JPH08109028A - Method for supplying molten glass and apparatus therefor - Google Patents

Abstract

PURPOSE: To obtain a glass having high quality and low viscosity and free from defects such as crystal nucleus and devitrification by using a process comprising a step to melt a glass in a crucible, a step to heat the glass and a step to supply the molten glass to a lower mold. CONSTITUTION: A glass is melted at a temperature corresponding to the glass viscosity of 10<2> to 10<3> poise in a glass-melting crucible 11 made of platinum or a platinum alloy and having a crucible heater 12 at the outer circumferential part. The upper part of a feeding nozzle 13 having a nozzle heater at the upper part of the outer circumference is heated at a temperature corresponding to the glass viscosity of 10 to 10<2> poise. A crystallization prevention heater 15 is placed under the nozzle heater, the tip end of the feeding nozzle 13 is heated by high-frequency heating to a dripping temperature (about 1050 deg.C) below a temperature higher than the glass crystallization temperature (about 1100 deg.C) by 100 deg.C and the glass is supplied to a lower mold 16 placed on the axial line of the feeding nozzle 13 and below the nozzle as a glass gob 21 free from crystal nucleus. The formed lens is taken out of the mold by a transfer jig 17 placed at the outer circumference of the lower mold 16.

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 supplying molten glass, and more particularly to a method and apparatus for supplying molten glass to obtain a glass gob for forming an optical element by forming a molten glass.

[0002]

2. Description of the Related Art Conventionally, there have been inventions described in Japanese Patent Publication No. 4-16414 and Japanese Patent Publication No. 4-32772, for example, as a method and apparatus for supplying molten glass. Japanese Patent Fair 4-1
In the invention described in Japanese Patent No. 6414, the molten glass is dropped by controlling the distance between the dropping nozzle and the mold, and the surface temperature of the supply glass gob is set to the softening point or lower, and the internal temperature is molded in the state of the glass softening point or higher. It supplies the mold. The above-described invention prevents shear marks that occur during glass cutting, which has been a problem in the past, and prevents fusion with the molding die by setting the temperature of the glass surface to a temperature not higher than the softening point.

In the invention described in Japanese Patent Publication No. 4-32772, the lower temperature of the glass supply nozzle is set to be higher than the upper temperature by 5
Molten glass is made to drop by raising the temperature by 0 to 200 ° C., and the distance between the dropping nozzle and the mold is controlled in the same manner as in the invention of Japanese Patent Publication No. 4-16414 to make the surface temperature of the glass gob supplied below the softening point. The internal temperature is supplied to the molding die in a state of being equal to or higher than the glass softening point. The above invention prevents shear marks generated during glass cutting, which has been a problem in the past, by controlling the temperature of the supply nozzle, and makes the temperature of the glass surface lower than the softening point to fuse with the molding die. Prevent.

[0004]

However, each of the above prior arts has the following drawbacks. That is, in the molten glass supply method using droplets, which is each of the conventional techniques, the glass temperature for dropping is about 10 in terms of glass viscosity.
^The temperature is equivalent to ² to 10 poises. However,
For example, lanthanum-based glass has a viscosity of about 10 ² to 1
There is a temperature at which the glass crystallizes near a temperature corresponding to 0 poise.

Crystallization of glass is such that a glass component which is easy to crystallize forms crystal nuclei near the crystallization temperature of the component,
It is a problem caused by growing up. When the crystal nuclei grow, devitrification occurs as opaque inside the glass. The crystal nuclei are generated by heating to a crystallization temperature or higher, and then being cooled or kept at a temperature near the crystallization temperature to generate crystal nuclei.

In each of the above-mentioned prior art methods, since the supply nozzle is heated and maintained near the glass crystallization temperature,
Depending on the type of glass, there is a problem that crystal nuclei are generated or the crystal nuclei grow and devitrify. Therefore, the supplied glass has a problem in optical characteristics. Further, the crystal nuclei and devitrification cannot be erased unless they are heated again to the crystallization temperature or higher.

An object of the present invention according to claims 1 and 2 is to provide a method for supplying a high-quality and low-viscosity glass which is free from defects such as crystal nuclei and devitrification when the molten glass is supplied and molded. On the device.

[0008]

According to a first aspect of the present invention, a step of melting glass in a crucible at a temperature corresponding to a glass viscosity of 10 ² to 10 ³ poise, and the molten glass at an upper portion of a supply nozzle. A step of heating to a temperature corresponding to 10 to 10 ² poise, and a step of heating the molten glass at a temperature of the glass crystallization temperature or higher at the tip of the supply nozzle to a temperature 100 ° C. higher than the glass crystallization temperature or lower; And a step of supplying the molten glass to the lower mold at a temperature of the molten glass.

