JPH10114530A - Molten glass feeder, its feeding method and production of optical element preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an optical element perform high in weight precision without excessively raising the temp. of a discharge nozzle. SOLUTION: A plunger 6 is vertically movable arranged on the center axis of a glass melting vessel 2. A columnar liq. droplet holding part 7 is furnished to the lower end of the plunger 6 and allowed to pierce a nozzle 3 while leaving a specified clearance. A fixing frame 10 is arranged above the vessel 2. A driving source 11 is mounted on the upper face of the frame 10, and the upper end of the plunger 6 is connected to the driving source 11. The size of a droplet 9 is measured and compared with the previously measured size of a droplet of reference weight, and the result is transmitted to a controller 14 as a comparison signal. The driving source 11 is controlled by the controller 14 in accordance with the difference in size between the droplet 9 and the droplet of reference weight, hence the plunger 6 is vertically moved, and the distance between the tip of the holding part 7 and that of the nozzle 3 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for supplying molten glass for obtaining an element material of a glass molded lens used in a pickup optical system or a camera lens of an optical disk apparatus, and a method of manufacturing an optical element material. About the method.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a glass lens, for example, a method disclosed in Japanese Patent Publication No. 60-127122 has been known. These molding methods are:
The optical element material heated to a predetermined temperature is pressed and molded using a pair of molds (a concave mold and a convex mold). The optical element material itself is generally manufactured as follows.
That is, first, as shown in FIG.
The molten glass 21 in 4 is caused to flow out of the outflow nozzle 22 to form a spherical glass droplet 23 at the tip of the outflow nozzle 22. Next, the glass element 23 is allowed to fall freely into a concave mold (not shown) and cooled to produce an optical element material.

[0003] A more specific method for producing an optical element material is as follows.
It is disclosed in JP-A-61-146721. In the manufacturing method of the optical element material described in the publication,
Spherical glass droplet 2 formed at the tip of outflow nozzle 22
3 is dropped until the surface temperature of the glass droplet 23 becomes lower than the softening temperature of the glass, that is, until the glass surface solidifies, whereby an optical element material is produced. In this case, the temperature of the outflow nozzle 22 is precisely controlled in order to obtain the glass droplet 23 with high weight accuracy. However, as shown in FIG. 7, the upper end of the glass melting vessel 24 is opened, and the atmospheric pressure and the pressure exerted by the gravity of the molten glass 21 stored in the glass melting vessel 24 cause the outflow nozzle 2.
Because it acts on the tip of No. 2, no matter how precisely the temperature of the outflow nozzle 22 (the temperature of the glass droplet 23) is controlled,
As the liquid level of the molten glass 21 in the glass melting container 24 decreases, the weight of the glass droplet 23 gradually decreases, and the time until the weight of the glass droplet 23 reaches a desired weight gradually increases. The diameter of the tip of the outflow nozzle 22 is a factor that affects the weight of the glass droplet 23, and the weight m of the glass droplet 23 formed at the tip of the outflow nozzle 22.
Substantially satisfies the relationship of mg = 2πrγ (r: tip diameter of outflow nozzle 22, γ: surface tension). For this reason, in the manufacturing method of the optical element material described in the publication, the time until the weight of the glass droplet 23 becomes a desired weight is measured, and the temperature of the outflow nozzle 22, that is, the surface tension γ is changed. Thus, a glass droplet 23 having a desired weight is obtained.

[0004]

However, when the temperature of the outflow nozzle is increased in a case where the molten glass contains a large amount of, for example, boric acid and alkali components, these components are formed on the surface of the glass droplet by evaporation, The composition differs between the surface and the inside of the obtained optical element material. For this reason, a large stress remains in the optical element material, and it is difficult to manufacture a precise glass lens. In addition, in the above-mentioned conventional method for producing a material for an optical element, since the weight of a glass droplet is substantially determined by the tip diameter of an outflow nozzle, a number of glass melting vessels corresponding to the type of glass lens is required. Therefore, complicated operations such as replacement of the glass melting container are required, and the productivity is reduced. Further, conventionally, the glass flowing out of the outflow nozzle has been cut using an opening / closing blade, but it has been difficult to produce a minute optical element material by this method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and it is an object of the present invention to provide an optical element material with high weight accuracy without increasing the temperature of an outflow nozzle. It is an object to provide a supply device and a supply method thereof. Another object of the present invention is to provide a method of manufacturing an optical element material that can obtain a fine optical element material by dividing a glass droplet into a plurality of pieces.

