JP2998948B2 - Method of manufacturing glass substrate for magnetic disk and method of manufacturing magnetic disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass substrate for a magnetic disk used for a hard disk or the like and a method for manufacturing a magnetic disk.

[0002]

2. Description of the Related Art Aluminum substrates have been widely used as glass substrates for magnetic disks. However, with the miniaturization and thinning of magnetic disks, glass substrates having higher flatness than aluminum substrates and capable of being made thinner have been developed. The rate of use is also increasing.

When a glass substrate is used as a magnetic disk substrate, the surface of the glass substrate is generally subjected to a chemical strengthening treatment by a low-temperature ion exchange method for the purpose of improving impact resistance and vibration resistance. .

[0004] The chemical strengthening is performed after the glass substrate is ground and polished. In addition, there is a substrate cleaning process as a pre-process of the chemical strengthening process. This washing step is performed with pure water, for example, as described in JP-A-2-285508.

[0005]

Conventionally, polishing of a glass substrate has been performed on the front and back surfaces of the glass substrate, but not on the outer peripheral end surface or the inner peripheral end surface of the glass substrate. Therefore, these end faces have a rough surface, and when carrying the glass substrate or taking the glass substrate in and out of the storage case, the end faces may be rubbed and dust may be generated from the end faces. Was.

In recent years, with the increase in density of magnetic disks, slight dusting has also become a problem.

Although it is possible to polish the end face, it is difficult to polish the surface to such a degree that dust can be prevented, which increases the cost. It is also possible to chemically etch the end face, but if the etching power is too strong, an end face with good surface roughness may not be obtained. The roundness may be impaired, causing misalignment and resulting in a defective product. On the other hand, if the etching force is too strong, the surface roughness of the end face may be deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in view of the above circumstances, and is capable of preventing generation of dust from a glass end face without deteriorating roundness and without deteriorating surface roughness of the end face. A first object is to provide a method for manufacturing a glass substrate for use.

A second object of the present invention is to provide a method for manufacturing a magnetic disk capable of eliminating defects due to dust generation from the glass end face, improving product yield, improving product quality, and reducing the occurrence of defects during product use. Aim.

[0010]

In order to achieve the above object, a method of manufacturing a glass substrate for a magnetic disk according to the present invention comprises treating at least an end surface of a glass substrate formed into a disk shape with a processing solution containing citric hydrofluoric acid. After the glass substrate formed into a disk shape is sanded or polished at least, the entire glass substrate is treated with a processing liquid containing hydrofluoric acid.

Further, the method for producing a glass substrate for a magnetic disk according to the present invention is the above method for producing a glass substrate for a magnetic disk, wherein the concentration of silicic acid is 0.01 to 10% by weight. A structure of aluminosilicate glass or soda lime glass, or a structure provided with a step of chemically strengthening the surface of a glass substrate by an ion exchange method as a post-process of the method of manufacturing a glass substrate for a magnetic disk.

Further, in the method of manufacturing a magnetic disk according to the present invention, at least a magnetic layer is formed on the glass substrate for a magnetic disk as a post-process of the method of manufacturing a glass substrate for a magnetic disk.

[0013]

According to the present invention, since the end surface of the glass substrate is treated with silica hydrofluoric acid, the surface roughness of the end surface of the glass substrate is improved, and dust generation from the glass end surface can be prevented.

Further, since the etching power of the silica hydrofluoric acid is not so strong, the surface roughness of the glass substrate end surface (Rmax 2 μm or less) can be made good enough to prevent dust generation, and the roundness of the glass substrate can be reduced. There is no loss.

Further, when the entire glass substrate is treated with hydrofluoric acid, polishing and grinding scratches on the surface of the glass substrate can be reduced.

Further, according to the method of manufacturing a magnetic disk of the present invention, it is possible to reduce the attachment of foreign matter due to dust generation, the polishing of the glass substrate surface, and the reduction of grinding flaws. Can be manufactured with high yield.

Hereinafter, the present invention will be described in detail.

In the method of manufacturing a glass substrate for a magnetic disk according to the present invention, at least the end surface (including the chamfered portion and the side wall portion) of the disk-shaped glass substrate is treated with a hydrofluoric acid-containing treatment solution (hereinafter referred to as a silicon fluoric acid). Acid treatment solution).

Here, the treatment with the hydrofluoric acid treatment solution (hereinafter referred to as the hydrofluoric acid treatment) may be performed after any of the steps of grinding and polishing the glass substrate formed into a disk shape, or May be performed after. Normally, it is preferable to perform a silica hydrofluoric acid treatment after the fine grinding step. The steps of grinding and polishing are usually roughly divided,
(1) Roughing (rough grinding), (2) Sanding (fine grinding),
It comprises (3) first polishing and (4) second polishing (final polishing).

