JP3665777B2 - Method for manufacturing glass substrate for magnetic recording medium, and method for manufacturing magnetic recording medium - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a glass substrate for a magnetic recording medium used for a magnetic recording medium capable of high-density recording and reproduction, and a method for manufacturing a magnetic recording medium.
[0002]
[Prior art]
In recent years, there has been a demand for magnetic recording media that can cope with higher density recording. In order to achieve high density recording of the magnetic recording medium, it is important to reduce the flying height of the magnetic head with respect to the surface of the magnetic recording medium. Since the flying height of the magnetic head has a correlation with the surface roughness of the surface of the magnetic recording medium, attempts have been made to make the surface roughness of the surface of the magnetic recording medium and the substrate for the magnetic recording medium more smooth.
[0003]
Conventionally, a glass substrate has been used as a magnetic recording medium substrate for reasons such as mechanical durability and high smoothness. And as a method of smoothing a glass substrate, Unexamined-Japanese-Patent No. 7-240025 and Unexamined-Japanese-Patent No. 10-241144 are known.
[0004]
[Problems to be solved by the invention]
The method described in JP-A-7-240025 discloses a method for producing a magnetic disk substrate using a colloidal particle (colloidal silica) solution adjusted to have an acidic pH as a removal step (polishing step). Has been.
[0005]
Further, the method described in Japanese Patent Laid-Open No. 10-241144 is a magnetic recording medium in which a grinding process is followed by a first and second polishing process using cerium oxide + water, and a third polishing process using colloidal silica + water. A method for producing a glass substrate for use is disclosed.
[0006]
However, the former method uses an acidic aqueous solution as the polishing liquid, and has a problem of slurry aggregation / surface plate corrosion (oxidation). In the latter method, a three-step polishing process is performed in order to make the glass substrate surface highly smooth, and manufacturing costs are high. In the third polishing step, since a polishing liquid of colloidal silica + water is used, the polishing rate is slow, the polishing time is long, and the productivity is inferior. Furthermore, as cleaning after the polishing step, ultrasonic cleaning is performed using water or an alkaline aqueous solution. However, in the case of water, the colloidal silica polishing abrasive grains cannot be sufficiently removed and a polishing residue is generated. In the case of cleaning with an alkaline aqueous solution (usually 7 wt% (14.243 for PH)), the colloidal silica abrasive grains are dissolved and removed, so there is no problem of polishing residue. However, in order to remove the colloidal silica abrasive grains There is a problem that the glass substrate is damaged by the alkaline aqueous solution (concave defect) when the concentration of the alkaline aqueous solution, the cleaning condition, etc. is increased, and this concave defect forms a magnetic recording medium by forming at least a magnetic layer on the substrate. When recording / reproducing is performed, a signal error is caused.
[0007]
Therefore, the present invention has been made in view of the above problems, and provides a glass substrate for a magnetic recording medium with high smoothness free from polishing residue and concave defects, and a method for producing a glass substrate for magnetic recording medium with good productivity, It is another object of the present invention to provide a method for manufacturing a magnetic recording medium.
[0008]
[Means for Solving the Problems]
Means for solving the above problems has the following configuration.
(Configuration 1)
After the surface of the disk-shaped glass substrate is ground , the surface of the disk-shaped glass substrate is polished to a predetermined surface roughness by polishing with a polishing liquid containing colloidal silica abrasive grains and then performing alkali cleaning. A method for producing a glass substrate for a magnetic recording medium to obtain a glass substrate,
The polishing liquid is adjusted so that the pH is more than 10.2 and not more than 12 by containing alkali .
The pH of the cleaning liquid in the alkali cleaning is adjusted to be higher than the pH of the polishing liquid in the polishing .
(Configuration 2)
In Configuration 1, the pH of the cleaning liquid in the alkali cleaning is 13.87 to 14.2 .
(Configuration 3)
In Configuration 1 or 2, the alkali component of the cleaning liquid in the alkali cleaning is NaOH , and the NaOH concentration is 3 wt% to 5 wt%.
(Configuration 4)
In any one of configurations 1 to 3, the main surface of the glass substrate for magnetic recording has a surface roughness of Rmax ≦ 3 nm.
Here, Rmax is the maximum height measured using an atomic microscope (AFM).
