JPH09221329A - Blank for forming optical element and production of optical element as well as apparatus for production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing optical elements which prevents the occurrence of the rugged wrinkle-like gob-in marks formed on the surfaces for contact with a receiving mold by adopting a specific method at the time of obtaining glass gob by receiving fused glass flow in the receiving mold. SOLUTION: The glass gob which is the blank for forming the optical elements is obtd. by receiving the fused glass flow flowing out of the outlet of an outflow pipe for the fused glass in the receiving mold. At this time, a low-temp. gas is injected to the front end of the fused glass flow before the front end of the fused glass flow flowing out of the outlet of the outflow pipe comes into contact with the receiving mold to lower the temp. of the surface of the front end of the fused glass flow. The fused glass flow in the state of the lowered temp. of the surface is received in the receiving mold to obtain the glass gob which is the blank for forming the optical elements. The effect is surely obtd. if the gas injected to the front end of the fused glass flow is below the glass transition temp. of the glass. Sound cooling is attained by supplying the high-pressure gas to the rear surface of the receiving mold formed of the porous material having air permeability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical element molding material and an optical element by using a glass lump in a high temperature softened state as a molding material and press-molding the molding material with a pair of molding dies. In particular, the present invention relates to a method of directly obtaining a glass lump in a high temperature softened state which is a material for molding, from a molten glass flow flowing out of an outflow pipe of a melting crucible of optical glass.

[0002]

2. Description of the Related Art In recent years, a technique for obtaining a molded optical element by using a glass lump in a high temperature softened state as a molding material and press-molding this molding material with a pair of molding dies, particularly for aspherical lenses at low cost As a manufacturing method, it is in the spotlight and is being developed.

Particularly, in recent years, in order to reduce the cost of a glass gob which is a material for molding, a step of melting an optical glass, a step of obtaining a glass gob from a molten glass flow, and a press molding of the glass gob Development of a manufacturing method for continuously producing optical elements from glass materials by continuously performing steps of obtaining optical elements is in progress.

For example, Japanese Patent Application Laid-Open No. 4-149032 discloses a method of manufacturing an optical element including the following steps.

Here, a step of receiving a molten glass flow into a receiving die called a heat processing jig to obtain a glass gob, heating a contact surface between the glass of the glass gob and the receiving die, and calling it an optical glass molded body A method for manufacturing an optical element is proposed, which includes a step of obtaining a molding material and a step of heating and molding the molding material with a pair of press molding dies to obtain an optical element.

In the known example, the upper surface of the glass gob received in the receiving mold is a free surface of the molten glass and thus is very smooth.

On the other hand, in this known example, the receiving mold is not heated to a high temperature in order to prevent fusion between the molten glass and the receiving mold. Therefore, the lower surface of the molten glass gob received on the receiving mold comes into contact with the receiving mold having a low temperature, and the surface thereof is rapidly cooled. As a result, uneven wrinkle-shaped goblin marks are formed on the lower surface of the glass gob.

Then, the contact surface between the glass of the glass gob and the mold, in which such uneven wrinkle-like goblin marks are generated, is heated to a temperature equal to or higher than the softening temperature of the glass to soften the glass. By doing so, the uneven wrinkled part
It is heat-deformed into a smooth mirror-like free surface.

That is, in this known example, the uneven wrinkle-like portion generated on the lower surface of the glass block received in the receiving mold is thermally deformed to form a smooth free surface, and as a result, the upper and lower surfaces are smooth. A molding material having a free surface is obtained, and the molding material is press-molded to obtain an optical element.

On the other hand, as a mold for molding a molten glass gob,
A mold made of a porous material is used and its porosity is utilized.
By sending high pressure gas from these backs and forming a thin gas layer between these molds and the molten glass,
It has been known for a long time that these molding dies and molten glass are prevented from directly contacting with each other, and glass fusing can be prevented, and the occurrence of uneven wrinkle-like goblin marks can be prevented. -22977.

Then, a mold made of this porous material is used as a receiving mold for the molten glass gob, high-pressure gas is sent from the back of the receiving mold, and the molten glass gob is received by the gas ejected from the pores of the mold. From the above, the material is floated and held in a non-contact state, the glass gob in the high temperature softened state in this state is conveyed to a molding die for molding an optical element, and the glass gob is press-molded to obtain an optical element. , JP-A-6-340430.

In this known example, the lower surface of the molten glass gob received in a non-contact state with the porous receiving die is kept in a non-contact state with the receiving die by the gas layer, and therefore has a smooth free surface. Has become. The upper surface of the molten glass gob is also a smooth free surface. That is, the surface of the glass gob thus obtained is entirely smooth and free.

Further, in this known example, high-temperature gas is supplied to the porous receiving mold. This is because the molten glass gob is floated and held by the high temperature gas to prevent the temperature of the glass gob from being lowered. That is, when the glass gob is floated and held by the gas at room temperature, the glass gob,
This is especially to prevent the surface portion from being rapidly cooled. In this way, when the temperature decrease of the glass gob is prevented, in the next step, the optical element molding step, the glass gob is press-molded without the reheating of the glass gob or with a slight reheating to form the optical element. Can be obtained.

Further, in this known example, since the molten glass gob received in the receiving mold of the porous material is floated and held by the high temperature gas, the temperature drop of the molten glass gob is small and the glass received in the receiving mold is small. Even when the lump is conveyed to a mold for molding an optical element, the temperature of the lump of glass is high and the glass lump is in a softened state. It is difficult to handle such a glass gob in a softened state and convey it to the mold.

[0015]

However, the method of manufacturing an optical element disclosed in Japanese Patent Laid-Open No. 4-149032, which is the conventional example, has the following problems.

The problem is that wrinkle-like goblin marks are formed on the lower surface of the glass gob, that is, on the contact surface with the receiving mold.

Therefore, in this known example, a smooth free surface is obtained by thermally deforming the uneven wrinkled gob-in mark.

There are two problems in this thermal deformation process: a long heating time and a high heating temperature. The long heating time means that it takes time to smooth the gob-in mark by thermal deformation. Specifically, according to the example of the known example, it takes 30 seconds to 3 minutes. Here, the heating condition in the example of a short heating time of 30 seconds is 1200 ° C., and the heating condition in the example of a long heating time of 3 minutes is 900 ° C. If the heating time is long in this way, the production tact becomes long and the number of products produced becomes small, resulting in an increase in production cost. The point that the heating temperature is high means that the heating temperature required to smooth the gob-in mark by thermal deformation is high. Specifically, according to the example of this known example, heating is performed at a temperature of 900 ° C to 1200 ° C. The temperature of 900 ° C to 1200 ° C is much higher than the softening point temperature of glass and is in the melting temperature range of glass. The heating at such a high temperature is for shortening the heating time required for the thermal deformation of the glass as much as possible.

However, when the glass gob is thermally deformed at a high temperature corresponding to the melting temperature range of such glass, there is a problem that the glass gob easily fuses to the jig on which the glass gob is placed. .

That is, this conventional example, Japanese Patent Laid-Open No. 4-1490
The fundamental drawback of the method for producing an optical element disclosed in No. 32 is that wrinkle-shaped goblin marks are formed on the lower surface of the glass gob, and it is necessary to remove the gobin marks. In the heat deformation step, there is a problem that the heating time is long, the production tact is long and the cost is high, and the heating temperature is high, so that the glass gobs are easily fused.

Another known method, the method of manufacturing an optical element disclosed in Japanese Patent Publication No. 48-22977, which is the conventional example, has the following problems.

