JPWO2014045653A1 - Method for manufacturing glass substrate for information recording medium, method for manufacturing information recording medium, and polishing pad - Google Patents

Abstract

In this method of manufacturing a glass substrate for information recording medium, in a state where slurry is supplied to the polishing pad (410), the adsorption force of the polishing pad (410) to the glass substrate (1) is 0.50 g / cm 2 or more, 15 g / cm 2 or less.

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, in a hard disk drive (HDD) device, the recording density has been increased. As the recording density is increased, the gap (flying height) between the information recording medium (medium) and the head that reads and writes the recording while floating on the information recording medium is reduced to about several nanometers.

  As the flying height becomes smaller, when an information recording medium is used in a hard disk drive device, a read error and / or a write error when accessing data recorded on the medium, a head crash where the magnetic head collides with the medium surface, etc. The problem is more likely to occur. In order to suppress these problems, since the size of defects on the substrate surface allowed as an information recording medium is also smaller, even as a glass substrate for information recording media, higher surface smoothness has been pursued, In order to suppress foreign matter adhering to the glass substrate surface and undulation of the glass substrate surface, various devices have been devised in the manufacturing method.

  On the other hand, in recent years, the storage capacity of HDDs has been further improved. Currently, a single 2.5-inch recording medium has a recording capacity of 500 GB (single-sided 250 GB) and a surface recording density of 630 Gbit / square inch or more. Things are being developed.

  In the manufacturing process of the glass substrate for information recording media, the process of grind | polishing the surface of a glass substrate using a double-side polish apparatus is employ | adopted. For example, Japanese Patent Laying-Open No. 2005-8353 (Patent Document 1) discloses a jig having a special structure for recovering a polished glass substrate from a lower polishing pad placed on a lower surface plate. Is used.

JP 2005-8353 A

  When the glass substrate after polishing is taken out from the lower polishing pad on the lower surface plate using the above jig, the glass substrate may be firmly adsorbed on the lower polishing pad. If the adsorption force for adsorbing the glass substrate by the lower polishing pad is large, a large force is required when the glass substrate is taken out from the lower polishing pad. May adhere to the glass substrate.

  After the glass substrate with dirt attached is converted into an information recording medium (magnetic disk), the recording characteristics are deteriorated.

  A large force when removing the glass substrate from the lower polishing pad is applied to the lower polishing pad and the lower surface plate, and there is a possibility that the lower polishing pad and the lower surface plate are damaged.

  When the lower polishing pad and the lower surface plate are damaged, defects such as scratches occur on the glass substrate polished using the lower polishing pad, and the recording characteristics are deteriorated after the information recording medium is formed. In the double-side polishing apparatus, the same problem may occur in the upper polishing pad and the upper surface plate.

  The present invention has been made in view of the above circumstances, and provides an information recording medium glass substrate that does not cause deterioration in recording characteristics after the information recording medium glass substrate is converted into an information recording medium. An object of the present invention is to provide a method for producing a glass substrate for an information recording medium.

  A method for producing a glass substrate for an information recording medium according to the present invention includes a polishing apparatus for mounting a polishing pad made of a member including a plurality of foam holes on a surface plate and polishing the surface of the glass substrate using the polishing pad. Is a method for manufacturing a glass substrate for an information recording medium, comprising the following steps.

  The step of placing the glass substrate on the surface plate, the step of polishing the surface of the glass substrate while supplying a liquid abrasive to the glass substrate by the polishing apparatus, and after polishing from the surface plate Removing the glass substrate.

In a state where the liquid abrasive is supplied to the polishing pad, the adsorption force of the polishing pad to the glass substrate is 0.50 g / cm ² or more and 15 g / cm ² or less.

In another embodiment, the polishing pad has a plurality of communication holes that communicate the adjacent foam holes, and a cross-sectional area of the polishing pad in a longitudinal section along the normal direction of the surface plate is 0. 0. 01Mm ² or more of the communication hole is present at 30 or more density per 25 mm ² in the longitudinal section.

In another embodiment, in the longitudinal section of the polishing pad along the normal direction of the surface plate, the communication hole having a cross-sectional area of 0.01 mm ² or more has a density of 80 or more per 25 mm ^{2 in the} longitudinal section. Exists.

  In another embodiment, in the step of taking out the glass substrate after polishing from the surface plate, the glass substrate after polishing is taken out from the surface plate while the polishing pad contains the liquid abrasive.