(Configuration 5)
In any one of Configurations 1 to 4, the colloidal silica abrasive has a particle size of 0.02 to 0.5 μm.
(Configuration 6)
In any one of Configurations 1 to 5, the glass substrate for magnetic recording is made of aluminosilicate glass.
(Configuration 7)
At least a magnetic layer is formed on the main surface of the glass substrate for magnetic recording media obtained by the method for manufacturing a glass substrate for magnetic recording media according to any one of Structures 1 to 6.
[0009]
According to the said structure 1, high smoothness is obtained by using the fine abrasive | polishing agent of a colloidal silica abrasive grain as polishing liquid, and the pH of polishing liquid exceeds 10.2 by containing an alkali in polishing liquid, Since it is adjusted to be 12 or less, the polishing rate for the glass substrate can be increased while maintaining smoothness. Therefore, after the grinding process as in the prior art, a multi-stage polishing process using cerium oxide abrasive grains is performed, and the precision polishing using colloidal silica abrasive grains is performed as the final polishing process. The process can be omitted once or the productivity can be improved and a highly smooth glass substrate can be obtained.
[0010]
When the pH of the polishing liquid is alkaline at 10.2 or less, the polishing rate for the glass substrate is slow, which is not preferable because the productivity is poor. Moreover, when pH exceeds 12, since colloidal silica abrasives melt | dissolve and precision polishing cannot be performed, it is unpreferable. Moreover, when PH of polishing liquid becomes small, colloidal silica abrasive grains may aggregate and it may become unable to grind | polish suitably.
[0011]
Examples of the alkali that adjusts the pH of the polishing liquid include NaOH, KOH, and the like. It is preferable to adjust the pH of the polishing liquid with NaOH because it can be suitably polished.
[0012]
The pH of the polishing liquid is preferably 10.5 or more and 11 or less from the viewpoints of productivity and alkali resistance of the polishing pad.
[0013]
The average particle size of the colloidal silica abrasive is appropriately adjusted depending on the smoothness (surface roughness) of the substrate obtained after polishing. For example, it is set to 0.02 to 0.5 μm. In order to obtain a glass substrate with high smoothness (surface roughness Rmax ≦ 3 nm) capable of high-density recording / reproduction in recent years, the average abrasive diameter of colloidal silica needs to be 0.5 μm or less.
[0014]
Moreover, the density | concentration of a colloidal silica abrasive grain is suitably adjusted according to a processing speed and surface roughness. For example, it is preferably 20 to 35 wt% in consideration of the processing speed. As the abrasive concentration increases, the surface of the substrate becomes rougher.
[0015]
There is no restriction | limiting in particular in the material of the glass substrate used for this invention. Examples thereof include quartz glass, soda lime glass, aluminosilicate glass, borosilicate glass, aluminoborosilicate glass, alkali-free glass, and crystallized glass.
[0016]
After polishing with an alkali-containing colloidal silica abrasive, by performing alkali cleaning, the polishing residue of the colloidal silica can be surely eliminated, and the alkali used to dissolve and remove the colloidal silica abrasive Since the load (alkali concentration and PH) on the glass substrate for cleaning can be reduced, the occurrence of concave defects can be suppressed. The concentration of alkali cleaning after polishing is desirably higher than the alkali concentration in the polishing step in order to eliminate polishing residue, and is preferably pH 14 or higher. However, the concentration (pH) at which damage (concave defect) to the glass substrate due to alkali cleaning does not occur is good. As a result of researches by the present inventors from the above viewpoint, it is desirable that the pH of the cleaning solution suitable for alkali cleaning of the glass substrate after polishing is 13.87 to 14.20.
[0017]
By using the same alkali component, especially NaOH, as the alkali contained in the polishing liquid and the alkali used for the alkali cleaning after polishing, it is preferable because deposits such as abrasive residue on the substrate surface can be effectively removed. When NaOH is used in the alkali cleaning after the polishing, it is preferable that the concentration of NaOH contained in the cleaning liquid is 3 wt% to 5 wt%.
[0018]
The use of aluminosilicate glass as the material for the glass substrate is preferable because the chemical durability against alkali is good and the occurrence of concave defects can be reduced.
[0019]
The composition of an aluminosilicate glass having good chemical durability against alkali is a glass containing 58 to 75% by weight of SiO2, 5 to 23% by weight of Al2O3, 3 to 10% by weight of Li2O and 4 to 13% by weight of Na2O. Is mentioned.
