JP2012203942A - Manufacturing method for glass substrate for information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a glass substrate for an information recording medium, in which chemical strengthening processing can be performed on a surface of the glass substrate more uniformly.SOLUTION: A manufacturing method for a glass substrate for an information recording medium in which a magnetic recording layer is formed on a glass substrate 1 formed in a circular disk form includes: a step of preparing a holding jig 7 including a linear metal member; and a step of performing chemical strengthening processing on a surface of the glass substrate 1 by immersing the glass substrate 1 in a chemical strengthening processing liquid using the holding jig 7. The periphery of the holding jig 7 is open so that the convection of the chemical strengthening processing liquid is generated around the glass substrate 1 in the state that the glass substrate 1 is immersed in the chemical strengthening processing liquid.

Description

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

  An information recording medium such as a magnetic disk is mounted on a computer or the like as a hard disk. The information recording medium is manufactured from a glass substrate for information recording medium (hereinafter also referred to as a glass substrate).

  The recording density of information recording media tends to increase year by year. Along with this, the distance (head flying height) between the information recording medium and the magnetic head tends to decrease. When a DFH (Dynamic Flying Height) mechanism is employed for the information recording medium, the head flying height may be configured to be 3 nm or less. Under such a background, higher quality is required for information recording media and glass substrates for information recording media.

  As disclosed in Japanese Patent Application Laid-Open No. 2008-171502 (Patent Document 1), the method for manufacturing a glass substrate for information recording medium includes a chemical strengthening step of forming a chemically strengthened layer on the surface of the glass substrate. The chemical strengthening treatment needs to be uniformly applied to the entire surface of the glass substrate.

  A general chemical strengthening process will be described with reference to FIGS. 8 and 9. FIG. 8 is a cross-sectional view showing a holding jig 70 used in a general chemical strengthening process. FIG. 9 is an enlarged cross-sectional view showing a portion where the holding jig 70 holds the glass substrate 1. The holding jig 70 is similar to that disclosed in Japanese Patent Application Laid-Open No. 2008-171502 (Patent Document 1).

  As shown in FIG. 8, the holding jig 70 sandwiches both outer end portions of the glass substrate 1. The glass substrate 1 is immersed together with the holding jig 70 in a chemical strengthening treatment tank (not shown) in which the chemical strengthening treatment liquid is stored.

  Referring to FIG. 9, in the holding jig 70, two wires 73 are stretched from the side wall 71 toward the end portion 72. The glass substrate 1 is clamped by the wires 73 arranged to intersect each other. The outer peripheral end face 1 </ b> D of the glass substrate 1 is located between the wires 73. In the holding jig 70, the distance between the side wall 71 and the glass substrate 1 is small. The space between the outer peripheral end face 1 </ b> D of the glass substrate 1 and the end 72 is also spatially closed.

  In the holding jig 70, the chemical strengthening treatment liquid is not easily convected sufficiently in the region 75 surrounded by the side wall 71 and the end portion 72. The ion exchange is not sufficiently performed around the outer peripheral end face 1D. Variations occur in the thickness of the chemically strengthened layer (compressive stress layer) formed by the chemical strengthening treatment, and the glass substrate 1 has problems such as strain or undulation. Strain or waviness causes a so-called head crash.

JP 2008-171502 A

  The present invention has been made in view of the above circumstances, and provides a method for producing a glass substrate for an information recording medium capable of performing chemical strengthening treatment more uniformly on the surface of the glass substrate. The purpose is to do.

  A method for manufacturing a glass substrate for information recording medium according to the present invention is a method for manufacturing a glass substrate for information recording medium in which a magnetic recording layer is formed on a glass substrate formed in a circular disk shape, and a linear metal member A step of preparing a holding jig including: a step of immersing the glass substrate in a chemical strengthening treatment liquid using the holding jig and subjecting the surface of the glass substrate to a chemical strengthening treatment. And the periphery of the holding jig is open so that convection of the chemical strengthening treatment liquid occurs around the glass substrate in a state where the glass substrate is immersed in the chemical strengthening treatment liquid.

