JP5250361B2 - Manufacturing method of glass substrate for magnetic disk - Google Patents

Description

  The present invention relates to a method for manufacturing a glass substrate for a magnetic disk mounted on a hard disk drive device.

  There is a magnetic disk as a magnetic recording medium mounted on a hard disk drive device (HDD device). A magnetic disk is manufactured by laminating a magnetic layer or a protective layer on a substrate, a glass substrate, or a ceramic substrate on which a NiP film is deposited on a metal plate made of an aluminum-magnesium alloy or the like. Conventionally, an aluminum alloy substrate has been widely used as a substrate for a magnetic disk. However, with recent downsizing, thinning, and high-density recording of magnetic disks, surface flatness and A glass substrate having excellent strength with a thin plate has been used.

  Such a glass substrate for a magnetic disk includes a material processing step and a first lapping step; an end shape step (a coring step for forming a hole, a chamfered surface at an end (outer peripheral end and / or inner peripheral end) Chamfering step (chamfered surface forming step)); end surface polishing step (outer peripheral end and inner peripheral end); second lapping step; main surface polishing step (first and second polishing step); chemical strengthening step Manufactured through a process such as an inspection process.

  In the inspection process described above, a method of optically detecting a defect is employed (Patent Document 1). Then, OK / NG of the magnetic disk glass substrate is determined based on the defect detection result. For example, if the glass substrate for magnetic disk has a predetermined number or more of defects (particles (dust), irregularities on the surface, etc.), the glass substrate for magnetic disk is determined to be NG.

The recording density of magnetic disks has been increasing year by year, and along with this, the opportunity to use only one side as a recording surface has increased (see Patent Document 2). For example, for notebook personal computers. Although those having a recording capacity of 160 GB or more have already been marketed, 80 GB is sufficient depending on the intended use, and there are cases where only one side can be used as a magnetic recording surface. By using only one surface as the magnetic recording surface, it is possible to omit the formation of the magnetic recording layer on the surface not used as the magnetic recording surface, and it is possible to reduce the cost.
Japanese Patent Laid-Open No. 10-267858 JP 2001-351229 A

  However, for example, when the magnetic disk substrate is a glass substrate, since the glass is a transparent body, when the defect inspection is performed optically, the defect itself can be detected. It is impossible to determine which main surface it is on. For this reason, as described above, when a magnetic disk glass substrate using only one side as a magnetic recording surface is inspected, it is assumed that defect detection cannot be performed accurately.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing a glass substrate for a magnetic disk capable of accurately detecting which side of the glass substrate for a magnetic disk has a defect. And

The method for manufacturing a glass substrate for a magnetic disk according to the present invention is a method for manufacturing a glass substrate for a magnetic disk including an inspection process for inspecting the glass substrate for a magnetic disk having a pair of main surfaces that is manufactured. The glass substrate for magnetic disk is inspected for defects by optical automatic appearance inspection, and when the number of defects on one main surface of the glass substrate for magnetic disk exceeds a predetermined number, the glass substrate for magnetic disk is The magnetic disk glass is determined in a state in which the optical system having a single lens reflex function is focused on the one main surface of the magnetic disk glass substrate. the number of defects is the number of defects present on said one main surface of the substrate is measured, several number of defects is given on the one main surface of the glass substrate for a magnetic disk other than If it is, and wherein the determining a non-defective glass substrate for a magnetic disk which only a recording surface wherein the one main surface.

  According to this method, in the inspection process for inspecting the manufactured magnetic disk glass substrate, the defect inspection is performed by the optical automatic visual inspection on the magnetic disk glass substrate, and then the optical automatic visual inspection is specified. Further, the defect inspection is performed with respect to the position of the defect using an optical system having a single lens reflex function having a relatively shallow depth of focus. For this reason, it becomes possible to accurately detect which side of the glass substrate for a magnetic disk, which is a transparent body, has defects. This makes it possible to accurately inspect a glass substrate for a magnetic disk that uses only one side as a recording surface, increase the number of non-defective products for such a glass substrate for a magnetic disk, and improve the product yield. it can.

In the method for manufacturing a glass substrate for a magnetic disk of the present invention, when the number of defects specified by the optical automatic appearance inspection is a predetermined number or less, both main surfaces of the glass substrate for a magnetic disk are good. Whether the optical disk having the single-lens reflex function is focused on the glass substrate for a magnetic disk, which is determined not to be a good product on both sides and determined to be a temporary defective product. It is preferable to measure the number of defects, which is the number of defects present on the one main surface of the glass substrate for a magnetic disk, in a state matched with the one main surface .

