JPH0729781B2 - Optical element manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an optical element by press molding, and more specifically, it relates to surface accuracy without steps such as grinding and polishing after press molding. And a method for producing a preform suitable for use in an optical element having good weight accuracy or its reheat press.

(Prior Art) In recent years, a method for molding a high-precision optical element that does not require post-processing such as grinding and polishing by accommodating a glass material in a molding die having a predetermined surface accuracy and performing press molding. Is being developed.

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

The reheat press method is to cut a necessary amount of glass material that has been melted and solidified in advance, adjust the weight by a method such as sanding to make a glass small piece, put this 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 press-transferring the optical functional surface formed on the molding mold by press molding.

On the other hand, the direct pressing method cuts a necessary amount of the molten glass flow outflowing or pressed from the molten glass outflow orifice with a cutting blade and directly dropping it into a molding die or throwing it in with a chute, followed by molding. This is a method of molding an optical element by pressing a mold.

Further, in the above reheat press method, the molten glass is put into a molding die and press-molded into a final product as in the above direct press method without passing through low productivity steps such as cutting and sand shaving. After obtaining a preformed product (preform) having an approximate shape, the preform is put into a molding die having an optical functional surface having the same or higher accuracy as the shape and surface accuracy of the final product and press molding. There is a way to do.

(Problems to be Solved by the Invention) The optical element obtained by these molding methods is required to have predetermined surface accuracy and dimensional accuracy so as to obtain good image forming quality. Even in the above, the glass material supplied to the press molding for obtaining the final product must be sufficiently adjusted in weight.

However, in the method of press-molding using the above-mentioned small glass pieces, since the weight adjustment of the small glass pieces is performed by cutting and sanding, etc., sand grains remain on the surface of the molded product,
When heating a small glass lump before press molding, the mold release applied to prevent fusion between the glass and the heating pan bites into the surface of the molded product during pressing and the surface accuracy of the molded product deteriorates significantly. There is a problem of doing.

Also, in the method of press molding using molten glass directly,
When cutting with a cutting blade, there is a problem that a cut mark called a shear mark is generated on the molded product, and the surface accuracy of the molded product deteriorates. Further, in this press molding method, since the weight of the molded product is adjusted by cutting the molten glass flow, the molded product has a weight variation due to temperature change of the molten glass flow, cutting timing, pulsation of the glass flow, etc. There is also a problem that the dimensional accuracy of is not obtained.

Incidentally, as a press molding method in which the occurrence of shear marks is particularly prevented, there is a Japanese Patent Publication No. Sho 41-9190 or Japanese Patent Laid-Open No. Sho 61-132523.
There is one described in the publication.

In the molding method described in JP-B-41-9190, there is a method of pressing the molding die in a direction perpendicular to the direction of flow of the molten glass to fill the molten glass in the mold cavity and press-molding it. When the molding die is pressed, a phenomenon occurs in which excess glass in the mold cavity flows out between the molding die and the anvil facing the molding die. As the pressing operation of the molding die progresses, this excess glass increases its outflow resistance and is cooled by the molding die to increase its viscosity, which is completely cut off between the molding die and the anvil facing it. It is cooled without being formed to form a protruding portion on the outer periphery of the molded product. Therefore, it is necessary to finish the fracture and the fracture surface of the protruding portion after the press molding. Further, due to the change in the size of the molten glass flow, the thickness of the glass between the above-mentioned molded product and the protruding portion fluctuates and the thickness of the molded product varies, so that the weight can be adjusted with high accuracy. There is also the problem of not having 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, and the like, so that a highly accurate dimensional shape can be obtained. It requires a rod or glass sheet to have.

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

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

(Means for Solving the Problems) In order to achieve the above-mentioned object, a method for manufacturing an optical element according to the present invention includes a pair of left and right moldings sandwiching a glass fluid continuously flowing down from an outflow nozzle of a glass melting furnace. Forming molds are arranged to face each other, and the glass fluid is pressed by the molding mold to form a molding part, and then a cutting member provided on the outer periphery of the molding mold is operated to operate the molding part and other parts. The glass fluid flowing down from the nozzle is cut and separated on the way by a cutting blade provided between the nozzle and the molding die while cutting and separating the portion, and the glass fluid continuously flowing down from the nozzle is the cutting. The nozzle and the cutting blade are spaced from each other so as not to contact the blade and the molding die.

