Substrate for information recording media and manufacturing method thereof, information recording medium, and starting material glass plate

Substrate for data recording medium and its manufacturing method, data recording medium and starting material glass plate

Technical field

The present invention relates to a substrate for a data recording medium and its manufacturing method, data recording medium and starting material glass plate, and more particularly to a magnetic disk substrate used as a hard disk drive or similar device for data The substrate used for the recording medium and its manufacturing method, as well as the data recording medium such as magnetic disk, optical magnetic disk or optical disk, and the starting material glass plate for the data recording medium as the starting material of the substrate.

Background technique

In recent years, significant progress has been made in data technology, and different types of data recording media used to store data, such as magnetic disks, optical disks, and optical disks, have been in progress.

Among these types of data recording media, taking a magnetic disk as an example, a magnetic film is formed on the surface of at least one doughnut-shaped magnetic disk substrate, and a magnetic read head is used to slide over the data zone formed on the disk substrate. To record and play data.

A method of manufacturing such a magnetic disk substrate has been proposed, in which a thin-film magnetic material is directly formed on the surface of at least a sheet of starting material glass plate, which has been manufactured by a suspension method or the like, and There is no need to grind off the starting material glass plate (for example, see Japanese Patent Laid-Open Application No. 60-159531 (Kokai)).

However, with this method, it is difficult to produce a magnetic disk with good flatness that can cope with the increase in recording density of the data zone that has occurred in recent years. At present, it is still common to grind off the glass plate of the starting material when manufacturing the disk substrate.

Figure 1 is a flow chart showing a conventional method for manufacturing such a disk substrate.

In this traditional method, the starting material glass plate 101 is cut into a doughnut shape in the magnetic disk processing step 102, and then in the edge processing step 103, the inner surface and the outer surface of the starting material glass plate 101 are processed into preforms. Set the size, then in the surface polishing step 104, the main surface of the starting material glass plate 101 is polished, and then in the chemical strengthening treatment step 105, if necessary, the substrate is strengthened, and then the completion cleaning step 106 is performed. The manufacture of the disk substrate 107 is completed.

In the surface grinding step 104, the grinding of the surface of the starting material glass plate 101 is performed in three stages, namely rough grinding 104a, pre-grinding 104b and precise grinding 104c.

The surface of the magnetic disk substrate 107 manufactured from the sheet-like starting material glass plate 101 has a wave shape on a microscopic scale, in which a plurality of surface wave patterns classified according to the wavelength band are superimposed on one another , Such as the long-wavelength wave 108, the medium-wavelength wave 109 and the short-wavelength wave 110 in FIG. 2. The magnetic read head 111 is stacked on a magnetic disk substrate 107 with such surface waves.

However, with the increase in the recording density of the data zone in recent years, the surface wave characteristics have become a great influence on the electromagnetic conversion characteristics. If the ability of the magnetic read head to follow the surface waves is not good, there is a risk of malfunction during recording and/or playback, so the disk substrate needs a high degree of flatness.

Therefore, the surface grinding step 104 is traditionally divided into three stages, as described above. First, the rough grinding 104a is performed using grinding particles having a large average diameter. As a result, the thickness of the starting material glass plate 101 is adjusted to a preset value. In addition, surface waves, especially long-wavelength waves, will be reduced, so The flatness of the starting material glass plate 101 is corrected. Then, in the pre-grinding 104b and the precision-grinding 104c, the small defects and the surface waves of very short wavelengths (medium wavelength waves and short wavelength waves) formed on the surface of the starting material glass plate 101 will be removed.

In recent years, in order to cope with the increase in the recording density of the data zone, there have been good technological developments to reduce the size of the magnetic read head 111, and set the flying height of the smaller magnetic read head 111 to a lower value. , And allow the magnetic reading head 111 to steadily fly over the disk substrate 107 at the lower flying height. Now, the length of the magnetic read head has been reduced from 2mm to 1mm or less.

As shown in Fig. 3, the long-wavelength wave 108 is a fairly gentle slanting wave. Therefore, after the long-wavelength wave 108, the magnetic reading head 111 is likely to fly over the disk substrate 107, and hit the magnetic reading head. A small fixed gap t is maintained between 111 and the disk base 107.

In contrast, as shown in FIG. 4, the medium-wavelength waves 109 and the short-wavelength waves 110 have steep slopes 112, so the magnetic read head 111 cannot be the same as the long-wavelength waves 108 in the magnetic read head 111 and the disk substrate. A small fixed gap t is maintained between 107, and it flies and slides on the disk substrate 107, that is, the magnetic read head 111 cannot follow the medium-wavelength waves 109 and the short-wavelength waves 110. If the medium-wavelength waves 109 and the short-wavelength waves 110 are on the surface of the substrate, abnormal functions may be caused during recording and/or playback. In order to obtain the required high-quality magnetic disk substrate, which is sufficient to cope with the increased recording density of the data zone, it is necessary to perform surface polishing so that the medium-wavelength waves 109 and the short-wavelength waves 110 are removed.

However, in the above-mentioned traditional manufacturing method, although it is possible to detect the degree of flatness in the rough grinding step 104a due to the lack of long-wavelength waves 108, new medium-wavelength waves 109 and short-wavelength waves 110 will pass through The rough grinding step 104a is formed on the surface of the starting material glass plate 101, so the amount of grinding in the pre-grinding 104b and the precise grinding 104c must be increased. In the traditional manufacturing method, the problem is that a certain predetermined amount must be used to thicken the starting material glass root 101 at the beginning. In addition, a large amount of grinding waste will be released during grinding, resulting in an increase in the amount of industrial waste. Increase manufacturing costs.

In addition, the grinding particles used in the rough grinding step 104a have a larger diameter than the grinding particles used in the pre-grinding 104b and the precise grinding 104c. Therefore, the surface of the starting material glass plate 101 is easily scratched, and the subsequent The amount of grinding must be increased to remove these surface scratches; therefore, the problem is that the starting material glass plate 101 must become thicker by a predetermined amount at the beginning for this purpose.

In addition, because the rough grinding step 104a using abrasive particles with a larger diameter is performed after the inner peripheral surface and the outer peripheral surface of the starting material glass plate 101 are ground and polished in the edge treatment step 103, so Even though the inner peripheral surface and the outer peripheral surface have been mirror-polished hard in the edge treatment step 103, once they are ground again with coarse abrasive particles in the rough grinding step 104a, the problem is that the inner peripheral surface and the outer peripheral surface The surface roughness of the peripheral surface will be reduced, resulting in a reduction in product quality.

In addition, because the surface grinding step 104 is divided into three stages as described above (rough grinding 104a, pre-grinding 104b and precise grinding 104c), the problem is Yes, the number of processing steps required in surface grinding will be many, so it will take a long time to complete the manufacturing. In addition, there is a risk of scratching the surface of the starting material glass plate 101, because the substrate comes into contact with each step. Another substrate or sieve or similar device, so the yield is very poor.

Disclosure of the invention

In view of the above problems, the object of the present invention is to provide a substrate for a data recording medium, which has a high degree of flatness, high product quality and high reliability.

In addition, another object of the present invention is to provide a method for manufacturing the above-mentioned substrate for data recording media, so that the substrate for data recording media can be manufactured in a very short time and with a low grinding amount, thus increasing Its output.

In addition, another object of the present invention is to provide a data recording medium capable of coping with high recording density using the above-mentioned substrate, and to provide a starting material glass plate suitable for manufacturing a substrate for data recording media.