[0006]

In order to achieve the above object, an apparatus for supplying molten glass according to the present invention is provided with an outflow nozzle provided at a lower end of a glass melting vessel, and the molten glass is dropped from the outflow nozzle. A molten glass supply device, which has a droplet holding portion at the tip, a plunger inserted through the outflow nozzle with a predetermined clearance, and driving means for vertically moving the plunger,
Measuring means for measuring the size of the spherical glass droplet flowing out to the liquid droplet holding unit; andcontrol means for controlling the driving means based on a measurement value obtained by the measuring means. Features. According to the configuration of the molten glass supply device, the following operation can be achieved. That is, the weight m of the glass droplet that has flowed into the droplet holding unit and has become spherical is approximately mg = 2πrγ (g: gravitational acceleration, r: tip diameter of the droplet holding unit or outflow nozzle, γ: surface tension). Satisfy the relationship. For this reason, the weight of the glass droplet is substantially determined by the diameter of the droplet holding unit when the plunger is lowered to the lowest value (when the tip of the droplet holding unit projects from the tip of the outflow nozzle). When the plunger is raised to make the tip position of the droplet holding unit and the tip position of the outflow nozzle the same, it is generally determined by the outer diameter of the outflow nozzle. Also, in the process of changing the state in which the tip of the droplet holding unit protrudes from the tip of the outflow nozzle to a state in which the tip position of the droplet holding unit and the tip position of the outflow nozzle become the same, the weight of the glass droplet is reduced. It grows gradually. Therefore, the size of the glass droplet is measured by the measuring unit, and the driving unit is controlled based on the measured value to move the plunger up and down, thereby to set the position of the tip of the droplet holding unit (with the tip of the droplet holding unit). The distance from the tip of the outflow nozzle) can be adjusted to adjust the weight of the glass droplet. In this way, the weight of the glass droplets can be adjusted without increasing the temperature of the outflow nozzle, so that even when the molten glass contains a large amount of boric acid and alkali components, these components are evaporated. It is formed on the surface of the glass droplet, and the composition does not differ between the surface and the inside of the optical element material. For this reason, since a large stress does not remain in the optical element material, a precise glass lens can be manufactured. Further, since the weight of the glass droplet can be adjusted by adjusting the position of the tip of the droplet holding unit, it is not necessary to prepare a number of glass melting containers corresponding to the type of glass lens. This eliminates the need for complicated operations such as replacement of the glass melting container, thereby improving productivity.

In the configuration of the apparatus for supplying molten glass according to the present invention, the measured value obtained by the measuring means is compared with the size of a glass droplet having a reference weight measured in advance, and the control means is provided as a comparison signal. Preferably, a comparison circuit is further provided for transmitting the data to According to this preferred example, the weight of the glass droplet can be precisely adjusted to the reference weight, so that an optical element material with high weight accuracy can be obtained.

Further, in the configuration of the apparatus for supplying molten glass of the present invention, the measuring means is provided below the outflow nozzle with the center axis of the outflow nozzle interposed therebetween and emits laser light. And a light receiver for receiving the laser light emitted from the light emitter. According to this preferred example, a part of the laser light emitted from the light emitting device and received by the light receiving device is blocked by the glass droplet, and by detecting the cutoff size of the laser light by the glass droplet, the Dimensions can be measured.

