WO2012131814A1

WO2012131814A1 - Method for producing glass substrate for magnetic information recording medium, and glass substrate for magnetic information recording medium

Info

Publication number: WO2012131814A1
Application number: PCT/JP2011/005776
Authority: WO
Inventors: 直之福本
Original assignee: コニカミノルタオプト株式会社
Priority date: 2011-03-30
Filing date: 2011-10-14
Publication date: 2012-10-04

Abstract

The objective of the present invention is to provide a method for producing a glass substrate for a magnetic information recording medium wherein ion based contamination is reduced, defective drying does not occur, and as a result, head crash does not occur even if the glass substrate is mounted on a hard disk having a minute head flying height. A method for producing a glass substrate for a magnetic information recording medium comprises a transfer step for transferring a glass substrate using a transfer rod tool, wherein the transfer rod tool is provided, on its peripheral surface, with a plurality of points juxtaposed on a first line extending in the longitudinal direction of the tool, a plurality of points juxtaposed on a second line which is different from the first line, and a plurality of grooves which connect the points on the first line and the points on the second line one-to-one from one end side in the longitudinal direction of the tool, and wherein the transfer rod tool has a first pitch corresponding to the point-to-point distance of the plurality of points juxtaposed on the first line extending in the longitudinal direction of the tool, and a second pitch corresponding to the point-to-point distance of the plurality of points juxtaposed on the second line, and the first pitch and the second pitch are different.

Description

Manufacturing method of glass substrate for magnetic information recording medium and glass substrate for magnetic information recording medium

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

The magnetic information recording apparatus records information on an information recording medium by using magnetism, light, magneto-optical, and the like. A typical example is a hard disk drive device. A hard disk drive device is a device that magnetically records information on a magnetic disk as an information recording medium having a recording layer formed on a substrate by a magnetic head. As a base material of such an information recording medium, a so-called substrate, a glass substrate is preferably used.

In addition, the hard disk drive device records information on the magnetic disk while rotating it at a high speed about several nanometers without rotating the magnetic head in contact with the magnetic disk. Furthermore, in recent years, the recording density of hard disks has been further improved, and accordingly, the difference between the magnetic head and the magnetic disk (hereinafter referred to as the head flying height) has been reduced. In particular, in a hard disk having a DFH (Dynamic Flying Height) mechanism, a head flying height of 3 nm or less has been developed. However, in the DFH mechanism, since the head flying height is extremely small, a problem that the head crashes due to the collision between the magnetic head and the magnetic disk frequently occurs.

Also, recent hard disk drive devices have been required to have a high surface cleanliness of the substrate used for the hard disk due to the improved recording density. Furthermore, in order to improve the surface cleanliness of the substrate, a glass substrate for a magnetic information recording medium is strongly required to have fine deposits removed.

In Patent Document 1, in order to prevent the head crash, the atmosphere when the glass substrate for magnetic information recording medium is stored in a storage container is subjected to a treatment for irradiating the photocatalyst with light to decompose compounds in the atmosphere. A technique for storing an atmosphere and storing a glass substrate for a magnetic disk in a storage container is disclosed.

However, in the above method, ionic contamination enters electrostatically from air or the like, and the ionic contamination adheres to the glass substrate. In addition, since the inside of the storage container has a complicated shape so that the glass substrate can be stored, there is a problem that contamination cannot remain in the container because light cannot be uniformly irradiated.

JP 2008-243313 A

The purpose of the present invention is to prevent the occurrence of surface defects due to handling errors and environmental recontamination by performing transfer of substrates between each process easily in a short time in the manufacturing process of a glass substrate, and as a result An object of the present invention is to provide a method for producing a glass substrate for a magnetic information recording medium which does not cause head crash even when mounted on a hard disk having a very small head flying height.

That is, the method for manufacturing a glass substrate for a magnetic information recording medium according to the present invention includes the transfer step of transferring the glass substrate using a transfer rod jig, in the method for manufacturing a glass substrate for a magnetic information recording medium. A plurality of points arranged in parallel on a first line extending in the longitudinal direction of the jig and a plurality of lines arranged in parallel on a second line different from the first line on the circumferential surface of the mounting jig. A plurality of grooves formed on the peripheral surface of the jig so as to be connected one-to-one in order from one end side in the longitudinal direction of the jig, on a first line extending in the longitudinal direction of the jig A transfer rod jig having a different first pitch between a plurality of points arranged in parallel and a second pitch between the plurality of points arranged in parallel on the second line is used.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

It is the schematic explaining the process which transfers a glass substrate with the transfer rod jig | tool used with the manufacturing method of the glass substrate for magnetic information recording media which concerns on this embodiment. It is a front view explaining before and behind rotation of the transfer rod jig used with the manufacturing method of the glass substrate for magnetic information recording media concerning this embodiment. It is a perspective view explaining the operation | movement which transfers a several glass substrate using the transfer rod jig | tool used with the manufacturing method of the glass substrate for magnetic information recording media concerning this embodiment. It is a front view explaining the order by the transfer process in the manufacturing method of the glass substrate for magnetic information recording media concerning this embodiment. It is detail drawing of the transfer rod jig | tool used by the manufacturing method of the glass substrate for magnetic information recording media concerning this embodiment, and a glass substrate. It is a top view which shows the glass substrate for magnetic information recording media manufactured by the manufacturing method of the glass substrate for magnetic information recording media concerning this embodiment. It is a schematic sectional drawing which shows an example of the grinding | polishing apparatus used at the rough grinding | polishing process and the precision grinding | polishing process in the manufacturing method of the glass substrate for magnetic information recording media which concerns on this embodiment. 1 is a partial cross-sectional perspective view showing a magnetic disk as an example of a magnetic recording medium using a glass substrate for magnetic information recording medium manufactured by the method for manufacturing a glass substrate for magnetic information recording medium according to the present embodiment.

