JP2000109330A - Original glass substrate for information recording medium, production mold and production method thereof - Google Patents

Abstract

(57) [Abstract] [Problem] To significantly reduce the number of machining steps and reduce costs. SOLUTION: A molten glass 6 having a viscosity of 10 ^2.5 poise to 10 ⁵ poise is dropped into a mold space S of a lower mold 2, and the molten glass 6 is centrifugally applied while maintaining the viscosity of the molten glass 6 at 10 ⁷ poise or less. While extending 6 radially outward,
The outer peripheral portion of the molten glass 6 is regulated by the peripheral surfaces 4 a and 5 a of the slide dies 4 and 5, and the upper die 7 is connected to the protrusion 3 of the lower die 3.
The central portion of the molten glass 6 placed in the mold space S in contact with the mold space 1 is punched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an original glass substrate for an information recording medium, a mold for producing the same, and a method for producing the same.

[0002]

2. Description of the Related Art As a substrate for an information recording medium such as an HDD (hard disk drive) or the like, a glass substrate having excellent smoothness and durability has attracted attention instead of a conventional aluminum substrate. Conventionally, such a glass substrate is formed by cutting a predetermined shape from a sheet glass into a glass base substrate (hereinafter simply referred to as a base substrate), coring (ring processing), inner and outer chamfering (chamfering), polishing, lapping, and the like. Although it is manufactured by repeatedly performing machining such as polishing, a large number of man-hours are required for machining, and this has caused a cost increase. Further, there is also a problem that chipping or the like occurs due to coring or processing of the inner and outer peripheries, which lowers the yield.

[0003]

Therefore, instead of cutting out the original substrate from the plate glass, as shown in FIG. 10, the molten glass 6 is filled in a lower mold 101 having a circular container-shaped mold space opened upward. After that, the upper die 102 having a smaller diameter than the die space is inserted to mold the original substrate having a predetermined thickness h. In this case, however, machining such as coring is necessary. In addition, when the original substrate has a predetermined thickness h, extra molten glass 6 intrudes between the outer periphery of the upper die 102 and the inner periphery of the lower die 101 as shown in FIG. Therefore, there is a problem that it takes a long time to cut and remove the raised portion.

In view of the above, the present invention has been made to solve such a problem, and a glass base substrate for an information recording medium capable of greatly reducing the number of machining steps to reduce the cost and improve the yield. It is intended to provide a mold and a manufacturing method.

[0005]

In order to achieve the above-mentioned object, the glass substrate for information recording medium (1 ') according to the first aspect of the present invention comprises an annular glass plate and has at least an outer peripheral surface (1'a). ) And the inner peripheral surface (11 ') of the central opening (11').
'A) is a smooth surface immediately after dissolution.

The original glass substrate in the first invention is annular in shape having a central opening, and at least the outer peripheral surface and the inner peripheral surface of the central opening are smooth surfaces immediately after melting. Coring (ring processing) and inner and outer chamfering (chamfering) are not required, so that the number of processing steps, cost, and yield can be reduced.

One manufacturing die for manufacturing the glass substrate for an information recording medium according to the second aspect of the invention forms a circular container-shaped die space (S) which is open upward, and is formed around a center line (C) on the bottom surface. A lower mold (2,3,4,5) to be rotated is provided, and the peripheral surface (4a, 5a) of the lower mold (2,3,4,5) follows the outer peripheral shape of the raw glass substrate (1 '). In addition to being formed on the mold surface, the center of the bottom surface of the lower mold (2, 3, 4, 5) follows the shape of the lower half of the inner periphery of the central opening (11 ') of the raw glass substrate (1'). A protruding part (31) having a mold surface (31a) is formed, while a central opening (11) of the glass raw substrate (1 ') is formed.
An upper die (7) having a die surface (71a) following the shape of the upper half of the inner periphery of (1) and being brought into contact with the protruding portion (31) is provided.

Another manufacturing die for manufacturing the glass substrate for an information recording medium according to the third aspect of the present invention forms a circular container-shaped die space (S1) which is opened upward, and a projection (91) is formed at the center of the bottom surface. ) Is formed to provide a lower mold (9) having a mold surface following the shape of the lower half of the glass substrate (1 '),
Form a circular container-shaped mold space (S2) that opens downward,
A projection (81) is formed in the center of the bottom surface, and has a mold surface that follows the shape of the upper half of the glass substrate (1 '). The projection (81) is the projection of the lower mold (9). An upper die (8) is provided to abut against the lower die (9) and abut against the lower die (9) to seal the die space (S1, S2), and the upper die (8) and / or the lower die (9). A vacuum exhaust path (82, 83, 84) is formed to communicate with the outer peripheral portion and / or the inner peripheral portion of the mold space (S1, S2).