  In another embodiment, in the step of removing the glass substrate after polishing from the surface plate, the concentration of the liquid abrasive is such that the liquid abrasive in the step of polishing the surface of the glass substrate by the polishing apparatus. It is 1.5 times or more compared with the concentration of.

  According to the present invention, an information recording medium glass substrate capable of providing a glass substrate for information recording medium that does not cause deterioration in recording characteristics after the information recording medium glass substrate is converted into an information recording medium. A manufacturing method is provided.

It is a perspective view which shows the glass substrate used for a magnetic disc. It is a perspective view which shows the magnetic disc provided with the glass substrate. It is a flowchart which shows the manufacturing method of the glass substrate in embodiment. It is a fragmentary perspective view of the double-side polish apparatus used for a grinding | polishing process. It is a flowchart which shows the breakdown of the 2nd polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is an expanded longitudinal cross-sectional view of the lower side polishing pad in background art. It is an expansion longitudinal cross-sectional view of the lower side polishing pad in embodiment. It is a figure which shows the defect test result and the read / write test result in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 3.

  Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of the embodiments and 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.

(Glass substrate 1 / 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 provided with the glass substrate 1 are demonstrated first. FIG. 1 is a perspective view showing a glass substrate 1 used for a magnetic disk 10 (see FIG. 2). 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 a magnetic disk 10 has an annular disk shape with a hole 1H formed in the center. The circular disk-shaped 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.

  The size of the glass substrate 1 is not particularly limited, and is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch outer diameter. The thickness of the glass substrate 1 is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage. As for the size of the glass substrate 1 in the present embodiment, the outer diameter is about 65 mm, the inner diameter is about 20 mm, and the thickness is 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-symmetric on the glass substrate 1.

  As shown in FIG. 2, in the magnetic disk 10, a magnetic film is formed on the front main surface 1A of the glass substrate 1 to form a magnetic thin film layer 2 including a magnetic recording layer. 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 also 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 about 1.2 μm in the case of the spin coating method, and about 0.04 μm to about 0.00 in the case of the sputtering method. In the case of the electroless plating method, the thickness is about 0.05 μm to about 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. 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.

  Furthermore, you may provide a base layer and / or a protective layer as needed. The underlayer in the magnetic disk 10 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 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 with an in-line type sputtering apparatus, such as an underlayer and a magnetic film. These protective layers 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, tetraalkoxysilane 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)
Next, a method for manufacturing a glass substrate for information recording medium (hereinafter simply referred to as a glass substrate) in the present embodiment will be described with reference to the flowchart shown in FIG. FIG. 3 is a flowchart showing a method for manufacturing the glass substrate 1 in the embodiment.

  The glass substrate manufacturing method in the present embodiment includes a glass blank material preparation step (step S10), a glass substrate formation / grinding step (step S20), a polishing step (step S30), a chemical strengthening step (step S40), and a cleaning. The process (step S50) is provided. The magnetic thin film forming step (step S60) may be performed on the glass substrate (corresponding to the glass substrate 1 in FIG. 1) obtained through the chemical strengthening treatment step (step S40). The magnetic disk 10 as an information recording medium is obtained by the magnetic thin film forming step (step S60).

  Hereinafter, details of each of these steps S10 to S60 will be described in order. In the following, simple cleaning appropriately performed between steps S10 to S60 is not described.

(Glass blank material preparation process)
In the glass blank material preparation step (step S10), the glass material constituting the glass substrate is melted (step S11). For example, general aluminosilicate glass is used as the glass material. Aluminosilicate glass, and SiO ₂ of 58 wt% to 75 wt%, and _Al 2 _{O 3} of 5 wt% to 23 wt%, and Li ₂ O 3 wt% to 10 wt%, 4 wt% to 13 wt % Na ₂ O as a main component. The molten glass material is poured onto the lower mold and then press-molded with the upper mold and the lower mold (step S12). A disk-shaped glass blank (glass base material) is formed by press molding.

  The glass blank material may be formed by cutting out a sheet glass (sheet glass) formed by a downdraw method or a float method with a grinding wheel. Further, the glass material is not limited to aluminosilicate glass, and may be any material.

(Glass substrate formation / grinding process)
Next, in the glass substrate formation / grinding process (step S20), the first lapping process is performed on both main surfaces of the press-molded glass blank material for the purpose of improving dimensional accuracy and shape accuracy. (Step S21). Both main surfaces of a glass blank material are the main surfaces used as the front main surface 1A and the main surface used as the back main surface 1B in FIG. 1 through each process mentioned later (henceforth, both main surfaces) Also called). For example, alumina abrasive grains having a particle size of # 400 (particle size of about 40 to 60 μm) are used, and the surface roughness Rmax is finished to about 6 μm.

