CN106881663A - The manufacture method of glass base plate for magnetic recording carrier - Google Patents

Abstract

A method of manufacturing a glass substrate for a magnetic recording medium capable of suppressing the occurrence of linear damage on a main surface in a step of polishing the main surface. This method of manufacturing a glass substrate for a magnetic recording medium includes a main surface grinding step of grinding the main surface of the glass substrate for a magnetic recording medium, and the main surface grinding step sequentially includes a first main surface grinding step in which In the surface grinding step, the grinding sheet is pressed against the main surface of the glass substrate for magnetic recording media, and while the polishing liquid is supplied, the glass substrate for magnetic recording medium and the grinding sheet are rotated to perform polishing on the main surface. Grinding; a first dynamic water cleaning step in which water is supplied instead of the grinding liquid, and the glass substrate for magnetic recording medium and the grinding sheet are rotated to clean; and the second main In the surface polishing step, in the second main surface polishing step, a polishing liquid is supplied instead of water, and the glass substrate for magnetic recording media and the polishing sheet are rotated to polish the main surface.

Description

Manufacturing method of glass substrate for magnetic recording medium

technical field

This invention relates to the manufacturing method of the glass substrate for magnetic recording media.

Background technique

As a substrate for a magnetic recording medium used in a magnetic disk recording device or the like, an aluminum alloy substrate is currently used. However, in recent years, glass substrates which are harder than aluminum alloy substrates and have excellent flatness and smoothness have become mainstream in response to demands for higher recording densities.

The glass substrate for a magnetic recording medium has a disk shape having a concentric opening in the center, and is manufactured by performing the process of processing into the above-mentioned shape, the process of grinding the main surface, the process of grinding the end surface, and the like.

Since the main surface of the substrate for magnetic recording media is the recording surface, various studies have been made on the process of polishing the main surface in order to obtain the main surface with desired characteristics.

Regarding the method of grinding the main surface of a glass substrate for magnetic recording media, for example, Patent Document 1 discloses a method for manufacturing a substrate for magnetic recording media, which includes grinding the surface of the substrate while supplying a slurry containing abrasive grains. substrate grinding process. Specifically, it discloses a method of manufacturing a glass substrate for magnetic recording media. The substrate polishing step includes supplying a slurry and polishing the substrate in a state where a potential having the same sign as the zeta potential of abrasive grains is applied to the surface of the substrate. A slurry polishing process for the surface of the substrate; and a cleaning and polishing process for cleaning and polishing the surface of the substrate by supplying a cleaning liquid instead of the slurry in a state where a potential is applied to the surface of the substrate. According to the manufacturing method of the glass substrate for magnetic recording media disclosed in patent document 1, the abrasive residue after grinding|polishing can be reduced.

However, in the method for manufacturing a glass substrate for magnetic recording media described in Patent Document 1, the substrate to be polished is limited to a substrate having conductivity at least on the surface, and as a glass substrate for magnetic recording media, it cannot be applied to the magnetic field that has become mainstream in recent years. Glass substrate for recording media.

For example, using a double-sided grinding device, the grinding sheet is pressed against the main surface of the glass substrate for magnetic recording media, and while the polishing liquid is supplied, the glass substrate for magnetic recording media and the grinding sheet are rotated, so that the glass for magnetic recording media can be polished. Process for the main surface of the substrate.

By grinding the main surface of the glass substrate for magnetic recording media as described above, the flatness, waviness, and surface roughness of the main surface of the glass substrate for magnetic recording media can be set to a desired range. The dielectric glass substrate is set to a desired plate thickness.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2006-53965

However, in the step of polishing the main surface of the glass substrate for magnetic recording media, linear damage may occur on the main surface. In recent years, higher recording densities of magnetic recording media have been demanded, and reduction in damage to the main surface, which is the recording surface, has been particularly demanded.

Therefore, in the step of polishing the main surface, it is required to suppress generation of linear damage on the main surface of the glass substrate for magnetic recording media.

Contents of the invention

Therefore, the present invention is made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a method of manufacturing a glass substrate for a magnetic recording medium capable of suppressing the generation of linear damage on the main surface in the process of polishing the main surface. .

In order to solve the above-mentioned technical problems, the manufacturing method of the glass substrate for magnetic recording medium of the present invention has the main surface grinding process that the main surface of the glass substrate for magnetic recording medium is ground, and the main surface grinding process includes in sequence: the first main surface In the grinding step, in the first main surface grinding step, the grinding sheet is pressed against the main surface of the glass substrate for magnetic recording medium, and the glass substrate for magnetic recording medium and the grinding sheet are rotated while supplying the polishing liquid. , to grind the main surface; the first dynamic water cleaning step, in the first dynamic water cleaning step, water is supplied to replace the grinding liquid, and the glass substrate for the magnetic recording medium and the grinding sheet are rotated and a second main surface grinding step, in which a grinding liquid is supplied instead of water, and the glass substrate for magnetic recording medium and the grinding sheet are rotated to grind the The main surface is ground.

According to the manufacturing method of the glass substrate for magnetic recording media of this invention, the manufacturing method of the glass substrate for magnetic recording media which can suppress generation|occurrence|production of linear damage in a main surface in the process of grinding|polishing a main surface can be provided.

Description of drawings

FIG. 1 is an explanatory diagram of a configuration example of a double-side polishing device.

FIG. 2 is a flowchart of a main surface polishing step according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing temporal changes in polishing pressure and rotation speed of a fixed plate in a main surface polishing step according to an embodiment of the present invention.

Fig. 4 is a flow chart of a main surface polishing step according to the embodiment of the present invention.

