JP2000086301A - Cleaning of glass substrate for magnetic disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning a glass substrate for a magnetic disc, capable of selectively removing alkali metals from the surfaces of the glass substrate produced by an alkali ion exchange reinforcement method by cleaning the surfaces of the glass substrate with ion water activated by an electric polarization method, and to provide a glass substrate for a magnetic disc having a magnetic medium hardly corroded and having a good S/N ratio. SOLUTION: This method for cleaning a glass substrate for a magnetic disc uses a glass substrate or crystallized glass substrate pulled up from a chemically reinforcing treatment liquid by an alkali ion exchange method. Therein, after a final polishing process for producing the glass substrate for the magnetic disc the glass substrate is cleansed with anode water activated by an electric polarization method to selectively remove alkali metals contained near to the surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass substrate for a magnetic disk used for a hard disk or the like used as a large-scale storage medium for a computer, and more particularly, to a method for manufacturing a glass substrate for chemical strengthening by alkali ion exchange. The present invention relates to a method for manufacturing a glass substrate for a magnetic disk or the like, characterized by washing a glass substrate, a crystallized glass substrate, and the like with active ion water by electric polarization.

[0002]

2. Description of the Related Art Conventionally, as a substrate for a magnetic disk, a substrate using an aluminum alloy and having its surface plated with nickel phosphorus has been widely used. Due to the necessity of lowering the flying height of the head and improving impact resistance, the proportion of glass substrates used has been increasing.

A glass substrate for a magnetic disk is required to have properties such as withstanding a centrifugal force due to rotation of a drive and an impact force due to collision with a magnetic head, and a glass substrate having a large mechanical strength different from ordinary glass is required. .

In order to satisfy the above-mentioned mechanical strength, it is necessary to use a crystallized glass having a structure in which fine crystals are dispersed in a matrix and formed as a glass substrate, and the glass has a structure in which the glass is strengthened by its strain. Alternatively, after processing a glass substrate into a predetermined shape, an alkali metal having a large ionic radius (for example, K ⁺ ) is infiltrated into the surface thereof by thermal diffusion, and a large compressive stress due to a difference in ionic radius is applied to the surface of the glass substrate. As described above, an ion-strengthened glass substrate is used which strengthens the glass substrate.

[0005] In particular, in recent years, the use of MR heads (magnetoresistive heads) and GMR heads (high-density magnetoresistive heads) has increased the density of storage elements of hard disks. The magnetic head is
It is required that the surface of the disk substrate fly above the surface of the disk substrate to have a smooth surface that is less than 300 angstroms (sometimes referred to as an angstrom as A).

[0006]

However, since the size of the crystallized glass in the crystallized glass is on the order of microns, when the glass surface is polished, the matrix-like amorphous material and the crystallized material are not polished. It has been pointed out that due to the difference in hardness or the difference in its chemical properties, the surface that should be smooth originally fluctuates on the order of microns. This means that when such a glass substrate is used for a magnetic disk, it is difficult to lower the head such as the MR head or the GMR head by approaching the head, that is, to reduce the flying height. However, with the increase in the density of the magnetic disk, when a storage track is formed in a narrow area, that is, when a track is sandwiched between tracks, a so-called modulation (adjustment node) is observed in the reproduction output. I have. In order to avoid such a problem, it has become difficult to secure a predetermined smooth surface accuracy on the disk substrate surface in a magnetic disk using the above-mentioned crystallized glass. For this reason, it has been considered to use Ni-P plated on a polished surface of a crystallized glass substrate. In this case, since an alkaline polishing liquid is generally used for polishing glass, an alkaline component remains on the surface of the amorphous portion, and the gap between the crystalline body and the amorphous body, thereby deteriorating the adhesion of plating. In addition, there is a problem in that it reacts with moisture or carbon dioxide gas in the air to produce projection-like corrosion.

At present, tempered glass by alkali ion exchange is widely used for magnetic disks. However, in a hard disk using such tempered glass by alkali ion exchange, especially in the drive of a disk using the above-mentioned MR and GMR heads, the limit of the recording density is as follows.
From the viewpoint of medium noise, the magnetic storage layer on the surface of the disk substrate is made thinner to 100 Å or less, and a protective film formed on the surface of the head substrate is also formed to reduce space loss due to the medium of the head itself. What has been required about 150 Å in the past has been reduced to about 50 Å.

