JPH0827935B2 - Glass substrate for magnetic disk and manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a glass substrate for a magnetic disk, which is suitable for a magnetic recording medium having excellent durability.

[Prior Art] A magnetic disk substrate and sputtering, plating,
A structure composed of a magnetic film and a protective film formed by a process such as vapor deposition is called a magnetic recording medium (hereinafter, referred to as a medium).

A magnetic storage device has this medium and a recording / reproducing magnetic head (hereinafter referred to as a head) as main components, and by setting the head and the medium in contact with each other at the start of operation, and then applying the required rotation to the medium. A space for the air layer is formed between the head and the medium surface, and the recording / reproducing operation is performed in this state. At the end of the operation, the rotation of the medium stops, and at this time, the head and the medium return to the contact state as at the start of the operation.

As described above, the contact frictional force generated between the head and the medium at the time of starting and stopping the device wears the head and the medium and causes deterioration of the magnetic characteristics (this method is commonly called contact start / stop CSS). Exist).

Further, when the medium is left in a humid atmosphere and water is adsorbed on the surface of the medium, water enters between the head and the medium, causing an adhesion phenomenon. Therefore, when activated in this state, a large resistance force is generated in the head and the medium, which may lead to damage of the head and destruction of the medium (this is commonly called a head stick or a head crash).

In general, glass has attracted attention as a magnetic disk substrate suitable for high density because of its excellent surface smoothness, hardness, large deformation resistance, and few surface defects (Japanese Patent Laid-Open No. Sho 122-122707). .

However, with respect to the CSS resistance and the head stick property described above, since glass has excellent mirror surface properties,
The media using the glass substrate has a problem in that the contact area between the head and the media is increased as compared with the media using other substrates having inferior smoothness, which causes an increase in frictional resistance and an adhesive force.

In order to eliminate such drawbacks, there is a method of reducing frictional force and cohesive force generated between a head and a medium by forming minute irregularities on the surface of the substrate by mechanical means, which is disclosed in JP-A-53-123906. Has been proposed to.

Further, a method of forming irregularities on the surface of a glass substrate by chemical etching has been proposed in JP-A-60-136035.

[Problems to be Solved by the Invention] The present invention has the above-mentioned durability of the glass substrate for a magnetic disk.
It aims to solve problems such as CSS characteristics and head stick properties.

In the case of using a brittle material such as glass as a substrate in the method of forming irregularities by a conventional mechanical method, cracks may occur on the glass surface, which may impair the flatness and decrease the strength of the glass substrate surface. The problems due to the cracks, such as the possibility of causing them, could not be denied.

In addition, the gaps formed by sharp recesses and cracks are insufficiently washed and dried, leaving residues such as stains, which causes deterioration of magnetic properties over time. In addition, when the magnetic head collides during CSS, the convex portion of the glass may be chipped off, causing a head crash. Furthermore, in order to minimize these problems as much as possible, it is necessary to lengthen the creasing work time in the case of a method of softly streaking with abrasive grains of small particle size, and use a large amount of tape material and abrasive grains. It was also a result. Further, it was not possible to form the desired unevenness with the abrasive grains having a small grain size.

Further, in the chemical method proposed in JP-A-60-136035, it was necessary to previously form a metal layer on a glass substrate and heat-treat it.

[Means for Solving Problems] The present invention has been made to solve the above-mentioned problems, and the peaks of the irregularities whose height is in the range of 50 to 700Å are 0.1 to
A method for manufacturing a glass substrate for a magnetic disk, which is formed with a pitch in the range of 10 μm, in which fine surface irregularities are formed on the surface of the glass substrate by a mechanical method and then a chemical surface treatment is performed. A method for manufacturing a glass substrate for a magnetic disk, which is a feature of the present invention.

The heights of the above-mentioned peaks are
It is desirable that the height is 700 Å or less, but peaks exceeding 700 Å may exist within a range that does not hinder the achievement of the above-mentioned object of the present invention.

The shape of the irregularities and the pitch of the peaks are measured by using a stylus type surface roughness meter and scanning the surface of the substrate with a stylus having a radius of 2.5 μm at a needle load of 25 mg and a scanning speed of 5 μm / min.