(Operation) In the method for manufacturing an optical element configured as described above, when the left and right mold members that make up the pair of molding dies are the first mold member and the second mold member, these mold members form a melting path. They can be arranged so as to face each other in a substantially right-angled direction through the glass fluid flowing from the outflow nozzle. That is, it is possible to adopt a configuration in which the mold members are pressed against each other from a direction substantially perpendicular to the flow direction of the glass fluid, and by adjusting the pressing timing of each mold member against the glass fluid. The molded portion can be formed while avoiding the tip portion of the glass fluid, that is, the cut mark.

The wall thickness of the portion to be molded is determined by setting the cavity of the molding die in advance. This cavity can be set by making the molding surface distance at the time of press molding of the respective facing mold members correspond to the desired functional surface distance of the optical element.

When a sufficient volume of glass fluid is supplied between each mold member during press molding, excess glass generated when pressing each mold member freely flows out of the molding surface, and the thickness of the molded product is supplied. If the glass has a certain capacity or more, it can be formed to have a predetermined wall thickness regardless of the glass capacity.

Then, after the glass fluid is pressed by each mold member to form the molding target portion, the cutting member provided on the outer periphery of the molding die is operated to cut and separate the molding target portion and other surplus portions from each other. The shape of the outer peripheral side surface of the molding portion is formed.

Further, the glass fluid that continuously cuts down from the melting furnace while cutting the part to be molded is cut midway by a cutting blade provided between the nozzle and the molding die, and the glass fluid once cut continues to flow. The nozzle and the cutting blade are separated from each other so as not to come into contact with the cutting blade and the molding die. By doing so, it is supplied as a glass fluid having good properties required for the next press molding.

This point will be described with reference to FIGS. 10 (A) to (C). As shown in FIG. A, after the glass fluid 2 flowing out from the nozzle 1 provided in the melting furnace (not shown) is pressed against each other by the first and second molding dies 5 and 6 to operate the cutting blade 4, As shown in FIG. B, when the distance between the cutting blade 4 and the nozzle 1 is left as it is, the glass fluid 2 continues to flow down from the nozzle 1, so that the glass fluid flowing down the cutting blade. 4 is brought into contact with the upper surface of the cutting blade 4 and is cooled by the temperature difference between the cutting blade and the cutting blade, and the temperature distribution in the glass becomes extremely uneven. This means that when the cutting blade 4 is in the open state,
The same occurs when the glass fluid 2 comes into contact with the molding die. When this glass fluid is press-molded, the molded product is likely to be distorted or sinked, and the glass fluid subsequently flowing down is tapered due to its own weight, which causes various problems. However, as shown in FIG. C, for example, when the cutting blade 4 is kept away from the nozzle 1 together with the mold members 5 and 6, even if the glass fluid 2 continuously flows out from the nozzle 1, the cutting blade 4 may come into contact with the cutting blade. Instead, the glass fluid 2 flowing out of the nozzle 1 is again in an ideal state of thickening and is supplied to the next press molding. Further, if the glass fluid 2 flows down between the molding dies 5 and 6 after the press molding and before the molded product is taken out, the molded product cannot be taken out.

The present invention is designed to separate the relative distance between the nozzle, which is the supply port of the glass fluid, and the cutting blade before the continuously fluidized glass fluid after cutting contacts the cutting blade and causes various disadvantages. The glass fluid having good properties is stably supplied to the next press molding.

The molded product thus obtained does not have a surface defect such as a shear mark because it is formed from a portion that does not include a cutting trace of the glass fluid, and the outer periphery of the molded portion is set by the set cavity and cutting member, and By performing press molding on the glass fluid supplied in a good condition, sink marks and distortion are suppressed as much as possible, and a molded product with highly accurate volume and weight adjustment can be obtained.

