JP2009279696A - Method of manufacturing glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a glass substrate capable of manufacturing, with high productivity, the glass substrate which meets a requirement of a standard value of the minute weave of the main surface thereof. <P>SOLUTION: This method of manufacturing a glass substrate which is used for a recording disk and having a minute weave of 0.6 nm or smaller on the main surface thereof comprises a glass substrate preparation step of preparing a plurality of glass substrates which have disk-like shapes and difference thicknesses, and the thicknesses of 2 μm or smaller, and a glass substrate polishing step of holding the plurality of glass substrates collectively from the upper and lower sides and simultaneously polishing the plurality of glass substrates in such a manner that a set polishing amount for the main surface on one side is 9 μm or larger. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a glass substrate used for a recording disk such as a magnetic disk or an optical disk.

  Conventionally, glass substrates have been used as semiconductor element substrates, spacers used in field effect flat panel displays, or recording disk substrates such as magnetic disks and optical disks. For example, as a glass substrate for a magnetic disk, a donut-shaped glass substrate having a circular hole at the center of a disk is used (see Patent Document 1). This glass substrate is manufactured as follows, for example. That is, first, a thin glass plate is cored to prepare a plurality of glass substrates formed into a donut shape. Next, using a batch-type double-side polishing apparatus, these glass substrates are simultaneously polished to increase the surface accuracy and finish the thickness within a predetermined standard range (see Patent Document 2). Thus, productivity is improved by simultaneously polishing a plurality of glass substrates.

  Here, various standard values are defined for the glass substrate for the magnetic disk. For example, in the case of a glass substrate having a diameter of 2.5 inches (63.5 mm), the standard value of the thickness is 635 μm ± 10 μm. As for the surface accuracy of the main surface, for example, the standard value of slight waviness is 0.6 nm or less. In addition, the minute waviness is an arithmetic average waviness having a wavelength of 1.5 to 5 mm on the main surface, and can be measured by, for example, a surface shape measuring machine (Optiflat manufactured by Phase Shift).

JP-A-6-198530 JP-A-10-241144

  As described above, for a glass substrate for a magnetic disk, a slight waviness on the main surface is defined as a standard. In the conventional manufacturing method, the polishing amount of the main surface necessary for satisfying this standard value is determined in advance by experiments or the like, and the glass substrate is manufactured by polishing at least the determined polishing amount. On the other hand, in order to improve productivity, the number of glass substrates to be polished simultaneously has increased in recent years. For example, for a glass substrate having a diameter of 63.5 mm, 100 or more glass substrates are polished simultaneously. It is becoming.

  However, as the number of glass substrates to be polished at the same time increases, even if the polishing amount is set to a predetermined amount, the number of manufactured glass substrates whose fine waviness does not satisfy the standard value increases. became. Therefore, there is a problem that productivity does not increase even if the number of glass substrates to be polished simultaneously is increased.

  This invention is made | formed in view of the above, Comprising: It aims at providing the manufacturing method of the glass substrate which can manufacture the glass substrate which the slight waviness of a main surface satisfy | fills a specification value with high productivity.

  In order to solve the above-described problems and achieve the object, a method for producing a glass substrate according to the present invention is a method for producing a glass substrate having a microwaviness of 0.6 nm or less on a main surface used for a recording disk, A glass substrate preparation step of preparing a plurality of glass substrates having a disk-like shape, different thicknesses, and a difference of 2 μm or less, and the plurality of glass substrates from above and below in a lump And a glass substrate polishing step of simultaneously polishing the plurality of glass substrates so that the set polishing amount with respect to the main surface on one side is 9 μm or more.

  Moreover, the manufacturing method of the glass substrate which concerns on this invention WHEREIN: In said invention, the said glass substrate preparatory process heats and softens a base material glass plate, A glass plate is used using the redraw method extended to desired thickness. And a glass substrate forming step of forming the plurality of glass substrates from the formed glass plate.

  According to the present invention, there is an effect that a glass substrate satisfying a standard value with a slight waviness on the main surface can be produced with higher productivity.

