JP2003313032A - Method for making glass gob - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-quality glass gob free of undulation. <P>SOLUTION: The method for making the glass gob by allowing the prescribed amount of the molten glass to flow down onto a support die 5 from an outflow port 3 for letting out the molten glass comprises setting the distance H from the front end of the outflow port to the surface of the support die at ≤1/2 the external diameter of the outflow port at least at the point of the time the downflow of the molten glass from the outflow port is started. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing a glass gob which is a raw material for producing an optical element.

[0002]

2. Description of the Related Art When molten glass is received in a mold to obtain a glass gob, swelling often occurs on the lower surface of the glass gob.

In order to prevent this, Japanese Patent Laid-Open No. 9-2634
Japanese Unexamined Patent Publication (Kokai) No. Hei 1 (1999) discloses a technique in which a molten glass gob is dropped by 20 to 200 cm and received by a receiving mold.
No. 0-203830 discloses a technique in which the distance between the lower end of the outflow nozzle and the receiving mold is set to a distance at which the glass flow and the molten glass gob can be separated, and the molten glass is caused to flow out by a plunger.

[0004]

Although these known examples can prevent the lumps of glass from swelling, the following problems remain.

According to the method disclosed in Japanese Patent Laid-Open No. 9-263415, it is difficult to change the weight of the molten glass gob to any desired value.

Further, in the method disclosed in Japanese Patent Laid-Open No. 10-203830, since the plunger is installed in the glass melting tank, striae are likely to occur in the molten glass and the quality of the optical glass is poor. .

Therefore, the present invention has been made in view of the above problems, and an object thereof is to obtain a high quality glass gob without swelling.

[0008]

[Means for Solving the Problems]
In order to achieve the object, the method for producing a glass gob according to the present invention is a glass gob for producing a glass gob for producing a glass gob by allowing a predetermined amount of the molten glass to flow down from an outlet for letting out the molten glass. In the manufacturing method, at least at a time point when the molten glass is started to flow down from the outlet, the distance from the tip of the outlet to the surface of the receiving mold is set to 1/2 or less of the outer diameter of the outlet. It is characterized by doing.

In the method for manufacturing a glass gob according to the present invention, after the molten glass is started to flow down from the outlet, the tip of the outlet is gradually moved away from the surface of the receiving mold so that the upper surface of the receiving mold is raised. It is characterized in that a predetermined amount of molten glass that has flowed down is cut from the molten glass on the outlet side by its surface tension.

Further, in the method for producing a glass gob according to the present invention, after a predetermined amount of molten glass is supplied onto the receiving mold, the predetermined amount of molten glass is pressed by the upper mold to produce a shaped glass gob. It is characterized by doing.

Further, the method for producing a glass gob according to the present invention is a method for producing a glass gob for producing a glass gob by causing a predetermined amount of the molten glass to flow down onto a mold from an outlet for letting out the molten glass. , At least at the time of starting the flow of the molten glass from the outlet,
The distance from the tip of the outlet to the surface of the receiving mold,
It is characterized in that it is set to 1/50 or less of the height from the tip of the outlet to the liquid surface of the molten glass in the crucible for melting the glass.

Further, in the method for manufacturing a glass gob according to the present invention, after the molten glass is started to flow down from the outlet, the tip of the outlet is gradually separated from the surface of the receiving mold, and the upper surface of the receiving mold is raised. It is characterized in that a predetermined amount of molten glass that has flowed down is cut from the molten glass on the outlet side by its surface tension.

Further, in the method for manufacturing a glass gob according to the present invention, after a predetermined amount of molten glass is supplied onto the receiving mold, the predetermined amount of molten glass is pressed by an upper mold to manufacture a shaped glass gob. It is characterized by doing.

Further, the method for producing a glass gob according to the present invention is a method for producing a glass gob for producing a glass gob by allowing a predetermined amount of the molten glass to flow down from an outlet for letting out the molten glass onto a receiving mold. , At least at the time of starting the flow of the molten glass from the outlet,
The distance from the tip of the outlet to the surface of the receiving mold,
The feature is that it is set to 4 mm or less.

Further, in the method for manufacturing a glass gob according to the present invention, after the molten glass is started to flow down from the outlet, the tip of the outlet is gradually separated from the surface of the receiving mold so that the upper surface of the receiving mold is raised. It is characterized in that a predetermined amount of molten glass that has flowed down is cut from the molten glass on the outlet side by its surface tension.