A glass substrate for a magnetic disk manufactured according to the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a magnetic disk glass substrate (hereinafter referred to as a glass substrate or a substrate). As the glass substrate, ordinary soda lime silicate glass, non-alkali glass, borosilicate glass, quartz glass, physically strengthened glass by air cooling or liquid cooling, chemically strengthened glass, crystallized glass, or the like can be used.

As an example of the concavo-convex pattern, FIG. 2 (a) is a concentric circle shape, and FIG. 2 (b) is a single or plural spiral shape. FIG. 4 (a) illustrates a linear pattern, and FIGS. 4 (b) and (c) illustrate a radial pattern. Further, FIG. 2 (c) shows an example of a substrate having concavities and convexities formed only in a portion corresponding to a portion (CSS zone) with which the head is in contact when the medium is not rotating. In addition to this, a pattern in which a plurality of these typical patterns are superposed, or a substrate having no specific regular pattern and in which unevenness is uniformly distributed can be used.

FIG. 5 is an enlarged cross-sectional view of the vicinity of C when cut along the line AB in FIG. The same is true for the vicinity of C when cut along the line A-B in FIG. 2 (b), and the cross-sectional form is also taken for the vicinity of C during the A-B cut in FIGS. 4 (a) and 4 (b). Are almost similar.

FIG. 6 is a sectional explanatory view in which FIG. 5 is further enlarged.
In the present invention, the "mountain height" represents the drop H between the peak and the valley, and the "mountain pitch" represents the distance W between the tips of adjacent peaks.

Here, the glass plate before the surface unevenness is formed is referred to as a glass base plate or a base plate. As a bare plate,
Usual soda lime silicate glass, alkali-free glass, borosilicate glass, quartz glass, physically strengthened glass by air cooling or liquid cooling, chemically strengthened glass, crystalline glass or crystallized glass can be used.

As the magnetic disk substrate of the present invention, use of ordinary soda lime silicate glass, alkali-free glass, borosilicate glass, quartz glass, physically strengthened glass by air cooling or liquid cooling, chemically strengthened glass, or crystallized glass, etc. You can The substrate of the present invention composed of the physically strengthened glass or the chemically strengthened glass can use the physically strengthened glass or the chemically strengthened glass as the base plate, respectively, as described above. It may be one obtained by forming unevenness on the surface of a base plate other than tempered glass and chemically strengthened glass and then subjecting it to physical strengthening treatment or chemical strengthening treatment.

As a mechanical method used for forming irregularities in the method for manufacturing a glass substrate of the present invention, scratches are obtained by rubbing the surface of a glass base plate with a tape having abrasive grains fixed by an adhesive (hereinafter referred to as polishing tape). To form minute irregularities by attaching a pad, a method of forming minute irregularities on the surface of a glass base plate by pressing it against a rotating pad or surface plate with a liquid containing abrasive grains intervening, or a rotating pad or rotating plate. There is a method of forming fine concavities and convexities by pressing a glass base plate against a disc on which abrasive grains have been fixed in advance.

In the method of forming these minute irregularities, the diameter of the abrasive grains is 0.
Good irregularities can be made by using abrasive grains of 3 μm to 20 μm.
The types of abrasive grains are aluminum oxide, zirconium oxide,
Not only oxide particles such as silicon oxide, chromium oxide and iron oxide, but also carbides such as titanium carbide and silicon carbide,
Aluminum nitride, silicon nitride, nitrides such as titanium nitride, borides such as zirconium boride, and diamond are preferable.

As a chemical method, it is preferable to perform chemical etching with a solution containing hydrofluoric acid or fluoride. A solution having a hydrofluoric acid concentration of 50% by weight or less can be used, but a range of 0.1 to 20% by weight is preferable from the viewpoint of erosion rate. In this specification,% representing concentration is weight%.

