JP2002150548A - Method of manufacturing glass substrate for information recording medium and method of manufacturing information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a glass substrate for information recording medium which maintains high surface smoothness while suppressing the occurrence of a surface defect and can be rapidly polished, and a method of manufacturing an information recording medium. SOLUTION: When a polishing liquid is interposed between the surface of a glass substrate and a polishing member and the glass substrate is subjected to polishing by relatively moving the glass substrate and the polishing member, the glass substrate is a crystallized glass having a glass phase and ceramics phase on at least the substrate surface and a polishing liquid prepared by mixing a first polishing agent having a mechanochemical polishing effect to the glass phase and a second polishing agent having a mechanochemical polishing effect to the ceramics phase is used as the polishing liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a glass substrate for an information recording medium used for an information recording medium such as a magnetic disk, a magneto-optical disk, and an optical disk, and a method of manufacturing the information recording medium.

[0002]

2. Description of the Related Art As a typical information recording medium, there is a magnetic disk. Until now, aluminum alloys have been mainly used as substrate materials for magnetic disks. Recently, the flying height of a magnetic head has been remarkably reduced with the miniaturization of hard disk drives for notebook personal computers and the densification of magnetic recording. Accordingly, extremely high accuracy has been required for the surface smoothness of the magnetic disk substrate.

[0003] However, in response to the above demand, aluminum alloys are not necessarily sufficiently hard, and even if polishing is performed using a high-precision abrasive and machine tools, this polishing is not possible. The surface may be plastically deformed, and it is difficult to manufacture a flat surface with a high degree of accuracy. Even if nickel-phosphorus plating is applied to the surface of an aluminum alloy, it is extremely difficult to make the average surface roughness Ra 5 angstrom or less. Further, as hard disk drives have become smaller and thinner, there is a strong demand for reducing the thickness of the magnetic disk substrate. However, in response to such a request,
Since the aluminum alloy has insufficient strength and rigidity, it is difficult to make the disk thin while maintaining a predetermined strength required by the specifications of the hard disk drive.

Therefore, as a substrate for a magnetic disk that requires high strength, high rigidity, high impact resistance, and high surface smoothness,
Glass substrates have appeared. As a glass substrate for a magnetic disk, a chemically strengthened glass substrate whose substrate surface is strengthened by an ion exchange method or the like, a crystallized glass substrate subjected to a crystallization treatment, and the like are known. Among them, a crystallized glass substrate having high strength, high rigidity, and high impact resistance has attracted attention in recent years.

Since the surface of a crystallized glass substrate is composed of a crystal part and an amorphous part, even if the substrate surface is precisely polished, the average particle size of the crystal particles in the crystal part is large, so that high surface smoothness can be obtained. However, in recent years, there has been proposed a crystallized glass substrate capable of obtaining high surface smoothness for the purpose of reducing the average particle size of the crystal particles (for example, Japanese Patent Application No. 2000-139,197).
000-216159, etc.). In order to obtain high surface smoothness, the precision polishing method is also an important element in addition to the refinement of the average particle diameter of the crystal particles described above. As a conventional method for polishing a crystallized glass substrate, for example,
No. 4656, and Japanese Patent No. 2736869.
And those described in the specification.

In the method of polishing a crystallized glass substrate described in Japanese Patent Publication No. 4-4656, a spherical anhydrous alumina fine powder having a specific surface area of 130 m ² / g or less and a particle size of 320 angstrom or less is suspended in pure water. Using the liquid as a polishing liquid,
A method for manufacturing a glass substrate for a magnetic disk in which a surface layer having a surface roughness of 80 Å or less and no distortion is formed by precision polishing with a lap load of 0.1 to ² kg / cm ² is described.

[0007] Japanese Patent No. 2,736,869 describes this.
The method of polishing a crystallized glass substrate described in
Titanium (Li_TwoO.2SiO_Two) And α-quartz (α-S
iO _Two), Α-quartz grown crystal particles aggregate,
Crystallized glass having a spherical particle structure of 0.3 to 3.0 μm
Polish the substrate with an abrasive with an abrasive particle size smaller than the particle size of the spherical particles.
Is described. Specifically, the average grain
It has a crystalline phase in which spherical particles with a diameter of 3 μm or less are dispersed.
The crystallized glass to be converted to an acid having a particle size equal to or greater than that of the spherical particles.
After polishing with cerium bromide, smaller than the particle size of the spherical particles
To be polished with colloidal silica
To obtain a smooth surface with an average surface roughness of 18 Å
It is described.

[0008]

As described above, in the conventional method for polishing a crystallized glass substrate, aluminum oxide, cerium oxide, colloidal silica or the like is used. However, even when cerium oxide, which is generally used for precision polishing of amorphous glass (amorphous glass: for example, chemically strengthened glass), is applied to polishing of crystallized glass, polishing is performed between the crystal part and the amorphous part. It was found that the difference in speed was large, and fine protrusions and concave portions were formed on the polished surface, and high smoothness could not be obtained.

