WO2014148421A1

WO2014148421A1 - Method for producing glass substrate for information recording medium

Info

Publication number: WO2014148421A1
Application number: PCT/JP2014/057103
Authority: WO
Inventors: 葉月中江
Original assignee: Hoya株式会社
Priority date: 2013-03-22
Filing date: 2014-03-17
Publication date: 2014-09-25

Abstract

This method for producing a glass substrate for an information recording medium is a method for producing a glass substrate for magnetic recording, said method being provided with: a step for molding a disc-shaped glass substrate; a first cleaning step (S191) for, upon polishing the glass substrate using an abrasive, cleaning the polished glass substrate using a brush; and a second cleaning step (S192) for, subsequent to the first cleaning step (S191), emitting a liquid to which ultrasonic waves have been applied to the glass substrate so as to clean the glass substrate. The second cleaning step (S192) is started without immersing the glass substrate for which the first cleaning step (S191) has been completed in another liquid and before the surface of the glass substrate has dried.

Description

Manufacturing method of glass substrate for information recording medium

The present invention relates to a method for producing a glass substrate for an information recording medium.

Conventionally, an aluminum substrate or a glass substrate is used as an information recording medium (magnetic disk recording medium) used in a computer or the like. A magnetic thin film layer is formed on these substrates, and information is recorded on the magnetic thin film layer by magnetizing the magnetic thin film layer with a magnetic head.

Recently, a hard disk drive device has been developed which has a recording capacity of 500 GB (single side 250 GB) and a surface recording density of 630 Gb / square inch or more with one 2.5 inch recording medium.

Since a glass substrate for hard disk (hereinafter simply referred to as “glass substrate”) used for an information recording medium (platter) of a hard disk drive device affects reading / writing of recording, cleanliness is particularly required. For glass substrate cleaning, there are known batch-type ultrasonic cleaning methods in which ultrasonic waves are applied to the liquid in which the glass substrate is immersed to clean the glass substrate, and scrub cleaning process methods in which the brush is cleaned while contacting the substrate surface. It has been.

These cleaning methods have several problems. In the batch type ultrasonic cleaning method, an object to be cleaned is immersed in a liquid (mainly water, cleaning liquid, etc.), and cleaning is performed by applying ultrasonic waves (US) from a certain direction. The cleaning effect is generally low, and the dirt peeled off from the substrate by ultrasonic waves diffuses into the liquid. However, some dirt cannot be diffused and reattaches to the surface of the glass substrate. In particular, a minute defect is less likely to be diffused into the liquid, and thus reattachment of dirt is likely to occur.

The scrub cleaning process has a very strong cleaning power because the brush is cleaned while directly contacting the object to be cleaned. However, the removed dirt is accumulated on the brush, and once removed, the dirt is rubbed against the glass substrate again, and often reattaches to the surface of the glass substrate.

As a method for solving such a problem, an apparatus that performs washing while applying ultrasonic waves to a liquid in running water and constantly irradiating an object to be washed with Japanese Unexamined Patent Application Publication No. 2009-166043 (Patent Document 1). And JP-A-2007-22866 (Patent Document 2).

JP 2009-166043 A JP 2007-22866 A

When a glass substrate manufactured by a method for manufacturing a glass substrate for an information recording medium including an ultrasonic cleaning method is mounted on a hard disk drive device having a high density storage capacity, a read / write error may occur. This is proportional to the number of residual deposits present on the surface of the glass substrate in the manufacturing process.

The present invention has been made in view of the above circumstances, and is an information recording medium capable of suppressing adhesion of residual deposits on the surface of a glass substrate in the manufacturing process of the glass substrate for information recording medium. An object of the present invention is to provide a method for manufacturing a glass substrate.

In the manufacturing method of the glass substrate for information recording media based on this invention, it is a manufacturing method of the glass substrate for magnetic recording, Comprising: The process of shape | molding a disk shaped glass substrate, The said glass substrate is grind | polished using an abrasive | polishing agent. And a first cleaning step of cleaning the polished glass substrate using a brush, and after the first cleaning step, the glass substrate is irradiated with a liquid to which an ultrasonic wave is applied, and the glass substrate A second cleaning step for cleaning the glass substrate, wherein the second cleaning step dries the surface of the glass substrate without immersing the glass substrate after the first cleaning step in another liquid. The second cleaning step is started before.

