JP2892217B2 - Method and apparatus for manufacturing glass material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a glass material for use in a high-precision optical glass element such as a lens or a prism for a repetitive press.

[0002]

2. Description of the Related Art In recent years, optical glass lenses have become more aspherical so that both the simplification of the lens structure of an optical device and the reduction of the weight of the lens portion can be achieved simultaneously. In manufacturing this aspheric lens, a method of manufacturing a conventional optical lens is to cut out a material from a glass block, a rod, a plate, or the like, and then grind and polish the material, or a method similar to the lens to be manufactured. Press the molten glass lump in advance with a mold,
In a polishing method such as a method of grinding and polishing this glass formed body, it is difficult to process and mass-produce, and a forming method using a mold is expected to be promising.

[0003] A molding method using a mold includes a direct pressing method of directly pressing a molten glass lump to obtain a high-precision optical glass element and a high-precision optical glass element by pressing a glass material of a preform used for molding. There is a reheat press method for obtaining

According to the former method, it is possible to manufacture a very inexpensive optical glass element. There are also many technical problems such as a shortened life and it is difficult to put it to practical use.

According to the latter method, the problem of the direct press method is improved, but the cost is relatively high because the number of steps for manufacturing the glass material is increased. The simplification of the process of manufacturing a glass material for reheat pressing is an important issue in manufacturing an optical glass element.

As an effective method for easily forming a glass material, according to a method of dropping a molten glass lump on a saucer and leaving it in that state to form a shape, a very inexpensive glass material for reheat press can be obtained. It can be manufactured (for example, JP-A-2-34525).

[0007]

The method of causing molten glass to flow down from the glass outlet of a melting furnace involves the following steps.
After lowering the viscosity of the glass to a high temperature of 000 degrees or more,
The molten glass block is dropped by natural dropping or cutting by a cutting blade.

A tray for receiving the molten glass lump is
It is important that the surface of the saucer be transferred to glass by polishing the surface to a smooth surface and having good wettability with the molten glass, or by heating the molten glass to a temperature at which the saucer gets wet with the saucer. .

For example, as shown in FIG. 7A showing a conventional example, in a saucer made of a material 2a having poor wettability with molten glass,
Wrinkles due to poor wetting occur on the contact surface 1b of the molten glass lump 1 with the tray.

If wrinkles due to such poor wetting occur and the smooth surface of the saucer cannot be transferred to the glass material 1 ', the performance of the optical glass element deteriorates because it remains as bubbles or holes in the lens even after reheat pressing. There is a problem of doing.

As shown in FIG. 7 (b), when a molten glass mass having a low viscosity and a high temperature is dropped and received by a saucer of a material 2b polished to a smooth surface and having good wettability with the molten glass, No wrinkle-like defects are generated, but since the pan is a single material, the wet angle between the molten glass lump 1 and the pan becomes large,
The outer periphery of the glass material has a shape protruding at an acute angle, and has a shape in which cracking and chipping easily occur. In addition, the deformation of the molten glass lump when it is dropped on the pan is reflected in the shape as it is under the influence of wetting, causing shape variations, and it is difficult to control the wetted area (transfer area) between the molten glass lump and the receiving mold. There is also a problem that it is difficult to produce a glass material 1 ′ in a desired shape, for example, a glass material having a large thickness cannot be obtained.

The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing a glass material capable of manufacturing a high-precision glass material at low cost and an apparatus for manufacturing the same.

[0013]

According to the present invention, a glass material for reheat pressing an optical glass element is manufactured as follows. First, a required amount of molten glass lump is accurately received in a saucer polished to a smooth surface. As the tray for receiving the molten glass block, a tray composed of at least two or more types of materials having different wettability with the molten glass is used. For example, the material of the tray is configured such that a material having good wettability is formed at the transfer center of the molten glass lump and a material having poor wettability is formed at the outer periphery of the transfer of the molten glass lump. A glass material is produced by cooling on such a tray. Alternatively, after receiving the molten glass lump in the tray, the molten glass lump is cooled and pressurized with a pressing die, and cooled to a removal temperature on the tray to produce a glass material.

[0014]

According to the structure of the present invention, a free surface formed by surface tension and a contact surface in contact with the tray are formed in the molten glass mass received by the tray.

