JPH08283028A - Method for forming optical element - Google Patents

Abstract

PURPOSE: To make it possible to uniformly and rapidly cool the glass optical element under forming from the entire periphery, to shorten the recycle time for forming and to prevent the distortion of formed goods by cooling the optical element while increasing the amt. of the gas to be ejected stepwise or proportionally linearly at the time of press forming the glass optical element with a pair of upper and lower dies and cooling the glass element by blowing a nonoxidizing gas to the optical element under forming. CONSTITUTION: The glass optical element is cooled while the temp. difference between its central part and outer peripheral part is kept low by gradually increasing the amt. of the nonoxidizing gas to be ejected at the time of cooling the formed glass optical element. An optical glass blank 15 is heated to soften by a heater 3a of a heating furnace 3 in Fig. This blank 15 is transported between the upper and lower dies 8 and 11 by a transporting arm 13. The lower die 11 is risen and the blank 15 is placed on its forming surface 11a. The lower die 11 is risen to press form the blank. The optical element is cooled by ejecting the nonoxidizing gas from an ejection port 12 while stepwise increasing the amt. of the gas to be ejected. The optical element is slowly cooled in a slow cooling furnace 4 and is then taken out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method for molding optical elements such as lenses, prisms and filters by press molding a glass material which has been softened by heating.

[0002]

2. Description of the Related Art Conventionally, as a method for molding an optical element such as a high precision glass lens, there is an invention described in Japanese Patent Application Laid-Open No. 2-74532. In the above invention, a plurality of spray nozzles connected to the non-oxidizing gas supply means are arranged around the upper and lower molds to uniformly cool the molded optical element.

According to the above construction, the molded optical element can be rapidly cooled more uniformly than the entire circumference, the molding cycle time can be shortened, and the distortion generated in the molded product can be prevented.

[0004]

However, the above-mentioned prior art has the following problems. That is, it is a method of spraying non-oxidizing gas from a plurality of spray nozzles to the entire circumference of the molded optical element to uniformly and rapidly cool it.
However, when molding a large-diameter lens, a significant temperature difference occurs between the lens central portion and the outer peripheral portion during cooling. Therefore, there are problems that the molded lens is distorted, the lens accuracy is deteriorated, and cracks are generated.

The object of claim 1 is to prevent the distortion of the lens by reducing the temperature difference between the central portion and the outer peripheral portion of the lens during cooling, and to condense the lens by the transport tray due to contraction due to rapid cooling. It is to prevent the generation of cracks. The object of claim 2 is, in addition to the object of claim 1, to further reduce the temperature difference between the lens central portion and the outer peripheral portion.

[0006]

According to a first aspect of the present invention, a heat-softened glass material is press-molded by a pair of upper and lower molding dies, and a non-oxidizing gas is blown onto the glass optical element being molded to cool it. In doing so, the method for forming an optical element is characterized in that the ejection amount of the non-oxidizing gas is cooled while increasing stepwisely or proportionally linearly.

According to a second aspect of the present invention, the heat-softened glass material is press-molded by a pair of upper and lower molding dies, and the non-oxidizing gas is blown onto the glass optical element during molding to cool it. A method of molding an optical element, which comprises cooling the temperature of the volatile gas stepwise from near the transition point temperature of the glass optical element to room temperature while cooling.

According to the third aspect of the present invention, the heat-softened glass material is press-molded by a pair of upper and lower molding dies, and a non-oxidizing gas is blown to the glass optical element during molding to cool the glass optical element. Optical element characterized by increasing the amount of the volatile gas jetted stepwise or proportionally linearly and cooling the temperature of the non-oxidizing gas stepwise from near the transition point temperature of the glass optical element to room temperature Molding method.

[0009]

According to the action of claim 1, when cooling the molded glass optical element, the temperature difference between the central portion and the outer peripheral portion of the glass optical element is increased by gradually increasing the ejection amount of the non-oxidizing gas. Keep small and cool.

According to the second aspect of the present invention, when the molded glass optical element is cooled, the temperature of the non-oxidizing gas ejected is lowered stepwise from near the transition point temperature of the glass optical element to room temperature. Cooling is performed while keeping the temperature difference between the central portion and the outer peripheral portion of the optical element small.

According to the action of claim 3, the cooling is performed while keeping the temperature difference between the central portion and the outer peripheral portion of the glass optical element smaller than that of the actions of the first and second aspects.