FIG. 5 is a schematic diagram showing temporal changes in the polishing pressure and the rotational speed of the fixed plate in the main surface polishing step according to the embodiment of the present invention.

FIG. 6 is a schematic diagram showing temporal changes in polishing pressure and rotation speed of a fixed plate in a main surface polishing step of Comparative Example 1. FIG.

7 is a graph showing the ratio of glass substrates for magnetic recording media having linear damage in Examples and Comparative Examples.

(Symbol Description)

16, 18 grinding disc

detailed description

Hereinafter, modes for implementing the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments, and various modifications and substitutions can be added to the following embodiments without departing from the scope of the present invention.

One structural example of the manufacturing method of the glass substrate for magnetic recording media of this embodiment is demonstrated.

The manufacturing method of the glass substrate for magnetic recording media of this embodiment has the main surface grinding|polishing process of grinding|polishing the main surface of the glass substrate for magnetic recording media.

Then, the main surface polishing process can have the following steps in order.

The first main surface polishing step: press the polishing sheet against the main surface of the glass substrate for magnetic recording media, and rotate the glass substrate for magnetic recording media and the polishing sheet while supplying the polishing liquid to polish the main surface.

The first dynamic water cleaning step: supplying water to replace the polishing solution, and rotating the glass substrate for magnetic recording media and the polishing sheet for cleaning.

The second main surface polishing step: supplying a polishing liquid to replace water, and rotating the glass substrate for magnetic recording media and the polishing sheet to polish the main surface.

The inventors of the present invention have intensively studied the cause of the linear damage generated in the main surface polishing step. As a result, it was found that due to the foreign matter mixed in the double-sided grinding device before starting the main surface grinding process, the grinding residue generated in the process of grinding the main surface, the agglomeration of the slurry of the grinding liquid, the magnetic recording medium was kept in the grinding process. The aforementioned damage was caused by foreign matter such as flying dust generated on the holder of the glass substrate (hereinafter also referred to as "glass substrate").

Therefore, the manufacturing method of the glass substrate for magnetic recording media of this embodiment can provide the dynamic water cleaning step which supplies water between two steps of polishing the main surface with a polishing liquid to replace the main surface grinding process. Grinding liquid, and make the grinding sheet and glass substrate rotate.

According to the above-mentioned main surface polishing step, after the first main surface polishing step of polishing the main surface with the polishing liquid, the first dynamic water washing step can reduce and remove foreign substances contained in the double-sided polishing device. Then, by performing the second main surface grinding step in an environment in which foreign matter in the double-sided grinding device is reduced and removed, new damage can be prevented, and even if linear damage occurs in the first main surface grinding process, It can also reduce and remove the above-mentioned damage. Therefore, in the main surface polishing step, it is possible to suppress the occurrence of linear damage on the main surface.

Each step will be described below.

(first main surface grinding step)

In the first main surface polishing step, the glass substrate for magnetic recording media whose main surface is polished is fixed to a double-sided polishing device, and the glass substrate and the polishing sheet are rotated while supplying the polishing liquid to polish the glass substrate for magnetic recording media. main surface.

Here, a configuration example of a double-side polishing device will be described using FIG. 1 .

FIG. 1(A) shows a structural example of a holder used in the main surface polishing step, and FIG. 1(B) shows a schematic diagram of a double-side polishing device.

When grinding the main surface of a glass substrate, a plurality of glass substrates are set on a support (main surface grinding jig) 10 having a glass substrate holding hole 11 capable of holding a glass substrate shown in FIG. In addition, in the figure, the holder 10 provided with the circular glass substrate holding hole 11 is shown as an example, but it is not limited to the above-mentioned embodiment, and the glass substrate holding hole matching the shape of the polished glass substrate can also be formed. 11. For example, when polishing a glass substrate before shape forming, the holder 10 having the rectangular glass substrate holding hole 11 can be used.

The holder 10 provided with the glass substrate is fixed to the double-side polishing device 12 shown in FIG. 1(B), and the sun gear 13 and the pinion gear 14 are driven to rotate at a predetermined rotation ratio. Thereby, the carrier 10 is rotated, and the carrier 10 is moved so as to revolve around the sun gear 13 . In addition, the upper fixed plate 15 and the lower fixed plate 17 can be rotated, whereby the polishing sheets 16 and 18 fixed to the upper fixed plate 15 and the lower fixed plate 17 are also rotated.

At this time, the two main surfaces of the glass substrate held by the holder 10 are clamped and pressed between the upper fixed disk 15 and the lower fixed disk 17, which are respectively equipped with grinding sheets 16, 18 on the surfaces opposite to the glass substrate. Both main surfaces of the substrate are ground simultaneously. In addition, when polishing, a polishing liquid can be supplied between the polishing surface and the glass substrate.

The glass substrate used for the manufacturing method of the glass substrate for magnetic recording media of this embodiment is not specifically limited if it is a glass substrate for magnetic recording media. For example, the type of glass may be amorphous glass, crystallized glass, or strengthened glass having a strengthening layer on the surface of the glass substrate. In addition, the glass substrate used in the main surface grinding step may be a disc-shaped glass substrate having a circular opening in the center, or may be a quadrangular glass substrate before processing into the disc shape, that is, before performing the shape forming step. glass substrate. As the glass substrate, for example, a glass substrate formed by a float method, a fusion method, a down-draw method, or a press molding method can be used.

