JP2009151905A - Method of manufacturing glass substrate for magnetic disk and method of manufacturing magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a glass substrate for a magnetic disk including an evaluation step of easily evaluating presence of an organic contamination on the glass substrate. <P>SOLUTION: The method of manufacturing the glass substrate for the magnetic disk including a mirror finishing step and a washing step of the glass substrate has a step of evaluating presence of the organic contamination on a principal surface of the glass substrate after the washing step. The presence of the organic contamination is evaluated by dyeing the principal surface of the glass substrate and using an optical surface analysis method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic disk mounted on a magnetic disk device such as a hard disk drive (HDD) or a method for manufacturing a glass substrate for a magnetic disk for manufacturing the magnetic disk.

One of recording media for information processing equipment such as a hard disk drive (HDD) is a magnetic disk. A magnetic disk is configured by forming a thin film such as a magnetic layer on a substrate, and an aluminum substrate has been used as the substrate. However, recently, in response to the pursuit of higher recording density, the proportion of the glass substrate that can narrow the gap between the magnetic head and the magnetic disk as compared with aluminum is gradually increasing. Further, the surface of the glass substrate is polished with high accuracy so as to increase the recording density so that the flying height of the magnetic head can be reduced as much as possible.
As described above, high smoothness on the surface of the magnetic disk is indispensable for reducing the flying height (flying height) necessary for increasing the recording density. In order to obtain a high smoothness on the surface of the magnetic disk, a substrate surface with a high smoothness is ultimately required. However, it is no longer possible to achieve a high recording density of the magnetic disk by simply polishing the substrate surface with high precision. Well done. In other words, no matter how much the polishing is performed, if the foreign matter adheres to the substrate, high smoothness cannot be obtained. Needless to say, foreign substances have been removed from the past, but foreign substances on the substrate, which have been allowed in the past, are regarded as a problem at the level of high density today.

A glass substrate having high smoothness can be obtained by precision polishing using a cerium oxide abrasive. However, there is a problem that the surface roughness cannot be reduced by leaving the protruding foreign matters that cannot be removed by ordinary cleaning after the polishing step with the cerium oxide-based abrasive. In many cases, the protruding foreign matter is formed with abrasive grains remaining on the substrate.
For example, in the technical field of glass substrates for information recording media, it is proposed to perform sulfuric acid cleaning after polishing using cerium oxide abrasive grains as a technique for removing protruding foreign substances formed by adhering cerium oxide abrasive grains. (Patent Document 1 below).

JP 2000-348338 A

Recently, information recording density of 60 Gbit / inch ² or higher has been required for hard disk drives (HDD). This is related to the fact that HDDs have been installed in mobile phones, navigation systems, digital cameras, etc., in addition to the need for conventional computer storage devices.
In these new applications, the housing space for mounting the HDD is significantly smaller than that of a computer, so it is necessary to downsize the HDD. For this purpose, it is necessary to reduce the diameter of the magnetic disk mounted on the HDD. For example, a 3.5-inch type or 2.5-inch type magnetic disk could be used in a computer application, but in the case of the new application, a smaller diameter, for example, a 0.8-inch type to a 1.8-inch type is used. A small-diameter magnetic disk such as an inch type is used. Even when the diameter of the magnetic disk is reduced in this way, it is necessary to store a certain amount of information capacity, which will increase the speed of information recording.