  The method for manufacturing a magnetic disk glass substrate according to the present invention includes a step of inspecting the magnetic disk glass substrate for defects by an optical automatic appearance inspection in an inspection step of inspecting the manufactured magnetic disk glass substrate. With respect to the position of the defect identified by the automatic visual inspection, the magnetic disk glass is in a state in which the focus of an optical microscope having an optical system having a relatively shallow depth of focus is aligned with the main surface of the magnetic disk glass substrate. Since the defect on the main surface of the substrate is detected, it is possible to accurately detect whether the defect of the glass substrate for magnetic disk is on both sides.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Here, aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used as the material of the magnetic disk glass substrate. In particular, aluminosilicate glass can be preferably used in that it can be chemically strengthened and can provide a glass substrate for a magnetic disk excellent in flatness of the main surface and substrate strength.

  The magnetic disk manufacturing process includes a material processing process and a first lapping process; an end shape process (a coring process for forming a hole, and a chamfered surface at an end (outer peripheral end and / or inner peripheral end). Chamfering step (chamfered surface forming step)); end surface polishing step (outer peripheral edge and inner peripheral edge); second lapping step; main surface polishing step (first and second polishing step); chemical strengthening step; recording layer It includes processes such as isoformation process.

Below, each process of the manufacturing process of a magnetic disc is demonstrated.
(1) Material processing step and first lapping step First, in the material processing step, for example, a molten glass is used as a material, and a known manufacturing method such as a press method, a float method, a down draw method, a redraw method, or a fusion method is used. Can be manufactured. Of these methods, if a press method is used, a sheet glass can be produced at a low cost.

  In the first lapping step, both main surfaces of the sheet glass are lapped to form a disk-shaped glass substrate. This lapping process can be performed using alumina free abrasive grains with a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed on both sides of the plate glass from above and below, the grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relative to each other for lapping. Do. By this lapping process, a glass substrate having a flat main surface can be obtained.

(2) End shape process (coring process for forming a hole, chamfering process for forming a chamfered surface at the end (outer peripheral end and inner peripheral end) (chamfered surface forming process))
In the coring step, for example, an inner hole is formed at the center of the glass substrate using a cylindrical diamond drill to obtain an annular glass substrate. In the chamfering step, the inner peripheral end surface and the outer peripheral end surface are ground with a diamond grindstone, and a predetermined chamfering process is performed.

(3) Second Lapping Step In the second lapping step, the second lapping process is performed on both main surfaces of the obtained glass substrate in the same manner as in the first lapping step. By performing this second lapping step, it is possible to remove in advance the fine unevenness formed on the main surface in the cutting step and end surface polishing step, which are the previous steps, and shorten the subsequent polishing step on the main surface. Will be able to be completed in time.

(4) End surface polishing step In the end surface polishing step, the outer peripheral end surface and the inner peripheral end surface of the glass substrate are mirror-polished by a brush polishing method. At this time, as the abrasive grains, for example, a slurry containing cerium oxide abrasive grains (free abrasive grains) can be used. By this end face polishing step, the end face of the glass substrate is in a mirror state that can prevent the precipitation of sodium and potassium.

(5) Main surface polishing step (first polishing step)
As the main surface polishing step, first, a first polishing step is performed. The first polishing process is a process whose main purpose is to remove scratches and distortions remaining on the main surface in the lapping process described above. In the first polishing step, the main surface is polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains can be used.

(6) Chemical strengthening step In the chemical strengthening step, the glass substrate that has been subjected to the lapping step and the polishing step described above is chemically strengthened. As a chemical strengthening solution used for chemical strengthening, for example, a mixed solution of potassium nitrate (60%) and sodium nitrate (40%) can be used. In the chemical strengthening, the chemical strengthening solution is heated to 300 ° C. to 400 ° C., the cleaned glass substrate is preheated to 200 ° C. to 300 ° C., and immersed in the chemical strengthening solution for 3 hours to 4 hours. In soaking, in order to chemically strengthen both surfaces of the glass substrate, it is preferable to perform the immersion in a state of being accommodated in a holder so that the plurality of glass substrates are held at the end surfaces.