Of these, the free surface of the molten glass lump is formed into an extremely smooth mirror surface by the action of surface tension. The contact surface of the molten glass mass with the saucer is, for example, a central portion in contact with a material having good wettability, the surface of the saucer having good surface accuracy is transferred to the molten glass mass, so that a mirror surface equivalent to the free surface is made, and Since the molten glass lump does not wet the outer peripheral portion in contact with the material having poor properties, the smooth surface of the receiving tray can be transferred to the glass material by a desired area. Further, since the wetted area of the molten glass lump and the saucer can be controlled, the shape of the glass material can be very stable.

The material having good wettability with the molten glass is, for example, a simple substance of a noble metal, tungsten, tantalum, rhenium, hafnium which reacts with or slightly adheres to austenitic steel, nichrome, glassy carbon or optical glass, or an alloy thereof. desirable. As a material having poor wettability with the molten glass and excellent releasability, for example, carbon, boron nitride, silicon carbide, silicon nitride, aluminum nitride, chromium nitride, and the like are suitable.

When controlling the wet area of the molten glass lump and the pan, the desired wet area may not be obtained only by receiving the molten glass lump with the pan due to the surface tension of the molten glass lump. In this case, a glass material having a desired transfer area and a desired thickness shape can be obtained by transferring the molten glass lump to a receiving tray and immediately cooling and pressing the free surface with a pressing die.

If the glass material thus obtained is used for forming a glass element, an extremely high-precision glass element can be obtained only by pressing.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method and apparatus for manufacturing a glass material according to the present invention will be described below in detail with reference to FIGS.

(Embodiment 1) FIG. 1 is a sectional view showing a method of manufacturing a glass material according to an embodiment of the present invention.

FIG. 1 shows a state in which a molten glass lump 1 is received by a tray 2 made of two kinds of constituent materials 2a and 2b having different wettability. The material composition of the tray 2 is such that the molten glass lump is dropped on the tray 2 (a part requiring surface accuracy), and the molten glass and the constituent material 2b having good wettability are formed. Is made of a constituent material 2a having a lower wettability than the constituent material 2b at the center.

A method for manufacturing a glass material according to one embodiment of the present invention will be described in the order of steps. First, if the pan 2 is heated before receiving the molten glass lump, the wettability of the molten glass lump and the pan is improved, and the surface transfer property is improved. The pan 2 is preheated to a temperature below the softening point.

Then, a predetermined amount of the glass melted in the glass melting furnace is supplied onto the tray 2. At this time, the center of the molten glass lump 1 is placed on the constituent material 2b having good wettability by the tray 2, so that the smooth surface of the tray 2 is transferred, and the outer periphery of the molten glass lump is wetted. Due to the poor material 2a, the releasability from the molten glass does not adhere well, so that a necessary transfer surface is obtained and a molten glass lump having a stable shape is formed. The free surface 1a is a very good mirror surface formed by the surface tension of the molten glass lump.

The molten glass lump is cooled on a plate to a temperature lower than the softening point of the glass and is taken out.

In this embodiment, an extremely smooth mirror surface and a glass material 1 'having a desired shape controlled to a good surface roughness can be obtained, and an excellent optical element can be obtained by molding this glass material. Was completed.

The shape of the tray 2 is, for example, as shown in FIG.
As shown in (a) and (b), if the material 2b having good wettability is processed into an uneven shape, it is also possible to produce a glass material 1 'that matches the shape of various glass elements. FIG.
As shown in (c), the desired glass material 1 can be obtained by using the material 2a having poor wettability as a base material and forming and using the saucer 2 on which a thin film of the material 2b having good wettability is formed. '
Is obtained.

(Embodiment 2) FIG. 5 is a sectional view showing a basic configuration of a manufacturing apparatus using the method for manufacturing a glass material of the first embodiment.

11 is a glass melting furnace, 12 is a molten glass outlet, 13, 15 and 17 are heaters, 14 is a cutting blade, 2 is a tray for molten glass lump, and 16 is a conveyor chain conveyor. Reference numeral 18 denotes a cooling gas, 19 denotes a cooling gas pipe, and 20 denotes a take-out robot.

The size of the central portion φ6 of the receiving mold 2 was used as a transfer surface, and austenitic steel (SUS316) was selected as a constituent material, and carbon was selected as a constituent material of an outer peripheral portion, and processed into a flat shape.

The molten glass is zirconia (ZrO ₂ ) 8
Weight percent, lanthanum oxide (La ₂ O ₃ ) 30 weight percent, boron oxide (B ₂ O ₃ ) 42 weight percent,
A lanthanum-based glass comprising 10% by weight of calcium oxide (CaO) and the balance being trace components was used.