In the method for manufacturing a glass gob according to the present invention, after a predetermined amount of molten glass is supplied onto the receiving mold, the predetermined amount of molten glass is pressed by the upper mold to manufacture a shaped glass gob. It is characterized by doing.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will be described below.

First, an outline of one embodiment will be described.

In the present embodiment, in the method for producing a glass gob which receives the molten glass flow flowing out in a droplet form from the molten glass outflow port into the receiving mold and obtains the molten glass gob, at the time when the receiving mold reaches the maximum, The shortest distance between the receiving mold and the molten glass outlet is set to 1/2 or less of the outer diameter of the molten glass outlet.

According to this structure, no swelling occurs on the lower surface of the glass gob, that is, the contact surface between the molten glass and the receiving mold, and a smooth surface can be obtained.

The operation will be described below.

First, the swelling that occurs in the lower surface of the glass gob, which is the contact surface between the molten glass and the receiving mold, which occurs when not according to this embodiment, will be described.

This swelling occurs concentrically in the shape of a tree ring, and when the temperature of the receiving mold is low, the pitch (interval of the swelling) is short, and when the temperature of the receiving mold is high, the swelling of the pitch is large. It becomes a long swell. However, if the temperature of the receiving mold is further raised, the adhesion between the receiving mold and the glass lump becomes stronger, and this swelling cannot be solved by raising the temperature of the receiving mold.

The generation mechanism of this concentric swelling can be considered as follows.

Since the molten glass has a large surface tension, the front end of the molten glass flow has a hemispherical shape, and in that state, the molten glass flow continues to descend and the contact with the receiving mold starts. The first contact between the receiving mold and the molten glass stream is at the center of the hemispherical molten glass stream. Since the temperature of the receiving mold is much lower than the temperature of the molten glass, the glass is cooled at the contact portion with the receiving mold and solidifies in the shape at the time of contact. Since the molten glass continues to flow out, the molten glass around the first contact-solidifying portion comes into contact with the receiving mold. At this time, the contact state between the receiving mold and the glass is such that the central portion is in contact, the ring-shaped non-contact portion by cooling and solidification is formed outside the central portion, and the ring-shaped contact portion is further formed outside. Then, as the molten glass flows out in this manner, concentric swells are formed on the lower surface of the glass gob.

That is, it is understood that the swelling on the lower surface of the glass gob is due to the molten glass gradually growing in the peripheral direction on the receiving mold to obtain the molten glass gob.

Further, it can be seen that the ring-shaped non-contact portion once formed remains without disappearing, which is also a cause of swelling. That is, even if the ring-shaped non-contact portion is formed once, it is understood that the swelling is eliminated if sufficient pressure is applied thereafter and the non-contact portion can be eliminated.

On the other hand, in the present embodiment, in order to receive the molten glass flow, the receiving die is raised to a position extremely close to the molten glass outlet. When the receiving mold and the molten glass outlet are brought close to each other to receive the molten glass as described above, the contact of the molten glass with the receiving mold is almost instantaneously made to the entire receiving surface of the receiving mold. Does not gradually develop in the peripheral direction on the receiving mold, so no swelling occurs on the lower surface of the glass gob.

Further, in this embodiment, since the receiving die is raised to a position extremely close to the molten glass outlet, the molten glass near the molten glass outlet is subjected to a pressure close to the head pressure of the molten glass. . Therefore, even if a non-contact portion is formed on the lower surface of the molten glass above the receiving mold, the non-contact portion is eliminated by the head pressure of the molten glass, and no swelling occurs on the lower surface of the glass gob.

As a result of experiments conducted by the inventor of the present application, when the shortest distance between the receiving mold and the molten glass outlet is not more than 1/2 of the outer diameter of the molten glass outlet at the time when the receiving mold is fully raised. It was found that the swelling on the lower surface of the glass gob can be surely prevented.

Furthermore, in the present embodiment, when it is desired to obtain glass lumps having different desired weights, it can be easily performed by adjusting the descending speed and the descending distance of the receiving mold, and the descending speed and the descending speed of the receiving mold can be easily adjusted. By controlling the distance, the weight accuracy of the glass gob is increased.