The specific grinding conditions in the first main surface grinding step are not particularly limited, and the grinding time, the rotating speed of the upper fixed plate and the lower fixed plate of the double-sided grinding device, etc. can be arbitrarily selected according to the amount of grinding required for the glass substrate to be ground. . Grinding conditions vary depending on the size of the plate, but for example, the grinding time can be set to 10 minutes to 60 minutes, and the rotation speed of the upper and lower plate can be set to 0.1 rpm to 100 rpm.

The grinding pressure can also be selected arbitrarily, but in order to perform grinding of the main surface with high productivity, the grinding pressure is preferably 80 g/cm ² or more. However, when the grinding pressure is too high, the glass substrate may be damaged, etc. Therefore, the grinding pressure is preferably 140 g/cm ² or less. In addition, the polishing pressure refers to the pressure of pressing the glass substrate by the upper fixed plate 15 and the lower fixed plate 17 in the double-sided grinding device shown in FIG. The following description is also the same.

In addition, the polishing liquid used in the first main surface polishing step is not particularly limited, and can be selected according to the amount of polishing required for the glass substrate to be polished. For example, a polishing liquid containing cerium oxide abrasive grains, colloidal silica, and the like can be used as the polishing liquid. However, according to the main surface polishing step described herein, the occurrence of linear damage can be suppressed. Therefore, when there are a plurality of steps for polishing the main surface, it is preferable that the main surface polishing step is a step of polishing the main surface. The final process in. Therefore, colloidal silica is particularly preferably used as the polishing liquid.

(first dynamic water cleaning step)

In the first dynamic water cleaning step, water is supplied to replace the polishing solution, and the glass substrate and the polishing sheet are rotated for cleaning.

As described above, by performing the first dynamic water cleaning step, foreign matter generated in the first main surface polishing step and foreign matter mixed before the first main surface polishing step in the double-sided polishing device can be reduced and removed. Then, by performing the second main surface polishing step described later in an environment in which foreign matter is reduced and removed, even if linear damage occurs on the main surface of the glass substrate in the first main surface polishing step, it can be reduced and removed. above damage.

The water used in the first dynamic water cleaning step is not particularly limited, but as described above, it is water supplied to remove foreign matter in the double-sided polishing device, so it is desirable to use water containing less foreign matter. , so that no new foreign matter is mixed. For example, primary purified water filtered through a reverse osmosis membrane can be preferably used, and primary purified water obtained by reducing and removing foreign matter through a filter is more preferably used.

In the first dynamic water cleaning step, the flow rate (supply speed) of water is not particularly limited, but the first dynamic water cleaning step is to make water flow through the double-sided grinding device to reduce and remove foreign matter in the double-sided grinding device Steps, therefore, supply water at a sufficient flow rate, which is more desirable. Therefore, regarding the flow rate of water, the flow rate per unit area of the workpiece is preferably 1.5 ml/cm ² ·min or more, and more preferably 2.0 ml/cm ² ·min or more. However, even if the flow rate of water is excessively increased, the effect of removing foreign matter is hardly improved. Therefore, the flow rate per unit area of the workpiece is preferably 5.0ml/cm ² ·min or less, which is 4.0ml/cm ² ·min The following is more ideal.

The grinding pressure in the first dynamic water cleaning step is not particularly limited, but the friction force can be increased higher than that during grinding by introducing water, so when the grinding pressure is too high, the load on the double-sided grinding device may increase . However, when the grinding pressure is too low, the rotation of the fixed plate of the double-sided grinding device may become unstable. Therefore, the grinding pressure is preferably not less than 20 g/ ^cm2 and not more than 80 g/ ^cm2 , and more preferably not less than 30 g/cm2 and not more than 50 g/cm2.

In addition, although polishing is not performed in the first dynamic water cleaning step, the pressure for pressing the glass substrate by the upper and lower platens is generally called the polishing pressure, and thus will be described as the polishing pressure.

In addition, the rotation speed of the fixed plate in the first dynamic water cleaning step is not particularly limited, but since the frictional force is increased higher than that during grinding by introducing water, it is preferable to make the rotation speed higher than that during the first main surface grinding step. The speed is small. But because the first dynamic water cleaning step is to make water flow through the double-sided grinding device to reduce and remove the foreign matter in the double-sided grinding device, therefore, when the rotating speed is too small, it is necessary to make the water flow through the double-sided grinding device. time, this is not ideal.

Therefore, the rotational speed of the fixed plate in the first dynamic water cleaning step is preferably 20% to 60% of the rotational speed of the fixed plate in the first main surface grinding step, and more preferably 30% to 50% of. In addition, in the first main surface grinding step, if the rotation speed of the upper fixed disk is different from that of the lower fixed disk, it is more ideal that the rotation speeds of the corresponding fixed disks are within the above range.

The time for implementing the first dynamic water cleaning step is not particularly limited, and it is ideal to select the time for implementing the first dynamic water cleaning step so that water can flow through the double-sided grinding device to remove foreign matter. For example, it is ideal to select the time for implementing the first dynamic water cleaning step so that the upper fixed plate rotates at least 0.5 times during the first dynamic water cleaning step. In particular, it is more ideal to select the time for implementing the first dynamic water cleaning step so that at least the upper fixed plate can rotate more than one revolution during the first dynamic water cleaning step.

In addition, here, the time for performing the first dynamic water cleaning step is described based on the rotation speed of the upper fixed plate, but the reason is that water is usually supplied into the double-sided polishing device from the supply port provided on the upper fixed plate.

(Second main surface grinding step)

In the second main surface polishing step, a polishing liquid may be supplied instead of water, and the glass substrate and the polishing sheet may be rotated to polish the main surface of the glass substrate.