The present invention will be disclosed in the form of outlines.

Using data recording media such as current magnetic disks, because the magnetic read head has been reduced in size, it is likely that the magnetic read head can follow long-wavelength waves, as mentioned in the "Technical Background" above (see Figure 3). Therefore, in the stage that has been reached, the necessity of the rough grinding step must be tested, including newly generated medium-wavelength waves and short-wavelength waves.

In this regard, it has been proposed to manufacture glass substrates for magnetic media (that is, substrates for data recording media) without the need for rough grinding (Japanese Patent Laid-Open Application No. 2000-351653). (Kokai); Hereafter referred to as "used technology").

However, in order to cope with the increase in the recording density of the data zone, the surface of the glass substrate has a high degree of flatness, and the surface must be polished in a certain type.

However, in the above-mentioned conventional technology, although it has been revealed that "the substrate for the data recording medium is manufactured without rough grinding (patching processing)", there is no specific disclosure about what kind of technical device can be used. To ensure a high degree of flatness.

For the surface waves that define long-wavelength waves, medium-wavelength waves and short-wavelength waves on the glass surface-the long-wavelength waves are measured by the Optiflat optical surface wave measuring instrument manufactured by PhaSeShift Technology Company at 0.4 nm to The average wave is measured in the 5.0 nm wavelength band and the average wave is Wa, the medium wavelength wave is measured using the above Optiflat measuring instrument in the 0.4 nm to 2.0 nm wavelength band and the average wave is Wa, and the short-wavelength wave is made by Zygo The Newview 200 optical surface roughness meter measures the average roughness in the 0.2 nm to 1.4 nm wavelength band and the average roughness is Ra. Therefore, this invention conducts special research, and the result is that if the surface of the glass plate of the starting material is wavy Good, the substrate for data recording media with excellent flatness can be easily obtained in a short period of time, and only a very low amount of precision grinding with ultra-fine grinding particles of a preset diameter, and no Need rough grinding treatment.

Based on this discovery, the method of manufacturing a substrate for data recording media includes the step of performing surface grinding on at least one surface of a sheet-like starting material glass plate, wherein the surface grinding only includes the use of a super Precise grinding of fine abrasive particles.

According to the above method, the surface grinding is performed using only ultra-fine grinding particles with a first predetermined diameter. As a result, there are no longer medium-wavelength waves and short-wavelength waves newly generated by rough grinding, and a substrate with good flatness for data recording media can be manufactured in a very short time and with a very low grinding amount. In addition, because the amount of grinding is small, the release of industrial waste can be suppressed, which is very environmentally friendly.

In addition, from the results of further experiments, the inventors revealed that before performing precise grinding, pre-grinding of fine grinding particles with a second predetermined diameter is performed, and the second predetermined diameter is greater than the first predetermined diameter. Then, the required substrate for data recording media can be obtained in a shorter time, without the need for new medium-wavelength and short-wavelength waves to occur.

Therefore, according to another aspect of the present invention, the method of manufacturing a substrate for a data recording medium includes a step of performing surface grinding on at least one surface of a sheet-like starting material glass plate, wherein the surface grinding only includes pre-grinding and precision grinding. In terms of grinding, precise grinding uses ultra-fine grinding particles with a first predetermined diameter, and pre-grinding uses fine grinding particles with a second predetermined diameter, which is larger than the first predetermined diameter.

In addition, in order to avoid the formation of micro-defects on these surfaces of the starting material glass plate, but also to avoid a reduction in the polishing rate, the first preset diameter is preferably within the range of the average particle size of 0.01 μm to 1.3 μm, and The 90% diameter in the volume particle size distribution is in the range of 0.02 μm to 3.5 μm (hereinafter referred to as "90% diameter").

In addition, during the pre-grinding, it is necessary to avoid the formation of micro-pits and From the point of view of the short-wavelength waves on the substrate for data recording media, the second preset particle diameter is preferably such that the average particle diameter is in the range of 0.3 μm to 5 μm, and 90% of the diameter of the volume particle size distribution is Within the range of 1μm to 15μm.

It should be noted in the present invention that the "average particle diameter" means that when the particle diameter is integrated from the smallest particle diameter to the volume particle size distribution, the integrated volume particle size becomes 50% of the entire integrated volume particle in the volume particle size distribution. When the particle diameter is integrated from the smallest particle diameter to the volume particle size distribution, the integrated volume particle size becomes 90% of the entire integrated volume particle size in the volume particle size distribution. The diameter of the particles at the time.

In addition, the inventors conducted further in-depth research and found that when manufacturing the sheet-shaped starting material glass plate, the forming conditions are appropriately controlled, and the long-wavelength waves can be kept down at any time not to exceed 6nm. The starting material glass plate with long-wavelength waves exceeding 6nm is subjected to the above-mentioned surface grinding, and a substrate for data recording media with very good surface wave characteristics and good flatness can be easily obtained.

Therefore, in the method of manufacturing a substrate for a data recording medium according to the present invention, it is preferable to use a glass plate of starting material having a plurality of surface wave patterns, and the classification of the surface wave pattern is based on the starting material glass plate at least The wavelength bands formed by overlapping each other on a surface, in which the long-wavelength waves formed do not exceed 6nm, which is the highest wavelength band among these surface waves.

In addition, considering the yield, it is best to form a starting material not exceeding 0.4nm The long-wavelength waves of the material glass plate. In addition, in order to carry out effective and precise grinding, the formed starting material glass plate should preferably have short-wavelength waves in the lowest wavelength band in the range of 0.1nm to 0.7 nm, and long-wavelength wave wavelength bands and short-wavelength wave wavelength bands. The mid-wavelength waves in between are in the range of 0.25 nm to 2 nm.

In addition, considering the yield and similar characteristics, it is best to use the suspension process as a starting material glass plate with long-wavelength waves maintained to no more than 6 nm. Therefore, it is best to manufacture the starting material glass plate from a glass ribbon in a preset high temperature state formed by pouring the glass raw material on the molten tin.

In addition, in order to remove minute defects from at least one surface of the starting material glass plate during grinding, the grinding amount for the surface grinding from at least one surface of the starting material glass plate is preferably 1 μm to 75 m Within the range, more preferably within the range of 1 μm to 25m.

In addition, in order to perform precise grinding and maintain a good grinding rate without damaging the starting material glass plate, it is best to use selenium oxide, aluminum oxide, zirconium oxide, silicon oxide and manganese oxide. The selected at least one material is used as the ultrafine abrasive particles used in surface polishing; in particular, selenium oxide is best used.

In addition, the substrate for data recording media according to the present invention is characterized by being manufactured by any of the above-mentioned manufacturing methods, in which a plurality of surface wave patterns classified according to wavelength bands are formed on at least one surface of the glass plate of the starting material Formed by overlapping each other. In addition, the long-wavelength wave of the highest wavelength band formed is preferably 0.3 nm to 1.2 nm, the short-wavelength wave of the lowest wavelength band is preferably 0.1 nm to 0.6 nm, and the long-wavelength wave wavelength band and the short wave The mid-wavelength waves between the long wave wavelength bands are in the range of 0.2nm to 0.9nm.

According to the above structure, a substrate for a data recording medium can be obtained easily and in a short time, with good surface wave characteristics and excellent flatness.

In addition, the data recording medium according to the present invention includes the aforementioned substrate for the data recording medium, and a data recording layer on at least one surface of the substrate.

According to the above structure, a data recording medium with excellent flatness can be easily obtained, so that it can cope with the increased recording density of the data zone.