In another form, in the second cleaning step, the frequency of the ultrasonic wave applied to the liquid is 400 kHz or more and 1.5 MHz or less, and the output is 5 W / cm ² or more and 50 W / cm ² or less.

In another embodiment, in the second cleaning step, the glass substrate is cleaned by holding the glass substrate so that the planar portion of the glass substrate is vertical.

In another embodiment, in the second cleaning step, the glass substrate is cleaned by rotating the glass substrate to 200 rpm or more and 2000 rpm or less.

In another embodiment, in the second cleaning step, the glass substrate is cleaned by irradiating both surfaces of the glass substrate with a liquid to which ultrasonic waves are applied simultaneously.

According to the method for manufacturing a glass substrate for information recording medium based on the present invention, in the manufacturing process of the glass substrate for information recording medium, it is possible to suppress the adhesion of residual deposits on the surface of the glass substrate. It is possible to provide a method for manufacturing a glass substrate for a medium.

It is a perspective view which shows an information recording device. It is a top view which shows the glass substrate manufactured by the manufacturing method of the glass substrate for information recording media based on this Embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a top view which shows the information recording medium provided with the glass substrate 1 as an information recording medium. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. It is a flowchart which shows the manufacturing method of a glass substrate. It is a front view which shows typically the holding state of a glass substrate. It is a right view which shows typically the holding state of a glass substrate. It is a front view which shows typically schematic structure of the holding | maintenance apparatus of a glass substrate. It is a right view which shows typically schematic structure of the holding | maintenance apparatus of a glass substrate. It is a front view which shows roll scrub cleaning typically. It is a right view which shows roll scrub cleaning typically. It is a front view which shows cup scrub cleaning typically. It is a right view which shows cup scrub cleaning typically. It is a front view which shows US shower washing | cleaning typically. It is a right view which shows US shower washing | cleaning typically. It is a figure which shows the number of residual deposits of Examples 1-7 and Comparative Examples 1-3.

Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of the embodiments and the examples, when the number, amount, and the like are referred to, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the description of the embodiment and each example, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment]
(Information recording device 30)
First, the information recording device 30 will be described with reference to FIG. FIG. 1 is a perspective view showing the information recording apparatus 30. The information recording apparatus 30 includes the glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium (hereinafter also simply referred to as a glass substrate) in the embodiment as the information recording medium 10.

Specifically, the information recording device 30 includes an information recording medium 10, a housing 20, a head slider 21, a suspension 22, an arm 23, a vertical shaft 24, a voice coil 25, a voice coil motor 26, a clamp member 27, and a fixing screw. 28. A spindle motor (not shown) is installed on the upper surface of the housing 20.

An information recording medium 10 such as a magnetic disk is rotatably fixed to the spindle motor by a clamp member 27 and a fixing screw 28. The information recording medium 10 is rotationally driven by this spindle motor at, for example, several thousand rpm. Although details will be described later with reference to FIGS. 4 and 5, in the information recording medium 10, a compression stress layer 12 (see FIG. 5) and a magnetic recording layer 14 (see FIGS. 4 and 5) are formed on the glass substrate 1. To be manufactured.

The arm 23 is attached so as to be swingable around the vertical axis 24. A suspension 22 formed in a leaf spring (cantilever) shape is attached to the tip of the arm 23. A head slider 21 is attached to the tip of the suspension 22 so as to sandwich the information recording medium 10.

A voice coil 25 is attached to the opposite side of the arm 23 from the head slider 21. The voice coil 25 is clamped by a magnet (not shown) provided on the housing 20. A voice coil motor 26 is constituted by the voice coil 25 and the magnet.

A predetermined current is supplied to the voice coil 25. The arm 23 swings around the vertical axis 24 by the action of electromagnetic force generated by the current flowing through the voice coil 25 and the magnetic field of the magnet. As the arm 23 swings, the suspension 22 and the head slider 21 also swing in the direction of the arrow AR1. The head slider 21 reciprocates on the front and back surfaces of the information recording medium 10 in the radial direction of the information recording medium 10. A magnetic head (not shown) provided on the head slider 21 performs a seek operation.