The problem is that when a high temperature and high pressure gas is supplied to the back of the receiving mold made of a porous material and the high temperature gas is ejected from the pores of the receiving mold, the molten glass flow is generated. When receiving a molten glass gob in the receiving mold, when the molten glass flow begins to be received by the receiving mold, the molten glass and the receiving mold come into contact with each other, and the uneven shape of the pores of the receiving mold made of a porous material is formed on the glass. It is a transfer.

As described above, in order to prevent contact between the molten glass and the receiving mold, which occurs when the molten glass lump is received in the receiving mold in which the high temperature gas is ejected, the temperature of the gas is set to Two measures can be taken: lowering the gas flow rate and increasing the gas flow rate very much.

However, when the temperature of the gas is lowered, the temperature of the glass gob is rapidly lowered, and it takes a long time to reheat the glass gob prior to the next step of forming an optical element, resulting in a long forming tact. Therefore, it is not preferable.

On the other hand, when the flow rate of the gas is made extremely high, contact between the molten glass and the receiving mold can be prevented when the molten glass flow starts to be received by the receiving mold. Since a large amount of high-temperature gas is blown, the bottom surface of the molten glass gob is thermally deformed, and the bottom surface is largely deformed to a shape lifted up. That is, when the flow rate of the high-temperature gas is made extremely large, the contact between the molten glass gob and the receiving mold can be prevented, but the bottom surface is largely recessed, and the shape of the glass gob differs greatly from the desired shape. It is not preferable because it is lost.

That is, this conventional example, Japanese Patent Laid-Open No. 6-3404
A drawback of the method for producing an optical element disclosed in No. 30 is that when a molten glass gob is floated and held using a high temperature gas, the receiving mold and the glass come into contact with each other. To prevent this, if the gas temperature is lowered, the molding tact becomes longer and the cost increases, and if the gas flow rate is increased, there arises a problem that a glass gob having a desired shape cannot be obtained.

In order to solve the problems of the conventional example described above, a material for molding an optical element and a method for manufacturing a molded optical element, which achieve the following objects, are provided.

A first object of the present invention according to the present application is that when a molten glass flow is obtained in a receiving glass lump in a receiving mold, uneven wrinkles are formed on a lower surface of the glass lump, that is, a contact surface with the receiving mold. It is to prevent the formation of a gob-in mark in the shape of a glass. In the case of obtaining it, it is to prevent the molten glass and the porous receiving die from contacting each other and transferring the uneven shape of the pores of the receiving die made of the porous material to the glass.

The second object of the present invention is to eliminate the uneven wrinkle-like goblin mark on the lower surface of the glass gob,
For molding optical elements with high shape accuracy and good appearance by press-molding glass lumps with smooth upper and lower surfaces without transfer of irregularities of receiving type pores made of porous material To obtain a material or an optical element.

The third object of the present invention is to transfer the uneven wrinkle-shaped goblin mark generated on the lower surface of the glass gob and the uneven transfer of the receiving type pores made of a porous material. , More surely to prevent.

A fourth object of the present invention is to prevent transfer of the uneven shape of the pores of the receiving mold to the glass when receiving the glass gob with the receiving mold made of a porous material. To provide a reliable and easy method.

[0032]

In order to achieve the above object, a first aspect of the present invention is directed to an optical element for receiving a molten glass flow flowing out from an outlet of a molten glass outflow pipe in a receiving mold. When obtaining a glass gob to be a forming material, a low-temperature gas is jetted to the tip of the molten glass flow until the tip of the molten glass flow flowing out of the outlet of the outflow pipe comes into contact with the receiving mold. It is characterized in that the temperature of the surface of the front end of the flow is lowered and the molten glass flow in the state where the temperature of the surface is lowered is received by a receiving mold to obtain a glass gob which is a raw material for forming an optical element.

Next, the operation of the first invention according to the present application in the method for manufacturing a glass gob having the above-mentioned structure will be described.

The molten glass melted in the optical glass melting crucible flows out from an outflow pipe installed in the lower part of the melting crucible. From the outlet of the molten glass outflow pipe, the molten glass flow flows out in the form of droplets.

As described above, in the glass stream flowing out in the form of droplets, after one droplet naturally drops and the glass stream is naturally cut, or the step of obtaining a glass lump as a previous step is completed. Then, after the glass flow is naturally cut, a receiving mold is installed at a position close to the lower end of the molten glass flow. As the molten glass flows out, the front end of the molten glass flow descends and eventually comes into contact with the receiving mold.

By further holding the receiving mold in this state, the molten glass accumulates on the receiving mold, and a molten glass block can be obtained on the receiving mold. When the weight of the molten glass gob reaches a desired weight, the receiving mold is rapidly lowered by a predetermined distance. Then, the portion of the glass flow that connects the outlet of the outflow pipe for molten glass and the molten glass gob is constricted, and the constriction proceeds and spontaneous cutting is immediately performed.

The glass gob thus obtained does not have a poor appearance due to entrainment of fine bubbles called a shear mark, which is obtained when the glass flow is cut by a cutting blade (shear), and the glass gob Since the free surface of the molten glass gob has solidified in that state,
Its surface is specular and very smooth.

According to the present invention, the temperature of the molten glass flow at the low temperature reaches the tip of the molten glass flow until the tip of the molten glass flow flowing out from the outlet of the molten glass flows down and comes into contact with the receiving mold. Is injected to lower the temperature of the surface of the front end of the molten glass flow. As a means for injecting this low-temperature gas, a gas injection nozzle or the like is installed in the vicinity of the outlet of the outflow pipe and the receiving mold, and its mounting direction is adjusted to melt the injected low-temperature gas. There is a method to hit the tip of the glass flow.

Thus, when the low temperature gas is jetted to the surface of the front end of the molten glass flow, the temperature of the surface of the molten glass decreases. Then, when the temperature of the surface of the molten glass is lowered to a temperature lower than the softening point temperature of the glass, it can be considered that the surface of the molten glass is solidified.

The tip of the molten glass flow obtained in this manner is a free-surface state of the molten glass, and since the surface is solidified, it has a very smooth mirror surface state. Then, as the outflow of the molten glass progresses, the front end portion of the molten glass flow whose surface is solidified descends and comes into contact with the receiving mold.

When the molten glass flow with the surface of the tip portion solidified in this way is received in a receiving mold to obtain a molten glass gob, there are mainly three advantages as described below.

Less reactive with receiving mold:
The surface of the molten glass is cooled to a temperature lower than the softening point temperature and low in reactivity with the receiving mold. As a result,
No fusion of the molten glass to the receiving mold occurs, and no foreign matter due to reaction products occurs in the glass gob or the receiving mold. As a result, it is possible to raise the temperature of the receiving mold, and it is possible to use a material such as metal or ceramics as the material of the receiving mold.

No goblin mark is generated: Cooling is performed by injecting a low-temperature gas to the front end of the molten glass flow, so the front end of the glass flow is cooled with a relatively gentle temperature gradient. That is, it is cooled to a relatively deep portion of the surface of the glass flow. Therefore, even when a glass gob is obtained by receiving a molten glass flow in a general receiving mold having a low temperature, no uneven wrinkled gob-in mark is generated on the lower surface of the glass gob. This is because when a molten glass flow that has not cooled the surface is received by a general receiving mold having a low temperature, the molten glass is rapidly quenched at the contact surface at the moment of contact with the receiving mold, and the contact surface Only the solidified layer remains, and the other parts remain in the molten state.
When cooling progresses in this state, the coefficient of thermal expansion of glass is small in the solidified state and very large in the molten state, so that the amount of shrinkage during cooling in the contact-solidified layer on the lower surface of the glass gob and other portions is small. The difference is that the contact solidification layer on the lower surface of the glass lump deforms into uneven wrinkles due to the distorted deformation during the cooling shrinkage. On the other hand, in the present invention, before the molten glass flow comes into contact with the receiving mold, the surface of the molten glass flow has already been cooled and is in a solidified state. Since it is cooled by a low-temperature gas, the cooling becomes slower and the temperature gradient is gentle compared to the case where it is rapidly cooled by contact with a low-temperature receiving mold. From the two points of being cooled and solidified to a relatively deep portion of the surface of the glass gob, in the step of cooling the glass gob, the lower surface of the glass gob has uneven wrinkles caused by shrinkage deformation during cooling of the glass. The gob-in mark does not occur.