The glass substrate for magnetic information recording media is usually stored in a plastic storage case and transferred to the next process. The movement of the glass substrate between each process is likely to be a source of surface defects and re-contamination as it is closer to the final process. That is, reducing the number of substrate movements as much as possible and ending the movement in a short time leads to prevention of recontamination.

On the other hand, a board shipment case stores a predetermined number of disks (for example, 25 sheets per case) at a specific pitch, that is, an interval between disks, because of physical distribution, and it is difficult to change this number.

If a storage case with the same pitch is used in the process prior to processing and cleaning, there will be no major problem in transferring the substrate in the case between each process. In processing and cleaning, different numbers of sheets and different pitches may be used. Further, even with the same number of transporting / supporting jigs, the pitch between the disks may be different in order to improve the quality.

For this reason, it becomes difficult to transfer the substrate in the case between processes, and in extreme cases, it is transferred by machine transport one by one, so that surface defects due to handling errors and recontamination due to the environment frequently occur. It was. Furthermore, due to the occurrence of surface defects and re-contamination, many read / write errors have occurred in media evaluation.

In order to solve the above-mentioned problems, the present inventors have made extensive studies focusing on the transfer in the manufacturing process of the glass substrate for magnetic information recording medium and the transfer jig used for the storage. As a result, when the holding pitch of the glass substrate is different between the processes, a plurality of grooves on one end of the peripheral surface and a plurality of grooves on the other end are continuously engraved, and the inner diameter of the glass substrate is reduced. For magnetic information recording media with high cleanliness due to less contamination due to re-attachment caused by the environment by storing and transporting using a transfer rod jig that can be held in these grooves and rotated to change the pitch. It has been found that a glass substrate can be produced. Further, it has been found that the above-mentioned glass substrate for magnetic information recording medium is less likely to cause head crash even when mounted on a hard disk having a head flying height of 3 nm or less.

Hereinafter, preferred embodiments and examples of the present invention will be described. However, the present invention is not limited to the manufacturing methods of the embodiments and examples described below.

The method for manufacturing a glass substrate for magnetic information recording medium according to the present embodiment includes the transfer step in the method for manufacturing a glass substrate for magnetic information recording medium, which includes a transfer step of transferring the glass substrate using a transfer rod jig. On the peripheral surface of the bar jig, a plurality of points arranged in parallel on a first line extending in the longitudinal direction of the jig, and a plurality of points arranged in parallel on a second line different from the first line. A plurality of grooves formed on the peripheral surface of the jig are provided so as to connect the points one-to-one in order from one end side in the longitudinal direction of the jig, and are arranged on a first line extending in the longitudinal direction of the jig. A transfer rod jig is used in which a first pitch between a plurality of points provided is different from a second pitch between a plurality of points provided side by side on the second line.

In addition, the method for manufacturing a glass substrate for a magnetic information recording medium according to this embodiment may include a transfer process using the transfer rod jig before and after each process of the glass substrate manufacturing process described later. There is no particular limitation. Among these steps, the transfer step in the manufacturing method of the present invention can be most effectively used when transferring the glass substrate that has been subjected to the final cleaning step to the shipping case.

Examples of the method for producing a glass substrate for a magnetic information recording medium include a glass melting step, a forming step, a heat treatment step, a first lapping step, a coring step, an inner / outer diameter step, a second lapping step, and an end surface polishing step. Examples include a process, a first polishing process (rough polishing process), a chemical strengthening process, a second polishing process (precision polishing process), a cleaning process, a transfer process, an inspection process, and the like. The steps may be performed in this order, or the order of the chemical strengthening step and the second polishing step may be switched. Furthermore, a method including steps other than these may be used.

In particular, the cleaning process may be performed after the first polishing process, after the second polishing process, or may be performed once after the first polishing process and the second polishing process.

<Transfer process>
Hereinafter, the transfer rod jig used in the transfer process in the manufacturing method of the present invention will be described.

FIG. 1 is a schematic view showing an example of a case where a glass substrate is transferred using the transfer rod jig of the present invention. In the figure, 2 is a transfer rod jig, and 10 is a glass substrate. 10 is held by the transfer rod jig 2 so as to insert the transfer rod jig into the hole of the glass substrate.

As shown in FIG. 2, the transfer rod jig 2 of the present invention has a plurality of points arranged in parallel on a first line extending in the longitudinal direction of the jig on the peripheral surface, and the first line. A plurality of grooves formed on the peripheral surface of the jig are provided so as to connect a plurality of points arranged in parallel on different second lines one-to-one in order from one end side in the longitudinal direction of the jig. Moreover, between the 1st pitch between several points arranged in parallel on the 1st line extended in the longitudinal direction of the transfer rod jig | tool of this invention, and the several points arranged in parallel on the said 2nd line. The second pitch is different. In this way, by rotating the transfer rod, the glass substrate held on the first line is held on the second line adjacent to the second pitch different from the first pitch. Can do.

FIG. 3 is a perspective view in which a plurality of glass substrates 10 arranged in a plurality of rows in a case in the process before the transfer process are transferred using the transfer rod jig 2. By using the transfer rod jig of the present invention, it is possible to transfer a plurality of glass substrates arranged in a plurality of rows in this manner for each row. As a result, the glass substrates can be transferred by the number of sheets in one row at the same time without transferring them one by one as in the prior art, so that the transfer efficiency is remarkably improved.