Further, in the present embodiment, it is possible to increase the pressure of the molten glass on the receiving mold without installing a plunger in the melting crucible, so that the inside of the crucible can be uniformly stirred. It becomes possible to obtain a glass gob made of high quality optical glass.

Further, in the present embodiment, the molten glass stream flowing out in the form of droplets from the molten glass outlet is received by the receiving mold,
In the method for producing a glass gob to obtain a molten glass gob, at the time when the receiving die has risen to the maximum, the shortest distance between the receiving die and the molten glass outlet is set to the head height of the molten glass (that is, the molten glass in the melting crucible is The height from the surface to the molten glass outlet is 1/50 or less.

The operation is similar to that described above. Further, as a result of the experimental study by the inventor of the present application, at the time when the receiving mold is the highest, the shortest distance between the receiving mold and the molten glass outlet is the head height of the molten glass (that is, the surface of the molten glass in the melting crucible). To the molten glass outlet)) 1
It was found that the swelling on the lower surface of the glass gob can be surely prevented when it is / 50 or less.

Further, in this embodiment, the molten glass stream flowing out in the form of droplets from the molten glass outlet is received by the receiving mold,
In the method for manufacturing a glass gob to obtain a molten glass gob, the shortest distance between the receiving mold and the molten glass outflow port is set to 4 mm or less when the receiving mold rises to the maximum.

The operation is similar to that described above. Further, as a result of experiments conducted by the inventor of the present application, at the time when the receiving mold has risen to the maximum, the shortest distance between the receiving mold and the molten glass outlet is 4 m.
It was found that the swelling on the lower surface of the glass gob can be surely prevented when it is m or less.

Further, in this embodiment, the molten glass gob obtained by the above-mentioned method for producing a glass gob is press-molded by the upper mold to obtain a molded glass gob.

The operation will be described.

According to the above-described method for manufacturing a glass gob, it is possible to obtain a molten glass gob without swelling on the lower surface. By press-molding this molten glass gob with the upper mold, it is possible to obtain a molded glass gob having both upper and lower surfaces formed by molding surfaces and having smooth surfaces without swelling.

The molded glass gob thus obtained is
When the shape is close to the desired shape of the molded optical element, it is preferable to use the molded glass gob as a molding material because the heating time and the molding time can be shortened and the mold durability can be improved. In particular, the molded glass gob obtained according to the present embodiment is smooth without swelling on the molding surface,
When the molded optical element is used, its appearance is good and a high quality molded optical element can be obtained.

Further, when an optical element is obtained by grinding and polishing the surface of the molded glass gob to remove the surface layer of the molded glass gob, the molding surface of the molded glass gob has no swelling and the mold shape is transferred with high accuracy. Therefore, the removal processing amount can be significantly reduced, and the optical element can be processed efficiently and highly accurately.

An embodiment of the present invention will be specifically described below.

1, 2 and 3 are diagrams for explaining an embodiment of the present invention. 4 and 5 are diagrams for explaining a conventional example.

FIG. 1 is a diagram showing the configuration of the entire apparatus in an embodiment of the present invention.

In FIG. 1, 1 is a melting crucible, 2 is a molten glass melted in the melting crucible 1, 3 is a molten glass outflow pipe connected to the melting crucible 1, 4 is a molten glass flowing out in the molten glass outflow pipe 3. Glass stream 5 is a receiving mold for receiving a desired amount of molten glass stream 4 to obtain a molten glass gob,
6 is a vertical single-axis NC (numerical control) moving device for moving the receiving mold 5 to a predetermined position at a predetermined speed, and 7 is a lateral device for moving the receiving mold 5 to a predetermined position at a predetermined speed. Unidirectional NC moving device in the direction, 8 is a controller for controlling these 1-axis NC moving devices, 9 is these 1-axis NC moving devices
A personal computer for setting the set value of the C moving device, 10 is an upper mold for press-molding a molten glass block (not shown) on the receiving mold 5, and 12 is a homogenized molten glass 2 in the melting crucible 1. It is a stirring device for stirring in a state. The reference symbol h in FIG. 1 indicates the head height of the molten glass, that is,
The difference between the height of the liquid surface of the molten glass 2 in the melting crucible 1 and the height of the outlet of the molten glass outflow pipe 3 is shown.

