JPH01153540A - 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 molds, cutting and separating by a cutting member and cutting with a cutting blade. CONSTITUTION:Glass fluid 2 having 10-10<7> poise viscosity continuously falling from a flow nozzle 1 of a glass melting furnace is dropped until a cut mark 3 thereof is lowered than molding faces 5a and 6a of a pair of left and right molds 5 and 6. The molds 5 and 6 and a cutting blade 4 are worked. After pressing functioning to the fluid 2 is started, a cutting ring 7 formed on the outer periphery of the mold 6 is operated to cut the fluid 2, an outer shape of part 21 to be molded is formed and simultaneously the part 21 to be molded is separated from cut pieces 22. Then the molds 5 and 6 are lowered, the fluid 2 is separated at an interval not to be brought into contact with the cutting blade 4 and the molds 5 and 6 and the part 21 to be molded is press molded by the molding faces 5a and 6a.

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 weight 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 purpose, none of the above Even in the process, the glass material fed to the 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 release foil 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, there is a problem in that a cut edge called a shear mark occurs on the molded product, and 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 ff1-1it fluctuations may occur in the molded product due to temperature changes in the molten glass flow, cutting timing, pulsation of the glass flow, etc. However, 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 compressed, a phenomenon occurs in which excess glass in the mold cavity flows out from between the mold and the anvil facing it. 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 weight. 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 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 involves molding a pair of left and right glass fluids continuously flowing down from an outflow nozzle of a glass melting furnace. After arranging molds facing each other and pressing the glass fluid with the mold to form a molded part, a cutting member provided on the outer periphery of the mold is operated to separate the molded part and other parts. At the same time, the glass fluid flowing down from the nozzle is cut and separated in the middle by a cutting blade provided between the nozzle and the molding die, and the glass fluid continuing to flow down from the nozzle is cut and separated. It is characterized in that the nozzle and the cutting blade are spaced apart so as not to come into contact with the blade and the mold.

(Function) In the method for manufacturing an optical element configured as described above, when the left and right mold members constituting the pair of molding molds are used as the first mold member and the second mold member, these mold members are arranged in the melting path. They can be arranged to face each other in a substantially perpendicular direction through the glass fluid flowing from the outflow nozzle. 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.

The distance between the molding surfaces of the opposing mold members during press molding can be set by making it correspond to the distance between the functional surfaces 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 thickness of the molded product is maintained. If the glass has a certain capacity or more, it can be formed to a predetermined thickness regardless of the glass capacity.

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, while cutting this part to be formed, the glass fluid continuously flowing down from the melting furnace is cut midway by a cutting blade provided between the nozzle and the mold, and this once cut glass fluid continues to flow down from the melting furnace. The distance between the nozzle and the cutting blade is kept so that the nozzle and the cutting blade do not come into contact with each other due to flow. By doing so, it is supplied as a glass fluid having good properties required for the next press molding.

This point will be explained with reference to FIGS. 10(A) to 10(C). As shown in Figure A, the glass fluid 2 flowing out from a nozzle l provided in a melting furnace (not shown) is
After activating the cutting blade 4 by pressing each other with the forming mold 5.6, if the distance between the cutting blade 4 and the nozzle l remains as it was, as shown in Figure B, the distance from the nozzle l to As the glass fluid 2 continues to flow down, this flowing glass fluid comes into contact with the top of the cutting blade 4 and is cooled due to the temperature difference with the cutting blade, making the temperature distribution inside the glass extremely uneven. This is because when the cutting blade 4 is in the open state,
A similar phenomenon occurs when the glass fluid 2 comes into contact with the mold. When this glass fluid is press-molded, the molded product tends to be distorted or sink, and the glass fluid that continues to flow down becomes tapered due to its own weight, causing various problems. However, as shown in Figure 0, for example, if the cutting blade 4 is moved away from the nozzle 1 together with the mold members 5 and 6, even if the glass fluid 2 continues to flow out from the nozzle 1, it will not come into contact with the cutting blade. Therefore, the glass fluid 2 flowing out from the nozzle 1 is again in an ideal state of being thickened before being supplied to the next press molding. Further, if the glass fluid 2 flows down between the molds 5 and 6 before the molded product is taken out after press molding, there is also the inconvenience that the molded product cannot be taken out.