[0012]

Embodiment 1 FIGS. 1 to 5 show the present embodiment, FIG. 1 is a vertical sectional view, FIG. 2 is a plan view of a transfer arm, FIG. 3 is a vertical sectional view at the time of molding, and FIGS. 4 and 5 are graphs. Is. 1 is a molding apparatus used in the present embodiment, and the molding apparatus 1 is composed of a molding chamber 2, a heating furnace 3 and a slow cooling furnace 4 which are connected to the molding chamber 2. The molding chamber 2 is surrounded by a side wall 5 and is connected to an atmosphere gas generator 6 so that the inside of the molding chamber 2 has a non-oxidizing atmosphere.

An upper mold 8 of a press mold is fixed to the upper base 7 of the molding chamber 2. On the other hand, a lower mold base 10 connected to a driving device (not shown) is slidably fitted to the lower base 9 of the molding chamber 2. A lower mold 11 is fixed to the upper end of the lower mold base 10, and the lower mold 11 is configured to move up and down on the axis of the upper mold 8.

The upper mold 8 and the lower mold 11 are provided with a heating device (not shown) so that the temperature control device sets a predetermined temperature. Further, a plurality of cooling gas ejection ports 12 are provided near the tips of the upper mold 8 and the lower mold 11, and the cooling gas can be ejected toward the molding position to uniformly cool the optical element from the entire circumference. Are evenly spaced.

Reference numeral 13 denotes a transfer arm movably supported in the heating furnace 3 and the molding chamber 2, and a semi-circular transfer tray mounting portion 14 is formed at the tip of the transfer arm 13 (FIG. 2). reference). The transport tray 16 on which the optical glass material 15 is placed and transported is held in the transport tray placing section 14. Transport plate 16
Is formed of a material having a linear expansion coefficient smaller than that of the optical glass material 15, and its inner diameter is set so as to fit with the outer diameter of the optical glass material 15 during heating.

In the molding method using the apparatus having the above-described structure, first, the carrier plate 16 on which the optical glass material 15 is placed is held by the carrier arm 13 and carried into the heating furnace 3. Then, the optical glass material 15 is heated by the heater 3a of the heating furnace 3.
Is heated and softened until it becomes a moldable state. This time,
The optical glass material 15 and the carrying tray 16 are heat-fitted. After the heating and softening are completed, the transfer arm 13 advances to transfer the optical glass material 15 together with the transfer tray 16 between the upper and lower molds 8 and 11.

Next, the lower die 11 is raised to raise the transfer arm 1.
Lift the transport tray 16 from 3. At this time, the optical glass material 15 is placed on the molding surface 11 a of the lower mold 11. At this point, the transfer arm 13 retracts to the outside of the molding chamber 2. Subsequently, the lower mold 11 is further raised to press-mold the softened optical glass material 15. During the press molding (the state where the wall thickness is not changed by pressing), the non-oxidizing gas is gradually increased from the gas ejection port 12 while the optical element 17 is being ejected.
Is ejected toward the optical element 17 and the optical element 17 is cooled.

After press molding, the lower mold 11 is lowered to release the optical element 17. After that, a carry-out carrying arm (not shown) for the optical element 17 advances to carry the optical element 17 into the annealing furnace 4. After being gradually cooled in the annealing furnace 4 for a certain period of time,
The press-molded optical element 17 is taken out.

In this embodiment, BAL12 (Tg 478 ° C.) was used as the optical glass material 15, and a biconvex lens having a diameter of 27 mm, a radius of curvature of 52 mm and 123 mm, and a thickness of 4 mm was molded. The heating furnace 3 was set to 920 ° C., softened by heating for 20 seconds, and the upper and lower molds 8 and 11 were set to a mold temperature of 470 ° C.
Was pressed for 15 seconds for molding.

In the above-mentioned molding, the temperature of the non-oxidizing gas jetted from the cooling gas jet port 12 is set to a constant 25 degrees,
The central portion 2 of the optical element under the molding condition in which the ejection amount 21 is set to 7 liters / second for 5 seconds, 20 liters / second for 5 seconds, and 35 liters / second for 5 seconds after the start of molding.
2 shows the temperature change between the outer peripheral portion 23 and the outer peripheral portion 23. In addition, the ejection amount 24 of the non-oxidizing gas is fixed at 30 liters /
The graph of FIG. 5 shows the temperature change between the central portion 25 and the outer peripheral portion 26 of the optical element under the same molding conditions as described above except that the temperature was set to seconds.

As is clear from the comparison between FIG. 4 and FIG.
Compared to the temperature difference between the central portion and the outer peripheral portion of the optical element during molding when cooling with a constant flow rate of the non-oxidizing gas,
The temperature difference between the central portion and the outer peripheral portion of the optical element when the ejection amount of the non-oxidizing gas is controlled according to this embodiment is greatly reduced.

