JP2003054965A - Method for press-molding glass and method for manufacturing glass substrate for hard disk using the same method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for press-molding glass having high precision in parallelism, flatness and thickness dispersion and to provide a method for manufacturing a glass substrate for a hard disk by which manufacturing cost can be reduced by reducing the number of processes. SOLUTION: The method for press-molding glass is characterized by pressing the glass 6 between an upper mold 1 and a lower mold 2 while interposing parallel spacers 5 between the upper mold 1 and the lower mold 2 and maintaining a noncontacting state between an outer peripheral part of the glass 6 and the parallel spacers 5. Further a method for manufacturing the glass substrate for the hard disk adopting the press-molding method, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass press molding method and a method for manufacturing a glass substrate for a hard disk using the method.

[0002]

2. Description of the Related Art As a hard disk used as an information recording medium of a computer, there is known a hard disk of a type in which a metal layer is laminated on a glass disk-shaped substrate. The glass substrate used for such a hard disk is conventionally manufactured through several steps as shown in the flowchart of FIG. First, a glass material is melted (glass melting step), molten glass is poured onto a lower mold, and press-molded by the upper mold (press molding step). In the press molding process, generally, the method as shown in FIGS. 9 and 10 is adopted. In FIG. 9, a glass material 103 is simply press-molded to a predetermined thickness by an upper mold 101 and a lower mold 102 having a molding surface having a planar shape (JP-A-11-255524). In FIG. 10, a glass material 108 is press-molded with a ring-shaped outer diameter restricting frame 107 interposed between an upper mold 105 and a lower mold 106 having a molding surface having a planar shape. In the method shown in FIG. 10, more specifically, the glass material 108 has its outer peripheral end surface in contact with the ring-shaped outer diameter regulating frame 107 during press molding, and the outer diameter of the glass substrate is regulated (JP-A-7-133121). .

The press-molded glass material (glass substrate) is crystallized or annealed and cooled (crystallization step or annealing step). The cooled glass substrate is
After punching the center portion as desired, at least the outer peripheral edge portion of the glass substrate is cut, and further the inner and outer end surfaces are ground to preliminarily adjust the outer diameter dimension and the roundness of the glass substrate (coring step or Rough outer peripheral process) A glass substrate whose outer diameter dimensions have been preliminarily adjusted, such as inner and outer diameter processing by grinding, is subjected to the first lapping process, both surfaces are ground, and the entire shape of the glass substrate, that is, the parallel shape of the glass substrate Degree, flatness and thickness are pre-adjusted (first lapping step). The glass substrate whose parallelism and the like have been preliminarily adjusted is ground or chamfered on the outer peripheral end face and the inner peripheral end face of the hole in the glass substrate, and the outer diameter and roundness of the glass substrate, the inner diameter of the hole, and the glass The concentricity between the substrate and the holes is finely adjusted (end face precision machining process). The outer peripheral end face and the inner peripheral end face of the hole of the glass substrate whose outer diameter dimension and the like have been finely adjusted are polished to remove fine scratches (end face polishing step). Both surfaces of the glass substrate whose end faces have been polished are ground again to finely adjust the overall shape of the glass substrate, that is, the parallelism, flatness and thickness of the glass substrate (second lapping step). The glass substrate whose parallelism and the like have been finely adjusted is subjected to a polishing step, both surfaces thereof are polished, and the surface irregularities are leveled. If desired, the polishing step is performed in two steps using abrasives having different particle sizes (first polishing step, second polishing step). The polished glass substrate is finally cleaned and inspected, and only those which have passed can be used as a substrate for a hard disk.

[0004]

However, in the conventional method, the precision of the press molding process is particularly poor, and it is necessary to adjust the overall shape of the glass substrate by the lapping process or the like as described above. Since this increases, the manufacturing cost increases, which is a problem. That is, in the method as shown in FIG. 9, since the thickness of the glass substrate is controlled by the distance between the upper mold and the lower mold, it is difficult to obtain a glass substrate having a predetermined thickness. Further, when the glass substrate was repeatedly manufactured, one axis of the upper mold center axis and the lower mold center axis was easily inclined with respect to the other axis, and the parallelism deteriorated. Further, in the method as shown in FIG. 10, since the glass comes into contact with all of the upper mold, the lower mold and the outer diameter regulating frame during press molding, the amount of glass is slightly increased, and the pressure is applied to the glass. And the parallelism and flatness were easily deteriorated. In addition, there was a large variation in thickness during repeated molding.

It is an object of the present invention to provide a press molding method with high accuracy in parallelism, flatness and thickness variation, and a method for manufacturing a glass substrate for a hard disk, which can reduce the manufacturing cost by reducing the number of steps. To do.