Also, in order to effectively use the limited disk area, a HDD of LUL (Load Unload) method has been used instead of the conventional CSS (Contact Start and Stop) method. In the LUL method, when the HDD is stopped, the magnetic head is retracted to an inclined table called a ramp located outside the magnetic disk, and during the start-up operation, after the magnetic disk starts to rotate, the magnetic head is moved from the ramp onto the magnetic disk. Slide and fly to record and playback. During the stop operation, the magnetic head is retracted to the ramp outside the magnetic disk, and then the rotation of the magnetic disk is stopped. This series of operations is called LUL operation. Magnetic disks for LUL HDDs do not need to have a contact sliding area (CSS area) with the magnetic head as in the CSS system, and can expand the recording / playback area, which is preferable for high information capacity. is there.
In order to improve the information recording density under such circumstances, it is necessary to reduce the spacing loss as much as possible by reducing the flying height of the magnetic head. In order to achieve an information recording density of 60 gigabits or more per square inch, the flying height of the magnetic head needs to be 10 nm or less. Unlike the CSS method, the LUL method does not require a concave / convex shape for CSS on the magnetic disk surface, and the magnetic disk surface can be extremely smoothed. Therefore, in the magnetic disk for LUL method, the flying height of the magnetic head can be further reduced compared to the CSS method, so that the S / N ratio of the recording signal can be increased and the recording capacity of the magnetic disk device can be increased. There is also an advantage of being able to contribute.

Due to a further drop in the flying height of the magnetic head accompanying the recent introduction of the LUL method, it has become necessary to operate the magnetic disk stably even at an extremely low flying height of 10 nm or less.
As described above, the recording capacity of the magnetic disk has been increasing year by year, and accordingly, the flying height of the magnetic head has reached 10 nm. In this area, even a very small defect on the magnetic disk greatly affects the reliability. Until now, the cleanliness of the surface of a magnetic disk and its glass substrate has been evaluated by defect inspection with an optical surface analyzer. In particular, in recent years, the magnetic disk has shifted from the in-plane magnetic recording system to the perpendicular magnetic recording system, and there is a strong demand for an increase in capacity of the magnetic disk and a reduction in flying height associated therewith.

At present, there are few known effective means for evaluating the specs despite the strict spec requirements for magnetic disks.
Reliability is the most important factor in the magnetic disk manufacturing process. For the evaluation of reliability, there is a method of inspecting the adhesion state of foreign matters such as irregularities and particles on the surface of the magnetic disk. As a magnetic disk inspection method, Glide inspection and Certify inspection are generally performed, but some of the magnetic films themselves may be peeled off (film peeling). It has been confirmed. In a reliability test in a high-temperature and high-humidity state (for example, 90 ° C. and 90% RH), foreign matter under the film expands and the magnetic film swells up, and the magnetic head collides with the portion to peel off the film. It has been confirmed that this causes problems such as film breakage (film breakage, film breakage) and head crash.

  According to the study of the present inventor, it has been found that organic contamination adheres to the glass substrate, which is the substrate of the magnetic disk, as one of the causes of the above film peeling and film swelling. Examples of the source include transportation of the glass substrate and adhesion from the atmosphere, organic substances contained in the cleaning agent, adhesion of the organic solvent in the drying step after cleaning, and the like. Many of these organic contaminants adhered to the glass substrate are difficult to confirm by conventional surface defect inspection methods. At present, for example, it is not possible to evaluate the contamination distribution on the substrate surface and the amount of contamination change before and after cleaning. Is possible.

However, according to the study by the present inventor, it is considered possible to evaluate by a technique for destroying a sample as shown below. That is, the glass substrate to be evaluated is crushed and sealed in a closed system. When the system is heated to 200 ° C. or higher, organic substances are burned to form carbon dioxide and released into the system. When the gas in the system is passed through a GC-MS tester (a composite device of two types of gas chromatography and mass spectrum) together with a carrier gas, a carbon dioxide signal is observed, and from the signal area, the amount of carbon dioxide gas, that is, It is possible to quantify the amount of organic contamination.
However, according to such an evaluation method, even if the amount of organic contamination can be evaluated, it is needless to say that the glass substrate can no longer be used as a product, and it is also impossible to perform 100% inspection. In addition, when organic contamination adheres on the substrate surface, the distribution state cannot be grasped. Furthermore, for example, it is impossible to evaluate how much the amount of organic contamination on the glass substrate has changed before and after the cleaning in order to confirm the cleaning effect.