While the seek operation is performed, the head slider 21 receives a levitation force due to the air flow generated as the information recording medium 10 rotates. Due to the balance between the levitation force and the elastic force (pressing force) of the suspension 22, the head slider 21 travels with a constant flying height with respect to the surface of the information recording medium 10. By the traveling, the magnetic head provided on the head slider 21 can record and reproduce information (data) on a predetermined track in the information recording medium 10. The information recording apparatus 30 on which the glass substrate 1 is mounted as a part of the members constituting the information recording medium 10 is configured as described above.

(Glass substrate 1)
FIG. 2 is a plan view showing glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium according to the present embodiment. 3 is a cross-sectional view taken along the line III-III in FIG.

As shown in FIGS. 2 and 3, the glass substrate 1 (glass substrate for information recording medium) used as a part of the information recording medium 10 (see FIGS. 4 and 5) has a main surface 2, a main surface 3, It has the inner peripheral end surface 4, the hole 5, and the outer peripheral end surface 6, and is formed in a disk shape as a whole. The hole 5 is provided so as to penetrate from one main surface 2 toward the other main surface 3. A chamfer 7 is formed between the main surface 2 and the inner peripheral end surface 4 and between the main surface 3 and the inner peripheral end surface 4. Between the main surface 2 and the outer peripheral end surface 6 and between the main surface 3 and the outer peripheral end surface 6, a chamfered portion 8 (chamfer portion) is formed.

The size of the glass substrate 1 is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. It is possible to make the size smaller than this or larger than this. The thickness of the glass substrate is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage. In the present embodiment, the glass substrate has an outer diameter of about 64 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm. The thickness of the glass substrate is a value calculated by averaging the values measured at a plurality of arbitrary points to be pointed on the glass substrate. From the viewpoint of increasing the hardness of the glass substrate, the Vickers hardness of the glass substrate 1 is preferably 610 kg / mm ² or more.

(Information recording medium 10)
FIG. 4 is a plan view showing an information recording medium 10 provided with a glass substrate 1 as an information recording medium. FIG. 5 is a cross-sectional view taken along the line VV in FIG.

4 and 5, the information recording medium 10 includes a glass substrate 1, a compressive stress layer 12, and a magnetic recording layer 14. The compressive stress layer 12 is formed so as to cover the

main surfaces

2 and 3, the inner peripheral end face 4, and the outer peripheral end face 6 of the glass substrate 1. The magnetic recording layer 14 is formed so as to cover a predetermined region on the

main surfaces

2 and 3 of the compressive stress layer 12. By forming the compressive stress layer 12 on the inner peripheral end face 4 of the glass substrate 1, a hole 15 is formed inside the inner peripheral end face 4. The information recording medium 10 is fixed to a spindle motor provided on the housing 20 (see FIG. 1) using the holes 15.

In the information recording medium 10 shown in FIG. 5, the magnetic recording layer 14 is formed on both the compressive stress layer 12 formed on the main surface 2 and the compressive stress layer 12 formed on the main surface 3 (both sides). Is formed. The magnetic recording layer 14 may be provided only on the compression stress layer 12 (one side) formed on the main surface 2, or on the compression stress layer 12 (one side) formed on the main surface 3. It may be provided.

The magnetic recording layer 14 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the compressive stress layer 12 on the

main surfaces

2 and 3 of the glass substrate 1 (spin coating method). The magnetic recording layer 14 may be formed by a sputtering method or an electroless plating method performed on the compressive stress layer 12 on the

main surfaces

2 and 3 of the glass substrate 1.

The thickness of the magnetic recording layer 14 is about 0.3 μm to 1.2 μm for the spin coating method, about 0.04 μm to 0.08 μm for the sputtering method, and about 0.05 μm to about the electroless plating method. 0.1 μm. From the viewpoint of thinning and high density, the magnetic recording layer 14 is preferably formed by sputtering or electroless plating.

As a magnetic material used for the magnetic recording layer 14, a Co-based alloy or the like containing Ni or Cr as a main component is added for the purpose of adjusting the residual magnetic flux density. Is preferably used. In recent years, Fe—Pt magnetic materials have been used as magnetic layer materials suitable for heat-assisted recording.