On the other hand, when aluminum oxide is used,
The abrasive grains are hard, have a strong mechanical polishing action, and cause micro scratches on the polished surface. In addition, when colloidal silica is used, the above problem does not occur,
Although a polished surface having an average surface roughness Ra of less than 1 nm without a surface defect can be obtained, colloidal silica has a very low polishing rate and extremely poor processing efficiency. In addition, clogging of the polishing pad is apt to occur due to the chemical action in the polishing liquid, and the abrasive grains are as small as several nm to several hundred nm, so that they are not caught by the polishing pad and slip with the workpiece. I understand. That is, there has been a problem that the polishing rate becomes slow as the polishing time elapses. The present invention has been made under the above-mentioned background, and a method of manufacturing a glass substrate for an information recording medium and an information recording medium capable of maintaining high surface smoothness while suppressing occurrence of surface defects and capable of quick polishing. It is an object of the present invention to provide a method for producing the same.

[0010]

Means for Solving the Problems As means for solving the above problems, a first means is to interpose a polishing liquid between the surface of a glass substrate and a polishing member, and to connect the glass substrate and the polishing member to each other. In the method for manufacturing a glass substrate for an information recording medium, which is polished by relative movement, the glass substrate is crystallized glass having at least a glass phase and a ceramic phase on a substrate surface, and the polishing liquid is a glass phase ( A first abrasive having a mechanochemical (mechanochemical) polishing action on the amorphous phase) and a second abrasive having a mainly mechanical (mechanical) polishing action on the ceramics phase (crystal phase).
A method for manufacturing a glass substrate for an information recording medium, characterized by being mixed with an abrasive. The second means is
As the first abrasive having a mechanochemical (mechanochemical) polishing action on the glass phase (amorphous phase), at least one selected from cerium oxide, zirconium oxide, iron oxide and manganese oxide And mainly mechanically (mechanically) with respect to the ceramic phase (crystal phase).
The second abrasive having an effective polishing action is at least one selected from colloidal silica and titanium oxide. The method according to the first means, wherein the glass substrate for an information recording medium is manufactured. The third means is that the content of the second abrasive having a mainly mechanical (mechanical) polishing action on the ceramic phase (crystal phase) in the polishing liquid is 3 to 30 wt%. A method of manufacturing a glass substrate for an information recording medium according to the first or second means. The fourth means is to adjust the content of the first abrasive having a mechanochemical (mechanical) polishing action on the glass phase (amorphous phase) in the polishing liquid,
A method of manufacturing a glass substrate for an information recording medium according to a third means, characterized in that the content is 1 to 20 wt%. Fifth
Means, a glass substrate held by a carrier,
A method of manufacturing a glass substrate for an information recording medium, comprising a polishing step of polishing a surface of a glass substrate by sandwiching the upper and lower platens covered with a polishing cloth and supplying a polishing liquid to rotate the respective upper and lower platens. The polishing liquid, with one or both of cerium oxide and zirconium oxide,
A method for producing a glass substrate for an information recording medium, wherein the glass substrate is a mixture of colloidal silica. Sixth
The means is a method for producing a glass substrate for an information recording medium according to the fifth means, wherein the content of colloidal silica contained in the polishing liquid is 3 to 30 wt%. The seventh means is that the content of cerium oxide and / or zirconium oxide in the polishing liquid is 1 to 20 wt.
% Of the glass substrate for an information recording medium according to the sixth means. Eighth means is that the cerium oxide and zirconium oxide have an average particle size of 0.1.
1 to 3 μm, the average particle size of colloidal silica is 0.01 to
A method of manufacturing a glass substrate for an information recording medium according to any one of the fifth to seventh means, wherein the thickness is 0.2 μm. Ninth means is the method for manufacturing a glass substrate for an information recording medium according to any one of the fifth to eighth means, wherein the substrate is a crystallized glass substrate. A tenth means is the method for producing a glass substrate for an information recording medium according to the first or ninth means, wherein the main crystal of the crystallized glass is enstatite and / or a solid solution thereof. An eleventh means is the method for producing a glass substrate for an information recording medium according to the first or ninth means, wherein the average particle diameter of the crystal particles of the crystallized glass is 100 nm or less. The twelfth means is the first to
An information recording medium manufacturing method characterized by forming at least a recording layer on an information recording medium glass substrate manufactured by the method for manufacturing an information recording medium glass substrate according to any of the eleventh means. . The thirteenth means is
The method according to the twelfth aspect, wherein the recording layer is a magnetic layer.

[0011] In the method of manufacturing a glass substrate for an information recording medium according to the first means, when the glass substrate is a crystallized glass substrate having a glass phase and a ceramic phase, a mechanochemical polishing action is performed on the glass phase. By using a mixture of the first abrasive having the above and the second abrasive having a mechanical polishing action on the ceramic phase, it is possible to obtain a glass substrate having a high polishing rate and a higher surface smoothness. Is possible. This point has been elucidated for the first time as a result of the inventors repeating experiments by trial and error for various abrasives. That is, in the course of the experimental results, the type of the first abrasive is changed, a plurality of types are combined as the first abrasive, or the polishing with the second abrasive is performed after the polishing with the first abrasive. Attempts to do so have been made thoroughly under various conditions. However, in both cases, no results were obtained that sufficiently satisfied both the polishing accuracy and the polishing time from a practical viewpoint. Thus, finally, an attempt was made to mix and polish the first abrasive and the second abrasive, just in case. This attempt was predicted to some extent as a combination of the polishing action of the first abrasive alone and the polishing action of the second abrasive alone, which had been obtained up to that point, and was not so expected according to the prediction. However, contrary to the prediction, it has been found that as the experiment progresses, a remarkable action which cannot be explained as an action obtained by simply combining the actions of the above-mentioned single abrasives can be obtained. In particular, it has been found that the polishing time can be remarkably shortened while the polishing accuracy is kept within a predetermined accuracy even for a crystallized glass substrate which has been quite difficult to date. The present invention has been made based on such clarified facts.

