JP2001195728A - Method for manufacturing glass substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass substrate for a magnetic disk while preventing foreign materials from depositing onto the glass substrate. SOLUTION: This method for manufacturing the glass substrate for the magnetic disk comprises a chemical reinforcement step to chemically reinforcing the polished glass substrate by ion exchange while immersing it in a fused liquid for ion exchange in such a state that it is housed in a housing frame and a washing step to wash the chemically reinforced glass substrate in such a state that it is housed in another housing frame made of the material different from that used at the chemical reinforcement step. The housing frame is provided with plural glass substrate holding members 1 parallel to one another and plural glass substrate holding parts 2 each of which is positioned in the part opposite to each of the members 1 and has V-shaped grooves formed almost at even intervals correspondingly to each of the members 1.

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 strengthened by chemical strengthening.

[0002]

2. Description of the Related Art Conventionally, aluminum has been used as a magnetic disk substrate of a magnetic disk device. However, recently, as the recording density of the magnetic disk device has been increased, in order to make the distance between the magnetic head and the magnetic disk narrower, the magnetic disk device has been replaced with a device using a glass substrate capable of this.

A glass substrate for a magnetic disk is polished with high precision so that the flying height of a magnetic head can be reduced, and has a strength enough to withstand use in a magnetic disk device. It is manufactured with increased strength by chemical strengthening.

However, such a conventional technique has the following problems. First, by increasing the recording density,
A high level of flatness on the surface of the magnetic disk is indispensable, and any protrusions on the surface of the magnetic disk will cause trouble in running the magnetic head. In order to reduce the flying height of the magnetic head, the surface of the magnetic disk is required to have a high flatness and a small surface roughness, and therefore, in addition to performing high-precision polishing, It is an important issue to prevent foreign matter from adhering to the glass substrate to form a projection. When a magnetic disk is formed on a glass substrate with extremely small foreign matter that cannot be removed by ordinary cleaning, and the magnetic film is formed on a magnetic disk, even the minute protrusions, even with the recent low head flying height, can be used. A disk device can cause trouble. Therefore, it is desired to prevent such minute foreign matter from adhering.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and provides a method of manufacturing a glass substrate for a magnetic disk in which foreign matter is prevented from adhering. Even if it is a minute foreign matter which has not been a problem in the related art, the foreign matter is prevented from adhering.

[0006]

According to a method of manufacturing a glass substrate for a magnetic disk of the present invention, a glass substrate having a polished surface is housed in a housing frame and immersed in a melt for ion exchange, and chemically strengthened by ion exchange. And a cleaning step of cleaning the glass substrate that has been subjected to the chemical strengthening treatment in a storage frame, wherein the chemical strengthening treatment step and the cleaning step are performed. And the storage frame for storing the glass substrate is made of a different material.

[0007] In the present invention, the above-mentioned storage frame is, for both reinforcement and cleaning, three parallel storage frames as shown in, for example, a plan view (a) and an elevation view (b) of FIG. A glass substrate holding member 1 is provided, and the glass substrate holding members 1
A plurality of glass substrate holders 2 each having a V-shaped groove formed in correspondence with each other are formed, and the glass substrates are held by the corresponding glass substrate holders 2 of the respective glass substrate holders 1. It has become. 2A and 2B show examples of the storage frame in which the number of the glass substrate holding members 1 is increased.

In the present invention, it is preferable that the storage frame in the chemical strengthening process is made of metal and the storage frame in the cleaning process is made of plastic resin.

The storage frame in the chemical strengthening process is preferably made of a metal that can withstand the high-temperature solution of the strengthening process, and the metal material may be, for example, S in consideration of corrosion resistance and durability.
Stainless steels such as US316, 304, 310 are preferably used. If the storage frame of the chemical strengthening process is used as it is in the cleaning step, cleaning of the storage frame is required, which takes a great deal of time. Therefore, it is preferable to replace the storage frame. A plastic resin having a lower hardness than glass is preferably used for the storage frame in the cleaning step. And, considering that the temperature of the cleaning liquid is usually 50 ° C. or higher, cleaning is performed,
For example, a heat-resistant material such as a polyacetal resin is preferably used.

In the present invention, the interval between the glass substrate holders 2 is substantially constant, and the interval is 3 mm or more.
It is preferably 0 mm or less.