  After the first lapping step, a coring (inner peripheral cut) process is performed on the center portion of the glass blank using a cylindrical diamond drill or the like (step S22). By the coring process, an annular glass substrate having a hole in the center is obtained. A predetermined chamfering process may be performed on the hole in the center.

  The inner peripheral end surface and the outer peripheral end surface of the glass substrate are polished into a mirror surface by a brush (step S22). As the abrasive grains, a slurry containing cerium oxide abrasive grains is used.

  Next, a second lapping step is performed on both main surfaces of the glass substrate (step S23). The second lapping step is performed using a double-side grinding apparatus that uses a planetary gear mechanism. Specifically, press the surface plate from above and below both main surfaces of the glass blank material, supply water, grinding liquid or lubricating liquid onto both main surfaces, and move the glass blank material and the lapping surface plate relatively. Then, the second lapping step is performed.

  By the second lapping step, the approximate parallelism, flatness, thickness, etc. of the glass substrate are preliminarily adjusted, and a glass base material having a substantially flat main surface is obtained. In the second lapping step, fine abrasive grains are used as compared with the first lapping step in order to reduce the generated grinding marks. For example, by attaching fixed abrasive grains such as a diamond tile pad on a surface plate, both surfaces of the glass substrate are finished to a surface roughness Rmax of about 2 μm.

(Polishing process)
Next, in the polishing process (step S30), as a first polishing process (rough polishing), while removing scratches remaining on both main surfaces of the glass substrate in the second lapping process (step S23), The warp is corrected (step S31). In the first polishing process, a double-side polishing apparatus using a planetary gear mechanism is used. For example, polishing is performed using a polishing pad such as hard velor, foamed polyurethane, or pitch-impregnated suede. As the abrasive, a slurry as a liquid abrasive mainly composed of general cerium oxide abrasive grains is used. The substrate polished in the first polishing process is recovered in the first polishing removal process.

  In the second polishing step (precise polishing), the glass substrate is subjected to polishing again, and minute defects and the like remaining on both main surfaces of the glass substrate are eliminated (step S33). Both main surfaces of the glass substrate are finished to have a mirror-like surface, thereby forming a desired flatness and eliminating the warpage of the glass substrate. In the second polishing step, a double-side polishing apparatus using a planetary gear mechanism is used. Polishing is performed using, for example, a suede pad, which is a soft polisher made of foamed polyurethane. As the abrasive, a slurry as a liquid abrasive mainly composed of general colloidal silica, which is finer than the cerium oxide used in the first polishing step, is used.

  Here, a schematic configuration of the double-side polishing apparatus 2000 will be described with reference to FIG. FIG. 4 is a partial perspective view of a double-side polishing apparatus 2000 used in the polishing process.

  The double-side polishing apparatus 2000 includes an upper surface plate (upper whetstone holding surface plate) 300, a lower surface plate (lower whetstone holding surface plate) 400, and a side (glass substrate side) facing the lower surface plate 400 of the upper surface plate 300. The upper polishing pad 310 mounted on the lower surface and the lower polishing pad 410 mounted on the upper surface on the side facing the upper surface plate 300 (glass substrate side) of the lower surface plate 400 are provided.

  The upper polishing pad 310 and the lower polishing pad 410 are processing members for polishing both main surfaces of the glass substrate 1. The upper surface plate 300 and the lower surface plate 400 rotate in directions opposite to each other with respect to the revolution direction of the carrier 500. A surface of the upper polishing pad 310 facing the lower surface plate 400 forms an upper polishing surface 311. The surface of the lower polishing pad 410 facing the upper surface plate 300 forms a lower polishing surface 411. Carrier 500 is arranged in a gap formed between upper surface plate 300 and lower surface plate 400. A plurality of disk-shaped glass substrates 1 are held by the carrier 500.

  The glass substrate 1 is sandwiched between an upper surface plate 300 and a lower surface plate 400, and stress is applied in the thickness direction of the glass substrate by the upper surface plate 300 and the lower surface plate 400. As a result, both main surfaces of the glass substrate are pressed against the polishing surface 311 of the upper polishing pad 310 and the polishing surface 411 of the lower polishing pad 410. In this state, the polishing surface 311 of the upper polishing pad 310 moves relative to one main surface of the glass substrate, whereby the one main surface is polished. At the same time, the polishing surface 411 of the lower polishing pad 410 moves relative to the other main surface of the glass substrate, whereby the other main surface is polished. In this manner, both main surfaces of the glass substrate are simultaneously polished using the double-side polishing apparatus 2000.

