JP2013077351A - Method for manufacturing glass substrate for information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass substrate for information recording medium capable of reducing failures that occur in a step for manufacturing a glass substrate for information recording medium.SOLUTION: A step for cleaning a glass substrate includes a step for performing roll scrub cleaning of a glass substrate by using a roll scrub cleaning device, and a step for performing cup scrub cleaning of the glass substrate by using a cup scrub cleaning device after the roll scrub cleaning. The cup scrub cleaning is executed before a principal surface of the glass substrate after the roll scrub cleaning is dried.

Description

  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.

  In recent years, hard disk drives have been developed that have a recording capacity of 500 GB (single-sided 250 GB), a surface recording density of 630 Gb / square inch or more, with one 2.5-inch recording medium. The distance (flying height) between the head and the information recording medium is further reduced.

  As the flying height is reduced, in order to suppress defects (head crashes) when the information recording medium is used in a hard disk drive device, the size of defects on the substrate surface allowed as the information recording medium is also becoming smaller. In addition, with respect to the surface defects of the glass substrate for information recording media, the demands on the size and the number are increasing.

  In order to satisfy these strict requirements, an effort has been made to reduce defects in the glass substrate for information recording medium by devising polishing and cleaning methods for the glass substrate for information recording medium. However, due to the DFH (Dynamic Flying Hight) mechanism employed in magnetic heads, the accuracy of information recording media is becoming increasingly strict.

JP 2009-158030 A

  The problem to be solved by the present invention is that there is an increasing demand for reducing defects in the glass substrate for information recording medium in the manufacturing process of the glass substrate for information recording medium.

  The present invention has been made in view of the above circumstances, and provides a method for manufacturing a glass substrate for information recording medium, which can reduce defects that occur during the manufacturing process of the glass substrate for information recording medium. With the goal.

  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 forming a surface reinforcement layer in the main surface of a glass substrate by chemical strengthening processing, After the surface enhancement layer is formed on the main surface, the step of polishing the main surface and the step of cleaning the glass substrate after polishing the main surface are provided.

  The step of cleaning the glass substrate includes a step of performing roll scrub cleaning on the glass substrate using a roll scrub cleaning device, and a step of cleaning the glass substrate using a cup scrub cleaning device after the roll scrub cleaning. And cup scrub cleaning.

  The cup scrub cleaning is performed before the main surface of the glass substrate after the roll scrub cleaning is not dried.

  In another embodiment, the roll scrub cleaning and the cup scrub cleaning are each performed in a flowing water tank.

  In another embodiment, the roll scrub cleaning and the cup scrub cleaning each perform ultrasonic cleaning of the glass substrate while applying ultrasonic waves.

  In another embodiment, the step of cleaning the glass substrate includes a step of performing high-frequency cleaning in the rinsing tank while applying a high frequency of 430 to 950 kHz after the cup scrub cleaning.

In another form, 0.5-1 ppm hydrogen water is used in the said rinse tank.
In another embodiment, a filter having an opening diameter of 0.02 μm is used in the rinse tank.

  According to the manufacturing method of the glass substrate for information recording media based on this invention, the manufacturing method of the glass substrate for information recording media which can reduce the defect which arises in the manufacture process of the glass substrate for information recording media is provided. Make it possible.