Further, since the functional surface of this molded product is formed by transferring the molded surface of each mold member, the surface texture of each molded surface is equal to or higher than the desired surface texture of the molded product. A molded product having a highly accurate functional surface can be obtained by finishing the product and press-molding it.

The viscosity of the glass fluid in the present invention is preferably 10 to 10 ⁷ poise. When the glass viscosity becomes lower than 10 poise, the glass flow becomes filamentous and the glass capacity required in the cavity of the molding die becomes insufficient. On the other hand, when the glass viscosity is higher than 10 ⁷ poise, it becomes difficult to cut the glass after press molding. The viscosity of these glass fluids is optimally 10 ³ to 10 ⁵ poises.

Further, the temperature of the molding die is 100 ° C. lower than the glass transition temperature (hereinafter referred to as Tg, which corresponds to about 10 ¹³ in glass viscosity) from the temperature corresponding to 10 ⁸ poise in glass viscosity (Tg-
It must be set within the range of 100 ℃). When the mold temperature exceeds a temperature equivalent to 10 ⁸ poise, the hardness change of the glass surface in the molded part formed after the press molding to the cutting is slow, and when the outer periphery of the molded part is cut and formed. However, the predetermined shape accuracy and surface accuracy cannot be obtained. Further, fusion between the glass and the molding surface of the mold is likely to occur, which is not preferable. On the other hand, when the mold temperature is lower than Tg-100 ° C., when cutting the outer periphery of the part to be molded, not only the cutting becomes difficult, but also cracks may occur from the cut part.

The temperature of the cutting member is preferably the same as the mold temperature of the molding die in order to make the influence of the temperature change of the glass the same as in the molding die.

Further, the viscosity at the time of taking out the molded product, when this molded product is used as a preform for reheat press, it can be sufficiently used by cooling until it has a viscosity of 10 ⁸ poises or more, but when used as it is for an optical lens or the like, It can be used as an optical element having good shape accuracy and surface accuracy if it is cooled in a molding die while applying pressure and taken out when the viscosity reaches about 10 ^14.5 poise.

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

(Example) Hereinafter, the Example of this invention is described, referring drawings.

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

In FIG. 1, reference numeral 1 is a nozzle for flowing molten glass out of a melting furnace (not shown), 2 is a glass fluid flowing out of this nozzle, and 3 is a cutting trace generated at the tip of the glass fluid 2.

A cutting blade 4 is provided near the lower portion of the nozzle 1 and cuts the glass fluid 2 by performing an opening / closing operation by a driving device (not shown). The cutting blade 4 is actuated to cut the glass fluid 2 on the way, whereby a cutting mark 3 is generated.

The press molding apparatus shown in the present embodiment is configured for a type in which the glass fluid 2 flows down from the nozzle 1, and
The first mold member 5 and the second mold member 6 forming the pair of molding dies are arranged so as to face each other so as to narrow the glass fluid 2 from the substantially perpendicular direction. Each of the mold members 5 and 6 has molding surfaces 5a and 6a whose surfaces facing each other are mirror-finished.

The first die member 5 is held by a slider 14, and the slider 14 is slidably supported by a slide shaft 18. Reference numeral 16 is a cylinder for driving the slider 14, and the operation of the cylinder 16 causes the slider 14 to move in the sliding direction of the slide shaft 18 to press the first die member 5.

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

The cavity formed by the molding surfaces 5a and 6a of the mold members 5 and 6 can be set by the stroke of the cylinders 13 and 16.

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 the cutting ring 7 is slidably supported by a slide shaft 18. Is connected to the slider 15. In addition, slider 15
Is connected to a cylinder 17, and by the operation of this cylinder 17, the cutting ring 7 can slide on the outer periphery of the second mold member 6 independently of the second mold member 6.

Further, heaters 8 and 9 are provided inside the mold members 5 and 6, respectively. Reference numerals 10 and 11 are conductors connected to the respective heaters. 1
Reference numeral 9 is a base of the entire apparatus, and firmly supports the cylinders 13, 16, 17 and the slide shaft 18.