According to a second aspect of the present invention, there is provided a melting crucible having a heating device for melting glass, a supply nozzle having a heating device provided at a lower portion of the melting crucible and having an upper portion, and provided at a tip portion of the supply nozzle. And a heating device for preventing glass crystallization, which is a molten glass supply device.

[0010]

The operation of claim 1 will be described with reference to FIGS. 1 and 2 show changes in glass temperature from glass melting to supply, FIG. 1 is a graph showing the present invention, and FIG. 2 is a graph showing a conventional example. First, a conventional example will be described with reference to FIG. In the method of the conventional example, glass melted in a crucible is passed through a nozzle having a temperature higher than the glass melting temperature, and dropped into a mold or the like with a viscosity capable of dropping. In this method, the glass temperature is within the glass crystallization region. When glass crystallization is heated and held at the temperature of the crystallization region for a long time, crystal nuclei of a component that easily forms crystal nuclei are generated. Further, with the passage of time, there arises a problem that crystal nuclei grow and devitrify.

However, in the present invention, as shown in FIG. 1, the temperature is the same as in the conventional method up to the supply temperature, but after the temperature drops to the supply nozzle, the temperature rapidly rises to a temperature above the crystallization region due to the disappearance of crystal nuclei. Keep heating. As a result, the generated crystal nuclei melt again in the glass. After that, since the temperature is rapidly dropped to a temperature below the crystallization region by dropping, the temperature decreases before crystal nuclei are generated, and glass can be supplied without crystallization or devitrification.

A method of raising the temperature above the crystallization region at the time of supply can be considered, but if the temperature is higher than the crystallization temperature in the supply nozzle, the glass viscosity becomes too low to form a droplet state, and it continuously flows out. Come to do. Therefore, it is necessary to heat only the tip of the supply nozzle to the crystallization temperature or higher. Further, the temperature at the tip of the nozzle is limited to a range not lower than the crystallization temperature and not higher than the crystallization temperature by 100 ° C.
This is because the glass component is likely to be volatilized at a temperature higher than the crystallization temperature by 100 ° C. or more, which causes striae.

The operation of claim 2 will be described with reference to the conceptual diagram of FIG. 1 is a crucible for melting glass. This crucible 1
A crucible heater 2 is arranged on the outer peripheral portion of the. A supply nozzle 3 is installed below the crucible 1. A nozzle heater 4 is arranged above the outer peripheral portion of the supply nozzle 3. Further, a crystallization preventing heater 5 for erasing crystal nuclei is arranged at the tip of the outer peripheral portion of the supply nozzle 3.

In order to bring the molten glass into a droplet state, it is necessary to bring it to a temperature corresponding to a glass viscosity of 10 to 10 ² poise. However, from the crucible 1 to the entire nozzle 3,
If the temperature is set to 0 to 10 ² poises, the viscosity of the entire glass will be low and the glass will flow out continuously,
Does not become water drops. Therefore, by increasing the glass viscosity in the crucible 1 to suppress the glass flow and reducing the nozzle viscosity to facilitate the flow, the glass gob 6 of water droplets is formed.
You can

Therefore, the temperature of the crucible 1 is 10 in terms of glass viscosity.
^The temperature is set to be equivalent to ² to 10 ³ poise, and the temperature of the nozzle 3 is set to 10 to 10 ² poise in terms of glass viscosity. The reason for setting the above glass viscosity is that when the crucible 1 temperature is 10 ² poise or less in terms of glass viscosity, the glass easily flows and does not become water drops. On the contrary, when the temperature of the crucible 1 is 10 ³ poise or more in terms of glass viscosity, the glass viscosity is so high that the glass in the crucible 1 does not flow. Therefore, the above range is set. The same applies to the nozzle 3, and if the temperature of the nozzle 3 is set to 10 poise or less in terms of glass viscosity, all the glass in the nozzle 3 will flow out. On the contrary, when the temperature of the nozzle 3 is set to a glass viscosity of 10 ² poise or more, the glass is not in the form of water drops but in a string-pulled state. Therefore, the above range is set.

However, when the temperature of the nozzle 3 is set to 10 to 10 ² poise in terms of glass viscosity, the above crystallization problem occurs. Therefore, in the present invention, the crystallization prevention heater 5 is installed at the tip of the nozzle 3 to prevent the generation of crystal nuclei. A method of making the temperature of the nozzle heater 4 and the temperature of the crystallization prevention heater 5 the same can be considered, but since the temperature of the nozzle 3 becomes high, the flow amount of glass increases and the water drops do not form. However, by setting the nozzle 3 to a temperature at which the liquid droplets are formed,
Both the droplet and the prevention of crystallization can be achieved by raising the temperature of only the tip. Therefore, the glass melting temperature is divided into three parts.