Molten glass 2 melted in a melting crucible 1
Is stirred in a uniform state by the stirrer 12 and then is made to flow out through the molten glass outflow pipe 3 in the form of droplets from the outlet. Then, the receiving die 5 is moved to directly below the outlet, and the molten glass flow 4 begins to be received on the receiving die 5 in a state where the receiving die 5 and the outlet are close to each other.

FIG. 2 is a view for explaining the relationship between the outlet of the molten glass outflow pipe 3 and the size of the receiving die 5 in one embodiment. Reference numeral D in FIG. 2 is the outer diameter of the molten glass outlet, and reference numeral H is the receiving die 5 at the time when the receiving die is most raised.
And the shortest distance between the molten glass outlet and the molten glass outlet.

FIG. 3 shows that the molten glass flow out of the molten glass outflow pipe in one embodiment is received by a mold.
It is a figure explaining the process of obtaining a molten glass gob. In FIG. 3, 11 is a molten glass gob.

As shown in FIG. 3, in one embodiment, the contact between the tip of the molten glass flow and the receiving mold 5 is made by contacting almost the entire contact surface instantaneously. This is possible because the receiving die 5 and the molten glass outlet are extremely close to each other when the receiving die 5 is at the highest position. Further, when the receiving mold has risen to the maximum, the receiving mold and the molten glass outlet are extremely close to each other, so that sufficient pressure due to the head pressure of the molten glass is applied to the molten glass near the receiving mold. There is no swelling due to cooling shrinkage.

On the other hand, FIG. 4 is a view for explaining the relationship between the outlet of the molten glass outflow pipe 3 and the size of the receiving die 5 which have been conventionally used. Comparing FIG. 2 showing one embodiment with FIG. 4 showing a conventional example, in the conventional example, the shortest distance H between the receiving die 5 and the molten glass outlet is large at the time when the receiving die is most raised, and the molten glass is It can be seen that the outer diameter D of the outlet is small.

FIG. 5 is a diagram for explaining a step of obtaining a molten glass gob in this conventional example.

As shown in FIG. 5, in the conventional example, the shortest distance H between the receiving mold 5 and the molten glass outlet is large when the receiving mold is most raised, and the outer diameter D of the molten glass outlet is small. The molten glass received in the receiving mold propagates laterally from the center of the receiving mold to the periphery. At this time, the glass is cooled and solidified at the contact portion between the molten glass and the receiving mold, and further the molten glass progresses to the outside to generate groove-like swelling,
As a result, annual ring-shaped concentric swells are formed on the lower surface of the glass gob.

Thus, the greatest feature of this embodiment is that
This is the point at which the receiving mold 5 and the molten glass outlet are extremely close to each other when the receiving mold reaches the maximum position. As a result, the lower surface of the obtained glass gob is smooth, and defects such as swelling do not occur.

In the present embodiment, at the time when the receiving mold has risen to the maximum, the shortest distance between the receiving mold and the molten glass outlet is 1/2 or less of the outer diameter of the molten glass outlet or the height of the molten glass head. (That is, the height from the molten glass outlet to the liquid surface of the molten glass in the melting crucible) is 1/50 or less, or 4 mm or less.

In the present embodiment, as shown in FIG. 3, the receiving mold 5 descends at a slight speed from the time when the receiving mold 5 is highest. By presetting the time for descending at this slow speed, a desired weight of molten glass is obtained on the receiving mold 5. Then, when the receiving die 5 is suddenly lowered by a predetermined distance, the molten glass flow is constricted at that position, and the molten glass flow is cut by the surface tension of the molten glass at the constricted portion, and a molten glass block is obtained on the receiving mold 5. To be

In this embodiment, the personal computer 9 allows the vertical N
Since the moving speed and moving position of the C moving device 6 can be easily changed, glass lumps of various sizes can be easily obtained.

Further, the molten optical glass 2 in the melting crucible 1
Is homogeneously stirred by the stirrer 12, so that optical defects such as striae do not occur in the glass gob obtained in this embodiment.

The glass gob thus obtained is smooth without any undulations on its lower surface and also has a smooth upper surface as a free surface, and is therefore very suitable as a material for molding optical elements and of high quality. A molded optical element can be obtained.

Alternatively, the molten glass gob obtained on the receiving die 5 may be press-formed with the upper die 10 to obtain a shaped glass gob. This molded glass gob is obtained by press-molding a molten glass gob having smooth upper and lower surfaces, and as a result, the upper and lower surfaces of the molded glass gob are also smooth.

