JP2005225713A - Method of manufacturing glass substrate for magnetic disk and method of manufacturing magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture a small diameter glass substrate for a magnetic disk by cutting a zone to become the glass substrate for the magnetic disk from a glass base material so as not to be tapered in the end face to facilitate a post shaping process. <P>SOLUTION: The method of manufacturing the glass substrate for the magnetic disk comprises: making a 1st incision C1 forming the outside edge of zone 3 to become the glass substrate for the magnetic disk on the main surface of the glass base material 2; making a 2nd incision C2 ranging from the vicinity of the 1st incision to the vicinity of the outer peripheral part of the glass base material 2; and applying force to both side parts of the 2nd incision C2 along the main surface of the glass base material 2 in the direction apart from the 2nd incision C2 to separate individual portions in the 2nd incision C2 and the 1st incision C1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a glass substrate for a magnetic disk used in a magnetic disk device such as an HDD (hard disk drive), and a method for manufacturing a magnetic disk.

Today, information recording technology, particularly magnetic recording technology, is required to undergo dramatic technological innovation with the development of the so-called IT industry. In contrast to other magnetic recording media such as magnetic tapes and flexible disks, magnetic information mounted on magnetic disk devices such as HDDs (Hard Disk Drives) used as computer storage is rapidly increasing in information recording density. Has been continued. The information capacity that can be stored in the personal computer device has been dramatically increased, supported by such an increase in the information recording density of the magnetic disk.
A glass substrate can be suitably used as the magnetic disk substrate. This is because a smooth surface can be obtained on a glass substrate, so that the flying height of a magnetic head that performs recording and reproduction while flying over a magnetic disk can be reduced. That is, a magnetic disk having a high information recording density can be obtained by using a glass substrate.

  Usually, as a glass substrate that contributes to high recording density of a magnetic disk, for example, as described in Examples in Patent Document 1, first, a glass disk press-molded from molten glass into a disk shape is prepared. These glass disks are manufactured by sequentially performing grinding (lapping) processing, polishing (polishing) processing, and the like.

  In addition, as a method for manufacturing a glass substrate for a magnetic disk, a method of cutting and manufacturing from a glass base material has been proposed. For example, Patent Document 2 describes that when a glass substrate is cut out from the glass base material, the glass base material is cut using an inclined cutter in order to form a taper in the glass substrate. . Patent Document 3 describes that when a silicon substrate is cut out from a silicon base material, it is cut out with a laser beam.

JP 11-154325 A (Patent No. 3184495) JP-A-6-76282 JP-A-7-223828

  By the way, in recent years, the information recording density of magnetic disks has reached 40 gigabits per square inch, and an extremely high recording density exceeding 100 gigabits per square inch is being realized. Yes. The recent magnetic disks that have achieved such high information recording density have the feature that they can store a practically sufficient amount of information even with a much smaller disk area than conventional magnetic disks. doing.

  In addition, the magnetic disk has a feature that information recording speed and reproduction speed (response speed) are extremely fast compared with other information recording media, and information can be written and read at any time. .

  As a result of attention paid to various features of such a magnetic disk, in recent years, so-called mobile phones, digital cameras, portable information devices (for example, PDA (personal digital assistant)), or “car navigation system” Thus, there is a need for a small hard disk drive that can be mounted on a device that is much smaller than a personal computer device and requires a high response speed.

  Such a small hard disk drive used in a portable so-called “mobile device” is always exposed to an impact such as an impact caused by dropping or vibration. Therefore, the usefulness of a magnetic disk using a glass substrate is attracting attention as a magnetic disk used in a hard disk drive used in such a device. This is because a glass substrate made of glass, which is a hard material, has a feature of higher rigidity than a substrate made of metal, which is a soft material. Moreover, it is because the glass substrate has the characteristic that desired intensity | strength can be obtained by means, such as chemical strengthening.

  However, when the inventor tried to manufacture a small-diameter glass substrate for mounting on a small hard disk drive, the conventional “2.5 inch hard disk drive” or “3.5 inch hard disk drive” was used. It has been found that various difficulties are encountered in comparison to the production of glass substrates for use.

  In manufacturing a conventional glass substrate for a magnetic disk, as described above, first, a molten glass is press-molded into a disk shape to create a glass disk, and then grinding (lapping) processing and polishing (polishing) processing are performed. ing. By this manufacturing method, when trying to manufacture a glass substrate having a smaller diameter than before, it is industrially difficult to stably manage all the molding apparatuses for press molding the glass disk under the same molding conditions, It has been found that it is difficult to stably supply a large amount of small-diameter glass substrates. That is, if there is a large variation in the quality of the glass disk that is put into the subsequent processes such as the grinding process and the polishing process, it becomes a major manufacturing restriction to correct the variation in these subsequent processes.

  Further, in order to manufacture a glass substrate having a smaller diameter than the conventional one by such a manufacturing method, it is necessary to newly design and manufacture a large number of small-diameter molding apparatuses. On the other hand, hard disk drives used in portable so-called “mobile devices” are required to supply a large amount of glass substrates at a lower price. Here, if a large capital investment is made to newly manufacture a molding apparatus, the manufacturing cost of the small-diameter disk substrate will rise, and a large amount of hard disk drives using small-diameter magnetic disks will be supplied at a low price. This causes a problem of obstructing.