Do not transfer the irregularities of the porous receiving mold: In the present invention, the receiving mold is received in the state where the front end portion of the molten glass flow is cooled and solidified. Therefore, even when the receiving mold is made of a porous material. The uneven shape of the receiving type pores is not transferred to the glass. When a molten glass lump is received from a molten glass flow in a state where gas is ejected from the pores of a porous receiving mold, the molten glass flow receives the molten glass at the moment when the tip of the molten glass flow descends and contacts the receiving mold. It is always levitated by the gas ejected from, and strictly speaking, it is desirable that the molten glass and the receiving die do not come into contact with each other. However, by using the method according to the present invention, even if the molten glass comes into contact with the receiving mold,
It is possible to obtain a glass lump having a good shape without transferring the irregular shape of the receiving type pores to the glass. This is particularly effective in the method of floating and holding a glass gob with a high-temperature gas, in which it was difficult to obtain a glass gob having a good appearance by the conventional method. Furthermore, according to the method of the present invention, even when gas is not ejected from the porous pores at the time of starting to receive the molten glass flow in the porous mold, the porous mold has a porous glass mold. The uneven shape of the receiving type pores is not transferred to the lower surface of the received glass gob.

As described above, the glass gob obtained by the method according to the first aspect of the present invention has a very smooth upper surface, and the lower surface has neither fusion with the receiving mold nor reaction products. No uneven wrinkle-like goblin mark is generated, and when it is received by a porous receiving mold, the uneven shape of pores is not transferred, which is very smooth. Therefore, the glass gob thus obtained is suitable as a material for forming an optical element, or a material for forming a material for forming an optical element, because the entire surface is very smooth. There is.

In order to achieve the above object, the second invention of the present application is to receive a molten glass flow flowing out from the outlet of the molten glass outflow pipe in a receiving mold to obtain a glass gob, Immediately press-molding the glass gob of to obtain an optical element molding material or an optical element, the tip of the molten glass flow, which comes out from the outlet of the outflow pipe, comes into contact with the receiving mold. A low-temperature gas is injected into the part to lower the temperature of the surface of the front end of the molten glass flow, and the molten glass flow in the state where the surface temperature has dropped is received by a receiving mold to obtain a glass gob, and this glass gob Is press-molded to obtain an optical element molding material or an optical element.

Next, the operation of the second invention according to the present application in the optical element molding material or the method of manufacturing a molded optical element having the above-described structure will be described.

As described in the section of the operation of the first invention,
By the time the tip of the molten glass stream flowing out from the outlet of the outflow pipe contacts the receiving mold, a low-temperature gas is jetted to the tip of the molten glass stream to lower the temperature of the surface of the tip of the molten glass stream. The entire surface of the glass gob obtained by receiving the molten glass flow with the temperature of the surface lowered in the receiving mold is very smooth.

Therefore, when the glass gob thus obtained is press-formed to obtain an optical element molding material or an optical element, a surface defect portion formed on the surface of the glass gob as seen in the conventional example. Since the step of smoothing by heat deformation is unnecessary, the glass gob thus obtained can be immediately press-molded to obtain an optical element molding material or an optical element.

In a specific embodiment, the glass gob may be reheated to a temperature suitable for pressing before press-molding the glass gob, but the heating time and the heating temperature required for this reheating are necessary. Is much smaller than the heating time and the heating temperature required for the thermal deformation of the surface defect portion of the glass gob found in the conventional example.

In order to achieve the above object, a third invention according to the present application is the method for producing an optical element molding material or an optical element according to claim 1 or 2, wherein the melting is performed. It is characterized in that the temperature of the gas injected at the tip of the glass flow is equal to or lower than the glass transition temperature of the glass.

Next, the operation of the third invention according to the present application in the optical element molding material or the method of manufacturing an optical element having the above-described structure will be described.

As described in the section of the operation of the first invention,
A state in which the temperature of the surface of the tip of the molten glass flow is lowered below the softening point temperature of the glass by injecting a low-temperature gas to the tip of the molten glass flow flowing out from the outlet of the outflow pipe, and the surface of the tip is solidified. Receive the molten glass flow of
A very smooth glass lump is obtained on the entire surface. This time,
When the temperature of the gas injected to the tip of the molten glass flow is high, the surface of the molten glass does not cool and the surface of the molten glass flow solidifies at the moment when the tip of the molten glass flow contacts the receiving mold. In some cases, the state described above is not obtained, and as a result, the action as described in the section of the action of the first invention cannot be obtained, and a glass gob having a smooth lower surface may not be obtained.

In order to prevent this, when the gas injected at the tip of the molten glass flow is a gas at a temperature lower than the glass transition temperature of the glass, the tip of the molten glass flow is discharged from the outlet of the outflow pipe. It is sufficiently cooled before it reaches the receiving mold, and the surface thereof becomes below the yield point temperature and the surface is solidified. Therefore, it is possible to reliably obtain the operation described in the section of the operation of the first invention. It is possible to obtain a glass lump that is very smooth on the entire surface.

The lower limit temperature of the cooling gas at the tip of the molten glass is room temperature for practical use. In the embodiment, the temperature of the cooling gas is selected from the room temperature to the glass transition temperature, and the optimum temperature is selected in consideration of the process conditions including the post-process, the glass gob weight, and the like. Further, as the kind of the cooling gas, an inert gas such as nitrogen gas is desirable, but there is no problem in using air from the economical point of view.

Further, in order to achieve the above object, a fourth invention according to the present application is the method for manufacturing an optical element molding material or an optical element according to claim 1 or 2 described above. The mold is made of a breathable porous material, the high pressure gas is supplied to the back of this receiving mold, and the gas ejected through the pores of the porous material causes the tip of the molten glass flow to flow. It is characterized by lowering the temperature of the surface of.

Next, the operation of the fourth invention according to the present application in the optical element molding material or the method for manufacturing a molded optical element having the above-described structure will be described.

In the present invention, the receiving die made of a porous material having a function of holding the glass gob in a floating state is also provided with a cooling gas ejection function for cooling the front end portion of the molten glass flow.

That is, prior to receiving the molten glass flow into the porous receiving mold, a cooling gas is jetted from the porous receiving mold to cool the front end of the molten glass flow with the cooling gas. The molten glass flow with the surface of the solidified,
A molten glass gob is obtained by receiving it in a porous receiving mold.

In the present invention, in the step of ejecting the cooling gas from the porous receiving mold, since the porous receiving mold is located immediately below the molten glass outflow pipe, the high pressure supplied to the back surface of the receiving mold is high. The cooling gas is jetted upward through the receiving type pores to cool the front end of the molten glass flow. In the case where the tip of the molten glass flow is cooled by the method according to the present invention, the injection nozzle for cooling gas and the piping associated therewith are not necessary. It becomes possible to easily cool the tip portion of the. Further, in the method according to the present invention, the cooling gas jetting upward from the porous receiving mold surely hits the tip of the molten glass flow and cools that portion,
It is not necessary to adjust the angle as in the case of using a cooling gas injection nozzle or the like, and the tip of the molten glass flow can be reliably cooled.