According to this embodiment, it is possible to reduce the temperature difference between the central portion and the outer peripheral portion of the optical element during cooling during molding. Moreover, since the amount of non-oxidizing gas ejected at the initial stage of molding is small, molding can be performed without the transport tray tightening the optical element.

[0023]

Embodiment 2 FIGS. 6 and 7 are graphs showing this embodiment. The molding apparatus used in this embodiment is the same as the molding apparatus of the first embodiment, except that a temperature control device (not shown) for the non-oxidizing gas is provided. Therefore, the description of the configuration will be omitted using FIGS. 1 to 3.

The molding using the apparatus having the above-mentioned structure is the same as that of the first embodiment, except for the cooling method when cooling with a non-oxidizing gas. In this embodiment, the ejection amount of the non-oxidizing gas is constant, but the temperature of the ejecting non-oxidizing gas is gradually reduced from a high temperature to a low temperature.

In this example, LAH60 (Tg 612 ° C.) was used as the optical glass material 15, and a biconvex lens having a diameter of 22 mm, a radius of curvature of 35 mm, 47 mm, and a thickness of 4.7 mm was molded. Set the heating furnace 3 to 930 ° C and set 22
Upper and lower molds 8,1 which are softened by heating for 2 seconds and set at mold temperature 585 ℃
1 was pressed for 15 seconds for molding.

At the time of molding, the amount of non-oxidizing gas ejected from the cooling gas ejection port 12 is fixed at 35 liters /
Second, set the non-oxidizing gas temperature 31 to 5 from the start of molding.
The temperature change between the central portion 32 and the outer peripheral portion 33 of the optical element under the molding conditions of 600 ° C. for seconds, 520 ° C. for 6.5 seconds, and room temperature (25 ° C.) for 3.5 seconds is shown in FIG. Shown in the graph. In addition, the ejection amount of non-oxidizing gas is fixed at 3
The temperature change between the central portion 34 and the outer peripheral portion 35 of the optical element under the same molding conditions as described above except that the temperature of the non-oxidizing gas to be jetted was set to a constant value of 25 ° C. was set to 5 liters / second.
Is shown in the graph.

As is clear from the comparison between FIG. 6 and FIG.
Compared to the temperature difference between the central portion and the outer peripheral portion of the optical element during molding when the temperature of the non-oxidizing gas is kept constant and cooled,
The temperature difference between the central portion and the outer peripheral portion of the optical element when the temperature of the non-oxidizing gas is controlled according to this embodiment is greatly reduced.

According to this embodiment, it is possible to reduce the temperature difference between the central portion and the outer peripheral portion of the optical element during cooling during molding. In addition, since the conveying tray can be kept at a high temperature in the initial stage of molding, only the optical element in the press is cooled down by the molding die and the temperature is lowered first to cause volume contraction.
It is possible to prevent the transport tray from tightening the optical element.

[0029]

The effects of claims 1 to 3 can reduce the temperature difference between the central portion and the outer peripheral portion of the optical element during cooling during molding. Further, since there is no tightening of the optical element by the carrying tray, it is possible to form a glass optical element free from distortion and cracks.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment.

FIG. 2 is a plan view showing the first embodiment.

FIG. 3 is a vertical sectional view showing the first embodiment.

FIG. 4 is a graph showing Example 1.

5 is a graph showing Example 1. FIG.

FIG. 6 is a graph showing Example 2.

FIG. 7 is a graph showing Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding apparatus 2 Molding chamber 3 Heating furnace 4 Slow cooling furnace 5 Side wall 6 Atmosphere gas generating device 7 Upper base 8 Upper mold 9 Lower base 10 Lower mold base 11 Lower mold 12 Cooling gas jet 13 Transfer arm 14 Mounting part 15 Optical glass material 16 Transport plate 17 Optical element

Claims (3)

[Claims] 1. The amount of the non-oxidizing gas jetted when the heat-softened glass material is press-molded by a pair of upper and lower molding dies and a non-oxidizing gas is blown onto the glass optical element being molded to cool it. A method for forming an optical element, which comprises cooling while increasing stepwise or proportionally linearly. 2. The temperature of the non-oxidizing gas is controlled by pressing the heat-softened glass material with a pair of upper and lower molding dies and blowing the non-oxidizing gas to the glass optical element being molded to cool it. A method for molding an optical element, which comprises cooling the glass optical element while gradually lowering it from near the transition point temperature to room temperature. 3. A spray amount of the non-oxidizing gas when the heat-softened glass material is press-molded by a pair of upper and lower molding dies and a non-oxidizing gas is blown onto the glass optical element being molded to cool it. Is gradually and linearly increased, and the temperature of the non-oxidizing gas is gradually decreased from near the transition point temperature of the glass optical element to room temperature and cooled, and then the optical element is molded.