Further, a method for supplying molten glass according to the present invention is a method for supplying molten glass by dropping molten glass from an outflow nozzle provided at the lower end of a glass melting container, wherein a predetermined amount of molten glass is supplied to the outflow nozzle. By controlling the positional relationship between the tip of the droplet holding portion of the plunger, which is inserted with a clearance and protrudes from the tip of the outflow nozzle, and the tip of the outflow nozzle, it is possible to adjust the weight of the molten glass dropped. Features. According to the molten glass supply method, the weight of the glass droplets can be adjusted without increasing the temperature of the outflow nozzle, so even when the molten glass contains a large amount of boric acid or an alkali component, These components are formed on the surface of the glass droplet by evaporation, and the composition does not differ between the surface and the inside of the optical element material. For this reason, since a large stress does not remain in the optical element material, a precise glass lens can be manufactured.

In the method of supplying molten glass according to the present invention, the size of the molten glass dropped is measured, and the tip of the droplet holding portion of the plunger is measured so that the measured size is substantially the same as the reference size. It is preferable to control the positional relationship between the nozzle and the tip of the outflow nozzle. According to this preferred example,
Since the weight of the glass droplet can be precisely adjusted to the reference weight, an optical element material with high weight accuracy can be obtained.

Further, in the method of manufacturing an optical element material according to the present invention, a predetermined amount of molten glass is dropped from an outflow nozzle provided in a glass melting vessel, and the droplet is separated by a separator provided vertically below the outflow nozzle. It is divided into a plurality. According to the method for manufacturing an optical element material, not only a minute optical element material, which has been difficult in the past, can be manufactured, but also productivity is dramatically improved.

In the method for producing an optical element material according to the present invention, it is preferable to use a knife edge as the separator. According to this preferred example, the glass droplet is divided into optical element materials having substantially the same weight by the impact of the drop.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments. <First Embodiment> FIG. 1 is a sectional view showing a molten glass supply apparatus according to a first embodiment of the present invention. As shown in FIG. 1, a cylindrical outflow nozzle 3 is provided at the center of the bottom of a platinum glass melting vessel 2 in which the upper end is open and the molten glass 1 is stored. A heater 4 is provided around the glass melting vessel 2, and a heater 5 is provided around the outflow nozzle 3. Inside the glass melting vessel 2, a plunger 6 is disposed on the center axis so as to be vertically movable. At the lower end of the plunger 6, a columnar droplet holding section 7 is provided, and the droplet holding section 7 is inserted into the outflow nozzle 3. Here, the droplet holding unit 7 is inserted through the outflow nozzle 3 with a predetermined clearance, and a predetermined gap 8 is formed between the droplet holding unit 7 and the inner peripheral surface of the outflow nozzle 3. .
For this reason, the molten glass 1 in the glass melting vessel 2
Through the outflow nozzle 3, a spherical glass droplet 9 is formed at the tip of the droplet holding unit 7. This glass droplet 9
Are sequentially dropped at regular time intervals. A fixed frame 10 is arranged above the glass melting vessel 2. A drive source 11 is attached to the upper surface of the fixed frame 10, and the upper end of the plunger 6 is connected to the drive source 11. Therefore, the distance between the tip of the droplet holding unit 7 and the tip of the outflow nozzle 3 is adjusted by driving the drive source 11 and moving the plunger 6 in the vertical direction (± Z direction in FIG. 1). Can be. FIG. 1 shows a state in which the plunger 6 is lowered to the lowest value (a state in which the tip of the droplet holding unit 7 protrudes from the tip of the outflow nozzle 3), and FIG. The state where the tip position of the droplet holding unit 7 and the tip position of the outflow nozzle 3 are the same is shown.