In addition, a plurality of surface wave-shaped starting material glass plates classified by wavelength bands according to the present invention are formed on at least one surface in an overlapping manner, and are characterized by the formed long-wavelength waves in the highest wavelength band. It does not exceed 6nm, the short-wavelength wave in the lowest wavelength band does not exceed 0.7nm, and the medium-wavelength wave between the long-wavelength wave wavelength band and the short-wavelength wave wavelength band does not exceed 2nm. In addition, the starting material glass plate is preferably manufactured from glass ribbons in a preset high temperature state formed by pouring glass raw materials on molten tin.

According to the above structure, the starting material glass plate with suppressed long-wavelength waves can be easily obtained by the suspension process, and the starting material glass plate suitable for manufacturing the substrate for the data recording medium can be improved.

Figure 1 is a flow chart showing a conventional method of manufacturing a substrate for data recording media; Figure 2 is a schematic diagram of the state of waves on the glass plate of a traditional starting material; Figure 3 is a schematic diagram useful for explaining the relationship between the magnetic read head and the disk substrate in the case of long-wavelength waves; Figure 4 is a schematic diagram of the medium-wavelength waves Or a schematic diagram useful for explaining the relationship between the magnetic read head and the disk substrate in the case of short-wavelength waves; FIG. 5 is a cross-sectional view showing the main part of the data recording medium according to an embodiment of the present invention; A flowchart of manufacturing a substrate for a data recording medium according to an embodiment of the present invention; FIG. 7 is a schematic diagram showing the structure of a floating plate glass manufacturing device; FIG. 8 is a diagram showing another embodiment of the present invention for manufacturing a substrate for data recording media The flow chart of the substrate; and FIG. 9 is a schematic diagram showing the structure of the pull-down plate glass manufacturing device. The best mode for implementing the present invention will now be described in detail with reference to the drawings. FIG. 5 is a cross-sectional view showing a data recording medium according to an embodiment of the present invention, especially a magnetic disk. The magnetic disk includes a magnetic disk substrate 1 with a substrate layer 2, a magnetic layer 3 and a protective layer 4, which are formed on the surface sequentially using a known sputtering method.

The magnetic disk substrate 1 is manufactured by the following manufacturing method, and minute surface waves are formed on the surface of the substrate. In particular, the surface waves are classified into three categories, which are defined in the above-mentioned "Revelation of Invention" (long-wavelength waves, medium-wavelength waves and short-wavelength waves), and the formation of the magnetic disk substrate 1 makes the long-wavelength waves become 0.3nm To 1.2nm, the medium wavelength wave becomes 0.2nm to 0.9nm and the short wavelength wave becomes 0.1nm to 0.6nm.

The reason for setting the long-wavelength, medium-wavelength, and short-wavelength waves of the disk substrate 1 to fall within the above-mentioned range will now be explained.

If the long-wavelength waves exceed 1.2nm, and/or the medium-wavelength waves exceed 0.9nm, and/or the short-wavelength waves exceed 0.6nm, the entire surface waves will become large, causing the magnetic read head to fly at a very low flying height When flying over the magnetic disk substrate 1, it is difficult to follow the surface waves. Now the magnetic disk substrate 1 is made with a very high recording density, so high-quality disk substrate 1 cannot be obtained. On the other hand, even if the long-wavelength waves are less than 0.3nm, and/or the medium-wavelength waves are less than 0.2nm, and/or the short-wavelength waves are less than 0.1nm, the product quality cannot be further improved and is already peaked. In this embodiment, the magnetic disk substrate 1 is manufactured so that the long-wavelength waves become 0.3 nm to 1.2 nm, the medium-wavelength waves become 0.2 nm to 0.9 nm, and the short-wavelength waves become 0.1 nm to 0.6 nm.

It should be noted that because the three surface waves classified by wavelength bands are formed by overlapping on the surface of the disk substrate 1, even if one of the three surface waves exceeds the above range, the magnetic read head The electromagnetic conversion characteristics will be deteriorated, and the product quality of the magnetic disk substrate 1 will be degraded. Therefore, the range of all three surface waves must be met.

In addition, in the magnetic disk, CrMo, Cr, CrV or similar materials can be used as the material of the base layer 2, and the cobalt alloy such as CoPtCr or CoPtCrTa with excellent data recording/playback characteristics and the film adhesion to be ensured can be used as As the material of the magnetic layer 3. Carbon materials such as hydrogenated carbon are materials that can be used as the protective layer 4.

The method of manufacturing the magnetic disk substrate 1 will now be explained in detail.

FIG. 6 is a diagram showing the method of manufacturing the magnetic disk substrate 1 according to the first embodiment of the present invention Flow chart of the law. For example, a piece of suspended glass manufactured by the suspension process is used as the starting material glass plate 5. The disk substrate 1 is sequentially processed through the disk processing step 6, the edge processing step 7, the surface polishing step 8, and the chemical strengthening processing step. 9 and polishing cleaning step 10 are manufactured.

Fig. 7 is a schematic diagram showing the structure of a floating plate glass manufacturing device. The floating plate glass manufacturing device has the main part of the melting furnace 11, the sealed forming tank 13 and the annealing high-temperature furnace 15. The preset glass material powder is poured into the melting furnace 11, and the glass material powder is in the melting furnace 11. Melting in a preset high-temperature atmosphere, the sealed forming tank 13 is placed at a low pressure and contains molten tin 12, and the glass ribbon 14 drawn from the forming tank 13 is annealed in a high-temperature annealing furnace 15.

There is no particular restriction on the glass material. For example, you can use SiO₂, Na₂Sodium carbonate lime glass with O and CaO as the main components, with SiO₂'Al₂O₃, Na₂O and Li₂Aluminum silicate glass, borosilicate glass, Li₂O-SiO₂Glass, Li₂O-Al₂O₃-SiO₂Glass or RO-Al₂O₃-SiO₂Glass (where R=Mg, Ca, Sr or Ba). In addition, glass for glass strengthening can be used, in which ZrO₂, TiO₂Or similar materials have been added to the above-mentioned glass materials, or crystal glass that is not chemically strengthened is used.

In the above-mentioned floating plate glass manufacturing device, the glass material powder that has been prepared into a preset composition is added to the melting furnace 11 heated to 1500 to 1600°C, wherein the glass material powder is melted in the melting furnace 11 to form The molten glass then flows into the forming tank 13. The forming tank 13 as described above contains molten tin 12. Molten glass has a lower specific gravity than molten tin 12, so it will float On the molten tin 12, it moves in the direction of arrow A in FIG. 7. As a result of floating on the molten tin 12, the molten glass forms a linear shape, and thus becomes a glass ribbon 14 having a predetermined thickness.

The produced glass ribbon 14 is pulled into the annealing high-temperature furnace 15 via the roller conveyor 16, and is conveyed in the direction of arrow B in FIG. 7. Then the glass ribbon 14 is cooled to room temperature in a medium annealing high temperature furnace 15 to complete the cooling process to avoid warping. The glass ribbon 14 cooled to room temperature is then released from the annealing high-temperature furnace 15 and cut into a rectangular shape, thereby manufacturing a large number of starting material glass plates 5 from a single manufacturing batch.

In the above-mentioned floating plate glass manufacturing apparatus, the lower surface of the glass ribbon 14 in contact with the molten tin 12 is cooled when it contacts the molten tin 12 with a free surface, and the lower surface of the glass ribbon 14 is viewed on a macro scale. To be very flat. In addition, the upper surface of the glass ribbon 14 is the space 17 in contact with the molten tin 12, which will expand in the horizontal direction through the viscous flow; therefore, the upper surface of the glass ribbon 14 must also be very large in a macroscopic view. flat.

