JPH01153538A - Production of optical element - Google Patents

Abstract

PURPOSE:To produce an optical element having excellent dimensional accuracy and weight accuracy free from surface defects by pressing glass fluid dropping from a nozzle by a pair of left and right molds, molding and cutting part to be molded from surplus part. CONSTITUTION:Glass fluid 2 having 10-10<7> poise viscosity is dropped from a flow nozzle 1 of a glass melting furnace. At a point of time when a cut mark 3 of the fluid 2 flows down lower than molding aces 5a and 6a of a pair of left and right molds 5 and 6, pressing functioning of the molds 5 and 6 is started. Simultaneously functioning of a cutting blade 4 is started and cutting of the fluid 2 is started in the vicinity of the flow position of the nozzle 1. After pushing functioning of the molds 5 and 6 on the fluid 2 is started, a cutting ring 7 is operated, cutting of the fluid 2 by the ring 7 is completed simultaneously with completion of cutting of the fluid 2 by the cutting blades 4, part 21 to be molded is separated from cut pieces 22 and the part 21 to be molded is press molded by the molding faces 5a and 6a of the molds 5 and 6.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing an optical element by press molding, and more specifically, to improve surface accuracy without undergoing processes such as grinding and polishing after press molding. The present invention also relates to a method for manufacturing an optical element with good l-plane accuracy or a preform suitable for reheat pressing thereof.

(Prior art) In recent years, a method of molding high-precision optical elements that eliminates the need for post-processing such as grinding and polishing has been developed by housing a glass material in a mold with a predetermined surface accuracy and press-molding it. is being developed.

This press molding method generally includes a reheat press method and a direct press method.

In the reheat press method, the necessary amount of glass material that has been melted and solidified in advance is cut, the weight is adjusted using methods such as sanding, and the resulting glass pellets are placed in a mold for molding. This is a method of molding an optical element by heating the molds simultaneously or separately to a pressing temperature, and then pressing and transferring the optical functional surface formed on the mold by press molding.

On the other hand, in the direct press method, the necessary amount of molten glass flowing out or extruded from a molten glass outflow orifice is cut by a cutting blade, and the cut is directly dropped into a mold or charged into a chute, and then molded. This is a method of molding an optical element by pressing a mold.

In addition, in the above reheat press method, molten glass is put into a mold and press-formed into a final product, as in the above direct press method, without going through low productivity steps such as cutting and sanding. Preformed products with similar shapes (
There is a method in which press molding is performed by obtaining a preform and placing the preform into a mold having an optically functional surface with the same or higher precision than the shape and surface precision of the final product.

(Problems to be Solved by the Invention) Optical elements obtained by these molding methods are required to have predetermined surface accuracy and dimensional accuracy in order to obtain good image forming quality, and for this reason, neither of the above methods Also, the weight of the glass material supplied to press molding to obtain the final product must be sufficiently adjusted.

However, in the above-mentioned method of press molding using small glass lumps, the weight of the small glass lumps is adjusted by cutting, sanding, etc., so that grains may remain on the surface of the molded product.
When heating a small glass lump before press molding, the mold release agent applied to prevent the glass and the heating tray from fusing together bites into the surface of the molded product during pressing, significantly deteriorating the surface precision of the molded product. There is a problem with doing so.

In addition, in the method of press forming directly using molten glass,
When cutting with a cutting blade, cutting marks called shear marks are generated on the molded product, which causes a problem in that the surface precision of the molded product deteriorates. In addition, in this press molding method, the weight of the molded product is adjusted by cutting the molten glass flow, so weight fluctuations occur in the molded product due to temperature changes in the molten glass flow, cutting timing, pulsation of the glass flow, etc. There is also the problem that a predetermined dimensional accuracy cannot be obtained.

In addition, as a press molding method that particularly prevents the occurrence of shear marks, Japanese Patent Publication No. 41-9190 or Japanese Patent Application Laid-open No. 6
There is one described in Publication No. 1-132523.

