JP2002338278A - Method for manufacturing glass substrate and apparatus for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a forming cycle by improving the heat resistance of a glass blank just before being fed to a forming process step by using preheated dies. SOLUTION: The method has a preheating process step of preheating the glass blank by a heat transfer system up to a temperature necessary for forming the glass blank, a forming process step of press forming the glass blank after the preheating to a shape of a glass substrate for information recording disks and a transfer process step of transferring the glass blank from the preheating process step to the forming process step while maintaining the heat transfer state thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass substrate and an apparatus for manufacturing the same, and more particularly, to a method for manufacturing a glass substrate suitable for manufacturing a glass substrate for a magnetic disk, an optical disk, and other information recording disks. It relates to the manufacturing apparatus.

[0002]

2. Description of the Related Art For example, a magnetic disk which is one of information recording disks has high rigidity as a substrate material thereof.
A glass substrate which has high hardness, is easy to smooth, and is extremely advantageous for high density and high reliability is being studied.

As one of the methods for forming the glass substrate into the shape of an information recording disk, there is a press forming method in which a glass material is heated, formed, and cooled, and a mold forming surface is transferred with high precision. In the case of the molding method, since post-processing is not required, attention has been paid to a low-cost, high-productivity, and high-quality glass substrate.

In this press molding method, the information recording disk has a very small substrate thickness for its outer diameter.
It has a different problem from other fields such as press molding of a glass substrate in an optical lens.

[0005] For example, as a method of forming a glass substrate, as described in, for example, JP-A-11-92159, the upper surface of a glass material is heated by radiant heating in a heating furnace, and the lower surface thereof is heated by heat transfer heating. Heating.

[0006]

However, in the above-mentioned conventional configuration, uneven heating of the glass material easily occurs, and it is difficult to uniformly heat the entire glass material. In addition, a specific location is cooled by the influence of the flow of an atmosphere gas such as an inert gas, and as a result, it is difficult to equalize the temperature of the entire glass material.

For this reason, it takes time to uniformly heat the glass material to a temperature at which molding can be performed in the molding step, and the molding cycle is extended, and as a result, the production yield of molded products is reduced.

Therefore, the present invention improves the uniformity of the glass material immediately before being introduced into the forming step, shortens the forming cycle, and improves the yield in the manufacture of a formed product, thereby making it possible to manufacture a glass substrate at low cost. Is a common solution.

[0009]

(1) A method of manufacturing a glass substrate for an information recording disk according to the present invention comprises the steps of: preheating a glass material to a required temperature; It is characterized by comprising a forming step of press forming into a shape of a glass substrate, and a transferring step of transferring the glass material from the preheating step to the forming step while maintaining a heat transfer state.

According to the present invention, in the preheating step, the glass material is heated, and after the preheating step, the glass material is transferred to the forming step. In the transferring step, the glass material is transferred while maintaining the heat transfer state. Therefore, the molding can be performed while maintaining the uniformity of the glass material during molding, and the molding cycle can be shortened. As a result, the glass substrate can be manufactured at low cost by improving the manufacturing yield of the molded product. (2) In the preheating step, when the temperature of the glass material is gradually increased until the molding step, uneven heating of the glass material is less likely to occur, and the entire glass material is uniformly heated. It is preferable because it becomes easy. (3) In the preheating step, the preheating mold and the glass material are preheated in a heating furnace while holding the glass material in the preheating mold. When the glass material is transferred to the molding step while being held in a mold, the glass material can be transferred while being kept in a more heat-transferred state, and the glass material can be formed while maintaining the uniformity of the glass material during molding. Is more preferably shortened. More specifically, in the conventional technology described in, for example, Japanese Patent Application Laid-Open No. 11-92159, contaminants adhering to a furnace wall or the like on a glass substrate master in a transfer path of a heating furnace are regarded as foreign matters as glass. If it remains on the surface of the material, it is molded by a mold in that state, and the foreign matter is left as if it bites into the surface of the molded glass substrate. In addition, if it is attempted to omit the mirror polishing process on the surface of the glass substrate after molding, since the surface after molding becomes the surface of the final molded product, the mirror surface processing cannot be omitted, and the production yield of the molded product decreases. It is. Therefore, in order to improve the production yield, it is absolutely necessary to avoid the above-mentioned foreign matter biting. On the other hand, in the above (3), since the molding can be performed while maintaining the cleanliness of the glass material surface with the heating furnace and the preheating mold, the molding can be performed without biting foreign matter,
By improving the production yield of molded articles, it becomes possible to produce glass substrates at low cost.