  Thus, by immersing in the chemical strengthening solution, the lithium ions and sodium ions in the surface layer of the glass substrate are respectively replaced with sodium ions and potassium ions having a relatively large ion radius in the chemical strengthening solution. Will be strengthened.

(7) Main surface polishing process (final polishing process)
Next, a second polishing process is performed as a final polishing process. The second polishing step is a step aimed at finishing the main surface into a mirror surface. In the second polishing step, both main surfaces are mirror-polished using a soft foam resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the slurry, cerium oxide abrasive grains or colloidal silica finer than the cerium oxide abrasive grains used in the first polishing step can be used.

(8) Inspection Process In the inspection process, a defect in the glass substrate 100 for a magnetic disk is detected using an appearance inspection apparatus 300 using an optical automatic appearance inspection (AOI) as shown in FIG. The appearance inspection apparatus 300 shown in FIG. 1 includes two defect detection probe lasers 302a and 302b, and four detectors 304a to 304d that each detect scattered light in almost all directions of the laser light. . The two defect detection probe lasers 302a and 302b are spaced apart with the same laser output direction. The defect detection probe laser 302a emits measurement laser light, and the defect detection probe laser 302b emits reference laser light. The detectors 304a, 304b, and 304c are arranged at positions where the diffracted / scattered light at the laser irradiation position of the defect detection probe laser 302a can be detected, and detect the diffracted / scattered light from the magnetic disk glass substrate 100, respectively. Obtain scattered light intensity information. If the scattered light intensity of the detectors 304a, 304b, and 304c is strong, a defect exists. The detector 304b is arranged so as to detect one of the lights divided by the beam splitter 305 arranged in the preceding stage of the detector 304c. The detector 304d is disposed at a position where the diffracted / scattered light at the laser irradiation position of the laser 302b for defect detection probe can be detected, and is used as a reference for a defect-free portion of the glass substrate 100 for magnetic disk. Scattered light is detected and reference scattered light intensity information is acquired.

  In the appearance inspection apparatus 300 shown in FIG. 1, since the laser diameter is small, for example, about 5 μm, the laser wavelength is short, and the power is high, the defect detection sensitivity is high. In the appearance inspection apparatus 300 having such a configuration, laser light is emitted from the two defect detection probe lasers 302 a and 302 b to the surface of the magnetic disk glass substrate 100 while moving the magnetic disk glass substrate 100. Irradiation is performed, and the diffracted / scattered light at that time is detected by the detectors 304a to 304d. Thereafter, an output signal from each of the detectors 304a to 304d is taken in by a determination circuit (not shown), and a defect of the magnetic disk glass substrate 100 is detected based on the output signal.

  Since the glass substrate 100 for magnetic disks is a transparent body, in the appearance inspection apparatus shown in FIG. 1, even if the position of the defect can be specified, which main surface of the glass substrate 100 the defect exists on, or the glass substrate It is difficult to determine whether it exists inside 100. For this reason, in this inspection process, it is determined on which main surface of the glass substrate 100 the defect specified by the appearance inspection apparatus is present. In the present invention, in order to make this determination, observation is performed using an optical system that has a relatively shallow depth of focus and can be focused on a glass substrate for a magnetic disk. That is, an optical system having a single-lens reflex function with a relatively shallow depth of focus, for example, an optical system having a single-lens reflex function, is used with the main surface of the magnetic disk glass substrate being focused on the main surface of the optical microscope. Observe defects on the surface.

  FIG. 2 is a view showing an example in which an optical system 400 having a single-lens reflex function is arranged toward one main surface of the magnetic disk glass substrate 100. The optical system 400 having the single-lens reflex function mainly includes a lens, a finder that forms an image of the surface of the magnetic disk glass substrate 100, and a reflecting mirror disposed between the lens and the finder. ing. By using the optical system 400 having such a single-lens reflex function, it is possible to focus on one main surface and the other main surface of the glass substrate 100 for magnetic disks. That is, in FIG. 2, an optical system having a single-lens reflex function is disposed only on one side of the magnetic disk glass substrate, and the focal point is adjusted to focus on both main surfaces. In the present invention, the optical system is not limited to an optical system having a single-lens reflex function, and an optical system capable of focusing on one main surface and the other main surface of the magnetic disk glass substrate 100 is also the same. Can be used.