In particular, regarding the medium noise, the factors that determine the medium noise are the surface smoothness of the glass substrate and
This is attributed to moisture adsorbed during the magnetic film sputtering attachment process. That is, the glass substrate is washed immediately before entering the medium manufacturing process. However, if an alkali component is present on the surface of the glass substrate, moisture is easily adsorbed, and the S / N ratio, which is a characteristic of the medium, is reduced by the adsorbed moisture. become worse. Furthermore, when an alkali component is present on the surface of the glass substrate, the alkali component penetrates into the magnetic film formed on the surface of the glass substrate, causing corrosion (erosion / corrosion). Among some alkali components, particularly when sodium ions are present, the worst state such as deterioration of the storage medium layer upon formation of the film of the storage medium or deterioration of the storage medium layer after formation is brought about.

For this reason, conventionally, it has been proposed to wash the glass substrate with a phosphoric acid phosphoric acid solution immediately after the chemical treatment of the glass and to remove an alkali component on the surface of the glass substrate immediately before the medium manufacturing process. (Japanese Unexamined Patent Publication No.
-22525). In addition, surface roughness Ra is 10-2.
In the case of manufacturing a glass substrate having a thickness of about 0 Å, it is not necessary to consider the presence of the alkali component, particularly the presence of sodium ions, but it is necessary to consider a glass having a recently required surface roughness Ra of 5 Å or less. For substrates, a final polishing step is required to obtain finer surface roughness. However, when the surface of the glass substrate is polished in the final step, a new surface is exposed as a result of the polishing, so that the concentration of the alkali component present on the surface of the glass substrate is reduced. It will not go down. In addition, when micro cracks, which are fine cracks, are present in the glass substrate, in the polishing step, a polishing solution or the like penetrates into the micro cracks, and as a result, the magnetic properties of the glass substrate that has become a product are eventually determined. On the disc,
There is a problem that the medium causes corrosion of the surface.

[0010] Even after the final polishing step, the alkaline component on the surface is removed and the surface is washed with a normal acid or the like, the alkaline component can be removed, but the acid-containing solution can be removed. The surface treatment lowers the surface roughness, and further requires a new cleaning step to remove the acid component remaining on the surface of the glass substrate. And
In the case of cleaning with an acid, components mainly composed of an acid still remain on the surface, or penetrate into microcracks on the glass substrate, and these surface residues and permeates into the microcracks. Thus, during sputtering of the magnetic recording medium, it is mixed into the film of the magnetic recording medium, and
This results in lowering the medium SN ratio.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in the prior art. A step of performing an ion exchange reaction for a predetermined time in an ion salt bath, and a step of dissolving and removing an alkali salt attached to the surface of the glass substrate with a normal acid,
For the glass substrate that has been subjected to the final polishing step of spraying a polishing liquid onto the surface until the surface roughness Ra of the glass substrate becomes 5 Å or less, containing active ion water by electric polarization containing hydronium ions of a predetermined concentration. A cleaning step is performed, followed by a step of cleaning with pure water, and a step of drying after cleaning with pure water. Further, the present invention performs a step of washing the crystallized glass substrate that has been subjected to the final polishing step with an alkaline polishing liquid, containing a predetermined concentration of hydronium ions, with active ionized water by electric polarization, and thereafter Washing with pure water,
After washing with pure water, a drying step is performed.

That is, the invention according to claim 1 of the present application relates to a method of cleaning a glass substrate for a magnetic disk, and particularly to a method of cleaning a glass substrate or a crystallized glass substrate pulled up from a chemical strengthening treatment solution by alkali ion exchange. It is characterized in that it is washed with water to selectively remove the alkali metal on the substrate surface.

According to a third aspect of the present invention, in the method for cleaning a glass substrate for a magnetic disk according to the first aspect, the active ionic water is anodic electrolyzed water.