It is a perspective view of the glass substrate for information recording media in an embodiment. It is a perspective view of the information recording medium in an embodiment. It is a flowchart which shows the manufacturing method of the information recording medium in embodiment. FIG. 3 is a schematic diagram showing each cleaning step in Example 1. It is a schematic diagram (perspective view) showing a configuration of a roll scrub cleaning device used for roll scrub cleaning in Example 1. It is a conceptual diagram (plan view) showing the configuration of a roll scrub cleaning apparatus used for roll scrub cleaning in Example 1. FIG. 3 is a first conceptual diagram showing a cleaning state of roll scrub cleaning in Example 1. FIG. 6 is a second conceptual diagram showing a cleaning state of roll scrub cleaning in Example 1. It is a schematic diagram (front view) which shows the structure of the cup scrub cleaning apparatus used for the cup scrub cleaning in Example 1. It is a schematic diagram (side view) which shows the structure of the cup scrub cleaning apparatus used for the cup scrub cleaning in Example 1. FIG. 3 is a first conceptual diagram illustrating a cleaning state of cup scrub cleaning in the first embodiment. FIG. 6 is a second conceptual diagram illustrating a cleaning state of cup scrub cleaning in the first embodiment. 6 is a conceptual diagram illustrating a cleaning state of roll scrub cleaning in Example 2. FIG. 6 is a conceptual diagram showing a cleaning state of cup scrub cleaning in Example 2. FIG. 6 is a conceptual diagram showing a cleaning state of roll scrub cleaning in Example 3. FIG. FIG. 10 is a conceptual diagram showing a cleaning state of cup scrub cleaning in Example 3. It is a schematic diagram which shows the positional relationship of the magnetic head and deposit | attachment in a flying test. It is a 1st schematic diagram which shows the positional relationship of a glass substrate and a deposit | attachment. It is a 2nd schematic diagram which shows the positional relationship of a glass substrate and a deposit | attachment. It is a 3rd schematic diagram which shows the positional relationship of a glass substrate and a deposit | attachment. It is a figure which shows the error incidence rate (n = 100) after the flying test and full surface scanning in Examples 1-6 and a comparative example.

  Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of the embodiments and examples, when referring to the number, amount, and the like, 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 embodiments and examples, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

(Configuration of information recording medium 1)
With reference to FIG. 1 and FIG. 2, the structure of the glass substrate 1G for information recording media and the information recording medium 1 is demonstrated. FIG. 1 is a perspective view of a glass substrate 1G for an information recording medium, and FIG. 2 is a perspective view of the information recording medium.

  As shown in FIG. 1, an information recording medium glass substrate 1G used for the information recording medium 1 (hereinafter referred to as “glass substrate 1G”) has an annular disk shape with a hole 11 formed in the center. ing. The glass substrate 1G has an outer peripheral end face 12, an inner peripheral end face 13, a front main surface 14, and a back main surface 15. As the glass substrate 1G, amorphous glass or the like is used. For example, the outer diameter is about 65 mm, the inner diameter is about 20 mm, the thickness is about 0.8 mm, and the surface roughness is about 2.0 mm or less.

  The inch size of the glass substrate 1G is not particularly limited, and various glass substrates 1G of 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, and 3.5 inch are manufactured as disks for information recording media. May be.

  The thickness of the glass substrate 1G is preferably 0.30 mm to 2.2 mm because it is effective against cracking of the glass substrate 1G due to drop impact. The thickness of the glass substrate 1 </ b> G here means an average value of values measured at some arbitrary points to be pointed on the substrate.

  As shown in FIG. 2, in the information recording medium 1, a magnetic thin film layer 23 is formed on the front main surface 14 of the glass substrate 1G. In the figure, the magnetic thin film layer 23 is formed only on the front main surface 14, but it is also possible to provide the magnetic thin film layer 23 on the back main surface 15.

  As a method for forming the magnetic thin film layer 23, a conventionally known method can be used. For example, a method of spin-coating a thermosetting resin in which magnetic particles are dispersed, a method of forming by sputtering, a method of electroless The method of forming by plating is mentioned.

  The film thickness by spin coating is about 0.3 to 1.2 μm, the film thickness by sputtering is about 0.04 to 0.08 μm, and the film thickness by electroless plating is 0.05 to 0.1 μm. From the viewpoint of thinning and high density, film formation by sputtering and electroless plating is preferable.

  The magnetic material used for the magnetic thin film layer 23 is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Co having high crystal anisotropy is basically used for the purpose of adjusting the residual magnetic flux density. Co-based alloys to which Ni and Cr are added are suitable. In recent years, FePt-based 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 thin film layer 23 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 freon-based solvent.

  If necessary, an underlayer and a protective layer may be provided. The underlayer in the information recording medium 1 is selected according to the 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 is not limited to a single layer, and may have a multi-layer 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 thin film layer 23 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. The protective layer can be formed continuously with an in-line sputtering apparatus, such as an underlayer and a magnetic film. The protective layer may be a single layer, or may have a multilayer structure composed of the same or different layers.