Further, the press-molding attachment configured as described above is supported by a cylinder 20 provided below a base 19 that holds the entire apparatus, and can be moved in the vertical direction by driving the cylinder. ing. However, the cutting blade 4 is attached to this device,
It moves up and down as the device moves up and down. Further, the nozzle 1 is provided at a position different from that of this device. Therefore the cylinder
When the device is moved up and down by driving 20, the distance between the cutting blade 4 and the nozzle 1 is relatively changed.

Next, regarding the operation of the present apparatus configured as described above,
7 to 8 and FIG.

2 to 7 are cross-sectional views of essential parts showing the operating state of each step of this apparatus. FIG. 8 is a timing chart showing the operation timings of the operating section of the present apparatus, that is, the first die member 5, the second die member 6, the cutting blade 4 and the cutting ring 7, and the entire press forming apparatus. Yes, the horizontal axis represents time T. These operation timings can be controlled by a controller (not shown) connected to each operation unit.

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 flows down from the nozzle 1.

Then, at the time when the tip of the glass fluid 2, that is, the cut mark 3 flows down from the facing molding surfaces 5a, 6a, the pressing operation of the first mold member 5 and the second mold member 6 is started. In FIG. 8, T = 0 indicates the operation start timing of both mold members 5 and 6. The operation start timing of these mold members 5 and 6 may be the same for both, but the pressing operation end time T ₂ of the mold members 5 and 6 against the glass fluid ₂ is the same for both, or at most ± 0.
It is preferable to fit within the error of 05s. If this error is large, only one of the mold members 5 and 6 collides with the glass fluid 2 and the glass fluid 2 is laterally shaken, which is not preferable.

After that, as shown in FIG. 3, the mold members 5 and 6 are kept in a state in which the molded portion 21 of the glass fluid 2 is pressed for a predetermined time (T ₂
.About.T ₆ ) and during this time, the pressure transfer by the respective molding surfaces 5a, 6a is performed on both surfaces of the molded portion 21.

The operation start timing of the cutting blade 4 may be the same as the operation start timing T = 0 of the mold members 5 and 6, but the cutting end timing T ₂ of the glass fluid 2 by the cutting blade 4 is set to the mold members 5 and 6. Glass fluid 2
Must be held at the same time or at least after holding. After that, the cutting blade 4 is returned to the original state. In FIG. 8, the recovery start time of the cutting blade 4 is shown as T ₄ , and the recovery end time is shown as T ₅ . Preferably,
The time required from the operation starting time T = 0 of the cutting blade 4 to the cutting end timing T ₂ and 0.3～0.4S.

At the same time as the operation of the cutting blade 4 or slightly later, the cylinder
20 is driven to move the entire apparatus downward. The cutting of the glass fluid 2 by the cutting blade 4 is completed while the device is descending. If the cutting end time is the same as the start of the descent of the apparatus, the descent amount of the glass fluid 2 will be insufficient and it will not be possible to supply a sufficient amount of glass for the next press molding.

As shown in FIG. 5, at the operation start timing T ₁ of the cutting ring 7, the cutting of the glass fluid 2 by the cutting blade 4 ends at least before the outer peripheral cutting (T ₃ ) of the molded part 21 by the cutting ring 7 ends ( T ₂ ) It is necessary to set so that it will be in the state.
By doing so, the glass fluid 2 is already separated by the cutting blade 4 at the time when the cutting operation of the cutting ring 7 is completed, and the cut piece cut by the cutting ring 7 is cut off.
22 can be easily moved to the outside of the first mold member 5.

Thus, the cutting ring 7 slides along the outer periphery of the second die member 6 to cut the outer periphery of the molded portion 21, and the molded portion 21
The shape of the outer peripheral side surface is formed. After that, the cutting ring 7 maintains the state at the time of completion of cutting (T ₃ ), and while the outer peripheral side surface of the molding target portion 21 is held, the molding target portion 21 is cooled from the outer circumference by the temperature difference, and the molding target portion 21 is cooled. Viscosity increases near the outer periphery and its shape is fixed. On the other hand, after being pressed by the mold members 5 and 6, due to the temperature difference between the mold member and the molded part 21, the molded part 21 is cooled from both surfaces to increase the viscosity and the surface shape is stabilized.