FIG. 4 is a front view for explaining the order of the transfer process for transferring using the transfer rod jig of the present invention. In FIG. 4, 4 is a storage case before the transfer process, and 6 is a storage case after the transfer process.

The transfer rod jig 2 in a state before being transferred has the shape shown in FIG. 4A, and the interval between the glass substrates stored in the process before the transfer step is determined by the transfer rod jig 2. This corresponds to the first pitch. Therefore, when the glass substrate is transferred, as shown in FIG. 4B, the first line having the first pitch arranged in parallel is stored in the case 4 before the transfer. It is necessary to insert the transfer rod jig 2 into the holes of the plurality of glass substrates 10.

As shown in FIG. 4 (c), after the transfer rod jig 2 is inserted into the hole of each glass substrate 10, it is lifted as it is so that the second line having the second pitch arranged in parallel is turned up. Rotate. Here, on the peripheral surface of the transfer rod jig, a group consisting of a plurality of points different from the group consisting of a plurality of points arranged side by side on the second line is provided in the jig longitudinal direction, Since the distance D in the jig longitudinal direction between the points closest to the other group in the group is larger than the second pitch, as shown in FIG. The sorted glass substrate can be obtained on a transfer rod jig.

Furthermore, since the intervals of the plurality of glass substrates in the case 6a stored in the process after the transfer process correspond to the second pitch of the transfer bar jig 2, as shown in FIG. In addition, the transfer rod jig 2 holding the glass substrate can be stored in the storage case 6a after the transfer process with the second line facing upward. If another storage case 6b is arranged next to the storage case 6a, glass substrates held in different groups can be stored in the storage case 6b without causing surface defects or recontamination. Some glass substrates stored in the storage case 6b can be used without waste for inspection.

As described above, insertion, rotation, and storage of the transfer rod jig in the glass substrate hole in the transfer step are usually performed as long as the glass substrate is transferred before and after each step in the manufacturing method of the present invention. Repeated. In addition, after storing in the storage case after a transfer process as mentioned above, a transfer rod jig | tool is extracted from a glass substrate, it wash | cleans, returns to the original state, and repeats the same procedure. In this manner, the glass substrate for a magnetic information recording medium is manufactured as a transfer process that is a part of each manufacturing process by sequentially inserting, rotating, and storing the glass substrate.

The cross-sectional shape of the groove on the peripheral surface of the transfer rod jig of the present invention is preferably a V-shape of 90 to 120 degrees. FIG. 5 is an enlarged detailed view of the transfer rod jig 2 and the glass substrate 10, but when the V-shaped angle is less than 90 degrees, the V groove surface is in contact with both main surfaces of the glass substrate for recording. May cause damage to the surface. On the other hand, if it is larger than 120 degrees, the holding becomes unstable, and it cannot be moved smoothly along the V-groove. If the groove has a V-shaped angle of 90 to 120 degrees, when the transfer rod is rotated, contact between the V-groove and both main surfaces of the glass substrate is prevented, and the glass substrate is stably and smoothly V-shaped. It can be moved along the groove.

Further, the surface roughness Ra of the surface of the transfer rod jig of the present invention is preferably 1.0 μm or less. If the surface roughness Ra is larger than 1.0 μm, there is a risk of scratching the end surface of the glass substrate when the glass substrate is moved along the V-groove, and it is dropped when used as an information recording medium (drive). It may be the starting point of impact cracking.

Moreover, it is preferable that the surface friction coefficient of the transfer rod jig of the present invention is 0.2 or less. If the coefficient of friction is greater than 0.2, the glass substrate cannot be moved smoothly along the V-groove, and dust generation contamination may occur due to contact between the V-groove and the glass substrate end surface.

The present invention provides a method for manufacturing a glass substrate for a magnetic information recording medium including a transfer step using a transfer rod jig having the above-described configuration. There is no need to transfer the sheets by mechanical transport. Insert a transfer rod jig that has a unique groove in the hole of the glass substrate arranged in each row, and use the glass substrate as the transfer rod jig. The glass substrates of a desired number of groups can be separated by rotating while holding them and raising the peripheral surface provided with grooves at the same pitch as that of the storage case after transfer. Therefore, if such operations are performed sequentially, the glass substrate transfer time between the steps can be drastically reduced, and the number of movements of the glass substrate can be further reduced. As a result, recontamination can be prevented, and as a result, there is little dust generation contamination. As a result, even if it is mounted on a hard disk with a small head flying height, there is a remarkable effect that head crash does not occur.

Hereafter, each process of the manufacturing method of the glass substrate for magnetic information recording media of this invention is explained in full detail. As described above, the transfer rod jig of the present invention can be used between any steps.

<Glass melting process>
First, a glass material is melted as a glass melting step. As a material of the glass substrate, for example, soda lime glass mainly composed of SiO ₂ , Na ₂ O, CaO; mainly composed of SiO ₂ , Al ₂ O ₃ , R ₂ O (R = K, Na, Li) Aluminosilicate glass; borosilicate glass; Li ₂ O—SiO ₂ glass; Li ₂ O—Al ₂ O ₃ —SiO ₂ glass; R′O—Al ₂ O ₃ —SiO ₂ glass (R ′ = Mg) , Ca, Sr, Ba) and the like can be used. Among these, aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.