After melting this glass at 1400 ° C.,
Approximately 1 gram of molten glass lump 10 flows out of outlet 12 maintained at 950 ° C. by heater 13,
By cutting at 4, it is supplied to the tray 2 which has been heated to 400 ° C. in advance. Thereafter, in a cooling stage, a cooling gas 18 whose temperature is controlled by a heater 17 is sprayed on the upper surface of the molten glass lump 1 to cool the glass to a temperature lower than the softening point of the glass, and gradually cooled to 100 ° C. or lower. 'Was taken out of the apparatus by the take-out robot 20.

Glass material 1 'obtained by this embodiment
Of the sample, the center point average roughness was 1.0 μm or less, and the shape stability was 0.1 mm or less. As a result of observation with an optical microscope, no defects such as adhesion of foreign matter and scratches were found on the surface.

The inside of the apparatus is usually provided with an appropriate non-oxidizing atmosphere in order to prevent the tray from being deteriorated by oxidation. Trichlorotrifluoroethane (C ₂ Cl ₃
F ₃ ) A halogenated hydrocarbon atmosphere mixed at a rate of 1 liter / minute of gas was used.

Example 3 Glass materials having different glass compositions were produced using a production apparatus having the same function as that shown in FIG. FIG.
Silicon carbide (SiC) was selected as the base material of the receiving die 2 having the shape of (c), and a platinum-iridium-osmium (Pt-Ir-Os) thin film was formed as the material using the size of the center part φ5 as a transfer surface. Filmed. The molten glass is 65% by weight of silicon oxide (SiO ₂ ), 9% by weight of potassium oxide (K ₂ O), 10% by weight of boron oxide (B ₂ O ₃ ), and sodium oxide (Na ₂ O). Borosilicate glass consisting of 10% by weight and the balance of trace components was used.

After melting this glass at 1350 ° C.,
About 1 gram of the molten glass 10 is supplied from the outlet 12 maintained at 920 ° C. to the pan 2 which has been heated to 350 ° C. in advance. Thereafter, in a cooling stage, a cooling gas 18 whose temperature is controlled by the heater 17 is sprayed on the upper surface of the molten glass lump 1 to cool the glass to a temperature lower than the softening point of the glass,
The glass material 1 ′ was gradually cooled to a temperature of not more than 0 ° C. and was taken out of the apparatus by the robot 20.

Glass material 1 'obtained according to this embodiment
Of the sample, the center point average roughness was 1.0 μm or less, and the shape stability was 0.1 mm or less. As a result of observation with an optical microscope, no defects such as adhesion of foreign matter and scratches were found on the surface.

In this embodiment, the atmosphere in the apparatus was a hydrocarbon atmosphere in which argon gas was mixed at a rate of 20 L / min and ethylene (C ₂ H ₄ ) at a rate of 1 L / min.

(Embodiment 4) FIG. 3 is a sectional view showing a method of manufacturing a glass material according to an embodiment of the present invention.

A method for manufacturing a glass material according to one embodiment of the present invention will be described in the order of steps. FIG. 3A shows a state where the molten glass lump 1 is received in the tray 2 having the same configuration as that shown in FIG. 1 in the first embodiment. As shown in FIG.
Difference in weight of molten glass mass and surface tension of molten glass mass,
Alternatively, depending on the size of the desired transfer surface, the molten glass lump 1 may not sufficiently spread on the transfer surface of the constituent material 2b having good wettability.

In FIG. 3B, in order to form a transfer surface of a desired tray on a glass material, a high-temperature molten glass lump 1 is cooled and pressurized using a pressing die, and is melted on a surface of a material 2 having good wettability. The state where the glass lump 1 is being spread is shown.

In FIG. 3 (c), the molten glass lump 1 is cooled to a temperature lower than the softening point of the glass in a state where the molten glass lump 1 is spread over a desired transfer surface (the surface of the material 2b having good wettability). Then, the pressing die is opened, and the molten glass lump is returned to the shape by the surface tension of the molten glass lump. The free surface 1a of the molten glass lump 1 whose shape has been restored returns to a very good mirror surface. Even after the molten glass lump recovers its shape, the surface in contact with the material 2b having good wettability is kept as it is and is cooled, so that the glass material 1 'having a highly accurate transfer surface of a saucer by a desired area is used. It can be easily manufactured.