Another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, tetraalkoxylane is diluted with an alcohol-based solvent on a Cr layer, and then colloidal silica fine particles are dispersed and applied, followed by baking to form a silicon oxide (SiO ₂ ) layer. It may be formed.

(Manufacturing process of glass substrate 1G)
Next, a method for manufacturing the glass substrate 1G and the information recording medium 1 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a method for manufacturing the glass substrate 1G and the information recording medium 1.

  First, in the “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 the “press molding step” of S11, 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 cylindrical diamond drill was used to form a hole in the center of the glass substrate 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 face 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, main surface polishing was performed. 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 1G. Specifically, chemical strengthening was performed by immersing the glass substrate 1G 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.

  In the “second polishing step” of S18, a main surface polishing step was performed. 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 the “Final Cleaning” of S19, final cleaning of the main surface and the end surface of the glass substrate is performed. Thereby, the deposits remaining on the glass substrate are removed.

  In the “magnetic thin film layer deposition step” of S20, after cleaning the glass substrate obtained through the above-described steps, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, Ru An information recording medium of a perpendicular magnetic recording system was manufactured by sequentially forming an orientation control underlayer made of, 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. Thereafter, the “post-heat treatment step” of S21 is performed to complete the information recording medium.

<Example>
Hereinafter, specific cleaning steps of the final cleaning step (S19) will be described as examples and comparative examples for the glass substrate for magnetic recording media and the information recording medium obtained by the above-described steps.

Example 1
In the “final cleaning step (S19)”, the glass substrate was cleaned using the cleaning apparatus 100 shown in FIG. The cleaning apparatus 100 includes a glass substrate loading station LD, a first cleaning station 101 (cleaning using acid or alkali), a second cleaning station 102 (roll scrub cleaning), and a third cleaning station 103 (using rinse or alkali). Cleaning), fourth cleaning station 104 (cup scrub cleaning), fifth cleaning station 105 (rinse cleaning), sixth cleaning station 106 (rinse cleaning), seventh drying station 107 (drying), and glass substrate unloading station A glass substrate is sequentially transferred between the stations.

  An alkaline detergent having a concentration of about 2% was used for the first cleaning station 101, the second cleaning station 102, the third cleaning station 103, and the fourth cleaning station 104. In the second cleaning station 102, roll scrub cleaning using a roll scrub cleaning apparatus 200 was performed. In the fourth cleaning station 104, cup scrub cleaning using the cup scrub cleaning device 300 was performed.

  Rinse cleaning was performed at the fifth cleaning station 105 and the sixth cleaning station 106, and a drying process was performed at the seventh drying station 107. The drying process at the seventh drying station 107 uses IPA vapor, but is not limited thereto, and may be warm pure water drying, spin drying, or the like.

  In the transition from the roll scrub cleaning of the second cleaning station 102 to the cup scrub cleaning of the fourth cleaning station 104, the transition from the second cleaning station 102 to the third cleaning station 103 and the third cleaning station 103 to the second scrub cleaning are performed. In the movement to the 4 cleaning station 104, the main surface of the glass substrate is transferred without drying. Transition without drying the main surface of the glass substrate means that the entire surface of the glass substrate is wet between each cleaning step. This is because, even if a part of the surface of the glass substrate is dried, the deposits present at that part are difficult to remove in the next cleaning step.

(Roll scrub cleaning)
Roll scrub cleaning using the roll scrub cleaning apparatus 200 in the second cleaning station 102 will be described with reference to FIGS. FIG. 5 is a schematic diagram (perspective view) showing a configuration of a roll scrub cleaning apparatus 200 used in the roll scrub cleaning process, and FIG. 6 is a conceptual diagram showing a configuration of the roll scrub cleaning apparatus 200 used in the roll scrub cleaning process. FIG. 7 and FIG. 8 are first and second conceptual views showing the cleaning state of the roll scrub cleaning step.

