacturing a magnetic recording medium according to claim 6, wherein the binder is made of a metal oxide. 11. The method for manufacturing a magnetic recording medium according to claim 1, wherein the protective layer is formed by a sputtering method.