The hydrofluoric acid treatment may be performed by bringing only the end surface of the glass substrate into contact with the hydrofluoric acid treatment liquid, or may be performed by bringing the entire glass substrate into contact with the hydrofluoric acid treatment liquid. In order to contact only the end face of the glass substrate with the hydrofluoric acid treatment solution, for example, the glass substrates are overlaid,
This may be immersed in a hydrofluoric acid treatment solution.

When the entire glass substrate is brought into contact with the hydrofluoric acid treatment liquid, the surface of the glass substrate can be washed together. Therefore, if the cleaning with the fluorinated acid treatment liquid is performed instead of the conventional cleaning with pure water or the like, the cleaning of the glass substrate and the end face treatment of the glass substrate can be performed simultaneously in one step, and the cost increase due to the increase in the number of steps can be avoided. .

The silica hydrofluoric acid treatment is preferably performed on the outer peripheral end face and the inner peripheral end face of the glass substrate, but it is also possible to treat only one of them.

A typical example of hydrofluoric acid is hydrofluoric acid (H ₂ SiF ₆ ).
To enhance the cleaning effect, etc., add a small amount of hydrofluoric acid (hydrofluoric acid, etc.) or a commercially available cleaning agent (neutral detergent, surfactant, alkaline detergent, etc.) to the silica hydrofluoric acid treatment liquid to enhance the cleaning effect, etc. You may.

The concentration of silicic acid is preferably about 0.01 to 10% by weight. When the concentration of silica hydrofluoric acid is
If it is less than 0.01%, the etching effect and the cleaning effect are reduced, and if it exceeds 10%, the surface becomes rough and dust is generated.

The processing time is preferably in the range of about 1 to 10 minutes. If the processing time is less than 30 seconds, the surface roughness of the glass substrate does not become good enough to prevent dust generation (Rmax 2 μm or less), and if it exceeds 15 minutes, the roundness of the glass substrate is impaired, The surface roughness of the end face is deteriorated. When the hydrofluoric acid treatment is performed after each of the grinding and polishing steps, the total treatment time may be within this range.

The processing temperature is preferably about 10 to 50 ° C.

The type, size, thickness and the like of the glass substrate are not particularly limited. Examples of the material of the glass substrate include aluminosilicate glass, soda lime glass, sodaaluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, and chain silicate glass. Silica hydrofluoric acid has good controllability of chemical etching especially for aluminosilicate glass, and therefore, it is possible to very easily make the glass substrate end surface have a good surface roughness enough to prevent dust generation. Does not impair the roundness of the

As the aluminosilicate glass, Si
O ₂ : 62 to 75% by weight, Al ₂ O ₃ : 5 to 15% by weight,
Li ₂ O: 4 to 10% by weight, Na ₂ O: 4 to 12% by weight,
ZrO _2: 5.5 to 15 with containing by weight% as the main component, the weight ratio of Na ₂ O / ZrO ₂ is 0.5 to 2.
0, a glass for chemical strengthening or the like having a weight ratio of Al ₂ O ₃ / ZrO ₂ of 0.4 to 2.5 is preferred. Such an aluminosilicate glass is enhanced in bending strength by chemical strengthening, has a deep compressive stress layer, and is excellent in Knoop hardness.

In the present invention, a step of chemically strengthening the surface of the glass substrate by an ion exchange method may be provided as a post-process of the method of manufacturing the glass substrate for a magnetic disk. Here, the chemical strengthening method is not particularly limited as long as it is a conventionally known chemical strengthening method. For example, low-temperature chemical strengthening in which ion exchange is performed in a region not exceeding a transition temperature from the viewpoint of a glass transition point is preferable. . Examples of the alkali molten salt used for chemical strengthening include potassium nitrate and sodium nitrate, and nitrates obtained by mixing them.

It is also possible to subject the glass substrate for a magnetic disk after chemical strengthening to the above-mentioned hydrofluoric acid treatment.

The method for manufacturing a glass substrate for a magnetic disk according to the present invention can also be used as a method for treating an end surface of a glass substrate for a magneto-optical disk or an electronic optical disk substrate such as an optical disk which does not want to generate dust.

Next, a method for manufacturing a magnetic disk according to the present invention will be described.

The method for manufacturing a magnetic disk according to the present invention includes the following steps as a step after the method for manufacturing a glass substrate for a magnetic disk.
At least a magnetic layer is formed on a glass substrate for a magnetic disk.