[0006]

According to the present invention, a parallel spacer is interposed between an upper mold and a lower mold, and the outer peripheral portion of the glass and the parallel spacer are kept in non-contact with each other. The present invention relates to a glass press-molding method, which comprises pressing glass between a lower mold.

The present invention also relates to a method for manufacturing a glass substrate for a hard disk, which adopts the above-mentioned press molding method.

In the present specification, the parallelism refers to "a surface to which a molding surface of an upper mold is transferred (a top surface of a molding surface, which is generated when one of the upper mold center axis and the lower mold center axis is inclined with respect to the other axis. ) And the surface (lower surface) to which the lower die molding surface is transferred ”. In the present invention, the inclination between the upper surface and the lower surface is "the inclination of the upper surface when the lower surface is regarded as a horizontal plane", and the parallelism is the height difference due to the inclination of the upper surface per 100 mm length of the lower surface in the cross section where the inclination is the largest. It represents. In the present invention, such parallelism uses a value measured by a Digimatic indicator (manufactured by Mitutoyo Co., Ltd.), but it does not have to be measured by the above device, and a device capable of measuring the above parallelism. So long as it is measured by any device.

The flatness is one index showing the degree of warpage of a molded product, and is represented by the distance between the uppermost point of the upper surface when the molded product is placed on a horizontal plane and the horizontal plane. In the present invention, such flatness uses a value measured by a Digimatic indicator (manufactured by Mitutoyo Co., Ltd.), but it does not have to be measured by the above device, and a device capable of measuring the above flatness. So long as it is measured by any device.

The thickness means the thickness of the thinnest part in the molded product. The thickness variation is the difference between the average thickness when a plurality of molded products are molded and the thickness having the largest difference from the average thickness. In the present invention, the thickness is a value measured by a digital micrometer (manufactured by Mitutoyo), but it may be measured by any device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Press Molding Apparatus) A press molding apparatus suitable for carrying out the press molding method of the present invention will be briefly described with reference to the drawings. FIG. 1 (A) is a schematic cross-sectional view of an example of a press-molding apparatus suitable for carrying out the press-molding method of the present invention (the cross-sectional view passes through the central axis), and the upper mold of the apparatus is viewed from below. A schematic sketch when the mold is viewed and a schematic sketch when the lower mold is viewed from above are shown. Figure 1 (B) is Figure 1
FIG. 3 is a schematic state diagram of the upper die and the lower die when pressed using the device of (A) (the state diagram is a cross-sectional view passing through the central axis).

In the apparatus of FIG. 1 (A), the upper mold 1 and the lower mold 2 are provided with molding surfaces 3 and 4 each having a planar shape, and a parallel spacer 5 is provided between the upper mold 1 and the lower mold 2. Is intervening. The parallel spacer 5 has a spacer function capable of keeping the molding surfaces of both molds parallel to each other immediately before the completion of press molding in the press molding process. The parallel spacer 5 is installed at the outer edge of the molding surface so that the outer periphery of the glass and the parallel spacer can be kept in non-contact with each other during press molding of the molten glass 6 (see FIG. 1 (B)). .

In FIG. 1A, the parallel spacer 5 is installed in the upper mold 1, but it may be installed in the lower mold 2. When the parallel spacers 5 are installed on the upper mold 1, if a plurality of lower molds are used for one upper mold to perform simultaneous molding, a minimum number of parallel spacers can be prepared. The molded product on the lower mold can be easily taken out after the molding is completed.

Further, in FIG. 1 (A), the parallel spacer 5 has a prismatic shape and is in surface contact with the lower die molding surface 4, but the shape is not particularly limited as long as the molding surfaces of both molds can be kept in parallel.
For example, it may have a substantially prismatic shape, a substantially cylindrical shape, a substantially pyramidal shape, a substantially conical shape, a substantially rod shape, a substantially pin shape, or the like.
Depending on such shape, the parallel spacers contact the molding surface 4 at points, lines or surfaces. From the viewpoint of obtaining a molded product having excellent parallelism, flatness, thickness and other precision over a longer period of time, it is preferable to use a parallel spacer that comes into surface contact with the lower mold molding surface. The present invention, as long as the glass and the parallel spacer do not contact during press molding,
It does not prevent the parallel spacers from having a ring shape.

Further, although four parallel spacers 5 are used in FIG. 1 (A), the number of parallel spacers is not particularly limited as long as the molding surfaces of both molds can be kept in parallel, and the lower mold molding surface and the surface can be used. At least two, preferably three in line contact, and three in point contact with the lower molding surface are suitable.