  For this reason, the inventor first tried to produce a relatively large diameter glass base material and cut the glass base material to cut out a small diameter glass disk from the glass base material. According to this manufacturing method, a large number of glass disks of the same quality can be obtained simultaneously. Moreover, in this manufacturing method, since there is little dispersion | variation in the quality of the glass disk obtained, it is possible to suppress the process load in a post process. Therefore, according to this manufacturing method, a large amount of glass substrates with stable quality should be able to be supplied at low cost.

  However, a small-diameter glass substrate has a smaller diameter than a glass substrate used for a conventional “2.5 inch hard disk drive” or “3.5 inch hard disk drive” magnetic disk, or Since the thickness (thickness of the disk) is thin, a problem has been found that defects such as chipping, cracking and cracking are likely to occur when a glass disk is cut out from a glass base material.

  When a glass substrate is manufactured using a glass disk having such a defect, there arises a problem that an error occurs in a recording signal in such a defective portion. In particular, in a magnetic disk having an information recording density of 60 gigabits or more per square inch, the maximum recording density exceeds 700 kFCI (magnetic flux reversal density per inch), which is a minute defect compared to a conventional magnetic disk. Even in this case, a signal error may be caused and normal information recording / reproduction may be hindered. In addition, when a glass substrate is manufactured using a glass disk having such a defect, there is a problem of an increase in manufacturing cost due to a decrease in manufacturing yield.

  Moreover, in the technique described in the said patent document 1, since the end surface of the glass substrate cut out from the glass base material will taper, there exists a problem that a subsequent shape processing process becomes complicated. And in the technique described in the said patent document 2, it is difficult to cut out a glass base material favorably with a laser beam.

  Accordingly, the present invention has been made in view of the above-described circumstances, and a first object of the present invention is to stably supply an inexpensive glass substrate for a magnetic disk or a magnetic disk in a large amount. is there.

  A second object of the present invention is to provide a flat and smooth glass substrate for a magnetic disk or a magnetic disk that has few defects and can realize a high recording density of, for example, 60 gigabits per square inch or more. That is.

  Furthermore, a third object of the present invention is a personal computer such as a mobile phone, a digital camera, a portable information device (for example, a personal digital assistant (PDA)) or a “car navigation system”. It is an object to provide a glass substrate for a magnetic disk or a magnetic disk suitable for use in a small hard disk drive that has a smaller housing and can be mounted on equipment that requires a high response speed.

  As a result of advancing research to solve the above problems, the present inventor draws a closed curve that forms an outer edge of a region that becomes a glass substrate for a magnetic disk with respect to the main surface of the glass base material in the manufacturing process of the glass substrate for a magnetic disk. A second notch extending from the vicinity of the first notch to the vicinity of the outer edge of the glass base material with respect to the main surface of the outer portion of the closed curve drawn by the first notch in the glass base material while making the first incision. It was found that the above problem can be solved by adding.

  That is, the present invention has the following configuration.

[Configuration 1]
A method for manufacturing a glass substrate for a magnetic disk by cutting out a glass substrate for a magnetic disk from a plate-shaped glass base material, wherein an outer edge of a region to be a glass substrate for a magnetic disk in the glass base material is formed on the main surface of the glass base material. A first notch that draws a closed curve is formed, and extends from the vicinity of the first notch to the outer edge of the glass base material with respect to the main surface of the outer portion of the closed curve drawn by the first notch in the glass base material. These are obtained by making a second cut and applying a force in a direction away from the second cut along the main surface of the glass base material to the one side and the other side of the second cut. Each part is separated at the second cut, and each part is separated from a region to be a glass substrate for a magnetic disk at the first cut. It is.

[Configuration 2]
In the method for manufacturing a glass substrate for a magnetic disk according to Configuration 1, at least the first cut among the cuts is formed substantially perpendicular to the main surface of the glass base material.

[Configuration 3]
In the method for manufacturing a glass substrate for a magnetic disk according to Configuration 2, each cut is formed by a cutter blade, and when forming at least the first cut among the cuts, the cutter blade is formed on both sides of the ridge line of the cutter blade. The blade angle with respect to the main surface of the base material is substantially the same and is used.

[Configuration 4]
In the method for manufacturing a glass substrate for a magnetic disk according to any one of Configurations 1 to 3, the thickness of the glass base material is 2.0 mm or less, and a region to be the glass substrate for a magnetic disk has a diameter of 30 mm or less. It is characterized by having a circular shape.

[Configuration 5]
In the method for manufacturing a glass substrate for a magnetic disk according to any one of Configurations 1 to 4, a distance between an end portion of the second cut near the first cut and the first cut is 1 mm or less. It is characterized by being.

[Configuration 6]
In the method for manufacturing a glass substrate for a magnetic disk according to any one of Configurations 1 to 5, a plurality of second cuts are formed, and each second cut is formed without intersecting each other. It is a feature.

[Configuration 7]
In the method for manufacturing a glass substrate for a magnetic disk according to any one of Configurations 1 to 6, the glass base material is made of aluminosilicate glass.

[Configuration 8]
A method of manufacturing a glass substrate for a magnetic disk according to any one of Configurations 1 to 7, wherein the glass substrate is mounted on a 1-inch hard disk drive or a hard disk drive using a magnetic disk having a smaller diameter than the 1-inch hard disk drive. A glass substrate for a magnetic disk is manufactured.

[Configuration 9]
A method for manufacturing a magnetic disk, comprising forming at least a magnetic layer on a surface of a glass substrate for a magnetic disk obtained by the method for manufacturing a glass substrate for a magnetic disk according to any one of Configurations 1 to 8. It is a feature.