  Referring to FIGS. 5 and 6, roll scrub cleaning apparatus 200 includes a first roller 216 a and a second roller 216 b that are juxtaposed in parallel with each other. A sponge brush 211a is wound around the surface of the first roller 216a. Similarly, a sponge brush 211b is wound around the surface of the second roller 216b. A plurality of protrusions 211p are provided on the surfaces of the sponge brush 211a and the sponge brush 211b.

  A glass substrate 1G is sandwiched between the first roller 216a and the second roller 216b, and the lower end of the glass substrate 1G is rotatably supported by a rotation support roller 213.

  The first roller 216a and the second roller 216b are rotationally controlled by the control device 215 by a driving device (not shown) in the directions indicated by arrows R1 and R2 (counter direction) in the drawing. The rotation support roller 213 is rotationally controlled by the control device 215 by a driving device (not shown) in the direction of the arrow R3 in the drawing. Thereby, the glass substrate 1G rotates in the direction of the arrow R4 in the drawing.

  A cleaning agent discharge nozzle 214 is provided above the first roller 216a and the second roller 216b, and the cleaning agent is supplied from the cleaning agent discharge nozzle 214 toward the glass substrate 1G.

  Referring to FIG. 7, in cleaning glass substrate 1G using roll scrub cleaning apparatus 200, sponge brush 211a and sponge brush 211b rotate while glass substrate 1G is rotated by rotation support roller 213. As a result, the surface of the glass substrate 1G is cleaned.

  Since the sponge brush 211a and the sponge brush 211b are provided with a plurality of projections 211p, the pressing force concentrates on the operating point of the projection 211p. Thereby, the physical cleaning effect can be enhanced. As shown in FIG. 8, the trajectory T of the protrusion 211p viewed from the glass substrate 1G is formed in the circumferential direction of the glass substrate 1G, and the particles P on the glass substrate 1G are removed along this trajectory.

(Cup scrub cleaning)
Next, cup scrub cleaning using the cup scrub cleaning apparatus 300 in the fourth cleaning station 104 will be described with reference to FIGS. FIG. 9 is a schematic diagram (front view) showing a configuration of a cup scrub cleaning apparatus 300 used in the cup scrub cleaning process, and FIG. 10 is a schematic diagram showing a configuration of the cup scrub cleaning apparatus 300 used in the cup scrub cleaning process. FIG. 11 and FIG. 12 are first and second conceptual views showing the cleaning state of the cup scrub cleaning step.

  Referring to FIGS. 9 and 10, cup scrub cleaning apparatus 300 includes a plurality of columnar sponge brushes 323 arranged radially from rotating shaft 321. A plurality of the sponge brushes 323 are arranged with a predetermined gap along the axial direction of the rotating shaft 321. End disks 322 are provided at both ends of the rotating shaft 321.

  A glass substrate 1G is sandwiched between sponge brushes 323 adjacent in the axial direction. The lower end of the glass substrate 1G is rotatably supported by a rotation support roller 313.

  The rotation shaft 321 is rotationally controlled by the control device 315 by a driving device (not shown) in the direction of the arrow R11 in the drawing. In accordance with the operation, the glass substrate is cleaned while being rotated in the direction opposite to R14. At this time, the rotation support roller 313 functions only as a support roller, and the rotation support roller 313 rotates following the rotation of the sponge brush 323.

  A cleaning agent discharge nozzle 314 is provided above the sponge brush 323, and the cleaning agent is supplied from the cleaning agent discharge nozzle 314 toward the glass substrate 1G.

  Referring to FIG. 11, in cleaning glass substrate 1G using roll scrub cleaning apparatus 300, the surface of glass substrate 1G is cleaned by rotating sponge brush 323.

  As shown in FIG. 12, the locus T of the columnar sponge brush 323 viewed from the glass substrate 1G is formed in a fan shape on the surface of the glass substrate 1G, and the particles P on the glass substrate 1G are removed along this locus. The Thereby, a large work area by the sponge brush 323 can be secured.

  As shown in FIG. 8, in roll scrub cleaning, the force concentrates on the portion of the protrusion 211p, which is suitable for removing a deposit having a relatively large size (500 nm to several μm) existing on the locus T. It is difficult to completely remove small-sized (500 nm or less) deposits. Further, it is easy to place a stamp mark at the position where the protrusion 211p is in contact.