If the distance between the glass substrate holding portions is less than 3 mm, the glass substrates are adjacent to each other due to the vibration of the glass substrates when the glass substrates are lifted up when the glass substrates are discharged from the storage frame using the glass substrate transfer jig. There is a possibility that the glass substrate comes into contact and the main surface of the glass substrate is scratched. Further, when the distance between the glass substrate holding portions exceeds 20 mm, the amount of air directly hitting the glass substrate increases, and the drying of the strengthening solution and the cleaning solution attached to the glass substrate surface after the strengthening process and the cleaning process is accelerated. There is a risk of causing poor quality such as warpage.

The glass substrate holding portion 2 of these storage frames is preferably formed in a V-shape when viewed from the side, and the angle of the V-shape is suitably 50 ° or more and 100 ° or less.

When the glass substrate holding portion is formed in a V-shape, a portion where the glass substrate holding portion 2 and the glass substrate are in point contact with each other and hardly contact with the liquid is minimized, so that a good processing result can be obtained.

If the opening angle of the V-shape is less than 50 °, the opening of the glass substrate holding portion 2 becomes narrower, so that all the glass substrates carried by the glass substrate transfer jig are simultaneously glass-coated. It is difficult to store the glass substrate in the substrate holding unit 2, and the possibility that the glass substrate that is not stored in the glass substrate holding unit comes into contact with an adjacent glass substrate increases, and the main surface of the glass substrate may be damaged. Occurs. Conversely, when the opening angle of the V-shape exceeds 100 °, the deflection of the glass substrate housed in the glass substrate holding unit 2 increases, so that the glass substrate transfer jig discharges the glass substrate. In addition, the glass substrate cannot be mounted on the desired glass substrate mounting portion. Therefore, it is difficult to house the glass substrate in the housing frame or the transport cassette in the next step without damaging the glass substrate.

Further, in the method of manufacturing a glass substrate for a magnetic disk according to the present invention, a plurality of glass substrates whose surfaces have been polished are parallelly arranged at regular intervals and stored in a storage frame for chemical strengthening treatment to form a molten liquid for ion exchange. A chemical strengthening process of immersing and performing a chemical strengthening process by ion exchange, and a washing process of washing a plurality of chemically strengthened glass substrates in a state of being stored in a washing housing frame in parallel at regular intervals. In the method for manufacturing a glass substrate for a magnetic disk, the glass substrate for a magnetic disk after the chemical strengthening process is washed from a storage frame for the chemical strengthening process by a glass substrate transfer jig in a state where the glass substrate is paralleled at regular intervals. It is characterized by being transferred to a glass substrate storage frame.

The glass substrate transfer jig 11 stores and discharges a plurality of glass substrates in a storage frame for strengthening and cleaning at one time. For example, as shown in FIG.
Further, a circular groove, that is, a glass substrate mounting portion 12 is formed at the same interval as the glass substrate holding portion 2 of the glass substrate holding member 1.

The glass substrate transfer jig 11 is inserted into the center hole of a donut-shaped glass substrate and hooks the glass substrate on each of the glass substrate mounting portions 12. After being placed on the substrate holding portion, the glass substrate is pulled out from the center hole of the glass substrate, whereby a large number of glass substrates can be stored in the storage frame at one time.

When detaching the glass substrates from the storage frame, the glass substrate transfer jig 11 is inserted into the center hole of each glass substrate placed on the storage frame, and After the glass substrates are hooked and lifted for each part 12, all the glass substrates can be taken out of the storage frame at a time.

The transfer of the glass substrate from the storage frame for chemical strengthening treatment to the storage frame for cleaning glass substrate can be performed in the same manner.

The glass substrate mounting portion 12 of the glass substrate transfer jig 11 is also preferably formed as a V-shaped groove.
The opening angle of the V-shaped groove is preferably 50 ° or more and 100 ° or less.

The reason why the opening angle of the V-shaped groove of the glass substrate transfer jig 11 is not less than 50 ° and not more than 100 ° is that the V-shaped angle of the glass substrate holding portion 2 of the storage frame is 5 °.
This is the same as the reason for setting the angle between 0 ° and 100 °.

[0022]

(Embodiment 1) By the following steps,
A glass substrate for a magnetic disk was manufactured.

First lapping step: First, a pressed glass base material is polished with an abrasive particle size of 30 μm, and the plate thickness is 0.9 mm.
Finished below. The base material may be formed by a float method.

Shape processing step: Next, a hole was made in the center of the glass substrate with a cylindrical grindstone, and then the inner and outer circumferences were ground to finish to predetermined outer and inner diameter dimensions. Thereafter, the end surface of the glass substrate was polished to a mirror-like shape while rotating the glass substrate by brush polishing, thereby preventing polishing flaws and adhesion of debris due to chipping in a later step.