  In the method for manufacturing a glass substrate for a magnetic disk according to the present invention, a first notch that draws a closed curve that forms an outer edge of a region to be a glass substrate for a magnetic disk in the glass base material is made in the main surface of the glass base material. A second cut extending from the vicinity of the notch of the glass base material to the vicinity of the outer edge of the glass base material is made, and each part on one side and the other side of the second notch is separated in the second notch, and the respective parts Are separated from the region to be the magnetic disk glass substrate in the first cut.

  Therefore, according to the present invention, in the region to be the magnetic disk glass substrate cut out from the glass base material, the end face is substantially perpendicular to the main surface, and the subsequent shape processing is facilitated, so that inexpensive magnetic It is possible to stably supply a large number of disk glass substrates or magnetic disks.

  Further, according to the present invention, it is possible to provide a flat and smooth glass substrate for a magnetic disk or a magnetic disk that has few defects and can realize a high recording density of, for example, 60 gigabits per square inch or more. .

  Furthermore, according to the present invention, a portable telephone, a digital camera, a portable information device (for example, a personal digital assistant (PDA)), or a personal computer such as a “car navigation system” is used. A glass substrate for a magnetic disk or a magnetic disk suitable for use in a small hard disk drive that can be mounted on a device that is small in size and requires a high response speed can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the method for manufacturing a glass substrate for a magnetic disk according to the present invention comprises lapping (grinding) the surface of a sheet glass 1 to form a glass base material 2, and cutting the glass base material 2. The glass disk 3 is cut out, and at least the surface of the glass disk 3 is polished (polished) to produce the magnetic disk glass substrate 4.

  In the present invention, various plate glasses can be used as the plate glass 1 subjected to lapping. The shape of the plate-like glass 1 may be a rectangular shape or a disc shape (disc shape). The disk-shaped plate-like glass can be lapped using a lapping apparatus used in the production of a conventional magnetic disk glass substrate, and a highly reliable process can be performed at low cost.

  The size of the plate glass 1 needs to be larger than the glass substrate 4 for magnetic disk to be manufactured. For example, when manufacturing a glass substrate 4 for a magnetic disk used for a magnetic disk mounted on a “1 inch type hard disk drive” or a small hard disk drive having a size smaller than that, the glass substrate 4 for the magnetic disk is manufactured. Since the diameter is about 20 mm to 30 mm, the diameter of the disk-shaped plate glass 1 is preferably 30 mm or more, and preferably 48 mm or more. In particular, when a disk-shaped plate glass 1 having a diameter of 65 mm or more is used, a magnetic disk glass substrate 4 used for a magnetic disk mounted on a plurality of “1-inch hard disk drives” is obtained from a single sheet glass 1. It can be collected and is suitable for mass production. The upper limit of the size of the plate-like glass 1 is not particularly limited, but in the case of the disk-like plate-like glass 1, it is preferable to use a glass having a diameter of 100 mm or less.

  This plate-like glass 1 can be manufactured using a known manufacturing method such as a press method, a float method, or a fusion method, for example, using molten glass as a material. Among these, if the press method is used, the sheet glass 1 can be manufactured at low cost.

  Moreover, as a material of the sheet glass 1 used in the present invention, amorphous glass or glass ceramics (also referred to as crystallized glass) can be used. In view of workability and safety in cutting out a glass disk, which will be described later, amorphous glass is preferable. As such an amorphous glass, an aluminosilicate glass can be preferably used.

  The lapping process is a process aimed at improving the shape accuracy (for example, flatness) and dimensional accuracy (for example, plate thickness accuracy) of the main surface of the workpiece, that is, the sheet glass 1. This lapping process is performed by pressing a grindstone or a surface plate against the main surface of the plate glass 1 and relatively moving the plate glass 1 and the grindstone or surface plate. This is done by grinding. Such lapping can be performed using a double-sided lapping device using a planetary gear mechanism.

  Moreover, in this lapping process, it is good to wash a sludge (grinding waste) from a grinding surface by supplying a grinding liquid to the main surface of the sheet glass 1, and to cool a grinding surface. Furthermore, a slurry in which free abrasive grains are contained in this grinding liquid may be supplied to the main surface of the workpiece for grinding.

  As a grindstone used in the lapping process, a diamond grindstone can be used. Further, as the free abrasive grains, it is preferable to use hard abrasive grains such as alumina abrasive grains, zirconia abrasive grains, or silicon carbide abrasive grains.

  By this lapping process, the shape accuracy of the sheet glass 1 is improved, the shape of the main surface is flattened, and the glass base material 2 reduced until the sheet thickness reaches a predetermined value is formed.

  In the present invention, the main surface of the glass base material 2 is flattened by lapping, and the plate thickness is reduced. Therefore, the glass base material 2 is cut and the glass base material 2 is cut from the glass base material 2. Can be cut out. That is, in the present invention, it is possible to prevent the occurrence of defects such as chipping, cracking and cracking when the glass disk 3 is cut out from the glass base material 2.

The flatness of the glass base material 2 is, for example, preferably 30 μm or less and more preferably 10 μm or less in 7088 mm ² (area of a circle having a diameter of 95 mm). It has been found that when the flatness of the glass base material 2 exceeds 30 μm, the surface flatness is not sufficient and defects such as chipping, cracking and cracking are likely to occur when the glass disk 3 is cut out.