As an embodiment of the present invention, the same gas may be continuously ejected from the porous receiving mold in the molten glass flow cooling step, the molten glass gob receiving step, and the glass gob conveying step. Further, as another embodiment, in these steps, different gas suitable for each step, for example,
Gases having different gas temperatures and gas flow rates may be ejected from a porous receiving mold. Further, as another embodiment, there is a mode in which the cooling gas is ejected from the porous receiving mold only in the molten glass flow cooling step, and the gas is not ejected from the porous receiving mold in the other steps.

[0062]

Embodiments of the present invention will be described below.

The types of optical glass used in the respective examples described below are the same, the optical characteristics thereof are a refractive index n _d = 1.58, the Abbe number ν _d = 60, and the thermal characteristics thereof are , Glass transition temperature is 500 ℃, softening temperature is 6
40 ° C. Then, in each example, this optical glass was melted and flowed out under the same conditions, this optical glass was heated to 1200 ° C. in a melting crucible and melted, and this molten glass was discharged from an outflow pipe kept at 1050 ° C. It flowed out, and a 1000 ° C. molten glass flow was discharged from the outlet of the outflow pipe.

An embodiment for obtaining an optical element molding material or a molded optical element according to the present invention from this molten glass flow will be described below.

(First Example) In the first example, an embodiment in which a molten glass flow is received by a receiving mold to obtain a glass gob which is a raw material for forming an optical element will be described.

FIG. 1 is a diagram for schematically explaining the construction of an apparatus for obtaining a glass gob which is a raw material for molding an optical element according to the first embodiment of the present invention.

1 is an outflow pipe for flowing out the molten glass flow, 2 is a molten glass flow flowing out of the inside of the outflow pipe 1, 3 is a receiving type for receiving the molten glass flow, 4 Reference numeral 5 is a heating block containing a heater (not shown) for holding and heating the receiving mold 3, and reference numeral 5 is cooling for cooling the tip of the molten glass flow 2 flowing out from the outlet of the outflow pipe 1. A ring-shaped nozzle for injecting gas, 6 is an injection port for injecting a cooling gas opened in the ring-shaped injection nozzle 5, and 7 is a crucible for melting optical glass (not shown). No. 2) is an outer wall of the electric furnace for storing and heating the ring, and the ring-shaped injection nozzle 5 is fixed to the outer wall 7 of the electric furnace.

2 to 7 are views for explaining the operation for obtaining a glass gob using the apparatus having the configuration of FIG. 1 in this embodiment. In addition, in FIG. 7, 8 is a glass gob obtained on the receiving mold 3.

FIG. 2 is a diagram showing an initial state of the operation of receiving the glass gob, in which the front end of the molten glass flow 2 is slightly out of the outlet of the outflow pipe. At this time, a low-temperature gas for cooling the tip portion of the molten glass flow 2 is jetted from the jet port 6 of the ring-shaped jet nozzle 5, and the jetted low-temperature gas is It hits the tip and cools that part. As a result, the surface of the front end of the molten glass flow is cooled and the surface is solidified. This solidified portion of the surface is shown by diagonal hatching in FIG.

FIG. 3 shows a state in which the molten glass flow 2 has advanced from the state of FIG. The lower end of the molten glass flow 2 advances, and even in this state, a low-temperature gas for cooling the molten glass flow 2 is jetted from the jet port 6 of the ring-shaped jet nozzle 5.

FIG. 4 shows a state where the molten glass flow 2 has further flown out from the state shown in FIG. In this state, the front end of the molten glass flow 2 is further lowered, and is in a state very close to the receiving mold 3. In this state, the injection of the low-temperature gas from the ring-shaped injection nozzle 5 is completed.

FIG. 5 shows a state where the molten glass flow 2 has further flown out from the state shown in FIG. In this state, molten glass having a desired weight is obtained on the receiving mold 3. Even in this state, the ring-shaped injection nozzle 5
There is no injection of low temperature gas from. Therefore, in this state, the outlet of the outflow pipe 1 and the receiving mold 3
The molten glass between the two is not cooled and is in a high temperature state.

FIG. 6 shows a state in which the receiving die 3 is lowered downward from the state of FIG. 5 by a predetermined distance. By lowering the receiving mold, the high temperature molten glass between the outlet of the outflow pipe 1 and the receiving mold 3 is elongated and constricted.

FIG. 7 shows a state after holding the state of FIG. 6 for a while. When the receiving mold 3 is lowered to the state shown in FIG. 6 and the receiving mold 3 is held in that state, the narrowed portion of the molten glass has a high temperature and a low viscosity, so that the molten glass lump 8 is immediately obtained by spontaneous cutting. be able to.

Molten glass gob 8 thus obtained
Is extremely smooth on both the upper and lower surfaces, and is very suitable as a material for molding an optical element.

FIG. 8 and FIG. 9 show another example of the device configuration for carrying out the present embodiment.

In FIG. 8, the ring-shaped injection nozzle 5 is fixed to the heating block 4 holding the receiving mold 3.

Further, in FIG. 9, reference numeral 51 is a pipe-shaped injection nozzle for injecting a low-temperature gas for cooling the front end of the molten glass flow 2, and from the front end opening of the injection nozzle 51. Gas for cooling is jetted. The jet nozzle 51 is fixed to the heating block 4 holding the receiving mold 3.

That is, according to the present embodiment, when a glass gob to be used as a material for molding an optical element is obtained, a device for injecting a low-temperature gas for cooling the tip of the molten glass stream 2 has a structure shown in FIG. Such a configuration, the configuration shown in FIG. 8, the configuration shown in FIG. 9, or another configuration may be used, and an optimal configuration may be selected in consideration of cost and the like.

Next, a detailed embodiment of this embodiment will be described.

From the outflow pipe 1 at a temperature of 1050 ° C., 1000 ° C.
The molten glass stream 2 of No. 2 is flowing out in the form of droplets. In the glass stream flowing out in the form of droplets, after the step of obtaining the glass gob that is the previous step is completed and the glass stream is naturally cut,
The receiving mold 3 was set at a position below the tip of the molten glass flow 2. At this time, the receiving mold 3 was set at a position 10 mm below the outlet of the outflow pipe. At this time, the tip portion of the molten glass flow 2 is in a state of slightly hanging down from the outlet of the outflow pipe 1, as shown in FIG.

The receiving die 3 is made of stainless steel, and its receiving surface is processed into a spherical surface having a radius of 15 mm. The heating block 4 is heated to 300 ° C. by a built-in heater (not shown).

The ring-shaped injection nozzle 5 is made of a ring-shaped pipe, and the injection port 6 has an angle such that the gas ejected from the injection port 6 hits the tip of the molten glass flow.
It consists of 18 holes with a diameter of 0.5 mm drilled on the circumference.

Immediately after the receiving die 3 was set at a position below the molten glass flow 2, room temperature air having a pressure of 0.1 MPa was supplied to the inside of the ring-shaped injection nozzle 5 and air having a flow rate of 30 l / min was supplied. Was jetted from the jet port 5 to start cooling the tip portion of the molten glass flow 2.

Two seconds after the start of cooling, the injection of air was stopped. At this time, the front end of the molten glass flow 2 was lowered to a position intermediate between the outlet of the outflow pipe 1 and the receiving mold 3.

Then, one second later, the tip of the molten glass stream 2 came into contact with the receiving mold 3. Immediately before that, the surface temperature of the front end portion of the molten glass stream 2 was 620 ° C.