According to a fourth aspect of the present invention, in the method for cleaning a glass substrate for a magnetic disk according to the first aspect, the active ionic water is anodic electrolyzed water having a hydrogen ion concentration of pH 5 to 6. It is characterized by the following. Further, the invention according to claim 5 of the present application relates to a method for manufacturing a glass substrate for a magnetic disk, in which a glass substrate or a crystallized glass substrate pulled up from a chemical strengthening treatment solution by alkali ion exchange is treated with active ion water by electric polarization. It is characterized in that the substrate is washed to selectively remove the alkali metal on the substrate surface. The invention according to claim 6 of the present application is directed to a method of manufacturing a glass substrate for a magnetic disk having improved corrosion resistance and plating adhesion, particularly, by cleaning a crystallized glass substrate with active ion water by electrolysis. It is characterized in that alkali components on the glass surface and at the interface between the crystal and the amorphous glass are selectively removed. The invention according to claims 5 and 6 of the present application exerts the best effects by being carried out using anodic electrolyzed water as active ion water, particularly anodic electrolyzed water having a hydrogen ion concentration of pH 5 to 6. obtain.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment First, pellets are prepared by melting oxides of the following components as alkali ion exchange strengthened glass. SiO ₂ 61.8 WT% Al ₂ O ₃ 3.0 B ₂ O ₃ 1.1 Na ₂ O 9.0 K ₂ O 9.0 Mg0 3.0 ZnO 12.0 TiO ₂ 0.6 As ₂ O ₃ 0.2 Sb ₂ O ₃ 0.3 Next, the obtained pellets are compression-molded to a predetermined size by a hot press to obtain a glass material substrate without bubbles. Then, it is processed to a predetermined size through inner and outer peripheral processing and rough polishing and precision polishing.

Next, the processed glass substrate is placed in a molten salt containing potassium nitrate or the like at a temperature of 400 ° C. for 3 to 3 hours.
An ion exchange reaction is performed for 5 hours to form a reinforcing layer of about 40 microns on the surface of the glass material substrate. After the formation of the reinforcing layer, the surface of the glass material substrate is polished using an abrasive such as colloidal silica so that the surface roughness Ra is 5 Å or less.

The glass material substrate is immersed in anodic electrolyzed water having various ion concentrations (hereinafter sometimes referred to as “active ionic water”) for a predetermined time to be washed, and then washed with pure water. After that, rotate the glass substrate material itself,
Spin drying was performed, and then a corrosion resistance test was performed at 80 ° C. and 90% RH for 10 days, which is a kind of semiconductor evaluation standard, to measure the surface roughness and the maximum protrusion amount of the glass substrate material. Table 1 shows the state of processing the glass substrate with ionized water.

[0018]

[Table 1]

In Table 1, the symbol Ra indicates the initial center line average roughness, and a portion of the measured length is extracted from the roughness curve in the direction of the center line, and the center line of the extracted portion and the roughness curve are extracted. Is the value obtained by arithmetically averaging the absolute values of the deviations from each other, and specifically, the same sign RP indicates the difference between the maximum peak height and the minimum valley depth on the measured line, that is, the so-called peak-to-peak value. This indicates a peak. As can be seen from Table 1, it can be seen that the surface roughness of the glass substrate is not deteriorated by the washing, even when the glass substrate is immersed in the anodic electrolyzed water having an ion concentration of about 4 to 6 and washed. In addition, the ion-treated glass substrate is 80 ° C. 90%
A corrosion resistance test was performed for 10 days at RH to verify the maximum surface protrusion on the glass substrate surface. Table 2 shows the verification results.

[0020]

[Table 2]

In general, when the surface of the alkali ion exchange strengthened glass substrate is treated in a state where the pH ion concentration is high, the glass matrix is broken and the corrosion of the surface of the glass substrate is accelerated. As shown in Table 2, when the surface of the glass substrate is washed with anodic electrolyzed water having a moderate pH concentration, that is, in this embodiment, the pH concentration (ion concentration) is 5 to 6 anodic electrolyzed water, It can be seen that the alkali metal present on the surface of the glass substrate is removed without breaking the glass matrix, and as a result, the corrosion resistance of the glass substrate is rather improved.

Further, the glass substrate washed and immersed in anodic electrolyzed water having an ion concentration of about pH 5 to about 6 has a low alkali surface concentration, and therefore has a small amount of adsorbed water and is suitable as a high-density magnetic recording medium. I have. Therefore, degassing measurement was performed on the glass substrate subjected to such treatment and the untreated glass substrate using a quadrupole mass spectrometer, and the gas generation state from the glass substrate was verified. For this degassing measurement, a sample dried and spin-dried with pure water, which is a pretreatment of a normal magnetic disk sputtering process, was heated in a vacuum and subjected to gas analysis by the quadrupole mass spectrometer. The result is shown in FIG.