In the molding method described in Japanese Patent Publication No. 41-9190, press molding is performed by pressing a mold in a direction perpendicular to the direction of flow of molten glass to fill the mold cavity with molten glass. When the mold is pressed, a phenomenon occurs in which excess glass in the mold cavity flows out from between the mold and the anvil facing the mold. As the pressing operation of the mold progresses, this excess glass increases its outflow resistance and is cooled by the mold, increasing its viscosity, until it is completely cut off between the mold and the opposing anvil. The molded product is cooled without being completely wet, and a protruding portion is formed on the outer periphery of the molded product. Therefore, after press forming, it is necessary to break the protruding portion and finish the broken surface. Furthermore, due to variations in the size of the molten glass flow, the glass thickness between the above-mentioned molded product and the protruding portion changes, causing variations in the thickness of the molded product, making it difficult to adjust the weight with high precision. There is also the problem of not having one.

On the other hand, in the molding method described in JP-A No. 61-132523, the accuracy of the molded product depends on the size of the flowing glass body before punching it, and highly accurate dimensions and shapes can be produced. A rod or glass sheet is required.

In order to solve the above-mentioned problems, the present inventors have already proposed a method for manufacturing an optical element in which the molded product is free from surface defects such as sha marks and has excellent dimensional and weight accuracy.

The present invention relates to this manufacturing method, and in particular proposes a method for manufacturing an optical element in which a glass fluid continuously flowing down from an outflow nozzle of a melting furnace is supplied in good condition during press molding.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the method for manufacturing an optical element of the present invention includes a pair of left and right molding molds sandwiching a glass fluid flowing down from an outflow nozzle of a glass melting furnace. After forming a molded part by pressing the glass fluid with the mold, a cutting member provided on the outer periphery of the mold is operated to separate the molded part and other parts. In the method for manufacturing an optical element, in which the glass fluid is cut and separated near the outflow position of a nozzle, the glass fluid is cut at the same time as the cutting member cuts and separates the molded part from other parts. It is characterized by being before that.

(Function) In the method for manufacturing an optical element configured as described above, 1
When the left and right mold members constituting a pair of molding molds are referred to as a first mold member and a second mold member, these mold members face each other in a substantially perpendicular direction through the glass fluid flowing down from the outflow nozzle of the melting furnace. It can be arranged as desired. That is, it is possible to adopt a structure in which each mold member is pressed against each other from a direction substantially perpendicular to the flow direction of the glass fluid, and by adjusting the timing of pressing each mold member against the glass fluid. , it is possible to form a molded part while avoiding the tip of the glass fluid, that is, the cutting trace.

The wall thickness of the part to be molded is determined by setting the cavity of the mold in advance. This cavity can be set by making the distance between molding surfaces of the opposing mold members during press molding correspond to the distance between functional surfaces of a desired optical element.

When a sufficient volume of glass fluid is supplied between each mold member during press molding, the excess glass generated when each mold member is pressed freely flows out of the molding surface, and the wall thickness of the molded product is adjusted to the above molding level. Determined by the mold cavity.

After pressing the glass fluid with each mold member to form a molded part, the molded part and other surplus parts are cut and separated by operating a cutting member provided on the outer periphery of the mold. The shape of the outer peripheral side surface of the molded part is formed.

Furthermore, by cutting the glass fluid that is continuously flowing from the melting furnace near the outflow position of the nozzle before the cutting operation for the part to be formed is completed, the glass capacity required for the next press forming can be reduced. Stable supply.

This point will be further explained with reference to FIG. FIG. 1O shows an example in which a mold according to the present invention is formed on the molten glass flowing out from the melting nozzle l. FIG. 10(A) shows an ideal flow situation of the glass fluid 2 flowing out from the nozzle 1, and FIG. FIG. 3 is a cross-sectional view of the vicinity of the mold, showing a situation when the part to be molded 21 is cut by the member 7; 1
FIG. 0(C) is a cross-sectional view of the vicinity of the mold when the glass fluid 2 is cut near the outflow position of the nozzle 1 before cutting the part to be formed 21.