[0017]

[Embodiment 1] FIG. 4 is a schematic configuration diagram of an apparatus used in this embodiment. The present embodiment is an embodiment of a method and apparatus for supplying a molten glass gob whose crystallization has been prevented to an optical element molding die for molding. A crucible heater 12 is arranged on the outer peripheral portion of the glass melting crucible 11 to heat and melt the glass to a predetermined temperature. The melting crucible 11 may be made of platinum or an alloy with platinum because the reaction with the glass is small. The crucible heater 12 uses a resistance heater or the like and is covered with a heat insulating material or the like to keep the temperature.

A molten glass supply nozzle 13 is installed below the molten crucible 11. A nozzle heater 14 is arranged above the outer peripheral portion of the supply nozzle 13 to heat the supply nozzle 13 to a predetermined temperature. A crystallization prevention heater 15 is arranged below the nozzle heater 14. The crystallization prevention heater 15 heats the tip of the supply nozzle 13 by high frequency heating in order to enhance the heating / cooling response. By this high-frequency heating, the molten glass can be instantly heated to the crystallization temperature or higher, so that glass without crystal nuclei can be dropped.

A lower mold 1 is provided on the lower side of the axis of the supply nozzle 13.
6 are arranged. The transfer jig 1 is provided on the outer peripheral portion of the lower mold 16.
7 is installed to facilitate removal of the lens after molding. The lower mold 16 is fixed on the lower mold heater 18.
The lower die heater 18 heats and holds the lower die 16 at a predetermined temperature. The entire lower die 16 is installed on the lower die drive guide 19 and moves between the supply nozzle 13 and the axis of the upper die 20.
When the glass gob 21 is supplied, the lower mold drive guide 19 moves the lower mold 16 downward on the axis of the upper mold 20.

Like the lower mold 16, the upper mold 20 is heated and maintained at a predetermined temperature by the upper mold heater 22. The upper die heater 22 is installed below the main shaft 23. After the lower mold 16 moves downward on the shaft of the upper mold 20, the main shaft 23 is driven and molded. The main shaft 23 is driven by a motor, and the press pressure is controlled by pneumatic pressure. After molding, the transfer arm 24 is driven and the lens in the transfer jig 17 is taken out from the lower mold 16. After taking out, another transport jig 17 is attached to the transport arm 2.
It is installed at the tip of No. 4 and placed in the lower mold 16.

A method of supplying molten glass using the apparatus having the above-mentioned structure will be described. In this embodiment, the crystallization temperature is about 1100 ° C., and the La temperature is a dropping temperature of 1050 ° C. where water drops.
It is an example in the case of molding glass of SF03. The glass in the melting crucible 11 is heated and melted by the crucible heater 12 to a temperature corresponding to a glass viscosity of 10 ² poise. After heating and melting, the molten glass flows out to the supply nozzle 13. The molten glass is heated by the supply nozzle heater 14 to a temperature corresponding to a glass viscosity of 10 ^1.5 poise.

The heated glass descends in the supply nozzle 13, and the crystallization preventing heater 15 is provided at the tip of the supply nozzle 13.
Is heated to 1150 ° C. The molten glass gob 21 in the form of water droplets can be dropped by this temperature change, and the molten glass in which crystal nuclei are generated is dropped by the crystallization prevention heater 15 into the lower mold 16 as the glass gob 21 having no crystal nuclei.
The lower die 16 has a glass viscosity of 10 ¹⁵ by the lower die heater 18.
It is heated and held at a temperature equivalent to Poise.

After the glass gob 21 is supplied to the lower mold 16, the lower mold drive guide 19 moves the lower mold 16 downward on the axis of the upper mold 20. Like the lower mold 16, the upper mold 20 is heated and held by the upper mold heater 22 at a temperature corresponding to a glass viscosity of 10 ¹⁵ poise. After moving, the upper die 20 is moved by the main shaft 23.
Falls, and the glass gob 21 is press-molded. The press molding is carried out at an initial pressure of 5 kgf / cm ² for 10 seconds and then at 50 kgf / cm ² for 20 seconds. After the molding, the upper die 20 is raised and the carrying jig 24 is taken out by the carrying arm 24.

According to this embodiment, it is possible to supply the glass gob which is free of devitrification and crystal nuclei. Furthermore, since the supplied glass has a low viscosity, it is possible to directly form an optical element from molten glass, and an optical element having high optical characteristics can be formed.