  Since each optical microscope 400 is an optical system having a single-lens reflex function with a relatively shallow depth of focus, each optical microscope 400 can be focused on the main surface of the magnetic disk glass substrate 100. Only the surface can be observed. In order to move the optical system 400 to the position of the defect, the XY stage in the appearance inspection apparatus 300 is used, and based on the defect position information (information on the position where the defect is specified) from the appearance inspection apparatus 300, The optical system 400 is moved to the defect position in conjunction with the XY stage. Since the optical system 400 is focused on one main surface of the glass substrate for magnetic disk, is there a defect on one main surface by illuminating the glass substrate for magnetic disk with incident light? Can be recognized. In order to confirm a defect on the other main surface of the magnetic disk glass substrate 100, the optical system 400 is focused on the other main surface.

  In this inspection process, the glass substrate for magnetic disk is inspected for defects by optical automatic appearance inspection, and the glass substrate for magnetic disk having both main surfaces as recording surfaces based on a predetermined criterion. If it is determined that the optical disk cannot be used, the focus of the optical system having a single-lens reflex function is determined for the position of the defect specified by the optical automatic visual inspection. Detects defects on the main surface of the magnetic disk glass substrate in a state aligned with the main surface of the glass substrate for use, and uses it as a glass substrate for magnetic disk with only one main surface as a recording surface based on the detection result Determine if you can.

  As described above, according to the present invention, when the defect is detected in the magnetic disk glass substrate 100 by the visual inspection apparatus 300 and a defect is detected, at least one of the two main surfaces of the magnetic disk glass substrate 100 is detected. An optical system 400 having a single-lens reflex function having a relatively shallow focal depth is moved to the defect position and observation is performed at a low focal depth, and the defect of the magnetic disk glass substrate 100 is confirmed from the observation result. It is possible to accurately detect which of the main surfaces the defect of the glass substrate 100 is on.

  Since such an accurate defect inspection can be performed, the number of non-defective glass substrates for magnetic disks that use only one surface as a recording surface can be increased, and the product yield can be improved. FIG. 3 is a flowchart showing a procedure for defect inspection including non-defective determination of the glass substrate for magnetic disk using only one side as a recording surface.

  As shown in FIG. 3, using the apparatus shown in FIG. 1, the substrate state measuring step (ST10) and the defect in-plane position specifying step are performed on the magnetic disk glass substrate 100 using the appearance inspection device 300 ( ST11). At this time, first, it is inspected whether or not there is a surface defect on one surface (referred to as “A surface”) of the glass substrate 100 for magnetic disk (ST12). It is determined whether the number of surface defects is equal to or less than a predetermined number of defects (threshold) (ST13). And when the number of defects on the A surface exceeds the threshold value, there is a possibility that it can be used as a glass substrate for a magnetic disk having only one surface (B surface) as a recording surface, so that only one surface is recorded as a temporary defective product. It is determined whether it can be used as a glass substrate for a magnetic disk to be used as (ST14), and the defect surface is confirmed (ST15).

  Further, an inspection is performed to determine whether or not there is a surface defect on the other surface of the glass substrate 100 for magnetic disk (this is referred to as “B surface”) (ST16). It is determined whether the number is equal to or less than a predetermined number of defects (threshold) (ST17). If the number of defects on the B surface exceeds the threshold value, it may be used as a glass substrate for a magnetic disk having only one surface (A surface) as a recording surface, so that only one surface is recorded as a temporary defective product. It is determined whether it can be used as a glass substrate for a magnetic disk to be used as a magnetic disk, and a defective surface is confirmed (ST19).

  If the number of defects on the B surface is less than or equal to the threshold value, it may be used as a glass substrate for a magnetic disk having both surfaces as recording surfaces. (ST20). If both sides are good, it is set as double-sided non-defective (DS (Double Side) -OK) (ST21). On the other hand, if the number of surface defects on the B surface exceeds the threshold value or if both surfaces are judged to be NG, there is a possibility that it can be used as a glass substrate for a magnetic disk having only one surface as a recording surface. Therefore, it is determined whether or not it can be used as a glass substrate for a magnetic disk that uses only one side as a recording surface as a temporary defective product (ST14, ST18), and the defect surface is confirmed (ST15, ST19).