When this molded glass gob is used as a molding material, the molded glass gob is placed between a pair of upper and lower precision molding dies (not shown), and these are heated to a desired pressing temperature and then press-molded. , A molded optical element is obtained. When the molded glass gob is used as a molding material, the effects of shortening the heating time and the molding time and improving the mold durability can be obtained.

When the molded glass gob is used as a polishing material, the molded glass gob is subjected to precise grinding with a pellet grindstone and then to polishing. Since the molding surface of the molded glass gob according to the present embodiment has no swelling and the mold shape is transferred with high accuracy, the conventional rough grinding step with a cup grindstone can be omitted, and the removal processing amount can be reduced. The effect is obtained.

[0062]

Example 1 In Example 1, according to the method of one embodiment, a molten glass flow was received on a receiving mold to obtain a molten glass gob, and this glass gob was press-molded by a pair of upper and lower precision molding dies. Then, an example of obtaining a molded optical element will be described.

In this embodiment, description will be made of a case where a molded optical element having a weight of 5 g, a biconvex shape, a diameter of 22 mm, and a radius of curvature of 70 mm and 22 mm is molded using an optical glass corresponding to SK12.

In this embodiment, the liquid level of the molten glass in the melting crucible 1 is 50 mm, the length of the molten glass outflow pipe 3 is 250 mm, the head height h of the molten glass, that is, the liquid of the molten glass. The height from the surface to the outlet of the molten glass outflow pipe 3 is 300 mm.

The molten crucible 1 and the molten glass outflow pipe 3 are made of platinum, and the outer diameter D of the outflow port of the molten glass outflow pipe 3 is 20 mm.

The receiving die 5 is a carbon ceramic (specifically, a carbon ceramic in which fine ceramics are dispersed in carbon).
Rainbow technology KC carbon ceramics BS1060
It was produced in 9). The receiving die 5 is processed into a spherical surface having an opening diameter of 24 mm and a curvature radius of 20 mm.

The receiving mold 5 is constantly heated to 400 ° C. by a heater.
It is kept heated.

Various kinds of shortest distances between the receiving mold 5 and the molten glass outlet when the receiving mold 5 is raised to the maximum are set. As a result, the condition of swelling on the lower surface of the glass gob, the receiving mold 5 is raised to the maximum. The relationship between the shortest distance (= H) between the receiving mold and the molten glass outlet (= H) and the outer diameter of the molten glass outlet (= D) (= H / D), and the height of the molten glass head (= h)
FIG. 6 shows a more specific implementation result and comparison result regarding the relationship (= H / h) with.

The glass gob thus obtained was press-molded with a pair of upper and lower precision molding dies to obtain a molded optical element.

The precision forming die is made of cemented carbide, and the forming surface has a radius of curvature of 22 mm for the upper die and a radius of curvature of 7 for the lower die.
It is ground to 0 mm.

The precision molding die is installed in a molding chamber kept in a nitrogen atmosphere, heated to a pressing temperature of 610 ° C., and then press-molded by applying a pressing force of 3000N,
After cooling, the molded optical element was taken out.

The appearance evaluation results of the molded optical element are shown in FIG.

From the results shown in FIG. 6, the glass gob obtained by the glass gob manufacturing method according to the present embodiment has no swelling on the lower surface, and as a result, the molded optical element obtained by press molding the glass gob of the present embodiment has an external appearance. The quality is very good.

Example 2 In Example 2, according to the method of one embodiment, a molten glass flow was received on a receiving mold to obtain a molten glass gob, and this molten glass gob was press-molded with an upper die to form a molded glass gob. And an example of using this molded glass gob as a polishing material will be described.

In this embodiment, an optical glass equivalent to SK12 is used, the weight is 1.5 g, the concave meniscus shape is 10 m in diameter.
A case will be described in which an optical element having m and a radius of curvature of 40 mm (convex surface) and 4 mm (concave surface) is manufactured.

In this embodiment, the liquid level of the molten glass in the melting crucible 1 is 50 mm, the length of the molten glass outflow pipe 3 is 250 mm, the head height h of the molten glass, that is, the liquid of the molten glass. The height from the surface to the outlet of the molten glass outflow pipe 3 is 300 mm.

The melting crucible 1 and the molten glass outflow pipe 3 are made of platinum, and the outer diameter D of the outflow port of the molten glass outflow pipe 3 is 8 mm.