The present invention separates the relative distance between the nozzle, which is a supply port for the glass fluid, and the cutting blade before the glass fluid that continuously flows after cutting comes into contact with the cutting blade and causes various problems. , to stably supply glass fluid with good properties to the next press molding.

The molded product thus obtained is formed from a part that does not include cut marks of the glass fluid, so there are no surface defects such as shear marks, and the outer periphery of the molded part is formed using the set cavity and cutting member. By performing press molding on glass fluid supplied in good condition, sink marks and distortion can be suppressed to the utmost, and a molded product with highly accurate volume and weight vR adjustment 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 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
'Poise is preferred. When the glass viscosity is lower than 10 poise, the glass flow becomes filamentous, resulting in a shortage of the required 8 circles of glass in the mold cavity.On the other hand, when the glass viscosity is higher than 107 poise, press forming It becomes difficult to cut the glass later. The optimum viscosity of these glass fluids is 103 to 105 poise.

Furthermore, the temperature of the molding die ranges from a temperature corresponding to 108 poise in terms of glass viscosity to the glass transition point (hereinafter referred to as T).

It is called. This corresponds to a glass viscosity of approximately 1013. ) It is necessary to set the temperature within the range of 100°C lower than (↑g - 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. In addition, the molding surfaces of the glass and the mold tend to cause fusion, which is undesirable.On the other hand, the mold temperature Tg-1
If the temperature is lower than 00°C, not only will it be difficult to cut the outer periphery of the part to be molded, but there is a risk that cracks will occur from the cut part.

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 use the strip if it is cooled to a viscosity of 1Q14.5 poise or higher, but if it is to be 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. If this is done, it can be used as an optical element with good shape accuracy and surface accuracy.

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.

Reference numeral 4 denotes a cutting blade that is provided near the bottom of the nozzle 1 and 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 for a type in which the glass fluid 2 flows down from a nozzle l.
A tfSi 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 a molding surface 5a whose opposing surfaces are mirror-finished.
, 6a.

The first mold member 5 is held by a slider 14, which is slidably supported by 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, and the first mold member 5 is suppressed.

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 cavities formed by the four mold parts 5a, 6a of these mold parts 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 second mold part 6 in a movement independent of the second mold part 6.

Furthermore, 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 device, which firmly supports the cylinders 13, 16, 17 and the slide shaft 18.

Further, the press molding device configured as described above is supported by a cylinder 20 provided below a base 19 that holds the entire device, and can be moved vertically by driving the cylinder. ing. However, the cutting blade 4 is attached to the device and moves up and down as the device moves up and down. Also, nozzle 1
is located at a different location from this device. Therefore, when this device moves up and down due to the drive of the cylinder 20, the cutting blade 4
The distance between the nozzle 1 and the nozzle 1 is relatively changed.

Next, we will discuss the operation of this device configured as described above.
This will be explained using FIGS. 7 and 8.

FIGS. 2 to 7 are sectional views of essential parts showing the operating state of the apparatus in each process order. FIG. 8 shows the operating part in one device, that is, the first mold member 5. It is a timing chart showing the operation timing of each part of the second mold member 6, the cutting blade 4, and the cutting ring 7, and the entire press molding apparatus, and the horizontal axis shows time T.

These operating timings can be controlled by a controller (not shown) connected to each operating section.

FIG. 2 shows the state immediately before press molding. At this time, the cutting blade 4 is close to the nozzle 1, and the glass fluid 2 is flowing down from the nozzle 1.