FIG. 1 shows the state of adsorption of water present on the surface by washing (immersion) in anodic electrolyzed water performed before sputtering of a glass substrate for a magnetic disk, as shown in FIG. FIG. 1B is a graph showing a gas generation state in a case where the glass substrate is immersed in anodic electrolyzed water having a pH of 5 for 1 minute for cleaning. As can be seen from FIGS. 1 (a) and 1 (b), when there is no washing with ion water, large gas generation is observed at a temperature of around 450 ° C. When the substrate is immersed for one minute for cleaning, it can be seen that gas generation is greatly suppressed.

In the above-described embodiment, the object to be cleaned is used for cleaning a glass substrate for a magnetic disk used for a hard disk as a computer storage medium. It is also applicable to semiconductor substrates for magnetic disks that are exposed during the polishing process.

(Second Embodiment) The inventors of the present invention used the alkali ion exchange strengthened glass of the first embodiment at a pH concentration of 5-6.
Anodic electrolyzed water with a ionic concentration of about
It is also called "ion water". The surface roughness of the glass substrate washed by immersion in ()) is improved, but the surface hardness of the glass substrate is improved depending on the change in the ion concentration or the immersion time, and further, the impact resistance is affected. To have a positive effect.

That is, in the final polishing step of manufacturing a medium for a glass substrate, a polishing liquid containing an alkali component is used in order to improve the surface roughness of the substrate. However, it reacts with the silicate component generated in the polishing step to break the Si—O bond, which is the skeleton with the medium glass, so that its surface hardness is significantly reduced. Therefore, in the final step of polishing, the substrate is immersed in ion water and washed to remove an alkali component, and the surface is subjected to a dealkalization treatment and an etching treatment at the same time, thereby improving the surface roughness and increasing the surface hardness. And the corrosion property can be improved.

FIGS. 2 and 3 show the results obtained by immersion in Blank (no treatment) and anodic electrolyzed water (ionic water) at pH 6 for 1 to 3 minutes, and for 1 minute each in anodic electrolyzed water (ionic water) at pH 3 to pH 5 for 1 minute. The hardness of the surface layer of each glass substrate when immersed and washed is 0.1 micron and the Vickers hardness up to 1 micron is measured by a NEC Thin Film Hardness Tester for HDD (MHA-400). In the figure,-◆-indicates that the glass substrate is SiO
_{2 When} polished using (silicon dioxide) (a),-■-
(B) shows the case where the glass substrate was polished using Ce (cerium). And as Test1, it is in ion water of pH6 for 1 minute, and as Test2,
2 minutes in ionic water of pH 6, as Test3, pH
6 for 3 minutes, as Test 4, 1 minute in pH 5 ionized water, as Test 5, 1 minute in pH 4 ionized water, and as Test 6, 1 minute in pH 3 ionized water for washing. Measured. In FIGS. 2 and 3, as Test7, Blank without treatment without washing by immersion in ion water or the like is shown as Blank.

As shown in FIGS. 2 and 3, when a polishing solution containing an alkali component is used in the final polishing step, the alkali component in the polishing solution and the silicic acid component generated in the polishing process are mixed. It can be seen that the Si-O bond, which is the skeleton of the glass substrate, is destroyed by the reaction, and the surface hardness is significantly reduced.

Next, the impact resistance of a 2.5-inch glass substrate subjected to these treatments was tested. This test was performed using a pendulum impact tester PST-300 manufactured by Yoshida Seiki.
The measurement was performed so that a half-sine waveform was drawn with the impact pendulum radius set to 300 mm, the action time set to 1.0 msec, and the test head spring pressure set to 0.5 grf. That is, a pendulum having a radius of 300 mm is dropped from the horizontal state to a pendulum vertical plane four times while changing G, and is immersed in ionic water for cleaning, and the conventional one without cleaning is performed. Was visually observed. Table 3 shows the damage state, in which a circle indicates an excellent impact resistance, and a cross indicates an improper one.

[0030]

[Table 3]

Table 4 shows the state of strengthening of the conventional glass substrate without cleaning. Table 4 shows sample A (lot number 970318) and sample B (lot number 97
0722) shows the surface stress (kg / mm ² ) and the stress depth (μm) of Sample A and Sample B before and after the final polishing step.

[0032]

[Table 4]

As shown by the measurement results shown in Table 4 above,
Before the final polishing step, the sample A is 77-86 k
g / mm²Of the sample B was 110-11
5kg / mm²Surface stress, which is
Later, in sample A, 65 to 70 kg / mm²of
It becomes the surface stress, and in Sample B, 100 kg / mm ²
It can be seen that it exhibits a surface stress of And at this time
The stress depth (μm) of sample A is 30-
33.8 μm, for sample B 29-30 μm
Met. As shown in FIG. 2 and FIG.
Glass substrates that have been cleaned by immersion in
The impact resistance performance does not change even if the
Can get.