In press molding, when forming the molded part 21 by pressing each mold member against the thickened part of the glass fluid shown in Fig. A, the necessary steps for press molding are performed. Glass capacity will be secured. However, as shown in Figure B, if the part to be formed 21 is cut by the cutting member 7 before the glass fluid 2 is cut by the cutting blade 4 near the outflow position of the nozzle 1, the glass fluid 2 will not reach the outlet of the nozzle l. As the cutting member 7 moves while still connected, it is pushed toward the first mold member 5, making it impossible to supply a stable glass fluid during the next molding.

On the other hand, as shown in Fig. 6, if the glass fluid 2 is cut near the outflow position of the nozzle 1 before cutting the part 21 to be formed by the cutting member 7, the glass fluid 2 becomes stable again with a thickened tip as shown in Fig. A. is obtained.

The present invention eliminates the above-mentioned disadvantages by cutting the glass fluid near the outflow position of the nozzle before cutting the molded part with the cutting member, thereby obtaining the glass fluid with a thick tip as shown in Figure A. are doing.

Moreover, by doing this, the glass fluid is in a separated state at the time when the cutting operation of the cutting member is completed,
The excess glass cut off by the cutting member can be easily transferred from one mold member provided with the cutting member to another mold member.

The thus obtained molded product is formed from a portion that does not contain cut marks of glass fluid supplied in a good condition as described above, so it has no surface defects such as shear marks and has a well-defined cavity. By forming the outer periphery of the part to be molded using a y-cutting member and press-forming the glass fluid supplied in good condition, a molded product with highly accurate volume t′ and gravity φ adjustment can be obtained. It will be done.

In addition, since the functional surface of this molded product is formed by transferring the molding surface of each mold member, the surface texture of each molding surface can be made with high precision equal to or higher than that of the desired molded product. By finishing the product and press-molding it, a molded product with high-precision functionality can be obtained.

Note that the viscosity of the glass fluid in the present invention is 10 to 10
7 poise is preferred. When the glass viscosity is lower than 10 poise, the glass flow becomes filamentous and the required glass capacity within the mold cavity becomes insufficient.On the other hand, when the glass viscosity is higher than LO7 poise, the glass flow becomes filamentous and the required glass capacity within the mold cavity becomes insufficient. It becomes difficult to cut the glass. Note that the optimum viscosity of these glass fluids is 103 to 105 poise.

In addition, the temperature of the mold is 100°C lower than the glass transition point (hereinafter referred to as Tg, which corresponds to about 1013 in terms of glass viscosity) from a temperature that corresponds to 108 Boas in terms of glass viscosity (Tg-100). It is necessary to set it within the range of (℃). If the mold temperature exceeds a temperature corresponding to 108 poise, the hardness of the glass surface in the molded part after press molding until cutting is slow, and when the outer periphery of the molded part is cut and formed, Predetermined shape accuracy and surface accuracy cannot be obtained. In addition, the molding surfaces of the glass and the mold tend to fuse, which is undesirable.On the other hand, if the mold temperature is lower than Tg-100°C, it will not only be difficult to cut the outer periphery of the molded part, but also difficult to cut. There is a risk of cracking in some parts.

The temperature of the cutting member is preferably equal to the mold temperature of the mold, so that the influence of temperature changes on the glass is similar to that of the mold.

Furthermore, the viscosity when taking out the molded product is 108 when this molded product is used as a preform for reheat press.
It is sufficient to cool it until the viscosity becomes less than Poise, but
When used as is for optical lenses, etc., it can be used as an optical element with good shape accuracy and surface accuracy by cooling it in a mold while applying pressure and taking it out when the viscosity reaches about 1Q14.5 poise. can do.

Note that the press molding and subsequent cutting treatment in the present invention are preferably performed in a non-oxidizing atmosphere in order to maintain the life of the mold and cutting member.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a press molding apparatus used in an embodiment of the present invention.

In FIG. 1, 1 is a nozzle through which molten glass flows out from a melting furnace (not shown), 2 is a glass fluid flowing out from this nozzle, and 3 is a cut mark produced at the tip of the glass fluid 2.

4 is provided near the bottom of the nozzle 1, and a drive wave (not shown);
This is a cutting blade that cuts the glass fluid 2 by opening and closing the blade. When the cutting blade 4 operates and the crow fluid 2 is cut midway, a cutting mark 3 is generated.