In order to improve the sliding of the magnetic head, the surface of the magnetic recording layer 14 may be thinly coated with a lubricant. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.

The magnetic recording layer 14 may be provided with a base layer or a protective layer as necessary. The underlayer in the information recording medium 10 is selected according to the type of magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.

The underlayer provided on the magnetic recording layer 14 is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.

Examples of the protective layer for preventing wear and corrosion of the magnetic recording layer 14 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus together with the underlayer and the magnetic film. These protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.

Other protective layers may be formed on the protective layer or instead of the protective layer. For example, instead of the protective layer, colloidal silica fine particles are dispersed and coated on a Cr layer with tetraalkoxylane diluted with an alcohol solvent, and then fired to form a silicon oxide (SiO2) layer. May be.

(Glass substrate manufacturing method)
Next, with reference to FIG. 6, the manufacturing method of the glass substrate 1 and the information recording medium 10 which concern on this Embodiment is demonstrated. FIG. 3 is a flowchart showing a method for manufacturing the glass substrate 1 and the information recording medium 10.

First, in a “glass melting step” of step 10 (hereinafter abbreviated as “S10”, the same applies to step 11 and subsequent steps), the glass material constituting the glass substrate is melted.

In S11 “press molding process”, a glass substrate was produced by pressing the molten glass material using an upper mold and a lower mold. The glass composition used was a general aluminosilicate glass. The method for producing the glass substrate is not limited to molding, and may be cut out from plate glass, which is a known technique, and the glass composition is not limited thereto.

In the “first lapping step” of S12, both main surfaces of the glass substrate were lapped. This first lapping step was performed using a double-sided lapping device using a planetary gear mechanism. Specifically, the lapping platen was pressed on both surfaces of the glass substrate from above and below, the grinding liquid was supplied onto the main surface of the glass substrate, and these were moved relatively to perform lapping. By this lapping process, a glass substrate having a substantially flat main surface was obtained.

In the “coring step” of S13, a hole was formed in the center of the glass substrate using a cylindrical diamond drill to produce an annular glass substrate. The inner peripheral end surface and the outer peripheral end surface of the glass substrate were ground with a diamond grindstone, and a predetermined chamfering process was performed.

In the “second lapping step” of S14, lapping was performed on both main surfaces of the glass substrate in the same manner as in the first lapping step (S12). By performing the second lapping step, the fine uneven shape formed on the main surface in the coring and end face processing in the previous step can be removed in advance. As a result, the polishing time of the main surface in the subsequent process can be shortened.

In the “peripheral polishing step” of S15, the outer peripheral end surface of the glass substrate was subjected to mirror polishing by brush polishing. At this time, as the abrasive grains, a slurry containing general cerium oxide abrasive grains was used.

In the “first polishing step” of S16, the main surface was polished. The first polishing step is mainly intended to correct scratches and warpage remaining on the main surface in the first and second lapping steps (S12, S14) described above. In the first polishing step, the main surface was polished by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, general cerium oxide abrasive grains were used.

In the “chemical strengthening step” of S17, a surface reinforcing layer was formed on the main surface of the glass substrate 1. Specifically, chemical strengthening was performed by immersing the glass substrate 1 in a mixed solution of potassium nitrate (70%) and sodium nitrate (30%) heated to 300 ° C. for about 30 minutes. As a result, the lithium ion and sodium ion on the inner peripheral end surface and outer peripheral end surface of the glass substrate are respectively replaced with sodium ions and potassium ions in the chemical strengthening solution, and a compressive stress layer is formed, thereby forming the main surface of the glass substrate and The end face was strengthened.

The main surface polishing step was performed in the “second polishing step” of S18. This second polishing step aims to eliminate the fine defects on the main surface that have been generated and remain in the above-described steps and finish it in a mirror shape, to eliminate warpage and finish it to a desired flatness. In the second polishing step, polishing was performed by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, colloidal silica having an average particle diameter of about 20 nm was used to obtain a smooth surface.

In S19 “Final Cleaning”, final cleaning of the main and end surfaces of the glass substrate is performed. Thereby, the deposits remaining on the glass substrate are removed.