  Embodiments of a glass substrate manufacturing method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment)
FIG. 1 is a flowchart of a method for manufacturing a glass substrate according to an embodiment of the present invention. The method for manufacturing a glass substrate according to the present embodiment is a method for manufacturing a glass substrate for a magnetic disk having a diameter of 63.5 mm. First, as shown in FIG. A plurality of glass plates having a difference of 2 μm or less are prepared (step S101), each prepared glass plate is cored, and a plurality of donut-shaped glass substrates are formed from each glass plate (step S102). Thus, a plurality of glass substrates having different thickness differences and having a difference of 2 μm or less are prepared. Next, as a glass substrate polishing step, a rough polishing step is performed in which the glass substrates formed in step S102 are collectively clamped from above and below with a polishing pad to simultaneously polish the plurality of glass substrates, and then in step S103. A precision polishing step is further performed to simultaneously polish each polished glass substrate (step S104), and a glass substrate to be a product is manufactured.

  Here, in the present embodiment, as the rough polishing step, polishing is performed so that the set polishing amount for the main surface on one side is 9 μm or more. As a result, all the glass substrates subjected to simultaneous polishing are polished by a predetermined polishing amount, that is, a polishing amount necessary to ensure that the slight waviness of the main surface satisfies the standard value. As a result, it is possible to manufacture a glass substrate that satisfies the standard value with minute waviness on the main surface with higher productivity. In order to reduce the polishing time as much as possible and further increase the productivity, it is preferable to perform polishing so that the set polishing amount in the rough polishing step is 10 μm or less.

  Hereinafter, each step will be specifically described. First, with respect to the preparation of the glass plate in step S101, for example, if a redraw method is used in which a base glass plate manufactured using a float method or the like is heated to soften and stretched to a desired thickness, the thickness varies. Since a glass plate having a small thickness can be relatively easily produced, a glass plate having a difference in thickness of 2 μm or less can be easily prepared.

  FIG. 2 is a schematic perspective view of an example of a heating and stretching apparatus for performing the redraw method. The heating and stretching apparatus 100 includes a heating furnace 101 having heaters 101 a to 101 c for heating the base glass plate 1, a base material feeding mechanism 102 for feeding the base glass plate 1 to the heating furnace 101, and a glass from the heating furnace 101. A take-out mechanism 103a, 103b for drawing out the strip 2 and a cutter 104 for forming a glass plate 3 having a predetermined length by cutting and cutting a groove on the surface of the glass strip 2 are provided. The glass plate 3 is formed by cutting the glass strip 2 formed to have a predetermined thickness by heating and stretching the base glass plate 1 with a heating furnace 101 into a predetermined length.

  The glass plate 3 preferably has a mirror surface in order to simplify and shorten the polishing process. For example, if Ra, which is the average surface roughness of the glass plate 3, is 100 nm or less, the surface is preferably a mirror surface, and Ra is more preferably 10 nm or less, particularly 1 nm or less. In addition, if the redraw method is used, such a glass plate 3 with small Ra can be manufactured comparatively easily. In this specification, the average surface roughness is based on the arithmetic average height of the roughness curve of JIS B0601: 2001. Further, as a material of the base glass plate 1, glass ceramics such as amorphous glass and crystallized glass can be used. In addition, it is preferable to use amorphous glass from the viewpoint of formability and workability. For example, aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, air cooling, liquid cooling, or the like It is preferable to use physically tempered glass or chemically tempered glass that has been subjected to.

  Next, the shaping | molding of the doughnut-shaped glass substrate of step S102 can be implemented by coring the glass plate 3 by the well-known coring process disclosed by patent document 1, for example. As a result, a doughnut-shaped glass substrate 4 having main surfaces 4a and 4b and having a circular hole 4c formed in the center as shown in FIG. Here, the thickness t1 of the glass substrate 4 is, for example, 645 to 647 μm, the average thickness is 646 μm, and the difference between the thicknesses is 2 μm or less.

