JP2010231834A - Method for manufacturing glass substrate, glass substrate and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing glass substrate, with which dimensional accuracy is maintained, irrespective of the variations in the chemical-reinforcing liquid with time, even when polishing is to be conducted after chemical reinforcement. <P>SOLUTION: In the method for manufacturing a glass substrate 1, a glass base material 1a is immersed in the chemical-reinforcing liquid 59 which is a solution containing ions, and chemical reinforcement is conducted by substituting an ion, existing on the surface of the glass base material 1a for the ion of the chemical-reinforcing liquid 59; and subsequently, principal surfaces 7a, 7b of the glass base material 1a subjected to the chemical reinforcement are polished. Here, in the polishing step, polishing is conducted by varying the polishing amount, according to the variations in the composition of the chemical-reinforcing liquid 59. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass substrate manufacturing method, a glass substrate manufactured by a glass substrate manufacturing method, and a magnetic recording medium.

  In recent years, with the advancement of information technology, information recording technology, particularly magnetic recording technology, has made remarkable progress.

  An aluminum substrate has been widely used as a substrate for a magnetic recording medium such as an HDD (Hard Disk Drive) which is one of such magnetic recording techniques.

  However, with the downsizing, thinning, and high-density recording of magnetic disks, in recent years, there has been an increasing demand for glass substrates that have superior substrate surface flatness and substrate strength compared to aluminum substrates.

  Conventionally, for example, as shown in paragraph [0004] of Patent Document 1, a glass substrate is chamfered by forming glass into a disk shape, and end faces and main surfaces are polished, and then impact resistance and vibration resistance are obtained. It has been manufactured by applying a chemical strengthening treatment for improving (Patent Document 1).

  In the chemical strengthening step for performing the chemical strengthening treatment, for example, as described in [0014] of Patent Document 1, the glass substrate to be treated is immersed in the chemical strengthening solution, and the glass substrate and the chemical strengthening solution are ion-exchanged. Is done by letting

  On the other hand, since chemical strengthening is also a process of replacing ions contained in glass with ions having a larger ion radius, the size and shape of the glass substrate change when chemical strengthening is performed.

  For this reason, there is a growing demand for higher recording density of magnetic disks, and as a result, stricter dimensional accuracy is required for glass substrates. As shown in [0012] of Patent Document 1, chemical strengthening is required. In some cases, the main surface of the glass substrate may be polished after the above.

Japanese Unexamined Patent Publication No. 2000-076652

  Here, in the manufacturing method in which polishing is performed after chemical strengthening, the chemically strengthened layer is scraped by polishing, and therefore the chemical strengthened layer in the manufactured glass substrate is likely to be thinner than in the manufacturing method in which chemical strengthening is performed after polishing.

  In addition, the chemical strengthening solution changes its composition when used repeatedly.

  Specifically, ions included in the ion-exchanged glass substrate increase, while ions included in the chemical strengthening solution initially decrease.

  Therefore, when the chemical strengthening solution is repeatedly used, the chemical strengthening layer in the glass substrate is gradually thinned, and in the manufacturing method in which polishing is performed after chemical strengthening, the chemical strengthening layer is further thinned by polishing.

  Also, the thinner the chemically strengthened layer, the more uneven the thickness of the chemically strengthened layers on the two main surfaces becomes different when the polishing amounts of the two main surfaces are different in the polishing step.

  For this reason, the glass substrate is warped due to the non-uniformity of the thicknesses of the chemically strengthened layers on the two main surfaces, and there is a possibility that the dimensional accuracy is deteriorated.

  However, Patent Document 1 does not consider the change in the composition due to repeated use of the chemical strengthening solution. Therefore, when the chemical strengthening solution is used repeatedly, the dimensional accuracy of the glass substrate may be deteriorated.

  The present invention has been made in view of the above problems, and its purpose is a glass substrate capable of maintaining dimensional accuracy regardless of changes in the composition of the chemical strengthening solution, even when polishing is performed after chemical strengthening. It is in providing the manufacturing method of.

