JP2002050024A - Molded glass substrate for magnetic disk, molding method and molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of manufacturing stages and to solve the problem of environment deterioration caused by discharging industrial waste of an abrasive, abrasion liquid and the like and of high cost caused by complicated stages, in the manufacture of a glass substrate for a magnetic disk. SOLUTION: In the glass substrate 11 for the magnetic disk having a doughnut shape, an internal diameter part is constituted of a hub member 13 and a magnetic medium forming surface of a principal surface 12 is constituted of a glass base material 27. The hub member 13 and the glass base material 27 are molded by simultaneously pressing and heating them using a molding die consisting of a core mold, a body mold, a top mold and a bottom mold to integrally weld them in a disk shape. Thus, the number of stages can be reduced and an adverse molding effect due to the difference between the coefficients of thermal expansion of the core mold and the glass base material can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk used for a storage device of a computer, and more particularly to a molded glass substrate for a magnetic disk for manufacturing a magnetic disk, a method for molding a molded glass substrate for a magnetic disk, The present invention relates to a molding die for a molded glass substrate for a magnetic disk.

[0002]

2. Description of the Related Art In recent years, in a magnetic disk drive (HDD), efforts have been made to solve the contradictory technical problems of high capacity and low price. In the conventional method of manufacturing a magnetic disk based on aluminum, in order to obtain a desired flatness and smoothness, machining mainly by a grinding method or a polishing method is performed, which requires an extremely complicated and large number of manufacturing steps. And had

[0003]

Therefore, glass substrates having high rigidity and high hardness are being used for magnetic disks instead of magnetic disks based on aluminum.
Since a magnetic disk made of a glass substrate is advantageous for smoothing, high capacity and high reliability are simultaneously satisfied. However, the manufacture of this magnetic disk follows a conventional machining method, and a large amount of industrial waste such as glass powder, abrasives, and solvents is generated during the processing. These industrial wastes are not preferable in terms of the environment, and there is a limit in reducing costs.

FIG. 6 is an explanatory view of a process of manufacturing a conventional general magnetic disk using a sheet glass material. FIG. 6 (a)
Is a step 1 of preparing a glass substrate obtained by a float method or a direct press. FIG. 6B shows a step 2 in which a ring is punched out by stress splitting or hot pressing.
FIG. 6C shows a step 3 in which inner and outer peripheries and chamfering are performed by grinding using a diamond grindstone. FIG. 6D shows a step 4 of lapping and polishing the main surface, which is the surface on which the magnetic medium is formed, and polishing the main surface. FIG. 6E is a step 5 of chemically strengthening the glass substrate by an ion exchange method or the like. FIG. 6F shows a step 6 in which the roughened surface is subjected to final polishing again to temper the main surface. FIG. 6G shows a step 7 of forming a magnetic medium on the main surface.
A number of cleaning steps are included between the steps described above. The machining methods in the steps 1 to 4 have a problem in that the number of processing steps is large and industrial waste is generated during processing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. In obtaining a glass substrate for a magnetic disk, industrial waste such as glass powder, abrasives, and grinding fluid is minimized. An object of the present invention is to obtain a molded glass substrate for a magnetic disk which can be manufactured with a small number of processing steps. It is another object of the present invention to establish a molding method for obtaining such a molded glass substrate for a magnetic disk, and to provide a molding die used in the molding method.

[0006]

According to a first aspect of the present invention, a hub member constituting an inner diameter portion and a glass member constituting a magnetic medium forming surface are integrally locked to form a disk. It is characterized by having.

According to a second aspect of the present invention, in the molded glass substrate for a magnetic disk according to the first aspect, the hub member comprises:
It is characterized by being composed of any of metal, ceramics and glass.

According to a third aspect of the present invention, a hub member forming an inner diameter portion and a glass material forming a magnetic medium forming surface are charged into a molding die and pressed and deformed at a softening temperature of the glass material. A molded glass substrate for a magnetic disk is obtained by integrally locking the hub member and the glass material.

According to a fourth aspect of the present invention, a hub member forming an inner diameter portion and a glass material fragment obtained by dividing a glass material forming a magnetic medium forming surface into a plurality of pieces are put into a molding die. By setting the total volume of the plurality of glass material fragments to be equal to or greater than the volume of the molded glass substrate, and fusing the plurality of glass material fragments to each other, a molded glass substrate for a magnetic disk is obtained. Things.