From the above circumstances, it is useful if organic contamination on the glass substrate, which can cause peeling of the magnetic film and film swelling when a magnetic disk is manufactured, can be easily evaluated at the glass substrate manufacturing stage. It is clear that the nature is extremely high.
The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to provide a magnetic disk glass comprising an evaluation step by means capable of simply evaluating organic contamination on a glass substrate. An object of the present invention is to provide a method for manufacturing a substrate, or a method for manufacturing a magnetic disk using a glass substrate manufactured by the manufacturing method and evaluated by the above evaluation step that organic contamination is not more than a predetermined reference value.

As a result of intensive studies to solve the above problems, the present inventor has completed the present invention.
That is, the present invention is an invention having the following configuration.
(Structure 1 of the invention)
A method for producing a glass substrate for a magnetic disk comprising a mirror polishing process and a cleaning process for a glass substrate, comprising a step of evaluating the presence or absence of organic contamination on the main surface of the glass substrate at least after the cleaning process. The evaluation of the presence or absence of organic contamination is performed by dyeing the main surface of the glass substrate and using an optical surface analysis method.

(Configuration 2)
2. The method for producing a glass substrate for a magnetic disk according to Configuration 1, wherein organic matter present on the main surface of the glass substrate is selectively dyed by the dyeing treatment.
(Structure 3 of the invention)
3. The method for producing a glass substrate for a magnetic disk according to Configuration 1 or 2, wherein the amount of change in organic contamination on the main surface of the glass substrate before and after the cleaning treatment step is evaluated.

(Configuration 4)
A glass substrate manufactured by the method for manufacturing a magnetic disk glass substrate according to any one of Configurations 1 to 3, wherein the amount of the organic contamination is evaluated to be equal to or less than a predetermined reference value. And at least a magnetic layer is formed.

According to the present invention, there is provided a method of manufacturing a glass substrate for a magnetic disk including a mirror polishing process and a cleaning process of a glass substrate, and at least after the cleaning process, presence or absence of organic contamination on the main surface of the glass substrate The evaluation of the presence or absence of the organic contamination is performed by dyeing the main surface of the glass substrate and using an optical surface analysis method, so that organic contamination on the glass substrate can be easily performed. An evaluation process with means that can be evaluated is provided, and the presence or absence of organic contamination on the glass substrate that causes film peeling and film swelling when a magnetic disk is manufactured (if present) Amount, distribution state, etc.) can be easily evaluated in advance at the manufacturing stage of the glass substrate for magnetic disks, and its usefulness is extremely high.
Further, a highly reliable magnetic disk manufactured by the above-described manufacturing method according to the present invention, and a magnetic disk manufacturing method using a glass substrate that has been evaluated by the evaluation step to have an organic contamination of a predetermined reference value or less. Can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail.
A method for producing a glass substrate for a magnetic disk according to the present invention is a method for producing a glass substrate for a magnetic disk comprising a mirror polishing process and a cleaning process of the glass substrate, and at least after the cleaning process, the glass substrate main surface A step of evaluating the presence or absence of organic contamination above, wherein the evaluation of the presence or absence of organic contamination is performed by dyeing the main surface of the glass substrate and using an optical surface analysis method. It is.
That is, according to the present invention, by providing an evaluation step by means capable of simply evaluating the organic contamination on the glass substrate, the magnetic film is peeled off when the magnetic disk is manufactured. The presence or absence of organic contamination on the glass substrate, which causes swelling or the like, can be simply and easily evaluated in advance at the manufacturing stage of the magnetic disk glass substrate.