Then, when the tip of the glass fluid 2, that is, the cut mark 3 flows downward from each opposing molding surface 5a, 6a, the first mold member 5 and the second mold member 6 start suppressing operations. In FIG. 8, T=O indicates the start time of the operation of both mold members 5.6. Although the start time of the operation of both mold members 5.6 may be the same, the glass fluid 2 of the mold member 5.6
Is the pressing operation end time T2 for both at the same time?
It is preferable to keep the error within ±0.05 s at most; if this error is large, only one side of the mold member 5.6 collides with the glass fluid 2, causing lateral wobbling of the glass fluid 2, which is undesirable.

Thereafter, as shown in FIG. 3, the mold members 5 and 6 keep pressing the molded part 21 of the glass fluid 2 for a predetermined period of time (T2 to Tb), and during this period, both surfaces of the molded part 21 are pressed. On the other hand, each molding surface 5a.

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 the end time T2 of cutting the glass fluid 2 by the cutting blade 4 is when the mold members 5 and 6 are made of glass. It must be at the same time as or at least after holding fluid 2. Thereafter, the cutting blade 4 is 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 0.43.

Further, the cylinder 20 is driven simultaneously or slightly after the operation of the cutting blade 4, and the entire apparatus is moved downward. Cutting blade 4
The cutting of the glass fluid 2 by the glass fluid 2 is completed during the lowering of the device. If the end of cutting is at the same time as the start of descent of the device, the amount of descent of the glass fluid 2 will be insufficient, making it impossible to supply enough glass powder for the next press forming.

As shown in FIG. 5, the operation start timing T 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). ). 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), and the part to be formed 21
While holding the outer peripheral side of the molded part 2 due to the temperature difference.
1 is cooled from the outer periphery, the viscosity near the outer periphery of the part to be formed 21 increases and the shape is fixed. On the other hand, after being suppressed by the mold member 5.6, the molded part 21 is cooled from both surfaces due to the temperature difference between the mold member and the molded part 21, increasing its viscosity and stabilizing the 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 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 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. Then, the entire apparatus is returned to the original press forming position at the same time as or after this return end time TIG. If the entire device is moved upwards faster than this, the glass fluid 2, which continues to flow down at a substantially constant speed even after cutting, will come into contact with the mold member 6.

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 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.

Further, the entire device is moved downward at the same time as the glass corrugated body 2 is cut by the cutting blade 4, and a gap is created between the nozzle l and the cutting blade 4, so that the glass fluid 2 flowing down does not come into contact with the cutting blade 4. Because of this structure, the glass fluid 2 is supplied with a good thickness for the next press molding. Therefore, sufficient glass capacity is ensured for the next press molding, and non-uniformity of the condensed layer due to cooling, as seen in the previously rolled glass fluid, is less likely to occur. Furthermore, if the glass fluid 2 flowing down comes into contact with the cutting blade 4 and is cooled unevenly and partially solidifies, it becomes impossible to mold the glass fluid 2, but this problem does not occur in this embodiment.

Also, the cavity formed by the molds 5, 6 can be set by the stroke of each cylinder 13, 16. That is, the set cylinder 13. The stroke of I6 determines the molding surface interval of the molding die 5.6 at the suppression end time T2. Since the wall thickness of the molded product 23 is determined by this molding surface spacing, 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 product is obtained. Further, the surface shape and properties of the molded product 23 are determined by the molding surfaces 5a and 6a of the molded members 5 and 6, respectively. 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 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 20I
I11, center thickness 2.7 ms+, edge thickness 1.29 mm, curvature R1 = 20 mm, R2 = 40 mm, glass capacity 0
．． 838 cc, weight 2. A convex meniscus-shaped Hg preform for reheat press was molded.

The mold members 5 and 6 are made of 5US420J.

Each molding surface 5a, 6a is polished to an optical mirror surface. The mold temperature of this mold member 5.6 is 400°C (Tg of SF8 = 44
The temperature is 43°C lower than 3°C) using heaters 8 and 9. Also, the stroke of the cylinder 13.16 is such that the maximum approach width during the pressing operation of each mold member 5.6 is 2.
．． Adjust so that the thickness is 7 ts to obtain the desired thickness.