In the present embodiment, after the “second polishing step” of S18 in which the glass substrate formed into a disk shape is polished using an abrasive, the polished glass substrate 1 is cleaned with a brush. A cleaning process (S191) and a second cleaning process (S192) for cleaning the glass substrate 1 by irradiating the glass substrate 1 with a liquid to which ultrasonic waves are applied after the first cleaning process are provided.

Further, in the second cleaning step (S192), the second cleaning is performed without immersing the glass substrate 1 after the first cleaning step (S191) in another liquid and before the surface of the glass substrate 1 is dried. The step (S192) is started.

Here, “before the surface of the glass substrate 1 is dried” refers to a state where there is no wetted portion in a range (area) of 1% or more of the recording surface of the glass substrate 1. Details of the “final cleaning step” in S19 will be described later.

In the “magnetic thin film layer forming step” of S20, after cleaning the glass substrate 1 obtained through the above-described steps, an adhesion layer made of a Cr alloy and a soft magnetic layer made of a CoFeZr alloy are formed on both main surfaces of the glass substrate 1. An information recording medium of a perpendicular magnetic recording system was manufactured by sequentially forming an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a C-based protective layer, and an F-based lubricating layer. This configuration is an example of a configuration of a perpendicular magnetic recording system, and a magnetic layer or the like may be configured as an in-plane information recording medium. As a magnetic layer material suitable for heat-assisted recording, an FePt-based material may be used. Thereafter, the “post-heat treatment step” of S21 is performed to complete the information recording medium.

Here, the “final cleaning process” of S19 will be described. The shower cleaning process using a liquid to which ultrasonic waves (US) are applied (hereinafter referred to as “US shower cleaning process”) can quickly discharge the cleaning waste liquid to the outside of the glass substrate.

However, there is a problem in the cleaning power when the final cleaning process is performed alone using only the US shower cleaning process. The inventors focused on performing the final cleaning step by combining the US shower cleaning step and the scrub cleaning step of cleaning the glass substrate with a brush.

However, as a result of research, it has been found that there is a problem in the cleanliness of the glass substrate even with the cleaning method combining the scrub cleaning process and the US shower cleaning process. As for this subject, it turned out that the main components of the deposit | attachment to a glass substrate are the fine silica particles used for an abrasive | polishing agent.

This fine silica particle is a deposit that has become a problem of redeposition in the scrub cleaning process. In other words, even if the US shower cleaning process is simply introduced after the scrub cleaning process, the adhering material reattached in the scrub cleaning process (hereinafter referred to as “residual adhering material”) has not been sufficiently removed. The result turned out.

Specifically, it was found that the remaining deposits were not sufficiently removed due to the following causes. Usually, during each cleaning step, the glass substrate is immersed in a storage solution (water, cleaning solution, etc.) so as not to be dried.

For example, the scrub cleaning process and the US shower cleaning process are different. Therefore, after the scrub cleaning process, the glass substrate held in the cleaning basket is once immersed in the detergent solution and stored (hereinafter referred to as “immersion storage process”). Thereafter, a US shower cleaning process is performed on the glass substrate taken out from the detergent solution. In the scrub cleaning process and the US shower cleaning process, the cleaning basket for holding the glass substrate may be exchanged.

When the residual deposits were considered, it was found that the residual deposits reattached to the glass substrate strongly adhered to the glass substrate in the immersion storage process between the scrub cleaning process and the US shower cleaning process. That is, in the state where the dirt once removed by the scrub cleaning process is weakly reattached to the surface of the glass substrate, the reattachment is strongly fixed to the glass substrate through the immersion storage process. Thereafter, even if a US shower cleaning process is performed, residual deposits cannot be removed, and as a result, a desired cleanliness cannot be obtained.

As a result of intensive research to prevent the generation of residual deposits on the glass substrate, the inventors have continuously cleaned the US shower after the scrub cleaning step without performing the immersion storage step after the scrub cleaning step. By irradiating the surface (implementing the US shower cleaning process), before the residual deposits are strongly reattached, the dirt near the surface of the glass substrate is removed and reattachment of the residual deposits to the glass substrate is suppressed. I found out that I can do it.