FIGS. 4 and 5 show the measurement results showing that the projections on the glass substrate surface due to the corrosion of the alkali component by the ionic water are preferentially dissolved and flattened. Similarly to the above, the maximum value was measured by changing the location on the sample at intervals of 200 microns using Tarystep manufactured by Rank Taylor Hobson.

As shown in the results of no treatment in FIGS. 4 and 5, when a gel layer containing an alkali component having low hardness is present on the surface of the glass substrate, the alkali component reacts with carbon dioxide gas in the air, Within a short period of time, protrusions are formed on the surface due to corrosion, and the surface roughness deteriorates.

Next, the present inventors again tried to measure the improvement of the surface roughness by washing with ion water. That is, changes in the surface roughness maximum value (Rt) and the center line average roughness (Ra) of the HDD (hard disk) glass substrate due to ionic water cleaning were measured.

This measurement was performed on silicon glass for HDD (hard disk) and Zn silicate glass.
The pH concentration of the ionic water is divided into 2 to 8 without treatment, and the silicon glass for HDD (hard disk) and the normal glass are immersed in the ionic water with different pH concentration (including no treatment) for 1 minute. Then, the substrate was washed, and then immersed in ultrapure water for 3 minutes, washed, blow-dried with nitrogen gas at room temperature, and one surface was measured four times. FIG. 4 shows the maximum surface roughness (Rt), and FIG. 5 shows the same surface roughness (Ra). 4 and 5,-■-indicates a silicon glass substrate for an HDD (hard disk), and-◆-indicates a maximum surface roughness (Rt) of Zn silicate glass.

The measurement was performed using a Tarystep measuring device manufactured by Rank Taylor Hobson Co., Ltd.
It was measured four times at intervals of 00 microns at different locations, and the maximum value was recorded.

As is clear from FIGS. 4 and 5, it is known that the surface roughness is improved because the alkali component of the glass substrate is removed and the surface is etched simultaneously by the ionic water cleaning treatment. sell. In particular, protrusions generated on the surface of the glass substrate selectively act on ionic water composed of carbonate rich in alkali components,
It can be seen that the reaction is promptly promoted, the protrusions based on the corrosion by the alkali component are preferentially removed, the glass surface is smoothed, and the surface roughness is improved. Furthermore, the inventors of the present application have improved the glass substrate surface roughness and removed the alkali component, thereby removing OH groups on the glass surface, and as a result, a smooth film of SiO 2 was formed. Therefore, the improvement of the orientation of the magnetic film sputter-formed on this film was measured.

[0040] Figure 6, the graph shown in FIG. 7 shows a [Delta] [theta] ₅₀ which is oriented performance of titanium crystal of the underlying magnetic layer sputtered on a glass substrate surface. Where Δθ
₅₀ refers to the angular width of a place where the diffraction line intensity is １ ／. The narrower the width, the better the index indicating that the orientation of the place is better.

FIGS. 6 and 7 are graphs showing the orientation of the titanium crystal (002) on the glass surface by the X-ray half width. These graphs are obtained by using a Cu target scintillation counter manufactured by Rigaku Denki's X-ray diffractometer, using a sputtering film pressure of 700 Å and a sputtering pressure of 0.2 Pa.
And a divergence slit 1/2 de using a high resolution RINT200 wide angle goniometer with an attachment ASC-5.
g. , Scattering slit 1/2 deg. , Receiving slit 0.
Scanning speed of 1.000 ° / mi at 15 mm with fully automatic monochrome count meter in continuous operation mode
n, scan step 0.010 °, operation axis (θ), search range 5.000 to 35,000 °, 2θ, fixed angle 0.
It was measured at 000 °.

FIG. 6 shows a measurement of a sample (sample name: S84ND-5 rocking) which has not been washed with ionized water, and FIG. 7 shows a sample (A84SD7 rocking) which has been washed by being immersed in ionized water.
Is measured. In FIG. 6, the Δθ ₅₀ is
In contrast to 5.83 °, the one subjected to the cleaning treatment by immersion in ion water has the Δθ as shown in FIG.
₅₀ is 4.38 °, indicating that the alignment performance has been enhanced.