[0020]
By forming at least a magnetic layer on the glass substrate for a magnetic recording medium obtained by the above configuration, a magnetic recording medium capable of high-density recording / reproduction is highly productive and highly reliable without causing an error. A medium is obtained.
[0021]
The material for the magnetic layer used in the present invention is not particularly limited. Examples thereof include CoCrPtB, CoCrPtTa, CoCrPtNi, CoCrPt, CoCrNiTa, CoCrTa, CoCrNi, and CoCrPtTaB.
[0022]
In addition, a seed layer, an underlayer, an intermediate layer, a protective layer, and a lubricating layer can be appropriately provided as necessary in accordance with magnetic characteristics, durability against a magnetic head, and sliding characteristics.
[0023]
The seed layer is provided for the purpose of controlling the crystal grain size of the layer formed thereon, and for example, a material such as NiAl, AlCo, CrTi, CrNi can be used.
[0024]
The underlayer generally has a bcc structure and is mainly provided for the purpose of improving the magnetostatic characteristics. For example, Cr or Cr alloy (CrMo, CrV, CrTi, CrW, CrTa, etc.) is used. Materials can be used.
[0025]
The intermediate layer generally has a hcp structure, and is provided for the purpose of adjusting the crystal orientation of the magnetic layer having the hcp structure. For example, a material such as CoCr, CoCrB, CoCrPt, or CoCrPtTa can be used. .
[0026]
The protective layer is provided for durability and corrosion resistance with respect to the magnetic head, and for example, materials such as carbon, hydrogenated carbon, carbon nitride, SiO2, and ZrO2 can be used.
[0027]
The lubricating layer is provided to improve the characteristics of the magnetic head, and for example, a perfluoropolyether lubricant is generally used.
[0028]
[Embodiments of the Invention]
The present invention will be specifically described with reference to examples.
[0029]
(Example 1)
In this example, (1) rough grinding step, (2) shape processing step, (3) end face polishing step, (4) fine grinding step, (5) first polishing step, (6) final polishing step, (7 And (8) a chemical strengthening step, (9) a post-strengthening cleaning step, and (10) a magnetic disk manufacturing step. Hereinafter, each process will be described.
[0030]
(1) Rough grinding process First, the molten glass is directly pressed using an upper mold, a lower mold, and a body mold to obtain a glass substrate made of a disc-shaped aluminosilicate glass having a diameter of 66 mmφ and a thickness of 1.2 mm. It was. In this case, in addition to the direct press, a disk-shaped glass substrate may be obtained by cutting out from a sheet glass formed by a downdraw method or a float method with a grinding wheel. As the aluminosilicate glass, chemically strengthened glass for glass containing SiO2: 58 to 75% by weight, Al2O3: 5 to 23% by weight, LiO2: 3 to 10% by weight, and Na2O: 4 to 13% by weight. It was used.
[0031]
Next, a grinding process was performed on the glass substrate. The grinding process aims to improve dimensional accuracy and shape accuracy. The grinding process was performed using a double-side grinding apparatus, and the grain size of the abrasive grains was # 400. Specifically, by using alumina abrasive grains having a particle size of # 400, the load L is set to about 100 kg, and the inner and outer rotation gears are rotated, so that both surfaces of the glass substrate housed in the carrier are surface systems 0 to 0. Finished to about 1 μm and a surface roughness Rmax of about 6 μm.
[0032]
(2) Shape processing step Next, a cylindrical grindstone is used to make a hole in the central portion of the glass substrate, and the outer peripheral end surface is ground to a diameter of 65 mmφ, and then a predetermined chamfer is formed on the outer peripheral end surface and the inner peripheral end surface. Processed. The surface roughness of the glass substrate end face (inner circumference, outer circumference) at this time was 4 μm in Rmax.
[0033]
(3) End face polishing step Next, the surface roughness of the end face (inner circumference, outer circumference) of the glass substrate was polished by brush polishing to about 1 μm at Rmax and about 0.3 μm at Ra while rotating the glass substrate. The surface of the glass substrate after the end face polishing step was washed with water.