However, the molten tin 12 does not have a fixed temperature throughout the process, but a temperature gradient in the direction of arrow A shown in FIG. 7, and the temperature is in the width direction of the glass ribbon 14 (the direction perpendicular to the paper surface of FIG. 7) Uneven. In addition, the temperature does not have a fixed temperature in the entire space 17. As a result, even though the upper surface and the lower surface of the glass ribbon 14 have excellent flatness on a macro scale, there are generally large surface waves on a micro scale. Even if the starting material glass plate 5 with a large surface wave is subjected to the precise grinding described below, it is still impossible to reduce the surface wave to a desired value in a short time and with a low grinding amount. In addition, if such large surface waves are to be removed If it falls, the starting material glass plate 5 must be made very thick at the beginning.

In this embodiment, by appropriately controlling the temperature of the forming groove 13 and controlling its forming conditions, the starting material glass plate 5 is formed in such a way that the surface waves of the starting material glass plate 5 will become smaller, especially for long wavelengths. wave.

In particular, by appropriately controlling the temperature gradient of the molten tin 12 in the direction of arrow A in FIG. 7 when contacting the glass ribbon 14, and performing temperature control of the molten tin 12, the temperature of the molten tin 12 in the width direction of the glass ribbon 14 changes It is as small as possible. In addition, the convection generated in the molten tin 12 is controlled, and the forming conditions are further controlled, so that the temperature fluctuation and convection disturbance in the space 17 on the molten tin 12 will be reduced, and the desired surface wave characteristics can be manufactured. The starting material glass plate. In particular, as the glass ribbon 14 moves in the direction of arrow A in Figure 7, the viscosity of the glass will increase, and the desired surface wave characteristics will be obtained. Near the exit of the forming groove 13, the temperature of the glass ribbon 14 in the width direction The distribution is preferably as uniform as possible, and prevents small changes from entering the molten tin 12 from the outside.

In particular, it is preferable to form the starting material glass plate 5 so that the long-wavelength waves are 0.4 nm to 6 nm, the medium-wavelength waves are 0.25 nm to 2 nm, and the short-wavelength waves are 0.1 nm to 0.7 nm.

The reason is that if the long-wavelength waves exceed 6 nm, and/or the medium-wavelength waves exceed 2 nm, and/or the short-wavelength waves exceed 0.7 nm, in order to obtain the disk substrate 1 with the required good flatness, as described below When precision grinding is performed in the surface grinding process, the grinding amount will be increased, and the grinding time will be longer. Therefore, it is difficult to control different forming conditions in terms of production technology, so that long-wavelength waves are less than 0.4 nm, and/or medium Wave length is less than 0.25 nm, and/or short-wavelength waves are smaller than 0.1 nm, and production costs will increase.

In this embodiment, when manufacturing the starting material glass plate 5, the forming conditions are controlled so that the long-wavelength waves become 0.4 nm to 6 nm, the medium-wavelength waves become 0.25 nm to 2 nm, and the short-wavelength waves become 0.1 nm to 0.7 nm.

Next, the starting material glass plate 5 with the above-mentioned surface wave characteristics is processed in different types, and the magnetic disk substrate 1 is made into a product through the above-mentioned different steps.

These manufacturing steps will now be described in the order in which they are performed.

(1) Disk processing step 6

In the disk processing step 6, use a hard metal cutter or a diamond knife to cut the starting material glass plate 5 along the outer edge surface and the inner edge surface at the same time, so that the starting material glass plate 5 has a preset outer diameter It is shaped like a doughnut with the inner diameter, and has good concentricity between the outer edge surface and the inner edge surface.

It should be noted that although in this embodiment, the outer edge surface and the inner edge surface are cut at the same time, it is also possible to cut the outer edge surface to a preset outer diameter first, and then use a cylindrical diamond grinding stone to drill To the preset inner diameter, or press the starting material glass plate 5 outward into the preset outer diameter, and then use this diamond grinding stone to drill to the preset inner diameter.

(2) Edge processing step 7

In the edge treatment step 7, the outer edge surface and the inner edge surface of the donut-shaped starting material glass plate 5 are ground and polished, so that the outer diameter and the inner diameter become the required outer and inner diameters of the disk substrate 1 Diameter, thus manufacturing a glass substrate. In particular, the use of diamond abrasive particles adhered to the research Grinding stone, the outer edge surface and the inner edge surface are polished in two stages, and the particle size of the diamond abrasive particles is different in the two stages, and then the corners of the outer edge surface and the inner edge surface are cut corners handle.

According to the required product quality, the particle size of the diamond abrasive particles used is set to the most suitable particle size. In addition, needless to say, if in the above-mentioned disk processing step 6, the starting material glass plate 5 has been cut so that the outside diameter and the inside diameter are close to the required outside and inside diameters of the disk base 1, then It is not necessary to perform the grinding treatment divided into two stages, and a single stage is sufficient.

Then use CeO₂The loose abrasive particles of (selenium oxide) are polished to make the outer edge surface and the inner edge surface (including the chamfered part; hereafter referred to as similar) smooth, so that the surface roughness Ra of the outer edge surface and the inner edge surface becomes The default value or smaller.

(3) Surface grinding step 8

In the surface grinding step 8, the main surface of the glass substrate is precisely ground 8a, and an abrasive is added to these surfaces. The preparation of the abrasive is to make the average particle diameter in the range of 0.01 μm to 1.3 μm and 90% Loose abrasive particles (ultrafine abrasive particles) with a diameter in the range of 0.02 μm to 3.5 μm are dispersed in the polishing liquid.

The reason for limiting the particle diameter of loose abrasive particles is as follows.

If the long-wavelength waves exceed 1.3μm and/or the 90% diameter exceeds 3.5μm, the particle diameter of the entire loose abrasive particles will become larger, and the newly formed medium-wavelength waves and short-wavelength waves may be dangerous during precise grinding. In addition, The surface of the glass substrate becomes easily scratched by loose abrasive particles. On the other hand, if the long-wavelength waves are less than 0.01 μm and/or the 90% diameter is less than 0.02 μm, the particle diameter of the loose abrasive particles will become smaller, so the time required for grinding will become longer and the output will decrease.

In this embodiment, loose abrasive particles with an average particle diameter in the range of 0.01 μm to 1.3 μm and 90% of the diameter in the range of 0.02 μm to 3.5 μm are used for precise grinding 8a.

In addition, in the precision grinding 8a, the grinding amount is such that 1 μm to 75 μm, preferably 1 μm to 25 μm of glass is removed from each surface of the glass substrate. In particular, when using loose abrasive particles with the above-mentioned particle diameter for precise grinding, and the loose abrasive particles are on a glass substrate with the above-mentioned good surface waves, if the grinding amount is less than 1 μm, the grinding amount is lower. It is not enough to remove the tiny defects formed on the surface of the glass substrate, and if the grinding amount exceeds 75 μm (25 μm is preferred), the grinding process will be performed too much, so time will be wasted on grinding and the yield will be reduced. .

In this embodiment, from the surface of the glass substrate, the grinding amount of the precise grinding 8a is therefore in the range of 1 μm to 75 μm, preferably in the range of 1 μm to 25 μm.