In the present invention, since a glass substrate with little dust and defects is used, the quality of the magnetic disk is high. In other words, there is far less dust generation than before,
By using a glass substrate having a good surface condition, bed crash does not occur when a magnetic disk is used, and a defect such as a defect in a film such as a magnetic layer does not cause an error.

The magnetic recording medium is usually manufactured by sequentially laminating an underlayer, a magnetic layer, a protective layer, and a lubricating layer on a glass substrate for a magnetic disk.

The magnetic recording medium usually has a predetermined flatness and surface roughness, and is provided with an underlayer, a magnetic layer, a protective layer and a lubricating layer on a magnetic disk glass substrate having a surface chemically strengthened. It is manufactured by sequentially laminating.

As the underlayer in the magnetic recording medium,
Non-magnetic thin films such as Cr, Mo, Ta, Ti, W and Al may be used, and a multi-layer underlayer such as Al / Cr / CrMo or Al / Cr / Cr may be used.

As the magnetic layer, for example, a magnetic thin film such as CoPtCr or CoNiCrTa containing Co as a main component can be cited. It may have a multilayer structure. Note that the magnetic layer may be either a horizontal magnetic recording or a perpendicular magnetic recording.

Examples of the protective layer include a Cr film, a Cr alloy film, a carbon film, a zirconia film, and a silica film. These protective films can be continuously formed with an underlayer, a magnetic layer, and the like by an in-line type sputtering apparatus. Further, these protective films may have a single-layer structure or a multi-layer structure composed of the same or different films. Another protective layer may be further formed on the protective layer. For example, on the protective layer, tetraalkoxylan is diluted with an alcohol-based solvent, applied, and further baked to form silicon oxide (Si).
O ₂ ) film may be formed.

The lubricating layer is prepared, for example, by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon, and applying it to the medium surface by dipping, spin coating, or spraying. It is formed by performing heat treatment.

[0041]

EXAMPLES The present invention will be described below more specifically based on examples.

Example 1

(1) Roughing Step First, a glass substrate made of aluminosilicate glass cut out from a sheet glass formed by a downdraw method into a disk shape having a diameter of 96 mmφ and a thickness of 3 mm with a grinding wheel,
Grinding with a relatively rough diamond wheel
It was molded to a diameter of 1.5 mm and a thickness of 1.5 mm.

As the aluminosilicate glass, SiO ₂ : 63% by weight, Al ₂ O ₃ : 14% by weight, L
i ₂ O: 6% by weight, Na ₂ O: 10% by weight, ZrO ₂ : 7
Glass for chemical strengthening containing wt% as a main component was used.

Next, both surfaces of the glass substrate were ground one by one with a diamond grindstone having a finer grain size than the grindstone. The load at this time was about 100 kg. As a result, the surface roughness of both surfaces of the glass substrate can be reduced to Rmax (JIS
(Measured with B0601).

Next, a hole is made in the center of the glass substrate using a cylindrical grindstone, and the outer peripheral end surface is also ground to a diameter of 95 mmφ. Then, the outer peripheral end surface and the inner peripheral surface are subjected to predetermined chamfering. did. At this time, the surface roughness of the end face of the glass substrate was about Rmax 4 μm.

First cleaning step

The surface of the glass substrate after the shape processing was washed with water.

(2) Sanding (Lapping) Step Next, the glass substrate was sanded. This sanding step aims at improving dimensional accuracy and shape accuracy.
The sanding process was performed using a lapping device, and was performed twice while changing the grain size of the abrasive grains to # 400 and # 1000.

More specifically, first, the load L was set to about 100 kg using alumina abrasive grains having a grain size of # 400.
By rotating the internal rotation gear and the external rotation gear, both sides of the glass substrate housed in the carrier are surface-accurate 0-1 μm,
Lapping was performed to a surface roughness (Rmax) of about 6 μm.

Next, the particle size of the alumina abrasive grains was changed to # 1000.
Perform lapping instead of surface roughness (Rmax) 2μ
m.

Second Cleaning Step The glass substrate after the above sanding was washed by sequentially immersing it in each of washing tanks of hydrofluoric acid (concentration: 2%), neutral detergent, neutral detergent and water.

The immersion time in the hydrofluoric acid was about 1 to 3 minutes. Ultrasonic waves were applied to each cleaning tank.

The surface roughness of the outer peripheral end face and the inner peripheral end face was reduced to 3 μm by the washing using the silica hydrofluoric acid. Further, the roundness was not impaired.

(3) First Polishing Step Next, a first polishing step was performed. This first polishing step is intended to remove scratches and distortion remaining in the above sanding step, and was performed using a polishing apparatus.