  Next, the rough polishing process in step S103 can be performed using, for example, a commercially available batch-type double-sided simultaneous polishing machine shown in FIGS. Here, FIG. 4 is a schematic view showing a part of the side surface of the double-sided simultaneous polishing machine. As shown in FIG. 4, the double-sided simultaneous polishing machine 200 includes an upper surface plate 201 and a lower surface plate 202 made of cast iron, and a carrier 205 that holds a plurality of glass substrates 4 between the upper surface plate 201 and the lower surface plate 202. And polishing pads 203 and 204 made of polyurethane or the like attached to the contact surfaces of the upper surface plate 201 and the lower surface plate 202 with the glass substrate 4.

  The double-sided simultaneous polishing machine 200 holds a plurality of glass substrates 4 between an upper surface plate 201 and a lower surface plate 202 by a carrier 205, and each glass substrate 4 is predetermined by the upper surface plate 201 and the lower surface plate 202. Clamp with the processing pressure of. Then, each glass substrate 4 is clamped by the polishing pads 203 and 204 collectively from above and below. Next, the upper surface plate 201 and the lower surface plate 202 are rotated in different directions with the axis A as the rotation axis while supplying a predetermined amount of polishing liquid between the polishing pads 203 and 204 and each glass substrate 4. Let Thereby, the glass substrate 4 slides on the surfaces of the polishing pads 203 and 204 and polishes both surfaces simultaneously.

  FIG. 5 is a schematic plan view of the double-sided simultaneous polishing machine 200 with the upper surface plate 201 removed. As shown in FIG. 5, in this embodiment, ten carriers 205 that can hold 15 glass substrates 4 are used, and 150 glass substrates 4 can be set simultaneously. Note that the number of simultaneous polishings can be appropriately set to 150 or less, and can be increased to more than 150 by changing the carrier or the like. A gear provided on the outer peripheral portion of the carrier 205 meshes with a gear provided on the outer peripheral portion of the sun wheel 206 and the internal gear 207. As a result, each carrier 205 moves around the sun wheel 206 around the axis A while rotating around the center thereof, and the 150 glass substrates 4 held by the carrier 205 have both surfaces uniformly and simultaneously. Polished.

  Next, in the precision polishing process of step S104, the polishing pads 203 and 204 of the double-sided simultaneous polishing machine 200 are replaced with softer polishing pads for precision polishing, and polishing grains made of colloidal silica having a smaller particle size, for example. The glass substrate 4 is polished by using the polishing pad while supplying the polishing liquid containing. As a result, the main surface of the glass substrate 4 is polished to a mirror surface. Note that the polishing amount in the precision polishing step is about 1 μm, and the fine waviness of the glass substrate 4 is almost determined in the rough polishing step in step S103.

  Here, in step S103, polishing is performed so that the total set polishing amount for the main surface on one side is 9 μm or more. The set polishing amount is the polishing amount of the main surface calculated from the polishing rate obtained by experiments or the like in advance on a plurality of glass substrates or a single glass substrate with little variation in thickness. This set polishing amount can be adjusted by adjusting. As described above, since each glass substrate 4 has a thickness difference of 2 μm or less, by performing polishing so that the set polishing amount is 9 μm or more, a slight undulation of the main surface of each glass substrate 4 is achieved. Is surely 0.6 nm or less. The reason will be described below.

  FIG. 6 is a diagram schematically illustrating a state in which the polishing pads 203 and 204 sandwich the glass substrates 41 and 42 having different thicknesses. As shown in FIG. 6, the glass substrates 41 and 42 have thicknesses t11 and t12, respectively. However, the thicknesses vary and are different by a difference Δt. Here, as shown in FIG. 6, since the polishing pads 203 and 204 have predetermined elasticity, the surface shape thereof is deformed according to the thickness of the glass substrates 41 and 42. Further, due to the elasticity of the polishing pads 203 and 204, even when a predetermined processing pressure is applied by the upper surface plate 201 and the lower surface plate 202, the thicker glass substrate 42 receives a higher processing pressure. As a result, the thicker glass substrate 42 is polished first, the glass substrate 42 is polished by a difference Δt, and the thickness of the glass substrates 41 and 42 becomes the same, and then the glass substrate 41 is polished. Become. As a result, if the difference Δt is large, the polishing amount of the thinner glass substrate 41 becomes smaller than the set polishing amount, and therefore the glass substrate 41 has a slight waviness on the main surface that does not satisfy the standard value due to insufficient polishing amount. It will be a thing. In addition, when the number of glass substrates to be simultaneously polished increases, the variation in the thickness of the glass substrate usually increases accordingly, and the number of glass substrates with insufficient polishing amount also increases.