In this case, as a polishing method, a plurality of glass substrates held by a carrier are sandwiched between upper and lower platens covered with a polishing cloth, and both surfaces of the glass substrate are polished by rotating the upper and lower platens. A double-side polishing method, a polishing method in which a brush hair made of nylon or the like is rotated on the surface of a glass substrate to polish the end surface of the substrate, and a polishing method in which a polishing tape is pressed while rotating the glass substrate to polish the substrate surface. Can be used.

The glass type and composition ratio of the glass substrate used in the present invention are not particularly limited. For example, aluminosilicate glass, soda lime glass, sodaaluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, crystallized glass, and the like can be given. In order to improve the mechanical properties of the glass substrate,
The present invention can be applied to a chemically strengthened glass substrate chemically strengthened by a low-temperature ion exchange method, and a crystallized glass substrate whose surface is crystallized by heat treatment. In particular, the present invention is useful for a crystallized glass substrate having a glass phase and a ceramic phase.

Further, as the polishing agent having a mechanochemical polishing action on the glass phase as in the second means,
As at least one abrasive selected from cerium oxide, zirconium oxide, iron oxide, and manganese oxide, as the abrasive having a mechanical polishing action on the ceramic phase, selected from colloidal silica and titanium oxide At least one abrasive can be used. Although colloidal silica is included in a silica abrasive in a broad sense, fumed silica or silica (powder) can be used instead.

The polishing rate is increased by setting the content of the polishing agent having a mechanical polishing action on the ceramic phase in the polishing liquid as 3% to 30% by weight as in the third means. It is preferable because a glass substrate having high surface smoothness with few surface defects can be obtained. When the content is less than 3 wt%, surface defects called pits (concave defects) occur on the surface of the glass substrate, which is not preferable. Clogging occurs and the polishing rate decreases, which is not preferable.

Further, as in the fourth means, by setting the content of the polishing agent having a mechanochemical polishing action on the glass phase in the polishing liquid to 1 to 20 wt%, the polishing rate can be reduced. It is preferable because a glass substrate having high surface smoothness can be obtained quickly and with few surface defects. If the amount is less than 1 wt%, the polishing rate decreases, which is not preferable.
Exceeding this is not preferred because the cleaning property after polishing deteriorates and the production cost increases.

In a preferred embodiment of the above-mentioned means, as in the fifth means, the polishing liquid is prepared by mixing one or both of cerium oxide and zirconium oxide with colloidal silica, thereby reducing the polishing rate. Is fast,
Further, a glass substrate having high surface smoothness can be obtained. In this case, the content of colloidal silica in the polishing liquid is 3
It is preferable to set it to 30 wt%. The reason for the upper limit value and the lower limit value is as described in the third means. Also,
It is preferable that the content of cerium oxide and / or zirconium oxide in the polishing liquid is 1 to 20% by weight. The reason for the upper limit value and the lower limit value is as described in the fourth means. Further, as in the eighth means, the average particle diameter of cerium oxide and zirconium oxide is 0.1 to 3 μm,
The average particle size of the colloidal silica is preferably 0.01 to 0.2 μm.

The polishing step can be performed once or in a plurality of steps. When performed in a plurality of stages, usually performed after the grinding step, the process-affected layer on the surface of the glass substrate, removing scratches, a polishing step performed for the purpose of controlling the end shape of the glass substrate, and a glass And a final polishing step performed for the purpose of smoothing the substrate surface and removing surface defects.

In the former step, a polishing pad (hard polisher) made of relatively hard urethane foam is used, and in the latter step, a polishing pad (soft polisher) made of relatively soft artificial leather suede is used. The primary purpose of the primary polishing is to remove surface defects such as scratches left by grinding, so that the primary focus is on the polishing rate. In final polishing, control of surface roughness and use of hard pad
The purpose is to completely remove the small surface defects remaining in the next polishing, and use a soft pad even if the processing speed is sacrificed.

In the case where the polishing step is performed in a plurality of steps, in the former polishing step, the preferable range of the content of the abrasive (colloidal silica or the like) in the third means and the sixth means is 10 to 30 wt%. It is. The preferable range of the content of the abrasive (cerium oxide, zirconium oxide, etc.) in the fourth means and the seventh means is 1 to 20% by weight. The particle size of the abrasive in the eighth means is such that colloidal silica or the like has a particle size of 0.01 to 0.2 μm, cerium oxide,
The particle size of zirconium oxide or the like is 1.5 to 3 μm.