(4) In the preheating step, a plurality of heating furnaces are arranged adjacent to each other in the transfer direction, and at least one of a pair of upper and lower preheating dies can be transferred into each heating furnace. In the heating step, the glass material is preheated, while the transfer step holds the one preheating mold in the transport unit, and the one preheating mold in a state of holding the glass material, The glass material is kept in a more heat-transferred state by moving the heating furnace from the charging side to the molding side, and sequentially moving it while pressing and heating it with the other preheating mold and raising the temperature. The molding can be performed while maintaining the uniformity of the glass material at the time of molding, and the molding cycle can be further shortened.

(5) In the transferring step, if the glass material is transferred in a state where the glass material is positioned in the preheating mold, the positional variation of the glass material in the forming step can be made extremely small, and It is preferable because the accuracy is increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments shown in the drawings. In the present invention, the glass substrate is applied to the information recording disk, but the present invention is not limited to this. The present invention is applicable to all glass substrates having a small thickness for the size of the outer diameter. be able to.

An apparatus for manufacturing a glass substrate for an information recording disk according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of the manufacturing apparatus, and FIG.
FIG. 3 is a diagram showing only the molding part of FIG. 1 and FIG.

The manufacturing apparatus 1 of the present embodiment includes a heating unit 2
A molding unit 3 and a transport unit 4 are provided. The heating unit 2 includes three heating furnaces 2a to 2c.

These heating furnaces 2a to 2c are respectively
Heating temperatures are set differently and are adjacent to each other, and a ceramic heater (not shown) utilizing far-infrared rays is arranged on each furnace wall.

In each of the heating furnaces 2a to 2c, the upper preheating mold 5 can be sequentially moved from the charging furnace 2a to the forming furnace 3c through the intermediate heating furnace 2b. Has been deployed. However, the number of the upper preheating mold 5 is one, and each heating furnace 2a to 2b can be sequentially moved. The lower preheating mold 6 is fixed on the bottom wall of each heating furnace 2a to 2b. Are located.

Although the lower preheating mold 6 in the embodiment is fixed, it is not limited to this, and may be movable similarly to the upper preheating mold 5.
Further, both the preheating dies 5 and 6 may be movable.
Further, while the upper preheating mold 5 is fixed, the lower preheating mold 6 may be movable.

The transport section 4 includes a heating section (not shown), and is heated to a predetermined temperature when the upper preheating mold 5 is mounted and transported.

The transport section 4 also has a suction section 4a.

The upper preheating mold 5 has a through-hole 5a vertically penetrating at the center of the bottom wall surface, whereby the transporting unit 4 sucks and transports the glass material 7 together with the upper preheating mold 5. be able to. The upper preheating mold 5 also has an annular vertical wall 5b having an inner diameter substantially matching the outer diameter of the glass material 7 on the periphery of the thick bottom wall, and a thin annular flange 5c extending horizontally outside the outer wall.

The lower preheating mold 6 has an inner peripheral wall which is inclined at a predetermined inclination angle connected to a horizontally flat bottom wall, and an annular inclined wall 6a which is perpendicular to the annular inclined wall 6a. An annular vertical wall 6c that rises vertically with a horizontal plane 6b extending flat by the thickness of the wall 5b therebetween. The annular inclined wall 6 a is for positioning the outer peripheral portion of the glass material 7. When the glass material 7 and the upper preheating mold 5 are transported by the transport unit 4 and set on the lower preheating mold 6, the glass material 7
Is positioned by the annular inclined wall 6a of the lower preheating mold 6.

The inner diameter of the annular inclined wall 6a is substantially equal to the outer diameter of the glass material 7, and its inclined shape is set to match the shape of the glass material 7. by this,
The positioning can be reliably achieved.

The inner diameter of the annular vertical wall 6c matches the outer diameter of the annular vertical wall 5b of the upper preheating mold 5.