The receiving mold 5 was manufactured by processing brass. The receiving die 5 is processed into a concave spherical surface having an opening diameter of 10 mm and a radius of curvature of 40 mm. The receiving mold 5 is constantly heated and held at 400 ° C. by the heater.

The upper die 10 is also made of brass and has a radius of curvature of 4 m.
It is processed into a convex spherical surface of m. The upper mold 10 is constantly heated and held at 200 ° C. by a heater.

In order to obtain the molten glass gob, various shortest distances between the receiving die 5 and the molten glass outlet at the time when the receiving die 5 is raised to the maximum are set, and as a result, the unevenness of the lower surface of the molded glass gob is obtained. Situation, the relationship between the shortest distance (= H) between the receiving mold and the molten glass outlet and the outer diameter (= D) of the molten glass outlet (= H / D), and FIG. 7 shows more specific implementation results and comparison results regarding the relationship (= H / h) with the head height (= h) of the molten glass.

The swelling that occurs on the upper surface of the molded glass gob is such that the pressing speed is 10 mm / s immediately before the pressing is completed.
Since this can be solved by the above, in this embodiment, the press speed is set to 20 mm / s to prevent swelling of the upper surface.

The molded glass gob thus obtained was
The molding surface was removed by precise grinding with a pellet grindstone, and then polishing was performed to obtain an optical element.

The amount of removal processing by fine grinding is shown in FIG.

From the results of FIG. 7, the molded glass gob obtained by the glass gob manufacturing method according to the present embodiment has no swelling on the lower surface, and as a result, the molded glass gob of the present embodiment is ground and polished to obtain an optical element. At this time, the amount of processing removed by fine grinding can be significantly reduced.

(Example 3) In Example 3, a molten glass flow was received on a receiving mold by the method according to one embodiment to obtain a molten glass gob, and this molten glass gob was press-molded with an upper die to form a molded glass gob. An example of obtaining a molded optical element by press-molding this molded glass gob with a pair of upper and lower precision molding dies will be described.

In this embodiment, description will be made of a case where a molded optical element having a weight of 5 g, a biconcave shape, a diameter of 18 mm, and a radius of curvature of 50 mm and 10 mm is manufactured using an optical glass corresponding to SK12.

In this embodiment, the liquid level of the molten glass in the melting crucible 1 is 50 mm, the length of the molten glass outflow pipe 3 is 250 mm, the head height h of the molten glass, that is, the liquid of the molten glass. The height from the surface to the outlet of the molten glass outflow pipe 3 is 300 mm.

The melting crucible 1 and the molten glass outflow pipe 3 are made of platinum, and the outer diameter D of the outflow port of the molten glass outflow pipe 3 is 16 mm.

The receiving mold 5 is a gold-nickel alloy (Au82.
5 wt% -Ni 17.5 wt%) was processed and manufactured. The receiving die 5 is processed into a convex spherical surface having an opening diameter of 18 mm and a radius of curvature of 45 mm. The receiving mold 5 is constantly heated and held at 400 ° C. by the heater.

The upper die 10 is also made of a gold-nickel alloy and is processed into a convex spherical surface having a radius of curvature of 9 mm. Also, the upper mold 1
0 is constantly heated and maintained at 200 ° C. by the heater.

In order to obtain a molten glass gob, various shortest distances between the receiving die 5 and the molten glass outlet at the time when the receiving die is most raised are set, and as a result, the unevenness of the lower surface of the formed glass gob is obtained. Situation, relationship between the shortest distance between the receiving mold and the molten glass outlet (= H) and the outer diameter of the molten glass outlet (= D) (= H / D) at the time when the receiving mold has risen to the maximum, and it and melting FIG. 8 shows more specific implementation results and comparison results regarding the relationship (= H / h) with the head height (= h) of glass.

It should be noted that the swelling generated on the upper surface of the molded glass gob is such that the pressing speed is 10 mm / s immediately before the pressing is completed.
Since this can be solved by the above, in this embodiment, the press speed is set to 20 mm / s to prevent swelling of the upper surface.

The glass gob thus obtained was press-molded with a pair of upper and lower precision molding dies to obtain a molded optical element.

The precision forming die is made of cemented carbide, and its forming surface has a radius of curvature of 10 mm for the upper die and 5 for the lower die.
It is ground to 0 mm.