  However, as in the present embodiment, a plurality of glass substrates having a thickness difference of 2 μm or less are prepared, and these are collectively clamped with a polishing pad from above and below, and the set polishing amount for the main surface on one side By simultaneously polishing so as to be 9 μm or more, all the glass substrates subjected to simultaneous polishing are necessary to ensure that a predetermined polishing amount, that is, a slight waviness of the main surface satisfies the standard value. Polished by the polishing amount. As a result, it is possible to manufacture a glass substrate that satisfies the standard value with minute waviness on the main surface with higher productivity. According to the experiments of the present inventors described later, when polishing a plurality of glass substrates having almost no thickness variation so that the slight waviness is 0.6 nm or less, the predetermined polishing amount is about 5 μm. is there.

  FIG. 7 is a view showing an upper surface and a side cross section of the glass substrate 5 after rough polishing. As shown in FIG. 7, the glass substrate 5 is a donut-shaped glass substrate having main surfaces 5a and 5b and a circular hole 5c formed in the center, and the thickness t2 is 635 μm ± 10 μm after precision polishing. The small waviness of the main surfaces 5a and 5b is 0.6 nm or less.

  In step S103, a hard material having a hardness (Asker C) of 85 or more, for example, a hard polishing pad made of polyurethane, is used as the polishing pads 203 and 204, and the particle size is 0.1 to 0.8 μm as the polishing liquid. For example, those containing abrasive grains made of cerium oxide can be used. By combining such abrasive grains and a hard polishing pad, polishing that can improve the surface accuracy and flatness of the substrate while suppressing the dub-off value of the glass substrate 4 to about 0 to 9 nm. Can do. Here, the dub-off value is a value indicating the bulge or settling (dub off) of the main surface at the outer peripheral edge of the glass substrate. The hardness (Asker C) is a value measured by a measurement method defined in the Japan Rubber Association standard (compliant standard: SRIS0101). Henceforth, the hardness in this specification shall apply to this unless otherwise indicated. Further, the polishing pads 203 and 204 to be used are not limited to polyurethane but may be made of a hard material having a hardness of 85 or more. Further, considering the occurrence of surface defects during polishing, a hardness of 95 or less is preferable. Further, subsequently, in step S104, a soft abrasive pad made of a material having a hardness of 60 to 80, for example, urethane foam, and an abrasive grain made of, for example, colloidal silica having a particle size of 0.01 to 0.1 μm. If the polishing liquid containing is used, the dub-off value of the glass substrate 4 can be made better.

  As described above, according to the method for manufacturing a glass substrate according to the present embodiment, it is possible to manufacture a glass substrate satisfying the standard value with a slight undulation on the main surface with higher productivity.

  Examples of the present invention, comparative examples, and reference examples are shown below. Note that the present invention is not limited thereby. In each of the following examples, a glass plate made of aluminosilicate glass having a width of 90 mm and a length of 10 m or more is manufactured using the redraw method, and the glass plate is cored to have an outer diameter of 65 mm and an inner diameter of the circular hole. A 20 mm donut-shaped glass substrate was formed. Further, a predetermined number of glass substrates are selected from the molded glass substrates, and these glass substrates are set in the double-sided simultaneous polishing machine shown in FIGS. At the same time.

In the rough polishing step, a urethane polishing pad having a hardness of 87 (manufactured by Hamai Sangyo Co., Ltd .: HPC-90D) and a cerium oxide polishing abrasive having a particle size of 0.1 to 0.4 μm and an average particle size of 0.19 μm. A polishing liquid was prepared by adding water to the grains to form free abrasive grains. In addition, as other polishing conditions in the rough polishing step, the rotation speed of the polishing platen was 25 rpm, the polishing liquid supply speed was 1500 cc / min, and the processing pressure was 120 g / cm ² . At this time, the polishing rate was 0.32 μm / min. The polishing rate is obtained by calculating the polished thickness per one side based on the difference in weight of the glass substrate before and after polishing, and converting the thickness using the polishing time.