In the latter polishing step, the preferred range of the content of the abrasive (colloidal silica or the like) in the third means and the sixth means is 3 to 30 wt%. In order to maintain the shape of the edge of the substrate obtained by the former polishing step, it is more preferably 3 to 10% by weight. The preferable range of the content of the abrasive (cerium oxide, zirconium oxide, etc.) in the fourth means and the seventh means is 1 to 20 wt%.
It is. The particle size of the abrasive in the eighth means is 0.01 to 0.2 μm for colloidal silica and the like, and 0.1 to 1.5 μm for cerium oxide and zirconium oxide.
It is preferable that

The material of the hard polisher and the soft polisher used in the polishing step is not particularly limited. As the hard polisher, a urethane pad, a nonwoven fabric pad, an epoxy resin pad, or the like can be used. As the soft polisher, a suede pad, a nonwoven fabric pad, or the like can be used.

Further, as in the ninth means, the method for producing a glass substrate for an information recording medium of the present invention is particularly useful for a crystallized glass substrate. Examples of the crystallized glass include those having main crystals of enstatite, mullite, fosterite, cordierite, quartz (α-quartz, β-quartz), spinel, garnite, canasite, lithium disilicate, and the like.

Above all, as in the tenth means, crystallized glass having enstatite and / or a solid solution thereof as a main crystal is very easy to polish, and a desired surface roughness can be obtained in a relatively short time. This is preferable from the viewpoint of the production advantage, the advantage of obtaining a high surface smoothness with a small crystal particle diameter, and the advantage of the mechanical properties that a high Young's modulus can be obtained even with a small crystal particle diameter. Specifically, S
iO _2: 35 to 65 mol%, Al ₂ O _3: 5~25 mol%, MgO: 10 to 40 mol%, TiO _2: 5~15 mol%, Y ₂ O _3: 0~10 mol%, ZrO ₂ : 0-6 mol%, R ₂ O: 0 to 5 mol% (wherein, R represents, Li, Na,
K represents at least one member selected from the group consisting of
O: 0 to 5 mol% (where R represents at least one selected from the group consisting of Ca, Sr and Ba), As ₂ O ₃ +
Sb ₂ O ₃ : 0 to 2 mol%, SiO ₂ + Al ₂ O ₃ + MgO
+ TiO ₂ : 92 mol% or more, and crystallized glass in which the main crystal is enstatite and / or a solid solution thereof.

Further, as in the eleventh means, it is preferable that the average particle diameter of the crystal particles of the crystallized glass is 100 nm or less. Preferably, it is 50 nm or less, more preferably, 30 nm or less. If the average particle size of the crystal particles exceeds 100 nm, not only the mechanical strength of the glass is reduced, but also the crystal may be lost during polishing, which may deteriorate the surface roughness of the glass substrate. Control of the size of such crystal grains is mainly
It can be carried out depending on the type of the included crystal phase and the heat treatment conditions. Under the heat treatment conditions under which the main crystals of enstatite and / or a solid solution thereof of configuration 11 are obtained, the above-mentioned fine crystal particle size can be obtained. As the heat treatment conditions, for example, after performing a heat treatment in the range of 700 to 850 ° C., the crystal can be further refined by raising the temperature to 850 ° C. to 1150 ° C.

Also, as in the twelfth means,
By forming at least a recording layer on the glass substrate for an information recording medium obtained by the ninth means, an information recording medium compatible with high-density recording can be obtained. Examples of the information recording medium include a magnetic disk, a magneto-optical disk, and an optical disk.

In particular, as in the thirteenth means, in a magnetic disk having a recording layer as a magnetic layer, the spacing between a magnetic head for performing recording and reproduction and the magnetic disk is extremely reduced with the recent increase in recording density. From the necessity, a glass substrate for a magnetic disk used for a magnetic disk is required to have a high surface smoothness, which is particularly useful. For the magnetic layer, a Co alloy is generally used.
Materials in which elements such as t, Cr, Ni, Ta, B, Nb, and W are spotted (CoPt, CoNi, CoCr, CoPtC
r, CoNiCr, CoCrTa, CoNiPt, Co
CrPtTa, CoCrPtB, CoNiCrTa, C
oNiCrPt, CoCrPtTaNb, etc.).

Further, in order to obtain desired magnetic characteristics, a seed layer, an underlayer, an intermediate layer, etc. may be formed between the glass substrate and the magnetic layer. Further, a protective layer or a lubricating layer may be provided on the magnetic layer. The seed layer has a role of controlling the crystal grain size of the underlayer and the magnetic layer. For example, NiAl, CrTi,
Materials such as CrNi and NiP are used. The underlayer mainly has a role of improving the magnetic properties of the magnetic layer.
Materials such as Cr and Cr alloy are used. Examples of the Cr alloy include CrV, CrMo, CrW, and CrTi, and a single layer or a plurality of layers may be provided. The intermediate layer mainly has a role of controlling the crystal orientation of the magnetic layer.
A material such as an HCP structure such as CoCrNb is used. The protective layer is provided for corrosion resistance and mechanical durability with respect to the magnetic layer, and is made of a material such as carbon, hydrogenated carbon, carbon nitride, SiC, SiO ₂ , and ZrO ₂ . The lubricating layer has a role of preventing adhesion of the magnetic head and reducing friction, and generally uses a perfluoropolyether lubricant. The thicknesses and composition ratios of these layers are appropriately adjusted so as to obtain desired magnetic properties, durability and the like.