Hereinafter, the “final cleaning step” of S19 in the present embodiment will be described with reference to FIGS. First, the holding mechanism for the glass substrate 1 will be described with reference to FIGS. 7 is a front view schematically showing a holding state of the glass substrate 1, FIG. 8 is a right side view schematically showing a holding state of the glass substrate 1, and FIG. 9 is a schematic configuration of a holding device for the glass substrate 1. FIG. 10 is a right side view schematically showing a schematic configuration of the holding device for the glass substrate 1.

As shown in FIGS. 7 and 8, the glass substrate 1 is supported by the

support rollers

211, 212, and 213 on the outer peripheral end surface 6 of the glass substrate 1 so that the

main surfaces

2 and 3 that are flat portions are vertical. The The glass substrate 1 may be held so that the

main surfaces

2 and 3 of the glass substrate 1 are horizontal.

In this embodiment, the glass substrate 1 is held using three support rollers, but the number of support rollers is not limited to three. Each

support roller

211, 212, 213 rotates around a rotation axis P1 extending in the horizontal direction. The support roller 211 is a drive roller connected to a drive motor. The

support rollers

212 and 213 are driven rollers. When the support roller 211 rotates in the R1 direction in the figure, the glass substrate 1 rotates in the R2 direction in the figure.

As shown in FIG. 9 and FIG. 10, each

support roller

211, 212, 213 is mounted on a cleaning bowl 200 having a holding device. A plurality of glass substrates 1 are held in a direction perpendicular to the drawing. The support roller 211 is rotatably held at the tip of the first arm 221 extending from the base frame 220. The support roller 213 is rotatably held at the tip of the third arm 223 extending from the base frame 220.

The support roller 212 is rotatably held at the tip of the second arm 222. The second arm 222 has a rotation center P2, and one end of a coil spring 230 as an urging member is connected to an end of the rotation arm P2 on the opposite side of the support roller 212. The other end of the coil spring 230 is connected to the base frame 220.

The state shown in FIG. 9 shows a state where the glass substrate 1 is held by the

support rollers

211, 212, and 213. The second arm 222 holds the glass substrate 1 by a lock member (not shown) so as to oppose the rotational force based on the expansion / contraction force of the coil spring 230 around the rotational center P2 (in the direction of arrow R3 in the figure). ).

In the state shown in FIG. 10, the lock member (not shown) is released, and the second arm 222 is pulled by the coil spring 230 (in the direction of arrow T in the figure). As a result, the second arm 222 rotates about the rotation center P2 in the direction of the arrow R4 in the drawing. In this state, the support of the glass substrate 1 by the support roller 212 is released, and the glass substrate 1 can be taken out from the cleaning bowl 200 or stored.

Next, scrub cleaning and US shower cleaning will be described with reference to FIGS. FIG. 11 is a front view schematically showing roll scrub cleaning, FIG. 12 is a right side view schematically showing roll scrub cleaning, FIG. 13 is a front view schematically showing cup scrub cleaning, and FIG. FIG. 15 is a front view schematically showing the US shower cleaning, and FIG. 16 is a right side view schematically showing the US shower cleaning.

11 and 12 show roll scrub cleaning among scrub cleaning. In the roll scrub cleaning, the roll brush 240 is disposed so that the rotation center axis P3 of the roll brush 240 having a cylindrical appearance is parallel to the main surface of the glass substrate 1. During cleaning, the roll brush 240 also rotates while rotating the glass substrate 1. The abrasive is supplied between the glass substrate 1 and the roll brush 240 from above.

FIG. 13 and FIG. 14 show cup scrub cleaning among scrub cleaning. In the cup scrub cleaning, the cup brush 250 is arranged so that the rotation center axis P4 of the cup brush 250 having an outer appearance is perpendicular to the main surface of the glass substrate 1. During cleaning, the cup brush 250 also rotates while rotating the glass substrate 1. The abrasive is supplied between the glass substrate 1 and the cup brush 250 from above.

The rotation speed of the glass substrate is preferably 500 rpm or more and 1000 rpm in the case of roll scrub cleaning. In the case of cup scrub cleaning, 100 rpm to 120 rpm is preferable.

15 and 16 show US shower cleaning. In the US shower cleaning, a US shower irradiation device 260 a is disposed on the main surface 2 side of the glass substrate 1, and a US shower irradiation device 260 b is disposed on the main surface 3 side of the glass substrate 1. That is, the glass substrate 1 can be cleaned by irradiating both surfaces of the glass substrate 1 with a liquid to which ultrasonic waves are simultaneously applied.