In this example, the LaSF03 glass was used. However, the present invention is not limited to this, and the supply nozzle temperature and the feed nozzle temperature may be adjusted according to the characteristics of the glass having different dropping viscosities and crystallization temperatures. By changing the temperature at the tip of the nozzle, it is possible to handle various types of glass.

[0026]

Embodiment 2 FIGS. 5 and 6 show an apparatus used in this embodiment, FIG. 5 is a schematic configuration diagram, and FIG. 6 is a sectional view of a receiving member. In this embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only different components will be described. In this embodiment, the glass is melted and the supply nozzle 1 is used.
The structure from the tip of No. 3 to the structure in which the glass gob 21 having no crystal nucleus is dropped is the same as that of the first embodiment. In this embodiment, a molten glass gob that is prevented from being crystallized is supplied to a receiving member, and a method and an apparatus for manufacturing a glass gob to be used for the main molding are formed by a centrifugal force into a shape similar to a desired lens outer diameter and shape. Here is an example.

The configuration different from that of the first embodiment will be described below. The receiving member 31 is arranged immediately below the center axis of the supply nozzle 13. As shown in FIG. 6, the receiving member 31 includes a lower die 32 and a receiving member heater 33 for heating the lower die 32.
And an outer peripheral member 34 that regulates the outer peripheral portion of the glass gob 21. The lower mold 32 may have any shape of unevenness, and the surface is processed to have a roughness Rmax of 0.1 μm or less.

The receiving member 31 is installed on the rotating arm 35, and the rotating arm 35 is installed on the centrifugal motor 36.
The centrifugal motor 36 has a rotation axis parallel to the central axis of the supply nozzle 13 and rotates at about 1000 rpm. The rotary arm 35 is installed in a direction perpendicular to the rotation axis of the centrifugal motor 36, and can freely rotate about the same direction. Receiving member 3
1 is held on the rotary arm 35 by a fixed shaft 37, and is freely driven around the fixed shaft 37. The centrifugally molded glass gob is taken out by the suction chuck 38.

A method for supplying molten glass using the apparatus having the above-mentioned structure will be described. This example is an example in the same manner as in Example 1, in which a glass of LaSF03 having a crystallization temperature of about 1100 ° C. and a dropping temperature of 1050 ° C. in the water droplet state was molded. In this embodiment, the operation from melting the glass to dropping the glass gob 21, which is a droplet without crystal nuclei, from the tip of the supply nozzle 13 is the same as the operation of the first embodiment, and the description of the operation is omitted. .

The glass gob 21 is dropped on the lower mold 32 inside the receiving member 31. The lower die 32 is heated and held by the receiving member heater 33 at a temperature corresponding to a glass viscosity of 10 ¹² poise. After the glass gob 21 is dropped, the receiving member 31 is rotated by the centrifugal motor 36 at a speed of about 1000 rpm for 10 seconds. After the rotation, the receiving member 31 stops on the shaft of the suction chuck 38, and the centrifugally molded glass gob is taken out.

According to this embodiment, a high quality glass gob without crystal nuclei and devitrification can be molded. Further, since the glass gob can be manufactured from the molten glass in one step, it can be mass-produced in a short time. Therefore, a low-cost optical element can be manufactured.

[0032]

The effects of the inventions according to claims 1 and 2 are that glass of high quality and low viscosity can be supplied without defects such as crystal nuclei or devitrification necessary for producing optical element molding materials. is there.

[Brief description of drawings]

FIG. 1 is a graph illustrating the present invention.

FIG. 2 is a graph illustrating the present invention.

FIG. 3 is a conceptual diagram illustrating the present invention.

FIG. 4 is a schematic configuration diagram showing a first embodiment.

FIG. 5 is a schematic configuration diagram showing a second embodiment.

FIG. 6 is a cross-sectional view showing a second embodiment.

[Explanation of symbols]

 1 crucible 2 crucible heater 3 supply nozzle 4 nozzle heater 5 crystallization prevention heater 6 glass gob

Claims (2)

[Claims] 1. A glass having a glass viscosity of 10 ^{2 in a} crucible.
10 ³ a step of melting at corresponding temperatures poise, and heating to a temperature corresponding to 10 to 10 ² poise the molten glass at a delivery nozzle top, glass the molten glass at a delivery nozzle tip A method for supplying molten glass, comprising a step of heating within a range not lower than a crystallization temperature and 100 ° C. higher than a glass crystallization temperature, and a step of supplying the molten glass temperature to a lower mold. 2. A melting crucible having a heating device for melting glass, a supply nozzle having a heating device at the lower part of the melting crucible and an upper part, and glass crystallization prevention provided at the tip of the supply nozzle. And a heating device for the molten glass.