Although a solution of only hydrofluoric acid has sufficient chemical etching ability, it is preferable to add other chemicals in order to improve the uniformity of etching. H ₂ SO ₄ can be used as this additive chemical, but HCI, HBr, HI, H ₃ P
Acids such as O ₄ and HNO ₃ can also be used, and are effective in solubilizing the insoluble reaction product generated by the reaction of glass and hydrofluoric acid. As the additive chemicals, in addition to those mentioned above, H ₂ SO ₃ , HCOO
_{H, R f COOH, R f} SO 3 H, (R f SO 2) 2 NH ( provided that, R _f: perfluoroalkyl, for _{example, CF 3 -, C 2 F} 5 -) can also be used.

In addition, since the fluoride solution has an effect such as a lower etching rate than hydrofluoric acid, it is possible to control the height and shape of the fine irregularities.

A metal fluoride can be used as the fluoride. For example, KF, NaF, CsF, fluorides of alkali metal elements such as LiF, fluorides of alkaline earth metal elements such as CaF ₂ , ammonium fluoride, ammonium hydrogen fluoride, etc. are good, and also IB group, IIB group, Group III, IV, V
Fluorides of group metal elements and other fluorides such as Co, Fe, Cr, Mn, and Ti can also be used.

When the glass surface is eroded by a chemical method, the erosion amount in the thickness direction of the substrate is preferably 0.1 to 5 μm on average. Especially 0.3-
2 μm is preferable. No effect if less than 0.1 μm, 5 μ
If it exceeds m, the width of the concave portion becomes too wide, or pits having a large diameter are likely to be generated, so that the S / N ratio is lowered, which is not preferable.

Fine irregularities are measured with a surface roughness meter using a stylus with a radius of 2.5 μm at the tip, and the height of 50 Å ~ 700 Å is 10 μm.
It is preferably formed with the following pitch. Mountains less than 50Å have little effect on preventing head sticks. 700Å
Peaks exceeding 10 are not preferable because they cause a decrease in S / N ratio, but they may exist in a range that does not hinder the achievement of the above-mentioned object of the present invention and a range that does not hinder the quality of the media. If the pitch exceeds 10 μm, the effect of preventing head stick is poor.

Further, as a glass substrate for a magnetic disk, one having a particularly high strength may be desired. In this case, the substrate after the chemical etching treatment in the present invention may be subjected to a chemical strengthening treatment such as an ion exchange method. Further, in this case, a base plate that has been chemically treated by an ion exchange method or the like may be used as the base plate before forming the unevenness on the surface.

[Operation] In the present invention, minute irregularities on the surface of a brittle material such as glass are formed by forming minute irregularities on the surface of the brittle material by a mechanical method and then performing chemical etching which is a chemical surface treatment. The chemical etching solution preferentially acts on the latent scratches as well as cracks, cracks and stress-remaining areas to remove them and stabilize the glass surface. Therefore, the surface of the glass substrate has mechanical strength, and the CSS resistance and the head stick resistance are also improved, as compared with a glass substrate having fine irregularities formed on the surface simply by a mechanical method.

In addition, the depth of the peaks and valleys of the fine irregularities formed by the mechanical method can be made 1 to 10 times deeper by chemical etching, so the fine irregularities formed by the mechanical method can be made shallower, and therefore flat by the mechanical method. It is possible to reduce loss of strength and decrease in surface strength. Moreover, the chemically etched glass surface has a shape in which minute cracks are removed and stress concentration is less likely to occur, so that the object can be achieved without reducing the strength of the entire glass substrate.

FIG. 3 (a) shows an example of a profile of minute irregularities formed on the surface of a raw plate by a mechanical method. Furthermore, the profile of the fine corrugations formed as a result of the dissolution and erosion of the glass surface when the chemical etching of the present invention is applied thereon is described in the third section.
It is shown in FIG.

Further, by melting the glass by chemical etching, a gap such as a crack portion or a sharp concave portion becomes a smooth curve, and an opening at the gap or bottom portion is widened to facilitate cleaning, so that a residue is less likely to remain. Further, by etching, the residue of the dirt component such as the abrasive grains, the binder and the glass fragments left in the gaps such as the cracks and the sharp recesses are also removed. Therefore, deterioration of the magnetic characteristics is significantly reduced due to the influence of the residue, and a magnetic disk with improved reliability can be obtained.