The specific polishing conditions in the second main surface polishing step are not particularly limited, and the polishing time, the rotational speed of the double-sided polishing apparatus, etc. can be arbitrarily selected according to the amount of polishing required for the glass substrate to be polished.

However, in the second main surface grinding step, the main surface is polished in an environment in which the foreign matter in the double-sided polishing device is reduced and removed by the first dynamic water cleaning step, even if the main surface of the glass substrate is damaged by the first main surface grinding step. Even when linear damage has occurred on the surface, the above damage can be reduced and removed. Therefore, it is desirable to ensure the polishing time to such an extent that the linear damage generated in the first main surface polishing step can be reduced and removed. For example, the time for the second main surface polishing step, that is, the polishing time is preferably 30 seconds or more. , more than 60 seconds is more ideal.

On the other hand, when the time of the second main surface polishing step (polishing time) is too long, foreign matter may regenerate and linear damage may regenerate. Therefore, the grinding time is preferably eight minutes or less, more preferably five minutes or less, and still more preferably three minutes or less.

The grinding pressure can also be selected arbitrarily, but in order to perform grinding of the main surface with high productivity, the grinding pressure is preferably 80 g/cm ² or more. However, if the grinding pressure is too high, the glass substrate may be damaged, etc. Therefore, the grinding pressure is preferably 140 g/cm ² or more.

In addition, the polishing liquid used in the second main surface polishing step is not particularly limited, and can be selected according to the amount of polishing required for the glass substrate to be polished. For example, a polishing liquid containing cerium oxide abrasive grains, colloidal silica, and the like can be used as the polishing liquid. However, according to the main surface polishing step described herein, the occurrence of linear damage can be suppressed. Therefore, when there are a plurality of steps for polishing the main surface, it is preferable that the main surface polishing step is one of the steps for polishing the main surface. the final process. Therefore, colloidal silica is particularly preferably used as the polishing liquid.

The above-described main surface polishing process can be performed sequentially as shown in the flow chart of FIG. In addition, it is preferable to carry out the above-mentioned three steps continuously, that is, without opening the double-sided polishing device, in order to prevent foreign matter from being mixed between the steps.

In addition, after the second main surface grinding step is completed, the static water cleaning step S4 of supplying water to the double-sided grinding device in a state where the rotation of the glass substrate and the grinding sheet is stopped is performed to reduce and remove the impurities in the double-sided grinding device. of grinding liquid. After the static water washing step S4, the ground glass substrate can be taken out from the double-side grinding device.

The preferred range of the flow rate of water that can be preferably used in the static water washing step is the same as that in the first dynamic water washing step, and therefore description thereof will be omitted here.

The time for performing the static water washing step is not particularly limited, but is preferably not less than 10 seconds and not more than 120 seconds, for example.

FIG. 3 schematically shows changes in the polishing pressure, the rotation speed of the fixed plate, and the supply of polishing liquid and water in the main surface polishing step described so far. In FIG. 3, the straight line represents the grinding pressure, and the dotted line represents the rotational speed of the fixed plate. In addition, the hatched block arrows shown in the lower part of the graph indicate the period during which the polishing liquid is supplied, and the hollow block arrows indicate the period during which water is supplied.

As shown in FIG. 3 , the first main surface polishing step ( S1 ) can be carried out by supplying a polishing liquid and increasing the polishing pressure and the rotational speed of the fixed plate immediately after the main surface polishing step starts. Then, after the first main surface grinding step (S1), the first dynamic water cleaning step (S2) can be implemented by supplying water instead of the grinding liquid, or reducing the grinding pressure and the rotation speed of the fixed plate. Next, the polishing liquid is supplied instead of water, and the polishing pressure and the rotational speed of the fixed plate are increased, so that the second main surface polishing step ( S3 ) can be performed. After the second main surface polishing step is completed, water is supplied instead of the polishing liquid, and the rotation of the fixed plate is stopped, so that the static water washing step (S4) can be performed.

In addition, in the same manner as the first dynamic water cleaning step, the glass substrate and the polishing sheet may be cleaned by supplying water and rotating it, instead of supplying water into the double-sided polishing device while the rotation of the glass substrate and the polishing sheet is stopped. static water washing step S4.

That is, the main surface grinding process may also have a second dynamic water washing step instead of the static water washing step S4. In this second dynamic water washing step, after the second main surface grinding step is completed, water is supplied instead of the grinding liquid, and the The magnetic recording medium is cleaned by rotating the glass substrate and the abrasive sheet. In this case, as shown in FIG. 4 , after the second main surface grinding step S3 , the second dynamic water washing step S5 can be implemented.

In this manner, by supplying water and rotating the glass substrate and the polishing sheet, rinse water can flow through the double-sided polishing apparatus. Therefore, it is possible to reduce and remove especially the abrasive particles adhering to the polishing liquid in the double-side polishing device, and it is particularly possible to suppress damage to the main surface of the glass substrate when the main surface of the glass substrate is subsequently polished by the same device.

The water that can be preferably used in the second dynamic water cleaning step, the preferred ranges of its flow rate, grinding pressure, and rotational speed are the same as those in the first dynamic water cleaning step, and therefore, description thereof is omitted here.

The time for implementing the second dynamic water cleaning step is not particularly limited, and it is ideal to select the time for implementing the second dynamic water cleaning step so that water can flow through the double-sided grinding device to remove foreign matter. For example, it is ideal to select the time for implementing the second dynamic water cleaning step so that the upper fixed plate rotates at least 0.2 times during the second dynamic water cleaning step. Particularly more ideally, the time for implementing the second dynamic water cleaning step is selected so that the upper fixed plate rotates at least 0.5 times during the second dynamic water cleaning step.