The method according to the fourth aspect of the present invention for producing the glass substrate for an information recording medium using the production mold according to the second aspect of the present invention comprises the steps of: melting the molten glass (6) having a viscosity of 10 ^2.5 poise to 10 ⁵ poise; a step of dropping charged into the mold space (S) of (2), is stretched molten glass (6) radially outward by a centrifugal force while maintaining viscosity below ¹⁰⁷ poise molten glass (6) At the same time, the step of regulating the outer peripheral portion of the molten glass (6) by the peripheral surface (4a, 5a) of the lower mold (2, 3, 4, 5), and the step of moving the upper mold (7) to the lower mold (2, 3, 4) ,
5) punching out the center of the molten glass (6) inserted into the mold space (S) by abutting on the projection (31) of (5).

The method according to the fifth aspect of the present invention for producing the glass substrate for an information recording medium using the production mold according to the third aspect of the present invention comprises sealing a molten glass (6) having a viscosity of 10 ^2.5 poise to 10 ⁵ poise. And a step of evacuating the molten glass (6) from the vacuum exhaust paths (82, 83, 84) while maintaining the viscosity of the molten glass (6) at 10 ⁷ poise or less. ing.

Note that the reference numerals in parentheses indicate the correspondence with specific means described in the embodiments described later.

[0012]

(First Embodiment) FIG. 1 shows a plan view of a finished glass substrate for an information recording medium (hereinafter simply referred to as a glass substrate), and FIG. 2 shows a cross section thereof. The glass substrate 1 is an annular plate having a center opening 11 and has an outer diameter of, for example, 2.5 inches (65 mmφ), a thickness of, for example, 0.635 mm, and an average surface roughness of, for example, several nm.
Below. The outer peripheral surface 1a of the glass substrate 1 and the inner peripheral surface 11a of the center opening 11 are "chipped" during handling.
In order to prevent the occurrence of the like, it has a smooth C-shaped convex angle cross section according to the IDEMA standard. The manufacturing process of the raw glass substrate for obtaining such a glass substrate 1 will be described below together with the structure of the mold used for the same.

FIG. 3 is a sectional view of the lower die. A cylindrical core mold 3 constituting a part of the lower mold 2 is inserted from below into the center of the thick flat lower mold 2, and an upper end portion thereof projects from the surface of the lower mold 2 by a predetermined amount. It has become. Projection 3
The outer peripheral surface 31a, which is a mold surface, has a half C-shaped concave cross section. On the lower mold 2, the lower mold 2 is placed on both sides of the core mold 3.
Semi-circular slide molds 4 and 5 which constitute a part of
The slide dies 4 and 5 move inward and come into contact with each other, so that the center line C
Is formed in a circular container-shaped mold space S centered at. Here, the peripheral surfaces 4a and 5a, which are the mold surfaces of the slide dies 4 and 5, have a C-shaped concave cross section. The lower mold 2 and the core mold 3 and the slide molds 4 and 5 integrated with the lower mold 2 are rotated around the center line C of the core mold 3 by an unillustrated drive mechanism (arrows in the figure).

In this state, a predetermined amount of molten glass 6 having a viscosity of 10 ^2.5 poise to 10 ⁵ poise is dropped from above the core mold 3 and charged into the mold space S. The loaded molten glass 6 extends radially outward due to centrifugal force, but moves inward (straight arrow in FIG. 4) to form a peripheral surface of the slide cores 4 and 5 forming a circular container-shaped mold space S. At 4a and 5a, further elongation is restricted, and the outer peripheral surface of the molten glass 6 is formed into a C-shaped convex angle cross section that follows the peripheral surfaces 4a and 5a of the slide cores 4 and 5. In addition, the upper surface of the outer peripheral portion of the molten glass 6 bulges slightly upward under the regulation by the slide cores 4 and 5, and the bulge 61
Becomes

Next, as shown in FIG. 5, the upper die 7 having the same diameter is lowered onto the core die 3, and the central portion of the molten glass 6 is punched to form a central opening 11 (see FIG. 1). The outer peripheral surface 71a, which is the mold surface of the lower end 71 of the upper mold 7, is the upper end 31 of the core mold 3.
Of the center opening 11 is formed into a C-shaped convex angle cross-sectional shape by the core mold 3 and the upper mold 7 which are in contact with each other. Molded. During such a process, the lower mold 2, the core mold 3, the slide molds 4, 5 and the upper mold 7 are temperature-controlled so as to maintain the viscosity of the molten glass 6 at 10 ⁷ poise or less.