The precision molding die is placed in a molding chamber kept in a nitrogen atmosphere, heated to a pressing temperature of 610 ° C., and then press-molded by applying a pressing force of 3000N,
After cooling, the molded optical element was taken out.

FIG. 8 shows the appearance evaluation result of the molded optical element.

From the results of FIG. 8, the molded glass gob obtained by the glass gob manufacturing method according to the present embodiment has no swell on the lower surface, and as a result, the molded optical element obtained by press-molding the molded glass gob of this embodiment is , The appearance quality is very good.

[0098]

As described above, according to the present invention,
It is possible to obtain a glass gob having a desired weight, which has no swelling on the lower surface in contact with the receiving mold and has excellent optical quality.

By using this glass gob as a material for molding an optical element, a molded optical element having a good appearance can be obtained.

If the molded glass gob according to the present invention is used as a material for manufacturing an optical element by grinding and polishing, the amount of processing removal can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a device configuration according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a mold configuration according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a step of obtaining a glass gob according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a conventional mold configuration.

FIG. 5 is a diagram illustrating a conventional step of obtaining a glass gob.

FIG. 6 is a diagram showing evaluation results of the molded optical element in Example 1.

FIG. 7 is a diagram showing an evaluation result of a molded optical element in Example 2.

FIG. 8 is a diagram showing evaluation results of a molded optical element in Example 3.

[Explanation of symbols]

1 melting crucible 3 Molten glass outflow pipe 4 Molten glass flow 5 Receiving type 10 Upper mold 11 glass lumps

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C03B 11/00 C03B 11/00 C

Claims (9)

[Claims] 1. A method for producing a glass gob for producing a glass gob by causing a predetermined amount of the molten glass to flow down a receiving mold from an outflow port for letting out molten glass, wherein the melting is performed at least from the outflow port. A method for manufacturing a glass gob, wherein the distance from the tip of the outlet to the surface of the receiving mold is set to 1/2 or less of the outer diameter of the outlet when the glass starts to flow. 2. After the molten glass is started to flow down from the outlet, the tip of the outlet is gradually separated from the surface of the receiving mold, and a predetermined amount of molten glass flowed down onto the receiving mold is removed. The method for producing a glass gob according to claim 1, wherein the molten glass on the outlet side is cut by surface tension. 3. A molded glass gob is manufactured by pressing a predetermined amount of molten glass onto the receiving mold and then pressing the predetermined amount of molten glass with an upper mold. Of the glass gob of. 4. A method for producing a glass gob for producing a glass gob by causing a predetermined amount of the molten glass to flow down a receiving mold from an outlet for letting out the molten glass, wherein the melting is performed from at least the outflow exit. At the time of starting the flow of the glass, the distance from the tip of the outlet to the surface of the receiving mold is 1/50 of the height from the tip of the outlet to the liquid surface of the molten glass in the crucible for melting the glass.
A method for manufacturing a glass gob characterized by setting the following. 5. After starting to flow down the molten glass from the outlet, the tip of the outlet and the surface of the receiving mold are gradually separated from each other, and a predetermined amount of the molten glass flowed down onto the receiving mold is removed. The method for producing a glass gob according to claim 4, wherein the molten glass on the outlet side is cut by surface tension. 6. The molded glass gob according to claim 5, wherein after a predetermined amount of the molten glass is supplied onto the receiving mold, the predetermined amount of the molten glass is pressed by the upper mold to produce a molded glass gob. Of the glass gob of. 7. A method for producing a glass gob for producing a glass gob by allowing a predetermined amount of the molten glass to flow down onto a receiving mold from an outflow port for letting out the molten glass, wherein the melting is performed from at least the outflow port. A method for producing a glass gob, wherein the distance from the tip of the outlet to the surface of the receiving mold is set to 4 mm or less at the time of starting the flow of the glass. 8. After the molten glass is started to flow down from the outlet, the tip of the outlet and the surface of the receiving mold are gradually moved away from each other, and a predetermined amount of molten glass flowed down onto the receiving mold is removed. The method for producing a glass gob according to claim 7, wherein the molten glass on the outlet side is cut by surface tension. 9. The molded glass gob according to claim 8, wherein after a predetermined amount of the molten glass is supplied onto the receiving mold, the predetermined amount of the molten glass is pressed by the upper mold to produce a molded glass gob. Of the glass gob of.