  In order to solve the above problems, the present invention has the following configuration.

(Configuration 1) Step (a) of performing chemical strengthening by immersing a glass base material in a chemical strengthening solution that is a solution containing ions and replacing ions on the surface of the glass base material with ions of the chemical strengthening solution. A step (b) of polishing the main surface of the glass substrate subjected to the chemical strengthening, and the step (b) changes the polishing amount in accordance with a change in the composition of the chemical strengthening solution. A method for producing a glass substrate, which is a step of performing polishing.

(Configuration 2) The method for manufacturing a glass substrate according to Configuration 1, wherein the step (a) is a step of performing chemical strengthening under a certain condition regardless of a change in the composition of the chemical strengthening solution.

(Structure 3) The said process (a) is a process of immersing a glass base material in a chemical strengthening liquid per batch, and the said process (b) batches the main surface of the said glass base material which performed the said chemical strengthening. 3. The method for producing a glass substrate according to Configuration 2, which is a step of polishing in units.

(Configuration 4) The method for manufacturing a glass substrate according to Configuration 3, wherein the step (b) is a step of performing polishing by reducing the polishing amount for each predetermined batch.

(Structure 5) A glass substrate manufactured by the method for manufacturing a glass substrate according to any one of Structures 1 to 4.

(Structure 6) A magnetic recording medium comprising: the glass substrate according to Structure 5; and an underlayer, a magnetic layer, a protective layer, and a lubricating layer provided on a main surface of the glass substrate.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where it grind | polishes after chemical strengthening, it can provide the manufacturing method of the glass substrate which can maintain a dimensional accuracy irrespective of the change of a composition of a chemical strengthening liquid.

1A is a plan view of the glass substrate 1, FIG. 1B is a cross-sectional view taken along the line AA of FIG. 1A, and FIG. 1C is a cross-sectional view showing the magnetic recording medium 100. It is a figure which shows the outline of the manufacturing method of the glass substrate. 4 is a flowchart showing details of a method for manufacturing the glass substrate 1. 2 is a cross-sectional view showing a grinding device 21. FIG. It is a perspective view which shows the chemical strengthening apparatus 51. FIG. It is sectional drawing which shows the grinding | polishing apparatus 21a.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, with reference to FIG. 1, the structure of the glass substrate 1 manufactured using the manufacturing method of the glass substrate 1 which concerns on this embodiment is demonstrated easily.

  As shown in FIG. 1A, the glass substrate 1 has a main body 3 having a disc shape, and an inner hole 5 is formed at the center of the main body 3.

  As shown in FIG. 1B, the main body 3 has substantially smooth main surfaces 7a and 7b.

  The main surfaces 7a and 7b are surfaces on which a layer for recording / reproducing information is formed. For example, as shown in FIG. 1C, one or both of the main surfaces 7a and 7b are provided with an underlayer 18a and magnetic layers. By providing the layer 18b, the protective layer 18c, and the lubricating layer 18d, the glass substrate 1 becomes the magnetic recording medium 100 (at least the magnetic layer 18b is necessary as a recording layer).

  Moreover, as shown in FIG.1 (b), the main body 3 has the inner peripheral end surface 11 and the outer peripheral end surface 9 which are orthogonal to the main surfaces 7a and 7b.

  The inner peripheral end face 11 and the outer peripheral end face 9 are chamfered, and an inner peripheral chamfered face 13 and an outer peripheral chamfered face 15 are provided, respectively.

  Furthermore, the chemical strengthening layer 17 is formed on the surface of the main body 3.

  Although details of the chemical strengthening layer 17 will be described later, for example, a part of the glass ions used as the raw material of the glass substrate 1 is replaced with ions having a larger ion radius to form a compressive stress layer.

  Next, with reference to FIGS. 2-6, the manufacturing method of the glass substrate 1 which concerns on this embodiment is demonstrated.

  In the following description, the glass in the manufacturing process is referred to as “glass substrate 1a”, and the finished product is referred to as “glass substrate 1”.