<Molding process>
Next, as a molding step, molten glass is poured into a lower mold and press-molded with an upper mold to obtain a disk-shaped glass substrate. Note that the disk-shaped glass substrate may be manufactured by cutting a sheet glass formed by, for example, a downdraw method or a float method with a grinding wheel, without using press molding.

There is no limitation on the size of the glass substrate obtained in this molding process. For example, the outer diameter r1 is 2.5 inches (about 64 mm), 1.8 inches (about 46 mm), 1 inch (about 25 mm), 0.8 It is processed into a disk-shaped glass substrate having a thickness of 2 mm, 1 mm, 0.63 mm or the like with an inch (about 20 mm) or the like. Further, when the outer diameter r1 is 2.5 inches (about 64 mm), the inner diameter r2 is processed to 0.8 inches (about 20 mm) or the like. FIG. 6 is a top view showing a glass substrate for magnetic information recording medium manufactured by the method for manufacturing a glass substrate for magnetic information recording medium according to the present embodiment.

<Heat treatment process>
This heat treatment process is a process in which a glass substrate for information recording medium is sandwiched between setter jigs and heated in a heat treatment furnace. A press glass substrate or a cut glass substrate is alternately laminated with a heat-resistant member setter, and a high temperature electric furnace step. Can be passed to promote the warpage of the substrate and glass crystallization.

Especially in the process of glass melting and molding by pressing, the glass cooling temperature is not uniform, and stress distortion occurs inside the glass. Due to this stress strain, if lapping or polishing is performed without performing a heat treatment step, minute cracks are generated according to the strain. Abrasives or foreign substances enter the cracks, and even if high-precision polishing is repeated, convex portions are generated, resulting in defective products. This stress strain inside the glass can be released by heat treatment immediately after the disk processing step, and even if lapping or polishing is performed thereafter, no cracks are generated and the occurrence of defective products can be reduced.

The temperature of the heat treatment step is preferably 20 to 50 ° C. lower than the glass transition temperature (Tg). If the temperature is lower than the above range, the internal stress of the glass is not sufficiently released, and microcracks are generated and foreign matter is buried. On the other hand, if the temperature is higher than the above range, it becomes close to the glass transition temperature, and unevenness on the surface tends to occur. The holding time at the heat treatment temperature is preferably 20 to 120 minutes.

Also, if the cooling speed is high (rapid cooling), another warp is generated, so it is preferable that the cooling speed is low.

As the material of the setter member, stainless steel (austenite or martensite), casting (FC or FCD), heat resistant alloy (Co or Ni), ceramic (SiC, SiCN ₃ ), or the like can be used. . In addition, the surface of the pressing member can be subjected to a treatment such as CR plating or Ni—P electroless plating which is hard and difficult to oxidize. As for the shape of the pressing surface, it is desirable that the upper and lower surfaces are flat and the upper and lower surfaces are parallel to each other. Since the shape of the setter surface changes depending on the temperature, it is determined in consideration of the use temperature, the expansion characteristics of the mold material, and the like so as to obtain a desired shape when the main surface of the glass substrate is pressed.

<First wrapping process>
The lapping process is a process for processing the glass substrate into a predetermined plate thickness. Specifically, the process etc. which grind | polish (lapping) the both surfaces of a glass substrate are mentioned. By processing in this way, the parallelism, flatness and thickness of the glass substrate can be adjusted. Further, this lapping step may be performed once or twice or more. For example, when it is performed twice, the parallelism, flatness and thickness of the glass substrate are preliminarily adjusted in the first lapping step (first lapping step), and the glass substrate is determined in the second lapping step (second lapping step). It is possible to finely adjust the parallelism, flatness and thickness of the film.

More specifically, examples of the first lapping step include a step of making the entire surface of the glass substrate have a substantially uniform surface roughness. At that time, for example, when the arithmetic average roughness Ra of the glass substrate is measured at a plurality of positions, the difference between the minimum value and the maximum value of Ra obtained is preferably about 0.01 to 0.4 μm.

<Coring process>
Next, in the coring process, a hole is made in the center of the glass substrate after the first lapping process. The hole is obtained by grinding with a core drill or the like provided with a diamond grindstone or the like in the cutter portion.

<Outer and inner diameter machining process>
Next, as the inner / outer diameter processing step, the inner and outer diameters are processed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with a grinding wheel such as a drum-shaped diamond.

<Second wrapping process>
The second lapping step may include a process of grinding the main surface of the roughened glass substrate using a fixed abrasive polishing pad. In this second wrapping step, for example, a roughened glass substrate is set in a wrapping apparatus, and a three-dimensional fixed abrasive with a surface pattern such as diamond tile is used. The surface can be wrapped.

When the second lapping process is performed, the polishing performed in the rough polishing process described later can be performed efficiently. In addition, the surface roughness Ra of the glass substrate used in the polishing process performed by the second lapping process is preferably 0.10 μm or less, and more preferably 0.05 μm or less.

<End polishing process>
The end surface polishing step is a step of polishing the outer peripheral surface and the inner peripheral surface of the glass substrate after the second lapping step using an end surface polishing machine.

<First polishing step (rough polishing step)>
The first polishing (rough polishing step) is a step of rough polishing the surface of the glass substrate that has been subjected to the lapping step. This rough polishing is intended to remove scratches and distortions remaining in the lapping step described above, and is performed using the following polishing method.