  Preferably, the holding jig is formed so as to linearly extend below the glass substrate, and to extend in a substantially V shape from the lower extension toward the upper side in the gravity direction. The first holding part sandwiches the first outer peripheral end face part located on the lower side in the gravity direction of the glass substrate.

  Preferably, the holding jig is attached to a side wall disposed around the glass substrate, and the holding jig is formed to extend in a substantially V shape from the side wall toward the glass substrate. The second holding part holds the second outer peripheral end face part located on both outer sides in the horizontal direction of the glass substrate.

Preferably, the metal member has a diameter of 0.01 mm or more and 5 mm or less. Preferably, the thermal expansion coefficient of the metal member is 24 × 10 ⁻⁶ / ° C. or less.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the glass substrate for information recording media which can perform a chemical strengthening process more uniformly with respect to the surface of a glass substrate can be obtained.

It is a perspective view which shows the glass substrate obtained by the manufacturing method of the glass substrate in embodiment. It is a perspective view which shows the magnetic disc provided with the glass substrate obtained by the manufacturing method of the glass substrate in embodiment. It is a flowchart figure which shows the manufacturing method of the glass substrate in embodiment. It is sectional drawing which shows the chemical strengthening processing apparatus used for the manufacturing method (chemical strengthening process) of the glass substrate in embodiment. It is a perspective view which shows the jig | tool for holding used for the manufacturing method (chemical strengthening process) of the glass substrate in embodiment. It is arrow sectional drawing along the VI-VI line in FIG. It is a perspective view which shows a mode that a glass substrate is hold | maintained at the jig | tool for holding used for the manufacturing method (chemical strengthening process) of the glass substrate in embodiment. It is sectional drawing which shows the holding jig used for the chemical strengthening process of a general glass substrate. It is sectional drawing which expands and shows the part by which the jig | tool for holding used for the chemical strengthening process of a common glass substrate hold | maintains a glass substrate.

  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.

[Glass substrate 1 and magnetic disk 10]
With reference to FIG. 1 and FIG. 2, the glass substrate 1 obtained by the manufacturing method of the glass substrate for information recording media based on this Embodiment and the magnetic disc 10 (refer FIG. 2) provided with the glass substrate 1 are demonstrated. . FIG. 1 is a perspective view showing a glass substrate 1 used for manufacturing a magnetic disk 10. FIG. 2 is a perspective view showing a magnetic disk 10 provided with a glass substrate 1 as an information recording medium.

  As shown in FIG. 1, a glass substrate 1 (glass substrate for information recording medium) used for manufacturing a magnetic disk 10 (see FIG. 2) is formed in a circular disk shape (annular disk shape). The glass substrate 1 has a front main surface 1A, a back main surface 1B, an inner peripheral end surface 1C, and an outer peripheral end surface 1D. A hole 1H is provided in the center of the glass substrate 1.

  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. The thickness of the glass substrate is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage. The glass substrate 1 in the present embodiment 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 1 is a value calculated by averaging the values measured at a plurality of arbitrary points that are point targets on the glass substrate 1.

  As shown in FIG. 2, the magnetic disk 10 is formed by forming a magnetic thin film layer 2 on the front main surface 1A of the glass substrate 1 described above. In FIG. 2, the magnetic thin film layer 2 is formed only on the front main surface 1A, but the magnetic thin film layer 2 may be formed on the back main surface 1B.

  The magnetic thin film layer 2 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the front main surface 1A of the glass substrate 1 (spin coating method). The magnetic thin film layer 2 may be formed on the front main surface 1A of the glass substrate 1 by a sputtering method, an electroless plating method, or the like.

  The film thickness of the magnetic thin film layer 2 formed on the front main surface 1A of the glass substrate 1 is about 0.3 μm to 1.2 μm in the case of the spin coating method, about 0.04 μm to 0.08 μm in the case of the sputtering method, In the case of the electroless plating method, the thickness is about 0.05 μm to 0.1 μm. From the viewpoint of thinning and high density, the magnetic thin film layer 2 is preferably formed by sputtering or electroless plating.