The frequency of the ultrasonic wave applied to the cleaning liquid is preferably 400 kHz or more and 1.5 MHz, which has high straightness and is effective in adhering a fine abrasive. More preferably, it is 900 kHz to 1000 kHz. If the frequency of the ultrasonic wave is less than 400 kHz, the detergency is poor. When the frequency of the ultrasonic wave exceeds 1.5 MHz, the cleaning effect is deteriorated because the attenuation effect is large.

The output of the ultrasonic wave is preferably 5 W / cm ² or more and 50 W / cm ² or less. More preferably, it is 10 W / cm ² or more and 30 W / cm ² or less. If it is less than 5 W / cm ² , the ultrasonic cleaning effect is poor. If it exceeds 50 W / cm ² , the shower tends to become mist-like and the cleaning effect is reduced.

The glass substrate 1 is rotated even during US shower cleaning by the US

shower irradiation devices

260a and 260b. The rotation speed is preferably 200 rpm or more and 2000 rpm or less. If it is less than 200 rpm, the rate of discharging the waste liquid (the cleaning liquid after being irradiated on the glass substrate 1) is slow, so that the cleaning performance is poor. If it exceeds 2000 rpm, the cleaning liquid is not supplied to the entire surface of the glass substrate, resulting in poor cleaning properties. Since the centrifugal force generated on the glass substrate 1 is too strong, the cleaning liquid is not held on the glass substrate 1 so much.

(Example)
Hereinafter, specific examples will be described. In each of Examples 1 to 7 and Comparative Examples 1 to 3 shown below, various conditions for the final cleaning step S19 are set in the manufacturing flow of the glass substrate for magnetic recording shown in FIG. The same. In the scrub cleaning step (S191), the cup scrub cleaning shown in FIGS. 13 and 14 was performed.

As an evaluation method of the glass substrate 1, the number of defects on the glass substrate 1 was measured using an optical surface analyzer (KLA, Candela 7120). Thereafter, defects were analyzed using SEM (S4800, manufactured by Hitachi High-Technologies Corporation), and the number of residual deposits (silica fine particles) was counted.

(Example 1)
The second polishing step (S18) was completed, and a scrub cleaning step (S191) was performed. The US shower cleaning step (S192) was performed without immersing the glass substrate 1 after the scrub cleaning step (S191) in another liquid and before the surface of the glass substrate 1 was dried.

It took 2 seconds from the scrub cleaning step (S191) to the US shower cleaning step (S192). Thereafter, a US immersion cleaning step was further performed, and finally the glass substrate 1 was dried with an IPA (isopropyl alcohol) vapor.

The cleaning conditions of the US shower cleaning step (S192) are: US frequency: 950 kHz, output: 30 W / cm ² , cleaning liquid: ultrapure water (10 L / min on one side), cleaning time: 50 sec, rotation speed: 500 rpm. The distance from the front-end | tip part of US

shower irradiation apparatus

260a, 260b to the

main surfaces

2 and 3 of the glass substrate 1 is 2 cm. The irradiation angle is about 30 ° with respect to the normal to the

main surfaces

2 and 3 of the glass substrate 1.

(Example 2)
The glass substrate 1 was manufactured with the manufacturing method similar to Example 1 except having changed the US frequency of US shower washing | cleaning process (S192) into 400 kHz.

(Example 3)
The glass substrate 1 was manufactured with the manufacturing method similar to Example 1 except having changed the US frequency of US shower washing | cleaning process (S192) into 1500 kHz.

Example 4
The glass substrate 1 was manufactured with the manufacturing method similar to Example 1 except having changed the output of US shower washing | cleaning process (S192) into 50 W / cm < ² >.

(Example 5)
The glass substrate 1 was manufactured with the manufacturing method similar to Example 1 except having changed the output of US shower washing | cleaning process (S192) into 5 W / cm < ² >.

(Example 6)
The glass substrate 1 was manufactured with the manufacturing method similar to Example 1 except having changed the rotation speed of US shower washing | cleaning process (S192) into 200 rpm.