Also, pits, scratches, etc. formed by a mechanical method are expanded in the depth and width directions by a chemical method, but by limiting the etching amount of glass by the chemical method to 0.1 to 5 μm, In particular, it is possible to suppress the formation of pits or grooves having a large size, which causes a noise or a defect at the time of recording / reproducing as a magnetic disk due to an excessive width in the width direction.

The appropriate unevenness formed on the surface of the substrate by the method of the present invention does not reduce the recording density and allows magnetic recording and reproduction,
By reducing the contact area between the head and the medium without increasing the signal noise, it is thought that the CSS resistance and the head stick property can be improved by reducing the friction between the head and the medium.

[Example] Example 1 A glass base plate was rubbed with a polishing tape having fixed abrasive grains to form fine irregularities on the surface. Next, this substrate was immersed in an aqueous solution containing HF prepared in advance, washed with water and dried. A Co-based magnetic film is formed on this substrate by the sputtering method, and a carbon protective film is further formed on the Co-based magnetic film.
The S characteristics, S / N ratio and defects were evaluated.

Example 2 A glass base plate was pressed against a rotating pad surface while interposing abrasive grains to obtain a substrate having fine irregularities formed on the surface. The substrate was immersed in a chemical etching solution containing an aqueous solution of fluoride, washed with water and dried. A magnetic film was formed on this substrate by a sputtering method, and a carbon protective film was further formed thereon, and then the CSS characteristics, the S / N ratio, and the defect were evaluated.

Example 3 While rubbing the glass base plate, rub it with a grinding tape,
Surface irregularities were formed. Next, this substrate was immersed in an aqueous solution containing HF and H ₂ SO ₄ to erode in an average of 1 μm in the thickness direction of the substrate, then washed with water and dried. After forming a magnetic film on this substrate by a sputtering method and further forming a carbon protective film, CSS characteristics, S / N ratio, and defects were evaluated.

The unevenness on the surface of this magnetic disk had a groove shape, and its pattern was formed by overlapping a part of concentric or spiral curves.

Example 4 A glass base plate was rubbed with a diamond grindstone while being pointed to form surface irregularities. Next, this substrate was immersed in an aqueous solution containing HF prepared in advance, and was eroded on the substrate by an average of 2 μm in the thickness direction, washed with water and dried. After forming a magnetic film on this substrate by a sputtering method and further forming a carbon protective film, CSS characteristics, S / N ratio, and defects were evaluated. At this time, the groove pattern on the surface was formed by overlapping some of concentric and spiral curves.

Example 5 A glass base plate was brought into contact with a pad through a polishing liquid containing polishing abrasive grains and relatively moved to form surface irregularities. Next, this substrate was immersed in an aqueous solution containing HF to cause an average erosion of 0.3 μm in the thickness direction of the substrate, then washed with water and dried. After forming a magnetic film on this substrate by a sputtering method and further forming a carbon protective film, CSS characteristics, S / N ratio, and defects were evaluated.

Example 6 A glass substrate was rubbed with a diamond tool while rotating to form surface irregularities. Next, this substrate was immersed in an aqueous solution containing HF, and was eroded by 4.5 μm on average in the thickness direction of the substrate, washed with water and dried. A magnetic film is formed on this substrate by the sputtering method, and then a carbon protective film is formed.
The S characteristics, S / N ratio and defects were evaluated.

The unevenness of the surface of this magnetic disk has a groove shape,
The pattern consisted of overlapping spiral-shaped curves.

Comparative Examples 1 and 2 The method of mechanically forming irregularities is to rub the surface of a glass base plate against the abrasive grain surface of a tape having fixed abrasive grains to form minute irregularities on the surface.

An aqueous solution containing HF was used as the chemical etching solution. Washing with water, drying, and formation of the Co-based magnetic film and the carbon protective film were performed in the same manner as in Examples 1-6. Next, CSS characteristics, S / N ratio and defects were evaluated.

 Table 1 shows the above results.

[Effects of the Invention] Since fine lines, cracks, etc. that start chemical etching are formed on the glass surface by a mechanical method, it is easy to control the interval between adjacent mountains, the depth of irregularities, the pattern of valleys, etc. Therefore, it is possible to obtain a glass substrate for a magnetic disk having desired characteristics.