More specifically, the first polishing step was carried out under the following polishing conditions using a hard polisher (cerium pad MHC15: manufactured by Speed Fam) as a polisher (polishing powder).

Polishing liquid: cerium oxide + water Load: 300 g / cm ² (L = 238 kg) Polishing time: 15 minutes Removal amount: 30 μm Lower platen rotation speed: 40 rpm Upper platen rotation speed: 35 rpm Gear rotation speed in the inner part: 14 rpm Outer gear rotation speed: 29 rpm

Third Cleaning Step The glass substrate after the first polishing step is subjected to a hydrofluoric acid (concentration: 2%), a neutral detergent, a neutral detergent, pure water, pure water, IP
A (isopropyl alcohol) and IPA (steam drying) washing tanks were sequentially immersed in each of the washing tanks for washing.

The immersion time in the hydrofluoric acid was about 1 to 3 minutes. In addition, ultrasonic waves were applied to each cleaning tank.

The surface roughness of the outer peripheral end face and the inner peripheral end face was reduced to 2 μm by the washing using the silica hydrofluoric acid. Further, the roundness was not impaired.

(4) Second Polishing Step Next, using the polishing apparatus used in the first polishing step, the polisher was changed from a hard polisher to a soft polisher (Polyak: manufactured by Speed Fam), and the second polishing step was performed. Carried out. The polishing conditions were the same as in the first polishing step, except that the load was 100 g / cm ² , the polishing time was 5 minutes, and the removal amount was 5 μm.

Fourth Cleaning Step The glass substrate after the second polishing step is sequentially placed in each of cleaning tanks of a neutral detergent, a neutral detergent, pure water, pure water, IPA (isopropyl alcohol) and IPA (steam drying). Soak and
Washed.

Note that ultrasonic waves were applied to each cleaning tank.

(5) Chemical Strengthening Step Next, the glass substrate after the grinding and polishing steps was chemically strengthened. For the chemical strengthening, a chemical strengthening solution in which potassium nitrate (60%) and sodium nitrate (40%) are mixed is prepared, and the chemical strengthening solution is heated to 400 ° C., and the cleaned glass substrate preheated to 300 ° C. is washed. The immersion was performed for 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, the immersion was performed in a state where a plurality of glass substrates were housed in a holder so as to be held at end faces.

As described above, by performing the immersion treatment in the chemical strengthening solution, the lithium ions and the sodium ions on the surface layer of the glass substrate become the sodium ions in the chemical strengthening solution,
The glass substrate is strengthened by being respectively substituted by potassium ions.

The thickness of the compressive stress layer formed on the surface of the glass substrate was about 100 to 200 μm.

The glass substrate having been subjected to the above-mentioned chemical strengthening is replaced by 20
It was immersed in a water bath at a temperature of 10 ° C. and rapidly cooled and maintained for about 10 minutes.

Fifth Cleaning Step The glass substrate which had been quenched was immersed in sulfuric acid heated to about 40 ° C., and washed while applying ultrasonic waves.

When the surface of the glass substrate thus obtained was inspected, no foreign matter was found. The cleaning using sulfuric acid did not change the surface roughness and the roundness of the outer peripheral end surface and the inner peripheral end surface.

(6) Magnetic Disk Manufacturing Process A Cr underlayer, a CrMo underlayer, a CoPtCr magnetic layer, and a C protection are formed on both surfaces of the glass substrate for a magnetic disk obtained through the above-described processes by using an in-line sputtering apparatus. The layers were sequentially formed to obtain a magnetic disk.

When a glide test was performed on the obtained magnetic disk, no hit (the head touches a protrusion on the magnetic disk surface) or crash (the head collides with the protrusion on the magnetic disk surface) was not recognized. . In addition, since no foreign matter or defect due to dust was generated on the substrate surface, it was confirmed that no defect was generated in the film such as the magnetic layer.

Example 2 A cleaning treatment with silica hydrofluoric acid (processing time: 5 minutes) was performed only in the second cleaning step, and the magnetic flux was processed in the same manner as in Example 1 except that silica hydrofluoric acid was not used in the other cleaning steps. A glass substrate for a disk and a magnetic disk were obtained.

The results were the same as in Example 1.

Example 3 A glass substrate for a magnetic disk and a magnetic disk were obtained in the same manner as in Example 1 except that the washing treatment with silica hydrofluoric acid was performed in each of the second to fourth washing steps.

The results were the same as in Example 1.