  First, an outline of the manufacturing method will be briefly described with reference to FIG.

  First, glass as a raw material is processed to produce a disk-shaped glass substrate 1a as shown in FIG.

  Next, the glass substrate 1a is chemically strengthened to form a compressive stress layer on the surface.

  Next, the main surfaces 7a and 7b of the glass substrate 1a subjected to chemical strengthening are polished to be substantially smooth.

  Here, as is apparent from FIG. 2, the present embodiment is a manufacturing method in which the main surfaces 7a and 7b are polished after chemically strengthening the glass substrate 1a, and polishing is performed after chemical strengthening.

  Next, a specific manufacturing method will be described with reference to FIGS.

  First, as shown in FIG. 3, glass as a raw material is formed into a disk shape to produce a glass substrate 1a (step 101).

  Examples of the glass used as a raw material include soda lime glass, aluminosilicate glass, borosilicate glass, and crystallized glass produced by a float method, a downdraw method, a redraw method, or a press method.

  In the following embodiments, glass manufactured by a press method will be described as an example.

  Next, as shown in FIG. 3, in order to adjust the plate thickness of the glass substrate 1a, the main surfaces 7a and 7b are ground (first lapping) using the grinding device 21 (step 102).

  Here, an example of the structure of the grinding apparatus 21 used for grinding and an example of the grinding method will be briefly described with reference to FIG.

  As shown in FIG. 4, the grinding device 21 meshes with the sun gear 23, the internal gear 25 arranged concentrically on the outer side thereof, the sun gear 23 and the internal gear 25, and the sun gear 23 and the internal gear A carrier 27 that revolves and rotates according to the rotation of the gear 25, an upper surface plate 29 and a lower surface plate 31 that can sandwich the glass substrate 1 a held by the carrier 27, and an upper surface plate 29 and a lower surface plate 31. A polishing liquid supply unit (not shown) for supplying a polishing liquid therebetween is provided.

  At the time of grinding, the grinding device 21 sandwiches the glass substrate 1a held by the carrier 27 between the upper surface plate 29 and the lower surface plate 31, and between the upper surface plate 29 and the lower surface plate 31 and the glass substrate 1a. While supplying the polishing liquid, the carrier 27 revolves and rotates according to the rotation of the sun gear 23 and the internal gear 25, whereby the upper and lower surfaces (main surfaces 7a, 7b) of the glass substrate 1a are ground.

  As the polishing liquid, for example, a slurry obtained by dispersing abrasive grains such as alumina in water is used.

  Next, as shown in FIG. 3, the inner hole 5 (see FIG. 1) is formed in the center of the glass substrate 1a (step 103).

  The inner hole 5 is formed using, for example, a core drill.

  When sheet glass is used, steps 101 to 103 are not performed. Instead, a process of cutting the glass from the sheet shape into a disk shape using a cutter and further cutting the inner hole 5 (cutting process) is performed.

  Next, as shown in FIG. 3, the inner peripheral end face 11 and the outer peripheral end face 9 are chamfered to remove cracks on the end face of the glass substrate 1a (step 104). The chamfering is performed using, for example, a grindstone to which diamond abrasive grains are attached.

  In addition, you may add the process of grinding (2nd lapping) main surface 7a, 7b after chamfering. Thereby, the unevenness | corrugation produced by formation and chamfering of the inner hole 5 can be ground, and the burden at the time of grinding | polishing can be reduced.

  Next, as shown in FIG. 3, the inner peripheral end face 11 and the outer peripheral end face 9 of the glass substrate 1a are polished, that is, end face polishing is performed (step 105).

  The end surface polishing is performed using, for example, a rotating brush.

  Next, as shown in FIG. 3, the glass substrate 1a is chemically strengthened to form the chemically strengthened layer 17 (step 106).

  Here, an example of the structure of the chemical strengthening apparatus 51 used for chemical strengthening and an example of the chemical strengthening method will be briefly described with reference to FIG.

