JP2007136583A - Method of producing magnetic disk substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a highly smooth substrate that is necessary for a magnetic disk substrate of high recording density, and particularly of high recording density of 50 G bit/inch<SP>2</SP>. <P>SOLUTION: The method of producing the magnetic disk substrate comprises a step of feeding a grinding liquid composition A containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm, to the substrate, grinding the substrate with a main machining pressure of ≥6 kPa, and thereafter grinding the substrate with a machining pressure of 20 to 80% of the main machining pressure. Alternatively the method comprises a step (step 1) of feeding a grinding liquid composition B containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm, to the substrate, and grinding the substrate with a main machining pressure of ≥6 kPa, and a step (step 2) of feeding a grinding liquid composition C containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm, to the substrate obtained by the step 1, and grinding the substrate with a machining pressure of 20 to 80% of the main machining pressure in the step 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic disk substrate.

  In order to reduce the minimum recording area of the hard disk and promote higher capacity, it is required to reduce the flying height of the magnetic head. In order to reduce the head flying height, the smoothness of the hard disk substrate is important. Up to now, the smoothness has typically been a surface roughness measured with a stylus diameter of 0.2 μm and a cutoff of 25 μm (ie, wavelength: 0.2 to 25 μm), a stylus diameter of 0.2 μm, and a cutoff of 800 μm. The surface roughness and the minute waviness as described above have been reduced in order to improve the smoothness, as evaluated by the slight waviness measured at (that is, wavelength: 0.2 to 800 μm).

As a method of manufacturing a substrate with improved smoothness, specifically with reduced surface roughness and micro-waviness as described above, control the polishing pad hole diameter, hardness control, and polishing processing conditions. Such mechanical conditions are being studied. For example, in Patent Document 1, a method of controlling the processing load and the rotational speed using alumina abrasive grains, and in Document 2, a polishing process by a plurality of stages is performed, and a metal oxide having a particle diameter of 0.3 to 5 μm is formed before final processing. A method has been studied in which polishing is carried out using a polishing solution containing the colloidal particles of 0.01 to 0.3 μm.
JP 9-330518 A Japanese Patent Laid-Open No. 11-10492

  However, although all of the methods disclosed in the above-mentioned patent documents can reduce the conventional surface roughness and microwaviness, magnetic recording for a hard disk having a high recording density, in particular, a high recording density exceeding 50 G (giga) bits per square inch. It is not a sufficient method for manufacturing a disk substrate.

  It is an object of the present invention to provide a method for producing a highly smooth substrate necessary for a magnetic disk substrate having a high recording density, particularly 50 Gbit / in 2 or more. In particular, it is an object of the present invention to provide a method for manufacturing a magnetic disk substrate that has a processing speed of an actual production level and satisfies the long waviness reduction over the entire surface.

That is, the gist of the present invention is as follows.
[1] After supplying the polishing composition A containing colloidal particles having a volume average particle size of 0.005 to 0.1 μm to the substrate and polishing the substrate with a main processing pressure of 6 kPa or more, A method for producing a magnetic disk substrate, comprising a step of polishing the substrate at a processing pressure of 20 to 80%,
[2] Method for producing a magnetic disk substrate having the following steps:
(Step 1) A step of supplying a polishing composition B containing colloidal particles having a volume average particle size of 0.005 to 0.1 μm to the substrate and polishing the substrate with a main processing pressure of 6 kPa or more, and (Step 2) ) A polishing liquid composition C containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm is supplied to the substrate obtained in step 1, and the processing pressure is 20 to 80% of the main processing pressure in step 1 Polishing the substrate with, and
[3] The method for manufacturing a magnetic disk substrate according to [2], further comprising the following polishing step 3 after the step 2:
(Step 3) A polishing liquid composition D containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm is supplied to the substrate obtained in Step 2, and the processing pressure is 80% or less of the processing pressure in Step 2. The present invention relates to a step of polishing the substrate with pressure.

  According to the present invention, it is possible to obtain a highly smooth substrate necessary for a magnetic disk substrate having a high recording density, particularly a high recording density of 50 Gbit / in 2 or more. In particular, there is an effect that it is possible to obtain a magnetic disk substrate that has a processing speed of an actual production level and satisfies the long-stress reduction over the entire surface.