The surface to be polished in the rough polishing step is a main surface and / or an end surface. The main surface is a surface parallel to the surface direction of the glass substrate. The end surface is a surface composed of an inner peripheral end surface and an outer peripheral end surface. Moreover, an inner peripheral end surface is a surface which has an inclination with respect to the surface of the inner peripheral side perpendicular to the surface direction of the glass substrate and the surface direction of the glass substrate. In addition, the outer peripheral end surface is a surface on the outer peripheral side that is perpendicular to the surface direction of the glass substrate and a surface that is inclined with respect to the surface direction of the glass substrate.

The polishing apparatus used in the rough polishing step is not particularly limited as long as it is a polishing apparatus used for manufacturing a glass substrate. Specifically, there is a polishing apparatus 1 as shown in FIG. FIG. 7 is a schematic cross-sectional view showing an example of the polishing apparatus 1 used in the rough polishing process and the precision polishing process in the method for manufacturing a glass substrate for a magnetic information recording medium according to this embodiment.

7 is an apparatus capable of simultaneous grinding on both sides. The polishing apparatus 11 includes an apparatus main body 11a and a polishing liquid supply unit 11b that supplies a polishing liquid to the apparatus main body 11a.

The apparatus main body 11a includes a disk-shaped upper surface plate 12 and a disk-shaped lower surface plate 13, and they are arranged at intervals in the vertical direction so that they are parallel to each other. Then, the disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13 rotate in directions opposite to each other.

A polishing pad 15 for polishing both the front and back surfaces of the glass substrate 10 is attached to each of the opposing surfaces of the disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13. The polishing pad 15 used in the rough polishing step is not particularly limited as long as it is a polishing pad used in the rough polishing step. Specifically, for example, a hard polishing pad made of polyurethane or the like can be used.

Further, a plurality of rotatable carriers 14 are provided between the disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13. The carrier 14 is provided with a plurality of substrate holding holes 51, and the glass substrate 10 can be fitted into the substrate holding holes 51. For example, the carrier 14 may have 100 substrate holding holes 51 so that 100 glass substrates 10 can be fitted and arranged. Then, 100 glass substrates 10 can be processed by one process (1 batch).

The carrier 14 sandwiched between the

surface plates

12 and 13 via the polishing pad holds the plurality of glass substrates 10 and rotates in the same direction as the lower surface plate 13 with respect to the center of rotation of the

surface plates

12 and 13 while rotating. Revolve to. The disk-shaped upper surface plate 12 and the disk-shaped lower surface plate 13 can be operated by separate driving. In the polishing apparatus 11 operating as described above, the polishing slurry 16 is supplied between the upper surface plate 12 and the glass substrate 10 and between the lower surface plate 13 and the glass substrate 10, thereby the glass substrate 10. Rough polishing can be performed.

The polishing slurry supply unit 11b includes a liquid storage unit 110 and a liquid recovery unit 120. The liquid reservoir 110 includes a liquid reservoir main body 110a and a liquid supply pipe 110b having a discharge port 110e extending from the liquid reservoir main body 110a to the apparatus main body 11a. The liquid recovery part 120 was extended to the liquid recovery part main body 120a, the liquid recovery pipe 120b extended from the liquid recovery part main body 120a to the apparatus main body part 11a, and the polishing slurry supply part 11b from the liquid recovery part main body 120a. And a liquid return pipe 120c.

Then, the polishing slurry 16 put in the liquid storage unit main body 110a is supplied from the discharge port 110e of the liquid supply pipe 110b to the apparatus main body part 11a, and from the apparatus main body part 11a via the liquid recovery pipe 120b, the liquid recovery part main body 120a. To be recovered. The recovered polishing slurry 16 is returned to the liquid storage part 110 via the liquid return pipe 120c and can be supplied again to the apparatus main body part 11a.

The polishing slurry 16 used here is a liquid in which an abrasive is dispersed in water, that is, a slurry liquid. Examples of the abrasive include an abrasive containing cerium oxide. The average particle diameter of the cerium oxide abrasive is preferably about 0.4 to 1.6 μm.

Further, the polishing pad 15 used here is a foam of synthetic resin such as urethane or polyester containing a cerium oxide abrasive.

<Chemical strengthening process>
If the chemical strengthening process in the manufacturing method of this invention is a well-known method, it will not specifically limit. Specifically, for example, a step of immersing a glass substrate in a chemical strengthening treatment liquid and the like can be mentioned. By doing so, a chemical strengthening layer can be formed in the surface of a glass substrate, for example, 5 micrometer area | region from the glass substrate surface. And by forming a chemical strengthening layer, impact resistance, vibration resistance, heat resistance, etc. can be improved.

More specifically, in the chemical strengthening step, by immersing the glass substrate in a heated chemical strengthening treatment liquid, alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are potassium ions having a larger ionic radius. It is carried out by an ion exchange method for substituting with alkali metal ions. Due to the strain caused by the difference in ion radius, compressive stress is generated in the ion-exchanged region, and the surface of the glass substrate is strengthened.

In the present embodiment, it is considered that the reinforcing layer is suitably formed by this chemical strengthening step by using the glass composition having the above glass composition as the glass substrate that is a raw material of the glass substrate. Specifically, among the Li ₂ O, Na ₂ O, and K ₂ O, which are alkali components of the glass substrate, the content of Na ₂ O is large, and the sodium ions of this Na ₂ O are added to the chemical strengthening treatment liquid. It is thought that it is easily exchanged for contained potassium ions. Furthermore, since the polishing agent used in the polishing step before the chemical strengthening step, here the rough polishing step, is an abrasive having the above composition, the amount of alkaline earth metal adhering to the surface of the glass substrate The chemical strengthening is considered to be uniform. Therefore, a glass substrate excellent in impact resistance can be produced by performing a precision polishing step on a glass substrate that has been subjected to suitable chemical strengthening as in this embodiment.