  After precision polishing using the double-side polishing apparatus, the glass substrate 1 attached to the polishing surface 311 of the upper polishing pad 310 and the polishing surface 411 of the lower polishing pad 410 is taken out from the polishing pad. The removal from the polishing pad of the glass substrate will be described later.

(Chemical strengthening process)
After the glass substrate 1 is washed, the chemical strengthening layer is formed on both main surfaces of the glass substrate 1 by immersing the glass substrate 1 in the chemical strengthening treatment liquid (step S40). After the glass substrate 1 is cleaned, the glass substrate 1 is immersed for about 30 minutes in a chemical strengthening treatment solution such as a mixture solution of potassium nitrate (70%) and sodium nitrate (30%) heated to 300 ° C. By doing so, chemical strengthening is performed.

  Alkali metal ions such as lithium ions and sodium ions contained in the glass substrate 1 are replaced by alkali metal ions such as potassium ions having a larger ion radius than these ions (ion exchange method).

  Compressive stress is generated in the ion-exchanged region due to strain caused by the difference in ion radius, and both main surfaces of the glass substrate 1 are strengthened. For example, on both the main surfaces of the glass substrate 1, a chemical strengthening layer may be formed in a range from the surface of the glass substrate 1 to about 5 μm to improve the rigidity of the glass substrate 1. As described above, a glass substrate corresponding to the glass substrate 1 shown in FIG. 1 is obtained.

  The glass substrate 1 may be further subjected to a polishing treatment with a machining allowance on both main surfaces of 0.1 μm or more and 0.5 μm or less. By removing the deposits remaining on the main surface of the glass substrate 1 after the chemical strengthening step, occurrence of head crashes in a magnetic disk manufactured using the glass substrate 1 is reduced. By setting the machining allowance on both the main surfaces in the polishing process to 0.1 μm or more and 0.5 μm or less, the unevenness of stress generated by the chemical strengthening process does not appear on the surface. The manufacturing method of the glass substrate in the present embodiment is configured as described above.

  A chemical strengthening step may be performed between the first polishing step (rough polishing) and the second polishing step (precision polishing).

(Washing process)
Next, the glass substrate is cleaned (step S50). By cleaning both main surfaces of the glass substrate 1 with detergent, pure water, ozone, IPA (isopropyl alcohol), UV (ultraviolet) ozone, etc., the deposits adhering to both main surfaces of the glass substrate 1 are removed. The

  Thereafter, the number of deposits on the surface of the glass substrate 1 is inspected using an optical defect inspection apparatus or the like.

(Magnetic thin film formation process)
The magnetic thin film layer 2 is formed by forming a magnetic film on both main surfaces (or one of the main surfaces) of the glass substrate (corresponding to the glass substrate 1 shown in FIG. 1) that has been subjected to the chemical strengthening treatment. Is done. 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 a magnetic thin film layer. The magnetic disk may be composed of a magnetic layer or the like as a so-called in-plane magnetic disk.

(Second polishing step S33)
Here, the details of the second polishing step S33 will be described with reference to FIGS. FIG. 5 is a flowchart showing the breakdown of the second polishing step S33, FIG. 6 is an enlarged longitudinal sectional view of the lower polishing pad 410 in the background art, and FIG. 7 is an enlarged longitudinal sectional view of the lower polishing pad 410 in the embodiment. FIG. Hereinafter, the lower polishing pad and the lower surface plate will be mainly described, but the same applies to the upper polishing pad and the upper surface plate.

  Referring to FIG. 5, the second polishing step S33 includes a carrier placement step (S331), a glass substrate placement step (S332), a polishing step (S333), a glass substrate removal step (S334), and a carrier removal step (S335). have.

  In each of these steps, the adsorption to the lower polishing pad 410 of the glass substrate 1 has been a problem in the glass substrate removal step (S334). As shown in FIG. 6, in the background art, the lower polishing pad 410 has individual foam holes 410h that are independent of the adjacent foam holes 410h or communicate with the adjacent foam holes 410h. This is because a polishing pad having a closed foam structure, in which very few are used, is used.

  Therefore, during the polishing step (S333), the glass substrate 1 is pressed while being sandwiched between the upper polishing pad 310 and the lower polishing pad 410, and thus the upper polishing pad 310 and the lower polishing pad 410 (in particular, There was a phenomenon in which the lower polishing pad 410) positioned on the lower side was firmly adsorbed to the glass substrate 1 (adsorption force indicated by arrow S2 in the figure).