  Further, the plate thickness of the glass base material 2 is preferably 2 mm or less, and more preferably 0.8 mm or less. If the glass base material 2 has a thickness of less than 0.2 mm, the glass base material 2 itself may not be able to withstand the load in the process of cutting the glass disk 3. Is preferably 0.2 mm or more. If the plate thickness of the glass base material 2 exceeds 2 mm, the plate thickness is too thick and there is a possibility that precise cutting cannot be performed, and when the glass disk 3 is cut out, defects such as chipping, cracking and cracking occur. There is a fear.

  The glass base material 2 needs to be larger than the magnetic disk glass substrate 4 to be manufactured. For example, when manufacturing a glass substrate 4 for a magnetic disk used for a magnetic disk mounted on a “1-inch hard disk drive” or a small hard disk drive having a size smaller than that, the diameter of the glass substrate 4 for the magnetic disk is used. Is approximately 20 mm to 30 mm, and thus the diameter of the glass base material 2 is preferably 30 mm or more, and preferably 48 mm or more. In particular, when a glass base material 2 having a diameter of 65 mm or more is used, a glass disk 3 to be a glass substrate 4 for a magnetic disk used for a magnetic disk mounted on a “1-inch hard disk drive” is obtained from one glass base material 2. Multiple sheets can be cut out, which is suitable for mass production. The upper limit of the size of the glass base material 2 is not particularly limited, but in the case of the disk-shaped glass base material 2, the diameter is preferably 100 mm or less.

  The glass base material 2 can be cut using a cutting blade or a grindstone containing a material harder than glass, such as a diamond cutter or a diamond drill. The glass base material 2 may be cut using a laser cutter. However, it may be difficult to precisely cut out a small glass disk 3 having a diameter of 30 mm or less using a laser cutter, and it is preferable to use a cutting blade or a grindstone because it can be cut out easily.

  In order to cut out the glass disk 3 from the glass base material 2, first, a closed curve is drawn on the main surface of the glass base material 2 that forms the outer edge of the region of the glass base material 2 that will be the glass substrate 4 for the magnetic disk. Make a first cut. Next, a second cut is made from the vicinity of the first cut to the vicinity of the outer edge of the glass base material on the main surface of the portion outside the closed curve drawn by the first cut in the glass base material 2.

  Then, by applying a force in a direction away from the second cut along the main surface of the glass base material 2 to each of the one side and the other side of the second cut, Are separated at the second cut and these portions are separated from the region to be the magnetic disk glass substrate at the first cut, whereby the glass disk 3 is cut out.

  Here, as a size of the glass disk 3 cut out from the glass base material 2, a particularly suitable size is 30 mm or less in diameter. In the case of cutting out such a small-diameter glass disc 3, the effects of the present invention are particularly exhibited.

  In the present invention, at least polishing processing is performed on the glass disk 3 cut out from the glass base material 2, and the main surface of the glass disk 3 is mirror-finished to obtain a glass substrate 4 for a magnetic disk. By performing this polishing process, the surface roughness of the main surface of the magnetic disk glass substrate 4 is set to 6 nm or less for Rmax and 0.6 nm or less for Ra. If the main surface of the magnetic disk glass substrate 4 has such a mirror surface, in the magnetic disk manufactured using the magnetic disk glass substrate 4, the flying height of the magnetic head is, for example, 10 nm. Even so, the occurrence of a so-called crash failure or thermal asperity failure can be prevented.

  In this polishing process, for example, a polishing method described in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 11-154325) can be used. That is, the polishing process is performed by pressing a work plate, that is, a surface plate having a polishing pad attached to the main surface of the glass disk 3, and supplying a polishing liquid to the main surface of the glass disk 3. And the surface plate is moved relatively, and the main surface of the glass disk 3 is polished. At this time, the polishing liquid may contain polishing abrasive grains. As the abrasive grains, cerium oxide or colloidal silica can be used.

  In the present invention, it is preferable to lapping the glass disk 3 before polishing. The lapping process at this time can be performed by the same means as the lapping process for the sheet glass 1 described above. By performing the polishing process after lapping the glass disk 3, it is possible to obtain the glass substrate 4 for a magnetic disk whose main surface is mirror-finished in a shorter time.

  In the present invention, the end face of the glass disk 3 is preferably mirror-polished. Since the end surface of the glass disk 3 has a cut shape, it is possible to suppress the generation of particles by polishing the end surface to a mirror surface, and the magnetic disk manufactured using the glass substrate 4 for the magnetic disk is used. This is because a so-called thermal asperity failure can be well prevented in the disk.

  In the present invention, it is preferable to perform a chemical strengthening treatment after the polishing process of the glass disk 3. By performing the chemical strengthening treatment, a high compressive stress can be generated on the surface of the magnetic disk glass substrate 4 and the impact resistance can be improved. In particular, when aluminosilicate glass is used as the material of the glass disk 3, chemical strengthening treatment can be suitably performed.

  In the present invention for manufacturing the magnetic disk glass substrate 4 as described above, the magnetic disk glass substrate 4 to be mounted on a “1 inch type hard disk drive” or a hard disk drive smaller than the “1 inch type”. It is suitable as a method for producing The diameter of the magnetic disk glass substrate 4 for manufacturing a magnetic disk to be mounted on the “1-inch hard disk drive” is about 27.4 mm. Moreover, the diameter of the glass substrate 4 for magnetic disk for manufacturing the magnetic disk mounted in the “0.85 inch type hard disk drive” is about 21.6 mm.