Since the thickness (height) of the parallel spacers 5 is reflected on the thickness and parallelism of the molded product, it is necessary that the thickness (height) of all the parallel spacers to be used be exactly equal. . As a material of the parallel spacer 5, a known material that can be used for a mold can be used, and examples thereof include stainless steel, cemented carbide, cast iron, and ceramics. As the material of the upper mold 1 and the lower mold 2, known materials conventionally used as mold materials for glass molding can be used, and examples thereof include stainless steel, cemented carbide, cast iron, and ceramics.

FIG. 2 (A) is a schematic cross-sectional view of another example of a press-molding apparatus suitable for carrying out the press-molding method of the present invention, a schematic sketch of the upper mold of the apparatus, and a bottom view. The schematic sketch when a model is seen from above is shown. Figure 2
(B) shows a schematic state diagram of the upper die and the lower die when pressed using the apparatus of FIG. 2 (A). In the apparatus shown in FIG. 2, the upper die 1 has a step portion 7, and the step portion 7 is provided with three parallel spacers 5 at equal intervals.
1 is installed, and the shape of the parallel spacer 5 is substantially prismatic, so that the description of the device will be omitted. The thickness (height) of the parallel spacer 5 in the explanation of the apparatus in FIG.
It corresponds to the thickness (height) in the direction of the mold axis in the part of the parallel spacer 5 projecting from the molding surface 3.

FIG. 3 (A) is a schematic cross-sectional view of another example of a press-molding apparatus suitable for carrying out the press-molding method of the present invention, a schematic sketch of the upper mold of the apparatus when viewed from below, and A schematic sketch of the lower mold seen from above is shown. Figure 3
(B) shows a schematic state diagram of the upper die and the lower die when pressed using the apparatus of FIG. 3 (A). The apparatus of FIG. 3 has three parallel spacers 5 installed at equal intervals, and the shape of the parallel spacers 5 is a conical shape.
Since it is similar to the device of FIG. 1, description of the device is omitted.

(Manufacturing Method of Glass Substrate for Hard Disk) The press molding method of the present invention, which is carried out by using the above apparatus, achieves molding with remarkably high accuracy such as parallelism, flatness and thickness variation. It can be effectively used in a press molding process in a method of manufacturing a molded product (for example, a glass substrate for a hard disk) that requires high accuracy. In particular, when the press molding method of the present invention is applied to a method for manufacturing a glass substrate for a hard disk, it is possible to omit the conventionally required first lapping step, preferably the first lapping step and the second lapping step, resulting in a hard disk. The manufacturing cost of the glass substrate can be easily reduced. Hereinafter, the press molding method of the present invention will be described in detail in the description of the method for manufacturing a glass substrate for a hard disk to which the method is applied.

(First Mode) A first mode of the method for manufacturing a glass substrate for a hard disk is shown in the flow chart of FIG. When manufacturing a glass substrate for a hard disk, first, a glass material is melted (glass melting step).
The glass material used is not particularly limited, and a glass material such as lithium aluminosilicate glass or aluminosilicate glass is appropriately selected according to the desired form (crystallized glass or amorphous glass) of the glass substrate to be obtained. And use it.

Next, after the molten glass is poured into the lower mold, a parallel spacer is interposed between the upper mold and the lower mold, and the outer peripheral portion of the glass and the parallel spacer are kept in non-contact with each other. , Press the glass between the upper mold and the lower mold (press molding step). The molding conditions may be the same as the molding conditions in the known method for manufacturing a glass substrate for a hard disk. For example, the press pressure is 20
Appropriate pressure is 100 to 100 kg / cm ² , and pressing time is 0.3 to 2.0 seconds.

More specifically, for example, when using the apparatus shown in FIG. 1, when the upper mold 1 and the lower mold 2 are moved close to each other to press the glass in the press molding step, the close movement is restricted by the parallel spacers 5. , The thickness of the molten glass 6 is specified (see FIG. 1 (B)). At this time, since the outer peripheral portion of the glass does not come into contact with the parallel spacer 5, it is possible to achieve excellent accuracy in terms of parallelism, flatness, and thickness variation, and the mold molding surface is effectively transferred to the glass substrate surface. be able to. When the glass comes into contact with the parallel spacer during press molding, the molten glass penetrates between the parallel spacer and the molding surface, deteriorating the parallelism and flatness of the obtained glass substrate. When the molding is further repeated, the parallelism and the flatness are significantly deteriorated, and the variation in the thickness is also remarkable.