[0029]

(Embodiment 1) A method for manufacturing a glass substrate for an information recording medium and a method for manufacturing an information recording medium according to this embodiment include (1) a disc-shaped glass substrate material manufacturing process, and (2) a crystal. Glass forming process, (3) shaping process, (4) edge polishing process, (5) grinding process, (6) first polishing process, (7) final polishing process, (8) magnetic disk manufacturing process Having. Hereinafter, each step will be described in detail.

(1) Disk-shaped glass substrate material manufacturing process First, SiO ₂ : 46.00 mol%, Al ₂ O ₃ : 10.10.
50 mol%, MgO: 31.00 mol%, Y ₂ O ₃ : 0.
50 mol%, ZrO ₂ : 1.97 mol%, TiO ₂ : 1
A raw material having a composition of 0.00 mol% and Sb ₂ O ₃ : 0.03 mol% was mixed, and this was mixed with a known melting device to about 1%.
The molten glass melted at a temperature of 550 ° C.
Using a barrel mold, press molding was performed on a disk-shaped glass substrate having a diameter of 66 mm and a thickness of 1.3 mm.

(2) Process of Producing Crystallized Glass The thickness and flatness of the above glass substrate were adjusted by a double-sided lapping apparatus having an abrasive grain size of # 400. The flatness obtained by this wrapping is
It was 0.5 μm. Thereafter, the glass plate is heat-treated at 750 ° C. for about 4 hours, and crystal nuclei are formed. Then, the crystal is maintained at a crystallization temperature of about 1000 ° C. for about 4 hours, so that the main crystal phase is enstatite and a crystallized glass having a solid solution thereof. A substrate was manufactured. The average particle size of the crystal particles was 28 nm according to observation with an electron microscope.

(3) Shape Processing Step The above-mentioned crystallized glass substrate is wrapped by the same double-sided lapping device as above to remove the warp of the glass substrate, and then ground by a relatively coarse diamond grindstone. A glass substrate was obtained by molding to a diameter of 65 mm and a thickness of 0.7 mm. Both sides of this glass substrate are ground with a fine-grained diamond grindstone, and a hole is made in the center of the glass substrate using a cylindrical grindstone, and the outer peripheral end surface is also ground. Chamfered. At this time, the surface roughness Rmax of the glass substrate was about 10 μm, and the surface roughness Rmax of the end surface of the glass substrate was Rmax.
Was about 14 μm.

(4) End-face polishing step Next, using an abrasive in which colloidal silica (10 wt%) and cerium oxide (17 wt%) were mixed, the wire diameter was reduced.
By rotating the glass substrate and the polishing brush with a brush made of 0.2 mm nylon brush, the inner and outer peripheral end surfaces of the glass substrate are polished, and the surface roughness Rmax of the outer and inner peripheral end surfaces is reduced to 0.1 μm. Was.

(5) Grinding Step A glass substrate is held by a carrier on the upper and lower platens to which pellets having diamond abrasive grains having a particle size of # 2000 (particle diameter of 6 to 8 μm) are fixed, and lubricating oil (coolant) is supplied. The upper and lower platens were rotated while grinding both surfaces of the glass substrate. The processing conditions are a processing pressure of 10 to 200 g / c.
m ² , lower platen and upper platen rotation speeds were adjusted at 3 to 50 rpm. The surface roughness of the glass substrate obtained in this grinding step was measured by a surf test using a stylus type surface profiler manufactured by Mitutoyo Corporation.
Good values of 3 μm and flatness of 1 μm were shown. The glass substrate after the above-described grinding step was sequentially immersed in each of washing tanks of a neutral detergent and pure water, and was subjected to ultrasonic washing.

(6) First Polishing Step Next, the ground glass substrate was polished using a double-side polishing apparatus. The double-side polishing machine makes the carrier hold the glass substrate held by the carrier between the upper and lower plates to which the polishing pad is attached, meshes the carrier with the sun gear and the internal gear, and holds the glass substrate between the upper and lower plates. Press. Thereafter, the polishing liquid is supplied and rotated between the polishing pad and the polishing surface of the glass substrate, thereby simultaneously polishing both surfaces of the glass substrate. The polishing was performed under the following conditions. Polisher: Hard polisher (hard urethane foam) Polishing liquid: Colloidal silica (30 wt%) + cerium oxide (17 wt%) + water Abrasive grain size: colloidal silica (0.1 μm), cerium oxide (1.6 μm) Processing pressure: Upper platen and lower platen at 120 g / cm ² Rotation speed: 5 to 70 rpm Removal amount: 20 μm Polishing time: 80 minutes

After the first polishing step, the glass substrate is
They were sequentially immersed in cleaning tanks of an aqueous solution of an acid mixed with hydrofluoric acid and silicic hydrofluoric acid, a neutral detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically washed and dried. When the surface roughness of the obtained glass substrate was measured by AFM (atomic force microscope), the average surface roughness Ra was 0.6 nm, and the maximum height Rmax was 4.2 nm. The polishing rate was 0.25 μm / min.