In this embodiment, an extremely smooth mirror surface and a glass material 1 'having a desired shape controlled to a good surface roughness can be obtained, and an excellent optical element can be obtained by molding this glass material. Can be.

Further, as shown in FIG. 4, for example, similarly to the tray, a pressing die 3 having a material 3b having a desired shape and a desired transfer area is formed of a material 3b having good wettability with molten glass.
By using, a glass material corresponding to the shape of various optical glass elements such as a flat plate, a concave, and a meniscus can be produced. When the above-described manufacturing method is used, the timing of releasing the cooling and pressurizing is set such that the molten glass lump 1 is released so as to prevent the molten glass lump 1 from returning to the shape due to the surface tension of the glass and maintain a desired shape. After being cooled to a temperature lower than the softening point of the glass, the pressing mold 3 is opened.

(Embodiment 5) FIG. 6 is a sectional view showing the basic structure of a manufacturing apparatus using the method for manufacturing a glass material of the fourth embodiment.

Austenitic steel (SUS316) was selected as the constituent material of the center part φ10 of the receiving mold 2 and carbon was selected as the constituent material of the outer peripheral part, and processed into a flat mold. Further, silicon carbide having poor wettability with molten glass was selected as a constituent material of the pressing die 3 and processed into a flat die.

The molten glass is made of zirconia (ZrO ₂ ) 8
Weight percent, lanthanum oxide (La ₂ O ₃ ) 30 weight percent, boron oxide (B ₂ O ₃ ) 42 weight percent,
A lanthanum-based glass comprising 10% by weight of calcium oxide (CaO) and the balance being trace components was used. After melting the glass at 1400 ° C., about 1 gram of the molten glass 10 flows out of the outlet 12 maintained at 950 ° C. by the heater 13 and supplied to the pan 2 previously heated to 400 ° C. by natural dropping. I do.

Next, the receiving tray 2 is moved below the pressing die 3 by the transport chain conveyor 16. In order to prevent the molten glass lump from being rapidly cooled during the movement and becoming lower than the glass softening point, the saucer 2 is also heated by the heater 15 during the movement.
As shown in FIG. 3B, the tray 2 is moved directly below the pressing die 3, and at the same time, the pressing die 3, the temperature of which is controlled at 250 ° C., presses the molten glass block by the pressing cylinder 21.
The molten glass lump 1 is cooled, but before the contact surface between the pressing die 3 and the molten glass lump 1 becomes lower than the softening point of the glass as shown in FIG. I do.

Thereafter, the molten glass lump is naturally cooled, and as shown in FIG. 3 (c), the contact surface 1b between the molten glass lump and the saucer is made of a very wet mirror-polished material 2b. The glass is cooled to a temperature below the softening point of the glass while keeping the glass in close contact. Glass material 1 'after gradually cooling to a temperature of 100 ° C or less
Was taken out of the apparatus by the take-out robot 20.

The glass material 1 'obtained according to this embodiment
Has a desired transfer surface in a mirror state having a center point average roughness of 1.0 μm or less, and has a shape stability of 0.1 mm or less. As a result of observation with an optical microscope, defects such as adhesion of foreign matter and scratches on the surface are I was not able to admit.

In this embodiment, the inside of the apparatus is filled with 20 liters / minute of nitrogen gas and trichlorotrifluoroethane (C ₂ Cl ₃ F ₃ ).
The atmosphere was a halogenated hydrocarbon atmosphere mixed at a rate of 1 liter / minute of gas.

Example 6 Glass materials having different glass compositions were produced using a production apparatus having the same functions as in FIG. Glassy carbon as the constituent material of the center part φ8 of the receiving mold 2,
Boron nitride was selected as the material of the outer periphery and Fig. 2
As shown in (a), it was mirror-finished into a concave shape. In addition, glassy carbon is selected as the material 3b having good wettability at the center portion φ8 of the pressing mold 3, and silicon carbide is selected as the material 3a having poor wettability at the outer periphery, and a convex mirror surface is formed as shown in FIG. processed.

The molten glass is made of silicon oxide (SiO ₂ ) 65
Weight percent, potassium oxide (K ₂ O) 9 weight percent, boron oxide (B ₂ O ₃ ) 10 weight percent, sodium oxide (Na ₂ O) 10 weight percent, balance from trace components Borosilicate glass was used. After melting this glass at 1350 ° C., about 1 gram of molten glass 10 was introduced at 350 ° C. from outlet 12 kept at 920 ° C.
Is supplied to the tray 2 which has been heated.