There are no special restrictions on loose abrasive particles; rare earth metal oxides, such as CeO, can be used₂Or La₂O₃, Or ZrO₂, MnO₂, Al₂O₃, SiO₂(Colloidal silica) or similar materials. However, from the viewpoint of obtaining good polishing efficiency, it is best to use abrasive particles of rare earth metal oxides, especially CeO₂Grinding particles.

In addition, there are no special restrictions on the polishing pad used in polishing; For example, non-woven polishing pads or foam polishing pads can be used. However, from the point of view of avoiding scratches on the glass substrate, it is best to use a suede pad from the base layer and the NAP layer. The NAP layer includes a continuous foam layer that has been polished on the surface. Form an opening.

In this embodiment, precision grinding 8a is performed at a grinding rate in the range of 0.1 μm/min to 0.8 μm/min.

In addition, after the precision grinding 8a, an acidic aqueous solution, an alkaline aqueous solution, and pure water will be similar to a lotion to clean the glass substrate.

(4) Chemical strengthening treatment step 9

In the chemical strengthening treatment step 9, in the molten salt that has been adjusted to a preset temperature, such as potassium nitrate (KNO₃) And sodium nitrate (NaNO₃), the glass substrate is immersed for a preset period of time, and then chemically strengthened. The chemical composition of the glass substrate is like Li⁺¹With Na⁺¹Ions are the same as K with a larger ion radius⁺¹Exchange. By performing this chemical strengthening treatment, the surface compressive stress is increased, and the magnetic disk made from the glass substrate can be prevented from breaking during high-speed rotation.

After being immersed in the molten salt, the glass substrate is annealed to a temperature close to room temperature, and then the molten salt adhered to the glass substrate is washed away in warm pure water.

It should be noted that, depending on the required strength of the magnetic disk substrate 1, the chemical strengthening treatment step 9 can be omitted. In addition, if the starting material glass plate 5 is formed from crystallized glass, it is impossible to have a chemical strengthening effect, so the chemical strengthening treatment step 9 is generally omitted.

(5) Grinding and cleaning step 10

In the grinding and cleaning step 10, the glass substrate that has been precisely ground, if If necessary, by immersing in acidic aqueous solution, alkaline aqueous solution, pure water or mixed solution, the chemical strengthening treatment is washed away, and if necessary, ultrasonic irradiation is used. Foreign substances such as abrasives or molten salt adhered to the surface of the glass substrate must be removed during the chemical strengthening process, thereby completing the manufacture of the magnetic disk substrate 1.

As mentioned above, in this embodiment, in the surface grinding step 8, only precision grinding 8a is performed, using loose grinding particles (ultra-fine grinding particles) with an average particle diameter in the range of 0.01 μm to 1.3 μm and 90% diameter In the range of 0.02 μm to 3.5 μm (the first preset particle diameter). Therefore, there is no need to perform rough grinding to produce a substrate for data recording media, and there are no medium-wavelength waves and/or short-wavelength waves newly formed due to rough grinding. In addition, selecting the starting material glass plate with good surface wave characteristics can easily produce a high-quality substrate with excellent flatness for data recording media in a short time and with a low grinding amount. In addition, because the amount of grinding is very low, industrial waste such as grinding waste will be reduced, which is good for environmental protection.

FIG. 8 is a flowchart of a method for manufacturing a magnetic disk substrate according to a second embodiment of the present invention, that is, a substrate for a data recording medium. In this embodiment, in the surface grinding step 8', the pre-grinding 8b' is performed before the precise grinding 8a', thereby further reducing the time required for the surface grinding step 8'.

Use loose abrasive particles (ultra-fine abrasive particles) for pre-grinding 8b'. The loose abrasive particles have a particle diameter larger than the loose abrasive particles used in precision grinding 8a'. In particular, the loose abrasive particles have an average particle diameter of 0.3 In the range of μm to 5 μm and 90% of the diameters are in the range of 1 μm to 15 μm Nene. In the enclosure.

The following is the reason for using loose abrasive particles with the above-mentioned particle diameter in the pre-grind 8b'.

If the average particle diameter exceeds 5 μm and/or 90% of the diameter exceeds 15 μm, the particle diameter will become larger, resulting in the risk of small defects or the formation of short-wavelength waves. On the other hand, if the average particle diameter is less than 0.3 μm and/or 90% of the diameter is less than 1 μm, the particle diameter becomes smaller, so the purpose of reducing the grinding time cannot be improved. In this embodiment, the pre-grinding 8b' is performed using loose abrasive particles having an average particle diameter in the range of 0.3 μm to 5 μm and 90% of the diameter in the range of 1 μm to 15 μm.

In addition, the type of loose abrasive particles used in the pre-grinding 8b' and the precision grinding 8a' can be the same as that used in the precision grinding 8a in the first embodiment, but between the pre-grinding 8b' and the precision grinding 8a', the most It is better to use different types of loose abrasive particles. For example, Al can be used in pre-polishing 8b' and precision-polishing 8a' respectively₂O₃With CeO₂, CeO₂With SiO₂(Colloidal silica), ZrO₂With CeO₂, Or CeO₂With MnO₂The combination of grinding treatment.

In the second embodiment, the pre-grinding 8b' is performed using loose grinding particles (ultrafine grinding particles) with an average particle diameter (first preset particle diameter), which is larger than the loose grinding particles used in the precision grinding 8a' The average particle diameter, in particular, the average particle diameter is in the range of 0.3 μm to 5 μm and 90% of the diameter is in the range of 1 μm to 15 μm, and then precision grinding is performed 8a'. As a result, the time required for surface polishing is further reduced, and the yield of manufacturing the magnetic disk substrate 1 with high product quality and excellent reliability is improved.

FIG. 9 is a schematic diagram showing the structure of the apparatus for manufacturing a down-drawn plate glass, which is another embodiment of an apparatus for manufacturing a glass plate of starting material. The pull-down plate glass manufacturing device has the main part of a melting furnace 21, a working tank 22, a groove 23, and an annealing furnace 24. In the melting furnace 21, a preset glass material powder is poured into it and placed in a preset high temperature atmosphere. The glass material powder is melted. In the working tank 22, the molten glass is adjusted to a preset temperature. The groove 23 is restricted and formed from platinum, and the molten glass is allowed to pass from the working tank 22 through the groove 23. It is pulled out to form a glass ribbon 25, and the glass ribbon 25 is annealed in an annealing furnace 24.

In the above-mentioned pull-down plate glass manufacturing device, the glass material powder prepared into a preset composition is poured into the melting furnace 21 heated to 1500 to 1600°C, wherein the glass material powder is melted in the melting furnace 21 to form a melt grass. Then the molten glass flows into the working tank 22, where the molten glass is homogenized and adjusted to a temperature suitable for forming. Then the molten glass flows downwardly out of the working tank 22 through the groove 23. The flow rate of the molten glass is adjusted to a preset rate using gravity (shown by arrow C in FIG. 9) and the rotating force of the roller 26, thereby forming a glass ribbon 25 with a preset thickness. Then, the glass ribbon 25 is cut into a preset rectangle to obtain the starting material glass plate.

In the down-draw method, the temperature of the molten glass passing through the groove 23, the glass temperature of the groove 23 itself, and the temperature distribution in the width direction of the groove 23 will determine the thickness distribution of the surface quality, such as the glass ribbon 25 (initial Material (glass plate) flatness (wave characteristics). Therefore, the recommended condition is that a glass ribbon 25 with good product quality can be obtained. For example, platinum restraint can be used as the groove 23 of FIG. 9 or a difficult-to-fusion tube can be used.