The chemical strengthening treatment solution is not particularly limited as long as it is a chemical strengthening treatment solution used in the chemical strengthening step in the method for producing a glass substrate for a magnetic information recording medium. Specifically, for example, a melt containing potassium ions, a melt containing potassium ions and sodium ions, and the like can be given.

Examples of these melts include melts obtained by melting potassium nitrate, sodium nitrate, potassium carbonate, sodium carbonate, and the like. Among these, it is preferable to use a combination of a melt obtained by melting potassium nitrate and a melt obtained by melting sodium nitrate from the viewpoint of low melting point and preventing deformation of the glass substrate. At that time, a melt obtained by melting potassium nitrate and a melt obtained by melting sodium nitrate are preferably mixed in approximately the same amount.

<Second Polishing Process (Precision Polishing Process)>
The precision polishing process is a mirror polishing process that finishes a smooth mirror surface having a surface roughness (Rmax) of about 6 nm or less, for example, while maintaining the flat and smooth main surface obtained in the rough polishing process. The precision polishing step is performed, for example, by using a polishing apparatus similar to that used in the rough polishing step and replacing the polishing pad from a hard polishing pad to a soft polishing pad. The surface to be polished in the precision polishing step is the main surface, similar to the surface to be polished in the rough polishing step.

Further, as the abrasive used in the precision polishing process, an abrasive that causes less scratching even if the polishing performance is lower than that used in the rough polishing process is used. Specifically, for example, a polishing agent containing silica-based abrasive grains (colloidal silica) having a particle diameter lower than that of the polishing agent used in the rough polishing step. The average particle diameter of the silica-based abrasive is preferably about 20 nm. And the polishing slurry liquid containing the said abrasive | polishing agent is supplied to a glass substrate, a polishing pad and a glass substrate are slid relatively, and the surface of a glass substrate is mirror-polished.

<Washing process>
Next, scrub cleaning is performed as a cleaning process after the second polishing process. In particular, it is not limited to scrub cleaning, and any cleaning method that can clean the surface of the glass substrate after the polishing step may be used.

ガラス Ultrasonic detergent cleaning and drying treatment are performed on the glass substrate that has been scrubbed if necessary. In the drying process, the cleaning liquid remaining on the glass substrate surface is removed using IPA or the like, and the substrate surface is dried. For example, on the glass substrate after scrub cleaning, detergent cleaning is performed in two tanks and a water rinse cleaning process is performed in three tanks for 3 minutes each to remove the residue of the cleaning liquid. Next, an IPA (isopropyl alcohol) cleaning process is performed for 3 minutes to remove water on the substrate. Finally, an IPA (isopropyl alcohol) vapor drying step is performed for 3 minutes, and the liquid IPA adhering to the substrate is dried while being removed by the IPA vapor. The substrate drying process is not limited to this, and a method generally known as a glass substrate drying method such as spin drying or air knife drying may be used.

<Inspection process>
In the inspection process, inspections such as scratches, cracks and adhesion of foreign substances are performed.
Foreign matter and adhesion that cannot be visually determined are inspected using an optical surface analyzer (OSA6100, manufactured by KLA-TENCOL).

Glass substrates that are judged to be non-defective products in the inspection process are stored in a glass substrate storage case in a clean environment and vacuum-packed so that foreign materials do not adhere to the surface. Shipped.

<Film formation process>
FIG. 8 is a partial cross-sectional perspective view showing a magnetic disk as an example of a magnetic recording medium using the glass substrate for magnetic information recording medium manufactured by the method for manufacturing a glass substrate for magnetic information recording medium according to the present embodiment. is there. The magnetic disk D includes a magnetic film 102 formed on the main surface of a circular glass substrate 101 for a magnetic information recording medium. For the formation of the magnetic film 102, a known method is used. For example, a formation method (spin coating method) for forming a magnetic film 102 by spin-coating a thermosetting resin in which magnetic particles are dispersed on a glass substrate 101 for a magnetic information recording medium, or a glass substrate for a magnetic information recording medium Examples include a formation method (sputtering method) for forming the magnetic film 102 on the substrate 101 by sputtering, a formation method (electroless plating method) for forming the magnetic film 102 on the glass substrate 101 for magnetic information recording medium by electroless plating, and the like. It is done.

The thickness of the magnetic film 102 is about 0.3 to 1.2 μm in the case of the spin coating method, and about 0.04 to 0.08 μm in the case of the sputtering method, and is based on the electroless plating method. In some cases, the thickness is about 0.05 to 0.1 μm. From the viewpoint of thinning and densification, film formation by sputtering is preferable, and film formation by electroless plating is preferable.

The magnetic material used for the magnetic film 102 can be any known material and is not particularly limited. The magnetic material is preferably, for example, a Co-based alloy based on Co having high crystal anisotropy in order to obtain a high coercive force, and Ni or Cr added for the purpose of adjusting the residual magnetic flux density. More specifically, CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiPt, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, CoCrPtSiO, and the like whose main component is Co can be given.

The magnetic film 102 has a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa, etc.) divided by a nonmagnetic film (for example, Cr, CrMo, CrV, etc.) in order to reduce noise. May be. Magnetic material used for the magnetic layer 102, in addition to the magnetic material, ferrite or iron - may be a rare earth, also, Fe in a non-magnetic film made of _SiO 2, BN, etc., Co, FeCo, CoNiPt and the like A granular material having a structure in which the magnetic particles are dispersed may be used. In addition, for recording on the magnetic film 102, either an inner surface type or a vertical type recording format may be used.