In the present invention, the evaluation of the presence or absence of organic contamination on the glass substrate main surface is carried out using an optical surface analysis method after dyeing the glass substrate main surface.
As described above, the source of organic contamination on the glass substrate includes the transportation of the glass substrate and adhesion from the atmosphere, organic substances contained in the cleaning agent, and organic solvent adhesion in the drying process after cleaning. Etc. In the dyeing treatment, it is desirable that the organic matter is selectively dyed with a stain exhibiting a specific reaction with the organic matter present on the main surface of the glass substrate. For this purpose, in the present invention, for example, a staining method using iodine, p-anisaldehyde, phosphomolybdic acid or the like is suitable. When organic matter is present on the main surface of the glass substrate by such dyeing treatment, the organic matter is dyed to facilitate observation of the surface of the glass substrate using an optical surface analysis method, which could not be observed conventionally. It is possible to observe and evaluate the distribution of organic contamination on the substrate surface.

The dyeing method will be described.
First, the dyeing method using iodine is a method in which a sample (glass substrate for magnetic disk) is left in gasified iodine vapor for a predetermined time to dye organic matter on the sample (red to brown).
In addition, the staining method using p-anisaldehyde or phosphomolybdic acid is a method in which an organic substance on a sample is stained by immersing the sample in each staining solution for a predetermined time. The p-anisaldehyde staining solution is a solution prepared by dissolving p-anisaldehyde in methanol and adding concentrated sulfuric acid under ice cooling. The concentration ratio in this case is adjusted by, for example, p-anisaldehyde: methanol: concentrated sulfuric acid = 10: 85: 5. Also, phosphomolybdic acid stain, phosphomolybdic acid _{(12MoO 3 · H 3 PO 4} · xH 2 O) was dissolved in ethanol, a solution with an adjusted concentration of, for example, 5%. The sample is preferably immersed, rinsed and dried using isopropyl alcohol (IPA) vapor, and then heated to about 200 ° C. to promote the dyeing reaction.
The sample used for the evaluation of organic contamination after dyeing can be further subjected to an appropriate cleaning method to remove organic substances on the glass substrate. Note that the present invention is not limited to the above dyeing method as long as it is a method capable of selectively dyeing organic substances present on the glass substrate.

In this invention, after dyeing the glass substrate main surface in this way, the organic contamination on a glass substrate main surface is evaluated using an optical surface analysis method.
For the evaluation using the optical surface analysis method, it is preferable to use an optical surface analyzer represented by, for example, OSA (Optical Surface Analyzer). In the present invention, the reason for using such an optical surface analysis method is that organic contamination on the main surface of the glass substrate subjected to the dyeing treatment can be easily observed, and the entire surface of the main surface of the substrate can be easily evaluated. It is because it is suitable for.

  The OSA is a measuring device that optically observes foreign matter or the like on a glass substrate. Specifically, a sample (glass substrate) that is an object to be inspected is rotated at high speed, and two laser beams are irradiated there from the radial direction and the circumferential direction, and the scattered light, reflected light, and phase difference are measured. Detect with a detector. For example, when a foreign substance adheres to the substrate surface, when the foreign substance is irradiated with laser light, scattering of the laser light and attenuation of reflected light are observed, so that the presence of the foreign substance can be detected. By scanning the entire surface of the sample with laser light while rotating the sample, laser light scattering, reflection, and phase difference are observed on the entire surface of the sample, and a defect (foreign particle defect) distribution can be obtained. In this case, the determination as to whether or not the defect is present is made by cutting the degree of scattering, reflection, and phase difference by a threshold value. However, if the threshold is set too severely (if the defect detection sensitivity is increased too much), it will be difficult to discriminate between defects such as foreign matter and irregularities on the substrate surface, and even defects that are not originally defects will be detected as defects. There is a fear.

For this reason, even if OSA is simply used, it is difficult to accurately detect organic contamination that is often low on the glass substrate and often adhered flatly. Dyeing the glass substrate prior to inspection makes it easier to detect the scattering, reflection, and phase difference of the laser light due to the stained organic contamination present on the glass substrate. Is possible.
Note that specific measurement conditions and the like necessary for the measurement by OSA or the like can be arbitrarily set as appropriate so that, for example, organic contamination can be easily observed.