10 seconds after the tip of the molten glass stream 2 contacted the receiving mold 3, the weight of the molten glass accumulated on the receiving mold 3 became the desired weight. Therefore, the receiving mold 3 is moved downward by 20 mm.
It plummeted and stopped at that position. As a result, the molten glass was squeezed into thin pieces and spontaneously cut immediately at that position.

The glass gob 8 thus obtained has a very smooth surface on both the top and bottom surfaces, and its weight is 2
g.

Although stainless steel was used as the material of the receiving mold 3 in this embodiment, other metals may be used, carbon may be used, and ceramics may be used. Also, even if a mold in which a thin film having a releasing action or a protective action is formed on the surface of a mold made of these materials is used, a glass lump having a very smooth surface can be similarly obtained.

As an effect peculiar to this embodiment, it is possible to obtain a glass gob whose surface is very smooth on both the upper and lower surfaces. When this glass gob is used as a molding material for a molded optical element,
An optical element with excellent accuracy can be obtained. Because the surface of this glass gob is very smooth, no surface defects occur in the molded optical element obtained by press-molding this glass gob, and an optical element with excellent accuracy can be obtained. Because.

(Second Embodiment) In the second embodiment, a molten glass flow is received by a receiving mold to obtain a glass gob which is a raw material for forming an optical element, and this glass gob is immediately press-formed to form a glass. An embodiment for obtaining an optical element will be described.

FIG. 10 is a diagram for schematically explaining the structure of an apparatus for obtaining a molded optical element according to the second embodiment of the present invention.

1 is a molten glass outflow pipe, 2 is a molten glass flow, 3 is a receiving mold, 5 is a ring-shaped nozzle for injecting a cooling gas for cooling the tip of the molten glass flow, 6
Is a cooling gas injection port opened in the ring-shaped nozzle 5, 7
Is an electric furnace, and 8 is a glass gob.

Reference numeral 9 denotes a melting crucible for melting the optical glass. The melting crucible 9 is installed in the electric furnace 7, and the outflow pipe 1 is provided below the melting crucible 9. Reference numeral 10 is a heating device for heating the glass gob 8 to a temperature at which it can be molded.

Numeral 11 is a lower mold for molding for molding the glass gob 8, 12 is an upper mold for molding, and 13 is a sleeve shape capable of sliding the lower mold 11 and the upper mold 12 coaxially. Body type of 14
Is a molded optical element obtained by press-molding the softened glass gob 8 with the lower mold 11 and the upper mold 12.

Next, the operation for obtaining a molded optical element using the apparatus having the configuration shown in FIG. 10 in this embodiment will be described.

The molten glass melted in the melting crucible 9 inside the electric furnace 7 flows out from the outlet of the outflow pipe 1 in a droplet form. Cooling gas injected from the injection port 6 of the ring-shaped nozzle 5 is applied to the tip of the molten glass stream 2 to lower the temperature of the surface of the tip portion of the molten glass stream to make the surface solidified. 2 is received by the receiving mold 3 and after a desired weight of molten glass is accumulated in the receiving mold 3, the receiving mold 3 is lowered by a predetermined distance to naturally cut the molten glass flow 2 into a confined state, and a molten glass block 8 is formed. Get on top of die 3. The glass gob 8 thus obtained is very smooth on both the upper and lower surfaces.

The glass gob 8 thus obtained is heated to a temperature at which it can be formed by using a heating device 10, and then the glass gob 8 is placed in a forming die composed of a lower die 11 and an upper die 12. The molded optical element 14 is obtained by carrying and immediately press-molding.

In this embodiment, the step of melting the glass is performed in the atmosphere due to maintenance problems, but the subsequent steps are particularly performed by press molding the glass gob 8 to form the molding optical element 14. The step of obtaining is preferably performed in an atmosphere of an inert gas such as nitrogen gas in order to protect the molding die. Note that FIG. 10 does not show a molding chamber or a substitution chamber for maintaining these atmospheres.

Further, in this embodiment, the step of heating the glass gob 8 to a temperature at which it can be molded is carried out before the glass gob 8 is conveyed into the molding die. , Heating the glass gob 8 to a temperature at which it can be molded,
You may press-mold.

In this embodiment, the glass gob 8 is press-molded to obtain the molded optical element 14. The glass mass 8 thus press-molded is used as a material for molding an optical element. It is also possible to do so. In this case, a high degree of shape transfer accuracy is not required, so precision molding technology to obtain a shape-transferred molded article by precisely controlling the pressing force and temperature is not required. It suffices to carry out pressing with an air cylinder or the like. In this case, molding is performed in the air without any problem.

Next, a detailed embodiment of this embodiment will be described.

In this embodiment, the step of receiving the glass gob 8 on the receiving mold 3 is exactly the same as that in the embodiment 1 of the first embodiment. In this way, a glass gob 8 having smooth upper and lower surfaces was obtained on the receiving mold 3 made of stainless steel. The temperature of the glass gob 8 at this time was 500 ° C.

In this embodiment, the heating device 10 and the lower mold
Since the forming die including the upper die 12, the upper die 12, and the body die 13 is provided in a forming chamber (not shown) kept in a nitrogen atmosphere, this glass gob 8 has a replacement chamber (not shown). Through, it is conveyed into a molding chamber (not shown).

This glass gob 8 was conveyed into the heating device 10. In this heating device 10, a heating device in which a halogen lamp and a reflecting mirror having a spheroidal surface are combined is installed so as to face each other vertically. The glass mass 8 can be press-molded by heating the glass gob 8 for 15 seconds inside the heating device 600.
Heated to ° C.

This glass gob 8 was immediately conveyed into the mold.

The lower mold 11 and the upper mold 12 are made of cemented carbide, and the lower mold 11 is polished into a spherical surface having a radius of 13 mm.
The upper die 12 is ground to a spherical surface having a radius of 7 mm. Also, the body mold 13 is made of a tungsten-based alloy,
A cartridge heater (not shown) is installed in the inside, and the temperature of the lower mold 11 and the upper mold 12 in the state of being fitted therein is controlled by heating or cooling the barrel mold 13. It can be heated or cooled while being heated. The lower mold 11 and the upper mold 12 are each connected to a hydraulic cylinder (not shown) capable of controlling the pressing force, and the glass lump 8 can be press-molded by controlling the pressing force.

After the heat-softened glass gob 8 was placed on the lower mold 11, the upper mold 12 was lowered and immediately press molding was started. The temperature at this time was 570 ° C. for both the lower mold 11 and the upper mold 12. Apply 2500N pressing force to the upper die 12 and press to
After a second, the press molding was completed.

Then, cooling was started at a cooling rate of 40 ° C./min. During the cooling, the pressing force of 2500 N was still applied to the upper mold 12. Lower mold 1 when cooled to 540 ℃
2000N press force was applied to 1. In this state, 47 more
After cooling to 0 ° C., the pressing by the lower mold 11 was stopped, the upper mold 12 was raised and the mold was opened, and the molded optical element 14 was taken out.

Molded optical element 14 thus obtained
Had no defects in appearance and had excellent shape transfer accuracy.

The shape of the molded optical element described in the present embodiment is a biconvex shape, but the embodiment of the present embodiment is not limited to this shape, and a convex meniscus shape or a concave meniscus shape is used. Needless to say, it can also be applied to a biconcave lens.

As an effect peculiar to this embodiment, since glass lumps having extremely smooth upper and lower surfaces are used as a material for forming an optical element, when the glass lumps are heated prior to press molding, the surface of the glass lumps is heated. Since there is no need to heat-deform the product to make it smooth, it is sufficient to heat it to a temperature at which press molding is possible, so the time required for heating is short, and as a result,
Since the molding takt time is shortened, the production cost is lowered, and the heating temperature may be low, there is no possibility that the glass lump and the jig are fused, and the yield rate is high.