In the present invention, in order to improve the accuracy of parallelism, flatness and thickness variation, the contact surface of the parallel spacer with the upper die and the lower die, and the contact surface of the upper die and the lower die with the parallel spacer. , And the molding surfaces of the upper and lower molds have a parallelism of 10 μm or less, preferably 5 μm.
It is preferable that the thickness is m or less and the flatness is 10 μm or less, preferably 5 μm or less. From the viewpoint of obtaining a glass substrate excellent in accuracy for a longer period of time, each of the above surfaces has a surface roughness (Ra) of 3 μm or less, preferably 1.5 μm or less and a maximum surface roughness (Rmax) of 20 μm or less, preferably It is preferably 8 μm or less. The thickness (height) of the parallel spacer 5 is not particularly limited and may be, for example, 0.8 to 2.0 mm.

In the present specification, the surface roughness (Ra) is JIS B0601.
Is the average value based on. Maximum surface roughness (Rmax) is JIS
This is the maximum value based on B0601.

The amount of the molten glass poured into the lower mold is not particularly limited as long as the outer peripheral portion of the glass does not come into contact with the parallel spacer in the press molding process. Usually, it is appropriately set in consideration of the desired size of the molded product and the size that can be molded between the upper mold and the lower mold without contacting the parallel spacers. In the method of the present invention, even if the molten glass is supplied in a slightly larger amount than a predetermined amount, it is possible to obtain a glass substrate with high accuracy of parallelism and thickness variation as long as the glass outer peripheral portion does not contact the parallel spacer in the press molding step. You can

Next, the press-molded glass substrate is subjected to crystallization treatment or annealing treatment, and as a result, is cooled (crystallization treatment or annealing treatment). Whether to perform the crystallization treatment or the annealing treatment depends on the desired morphology (crystalline or amorphous) of the glass substrate to be obtained,
That is, crystallization treatment is performed to obtain a crystalline glass substrate, and annealing treatment is performed to obtain an amorphous glass substrate.

As the crystallization treatment and the annealing treatment, the same methods as the crystallization treatment and the annealing treatment in the known method for manufacturing a hard disk glass substrate can be adopted. For example, in the crystallization process, usually, the lithium aluminosilicate glass substrate is heated to the glass transition point (Tg) + 50 ° C to Tg + 300 ° C of the glass material, and then the glass transition of the glass is performed while maintaining a constant temperature or controlling the temperature. The glass substrate is gradually cooled to a temperature (Tg) and then allowed to cool, but by appropriately selecting the heating temperature, the holding time, the cooling rate to Tg, and the like, the physical properties of the glass substrate, such as thermal expansion coefficient, Young's modulus, The crystallinity and the like can be controlled. In the annealing treatment, usually, the glass is kept at a temperature near Tg for a certain period of time, then cooled to a strain point at a relatively low cooling rate, and thereafter, cooled at a relatively high cooling rate.
In the present invention, in the crystallization treatment or the annealing treatment, particularly in the crystallization treatment, from the viewpoint of further improvement of flatness and space saving in the processing apparatus, and from the viewpoint of reducing flatness, a plurality of glass substrates are stacked, It is preferable to apply pressure from above and apply pressure. At this time, from the viewpoint of further improving parallelism and flatness and preventing fusion between the glass substrates, it is preferable that the glass substrates are alternately stacked and treated with the setter material. The shape accuracy of the setter material is usually higher than the shape accuracy of the glass substrate to be obtained, that is, the flatness is 5 μm or less.

When the above-mentioned treatment is carried out, the precision equal to or better than the precision first achieved after the first lapping treatment in the conventional method, that is, the parallelism is 20 μm or less, preferably 10 μm or less, and the flatness is 20 μm or less, Preferably 10μ
It is possible to obtain a glass substrate having a thickness of m or less and a thickness variation of ± 10 μm, preferably ± 5 μm. The upper and lower mold surfaces of the glass substrate are transferred well, and the glass substrate has a surface roughness of 3 μm or less, preferably 1.5 μm or less and a maximum surface roughness of 20 μm or less, preferably 8 μm or less.

Next, the glass substrate cooled in the crystallization step or the annealing step is subjected to coring treatment or rough outer peripheral processing (coring step or outer peripheral rough processing step). Whether to perform the coring treatment or the outer peripheral roughing treatment depends on whether or not it is necessary to form a hole in the central portion of the glass substrate to be obtained.