(Example 7)
The glass substrate 1 was manufactured with the manufacturing method similar to Example 1 except having changed the rotation speed of US shower washing | cleaning process (S192) into 2000 rpm.

(Comparative Example 1)
The second polishing step (S18) was completed, and a scrub cleaning step (S191) was performed. After the scrub cleaning step (S191) was completed, the glass substrate 1 was immersed in the solution, and a US immersion cleaning step was performed. Then, the glass substrate 1 was dried with IPA (isopropyl alcohol) vapor.

The ultrasonic wave used in the US immersion cleaning process was 950 kHz, the output was 5 W / cm ² , and the solution was pure water.

(Comparative Example 2)
The 2nd polish process (S18) end and the US shower washing process (S192) were performed. Thereafter, the glass substrate 1 was finally dried with IPA (isopropyl alcohol) vapor. Other conditions are the same as in the first embodiment.

(Comparative Example 3)
The second polishing step (S18) was completed, and a scrub cleaning step (S191) was performed. After the scrub cleaning step (S191) was completed, a US shower cleaning step (S192) was performed. At this time, an immersion process was provided between the scrub cleaning process (S191) and the US shower cleaning process (S192). Thereafter, a US immersion cleaning step was further performed, and finally the glass substrate 1 was dried with an IPA (isopropyl alcohol) vapor. The cleaning conditions are the same as in Example 1.

FIG. 17 shows the number of residual deposits on the glass substrate obtained by the manufacturing methods shown in Examples 1 to 7 and Comparative Examples 1 to 3. In all of Examples 1 to 7, the number of residual deposits was one digit, and good results were obtained.

Thus, according to the method for manufacturing a glass substrate for magnetic recording in the present embodiment, fine particles such as silica adhering to the glass substrate 1 are separated from the glass substrate 1 in the scrub cleaning step (S191). Thereafter, deposits staying near the main surface of the glass substrate 1 and / or deposits weakly reattached by scrub can be efficiently removed from the glass substrate 1 by the US shower cleaning process (S192). It is said. Thereby, it is possible to provide a method for manufacturing a glass substrate for an information recording medium capable of suppressing adhesion of residual deposits on the main surface of the glass substrate 1.

It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Glass substrate, 2, 3 Main surface, 4 Inner peripheral end surface, 5,15 hole, 6, Outer peripheral end surface, 10 Information recording medium, 12 Compression stress layer, 14 Magnetic recording layer, 20 Housing, 21 Head slider, 22 Suspension, 23 arm, 24 vertical axis, 25 voice coil, 26 voice coil motor, 27 clamp member, 28 fixing screw, 30 information recording device, 200 washing bowl, 211, 212, 213 support roller, 220 base frame, 221 first arm, 222 2nd arm, 223 3rd arm, 230 coil spring, 240 roll brush, 250 cup brush.

Claims

A method for producing a glass substrate for an information recording medium, comprising:
A step of polishing a disk-shaped glass substrate using an abrasive;
A first cleaning step of cleaning the polished glass substrate using a brush;
After the first cleaning step, a second cleaning step of cleaning the glass substrate by irradiating the glass substrate with a liquid to which ultrasonic waves are applied, and
The second cleaning step starts the second cleaning step without immersing the glass substrate after the first cleaning step in another liquid and before the surface of the glass substrate dries. A method for producing a glass substrate for a recording medium.
In the second cleaning step,
The method for producing a glass substrate for an information recording medium according to claim 1, wherein the ultrasonic wave applied to the liquid has a frequency of 400 kHz to 1.5 MHz and an output of 5 W / cm 2 to 50 W / cm 2. .
The glass substrate for an information recording medium according to claim 1 or 2, wherein in the second cleaning step, the glass substrate is cleaned by holding the glass substrate so that a planar portion of the glass substrate is vertical. Production method.
4. The information recording medium according to claim 1, wherein in the second cleaning step, the glass substrate is cleaned by rotating the glass substrate at a rotation speed of 200 rpm or more and 2000 rpm or less. 5. A method for producing a glass substrate.
5. The information recording according to claim 1, wherein in the second cleaning step, the glass substrate is cleaned by irradiating both surfaces of the glass substrate with a liquid to which ultrasonic waves are applied simultaneously. A method for producing a glass substrate for a medium.