As a result, the orientation of the underlying film on the surface of the glass substrate becomes uniform, so that the orientation of the magnetic film sputtered thereon also increases.
In the / N ratio, about 3 to 5 db can be improved.

As described above, in the method of manufacturing a glass substrate for a magnetic disk according to the present invention, the pH value of the alkaline component-rich carbon dioxide can be increased by appropriately selecting the pH value of the ionic water to be used. The projections on the substrate surface due to the salt are removed by reaction, and the surface roughness is further improved. Furthermore, by appropriately selecting the ion concentration and the cleaning (immersion) time, the surface hardness increases, and when this is used for an HDD (hard disk) base, its impact resistance is improved.

By preliminarily performing the immersion treatment with ion water, the surface roughness of the glass substrate is improved. As a result, the orientation of the base film and the magnetic film sputtered on the substrate surface is improved. Since the generation of gas at the sputtered area is also suppressed, Δθ ₅₀ of the film to be sputtered can be reduced accordingly, and the surface roughness of the magnetic film is also improved from this point. Thus, a noise reduction effect of about 5 db at the maximum can be achieved.

(Third Embodiment) The inventors of the present invention melted amorphous glass, molded it, heat-treated it for crystallization, and manufactured it by final polishing.
% Of the crystallized glass is immersed in anodic electrolyzed water having an ion concentration of about pH 6 (hereinafter, sometimes also referred to as “ion water”) and washed, whereby the plating adhesion is improved, Protrusions based on corrosion due to components are removed preferentially, the glass surface becomes smooth,
It was found that the surface roughness was improved.

That is, in the above-mentioned glass substrate, an alkaline polishing liquid is usually used in the final polishing step. However, this component remains on the surface of the amorphous glass and at the interface between the crystal and the amorphous glass, and the plating is carried out. It deteriorates adhesiveness and reacts with moisture and carbon dioxide in the air to produce projection-like corrosion. Then, after the final polishing step, by immersing in alkaline water to wash the alkaline components, the corrosion resistance and the plating adhesion can be improved.

First, the following components are dissolved as crystallized glass to form pellets. SiO ₂ 76.8 WT% Li ₂ O 15.0 Al ₂ O ₃ 4.0 K ₂ O 2.0 P ₂ O ₂ 2.0 As ₂ O ₃ 0.2 Next, the obtained pellets were 900 ° C, heat treated for crystallization for 90 minutes, using colloidal silica and alkaline polishing liquid (NaOH), and having a surface roughness Ra of 5 Å and a maximum surface roughness Rt of 47 Å,
A disk-shaped crystallized glass substrate having a predetermined size is obtained. FIG. 8 shows a roughness measuring device (Tecor) manufactured by Tencor, USA.
ncor P-1) is a measurement of the surface roughness of the crystalline glass substrate after the final polishing. One of the results of linearly scanning the substrate four times at a speed of 10 angstroms / sec over 500 μm by rotating the substrate by 90 degrees, where the surface roughness Ra is 5 angstroms,
It was confirmed that the maximum surface roughness Rt was 56 Å.

The glass substrate is washed by immersing it in anodic electrolyzed water having an ion concentration of pH 3 for 3 minutes. Thereafter, the glass substrate is washed with pure water, the glass substrate itself is rotated, and spin drying is performed. A corrosion resistance test was performed on C90% RH for 10 days to measure the surface roughness of the glass substrate. For comparison, a glass substrate that had not been immersed in anodic electrolyzed water and was not washed was subjected to a corrosion resistance test at 80 ° C. and 90% RH for 10 days to measure the surface roughness of the glass substrate.

FIGS. 9 and 10 show the results of measurement of the surface roughness of the untreated glass substrate for comparison. The substrate was rotated 90 degrees at a time, and two of the results of scanning four times linearly at a speed of 2 μm / sec over 200 μm were obtained.
Shows one. In the result of FIG. 9, the surface roughness Ra is 12
In FIG. 10, the surface roughness Ra is 106 Å and the surface roughness maximum value Rt is 116 Angstroms and the maximum surface roughness Rt is 202 Angstroms.
It is 1 angstrom, and it can be seen that protrusions were formed as compared with the surface roughness of the glass substrate before the corrosion resistance test. FIG. 11 shows an AFM obtained by observing the surface of the untreated glass substrate with a stylus diamond (0.5 r, 15 r).
mg load). A huge projection is formed, and it can be seen that the results of FIGS. 9 and 10 are correct. As shown in FIGS. 9 to 11, when a polishing liquid of an alkali component is used in the final polishing step, the alkali component remaining on the surface of the crystalline glass and the interface between the crystalline and the amorphous glass becomes air. It can be seen that it reacts with the moisture and carbon dioxide gas therein to cause corrosion and form huge projections.