  Next, the defect surface of the magnetic disk glass substrate 100 is confirmed using the apparatus shown in FIG. 2 (ST15, ST19). Thus, if any of the main surfaces satisfies a predetermined standard, the non-defective product is a glass substrate for magnetic disk (SS (Single Side)) using the main surface as a recording surface. That is, when the number of defects on one main surface is less than a predetermined number (threshold value), the magnetic disk glass substrate is determined to be OK (good) (SS-OK). In the defect surface confirmation, information on the position in the defect surface specified in the defect surface position specifying step is fed back to the apparatus shown in FIG.

  Specifically, the glass substrate 100 for a magnetic disk that has been temporarily defective in the A-side inspection may be judged NG in the A-side appearance inspection, including the number of defects on the B-side. Therefore, with the apparatus shown in FIG. 2, the threshold value is determined for the number of defects while focusing only on the A plane (ST22). Thereby, the number of defects existing only in the A plane can be confirmed. If the number of defects on the A side is equal to or smaller than the predetermined threshold, the process is terminated (ST23) as an A-side good product (SSA) that can use the A side. In addition, the glass substrate 100 for a magnetic disk that has become a temporary defective product in the B-side inspection may be judged NG in the B-side appearance inspection, including the number of defects on the A-side. With the apparatus shown in FIG. 2, the threshold value is determined for the number of defects while focusing only on the B surface (ST24). Thereby, the number of defects existing only on the B surface can be confirmed. If the number of defects on the B surface is equal to or less than a predetermined threshold, the processing ends as a B surface good product (SSB) that can be used on the B surface (ST25). On the other hand, if the number of defects on the A surface exceeds a threshold value, or if the number of defects on the B surface exceeds a predetermined threshold value, it is determined as a defective product (ST26).

Next, examples performed for clarifying the effects of the present invention will be described.
(Example)
First, the melted aluminosilicate glass was molded into a disk shape by direct pressing using an upper mold, a lower mold, and a body mold to obtain an amorphous plate glass material (blanks). At this point, the blank has a diameter of 66 mm. Next, after both first main surfaces of the blanks are lapped, a cylindrical core drill is used to form a hole in the center of the glass substrate and process (coring) the annular glass substrate. Implementation and a chamfering step (chamfered surface forming step) for forming a chamfered surface at the end (outer peripheral end and inner peripheral end) were performed, and then a second lapping process was performed.

  Next, the outer peripheral end of the glass substrate was mirror polished by a brush polishing method. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains was used.

  And the glass substrate which finished the mirror polishing process was washed with water. As a result, the diameter of the glass substrate was 65 mm, and the substrate used for the 2.5-inch magnetic disk could be obtained.

Next, as a main surface polishing step, a first polishing step was performed on both main surfaces of the glass substrate. In the first polishing step, a double-side polishing machine was used as the polishing apparatus. As a polishing pad in this polishing apparatus, a soft suede pad was used. A cerium abrasive was used as the abrasive. The polishing conditions were a processing surface pressure of 130 g / cm ² and a processing rotation speed of 22 rpm. Thereby, the arithmetic average roughness Ra of the glass substrate became about 1.5 nm.

Next, a second polishing process was performed. In the second polishing step, a double-side polishing machine was used as the polishing apparatus. As a polishing pad in this polishing apparatus, a soft suede pad (Asker C hardness: 54, compression deformation amount: 476 μm or more, density: 0.53 g / cm ³ or less) was used. Further, as the abrasive, a cerium abrasive having an average particle diameter of 100 nm was used. The polishing conditions were a processing surface pressure of 60 g / cm ² and a processing rotation speed of 20 rpm. The arithmetic average roughness Ra of the main surface used as the recording surface of the glass substrate was about 0.30 nm.

  The glass substrate after the second polishing step is immersed in a KOH solution, cleaned by applying ultrasonic waves for 120 seconds, scrubbed using an alkali cleaning solution for 4 seconds, diluted with a dilute sulfuric acid diluted in a trace amount, and After washing with the alkaline washing solution, IPA (isopropyl alcohol) was vapor-dried.

  Next, chemical strengthening was performed on the glass substrate after the second polishing step described above. For chemical strengthening, a chemical strengthening solution in which potassium nitrate (60%) and sodium nitrate (40%) are mixed is prepared, this chemical strengthening solution is heated to 380 ° C., and the cleaned glass substrate is placed therein for about 4 hours. This was done by dipping. Then, acid cleaning, alkali cleaning, and pure water cleaning were sequentially performed on the glass substrate after the chemical strengthening. Thus, a glass substrate for a magnetic disk was produced.