FIG. 3 shows the relationship between the position of the tip of the droplet holding unit and the weight of the droplet. The weight m of the glass droplet 9 formed at the tip of the droplet holding unit 7 is approximately mg = 2πrγ (g: gravitational acceleration, r: tip diameter of the droplet holding unit 7 or the outflow nozzle 3;
γ: surface tension). For this reason, as shown in FIG. 3, the weight of the glass droplet 9 is substantially determined by the diameter of the droplet holding unit 7 when the plunger 6 is lowered to the lowest value (the state of FIG. 1). In a state in which the jar 6 is raised to make the tip position of the droplet holding unit 7 and the tip position of the outflow nozzle 3 the same (the state in FIG. 2), the outer diameter of the outflow nozzle 3 is substantially determined. The weight of the glass droplet 9 gradually increases in the process of changing the position of the tip of the droplet holding unit 7 from the state of FIG. 1 to the state of FIG. When the tip position of the droplet holding unit 7 is higher than the tip position of the outflow nozzle 3, the weight of the glass droplet 9 is determined substantially by the outer diameter of the outflow nozzle 3, and the glass in the state of FIG. It is not so different from the weight of the droplet 9.

In order to adjust the weight of the glass droplet 9 to a reference weight based on the relationship between the tip position of the droplet holding unit 7 and the weight of the glass droplet 9, the following description will be made in the present embodiment. Such a configuration is adopted. That is, as shown in FIG. 1, a light emitting device 12 for emitting laser light and a light emitting device 12 for emitting laser light are provided below the glass melting vessel 2 at positions opposed to each other across the central axis of the outflow nozzle 3. A light receiver 13 for receiving laser light is provided. A control device 14 for controlling the drive source 11 is attached to the upper surface of the fixed frame 10.
4 includes a light emitting device 12 and a light receiving device 13 via a comparing circuit 20.
Is connected. Then, a part of the laser light emitted from the light emitter 12 and received by the light receiver 13 is blocked by the glass droplet 9, and the laser beam cutoff dimension (diameter of the glass droplet 9) by the glass droplet 9 is measured in advance. The cutoff dimension of the laser light by the set reference weight glass droplet is compared by the comparison circuit 20 and transmitted to the control device 14 as a comparison signal. When the cutoff size of the laser beam by the glass droplet 9 is smaller than the cutoff size of the laser beam by the glass droplet having the reference weight (when the weight of the glass droplet 9 is smaller than the reference weight), the control device 14 is driven. The plunger 6 is moved upward (+ Z direction in FIG. 1) by controlling the source 11 to increase the weight of the glass droplet 9 (see FIG. 3). Thereby, the weight of the glass droplet 9 is adjusted to the reference weight. If the cutoff size of the laser beam by the glass droplet 9 is larger than the cutoff size of the laser beam by the liquid droplet having the reference weight (when the weight of the glass droplet 9 is larger than the reference weight), the control device 14 operates. The drive source 11 is controlled to move the plunger 6 downward (the −Z direction in FIG. 1), thereby reducing the weight of the glass droplet 9 (see FIG. 3). Thereby, the weight of the glass droplet 9 is adjusted to the reference weight.

As described above, according to the molten glass supply apparatus of the present embodiment, even if the liquid level of the molten glass 1 in the glass melting container 2 drops as the glass droplets 9 are sequentially dropped, By adjusting the position of the tip of the droplet holding unit 7, the weight of the glass droplet 9 can be precisely adjusted to the reference weight, so that an optical element material with high weight accuracy can be obtained. Further, since the weight of the glass droplet 9 can be adjusted without increasing the temperature of the outflow nozzle 3,
Even when the molten glass 1 contains a large amount of boric acid and alkali components, these components are formed on the surface of the glass droplet 9 by evaporation, and the composition differs between the surface and the inside of the optical element material. There is no. For this reason, since a large stress does not remain in the optical element material, a precise glass lens can be manufactured. Further, the droplet holding unit 7
Since the weight of the glass droplet 9 can be adjusted by adjusting the position of the tip, there is no need to prepare a number of glass melting containers corresponding to the type of glass lens. This eliminates the need for complicated operations such as replacement of the glass melting container, thereby improving productivity.