  As described above, the organic contamination evaluation method of the present invention is suitable because the measurement can be performed nondestructively on the glass substrate to be evaluated, and the measurement can be performed without contact. If the subsequent glass substrate is a non-defective product, it can be used as a non-defective product, can be measured easily in a relatively short time, and the total number of glass substrates can be measured.

According to the method for manufacturing a glass substrate for a magnetic disk including the organic contamination evaluation step according to the present invention, the following effects can be obtained.
(1) Easily evaluate the presence or absence of organic contamination on the glass substrate, which can cause peeling of the magnetic film and swelling of the magnetic film when the magnetic disk is manufactured at the manufacturing stage of the magnetic disk glass substrate. Can do.
(2) When organic contamination is present (for example, attached) on the glass substrate, the amount thereof, the distribution state on the substrate, and the like can be evaluated.
(3) It is possible to provide a glass substrate for manufacturing a magnetic disk in which the amount of organic contamination on the glass substrate is evaluated in advance.
(4) The amount of change in organic contamination before and after the glass substrate cleaning step can be evaluated, and thereby, for example, the cleaning effect in the cleaning step can be evaluated.
(5) By being able to evaluate organic contamination on the glass substrate, it is possible to provide a glass substrate for a magnetic disk with even higher cleanliness by taking measures to reduce contamination, such as reviewing the cleaning process (cleaning method). .

  By manufacturing a magnetic disk using a glass substrate manufactured by the above-described manufacturing method according to the present invention and having an organic contamination evaluated to be equal to or lower than a predetermined reference value in the evaluation step, the magnetic film is peeled off. Further, the occurrence of film bulging, signal drop due to contact with the magnetic head, head fall, etc. can be remarkably reduced, and a highly reliable magnetic disk can be provided without failure even after long-term use. As the reference value, a level that does not cause a later problem such as peeling of the magnetic film may be set as appropriate.

The method for manufacturing a glass substrate for a magnetic disk according to the present invention includes at least a mirror polishing process and a cleaning process of the glass substrate.
In the present invention, the abrasive used for mirror polishing of the glass substrate is not particularly limited, and examples thereof include an abrasive containing a rare earth oxide as a main component. In particular, a cerium oxide-based abrasive containing cerium oxide as a main component is preferred.

  The method of mirror polishing in the present invention is not particularly limited, for example, while contacting the glass substrate and the polishing cloth, supplying the abrasive, relatively moving the polishing cloth and the glass substrate, The surface of the glass substrate may be polished in a mirror shape. A polishing pad can be used as the polishing cloth. The polishing pad is preferably a polishing pad of a soft polisher. The polishing pad preferably has an Asker C hardness of 60 to 80. The contact surface of the polishing pad with the glass substrate is preferably a foamed resin with an open foam pore, particularly foamed polyurethane. The average particle size of the abrasive grains contained in the abrasive can be 0.1 μm or more and 1 μm or less. When polishing is performed in this manner, the surface of the glass substrate can be polished into a smooth mirror surface.

In the present invention, the glass constituting the glass substrate is preferably an amorphous aluminosilicate glass. Such a glass substrate can be finished to a smooth mirror surface by polishing the surface. As such an aluminosilicate glass, SiO ₂ is 58 wt% to 75 wt%, Al ₂ O ₃ is 5 wt% to 23 wt%, Li ₂ O is 3 wt% to 10 wt%, Na ₂ An aluminosilicate glass containing O as a main component in an amount of 4 wt% or more and 13 wt% or less (however, an aluminosilicate glass containing no phosphorus oxide) can be used. For example, SiO ₂ is 62 wt% to 75 wt%, Al ₂ O ₃ is 5 wt% to 15 wt%, Li ₂ O is 4 wt% to 10 wt%, and Na ₂ O is 4 wt% to 12 wt%. Wt% or less, ZrO ₂ containing 5.5 wt% or more and 15 wt% or less as a main component, and a weight ratio of Na ₂ O / ZrO ₂ of 0.5 or more and 2.0 or less, Al ₂ O ₃ / ZrO _An amorphous aluminosilicate glass containing no phosphorous oxide having a weight ratio of ₂ of 0.4 to 2.5 can be obtained. In addition, it is desirable that the glass does not contain an alkaline earth metal oxide such as CaO or MgO. Examples of such glass include N5 glass (trade name) manufactured by HOYA Corporation.