According to a fifth aspect of the present invention, there is provided an upper and lower mold for forming a main surface which is a magnetic medium forming surface, a body mold for forming one outer diameter portion continuous with the main surface, And a core for regulating the other inner diameter portion and positioning the hub member.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A molded glass substrate for a magnetic disk according to an embodiment of the present invention is shown in FIG.
FIG. 2B illustrates a molding die and a molding method for obtaining the molded glass substrate for a magnetic disk.
This will be described with reference to FIG.

FIG. 1A is an external perspective view showing the structure of a molded glass substrate 11 for a magnetic disk in the present embodiment, and FIG. 1B is a sectional view including the center line thereof. The molded glass substrate 11 for a magnetic disk has a principal surface 12 precisely transferred by a molding die whose both surfaces are precisely finished.
And a hub member 13 as an inner diameter portion connected to the main surface. The outer diameter portion 14 is a transfer surface of the mold member. According to the magnetic disk molded glass substrate 11 having such a structure, the steps 1 to 4 described in the conventional manufacturing steps can be reduced to one step. Also, it is possible to eliminate all machining,
Industrial waste can be completely eliminated.

Next, a description will be given of a method of forming the glass substrate 11 for forming a magnetic disk according to the present embodiment and a forming die used in the forming method. FIG. 2 is a cross-sectional view showing the structure of a molding die 25 composed of a plurality of dies and a molding device equipped with the molding die 25. FIG. 3 is an external view of a glass material 27 used to obtain a molded glass substrate 11 for a magnetic disk according to the present embodiment. FIG. 4 is a perspective view showing the appearance of the hub member 13 used in the present embodiment before molding.

The molding die 25 includes an upper die 21, a lower die 22, a body die 23, and a core die 24. The upper mold 21 and the lower mold 22 are ring-shaped molds whose molding surfaces are mirror-polished to a predetermined surface roughness and finished. The body mold 23 is a mold for forming an outer diameter portion of the glass substrate. The core mold 24 is a mold that fits into the center holes of the upper mold 21 and the lower mold 22.

In the molding die 25, the hub member 13 is mounted on the lower die 22 by fitting into the core die 24. Hub member 1
A ring-shaped glass material 27 is placed on the lower mold 22 around the periphery of the mold 3. Such a molding die 25 is placed on a lower heating plate 29 in which a heater 28 is embedded. Mold 25
The upper heating plate 30 in which the heater 28 is buried is set. By energizing the heater 28, the molding die 25 is heated to a temperature equal to or higher than the softening temperature of the glass material 27. Then, a pressing force P is applied to the upper heating plate 30 in a direction indicated by an arrow in the figure by using a pressing mechanism (not shown). At this time, the molding die 25 excluding the pressing mechanism and the upper and lower heating plates 29, 30
Is set in a chamber in an inert gas (N ₂ gas) to perform molding.

Thus, the hub member 13a and the glass material 27
Is heated and the hub member 13 is heated at the softening temperature of the glass material 27.
a and the glass material 27 are pressed and deformed, and the hub member and the glass material are integrally locked. In this case, FIG.
A magnetic glass molded glass substrate 11 having a sectional shape as shown in FIG.

Here, the molded glass substrate 11 for a magnetic disk
The reason why the inner diameter portion is constituted by the hub member 13 will be described. If the main surface and the inner and outer diameters of the glass substrate can be formed precisely and in one shot, the number of steps and the environmental problems can be solved at once. However, because the molded product has a donut shape,
Various constraints arise. Among these, the major constraint condition is how to overcome the difference in thermal expansion in the mold configuration and the difference in thermal expansion between the mold member and the glass material. In general, a mold member used at a high temperature has a small thermal expansion coefficient such as ceramics and tungsten carbide.
On the other hand, the glass material shows a very large coefficient of thermal expansion in a region where the glass solidifies from the molding temperature (Tg point), that is, in an abnormal expansion region.

The reason that the problem caused by the difference in thermal expansion coefficient can be solved by the molding die of the present embodiment will be described. In relation to the magnitude of thermal expansion of each member, it is necessary to satisfy "core type> glass material> body type and vertical type". If this relationship is not satisfied, the molded product cannot be removed because the glass material tightens the core mold 24 even if molding can be performed. Therefore, the core mold 24 is required to have a larger thermal expansion coefficient than a glass material, and to have heat resistance and high-temperature strength. However, under these conditions, the possibility of material selection is extremely small. When the hub member 13 is used as in the present embodiment, it is possible to avoid the above-described constraint.

Next, a method of forming the glass substrate 11 for a magnetic disk by dividing the glass material 27 into a plurality of glass materials will be described. FIG. 5 is a diagram showing a cross-sectional shape of the divided glass material piece 51. Whether the total volume of the plurality of glass material pieces 51 is equal to the volume of the formed glass substrate,
Or set to be more. As in the case of the glass material 27 shown in FIG.
a and a plurality of glass material pieces 51 in a molding die.
Then, a plurality of glass material pieces 51 are fused together by heating to obtain a molded glass substrate 11 for a magnetic disk.