By performing the chemical etching, it is possible to eliminate the problems caused by the mechanical unevenness forming method. Therefore, since the surface of the glass substrate is stable, there is no change with time, and the CSS resistance is improved.

Since an etching solution that can deepen the depths of the peaks and valleys can be used by the chemical etching method, a mechanical method can be used by using abrasive grains having a minute particle diameter in forming the unevenness, and a large crack or A glass substrate for a magnetic disk with less defects such as chipping can be obtained. The depth of the irregularities formed by a mechanical method may be shallow, so that it can be formed in a short time and the amount of tape, abrasive grains, etc. used can be small.

The surface texture of glass has a great influence on forming minute irregularities only by chemical etching, but the irregularities are formed by a mechanical method prior to chemical etching, and then chemical etching is performed to make the surface texture constant. Therefore, it is possible to obtain uniform fine irregularities.

The chemical etching removes the residue in the crack gap and the bottom of the sharp recess and makes the shape easy to wash thereafter, so that a clean glass substrate for a magnetic disk can be obtained. Since the cleaning property is good, the performance of the magnetic film is not deteriorated and the reliability of the magnetic disk is improved.

The present invention reduces the frictional force by forming appropriate irregularities on the glass surface, has the effect of improving CSS resistance and bed stick properties, further adversely affects the magnetic properties because the irregularities are fine. Absent.

Since minute lines that start chemical etching, cracks, etc. are formed on the glass surface by a mechanical method, it is possible to easily control the distance between adjacent mountains, the depth of unevenness, the pattern of peaks and valleys, etc. It is possible to obtain a glass substrate for a magnetic disk having characteristics.

[Brief description of drawings]

FIG. 1 is a plan view of a glass substrate for a magnetic disk obtained by the method of the present invention, and FIGS. 2 (a, (b), (c) and 4).
Figures (a), (b) and (c) are explanatory views exemplifying patterns of irregularities on the surface of a glass substrate for a magnetic disk obtained by the method of the present invention, and Figures 3 (a) and (b) are irregularities on the substrate surface. FIG. 5 is an explanatory view of the profile of FIG.
(C), C of the A-B cross section in FIGS.
FIG. 6 is an enlarged cross-sectional explanatory view of a portion, and FIG. 6 shows “mountain height H”.
6A and 6B are explanatory diagrams of "mountain pitch W".

Claims (8)

[Claims] 1. Fine irregularities are formed on the surface and have a height of 50 to 50.
A method for manufacturing a glass substrate for a magnetic disk, wherein the unevenness peaks in the range of 700 Å are formed at a pitch of 0.1 to 10 μm, in which fine unevenness is formed on the surface of the glass substrate by a mechanical method. A method of manufacturing a glass substrate for a magnetic disk, which is characterized by performing a chemical surface treatment after that. 2. The method according to claim 1, wherein the mechanical method comprises a method of forming fine irregularities on the surface of the glass substrate with a tape having abrasive grains adhered thereto.
A method of manufacturing a glass substrate for a magnetic disk according to the item. 3. The mechanical method forms fine irregularities on the surface of a glass substrate by bringing a pad or a platen into contact with a glass substrate and moving them relative to each other with a polishing liquid containing abrasive grains interposed therebetween. A method of manufacturing a glass substrate for a magnetic disk according to claim 1, characterized in that the method comprises a method. 4. The glass substrate for a magnetic disk according to claim 1, wherein the chemical surface treatment is chemical etching with an aqueous solution containing hydrofluoric acid at a concentration of 20% by weight or less. Manufacturing method. 5. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the chemical surface treatment is chemical etching with an aqueous solution containing hydrofluoric acid and sulfuric acid. 6. The method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the chemical surface treatment is chemical etching with a solution containing a fluoride. 7. The chemical surface treatment is chemical etching, and the erosion amount in the thickness direction of the glass substrate due to the chemical etching is in the range of 0.1 to 5 μm on average. A method of manufacturing a glass substrate for a magnetic disk according to item 1. 8. A glass substrate for a magnetic disk according to claim 1, wherein the chemical surface treatment comprises chemical etching and then chemical strengthening. Method.