It should be noted that the preheating dies 5, 6 shown in FIG. 4 may be used instead of the preheating dies 5, 6 of the above-described embodiment.

In the preheating dies 5 and 6 shown in FIG.
The upper preheating mold 5 has a through hole 5a penetrating vertically in the center of the bottom wall surface, so that the transport unit 4 can adsorb and transport the glass material 7 together with the upper preheating mold 5. . The upper preheating mold 5 also has an annular vertical wall 5b having an inner diameter substantially matching the outer diameter of the glass material 7 on the periphery of the thick bottom wall.
And a thin annular flange 5c extending horizontally on the outside thereof.

The lower preheating mold 6 has an annular vertical wall 6c that rises vertically at the periphery of the bottom wall that is flat in the horizontal direction. The inner diameter of the annular vertical wall 6c matches the outer diameter of the annular vertical wall 5b of the upper preheating mold 5.

The annular vertical wall 5 formed on the preheating mold 5
b positions the outer peripheral portion of the glass material 7. When the glass material 7 is transferred by the transfer unit 4, the glass material 7 is sucked and transferred to the transfer unit 4 through the through hole 5 a of the upper preheating mold 5.

In this case, both the heating unit 2 and the molding unit 3 strictly control the oxygen concentration, and an inert gas such as nitrogen is preferable as a gas used for suction in the transport unit 4.

The heating unit 2 includes a plurality of heating furnaces 2a to 2
Although it is constituted by c, it may be constituted by a single heating furnace. In this case, the upper preheating mold 5 and the lower preheating mold 6 may be each one.

In the above configuration, the upper preheating mold 5 holding the glass material 7 is transferred from the loading furnace 2a to the forming section by the intermediate heating furnace 2b by the transfer section 4 as the transfer means. In the process of being conveyed to the heating furnace 2c, heating is performed in a state where the glass material 7 is sandwiched between the two preheating molds 5 and 6 in the respective heating furnaces 2a to 2c to be moved toward the lower preheating mold 6. The unit is arranged so that it can be moved sequentially while being heated for a certain period of time at the unit and then heated. Thus, each heating furnace 2a-
After being heated in 2c, the glass material 7 and the upper preheating mold 6 are sucked by the transfer unit 4, and only the glass material 7 is transferred to the forming unit 3.

The molding section 3 includes an upper molding die 8, a lower molding die 9, a regulating ring 10 for regulating the gap between the upper and lower molding dies 8, 9, and a heat retaining drum mold 11.

The upper and lower molding dies 8, 9 are preferably made of a material having excellent mechanical strength at a high temperature, such as a cemented carbide or a quartz glass mainly composed of tungsten carbide (WC) as a base material, and having a coefficient of thermal expansion. A smaller one is desirable.

On the press forming surfaces of the upper and lower forming dies 8, 9,
Platinum (Pt), ruthenium (Ru), iridium (I
r) A target made of a precious metal or alloy material such as r) is sputtered to form a thin protective film, which adheres to the press surface by repeated press molding of the glass under high temperature and high pressure, and the base material To prevent a decrease in surface smoothness due to surface roughness of the press-formed surface.

Further, the smoothness of the protective film is suitably 5 nm or less for an information recording disk, and such a smooth surface can be obtained by polishing using fine particles of cerium oxide.

The upper molding die 8 and the lower molding die 9 are connected to the heater blocks 14 and 1 via fixing rings 12 and 13, respectively.
5 is fixed.

The upper heater block 14 includes the cylinder head 1
The upper molding die 8 is vertically moved by the vertical movement of the cylinder head 16.

The regulating ring 10 is placed on the press-molding surface of the lower molding die 9 and is positioned by the heat retaining cylinder die 11, contacts the molding surface 8 a of the upper molding die 8, and is a glass molded product. The thickness of the substrate will be determined.