The press molding apparatus shown in this embodiment is configured to allow the glass fluid 2 to flow down from the nozzle 1.
A first mold member 5 and a second mold member 6 constituting a pair of molding molds are arranged to face each other so as to narrow the glass fluid 2 from a substantially right angle direction. Each mold member 5, 6 is
Molding surfaces 5a and 6 whose opposing surfaces are mirror-finished
It has a.

The first mold member 5 is held by the slider 14.

This slider 14 is slidably supported by a slide shaft 18. Reference numeral 16 denotes a cylinder for driving the slider/f goo 14, and the operation of this cylinder 16 causes the slider 14 to move in the sliding direction of the slide shaft 18, thereby suppressing the first mold member 5.

On the other hand, the second mold member 6 is connected to a cylinder 13 via an adapter 12, and the operation of the cylinder 13 causes the second mold member 6 to be suppressed.

The cavity formed by each molding surface 5a, 6a of these mold members 5, 6 can be set by the stroke of each cylinder 13.degree. 16.

Further, a cutting ring 7 having a cutting blade formed on the first molding member 5 side is provided on the outer periphery of the second molding member 6, and this cutting ring 7 is slidably supported by the slide shaft 18. The slider 15 is connected to the slider 15. Further, the slider 15 is connected to a cylinder 17, and this cylinder 1
7 allows the cutting ring 7 to slide around the outer periphery of the mold member 6 of said ft 52 in a movement independent of the second mold member 6.

Furthermore, a heater 8.9 is provided inside each mold member 5.6. 10 and 11 are conductive wires connected to each heater. 19 is the base of the entire device, which firmly supports the cylinders 13, 16, 17 and the slide shaft 18.

Next, the operation of this apparatus will be explained using FIGS. 2 to 7 and FIG. 8.

FIGS. 2 to 7 are sectional views of essential parts showing the operating state of the apparatus in each process order. FIG. 8 is a timing chart showing the operation timing of each part of the operating parts of this device, that is, the first mold member 5, the second mold member 6, the cutting blade 4, and the cutting ring 7, and the horizontal axis represents time T. The operation timings of these actuating parts shown can be controlled by a controller (not shown) connected to each actuating part.

FIG. 2 shows the state immediately before press molding, with glass fluid 2 flowing down from nozzle 1. At the point when the tip of the glass fluid 2, that is, the cutting mark 3 flows downward from each opposing molding surface 5a, 6a, the first mold member 5 and the second mold member 6
starts suppressing operation. In FIG. 8, T=O indicates the timing at which both mold members 5 and 6 start operating. These mold members 5,
6 may be started at the same time on both sides, but it is preferable that the end time T2 of the pressing operation of the mold members 5 and 6 against the glass fluid 2 is at the same time on both sides or within an error of ±0.05S at most. If this error is large, only one side of the mold member 5.6 collides with the glass fluid 2, causing lateral vibration in the glass fluid 2, which is undesirable.
As shown in FIG. 3, the state in which the glass fluid 2 is pressed against the molded part 21 is maintained for a predetermined period of time (72 to T6), and during this time the respective molding surfaces 5a are applied to both surfaces of the molded part 21.

Pressure transfer by 6a is performed.

The operation start time of the cutting blade 4 may be the same as the operation start time T=O of the mold member 5.6, but when the cutter blade 4 finishes cutting the glass fluid 2, the member 5.6 is already in the glass. At the same time as, or at least after, the fluid 2 is retained, the cutting blade 4 is then returned to its original state. In FIG. 8, the return start time of the cutting blade 4 is shown as T1, and the return end time is shown as T5. Preferably, from the operation start time T=O of the cutting blade 4 to the cutting end time T? The time required for this is set to 0.3 to 0.45.

During this time, the glass fluid 2 cut by the cutting blade 4 near the outflow position of the nozzle 1 as described above continues to flow out as the glass fluid 2 with a thick tip as shown in FIG. is supplied to

As shown in FIG.
3) Cutting of the glass fluid 2 by the cutting blade 4 is completed before (T
2) It is necessary to set it so that it is in the following state. By doing so, the glass fluid 2 after cutting flows out from the nozzle 1 again in a stable tapered shape and is supplied to the next booth molding. Further, at the time when the cutting operation of the 9J cutting ring 7 is completed, the glass fluid 2 has already been cut off by the cutting blade 4, and the cut piece 22 cut by the cutting ring 7 is easily cut into the first mold member 5. Can move outward.