As described above, waviness reduction has been demanded from the viewpoint of reducing the head flying height, but conventional waviness evaluation has been performed by measuring waviness in a very small area (approximately 5 mm square). Reduction of undulation has been pursued.
On the other hand, the present invention reduces the “long waviness over the entire surface (hereinafter sometimes referred to as“ in-plane average long wavelength waviness ”)” of the substrate, and in particular, the long wavelength waviness of the outer peripheral portion of the substrate. This is based on the finding that it is an important point to reduce the head flying height of a hard disk drive necessary for higher density recording.

Although the details of the cause of the worsening of the swell of the outer peripheral portion are unknown, it is estimated as follows. That is, since the polishing pressure is higher at the outer peripheral portion of the substrate where the vibration of the substrate during polishing is larger than the inner peripheral portion of the substrate where the vibration of the substrate is small, the chemical polishing force is increased due to heat due to pressurization. It is estimated that. Therefore, the present inventors have reduced the waviness of the entire outer surface of the substrate by reducing the deterioration of the waviness of the outer peripheral portion of the substrate caused by the difference between these pressures, and the waviness of the inner peripheral portion and the outer peripheral portion of the substrate. We found that the difference between the two becomes lower.
In this specification, “in-plane average long wavelength waviness” refers to the root mean square waviness in a certain area of the substrate, and “inner peripheral waviness” or “outer peripheral waviness” The root mean square undulation at a position of a constant radius of the peripheral portion or the peripheral portion.

  Accordingly, in the first aspect of the present invention, the polishing liquid composition A containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm is supplied to the substrate and the substrate is polished at a main processing pressure of 6 kPa or more. After that, the method for manufacturing a magnetic disk substrate (hereinafter referred to as “production method of embodiment 1”) is characterized by further comprising a step of polishing the substrate at a processing pressure of 20 to 80% of the main processing pressure. Yes). With this feature, the method for manufacturing a magnetic disk substrate according to the present invention can provide a magnetic disk substrate that satisfies the in-plane average long wavelength waviness reduction while having a processing speed of an actual production level. it can.

  Examples of the colloidal particles contained in the polishing composition A include colloidal silica particles, colloidal ceria particles, colloidal alumina particles, and colloidal titania particles. Among these, colloidal silica particles are more suitable from the viewpoints of reducing in-plane average long wavelength waviness and reducing nanoscratches that cause surface defects. The colloidal silica particles can be obtained, for example, by a production method in which the colloidal silica particles are generated from a silicic acid aqueous solution. Further, those obtained by surface modification or surface modification of these colloidal particles with functional groups, those obtained by compounding with surfactants or other abrasives, and the like can also be used as colloidal particles. Moreover, the said colloidal particle may be used independently and may be used in mixture of 2 or more types.

  The volume average particle diameter of the colloidal particles is 0.005 to 0.1 μm, preferably 0.008 to 0.08 μm, from the viewpoint of reducing the AFM surface roughness and in-plane average long wavelength waviness and improving the polishing rate. 0.01 to 0.05 μm is more preferable. These volume average particle diameters are obtained by taking a photograph observed with a transmission electron microscope (10,000 to 50,000 times) (trade name “JEM-2000FX”) into a scanner with a personal computer and analyzing software “WinROOF” (distributor: Mitani Corporation) ), The equivalent circle diameter of each colloidal particle is obtained from the colloidal particle data, and this is used as the diameter. Using the spreadsheet software “EXCEL” (manufactured by Microsoft), the particle diameter is converted to the particle volume. And obtained from the volume-based particle size distribution of silica. The number of observations is preferably at least 1000, more preferably 3000 or more, and still more preferably 5000 or more.

  From the viewpoint of reducing the surface roughness and reducing the in-plane average long wavelength waviness, the colloidal particles preferably have a volume average particle diameter of 0.05 μm or less, as described above, and 0.04 μm or less. It is more preferable.

  The average particle size of the primary particles of the colloidal particles is 0.005 to 0 from the viewpoint of reducing nanoscratches and the surface roughness (centerline average roughness: Ra, Peak to Valley value: Rmax). .05 μm is preferred. From the viewpoint of simultaneously improving the polishing rate, the thickness is more preferably 0.005 to 0.04 μm, and further preferably 0.005 to 0.03 μm.