  Next, an inspection process for inspecting whether or not there was a defect was performed on both main surfaces of the glass substrate. In the inspection process, using the appearance inspection apparatus shown in FIG. 1, the presence / absence of a defect and the position information when there is a defect were acquired. Furthermore, using the optical microscope shown in FIG. 2, it was moved to the defect detected with the visual inspection apparatus, and it was investigated on which surface of the glass substrate for magnetic discs the defect detected with the visual inspection apparatus. Then, a glass substrate for magnetic disk that can use only one side as a recording surface was selected according to the procedure shown in FIG. Thus, a glass substrate for a magnetic disk was produced.

  100 magnetic disks were prepared by sequentially laminating an underlayer, a magnetic layer, a protective layer, and a lubricating layer on a glass substrate for magnetic disk that can use only one side as a recording surface. When a glide test of GH (glide height): 6.0 nm was performed on these magnetic disks, the yield rate was 93% as shown in FIG.

(Comparative example)
A magnetic disk glass substrate was produced in the same manner as in the example except that only the appearance inspection apparatus shown in FIG. 1 was used to select a magnetic disk glass substrate that could use only one side as a recording surface. 100 magnetic disks were prepared by sequentially laminating an underlayer, a magnetic layer, a protective layer, and a lubricating layer on a glass substrate for magnetic disk that can use only one side as a recording surface. When a glide test was performed on these magnetic disks in the same manner as in the example, the yield rate was 85% as shown in FIG. This is because when using only an appearance inspection apparatus to select a glass substrate for a magnetic disk that can use only one side (A side) as a recording surface, it is impossible to accurately confirm which side a defect exists on. This is probably because some of the defects on the A plane that should be NG are mistakenly recognized on the B plane, and the number of defects on the A plane is counted to be OK.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. In the above embodiment, the case where an optical system having a single-lens reflex function is disposed only on one side of a glass substrate for a magnetic disk and focus adjustment is performed to focus on both main surfaces has been described. In the present invention, an optical system having a single-lens reflex function may be arranged on both sides of the magnetic disk glass substrate so as to focus on each main surface. Further, the material, number, size, processing procedure, and the like in the above embodiment are merely examples, and various modifications can be made within the range where the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

It is a figure which shows typically the external appearance inspection apparatus used in manufacture of the glass substrate for magnetic discs concerning embodiment of this invention. It is a figure which shows the optical microscope used in manufacture of the glass substrate for magnetic discs concerning embodiment of this invention. It is a flowchart which shows the procedure of the defect inspection in manufacture of the glass substrate for magnetic discs concerning embodiment of this invention. It is a figure which shows the difference in the non-defective rate in the case of only an appearance inspection apparatus, and a combination of an appearance inspection apparatus and an optical system having a single lens reflex function.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Glass substrate for magnetic discs 300 Visual inspection apparatus 302a, 302b Defect detection probe lasers 304a to 304d Detector 305 Beam splitter 400 Optical system having a single-lens reflex function

Claims (2)

A method for manufacturing a glass substrate for a magnetic disk, comprising an inspection step for inspecting a glass substrate for a magnetic disk having a pair of main surfaces, wherein the optical automatic appearance is applied to the glass substrate for a magnetic disk in the inspection step. Inspecting for defects by inspection, and determining that the glass substrate for magnetic disk is a temporary defective product when the number of defects on one main surface of the glass substrate for magnetic disk exceeds a predetermined number, the temporary defective product In the state where the focal point of the optical system having a single-lens reflex function is aligned with the one main surface of the glass substrate for magnetic disk, defects existing on the one main surface of the glass substrate for magnetic disk When the number of defects on the one main surface of the glass substrate for magnetic disks is equal to or less than a predetermined number, only the one main surface is defined as a recording surface. Method of manufacturing a glass substrate for a magnetic disk, wherein determining a non-defective glass substrate for a magnetic disk that. When the number of defects specified by the optical automatic appearance inspection is a predetermined number or less, it is determined whether both main surfaces of the glass substrate for magnetic disk are non-defective, and is not determined as double-sided non-defective With respect to the magnetic disk glass substrate determined to be a temporary defective product, the magnetic system is in a state in which the focus of the optical system having the single-lens reflex function is aligned with the one main surface of the magnetic disk glass substrate. 2. The method for manufacturing a glass substrate for a magnetic disk according to claim 1 , wherein the number of defects, which is the number of defects existing on the one main surface of the disk glass substrate, is measured .

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