[0034]
(4) Fine grinding step Next, the grain size of the abrasive grains was changed to # 1000, and the glass substrate surface was ground, so that the flatness was 3 μm, the surface roughness Rmax was about 2 μm, and Ra was about 0.2 μm. Rmax and Ra are measured by an atomic force microscope (AFM) (Nanoscope manufactured by Digital Instruments Co., Ltd.), and flatness is measured by a flatness measuring device. The highest part and the lowest part of the substrate surface. The distance (height difference) in the vertical direction (direction perpendicular to the surface). The glass substrate after the fine grinding step was washed by sequentially immersing it in each washing layer of neutral detergent and water.
[0035]
(5) First polishing step Next, a polishing step was performed. The polishing process is intended to remove scratches and distortions remaining in the above-described polishing process, and was performed using a double-side polishing apparatus. Specifically, a hard polisher was used as the polisher, and the polishing was performed under the following conditions.
Polishing liquid: cerium oxide (average particle diameter: 1.5 μm) + water load: 80 to 100 g / cm 2
Polishing time: 30-50 minutes Removal amount: 35-45 μm
The glass substrate after the first polishing step was sequentially immersed in each cleaning layer of neutral detergent, pure water, pure water, IPA, and IPA (steam drying) for cleaning.
[0036]
(6) Final polishing step Next, the same double-side polishing apparatus as the type used in the first polishing step was used, and the final polishing step was carried out by changing the polisher to a soft polisher. Polishing conditions are
Polishing liquid: colloidal silica (average particle size: 0.15 μm, polishing agent concentration: 32 wt%) + NaOH (concentration: 1 mol / l addition amount: 400 ml) + water (pH: 10.5 (measured by pH Scan manufactured by EUTEC))
Load: 60-120 g / cm2
Polishing time: 5 to 40 minutes Removal amount: 0.5 to 8 μm
It was.
As shown in FIG. 1, the polishing rate was 0.07 μm / min.
[0037]
(7) Cleaning process after final polishing The glass substrate after the final polishing process was immersed in an aqueous NaOH solution having a concentration of 3 to 5 wt% for alkali cleaning. The cleaning was performed by applying ultrasonic waves. Furthermore, it wash | cleaned by immersing in each washing tank of neutral detergent, a pure water, a pure water, IPA, and IPA (steam drying) sequentially. When the surface of the obtained glass substrate was observed with an AFM (Nanoscope manufactured by Digital Instruments), the polishing residue of colloidal silica was not confirmed. Moreover, there was no concave defect due to alkali cleaning damage.
The pH of the NaOH aqueous solution having a concentration of 3 wt% to 5 wt% is 13.875 to 14.097.
[0038]
(8) Chemical strengthening step Next, chemical strengthening was performed on the glass substrate after the grinding, polishing, and final post-polishing cleaning steps. For chemical strengthening, a chemically strengthened salt prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) is prepared. The chemically strengthened salt is heated to 375 ° C., and a cleaned glass substrate preheated to 300 ° C. It was immersed for 3 hours.
Thus, by immersing in the chemically strengthened salt, the lithium ions and sodium ions on the surface of the glass substrate are replaced with sodium ions and potassium ions in the chemically strengthened salt, respectively, and the glass substrate is strengthened. The thickness of the compressive stress layer formed on the surface layer of the glass substrate was about 100 to 200 μm. The glass substrate after the chemical strengthening was immersed in a 20 ° C. water bath and rapidly cooled, and maintained for about 10 minutes.
[0039]
(9) Cleaning step after strengthening The glass substrate after the rapid cooling was immersed in sulfuric acid heated to about 40 ° C. and cleaned while applying ultrasonic waves. When the surface roughness of the glass substrate thus obtained was measured with an AFM (Nanoscope manufactured by Digital Instruments), good results were obtained with Rmax = 2.62 nm and Ra = 0.31 nm.
Therefore, Rmax / Ra is 8.45.
Rmax and Ra are based on definitions defined in Japanese Industrial Standard (JIS) B0601.
[0040]
(10) Magnetic disk manufacturing process A NiAl seed layer, a CrV underlayer, a CoCrPtB magnetic layer, and a hydrogenated carbon protective layer are formed on a glass substrate for a magnetic disk obtained through the above-described processes using a sputtering apparatus. A perfluoropolyether lubricating layer was formed by a dip method to produce a magnetic disk.