  On the other hand, in the scrub cleaning, the trajectory T of the columnar sponge brush 323 passes through the surface of the glass substrate so as to sweep evenly, and therefore, there is an effect of collecting and removing small-sized adhesion in one place near the outer periphery. . Also, stamp marks are difficult to attach.

  Therefore, by combining cup scrub cleaning and roll scrub cleaning, the disadvantages of both can be compensated for by the advantages of both, and the cleaning effect can be further enhanced. From the above, in the case of only the roll scrub cleaning, the small size deposits cannot be removed. In the case of only cup scrub cleaning, the presence of large deposits prevents the sponge brush from uniformly sweeping the surface of the glass substrate, resulting in small deposits remaining or large There is a possibility that a minute crack is generated by dragging the deposit. A combination of both is necessary: removing large deposits after removing large deposits.

  The rotation speed of the first roller 216a and the second roller 216b for roll scrub cleaning was about 700 rpm, and the rotation speed of the columnar sponge brush 323 for cup scrub cleaning was about 110 rpm.

  If the rotational speed is too small, the amount of work becomes small, and if it is too large, the friction coefficient becomes small. As a result, the surface pressure of the sponge brush on the glass substrate is reduced, and the amount of work is reduced. Therefore, 500 rpm to 1000 rpm is preferable for roll scrub cleaning, and 100 rpm to 120 rpm is preferable for cup scrub cleaning.

  In the first embodiment, the integrated cleaning device 100 is used as shown in FIG. 4. However, if the glass substrate is transferred without drying using a roll scrub cleaning device, a cup scrub cleaning device, and each cleaning station. As shown in FIG. 4, the integrated cleaning apparatus 100 may not be used.

(Example 2)
Next, the “final cleaning step (S19)” in Example 2 will be described with reference to FIGS. FIG. 13 is a conceptual diagram showing a cleaning state of roll scrub cleaning, and FIG. 14 is a conceptual diagram showing a cleaning state of cup scrub cleaning.

  The difference from the “final cleaning step” in the first embodiment is that both the roll scrub cleaning in the second cleaning station 102 and the roll scrub cleaning in the fourth cleaning station 104 are as shown in FIG. 13 and FIG. It is in the point which washed in flowing water (flowing water tank).

  By washing in flowing water (flowing water tank), when the glass substrate is washed with each sponge brush, it is possible to avoid the deposits removed from the glass substrate from reattaching to the sponge brush.

(Example 3)
Next, the “final cleaning step (S19)” in Example 3 will be described with reference to FIG. 15 and FIG. FIG. 15 is a conceptual diagram showing a cleaning state of roll scrub cleaning, and FIG. 16 is a conceptual diagram showing a cleaning state of cup scrub cleaning.

  The difference from the “final cleaning step” in the second embodiment is that the roll scrub cleaning and the cup scrub cleaning are performed in flowing water (flow tank), and further, as shown in FIGS. The ultrasonic oscillator 400 was installed in the container, and ultrasonic waves were applied to the flowing water tank to clean the glass substrate.

  In this example, an ultrasonic wave of 120 kHz was applied using the ultrasonic oscillator 400. Thereby, the cleaning ability of the glass substrate was further improved. The frequency of the ultrasonic wave used is preferably in the range of 80 kHz to 430 kHz, and more preferably in the range of 120 kHz to 170 kHz.

Example 4
Next, the “final cleaning step (S19)” in Example 4 will be described. The difference from the third embodiment is that high-frequency cleaning is performed in the rinse cleaning step of the fifth cleaning station 105 after the cup scrub cleaning in the fourth cleaning station 104.

  The frequency of the high frequency applied in the rinse cleaning process of the fifth cleaning station 105 is 950 kHz. Approximate deposits can be removed by cleaning the glass substrate in the order of roll scrub cleaning and cup scrub cleaning.

  However, considering the size of the abrasive colloidal silica used, in order to completely remove deposits having a particle size of 20 nm (average particle size) to 100 nm (slightly agglomerated) from the main surface of the glass substrate, The microstreaming effect by high frequency cleaning was optimal.