(7) Final polishing step Next, using the double-side polishing apparatus used in the first polishing step, final polishing was performed under the following conditions. Polisher: Soft polisher (Suede pad) Polishing liquid: Colloidal silica (5 wt%) + cerium oxide (15 wt%) + water Abrasive grain size: colloidal silica (0.1 μm), cerium oxide (1.1 μm) Processing pressure: 120 g / cm ² the upper platen, the lower plate rotation: 5～70Rpm removal quantity: 3 [mu] m polishing time: a glass substrate having been subjected to 20 minutes the final polishing step, an aqueous solution of the acid mixed with hydrofluoric acid + hydrosilicofluoric acid, neutral It was immersed sequentially in each of the cleaning tanks of detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically washed, and dried.

The surface roughness of the obtained lath substrate was measured by AFM.
(Atomic force microscope), the average surface roughness R
a was 0.38 nm, and the maximum height Rmax was 3.9 nm. The minute undulation (95% PV value) is 1.8
nm and a good value. Further, the polishing rate is set at 0.1.
It was 13 μm / min. In addition, when the surface of the substrate was observed with a differential interference microscope, no defects such as scratches or pits (concave defects) were present on the substrate surface, and the surface was good. When the edge shape of the substrate was measured by a surf test (a stylus type surface shape measuring device), the ski-jump value was 0.00 μm, and the roll-off value was −0.03 μm.
It showed good values.

Here, the minute undulation (95% PV value) means the 95% PV value of the maximum height wa of the minute undulation. In this case, the maximum height wa of the minute waviness is a value of a difference between the highest point and the lowest point of the measurement curve at all measurement points in the measurement area. And 95% PV
The value is a method for removing measurement errors due to abnormal projections such as particles that do not directly relate to the surface state of the substrate itself.For all measurement points, the measurement values are plotted on the horizontal axis.
When a histogram (a distribution diagram showing the relationship between the measured values and the corresponding number, which is usually a normal distribution curve) is displayed on the vertical axis of the measured number at which the measured value is obtained, the distribution curve is obtained. In the above, when the number of measurements corresponding to each measured value is accumulated while gradually increasing the measured value from the minimum value, the measured value when the accumulated number becomes 95% of the total number is effective. This is the method of setting the maximum value of the measured value.
The maximum value according to this method is “95% PV value”, the “95% PV value” is the maximum height wa, and the maximum height w
a is expressed as a minute undulation (for details, refer to Japanese Patent Application No. 2000-99720).

The ski-jump and roll-off are defined as follows. The ski-jump value refers to the value of the highest point (Ski-jump point) when the shape of the outer peripheral edge of the substrate is based on the flat surface of the main surface of the glass substrate.
The ff value refers to a value of a point on a contour line (Roll-Off point) at an outer peripheral end position of the glide region when the flat surface is used as a reference surface. Specifically, it is measured as follows. As shown in FIG. 3, consider a cross section obtained by cutting the glass substrate along a plane passing through the center of the disk-shaped glass substrate and perpendicular to the main surface. In this section, two reference points are set in the recording area on the contour line of the main surface, and R1,
R2. Further, a point R3 (the outer peripheral end position of the glide area) is set with a certain distance margin in the outer peripheral direction from the outer peripheral end of the recording area. Next, the points R1 and R
Connect 2 and draw its extension. At that time, point R
In the region from the point 2 to the point R3, the distance between the point on the contour line of the substrate and the straight line R1R2 (or an extension thereof) is measured.
The point S on the contour line of the substrate where the distance is the highest in the positive direction is a Ski-jump (ski jump) point, and the value of the distance s is the Ski-jump value. The point R on the contour at the position of the point R3 is a Roll-Off (roll-off) point,
The distance r between the point R and the straight line R1R2 (or an extension thereof) is Ro
ll-Off value. Note that the points R1, R2, and R3 are appropriately selected according to the size of the substrate. For example, in the case of a substrate having an outer diameter of 2.5 inches, 3.0 inches, and 3.5 inches, the R3 point is 1 inward from the side wall surface (side wall portion) of the substrate.
mm. Further, in the case of a substrate having an outer diameter of 2.5 inches (outer diameter of 65 mmφ), for example, points (R1) and 27 (points) of 23 mm from the center of the substrate are 23 mm, respectively.
mm point (R2), 31.5 mm point (R3), 32.
It can be determined as a 5 mm point (side wall surface).

(8) Magnetic Disk Manufacturing Process On both main surfaces of the magnetic disk glass substrate obtained through the above process, using an in-line sputtering device,
A Cr underlayer, a CoCrPtB magnetic layer, and a hydrogenated carbon protective layer were sequentially formed, and a perfluoropolyether lubricating layer was further formed by a dipping method to obtain a magnetic disk.
When a touch-down height test was performed on the obtained magnetic disk, a good value of 5.5 nm was obtained. Also, the head did not crash even after the load / unload test (100,000 times).