  In the present invention, the surface of the glass substrate after the cleaning treatment is preferably a mirror surface having a maximum roughness Rmax of 6 nm or less. Such a mirror state can be realized by performing a mirror polishing process and a cleaning process in this order.

  You may perform a chemical strengthening process after a washing | cleaning process process. As a method of chemical strengthening treatment, for example, a low-temperature ion exchange method in which ion exchange is performed in a temperature range that does not exceed the temperature of the glass transition point, for example, a temperature of 300 degrees Celsius or more and 400 degrees Celsius or less is preferable. The chemical strengthening treatment is a process in which a molten chemical strengthening salt is brought into contact with a glass substrate, whereby an alkali metal element having a relatively large atomic radius in the chemical strengthening salt and a relatively small atomic radius in the glass substrate. This is a treatment in which an alkali metal element is ion-exchanged, an alkali metal element having a large ion radius is permeated into the surface layer of the glass substrate, and compressive stress is generated on the surface of the glass substrate. Since the chemically strengthened glass substrate is excellent in impact resistance, it is particularly preferable for mounting on a HDD for mobile use, for example. As the chemical strengthening salt, alkali metal nitric acid such as potassium nitrate or sodium nitrate can be preferably used.

  Further, a tape polishing process can be performed after the cleaning process. Recently, in order to improve the information recording density of a magnetic disk, magnetic anisotropy along the circumferential direction of the disk may be imparted to the magnetic layer of the magnetic disk. This is because the circumferential direction of the disk, that is, the moving direction of the magnetic head, contributes to higher recording density if magnetic anisotropy is given along this direction. By performing a tape polishing process on the surface of the disk-shaped glass substrate, it is possible to form a texture composed of streaks that are oriented in the circumferential direction of the disk. When a magnetic layer is formed on the textured glass substrate, magnetic anisotropy can be generated in the circumferential direction of the disk. In this texture treatment, a texture is formed on the surface of the glass substrate by bringing the polishing tape into contact with the glass substrate and relatively moving the polishing tape and the glass substrate.

  In the present invention, the magnetic disk is manufactured by forming at least a magnetic layer on the magnetic disk glass substrate according to the present invention. As the magnetic layer material, a hexagonal CoPt ferromagnetic alloy having a large anisotropic magnetic field can be used. As a method for forming the magnetic layer, a method of forming a magnetic layer on a glass substrate by sputtering, for example, DC magnetron sputtering can be used. Further, by interposing an underlayer between the glass substrate and the magnetic layer, the orientation direction of the magnetic grains of the magnetic layer and the size of the magnetic grains can be controlled. For example, by using a cubic base layer such as a Cr-based alloy, for example, the magnetization easy direction of the magnetic layer can be oriented along the magnetic disk surface. In this case, a magnetic disk of the in-plane magnetic recording system is manufactured. Further, for example, by using a hexagonal underlayer containing Ru or Ti, for example, the easy magnetization direction of the magnetic layer can be oriented along the normal of the magnetic disk surface. In this case, a perpendicular magnetic recording type magnetic disk is manufactured. The underlayer can be formed by sputtering as with the magnetic layer.