In addition, in the betting method, the glass ribbon 25 pulled out from the groove 23 flows down through the free space in the annealing furnace 24 under the action of gravity, and its tail end is sandwiched between the rollers 26. The flow rate and temperature gradient of the molten glass and the air flow and temperature distribution in the width direction of the free space through which the molten glass passes are all controlled to make the surface wave of the glass ribbon 25 (starting material glass plate) lower. As a result, a glass ribbon 25 (starting material glass plate) having long wavelength waves in the range of 0.4 nm to 6 nm, wavelength waves in the range of 0.25 nm to 2 nm, and short wavelength waves in the range of 0.1 nm to 0.7 nm was manufactured.

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, in the above-mentioned embodiment, the starting material glass plate 5 is manufactured by the suspension method or the down-draw method, but as long as it can produce long-wavelength waves in the range of 0.4nm to 6nm, the wavelength in the range of 0.25nm to 2nm The glass plate 5, which is the starting material for waves and short-wavelength waves in the range of 0.1 nm to 0.7 nm, has no particular limitation on the manufacturing method. For example, the starting material glass plate 5 can be manufactured using a redraw method, in which a sheet-like mother glass sheet is formed using a melting tank or similar device, and then reheated in a heating furnace to reduce the viscosity of the glass. Pull it out in the downward or horizontal direction to make the mother glass sheet thinner, and then perform annealing treatment in an annealing furnace.

A specific embodiment of the present invention will now be explained.

(First example)

The inventors produced the following test pieces: several pieces of floating glass (starting material glass plate) with good surface wave characteristics, several pieces of test pieces that were only accurately ground (Examples 1 to 5), and several Pre-grinding and finishing Test pieces that are accurately ground (Examples 6 to 8); use several pieces of down-drawn glass (starting material glass plate) with good surface wave characteristics, and several test pieces that are only accurately ground (Example 9); use several pieces with Suspended plate glass (starting material glass plate) with good surface wave characteristics, several test pieces subjected to rough grinding combined with surface grinding steps (comparative examples 1 and 2); and using a good surface wave outside the scope of the present invention The starting material of the glass plate, several test pieces with different surface grinding treatments (Comparative Examples 3 to 5). For each test piece, before and after the surface grinding treatment, measure the surface wave and evaluate the surface characteristics, that is, immediately after grinding the inner and outer edge surfaces and after finishing the precision grinding.

For each example and comparative time example, Table 1 shows the method of manufacturing the starting material glass plate, the surface characteristics of the starting material glass plate and the detailed grinding treatment; Table 2 shows the surface characteristics of the disk substrate obtained therein .

It should be noted that long-wavelength waves and medium-wavelength waves are measured in the diameter range of 38mm to 84mm, using the Optiflat optical surface wave measuring instrument manufactured by Phase Shift Technology Company, while short-wavelength waves are measured in the diameter range of 38mm to 84mm. The measurement was performed at three locations, namely the inner edge, the outer edge, and the circle between the inner edge and the outer edge, using a Newview 200 optical surface roughness meter manufactured by Zygo, and the average value was calculated. In addition, the measured values shown in the table are the average values of a large number of test pieces (300 or 500) manufactured in the examples or comparative examples.

In addition, a micrometer manufactured by Mitsutoyo Corporation was used to calculate the polishing amount by measuring the thickness of each test piece before and after polishing.

<tables><img file="TW563115B_D0001.tif" /></tables><img file="TW563115B_D0002.tif" />

The procedure for manufacturing test pieces of each example and the comparative example will now be explained.

(Example 1)

The inventor first used the floating plate glass manufacturing device shown in FIG. 7 to manufacture a lithium-alumina-silica type starting material glass plate. In particular, the glass material powder is added to the melting furnace so that the glass composition is 70mole% SiO₂, 15mole% Al₂O₃, 7mole% Li₂O and 8mole% Na₂O, and melt in the melting furnace. Then let the molten mixture flow into the forming tank to produce glass filaments Then, the glass ribbon is moved along the top of the molten tin, and the temperature of the forming tank is controlled according to the preset forming conditions to obtain good surface wave characteristics, and then the glass ribbon is transferred from the forming tank to the annealing furnace. Next, the glass ribbons obtained from the manufacturing batch were cut into rectangles to obtain 300 starting material glass plates with a thickness of about 1 mm.

Then, along the outer edge surface and the inner edge surface at the same time, use a diamond cutter to cut the starting material glass plate into a doughnut shape, so that the outside diameter becomes 95 mm and the inside diameter becomes 25 mm.

After that, use a grinding stone attached with diamond abrasive particles to grind off the inner and outer edges and cut the corners, and then use CeO₂Abrasive particles, mirror-polishing the inner edge surface and the outer edge surface including the corner portion.

Then, the surface of the glass plate of the starting material is subjected to precise grinding treatment for 40 minutes, and the abrasive is sent to the surface of the glass plate of the starting material. The preparation of the abrasive is to make the average particle diameter 1 μm and 90% diameter 3 μm CeO₂The abrasive particles were dispersed in the polishing liquid, and thus the test piece of Example 1 was prepared. It should be noted that the suede pad is used as a polishing pad.

(Example 2)

From 300 starting material glass plates in the same manufacturing batch of Example 1, the same disk processing and edge processing as Example 1 will be performed, and then the CeO of Example 1 will be used.₂The abrasive particles were subjected to precise grinding treatment for 60 minutes, and thus the test piece of Example 2 was manufactured.

(Example 3)

The manufacturing batch for preparing another glass ribbon uses the same glass as in Example 1. Material powder composition and forming conditions. Then cut the glass ribbon into a rectangle to obtain 500 starting material glass plates with a thickness of about 1 mm.

Then, perform the same disk processing and edge processing as in Example 1, and then use CeO with an average particle diameter of 1 μm and a 90% diameter of 2.8 μm₂The abrasive particles were subjected to precise grinding treatment for 60 minutes, and thus the test piece of Example 3 was manufactured.

(Example 4)

Obtain 300 glass plates of starting material from the same manufacturing batch of Example 3, and perform the same disk processing and edge processing as Example 1, and then use CeO with an average particle diameter of 0.3 μm and a 90% diameter of 1.2 μm.₂The abrasive particles were subjected to precise grinding treatment for 120 minutes, and thus the test piece of Example 4 was manufactured.

(Example 5)

The glass ribbon was prepared by using the same glass material powder composition as in Example 1, but changing the forming conditions to make the surface wave smaller. Then the glass ribbon was cut into a rectangle to obtain 300 starting material glass plates with a thickness of about 1 mm.

Then proceed with the same disk processing and edge processing as in Example 1, and then use the same CeO of Example 1₂The abrasive particles were subjected to precise grinding treatment for 20 minutes, and thus the test piece of Example 5 was manufactured.

(Example 6)

Obtain 300 glass plates of starting material from the same manufacturing batch of Example 1, and perform the same disk treatment and edge treatment as in Example 1, and then use CeO with an average particle diameter of 3 μm and 90% of a diameter of 8 μm.₂The grinding particles were pre-grinded for 7 minutes, and then the same CeO of Example 1 was used₂Grinding particles (average particle diameter of 1 μm and 90% diameter of 3 μm) for 20 minutes Grinding treatment, and thus the test piece of Example 6 was manufactured. Therefore, in Example 6, 7 minutes of pre-grinding and 20 minutes of precise grinding were performed, that is, a total of 27 minutes of surface grinding treatment.