The upper and lower molding dies 8 and 9 are
Straight tube type cartridge heater 1 embedded in 4, 15
According to 7 and 19, near the glass softening point Ts (about ± 50 ° C)
And a predetermined temperature between the vicinity of the glass transition point Tg (about ± 50 ° C.). In the above-mentioned manufacturing apparatus, in the forming unit 3, the heated glass material 7 is pressed by the press head 16 and deformed until the glass material 7 contacts the regulating ring 10 on the press forming surface 8 a of the upper forming die 8. By this, the press is completed. When the glass substrate 18 thus formed is cooled to the glass distortion point Ps or lower, the upper forming die 8 is raised to open the mold, and the glass substrate 18 is carried out of the mold by the transfer unit 4. Manufacturing of the glass substrate 18 using the manufacturing apparatus 1 will be described. This manufacturing includes a heating step, a transfer step, a temperature raising step, a pressing step, and a cooling step.

The heating step is performed in each heating furnace 2 in the heating section 2.
In steps a to 2c, each glass material 7 is sequentially heated and heated. In this case, in a state where the glass material 7 is suction-held by the upper preheating mold 5, the glass material 7 is sequentially transferred to each heating furnace 2 by the transport unit 4.
a to 2c are moved.

The transfer step is a step of transferring the glass material from the heating unit 2 to the forming unit 3 by the transfer unit 4.

The temperature raising step is a step of raising the temperature of the glass material 7 in the forming section 3.

The pressing step is a step of pressing the glass material 7 in the forming section 3.

In each of the above steps, the glass material 7 is always
Since the glass material obtained by the heating step is moved by the transfer unit 4 while being held by the upper preheating mold 5, the glass material obtained in the heating step can be formed by the forming unit 3. Furthermore, glass material 7
Is molded while maintaining its surface cleanliness,
It can be molded without biting foreign matter. In each of the above series of steps, the temperature profile of each mold and glass material will be described with reference to FIG.

In FIG. 5, the horizontal axis represents time, the vertical axis represents temperature, the solid line represents a mold temperature characteristic line, and the broken line represents
The glass material temperature characteristic line is shown. For the characters written along the time axis, (Heating a), (Heating b),
(Heating c) is performed in each heating furnace 2 in the heating unit 2.
a to 2c heating time zone, (transfer) is a time zone of transfer from the heating unit 2 to the molding unit 3, (heating) is a heating time zone of the molding unit 3, and (press) is The time zone of the press forming in the forming section 3 and (cooling) are the time zone of the cooling in the forming section 3.

In this embodiment, as is apparent from FIG. 5, the heating temperature in each of the heating furnaces 2a to 2c in the heating section 2 is set in a stepwise manner. The temperature is set to be the same as the temperature at the start of the temperature raising step in the section 3.

When the glass material 7 is conveyed to the forming section 3, the glass material 7 itself is suppressed by a rapid change in temperature by being conveyed by the conveying section 4 set to the same temperature as the heating temperature c in the heating furnace 2c. I am trying to do it.

As a result, the glass material 7 is placed in the upper preheating mold 5
Indirectly transported through the glass material, the influence of thermal disturbance can be suppressed as much as possible, so that the glass material 7 can be transported without deteriorating its uniformity.

In this case, the forming temperature rise start temperature is set to a temperature lower than the transition point temperature Tg. When the glass material 7 is placed on the lower molding die 9 of the molding section 3, the upper molding die 8 is lowered to start the temperature rise. When the temperature rise is completed, the heating temperature is kept for a certain period of time, followed by press molding, and cooling is started after the press molding. And
The temperature at which the cooling is completed and the mold is opened is set to a temperature lower than the transition point temperature Tg.

The inventor applied specific numerical values for the above molding as follows.

The glass material has a transition point temperature Tg = 501.
° C, softening point temperature Ts = 670 ° C, linear expansion coefficient α = 95 ×
It is an aluminosilicate glass of 10 ⁻⁷ / ° C., weighing 6.5 g ± 0.5 g, outer diameter of 22.3 mm ± 0.3 mm,
A dropping glass material having a thickness of 8 mm ± 0.5 mm was used.

As the molding conditions, (heating a) is 200 ° C.
(Heating b) was set at 350 ° C, (Heating c) was set at 400 ° C,
The molding dies 8 and 9 are 700 ° C and the molding pressure is 400 kg / c.
m ² and the molding time was 1 minute. Thereafter, the heating was stopped, the cooling was performed with the press pressure set to 100 kg / cm ² , and the heater temperature monitor was opened at 400 ° C.