Next, first, as shown in FIG. 6, the first mold member 5 is returned to the original state. When the operation start time is T ₆ , the operation end time is T _7, and the start time for operating the cutting ring 7 to the original state is the same as the return end time T ₇ of the first mold member 5 or after the end. Before the start of the operation of the cutting ring 7, the molded part 21 is held by the cutting ring 7 and does not fall naturally.

Then, at the same time as the time T ₈ at which the cutting ring 7 is returned, the part to be molded, ie, the molded product 23 is taken out. This can be performed using a known suction hand or the like. After the completion of this take-out work, the second mold member 6 is returned to its original state. In FIG. 8, the return start timing of the second mold member 6 is T ₉ , and the return end timing is T ₁₀ . Then, the entire apparatus is returned to the original press-molding position at the same time as or after the return end time T ₁₀ . If the whole apparatus is moved upward faster than this, the glass fluid 2 that continues to flow down at a substantially constant speed after cutting will contact the mold member 6.

If the cutting ring 7 is returned to the original state before the molded product 23 is taken out, as shown in FIG. 7, the molded product 23 releases the holding of the cutting ring 7 and falls naturally.

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

At the same time that the glass fluid 2 is cut by the cutting blade 4, the entire apparatus is moved downward so that the nozzle 1 and the cutting blade 4 are spaced from each other so that the flowing glass fluid 2 does not come into contact with the cutting blade 4. Since it is configured as described above, a favorable thickened glass fluid 2 is supplied for the next press molding. Therefore, a sufficient glass capacity is secured for the next press molding, and unevenness of the shrinkage layer due to cooling, which is observed in a tapered glass fluid, is unlikely to occur. Further, the glass fluid 2 flowing down comes into contact with the cutting blade 4 and is nonuniformly cooled, and if it partially solidifies, it becomes impossible to mold, but in the present embodiment, such a disadvantage does not occur.

Further, the cavity formed by the molding dies 5 and 6 can be set by the stroke of each cylinder 13 and 16. That is, the set strokes of the cylinders 13 and 16 determine the molding surface spacing of the molding dies 5 and 6 at the pressing end time T ₂ . Since the wall thickness of the molded product 23 is determined by this molding surface distance, by setting the stroke of the cylinders 13 and 16 in accordance with the wall thickness of the molded product 23 to be manufactured, it always has a predetermined wall thickness. A molded product is obtained. or,
The surface shape and properties of the molded product 23 are determined by the respective molding surfaces 5a and 6a of the respective molding members 5 and 6. Further, 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, specific examples using the above-described press molding method will be described with reference to FIGS. 1 to 8.

(Example 1) Optical glass SF8 (Tg = 4) which is usually used for camera lenses, etc.
43 ° C, specific gravity 4.22), outer diameter 20 mm, center wall thickness 2.7 m
m, edge thickness 1.29 mm, curvature R ₁ = 20 mm, R ₂ = 40 mm, glass capacity 0.636 cc, and a convex meniscus preform for reheat press having a weight of 2.68 g were molded.

The mold members 5 and 6 are made of SUS420J, and the respective molding surfaces 5a and 6a are polished to optical mirror surfaces. The mold temperature of these mold members 5, 6 is 400 ℃
Heat with heaters 8 and 9 so that (Tg of SF8 = 43 ° C lower than 443 ° C). Also, the maximum approach width is 2.7 when the stroke of the cylinders 13 and 16 is pressed by the mold members 5 and 6, respectively.
The thickness is adjusted to be mm so that the desired wall thickness can be obtained.