Further, since the glass lumps having extremely smooth upper and lower surfaces are used as the material for molding the optical element, there is no defect in the appearance of the obtained molded optical element, and there is an effect that the non-defective rate is increased.

(Third Example) In the third example, a molten glass flow is received by a receiving mold made of a porous material having air permeability to obtain a glass block as a material for molding an optical element. Will be described.

FIG. 11 is a diagram for schematically explaining the construction of an apparatus for obtaining a glass gob to be a raw material for molding an optical element according to the third embodiment of the present invention.

Reference numeral 1 is a molten glass outflow pipe, 2 is a molten glass flow, 4 is a heating block, 15 is a receiving mold made of a porous material having air permeability, and 16 is a rear surface of a porous receiving mold 15. A gas supply chamber 17 is a gas supply pipe for supplying gas to the gas supply chamber 16.

As the porous receiving material, a product of Nippon Carbon Co., Ltd., Vitro P, F (VCP-0.5)
It is good to use.

Next, an operation for obtaining a glass gob to be a raw material for forming an optical element by using the apparatus having the configuration shown in FIG. 11 in the present embodiment will be described.

When the molten glass flow 2 has started to flow out from the outlet of the outflow pipe 1, a high-pressure cooling gas is supplied into the gas supply chamber 18 through the gas supply pipe 17. The high-pressure cooling gas supplied into the gas supply chamber 18 passes through the pores of the porous receiving die 15 and is ejected upward. The cooling gas ejected from the surface of the porous receiving mold 15 hits the tip of the molten glass flow 2 flowing out of the outflow pipe 1, and as a result, the surface temperature of that portion is lowered and the surface is solidified. become.

As described above, the molten glass stream 2 with the surface of the tip solidified is received by the porous receiving die 15, and the weight of the molten glass accumulated on the porous receiving die 15 is a desired weight. When it becomes, lower the porous receiving mold 15 by a predetermined distance,
The molten glass stream 2 is constricted and naturally cut to obtain a molten glass gob.

The molten glass gob thus obtained was
Both the upper and lower surfaces are smooth and suitable for forming optical elements.

In this embodiment, in the step of receiving the glass stream 2 with the surface of the tip solidified in the porous receiving die 15, gas is ejected from the surface of the porous receiving die 15. Alternatively, the gas may not be jetted out.

That is, when the gas is ejected, the molten glass gob floats from the porous receiving mold 15 and is always in a non-contact state. It has a smooth surface.

On the other hand, even when the gas is not ejected, the surface of the front end of the glass flow 2 is solidified, so that the lower surface of the glass gob has a porous receiving surface with the surface already solidified. Since it is in contact with 15, it does not transfer the irregularities of the pores of the porous receiving mold 15 to the lower surface of the glass lump, and the lower surface of the glass lump is smooth, making it suitable as a material for molding optical elements. ing.

Next, a detailed embodiment of this example will be described.

From the outflow pipe 1 at a temperature of 1050 ° C, 1000 ° C
The molten glass stream 2 of No. 2 is flowing out in the form of droplets. In the glass stream flowing out in the form of droplets, after the step of obtaining the glass gob that is the previous step is completed and the glass stream is naturally cut,
A porous receiving mold 15 was set at a position below the tip of the molten glass flow 2. At this time, the porous receiving mold 15 was set at a position 10 mm below the outlet of the outflow pipe. At this time, the tip of the molten glass flow 2 is in a state of slightly hanging down from the outlet of the outflow pipe 1.

The porous receiving mold 15 is made of carbon having pores with an average diameter of 15 μm, and the receiving surface has a radius of
It is processed into a spherical surface of 15 mm. Also, the heating block 4
Is heated to 300 ° C by a built-in heater (not shown).

After the porous receiving mold 15 was set at the position below the molten glass flow 2, immediately, room temperature air having a pressure of 0.1 MPa was supplied into the gas supply chamber 16 through the gas supply pipe 17. Then, air at a flow rate of 30 l / min was ejected from the pores of the receiving mold 15 in the porous chamber to start cooling the tip portion of the molten glass flow 2. At this time, the temperature of the air ejected from the pores of the receiving mold 15 in the porous chamber was 200 ° C. because the porous receiving mold 15 was heated.

After 3 seconds from the start of cooling, the tip of the molten glass stream 2 descended to the surface of the porous receiving mold 15. Immediately before this, the surface temperature at the tip of the molten glass stream was 600 ° C.

After another 1 second, the flow rate of the air ejected from the pores of the porous receiving mold 15 was reduced to 10 l / min. In that state, after 9 seconds, the weight of the molten glass accumulated on the porous receiving mold 15 became the desired weight. Then, the porous receiving mold 15 was suddenly lowered by 20 mm and stopped and held at that position. As a result, the molten glass was squeezed into thin pieces and spontaneously cut immediately at that position. During this period, air at a flow rate of 10 l / min continued to flow from the surface of the porous receiving die 15, and the molten glass gob was in a state of floating from the porous receiving die 15.

The glass gob thus obtained had a very smooth surface on both the upper and lower surfaces, and its weight was 2 g.
Met.

Although carbon is used as the material of the porous receiving mold 15 in this embodiment, a metal such as stainless steel or ceramics may be used. Similarly, a glass block having a very smooth surface is used. Can be obtained.

Further, in this embodiment, air is used as the gas for cooling the tip of the molten glass flow, but the same effect can be obtained by using an inert gas such as nitrogen gas. Needless to say.

As an effect peculiar to this embodiment, since the front end portion of the molten glass flow can be surely cooled, it is possible to surely obtain a glass lump having a very smooth upper and lower surfaces. When is used as a material for molding a molded optical element, an optical element with excellent accuracy can be obtained.
Because the surface of this glass gob is very smooth, no surface defects occur in the molded optical element obtained by press-molding this glass gob, and an optical element with excellent accuracy can be obtained. Because.

(Fourth Embodiment) In the fourth embodiment, a molten glass flow is received by a receiving mold made of a porous material having air permeability to obtain a glass gob which is a raw material for forming an optical element. Will be described.

FIG. 12 is a diagram for schematically explaining the construction of an apparatus for obtaining a glass gob to be a raw material for molding an optical element according to the fourth embodiment of the present invention.

1 is a molten glass outflow pipe, 2 is a molten glass flow, 4 is a heating block, 5 is a ring-shaped nozzle for injecting a cooling gas for cooling the tip of the molten glass flow, and 6 is a ring-shaped nozzle. A cooling gas injection port opened in the nozzle 5 and an outer wall 7 of the electric furnace. Further, 15 is a porous receiving mold, 16 is a gas supply chamber provided on the back surface of the porous receiving mold 15, 17 is a gas supply pipe for supplying gas to the gas supply chamber 16, and 18 is gas supply. It is a heater for heating the gas flowing inside the pipe 17.

Next, the operation for obtaining a glass gob to be a material for forming an optical element by using the apparatus having the configuration shown in FIG. 12 in the present embodiment will be described.

In the state where the molten glass flow 2 has started to flow out from the outlet of the outflow pipe 1, a cooling gas is supplied to the ring-shaped cooling nozzle 5, and this cooling gas is injected from the injection port 6 to melt the molten glass. The tip of stream 2 is applied and cooled. As a result, the surface temperature of the tip portion of the molten glass flow 2 is lowered and the surface is solidified.

As described above, the molten glass stream 2 with the tip surface solidified is received by the porous receiving mold 15.

In the present embodiment, the gas supply chamber 16 is supplied with high-temperature gas heated by the heater 18 installed inside the gas supply pipe 17. Then, the high-temperature gas is ejected from the pores of the porous receiving die 15.