The glass substrate 18 thus obtained is
Has an outer diameter of 70 mm and a thickness of 0.635 mm.

The smoothness was Ra = 0.5 nm ± 0.2 nm, and it was confirmed that the smoothness of the press-formed surfaces of the molding dies 8 and 9 was transferred almost as it was.

[0055]

According to the present invention, the transfer from the heating section for preheating the glass material to the molding section for molding is performed while maintaining the heat transfer state with respect to the glass material. The molding cycle can be shortened, and as a result, the production yield of the molded article can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for manufacturing a glass substrate for an information recording disk according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of only a molded portion of FIG.

FIG. 3 is an enlarged side view of the upper and lower preheating mold in the heating unit of FIG. 1;

FIG. 4 is an enlarged side view showing another modification of the upper and lower preheating mold of FIG. 1;

FIG. 5 is a temperature profile of molding by the manufacturing apparatus of FIG.

[Explanation of symbols]

 1, 4 ... mold for molding glass substrate 6 ... regulating ring 7 ... glass material 10, 14 ... heater block 12 ... cylinder head 18 ... glass substrate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kengo Kainuma 1-1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term F-term (reference) 5D112 AA02 BA03 BA10

Claims (10)

[Claims] 1. A preheating step of preheating a glass material to a required temperature, a forming step of press-forming the preheated glass material into a required glass substrate shape, and a step of transferring the glass material from the preheating step to the forming step. A method for manufacturing a glass substrate, comprising: a transfer step of transferring while maintaining a thermal state. 2. The method for manufacturing a glass substrate according to claim 1, wherein in the preheating step, the temperature of the glass material is sequentially raised until the forming step. Method. 3. The method for manufacturing a glass substrate according to claim 1, wherein in the preheating step, the preheating mold and the glass material are preheated in a heating furnace while the glass material is held by the preheating mold. The method of manufacturing a glass substrate, wherein, in the transferring step, the glass material is transferred to the forming step while the glass material is held by the preheating mold. 4. The method for manufacturing a glass substrate according to claim 1, wherein in the preheating step, a plurality of heating furnaces are arranged adjacent to each other in the transfer direction, and at least a pair of upper and lower preheating metals are provided in each heating furnace. At least one of the molds is pre-heated by the heating unit capable of transferring the glass material, while the transferring step holds the one pre-heating mold in the transfer unit, and holds the glass material. The above one preheating mold, while heating and heating the inside of each heating furnace from the charging side to the molding side, and pressurizing and heating between the other preheating mold,
Moving the glass substrate. 5. The method of manufacturing a glass substrate according to claim 3, wherein in the transferring step, the glass material is transferred while being positioned in a preheating mold. Production method. 6. The method for manufacturing a glass substrate according to claim 1, wherein said glass substrate is used for an information recording disk having a small substrate thickness for an outer diameter. A method for manufacturing a glass substrate. 7. A pair of upper and lower preheating dies capable of preheating while holding a glass material, a heating section for radiantly heating the preheating die, and a glass material heated by the preheating die. A forming section for obtaining a glass substrate by pressure forming, while transferring the preheating mold and the glass material from the heating section to the forming section while holding the glass material in the preheating mold, and transferring the glass material to the forming section. A glass substrate manufacturing apparatus, comprising: transfer means for mounting at a predetermined position. 8. The glass substrate manufacturing apparatus according to claim 7, wherein said transfer means directly holds said preheating mold and adsorbs and holds a glass material via said preheating mold. apparatus. 9. The glass substrate manufacturing apparatus according to claim 7, wherein the heating unit includes a plurality of heating units provided with lower preheating dies on a bottom surface and different heating temperature settings for the glass material. A furnace, wherein the transfer means lowers the upper preheating mold holding the glass material from the charging-side heating furnace to the forming-section-side heating furnace via an intermediate heating furnace. A glass substrate manufacturing apparatus characterized in that the glass substrate manufacturing apparatus is provided so as to be sequentially movable while being lowered toward a mold and with a glass material sandwiched between the two preheating molds while being heated by the heating unit. 10. The glass substrate manufacturing apparatus according to claim 7, wherein said preheating mold has a structure for positioning and holding a glass material.