When the obtained magnetic disk was subjected to a glide height and load / unload test (400,000 times), it was confirmed that no contact occurred between the head and the medium up to a flying height of 4.5 nm. Also, no crash occurred and there was no signal error in the recording / reproducing test. In terms of glide height, it is preferable that contact between the head and the medium does not occur up to 5.0 nm. That is, the glide height is preferably 5.0 nm or less.
[0041]
(Example 2)
Next, a glass substrate for a magnetic disk and a magnetic disk were produced in the same manner as in Example 1 except that the amount of alkali contained in the polishing liquid was adjusted and the pH concentration of the polishing liquid was adjusted.
[0042]
As a result, as shown in FIG. 1, it can be confirmed that the polishing rate for the glass substrate is improved as the pH concentration is increased. In addition, when the pH concentration of the polishing liquid exceeded 12, the dissolution of colloidal silica started and the processing was impossible.
[0043]
In addition, when the surface roughness of the glass substrate obtained by changing the pH concentration within the range where the pH concentration of the polishing liquid is 12 or less was confirmed by AFM (Nanoscope manufactured by Digital Instruments), it was about the same as Example 1. It was confirmed that there was almost no change in the surface roughness.
[0044]
As in Example 1, the polishing residue of colloidal silica on the surface of the obtained glass substrate was not confirmed, and there was no concave defect due to alkali cleaning damage.
[0045]
Further, when the obtained magnetic disk was subjected to a glide height and a load / unload test (400,000 times), it was confirmed that no contact occurred between the head and the medium up to a flying height of 4.5 nm. . Also, no crash occurred and there was no signal error in the recording / reproducing test.
[0046]
(Comparative Example 1)
Next, in the final polishing step in Example 1, a glass substrate for a magnetic disk and a magnetic disk were produced in the same manner as in Example 1 except that NaOH was not added as the polishing liquid (pH concentration of the polishing liquid: 10.2). . In order to eliminate the polishing residue of the colloidal silica abrasive grains, the NaOH concentration in the alkali cleaning was set to 7 wt%, and ultrasonic waves were strongly applied. The pH was 14.243 when the NaOH concentration in alkali cleaning was 7 wt%. The results of Comparative Example 1 are shown in FIG.
[0047]
As a result, as shown in FIG. 1, the polishing rate decreased to 0.04 μm / min. Accordingly, it takes an extra polishing time to finish the surface roughness similar to that of the embodiment, which corresponds to 100 sheets compared to the number of sheets produced. (In addition, as disclosed in Japanese Patent Laid-Open No. 10-241144, when the polishing process is performed in three stages and compared with the embodiment, it corresponds to 150 sheets as compared with the number of production.)
[0048]
In Example 1, since the polishing rate was 0.07 μm / min, for example, when the removal amount necessary for polishing is 1.5 μm, a polishing time of 21.4 minutes is required.
In Comparative Example 1, the polishing rate was 0.04 μm / min. Therefore, for example, when the removal amount necessary for polishing is 1.5 μm, a polishing time of 37.5 minutes is required.
[0049]
Therefore, for example, in the case of using a polishing apparatus that polishes 100 glass substrates for a magnetic disk at a time, in the case of Example 1, about 300 sheets can be polished in one hour. In the case of Example 1, since only about 100 to less than 200 sheets can be polished in one hour, the manufacturing cost increases.
In the present invention, the polishing rate is preferably 0.05 μm / min or more. In this case, for example, when the removal amount necessary for the polishing process is 1.5 μm, the polishing time is 30 minutes. For example, a polishing apparatus that polishes 100 glass substrates for magnetic disks at a time is used. In such a case, 200 sheets can be polished in one hour.
[0050]
In addition, the polishing residue of colloidal silica on the surface of the glass substrate was not confirmed, but the alkali (NaOH) concentration was high to remove the abrasive, the cleaning conditions (ultrasonic waves) were strong, and concave defects due to alkali cleaning damage were also observed It was.
[0051]
Further, as a result of performing a glide height and a load / unload test on the obtained magnetic disk, no difference from the example was observed, but a signal error due to a concave defect was confirmed in the recording / reproducing test.