Examples 4-5 Glass for magnetic disks was prepared in the same manner as in Example 1 except that soda lime glass (Example 3) and soda aluminosilicate glass (Example 4) were used instead of aluminosilicate glass. A substrate and a magnetic disk were obtained.

As a result, in the case of soda-lime glass, the surface roughness of the outer peripheral end surface and the inner peripheral end surface of the glass substrate was 3 μm, which was slightly rougher than aluminosilicate glass, but was practically used in terms of dust generation prevention. There was no problem.

Example 6 On both surfaces of the glass substrate for a magnetic disk obtained in Example 1, Al (film thickness 50 Å) / Cr (100
0 Å / CrMo (100 Å), CoPtCr (120 Å) / CrMo (50 Å) / Co
A magnetic layer made of PtCr (120 Å),
A Cr (50 Å) protective layer was formed by an in-line type sputtering apparatus.

The above substrate is immersed in an organic silicon compound solution (a mixed solution of water, IPA and tetraethoxysilane) in which fine silica particles (particle size: 100 Å) are dispersed,
A protective layer made of SiO ₂ is formed by firing, and a dip treatment is performed on the protective layer with a lubricant made of perfluoropolyether to form a lubricating layer.
A magnetic disk for an R head was obtained.

When a glide test was performed on the obtained magnetic disk, no hit or crash was recognized. It was also confirmed that no defect occurred in the film such as the magnetic layer.

Example 7 The underlayer was made of Al / Cr / Cr, and the magnetic layer was made of CoNiCr.
A magnetic disk for a thin film head was obtained in the same manner as in Example 5 except that Ta was used.

It was confirmed that the magnetic disk was the same as in Example 5.

Reference Example 1 A glass substrate for a magnetic disk and a magnetic disk were obtained in the same manner as in Example 1 except that no washing treatment with silica hydrofluoric acid was performed and hydrofluoric acid was used instead of silica hydrofluoric acid in the cleaning step. Was.

As a result, the surface roughness of the outer peripheral end face and the inner peripheral end face of the glass substrate was 4 to 5 μm, and the roundness was degraded to a value outside the permissible range, resulting in misalignment and a defective product. . Thus, it can be seen that the treatment with hydrofluoric acid causes large damage to the glass and poor etching controllability.
When a glide test was performed on the obtained magnetic disk, hits and crashes were found.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not necessarily limited to the above embodiments.

For example, in the washing step, a commercially available surfactant or detergent (including an alkaline type) can be used instead of the neutral detergent.

Further, cerium oxide (Ce) was used as an abrasive.
O ₂ ), alumina (γ-Al ₂ O ₃ ), and red iron (Fe ₂ O)
₃ ), chromium oxide (Cr ₂ O ₃ ), zirconium oxide (Z
rO ₂ ), titanium oxide (TiO ₂ ) and the like can also be used. As the soft polisher, a material made of suede or velor may be used. As the hard polisher, a hard velor, urethane foam, pitch impregnated suede, or the like may be used.

[0088]

As described above, according to the method of manufacturing a glass substrate for a magnetic disk of the present invention, the end surface of the glass substrate is treated with hydrofluoric acid, so that the surface roughness of the end surface of the glass substrate is improved. In addition, dust generation from the glass end face can be prevented.

Further, since the etching power of the silica hydrofluoric acid is not so strong, the roundness of the glass substrate is not impaired and the surface roughness of the end face of the glass substrate is not deteriorated.

Further, according to the method of manufacturing a magnetic disk of the present invention, it is possible to reduce the attachment of foreign matter due to dust generation, the polishing of the glass substrate surface, and the reduction of grinding scratches. Can be manufactured with high yield.

Claims (6)

(57) [Claims] 1. A method for manufacturing a glass substrate for a magnetic disk, comprising: treating at least an end surface of a glass substrate formed into a disk shape with a processing liquid containing silica hydrofluoric acid. 2. A method for manufacturing a glass substrate for a magnetic disk, comprising: after at least sanding or polishing a disk-shaped glass substrate, treating the entire glass substrate with a treatment liquid containing silicic acid. 3. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the concentration of silicic acid is 0.01 to 10% by weight. 4. The method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the glass substrate is aluminosilicate glass or soda lime glass. 5. The magnetic method according to claim 1, wherein a step of chemically strengthening the surface of the glass substrate by an ion exchange method is provided as a post-process of the method for manufacturing a glass substrate for a magnetic disk according to claim 1. A method for manufacturing a glass substrate for a disk. 6. A magnetic disk according to claim 1, wherein at least a magnetic layer is formed on the magnetic disk glass substrate as a post-process of the method for manufacturing a magnetic disk glass substrate according to claim 1. Manufacturing method.