  On the other hand, FIG. 7 shows an enlarged view of the lower polishing pad 410 in the present embodiment. The lower polishing pad 410 in this embodiment has a continuous foam structure instead of an independent foam structure, but employs a polishing pad. Therefore, in the lower polishing pad 410, a communication hole 410c that communicates with the adjacent foam hole 410h is formed. Specific examples of the material include a polyurethane foam material and a suede pad formed by a wet coagulation method.

  Thus, by using a continuous foam structure for the lower polishing pad 410, a slurry flow and an air flow (arrows in the horizontal direction in FIG. 7) are generated between the adjacent foam holes 410h. The adsorption force (adsorption force indicated by arrow S1 in FIG. 7) of the glass substrate 1 by 410 can be reduced.

Here, in the polishing step (S333) in which the slurry is supplied to the lower polishing pad 410, the adsorption force of the glass substrate 1 by the lower polishing pad 410 is 0.50 g / cm ² or more and 15 g / cm ^2. The following is preferable.

This is because if the adsorption force is less than 0.50 g / cm ² , slippage between the glass substrate 1 and the polishing pad increases, and polishing of the surface of the glass substrate 1 by the polishing pad cannot be expected. This is because when the adsorption force exceeds 15 g / cm ² , the force applied when the glass substrate 1 is taken out from the lower polishing pad 410 becomes too large (the adsorption force is too large).

The lower polishing pad 410 includes a communication hole 410c having a cross-sectional area S of 0.01 mm ² or more in a longitudinal section (cross section shown in FIG. 7) of the lower polishing pad 410 along the normal direction of the lower surface plate 400. It may be present at a density of 30 or more per 25 mm ^{2 on the} surface. Thereby, the adsorption | suction force of the glass substrate 1 by the lower side polishing pad 410 can be set to the said range.

Preferably, in the longitudinal cross section of the lower polishing pad 410, the communication holes 410c having a cross-sectional area S of 0.01 mm ² or more are present at a density of 80 or more per 25 mm ^{2 in} the longitudinal cross section. Thereby, the adsorption | suction force of the glass substrate 1 by the lower side polishing pad 410 can be set to a more preferable range.

  In the glass substrate removal step (S334), it is preferable to take out the polished glass substrate 1 from the lower surface plate 400 while the lower polishing pad 410 contains slurry. In the background art, cleaning for washing away the slurry is performed after the polishing step (S333). However, it has been found that by performing this cleaning, the adsorption power of the glass substrate 1 by the lower polishing pad 410 is increased. In the present embodiment, the glass substrate 1 and the lower polishing pad 410 are cleaned after the glass substrate removing step (S334).

  Furthermore, it is preferable that the concentration of the slurry in the glass substrate extraction step (S334) is 1.5 times or more compared to the concentration in the polishing step (S333) by the double-side polishing apparatus 2000. Thereby, the adsorption | suction power of the glass substrate 1 by the lower side polishing pad 410 in a glass substrate extraction process (S334) can be reduced further. Specifically, a new slurry may be added in the glass substrate extraction step (S334).

(Example)
Hereinafter, an example based on the present embodiment will be described with reference to FIG. FIG. 8 is a diagram showing the defect inspection result and the read / write test result in Example 1 to Example 5 and Comparative Example 1 to Comparative Example 3. In Examples 1 to 5 and Comparative Examples 1 to 3, all the steps shown in FIG. 3 are adopted up to the first polishing step (S31).

  The concentration of the slurry used in the polishing step (S333) of the second polishing step (S33) was all 15 wt%. In the glass substrate taking-out process (S334), the polishing pads to be used (upper polishing pad 310 and lower polishing pad 410) and the slurry state after the polishing process (S333) are classified into eight conditions (from Example 1). The process was divided into Example 5 and Comparative Example 1 to Comparative Example 3).

  In Example 1 and Comparative Example 1, a cleaning process was performed after the polishing process (S333) and before the glass substrate extraction process (S334).

  In Example 2 and Example 3, after completion of the polishing step (S333), before the glass substrate extraction step (S334), the concentration of the slurry, which was 15 wt% at the start of the polishing step (S333), was glass At the start of the substrate removal step (S334), a high-concentration slurry was sprayed on the polishing pad so as to increase the concentration.