FIG. 12 shows the results of measuring the surface roughness of a glass substrate washed by immersion in the anodic electrolyzed water for 3 minutes.
Rotate the substrate 90 degrees at a time, 2 μm over 200 μm
One of the results of four linear scans at a speed of / sec is shown. The results of FIG. 12 show that the surface roughness Ra is 15 angstroms and the surface roughness maximum value Rt
Is 164 angstroms. As shown in this figure, when the crystallized glass substrate is immersed in ion water and washed,
Alkali components on the substrate surface, in particular, when a polishing solution of an alkali component is used in the final polishing step, the alkali components remaining on the crystalline glass surface and the interface between the crystal and the amorphous glass can be selectively removed. As a result, it can be seen that the formation of projections due to corrosion due to the remaining alkali component is prevented, the surface of the glass substrate is smoothed, and the surface roughness is improved.

Further, the present inventors have found that Ni-
P plating was performed, and the adhesion of the plating was measured. First, a crystallized glass having a surface roughness Ra of 5 angstroms and a maximum surface roughness Rt of 56 angstroms is obtained as described above. This glass substrate is washed by immersing it in anodic electrolyzed water having an ion concentration of pH 3 for 3 minutes, then washed with pure water, and the glass substrate itself is rotated to perform spin drying. Then, after activating the glass surface with a Pt catalyst, Ni-P was plated to a thickness of 2 μm with an electrolytic plating solution manufactured by Uemura Kogyo and an adhesion test was performed using a tape. For comparison, a glass substrate that had not been immersed in anodic electrolyzed water and was not washed was activated with a Pt catalyst on the glass surface, then plated with Ni-P to a thickness of 2 microns, and adhered using tape. Tested.

As a result, in the glass substrate washed with the ionized water, the adhesion to the uncleaned glass substrate was 100%.
, 150-250%, twice the average adhesion was exhibited. As shown in the results, when the crystallized glass substrate is immersed in ionic water and washed, the alkali component on the substrate surface, particularly when the polishing liquid of the alkaline component is used in the final polishing step, the amorphous glass surface and the crystal The alkali component remaining at the interface between the body and the amorphous glass can be selectively removed,
Thereby, it can be seen that the plating adhesion to the glass surface is improved.

[0054]

As described above, the cleaning of an ion-exchange-strengthened magnetic disk substrate or a crystallized glass substrate with ionized water containing hydronium ions reduces the alkali component concentration on the substrate surface without lowering its surface roughness. The problems with this type of substrate are substrate corrosion and medium S
Effectiveness can be expected in improving the N ratio and preventing corrosion of the magnetic recording film. The ion concentration used can be appropriately changed depending on the glass component and the conditions of ion strengthening.

That is, the present invention focuses on the phenomenon that the diffusion of alkali metal in glass is remarkably accelerated by hydronium ions H ₃ O. It is used for cleaning a magnetic disk substrate and a crystallized glass substrate. Anode electrolyzed water, obtained by electrolysis of water, is very active and selectively replaces the alkali metal component on the surface of the glass substrate, thereby reducing the alkali component concentration on the surface of the glass substrate. More specifically, since the substitution reaction with the alkali component is selectively performed, the surface roughness of the glass substrate can be adjusted by appropriately setting the concentration of the anode electrolyzed water to be used. There is a remarkable effect that only the alkali ion concentration on the surface of the glass substrate can be reduced without deteriorating the density.

In addition, the anode electrolyzed water generally has a small molecular size, has good permeability to microcracks (microcracks) in a glass substrate, and easily penetrates into cracks. Even if a component is present, the alkali component in the crack can be efficiently removed. Furthermore, since other base ions other than hydronium ions need only be relatively small,
After washing with anode electrolyzed water, there is no need to use a special acid or alkali-based detergent, and only washing with pure water is sufficient.Conventionally, there is no need to take the extra washing step required. This has the effect.

In the method of cleaning a glass substrate for a magnetic disk according to the present invention, by appropriately selecting the pH value of the ionic water to be used, the projections on the substrate surface due to the carbonate rich in the alkali component are removed by reaction. The surface roughness can be further improved, and as a result, the orientation of the base film and the magnetic film sputtered on the substrate surface is improved, and the generation of gas at the sputter ground is suppressed. Δθ ₅₀ of the film to be sputtered can be reduced, and the surface roughness is also improved from this point. As a result, a noise reduction effect of about 5 db at the maximum can be achieved in terms of medium noise.