Example 2 Example 1 was the same as Example 1 except that cerium oxide was changed to zirconium oxide.
A glass substrate for a magnetic disk and a magnetic disk were prepared in the same manner as described above (the zirconium oxide concentration was 10 wt%, the particle size was 2.4 μm for primary polishing and 1.0 μm for secondary polishing).

The surface roughness of the obtained lath substrate was measured by AFM.
(Atomic force microscope), the average surface roughness R
a was 0.5 nm, and the maximum height Rmax was 7 nm. Further, the fine waviness (95% PV value) was as good as 2.0 nm. The polishing rate was 0.28 μm / min in the first polishing step, and 0.15 μm / min in the final polishing step.
μm / min. In addition, when the surface of the substrate was observed with a differential interference microscope, no defects such as scratches or pits (concave defects) were present on the substrate surface, and the surface was good. When the edge shape of the substrate was measured by a surf test (a stylus type surface shape measuring device), the ski-jump was 0.00.
μm and roll-off were −0.03 μm, which were good values.
When a touchdown height test was performed on the obtained magnetic disk, a good value of 6.5 nm was shown. Also, the head did not crash even after the load / unload test (100,000 times).

(Comparative Examples 1 to 3)
Except that the polishing liquid was changed to cerium oxide (17 wt%) + water (Comparative Example 1), zirconium oxide (10 wt%) + water (Comparative Example 2), colloidal silica (30 wt%) + water (Comparative Example 3), In the same manner as in Example 1, a glass substrate for a magnetic disk and a magnetic disk were manufactured.

As a result, in Comparative Examples 1 and 2, defects such as scratches and pits are generated on the substrate surface (because the processing speed is remarkably different between the glass phase, the ceramic phase, and the solid solution portion), and the mirror surface is not obtained. The surface roughness could not be measured. The polishing rate was 0.08 μm in the first polishing step when only cerium oxide was used, and 0.04 μm in the final polishing step.
μm, in the case of only zirconium oxide, 0.09 μm in the first polishing step, and 0.07 μm in the final polishing step.
And the polishing rates were almost the same. It is considered that the reason why these polishing rates were reduced is that these polishing agents have extremely low polishing rates for the crystal phase and the solid solution phase.

In Comparative Example 3, the surface roughness was similar to that obtained in Example 1, but no defects such as scratches and pits were found on the substrate surface. However, the polishing rate in the first polishing step was extremely low at 0.08 μm / min, and the polishing rate in the final polishing step was extremely low at 0.08 μm / min. It took twice as long. This is considered to be because the polishing rate of colloidal silica is generally low with respect to the glass substrate, and as the polishing time becomes longer, the polishing pad is clogged and the polishing rate decreases. On the other hand, in the case of Example 1, since cerium oxide (1-2 μm) having a larger particle diameter than colloidal silica (0.1 μm) is contained, abrasive grains are easily trapped by the pad, and the surface to be processed and the pad It is considered that since the slippage during the polishing is suppressed, the polishing rate is hardly reduced due to clogging.

Further, a touchdown height test and a load unload test were performed on the magnetic disks using these glass substrates. As a result, in Comparative Examples 1 and 2, the touchdown height was measured because the surface condition of the substrate was poor. The head crash occurred in the load / unload test. In Comparative Example 3, the touchdown height was 5.5 nm, which was almost the same as that of Example 1. In the load / unload test, no head crash occurred.

(Examples 3 to 6, Reference Example 1) Next, an example in which the first polishing step was performed in the same manner as in Example 1 except that the abrasive concentration of the polishing liquid in the first polishing step was changed. Examples 3 to 6 are listed as Reference Example 1. FIG. 1 is a table showing polishing rates and surface roughnesses Ra in the case of Examples 3 to 6 and Reference Example 1 in which polishing was performed by changing the polishing agent concentration of the polishing liquid in the first polishing step.

As shown in the table of FIG. 1, it can be seen that the polishing rate increases as the concentration of colloidal silica increases. When the concentration of colloidal silica is 5 wt%, scratches and pits are generated on the surface, indicating that the colloidal silica concentration needs to be 10 wt% or more. Further, even if the concentration of colloidal silica is increased, the surface roughness Ra of the obtained substrate does not change. Therefore, from the viewpoint of economy, 10 to 30 wt% is preferable.

(Examples 7 to 11, Comparative Example 4, Reference Example 2)
Next, examples in which the final polishing step was performed in the same manner as in Example 1 except that the abrasive concentration of the polishing liquid in the final polishing step was changed are listed as Examples 7 to 11, Comparative Example 4, and Reference Example 2. FIG. 2 is a table showing polishing rates and surface roughnesses Ra in Examples 7 to 11, Comparative Examples 4 and Reference Example 2 in which polishing was performed while changing the polishing agent concentration of the polishing liquid in the final polishing step. .

As shown in the table of FIG. 2, when the concentration of colloidal silica is 2 wt%, scratches and pits are generated on the substrate surface. The polishing rate is 2 to
It was constant at 30 wt%. In addition, when the colloidal silica abrasive concentration and the end shape were observed, the higher the abrasive concentration, the larger the roll-off value, indicating that the abrasive concentration is preferably 5 to 10 wt%. . In Comparative Example 4 and Reference Example 2, the substrate surface was damaged.
Due to the occurrence of pits, the measurement with a stylus-type measuring instrument was not reproducible and could not be performed.