  The magnetic material used for the magnetic thin film layer 2 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. A Co-based alloy to which Ni or Cr is added is suitable. Further, as a magnetic layer material suitable for heat-assisted recording, an FePt-based material may be used.

  In order to improve the sliding of the magnetic recording head, the surface of the magnetic thin film layer 2 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.

  If necessary, an underlayer or a protective layer may be provided. The underlayer in the magnetic disk 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 is not limited to a single layer structure, and may be a multi-layer structure in which the same or different layers are stacked. The underlayer may have a multilayer structure made of, for example, Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV.

  Examples of the protective layer that prevents wear and corrosion of the magnetic thin film layer 2 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 by using an in-line sputtering apparatus together with an underlayer or a magnetic film. These protective layers may be composed of a single layer structure, or may be composed of a multilayer structure including 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.

[Glass substrate manufacturing method]
With reference to the flowchart shown in FIG. 3, the manufacturing method of the glass substrate (glass substrate for information recording media) in this Embodiment is demonstrated.

  The manufacturing method of the glass substrate in the present embodiment includes a rough lapping step (step S10), a shape processing step (step S20), a roughening step (step S30), a fine lapping step (step S40), and an end surface polishing step (step). S50), a main surface polishing step (step S60), a chemical strengthening step (step S70), and a cleaning step (step S80).

  A magnetic thin film forming step (step S90) is performed on the glass substrate (corresponding to the glass substrate 1 in FIG. 1) obtained through the cleaning step (step S80). The magnetic disk 10 (see FIG. 2) is obtained by the magnetic thin film forming step (step S90).

  The above steps are not necessarily required, and may be omitted or added as necessary. Hereinafter, each of these steps S10 to S90 will be described in order. In the following, simple cleaning appropriately performed between steps S10 to S90 is not described.

(Coarse lapping process: Step S10)
First, an upper mold, a lower mold, and a body mold are prepared, and the molten glass is directly pressed by these. A disk-shaped glass substrate having a diameter of 66 mmφ and a thickness of 1.2 mm is obtained. The glass material of the glass substrate is, for example, aluminosilicate glass. In addition to the direct press method, a disk glass substrate may be obtained by forming a sheet glass using a downdraw method or a float method and cutting out from the sheet glass with a grinding wheel.

The composition of aluminosilicate glass, for example, SiO ₂ is 58 wt% to 75 wt%, _Al 2 _{O 3} is 5 wt% to 23 wt%, Li ₂ O is 3% to 10% by weight, Na ₂ O 4 It contains from mass% to 13 mass% as a main component.

  A glass substrate obtained by direct pressing or the like is subjected to lapping. This lapping process is performed by a double-sided lapping apparatus for the purpose of improving dimensional accuracy and shape accuracy.

  The grain size of the abrasive grains used in the lapping process is, for example, # 400 (particle diameter of about 40 μm to 60 μm). In the polishing apparatus, alumina abrasive grains having a particle size of # 400 are used, and the load of the upper surface plate is set to about 100 kg. Both surfaces of the glass substrate housed in the carrier are finished to a surface accuracy of 0 μm to 1 μm and a surface roughness Rmax of about 6 μm.

(Shape processing step: Step S20)
As for the glass substrate which passed the rough lapping process, an outer peripheral end surface and an inner peripheral end surface are each ground. By the grinding, the outer diameter of the glass substrate becomes about 65 mm. The inner diameter of the glass substrate (the diameter of the hole 1H at the center) is about 20 mm. A predetermined chamfering process is performed on the outer peripheral end surface and the inner peripheral end surface. As for the surface roughness of the end surface of the glass substrate at this time, Rmax is about 2 μm. Generally, a glass substrate having an outer diameter of 65 mm is used for a 2.5-inch hard disk.

(Roughening step: Step S30)
The glass substrate that has undergone the shape processing step has a roughened surface. In this roughening step, a flat polishing machine is used. A plane polishing machine performs mechanical surface roughening on a glass substrate using loose abrasive polishing. The entire surface of the glass substrate is polished so as to have a substantially uniform surface roughness (Ra = 0.01 μm to 0.4 μm or so). The target surface roughness in the roughening step may be set in relation to the particle size of the fixed abrasive used in the fine lapping step (step S40) described below.