  In each of the examples and comparative examples, the adsorbing force was set immediately after the polishing step (S333), with a test piece having the same shape and the same surface roughness as the glass substrate placed on the lower polishing pad, and the same pressure as in the polishing step. After adding, was pulled up and measured with a digital force meter.

  After completion of the second polishing step (S33), in all the examples and comparative examples, the glass substrate 1 is subjected to a surface defect inspection through a chemical strengthening step (S40) and a cleaning step (S50). It was. For defect inspection, an optical defect inspection apparatus Candela-OSA6100 manufactured by KLA-Tencor was used as a test apparatus.

  In the defect inspection, a total of 100 glass substrates processed in each example and each comparative example are inspected, and a substrate determined to have a deposit of 10 or less and a scratch of 2 or less is determined to be a non-defective product. Evaluate as A (excellent) when there are more than 90 sheets, B (good) when 90 sheets or less less than 95 sheets, C (good) when less than 90 sheets and 85 sheets or more, and D (defect) when less than 85 sheets did.

  Further, after a magnetic thin film forming step (S60), the glass substrate was used as an information recording medium (media), and then a read / write test was performed.

  In the read / write test, a test for measuring magnetic recording characteristics was performed on a glass substrate (information recording medium) which was similarly processed 100 pieces under each condition. A (excellent) when the number of substrates that have passed the test is 96 or more, B (good) when the number is less than 96 and 92 or more, C (possible) when the number is less than 92 and 88 or more, and less than 88 Was evaluated as D (impossible).

Example 1
In the glass substrate of Example 1, the adsorbing force is 15.0 g / cm ² , the number of communication holes of the polishing pad is 35, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) is accumulation, The slurry concentration at that time was 15 wt%. After the polishing step (S333), a cleaning step was performed before the glass substrate removal step (S334). In Example 1, the evaluation of the defect inspection was “B”, and the evaluation of the read / write test was “B”. The number of communication holes of the polishing pad means that the communication holes having a cross-sectional area S of 0.01 mm ² or more in the longitudinal cross section of the lower polishing pad 410 and the upper polishing pad 310 along the normal direction of the lower surface plate 400 are 25 mm. ^It means the number existing per ^two . The same applies hereinafter.

(Example 2)
In the glass substrate of Example 1, the adsorption force is 14.5 g / cm ² , the number of communication holes of the polishing pad is 35, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) is accumulation, The concentration of the slurry at that time was 20 wt%. After the polishing step (S333), the cleaning step is not performed before the glass substrate removal step (S334). In Example 2, after completion of the polishing step (S333), a high-concentration slurry was sprayed on the polishing pad before the glass substrate extraction step (S334). In Example 2, the evaluation of the defect inspection was “B”, and the evaluation of the read / write test was “B”.

(Example 3)
In the glass substrate of Example 3, the adsorbing force is 13.0 g / cm ² , the number of communication holes of the polishing pad is 35, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) is accumulation, The concentration of the slurry at that time was 25 wt%. After the polishing step (S333), the cleaning step is not performed before the glass substrate removal step (S334). In Example 3, after completion of the polishing step (S333), a slurry having a high concentration was sprayed on the polishing pad before the glass substrate extraction step (S334). In Example 3, the evaluation of the defect inspection was “A”, and the evaluation of the read / write test was “A”.

Example 4
In the glass substrate of Example 4, the adsorption force is 14.0 g / cm ² , the number of communication holes of the polishing pad is 63, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) is accumulation, The slurry concentration at that time was 15 wt%. After the polishing step (S333), the cleaning step is not performed before the glass substrate removal step (S334). In Example 4, the evaluation of the defect inspection was “B”, and the evaluation of the read / write test was “B”.

(Example 5)
In the glass substrate of Example 5, the adsorptive power is 13.0 g / cm ² , the number of communication holes of the polishing pad is 88, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) is accumulation, The slurry concentration at that time was 15 wt%. After the polishing step (S333), the cleaning step is not performed before the glass substrate removal step (S334). In Example 3, the evaluation of the defect inspection was “A”, and the evaluation of the read / write test was “A”.

(Comparative Example 1)
In the glass substrate of Comparative Example 1, the adsorption force was 17.5 g / cm ² , the number of communication holes of the polishing pad was 24, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) was not accumulated. . After the polishing step (S333), a cleaning step was performed before the glass substrate removal step (S334). In Comparative Example 1, the evaluation of the defect inspection was “D”, and the evaluation of the read / write test was “D”.