As the coring treatment and the outer peripheral roughing treatment, the same methods as the coring treatment and the outer peripheral roughening treatment in the known method for manufacturing a glass substrate for a hard disk can be adopted. For example, in the coring process, the outer peripheral edge of the substrate is cut with a diamond cutter or the like, the central portion is cut (holes are formed), and further, the outer peripheral edge and the inner peripheral edge of the hole are ground to obtain a glass. Preliminarily adjust the outside diameter and roundness of the substrate, the inside diameter of the hole, and the concentricity between the glass substrate and the hole. In the outer peripheral roughing treatment, the outer peripheral edge of the substrate is cut by a diamond cutter or the like, and further, the outer peripheral end face is ground, whereby the outer diameter dimension and the circularity of the glass substrate are preliminarily adjusted. Here, the preliminary adjustment refers to roughly adjusting the dimensions and the like to the prescribed dimensions and the like in the subsequent steps.

The glass substrate whose outer diameter and the like have been preliminarily adjusted in the coring step or the rough outer peripheral processing step does not need to be subjected to the first lapping step as in the conventional case, but is subjected to the end face precision processing step ( End face precision machining process). By the press molding process, a glass substrate having excellent accuracy such as parallelism, flatness and thickness variation is obtained.
This is because it is not necessary to preliminarily adjust the parallelism, flatness and thickness of the glass substrate by grinding, and the first lapping process can be omitted.

As the method of precision processing of the end surface, the same method as the method of precision processing of the end surface in the known method for manufacturing a glass substrate for a hard disk can be adopted. For example, for a glass substrate that has undergone the coring step, the outer peripheral end face and the inner peripheral end face of the hole in the glass substrate are ground or chamfered, and the outer diameter dimension and the roundness of the glass substrate,
The inner diameter of the hole and the concentricity between the glass substrate and the hole are finely adjusted to the specified size and degree. Further, for the glass substrate that has undergone the rough outer peripheral processing step, the outer peripheral end face of the glass substrate is ground or chamfered to finely adjust the outer diameter dimension and roundness of the glass substrate to the prescribed dimensions and degrees. Fixed abrasive grains (diamond pellets), loose abrasive grains (slurries such as alumina and SiC) can be used as the abrasive.

Then, in the end face precision processing step, the end face polishing process of the glass substrate whose outer diameter dimension and the like are finely adjusted is performed (end face polishing process step). As the method of the end surface polishing processing, the same method as the method of the end surface polishing processing in the known method for manufacturing a glass substrate for a hard disk can be adopted. For example, for a glass substrate that has undergone the coring process, the outer peripheral end surface and the inner peripheral end surface of the hole in the glass substrate are polished to remove fine scratches and the like. For the glass substrate that has undergone the outer peripheral roughing process, the outer peripheral end surface of the glass substrate is polished to remove fine scratches and the like. This is because if the end surface has scratches, the glass substrate is easily damaged by impact. Examples of the abrasive used in this step include cerium oxide.

Then, both surfaces of the glass substrate whose end faces have been polished in the end face polishing process are ground to create (correct) the shape accuracy of the faces (lapping process;
Corresponding to the conventional second lapping process). That is, the final quality of the shape of the disk (parallelism, flatness and thickness) is achieved, and at the same time, the surface roughness and the maximum surface roughness that can be adjusted in the polishing step described later are achieved.

As the method of the lapping treatment, the same method as the method of the second lapping treatment in the known method for manufacturing a glass substrate for a hard disk can be adopted. Specifically, it is ground with a grinding material such as fixed abrasive grains (diamond pellet) or loose abrasive grains (slurry such as alumina, SiC) having a grain size of # 1000 or more and # 2000 or less, preferably # 1200 or more and # 2000 or less. , Parallelism of 10 μm or less, preferably 5 μm or less,
Flatness 10μm or less, preferably 5μm or less, thickness variation ± 10μm, preferably ± 5μm, surface roughness (Ra) 2μm or less, preferably 1μm or less, maximum surface roughness (Rmax) 5μm or less, preferably 3μm or less To do. As a result, the glass substrate is usually ground on both sides of t / 3 to t / 20 with respect to the thickness t in the thickness direction (thickness immediately before the step). As the lapping device, for example, a double-sided lapping device (manufactured by Hamai) or a double-sided lapping device (manufactured by Speedfam) is used.

Next, the lapping-processed glass substrate is polished to create (adjust) the smoothness of the surface (polishing step). That is, the unevenness of the surface is leveled to achieve the final smoothness (surface roughness, maximum surface roughness) of the disk.