(Fine wrapping process: Step S40)
The glass substrate that has undergone the roughening step is set in a lapping apparatus. The main surface of the glass substrate is ground with a fixed abrasive polishing pad or a diamond sheet. The glass substrate is ground, for example, so that the surface roughness Ra is 0.1 μm or less and the flatness is 7 μm or less.

  Here, the main surface of the glass substrate is roughened in the roughening step (step S30). Since the catch made of fine fixed abrasive grains is formed on the main surface of the glass substrate, the problem that the fixed abrasive grains slide on the surface of the glass substrate is prevented. Therefore, the processing rate in the fine lapping process can be realized at a high processing rate from the start of surface polishing.

(End face polishing process: Step S50)
In the end surface polishing step, a brush polishing method is used. With the glass substrate rotated, the outer peripheral end surface and the inner peripheral end surface of the glass substrate are each polished. For example, the outer peripheral end surface and the inner peripheral end surface of the glass substrate have a surface roughness of about 0.4 μm for Rmax and about 0.1 μm for Ra. The surface of the glass substrate that has been subjected to end face polishing is washed with water.

(Main surface polishing step: Step S60)
The main surface polishing step has a first polishing step and a second polishing step. In the first polishing step, the main surface of the glass substrate is polished using the above-described double-side polishing apparatus. The scratches or distortions remaining in the fine wrapping process (step S40) are removed. In the first polishing step, for example, a polishing pad (a polisher is, for example, a suede pad) is used under the following conditions.

Polishing liquid: Cerium oxide (average particle size 1.3 μm) + water load: 80 g / cm ^{2 to} 100 g / cm ²
Polishing time: 30 minutes to 50 minutes Removal method: 35 μm to 45 μm
Next, the surface of the glass substrate is cleaned. The abrasive adhered to the surface of the glass substrate is removed. As a cleaning method, a cleaning liquid in which 1% by mass of HF and 3% by mass of sulfuric acid are mixed is used.

  For example, an ultrasonic wave of 80 kHz is applied to the cleaning liquid while the glass substrate is immersed in the cleaning liquid. Then, for example, 120 kHz ultrasonic waves are applied to the neutral detergent in a state where the glass substrate is immersed in the neutral detergent. Thereafter, the glass substrate is cleaned by rinsing using pure. Finally, the glass substrate is dried by IPA (Isopropyl alcohol).

  Thereafter, in the second polishing step, the main surface of the glass substrate is polished using a polishing pad that is a soft polisher (suede). As the abrasive, silica abrasive finer than the cerium oxide used in the first polishing step is used.

(Chemical strengthening process: Step S70)
Next, the chemical strengthening step will be described with reference to FIGS. FIG. 4 is a cross-sectional view schematically showing a chemical strengthening treatment apparatus 8 used in the chemical strengthening process. In the chemical strengthening step, the chemical strengthening processing device 8 is used. The chemical strengthening treatment apparatus 8 has a chemical strengthening treatment tank 9 that stores the chemical strengthening treatment liquid 6 therein. A molten salt is used as the chemical strengthening treatment liquid 6. This molten salt is obtained by heating a salt obtained by mixing potassium nitrate and sodium nitrate at 450 ° C.

  A holding jig 7 attached to the fixed body 4 is disposed inside the chemical strengthening treatment tank 9. The fixed body 4 is configured in a rectangular tube shape from the side walls 4A to 4D (see FIG. 5). An opening 4H is provided in the lower part of the fixed body 4. The holding jig 7 is surrounded by the side walls 4A to 4D. The plurality of glass substrates 1 that have undergone the main surface polishing step (step S <b> 60) are immersed in the chemical strengthening treatment liquid 6 while being held by the holding jig 7.

  The plurality of glass substrates 1 are arranged so that the adjacent glass substrates 1 face each other. Each surface of the plurality of glass substrates 1 is in a parallel positional relationship.