  The content of the colloidal particles in the polishing liquid composition A at the time of use is preferably 0.5% by weight or more, more preferably 1% by weight or more, further preferably 3% by weight or more, from the viewpoint of improving the polishing rate. Further more preferably 5% by weight or more, and from the viewpoint of economically improving the surface quality, it is preferably 20% by weight or less, more preferably 15% by weight or less, still more preferably 13% by weight or less, and even more preferably. Is 10% by weight or less. Therefore, from the viewpoint of improving the polishing rate and economically improving the surface quality, the content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, and further preferably 3 to 13% by weight. %, Even more preferably 5 to 10% by weight. The content of the colloidal particles may be either the content at the time of producing the polishing liquid composition A or the content at the time of use. Usually, it is produced as a concentrated liquid, and this may be used after being diluted. Many.

  Examples of water used in the polishing liquid composition A include ion exchange water, distilled water, and ultrapure water. The water content corresponds to the balance obtained by removing colloidal particles and other components from 100% by weight of the polishing liquid composition, preferably 60 to 99% by weight, and more preferably 80 to 97% by weight.

  From the viewpoint of reducing in-plane average long wavelength waviness and reducing nanoscratches, it is preferable that the polishing composition A further contains an acid. Specific examples of such acids include nitric acid, sulfuric acid, nitrous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, amidosulfuric acid and the like, 2- Aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane -1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2 -Diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobuta Organic phosphonic acids such as -2,3,4-tricarboxylic acid and α-methylphosphonosuccinic acid, aminocarboxylic acids such as glutamic acid, picolinic acid and aspartic acid, carboxylic acids such as oxalic acid, nitroacetic acid, maleic acid and oxaloacetic acid An acid etc. are mentioned. Of these, inorganic acids or organic phosphonic acids are preferred from the viewpoint of reducing nanoscratches.

  Among inorganic acids, nitric acid, sulfuric acid, hydrochloric acid or perchloric acid is more preferable. Among organic phosphonic acids, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra ( Methylenephosphonic acid) or diethylenetriaminepenta (methylenephosphonic acid) is more preferred. These acids may be used alone or in admixture of two or more.

  The content of the acid in the polishing liquid composition A is preferably from 0.1 to 10% by weight, more preferably from 0.2 to 5% by weight, from the viewpoint of reducing in-plane average long wavelength waviness and reducing nanoscratches. More preferably, it is 0.3 to 3% by weight.

  Further, although it cannot be generally defined by the material of the object to be polished, in general, an oxidizing agent can be added to the polishing composition A from the viewpoint of improving the polishing rate for metal materials. Examples of the oxidizing agent include hydrogen peroxide, permanganic acid, chromic acid, nitric acid, sulfuric acid, peroxo acid, oxyacid, or salts thereof and oxidizing metal salts. Among these, hydrogen peroxide is preferable from the viewpoint of contamination of the surface of the substrate to be polished. The said oxidizing agent may be used independently and may be used in mixture of 2 or more types.

  The content of the oxidizing agent in the polishing composition A is preferably 0.002 to 10 from the viewpoint of improving the polishing rate, reducing the in-plane average long wavelength waviness, and reducing surface defects such as pits and scratches. % By weight, more preferably 0.005 to 5% by weight, still more preferably 0.007 to 3% by weight.

  There is no restriction | limiting in particular about pH of polishing liquid composition A, It is preferable to determine according to the kind and required characteristic of to-be-polished object. When the material of the object to be polished is a metal material, the pH is preferably 6 or less, more preferably 5 or less, and even more preferably 4 or less, from the viewpoint of improving the polishing rate. Further, from the viewpoint of the influence on the human body and the prevention of corrosion of the polishing apparatus, the pH is preferably 0.5 or more, more preferably 1 or more, and still more preferably 1.4 or more. In particular, in the case of a precision component substrate whose material to be polished is a metal material, such as a nickel-phosphorus (Ni-P) plated aluminum alloy substrate, the pH is 0.5 to 6 in consideration of the above viewpoint. More preferably, it is 1.0-5, More preferably, it is 1.4-4.