[0020]

EXAMPLE 1 Next, a specific molding method for obtaining the magnetic disk molded glass substrate 11 shown in FIG. 1 using the glass material 27 shown in FIG. 3 will be described.
In the molding die 25 shown in FIG. 2, the upper die 21, the lower die 22,
Tungsten carbide was used as a material for the body mold 23 and the core mold 24. The outer diameter of the upper mold 21 and the lower mold 22 is φ35m
m and thickness were 24 mm. And the faces facing each other,
That is, polishing was performed so that the surface to which the glass was transferred had only irregularities of 1.5 nm or less, that is, an optical mirror surface. Further, a noble metal-based material was formed to a thickness of 2 μm on the surface by a sputtering method for the purpose of preventing fusion with glass. The outer peripheral surface of the core mold 24 was also processed into a mirror surface.

As the glass material 27 shown in FIG. 3, ring-shaped barium borosilicate glass (bending point: 549)
° C, glass transition point: 501 ° C, specific gravity: 3.09), and processed into a shape of outer diameter φ20 × inner diameter φ15 × thickness t1.6 mm. The above dimensions are the same as the desired volume of the magnetic glass molded glass substrate 11. As the dimensions of the molded glass substrate 11 for a magnetic disk, an outer diameter φ30 × inner diameter φ10 × thickness t 0.381 mm is set. From the viewpoint of discharge of industrial waste and the environment, it is desirable to obtain a ring-shaped glass material directly from molten glass. However, in this example, a machined material is used to confirm the effects of the invention. Was.

The hub member 13a before molding shown in FIG. 4 is made of sintered alumina having a small thermal expansion and has an outer diameter φ12 ×
A shape having an inner diameter of φ10 and a thickness of 0.3 mm was prepared. The inner diameter of the hub member 13a is finished to a desired size as a molded glass substrate for a magnetic disk.
Is provided with a predetermined clearance in consideration of the difference in thermal expansion.

Next, a method of forming the magnetic disk formed glass substrate 11 using the above-described forming die 25, glass material 27, and hub member 13a will be described with reference to FIG. 2 again. First, the lower mold 22, the core mold 24 and the body mold 23 are assembled on the lower heating plate 29, and the hub member 13a
And the glass material 27 were inserted into the lower mold 22. The hub member 13a was positioned by the core mold 24, and the glass material 27 was placed around the hub member 13a without being eccentric.

Further, the upper mold 21 was assembled so as to be fitted to the body mold 23 and the core mold 24. While the heating plate 30 was in contact with the upper die 21, the upper and lower heaters 28 were energized, heated to 610 ° C., which is the softening temperature of the glass material, and held for 2 minutes. Thereafter, a pressing force P of 20000 N was applied through the heating plate 30 in the direction of the arrow in the figure using a pressing mechanism by an air cylinder (not shown) to deform the glass material 27. Then, after confirming that the upper end surface of the body mold 23 and the heating plate 30 were in contact with each other, the heater 28 was turned off. Next, after cooling to 500 ° C. while maintaining the pressurization, the system was cooled to room temperature with the pressurization stopped.

Thereafter, the molded glass substrate 1 for a magnetic disk
1 was taken out of the molding die 25, and the flatness was measured using a Fizeau-type interferometer. As a result, one main surface was 5 microns and the other main surface was 3 microns. In addition, it was confirmed that the glass material 27 after molding and the hub member 13 were fused to a practically usable range. The temperatures described are the set temperatures of the upper and lower heating plates, and it is natural that precise temperature control is required.

When the same molding as above was performed using a heat-resistant stainless steel material as the hub member 13a,
Although slight discoloration was observed, it was confirmed that the hub member 13 was fused to the glass material 27. It is considered that a similar effect can be obtained by selecting a high melting point glass material in addition to the ceramic and metal members as the hub member 13.
It is desirable to optimize the difference between the coefficients of thermal expansion to be welded and their magnitude relationship.

(Embodiment 2) Next, the glass material 27 is divided into a plurality of glass materials, and the glass
The method of forming 1 will be specifically described. The glass material fragment 51 shown in FIG. 5 is an aluminum silicate-based glass having a thermal property of a softening point of 665 ° C. and a glass transition point of 503 ° C.
This glass material is melted at 1400 ° C. and
Drops were weighed to 45 mg and solidified. The surface of the solidified glass material fragment was in a mirror state.