(Holding jig 7)
The holding jig 7 will be described in detail with reference to FIGS. FIG. 5 is a perspective view showing the holding jig 7. In FIG. 5, the glass substrate 1 is not shown for convenience of illustration. In FIG. 5, the side wall 4A and a part of the side wall 4B are shown as being broken, but are actually continuous. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. FIG. 7 is a perspective view showing a state in which the glass substrate 1 is held by the holding jig 7.

  As shown in FIGS. 5 to 7, the holding jig 7 includes a first holding part 7A, second holding parts 7B1 and 7B2, an upper extending part 7C, and a lower extending part 7D. The holding jig 7 (the first holding portion 7A, the second holding portions 7B1 and 7B2, the upper extending portion 7C, and the lower extending portion 7D) is composed of a linear metal member.

The linear metal member is a wire or a wire. The diameter of the linear metal member is preferably 0.01 mm or more and 5 mm or less. The thermal expansion coefficient of the linear metal member is preferably 24 × 10 ⁻⁶ / ° C. or less. The periphery of the holding jig 7 is surrounded by side walls 4 </ b> A to 4 </ b> D constituting the fixed body 4. The holding jig 7 and the fixed body 4 are configured in a so-called netting shape by being assembled.

  Lower extension part 7D is extended linearly along the direction (FIG. 6 paper surface left-right direction) where the glass substrate 1 is arranged. One end and the other end of the lower extension 7D are fixed to the side wall 4A and the side wall 4C, respectively.

  7 A of 1st holding parts are formed so that it may extend in a substantially V shape toward the upper part from the downward direction of a gravitational direction. The lower end of the first holding portion 7A is supported upward by the lower extending portion 7D (see FIGS. 5 and 7).

  A plurality of upper extending portions 7C are provided in a straight line so as to bridge between the side wall 4B and the side wall 4D. The plurality of upper extending portions 7C are arranged at equal intervals in the direction in which the glass substrates 1 are arranged (the left-right direction in FIG. 6). Between the adjacent upper extending portions 7C, the glass substrate 1 is disposed (see FIGS. 6 and 7). One upper end and the other upper end of the first holding portion 7A are respectively fixed to the adjacent upper extending portions 7C.

  The second holding portions 7B1 and 7B2 extend in the horizontal direction in a substantially V shape from the outer side to the inner side of the glass substrate 1 in the horizontal direction. The second holding unit 7B1 and the second holding unit 7B2 are arranged to face each other.

  One of the distal end portions in the extending direction of the second holding portion 7B1 and the other distal end portion are respectively fixed on the adjacent upper extending portions 7C. The rear end portion of the second holding portion 7B1 in the extending direction is fixed to the side wall 4B. Similarly, one of the leading end portions in the extending direction of the second holding portion 7B2 and the other leading end portion are respectively fixed on the adjacent upper extending portions 7C. The rear end portion of the second holding portion 7B2 in the extending direction is fixed to the side wall 4D.

  Referring to FIG. 7, first holding portion 7 </ b> A sandwiches first outer peripheral end surface portion 1 </ b> DA located on the lower side of glass substrate 1 in the gravity direction. The second holding portion 7B1 sandwiches the second outer peripheral end face portion 1DB1 located on one outer side of the glass substrate 1 in the horizontal direction. Similarly, 2nd holding | maintenance part 7B2 clamps 2nd outer peripheral end surface part 1DB2 located in the other outer side of the horizontal direction of the glass substrate 1. As shown in FIG. The glass substrate 1 is held by the first holding part 7A and the second holding parts 7B1 and 7B2.

  As described above, the holding jig 7 in the present embodiment is composed of a linear metal member. A linear metal member is comprised from the wire or wire which has a diameter of 0.01 mm or more and 5 mm or less, for example. As shown in FIG. 6, the holding jig 7 is surrounded by the chemical strengthening treatment liquid 6 around the glass substrate 1 in a state where the glass substrate 1 is immersed in the chemical strengthening treatment liquid 6 (see FIG. 4). Open to allow sufficient convection. With this configuration, uniform chemical strengthening treatment can be satisfactorily performed on the entire surface of the glass substrate 1.