In the present invention, a protective layer and a lubricating layer are preferably formed in this order on the magnetic layer. As the protective layer, an amorphous hydrogenated carbon-based protective layer is suitable. For example, the protective layer can be formed by a plasma CVD method. The thickness of the protective layer is preferably 30 angstroms to 80 angstroms. Further, as the lubricating layer, a lubricant having a functional group at the end of the main chain of the perfluoropolyether compound can be used. In particular, it is preferable that the main component is a perfluoropolyether compound having a terminal hydroxyl group as a polar functional group. The film thickness of the lubricating layer is preferably 5 angstroms to 15 angstroms. The lubricating layer can be applied and formed by a dip method.
The highly reliable magnetic disk obtained by using the glass substrate of the present invention is particularly preferable as a magnetic disk for a hard disk drive mounted on a mobile device such as a mobile phone, a navigation system, or a digital camera.

Hereinafter, the manufacturing method of the glass substrate for magnetic disks and the manufacturing method of the magnetic disk will be described in more detail with examples.
(1) Roughing step, (2) End mirror polishing step, (3) Lapping step, (4) First polishing step, (5) Second polishing step (main surface mirror polishing step), (6) Cleaning The glass substrate for magnetic disks was manufactured through the process (cleaning process after mirror polishing).

(1) Roughening process First, a glass disk molded by the press method was ground with a relatively rough diamond grindstone. Next, both surfaces of the glass disk were ground with a diamond grindstone having a finer particle size than the grindstone. Thereby, the surface roughness of the glass substrate surface was finished to about 10 μm by Rmax (measured by JISB0601). Next, using a cylindrical grindstone, a hole was made in the center of the disk-shaped glass substrate to obtain a donut-shaped glass substrate.

(2) End Mirror Polishing Step Next, the surface roughness of the end surface of the glass substrate was mirror-polished to about 1 μm at Rmax and about 0.3 μm at Ra while rotating the glass substrate by brush polishing. A cerium oxide abrasive was used as the abrasive. Thereafter, the surface of the glass substrate was washed with water.
(3) Lapping process Next, the lapping process was performed to the glass substrate. This lapping process aims to improve dimensional accuracy and shape accuracy. The lapping process was performed using a lapping apparatus, and was performed twice, changing the grain size of the abrasive grains to # 400 and # 1000.

(4) First polishing step Next, a first polishing step was performed. This first polishing step is intended to remove scratches and distortions remaining in the lapping step described above, and was performed using a polishing apparatus. Specifically, a hard polishing pad made of polyurethane was used, and a cerium oxide abrasive was used as the abrasive. The glass substrate after the first polishing step was sequentially immersed in each of washing baths of neutral detergent, pure water, pure water, IPA (isopropyl alcohol), and IPA (steam drying) and washed.
(5) Second polishing step (main mirror polishing step)
Next, using the same polishing apparatus as used in the first polishing step, the polishing pad was changed from the hard polishing pad to the soft polishing pad, and the second polishing step was performed. The processing performed in the second polishing step is, for example, mirror polishing that finishes a smooth mirror surface having a surface roughness Rmax of about 6 nm or less while maintaining the flat main surface obtained in the first polishing step. It is processing. As the polishing pad, a soft polishing pad having Asker C hardness of 72 was used. The polishing liquid was a polishing liquid in which a cerium oxide abrasive was dispersed in pure water.

(6) Cleaning process (cleaning process after mirror polishing)
This cleaning process is a cleaning process for removing the abrasive remaining on the surface of the glass substrate that has been mirror-finished in the mirror polishing process. A cleaning liquid containing sulfuric acid was prepared, and a cleaning process was performed using this cleaning liquid. It was immersed in this cleaning solution (about 40 ° C.) for about 5 minutes.
When the surface roughness of the square area of 5 μm in length and 5 μm in width on the main surface of the glass substrate after this cleaning treatment was measured with an atomic force microscope (AFM), it was 4.0 nm for Rmax and 0.4 nm for Ra. It was.