Next, the receiving tray 2 is moved below the pressing die 3 by the transport chain conveyor 16. In order to prevent the molten glass lump from being rapidly cooled during the movement and becoming lower than the glass softening point, the saucer 2 is also heated by the heater 15 during the movement.
As shown in FIG. 4B, the tray 2 is moved directly below the pressing die 3, and at the same time, the pressing die 3, the temperature of which is controlled at 300 ° C., presses the molten glass block by the pressing cylinder 21.
Until the molten glass lump 1 is cooled to a temperature lower than the softening point of the glass, the state in which the molten glass lump 1 is pressed by the pressing mold 3 as shown in FIG. After the molten glass lump 1 is cooled to a temperature below the softening point of the glass, the pressure is released and the molten glass lump 1 is conveyed to the next stage. At this time, the contact surface 1a of the molten glass lump with the pressing die has a good mirror surface of the pressing die 3 transferred to a desired size and the molten glass lump is cooled to a temperature below the softening point. Is maintained.

Thereafter, the glass material 1 'is naturally cooled, but as shown in FIG. 4 (c), the contact surface 1b between the glass material and the saucer is made of a very wet mirror-polished material 2b. The glass material 1 ′ was cooled down to 100 ° C. or less while keeping the contact, and the glass material 1 ′ was taken out from the apparatus by the robot 20.

Glass material 1 'obtained according to this embodiment
Has a desired transfer surface in a mirror state having a center point average roughness of 1.0 μm or less, and has a shape stability of 0.1 mm or less. As a result of observation with an optical microscope, defects such as adhesion of foreign matter and scratches on the surface are I was not able to admit.

Although the embodiments of the present invention have been described in detail above, the material and shape of the saucer described in each embodiment are limited in consideration of the temperature of the molten glass, the glass composition, or the shape of the glass material. It does not do. For example, a saucer for directly receiving molten glass can be used in a combination of various materials such as ceramic, alumina, and zirconia.

The non-oxidizing atmosphere may be an inert gas such as nitrogen, argon or helium, or hydrogen or carbon monoxide, carbon oxides of carbon dioxide, methane, ethane, ethylene, toluene or the like. A mixture of hydrocarbons, halogenated hydrocarbons such as trichloroethylene and trichlorotrifluoroethane, alcohols such as ethylene glycol and glycerin, and fluorocarbons such as F-113 and F-11. is there.

The present invention is not limited to the composition of the optical glass, the shape of the glass material, the method and conditions for heating the glass melting furnace and the saucer described in each embodiment.

[0059]

According to the present invention, it is possible to mass-produce a glass material for a reheat press having a desired shape without defects on the surface without etching and polishing steps, thereby improving productivity and reducing production costs. It has a remarkable effect on reduction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method of manufacturing a glass material according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a tray used in the embodiment.

FIG. 3 is a sectional view showing steps of a method for manufacturing a glass material according to one embodiment of the present invention.

FIG. 4 is a sectional view showing a method for manufacturing a glass material according to one embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of a glass material manufacturing apparatus according to one embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a configuration of an apparatus for manufacturing a glass material according to one embodiment of the present invention.

FIG. 7 is a cross-sectional view for explaining a conventional method for manufacturing a glass material.

[Explanation of symbols]

 Reference Signs List 1 molten glass lump 1 'glass material 1a free surface 1b contact surface 2 saucer 2a, 3a material with poor wettability 2b, 3b material with good wettability 3 pressing mold 10 molten glass 11 glass melting furnace 12 outlet for molten glass 13, 15, 17 Heating heater 14 Cutting blade 16 Conveyor 18 Cooling gas 19 Cooling gas pipe 20 Take-out robot 21 Press cylinder

Continued on the front page (72) Inventor Takashi Inoue 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshihiko Muroi 1-28 Kandasudacho, Chiyoda-ku, Tokyo Sumita Optical Glass Co., Ltd. (56) References JP-A-3-60435 (JP, A) JP-A-6-40730 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C03B 11/00 C03B 40 / 00

Claims (25)