As the method of polishing treatment, the same method as the method of polishing treatment in the known method for manufacturing a glass substrate for a hard disk can be adopted. Specifically, the average primary particle size is 2 μm or less, preferably 1 μm or less, and the surface roughness (Ra) of 1 n is polished by using an abrasive such as cerium oxide.
m or less, preferably 0.5 nm or less, maximum surface roughness (Rmax) 20
Achieving nm or less, preferably 10 nm or less. as a result,
The glass substrate usually has a thickness t in the thickness direction in the process.
(Thickness immediately before the process) t / 20 to t / 500 on both sides
To be polished. In such a polishing process,
When the diameter of the glass substrate is L and the polishing depth per one surface in the step is M, the "waviness" of the waviness frequency L / 20 or less and the waviness amount M / 5 or less can be easily removed. Here, "waviness" is a phenomenon in which a glass surface has a specific repeating unit and gently undulates. As the polishing device, for example, a double-sided polishing machine (manufactured by Hamai) is used.

Finally, the polished glass substrate is washed and inspected (washing step and inspecting step).
In the cleaning step, the glass debris on the substrate surface may be removed by exposing the glass substrate to running water at room temperature. In the inspection process, the parallelism, flatness, thickness, surface roughness, maximum surface roughness, concentricity, roundness, edge shape (roll-off), minute swell, etc. of the substrate should be within the desired range. Was confirmed and used as a substrate for hard disk.

In the above-described method for manufacturing a glass substrate for a hard disk according to the first aspect, since the specific press molding process using the parallel spacer is performed, the parallelism can be reduced even if the conventional first lapping step is omitted. It is possible to easily and repeatedly obtain a glass substrate for a hard disk, which has high accuracy of flatness and variation in thickness and is excellent in surface roughness and maximum surface roughness.

(Second Embodiment) In the second embodiment of the method for manufacturing a glass substrate for a hard disk, by selecting the upper die, the lower die and the parallel spacer, not only the conventional first lapping step but also the second lapping step can be performed. Lapping process (in the above-mentioned first embodiment, simply “lapping process”)
Can be omitted. That is, by using a material having high rigidity as the material for the upper die, the lower die and the parallel spacer, and improving their precision, the glass substrate subjected to the edge polishing processing can be directly subjected to the polishing step.

The second mode is shown in the flowchart of FIG.
A method of manufacturing a glass substrate for a hard disk according to a second aspect uses a material having a high rigidity as a material for the upper die, the lower die and the parallel spacer, and enhances their precision, and a glass substrate subjected to an end surface polishing process. Since it is the same as the method of the first aspect except that the above is directly subjected to the polishing step, the description of the common portions will be omitted.

In the second embodiment, stainless steel, cemented carbide, cast iron, ceramics, etc. are used as the material for the upper and lower dies and the parallel spacers. Further, the contact surface with the upper mold and the lower mold in the parallel spacer, the contact surface with the parallel spacer in the upper mold and the lower mold, and the molding surface of the upper mold and the lower mold, the parallelism is 10 μm or less,
Preferably 5 μm or less, flatness 10 μm or less, preferably 5
μm or less, surface roughness is 1 μm or less, preferably 0.8 μm or less, and maximum surface roughness is 5 μm or less, preferably 3 μm or less.

When the above-mentioned press molding treatment and annealing treatment or crystallization treatment are performed using such upper and lower dies and parallel spacers, the parallelism which was first achieved after the lapping step in the first embodiment, It is possible to obtain a glass substrate having flatness, surface roughness and maximum surface roughness. Therefore, the glass substrate subjected to the end surface polishing processing can be directly subjected to the polishing step without being subjected to the lapping step.

When the conventional first and second lapping steps are omitted as described above, the polishing process is facilitated by further improving the accuracy of the molding surfaces of the upper mold and the lower mold. That is, if the surface roughness of the molding surface of the upper mold and the lower mold is 0.8 μm or less and the maximum surface roughness is 3 μm or less, the press molding treatment causes the glass substrate to have a surface roughness of 0.8 μm or less and a maximum surface roughness of 3 μm or less. And the processing time in the polishing step is shortened.

(Third Mode) In the press molding step of the first mode, the outer peripheral portion of the glass does not come into contact with the parallel spacers,
Since the glass substrate has a good free end surface (curved surface), the number of steps in the method for manufacturing a glass substrate for a hard disk can be obtained by obtaining the glass substrate while leaving the free end surface (curved surface) of the outer peripheral portion untreated. Can be further reduced. That is, in the third aspect, not only the conventional first lapping step but also the processing step for the outer peripheral portion (outer peripheral end portion, outer peripheral end surface) can be omitted.

The third mode is shown in the flowchart of FIG.
The method for producing a glass substrate for a hard disk of the third aspect is the same as the method of the first aspect, except for the following matters,
Descriptions of common parts are omitted. When the glass substrate that has been crystallized or annealed is subjected to coring treatment, only the inner peripheral edge surface is processed in the end face precision processing step and the end surface polishing processing step. If no coring treatment is required, directly attach the glass substrate
Provided to the lapping process (the outer peripheral end face does not need to be roughened and the coring process does not need to be performed, so the inner peripheral end face to be processed in the end face precision processing process and the end face polishing process not exist).