A glass substrate for magnetic disk (sample A) was manufactured as described above.
In addition, a magnetic disk glass substrate (sample B) was produced in the same manner except that the washing conditions in the washing step were relaxed.
Sample A and Sample B are stained as follows, and then organic contamination on the glass substrate using OSA (using a measurement recipe that allows observation of defects using OSA6100 from KLA-TENCOL) Nation was evaluated.
In this example, a dyeing method using iodine was employed, and the sample A and the sample B were left in gasified iodine vapor for a predetermined time to perform a dyeing process.

  As a result, when compared with sample A, an increase in iodine-stained defects was observed for sample B. Therefore, it was found that organic contamination adhered to the surface of the glass substrate of Sample B, where the cleaning conditions after polishing were relaxed.

  As a reference example, when the same evaluation was performed using OSA (however, the above-described staining treatment was not performed) and GC-MS, Sample A was determined to be a non-defective product by either method. Regarding sample B, it was determined that the product was non-defective in OSA and defective in GC-MS. That is, it is possible to evaluate organic contamination that cannot be confirmed when inspected prior to OSA measurement without performing dyeing processing, by performing dyeing processing in advance and inspecting with OSA. Although it can be evaluated by GC-MS, since the sample is destroyed and evaluated, repeated measurement is impossible and reproducibility of evaluation cannot be obtained. According to the organic contamination evaluation method of the present invention, repeated measurement is possible, and evaluation reproducibility is also obtained.

  Next, each of sample A and sample B of the magnetic disk glass substrate obtained through the above-described steps, which was separately manufactured separately from sample A and sample B used for the evaluation of organic contamination, was applied to a DC magnetron type. Using a sputtering apparatus, a Ti-based adhesion layer, an Fe-based soft magnetic layer, a NiTa first underlayer, a Ru second underlayer, and a CoCrPt magnetic layer are sequentially formed, and then hydrogenated carbon is formed by plasma CVD. A protective layer was formed to a thickness of 40 Å, and an alcohol-modified perfluoropolyether lubricant was applied to a thickness of 10 Å by a dip method to produce a magnetic disk. This magnetic disk is a magnetic disk for perpendicular magnetic recording.

With respect to the magnetic disk obtained as described above, a predetermined glide test (a test for confirming that the height (glide height) for guaranteeing the flying of the slider on the disk is equal to or less than a predetermined reference value), certification ( Certify) test (test to record / reproduce the entire recording area of the recording medium with a head and detect recording failure due to a medium defect) and high temperature and high humidity test (magnetic disk at 90 ° C., 90% RH for 72 hours) As a result of performing the above glide test and certify test after standing), the magnetic disk using the sample A as a substrate passed both tests. On the other hand, the magnetic disk using Sample B as a substrate failed any test. This is thought to be due to the adhesion of organic contamination on the substrate surface of sample B. However, the evaluation of organic contamination on the glass substrate surface according to the present invention reflects the result in the magnetic disk evaluation as it is. The usefulness of the invention has been demonstrated.

Claims (4)

A method for producing a glass substrate for a magnetic disk including a mirror polishing process and a cleaning process of a glass substrate,
At least after the cleaning treatment step, there is a step of evaluating the presence or absence of organic contamination on the main surface of the glass substrate. The evaluation of the presence or absence of organic contamination is performed by dyeing the main surface of the glass substrate, The manufacturing method of the glass substrate for magnetic discs characterized by performing using an analysis method.   2. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein organic matter present on the main surface of the glass substrate is selectively dyed by the dyeing treatment.   The method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the amount of change in organic contamination on the main surface of the glass substrate before and after the cleaning process is evaluated. A glass substrate manufactured by the method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the amount of the organic contamination is evaluated to be equal to or less than a predetermined reference value. A method of manufacturing a magnetic disk, comprising forming at least a magnetic layer thereon.