For example, four pieces of the obtained glass material pieces 51 were prepared, and the glass material pieces 51 were symmetrically arranged in the molding die 25 of FIG. Naturally, the use of the hub member 13 is the same as the case of the glass material 27. Upper and lower heating plates 30,
The set temperature of 29 is 690 ° C., and the pressure P is 26000.
N. After the deformation of the glass material piece 51 is completed, it is cooled to 520 ° C. while the pressurization is continued.
The pressure was released and cooled to room temperature. When the molded glass substrate 11 for a magnetic disk was taken out and flatness was evaluated, one side of the main surface 12 was 8 microns, and the other was 6 microns.
Molded with micron precision. Further, the four glass material pieces 51 were fused together with the hub member 13 together with the fusion. The use of such a piece of glass material piece 51 makes it possible to eliminate the conventional machining.

[0029]

According to the structure of the glass substrate formed with a magnetic disk, the inner diameter portion is formed of a hub member, and the surface on which the magnetic medium is formed is formed of glass. In addition, the number of manufacturing steps can be reduced, and the manufacturing cost can be reduced. Also, since no industrial waste is discharged, it is environmentally preferable.

In particular, according to the first aspect of the present invention, a hub member is provided on the inner diameter portion of the glass substrate for a magnetic disk, and the surface on which the magnetic medium is formed is made of press-molded glass and is press-formed. A molded glass substrate for a magnetic disk having a configuration in which the glass and the hub member are integrally locked can be obtained.

In particular, according to the second aspect of the present invention, the options of the hub member used for the inner diameter portion of the molded glass substrate for a magnetic disk can be expanded.

According to the third aspect of the present invention, of the glass member forming the inner surface of the magnetic disk glass substrate and the magnetic medium forming surface, the glass material is softened in the molding die. By pressing and deforming, a magnetic medium forming surface fused to the hub member can be obtained.

In particular, according to the fourth aspect of the present invention, the volume of the hub member constituting the inner diameter of the glass substrate for a magnetic disk and the plurality of glass material pieces is equal to or greater than the volume of the molded glass substrate. By doing so, a molding method without mechanical processing is realized.

In particular, according to the fifth aspect of the invention, the coaxiality between the magnetic medium forming surface and the hub member can be ensured, and the dimensional control of the disk outer diameter and the disk thickness becomes easy.

[Brief description of the drawings]

FIG. 1 is an external view and a cross-sectional view of a glass substrate for a magnetic disk obtained in an embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of a molding apparatus equipped with a molding die used in the present embodiment.

FIG. 3 is an external perspective view of a glass material used in the present embodiment.

FIG. 4 is an external perspective view of a hub member used in the present embodiment.

FIG. 5 is a cross-sectional view of a glass material fragment used in the present embodiment.

FIG. 6 is an explanatory view of a conventional general magnetic disk manufacturing process using a sheet glass material.

[Explanation of symbols]

 Reference Signs List 11 molded glass substrate for magnetic disk 12 main surface 13, 13a hub member 14 outer diameter portion 21 upper die 22 lower die 23 trunk die 24 core die 25 molding die 27 glass material 28 heater 29, 30 heating plate 51 glass material fragment

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidenao Kataoka 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. Terms (Reference) 5D006 CB04 CB07

Claims (5)

[Claims] 1. A molded glass substrate for a magnetic disk, wherein a hub member forming an inner diameter portion and a glass member forming a magnetic medium forming surface are integrally locked to form a disk shape. 2. The molded glass substrate for a magnetic disk according to claim 1, wherein the hub member is made of one of metal, ceramics, and glass. 3. A hub member forming an inner diameter portion and a glass material forming a magnetic medium forming surface are charged into a molding die.
By pressing and deforming at the softening temperature of the glass material, by integrally locking the hub member and the glass material,
A method for forming a molded glass substrate for a magnetic disk, comprising obtaining a molded glass substrate for a magnetic disk. 4. A hub member forming an inner diameter portion and a glass material fragment obtained by dividing a glass material forming a magnetic medium forming surface into a plurality of pieces are put into a molding die. The volume of the molded glass substrate is set to be equal to or greater than the volume of the molded glass substrate, and the plurality of glass material fragments are fused together to obtain a molded glass substrate for a magnetic disk. Molding method. 5. An upper and lower mold for forming a main surface which is a magnetic medium forming surface, a body mold for forming one outer diameter portion continuous with the main surface, and regulating the other inner diameter portion continuous with the main surface. A core for positioning a hub member, and a molding die for a molded glass substrate for a magnetic disk.