The upper limit of the time for implementing the second dynamic water cleaning step is not particularly limited, but from the viewpoint of not reproducing foreign matter, the time for implementing the second dynamic water cleaning step is selected so that the upper limit during the second dynamic water cleaning step The rotational speed of the disk is less than three revolutions, which is ideal.

It is also possible to open the double-sided grinding device to take out the glass substrate after the second dynamic water cleaning step is finished, but the above-mentioned static water cleaning step S4 can also be further implemented as shown in Figure 4. In this static water cleaning step S4, after stopping Water was continuously supplied while the glass substrate and the polishing sheet were rotating.

After the second dynamic water cleaning step is completed, the static water cleaning step is also implemented, so as to further reduce the abrasive particles remaining in the double-sided grinding device, so it is more ideal.

As mentioned above, by performing the second dynamic water cleaning step, the abrasive grains in the double-sided polishing device can be reduced and removed, but the removal may not be sufficiently performed only by the second dynamic water cleaning step. In addition, if the second dynamic water cleaning step is carried out for a long time, there is a risk of new foreign matter being generated. Therefore, it is more desirable to implement a static water cleaning step in which water is continuously supplied while the rotation of the glass substrate and the polishing sheet is stopped. of.

The water that can be preferably used in the static water washing step, the supply amount thereof, and the like have already been described, and therefore, description thereof will be omitted here.

Fig. 5 schematically shows the grinding pressure in the main surface grinding process, the rotating speed of the fixed disk and the grinding liquid, Water supply changes. Same as in Fig. 3, the straight line represents the grinding pressure, and the dotted line represents the rotation speed of the fixed plate. In addition, the hatched block arrows shown in the lower part of the graph indicate the period during which the polishing liquid is supplied, and the hollow block arrows indicate the period during which water is supplied.

It is the same as the case of FIG. 3 up to the 2nd main surface grinding|polishing process (S3). Then, after the second main surface grinding step is completed, water is supplied to replace the grinding liquid, and the grinding pressure and the rotation speed of the fixed plate are reduced, so that the second dynamic water cleaning step ( S5 ) can be implemented. Next, the rotation of the fixed plate is stopped to implement the static water washing step (S4).

So far, the main surface polishing step has been described, but the timing at which the above main surface polishing step is performed is not particularly limited, and can be performed at any desired timing.

In the manufacturing method of the glass substrate for magnetic recording media, the process of grinding|polishing the main surface of the glass substrate for magnetic recording media can be comprised severally. In the case where there are a plurality of steps of polishing the main surface of the glass substrate for magnetic recording media, the main surface described so far is implemented in the last step of the steps of polishing the main surface of the glass substrate for magnetic recording media. A grinding process is ideal.

In the case of having a plurality of steps of polishing the main surface of the glass substrate, usually, polishing is performed with a polishing liquid containing relatively large abrasive grains in order to secure a sufficient amount of polishing in the initial step. Then, in a later step, precision polishing is performed so that the main surface of the glass substrate has a desired shape.

Therefore, it is particularly required to remove damage from the main surface of the glass substrate in a later step. In addition, according to the main surface polishing step described so far, linear damage caused by foreign matter and the like can be reduced and removed, so it is preferably applied to a later step in which removal of damage is particularly required, and is especially suitable for the final step.

In particular, in recent years, along with the need to increase the recording density of magnetic recording media, it is required to reduce and remove even shallow damage with a depth of about 1 nm on the main surface as the recording surface. In addition, in the main surface grinding process described so far, the above-mentioned relatively shallow damage can be reduced and removed. Therefore, it is preferably applied to the last process of a plurality of processes for grinding the main surface of the glass substrate. , can also be removed.

The main surface grinding process of the glass substrate for magnetic recording media of this embodiment has been described so far, but the glass substrate for magnetic recording media of this embodiment may have various processes other than the main surface grinding process.

The manufacturing method of the glass substrate for magnetic recording media of this embodiment can include the following process 1-5, for example.

(Step 1) A shape forming step of processing a glass substrate into a disk-shaped glass substrate having a hole in the center from a glass substrate.

(Process 2) The chamfering process of chamfering the end surface part of the inner periphery and outer periphery of a glass substrate.

(Process 3) An end surface grinding process of grinding|polishing the end surface (inner peripheral end surface and outer peripheral end surface) of a glass substrate.

(Process 4) The process of grinding|polishing the main surface of a glass substrate.

(Step 5) A washing and drying step of washing and drying the glass substrate.

The above steps do not need to be performed in the order described above, for example, the step of grinding the main surface may be performed before the shape forming step. In addition, each step is not limited to one time, and can be performed any number of times according to the specifications of the required glass substrate and the like. For example, the process of grinding the main surface can be performed after the shape forming process, and then the process of grinding the main surface can be performed again after the chamfering process and the end face grinding process.

Here, in the shape forming step of (Step 1), a glass substrate formed by a float method, a fusion method, a press molding method, a down-draw method, or a redraw method is processed into a disk-shaped glass substrate having a round hole in the center. . In addition, the glass-based substrate used may be amorphous glass, crystallized glass, or tempered glass having a strengthening layer on the surface of the glass substrate.

In the chamfering process of (process 2), it is possible to chamfer the inner circumference of the glass substrate and the end face portion of the outer circumference.

The end surface grinding process of (process 3) can grind the end surface (side surface part and chamfer part) of a glass substrate.

In the step of polishing the main surface of (step 4), the main surface of the glass substrate can be polished using, for example, a double-sided polishing apparatus shown in FIG. 1(B) .