Further, in order to improve the sliding of the magnetic head, the surface of the magnetic film 102 may be thinly coated with a lubricant. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.

Further, if necessary, an underlayer or a protective layer may be provided for the magnetic film 102. The underlayer in the magnetic disk D is appropriately selected according to the magnetic film 102. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni. For example, in the case of the magnetic film 102 containing Co as a main component, the material of the underlayer is preferably Cr alone or a Cr alloy from the viewpoint of improving magnetic characteristics.

Further, the underlayer is not limited to a single layer, and may have a multi-layer structure in which the same or different layers are stacked. Examples of such an underlayer having a multilayer structure include multilayer underlayers such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, and NiAl / CrV. Examples of the protective layer that prevents wear and corrosion of the magnetic film 102 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be continuously formed with the underlayer and the magnetic film 102 by an in-line sputtering apparatus. These protective layers may be a single layer, or may be a multi-layer structure composed of the same or different layers.

Note that another protective layer may be formed on the protective layer or instead of the protective layer. For example, instead of the protective layer, a SiO ₂ layer may be formed on the Cr layer. Such a SiO ₂ layer is formed by dispersing and applying colloidal silica fine particles in a tetraalkoxysilane diluted with an alcohol-based solvent on the Cr layer and further baking.

In such a magnetic recording medium based on the glass substrate 101 for magnetic information recording medium according to this embodiment, the glass substrate 101 for magnetic information recording medium is formed with the above-described composition. It can be done with high reliability.

In addition, although the case where the glass substrate 101 for magnetic information recording media in this embodiment was used for a magnetic recording medium was demonstrated above, it is not limited to this, The glass substrate for magnetic information recording media in this embodiment 101 can also be used for magneto-optical disks, optical disks, and the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

First, a general glass substrate used for manufacturing a glass substrate for information recording media is prepared, and each manufacturing process (glass melting process, forming process, heat treatment process, first lapping process, coring process, inner and outer diameters) A glass substrate obtained by a processing step, a second lapping step, an end surface polishing step, a first polishing step (rough polishing step), a chemical strengthening step, a second polishing step (precision polishing step), and a cleaning step) The sample was transferred with the transfer rod jig of Examples 1 to 7, and the media evaluation of the subsequent glass substrate was performed.

Example 1
As the transfer rod jig of Example 1, a transfer rod jig having a surface roughness Ra of 1.5 μm, a friction coefficient of 0.3, and a groove angle of 70 degrees was used.

(Example 2)
The transfer rod jig of Example 2 was used with a surface roughness Ra of 1.5 μm, a friction coefficient of 0.3, and a groove angle of 100 degrees.

(Example 3)
The transfer rod jig of Example 3 was used with a surface roughness Ra of 1.5 μm, a friction coefficient of 0.3, and a groove angle of 130 degrees.

Example 4
As the transfer rod jig of Example 4, a transfer rod jig having a surface roughness Ra of 1.0 μm, a friction coefficient of 0.3, and a groove angle of 100 degrees was used.

(Example 5)
As the transfer rod jig of Example 5, a transfer rod jig having a surface roughness Ra of 0.5 μm, a friction coefficient of 0.3, and a groove angle of 100 degrees was used.

(Example 6)
The transfer rod jig of Example 6 was used with a surface roughness Ra of 1.0 μm, a friction coefficient of 0.2, and a groove angle of 100 degrees.

(Example 7)
The transfer rod jig of Example 7 was used with a surface roughness Ra of 1.0 μm, a friction coefficient of 0.1, and a groove angle of 100 degrees.

(Media evaluation of read / write errors)
Next, Table 1 shows the results of the media evaluation of the read / write error in the magnetic recording medium manufactured by transferring with the transfer rod jig of Examples 1 to 7. Table 1 shows the test evaluation of the read / write error in the recording medium. (N = 1000 measurement) is shown in Table 2.

From the evaluation criteria in Table 2 and the results in Table 1, it is clear that a glass substrate for a magnetic information recording medium with few read / write errors can be obtained by transfer using the transfer rod jig of the present invention. (Examples 1 to 7).

Among these, in particular, in Example 2 in which the angle of the V-shaped groove provided on the transfer rod jig was 100 degrees, compared to Examples 1 and 3 in which the angle deviated from 90 to 120 degrees was provided. Write errors were few, and the media evaluation was high.

Further, in Example 5 in which the surface roughness Ra of the transfer rod jig was 0.5 μm, the media evaluation was very high, and gradually became rougher as in Example 4 of 1.0 μm and Example 2 of 1.5 μm. Then the media evaluation was low. Accordingly, it has been clarified that the surface roughness Ra of the transfer rod jig is preferably 1.0 μm or less, although it is in a range where there is no problem in exhibiting even if it is larger than 1.0 μm.

