JPH01145337A - Production of optical element - Google Patents

Abstract

PURPOSE:To facilitate the production of an optical element having high dimensional and weight accuracy and free from surface defects such as shear mark, by directly pressing molten glass while cutting the fluid glass simultaneous to the cutting and separation of the formed part. CONSTITUTION:A fluid glass 2 flowing down through an outlet nozzle 1 of a glass-smelting furnace is pressed with a pair of molds 5, 6 at the tip end of the glass, i.e. at a time when the cut end 3 is flowed down beyond each forming surface of the oppositely arranged forming molds 5, 6. A forming part 21 is formed by this process. Thereafter, a cutting ring 7 placed around the mold 6 is operated to cut and separate the forming part 21 from the other parts and, at the same time, the fluid glass 2 is cut at a part near the outlet position of the nozzle 1 with a cutting edge 4 placed near the lower face of the nozzle 1. An optical element 23 can be produced by this process as a molded article separated from a cut piece 22.

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 producing an optical element with good Ill accuracy or a preform suitable for reheat pressing thereof.

(Prior Art) In recent years, a glass material is housed in a mold having a predetermined surface accuracy and then press-molded.

Methods have been developed for molding high-precision optical elements that do not require post-processing such as grinding and polishing.

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. Preforms 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.

(Problem to be solved by the invention) Optical elements obtained by these molding methods.

A certain level of surface accuracy and dimensional accuracy are required to obtain good image formation quality, and for this reason, in any of the above methods, the glass material supplied for press forming to obtain the final product must be sufficiently weight-controlled. must be done.

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 accuracy 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 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. 8
1-132523.

There is something that was lost.

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 suppression action 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. Additionally, 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 accurately adjust the thickness. There is also the problem of not being able to do it.

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 rondo 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. The method is characterized in that the glass fluid is cut and separated and the glass fluid is cut near the outflow position of the nozzle.

(Function) In the method for manufacturing an optical element configured as described above, 1
Assuming that the left and right mold members constituting the pair of molding molds are the wSl mold member and the second mold member, these mold members face each other approximately at right angles through the glass fluid flowing down from the outflow nozzle of the melting furnace. It can be placed 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 molding surface spacing of the opposing mold members during press molding correspond to the al+1@plane spacing of the 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 flows continuously from the melting furnace in the vicinity of the nozzle outflow position along with this cutting operation on the part to be formed, the glass capacity required for the next press forming can be improved. Supplied.

This point will be further explained with reference to FIG. The M2O diagram is a diagram showing a flow situation of glass fluid flowing out from a nozzle.

Figure 10 (A) shows the glass fluid 2 flowing out from the nozzle l.
This shows an ideal flow situation. Press molding is a process in which mold members are pressed against each other to form a molded part (indicated by 21 in Figure B) against the thickened part of the glass fluid as shown in Figure A. , the glass capacity necessary for the press molding is ensured.

Next, during this press forming, as shown in FIG. 10(B), if the glass fluid 2 is cut near the outflow position of the nozzle 1, a tapered tip as shown in FIG. 10(A) can be obtained again. A glass fluid is obtained.

However, if the glass fluid 2 is not cut off near the outflow position of the nozzle l after press forming as described above, the problem shown in FIG.
As shown in C), the glass fluid 2 flowing out from the nozzle 1
The glass gradually stretches under its own weight and flows down from the vicinity of the outflow position of the nozzle 1 in a thin stream, making it impossible to obtain the glass capacity necessary for press molding.

Also, if the glass fluid becomes tapered as described above,
This is because it is easily affected by thermal changes, and the shrinkage layer created by being cooled by the outside air becomes uneven.

Molded products are more likely to have sink marks.

The present invention cuts the glass fluid near the outflow position of the nozzle before the glass fluid stretches under its own weight.
A glass fluid with a thick tip as shown in Figure (A) is obtained, and the above-mentioned disadvantages are solved.

As mentioned above, the molded product thus obtained is formed from a part that does not contain cut marks of the glass fluid, so there are no surface defects such as shear marks, and the outer periphery of the molded part by the set cavity and cutting member is not affected. By forming and press-molding the glass fluid supplied in good condition, a molded product whose volume and weight can be adjusted with high precision can be obtained.