  In the magnetic disk according to the present invention, the magnetic layer formed on the magnetic disk glass substrate 4 may be made of, for example, a cobalt (Co) ferromagnetic material. In particular, it is preferable to form a magnetic layer made of a cobalt-platinum (Co-Pt) ferromagnetic material system that provides a high coercive force. As a method for forming the magnetic layer, a DC magnetron sputtering method can be used.

  In the present invention, as a glass base material for cutting out a glass disk, a glass substrate for a magnetic disk that is manufactured for a “2.5-inch hard disk drive” or the like or is a semi-finished product in the manufacturing process. Can be used. This is because the main surface has been flattened to 30 μm or less through a lapping process.

  In this case, it is preferable to use a glass substrate for a magnetic disk having a diameter of 30 mm or more and a plate thickness of 2 mm or less, or a semi-finished product thereof. The glass substrate for magnetic disk for “2.5 inch hard disk drive” is manufactured with a diameter of 65 mm, a plate thickness of 0.635 mm, and a flatness of the main surface of 3 μm or less. Can be used.

  For example, among glass substrates for magnetic disks manufactured for "2.5 inch type hard disk drives" etc., due to reasons such as defects in the main surface, defects in the edge shape, or defects in the surface roughness of the main surface The stock that has not been shipped to the market can be reused as the glass base material in the present invention. These defective items can be sufficiently removed or corrected in the lapping process or polishing process after the glass disk is cut out.

  In this way, defective products in other products can be recycled, and there is no need to dispose of them as industrial waste. Therefore, it is possible to provide a manufacturing process and products (eco process and eco product) that are friendly to the global environment. Further, it is possible to further reduce the price of the magnetic disk.

  Hereinafter, the present invention will be specifically described by giving examples and comparative examples. In addition, this invention is not limited to the structure of these Examples.

[Example 1 (Example of manufacturing method of glass substrate for magnetic disk)]
In this example, a glass substrate for a magnetic disk was manufactured through the following steps.

(1) Shape processing step and first lapping step First, the melted aluminosilicate glass was molded into a disk shape by pressing to obtain an amorphous plate glass. In addition, the glass for chemical strengthening was used as aluminosilicate glass.

The obtained disk-shaped plate-like glass had a diameter of 96 mm, a plate thickness of 1.8 mm, and a flatness of 100 μm. This flatness is measured with a laser interferometer on substantially the entire main surface (the area of a circle having a diameter of 95 mm≈7088 mm ² ) on one side of the sheet glass.

  Next, both main surfaces of the plate glass were lapped to form a disk-shaped glass base material. This lapping process was performed using alumina free abrasive grains with a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed on both sides of the plate glass from above and below, the grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relative to each other for lapping. went.

  By this lapping process, a glass base material having a flat main surface was obtained. Moreover, the plate | board thickness of the glass base material was reduced rather than plate glass by this lapping process, and became 0.6 mm.

The flatness of the disk-shaped glass base material thus obtained was measured under the above-described conditions, that is, with respect to 7088 mm ² , and was 5 μm.

(2) Cutting process Next, the glass base material was cut | disconnected using the diamond cutter, and the glass disk of diameter 29mm was cut out from this glass base material. The diameter of the glass base material was 96 mm, and six glass disks could be collected from one glass base material.

  Cutting out the glass disk from the glass base material was performed as follows.

  FIG. 2A is a plan view showing notches formed in the glass base material in the step of cutting out the glass disk from the glass base material.

  That is, as shown in FIG. 2A, first, the glass base material 2 is fixed on the work table by the carrier 101. The carrier 101 is formed in a shape capable of fixing the glass base material 2 with a synthetic resin material such as glass epoxy, for example. And the 1st notch C1 is made with respect to the main surface of this glass base material 2 using a diamond cutter. The first cut C1 draws a closed curve that forms the outer edge of the region of the glass base material 2 that will be the glass substrate 4 for the magnetic disk. That is, the first cut C1 draws a circle having a diameter of 30 mm or less or 1 inch or less. In the example shown in FIG. 2A, a first cut for cutting out five glass disks from one glass base material 2 is shown.

  The first cut C <b> 1 is formed substantially perpendicular to the main surface of the glass base material 2. That is, when the first cut C1 is formed, the cutter blade of the diamond cutter is used such that the blade angles with respect to the main surface of the glass base material 2 on both sides of the ridge line of the cutter blade are substantially the same.

  Next, a second notch C2 is made using a diamond cutter on the main surface of the outside portion of the closed curve drawn by the first notch C1 in the glass base material 2. The second cut C2 is formed from the vicinity of the first cut C1 to the vicinity of the outer edge portion of the glass base material 2. In the second cut C2, the distance between the end portion near the first cut C1 and the first cut C1 is 1 mm or less.

  A plurality of the second cuts C2 are formed, but it is preferable that the second cuts C2 do not cross each other. That is, as shown in FIG. 2A, the second cuts C2 are located in the vicinity of the outer edge of the glass base material 2 from the two portions of each first cut C1 (each region that becomes the magnetic disk glass substrate 4). Can be formed.

  FIG. 2B is a plan view showing another example of how to make the second cut.

  As shown in FIG. 2B, various methods of making the second cut C2 can be considered.

  FIG. 3A is a plan view showing a state in which the glass base material is broken at the second cut.

  Next, a force is applied to each part on one side and the other side of a second notch C2 along the main surface of the glass base material 2 in a direction away from the second notch C1. Then, by this force, as shown in FIG. 3A, these portions are separated at the second cut. That is, at this time, the glass base material 2 is broken at a certain second cut C2.