(Example 7)

Obtain 500 glass plates of starting material from the same manufacturing batch of Example 3, and perform the same disk processing and edge processing as Example 1, and then use CeO with an average particle diameter of 3 μm and a 90% diameter of 7.5 μm.₂The grinding particles were pre-grinded for 9 minutes, and then the same CeO of Example 4 was used₂The abrasive particles (average particle diameter of 0.3 μm and 90% diameter of 1.2 μm) were subjected to precise grinding treatment for 30 minutes, and thus a test piece of Example 7 was manufactured. Therefore, in Example 7, 9 minutes of pre-grinding and 30 minutes of precise grinding were performed, that is, a total of 39 minutes of surface grinding treatment.

(Example 8)

Obtain 500 glass plates of starting material from the same manufacturing batch of Example 3, and perform the same disk processing and edge processing as in Example 1, and then use CeO with an average particle diameter of 1 μm and 90% of a diameter of 3 μm.₂The abrasive particles were subjected to a pre-grinding treatment for 40 minutes, and then colloidal silica with an average particle diameter of 0.02 μm and a 90% diameter of 0.03 μm was used for precision polishing for 30 minutes, thereby manufacturing a test piece of Example 8. Therefore, in Example 8, 40 minutes of pre-grinding and 30 minutes of precise grinding were performed, that is, a total of 70 minutes of surface grinding treatment.

(Example 9)

The starting material glass plate was manufactured using the same glass material powder composition as in Example 1, but a down-drawn plate glass manufacturing device was used, as shown in FIG. 9. special Yes, add the glass material powder to the melting furnace to prepare molten glass, and then use gravity to let the molten glass flow down from the platinum pores (slits) to form glass flakes, and then perform annealing treatment in the annealing furnace , And cut the glass sheet into a rectangle to obtain 300 glass plates of starting material.

Then, the same disk processing and edge processing as in Example 1 were performed, and thus the test piece of Example 9 was manufactured.

(Comparative example 1)

Use the same manufacturing batch of Example 1 to obtain 300 glass plates of starting material, and perform the same disk processing and edge processing as Example 1, and then use Al with an average particle diameter of 5.5 μm and 90% of a diameter of 10 μm₂O₃The abrasive particles were subjected to a rough grinding treatment for 35 minutes, and then subjected to a precise grinding treatment as in Example 1, thereby preparing a test piece of Comparative Example 1. In Comparative Example 1, a rough grinding treatment for 35 minutes and a precise grinding treatment for 40 minutes were performed, that is, a surface grinding treatment for a total of 75 minutes.

(Comparative Example 2)

300 glass plates of starting material were obtained from the same manufacturing batch of Example 1, and subjected to the same disk treatment and edge treatment as in Example 1, and then the surface grinding treatment was divided into three stages, rough grinding, pre-grinding and conventional Precise grinding on the surface. In particular, first use Al with an average particle diameter of 9 μm and 90% of a diameter of 20 μm₂O₃The abrasive particles are subjected to a rough grinding treatment for 20 minutes, and then CeO with an average particle diameter of 3 μm and a 90% diameter of 7.5 μm is used₂The grinding particles are pre-grinded for 30 minutes, and CeO as in Example 1 is used₂The abrasive particles (average particle diameter of 1 μm and 90% diameter of 3 μm) were subjected to precise grinding treatment for 40 minutes, thus preparing comparative example 2 Test piece. In Comparative Example 2, a rough grinding treatment of 20 minutes, a pre-grinding treatment of 30 minutes and a precise grinding treatment of 40 minutes were performed, that is, a total of 90 minutes of surface grinding treatment.

(Comparative Example 3)

Using the same glass material powder composition as in Example 1, the glass ribbon was manufactured by the floating plate glass manufacturing device, but without sufficient temperature control in the forming tank, the glass ribbon was cut into rectangles to obtain 300 pieces of about 1mm thick. Starting material glass plate.

Then, the same disk treatment and edge treatment as in Example 1 were carried out, and then the rough grinding treatment as in Comparative Example 2 was carried out for 20 minutes, and the precise grinding treatment as in Example 1 was carried out for 35 minutes, thus preparing the comparative example 3 Test piece. In Comparative Example 3, 20 minutes of rough grinding treatment and 35 minutes of precise grinding treatment were performed, that is, a total of 55 minutes of surface grinding treatment.

(Comparative Example 4)

From the same manufacturing batch of Comparative Example 3, 300 starting material glass plates were obtained, and the same disk treatment and edge treatment as in Example 1 were performed, and then the rough grinding treatment was performed under the same conditions of Example 6 for 60 minutes. And for 40 minutes of precise grinding treatment, a test piece of Comparative Example 4 was prepared.

(Comparative Example 5)

From the same manufacturing batch of Comparative Example 3, 300 glass plates of starting material were obtained, and the same disk processing and edge processing as in Example 1 were performed, and then CeO as in Example 1 was used.₂The abrasive particles were subjected to a precise grinding treatment for 200 minutes, and thus a test piece of Comparative Example 5 was prepared.

From the measurement results in Tables 1 and 2, it can be seen that the starting material glass in Example 1 The long-wavelength waves, medium-wavelength waves and short-wavelength waves of the glass plate are as low as 3.5 nm, 1.6 nm and 0.7 nm respectively. After precise grinding treatment, the long-wavelength waves, medium-wavelength waves and short-wavelength waves of the disk substrate are as low as 1.0 nm, 0.6 nm and 0.4 nm respectively. Therefore, it is possible to produce a disk substrate with excellent flatness, especially the mid-wavelength and short-wavelength waves are suppressed. In addition, the polishing amount is as low as 10 μm, so it is possible to obtain excellent surface wave characteristics with low polishing amount. In addition, when visual observation is used to verify whether there are micro-defects, very good results are obtained, that is, the micro-defects are only one of the 300 test specimens. Therefore, it has been found that the probability of occurrence of small defects is very low.

In Example 2, the grinding time was increased by 1.5 times compared with Example 1. As the polishing time increases, the polishing amount will become slightly to 15 μm, but the surface wave characteristics of the disk substrate will be further improved.

In Example 3, the magnetic disk substrate was prepared from the starting material glass plate under the same conditions as in Example 2. As can be seen from the table, a surface wave similar to Example 2 is thus obtained.

In Example 4, compared with Examples 1 to 3, CeO used as loose abrasive particles₂The particle diameter of the abrasive particles will decrease. In particular, the average particle diameter becomes 0.3 μm and the 90% diameter is 1.2 μm. Therefore, the polishing rate will be slightly slower, regardless of the long polishing time of 120 minutes, the polishing amount will be as low as 12 μm. However, compared with Examples 1 to 3, short-wavelength waves are improved. Therefore, it was found that finer loose abrasive particles can be used for precise grinding and reduce short-wavelength waves.

In Example 5, the surface wave characteristics of the starting material glass plate are better than those of Example 1. Up to 4 is good, especially for long-wavelength waves. Therefore, it is possible to manufacture a disk substrate with very good flatness in a short polishing time of 20 minutes and a low polishing volume of 5 μm.

In Example 6, CeO with an average particle diameter of 3 μm and 90% diameter of 8 μm was used₂The abrasive particles were subjected to pre-grinding treatment, and then subjected to the precise grinding treatment as in Example 1. Because of the pre-grinding treatment, it is possible to obtain a magnetic disk substrate with excellent surface quality characteristics in a shorter time than in Example 1. However, because it uses CeO whose average particle diameter is larger than the precision grinding process₂The grinding particles are pre-grinding, so the frequency of generating fine particles in 4 out of 300 test pieces is slightly higher than when only precision grinding is performed. In any case, the yield rate is 99%, so a sufficiently satisfactory result is obtained.