  The polishing liquid composition A can be produced by adding and mixing target components by any method, but other components can be further blended as necessary. Examples of such other components include a thickener, a dispersant, a rust inhibitor, a basic substance, and a surfactant.

  In the production method of aspect 1, the polishing liquid composition A produced as described above is supplied to the substrate, the substrate is polished at a main processing pressure of 6 kPa or more, and then 20 to 80% of the main processing pressure. A step of polishing the substrate with a processing pressure. As the polishing step, for example, the substrate to be polished is sandwiched between polishing boards to which a nonwoven fabric or an organic polymer polishing cloth (polishing pad) is attached, and the polishing composition A is supplied, that is, the polishing pad is applied. The polishing liquid composition A is supplied to the substrate polishing surface sandwiched between the attached polishing discs, and polishing is performed by moving the polishing disc and / or the substrate under a predetermined processing pressure.

  The main processing pressure in the present invention refers to the maximum processing pressure during the polishing process. From the viewpoint of obtaining a polishing amount of a certain amount or more necessary for removing defects such as pits and scratches in the substrate before polishing in a short time, that is, from the viewpoint of mass production, the main processing pressure is 6 kPa or more, 7 kPa or more is preferable, and 7.5 kPa or more is more preferable. In addition, from the viewpoint of avoiding troubles such as polishing machine stoppage by appropriately maintaining the friction between the substrate and the polishing pad, the main processing pressure is preferably 15 kPa or less, more preferably 13 kPa or less, and even more preferably 12 kPa or less. It is. That is, the main processing pressure is 6 kPa or more, preferably 6 to 15 kPa, more preferably 7 to 13 kPa, and even more preferably 7.5 to 12 kPa.

  In the polishing step of the production method of aspect 1, after polishing the substrate with the main processing pressure as described above (hereinafter, sometimes referred to as “main processing pressure polishing”), the polishing process further comprises 20 to 80% of the main processing pressure. The substrate is polished with a processing pressure (hereinafter, sometimes referred to as “light processing pressure polishing”). By polishing with such a light processing pressure, the vibration of the substrate is reduced, so that the pressure applied to the outer periphery of the substrate is averaged. As a result, the chemical polishing force due to the friction between the substrate and the polishing pad at the outer peripheral portion becomes the same as that at the inner peripheral portion, so that it is estimated that the effect of improving the outer peripheral waviness is achieved.

  From the viewpoint of obtaining a sufficient effect of improving the outer peripheral waviness, the light working pressure polishing is preferably performed at 70% or less, more preferably 60% or less of the main working pressure. In addition, from the viewpoint of obtaining a desired polishing amount in order to achieve a sufficient effect of improving the waviness of the outer peripheral portion and from the viewpoint of avoiding damage to the polishing pad due to detachment of the substrate from the substrate carrier of the polishing apparatus, Polishing is preferably performed at 25% or more, more preferably 30% or more of the main working pressure. Therefore, in the manufacturing method of aspect 1, the light working pressure polishing is performed at a working pressure of 20 to 80%, preferably 25 to 70%, more preferably 30 to 60% of the main working pressure.

  From the viewpoint of improving the waviness of the outer peripheral portion and preventing the substrate from being detached from the substrate carrier of the polishing apparatus, the light processing pressure polishing is preferably 1.5 to 6 kPa, more preferably 1.7 to 5.5 kPa. More preferably, it is performed at 1.9 to 5 kPa.

  The adjustment of the processing pressure from the main processing pressure to the light processing pressure may be performed in one step, or may be performed gradually over a plurality of times.

  In the manufacturing method of aspect 1, the long wavelength waviness of the outer peripheral portion of the substrate can be further improved by reducing the relative speed between the magnetic disk substrate and the polishing pad in the polishing step. From the viewpoint of reducing long wavelength waviness, the relative speed during main processing pressure polishing is preferably 0.9 m / s or less, more preferably 0.8 m / s or less, and even more preferably 0.7 m / s or less. The relative speed at the time of light working pressure polishing is preferably 0.6 m / s or less.