Secondary rubbing step: Next, in order to remove scratches and pits generated in the primary rubbing and shape processing, polishing was performed with an abrasive particle size of 10 μm or less. After this polishing, the glass substrate was sequentially immersed in a chemical solution and pure water to wash off the abrasive and dry.

Primary polishing: Next, primary polishing was performed. The purpose of this step is to form the inner and outer peripheral end portions, and the polishing time was 60 minutes to remove 30 μm.

The glass substrate after this step was washed off the abrasive with a three-tank washer and then spin-dried.

Secondary polishing: Next, for the purpose of obtaining a glass substrate surface having good flatness and surface roughness, the polishing conditions were a pressure of 50 g / cm ² and a lower platen rotation speed of 50 rpm.
m, and removal of 5 μm was performed in a polishing time of 20 minutes.

After the completion of this step, the glass substrate was sequentially immersed in a bath of an acid detergent, an alkaline detergent, pure water and IPA to wash off the abrasive. In each tank, the supersonic liquid was applied while rocking.

Transfer step: Next, the glass substrate was transferred to a stainless steel storage frame for chemical strengthening by an automatic transfer device having a glass substrate mounting portion.
In this storage frame, the glass substrate is held by a glass substrate holding member on which a plurality of glass substrate holding portions are formed, and the glass substrate holding member is provided with three storage frames as shown in FIG. .

Chemical strengthening step: Next, chemical strengthening was performed to increase the strength of the glass substrate. The chemical strengthening was performed by placing a preheated glass substrate in a processing bath capable of controlling the temperature of the chemical strengthening processing solution, immersing the glass substrate in the strengthening bath for a predetermined time by automatic conveyance, and then gradually cooling the glass substrate.

Transfer step: Next, in order to prevent the storage frame for chemical strengthening with the strengthening solution from being carried into the cleaning tank in order to perform cleaning, the glass substrate is placed in a storage frame made of fluororesin dedicated to cleaning. Transferred. In addition, in this storage frame, the glass substrate is held by a glass substrate holding member in which a plurality of glass substrate holding portions are formed. As shown in FIG. 1, three glass substrate holding members are provided in the storage frame. I have.

Cleaning step: Next, in order to improve the surface roughness of the chemically strengthened glass substrate, the glass substrate after this step is sequentially immersed in a bath of an acid detergent, an alkaline detergent, pure water and IPA. To remove the deposits. In each tank, ultrasonic waves were applied while being rocked.

The surface roughness Ra of the main surface of the glass substrate obtained through the above steps was 0.5 nm or less. Furthermore, no deposits affecting glide height were found,
In particular, no deposits of 3 μm or less were observed.

The above results were obtained regardless of whether the size of the glass substrate was 3.0 inches or 3.5 inches and the thickness was changed.

(Examples 2 to 8 and Comparative Examples 1 to 4) A material which was used as an aluminosilicate glass base material and was pressed to a diameter of 67 mm and a thickness of 1.4 mm was firstly subjected to # 400 alumina using a double-side polishing machine. Wrapping of the front and back surfaces was performed with abrasive grains. Next, a prepared hole was formed on the inner periphery, and a predetermined chamfering process was performed on the inner peripheral surface and the outer peripheral surface side surface using an inner and outer peripheral processing machine.

Next, using a double-side polishing machine, lapping treatment was performed on the front and back surfaces using # 1000 alumina abrasive grains.
Subsequently, primary polishing was performed using cerium oxide as an abrasive. Further, final polishing was performed using cerium oxide and a soft polisher.

After that, before the chemical strengthening treatment, the flatness of the substrate was measured in advance, and it was confirmed by inspection that there was no flaw.
The glass substrate was held in a storage frame, preheated at 320 ° C. for 20 minutes, and then immersed in a chemical strengthening treatment solution at 400 ° C. for 60 minutes to perform a chemical strengthening treatment. Here, 6 mm, 9 mm, 12 mm, and 15 mm were set as the distance between the substrates of the storage frame of the embodiment of the present invention.
Of 4 mm, and 2 mm and 50 m as comparative examples
m.

Thereafter, the glass substrate held in the annealing furnace kept at 350 ° C. was put into the furnace, and cooled slowly for 40 minutes, and the flatness of the taken-out substrate was measured, and the change in the flatness before reinforcement was examined. . When the depth of the groove of the glass substrate mounting portion is less than 2 mm, it is easy to make contact with the adjacent glass, and when it exceeds 8 mm, it is too deep and the main surface of the glass easily hits the jig with a little shaking. The flatness was measured using a laser interferometer (F601, manufactured by FUJINON Corporation). In addition, after the substrate was washed, inspection was performed using a light source of 200,000 lux for scratches due to handling and scratches due to contact with the disk. Table 1 shows the results.