(Fourth Mode) In the press molding process of the second mode, the outer peripheral portion of the glass does not come into contact with the parallel spacers,
Since the glass substrate has a good free end surface (curved surface), the number of steps in the method for manufacturing a glass substrate for a hard disk can be obtained by obtaining the glass substrate while leaving the free end surface (curved surface) of the outer peripheral portion untreated. Can be further reduced. That is, in the fourth aspect, not only the conventional first lapping step and second conventional lapping step but also the processing step relating to the outer peripheral portion (outer peripheral end portion, outer peripheral end surface) can be omitted.

The fourth mode is shown in the flowchart of FIG.
The method for manufacturing a glass substrate for a hard disk of the fourth aspect is the same as the method of the second aspect, except for the following matters,
Descriptions of common parts are omitted. When the glass substrate that has been crystallized or annealed is subjected to coring treatment, only the inner peripheral edge surface is processed in the end face precision processing step and the end surface polishing processing step. If no coring treatment is required, directly attach the glass substrate
To be subjected to polishing process (the outer peripheral end face does not need to be processed, so the outer peripheral rough processing does not need to be performed, and since coring is not required, the inner peripheral end face to be processed in the end face precision processing process and the end face polishing process not exist).

[0049]

Example A glass substrate was manufactured under the conditions shown in the following table based on the flowcharts shown in FIGS. Example 1 3000 glass substrates having a diameter of 65 mm were manufactured based on the flowchart of FIG. The values other than the thickness variation regarding the glass substrate in the table are average values. Various values of the glass substrate after the second polishing can be regarded as values of the glass substrate finally obtained.

[0050]

[Table 1]

[0051]

[Table 2]

Example 2 A glass substrate was manufactured based on the flowchart of FIG. In addition, the amount of molten glass poured into the lower mold is increased or decreased within the range where the outer periphery of the glass does not come into contact with the parallel spacer during press molding, and 1000 glass substrates each having a diameter of 30 mm, 50 mm, 67 mm, 78 mm, 86 mm and 97 mm. Manufactured one by one.
The values other than the thickness variation regarding the glass substrate in the table are average values.

[0053]

[Table 3]

[0054]

[Table 4]

Comparative Example 1 In the same manner as in the method for manufacturing a glass substrate in Example 1, except that the amount of molten glass poured into the lower mold was increased and the outer peripheral portion of the glass was brought into contact with the parallel spacer during press molding. I tried to make a glass substrate. However, the glass substrate immediately after the crystallization treatment has a parallelism of 50 μm, a flatness of 50 μm, a thickness of 13000 μm, and a thickness variation of ± 100 μm, and thus the conventional first lapping step cannot be omitted, and as a result, the flowchart shown in FIG. in accordance with,
Parallelism 3 μm, flatness 3 μm, thickness 635 μm, thickness variation ±
A glass substrate having a surface roughness of 10 μm, a surface roughness of 0.5 nm and a maximum surface roughness of 20 nm was manufactured.

From the above results, in Comparative Example 1, it is difficult to obtain a glass substrate having the same degree of parallelism, flatness, thickness variation, surface roughness and maximum surface roughness as in Example, and the number of steps It can be seen that the manufacturing cost is high because there are many In the above embodiment, at least FIG.
The process corresponding to the first lapping step of the conventional flowchart in, preferably the first lapping step of the conventional flowchart.
The steps corresponding to the lapping step and the second lapping step can be omitted, and the manufacturing cost can be significantly reduced.

[0057]

According to the press molding method of the present invention, the parallelism,
It is possible to easily obtain a molded product having excellent accuracy in flatness and thickness variation. By adopting the press molding method of the present invention in the press molding step in the method for manufacturing a glass substrate for a hard disk, the number of steps in the manufacturing method can be reduced, and as a result, the manufacturing cost of the glass substrate can be significantly reduced. You can

[Brief description of drawings]

FIG. 1A is a schematic cross-sectional view of an example of a press-molding apparatus suitable for carrying out the press-molding method of the present invention, a schematic sketch of the upper mold of the apparatus when viewed from below, and a lower mold above. FIG. 2B is a schematic plan view when viewed from above, and FIG. 3B is a schematic state diagram of an upper die and a lower die when pressed using the apparatus of FIG.

FIG. 2 (A) is a schematic cross-sectional view of an example of a press-molding apparatus suitable for carrying out the press-molding method of the present invention, a schematic sketch of the upper mold of the apparatus when viewed from below, and a lower mold above. FIG. 2B is a schematic plan view when viewed from above, and FIG. 3B is a schematic state diagram of an upper die and a lower die when pressed using the apparatus of FIG.