The temperature control of the lower mold 2 and the upper mold 7 is stopped, and the mold is released immediately after the viscosity of the molten glass 6 reaches about 10 ⁷ poise. FIG. 6 shows a cross section of the released glass raw substrate (hereinafter simply referred to as the original substrate) 1 ′. The outer peripheral surface 1 ′ a of the original substrate 1 ′ and the inner peripheral surface 11 ′ a of the center opening 11 ′ are C
The bottom surface 1'b of the original substrate 1 'is also a flat smooth surface immediately after melting, as well as a smooth surface immediately after melting, which has a U-shaped convex cross section. Such an original substrate 1 ′ is placed in an annealing furnace set at a temperature about 5 ° C. higher than the annealing point (viscosity of 10 ¹³ poise) of the glass and is held for 5 to 30 minutes. Furnace cooled to a viscosity of 10 ^14.5 poise)
Then, it is air-cooled to room temperature.

When the glass substrate 1 shown in FIGS. 1 and 2 is manufactured from the original substrate 1 ', conventional machining such as coring and chamfering is unnecessary, and only lapping and polishing of the substrate surface are performed. Thereby, the number of man-hours for machining is greatly reduced, the cost is reduced, and the yield is improved.

(Second Embodiment) FIG. 7 is a sectional view of a mold, and the mold comprises an upper mold 8 and a lower mold 9. A circular container-shaped mold space S1 opening upward is formed on the upper surface of the lower mold 9, and a protruding portion 91 is formed at the center of the bottom surface. The outer peripheral surface 91a serving as a mold surface of the protruding portion 91 and the peripheral surface 9a serving as a mold surface of the mold space S1 have a semi-C-shaped concave angle cross section. On the other hand, a circular container-shaped mold space S2 that opens downward is formed on the lower surface of the upper die 8, and a protrusion 81 similar to the lower die 9 is formed at the center of the bottom surface. The outer peripheral surface 81a as the mold surface and the peripheral surface 8a as the mold surface of the mold space S2 have a half-C-shaped concave angle cross section.

When the upper mold 8 and the lower mold 9 are abutted as shown in FIG. 7, the mold spaces S1 and S2 are closed and the closed mold space S is closed.
The cross-sectional shapes of S1 and S2 are the same as those of the glass substrate 1 shown in FIG. In one or both of the upper mold 8 and the lower mold 9, an injection path (not shown) for injecting the molten glass 6 into the sealed mold spaces S 1 and S 2 is formed.
Vacuum evacuation passages 82 and 83 extending from outside the mold to the outer peripheral portions of the mold spaces S1 and S2 are formed in the abutting portion.

When the glass substrate 1 is formed, the viscosity 1
The molten glass 6 of 0 ^2.5 poise to 10 ⁵ poise is injected into the mold spaces S1 and S2 via the injection path, and at the same time, the interior of the mold spaces S1 and S2 is exhausted through the vacuum exhaust paths 82 and 83.
By this exhaust, the molten glass 6 is sucked into the mold spaces S1 and S2, and the outer peripheral surfaces 81a and 91a of the protrusions 81 and 91 having a C-shaped concave section and the peripheral surfaces 8 of the mold spaces S1 and S2.
a, 9a (FIG. 8). During this time, the temperature of the lower mold 9 and the upper mold 8 is adjusted so as to maintain the viscosity of the molten glass 6 at 10 ⁷ poise or less.

The temperature control of the lower mold 9 and the upper mold 8 is stopped,
Immediately after the viscosity of the molten glass 6 reaches about 10 ⁷ poise, the inside of the mold is pressurized through an injection path to release the mold. The released original substrate has the same shape as the glass substrate 1 shown in FIGS. 1 and 2, and most of the outer surface of the original substrate including the outer peripheral surface and the inner peripheral surface of the central opening becomes a smooth surface immediately after melting. . Such an original substrate has a temperature lower than the annealing point (viscosity of 10 ¹³ poise) of glass.
5 to 3 in an annealing furnace set at a temperature as high as
After holding for 0 minutes and removing the strain, the mixture is furnace-cooled to the strain point (viscosity: 10 ^14.5 poise) and air-cooled to room temperature.

When the final product glass substrate 1 is manufactured from such an original substrate, wrapping is not required in addition to the conventional coring and chamfering.
It is only necessary to remove burrs generated when a part 61 of the molten glass 6 enters the vacuum evacuation paths 82 and 83 (see FIG. 8), to polish this part, and to polish the whole thereafter. As a result, the number of man-hours for machining is significantly reduced, and cost reduction and improvement in yield are realized.