In addition, when polishing the main surface of the glass substrate, it is not limited to the method of polishing using free abrasives such as polishing liquid as described so far, and it is also possible to polish using fixed abrasives. In the case of polishing using fixed abrasive grains, in the double-sided polishing apparatus 12 shown in FIG. 1(B), it is possible to replace the polishing sheets 16 and 18 with the fixed abrasive grain step.

In the case of carrying out the process of grinding the main surface multiple times, it is more desirable to implement the above-mentioned main surface grinding process at least once, and it is more desirable to implement the above-mentioned main surface grinding process in the last process of grinding the main surface. of.

The washing and drying step of (step 5) is a step of washing and drying the polished glass substrate. A specific cleaning method is not particularly limited. For example, cleaning can be performed by scrub cleaning using a cleaning agent, ultrasonic cleaning in a state of being immersed in a cleaning agent solution, ultrasonic cleaning in a state of being immersed in purified water, or the like. In addition, the drying method is not particularly limited, and, for example, it can be dried with isopropanol vapor.

In addition, cleaning of the glass substrate (cleaning between processes) and etching of the surface of the glass substrate (etching between processes) may be performed between each of the above-mentioned processes. In addition, when a high mechanical strength is required for the glass substrate, the surface layer of the glass substrate may be strengthened before, after, or between the polishing steps exemplified in steps 3 and 4. Layer strengthening process (such as chemical strengthening process).

Moreover, the process of forming a thin film, such as a magnetic layer, on the main surface is further performed on the glass substrate obtained by the manufacturing method including each process mentioned above, and it becomes a magnetic recording medium.

In the method for manufacturing a glass substrate for a magnetic recording medium according to the present embodiment described above, in the main surface grinding step, preferably in the last main surface grinding step, the first main surface grinding step and the second main surface grinding step with a first dynamic water wash step in between. In addition, it is possible to reduce and remove foreign substances generated in the double-sided polishing device in the first main surface grinding step by the first dynamic water cleaning step, and to reduce and remove foreign substances by the second main surface grinding step. Grinding of the main surface is carried out.

Therefore, in the main surface grinding process, generation|occurrence|production of linear damage on the main surface of the glass substrate for magnetic recording media can be suppressed.

[Example]

Although specific examples are illustrated below, the present invention is not limited to the above examples.

(Example 1)

The glass substrate for magnetic recording media was manufactured by the following procedure.

First, a disc-shaped glass substrate was processed from an aluminosilicate glass substrate mainly composed of _SiO2 formed by the float process to obtain a magnetic disk with a diameter of 65 mm and a concentric hole with a diameter of 20 mm. Glass substrate for recording media (shape shaping process).

Then, the inner periphery and the end face portion of the outer periphery of the glass substrate are chamfered (chamfering process).

Next, the upper and lower main surfaces of the glass substrate are ground using alumina abrasive grains (primary grinding process). In one grinding process, a double-sided grinding device (manufactured by Sotech Denshiki (company name: speedfam), product name: DSM-16B- 5PV-4MH) grinds (primary cutting) the upper and lower main surfaces of the glass substrate. After a grinding process, clean the glass substrate to remove the grinding liquid and other dirt.

Next, the peripheral side surface and the peripheral chamfer are polished using a polishing brush and cerium oxide abrasive grains to remove scratches on the peripheral side surface and the peripheral chamfer, and the peripheral end surface is polished to form a mirror surface. Then, the abrasive grains of the glass substrate after grinding|polishing the outer peripheral end surface are cleaned and removed (outer peripheral end surface grinding process).

Next, use a polishing brush and cerium oxide abrasive grains to polish the inner peripheral side and inner peripheral chamfer of the glass substrate, remove scratches on the inner peripheral side and inner peripheral chamfer, and polish the inner peripheral end surface to form a mirror surface Processing, cleaning and removal of abrasive grains (inner peripheral end face grinding process).

Next, using a fixed abrasive tool containing diamond particles with an average particle diameter of 4 μm and a grinding fluid containing a surfactant as a grinding tool, a double-sided grinding device (manufactured by Chuangji Denshiki (company name: speedfam), product name : DSM-16B-5PV-4MH) The upper and lower main surfaces are ground (secondary cutting) (secondary grinding process). After the secondary grinding process, the glass substrate is cleaned to remove grinding fluid and other dirt.

Then, by polishing the main surface of this glass substrate, the glass substrate for magnetic discs with an outer diameter of 65 m, an inner diameter of 20 mm, and a board thickness of 0.8 mm was produced.

In the main surface grinding step, grinding is first performed once. Specifically, a soft polyurethane abrasive sheet (leather abrasive sheet) and a grinding liquid containing cerium oxide abrasive grains were used as the abrasive tool, and a 16B type double-sided polishing device (Chuangji Electronics (company name: speedfam) was used. ) manufactured, product name: DSM-16B-5PV-4MH) The upper and lower main surfaces of the glass substrate were polished once. In addition, as a polishing liquid containing alumina abrasive grains, a polishing liquid composition mainly composed of alumina having an average particle diameter (hereinafter simply referred to as the average particle diameter) of about 1.0 μm was used. In addition, the main grinding pressure for one grinding is 120g/cm ² , the speed of the lower fixed plate is 30rpm, the rotational speed of the upper fixed plate is 10rpm in the opposite direction to that of the lower fixed plate, the revolution speed of the grinding support is 10rpm, and the self-rotation speed is 3rpm. Both the upper and lower main planes were polished to a total of 30 μm in the thickness direction. After one grinding session, the glass substrate was cleaned to remove cerium oxide. (one grinding process)

Next, the upper and lower main surfaces of the glass substrate are subjected to secondary polishing in the following procedure (secondary polishing process).