FIG. 3 (A) is a schematic cross-sectional view of an example of a press-molding apparatus suitable for carrying out the press-molding method of the present invention, a schematic sketch of the upper mold of the apparatus as seen from below, and a lower mold above. FIG. 2B is a schematic plan view when viewed from above, and FIG. 3B is a schematic state diagram of an upper die and a lower die when pressed using the apparatus of FIG.

FIG. 4 shows a flowchart of an example of a method for manufacturing a glass substrate for a hard disk of the present invention.

FIG. 5 shows a flowchart of an example of a method for manufacturing a glass substrate for a hard disk of the present invention.

FIG. 6 shows a flowchart of an example of a method for manufacturing a glass substrate for a hard disk of the present invention.

FIG. 7 shows a flowchart of an example of a method for manufacturing a glass substrate for a hard disk of the present invention.

FIG. 8 shows a flowchart of a conventional method for manufacturing a glass substrate for a hard disk.

FIG. 9 is a schematic configuration diagram of a mold for explaining a conventional press molding method.

FIG. 10 is a schematic configuration diagram of a mold for explaining a conventional press molding method.

[Explanation of symbols]

1; upper mold, 2; lower mold, 3; molding surface, 4; molding surface, 5; parallel spacer, 6; glass, 7; step, 101; upper mold, 102; lower mold, 103; glass, 105; Upper mold, 106; Lower mold, 107; Ring-shaped outer diameter regulating frame, 108; Glass.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G11B 5/84 G11B 5/84 Z (72) Inventor Hideki Kawai 2-3, Azuchi-cho, Chuo-ku, Osaka-shi, Osaka No. 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Toshiharu Mori 2-33 Azuchi-cho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Co. (72) Inventor Shinji Fukumoto Osaka Prefecture 2-3-13 Azuchi-cho, Chuo-ku, Osaka City F-term in Minolta Co., Ltd., Osaka International Building 4G015 CA01 EA02 4G059 AA09 AB01 AB03 AB11 AC03 5D112 AA02 BA03 BA10 GA09 GB02

Claims (5)

[Claims] 1. A glass is interposed between the upper mold and the lower mold while a parallel spacer is interposed between the upper mold and the lower mold, and the outer peripheral portion of the glass and the parallel spacer are kept in non-contact with each other. A method for press-molding glass, which comprises pressing. 2. A glass is interposed between the upper mold and the lower mold while a parallel spacer is interposed between the upper mold and the lower mold, and the outer peripheral portion of the glass and the parallel spacer are kept in non-contact with each other. A method of manufacturing a glass substrate for a hard disk, which comprises a press molding step of pressing glass. 3. A glass substrate having a parallelism of 20 μm or less, a flatness of 20 μm or less and a thickness variation of ± 10 μm is obtained by crystallization treatment or annealing treatment after the press molding treatment, and the glass substrate is subjected to coring treatment or rough outer peripheral treatment treatment. rear,
The method for manufacturing a glass substrate for a hard disk according to claim 2, wherein an end face precision working process, an end face polishing working process, a lapping process, a polishing process and a cleaning process are performed. 4. An upper die, a lower die and a parallel spacer made of stainless steel, cemented carbide, cast iron or ceramics, wherein the parallel spacer has a contact surface with the upper die and the lower die, and a parallel spacer in the upper die and the lower die. An upper mold, a lower mold and a parallel spacer whose contact surface with and the molding surfaces of the upper mold and the lower mold have a parallelism of 10 μm or less, a flatness of 10 μm or less, a surface roughness of 1 μm or less and a maximum surface roughness of 5 μm or less were used. After press molding, a glass substrate with parallelism of 20 μm or less, flatness of 20 μm or less and thickness variation of ± 10 μm is obtained by crystallization treatment or annealing treatment. The method for producing a glass substrate for a hard disk according to claim 2, wherein the glass substrate for a hard disk is subjected to processing, edge polishing, polishing, and cleaning. 5. A surface having a waviness frequency of L / 20 or less (L: substrate diameter) and a waviness amount of M / 5 or less (M: polishing amount per one side in the polishing step) by crystallization treatment or annealing treatment after press molding treatment. Obtain a glass substrate having a state,
The glass substrate is subjected to a coring treatment or a rough outer periphery roughening treatment, and then an end face precision working treatment, an end face polishing working treatment, a polishing treatment and a cleaning treatment.
2. The method for manufacturing a glass substrate for a hard disk according to 2 or 4.