[0040]

[Table 1]

As a result, as shown in Table 1, when the distance between the substrates is 2 to 15 mm, the change in flatness before and after the chemical strengthening step is 0.5 to 0.7 μm on average in absolute value. On the other hand, when the substrate interval is 50 mm, the flatness change amount is as large as 3.6 mm. As for the flaws generated on the disc, the rate of occurrence was as large as 24% in the comparative example in which the distance between the substrates was 2 mm, and the others were as good as 3% or less.

As is apparent from the above results, when performing the chemical strengthening treatment and the slow cooling step after the final polishing according to the present invention, the distance between the storage frames of the glass substrates is kept at regular intervals within a certain range. Accordingly, it is possible to reduce the amount of change in flatness due to the chemical strengthening process, which has been difficult in the past, to reduce scratches, and to manufacture a glass substrate with a high yield.

[0043]

As described above, according to the method for manufacturing a glass substrate of the present invention, it is possible to prevent foreign substances from adhering to the glass substrate, so that a glass substrate for a magnetic disk having excellent surface properties can be manufactured and a low magnetic property can be obtained. The present invention can be used for a magnetic disk medium used in a magnetic disk device that performs high-density recording at a head flying height.

[Brief description of the drawings]

FIG. 1A is a plan view schematically showing a storage frame for storing a glass substrate according to an embodiment of the present invention. (B) is an elevation view which shows typically the storage frame which stores the glass substrate in one Example of this invention.

FIG. 2A is a schematic plan view showing a storage frame for storing a glass substrate according to another embodiment of the present invention. (B)
FIG. 4 is a schematic elevation view showing a storage frame for storing a glass substrate in another embodiment of the present invention.

FIG. 3 is a plan view schematically showing a main part of a rod-shaped member of a glass substrate transfer jig according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate holding member, 2 ... Glass substrate holding part, 11 ... Bar-shaped member, 12 ... Glass substrate mounting part.

Continuation of the front page (72) Inventor Masashi Iwashita 5358 Kawajiri, Yoshida-cho, Haibara-gun, Shizuoka Prefecture F-term in Asahi Techno Glass Co., Ltd. 5D112 AA02 AA24 BA03 GA08 GA26 KK01

Claims (7)

[Claims] 1. A chemical strengthening process in which a glass substrate whose surface is polished is immersed in a melt for ion exchange in a state of being stored in a storage frame to perform chemical strengthening by ion exchange; and A method for manufacturing a glass substrate for a magnetic disk, comprising: a cleaning step of cleaning while being stored in a storage frame, wherein the storage frame for storing the glass substrate is made of a different material in the chemical strengthening treatment step and the cleaning step. A method for producing a glass substrate for a magnetic disk. 2. The manufacturing of a glass substrate for a magnetic disk according to claim 1, wherein the storage frame used in the chemical strengthening process is made of metal, and the storage frame used in the washing process is made of plastic. Method. 3. The storage frame has a plurality of glass substrate holders each capable of holding a glass substrate, and a distance between the respective glass substrate holders is constant. A method for producing a glass substrate for a magnetic disk as described above. 4. The method of manufacturing a glass substrate for a magnetic disk according to claim 3, wherein an interval between the glass substrate holding portions of the storage frame is 3 mm or more and 20 mm or less. 5. The storage frame according to claim 1, wherein the glass substrate holding portion of the storage frame comprises V-shaped grooves formed at substantially equal intervals in a plurality of substrate holding members parallel to the storage frame. A method for producing a glass substrate for a magnetic disk according to any one of the preceding claims. 6. The angle of the V-shaped groove is 50 ° or more,
6. The method for manufacturing a glass substrate for a magnetic disk according to claim 5, wherein the angle is 100 [deg.] Or less. 7. A chemical strengthening process in which a plurality of glass substrates whose surfaces have been polished are immersed in an ion-exchange melt while being stored in a storage frame for chemical strengthening treatment in parallel at regular intervals, and subjected to chemical strengthening treatment by ion exchange. A method for manufacturing a glass substrate for a magnetic disk, comprising: a processing step; and a cleaning step of cleaning a plurality of the glass substrates subjected to the chemical strengthening treatment in a state of being stored in a cleaning storage frame in parallel at regular intervals. The glass substrate for magnetic disk after the tempering process is transferred from the storage frame for chemical strengthening process to the glass frame for cleaning by using a glass substrate transfer jig with the glass substrate transfer jig kept in parallel at regular intervals. Of manufacturing a magnetic disk glass substrate.