(Comparative Example 2)
In the glass substrate of Comparative Example 2, the adsorption force is 17.0 g / cm ² , the number of communication holes of the polishing pad is 24, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) is accumulation, The slurry concentration at that time was 15 wt%. After the polishing step (S333), the cleaning step is not performed before the glass substrate removal step (S334). In Comparative Example 2, the evaluation of the defect inspection was “D”, and the evaluation of the read / write test was “D”.

(Comparative Example 3)
In the glass substrate of Comparative Example 3, the adsorbing force was 16.0 g / cm ² , the number of communication holes of the polishing pad was 35, and the accumulation state of the slurry on the polishing pad in the glass substrate extraction step (S334) was not accumulated. . After the polishing step (S333), the cleaning step is not performed before the glass substrate removal step (S334). In Comparative Example 3, the evaluation of the defect inspection was “C”, and the evaluation of the read / write test was “C”.

From the evaluation results based on the adsorptive powers of Examples 1 to 5 and Comparative Examples 1 to 3, in the wet state in which slurry was supplied to the polishing pad, the adsorptive power of the polishing pad to the glass substrate 1 was 0.50 g / It was confirmed that it was preferably not less than cm ^{2 and not} more than 15 g / cm ² .

From the evaluation results based on the number of communication holes in Examples 1 to 5 and Comparative Examples 1 to 3, in the longitudinal section of the polishing pad along the normal direction of the surface plate, the cross-sectional area S is 0.01 mm ² or more. It was confirmed that the communication holes 410c are preferably present at a density of 30 or more per 25 mm ² in the longitudinal section, and more preferably 80 or more from Example 5.

From the evaluation results based on the number of communication holes in Examples 1 to 5 and Comparative Examples 1 to 3, in the longitudinal section of the polishing pad along the normal direction of the surface plate, the cross-sectional area S is 0.01 mm ² or more. It was confirmed that the communication holes 410c are preferably present at a density of 30 or more per 25 mm ² in the longitudinal section, and more preferably 80 or more from Example 5.

  In Example 1, a cleaning process is performed after the polishing process S333 is completed and before the glass substrate extracting process S334. In Comparative Example 3, a cleaning process is performed after the polishing process S333 is completed and before the glass substrate extracting process S334. Therefore, it was confirmed that it is better to take out the polished glass substrate 1 from the surface plate while the polishing pad contains the slurry.

  In Example 3, the concentration of the slurry, which was 15 wt% at the start of the polishing step S333 after the polishing step S333 was completed and before the glass substrate extraction step S334, was 1. Since the slurry having a high concentration is dispersed on the polishing pad so as to be 5 times or more, the concentration of the slurry is used to polish the surface of the glass substrate 1 in the step of removing the polished glass substrate 1 from the surface plate. It was confirmed that the concentration was preferably 1.5 times or more as compared with the concentration of the slurry in the step of performing.

  In the above-described embodiments and examples, the case where a double-side polishing apparatus is used has been described, but the present invention is not limited to the double-side polishing apparatus.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The 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, 1A front main surface, 1B back main surface, 1C inner peripheral end surface, 1D outer peripheral end surface, 1H hole, 2 magnetic thin film layer, 10 magnetic disk, 300 upper surface plate (upper whetstone holding surface plate), 310 upper surface polishing Pad, 311, 411 polishing surface, 400 lower surface plate (lower grinding wheel holding surface plate), 410 lower surface polishing pad, 410c communication hole, 410h foaming hole, 500 carrier, 2000 double-side polishing apparatus.

The present invention relates to a method for manufacturing a glass substrate for an information recording medium, a method for manufacturing an information recording medium, and a polishing pad .

The present invention has been made in view of the above circumstances, and provides an information recording medium glass substrate that does not cause deterioration in recording characteristics after the information recording medium glass substrate is converted into an information recording medium. An object of the present invention is to provide a method for producing a glass substrate for information recording medium, a method for producing an information recording medium, and a polishing pad .

In another aspect of the method for producing a glass substrate for an information recording medium according to the present invention, a polishing pad made of a member including a plurality of foam holes is mounted on a surface plate, and the surface of the glass substrate is formed using the polishing pad. A method of manufacturing a glass substrate for an information recording medium using a polishing apparatus for polishing, wherein a liquid abrasive is supplied to the glass substrate by the step of placing the glass substrate on the surface plate and the polishing apparatus. while, the step of polishing the surface of the glass substrate, and a step of taking out the glass substrate after polishing from the platen, the polishing pad includes a plurality of communication holes for communicating the adjacent the foam pores It has formed a continuous foam structure, in cross section of the polishing pad along the normal direction of the surface plate, the cross-sectional area 0.01 mm ² or more of the communication hole, 30 or more per 2 5 mm ² Exist in density And, in a state where the supplying the liquid abrasive to the polishing pad, the suction force to the glass substrate of the polishing pad, 0.50 g / cm ² or more and 15 g / cm ² or less.