In the chemical strengthening step, a chemical strengthening process is performed on the glass substrate. Ions present on the surface of the glass substrate are exchanged for other ions having an ionic radius larger than the ions. For example, when the glass substrate is an aluminosilicate glass, Li ⁺ and Na ⁺ are exchanged for ions having a larger ionic radius than Li ⁺ and Na ⁺ (such as Na ⁺ and K ⁺ ).

  In the chemical strengthening step, ion exchange is performed from the glass substrate surface to a depth of about 5 μm (in the thickness direction of the glass substrate). By applying a compressive stress to the surface of the glass substrate, the rigidity of the glass substrate is improved.

(Washing process: Step S80)
Referring to FIG. 3 again, the glass substrate 1 on which the chemical strengthening process (step S70) has been completed is immersed in an alkaline cleaning liquid. An ultrasonic wave of 80 kHz is applied to the cleaning liquid. Thereafter, the glass substrate 1 is immersed in a cleaning liquid made of an acidic detergent. Ultrasonic waves of 430 kHz and 950 kHz are sequentially applied to the cleaning liquid. Further, a plurality of glass substrates 1 are subjected to a drying process using 950 kHz rinse (pure water 18 MΩ · cm).

  The above rough lapping process (step S10), shape processing process (step S20), roughening process (step S30), fine lapping process (step S40), end face polishing process (step S50), main surface polishing process (step S60). ), Chemical strengthening step (step S70), and washing step (step S80), the information recording medium glass substrate 1 (see FIG. 1) is obtained. The second polishing step in the main surface polishing step (step S60) may be performed after the chemical strengthening step (step S70).

(Magnetic thin film forming step: Step S90)
A magnetic thin film layer 2 (see FIG. 2) is formed on both main surfaces (or one of the main surfaces) of the glass substrate (corresponding to the glass substrate 1 shown in FIG. 1) for which the cleaning process (step S80) has been completed. The The magnetic thin film layer 2 is made of an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and an F system. The lubricating layer is formed by sequentially forming a film.

  By forming the magnetic thin film layer 2, a perpendicular magnetic recording disk corresponding to the magnetic disk 10 shown in FIG. 2 can be obtained. The magnetic disk in the present embodiment is an example of a perpendicular magnetic disk composed of the magnetic thin film layer 2. The magnetic disk may be composed of a magnetic layer or the like as a so-called in-plane magnetic disk.

(Action / Effect)
According to the method for manufacturing a glass substrate for information recording medium in the present embodiment, a uniform chemical strengthening process can be performed on the entire surface of glass substrate 1 in the chemical strengthening step (step S70).

  Here, the linear metal member constituting the holding jig 7 is composed of a wire or a wire having a diameter of 0.01 mm or more and 5 mm or less. If the diameter is smaller than 0.01 mm, the holding jig 7 may be damaged on the glass substrate 1.

  If the diameter is larger than 5 mm, the chemical strengthening layer is hardly formed well at the contact portion between the holding jig 7 and the glass substrate 1. Therefore, the linear metal member constituting the holding jig 7 is preferably composed of a wire or a wire having a diameter of 0.01 mm or more and 5 mm or less.

Moreover, the thermal expansion coefficient of the linear metal member constituting the holding jig 7 is preferably 24 × 10 ⁻⁶ / ° C. or less. When the thermal expansion coefficient is larger than this value, the holding jig 7 expands too much in the chemical strengthening treatment liquid 6 (molten salt), and thus it becomes difficult to hold the glass substrate 1. As a minimum of a thermal expansion coefficient, it is good to have a certain amount of hardness from a viewpoint that it has the intensity | strength which can hold | maintain the glass substrate 1. FIG.

  In the above-described embodiment, the holding jig 7 is attached to the fixed body 4 (side walls 4A to 4D). Instead of using the fixed body 4, the holding jig 7 may be configured to be able to stand on its own only from a wire-like member. Even in this case, since the good convection of the chemical strengthening treatment liquid 6 is obtained around the holding jig 7, the same operation and effect as the above-described embodiment can be obtained.