In this way, the cutting ring 7 cuts the outer periphery of the molded part 21 while sliding along the outer periphery of the second mold member 6, thereby forming the shape of the outer peripheral side surface of the molded part 21. Thereafter, the cutting ring 7 maintains the state at the end of cutting (T3), and the part to be formed 2
The molded part 21 is cooled from the outer periphery by the temperature difference while holding the outer peripheral side surface of the molded part 21, and the vicinity of the outer periphery of the molded part 21 increases in viscosity and its shape is fixed. On the other hand, after being pressed by the mold members 5 and 6, the molded part 21 is cooled from both surfaces due to the temperature difference between the mold members and the molded part 21, increasing its viscosity and stabilizing its surface shape. Next, first, as shown in FIG. 6, the first mold member 5 is returned to its original state. Assuming that the operation start time is T6, the operation end time is T7, and the start time for returning the cutting ring 7 to its original state is at the same time as or after the return end time T+ of the first mold member 5, the cutting ring 7, the part to be formed 21 is held by the cutting ring 7 and does not fall off naturally.

Then, at the same time as the return completion time T8 of the cutting ring 7, the part to be molded, that is, the molded product 23 is taken out. This can be done using a known suction hand or the like. After this removal operation is completed, the second mold member 6 is returned to its original state. In FIG. 8, the return start time of the second mold member 6 is shown as T9, and the return end time is shown as TIG. Regarding the return operation of the second mold member 6, considering that the glass fluid 2 cut by the cutting blade 4 continues to flow out as described above, this glass fluid 2 is returned to the second mold member 6. It is necessary to take the timing to start the return of the second mold member 6 before contact is made.

Note that if the cutting ring 7 is returned to its original state before taking out the molded product 23, the molded product 23 will be released from the hold of the cutting ring 7 and will fall naturally, as shown in FIG.

In the above-described operation, press forming by the molding dies 5 and 6 is performed on the tip of the glass fluid 2, that is, the portion excluding the cut marks 3, so that the resulting molded product 23 has surface marks such as shear marks. No defects occur.

In addition, since the portion of the fluidized glass fluid 2 where the molded portion 21 is formed is supplied with a tapered tip, sufficient glass volume is secured for press molding, and the glass fluid 2 is supplied with a tapered shape as seen in the tapered glass fluid. Non-uniformity in the shrinkage layer due to rapid cooling is less likely to occur.

The cavity formed by the molds 5, 6 can be set by the stroke of each cylinder 13, 16. That is, by the set stroke of the cylinder 13, 16, the mold 5.
6 is determined. Since the wall thickness of the molded product 23 is determined by the distance between the molded surfaces, the cylinder
By setting the strokes 13 and 16 according to the thickness of the molded product 23 to be manufactured, a molded product always having a predetermined thickness can be obtained. The surface shape and properties of the molded product 23 are the molded surfaces 5a of each molded member 5.6.

6a. Furthermore, the outer peripheral shape of the molded product 23 is determined by the inner peripheral shape of the cutting ring 7, and the lino cutting ring 7
At the same time as the cutting operation, the outer periphery of the molded product 21 is formed.

Next, a specific example using the press molding method as described above will be described with reference to FIGS. 1 to 8.

(Example 1) Optical glass SF8 (
Tg=443℃, specific gravity 4.22), outer diameter 20m
m, center wall thickness 2.711 layers, edge thickness 1.29 mm, curvature R1 = 20 mm, R2 = 40 am, glass capacity 0
．． A reheat press preform having a convex meniscus shape and weighing 1 cc and 2.88 g was molded.

The mold members 5 and 6 are made of 5US420J, and the respective molding surfaces 5a and 6a are polished to optical mirror surfaces. This mold member 5
, 6 mold temperature is 400℃ (SF8 Tg = 443℃, 4
Heat with heaters 8 and 9 until the temperature is 3°C lower.