In still another aspect of the method for producing a glass substrate for an information recording medium according to the present invention, a polishing pad made of a member including a plurality of foam holes is mounted on a surface plate, and the surface of the glass substrate is used using the polishing pad. A method for producing a glass substrate for an information recording medium using a polishing apparatus for polishing a glass substrate, the step of placing the glass substrate on the surface plate, and a liquid abrasive agent on the glass substrate by the polishing apparatus. A step of polishing the surface of the glass substrate while supplying, and a step of removing the glass substrate after polishing from the surface plate, wherein the polishing pad communicates with the adjacent foam holes. has a continuous foam structure but formed in longitudinal section of the polishing pad along the normal direction of the surface plate, the cross-sectional area 0.01 mm ² or more of the communication hole, 25 mm 30 or more per ² Exist in degrees.

In another embodiment, in the cross section of the polishing pad along the normal direction of the surface plate, the communication holes having a cross-sectional area of 0.01 mm ² or more exist at a density of 80 or more per 25 mm ² .

In another form, in the step of taking out the glass substrate after polishing from the surface plate, the glass substrate after polishing is taken out from the surface plate while the polishing pad contains the liquid abrasive.
In another embodiment, in the step of removing the glass substrate after polishing from the surface plate, the concentration of the liquid abrasive is such that the liquid abrasive in the step of polishing the surface of the glass substrate by the polishing apparatus. It is 1.5 times or more compared with the concentration of.
An information recording medium manufacturing method according to the present invention includes forming at least a magnetic film on a surface of an information recording medium glass substrate obtained by any of the above-described methods for manufacturing an information recording medium glass substrate. It is characterized by.
A polishing pad according to the present invention is a polishing pad that is mounted on a surface plate of a polishing apparatus and used for a polishing process, and the polishing pad includes a plurality of foam holes and a plurality of adjacent foam holes that communicate with each other. The communication hole having a communication hole and having a cross-sectional area of 0.01 mm ² or more in the cross section along the normal direction of the polishing pad has a density of 30 or more per 25 mm ^{2 in the} cross section. Features.

According to the present invention, an information recording medium glass substrate capable of providing a glass substrate for information recording medium that does not cause deterioration in recording characteristics after the information recording medium glass substrate is converted into an information recording medium. A manufacturing method , a method for manufacturing an information recording medium, and a polishing pad are provided.

Claims (5)

A method for producing a glass substrate for an information recording medium, wherein a polishing pad comprising a member including a plurality of foam holes is mounted on a surface plate and a polishing apparatus for polishing the surface of the glass substrate using the polishing pad is used.
Placing the glass substrate on the surface plate;
Polishing the surface of the glass substrate while supplying a liquid abrasive to the glass substrate by the polishing apparatus;
Removing the glass substrate after polishing from the surface plate;
With
In a state where the liquid abrasive is supplied to the polishing pad, the adsorption force of the polishing pad to the glass substrate is 0.50 g / cm ² or more and 15 g / cm ² or less. Manufacturing method. The polishing pad is
A plurality of communication holes communicating the adjacent foam holes;
The longitudinal direction of the said polishing pad along the normal direction of the said surface plate WHEREIN: The said communicating hole with a cross-sectional area of 0.01 mm < ² > or more exists in the said longitudinal cross-section with the density of 30 or more per 25 mm < ² >. The manufacturing method of the glass substrate for information recording media of 1. In longitudinal section of the polishing pad along the normal direction of the surface plate, the cross-sectional area of 0.01 mm ² or more of the communication holes, present in 25 mm ² 80 or more density per in the longitudinal section, claim 2. A method for producing a glass substrate for information recording medium according to 2. In the step of taking out the glass substrate after polishing from the surface plate,
The method for producing a glass substrate for an information recording medium according to any one of claims 1 to 3, wherein the polished glass substrate is taken out from the surface plate while the polishing pad contains the liquid abrasive. In the step of taking out the glass substrate after polishing from the surface plate,
The density | concentration of the said liquid abrasive | polishing agent is 1.5 times or more compared with the density | concentration of the said liquid abrasive | polishing agent in the process of grind | polishing the surface of the said glass substrate with the said grinding | polishing apparatus. A method for producing a glass substrate for an information recording medium.

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