  Although it does not specifically limit about the polishing pad used with the manufacturing method of aspect 1, A suede type is preferable from a viewpoint of a polishing rate improvement, waviness reduction, and nano scratch reduction. Here, the suede type refers to a polishing pad having a structure having at least a base layer and a foamed surface layer. As the material of the base layer, a high-hardness resin such as polyethylene terephthalate (PET) is preferable. The material for the surface layer is preferably a polyurethane resin. Furthermore, the surface average pore diameter of the polishing pad is preferably 5 to 70 μm, more preferably 10 to 60 μm, more preferably 15 to 60 μm, from the viewpoints of retention of the polishing composition relating to the polishing rate, dischargeability and undulation, nanoscratch reduction, and the like. 50 μm is more preferable. Examples of the suede type polishing pad include those described in JP-A-11-335979 and JP-A-2001-62704, for example.

  The substrate to be polished in the production method of aspect 1 is not particularly limited as long as it is a generally known substrate used as a hard disk substrate. For example, Ni-P plated aluminum alloy substrate, Ni-P plated glass substrate Examples thereof include a substrate having a metal layer on the surface layer such as an aluminum disk, a substrate having a glassy substance or ceramic material such as a carbon disk or a glass substrate, and a substrate in which they are combined. Among them, the effect of the manufacturing method of the present invention is more remarkably exhibited in a substrate having a metal layer on a surface layer such as a Ni—P plated aluminum alloy substrate, a Ni—P plated glass substrate, an aluminum disk, or the like. .

  The substrate to be polished is preferably subjected to a rough polishing step in advance from the viewpoint of reducing the in-plane average long wavelength waviness, for example, the waviness is about 2.5 nm and the surface roughness is about 1.5 nm. Are preferred. As the abrasive used in the rough polishing process, those generally used for polishing can be used, such as metal, metal or metalloid carbide, nitride, oxide, boride, diamond, etc. Is mentioned. The metal or metalloid element is derived from Group 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A or Group 8 of the periodic table (long period type). Specific examples of the abrasive include silica, alumina, silicon carbide, diamond, manganese oxide, magnesium oxide, zinc oxide, titania, ceria, zirconium oxide, and the like. It is preferable from the viewpoint of improvement. Among these, silica, alumina, titania, ceria, zirconium oxide, and the like are preferable from the viewpoints of improving the polishing rate and economy.

  There are no particular restrictions on the polishing conditions other than those described above.

A second aspect of the present invention is a method for manufacturing a magnetic disk substrate having the following steps (hereinafter, may be referred to as “manufacturing method according to aspect 2”):
(Step 1) A step of supplying a polishing composition B containing colloidal particles having a volume average particle size of 0.005 to 0.1 μm to the substrate and polishing the substrate with a main processing pressure of 6 kPa or more, and (Step 2) ) A polishing liquid composition C containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm is supplied to the substrate obtained in step 1, and the processing pressure is 20 to 80% of the main processing pressure in step 1 The step of polishing the substrate. With this feature, the method for manufacturing a magnetic disk substrate according to the present invention can provide a magnetic disk substrate that satisfies the in-plane average long wavelength waviness reduction while having a processing speed of an actual production level. it can.

  Examples of the polishing liquid composition B and the polishing liquid composition C used in the production method of aspect 2 can be the same as the polishing liquid composition A described above. Therefore, the colloidal particles contained in the polishing liquid composition B and the colloidal particles contained in the polishing liquid composition C may be the same, or may be of different types or different particle sizes. . Moreover, the composition of the polishing liquid composition B and the polishing liquid composition C may be the same or different.

  Here, it is preferable that polishing composition B and / or C contain an acid from a viewpoint of nano scratch reduction and an in-plane average long wavelength waviness reduction. Preferred acid types and their contents are the same as those described in the first embodiment.

  Moreover, it is preferable that polishing composition B and / or C contain an oxidizing agent from a viewpoint of a polishing rate improvement. Preferred types and contents of the oxidizing agent are the same as those described in the first embodiment.

  Therefore, from the viewpoint of reducing the in-plane average long wavelength waviness and improving the polishing rate, the polishing composition B or C contains an acid and the other contains an oxidizing agent, or the polishing composition B and / or Or it is more preferable that C contains an acid and an oxidizing agent.