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 the surface texture 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 107 poise, the glass flow becomes filamentous and the required glass capacity within the mold cavity is insufficient.On the other hand, when the glass viscosity is higher than 107 poise, 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 JO & molding mold ranges from a temperature corresponding to 108 poise in terms of glass viscosity to 100 points below the glass transition point (hereinafter referred to as Tg, which corresponds to approximately 1013 in terms of glass viscosity).
It is necessary to set it within the range of (lower temperature CTg - 100°C). 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. Also, the molding surfaces of the glass and the mold tend to fuse, which is undesirable.On the other hand, when the mold temperature is Tg-1oo'
When cutting the outer periphery of the part to be formed, if it is lower than c.

Not only will it be difficult to cut, but there is a risk that cracks will occur at the cut portion.

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 at the time of taking out the molded product is to
It can be used as long as it is cooled to a viscosity of 1Q14.5 poise or higher, but if it is used as is for optical lenses etc., it should be cooled in a mold with pressure applied and removed when the viscosity reaches 1Q14.5 poise. Then, it can be used as an optical element with good shape accuracy and surface accuracy.

It is desirable that the press molding and subsequent cutting treatment in the present invention be carried out 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.

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

In Fig. 1, ■ is a nozzle (not shown) that flows out the molten glass from the melting furnace, 2 is the glass fluid flowing out from this nozzle, and 3 is the cut mark created at the tip of the glass fluid 2. It is.

Reference numeral 4 denotes a cutting blade which is provided near the bottom of the nozzle l and which cuts the glass fluid 2 by opening and closing operations by a drive device (not shown). When the cutting blade 4 operates and cuts the glass fluid 2 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 a slider 14, which is slidably supported on a slide shaft 18. 16 is a cylinder that drives the slider 14, and the operation of this cylinder 16 causes the slider 1 to move.
4 moves in the sliding direction of the slide shaft 18 to press 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 pressed.

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 side of the first mold member 5 is provided on the outer periphery of the second mold member 6, and this cutting ring 7 is slidable on the slide shaft 18. It is connected to a slider 15 supported by a lever. Furthermore, the slider 15 is connected to a cylinder 17 whose actuation allows the cutting ring 7 to slide around the outer periphery of the second mold part 6 in a movement independent of the second mold part 6. .

Additionally, heaters 8 and 9 are provided inside each mold member 5 and 6. 10 and 11 are conductive wires connected to each heater. 19 is the base of the entire water 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 one 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 the pressing operation. In FIG. 8, T=O indicates the timing at which both mold members 5 and 6 start operating.
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 member 5.6 against the glass fluid 2 is at the same time on both sides or within an error of at most ±0.055. If it is too large, only one of the mold members 5 and 6 will collide with the glass fluid 2, causing lateral wobbling in the glass fluid 2, which is undesirable.
As shown in the figure, 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.

6a performs pressure transfer.

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 the time T2 when the cutting blade 4 finishes cutting the glass fluid 2 is when the mold member 5.6 is made of 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 T4, and the return end time is shown as T5. Preferably, the time required from the operation start time T=O of the cutting blade 4 to the cutting end time T2 is set to 0.3 to 0.4S. During this time, the cutting blade 4 is placed near the outflow position of the nozzle l as described above.
The cut glass fluid 2 continues to flow out into the glass fluid 2 having a thick tip as shown in FIG. 2, and is supplied to the next press molding.

As shown in FIG. 5, the operation start timing TI of the cutting ring 7 is such that the cutting blade 4 finishes cutting the glass fluid 2 (T2) at least before the cutting ring 7 finishes cutting the outer periphery of the molded part 21 (T3). It is necessary to set it so that it is in the same state. By doing this, when the cutting operation of the cutting ring 7 is completed, the glass fluid 2 is already cut off by the cutting blade 4, and the cut piece 22 cut by the cutting ring 7 is easily attached to the first mold member. 5 can be moved 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), cools the molded part 21 from the outer periphery due to the temperature difference while holding the outer peripheral side surface of the molded part 21, and cools the molded part 21 from the outer periphery. The viscosity increases in the vicinity and the shape becomes 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 TI, and the start time for the cutting ring 7 to return to its original state is at the same time as or after the return end time T7 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 well-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 TIO. 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, the glass fluid 2 flowing into the glass fluid 2 is supplied with a thicker tip at the portion where the molded portion 21 is formed.