(Third Embodiment) In the mold described in the second embodiment, a vacuum exhaust path may be provided as shown in FIG. That is, in FIG. 9, a vacuum exhaust path 84 is formed at the abutting portion of the upper die 8 and the lower die 9 by connecting the inner peripheral portions of the die spaces S1 and S2. Extends downward to open outside the mold. With the mold having such a structure, the same original substrate as in the second embodiment can be manufactured in the same process.

The vacuum evacuation passages in the second and third embodiments need not necessarily be provided at the abutment portion between the upper die and the lower die. In the above embodiments, the inner and outer peripheral surfaces of the glass substrate have a C-shaped square cross section, but may have a C-shaped curved cross section.

[0025]

As described above, according to the present invention, it is possible to greatly reduce the number of machining steps, thereby reducing costs and improving the yield.

[Brief description of the drawings]

FIG. 1 is a plan view of a glass substrate for an information recording medium.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of the glass raw substrate in the first embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of the glass raw substrate.

FIG. 5 is a cross-sectional view for explaining a manufacturing process of the raw glass substrate.

FIG. 6 is a sectional view of an original glass substrate.

FIG. 7 is a cross-sectional view illustrating a manufacturing process of a raw glass substrate in a second embodiment of the present invention.

FIG. 8 is an enlarged sectional view of a portion A in FIG. 7;

FIG. 9 is a cross-sectional view illustrating a manufacturing process of a glass raw substrate in a second embodiment of the present invention.

FIG. 10 is a cross-sectional view for explaining a conventional glass raw substrate manufacturing process.

[Explanation of symbols]

1 ': glass substrate, 1'a: outer peripheral surface, 11': central opening, 11'a: inner peripheral surface, 2 ... lower mold, 3 ... core mold, 31 ...
Projecting portion, 31a: outer peripheral surface, 4, 5: slide type, 4a,
5a: peripheral surface, 6: molten glass, 7: upper die, 71a: outer peripheral surface, 8: upper die, 81: projection, 82, 83, 84: vacuum exhaust path, 9: lower die, 91: projection, C: Center line, S, S
1, S2 ... mold space.

Claims (5)

[Claims] 1. An original glass substrate for an information recording medium, comprising an annular glass plate, wherein at least an outer peripheral surface and an inner peripheral surface of a center opening are smooth surfaces immediately after melting. 2. A manufacturing die for receiving a molten glass to manufacture the glass substrate for an information recording medium according to claim 1, wherein a circular container-shaped die space which opens upward is formed around a center line of a bottom surface. A lower mold that is rotated is provided, and a peripheral surface of the lower mold is formed into a mold surface that follows the outer peripheral shape of the glass raw substrate, and a central opening of the glass raw substrate is provided at a bottom center of the lower die. Forming a projection having a mold surface following the shape of the lower half of the inner periphery of the glass substrate, and having a mold surface following the shape of the upper half of the inner periphery of the central opening of the glass substrate; A production die for an original glass substrate for an information recording medium, comprising an upper die which is brought into contact with the substrate. 3. A production mold for receiving the molten glass to produce the glass substrate for information recording media according to claim 1, wherein a mold space in the shape of a circular container which is opened upward is formed, and the center of the bottom surface is formed. A lower mold having a mold surface having a shape following the shape of the lower half of the glass base substrate is formed, and a circular container-shaped mold space which is opened downward is formed; Is formed, and has a mold surface following the shape of the upper half of the glass base substrate. The protrusion is brought into contact with the protrusion of the lower mold to abut the lower mold to seal the mold space. An upper mold and an upper and / or lower mold are provided with a vacuum exhaust passage leading to an outer peripheral part and / or an inner peripheral part of the mold space. Production type of raw glass substrate. 4. A step of dropping molten glass having a viscosity of 10 ^2.5 poise to 10 ⁵ poise into the lower mold space, and the centrifugal force while maintaining the viscosity of the molten glass at 10 ⁷ poise or less. A step of extending the molten glass radially outward and regulating the outer peripheral portion of the molten glass by a peripheral surface of the lower mold; and And punching a central portion of the molten glass charged in the glass substrate. 3. A method for manufacturing a glass substrate for an information recording medium using a manufacturing die according to claim 2. 5. A step of injecting a molten glass having a viscosity of 10 ^2.5 poise to 10 ⁵ poise into the closed mold space, and applying a vacuum from the vacuum exhaust passage while maintaining the viscosity of the molten glass at 10 ⁷ poise or less. 4. A method for producing a glass substrate for an information recording medium using the production mold according to claim 3, comprising a step of drawing.