  In addition, the basic polishing composition is preferable in that the waviness of the outer peripheral portion can be reduced as compared with the acidic one. An acidic polishing liquid composition is preferred in that it is less likely to generate nanoscratches than a basic one, can reduce in-plane average long wavelength waviness, and can achieve a high polishing rate.

  Therefore, from the viewpoint of improving the polishing rate and further reducing the in-plane average long wavelength waviness, the polishing liquid composition B contains an acid and an oxidizing agent, and the polishing liquid composition C is basic, or the polishing liquid composition More preferably, B contains an acid and an oxidizing agent, and the polishing composition C contains an acid but no oxidizing agent. This is because, in such a combination of polishing liquid compositions, the chemical polishing power in step 2 becomes smaller, so that it is estimated that further improvement in the waviness of the outer peripheral portion is possible.

  About the process 1 and the process 2, even if it implements continuous grinding | polishing with the same grinding machine, it does not matter even if it passes through a separate grinding | polishing process. In the case of multi-stage processing, it is preferable to reduce the abrasive grain size stepwise, and these may be carried out continuously with the same polishing machine, but the previous stage abrasive grains and polishing liquid In order to avoid mixing, different polishing machines may be used, and when different polishing machines are used, it is preferable to clean the substrate after each step.

  As for the polishing amount of one surface of the magnetic disk substrate in step 1, the surface defects of the substrate to be polished such as scratches and pits generated during the rough polishing step are removed from the viewpoint of sufficiently reducing long-wave waviness in the surface. From a viewpoint, 0.05 micrometer or more is preferable, More preferably, it is 0.1 micrometer or more, More preferably, it is 0.15 micrometer or more. The amount of polishing on one side can be obtained as described in the examples below.

  Further, the ratio of the single-side polishing amount in step 2 to the single-side polishing amount in step 1 (single-side polishing amount in step 2 / single-side polishing amount in step 1) is from the viewpoint of obtaining a sufficient outer peripheral waviness reduction effect. 0.1 or more is preferable, 0.2 or more is more preferable, and 0.3 or more is more preferable. The ratio is preferably 1.0 or less, more preferably 0.9 or less, and even more preferably 0.8 or less from the viewpoint of obtaining a processing speed for mass production. That is, the ratio is preferably 0.1 to 1.0, more preferably 0.2 to 0.9, and still more preferably 0.3 to 0.8.

  The main processing pressure in step 1 and the processing pressure in step 2 may be the same as the main processing pressure and the light processing pressure in the manufacturing method of aspect 1, respectively.

  Further, the relative speeds of the polishing pad, the substrate to be polished, the magnetic disk substrate and the polishing pad used in step 1 and step 2 may be the same as those in the manufacturing method of aspect 1, and the polishing conditions are as follows. Other than the above, there is no particular limitation.

  The production method of aspect 2 is also a polishing liquid composition containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm on the substrate obtained in step 2 from the viewpoint of reducing waviness of the outer peripheral portion. It is preferable to have a step of supplying the product D and polishing the substrate with a processing pressure of 80% or less of the processing pressure in the step 2.

  As the polishing liquid composition D used in step 3, the same polishing liquid composition A as that described above can be exemplified. The colloidal particles contained in the polishing liquid composition D may be the same as the colloidal particles contained in the polishing liquid composition B or C, or may be of different types or different particle sizes. Good. Moreover, the composition of the polishing composition D and the polishing composition B or C may be the same or different.

  From the viewpoint of reducing the in-plane average long wavelength waviness and improving the polishing rate, it is preferable that the polishing composition D contains an oxidizing agent. Preferred types and contents of the oxidizing agent are the same as those described in the first embodiment.

  The processing pressure at the time of polishing in Step 3 is preferably 80% or less, more preferably 75% or less, and further preferably 70% or less of the processing pressure in Step 2 from the viewpoint of reducing the waviness of the outer peripheral portion. Further, from the viewpoint of improving the polishing rate, the processing pressure is preferably 40% or more, more preferably 45% or more, and further preferably 50% or more of the processing pressure in step 2. In addition, it is preferable to perform about 10% of the total polishing amount desired through the steps 1 to 3 in the step 3.