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, the tip of the glass fluid 2 is cut u3.
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 m/s.

Then, as shown in FIG. 3, after the mold member 5.6 starts suppressing the glass fluid 2, 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.
8 for each cylinder 1 using a controller not shown.
The operating pressure of the cylinder 17 that drives this cutting ring 7, which adjusts the operating timing of 3°16.17, is l.
oOkg, and the operating speed is 200 ram/s. 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 cylinder 13.16, the state shown in FIG. Thereafter, 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 by the cutting ring 7 and does not fall off by itself. Next, the cylinder 17 is actuated 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), the cylinder 13 is actuated, the first mold member 6 is returned to its original position, and the cutting is performed. The piece 22 is removed by a cut piece removal device (not shown).

Thus, the molded product 23 obtained in this example has an outer diameter accuracy of ±0.005 mm, a center wall thickness of ±0.01+am, and a heavy machinery weight of Q, 02 g (±0.7
%), no harmful surface defects such as shear marks occurred, and sink marks were also within 5.
It was within 10 #Lm at maximum for the shape of No. 6, and could be used not only as a preform for reheat press 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 5.6 are set at the glass transition point Tg of the glass material (T of SF8).
g = 443°C) was adjusted to 400°C, which is 43°C lower.

Further, the viscosity of the glass fluid 2 flowing from the nozzle 1 shown in FIG. 2 is about IQ4. b poise (815°±5°C).

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 between the mold members 5.6, and its viscosity changes from 1046 poise to 1014 poise.
In this embodiment, the mold member 5.
6 is 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 this mold member 5.6.

(Example 2) In this example, optical glass F8 (Tg=445
℃ and specific gravity of 3.36) using the same method as in Example 1 to obtain an outer diameter of 61 m and a center wall thickness of 4 II m.

Edge 53.08 layers, curvature R1=R2=10mm,
Glass capacity 0.100cc, f4 m 337 m
A preform for reheat press having a double convex shape as shown in g was molded.

In this example, mold members 5 and 6 similar to those in Example 1 were used, and heaters 8.9 were 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. I Poise (1080
℃~1050℃).

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+u+, a center wall thickness of ±0.02, and a weight of ±0.02 with respect to the desired molded product.
The variation was within 3B (±0.8%), and the sink mark at the center of the surface was about 407 tm 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 are produced.

(1) Since the glass fluid after cutting by the cutting blade does not come into contact with the cutting blade and the mold and is cooled unevenly,
The resulting molded product is less likely to suffer from sink marks or distortion, and because the part of the flowing glass fluid where the molded part is formed is supplied with a thicker tip, it is less likely to be cooled than 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 the need for post-processing such as grinding and 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 circumferential side surface by a subsequent cutting operation.

(3) Since the glass fluid used for molding does not require much precision, the device for discharging the molten glass etc. may be inexpensive and does not require high technology. Furthermore, since the melting furnace is flexible in response to changes in the flow rate and temperature of the outflowing glass due to fluctuations in the glass liquid level in the melting furnace, the melting furnace may also be inexpensive.

(4) 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 manufactured 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 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 the first example. FIG. 1O is a diagram showing the effect of moving the entire press device downward. 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...Patent attorney for molded products Jo Taira Yamashita Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 8 N 12 13 14 15 Figure 9 (A)

Claims (4)

[Claims] (1) A pair of left and right molding molds are arranged facing each other with the glass fluid continuously flowing down from the outflow nozzle of the glass melting furnace,
After pressing the glass fluid with the mold to form a molded part, actuating a cutting member provided on the outer periphery of the mold to cut and separate the molded part from other parts. A cutting blade provided between the nozzle and the molding die cuts and separates the glass fluid flowing down from the nozzle midway, and further, the glass fluid continuing to flow down from the nozzle is cut into the cutting blade and the molding die. A method for manufacturing an optical element, characterized in that the nozzle and the cutting blade are spaced apart so that they do not come into contact with each other. (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.