[0052]
(Example 3)
In the final polishing step (6) of Example 1, the alkali contained in the polishing liquid was replaced with NaOH to obtain KOH (Example 3). The same glass substrate by the same manufacturing method as in Example 1 except that the alkali contained in the polishing liquid is changed to KOH. The concentration of KOH was adjusted so that the polishing solution had a pH of 10.8. As a result, the polishing rate was 0.07 μm / min. When the surface roughness of the obtained glass substrate was measured in the same manner as in Example 1, Rmax = 2.91 nm and Ra = 0.29 nm. Therefore, Rmax / Ra = 10. Moreover, the polishing residue and the concave defect due to alkali cleaning damage were not confirmed.
[0053]
The obtained magnetic disk glass substrate was subjected to (10) magnetic disk manufacturing process in the same manner as in Example 1, and the obtained magnetic disk was tested in the same manner as in Example 1. As a result, the flying height was up to 4.8 nm. No contact occurred between the head and the medium. Also, no crash occurred and there was no signal error in the recording / reproducing test.
Comparing the results of Example 1 and Example 3 with the results, it can be seen that suitable results were obtained also in Example 3. In Example 1, the glide height was 4.5 nm. In Example 3, the glide height is slightly deteriorated to 4.8 nm. This is considered to be due to the fact that Rmax / Ra was 10 or more in Example 3. From the viewpoint of glide height, in the present invention, it is considered preferable that Rmax / Ra is less than 10.
[0054]
In addition, when the cause that the glide height was slightly deteriorated in Example 3 compared with Example 1 was investigated, it could not be confirmed by visual inspection, but as a result of precision inspection using an electron microscope (SEM), a very small amount was confirmed. It was found that the abrasive residue remained slightly on the substrate surface.
[0055]
(Reference example)
Next, a glass substrate for a magnetic disk and a magnetic disk were produced in the same manner as in Example 1 except that the glass substrate in Example 1 was changed to quartz glass and NaOH contained in the polishing liquid was changed.
[0056]
As a result, even if the pH concentration was changed, the polishing rate was hardly changed. Further, there were no concave defects due to alkali cleaning damage.
[0057]
Further, the same results as in Examples were obtained in the glide height, load / unload test, and recording / reproduction test for the obtained magnetic disk.
[0058]
Therefore, comparing the results of the example and the reference example, it was confirmed that an aluminosilicate glass that can adjust the polishing rate in consideration of productivity and has good chemical durability against alkali is suitable.
[0059]
【The invention's effect】
According to the present invention, it is possible to obtain a glass substrate for a magnetic recording medium having high smoothness free from polishing residue and concave defects, and to achieve high density recording of the magnetic recording medium.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the pH concentration of a polishing liquid and the polishing rate.

Claims (7)

After the surface of the disk-shaped glass substrate is ground , the surface of the disk-shaped glass substrate is polished to a predetermined surface roughness by polishing with a polishing liquid containing colloidal silica abrasive grains and then performing alkali cleaning. A method for producing a glass substrate for a magnetic recording medium to obtain a glass substrate,
The polishing liquid is adjusted so that the pH is more than 10.2 and not more than 12 by containing alkali .
The method for producing a glass substrate for a magnetic recording medium , wherein the pH of the cleaning liquid in the alkali cleaning is adjusted to be higher than the pH of the polishing liquid in the polishing . The pH of the cleaning solution in the alkali cleaning is 13.87 ~ 14.2 The method for producing a glass substrate for a magnetic recording medium according to claim 1, wherein: The alkali component of the cleaning liquid in the alkali cleaning is NaOH And that NaOH Concentration Three The method for producing a glass substrate for a magnetic recording medium according to claim 1, wherein the glass substrate is for wt% to 5 wt%. The surface roughness of the main surface of the glass substrate for magnetic recording is Rmax ≦ Three The method for producing a glass substrate for a magnetic recording medium according to any one of claims 1 to 3, wherein the thickness is nm.
However, Rmax Is the maximum height measured using an atomic force microscope (AFM). The colloidal silica abrasive has a particle size of 0.02 ~ 0.5 The method for producing a glass substrate for a magnetic recording medium according to any one of claims 1 to 4, wherein the glass substrate is μm. The magnetic recording glass substrate, method of manufacturing a glass substrate for a magnetic recording medium according to any one of claims 1 to 5, characterized in that it consists of aluminosilicate glass. A magnetic recording layer comprising at least a magnetic layer formed on a main surface of the glass substrate for a magnetic recording medium obtained by the method for manufacturing a glass substrate for a magnetic recording medium according to any one of claims 1 to 6. A method for manufacturing a medium.

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