  In addition, the relative speeds of the polishing pad, the substrate to be polished, the magnetic disk substrate and the polishing pad used in step 3 may be the same as those in the production method of aspect 1, and the polishing conditions are other than those described above. There are no particular restrictions.

  According to the manufacturing method of aspect 1 and aspect 2 of the present invention, the in-plane average long wavelength undulation is, for example, 1.2 nm or less, preferably 1.1 nm or less, more preferably 1.0 nm or less, and the outer circumference A magnetic disk substrate having a long-wavelength undulation of, for example, 1.8 nm or less, preferably 1.7 nm or less, and more preferably 1.6 nm or less is obtained. The in-plane average long wavelength waviness can be measured by an optical measuring instrument such as “THoT MODEL 4224” manufactured by THoT Technology.

  Furthermore, the surface roughness of the magnetic disk substrate obtained by the production method of Embodiment 1 and Embodiment 2 of the present invention is preferably 0.2 nm or less, more preferably 0.18 nm or less, from the viewpoint of reducing the head flying height. Preferably it is 0.15 nm or less.

  The surface roughness can be evaluated as roughness measurable at a short wavelength of 10 μm or less in an atomic force microscope (AFM), for example, and can be expressed as center line average roughness Ra (AFM-Ra).

  Since the obtained magnetic disk substrate has an extremely excellent surface performance, it can be suitably used as a substrate for producing a high recording density hard disk.

<Preparation of polishing liquid composition>
Predetermined amounts of 35% by weight hydrogen peroxide water (made by Asahi Denka), 60% by weight HEDP (1-hydroxyethylidene-1,1-diphosphonic acid) aqueous solution (made by Solusia Japan), and 95% by weight in ion-exchanged water % Of sulfuric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added so as to have the composition shown in Table 1, and the following colloidal silica slurry was added under stirring of the mixed aqueous solution to prepare polishing liquid compositions a to f.
In the polishing composition a, e, and f, colloidal silica slurry (manufactured by DuPont, primary particle volume average abrasive particle size 27 nm, silica particle concentration 40% by weight) was used. In the polishing composition b, a colloidal silica slurry (manufactured by Nissan Chemical Industries, volume average abrasive particle size of primary particles 14 nm, silica particle concentration 30% by weight) was used. In the polishing composition c and d, colloidal silica slurry (manufactured by Catalyst Kasei Kogyo Co., Ltd., volume average abrasive particle size of primary particles 25 nm, silica particle concentration 30% by weight) was used.

Examples 1-10 and Comparative Examples 1-5
A substrate ("THoT MODEL 4224") made of a Ni-P plated aluminum alloy (both sides area 131.9 cm ² , Ni-P plating density 8.4 g / cm ³ ) having a thickness of 1.27 mm and a diameter of 3.5 inches ( In-plane average long wavelength waviness of the substrate before polishing measured by THoT Technology) was 1.9 nm, inner peripheral long wavelength waviness was 1.4 nm, and outer peripheral long wavelength waviness was 2.5 nm. Was polished with a double-side processing machine under the following polishing conditions and the processing conditions described in Table 3. The obtained polished substrate was measured for long wavelength waviness and AFM surface roughness under the following conditions. The results are shown in Table 3.

1. Polishing conditions Polishing was performed with a double-sided processing machine under the following setting conditions.
<Setting conditions of double-sided machine>
・ Polishing tester: Speed Fam Co., double-sided 9B polishing machine ・ Polishing pad: FILWEL, urethane final polishing pad ・ Polishing liquid composition supply amount: 100 mL / min
・ Number of loaded substrates: 10 ・ Rotating plate speed / relative speed: See Table 2 ・ Processing pressure: See Table 2

<Evaluation method of polishing amount and polishing amount ratio>
For 10 substrates, the weight of each substrate before and after polishing is measured using BP-210S (trade name) manufactured by Sartorius, and based on the weight change of each substrate obtained, the amount of single-side polishing is calculated from the following formula. Asked.
The polishing amount ratio is calculated from the following formula based on the single-side polishing rate obtained by polishing the same substrate as the substrate to be polished used in Examples and Comparative Examples under the polishing conditions shown in Table 2 in advance. Obtained.