Sufficient glass capacity is ensured for press molding, and non-uniformity in the shrinkage layer due to cooling, which occurs with tapered glass fluids, 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, due to the set strokes of the cylinders 13 and 16, the molding die 5 at the pressing end time T2,
6 is determined. The wall thickness of the molded product 23 is determined by the distance between the molding surfaces. Therefore, by setting the stroke of the cylinder 13, 16 according to the wall thickness of the molded product 23 to be manufactured, a predetermined wall thickness can always be maintained. A molded article having the following properties is obtained. The surface shape and properties of the molded product 23 are the molded surfaces 5a of the molded members 5 and 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 outer periphery of the molded product 21 is formed simultaneously with the cutting operation of the cutting ring 7.

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

(¥Example 1) Optical glass 3F8 usually used for camera lenses, etc. (
Tg=443℃, specific gravity 4.22), outer diameter 20m
Layer, center thickness 2.7 mm, edge thickness 1, 29 m layer, curvature R1 = 20 m, R2 = 40 m, glass capacity 0.8
A convex meniscus-shaped glue preform for heat press with a volume of 38 cc and a weight of 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
．． The mold temperature of 6 is 400℃ (Tg of SF8 is 443℃, so 4
Heat with heaters 8 and 9 until the temperature is 3°C lower.

In addition, the maximum approach width when the stroke of the cylinder 13.16 is suppressed by each mold member 5, 6 is 2.71 mm.
Adjust so that the desired thickness can be obtained.

First, glass melted in a melting furnace (not shown) is heated to a glass fluid 2.
The glass fluid 2 was adjusted to have a viscosity of approximately 1046 boads (815°±5°C), and was flowed out from the nozzle 1. As shown in FIGS. 2 and 3, there are cut marks at the tip of the glass fluid 2. 3
When the molding surfaces 5a, 6a of the mold members 5, 6 flowed downward, the cylinders 13, 113 were activated, and at the same time, the cutting blade 4 was activated. This cylinder 13.16
The operating pressures are 120 kg and 300 kg, respectively, and the operating speeds are 200 m++/s for both.

Then, as shown in FIG. 3, after the pressing operation of the mold members 5 and 6 against the glass fluid 2 is started, the cutting ring 7 is activated. The cutting ring 7 is made of SK3, and the time from the time when the pressing operation of the mold member 5.6 is completed until the cutting by the cutting ring 7 is completed is 0.2.
5 for each cylinder with a controller (not shown).
The operating pressure of the cylinder 17 that drives this cutting ring 7 is adjusted to the operating timing of 3°16.17.
00kg, and the operating speed is 2001131/3. 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. Furthermore, as shown in the same figure, the outer peripheral shape of the part to be formed 21 is formed by the cutting operation of the cutting ring 7-, and at the same time, this part to be formed 21 and the cut piece 22 are separated.

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 cylinder 13.16, the temperature of the molded product 23 is approximately equal to the temperature of the mold member 5.6 (400°C) L < e6 for about 10 seconds rIII The state shown in Fig. 5 is maintained. , After that, as shown in FIG. 6, the cylinder 16
The first mold member 5 was separated from the molded product 23 by operating the chisel. At this time, the molded product 23 is held by the cutting ring 7 so that it does not fall off by itself.
7 to pull back the cutting ring 7, the molded product 23 is taken out by a handling device (not shown), the cylinder 13 is activated, the first mold member 6 is returned to its original position, and the cut piece 22 is removed. It is removed by a cut piece removing device (not shown).