  FIG. 3B is a plan view showing a state in which a glass disk is cut out from the glass base material.

  In this way, by dividing the glass base material 2 in each second cut C2, each region that becomes the glass substrate 4 for the magnetic disk passes through the first cut C1 as shown in FIG. 3B. They are separated from each other with the connected portions.

  FIG. 3C is a plan view showing a state in which a glass disk is cut out from the glass base material.

  Then, as shown in FIG. 3C, the portion connected to each region to be the magnetic disk glass substrate 4 via the first cut C <b> 1 from the region to be the magnetic disk glass substrate 4 in the first cut C <b> 1. The glass disk 3 is cut out by separating.

  Next, using a diamond drill, a circular hole was formed in the center of the glass disk to obtain a donut-shaped glass disk.

  About the obtained several glass disc, flatness was substantially the same, respectively, and plate | board thickness was also substantially the same.

  FIG. 4A is a plan view showing an image obtained by observing an edge portion of a glass disk cut out from a glass base material with a microscope.

  When these glass disks were inspected, as shown in FIG. 4A, defects such as chipping, cracking, and cracking, which were problems in manufacturing the magnetic disk, were not confirmed.

  FIG. 4B is a side view showing an image obtained by observing the edge portion of the glass disk cut out from the glass base material with a microscope.

  Further, when a plurality of these glass disks were inspected, it was found that the end surfaces of these glass disks were substantially smooth and perpendicular to the main surface, as shown in FIG. 4B. .

  In this manner, when 9000 glass disks were collected from 1500 glass base materials and inspected, 8972 glass disks passed the inspection. The yield was 99.7%, and it was found that this is a low cost and suitable manufacturing method for mass production.

(3) End surface polishing process Next, the end surface of the glass disk was mirror-polished by a conventionally used brush polishing method. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains was used. Next, the inner peripheral side end face was mirror polished by a magnetic polishing method.

  In this end surface polishing step, the glass disk is overlapped to polish the end surface, but in this case, in order to avoid scratches etc. on the main surface of the glass disk, before the first polishing step described later, Or it is preferable to carry out before and after the second polishing step.

  And the glass disk which finished the end surface polishing process was washed with water.

  By this end surface polishing step, the end surface of the glass disk was processed into a mirror surface state capable of preventing generation of particles and the like. When the diameter of the glass disk was measured after the end face polishing step, it was 27.4 mm.

(4) Second Lapping Step Next, a second lapping process was performed on both main surfaces of the obtained glass disk in the same manner as in the first lapping step. By performing this second lapping process, it is possible to remove in advance the fine irregularities formed on the main surface in the previous cutting process and end surface polishing process, and shorten the subsequent polishing process on the main surface. Will be able to be completed in time.

(5) Main surface polishing step (5-1) First polishing step Next, a first polishing step was performed as the main surface polishing step. The first polishing process is mainly intended to remove scratches and distortions remaining on the main surface in the lapping process described above. In the first polishing step, the main surface was polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains were used.

  The glass disk after the first polishing process is sequentially immersed in cleaning baths of neutral detergent, pure water (1), pure water (2), IPA (isopropyl alcohol), and IPA (steam drying), and cleaned. did.

(5-2) Second Polishing Step Next, a second polishing step was performed as a mirror polishing step for the main surface. The purpose of this second polishing step is to finish the main surface into a mirror surface. In the second polishing step, mirror polishing of the main surface was performed using a soft foam resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains finer than the cerium oxide abrasive grains used in the first polishing step were used.

  After the second polishing step, the glass substrate for magnetic disk is made into neutral detergent (1), neutral detergent (2), pure water (1), pure water (2), IPA (isopropyl alcohol), IPA (steam). (Dry) was sequentially immersed in each washing tank and washed. Note that ultrasonic waves were applied to each cleaning tank.

(6) Chemical strengthening process Next, the glass substrate for magnetic disks which finished the above-mentioned lapping process and polishing process was chemically strengthened. For chemical strengthening, a chemical strengthening solution prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) is prepared, and the chemically strengthened solution is heated to 400 ° C., and a cleaned glass substrate for a magnetic disk is prepared. This was performed by preheating to 300 ° C. and immersing in a chemical strengthening solution for about 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate for magnetic disk, the plurality of glass substrates for magnetic disk were stored in a holder so as to be held at the end surfaces.

  Thus, by immersing in the chemical strengthening solution, lithium ions and sodium ions in the surface layer of the glass substrate for magnetic disk are respectively replaced with sodium ions and potassium ions in the chemical strengthening solution, and the glass substrate for magnetic disk is Strengthened.

  The thickness of the compressive stress layer formed on the surface layer of the glass substrate for magnetic disk was about 100 μm to 200 μm.

  The glass substrate for magnetic disk that had been subjected to the chemical strengthening treatment was immersed in a water bath at 20 ° C. to be rapidly cooled and maintained for about 10 minutes.

  Then, the glass substrate for magnetic disk that had been quenched was immersed in concentrated sulfuric acid heated to about 40 ° C. for cleaning. Further, the magnetic disk glass substrate that had been subjected to the sulfuric acid cleaning was sequentially immersed in cleaning baths of pure water (1), pure water (2), IPA (isopropyl alcohol), and IPA (steam drying) to be cleaned. In addition, ultrasonic waves were applied to each cleaning tank.