First, glass melted in a melting furnace (not shown) into a glass fluid 2
The viscosity was adjusted to be about 10 ^4.6 poise (815 ° ± 5 ° C.), and the liquid was discharged from the nozzle 1. Next, FIG. 2 and FIG.
As shown in the figure, when the cutting trace 3 at the tip of the glass fluid 2 flows down from the respective molding surfaces 5a, 6a of the mold members 5, 6, the cylinders 13, 16 are operated, and at the same time, the cutting blade 4 is also operated. Activated. The operating pressures of the cylinders 13 and 16 are 120 kg and 30 respectively.
It is 0 kg, and the operating speed is 200 mm / 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 operated. The cutting ring 7 is formed of SK3, and the time from the completion of the pressing operation of the mold members 5 and 6 to the completion of the cutting by the cutting ring 7 is 0.2 s by a controller (not shown) for each cylinder. Adjust the operation timing of 13, 16 and 17. The operating pressure of the cylinder 17 that drives this cutting ring 7 is 100 kg, and the operating speed is 200 mm / s. Further, as shown in FIG. 5, when the cutting operation by the cutting ring 7 is completed, the cutting of the glass stream 2 by the cutting blade 4 is also completed. Further, as shown in the figure, by the cutting operation of the cutting ring 7, the molded portion 21
At the same time that the outer peripheral shape is formed, the molded portion 21 and the cut piece 22 are separated.

In addition, in FIG. 5, the first mold member 5 and the cutting ring 7 are in the engaged state, but the cutting state was good even in the state where they were in contact with each other.

Next, while the pressure is applied to the cylinders 13 and 16, the molded product 23
The state shown in FIG. 5 is maintained for about 10 seconds until the temperature of is substantially equal to the temperature of the mold members 5 and 6 (400 ° C.). After that, as shown in FIG. The mold member 5 of No. 1 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 by itself. Next, the cylinder 17 is operated to pull back the cutting ring 7, and at the same time, the molded product 23 is handled by a handling device (not shown).
Take out and operate the cylinder 13 to operate the first mold member 6
To the original position. Then, the cut pieces 22 are removed by a cut piece removing device (not shown).

Thus, the molded product 23 obtained by this example has an outer diameter accuracy of ± 0.005 mm and a center wall thickness of ± 0.00 with respect to the desired molded product.
It fits within a variation of 1 mm and 0.02 g (± 0.7%) by weight, no harmful surface defects such as shear marks are generated, and sink marks are 10 μ at maximum with respect to the shape of each mold member 5 and 6.
It was within m, and could be used not only as a reheat press preform but also as an optical lens that does not require very high accuracy.

FIG. 9 is a graph showing changes over time in the temperatures of the first mold member 5, the second mold member 6 and the glass that is the material to be molded in this example. In this description, the time T in FIG. 8 is used.

Initially (T = 0 in FIG. 8), first and second mold members
5 and 6 are glass transition points Tg of glass materials (SFg Tg = 443
℃) was adjusted to 400 ℃, which is 43 ℃ lower. The viscosity of the glass fluid 2 flowing from the nozzle 1 shown in FIG. 2 is about 10 ^4.6.
It was adjusted to be poise (815 ° ± 5 ° C).

In molding the period from the pressing operation end time T2 until the return operation start time T ₆ of the mold members 5, 6 (about 10 seconds), the molded part
The glass of 21 is rapidly cooled due to the temperature difference between the mold members 5 and 6, and the viscosity thereof is from 10 ^4.6 poise to 10 ^14.5 poise or more.
In this embodiment, the mold members 5 and 6 are 400 ° C. until the end of pressing.
Are heated by the heaters 8 and 9, respectively, and the glass temperature of the molded product 23 at this time is substantially the same as that of the mold members 5 and 6.

Example 2 In this example, molten glass of optical glass F8 (Tg = 445 ° C., specific gravity 3.36) was used, and the same method as in Example 1 was used to obtain an outer diameter of 6 mm, a center thickness of 4 mm, and an edge thickness of 3.08 mm. , The curvature is R ₁ ＝ R ₂ ＝
A biconvex preform for reheat press having a size of 10 mm, a glass capacity of 0.100 cc and a weight of 337 mg was molded.