2. Measurement conditions of long wavelength waviness The substrate after polishing was measured under the following conditions.
・ Equipment: THoT MODEL 4224 (manufactured by THoT Technology)
・ Measurement wavelength: 0.2mm-5mm
・ Gain: 16
・ Filter: 10kHz
・ Laser range: 5mm / s / V
Measurement area Inner Radius: 20 mm, Outer Radius: 46 mm (Measurement area: 54 cm ² )
・ Track pitch: 0.01mm
・ Spindle speed: 8000r / min

Of the 10 substrates after polishing, two substrates are arbitrarily extracted, and the long-wave waviness between the radii of 20 mm to 46 mm (measurement area of 54 cm ² ) on both surfaces of the substrate is averaged to obtain the “in-plane average long wavelength” "Swell". Further, the long wavelength waviness of the inner peripheral portion and the long wavelength waviness of the outer peripheral portion were obtained as long wavelength waviness of a radius 20 mm portion and a radius 46 mm portion, respectively.

3. Measurement conditions of AFM surface roughness Each substrate after polishing was measured under the following conditions.
Equipment: Atomic force microscope (Veeco: M5E)
・ Cantilever: UL20B
・ Mode: Non-Contact
・ Scanrate: 1.0 Hz
・ Scanarea: 5 μm × 5 μm
・ Needle diameter: 10nm

  The measurement area was selected so that the center of the measurement area was on the center line of the inner and outer circumferences of the disc and the long side of the area was in the tangential direction of the disc circle. This was measured evenly in the circumferential direction for each of the front and back 5 areas per disk, and the average value was defined as the “AFM surface roughness” of the disk.

  From Table 3, the substrate manufactured in Examples 1 to 10 has significantly reduced in-plane average long wavelength waviness and outer peripheral long wavelength waviness as compared to the substrates manufactured in Comparative Examples 1 to 5, and The surface roughness was also sufficiently reduced. Therefore, it turns out that all the substrates manufactured in Examples 1 to 10 have excellent surface smoothness.

  The magnetic disk substrate obtained by the manufacturing method of the present invention can be suitably used for manufacturing a high recording density hard disk. In particular, it is possible to industrially manufacture a hard disk with a high recording density of 50 Gbit / in 2 or more.

Claims (8)

  After polishing composition A containing colloidal particles having a volume average particle size of 0.005 to 0.1 μm is supplied to the substrate and the substrate is polished at a main processing pressure of 6 kPa or more, the main processing pressure of 20 to 80 is further increased. A method for manufacturing a magnetic disk substrate, comprising a step of polishing the substrate with a processing pressure of 1%.   The method for producing a magnetic disk substrate according to claim 1, wherein the polishing liquid composition A contains an acid. A method of manufacturing a magnetic disk substrate having the following steps:
(Step 1) A step of supplying a polishing composition B containing colloidal particles having a volume average particle size of 0.005 to 0.1 μm to the substrate and polishing the substrate with a main processing pressure of 6 kPa or more, and (Step 2) ) A polishing liquid composition C containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm is supplied to the substrate obtained in step 1, and the processing pressure is 20 to 80% of the main processing pressure in step 1 And polishing the substrate.   The single-side polishing amount of the substrate in step 1 is 0.05 μm or more, and the ratio of the single-side polishing amount in step 2 (single-side polishing amount in step 2 / single-side polishing amount in step 1) to the single-side polishing amount in step 1 is 0.1. The method for producing a magnetic disk substrate according to claim 3, which is from ˜1.0. 5. The method for manufacturing a magnetic disk substrate according to claim 3, further comprising the following polishing step 3 after the step 2:
(Step 3) A polishing liquid composition D containing colloidal particles having a volume average particle diameter of 0.005 to 0.1 μm is supplied to the substrate obtained in Step 2, and the processing pressure is 80% or less of the processing pressure in Step 2. Polishing the substrate with pressure.   The method for producing a magnetic disk substrate according to claim 3, wherein the polishing liquid composition B contains an acid.   The method for producing a magnetic disk substrate according to claim 3, wherein the polishing composition C contains an acid.   The method for producing a magnetic disk substrate according to claim 5, wherein the polishing liquid composition D contains an oxidizing agent.