  As shown in FIG. 5, the chemical strengthening apparatus 51 includes a holder 53 that holds the glass substrate 1 a and a treatment tank 57 that is filled with a chemical strengthening solution 59.

  The holder 53 is provided with a holding portion 55 for holding the glass substrate 1a.

  As is clear from FIG. 5, the chemical strengthening apparatus 51 has a structure in which the glass substrate 1a is chemically strengthened in batch units for every several tens to 100 sheets, but the present invention is a process in batch units. It is not limited to.

  When chemically strengthening the glass substrate 1 a using the chemical strengthening device 51, first, the glass substrate 1 a is accommodated in the holder 53 by hooking the glass substrate 1 a on the holding portion 55, and the holder 53 and the inside of the treatment tank 57 are contained. The glass substrate 1a is immersed in the chemical strengthening liquid 59.

  The composition of the chemical strengthening liquid 59 is, for example, potassium nitrate, sodium nitrate, silver nitrate or the like alone or a mixture of at least two kinds.

  The temperature of the chemical strengthening liquid 59 is preferably about 50 to 150 ° C. lower than the strain point of the material of the glass substrate 1a, and more preferably the temperature of the chemical strengthening liquid 59 itself is about 350 to 400 ° C.

  When the glass substrate 1a is immersed in the chemical strengthening solution 59, ions contained in the chemical strengthening solution 59 and ions contained in the glass substrate 1a are ion-exchanged.

  Specifically, for example, lithium ions and sodium ions contained in the glass substrate 1a are exchanged with sodium ions and potassium ions contained in the chemical strengthening solution 59, respectively.

  At this time, when ion exchange occurs with ions having a larger ion radius than the ions contained in the glass substrate 1a, the chemically strengthened layer 17 becomes a compressive stress layer, and the strength of the surface of the glass substrate 1a increases.

  It is desirable that the chemical strengthening conditions (temperature, strengthening time, etc.) be constant. The reason is that, in this embodiment, as will be described later, the polishing is performed by changing the polishing amount in accordance with the change in the composition of the chemical strengthening solution 59.

  Next, after chemical strengthening is completed, the glass substrate 1a is washed to remove the surface chemical strengthening solution, and then, as shown in FIG. 3, the flatness and surface roughness of the main surfaces 7a and 7b of the glass substrate 1a. In order to adjust the thickness (substantially smooth), the main surfaces 7a and 7b are polished (step 107).

  Here, the structure of the polishing apparatus 21a used for polishing will be described with reference to FIG.

  The structure of the polishing device 21a is the same as that of the grinding device 21, but a polishing pad 33 is attached to the upper surface plate 29 and the lower surface plate 31, as shown in FIG.

  During the polishing process, the polishing apparatus 21a sandwiches the glass substrate 1a held by the carrier 27 between the upper surface plate 29 and the lower surface plate 31, and supplies the polishing liquid between the polishing pad 33 and the glass substrate 1a. However, when the carrier 27 revolves and rotates according to the rotation of the sun gear 23 and the internal gear 25, the upper and lower surfaces (main surfaces 7a and 7b) of the glass substrate 1a are polished.

  The polishing pad 33 is preferably a polishing pad of a soft polisher. The polishing pad 33 preferably has an Asker C hardness of 60 to 90. The contact surface of the polishing pad 33 with the glass substrate 1a is preferably made of a foamed resin having foamed pores, particularly foamed polyurethane. When polishing is performed in this manner, the main surfaces 7a and 7b of the glass substrate 1a can be polished into a smooth mirror surface.

  As the polishing liquid, for example, a slurry obtained by dispersing abrasive grains such as cerium oxide, lanthanum oxide, and colloidal silica in water is used.

  Here, at the time of polishing, the polishing is performed by changing the polishing amount in accordance with the change in the composition of the chemical strengthening solution 59.

  More specifically, as the chemical strengthening liquid 59 is repeatedly used, the ions initially contained in the chemical strengthening liquid 59 are reduced and the chemical strengthening layer 17 is thinned. Polishing is performed by reducing the polishing amount of the main surfaces 7a and 7b.