In the above-mentioned molten glass supply device, the outflow nozzle 3 was set to have an outer diameter of 9.8 mm, an inner diameter of 8.8 mm, a diameter of the droplet holding section 7 of 7.4 mm, and barium borosilicate as the molten glass 1. (Tipping point: 549 ° C., glass transition point: 501 ° C.), glass droplets 9 were sequentially dropped. In this case, the glass droplets 9 were dropped with the temperature of the heaters 4 and 5 set to 1200 ° C. As a result, it was confirmed that the weight of the glass droplet 9 could be changed in the range of 440 mg to 520 mg. Also, at each position of the tip of the droplet holding section 7, a weight accuracy within ± 0.3% was realized.

Further, when an optical element material obtained by using the apparatus for supplying molten glass of the present embodiment was heated and compression-molded to produce a glass lens, a glass lens of a level having no problem was obtained. Was.

In the present embodiment, the droplet holding section 7 is separately provided at the lower end of the plunger 6, but the invention is not necessarily limited to this configuration.
The structure itself may also serve as the droplet holding unit.

In this embodiment, as means for measuring the size of the glass droplet 9, a light emitting device 12 for emitting laser light and a light receiving device for receiving laser light emitted from the light emitting device 12 are used. 13 is used, but is not necessarily limited to this configuration. For example, after the glass droplets 9 are dropped, the dimensions of the glass droplets 9 may be measured by directly measuring the total number or the weight of the extracted ones.

<Second Embodiment> FIG. 4 shows a second embodiment of the present invention.
It is sectional drawing which shows the manufacturing apparatus used for the manufacturing method of the optical element material in embodiment. As shown in FIG.
A separator 15 is provided below the glass melting vessel 2. The separator 15 includes a base 16 and a knife edge 17 provided vertically upward at the center of the base 16. Here, the knife edge 17 is formed by molding a silicon plate used as a semiconductor substrate, and is arranged on the central axis of the droplet holding unit 7 so as to be located at the center of the drop of the glass droplet 9. I have. The distance between the tip of the outflow nozzle 3 and the tip of the knife edge 17 is 20.
It is set to 0 mm. Since other configurations are the same as those of the first embodiment, the same portions are denoted by the same reference numerals and description thereof will be omitted.

Next, a method for manufacturing an optical element material using the optical element material manufacturing apparatus configured as described above will be described. First, the molten glass 1 in the glass melting vessel 2 is discharged from the outflow nozzle 3 in the same manner as in the first embodiment.
The glass droplet 9 formed at the tip of the droplet holding unit 7 is dropped in a state where the weight is precisely controlled. The dropped droplet 9 is divided into two by the tip of the knife edge 17 by the impact of the drop, and rolls on the base 16 as two optical element materials 18 and 19.

As described above, according to the method for manufacturing an optical element material according to the present embodiment, not only a minute optical element material, which has been conventionally difficult, can be manufactured, but also productivity is dramatically increased. To improve.

When the glass droplet 9 having a weight of 460 mg was actually dropped on the knife edge 17, the glass droplet 9 was divided into two parts, an optical element material 18 having a weight average of 228 mg and a glass element 9 having a weight average of 232 mg. An optical element material 19 was obtained.

In the present embodiment, as the device for dropping the glass droplet 9, the supply device of the first embodiment (a device provided with a mechanism for precisely controlling the weight of the glass droplet 9). Is used, but the present invention is not necessarily limited to this device, and a conventional device not provided with a mechanism for precisely controlling the weight of glass droplets may be used.

In this embodiment, the case where the glass droplet 9 is divided into two is described as an example. However, the present invention is not necessarily limited to the case where the glass droplet 9 is divided into two. The number of divisions can be arbitrarily selected. In this case, by disposing the same number of knife edges as the number of divisions radially, the glass droplet 9 can be divided into the same number of glass droplets as the number of knife edges. Specifically, when the glass droplet 9 is divided into three, as shown in FIG.
Two knife edges 17a, 17b, 17c
It may be arranged radially at an angle of 0 °. Also,
When dividing the glass droplet 9 into four, as shown in FIG. 6, four knife edges 17d, 17e, 17f, 17
g may be arranged radially at an angle of 90 ° to each other.