  The high frequency is preferably in the range of 430 to 950 kHz. This is generally effective for removing large adhesion when the ultrasonic frequency is lower than 430 kHz because of the relationship between cavitation and acceleration of ultrasonic cleaning, and the ultrasonic frequency is higher than 950 kH. This is because it is effective for removing small adhesions.

(Example 5)
Next, the “final cleaning step” of S19 in Example 5 will be described. The difference from Example 4 was that hydrogen water was used as functional water together with high-frequency cleaning in the rinse cleaning process of the fifth cleaning station 105. If the hydrogen concentration is too low, no effect can be obtained, and if the hydrogen concentration is too high, a bubbling phenomenon due to hydrogen occurs in the tank. Therefore, the hydrogen concentration was 0.7 ppm.

  In addition, the hydrogen concentration of hydrogen water has the preferable range of 0.5-1 ppm. This is because if the concentration is too lower than 0.5 ppm, the effect of removing the fine particles is weakened by only deaerated water (in a state where oxygen and nitrogen in the water are removed). If the concentration is higher than 1 ppm, the hydrogen saturation concentration is about 1.6 ppm, and hydrogen bubbles are generated, which becomes a disturbance factor for high-frequency cleaning.

  In this example, hydrogen water was used as the functional water, but hydrogen water that can improve the efficiency of the high-frequency cleaning was optimal for removing the minute deposits remaining on the glass substrate. Depending on the composition of the glass substrate, a combination with ozone water may be good.

(Example 6)
Next, the “final cleaning step” of S19 in Example 6 will be described. In this example, the difference from Example 5 was that a filter having an opening diameter of 0.02 μm was used in order to capture the removed fine deposits with a filter in the rinse cleaning process of the sixth cleaning station 106.

  This is because it is necessary to pump the inside of the tank and capture the deposits with a filter with an optimal opening. In the glass substrate manufacturing process, the size of the abrasive used in the final polishing process is Since it is 0.02μm and is actually agglomerated, the size of the abrasive is assumed to be 0.02μm to 0.1μm. Therefore, it is preferable to use a filter having an opening diameter of 0.02 μm.

(Comparative Example 1)
In the “Final Cleaning” of S19, the following cleaning process was performed as Comparative Example 1. Roll scrub cleaning using the roll scrub cleaning apparatus shown in FIGS. 7 and 8 was performed. The number of rotations of the sponge brush was set to 700 rpm while applying detergent in the shower from the top. Thereafter, the final cleaning was performed with another cleaning machine without drying the glass substrate.

  The detergent tank (1), the detergent tank (2), the pure water tank (1), the pure water tank (2), and the IPA (isopropyl alcohol) were sequentially immersed in each washing tank, and ultrasonic cleaning was performed for 5 minutes each. The ultrasonic frequency was 80 kHz in the detergent tank (1), 80 kHz in the detergent tank (2), 80 kHz in the pure water tank (1), and 80 kHz in the pure water tank (2). Thereafter, steam drying by IPA was performed.

(Comparative Example 2)
In the “Final Cleaning” of S19, the following cleaning process was performed as Comparative Example 2. Cup scrub cleaning using the cup scrub cleaning apparatus shown in FIGS. 9 and 10 was performed. The number of rotations of the sponge brush was set to 110 rpm while applying detergent in the shower from the top. Thereafter, the final cleaning was performed with another cleaning machine without drying the glass substrate.

  The detergent tank (1), the detergent tank (2), the pure water tank (1), the pure water tank (2), and the IPA (isopropyl alcohol) were sequentially immersed in each washing tank, and ultrasonic cleaning was performed for 5 minutes each. The ultrasonic frequency was 80 kHz in the detergent tank (1), 80 kHz in the detergent tank (2), 80 kHz in the pure water tank (1), and 80 kHz in the pure water tank (2). Thereafter, steam drying by IPA was performed.

  The levitation test shown in FIG. 17 was performed using the glass substrates prepared in Examples 1 to 6 and the comparative example. The magnetic head 2D is held by the suspension 2C, and the flying height (floating height) of the magnetic head 2D from the surface of the glass substrate 1G is F1.