  As described above, by applying the first lapping step, the cutting step, the end surface polishing step, the second lapping step, the first and second polishing steps, the precision cleaning, and the chemical strengthening step, flat and smooth, high rigidity A magnetic disk glass substrate was obtained.

  The obtained magnetic disk glass substrate has an inner diameter of 7 mm, an outer diameter of 27.4 mm, a plate thickness of 0.381 mm, and has the predetermined dimensions of the glass substrate for magnetic disks used in the “1.0 inch type” magnetic disk. I confirmed that there was.

  Further, the surface roughness Ra of the main surface of the glass substrate for magnetic disk obtained through the above-described steps was 0.2 nm to 0.6 nm (measured by AFM). Rmax was 2 nm to 6 nm (Ra and Rmax were in accordance with Japanese Industrial Standard (JIS) B0601). When the end surface was observed with an electron microscope (4000 times), it was in a mirror state.

  Further, the surface roughness of the inner peripheral side end face of the circular hole of the glass substrate for magnetic disk is 0.4 μm for the chamfered portion Rmax, 0.04 μm for Ra, 0.4 μm for the side wall portion Rmax, and 0.05 μm for Ra. there were. The surface roughness Ra at the outer peripheral end face was 0.04 μm at the chamfered portion and 0.07 μm at the side wall portion. As described above, it was confirmed that the inner peripheral side end face was finished in a mirror surface like the outer peripheral side end face.

  Further, no foreign matter or particles causing thermal asperity were found on the surface of the magnetic disk glass substrate, and no foreign matter or cracks were found on the inner peripheral side end face of the circular hole.

  And when the bending strength of this glass substrate for magnetic disks was measured using the bending strength tester (Shimadzu Autograph DDS-2000), it was 5 kg. In addition, when the bending strength was similarly measured by changing the chemical strengthening level, it was about 2 to 12 kg.

[Comparative Example (Comparative Example of Manufacturing Method of Glass Substrate for Magnetic Disk)]
The comparative example of the manufacturing method of the glass substrate for magnetic disks mentioned above was implemented as follows, and the occurrence condition of the defective part in the cutting process of a glass disk was investigated.

  In this comparative example, after the first and second cuts are made in the glass base material, the both sides of the cuts are separated from the cut along the main surface of the glass base material as described above. It was left without applying the power of.

  If the glass base material is left with the cuts, the cracks self-expand from the cuts, and the glass base material breaks at the portions of the cuts. Therefore, the glass disk can be taken out from the glass base material by leaving the glass base material with the cut. The glass disk thus taken out was used as a comparative example.

  FIG. 5 is a plan view showing an image obtained by observing an edge portion of a glass disk cut out from a glass base material with a microscope in a comparative example.

  When the glass disk in this comparative example was inspected, as shown in FIG. 5, a concave defect and a convex defect were confirmed, and it was found that the end surface polishing process, which is a subsequent process, could not be performed smoothly. Such a defect also poses a problem in manufacturing a magnetic disk. These concave defects and convex defects are because the crack self-expansion proceeds in a direction that is not perpendicular to the main surface of the glass base material. Therefore, in this comparative example, the end surface of the glass disk is not perpendicular to the main surface.

[Example 2 (Example of magnetic disk manufacturing method)]
Next, a magnetic disk was manufactured through the following steps.

  On both main surfaces of the glass substrate for magnetic disk obtained by the above-mentioned process, using a stationary facing DC magnetron sputtering apparatus, an Al—Ru alloy seed layer, a Cr—Mo alloy underlayer, Co—Cr—Pt A magnetic layer of -B alloy and a hydrogenated carbon protective layer were sequentially formed.

  FIG. 6 is a cross-sectional view schematically showing the layer structure of a magnetic disk manufactured by the implementation of the present invention.

  As shown in FIG. 6, the magnetic disk 10 includes a magnetic disk glass substrate 4 which is a nonmagnetic substrate, a magnetic layer 7 formed on the magnetic disk glass substrate 4, and a magnetic layer 7 formed on the magnetic layer 7. The protective layer 8 formed and the lubricating layer 9 formed on the protective layer 8 are provided at least.

  A nonmagnetic metal layer (nonmagnetic underlayer) composed of a seed layer 5 and an underlayer 6 is formed between the magnetic disk glass substrate 4 and the magnetic layer 7. In this magnetic disk 10, all but the magnetic layer 7 are layers made of a nonmagnetic material. In this embodiment, the magnetic layer 7, the protective layer 8, the protective layer 8 and the lubricating layer 9 are formed in contact with each other.

  That is, first, using an Al—Ru (aluminum-ruthenium) alloy (Al: 50 at%, Ru: 50 at%) as a sputtering target, an Al—Ru alloy with a film thickness of 30 nm is formed on the magnetic disk glass substrate 4. A seed layer 5 was formed by sputtering. Next, using a Cr—Mo (chromium-molybdenum) alloy (Cr: 80 at%, Mo: 20 at%) as a sputtering target, an underlayer 6 made of a 20 nm thick Cr—Mo alloy is formed on the seed layer 5. Was formed by sputtering. Next, as a sputtering target, a sputtering target made of a Co—Cr—Pt—B (cobalt-chromium-platinum-boron) alloy (Cr: 20 at%, Pt: 12 at%, B: 5 at%, balance Co) is used. A magnetic layer 7 made of a Co—Cr—Pt—B alloy having a thickness of 15 nm was formed on the underlayer 6 by sputtering.