Further, the stroke of the cylinder 13.16 is adjusted so that the maximum width of approach during the pressing operation of each mold member 5.6 is 2.7 cm, so that the desired wall thickness can be obtained.

First, glass melted in a melting furnace (not shown) is heated to a glass fluid 2.
The viscosity of the mixture was adjusted to about 1046 poise (815°±5°C), and the mixture was discharged from nozzle 1. Next, as shown in FIGS. 2 and 3, there is a cut mark 3 at the tip of the glass fluid 2.
When the liquid flowed down from each molding surface 5a, 6a of the mold member 5.6, the cylinder 13.16 was actuated, and at the same time, the cutting blade 4 was also actuated. The operating pressures of the cylinders 13 and 16 are 120 kg and 300 kg, respectively, and the operating speeds of both cylinders are 200 mta/s.

Then, as shown in FIG. 3, after the suppression operation of the mold member 5.6 against the glass fluid 2 is started.

Activate the cutting ring 7. The cutting ring 7 is made of SK3, and is controlled in advance by a controller (not shown) so that the time from the time when the pressing operation of the mold members 5 and 6 is completed until the cutting by the cutting ring 7 is completed is 0.2 seconds. The cylinder 1 that drives this cutting ring 7 adjusts the operation timing of each cylinder 13° 16.17.
The working pressure of 7 is lookkg, and the working speed is 200m
Maro/S Toshishita. Further, as shown in FIG. 5, when the cutting operation by the cutting ring 7 is completed, the cutting of the glass flow 2 by the cutting blade 4 is also completed. Further, as shown in the figure, the cutting operation of the cutting ring 7 forms the outer peripheral shape of the part to be formed 21 and at the same time separates the part to be formed 21 and the cut piece 22.

In FIG. 5, the first mold member 5 and the cutting ring 7 are in an engaged state, but the cutting condition was good even when the two were only in contact with each other.

Next, while applying pressure to the cylinders 13 and 18, the state shown in FIG. As shown in FIG. 6, only the cylinder 16 was operated and the first mold member 5 was separated from the molded product 23. At this time, the molded product 23 remains held in the cutting ring 7 so that it does not fall off by itself.Next, the cylinder 17 is activated to pull back the cutting ring 7, and at the same time, the molded product 23 is taken out by a handling device (not shown). cylinder 13
is operated to return the first mold member 6 to its original position, and the cut piece 22 is removed by a cut piece removing device (not shown).

Thus, the molded article 23 obtained in this example has an outer diameter accuracy of ±0.0 G5 rinm, a center wall thickness of ±0.01 m, and a weight of 0.02 g (±0. 7%
), no harmful surface defects such as shear marks have occurred, and sink marks are also within 5 and 6 of each mold member.
It can be used not only as a preform for reheat press, but also as a preform for reheat press.
It could be used satisfactorily as an optical lens that does not require much precision.

FIG. 9 is a graph showing temporal changes in temperature of the first mold member 5, the second mold member 6, and glass as the material to be molded in this embodiment. Incidentally, in this explanation, the time T shown in FIG. 8 is used.

Initially (T=O in FIG. 8), the first and second mold members 5 and 6 were adjusted to 400° C., which is 43° C. lower than the glass transition point Tg of the glass material (Tg of SF8=443° C.). Further, a glass fluid 2 flowing from the nozzle 1 shown in FIG.
The viscosity was adjusted to be approximately 1046 boads (815°±5°C).

During the molding period (approximately 10 seconds) from the end time T2 of the suppression operation of the mold members 5 and 6 to the start time T6 of the return operation,
The glass in the molded part 21 is rapidly cooled due to the temperature difference between the mold members 5.6, and its viscosity varies from 1046 Boaz to 1Q14.
It will be 5 poise or more. In this embodiment, the mold member 5,
6 are heated by heaters 8 and 9, respectively, so as to be maintained at 400° C. until the end of the suppression, and at this time, the glass temperature of the molded product 23 becomes approximately the same temperature as the mold members 5 and 6.