Thus, the molded product 23 obtained in this example has an outer diameter accuracy of ±0.005 cm, a center wall thickness of ±0.01 cm, and a set weight of 0.02 g C ±0.7 with respect to the desired molded product. %), no shear marks or more harmful surface defects occur, and sink marks are within a maximum of 10 pm for the shape of each mold member 5, 6, and the reheat press It could be used not only as an optical preform, but also 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 example. 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.). Moreover, the glass fluid 2 flowing from the nozzle l shown in FIG.
The viscosity of 7
, adjusted as follows.

During the molding period (approximately 10 seconds) from the end time T2 of the pressing operation of the mold member 5.6 to the start time T6 of the return operation,
The glass in the molded part 21 is rapidly cooled due to the temperature difference in the mold member 5.6, and the viscosity changes from 1Q4.6 poise to 1Q14 poise.
・In this embodiment, the mold member 5 is 5 poise or more.
．． 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=44
Using molten glass with a temperature of 5°C and a specific gravity of 3.38), an outer diameter of 6II+1, a center wall thickness of 4 mm, an edge thickness of 3.08 m, a curvature of R+ = R2 = 10 mm, and a glass capacity of 0. A biconvex preform for reheat press with a volume of 100 cc and a weight of 337 mg was molded.

In this example, the same mold member 5.6 as in Example 1 was used, and the heater 8.9 was adjusted so that the mold temperature was 375° C. (70° C. lower than F8's 7g, 445° C.).

Further, the glass fluid 2 melted in a melting furnace (not shown) has a viscosity of 1Q2.95 to 1Q3. l Poise (108
0°C to 1050°C). ``Then, the operating pressure of each cylinder 13, 16, and 17 was set to 50 kg, 200 kg, and 50 kg, respectively, and press forming and cutting were performed in the same manner as in Example 1.
When the molded product 23 had an internal viscosity of 109 poise (approximately 540°C), it was removed from the second mold member 6.
The obtained molded product 23 has an outer diameter accuracy of ±0.01 mm, a center wall thickness of ±0.02, and a weight of ±3 with respect to the desired molded product.
mg (±0.9%), and the sink mark at the center of the surface was about 407 zm on average, and the surface condition was also good and the precision was sufficient to be used as a reheat press preform.

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

(1) The part of the fluidized glass fluid where the molded part is formed is supplied with a tapered tip, so sufficient glass capacity is secured for press forming, and cooling is possible with a tapered glass fluid. The concomitant non-uniformity of the shrinkage layer does not occur.

(2) There are no surface defects such as shear marks on the surface of the molded product.
Optical elements such as optical lenses or reheat press preforms with high dimensional and weight accuracy can be manufactured without any post-processing such as grinding or polishing after press molding. In particular, an optical element with high capacity accuracy can be obtained by forming a functional surface during press molding and forming an outer peripheral side surface through a subsequent cutting operation.

(3) Since the precision of the glass fluid used for molding is not required, the outflow device for molten glass, etc. can be inexpensive and does not require high technology, and the flow rate of outflow glass due to fluctuations in the glass liquid level in the melting furnace. Since the melting furnace is flexible against temperature changes, the melting furnace may be inexpensive.

(4) Since the glass fluid is directly press-molded and cut, it is possible to easily manufacture small and thin molded products with high precision, which was difficult to conventionally perform press-forming.

[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 essential parts of the apparatus shown in FIG. 1, and show the operating state of the apparatus in the order of steps. 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 Example 51. FIG. 10 is a diagram showing the flow of glass fluid flowing out from the nozzle. l... Nozzle 2... Glass fluid 3... Cutting mark 4... Cutting blade 5... First die member 6... Second die member 7... Cutting ring 21...・Part to be molded 22... Cut piece ・ 23... Patent attorney for molded products Sekihei Yamashita Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 N7 Cause Figure 8 TI T2 T3 T4 T5 Figure 9 for crow and mu shape 1 (insert black space 6 poem period Figure 10 (A) (C)

Claims (4)

[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 A method for manufacturing an optical element, comprising activating 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 the outflow position of a nozzle. . (2) The optical element according to claim 1, wherein the cutting time of the glass fluid is at the same time as or before the cutting and separation of the molded part and other parts by the cutting member. manufacturing method. (3) The method for manufacturing an optical element according to claim 1, wherein the glass fluid has a viscosity of 10 to 10^7 poise. (4) 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.