In this example, the same mold members 5 and 6 as in Example 1 were used, and the heaters 8 and 9 were adjusted so that the mold temperature was 375 ° C. (70 ° C. lower than Tg445 ° C. of F8). .

Further, the glass melted in a melting furnace (not shown) was adjusted so that the viscosity of the glass fluid 2 was 10 ^2.95 to 10 ^3.1 poise (1080 ° C. to 1050 ° C.).

Then, the working pressure of each cylinder 13, 16, 17 is 50 kg, 2 respectively.
The pressure was set to 00 kg and 50 kg, press molding and cutting were performed in the same manner as in Example 1, and when the internal viscosity of the molded product 23 reached 10 ⁹ poise (about 540 ° C), it was taken out from the second mold member 6. As a result, the obtained molded product 23 fits within a variation of ± 0.01 mm in outer diameter accuracy, ± 0.02 in center wall thickness, and ± 3 mg (± 0.9%) in weight with respect to the desired molded product. The center sink was about 40 μm on average, and the surface condition was good enough to be used as a preform for reheat press.

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

(1) Since the glass fluid after cutting by the cutting blade does not contact the cutting blade and the molding die and is not unevenly cooled,
Sinks and distortions are less likely to occur in the obtained molded product. Further, since the portion where the molded portion of the flowing glass fluid is formed is thickened and supplied, nonuniformity of the shrinkage layer due to cooling as seen in the tapered glass fluid does not occur.

(2) There are no surface defects such as shear marks on the surface of the molded product,
It is possible to manufacture an optical lens having high dimensional accuracy and weight accuracy, or an optical element such as a preform for reheat press without any post-processing such as grinding and polishing after press molding. In particular, an optical element having high capacitance accuracy can be obtained by forming a functional surface during press molding and then forming an outer peripheral side surface by a cutting operation.

(3) Since the precision of the glass fluid used for molding is not so required, the outflow device for molten glass or the like may be inexpensive and does not require high technology. Further, the melting furnace can be inexpensive because it is flexible with respect to the flow rate and the temperature change of the outflowing glass due to the fluctuation of the glass surface of the melting furnace.

(4) Since the glass fluid is directly press-molded and cut, it is possible to easily manufacture a small and thin molded product which has been difficult to press-mold with high precision.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a press molding apparatus showing an embodiment of the present invention. 2 to 7 are cross-sectional views of the main part of the apparatus shown in FIG. 1, showing the operating state of the apparatus in the order of steps. FIG. 8 is a diagram showing a timing chart of each operating part of the press molding apparatus shown in FIG. FIG. 9 is a graph showing the changes over time in the temperature of the mold member and glass during press molding in the first embodiment. FIG. 10 is a view showing the function and effect of moving the entire press device downward. 1 ... Nozzle 2 ... Glass fluid 3 ... Cutting trace 4 ... Cutting blade 5 ... First mold member 6 ... Second mold member 7 ... Cutting ring 21 ... Molded part 22 ... Cutting Piece 23 …… Molded product

Claims (4)

[Claims] 1. A pair of left and right molding dies are opposed to each other with a glass fluid continuously flowing down from an outflow nozzle of a glass melting furnace interposed therebetween, and the glass fluid is pressed by the molding dies to form a molded portion. After that, by operating a cutting member provided on the outer periphery of the molding die to cut and separate the molded portion and other portions, and by a cutting blade provided between the nozzle and the molding die. The glass fluid flowing down from the nozzle is cut and separated on the way, and the nozzle and the cutting blade are spaced so that the glass fluid continuing to flow down from the nozzle does not come into contact with the cutting blade and the molding die. A method for manufacturing an optical element, comprising: 2. The glass fluid according to claim 1, wherein the cutting time of the glass fluid is at the same time as or before the cutting separation of the molded portion and the other portion by the cutting member. Optical element 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 pressed with a molding die within a temperature range corresponding to a glass viscosity of 10 ⁸ poise and a temperature 100 ° C. lower than the glass transition point (corresponding to a glass viscosity of about 10 ¹³ poise). Claim 1 characterized by molding
Item 8. A method for manufacturing an optical element according to item.