Subsequently, in Example 7 where the friction coefficient of the transfer rod jig was 0.1, evaluation of the media was much higher than in Examples 6 and 4 where the friction coefficient was 0.2. It became very expensive. In other words, if the above evaluation is taken into account, the groove angle is 90 to 120 degrees, the surface roughness Ra of the transfer rod jig is 1.0 μm or less, and the coefficient of friction is 0.2 or less. It has been clarified that the glass substrate for magnetic information recording medium after the transfer has very few read / write errors.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

The method for manufacturing a glass substrate for magnetic information recording medium according to the present invention is the method for manufacturing a glass substrate for magnetic information recording medium, comprising the transfer step of transferring the glass substrate using a transfer rod jig. A plurality of points arranged side by side on the first line extending in the longitudinal direction of the jig and a plurality of points arranged side by side on a second line different from the first line on the peripheral surface of the jig Are formed on the circumferential surface of the jig so as to be connected one-to-one in order from one end side in the longitudinal direction of the jig, and are arranged in parallel on a first line extending in the longitudinal direction of the jig A transfer rod jig having a different first pitch between the plurality of points and a second pitch between the plurality of points arranged in parallel on the second line is used.

According to such a configuration, since a plurality of glass substrates can be transferred simultaneously before and after the process, the glass for a magnetic information recording medium having a high degree of cleaning with less contamination due to environmental re-attachment or the like. A method for manufacturing a substrate can be provided. Further, it is possible to provide a glass substrate for a magnetic information recording medium that does not cause head crash even when mounted on a hard disk having a very small head flying height.

Further, an interval at which the plurality of glass substrates are arranged in the step before the transfer step corresponds to the first pitch, and the plurality of glass substrates is arranged in the step after the transfer step. It is preferable that the intervals respectively correspond to the second pitch. With such a configuration, it is possible to easily transfer a disk between processes in a short time, and it is possible to prevent the occurrence of surface defects or environmental recontamination due to contact between substrates. it can.

Further, on the peripheral surface of the transfer rod jig, a group consisting of a plurality of points different from the group consisting of a plurality of points arranged side by side on the second line is provided in the jig longitudinal direction, It is preferable that the distance in the jig longitudinal direction between the points closest to the other group in the group is larger than the second pitch. With such a configuration, even when the number of stored sheets before and after the transfer process is different, it is possible to easily transfer the disk between processes in a short time, and surface defects due to contact between the substrates And environmental re-contamination can be prevented.

Further, it is preferable that the cross-sectional shape of the groove on the peripheral surface of the transfer rod jig is a V shape of 90 to 120 degrees. With such a configuration, when the transfer rod is rotated, it is possible to prevent the V-groove and the glass substrate from contacting the main surfaces, and to move the glass substrate along the V-groove stably and smoothly. It becomes.

The surface roughness Ra of the surface of the transfer rod jig is preferably 1.0 μm or less. If it is such a structure, when moving a glass substrate along V groove | channel, the crack generation | occurrence | production to a glass substrate end surface can be prevented.

Moreover, it is preferable that the friction coefficient of the surface of the transfer rod jig is 0.2 or less. With such a configuration, the glass substrate can be moved smoothly along the V-groove, and dust generation contamination generated from contact between the V-groove and the glass substrate end surface can be prevented.

The glass substrate for magnetic information recording medium according to the present invention is produced by using the method for producing a glass substrate for magnetic information recording medium.

This application is based on Japanese Patent Application No. 2011-076212 filed on Mar. 30, 2011, the contents of which are included in the present application.

In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. It is interpreted that it is included in

According to the present invention, in the manufacturing process of the glass substrate, the transfer of the substrate between each process is easily performed in a short time, thereby preventing the occurrence of re-contamination caused by surface defects or environment due to contact between the substrates, As a result, it is possible to provide a method for manufacturing a glass substrate for a magnetic information recording medium that does not cause head crash even when mounted on a hard disk with a slight head flying height.

Claims

In the method of manufacturing a glass substrate for a magnetic information recording medium having a transfer step of transferring the glass substrate using a transfer rod jig,
On the peripheral surface of the transfer rod jig, a plurality of points arranged in parallel on the first line extending in the longitudinal direction of the jig and a second line different from the first line are arranged in parallel. A plurality of grooves formed on the peripheral surface of the jig so as to tie a plurality of points one-to-one in order from one end side in the longitudinal direction of the jig,
A first pitch between a plurality of points arranged in parallel on a first line extending in the longitudinal direction of the jig is different from a second pitch between a plurality of points arranged in parallel on the second line. A method of manufacturing a glass substrate for a magnetic information recording medium, wherein a transfer rod jig is used.
The interval at which the plurality of glass substrates are arranged in the step before the transfer step corresponds to the first pitch, and the interval at which the plurality of glass substrates are arranged in the step after the transfer step. The method for manufacturing a glass substrate for a magnetic information recording medium according to claim 1, wherein the glass substrate corresponds to each of the second pitches.
On the peripheral surface of the transfer rod jig, a group consisting of a plurality of points different from the group consisting of a plurality of points arranged side by side on the second line is provided in the jig longitudinal direction,
The glass substrate for a magnetic information recording medium according to claim 1 or 2, wherein a distance in the jig longitudinal direction between points closest to the other group in each group is larger than the second pitch. Manufacturing method.
The magnetic information recording medium according to any one of claims 1 to 3, wherein a cross-sectional shape of the groove on the peripheral surface of the transfer rod jig is a V-shape of 90 to 120 degrees. A method for producing a glass substrate.
5. The method for manufacturing a glass substrate for a magnetic information recording medium according to claim 1, wherein the surface roughness Ra of the surface of the transfer rod jig is 1.0 μm or less.
The method for producing a glass substrate for a magnetic information recording medium according to any one of claims 1 to 5, wherein a coefficient of friction of a surface of the transfer rod jig is 0.2 or less.
A glass substrate for a magnetic information recording medium produced by using the method for producing a glass substrate for a magnetic information recording medium according to any one of claims 1 to 6.