The secondary polishing process was carried out according to the flowchart shown in FIG. 2 . In addition, the polishing pressure of the double-sided polishing apparatus, the rotation speed of the fixed disk, and the supply of polishing liquid and water were changed as shown in FIG. 3 and implemented.

The secondary polishing of the main surface was performed by a 16B-type double-side polishing device 12 (manufactured by Sotech Denshiki (company name: speedfam), product name: DSM-16B-5PV-4MH) shown in FIG. 1 . The double-sided grinding device 12 includes: an upper fixed plate 15 on which grinding sheets 16 and 18 are installed on a surface opposite to the glass substrate; and a lower fixed plate 17 .

Next, the disk-shaped glass substrates after one lapping process were fixed to the holder 10, and the glass substrates were fixed to a double-sided lapping apparatus in batches of 100 to polish.

In the secondary polishing step of the main surface, first, the first main surface polishing step S1 is implemented.

In the first main surface grinding step, the glass substrate was pressed with the upper platen 15 and the lower platen 17 so that the grinding pressure was 100 g/cm ² , and the rotational speed of the upper platen 15 was 7 rpm and the rotational speed of the lower platen was 21 rpm. Driven and milled for thirty minutes. In addition, at this time, the sun gear 13 and the pinion gear 14 are driven to rotate, and the holder 10 is moved so as to revolve around the sun gear 13 while rotating on its own, thereby also rotating the glass substrate.

In addition, during polishing, a colloidal silica polishing liquid having an average particle diameter of about 20 nm was supplied as a polishing liquid between the polishing surface of the polishing sheet and the main surface of the glass substrate.

After the first main surface grinding step is finished, a first dynamic water cleaning step S2 is implemented.

The first dynamic water cleaning step was continuously performed for 30 seconds after the first main surface grinding step was completed without opening the double-side grinding device.

In the first dynamic water cleaning step, the grinding pressure of the grinder was changed to 40 g/cm ² , the rotation speed of the upper fixed plate was changed to 3 rpm, and the rotation speed of the lower fixed plate was changed to 9 rpm. In addition, primary purified water filtered through a filter is supplied instead of polishing liquid. The above-mentioned primary purified water was supplied so that the flow rate per workpiece area was 2.4 ml/cm ² ·min.

After the first dynamic water cleaning step is finished, the second main surface grinding step S3 is carried out.

The second main surface grinding step was carried out continuously for 5 minutes after the first dynamic water washing step was completed without opening the double-side grinding device.

The second main surface grinding step was carried out in the same manner as the first main surface grinding step except for the grinding time.

After the second main surface polishing step is completed, the rotation of the glass substrate and the surface plate is stopped, and the supply of the polishing liquid is also stopped. Next, the primary purified water filtered through the filter was supplied into the double-sided polishing device, and the static water washing step S4 was continuously performed for 40 seconds without opening the double-sided polishing device. In the static water washing step, the above-mentioned primary pure water was supplied so that the flow rate per unit area of the workpiece was 2.4 ml/cm ² ·min.

After the static water washing step, the double-side grinding device was opened, and the glass substrate for magnetic recording medium was taken out.

After the above-described secondary polishing step, scrub cleaning and ultrasonic cleaning in a state of immersion in purified water were performed, and drying with isopropanol vapor (washing and drying steps) was used for evaluation.

The evaluation method and evaluation results will be described below.

The presence or absence of linear damage formed on the surface of the glass substrate for magnetic recording media was evaluated using a light scattering method surface observation machine (company name: KLA Tencor company make, OSACandela7100). Moreover, as a result of calculating the ratio of the glass substrate for magnetic recording media which has linear damage, it was confirmed to be 2.1%.

In addition, when the number of particles adhering to the surface of the obtained glass substrate for magnetic recording media was evaluated using a light-scattering type surface observer, it was confirmed that the median number of OSA counts was 19. In addition, the smaller the numerical value of the OSA count, the smaller the number of attached particles.

(Example 2)

In Example 2, the secondary polishing process of the main surface was implemented according to the flowchart shown in FIG. 4 . In addition, the polishing pressure of the double-sided polishing apparatus, the rotation speed of the fixed disk, and the supply of polishing liquid and water were changed as shown in FIG. 5 and implemented.

That is, after the second main surface grinding step S3 and before the static water cleaning step S4, except for the point of implementing the second dynamic water cleaning step S5 and setting the time of the static water cleaning step to 30 seconds, all A glass substrate for a magnetic recording medium was produced in the same manner as in Example 1.

The second dynamic water cleaning step S5 was continuously implemented for 10 seconds after the second main surface grinding step was completed without turning on the double-side grinding device.

In the second dynamic water cleaning step, after the second main surface grinding step, the pressure of the grinder was changed to 40g/cm ² , in addition, the speed of the upper plate was changed to 3rpm, and the speed of the lower plate was changed to 9rpm. In addition, primary purified water filtered through a filter is supplied instead of polishing liquid. In the second dynamic water washing step S5, the above-mentioned primary pure water was supplied so that the flow rate per unit area of the workpiece was 2.4 ml/cm ² ·min.

The static water washing step S4 was continuously implemented for 30 seconds without opening the double-sided grinding device after the second dynamic water washing step.

In the static water washing step, the rotation of the glass substrate and the fixed plate is stopped. Then, the primary purified water filtered through the filter is supplied into the double-sided polishing device. In the static water washing step, the above-mentioned primary pure water was supplied so that the flow rate per unit area of the workpiece was 2.4 ml/cm ² ·min.