  Next, a protective layer 8 was formed on the magnetic layer 7, and a lubricating layer 9 made of alcohol-modified perfluoropolyether was formed by a dip method. Thus, the magnetic disk 10 was obtained.

  Using the obtained magnetic disk, a glide inspection was performed with a glide head having a flying height of 10 nm. As a result, no colliding foreign matter was detected, and a stable flying state could be maintained. Further, when a recording / reproducing test was conducted at 700 kFCI using this magnetic disk, a sufficient signal intensity ratio (S / N ratio) could be obtained. Further, no signal error was confirmed.

  Furthermore, when mounted and driven in a “1-inch hard disk drive” that requires an information recording density of 60 gigabits or more per square inch, recording and reproduction could be performed without any particular problem. That is, no crash failure or thermal asperity failure occurred.

  In the present invention, the diameter (size) of the glass substrate for magnetic disk is not particularly limited. However, the present invention exhibits excellent utility particularly when a small-diameter glass substrate for a magnetic disk is produced. The small diameter here is, for example, a glass substrate for a magnetic disk having a diameter of 30 mm or less.

  That is, for example, a small-diameter magnetic disk having a diameter of 30 mm or less is used in a storage device in an in-vehicle device such as a so-called “car navigation system” or a portable device such as a so-called “PDA” or a mobile phone terminal. This is because higher durability and impact resistance are required as compared with a normal magnetic disk in a used device.

It is process drawing which shows each process in the manufacturing method of the glass substrate for magnetic discs which concerns on this invention. It is a top view which shows the incision formed in a glass base material in the process of cutting out a glass disk from the glass base material in the manufacturing method of the said glass substrate for magnetic discs. It is a top view which shows the other example of how to make the 2nd cut in the manufacturing method of the said glass substrate for magnetic discs. It is a top view which shows the state which divided the glass base material in the 2nd notch in the manufacturing method of the said glass substrate for magnetic discs. It is a top view which shows the state which cut out the glass disk from the glass base material in the manufacturing method of the said glass substrate for magnetic disks. It is a top view which shows the state which cut out the glass disk from the glass base material in the manufacturing method of the said glass substrate for magnetic disks. It is a top view which shows the image which observed the edge part of the glass disk cut out from the glass base material with the microscope in the manufacturing method of the said glass substrate for magnetic discs. In the manufacturing method of the said glass substrate for magnetic discs, it is a side view which shows the image which observed the edge part of the glass disc cut out from the glass base material with the microscope. In a comparative example, it is a top view which shows the image which observed the edge part of the glass disc cut out from the glass base material with the microscope. It is sectional drawing which shows the structure of the magnetic disc which concerns on this invention manufactured using the glass substrate for magnetic discs manufactured with the manufacturing method of the glass substrate for magnetic discs which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plate glass 2 Glass base material 3 Glass disk 4 Glass substrate for magnetic disks 5 Seed layer 6 Underlayer 7 Magnetic layer 8 Protective layer 9 Lubricating layer 10 Magnetic disk C1 First cut C2 Second cut

Claims (9)

A method of manufacturing a magnetic disk glass substrate by cutting out a magnetic disk glass substrate from a plate-shaped glass base material,
With respect to the main surface of the glass base material, a first cut is drawn that draws a closed curve that forms an outer edge of a region that is a glass substrate for a magnetic disk in the glass base material,
With respect to the main surface of the outer portion of the closed curve drawn by the first cut in the glass base material, a second cut is made from the vicinity of the first cut to the vicinity of the outer edge of the glass base material,
By applying a force in a direction away from the second cut along the main surface of the glass base material to each of the one side and the other side of the second cut, A method for producing a glass substrate for a magnetic disk, comprising: separating at the second cut and separating each portion from an area to be a glass substrate for a magnetic disk at the first cut. 2. The method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein at least the first cut is formed substantially perpendicular to the main surface of the glass base material. Each notch is formed by a cutter blade,
When forming at least the first cut among the respective cuts, the cutter blade is used with the blade angles with respect to the main surface of the glass base material on both sides of the ridge line of the cutter blade being substantially the same. The method for producing a glass substrate for a magnetic disk according to claim 2, wherein: The thickness of the said glass base material is 2.0 mm or less, and the area | region used as the glass substrate for magnetic discs is a circle with a diameter of 30 mm or less. The Claim 1 thru | or 3 characterized by the above-mentioned. The manufacturing method of the glass substrate for magnetic disks of description. 5. The distance between the end of the second cut near the first cut and the first cut is 1 mm or less. 5. The manufacturing method of the glass substrate for magnetic disks of description. 6. The magnetic disk glass according to claim 1, wherein a plurality of the second cuts are formed, and each second cut is formed without intersecting each other. A method for manufacturing a substrate. The method for producing a glass substrate for a magnetic disk according to any one of claims 1 to 6, wherein the glass base material is made of aluminosilicate glass. It is a manufacturing method of the glass substrate for magnetic discs as described in any one of Claims 1 thru | or 7, Comprising:
A method of manufacturing a glass substrate for a magnetic disk, comprising: manufacturing a glass substrate for a magnetic disk mounted on a 1-inch hard disk drive or a hard disk drive using a magnetic disk having a smaller diameter than that of a 1-inch hard disk drive. A magnetic disk is produced by forming at least a magnetic layer on the surface of the glass substrate for a magnetic disk obtained by the method for producing a glass substrate for a magnetic disk according to claim 1. Method.

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