Then, when the tip of the molten glass flow 2 with the surface solidified descends to near the surface of the porous receiving mold 15, the high temperature gas is ejected from the surface of the porous receiving mold 15. Be started.

When the weight of the molten glass accumulated on the porous receiving mold 15 reaches a desired weight, the porous receiving mold 15
Is lowered by a predetermined distance, the molten glass flow 2 is constricted and naturally cut to obtain a molten glass gob.

The molten glass gob thus obtained was
Both the upper and lower surfaces are very smooth and suitable as a material for optical element molding.Because this molten glass gob is floated and held by the high-temperature gas ejected from the porous receiving mold 15, It is kept in a high temperature softened state and can be immediately pressed.

Next, a detailed embodiment of this example will be described.

From the outlet pipe 1 at a temperature of 1050 ° C, 1000 ° C
The molten glass stream 2 of No. 2 is flowing out in the form of droplets. In the glass stream flowing out in the form of droplets, after the step of obtaining the glass gob that is the previous step is completed and the glass stream is naturally cut,
A porous receiving mold 15 was set at a position below the tip of the molten glass flow 2. At this time, the porous receiving mold 15 is
It was set 10 mm below the outlet of the outflow pipe. At this time, the tip of the molten glass flow 2 is in a state of slightly hanging down from the outlet of the outflow pipe 1.

The porous receiving mold 15 is made of carbon having pores with an average diameter of 15 μm, and the receiving surface has a radius of
It is processed into a spherical surface of 15 mm. Also, the heating block 4
Is heated to 500 ° C by a built-in heater (not shown).

The ring-shaped jet nozzle 5 is made of a ring-shaped pipe, and the jet port 6 has an angle such that the gas jetted from the jet nozzle hits the tip of the molten glass flow.
It consists of 18 holes with a diameter of 0.5 mm drilled on the circumference.

Immediately after the receiving mold 3 was set at a position below the molten glass flow 2, room temperature nitrogen gas having a pressure of 0.1 MPa was supplied to the inside of the ring-shaped injection nozzle 5, and the flow rate was 30 l / min. Nitrogen gas was injected from the injection port 5 to start cooling the tip of the molten glass flow 2.

Two seconds after the start of cooling, the injection of nitrogen gas was stopped. At this time, the front end of the molten glass flow 2 was lowered to a position intermediate between the outlet of the outflow pipe 1 and the receiving mold 3.

One second later, the tip of the molten glass stream 2 was
It descended to the surface of the porous receiving mold 15. Immediately before that, the surface temperature of the front end portion of the molten glass stream 2 was 620 ° C.

At this time, from the porous receiving mold 15,
Eruption of hot gas begins. Nitrogen gas is supplied to the gas supply chamber 16 through the gas supply pipe 17. This nitrogen gas is supplied by the heater 18 inside the gas supply pipe 17 to 800
It is heated to ° C and supplied to the gas supply chamber 16. As a result, nitrogen gas at 700 ° C. is ejected from the receiving mold 3 of the porous chamber.

Keeping in that state, after 10 seconds, a porous receiving mold
The weight of molten glass accumulated on top of 15 was the desired weight. Therefore, the porous receiving mold 15 suddenly drops 20 mm downward,
Hold at that position. As a result, the molten glass was squeezed into thin pieces and spontaneously cut immediately at that position. During this time,
700 ℃ with a flow rate of 10 l / min from the surface of the porous receiving mold 15.
Of the nitrogen gas continued to flow, and the molten glass gob was floating from the porous receiving mold 15.

The glass gob thus obtained had a very smooth surface on both the upper and lower sides, and its weight was 2 g.
Met. The temperature of the obtained glass gob was 600 ° C., and it was floated and held on the porous receiving mold 15 in the softened state.

Although carbon is used as the material of the porous receiving mold 15 in this embodiment, a metal such as stainless steel or ceramics may be used. Similarly, a glass block having a very smooth surface is used. Can be obtained.

As the effect peculiar to this embodiment, by cooling the front end of the molten glass flow and by floating and holding the glass gob with a high temperature gas, the upper and lower surfaces are very smooth in a high temperature softened state. It is possible to obtain a glass gob of, and by pressing this glass gob immediately,
An optical element with excellent accuracy can be obtained. Because the surface of this glass gob is very smooth, no surface defects occur in the molded optical element obtained by press-molding this glass gob, and an optical element with excellent accuracy can be obtained. Because.

(Fifth Embodiment) In the fifth embodiment, a molten glass flow is received by a receiving mold made of a porous material having air permeability to obtain a glass lump as a raw material for forming an optical element. An embodiment in which a lump is immediately press-molded to obtain a molded optical element will be described.

FIG. 13 is a diagram for schematically explaining the structure of an apparatus for obtaining a molded optical element according to the fifth embodiment of the present invention.

1 is a molten glass outflow pipe, 2 is a molten glass flow, 5 is a ring-shaped nozzle for injecting a cooling gas for cooling the tip of the molten glass flow, and 6 is a ring-shaped nozzle 5. Cooling gas injection port, 7 electric furnace, 8
Is a glass block, 9 is a melting crucible, 11 is a lower mold for molding, 12 is an upper mold for molding, 13 is a barrel mold, 14 is a molding optical element, 15 is a porous receiving mold, 16 is a gas supply chamber, 17 is a gas supply pipe, 18
Is a gas heating heater.

Next, an operation for obtaining a molded optical element using the apparatus having the structure shown in FIG. 13 in this embodiment will be described.

The molten glass melted in the melting crucible 9 inside the electric furnace 7 flows out from the outlet of the outflow pipe 1 in the form of droplets. The cooling gas injected from the injection port 6 of the ring-shaped nozzle 5 is applied to the tip of the molten glass flow 2 to lower the temperature of the surface of the tip of the molten glass flow, and the surface is solidified.

The molten glass flow 2 is received by the receiving mold 15 of the porous chamber in the state where the high temperature gas is ejected, and a desired weight of molten glass is accumulated in the porous receiving mold 15, and then the porous receiving mold 15 is obtained. The mold 15 is lowered by a predetermined distance so that the molten glass flow 2 is constricted and naturally cut to melt the molten glass gob 8 into a porous receiving mold 15.
Get on. The glass gob 8 thus obtained is very smooth on both the upper and lower surfaces.

The glass gob 8 thus obtained is immediately conveyed into a molding die composed of a lower die 11 and an upper die 12 and press-molded to obtain a molded optical element 14.

In this embodiment, the step of melting the glass is performed in the atmosphere due to maintenance problems, but the subsequent steps are particularly performed by press molding the glass gob 8 to form the molding optical element 14. The step of obtaining is preferably performed in an atmosphere of an inert gas such as nitrogen gas in order to protect the molding die. Note that FIG. 13 does not show a molding chamber or a replacement chamber for maintaining these atmospheres.

In this embodiment, the glass gob 8 is press-molded to obtain the molded optical element 14. The glass gob 8 thus press-molded is used as a material for molding an optical element. It is also possible to do so. In this case, a high degree of shape transfer accuracy is not required, so precision molding technology to obtain a shape-transferred molded article by precisely controlling the pressing force and temperature is not required. It suffices to carry out pressing with an air cylinder or the like. In this case, molding is performed in the air without any problem.

Next, a detailed embodiment of this example will be described.

In this embodiment, the step of receiving the glass gob 8 on the porous receiving die 15 is exactly the same as that of the embodiment 4 of the embodiment. In this way, a glass lump 8 having smooth upper and lower surfaces was obtained on the receiving mold 15 made of a porous carbon material. The temperature of the glass gob 8 at this time was 600 ° C.