It can be seen from Examples 1 to 6, given that the starting material glass plate has approximately the same surface wave characteristics, the total grinding time will be reduced by pre-grinding.

In Example 7, approximately the same CeO as in Example 6 was also used₂Grind the particles for pre-grinding treatment, and then for precision grinding treatment. However, the CeO used in the precision grinding process₂The abrasive particles have an average particle diameter and 90% diameter, which are very low 0.3 μm and 1.2 μm, respectively. As a result, it can be seen that it is possible to obtain a magnetic disk substrate with excellent surface wave characteristics in a short time. In addition, in 5 out of 500 disk substrates, although the frequency of micro-defects is slightly increased compared to only the precision grinding process, the yield rate is still 99%, thus obtaining sufficiently satisfactory results.

In Example 8, CeO with a smaller particle diameter was used throughout₂Grinding particles for pre-grinding, especially 90% diameter of 3 μm, and Use fine colloidal silicon for precise grinding. Because the particle diameter is small, the grinding rate is slightly lower, especially the grinding amount is 10.3 μm in 70 minutes. However, to obtain good surface waves Laid properties.

In Example 9, the down-draw method was used to manufacture the starting material glass plate. It has been found that even if the starting material glass plate is manufactured by the down-draw method, with proper temperature control, the starting material glass plate with good surface wave characteristics can be prepared. In addition, as long as the starting material glass plate has a good surface With wave characteristics, a magnetic disk substrate with good flatness (surface wave characteristics) can be obtained, regardless of the method of manufacturing the starting material glass plate.

As mentioned above, in Examples 1 to 9, using the starting material glass plate with good surface wave characteristics, it is possible to carry out only precision grinding treatment or only pre-grinding treatment and precision grinding treatment without rough grinding treatment. Produce a magnetic disk substrate with good flatness and surface wave characteristics. In addition, because there is no rough grinding process, it is possible to manufacture a magnetic disk substrate in a very short time and with a very low grinding amount. In addition, the probability of occurrence of minor defects has proven to be as low as 1% or less.

In contrast to the above, in Comparative Example 1, A1 with an average particle diameter of 5.5 μm and a 90% diameter of 10 μm was used₂O₃For the abrasive particles, the starting material glass plate obtained from the same manufacturing batch in Example 1 was subjected to rough grinding treatment. After the precise grinding process, the measured surface wave characteristics of the disk substrate are that long-wavelength waves and medium-wavelength waves are as low as 1.0 nm and 0.8 nm, respectively, but short-wavelength waves increase to 1.5 nm. It is assumed that this is because the short-wavelength waves are newly formed after rough grinding. Incidentally, the surface wave characteristics were measured immediately after the rough grinding treatment, and it was found that the long-wavelength wave Waves have been suppressed to 2.5nm, but medium-wavelength waves and short-wavelength waves are as large as 1.8nm to 2.2nm, respectively. In addition, it has been found that through visual inspection, 72 of the 300 test pieces have minor defects, and it has been found that there is a probability of more than 20% of the manufactured defects.

In Comparative Example 2, the starting material glass plate obtained from the same manufacturing batch in Example 1 was subjected to a rough grinding treatment similar to that in Comparative Example 1. Therefore, it is assumed that medium-wavelength waves and short-wavelength waves are newly formed through rough grinding. Although it is possible to obtain good wave characteristics of the disk substrate surface, as shown in Table 2, in order to achieve this, a large amount of grinding must be performed on the substrate surface, especially 230 μm. If this is the case, the starting material glass plate must be made thicker at the beginning, and a large amount of grinding waste will be released, resulting in an increase in industrial waste.

In Comparative Example 3, rough grinding and precise grinding were performed as in Comparative Example 1, but a starting material glass plate with poor surface wave characteristics was used. Even with a lot of grinding, especially 210μm, the long-wavelength waves, medium-wavelength waves and short-wavelength waves of the disk substrate are 1.7nm, 1.0nm and 1.8nm respectively. In addition, it has been found that through visual inspection, 105 out of 300 test pieces have micro-defects, and the proportion of test pieces with micro-defects is greater than 30%.

In Comparative Example 4, the pre-grinding and precise grinding were performed as in Example 6, but the starting material glass plate obtained from the same manufacturing batch in Comparative Example 3 was used. It is possible to obtain a magnetic disk substrate with good surface wave characteristics, as shown in Table 2. However, because the surface wave characteristics of the starting material glass plate are very poor, in order to obtain a magnetic disk substrate with good surface wave characteristics, The grinding amount must be as high as 50 μm, and the total grinding time is as long as 100 minutes; therefore, this manufacturing method is not suitable for mass manufacturing.

In Comparative Example 5, the starting material glass plate obtained from the same manufacturing batch in Comparative Example 3 was used, and only the precise grinding treatment as in Example 1 was performed. As a result, in order to obtain good surface wave characteristics, a long polishing time of 200 minutes is required; therefore, this manufacturing method is not suitable for mass manufacturing.

(Second example)

Next, using the test pieces of Example 1 and Comparative Example 1, the inventors used a known sputtering method to sequentially build a base layer made of CrMo on the surface of each test piece, and a magnetic layer made of CoCrPt. Layer and a protective layer made of hydrogenated carbon, thus preparing a magnetic disk. Then carry out the drop height test, and the measurement and adjustment.

[Dropping height test]

The inventor conducted a drop height test, in which the magnetic read head was lowered when the disk was rotated, and evaluated the extremely small flying height when the magnetic read head can fly stably. For the test piece of Comparative Example 1, the descending height is as high as 11 nm, so there is a risk that it will not be able to cope with the low flying height of 10 nm or lower. For the test piece of Example 1, on the other hand, good results with a low fly height of 5 nm or less were obtained, so it was verified that the disk is suitable for low fly height use.

[Adjustment variable measurement]

Modulation M is defined in the following equation (1), where Vmax (mV) and Vmin (mV) are the maximum output and minimum output of the disk measured by an oscilloscope. Taking into account that the disk has good flatness, little surface adjustment, adjustment The change of M is preferably not more than 8%. M=((Vmax-Vmin)/(Vmax+Vmin))X100 (1)

For the disk of Comparative Example 1, the modulation M has a value of 10% or greater. For the disk of Example 1, the modulation M is as low as 4%, which shows that the disk of Example 1 has good flatness. .

Industrial application

According to the substrate for data recording media of the present invention and its manufacturing method, the substrate for data recording media is manufactured by precise grinding processing using only ultra-fine abrasive particles with a predetermined particle diameter, or only using a predetermined Pre-grinding treatment for fine abrasive particles with particle diameters and precise grinding treatment for ultra-fine abrasive particles with preset particle diameters. As a result, the use of the starting material glass plate with good surface wave characteristics can obtain a substrate with good flatness and good surface wave characteristics for data recording media in a short time and with a very low grinding amount. It is very useful in terms of output. In addition, because the substrate for data recording media has very good flatness, it can be ensured that even a small magnetic read head can follow the surface, and the substrate for data recording media of the present invention can be used as a current Substrate for data recording media with small size, large capacity and high recording density.

In addition, the starting material glass plate according to the present invention has good flatness and flatness, so it can be used in different applications that require a high degree of flatness and flatness.