  In this way, by performing polishing while changing the polishing amount in accordance with the change in the composition of the chemical strengthening solution 59, the chemically strengthened layer 17 after polishing becomes too thin, and the chemical strengthened layer on the main surfaces 7a and 7b. The nonuniformity of the thickness of 17 becomes remarkable, and it can prevent that a dimensional accuracy deteriorates by the curvature of the glass base material 1a.

  That is, the dimensional accuracy can be maintained regardless of the change in the composition of the chemical strengthening solution 59.

  In addition, it is desirable to perform the polishing with the polishing amount changed in batch units for each predetermined batch when chemical strengthening is performed in batch units.

  Polishing may be performed in two stages.

  Specifically, for example, as abrasive grains contained in the polishing liquid, two types of abrasive grains having different particle diameters are used, and first polishing is performed using abrasive grains having a relatively large particle diameter, and then the grains Second polishing is performed using abrasive grains having a relatively small diameter.

  When polishing is completed, the glass substrate 1a is washed to remove abrasives and impurities adhering to the surface during manufacture (step 108).

  Specific examples include physical cleaning such as scrub cleaning and ultrasonic cleaning, and chemical cleaning using a fluoride, organic acid, hydrogen peroxide, surfactant, and the like.

  Finally, product inspection (for example, inspection of the surface roughness of the main surfaces 7a and 7b and the amount of particles) is performed (step 109).

  Specifically, defect inspection is performed using, for example, ODT (Optical Defect Tester) or OSA (Optical Surface Analyzer).

  The glass substrate 1 is completed by the above process.

  Thus, according to the manufacturing method of the glass substrate 1 which concerns on this embodiment, after performing the chemical strengthening to the glass base material 1a, the main surfaces 7a and 7b are grind | polished, and in the grinding | polishing process, chemical strengthening is carried out. Polishing is performed by changing the polishing amount in accordance with the change in the composition of the liquid 59.

  Therefore, even when polishing is performed after chemical strengthening, the dimensional accuracy of the glass substrate 1 can be maintained regardless of the change in the composition of the chemical strengthening solution 59.

  In the above-described embodiment, the case where the present invention is applied to the manufacturing method for manufacturing the glass substrate 1 for a magnetic recording medium has been described. However, the present invention is not limited to this, and it is necessary to perform polishing after chemical strengthening. It can be applied to all glass manufacturing methods.

DESCRIPTION OF SYMBOLS 1 ............... Glass substrate 1a ............ Glass base material 3 ............... Main body 5 ............... Inner hole 7a ............ Main surface 17 ......... Chemical strengthening layer 18b ......... Magnetic layer 21 ............ Grinding device 21 a ...... Polishing device 51 ...... Chemical strengthening device 59 ………… Chemical strengthening solution

Claims (6)

(A) performing chemical strengthening by immersing the glass base material in a chemical strengthening solution that is a solution containing ions and replacing the ions on the surface of the glass base material with ions of the chemical strengthening solution;
Polishing the main surface of the glass substrate subjected to the chemical strengthening (b);
Have
The process (b) is a process for polishing by changing the polishing amount in accordance with the change in the composition of the chemical strengthening solution.   The method for producing a glass substrate according to claim 1, wherein the step (a) is a step of performing chemical strengthening under a certain condition regardless of a change in the composition of the chemical strengthening solution. The step (a) is a step of immersing the glass substrate in a chemical strengthening solution in batch units,
The said process (b) is a process of grind | polishing the main surface of the said glass base material which performed the said chemical strengthening in batch unit, The manufacturing method of the glass substrate of Claim 2 characterized by the above-mentioned.   The method of manufacturing a glass substrate according to claim 3, wherein the step (b) is a step of performing polishing while reducing a polishing amount for each predetermined batch.   A glass substrate manufactured by the method for manufacturing a glass substrate according to claim 1. A glass substrate according to claim 5;
An underlayer, a magnetic layer, a protective layer, a lubricating layer provided on the main surface of the glass substrate;
A magnetic recording medium comprising:

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