After the static water cleaning step was completed, the double-sided polishing device was opened, and the glass substrate for magnetic recording media was taken out, and was used for evaluation after cleaning and drying in the same manner as in Example 1.

As a result of calculating the ratio of the glass substrate for magnetic recording media which has linear damage similarly to Example 1, it confirmed that it was 0.9%.

Moreover, as a result of evaluating the number of particles adhering to the surface of the obtained glass substrate for magnetic recording media in the same manner as in Example 1, it was confirmed that the median of OSA counts was 14.

(comparative example 1)

Except that the first dynamic water cleaning step is not implemented, the grinding time of the first main surface grinding step is set to 35 minutes, and the second main surface grinding step is not implemented, the magnetic recording medium is manufactured in the same manner as in Example 1. Glass base board. That is, the first main surface polishing step and the second main surface polishing step are continuously performed as one polishing step.

Here, FIG. 6 schematically shows changes in the polishing pressure, the rotation speed of the fixed plate, and the supply of polishing liquid and water in the main surface polishing step in Comparative Example 1. In FIG. Same as in Fig. 3, the straight line represents the grinding pressure, and the dotted line represents the rotation speed of the fixed plate. In addition, the hatched block arrows shown in the lower part of the graph indicate the period during which the polishing liquid is supplied, and the hollow block arrows indicate the period during which water is supplied.

Immediately after the secondary polishing process of the main surface starts, the first main surface polishing step ( S1 ′) is performed by increasing the polishing pressure and the rotation speed of the table while supplying the polishing liquid. In addition, after the first main surface grinding step (S1') is finished, water is supplied instead of the grinding liquid, and the rotation of the table is stopped, thereby performing a static water washing step (S4).

After the static water cleaning step was completed, the double-sided polishing device was opened, and the glass substrate for magnetic recording media was taken out, and was used for evaluation after cleaning and drying in the same manner as in Example 1.

As a result of calculating the ratio of the glass substrate for magnetic recording media which has linear damage similarly to Example 1, it confirmed that it was 7.3%.

In addition, as in Example 1, the number of particles adhering to the surface of the obtained glass substrate for magnetic recording media was evaluated, and as a result, it was confirmed that the median of OSA counts was 20.

FIG. 7 shows a graph of the evaluation results of the ratio of the glass substrate for a magnetic recording medium having linear damage. In addition, in Table 1, the value of the median of the OSA count after evaluating the number of particles adhering to the surface of the glass substrate for magnetic recording media obtained by the said Example and the comparative example is shown collectively.

(Table 1)

Example 1 Example 2 Comparative example 1 Median OSA Count 19 14 20

According to the ratio of the glass substrate for magnetic recording media with linear damage shown in FIG. The proportion of glass substrates for magnetic recording media has been significantly reduced. This can be considered to be due to the following reasons: In Examples 1 and 2, unlike Comparative Example 1, the foreign matter in the double-sided grinding device can be reduced and removed by the first dynamic water cleaning step, and the foreign matter in the environment where the foreign matter has been reduced and removed can be reduced. Next, a second major surface grinding step is performed.

In addition, it was confirmed that the number of particles adhering to the surface of the glass substrate for magnetic recording media shown in Table 1 was significantly lower in Example 2 than in Example 1 and Comparative Example 1. In Example 1 and Comparative Example 1, since the same conditions were repeated to manufacture the glass substrate for magnetic recording media, abrasive grains and the like may remain in the double-sided polishing apparatus. But, in embodiment 2, consider owing to implementing the 2nd dynamic water cleaning step, therefore, can especially reduce the abrasive grain that remains in the double-sided polishing device, and can reduce the particle that adheres to the glass substrate for magnetic recording medium.

Claims (5)

1. A method for manufacturing a glass substrate for a magnetic recording medium, characterized in that, It has the main surface grinding process of grinding the main surface of the glass substrate for magnetic recording media, The main surface grinding process comprises successively: The first main surface grinding step, in the first main surface grinding step, the grinding sheet is pressed against the main surface of the glass substrate for magnetic recording media, and the glass substrate for magnetic recording media and the The grinding sheet rotates to grind the main surface; A first dynamic water cleaning step, in which water is supplied instead of the polishing solution, and the glass substrate for magnetic recording medium and the polishing sheet are rotated to clean; and A second main surface polishing step in which a polishing liquid is supplied instead of water, and the glass substrate for magnetic recording media and the polishing sheet are rotated to polish the main surface. 2. the manufacturing method of glass substrate for magnetic recording medium as claimed in claim 1, is characterized in that, The main surface grinding process also has a second dynamic water cleaning step. In the second dynamic water cleaning step, after the second main surface grinding step is completed, water is supplied instead of the grinding liquid, and the magnetic recording medium is made of glass. The substrate and the grinding sheet are rotated for cleaning. 3. the manufacturing method of glass substrate for magnetic recording medium as claimed in claim 1 or 2, is characterized in that, Having a plurality of steps of polishing the main surface of the glass substrate for magnetic recording media, The said main surface grinding|polishing process is implemented in the last process among the processes of grinding|polishing the main surface of the said glass substrate for magnetic recording media. 4. The manufacturing method of the glass substrate for magnetic recording media according to any one of claims 1 to 3, wherein The grinding liquid is colloidal silicon dioxide. 5. The manufacturing method of the glass substrate for magnetic recording media according to any one of claims 1 to 4, wherein The time of the second main surface grinding step is not less than 30 seconds and not more than 8 minutes.