(57) [Claims] The present invention is characterized in that a molten glass lump is received in a tray made of at least two or more kinds of materials having different wettability with the molten glass, and cooled to a take-out temperature on the tray to produce a glass material. Manufacturing method of glass material. 2. A molten glass lump is received in a tray made of at least two or more types of materials having different wettability with the molten glass, and the molten glass lump is cooled and pressed by a pressing mold, and the temperature of the molten glass lump is reduced to a take-out temperature on the pan. A method for producing a glass material, comprising cooling the glass material. 3. A means for receiving a lump of molten glass in a tray made of at least two or more materials having different wettability with the molten glass, and means for producing a glass material by cooling to a take-out temperature on the pan. An apparatus for manufacturing a glass material, at least comprising: 4. A means for receiving a molten glass lump in a tray made of at least two or more materials having different wettability with the molten glass, a means for cooling and pressing the molten glass lump with a pressing die, and At least means for producing a glass material by cooling to a take-out temperature. 5. A saucer in which a material having good wettability with molten glass is formed at the center of the transfer of the molten glass lump, and a saucer having a material having poor wettability with the molten glass is used at the outer periphery of the transfer of the molten glass lump. The method for producing a glass material according to claim 1. 6. The method according to claim 1, wherein the glass material has a desired transfer surface and shape by increasing or decreasing the contact area between the material having good wettability with the molten glass and the molten glass lump. 7. A saucer in which a material having good wettability with molten glass is formed at the transfer center of the molten glass lump and a material which is formed of a material having poor wettability with the molten glass is used at the outer periphery of the transfer of the molten glass lump. An apparatus for producing a glass material according to claim 3. 8. The method for producing a glass material according to claim 1, wherein the molten glass lump is received in a preheated pan. 9. The method for producing a glass material according to claim 1, wherein the tray for receiving the molten glass mass is heated to a temperature lower than the glass softening point before the molten glass mass contacts. 10. An apparatus for manufacturing a glass material according to claim 3, further comprising means for preheating the tray before receiving the molten glass lump. 11. The method according to claim 1, wherein the tray for receiving the molten glass mass has an optical surface approximate to a desired shape of the glass material. 12. After the molten glass mass has been transferred to a saucer,
3. The method for producing a glass material according to claim 2, wherein a gas whose temperature is controlled is blown onto the molten glass lump and cooled. 13. After the molten glass mass is transferred to a saucer,
The apparatus for producing a glass material according to claim 4, further comprising means for spraying a gas whose temperature is controlled to the molten glass lump to cool it. 14. The method for producing a glass material according to claim 2, wherein a pressing die having a shape approximate to a desired shape of the glass material is used. 15. The method for producing a glass material according to claim 2, wherein a pressing die made of at least two or more materials having different wettability from the molten glass is used. 16. A pressing die comprising a material having good wettability with glass on a surface in contact with the center of the molten glass lump and a material having poor wettability with glass on a surface in contact with the outer periphery of the molten glass lump. The method for producing a glass material according to claim 2. 17. The apparatus for manufacturing a glass material according to claim 4, wherein a pressing die made of at least two or more materials having different wettability from the molten glass is used. 18. A pressing die comprising a material having good wettability with glass on a surface in contact with the center of the molten glass lump and a material having poor wettability with glass on a surface in contact with the outer periphery of the molten glass lump. The apparatus for manufacturing a glass material according to claim 4. 19. After the molten glass mass is transferred to a saucer,
3. The method for producing a glass material according to claim 2, wherein cooling and pressurizing are performed before cooling to a temperature lower than the glass softening point. 20. After the molten glass mass is transferred to a saucer,
The apparatus for producing a glass material according to claim 4, further comprising means for cooling and pressurizing before cooling to a temperature lower than the glass softening point. 21. A glass material having a desired shape is obtained by cooling and pressurizing a molten glass mass transferred to a tray with a pressing die and releasing the pressing die from the glass before the temperature of the glass becomes lower than the softening point. 3. The method for producing a glass material according to claim 2, wherein 22. The glass material is cooled and pressurized with a pressing mold on the molten glass mass transferred to the tray, and the temperature of the glass is cooled to a softening point or lower, and then the pressing mold is released from the glass to obtain a desired glass material. 3. The method for producing a glass material according to claim 2, wherein the shape is obtained. 23. The apparatus for manufacturing a glass material according to claim 4, wherein the temperature of the pressing die is controlled to be equal to or lower than the glass softening point. 24. The apparatus according to claim 4, further comprising means for controlling the temperature of the pressing die. 25. The method according to claim 1, wherein the temperature at which the glass material is taken out is equal to or lower than the softening point of the glass.