[Examples and Comparative Examples]
An example based on the above-described embodiment and a comparative example for this will be described.

Example 1
In Example 1, the holding jig 7 was configured using a wire having a diameter of 0.5 mm. Under the conditions, the surface of the glass substrate 1 was subjected to a chemical strengthening process in the same manner as the above-described chemical strengthening step (Step S70). Thereafter, the magnetic thin film layer 2 was formed on the glass substrate 1 to obtain the magnetic disk 10. Using this magnetic disk 10, an HDD (Hard Disk Drive Device) was produced. The HDD was dropped so that an impact of 1000 G (1G: 9.80665 m / s ² ) was applied to the HDD. At that time, it was visually confirmed whether or not the magnetic disk 10 built in the HDD was broken.

  When this drop test was repeated 10 times, the magnetic disk 10 composed of the glass substrate 1 in Example 1 never cracked.

(Example 2)
In Example 2, the holding jig 7 was configured using a wire having a diameter of 0.8 mm. Under the conditions, the chemical strengthening treatment was performed in the same manner as in Example 1 above. When the same drop test as in Example 1 was performed, one or two cracks occurred in the magnetic disk 10 out of 10 times.

(Comparative example)
In the comparative example, the surface of the glass substrate 1 was chemically strengthened using the holding jig 70 shown in FIGS. 8 and 9 in the same manner as the above-described chemical strengthening step. When the same drop test as in Example 1 was performed, 6 or more cracks occurred in the magnetic disk 10 out of 10 times.

  From the above experimental results, a chemical strengthening layer (compressive stress layer) having high strength is formed on the glass substrate 1 by performing the chemical strengthening process using the holding jig 7 in the present embodiment. Recognize.

  The embodiment and each example based on the present invention have been described above, but the embodiment and each example disclosed this time are illustrative in all points and are not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 glass substrate (glass substrate for information recording medium), 1A front main surface, 1B back main surface, 1C inner peripheral end surface, 1D outer peripheral end surface, 1DA first outer peripheral end surface portion, 1DB1, 1DB2 second outer peripheral end surface portion, 1H hole, 2 Magnetic thin film layer, 4 fixed body, 4A, 4B, 4C, 4D, 71 side wall, 4H opening, 6 chemical strengthening treatment solution, 7, 70 holding jig, 7A first holding portion, 7B1, 7B2 second holding Part, 7C upper extension part, 7D lower extension part, 8 chemical strengthening treatment device, 9 chemical strengthening treatment tank, 10 magnetic disk, 72 end part, 73 wire, 75 region, S10, S20, S30, S40, S50, S60, S70, S80, S90 steps.

Claims (5)

A method for producing a glass substrate for an information recording medium in which a magnetic recording layer is formed on a glass substrate formed in a circular disk shape,
Preparing a holding jig containing a linear metal member;
Immersing the glass substrate in a chemical strengthening treatment liquid using the holding jig, and performing a chemical strengthening treatment on the surface of the glass substrate,
The periphery of the holding jig is opened so that convection of the chemical strengthening treatment liquid occurs around the glass substrate in a state where the glass substrate is immersed in the chemical strengthening treatment liquid.
A method for producing a glass substrate for an information recording medium. The holding jig is
A lower extending portion extending linearly below the glass substrate;
A first holding part formed so as to extend in a substantially V shape from the lower extension part upward in the direction of gravity,
The first holding portion sandwiches a first outer peripheral end surface portion located on the lower side in the gravity direction of the glass substrate.
The manufacturing method of the glass substrate for information recording media of Claim 1. The holding jig is attached to a side wall disposed around the glass substrate,
The holding jig includes a second holding portion formed so as to extend in a substantially V shape from the side wall toward the glass substrate,
The second holding part sandwiches the second outer peripheral end face part located on both outer sides in the horizontal direction of the glass substrate,
The manufacturing method of the glass substrate for information recording media of Claim 1 or 2. The diameter of the metal member is 0.01 mm or more and 5 mm or less.
The manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 3. The thermal expansion coefficient of the metal member is 24 × 10 ⁻⁶ / ° C. or less.
The manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 4.

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