Examples 12 to 15 Examples 12 to 15 are given as examples in which another type of crystallized glass is used in place of the crystallized glass in Example 1. That is, an example using a crystallized glass substrate of cordierite as a main crystal (Example 12), an example using a crystallized glass substrate of spinel (Example 13), and an example using a crystallized glass substrate of α-quartz. (Example 14) An example (Example 15) using a crystallized glass substrate of lithium disilicate. In these examples, a glass substrate for a magnetic disk and a magnetic disk were produced in the same manner as in Example 1, except that the type of glass was changed. However, within the scope of the present invention, the polishing conditions such as the particle size and concentration of the abrasive grains and the processing pressure were appropriately adjusted.

As a result, no defects such as scratches and pits are generated on the substrate surface, and the surface roughness Ra,
Rmax and fine swell also showed the same values as in Example 1 and were good. In the touchdown height test and the load unload test of the magnetic disk, no head crash occurred and the results were good.

[0054]

As described above in detail, the present invention relates to a case where a polishing liquid is interposed between the surface of a glass substrate and a polishing member, and the glass substrate and the polishing member are relatively moved to perform polishing. As the polishing liquid, a mixture of a first abrasive having a mechanochemical polishing action on a glass phase and a second abrasive having a mainly mechanical polishing action on a ceramic phase is used. Accordingly, a method for manufacturing a glass substrate for an information recording medium and a method for manufacturing an information recording medium capable of maintaining high surface smoothness while suppressing the occurrence of surface defects, and enabling quick polishing have been obtained. is there.

[Brief description of the drawings]

FIG. 1 is a table showing polishing rates and surface roughnesses Ra in Examples 3 to 6 and Reference Example 1 in which polishing was performed by changing the polishing agent concentration of a polishing liquid in a first polishing step.

FIG. 2 is a table showing polishing rates and surface roughnesses Ra in Examples 7 to 11, Comparative Examples 4 and Reference Example 2 in which polishing was performed by changing the polishing agent concentration of a polishing liquid in a final polishing step. is there.

FIG. 3 is an explanatory diagram of ski jump and roll-off.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C03C 10/14 C03C 10/14 F term (reference) 3C058 AA07 CA01 CA06 CB10 DA02 DA12 4G059 AA09 AB09 AC03 4G062 AA11 BB01 BB06 CC10 DA05 DA06 DB03 DB04 DC01 DD01 DE01 DF01 EA01 EA02 EA03 EB01 EB02 EB03 EC01 EC02 EC03 ED04 ED05 EE01 EE02 EE03 EF01 EF02 EF03 EG01 EG02 EG03 FA01 FB03 FB04 FC01 F01 F01 F01 FF01 F01 FF01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM27 NN33 QQ02 QQ05 QQ08 QQ16 5D112 AA02 BA03 GA09

Claims (7)

[Claims] 1. A method for manufacturing a glass substrate for an information recording medium, wherein a polishing liquid is interposed between a surface of a glass substrate and a polishing member, and the glass substrate and the polishing member are relatively moved to perform polishing. Is a crystallized glass having at least a glass phase and a ceramic phase on a substrate surface, wherein the polishing liquid has a mechanochemical (mechanochemical) polishing action on a glass phase (amorphous phase). (1) A glass substrate for an information recording medium, comprising: a mixture of an abrasive and a second abrasive mainly having a mechanical (mechanical) polishing action on a ceramic phase (crystal phase). Method. 2. The first abrasive having a mechanochemical (mechanochemical) polishing action on the glass phase (amorphous phase) is selected from cerium oxide, zirconium oxide, iron oxide and manganese oxide. At least one selected from the group consisting of at least one selected from colloidal silica and titanium oxide as the second abrasive having a mainly mechanical (mechanical) polishing action on the ceramic phase (crystal phase) 2. The method for manufacturing a glass substrate for an information recording medium according to claim 1, wherein: 3. The method according to claim 1, wherein the content of the second polishing agent having a mechanical (mechanical) polishing action on the ceramic phase (crystal phase) in the polishing liquid is 3 to 30 wt%. The method for producing a glass substrate for an information recording medium according to claim 1 or 2, wherein: 4. The content of the first abrasive having a mechanochemical (mechanochemical) polishing action on the glass phase (amorphous phase) in the polishing liquid is 1 to 20% by weight. 4. The method for manufacturing a glass substrate for an information recording medium according to claim 3, wherein: 5. The surface of a glass substrate is polished by holding a glass substrate held by a carrier between upper and lower platens covered with a polishing cloth, supplying a polishing liquid, and rotating the upper and lower platens, respectively. A method for manufacturing a glass substrate for an information recording medium having a polishing step, wherein the polishing liquid is a mixture of colloidal silica and one or both of cerium oxide and zirconium oxide. Of manufacturing glass substrates for use. 6. An information recording medium according to claim 1, wherein at least a recording layer is formed on the information recording medium glass substrate obtained by the method for producing an information recording medium glass substrate according to claim 1. Production method. 7. The method according to claim 6, wherein the recording layer is a magnetic layer.