In this embodiment, all of the apparatus except for the melting crucible 9 and the electric furnace 7 for heating the melting crucible 9 are provided in a molding chamber (not shown) kept in a nitrogen atmosphere.

Then, the glass lump 8 in the high temperature softened state
Was immediately transferred into the mold.

The lower mold 11 and the upper mold 12 are made of cemented carbide, and the lower mold 11 is polished into a spherical surface having a radius of 13 mm.
The upper die 12 is ground to a spherical surface having a radius of 7 mm. Also, the body mold 13 is made of a tungsten-based alloy,
A cartridge heater (not shown) is installed in the inside, and the temperature of the lower mold 11 and the upper mold 12 in the state of being fitted therein is controlled by heating or cooling the barrel mold 13. It can be heated or cooled while being heated. The lower mold 11 and the upper mold 12 are each connected to a hydraulic cylinder (not shown) capable of controlling the pressing force, and the glass lump 8 can be press-molded by controlling the pressing force.

After placing the glass lump 8 in a high temperature softened state on the lower mold 11, the upper mold 12 was lowered, and press molding was immediately started. The temperature at this time is 570 ℃ for both lower mold 11 and upper mold 12.
Met. 2500N press force is applied to the upper die 12 and pressed,
The press molding was completed after 20 seconds.

Then, cooling was started at a cooling rate of 40 ° C./min. During the cooling, the pressing force of 2500 N was still applied to the upper mold 12. Lower mold 1 when cooled to 540 ℃
2000N press force was applied to 1. In this state, 47 more
After cooling to 0 ° C., the pressing by the lower mold 11 was stopped, the upper mold 12 was raised and the mold was opened, and the molded optical element 14 was taken out.

Molded optical element 14 thus obtained
Had no defects in appearance and had excellent shape transfer accuracy.

The shape of the molded optical element described in this example is a biconvex shape, but the embodiment of this example is not limited to this shape, and a convex meniscus shape and a concave meniscus shape are not limited thereto. Needless to say, it can also be applied to a biconcave lens.

As an effect peculiar to this embodiment, since glass lumps in a high temperature softened state in which the upper and lower surfaces are very smooth are used as a material for forming an optical element, it is necessary to heat the glass lumps before press molding. There is absolutely no heating time, which results in a shorter molding takt time and lower production costs.

Further, since glass lumps having extremely smooth upper and lower surfaces are used as a material for molding an optical element, there is no defect in the appearance of the obtained molded optical element, and there is an effect that a good product rate is increased.

[0177]

As described above, according to the first invention of the present application, when a receiving glass gob is obtained in the receiving mold, the lower surface of the glass gob, that is, contact with the receiving mold. It is possible to prevent the occurrence of uneven wrinkle-like goblin marks that occur on the surface, and also to prevent fusion between the receiving mold and the glass, and also to prevent generation of a reaction product between the receiving mold and the glass. be able to.

Further, when a glass gob is obtained by receiving a molten glass flow in a receiving die made of a porous material, the molten glass and the porous receiving die are brought into contact with each other to form pores of the receiving die made of the porous material. It is possible to prevent the uneven shape from being transferred to the glass.

That is, since it is possible to reliably obtain a glass gob composed of smooth upper and lower surfaces suitable as a material for optical element molding, the accuracy of the glass gob to be a material for optical element molding can be improved and The manufacturing cost can be reduced.

According to the second invention of the present application, there is no uneven wrinkled gob-in mark on the lower surface of the glass gob,
For molding optical elements with high shape accuracy and good appearance by press-molding glass lumps with smooth upper and lower surfaces without transfer of irregularities of receiving type pores made of porous material Since the material or the optical element can be reliably obtained, the precision of these can be improved and the manufacturing cost thereof can be reduced.

According to the third invention of the present application, the uneven wrinkled gob-in mark generated on the lower surface of the glass gob and the transfer of the uneven shape of the receiving type pores made of the porous material are transferred. Since it can be prevented more reliably, the precision of the optical element molding material or the optical element can be improved and the manufacturing cost thereof can be further reduced.

According to the fourth invention of the present application, when receiving a glass lump with a receiving mold made of a porous material, it is possible to prevent the uneven shape of the pores of the receiving mold from being transferred to the glass. Since it can be performed reliably and easily, the precision of the optical element molding material or the optical element can be improved and the manufacturing cost thereof can be further reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a device configuration according to a first embodiment.

FIG. 2 is a diagram for explaining the operation of the first embodiment.

FIG. 3 is a diagram for explaining the operation of the first embodiment.

FIG. 4 is a diagram for explaining the operation of the first embodiment.

FIG. 5 is a diagram for explaining the operation of the first embodiment.

FIG. 6 is a diagram for explaining the operation of the first embodiment.

FIG. 7 is a diagram for explaining the operation of the first embodiment.

FIG. 8 is a diagram for explaining the device configuration of the first embodiment.

FIG. 9 is a diagram for explaining the device configuration of the first embodiment.

FIG. 10 is a diagram illustrating a second embodiment.

FIG. 11 is a diagram illustrating a device configuration of a third embodiment.

FIG. 12 is a diagram illustrating a device configuration of a fourth embodiment.

FIG. 13 is a diagram for explaining the fifth embodiment.

[Explanation of symbols]

 1 Molten Glass Outflow Pipe 2 Molten Glass Flow 3 Receiving Type 5 Cooling Gas Injection Nozzle 8 Glass Lump 11 Lower Mold 12 Upper Mold 14 Molding Optical Element 15 Porous Receiving Mold

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mizukazu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. When a molten glass flow flowing out from the outlet of the molten glass outflow pipe is received by a receiving mold to obtain a glass gob to be a raw material for forming an optical element, a molten glass flow outflowing from the outlet of the outflow pipe is used. Before the tip comes into contact with the receiving mold, a low-temperature gas is jetted to the tip of the molten glass flow to lower the surface temperature of the tip of the molten glass flow, and the melting of this surface temperature is reduced. A method of manufacturing an optical element, comprising: receiving a glass flow into a receiving mold to obtain a glass lump that is a raw material for forming an optical element. 2. The optical element molding according to claim 1 or 2, wherein the temperature of the gas injected at the tip of the molten glass flow is not higher than the glass transition temperature of the glass. Method of manufacturing material or optical element. 3. The receiving die is made of a gas permeable porous material, and high-pressure gas is supplied to the back surface of the receiving die, and the gas ejected through the pores of the porous material, The method for producing an optical element molding material or an optical element according to claim 1 or 2, wherein the temperature of the surface of the front end portion of the molten glass flow is lowered. 4. A raw material for forming an optical element or an optical element is obtained by immediately receiving a molten glass flow flowing out of an outlet of a molten glass outflow pipe in a receiving mold to obtain a glass gob, and press-molding the high temperature glass gob. In order to obtain, the low temperature gas is jetted to the front end of the molten glass flow until the front end of the molten glass flow flowing out from the outlet of the outflow pipe comes into contact with the receiving mold. It is possible to obtain a glass lump by lowering the temperature and receiving the molten glass flow with the surface temperature lowered in a receiving mold, and press-molding this glass lump to obtain an optical element molding material or an optical element. A method for producing an optical element molding material or an optical element, which is characterized. 5. The outflow end portion of the molten glass flowing out from the glass melting means is cooled while flowing down, and the cooled glass is received on a receiving member, and when the outflow glass reaches a predetermined amount, the outflow portion and the A method for manufacturing an optical element, characterized in that the outflowing glass is cut at a distance from the receiving members, and then the glass material held on the receiving members is pressed to form an optical element.