  Normally, a magnetic thin film layer is formed on the glass substrate 1G and the test is performed in the state of an information recording medium (magnetic disk recording medium). This time, only a lubricating layer is formed on the glass substrate 1G, and a floating test is performed. Carried out. The reason will be described with reference to FIGS.

  As shown in FIG. 18, the deposit 1p exists on the glass substrate 1G, and as shown in FIG. 19, when the magnetic thin film layers 401, 402, 403 (about 100 nm) are formed on the deposit 1p, The height of the protrusion due to the deposit on the information recording medium is smaller than the actual protrusion height of the deposit 1p deposit (h4). This is because the deposit 1p is gradually buried during the film formation process.

  Therefore, as shown in FIG. 20, it is a more severe test to perform the flying test by forming only the lubricating layer 401 (about several nm) on the glass substrate 1G.

  FIG. 21 shows the results of the error occurrence rate (n = 100) after the flying test and full-surface scanning of Examples 1 to 6 and Comparative Examples 1 and 2. In each example and comparative example, a floating test was performed on 100 glass substrates, and the error occurrence rate was investigated.

  In any of Examples 1 to 6, better results were obtained than in the comparative example. In the ascent test, “◎◎” is a satisfactory level for actual use, “◎” is a level that can be used sufficiently, “○” is a level that can be used, and “×” is a level that can be used. This is a level that is not suitable for practical use due to frequent occurrence of defects.

  Also, in Examples 1 to 6, it is possible to reduce defects that occur during the manufacturing process of the glass substrate, and the information recording medium (magnetic disk) manufactured in each example shows the result of the flying test on the glass substrate. This reflects the quality that can be used satisfactorily as a high-density magnetic disk without the occurrence of head crashes.

  As described above, in an information recording apparatus employing a DFH mechanism in which the flying height of the magnetic head is 5 nm or less, even if the surface recording density is a high-density information recording medium of 630 Gb / sq. And reading can be executed.

  It should be understood 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 Information recording medium, 1G Glass substrate for information recording media, 2 Information recording device, 11 hole, 12 Outer peripheral end surface, 13 Inner peripheral end surface, 14 Front main surface, 15 Back main surface, 23 Magnetic thin film layer, 200 Roll scrub cleaning apparatus 216a First roller, 216b Second roller, 211a, 211b, 323 Sponge brush, 211p protrusion, 213 Rotating support roller, 215, 315 Controller, 300 Cup scrub cleaning device, 321 Rotating shaft, 322 End disk, 214, 314 Cleaning agent discharge nozzle.

Claims (6)

A method for producing a glass substrate for an information recording medium, comprising:
Forming a surface reinforcing layer on the main surface of the glass substrate by chemical strengthening treatment;
A step of polishing the main surface after forming the surface enhancement layer on the main surface;
And a step of cleaning the glass substrate after polishing the main surface,
The step of cleaning the glass substrate includes:
Performing roll scrub cleaning on the glass substrate using a roll scrub cleaning device;
After the roll scrub cleaning, performing a cup scrub cleaning on the glass substrate using a cup scrub cleaning device,
The cup scrub cleaning is a method for manufacturing a glass substrate for an information recording medium, which is performed before the main surface of the glass substrate after the roll scrub cleaning is not dried.   The method for producing a glass substrate for an information recording medium according to claim 1, wherein the roll scrub cleaning and the cup scrub cleaning are each performed in a flowing water tank.   The method of manufacturing a glass substrate for an information recording medium according to claim 2, wherein the roll scrub cleaning and the cup scrub cleaning each perform ultrasonic cleaning of the glass substrate while applying ultrasonic waves.   The glass substrate for an information recording medium according to claim 3, wherein the step of cleaning the glass substrate includes a step of performing high-frequency cleaning in a rinsing tank while applying a high frequency of 430 to 950 kHz after the cup scrub cleaning. Manufacturing method.   The manufacturing method of the glass substrate for information recording media of Claim 4 using 0.5-1 ppm hydrogen water in the said rinse tank.   The method for producing a glass substrate for an information recording medium according to claim 5, wherein a filter having an opening diameter of 0.02 μm is used in the rinse tank.

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