  FIG. 8 is a diagram showing the quality of the manufacturing conditions, characteristics, and slight waviness of each example, comparative example, and reference example. Hereinafter, each example will be described with reference to FIG.

(Reference Examples 1-3)
As Reference Examples 1 to 3, 25 glass substrates having an average thickness value of 643 μm and a thickness difference of about 0 μm, that is, almost no thickness variation were selected from the molded glass substrates. When the slight waviness of these glass substrates was measured before polishing, the maximum values were 4 nm (Reference Examples 1 and 2) and 0.5 nm (Reference Example 3), respectively. Here, the “maximum value” is the maximum value among a plurality of glass substrates polished under the same conditions as the average value in the measurement region of one glass substrate. Further, the slight waviness is measured with a surface shape measuring device (Optiflat manufactured by Phase Shift), and the details of the measuring method are the same as the measuring method described in JP-A-2000-348330. Next, these glass substrates were set in a double-sided simultaneous polishing machine, and a rough polishing step was performed for each reference example. The set polishing amounts for the main surface on one side were 5 μm (Reference Example 1), 4 μm (Reference Example 2), and 3.5 μm (Reference Example 3), respectively.

  When the characteristics of each glass substrate after polishing were measured, the thicknesses were all satisfying the standard value of 635 μm ± 10 μm. The average thicknesses were 633 μm (Reference Example 1), 635 μm (Reference Example 2), and 636 μm (Reference Example 3), respectively. On the other hand, regarding the slight waviness, in Reference Example 1, the maximum value of each glass substrate was 0.5 nm and all the glass substrates satisfied the standard, but in Reference Example 2, the maximum value was 0.7 nm, and the standard was There was a glass substrate that was not filled. That is, when there is no variation in the thickness of the glass substrate before polishing, it was confirmed that the set polishing amount should be set to 5 μm or more in order to ensure that the slight waviness meets the standard. In Reference Example 3, the maximum value of the slight waviness is increased from 0.5 nm to 0.6 nm by polishing. This result shows that it is preferable to set the set polishing amount to a value of a certain level in order to make it even smaller even if the original slight waviness is small.

(Examples 1 and 2)
As Examples 1 and 2, 150 glass substrates having an average thickness value of 646 μm and a maximum thickness difference of 2 μm were selected from the molded glass substrates. When the slight waviness of these glass substrates was measured before polishing, each maximum value was 4 nm. Next, these glass substrates were set in a double-sided simultaneous polishing machine, and a rough polishing step was performed for each example. The set polishing amounts for the main surface on one side were 10 μm (Example 1) and 9 μm (Example 2), respectively.

  When the characteristics of each glass substrate after polishing were measured, the thicknesses were all satisfying the standard value of 635 μm ± 10 μm. In addition, the average value of thickness was 626 micrometers (Example 1) and 628 micrometers (Example 2), respectively. On the other hand, regarding the slight waviness, the maximum value of both Examples 1 and 2 was 0.5 nm, and all the glass substrates satisfied the standard.

(Comparative Example 1)
As Comparative Example 1, 150 glass substrates having an average thickness value of 646 μm and a maximum thickness difference of 4 μm were selected from the molded glass substrates. When the slight waviness of these glass substrates was measured before polishing, the maximum value was 4 nm. Next, these glass substrates were set in a double-sided simultaneous polishing machine, and a rough polishing process was performed. The set polishing amount for the main surface on one side was set to 10 μm. When the characteristics of each glass substrate after polishing were measured, the thicknesses all satisfy the standard value of 635 μm ± 10 μm, and the average value was 626 μm, but the maximum value of the slight waviness was 0.8 nm. There was a glass substrate that did not meet the standards.