In this embodiment, the distance between the tip of the outflow nozzle 3 and the tip of the knife edge 17 is 200.
mm, but is not necessarily limited to this configuration. The tip of the outflow nozzle 3 and the knife edge 1
The distance from the tip of 7 can be set arbitrarily.

[0028]

As described above, according to the present invention,
Since the weight of the droplet can be precisely adjusted to the reference weight, an optical element material with high weight accuracy can be obtained.
In addition, since the weight of the droplet can be adjusted without increasing the temperature of the outflow nozzle, even when the molten glass contains a large amount of boric acid and alkali components, these components are evaporated by evaporation of the glass droplet. Formed on the surface of the optical element material, and the composition does not differ between the surface and the inside of the optical element material. For this reason, since a large stress does not remain in the optical element material, a precise glass lens can be manufactured. Further, since the weight of the glass droplet can be adjusted by adjusting the position of the tip of the droplet holding unit, it is not necessary to prepare a number of glass melting containers corresponding to the type of glass lens. This eliminates the need for complicated operations such as replacement of the glass melting container, thereby improving productivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a molten glass supply device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which the tip position of a droplet holding unit and the tip position of an outflow nozzle of the molten glass supply device according to the first embodiment of the present invention are the same.

FIG. 3 is a diagram illustrating a relationship between a tip position of a droplet holding unit and a weight of a droplet according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a manufacturing apparatus used for a method for manufacturing an optical element material according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing another arrangement of a knife edge used in the method for manufacturing an optical element material according to the second embodiment of the present invention.

FIG. 6 is a perspective view showing still another arrangement of knife edges used in a method for manufacturing an optical element material according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a conventional molten glass supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molten glass 2 Glass melting container 3 Outflow nozzle 4, 5 Heater 6 Plunger 7 Droplet holding part 8 Gap 9 Droplet 10 Fixed frame 11 Drive source 12 Light emitting device 13 Light receiving device 14 Control device 15 Separator 16 Base 17, 17a to 17g Knife edge 18, 19 Optical element material 20 Comparison circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Umetani 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masaaki Haruhara 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] An outflow nozzle is provided at a lower end of a glass melting vessel, and is a supply device of molten glass supplied by dropping molten glass from the outflow nozzle, the apparatus having a droplet holding portion at a tip end, and the outflow nozzle is provided. A plunger inserted through a nozzle with a predetermined clearance, a driving unit for moving the plunger up and down, a measuring unit for measuring the size of a spherical glass droplet flowing out to the droplet holding unit, and the measuring unit And a control means for controlling the driving means based on the measurement value obtained by the means. 2. A comparison circuit according to claim 1, further comprising a comparison circuit for comparing the measurement value obtained by the measurement means with the size of a glass droplet having a reference weight measured in advance and transmitting the comparison result to the control means as a comparison signal. Molten glass feeder. 3. A light emitting device provided below the outflow nozzle with a center axis of the outflow nozzle interposed therebetween for emitting laser light, and a measuring means for receiving the laser light emitted from the light emitting device. And a photodetector for the same.
A supply device for a molten glass according to claim 1. 4. A method for supplying molten glass which is supplied by dropping molten glass from an outflow nozzle provided at a lower end of a glass melting container, wherein the molten glass is inserted through the outflow nozzle with a predetermined clearance, and is supplied from an end of the outflow nozzle. A method for supplying molten glass, comprising: controlling the positional relationship between the tip of a droplet holding section of a protruding plunger and the tip of the outflow nozzle to adjust the weight of molten glass dropped. 5. A method for measuring the size of molten glass dropped,
5. The method for supplying molten glass according to claim 4, wherein the positional relationship between the tip of the droplet holding portion of the plunger and the tip of the outflow nozzle is controlled such that the measured dimension is substantially the same as the reference dimension. 6. A method for producing an optical element material in which a predetermined amount of molten glass is dropped from an outflow nozzle provided in a glass melting vessel, and the droplet is divided into a plurality of pieces by a separator provided vertically below the outflow nozzle. 7. The method for producing an optical element material according to claim 6, wherein a knife edge is used as the separator.