Further, the crystallized glass substrate for a magnetic disk was washed with ion water to obtain an NI-P
The plating adhesion can be improved. As a result, an effect of preventing damage to the magnetic disk due to detachment of the plating layer or the like can be expected.

Further, by appropriately selecting the ion concentration and the immersion time, the surface hardness is increased, and when this is used for an HDD (hard disk) base, its impact resistance is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state of moisture adsorption by immersion in anodic electrolyzed water performed before sputtering of a glass substrate for a magnetic disk.

FIG. 2 shows the surface of a glass substrate without treatment (Blank) and immersed in anodic electrolyzed water (ionic water) at pH 6 and anodic electrolyzed water (ionic water) at pH 3 to pH 5 for 1 to 3 minutes, respectively. The figure which shows the result of having measured layer hardness and Vickers hardness.

FIG. 3 shows the surface of a glass substrate without treatment (Blank) and immersed in anodic electrolyzed water (ionic water) of pH 6 and anodic electrolyzed water (ionic water) of pH 3 to pH 5 for 1 to 3 minutes, respectively. The figure which shows the result of having measured layer hardness and Vickers hardness.

FIG. 4 is a view showing a measurement result indicating that projections on the surface of a glass substrate are preferentially dissolved and flattened by corrosion of an alkaline component of ionized water.

FIG. 5 is a view showing a measurement result indicating that projections on a glass substrate surface are preferentially dissolved and flattened by corrosion of an alkaline component of ionized water.

FIG. 6 is a graph showing Δ crystal orientation performance of a titanium film on the surface of a base film and a magnetic film sputtered on the surface of a glass substrate.
The figure which shows (theta) ₅₀ in a graph.

FIG. 7 is a graph showing Δ crystal orientation performance of a titanium film on the surface of a base film and a magnetic film sputtered on the surface of a glass substrate.
The figure which shows (theta) ₅₀ in a graph.

FIG. 8 is a view showing the results of measuring the surface roughness of a crystallized glass substrate after final polishing.

FIG. 9 is a view showing measurement results indicating that projections were formed on the surface of crystallized glass by corrosion of an alkali component.

FIG. 10 is a diagram showing measurement results indicating that projections were formed on the surface of crystallized glass by corrosion of an alkali component.

FIG. 11 is a diagram in which a projection formed on the surface of crystallized glass by corrosion of an alkali component is observed by AFM.

FIG. 12 is a diagram showing a measurement result indicating that a protrusion due to corrosion was not formed as a result of selectively removing an alkali component by a washing treatment with anode electrolyzed water (ionized water).

[Explanation of Symbols] Ra centerline average roughness (surface roughness) Rp centerline peak height Rt maximum surface roughness

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Claims (6)

[Claims] 1. A method for cleaning a glass substrate for a magnetic disk, wherein the substrate is cleaned with active ionized water by electric polarization to selectively remove an alkali component on the surface of the substrate. 2. The magnetic disk glass substrate according to claim 1, wherein the magnetic disk glass substrate is a glass substrate or a crystallized glass substrate pulled up from a chemical strengthening treatment solution by alkali ion exchange. Cleaning method. 3. The method for cleaning a glass substrate for a magnetic disk according to claim 1, wherein the active ionized water is electrolyzed anode water. 4. The method for cleaning a glass substrate for a magnetic disk according to claim 1, wherein the active ionized water is anode electrolyzed water having a hydrogen ion concentration of pH 5 to 6. 5. A method of manufacturing a glass substrate for a magnetic disk, wherein after the final polishing step for finishing the glass substrate to a predetermined surface roughness, the alkaline component on the substrate surface is selectively removed by washing with active ion water by electric polarization. A method for manufacturing a glass substrate for a magnetic disk, which comprises removing the glass substrate. 6. A method of manufacturing a glass substrate for a magnetic disk having improved corrosion resistance and plating adhesion, wherein the crystallized glass substrate is washed with active ion water by electric polarization after a final polishing step for finishing to a predetermined surface roughness. A method for manufacturing a glass substrate for a magnetic disk, wherein an alkali component on an amorphous glass surface and an interface between a crystal and an amorphous glass is selectively removed.