(Example 2) In this example, optical glass F8 (Tg=445
Using molten glass with a specific gravity of 3.36) and an outer diameter of 6 mm, a center wall thickness of 4 mm, and an edge thickness of 3.08 mm, the same method as in Example 1 was used.
m, curvature R1=R2=10 countries, glass volume i0.1
A double-convex preform for reheat press with a weight of 1,337 mg and a weight of 1,337 mg was molded.

In this example, the same mold members 5 and 6 as in Example 1 were used, and the A of the heater 8.9 was adjusted so that the mold temperature was 375°C (70°C lower than the F8 Tg of 445°C). .

Moreover, the viscosity of the glass fluid 2 is 1Q2.95 to 103.1 poise (108
0°C to 1050°C).

Then, set the operating pressure of each cylinder 13, 16, 17 to 50 kg, 200 kg, 50 kg,
Press molding and cutting were performed in the same manner as in Example 1, and the internal viscosity of the molded product 23 was 109 poise (approximately 540°
When the molded product 23 reached C), it was taken out from the second mold member 6, and the obtained molded product 23 had an outer diameter accuracy of ±0.01 mm, a center thickness of ±0.02 mm, and a center thickness of ±0.02 mm relative to the desired molded product. The weight variation is within ±3 mg (±0.9%), and the sink mark at the center of the surface is about 40 gm on average, and the surface condition is good and the precision is such that it can be used as a reheat press preform. Met.

(Effects of the Invention) As explained above, according to the present invention, the following effects occur.

(1) A stable and sufficient amount of glass capacity is supplied during press molding, there are no surface defects such as shear marks on the surface of the molded product, and optical elements such as optical lenses or preforms for reheat press with high dimensional and weight accuracy can be manufactured. It can be manufactured without any post-processing such as grinding or polishing after press molding.

(2) Since the precision of the glass fluid used for molding is not required, an inexpensive device for discharging the molten glass etc. is required, and high technology is not required. Also, the flow of the discharged glass due to fluctuations in the glass liquid level in the melting furnace Since the melting furnace is flexible with respect to layer and temperature changes, the melting furnace can also be inexpensive.

(3) Since the glass fluid is directly press-molded and cut, small and thin molded products, which were conventionally difficult to press-form, can be easily produced with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a press molding apparatus showing an embodiment of the present invention. FIGS. 2 to 7 are sectional views of main parts of the apparatus shown in FIG. 1, and show the operating state of the same mounting process. FIG. 8 is a diagram showing a timing chart of each operating section of the press molding apparatus shown in FIG. 1. FIG. 9 is a graph showing temporal changes in temperature of the mold member and glass during press molding in the first example. FIG. 1O is a diagram showing a flow situation of glass fluid flowing out from a nozzle. l... Nozzle 2... Glass fluid 3... Cutting mark 4... Cutting blade 5... First die member 6... Second die member 7... Cutting ring 21... - Molded part 22... Cut piece 23... Molded product! (Personal Patent Attorney Minoru Yamashita Figure 1 Figure 2 Figure 3r\I - Figure 4 Figure 5 Figure 6 Figure 70 Figure 8 1+ 12 13 - r415 Figure 9 (A) Figure 10 (C )

Claims (3)

[Claims] (1) A pair of left and right molding molds are arranged facing each other across the glass fluid flowing down from the outflow nozzle of the glass melting furnace, and after pressing the glass fluid with the molding molds to form a molded part, the molding In the method for manufacturing an optical element, the method comprises: operating a cutting member provided on the outer periphery of a mold to cut and separate the part to be molded from other parts, and cutting the glass fluid near an outflow position of a nozzle; A method for manufacturing an optical element, characterized in that the cutting time is at the same time as or before the cutting and separation of the molded part and other parts by the cutting member. (2) The method for manufacturing an optical element according to claim 1, wherein the glass fluid has a viscosity of 10 to 10^7 poise. (3) The glass fluid is heated at a temperature corresponding to a glass viscosity of 10^8 poise and a glass transition point (about 10^1 in glass viscosity).
2. The method for manufacturing an optical element according to claim 1, characterized in that pressure molding is carried out using a mold at a temperature 100° C. lower than 3 poise.