(Comparative Example 2)
As Comparative Example 2, 150 glass substrates having an average thickness value of 646 μm and a maximum thickness difference of 2 μm were selected from the molded glass substrates. When the slight waviness of these glass substrates was measured before polishing, the maximum value was 4 nm. Next, these glass substrates were set in a double-sided simultaneous polishing machine, and a rough polishing process was performed. The set polishing amount for the main surface on one side was 8 μm. When the characteristics of each glass substrate after polishing were measured, the thicknesses all satisfy the standard value of 635 μm ± 10 μm, and the average value was 630 μm, but the maximum value of the slight waviness was 0.8 nm. There was a glass substrate that did not meet the standards.
That is, when there is no variation in the thickness of the glass substrate before polishing, the set polishing amount should be set to 5 μm or more in order to ensure that the slight waviness meets the standard. When the thickness of the previous glass substrate has a variation within 2 μm, it was confirmed that the set value of the set polishing amount should be 9 μm or more.

  In addition, although the case where the glass plate manufactured using the redraw method was used was demonstrated in the said embodiment, it manufactured using well-known methods, such as the float method, fusion method, down-draw method, etc. which used the molten glass as a raw material, for example. A glass plate can also be used. Moreover, you may perform the lapping process which adjusts the thickness of a glass substrate after shaping | molding a glass substrate as one process of the preparation process of a glass substrate. In the above embodiment, a plurality of glass plates having a thickness difference of 2 μm or less are prepared, and a glass substrate is formed therefrom. After forming a plurality of glass substrates from the glass plate, From the above, glass substrates having a thickness difference of 2 μm or less may be selected. Moreover, in the said embodiment, although the grinding | polishing process included the process of two steps, a rough grinding | polishing process and a precision grinding | polishing process, in order to satisfy | fill other specification values of a glass substrate, a multi-stage grinding | polishing process was performed. You may perform the grinding | polishing process which contains suitably.

  The above embodiment relates to a method of manufacturing a glass substrate for a magnetic disk. However, the present invention is not limited to this, and manufacturing of a glass substrate for other recording disks such as an optical disk and a magneto-optical disk. It can also be applied to.

It is a flowchart of the manufacturing method of the glass substrate which concerns on embodiment of this invention. It is a typical perspective view of an example of the heating drawing apparatus for implementing a redraw method. It is a figure which shows the upper surface and side cross section of a glass substrate. It is the schematic which shows a part of side surface of a double-sided simultaneous grinder. It is the plane schematic diagram of the double-sided simultaneous grinder of the state which removed the upper surface plate. It is a figure which shows typically the state in which a polishing pad clamps the glass substrate from which thickness differs. It is a figure which shows the upper surface and side cross section of the glass substrate after rough polishing. It is the figure which showed the judgment of the quality etc. about the manufacturing conditions of each Example, a comparative example, and a reference example, a characteristic, and slight waviness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material glass plate 2 Glass strip 3 Glass plate 4, 5, 41, 42 Glass substrate 4a, 4b, 5a, 5b Main surface 4c, 5c Circular hole 100 Heat-stretching apparatus 101 Heating furnace 101a-101c Heater 102 Base material feed mechanism 103a, 103b Take-up mechanism 104 Cutter 200 Double-sided simultaneous polishing machine 201 Upper surface plate 202 Lower surface plate 203, 204 Polishing pad 205 Carrier 206 Solar wheel 207 Internal gear A-axis S101 to S104 Step t1, t2, t11, t12 Thickness Δt Difference

Claims (2)

A method for producing a glass substrate having a minor surface waviness of 0.6 nm or less used for a recording disk,
A glass substrate preparation step of preparing a plurality of glass substrates having a disk-like shape, different thicknesses, and a difference of 2 μm or less;
A glass substrate polishing step of simultaneously polishing the plurality of glass substrates so that the set polishing amount with respect to the main surface on one side is 9 μm or more by sandwiching the plurality of glass substrates from above and below with a polishing pad.
The manufacturing method of the glass substrate characterized by including.   The glass substrate preparing step includes a glass plate preparing step of forming a glass plate using a redraw method in which a base glass plate is heated and softened and stretched to a desired thickness, and the plurality of glasses are formed from the formed glass plate. A method for producing a glass substrate according to claim 1, further comprising a glass substrate forming step of forming the substrate.

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